National Emission Standards for Hazardous Air Pollutants: Final Standards for Hazardous Air Pollutants for Hazardous Waste Combustors (Phase I Final Replacement Standards and Phase II) [[pp. 59451-59500]]
[Federal Register: October 12, 2005 (Volume 70, Number 196)]
[Rules and Regulations]
[Page 59451-59500]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr12oc05-26]
[[pp. 59451-59500]]
National Emission Standards for Hazardous Air Pollutants: Final
Standards for Hazardous Air Pollutants for Hazardous Waste Combustors
(Phase I Final Replacement Standards and Phase II)
[[Continued from page 59450]]
[[Page 59451]]
emissions (e.g., operating practices, worker training, proper
maintenance, pollution control device type, etc).
D. Format of Standards
1. Thermal Emissions
EPA proposed, and is finalizing standards for HAP metals and
chlorine (the HAPs amenable to hazardous waste feed control) emitted by
energy recovery units (cement kilns, lightweight aggregate kilns, and
liquid fuel boilers) expressed in terms of pounds of HAP attributable
to the hazardous waste fuel per million british thermal units (BTUs) of
hazardous waste fired. 69 FR at 21219-20. EPA received many comments on
this issue to which we respond below and in the Response to Comment
Document. Some initial discussion of the issue is appropriate, however.
a. Expressing Standards in Terms of a Normalizing Parameter is
Reasonable. First, using a thermal emissions form of a standard is an
example of expressing standards in terms of a normalizing parameter.
EPA routinely normalizes emission standards either by expressing them
as stack HAP concentrations or by expressing the standards in units of
allowable mass emissions per amount of production or raw material
processed. Emission concentration-based standards normalize the size of
each source by accounting for volumetric gas flowrate, which is
directly tied to the amount of raw material each source processes (and
subsequently the amount of product that is produced). Metal and
particulate matter emission standards for commercial and industrial
solid waste incinerators are expressed in emission concentration
format. See Sec. 60.2105. The particulate matter standard for Portland
cement kilns is expressed as mass of allowable emissions per mass of
raw material processed. See Sec. 63.1342. The particulate matter,
mercury, and hydrogen chloride standards for nonhazardous waste
industrial boilers are expressed as pounds of allowable emissions per
million British thermal units (BTUs). See Sec. 63.7500.
Technology-based standards typically normalize emissions because
such a format assures equal levels of control across sources per amount
of raw material that is processed, and allows EPA to equally assess
source categories that comprise units that differ in size. By
normalizing the emissions standard we better ensure the same percentage
of emission reduction per unit of raw material processed by each
source.\101\ See Weyerhaeuser v. Costle, 590 F. 2d 1011, 1059 (D.C.
Cir. 1978) (technology-based standards are typically expressed in terms
of volume of pollutants emitted per volume of some type of unit of
production).
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\101\ A more familiar example of normalization is the Earned Run
Average (ERA), which normalizes a baseball pitchers' earned runs on
the basis of nine innings pitched in order to make comparisons among
pitchers possible.
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There is no legal bar to this approach since the statute does not
directly address the question of whether a source emitting 100 units of
HAP per unit of production but 100 units of HAP overall is a better
performer (or, for new sources, better controlled) than a source
emitting 10 units of HAP per unit of production but emitting 101 units
overall.\102\ One commenter appeared to suggest that we should assess
performance on mass feedrates and mass emission rates, without
normalizing. Such an approach would yield nonsensical results because
the best performing sources would more likely be the smallest sources
in the source category (smaller sources generally have lower mass
emission rates because they process less hazardous waste). This would
likely yield emission standards that would not be achievable by the
larger sources that more likely are better controlled sources based on
a HAP removal efficiency basis.\103\ Normalization by unit of
production is another way of expressing unit size, so that normalizing
on this basis is a reasonable alternative to subcategorization on a
plant size-by-plant size basis. See section 112(d)(1) (size is an
enumerated basis for subcategorizing).
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\102\ Or, put another way, the statute does not directly address
the question of whether a small source that emits 10 units of HAP is
better than a much larger source with better back-end control (but
feeding the same raw material at a higher mass feedrates) that emits
100 units of HAP.
\103\ See USEPA, ``Technical Support Document for the HWC MACT
Standards, Volume III: Selection of MACT Standards,'' September
2005, Section 6.0.
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b. Using Hazardous Waste Thermal Input as the Normalizing Parameter
is Permissible and Reasonable. Normalization of standards based on
thermal input is analogous. For energy recovery units (in this rule,
kilns and most liquid fuel boilers), normalizing on the basis of
thermal input uses a key feed input as the normalizing parameter,
allowing comparison of units with different inputs rather than
separately evaluating these units by size and type (see section
112(d)(1)). Again, this approach is legally permissible. The statute
does not answer the question of which source is better performing, the
source emitting 100 pounds of HAP per million BTUs hazardous waste but
100 pounds of HAP overall or the source emitting 10 pounds of HAP per
million BTUs hazardous waste but emitting 101 pounds overall.
The approach also is reasonable. First, as with other standards
expressed in normalized terms, by normalizing the emissions standard we
ensure the same percentage of emission reduction per unit of raw
material processed by each source, thus allowing meaningful comparison
among sources. For example, emission concentration-based standards
normalize the size of each source by accounting for volumetric gas
flowrate, which is directly tied to the amount of raw material each
source processes (and subsequently to the amount of product that is
produced), and assures equal levels of control per amount of product.
Normalization on the basis of HAP amount in hazardous waste per BTU
level in the hazardous waste similarly assures equal levels of control
across sources per amount of raw material that is processed. Here, the
raw material is the hazardous waste fuel, expressed as units of energy.
It is reasonable to regard a hazardous waste fuel as a raw material to
an energy recovery device. Indeed, fuels are the only input to boilers,
so fuels are necessarily such units' sole raw
material.104 105 Hazardous waste burning cement kilns and
lightweight aggregate kilns produce a product in addition to recovered
energy and so process other raw materials. However, the reason these
units use hazardous waste as inputs is typically to recover usable
energy from the wastes. Hence, the hazardous waste fuel is reasonably
viewed as a raw material to these devices.
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\104\ EPA thus has expressed the MACT standards for particulate
matter, mercury, and hydrogen chloride standards for nonhazardous
waste industrial boilers as pounds of allowable emissions per
million BTUs. Sec. See 63.7500. This normalization considers the
total heat input into the combustion device. Normalizing by total
heat input would not be appropriate for hazardous waste combustors
for metals and chlorine because this would implicitly account for,
and in turn require the use of, feed control of HAP in non hazardous
waste fuels. This is inappropriate for the reasons discussed in
Section III.B of this Part.
\105\We distinguish (i.e., subcategorize) liquid fuel boilers
that process hazardous waste with heating values less than 10,000
BTU/lb from those processing hazardous wastes with heating content
greater than 10,000 BTU/lb. Although boilers that process hazardous
waste with heating values less than 10,000 BTU/lb are still
considered to be energy recovery units, we conclude a thermal
emissions normalization approach for these sources is not
appropriate. See Part Four, Section VI.D.
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In this regard, we note that our choice of normalizing parameter
essentially says that best performers with respect to hazardous waste
fuel burned in energy recovery units are those using the lowest HAP
feedrate (for metals and chlorine) per amount of energy
[[Page 59452]]
recovered.\106\ This approach accords well with the requirement in
section 112(d)(2) that EPA take energy considerations into account in
developing MACT, and also that the Agency consider front-end means of
control such as input substitution (section 112(d)(2)(A)). In addition,
our choice furthers the RCRA goal of encouraging properly conducted
recycling and reuse (RCRA section 1003(b)(6)), which is of relevance
here in that Congress directed EPA to consider the RCRA emission
controls for hazardous waste combustion units in developing MACT
standards for these units, and to ensure ``to the maximum extent
possible, and consistent with [section 112 ]'' that section 112
standards are ``consistent'' with the RCRA scheme. CAA section
112(n)(7).\107\ Conversely, emission concentration-based standards, the
methodology that otherwise would be used to calculate emission
concentration-based standards, may result in standards that are biased
against sources that recover more energy from hazardous waste. This may
discourage sources from recovering energy from hazardous waste because
such standards do not normalize each source's allowable emissions based
on the amount of hazardous waste it processes for energy recovery
purposes. See 69 FR at 21219 and responses below.
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\106\ As explained earlier, the ultimate ranking of best
performers then further evaluates system removal efficiency, best
performers then being defined in terms of the combination of
hazardous waste thermal feed and system removal efficiency. See
USEPA, ``Technical Support Document for the HWC MACT Standards,
Volume III: Selection of MACT Standards'', September 2005, Section 7.3.
\107\ EPA would adopt the thermal format for the standards,
however, whether or not the approach furthered RCRA objectives.
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Second, use of this normalizing parameter makes it much more likely
that hazardous waste feed controls will be utilized by these devices as
an aspect of emissions control. See section 112(d)(2)(A) (use of
measures reducing the volume of pollutants emitted through
``substitution of materials''); CKRC, 255 F. 3d at 865 (EPA to consider
means of control in addition to back-end pollution control technology
when establishing MACT floors). As explained in our discussion of the
SRE/Feed methodology, the MACT floor level for metals and chlorine
reflects the best combination of hazardous waste feedrate, and total
HAP removal efficiency. See section III.B. However, if standards for
energy recovery units are expressed in terms of mass of HAP per volume
of stack gas, then it would be relatively easy for these energy
recovery devices to achieve a standard, without decreasing
concentrations of HAP in their hazardous waste fuels, by diluting the
HAP contribution of hazardous waste with emissions from fossil fuel. A
thermal emissions format prevents this type of dilution from happening
because it ignores additions of stack gases attributable to burning
fossil fuels. Weyerhaeuser, 590 F. 2d at 1059 (use of production of a
unit as a normalizing parameter serves ``the commendable purpose'' of
preventing plants from achieving emission limitations via dilution).
For example, assume there are two identical energy recovery units
with identical back-end control devices (that reflect the performance
of the average of the best performing sources). Source A fulfills 25%
of its energy demand from the combustion of hazardous waste; source B
fulfills 50% of its energy demand from the combustion of hazardous
waste. Also assume that the hazardous waste for these two sources have
equivalent energy contents. If these sources were required to comply
with an emission concentration based-standard (e.g., [mu]g/dscm),
source A would be allowed to feed hazardous waste containing twice the
metal content (on a mass concentration basis, e.g., ppm), and would be
allowed to emit metal HAP at the same mass emission rate relative to
source B. This is because this source is effectively diluting its
emissions with the emissions that are being generated by the fossil
fuels.\108\ A thermal emissions standard format does not allow sources
to dilute their emissions with the emissions from fossil fuel inputs
because it directly regulates the emissions and feeds associated with
the hazardous waste fuel. Under a thermal emissions format both sources
would be required to feed hazardous waste with the same thermal feed
concentrations (on a lb HAP per million BTU hazardous waste basis), and
source A would be required to process hazardous waste with an
equivalent concentration of metal HAP (on a mass basis) and also be
required to emit half as much metal HAP (on a mass emission rate basis)
relative to source B, because source A is processing half as much
hazardous waste fuel, thus vindicating the hazardous waste feed control
aspect of the standard (see also note below regarding the likelihood of
sources using hazardous waste feed control). Further, the thermal feed
concentration with which these sources must comply reflects the feed
control of the average performance of the best performing sources (on a
mass of HAP per million BTU basis). Such a requirement assures that
these sources are processing the cleanest hazardous waste fuels to
recover energy and are reducing HAP emissions to MACT levels.
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\108\ This example assumes there are no HAP emissions
attributable to the fossil fuels.
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We note that it would not be appropriate to express the emission
standards for incinerators, hydrochloric acid production furnaces, and
solid fuel boilers in terms of thermal emissions. As just explained,
the choice of a normalizing parameter is fitted to the nature of the
device to which it is applied in order to allow the most meaningful
comparisons between devices of like type. We therefore conclude that a
thermal emissions format (i.e., normalizing parameter) for incinerators
is not appropriate because the primary function of incinerators is to
thermally treat hazardous waste (as opposed to recovering energy from
the hazardous waste). See 67 FR at 17362 (April 19, 1996). Our database
indicates that most incinerators processed hazardous waste during their
emissions tests that had, on average, heating values below 10,000 BTU/
lb.\109\ We have emission test hazardous waste heating value
information for 62 incinerators in our database. Of these 62 sources,
40 sources processed hazardous waste with an average heating value of
less than 10,000 BTU/lb. The other 22 sources processed hazardous waste
with heating values greater than 10,000 BTU/lb in at least one test
condition, although we note that 14 of these 22 sources also processed
hazardous waste in different test conditions with heating values lower
than 10,000 BTU/lb.\110\
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\109\ As discussed later, the heating values of hazardous wastes
processed at cement kiln and lightweight aggregate kilns are
primarily 10,000 BTU/lb or greater.
\110\ These data are based on a compilation of heating contents
for every incinerator test condition in the database where the
source reported such heating content, and include both the most
recent test conditions as well as older test conditions. Incinerator
test condition heating values range from a low of 790 to a high of
19,800 BTU/lb, with a median value of 7800 BTU/lb.
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We assessed whether we should subcategorize incinerators, similar
to how we subcategorize liquid fuel boilers, based on the BTU content
of the hazardous waste. Incinerators do recover energy from processing
high BTU wastes. Some incinerators are equipped with waste heat
boilers, and high BTU hazardous waste can displace fossil fuels that
otherwise would have to be burned to thermally treat low BTU
wastestreams. However, such energy recovery is considered to be a
secondary product because their primary function is to thermally treat
hazardous waste. A
[[Page 59453]]
thermal emissions normalization approach for incinerators that combust
hazardous wastes with heating values greater than 10,000 BTU/lb would
therefore not be appropriate because the normalized parameter would not
be tied to the primary production output that results from the
processing of hazardous waste (i.e., treated hazardous waste). In
confirmation, no commenters suggested that we apply a thermal emissions
format to incinerators.
We also conclude that a thermal emission format is inappropriate
for hydrochloric acid production furnaces. These devices recover
chlorine, an essential raw material in the process, from hazardous
waste. The classic normalizing parameter of amount of product (HCl)
produced is therefore the obvious normalizing parameter for these
sources. It is true that some hydrochloric acid production furnaces
recover energy from high BTU hazardous wastes. See 56 FR at 7141/1 and
7141-42 (Feb. 21, 1991). Some sources are equipped with waste heat
boilers, and high BTU wastes help sustain the combustion process, which
is necessary to liberate the chlorine from the wastestreams prior to
recovering the chlorine in the scrubbing systems. Again, energy
recovery is not the primary function of these types of sources.\111\
Hydrochloric acid production furnace hazardous waste heating values
range from 1,100 to 11,000 BTU/lb (the median energy content for these
sources is slightly above 6,000 BTU/lb). The range of hazardous waste
heating contents from these sources is much lower than the ranges for
cement kilns, lightweight aggregate kilns, and liquid fuel boilers,
supporting the premise that energy recovery is of secondary importance.
In addition, and critically, the hazardous waste that is processed in
these units contains high concentrations of chlorine, confirming that
the wastes serve as feedstock for hydrochloric acid production, even if
the wastes also have energy value.\112\ No commenters suggested that we
apply a thermal emissions format to hydrochloric acid production furnaces.
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\111\ EPA notes that when first adopting RCRA air emission
standards for hydrochloric acid recovery furnaces (then called
`halogen acid furnaces'), EPA indicated that those furnaces designed
as boilers would be subject to the emission standards for boilers.
56 FR at 7040. This determination did not have regulatory
consequence, since all hydrochloric acid production furnaces were
subject to the same emission standards whether they were classified
as boilers or as industrial furnaces. Thus, EPA was not concluding
that some hydrochloric acid furnaces existed for the primary purpose
of recovering energy in the 1991 rulemaking. 56 FR at 7139
(``[Hydrochloric acid recovery furnaces] are typically modified
firetube boilers that process secondary waste streams containing 20
to 70 per cent chlorine or bromine to produce a halogen acid product
by scrubbing acid from the combustion gases'').
\112\ Hazardous waste chlorine feedrates that are included in
our database (expressed as MTECs) range from a low of 46,000,000
[mu]g/dscm to a high of 294,000,000 [mu]g/dscm. On a mass chlorine
percentage basis, these wastes range from 17% to 82%, noting that
these percentages did not include the chlorine that was also spiked
during the emissions tests). See USEPA, ``Technical Support Document
for the HWC MACT Standards, Volume III: Selection of MACT
Standards'', September 2005, Section 15.
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We consider the processing of hazardous waste in solid fuel boilers
to be more reflective of energy recovery (relative to incinerators and
hydrochloric acid production furnaces) because these sources directly
recover the heat that is released from the combustion of the waste
streams. However, as stated at proposal, not all these sources are
processing hazardous wastes for energy recovery. 69 FR at 21220. These
boilers are generally not commercial units, and so tend to burn
whatever hazardous wastes are generated at the facility where they are
located. Heating values for this source category range from 1,300 to
10,500 BTU/lb, with a median value of 8,000 BTU/lb. We therefore
conclude that thermal emission standards for these sources are not
appropriate because most of these sources are processing hazardous
waste with energy content lower than 10,000 BTU/lb. As discussed in
section VI.D, we conclude that 10,000 BTU/lb is an appropriate level
that distinguishes whether thermal emission standards or mass emission
concentration-based standards are appropriate. We also note that no
commenters suggested that we apply a thermal emissions format to solid
fuel boilers.
Comment: Commenters state that thermal emission standards are
inappropriate because sources burning hazardous waste with a higher
energy content or higher percent hazardous waste firing rate (i.e., one
that fulfills a greater percentage of its total energy demand from the
hazardous waste) would be allowed to emit more HAP.
Response: Part of this comment would apply regardless of what
normalizing parameter is used. Technology-based standards (including
MACT standards) are almost always expressed in terms of some type of
normalizing parameter, i.e., ``X'' amount of HAP may be emitted per
unit of normalizing parameter. This allows a meaningful comparison
between units of different size and production capacity. A consequence
is that the overall mass of HAP emissions varies, but the rate of
control remains constant per the normalizing unit. As explained in the
introduction to this section, this approach is both routine and permissible.
Cement kilns, lightweight aggregate kilns, and liquid fuel boilers
combust hazardous waste to recover valuable energy. Recovering energy
is an integral part of their production process. As discussed at
proposal, emission concentration-based standards (and the methodology
that otherwise would be used to calculate emission concentration-based
standards) may result in standards that are biased against sources that
recover more energy from hazardous waste. 69 FR at 21219. This may
discourage sources from recovering energy from hazardous waste because
such standards do not normalize each source's allowable emissions based
on the amount of hazardous waste it processes for energy recovery
purposes. A source that fulfills 100 percent of its energy demand from
hazardous waste would be required to limit its mass HAP emissions to
the same levels as an identical source that satisfies, for example,
only 10 percent of its energy demand from hazardous waste and 90% from
coal. This would inappropriately discourage the safe recovery of energy
from hazardous waste, and could in turn result in greater consumption
of valuable fossil fuels that otherwise would be consumed.
Sources which fulfill a greater percentage of their energy demand
from hazardous waste (either by processing hazardous wastes that are
higher in energy content, or by simply processing more hazardous waste)
will be allowed to emit more HAP (on a mass emission rate basis) than
an identical source that satisfies less of its total energy demand from
hazardous waste. This is appropriate because: (1) The source fulfilling
a greater percentage of its energy demand from hazardous waste is
processing more raw material than the other source (the raw material
being the energy content of the waste); and (2) The source fulfilling a
lower percentage of its energy demand requirements from hazardous waste
would not be allowed to dilute its emissions with nonhazardous waste
fuels, and we would thus assure that all sources implement hazardous
waste feed control to levels consistent with MACT.\113\ This
[[Page 59454]]
was illustrated in the example provided in the introduction to this
comment response section.
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\113\ Although the rule does not require use of feed control (or
any particular means of control to achieve a standard), the rule
assures that all sources' emissions will reflect the emissions of
the sources with the best hazardous waste federates expressed in
terms of amount of HAP per BTU of hazardous waste. Because this
format eliminates consideration of stack gas attributable to fossil
fuel emissions, and thus eliminates the dilutive effect of these
emissions, the likelihood that sources will in fact use hazardous
waste feed control as part of their control strategy is great.
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Similarly, two sources that combust hazardous waste with the same
energy content and the same metal concentrations (on both a thermal
concentration and mass-based concentration basis), but at different
hazardous waste firing rates, would be required to achieve identical
back-end control device operating efficiencies to comply with a thermal
emissions-based standard. Holding these factors constant, thermal
emission standards require sources to achieve identical percent
reductions of the HAP that is processed within the combustor via
removal with an air pollution control device. A thermal emission
standard format is thus equally stringent for these sources on a
percent HAP removal basis, irrespective of the amount of hazardous
waste it processes for energy recovery, and better assures that sources
burning smaller amounts of hazardous waste (from an energy recovery
perspective) are also controlling emissions as well as the average of
the best performing sources.
Sources processing higher energy content hazardous wastes would be
allowed to feed hazardous wastes with higher metal and chlorine mass-
based concentrations relative to other sources combusting lower energy
content wastes. To illustrate this, assume there are two sources (named
C and D) with identical back-end control systems and identical mass
feedrates of hazardous waste. Also assume the hazardous waste of source
C has twice the energy content as compared to the hazardous waste
processed by source D. A thermal emission standard will allow Source C
to feed a hazardous waste that has twice the metals concentration (as
measured on a mass basis) as compared to source D, even though both
sources would be required to comply with equivalent thermal feed rates
limitations. Notably, however: (1) Source C is displacing (i.e., not
using) twice as much valuable fossil fuel as the source with the lower
energy content hazardous waste, and is feeding twice as much raw
material--the raw material being energy content contained in the
hazardous waste; (2) source C cannot exceed the feed control levels
(expressed on a lbs of HAP per million BTU basis) that was achieved by
the average of the best performing sources (assuming its back-end
control efficiency is equivalent to the average performance
demonstrated by the best performing sources); and (3) source D is
required to have lower mass concentrations of metals in its hazardous
waste because it is firing poorer quality hazardous waste fuel (from an
energy recovery perspective) and because it is feeding less of the same
raw material (measured by energy content). Thus, the thermal emissions
format appropriately encourages and promotes the processing of clean,
high energy content hazardous waste fuels (consistent with evaluating
hazardous waste feed control as an aspect of MACT, and not just relying
on control solely through use of back end technology), and does so
equally for all sources because it normalizes the allowable emissions
based on the amount of energy each source recovers from the hazardous
waste. Put another way, source C in the above example is controlling
HAP emissions to the same extent as the average of the best performing
sources per every BTU of hazardous waste fuel it processes (as is source D).
We note that this is a hypothetical example. In practice the
average energy content of hazardous waste processed at cement kilns
does not vary significantly across sources. Cement kilns burn hazardous
wastes with relatively consistent energy contents because that is what
their production process necessitates. This is supported by our
database and by comments received from the Cement Kiln Recycling
Coalition.\114\ Heating values of hazardous wastes processed at cement
kilns during compliance tests (information which is included in our
database) range from 10,300 to 17,600 BTU/lb, with a median value of
12,400 BTU/lb. We note that these are snapshot representations of
hazardous waste heating content from these sources that originate from
compliance tests. We also have long term average hazardous waste
heating measurements from cement kilns indicating that the heating
content of the hazardous wastes on average range from 9,900 to 12,200
BTU/lb, with a median value of 11, 500 BTU/lb. We thus conclude that
the commenter's concern regarding sources being allowed to emit more
HAP if they process hazardous waste with higher energy content is
overstated for these sources.
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\114\ See comment submitted by the Cement Kiln Recycling
Coalition, USEPA, ``Comment Response Document to the Proposed HWC
MACT Standards, Volume 1: MACT Standards,'' September 2005, Section
3.3. Also see USEPA, ``Technical Support Document for the HWC MACT
Standards, Volume III: Selection of MACT Standards,'' September
2005, Section 23.
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Energy content of hazardous wastes processed in liquid fuel boilers
and lightweight aggregate kilns varies more than energy content of
hazardous wastes processed by cement kilns, and sources with higher
energy content wastes would be allowed to emit more metals than
identical sources burning identical volumes of lower energy content
wastes (although the degree of control is identical per BTU of
hazardous waste fuel processed).\115\ Again, these are hypothetical
examples. Each energy recovery unit will have an upper bound on the
amount of energy it can process from the hazardous waste. Sources that
process higher energy content hazardous wastes would not necessarily
feed the same volume of hazardous waste as compared to sources
processing lower energy content hazardous wastes because they cannot
exceed the thermal capacity of their combustion unit. Under a thermal
emission standard format, the mass emission rates that would be allowed
for identical sources that fulfill 100 percent of their energy demand
from hazardous waste and that have differing hazardous waste energy
contents would be identical. Although the source with the higher energy
content hazardous waste would have a higher allowable mass-based
hazardous waste feed concentration, this source would have to process
less hazardous waste (on a mass basis) to remain within its thermal
capacity. This helps to ensure that its mass HAP emission rate is
similar to other sources that process lower energy content hazardous waste.
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\115\ The hazardous waste heating values of liquid fuel boilers
range from 2,200 to 21,000 BTU/lb, with a median value of 14,800.
Heating values of lightweight aggregate kilns range from 4,900 to
16,900 BTU/lb, with a median value of 14,800. We note that the low
end heating value for lightweight aggregate kilns reflects one
source and is not typical of heating values used by the other
commercial lightweight aggregate kiln facilities, and are similar to
the heating values of cement kilns.
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One commenter's apparent concern with thermal emissions seems to
center on an assertion that sources will intentionally blend
nonhazardous, high heating value wastes or fuels with low energy, high
metal bearing hazardous wastes in order to increase the energy content
of these metal bearing wastes so that they will be subject to higher
allowable emissions via thermal emission standards. We specifically
address that comment later as it relates to commercial energy recovery
units (lightweight aggregate kilns and cement kilns). We note here,
however, that we do not consider that comment to be of practical
concern for liquid fuel boilers
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because they do not engage in commercial fuel blending practices.
Comment: A commenter states that EPA's assessment of thermal
emissions to identify the relevant best sources is inappropriate
because thermal emissions are not emission levels, but rather a ratio
of emissions to the heat content in a source's hazardous waste.
Response: This comment challenges the basic idea of normalization,
since the comment would be the same regardless of the normalizing
parameter being used. Thermal emissions are emission levels that are
normalized to account for the amount of energy (i.e., raw material)
these sources recover by processing hazardous waste. Similarly, a mass
emission concentration (i.e., [mu]g/dscm) is a ratio of the emissions
to the volume of combustion gas that is generated, which normalize
emissions to account for differences in the size of the combustion
units (as well as differences in production capacity). This rulemaking
assesses performance and expresses emission standards in both of these
formats; both formats normalize the emissions so that we may better
assess emission control efficiencies equally across sources based on
the percent of HAP in the feed (whether thermal feed or feed normalized
based on combustor size) \116\ that is controlled or removed from the
stack gas prior to being emitted into the atmosphere. As discussed
above, technology-based standards have historically assessed
performance after normalizing emissions based on the amount of raw
material processed by the given industry sector. Thermal emissions
normalize each source's emissions based on the amount of raw material
(hazardous waste fuel) it processes, and are therefore appropriate to
assess and identify the relevant best performers. Finally, as
previously explained, this approach is consistent with both the language
of section 112 (d) (2) and (3), and the purpose of these provisions.
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\116\ For emission concentration-based standards we normalize
hazardous waste feed control levels by calculating what we call
maximum theoretical emission concentrations, which are equivalent to
the HAP mass feed rate divided by gas flow rate.
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Comment: A commenter states that EPA's assessment of thermal
emissions to identify the relevant best sources is inappropriate
because it ignores HAP emissions attributable to the nonhazardous fuel
and raw material.
Response: Thermal emission standards do not directly control HAP
emissions attributable to the fossil fuels and raw material, in the
sense that we did not assess feed control of fossil fuels or raw
materials. However, this issue is not related to our choice to use
thermal content of hazardous waste as a normalizing parameter. Rather,
the issue is whether feed control of fossil fuels and raw materials is
a feasible means of control at all. We have determined that it is not,
and that only back-end control (expressed as system removal efficiency)
is feasible. Moreover, today's rule controls emissions from HAP in raw
material and fossil fuels. All non-mercury metal HAP emissions
attributable to fossil fuels or raw material are effectively and
efficiently controlled to the level of the average of the best
performing sources with the surrogate particulate matter standard, as
well as the system removal efficiency component of the SRE/Feed methodology.
Comment: EPA has failed to document sources' actual feedrates.
Feedrates are presented either as MTECs (where hazardous waste HAP
feedrates are divided by gas flow rates) or as thermal feedrates,
(where feedrate is expressed as the mass of HAP per million BTUs of
hazardous waste fired). This is impermissible, since it does not
measure actual feed levels.
Response: This comment essentially takes the position that it is
legally impermissible to normalize standards, i.e., express standards
on a common basis. EPA rejects this comment for the reasons stated in
the introduction to this section.
Comment: A commenter states that an increasing number of fuel
blenders are producing fuels with a minimum heating content and maximum
metals content in order to maximize revenues because high metal bearing
wastes command a higher revenue on the commercial waste market. The
commenter states that thermal emission standards are not appropriate
because they are based on the implicit assumption that energy recovery
entails metals feed.
Response: Contrary to what the commenter suggests, the thermal
emissions format will more likely discourage the alleged practice of
fuel blenders producing fuels with a minimum heat content and maximum
metals content because the standard limits the allowable metal
emissions based on the amount of energy contained in the hazardous
waste. Thus, a source with a lower energy waste would have to ensure
that the mass concentration of metals is also lower to comply with the
thermal emission formatted standard. The source would consequently emit
less metals (on a mass basis) because of the lower metal mass
concentration in the waste fuel. Thermal emission standards reflect the
reality that the hazardous waste fuels that are currently processed
safely and efficiently in energy recovery units to displace valuable
fossil fuel do in fact contain metal HAP. From a feed control
perspective, the thermal emissions format appropriately requires
sources to process high energy content hazardous waste fuels that
reflect the thermal feed control levels achieved by the average of the
best performing sources, and does so equally for all sources because it
normalizes the allowable emissions based on the amount of energy each
source recovers from the hazardous waste.
Comment: A commenter states that EPA should be concerned that fuel
blenders and kilns will use the thermal emission standard format to
increase the allowable metals feedrates for their units. The commenter
claims that sources could inappropriately convert non-hazardous waste
fuel to hazardous waste fuel by simply putting coal in a bunker in
which hazardous waste was once stored, or mixing nonhazardous waste
fuel oil with hazardous waste. The commenter states that a facility
with a low hazardous waste firing rate, and relatively low allowable
emissions can become a facility with a high hazardous waste percent
firing rate, with higher allowable emissions, simply by `creative' use
of the hazardous waste mixture rule. The commenter suggests that EPA
clearly state that the hazardous waste thermal emission standards apply
only to the hazardous waste portion of the fuel blend mixture. The
commenter further suggests that EPA require fuel blenders to report the
amount of nonhazardous waste fuel that is contained in the fuel blend,
and that cement kilns use this to determine allowable metal feed rates
based on the original hazardous waste energy content.
Response: We do not believe hazardous waste combustors will engage
in the practice of redesignating their fossil fuels, i.e., coal, as
hazardous wastes with creative use of the mixture rule in order to
increase their allowable metal HAP emission rate. That would require
large quantities of coal to be newly classified as hazardous waste. The
coal, and the unit where the coal is stored, would subsequently become
subject to all applicable subtitle C requirements, which include
storage and closure/post closure requirements. We believe this
disincentive will discourage this hypothetical practice.
Moreover, as previously discussed, today's rule does not allow
cement kiln or lightweight aggregate kiln emissions to exceed the
interim standards. The fact that we are issuing emission
[[Page 59456]]
standards for some pollutants in the thermal emissions standard format
will not encourage fuel blenders to send more metals to these
commercial energy recovery sources because their allowable emission
concentrations are, by definition, either equivalent to or more
stringent than the current limitations with which they are complying.
Thus, even if the fuel blenders and energy recovery units engaged in
this practice, they could not emit more metals than they are currently
allowed to emit. We therefore conclude that it is not necessary to
promulgate complicated regulatory provisions that would increase the
reporting and recordkeeping requirements of fuel blenders and energy
recovery units in order to address a hypothetical scenario that likely
would never occur.
Finally, we note that combustion of certain high HAP metal content
wastes is already prohibited under RCRA rules. See 40 CFR 268.3. Such
wastes remain prohibited from combustion even if they are mixed with
fossil fuel so that the mixture has a higher energy content. U.S. v.
Marine Shale Processors, 81 F. 3d 1361, 1366 (5th Cir. 1996) (an
unrecyclable hazardous waste is not recycled when it is mixed with a
usable non-waste and the mixture is processed). Thus, the dilution
prohibition in Sec. 268.3 serves as a further guard against the
commenter's concern.
Comment: A commenter states that the thermal emissions format may
be problematic because it is based on a flawed assumption that metal
HAP from the cement kiln raw material and hazardous waste partition in
equal proportions to the total stack gas emissions. The commenter
believes that metal retention in the raw materials is higher than the
hazardous waste, suggesting that thermal emission standards allow an
arbitrary increase in allowable hazardous waste metals emissions. The
commenter suggests that EPA require that compliance demonstrations be
conducted only under conditions where the metals content in the
hazardous waste is significantly higher than the metal content in the
raw material to minimize this bias.
Response: The commenter has not provided any emissions data to
support this claim, nor does the EPA know of data available that
reaches this conclusion. We do not believe there is a significant
difference in the partitioning rates of these metals in a cement
kiln.\117\ Even if there is a difference, this would not result in an
arbitrary increase of allowable hazardous waste metals emissions. The
thermal emission standards were calculated using thermal emissions data
that are based on each source's compliance test. These tests were
conducted at hazardous waste feed control levels that represented the
upper bound of feed control levels these sources see on a day-to-day
basis. To accomplish this, sources spiked metals into the hazardous
waste prior to combusting the wastes. The amount of metals that were
contained in the hazardous waste streams, after accounting for these
spiked metals, far exceeded the metal levels that were contained in the
raw material. Thus the differences in partitioning, if any, would
likely be overshadowed by the fact that the majority of the metals were
contained in the hazardous waste.
---------------------------------------------------------------------------
\117\ We reference comments submitted by the cement kiln
recycling coalition that address this very point. See USEPA,
``Comment Response Document to the Proposed HWC MACT Standards,
Volume 1: MACT Standards,'' September 2005, Section 3.3. We have
evaluated these comments and find them persuasive on this issue.
---------------------------------------------------------------------------
Notably, any partitioning bias that that may be present would also
have been present during these compliance tests. As a result, this
potential bias would be built into the emission standard and thus would
not result in an arbitrary increase in allowable hazardous waste metals
emissions because these sources will again demonstrate compliance under
testing conditions similar to those used to generate the data used to
calculate the MACT floors. We conclude that it is not necessary to
provide additional prescriptive regulatory language that would require
sources to demonstrate system removal efficiencies under testing
conditions that exhibit a high ratio of hazardous waste metal content
to raw material metal content because the regulations implicitly
require sources to demonstrate hazardous waste metal feed control
levels that represent the upper range of their allowable feed control
levels.\118\
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\118\ Although today's final rule allows sources to extrapolate
their allowable hazardous waste feed control levels to levels that
are higher than the level demonstrated in the comprehensive
performance test, sources must still spike metals into the hazardous
waste during the test in order to assure that the system removal
efficiency used for the extrapolation procedure is reliable and accurate.
---------------------------------------------------------------------------
Comment: A commenter states that compliance with standards
expressed in a thermal emissions format is problematic because the
measurement of energy content of hazardous waste fuel blends is subject
to significant variability due to the nature of the test. The commenter
also claims that heating value measurements of waste streams that are
mixtures of solids and liquids tend be biased high, which would
inappropriately give these sources higher allowable metal emission
limitation.
Response: There are standard ASTM procedures that reliably measure
the energy content of the hazardous waste. Any parameter that is
measured for compliance purposes is subject to method imprecision and
variability. We do not believe that hazardous waste energy content
measurements result in imprecision and variability above and beyond the
measurement methods that are currently used to assure compliance with
emission concentration-based standards.
The commenter did not provide evidence that supports the claim that
energy content measurement and/or sampling methods consistently result
in a positive bias. If a bias were consistently present for these types
of wastes, then one would expect it to be also reflected in the
measured data for which we based the emission standards, which would
fully address the commenter's concern. Nonetheless, we note that all
hazardous waste sampling and analysis procedures must be prescribed in
each source's feedstream analysis plan, which can be reviewed by the
permitting authority upon request. These feedstream analysis plans must
ensure that sampling and analysis procedures are unbiased, precise, and
that the results are representative of the feedstream. See Sec.
63.1208(b)(8). More information on obtaining a representative samples
can be found in EPA's SW-846 publication.\119\ These procedures involve
acquiring several sub-samples that provide integration over the
breadth, depth and surface area of the waste container and obtaining
replicate samples (see Ch. 13.3.1 of SW-846).
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\119\ SW-846, ``Test Methods for Evaluating Solid Waste,
Physical/Chemical Methods.''
---------------------------------------------------------------------------
Comment: A commenter states that BTU measurements can be reported
as either a higher heating value or a lower heating value, and suggests
that EPA require sources to use the lower heating value calculation
when determining allowable hazardous waste feed control levels. The
commenter seems to imply that use of higher heating values will
inappropriately result in higher allowable metal feed rates for fuel
blends that contain aqueous waste.
Response: The BTU data in our database that we use to calculate the
emission standards reflect higher heating values. It is standard
practice in the incineration/combustion industry to report the gross
heat of combustion (or
[[Page 59457]]
higher heating value). We conclude that sources should use the higher
heating value rather than the lower heating value for all compliance
determinations because these are method-based emission standards. Fuel
blends that contain aqueous wastes will not be inappropriately rewarded
with higher allowable feed rates because any fuel mixture that contain
aqueous mixtures will have lower reported heating values, irrespective
of whether they are reported as higher heating values or lower heating
values.\120\
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\120\ The difference between the higher heating value and lower
heating value of an aqueous waste is insignificant relative to the
difference in heating value between an aqueous waste and an organic
liquid waste fuel.
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E. Standards Can Be No Less Stringent Than the Interim Standards
Comment: Several commenters oppose EPA's position in the proposed
rule that the replacement standards can be promulgated at a level no
less stringent than the interim standards for incinerators, cement
kilns, and lightweight aggregate kilns. In instances where the
calculated replacement standard is less stringent than the interim
standard, the commenters oppose EPA's position of ``capping'' the
replacement standard at the level of the interim standard to prevent
backsliding from those levels. Instead, commenters recommend that EPA
calculate and finalize the existing and new source floor levels without
regard to the interim standards. One commenter also notes that the
interim standards are simply a placeholder without the necessary
statutory basis to qualify as emission limitations for purposes of
establishing MACT floors. Another commenter, however, supports EPA's
position to prevent backsliding to levels less stringent than the
interim standards.
Response: We maintain that the replacement standards can be no less
stringent than existing standards, including the interim standards
under Sec. Sec. 63.1203-1205, for incinerators, cement kilns, and
lightweight aggregate kilns. These standards were promulgated on
February 13, 2002, and sources were required to comply with them no
later than September 30, 2003, unless granted a one-year extension (see
Sec. 63.1206(a)). Thus, all hazardous waste combustors are currently
complying with the interim standards. The comment that the standards
lack some type of requisite statutory pedigree misses the central point
of our interpretation of the statute: motivation for achieving a
standard (be it regulatory compulsion, statutory requirement, or some
other reason) is irrelevant in determining levels of MACT floors.
National Lime v. EPA, 233 F. 3d at 640. What matters is the level of
performance, not what motivated that level.
As a result, the replacement standards promulgated today ensure
that sources will emit HAP at levels no higher than levels achieved
under current regulations. We do this in this rule, when necessary, by
either capping a calculated floor level by the interim standard (when
both the calculated floor level and interim standard are expressed in
the same format of the standard) or by adopting dual standards in cases
where formats of the standard vary (so that comparison of stringency
cannot be uniformly determined (as for cement kilns and lightweight
aggregate kilns, as explained in the preceding section above and in the
following response). In this case, the sources are subject to both the
replacement and interim standards.
Comment: One commenter states that some proposed standards
expressed in a thermal emissions format would allow some sources to
emit semivolatile metals at levels higher than the interim standard.
The commenter states that EPA reached incorrect conclusions when making
relative stringency comparisons between standards expressed in a
thermal emissions and mass concentrations format because, in part, EPA
assumed an average F-factor (e.g., semivolatile metals for cement
kilns).\121\ In addition, the commenter notes that the actual
relationship between standards expressed in terms of thermal emissions
and mass concentrations is complex and depends on a number of factors.
As a result, the commenter urges EPA to adopt dual standards (i.e.,
promulgate the MACT standard as both the standard expressed in a
thermal emissions format and also the interim standard expressed in a
mass concentration format) to prevent backsliding.
---------------------------------------------------------------------------
\121\ An F-factor is an estimate of the amount of combustion gas
volume that is generated per fuel heat input for a given type of
fuel, expressed in units, for example, cubic feet of combustion gas
per million British thermal units (BTU) of fuel burned. In the
proposal, EPA used F-factors to convert the emission standards
expressed on a thermal basis to mass concentrations in order to make
a judgment as to the relative stringency of the proposed MACT
standards relative to the interim standards.
---------------------------------------------------------------------------
Response: Even though a source may operate in compliance with a
standard expressed in a thermal emission format, a source may or may
not also be in compliance with the corresponding mass concentration
interim standard (e.g., the semi- and low volatile metal emission
standards for cement and lightweight aggregate kilns of Sec. Sec.
63.1204 and 63.1205, respectively). As reflected in the comment, making
a judgment as to whether a replacement standard is more stringent than
the interim standard for the HAP is not always a straight-forward
calculation. As we discussed in the proposed rule \122\ and echoed by
the commenter, comparing standards in the thermal emissions format to
those in a mass concentration format involves assumptions that vary on
a site-specific basis and can vary over time, including the hazardous
waste fuel replacement rate, contributions to emissions from
nonhazardous waste inputs such as raw materials and nonhazardous waste
fuels such as coal, how close to the standard a source elects to
comply, the system removal efficiency demonstrated during testing, and
the type and composition, including heating value, of fuels burned.
---------------------------------------------------------------------------
\122\ For example, see 69 FR at 21255-258, 267-271.
---------------------------------------------------------------------------
To ensure that sources operating under standards expressed in a
thermal emissions format will not emit HAP metals at levels higher than
currently achieved under the interim standards, we adopt a dual
standard to prevent emissions increasing to levels higher than the
interim standards. The dual standard structure includes both the
standard expressed in a thermal emissions format and the interim
standard, which is expressed in a mass concentration format. We apply
this concept to several standards including semivolatile metals, low
volatile metals, and mercury \123\ for cement kilns and semivolatile
metals and low volatile metals for lightweight aggregate kilns. This
approach ensures that sources are not emitting HAP metals above the
levels of the interim standards because we cannot reliably determine
that emissions under a standard expressed in a thermal emissions format
would not exceed the interim standard for all sources in the category.
See Sec. Sec. 63.1220(a)(2)-(a)(4), and (b)(2)-(b)(4) and
63.1221(a)(3)-(a)(4) and (b)(3)-(b)(4).
---------------------------------------------------------------------------
\123\ Although the mercury standard promulgated for cement kilns
is not expressed using a thermal emission format basis, the same
concept applies because the mercury standard is a hazardous waste
feed concentration standard, which is a different format than the
interim standard.
---------------------------------------------------------------------------
We evaluated the relative stringency of the standards expressed in
the thermal emissions format compared to the interim standards for the
entire source category in order to determine if the dual standard
scheme could be avoided. We determined that we could not. For some HAP
groups we found that many sources in the category would have the
potential to exceed the interim
[[Page 59458]]
standards for that HAP.\124\ In this case, we considered simply
``capping'' the standard expressed in the thermal emission format by
the interim standard (i.e., the promulgated standard would only be
expressed in a mass concentration format). However, we conclude that
this approach would not be appropriate because the standard expressed
in a thermal emission format would likely be more stringent than the
mass concentration for some sources, and the statute requires that MACT
floors reflect this superior level of performance.
---------------------------------------------------------------------------
\124\ An example for each category is semivolatile metals
thermal emissions standard for existing cement and lightweight
aggregate kilns. See USEPA, ``Final Technical Support Document for
the HWC MACT Standards, Volume III: Selection of MACT Standards,''
Section 23.1, September 2005.
---------------------------------------------------------------------------
In other cases we found that the standards expressed in the thermal
emissions format would not likely exceed the interim standards by the
majority of sources operating under typical conditions.\125\ While our
analysis (based on information in our data base) shows in these cases
that the emission standard expressed in a thermal emission format would
not likely result in an exceedance of the interim standard, this
conclusion may not be true because the assumptions may not be valid for
a particular source or site-specific factors may change in future
operations. For example, HAP metal emissions could increase over time
due to increases in HAP contributions from raw materials or alternative
raw materials. Given this potential, we adopt dual standards for the
HAP metal standards in order to ensure that standards expressed in a
thermal emissions format will not exceed emission levels achieved under
the interim standards.\126\
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\125\ An example is the emission standards for low volatile
metals for existing and new cement kilns and new lightweight
aggregate kilns. See USEPA, ``Final Technical Support Document for
the HWC MACT Standards, Volume III: Selection of MACT Standards,''
Section 23.1, September 2005.
\126\ In response to a comment regarding the implementation of
dual standards, we note the promulgation of a new provision allowing
sources to petition the Administrator to waive the HAP metal
feedrate operating parameter limits for either the emissions
standards expressed in a thermal emissions format (or the mercury
feed concentration standard for cement kilns) or the interim
standards based on documentation that the feedrate operating
parameter limit is not needed to ensure compliance with the relevant
standard on a continuous basis. See new Sec. 63.1209(g)(1)(iv) and
Comment Response Document, Volume I, Section 3.5.
---------------------------------------------------------------------------
Comment: Several commenters state that the interim standards do not
reflect the average performance of the best sources, and so cannot be
the basis for floor levels.
Response: In those few situations where we have established floor
levels at the level of the interim standards, we have done so as the
best means of estimating performance of the best performing sources.
Based on the available data to us, the average of the best performing
sources exceeds the level of the interim standards in a few instances.
Under these circumstances, the binding regulatory limit becomes the
best means available to us to estimate performance. See Mossville, 370
F. 3d at 1241-42 (accepting regulatory level as a floor standard where
sources' measured performance is not a valid means of determining floor
levels, and where such data contains results as high as those
regulatory levels).
F. How Can EPA's Approach to Assessing Variability and its Ranking
Methodologies Be Reasonable When They Result in Standards Higher Than
the Interim Standards?
A commenter argued that EPA's floor methodologies, in particular
its consideration of variability beyond that demonstrated in single
test conditions, the SRE/feed and Air Pollution Control Device
methodologies, must be arbitrary because in a few instances projected
standards using these approaches were higher than the current interim
standards, a level every source (not just the best performers) are
achieving. Commenters also noted that one of the new source standards
calculated under these approaches was higher than an existing source
standard, another arbitrary result.
EPA believes that these seeming anomalies (which are infrequent)
result from the database used to calculate performance and standards,
rather than from the approaches to assessing variability or the two
questioned floor methodologies. The data base is from test results
which preceded EPA's adoption of the interim standards. Thus, the level
of performance required by the later rule is not necessarily reflected
in pre-rule test data. In confirmation, some of the standards computed
using straight emission approaches also are higher than the interim
standards. Other anomalies arise simply due to scarcity of data (floor
levels for certain HAP emitted by lightweight aggregate kilns
especially, where there are only nine sources total). In these
situations there is a greater likelihood that one or more of the best
performing sources will have relatively high emissions because we are
required to use data from five sources to comprise the MACT pool
whenever we have data from fewer than 30 sources, and a small amount of
data can skew the result. See Sec. 112(d)(3)(B).\127\
---------------------------------------------------------------------------
\127\ See USEPA, ``Technical Support Document for the HWC MACT
Standards, Volume III: Selection of MACT Standards,'' September
2005, Section 19, for further discussion.
---------------------------------------------------------------------------
For example, many of the calculated new source chlorine floors were
slightly higher than the calculated existing source standards because
we assumed all sources with measured emissions below 20 ppmv were in
fact emitting at 20 ppmv (see part four, section I.C). We generally are
unable to differentiate a single best performing source among these
best performers because many/all of the best performing sources
emissions are adjusted to the same emission level. The calculated new
source floor can be slightly higher than the existing source floor
because the variability factor that is applied to the single best
performing source is based on only one test condition (with three
emission test runs). This results in a higher level of uncertainty
relative to the existing source standard, which is based on a
compilation of emissions data from several sources that have
essentially the same projected emissions as a result of the method bias
correction factor. The variability factor that is applied to the
emissions of the single best performing source is therefore higher than
the variability factor for the existing source floor because there are
fewer degrees of freedom in the statistical analysis.\128\ Likewise,
many of the calculated solid fuel boiler new source standards were
slightly higher than the calculated existing source standards because,
as discussed above, there are fewer degrees of freedom when assessing
the variability from a single best performing source. The solid fuel
boiler ``anomalies'' also occur using a straight emissions methodology.
See USEPA, ``Technical Support Document for the HWC MACT Standards,
Volume III: Selection of MACT Standards,'' September, 2005, Section 19,
for further discussion that summarizes and explains these so-called
anomalies.
---------------------------------------------------------------------------
\128\ For a single test condition the t factor used in
variability factor calculation has n-1 degrees of freedom where n is
the number of runs for that condition. For the MACT floor
calculation the t factor has X-N degrees of freedom where X is the
total number of runs from all sources in the MACT pool and N is the
number of sources in the pool. See USEPA, ``Technical Support
Document for the HWC MACT Standards, Volume III: Selection of MACT
Standards,'' September, 2005, Section 7.1 for more information on
the floor calculation procedure.
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[[Page 59459]]
IV. Use of Surrogates
A. Particulate Matter as Surrogate for Metal HAP
Comment: A commenter states that EPA's use of particulate matter as
a surrogate for nonenumerated metals is unlawful and arbitrary and
capricious because although particulate matter emissions may provide
some indication of how good a source's end-of stack control of such
metals is, it does not indicate what its actual metal emission levels
are.\129\ The commenter states that emissions of these metals can vary
based on metal feed rate without having any appreciable effect on
particulate matter emission levels. Thus a particulate matter standard
does not necessarily ensure that metal emissions are reduced to the
metal emission levels achieved by the relevant best performing sources.
To support this assertion, the commenter states that EPA is on record
saying ``low particulate matter emissions do not necessarily guarantee
low metal HAP emissions, especially in instances where the hazardous
waste feeds are highly concentrated with metal HAP.'' 69 FR at 21221.
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\129\ ``Enumerated'' metals are those HAP metals directly
controlled with an emission limit, i.e., lead, cadmium, chromium,
arsenic and beryllium. The remaining nonmercury metal HAP (i.e.,
antimony, cobalt, manganese, nickel, and selenium) are called
``nonenumerated'' metal HAP (note that arsenic and berrylium are
nonenumerated metals for liquid fuel boilers because the low
volatile metal emission standard applies only to chrome).
---------------------------------------------------------------------------
Response: The final rule uses a particulate matter standard as a
surrogate to control: (1) Emissions of nonenumerated metals that are
attributable to all feedstreams (both hazardous waste and remaining
inputs); and (2) all nonmercury metal HAP emissions (both enumerated
and nonenumerated metal HAP) from the nonhazardous waste process feeds
at cement kilns, lightweight aggregate kilns, and liquid fuel boilers
(e.g., emissions attributable to coal and raw material at a cement
kiln, and emissions attributable to fuel oil for liquid fuel boilers).
Incinerators, liquid and solid fuel boilers may elect to comply with an
alternative to the particulate matter standard that would limit
emissions of all the semivolatile metal HAPs and low volatile metal
HAPs. See Sec. 63.1219(e).
The particulate matter standard is a necessary, effective, and
appropriate surrogate to control nonmercury metal HAPs. The record
demonstrates overwhelmingly that when a hazardous waste combustor emits
particulate matter, it also emits nonmercury HAP metals as part of that
particulate matter, and that when particulate matter is removed from
emissions the nonmercury HAP metals are removed with it.\130\
Nonmercury metal HAP emissions are therefore reduced whenever
particulate matter emissions are reduced. The particulate matter
standard thus is an effective and appropriate surrogate that assures
sources are controlling these metal HAP with an appropriate back-end
control technology. National Lime v. EPA, 233 F. 3d at 639. The
nonenumerated metal HAP are no different than other semivolatile or low
volatile metals in that they also will be effectively controlled with a
back-end particulate matter air pollution control device.
---------------------------------------------------------------------------
\130\ This statement is equally true for any emitting source,
not just hazardous waste combustors. It is well established that
semivolatile and low volatile metals exist in solid particulate form
at typical air pollution control device operating temperatures. This
is supported by (1) known operating temperature ranges of air
pollution control devices used by hazardous waste combustors; (2)
known metal volatility equilibrium relationships; and (3) extensive
technical literature. See USEPA, ``Technical Support Document for
the HWC MACT Standards, Volume III: Selection of MACT Standards,''
September 2005, Section 3.1.
---------------------------------------------------------------------------
We also considered the possibility of developing a standard for
nonenumerated HAP metals instead of a PM standard (i.e., regulating
these metals directly, rather than through use of a surrogate). We
conclude for several reasons, however, that issuing emission standards
for these nonenumerated metals in lieu of a particulate matter standard
would not adequately control nonmercury metal HAPs to levels achieved
by the relevant best performing sources.
We generally lack sufficient compliance test emissions data for the
noneneumerated metals to assess the relevant best performing sources,
because, as discussed below, most of these metals were not directly
regulated pursuant to RCRA air emission standards.\131\ Although we
have more emissions data for these metals that are based on (so called)
normal operations, we still lack sufficient emissions data to establish
nonenumerated metal standards for all the source categories. Use of
normal data may also be problematic because of the concern raised by
the cement kiln and lightweight aggregate kiln stakeholders that our
normal metals emissions data obtained from compliance tests are not
representative of the range of actual emissions at their sources.
Cement kiln and lightweight aggregate kiln stakeholders submitted long-
term hazardous waste mercury feed control data that support their
assertion. Although these stakeholders did not submit long-term normal
hazardous waste feed control data for the nonenumerated metals, we can
still see that use of the normal nonenumerated metal snapshot emissions
in our database to determine MACT floors could raise similar concerns
with respect to whether the normal data in fact represents average
emissions at these sources, and their level of performance.
---------------------------------------------------------------------------
\131\ At best, we may have enough compliance test data for
antimony and selenium to adequately assess relevant best performers
for only incinerators and lightweight aggregate kilns.
---------------------------------------------------------------------------
Use of particulate matter emissions data to assess the relevant
best performers for nonenumerated metal HAP is therefore more
appropriate for two reasons. Compliance test data better account for
emissions variability and avoid the normal emissions bias discussed
above. We also have much more particulate matter emissions data from
more sources, which better allows us to evaluate the true range of
emissions from all the sources within the source category and to assess
and identify the relevant top performing 12 percent of the sources.
It would be inappropriate to assess total stack gas emissions of
nonenumerated metals for cement kiln and lightweight aggregate kilns
when determining the relevant best performers because these emissions
would, in part, reflect the metal feed levels in these sources'
nonhazardous waste process feedstreams. This is not appropriate because
nonhazardous process feedstream control is not a feasible means of
control. See part four, section III.B.1. A potential solution to this
problem would be to identify the relevant best performers by assessing
each source's hazardous waste thermal emissions for these nonenumerated
metals (given that hazardous waste thermal emissions exclude by
definition emissions attributable to inputs other than hazardous waste,
i.e. raw materials and fossil fuels). This, however, would be
problematic because, aside from the data limitation issues, the
majority of the nonenumerated metals data reflect normal emissions
which often do not contain the highest feed rates used by the source.
As a result, we cannot assess performance on a thermal emissions basis
because of the uncertainty associated with system removal efficiencies
at such low metal feedrates. Furthermore, even if we could issue
hazardous waste thermal emissions standards for these metals, a
particulate matter emission standard would still be necessary to
control nonmercury metal HAP emissions from the nonhazardous waste
process feedstreams.
[[Page 59460]]
Emission standards for these nonenumerated metals could require
sources to implement hazardous waste feed control (for these metals) to
comply with the standard.\132\ We are less assured that these sources
were implementing hazardous waste feed control for these nonenumerated
metals at the time they conducted the emissions tests (which serve as
the basis for floor calculations) because most of these metals were
never directly regulated pursuant to the RCRA emission standards.\133\
This means that sources tended to optimize (or at least concentrate
their efforts on) control of the metals that are regulated. Although
these metals were being controlled with each source's back-end control
device, sources may not have been controlling these metal feedrates
because they probably were not subject to specific feedrate limitations
(feed control of the enumerated metal HAP does not ensure feed control
of these nonenumerated metal HAP). Furthermore, simultaneous feed
control of all these metals, when combined with enumerated semivolatile
and low volatile metals, may not be possible because the best
performing sources for all these metals may collectively represent a
hazardous waste feedstream that does not exist in practice (from a
combined metal concentration perspective) because there likely would be
different best performers for each of the metal HAP or metal HAP
groups.\134\ We thus conclude that back-end control as measured and
assessed by each source's particulate matter emissions is the
appropriate floor technology to assess when identifying the relevant
best performers for nonenumerated HAP metals and estimating these
sources' level of performance.
---------------------------------------------------------------------------
\132\ Sources that otherwise would be equipped with what is
considered to be a MACT back-end control devices (i.e., a control
device achieving the final rule particulate matter standard) may not
be able to achieve these metal emissions standards due to varying
metal feed levels (both within sources and across sources). Such an
outcome may require a source to limit the amount of metal that is
fed into the combustion unit to achieve the standard.
\133\ Antimony is the only nonenumerated metal that is directly
regulated pursuant to the boilers and industrial furnace
regulations. See Sec. 266.106.
\134\ We generally cannot combine these nonenumerated metals
into the associated semivoltile or low volatile metal volatility
groupings promulgated in this final rule for purposes of
establishing ``grouped'' emission standards because we cannot mix
compliance test data with normal emissions data when calculating
floors (the majority of the standards included in this final rule
are based on compliance test data, and the majority of the data we
have for nonenumerated metals being normal). Furthermore, if we were
to separately group the normal nonenumerated metal emission data
into their associated semivolatile or low volatile metal group, we
may encounter data limitation issues because each source would need
to have measured each of the nonenumerated metals in that associated
metal volatility group in order for us to conclude that the emission
data adequately represents the sources combined emissions of
semivolatile or low volatile metals.
---------------------------------------------------------------------------
Comment: A commenter states that EPA's rationale for use of
particulate matter as a surrogate for nonenumerated metals is flawed
because EPA has provided no data in the proposal to justify its
hypothesis that particulate matter is an appropriate surrogate for non-
enumerated metal HAP. The commenter also states that the proposed
emission standards for particulate matter for existing sources
discriminate against boilers and process heaters that burn clean (i.e.,
little or very low concentrations of HAP metals) hazardous waste fuels.
The commenter suggests that if there are sufficient data, EPA should
consider developing an alternative emission standard for total HAP
metals for new and existing liquid fuel boilers, as was done for the
Subpart DDDDD National Emission Standards for Hazardous Air Pollutants
for Industrial/Commercial/Institutional Boilers and Process Heaters.
Response: As previously discussed in this section, particulate
matter reflects emissions of nonmercury metal HAPs because these
compounds comprise a percentage of the particulate matter (provided
these metals are fed into the combustion unit). The technologies that
have been developed and implemented to control particulate matter also
control nonmercury metal HAP. Since non-mercury metal HAP is a
component of particulate matter, we can use particulate matter as a
surrogate for these metals. Further justification for the use of
particulate matter as a surrogate to control metal HAP is included in
the technical support document.\135\
---------------------------------------------------------------------------
\135\ See USEPA, ``Technical Support Document for the HWC MACT
Standards, Volume III: Selection of MACT Standards,'' September
2005, Section 3.1.
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We conclude that we do not have enough nonenumerated metal
emissions data to calculate alternative total metal emission floors for
liquid fuel boilers. The most problematic of these metals are manganese
and cobalt, where we have emission data from only three sources. We
have much more compliance test particulate matter emissions data from
liquid fuel boilers, and thus conclude that the particulate matter
standard best reflects the emission levels achieved by the relevant
best performers.
Similar to the above discussion, calculating an alternative total
metal emissions floor raises questions regarding the method used to
calculate such floors. Hazardous waste combustor metal emissions have
traditionally been regulated in volatility groupings because the
volatility of the metal affects the efficiency of back-end control
(i.e., semivolatile metals are more difficult to control than low
volatile metals because they volatilize in the combustor and then
condense as small particulates prior to or in the emission control
device). When identifying the best performing sources, we previously
have, in general, only evaluated sources that have metal emissions
information for every metal in the volatility grouping. This approach
could prove to be problematic since it is not likely many sources will
have emissions data for all the metals.
Although we could not calculate alternative total metal emission
floor standards based on the available emissions data we have, we agree
with the commenters' view that sources that burn hazardous waste fuels
with low levels of nonenumerated metals should be allowed to comply
with a metals standard rather than the particulate matter standard. We
proposed an alternative to the particulate matter standard (see 69 FR
at 21331) for incinerators, liquid, and solid fuel boilers that was a
simplified version of the alternative particulate matter standard that
is currently in effect for incinerators pursuant to the interim
standards (see Sec. 63.1206(b)(14)). We received no adverse comment
and are promulgating this alternative as proposed. The alternative
metal standards apply to both enumerated and nonenumerated metal HAP,
excluding mercury. For purposes of these alternative requirements, each
nonenumerated metal is classified as either a semivolatile or a low
volatile metal and subsequently grouped with the associated
semivolatile and low volatile enumerated metals. The semivolatile and
low volatile metals standards under this alternative are the same as
those that apply to other liquid fuel boilers, but the standard would
apply to all metal HAP, not just those enumerated in the generic low
volatile metal and semivolatile metal standards. See Sec. Sec. Sec.
63.1216(e), 63.1217(e) and 63.1219(e).
B. Carbon Monoxide/Hydrocarbons and DRE as Surrogates for Dioxin/Furan
Comment: One commenter states that the dioxin/furan floors for new
and existing solid fuel boilers is unlawful and arbitrary and
capricious. EPA established the floor for dioxin/furan for these
sources as compliance with the carbon monoxide or hydrocarbon standard
and the destruction and removal efficiency (DRE) standard. The
[[Page 59461]]
commenter states that EPA has not shown that carbon monoxide or
hydrocarbon emissions correlate to dioxin/furan emissions, and,
accordingly, has not shown that the carbon monoxide or hydrocarbon
standard, together with the DRE standard, are valid surrogates.
This commenter also states that it is inappropriate for EPA to use
carbon monoxide or hydrocarbons and DRE as surrogates to establish
dioxin/furan floors for liquid fuel boilers with wet or no air
pollution control devices and for hydrochloric acid production
furnaces. The commenter believes EPA inappropriately justifies these
surrogates by claiming that a numerical dioxin/furan floor would not be
replicable by the best sources or duplicable by the others. The
commenter states that EPA has no discretion to avoid setting floors for
a HAP just because it believes that HAP is not controlled with a
technology. Rather, EPA must set floors reflecting the relevant best
sources' actual performance. Such floors necessarily will be duplicable
by the relevant best sources themselves. That they cannot be replicated
by other sources is irrelevant according to the commenter.
In addition, the commenter states that EPA does not claim or
demonstrate that the carbon monoxide and hydrocarbon floors for solid
fuel boilers reflect the average emission levels achieved by the
relevant best sources.
Finally, the commenter also notes that EPA appears to argue that
its carbon monoxide or hydrocarbon standard and DRE standard could be
viewed as work practice standards under section 112(h) which allows EPA
to establish work practice standards in lieu of emission standards only
if it is not be feasible to set the former. Because EPA has made no
such demonstration, setting work practice standards to control dioxin/
furan emissions from boilers would be unlawful according to the commenter.
Response: The commenter raises four issues: (1) Are the carbon
monoxide/hydrocarbon standard and the DRE standard adequate surrogate
floors to control dioxin/furan; (2) floors for existing sources must be
established as the average emission limitation achieved by the best
performing sources irrespective of whether the limitation is duplicable
by the best performing sources or replicable by other sources; (3) EPA
has not explained how the carbon monoxide and hydrocarbon floors
reflect the average emission limitation achieved by the relevant best
sources; and (4) EPA cannot establish work practice standards for
dioxin/furan under section 112(h) because it has not demonstrated that
setting an emission standard is infeasible under section 112(h)(1).
Carbon Monoxide and Hydrocarbons Are Adequate Surrogates to Control
Dioxin/Furan when Other Controls Are Not Effective or Achievable.
Carbon monoxide and hydrocarbons (coupled with the DRE standard) are
the best available surrogates to control dioxin/furan emissions when a
numerical floor would not be achievable and when other indirect
controls, such as control of the gas temperature at the inlet of a dry
particulate matter control device to 400F, are not applicable or
effective.\136\
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\136\ As discussed in Part Two, Section V, we view the carbon
monoxide, hydrocarbon, and destruction removal efficiency standards
as unaffected by the Court's vacature of the September 1999
challenged regulations for incinerators, cement kilns, and
lightweight aggregate kilns. We are therefore not re-promulgating
and reopening consideration of these standards in today's final rule
for these source categories.
---------------------------------------------------------------------------
As we explained at proposal, operating under good combustion
conditions to minimize emissions of organic compounds such as
polychlorinated biphenyls, benzene, and phenol that can be precursors
to dioxin/furan formation is an important requisite to control dioxin/
furan emissions.\137\ See 69 FR at 21274. Minimizing dioxin/furan
precursors by operating under good combustion practices plays a part in
controlling dioxin/furan emissions, and that role is substantially
enhanced when there are no other dominant factors that relate to
dioxin/furan formation and emission (e.g., operating a dry particulate
matter control device at temperatures above 400F).
---------------------------------------------------------------------------
\137\ Operating under good combustion conditions also helps
minimize soot formation on boiler tubes. Research has shown that
operating under conditions that can form soot followed by operating
under good combustion conditions can lead to dioxin/furan formation.
See Section 2.4 of Volume III of the Technical Support Document.
---------------------------------------------------------------------------
Carbon monoxide and hydrocarbons are widely accepted indicators of
combustion conditions. The current RCRA regulations for boilers and
hydrochloric acid production furnaces use emissions limits on carbon
monoxide and hydrocarbons to control emissions of toxic organic
compounds. See 56 FR 7150 (February 21, 1991) documenting the
relationship between carbon monoxide, combustion efficiency, and
emissions of organic compounds. In addition, carbon monoxide and
hydrocarbons are used by many CAA standards for combustion sources to
control emissions of organic HAP, including: MACT standards for
hazardous waste burning incinerators, hazardous waste burning cement
kilns, hazardous waste burning lightweight aggregate kilns, Portland
cement plants, and industrial boilers; and section 129 standards for
commercial and industrial waste incinerators, municipal waste
combustors, and medical waste incinerators. Finally, hydrocarbon
emissions are an indicator of organic hazardous air pollutants because
hydrocarbons are a direct measure of organic compounds.
Commenters on our proposed MACT standards for hazardous waste
incinerators, cement kilns, and lightweight aggregate kilns stated that
EPA's own surrogate evaluation \138\ did not demonstrate a relationship
between carbon monoxide or hydrocarbons and organic HAP at the carbon
monoxide and hydrocarbon levels evaluated. See 64 FR at 52847
(September 30, 1999). Several commenters on that proposed rule noted
that this should not have been a surprise given that the carbon
monoxide and hydrocarbon emissions data evaluated were generally from
hazardous waste combustors operating under good combustion conditions
(and thus, relatively low carbon monoxide and hydrocarbon levels).
Under these conditions, emissions of HAP were generally low, which made
the demonstration of a relationship more difficult. These commenters
noted that there may be a correlation between carbon monoxide and
hydrocarbons and organic HAP, but it would be evident primarily when
actual carbon monoxide and hydrocarbon levels are higher than the
regulatory levels. We agreed with those commenters, and concluded that
carbon monoxide and hydrocarbon levels higher than those we established
as emission standards for hazardous waste burning incinerators, cement
kilns, and lightweight aggregate kilns are indicative of poor
combustion conditions and the potential for increased emissions organic
HAP. We continue to believe that carbon monoxide and hydrocarbons are
adequate surrogates for organic HAP which may be precursors for dioxin/
furan formation and note that the commenter did not explain why our
technical analysis is problematic.
---------------------------------------------------------------------------
\138\ See Energy and Environmental Research Corporation,
``'Surrogate Evaluation of Thermal Treatment Systems,''' Draft
Report, October 17, 1994.
---------------------------------------------------------------------------
Emissions that Are Not Replicable or Duplicable Are Not Being
``Achieved''. The commenter believes that floors must be established as
the average emission limitation of the best performing sources
irrespective of whether they are replicable by the best performing
sources or duplicable by other sources. To the contrary, emission
[[Page 59462]]
levels that are not replicable by the best performing sources are not
being ``achieved'' by those sources and cannot be used to establish the
floor.
For solid fuel boilers, we explained at proposal why dioxin/furan
emissions are not replicable by the best performing sources (or
duplicable by other sources): there is no dominant, controllable means
that sources are using that can control dioxin/furan emissions to a
particular level. See 69 FR at 21274-75. We explained that data and
information lead us to conclude that rapid quench of post-combustion
gas temperatures to below 400 [deg]F--the control technique that is the
basis for the MACT standards for dioxin/furan for hazardous waste
burning incinerators, and cement and lightweight aggregate kilns--is
not the dominant dioxin/furan control mechanism for coal-fired boilers.
We believe that sulfur contributed by the coal fuel is a dominant
control mechanism by inhibiting formation of dioxin/furan. Nonetheless,
we do not know what minimum level of sulfur provides significant
control. Moreover, sulfur in coal causes emissions of sulfur oxides, a
criteria pollutant, and particulate sulfates. For this reason, as well
as reasons stated at 69 FR 21275, we are not specifying a level of
sulfur in coal for these sources as a means of dioxin/furan control.
The same rationale applies to liquid fuel boilers with no air
pollution controls or wet air pollution control systems and to
hydrochloric acid production furnaces--there is no dominant,
controllable means that sources are using that can control dioxin/furan
emissions to a particular emission level.\139\ Thus, best performer
dioxin/furan emissions are not replicable by the best performing
sources (or duplicable by other sources). For these sources, the
predominant dioxin/furan formation mechanism for other source
categories--operating a fabric filter or electrostatic precipitator
above 400F--is not a factor.
---------------------------------------------------------------------------
\139\ We note that the same rationale also applies to
incinerators with wet or no air pollution control equipment and that
are not equipped with a waste heat boiler.
---------------------------------------------------------------------------
Given that these sources are not using controllable means to
control dioxin/furan to a particular emission level, there is no
assurance that the best performers can achieve in the future the
emission level reported in the compliance test in our data base. Put
another way, the test data do not reflect these sources' variability,
and the variability is largely unquantifiable given the uncertainties
regarding control mechanisms plus the environmental counter-
productiveness of encouraging use of higher sulfur coal. Hence, that
reported emission level is not being ``achieved'' for the purpose of
establishing a floor.
Finally, we note that beyond-the-floor controls such as activated
carbon can control dioxin/furan to a particular emission level. If a
source were to install activated carbon, it could achieve the level
demonstrated in a compliance test, after adjusting the level to account
for emissions variability to ensure the measurement was replicable. The
commenter argues that such a result is mandatory under the straight
emissions approach (the only way the commenter believes best performers
can be determined). Doing so, however, would amount to a surreptitious
beyond-the-floor standard (forcing adoption of a control technology not
used by any existing source), without considering the beyond-the-floor
factors set out in section 112(d)(2). In fact, we considered beyond-
the-floor standards based on use of activated carbon for these
sources--solid fuel boilers, liquid fuel boilers with wet or no
emission control device, and hydrochloric acid production furnaces--but
rejected them for reasons of cost. The cost-effectiveness ranged from
$2.5 million to $4.9 million per gram TEQ of dioxin/furan removed. In
contrast, the cost-effectiveness of the beyond-the-floor standard we
promulgate for liquid fuel boilers equipped with dry emission control
devices is $0.63 million per gram TEQ of dioxin/furan removed.\140\
---------------------------------------------------------------------------
\140\ See USEPA, ``Technical Support Document for the HWC MACT
Standards, Volume III: Selection of MACT Standards,'' September
2005, Sections 12, 13, and 15.
---------------------------------------------------------------------------
Consequently, we are not promulgating a beyond-the-floor standard
for dioxin/furan for these sources, and do not believe we should adopt
such a standard under the guise of determining floor levels.
The Carbon Monoxide and Hydrocarbon Floors Are Appropriate MACT
Floors. We explained at proposal why the carbon monoxide standard of
100 ppmv and the hydrocarbon standard of 10 ppmv are appropriate
floors. See 69 FR at 21282. The floor level for carbon monoxide of 100
ppmv is a currently enforceable Federal standard. Although some sources
are achieving carbon monoxide levels below 100 ppmv, it is not
appropriate to establish a lower floor level because carbon monoxide is
a conservative surrogate for organic HAP. Organic HAP emissions may or
may not be substantial at carbon monoxide levels greater than 100 ppmv,
and are extremely low when sources operate under the good combustion
conditions required to achieve carbon monoxide levels in the range of
zero to 100 ppmv.\141\ (See also the discussion below regarding the
progression of hydrocarbon oxidation to carbon dioxide and water). As
such, lowering the carbon monoxide floor below 100 ppmv may not provide
significant reductions in organic HAP emissions. Moreover, it would be
inappropriate to establish the floor blindly using a mathematical
approach--the average emissions for the best performing sources--
because the best performing sources may not be able to replicate their
emission levels (and other sources may not be able to duplicate those
emission levels) using the exact types of good combustion practices
they used during the compliance test documented in our data base. This
is because there are myriad factors that affect combustion efficiency
and, subsequently, carbon monoxide emissions. Extremely low carbon
monoxide emissions cannot be assured by controlling only one or two
operating parameters.
---------------------------------------------------------------------------
\141\ We note, however, that this general principle may not
always apply. There are data that indicate that even though carbon
monoxide levels are below 100 ppmv, hydrocarbon levels may not
always be below 10 ppmv. See 64 FR at 52851 and Part Four, Section
IV B. and C. of this preamble. An example of how this might occur,
although not a likely practical scenario, is if combustion is
quenched before substantial carbon monoxide can be generated,
leaving unburned hydrocarbons in the stack gas. Because of this
potential (although unlikely) concern, the rule requires sources
that elect to monitor carbon monoxide rather than hydrocarbons to
conduct a one-time test to document that hydrocarbons are below 10
ppmv and to establish operating limits on parameters that affect
combustion conditions (i.e., the same operating parameters that we
use for compliance assurance with the DRE standard). See Sec.
63.1206(b)(6).
---------------------------------------------------------------------------
We proposed a floor level for hydrocarbons of 10 ppmv even though
the currently enforceable standard for boilers and hydrochloric acid
production furnaces is 20 ppmv because: (1) Although very few sources
elect to comply with the RCRA standard for hydrocarbons rather than the
standard for carbon monoxide, those that comply with the hydrocarbon
standard have hydrocarbon levels well below 10 ppmv; and (2) reducing
hydrocarbon emissions within the range of 20 ppmv to 10 ppmv may reduce
emissions of organic HAP.
Although all sources are likely to be achieving hydrocarbon levels
below 10 ppmv, it is not appropriate to establish a lower floor level
because hydrocarbons are a surrogate for organic HAP. Although total
hydrocarbons would be reduced at a floor level below 10 ppmv, we do not
know whether
[[Page 59463]]
organic HAP would be reduced substantially. As combustion conditions
improve and hydrocarbon levels decrease, the larger and easier to
combust compounds are oxidized to form smaller compounds that are, in
turn, oxidized to form carbon monoxide and water. As combustion
continues, carbon monoxide is then oxidized to form carbon dioxide and
water. Because carbon monoxide is a difficult-to-destroy refractory
compound (i.e., oxidation of carbon monoxide to carbon dioxide is the
slowest and last step in the oxidation of hydrocarbons), it is a
conservative surrogate for destruction of hydrocarbons, including
organic HAP, as discussed above. As oxidation progresses and
hydrocarbon levels decrease, the larger, heavier compounds are
destroyed to form smaller, lighter compounds until ideally all
hydrocarbons are oxidized to carbon monoxide (and then carbon dioxide)
and water. Consequently, the relationship between total hydrocarbons
and organic HAP becomes weaker as total hydrocarbon levels decrease to
form compounds that are not organic HAP, such as methane and acetylene.\142\
---------------------------------------------------------------------------
\142\ USEPA, Technical Support Document for HWC MACT Standards,
Volume III: Selection of MACT Standards and Technologies, July 1999,
Section 12.1.2.
---------------------------------------------------------------------------
Moreover, as discussed above for carbon monoxide, it would be
inappropriate to establish the floor blindly using a mathematical
approach--the average emissions for the best performing sources--
because the best performing sources may not be able to replicate their
emission levels (and other sources may not be able to duplicate those
emission levels) using the exact types of good combustion practices
they used during the compliance test documented in our data base. This
is because there are myriad factors that affect combustion efficiency
and, subsequently, hydrocarbon (and carbon monoxide) emissions.
Extremely low hydrocarbon emissions cannot be assured by controlling
only one or two operating parameters.
The Standards for CO and HC Are Not Work Practice Standards. The
floor standards for CO or HC for boilers and hydrochloric acid
production furnaces are quantified emission limits. The standards
consequently are not work practice standards (even though they
represent levels showing good combustion control). CAA section 302(k).
EPA's reference to section 112(h)(1) at proposal (69 FR at 21275) was
consequently erroneous.
C. Use of Carbon Monoxide and Total Hydrocarbons as Surrogate for Non-
Dioxin Organic HAP 143
Comment: A commenter states that neither the total hydrocarbon nor
carbon monoxide standard alone provides adequate surrogate control for
organic HAP. Accordingly, EPA must include standards for both.
Hazardous waste combustors could have total hydrocarbon levels below
the standard during the carbon monoxide compliance tests, but higher
total hydrocarbon levels at other times during normal operation because
there are many variables that can affect total hydrocarbon emissions,
and these will not all be represented during the carbon monoxide
compliance test. The commenter states that EPA is on record stating
that carbon monoxide limits alone may not by itself minimize organic
emissions because products of incomplete combustion can result from
small pockets within the combustion zone where adequate time,
temperature, turbulence and oxygen have not been provided to completely
oxidize these organics. The commenter also states that EPA is on record
stating that total hydrocarbon levels can exceed good combustion
condition levels when carbon monoxide levels are below 100 ppmv.
---------------------------------------------------------------------------
\143\ As discussed in part two, section V, we view carbon
monoxide, hydrocarbon, and destruction removal efficiency standards
as unaffected by the Court's vacature of the September 1999
challenged regulations for incinerators, cement kilns, and
lightweight aggregate kilns. We are therefore not re-promulgating
and did not reconsider these standards in today's final rule for
these source categories.
---------------------------------------------------------------------------
Response: The final rule requires compliance with destruction and
removal efficiency and carbon monoxide or hydrocarbon standards as
surrogates to control non-dioxin organic HAP emissions \144\ from
liquid fuel boilers, solid fuel boilers, and hydrochloric acid
production furnaces. These are effective and reliable surrogates to
control organic HAP. We conclude that simultaneous measurement of both
total hydrocarbons and carbon monoxide with continuous emission
monitors is not necessary because each serves as a reliable surrogate
to control organic HAP emissions. The commenter has cited EPA preamble
language that was included in the April 19, 1996 proposed rule for
hazardous waste incinerators, cement kilns, and lightweight aggregate
kilns. In that rule we proposed to require compliance with both the
total hydrocarbon standard and the carbon monoxide standard. We
requested comment on whether these requirements were redundant, and we
later requested comment on whether we should allow sources to comply
with either the carbon monoxide standard or the total hydrocarbon
standard. We clarified, however, that allowing sources to comply with
the carbon monoxide standard would be contingent on the source
demonstrating compliance with the hydrocarbon standard during the
compliance test. We believed this was necessary because we had limited
data that showed a source could have total hydrocarbon levels exceeding
10 ppmv even though their carbon monoxide emission levels were below
100 ppmv. EPA subsequently promulgated this approach in the September
1999 Final Rule. 62 FR 52829.
---------------------------------------------------------------------------
\144\ As discussed in the previous section, these standards are
also used as surrogates to control dioxin/furans for hydrochloric
acid production furnaces, solid fuel-fired boilers, and liquid fuel-
fired boilers that are not equipped with dry air pollution control devices.
---------------------------------------------------------------------------
Today's rule adopts the same approach for liquid and solid fuel
boilers and hydrochloric acid production furnaces. We again conclude
that it is not necessary to require sources to verify compliance with
both of these standards on a continuous basis with two separate
continuous emission monitors, given the redundancy of these measurement
techniques. Total hydrocarbon emission measurements are a more direct
indicator of organic HAP emissions than carbon monoxide. Hence,
continuous compliance with this standard always assures that organic
HAP are well controlled. Carbon monoxide is a conservative indicator of
combustion efficiency because it is a product of incomplete combustion
and because it is a refractory compound that is more thermally stable
than hydrocarbons. The hydrocarbon products of incomplete combustion
that are simultaneously formed during incomplete, or inefficient,
combustion conditions can be subsequently oxidized later in the
combustion process. In such instances carbon monoxide will likely still
be prevalent in the exhaust gas even though the products of incomplete
combustion were later oxidized. The conservative nature of carbon
monoxide as an indicator of good combustion practices is supported by
our data. At carbon monoxide levels less than 100 ppmv, our data
indicates that there is no apparent relationship between carbon
monoxide and hydrocarbons (other than that hydrocarbon levels are
generally below 10 ppm when carbon monoxide levels are below 100 ppm).
For example, a source with a carbon monoxide level of 1 ppm is no more
likely to have lower
[[Page 59464]]
measured hydrocarbons than a source achieving a carbon monoxide
emission level of 100 ppm. \145\
---------------------------------------------------------------------------
\145\ See USEPA, ``Technical Support Document for the HWC MACT
Standards, Volume III: Selection of MACT Standards,'' September
2005, Section 3.2 and USEPA, ``Final Technical Support Document for
the HWC MACT Standards, Volume III: Selection of MACT Standards and
Technologies,'' July 1999, Section 5.1.
---------------------------------------------------------------------------
We consider the few instances where the data showed total
hydrocarbon levels above 10 ppmv while carbon monoxide levels are below
100 ppmv to be anomalies. Even so, we have accounted for this by
requiring compliance with the hydrocarbon standard during the
compliance test if a source elects to comply with the carbon monoxide
standard. See Sec. Sec. Sec. 63.1216(a)(5)(i), 1217(a)(5)(i), and
1218(a)(5)(i).
We disagree with the commenter's assertion that the total
hydrocarbon compliance demonstration during the compliance test is
insufficient. Sources are required to establish numerous operating
requirements based on operating levels that were demonstrated during
the test, including minimum operating temperature, maximum feed rates,
minimum combustion zone residence time, and operating requirements on
the hazardous waste firing system that control liquid waste atomization
efficiency. Sources must comply with these operating requirements on a
continuous basis. Compliance with these requirements, in addition to
the requirements to comply with the carbon monoxide and destruction and
removal standards, adequately assure sources are controlling organic
HAP emissions to MACT levels.
Comment: A commenter states that EPA's proposed use of surrogates
for organic HAP do not ensure that each of the organic HAP (e.g.,
polychlorinated biphenyls and polyaromatic hydrocarbons) are reduced to
the level of the HAP emitted by the relevant best performing sources.
EPA has not shown the necessary correlation between either the total
hydrocarbon or carbon monoxide standards and organic HAP, and neither
is a reasonable surrogate according to the commenter.
Response: Carbon monoxide and total hydrocarbon monitoring are
widely used and accepted indicators of combustion efficiency, and hence
control organic HAP, which are destroyed by combustion.\146\ Sources
that are achieving carbon monoxide of emission levels of 100 ppm or a
hydrocarbon emission levels of 10 ppm are known to be operating
pursuant to good combustion practices. This is supported by an
extensive data analysis we used to support identical standards for
incinerators, cement kilns, and lightweight kilns which were
promulgated in the September 1999 Final Rule. We are applying the same
rationale to support these standards for boilers and hydrochloric acid
production furnaces.
---------------------------------------------------------------------------
\146\ This is why almost all of the RCRA Land Disposal
Restiction treatment standards for organic waste, which standards
are for the most part established at an analytic detection level for
the organic HAP in question plus a variability factor, are based on
the performance of combustion technology. See 40 CFR Part 268.40-43.
---------------------------------------------------------------------------
Today's rule requires continuous compliance with either a carbon
monoxide and hydrocarbon standard, in combination with a destruction
and removal efficiency standard, as surrogates to control organic HAP.
We conclude that sources which comply with these standards are
operating under efficient combustion conditions, assuring non-dioxin
organic HAP are being oxidized, thus limiting emissions to levels
reflecting MACT. Efficient combustion of hazardous waste minimizes
emissions of organic HAP that are fed to the combustion chamber as well
as emissions attributable to products of incomplete combustion that may
form within the combustion chamber or post combustion. We are not
capable of issuing emission standards for each organic HAP because of
data limitations and because such emission standards may not be
replicable by individual sources or duplicable by the other best
performing sources because of the complex nature of combustion and post
combustion formation of products of incomplete combustion.
V. Additional Issues Relating to Variability and Statistics
Many commenters raised issues relating to emissions variability and
statistics other than those discussed above in Section III.A: (1)
Variability dampening for data sets containing nondetects; (2)
imputation of variability to address variability dampening for data
sets containing nondetects; and (3) our analysis of variance procedures
to identify subcategories. We present comments and responses on the
remaining topics below.
A. Data Sets Containing Nondetects
Comment: One commenter states that EPA's approach of assuming
measurements that are below detection limits are present at the
detection limit dampens the variability of the data set. Thus, the
variability of ranking parameters is understated when ranking sources
to identify the best performers and emissions variability is
understated when calculating the floor.
Response: We agree with the commenter. For the final rule, we use
an approach to address nondetects whereby a value is assigned to each
nondetect within its possible range such that the 99th percentile upper
prediction limit for the data set (i.e., test condition runs for each
source) is maximized. Although this approach maximizes the deviation
among runs containing nondetect measurements, the test condition
average is lower because we no longer assume the nondetect analyte is
present at the level of detection. See response to comments discussion
below for more information on this statistical approach to address
variability of nondetects.
We use this measurement imputation approach to address variability
of feedrate data sets containing nondetects for source ranking purposes
and to address variability of emissions data sets containing nondetects
when calculating floors. We do not apply the measurement implementation
approach to system removal efficiency (SRE) data sets where feedrates
or emissions contain nondetects, however. Statistical imputation of
nondetect SREs is complicated given that SRE is derived from feedrate
and emissions data, both of which could contain nondetect
measurements.\147\ Our inability to apply the imputation approach to
SREs is not a major concern, however, because system removal efficiency
is used as a source ranking criterion only (i.e., it is not used as the
standard, except for hydrochloric acid production furnaces where there
are no nondetect feedrate or emissions measurements), and there are few
instances where system removal efficiencies are derived from nondetect
feedrate or emissions data.
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\147\ See USEPA, ``Technical Support Document for the HWC MACT
Standards, Volume III: Selection of MACT Standards,'' September 2005
Section 7.3.
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B. Using Statistical Imputation To Address Variability of Nondetect Values
On February 4, 2005, EPA distributed by email to major commenters
on the proposed rule a direct request for comments on a limited number
of issues that were raised by the public comments on the proposed rule.
The nondetect measurement imputation approach discussed above was one
of the issues for which we requested comment. We discuss below the
major comments on the approach.
Comment: Most commenters state that they agree with either the
concept or the approach in principle but cannot
[[Page 59465]]
provide substantive comments. These commenters indicate they cannot
provide substantive comments because they cannot determine the
implications of using the approach given that we did not provide the
resulting floor calculations. One commenter suggests that, before
blindly applying this arbitrary estimate of a nondetect value, a
reality check should be done to validate that this is reasonable by
consulting what is published on the method variability, as well as by
checking variability factors derived for other data in the database
that are above the detection limit.
Another commenter voiced significant concerns with the approach.
The commenter states that EPA contradicts its assumption at proposal
that all data that are reported as nondetect are present at the
detection limits by now admitting that the true value is between zero
and the level of detection. The commenter concludes that EPA now
proposes to retreat from its assumption that undetected pollutants are
always present at the detection limits not because that assumption is
false but because it does not generate sufficiently lenient floors. The
commenter believes that this underscores that EPA's statistical
analysis approach cannot possibly give an accurate picture of any
source's actual emission levels. Accordingly, it cannot possibly
satisfy EPA's obligation to ensure that its floors reflect the average
emission levels achieved by the relevant best performing sources.
The commenter also states that EPA's imputation approach is
independently flawed because it assumes--again inaccurately--that the
value for a nondetect is always either the highest value or lowest
value in the allowable range. In reality the undetected values will
necessarily fall in a range between the highest and lowest, and thus
yield less variability than EPA would assume.
Response: We agree in theory with the commenter who suggests that
the results of the imputation approach should be checked to see if it
overstates variability for nondetect data by comparing the results of
the imputation approach with the actual variability for detected
measurements in the data set. We considered comparing the relative
standard deviation derived from the imputation approach for data sets
with nondetects, to the relative standard deviation for the data set
using a regression analysis. Under the regression analysis approach, we
considered relating the relative standard deviation of detected data
sets to the average measurement. We would determine this relationship
for each standard for which we have nondetect data, and use the
relationship to impute the standard deviation for a data set containing
nondetects.\148\
---------------------------------------------------------------------------
\148\ Note that, under this approach, we would continue to
assume that the nondetect analyte is present at the detection limit.
---------------------------------------------------------------------------
We could not perform this analysis, however, because: (1) We have
very few detected measurements for the data sets for several standards
and could not establish the relationship between relative standard
deviation and emission concentration for those data sets; and (2)
moreover, for many data sets where detected measurements would have
been adequate to establish the relationship, it would have been
problematic statistically to extrapolate the relationship to the very
low values assigned to the nondetect measurements (e.g., 100% of the
detection limit; the value assigned by our statistical imputation
approach).\149\
---------------------------------------------------------------------------
\149\ Note that this was not the case where we use a regression
analysis of relative standard deviation versus total chlorine
measurements to impute a standard deviation for values below 20 ppmv
that we corrected to 20 ppmv to address the low bias of Method 0050.
In that situation, we have several total chlorine measurements very
close to 20 ppmv.
---------------------------------------------------------------------------
This commenter also suggests that we check the resultant standard
deviation after imputation by consulting what is published on the
method variability. The commenter did not explain, however, how method
variability relates to the variability of nondetect data.
Moreover, we believe that the imputation approach is one approach
we could have reasonably used to estimate variability of nondetect
data. We first attempted to apply standard statistical techniques to
address the nondetect issue. We investigated standard interval
censoring techniques to calculate maximum likelihood estimates (MLE) of
the average and standard deviation that provide the best fit for a
normal distribution for the data containing nondetect values, taking
into account that each nondetect data point can be anywhere within its
allowable interval. These techniques are not applicable, however, to
data sets where all data are nondetects, as is the case for many of our
data sets. In that situation, we approximated the mean as the average
of the midpoints of the nondetect intervals, and the standard deviation
as one half of the possible range of the data.
After working with this MLE/Approximation approach for some time
and iteratively developing complicated algorithms to address problems
as they arose, we concluded that we needed a simpler approach that
could be applied to all data sets. Accordingly, we developed the
statistical imputation approach discussed in Section IV.A above.
For 22 separate floors, we compared the results of the approaches
we considered for nondetects: (1) Nondetects present at the detection
limit (i.e., full detection limit approach); (2) MLE; (3) MLE combined
with an approximation approach (i.e., MLE/Approximation approach; and
(4) statistical imputation.\150\ The MLE approach was only applicable
to 2 of the 22 floor data sets, and the numerical algorithm failed to
converge on an answer for one of those. The MLE/Approximation approach
sometimes results in floors that are unrealistically high (i.e., it
calculated 5 of 22 floors that were higher than the statistical
imputation approach, which always produces floors that are equal to or
higher than assuming nondetects are present at the full detection
limit), and sometimes fails to converge on an answer. Because of these
limitations, we do not use either the MLE or MLE/Approximation approach.
---------------------------------------------------------------------------
\150\ See USEPA, ``Technical Support Document for the HWC MACT
Standards, Volume III: Selection of MACT Standards,'' September
2005, Section 5.4.
---------------------------------------------------------------------------
We believe the statistical imputation approach is preferable to the
full detection limit approach because it: (1) Accounts for variability
of data sets containing nondetects; (2) can be applied to all data sets
containing nondetects; and (3) results in reasonable floor levels. In
most cases, floors calculated using statistical imputation are close to
those calculated by the full detection limit approach. The statistical
imputation approach can produce substantially higher floors than the
full detection limit approach, however, when a relatively high
nondetect is reported because of a high detection limit. Nonetheless,
the statistical imputation approach calculated floors that were 30%
higher than the full detection limit approach for only 2 of the 22 floors.
We reject the comment that our approach to handling nondetect data
is a mere manipulation to raise the floor. The commenter observes that
EPA appears to determine that its initial approach of assuming the
worst-case for nondetect data--that the data are present at the
detection limit--did not produce floors that were high enough, and
consequently applies another manipulation--statistical imputation of
nondetect measurements--that assumes the nondetect data are present at
lower levels but nonetheless generates floors that are even higher than
before. Although the commenter is correct
[[Page 59466]]
about the outcome of our handling of nondetect data'the floors are
generally higher after statistically imputing nondetect measurements
than if nondetects are simply assumed to be present at the detection
limit--our rationale for handling nondetects is sound. At proposal, we
assumed that nondetects are present at the detection limit. We do not
know (nor does anyone else) whether a nondetect value is actually
present at 1% or 99% of the detection limit. We thought that assuming
that all values were at the limit of detection would reasonably
estimate the range of performance a source could experience for these
nondetect measurements. This approach inherently maximizes the average
emissions but minimizes emissions variability.
Commenters on the proposed rule state that assuming nondetects are
present at the detection limit dampens emissions variability--a
consideration necessary to ensure that a source's performance over time
is estimated reasonably. Mossville, 370 F. 3d at 1242 (daily maximum
variability must be accounted for in MACT standards [including floors]
which must be achieved continuously). See also CMA, 870 F. 2d at 232
(EPA not even obligated to use data from plants that consistently
reported nondetected values in calculating variability factors for best
performing plants). We agree with these commenters, and are using the
statistical imputation approach to address the concern. Relative to our
proposed approach of assuming nondetect measurements are present at the
detection limit, the statistical imputation approach reduces the
average of the data set for a source while maximizing the deviation of
the data set. These are competing and somewhat offsetting factors when
calculating the floor for existing sources given that we use a modified
99th percentile upper prediction limit to calculate the floor--the
floor is the average of the test condition averages for the best
performers plus the pooled variance of their runs. See CMA, 870 F. 2d
at 232 (upholding approach to variability for datasets with nondetect
values where various conservative assumptions in methodology offset
less conservative assumptions).
We further disagree with this commenter's view that the statistical
imputation approach is independently flawed because it assumes that the
value for a nondetect is always either the highest value or lowest
value in the allowable range. The commenter states that, in reality,
the undetected values will necessarily fall in a range between the
highest and lowest, and thus yield less variability than EPA would
assume. Although the commenter is correct that the true value of a
nondetect measurement is likely to be in the range between the highest
or lowest value possible rather than at either extreme, we do not know
where the true value is within that range. To ensure that variability
is adequately considered in establishing a floor, the statistical
imputation approach, by design, maximizes the deviation by assuming the
nondetect value is at one end of the range or the other, whichever
results in a higher average for the data set.
C. Analysis of Variance Procedures To Assess Subcategorization
We use analysis of variance (ANOVA) to determine whether
subcategories of sources have significantly different emissions. For
two subsets of emissions, the variance of the data between the two
subsets is compared to the variance within the subsets. The ratio of
these two variances is called the F-statistic. The larger the F-
statistic the more likely the underlying data distributions are
different. To make a decision regarding the difference between the two
subsets, we compare this calculated F-statistic to an F-value
associated with a particular confidence level.
One commenter has raised several concerns with our use of the ANOVA
procedure in the selection of incinerator subcategories.
Comment: The ANOVA procedure is based upon the assumption that the
underlying distribution of both data sets has a normal shape. For
incinerator emissions data this assumption is not valid. A log-
probability plot shows that particulate emission data is better
described by a lognormal distribution. Prior to conducting the ANOVA
procedure, the data should be log-transformed.
Response: We use probability plots, Skewness Coefficients, and
Correlation Coefficient/Shapiro-Wilks testing to evaluate whether it is
more appropriate to analyze emissions data for ANOVA and floor
calculations assuming the data represent a normal or lognormal
distribution. We believe it is reasonable to assume the data represent
a normal distribution for several reasons.
The purpose of the ANOVA subcategorization analysis is to determine
if there is a significant difference in emission levels between
potential subcategories to warrant establishing separate floors for the
subcategories. Although in some cases it may appear that a data set in
its entirety may be better represented by a lognormal distribution, the
high emissions data causing the right-hand skew will be truncated when
we identify the best performing sources--those with the lowest
emissions--to calculate floors. This moves the appearance of a skewed
distribution toward one that is more symmetric and thus, more
representative of a normal distribution.
In addition, our analyses showed: (1) The probability plots do not
suggest that either assumed distribution is significantly or
consistently better; (2) the data set arithmetic averages tend to be in
the neighborhood of the medians, indicating the data sets are not
significantly skewed and more closely normal than lognormal; and (3) in
some cases, neither assumed distribution could be statistically
rejected.\151\
---------------------------------------------------------------------------
\151\ USEPA, ``Technical Support Document for the HWC MACT
Standards, Volume III: Selection of MACT Standards,'' September
2005, Section 8.2.
---------------------------------------------------------------------------
Comment: Some of the data sets used for comparison have very few
members. This means that the within-group variance for a small data set
would have to be very low for the two groups to be judged as separate.
Response: We agree, but note that as the sample sizes change, the
critical values are also changing depending on the degrees of freedom.
Comment: Only emissions data were considered in the ANOVA tests.
Feed rate and removal efficiency should have been considered as well.
Response: Differences between subcategories in feedrates or system
removal efficiency are irrelevant if there is no significant difference
in emissions between the subcategories. The purpose of considering
subcategorization is to determine if there are design, operation, or
maintenance differences between subcategories that could affect the
type or concentration of HAP emissions and thus sources' ability to
achieve the floor absent subcategorization. Consequently, it is
appropriate to consider emissions only when evaluating
subcategorization.
Comment: The confidence level used by EPA for the F-statistic in
all cases was 95 percent. If the calculated F-statistic were equal to
this 95 percent confidence value, it would mean that there is only a 5
percent chance that data for the two subsets were drawn from the same
parent distribution. A less stringent (lower) confidence level would be
more appropriate for this analysis.
The commenter evaluated particulate emissions for specialty
incinerators (i.e., munitions, chemical weapons and mixed waste
incinerators) and non-specialty incinerators (all others). The
commenter log-transformed the data and
[[Page 59467]]
determined that there was only a 30 percent chance that the two data
sets could come from the same parent distribution. This result,
together with the vastly different operating characteristics for the
two types of incinerators, argues for their being treated as separate
categories, according to the commenter.
Response: A confidence level of 95% assigns a probability of 0.95
of accepting the hypothesis when there is no difference between
subcategories and hence a probability of 0.05 of rejecting a true
hypothesis. This reduces the probability to 5% of rejecting a true
hypothesis. A less stringent confidence level would increase the
chances of rejecting a true hypothesis. The farther apart the averages
of the two potential subcategories are, the more likely they are to be
statistically different and the more likely you are to be wrong if you
hypothesize that they are not different.
A 95% confidence level is most often used for ANOVA because it is
generally believed that being wrong one time out of 20 is an acceptable
risk for purposes of ANOVA. In addition, statisticians are comfortable
with a 95% confidence level because, in a normal distribution, 95% of
the data fall within 2 (actually 1.96) standard deviations of the mean.
Other confidence levels could be used for ANOVA--99% or 90%--if
there is a good reason to deviate from the general default of 95%. A
99% confidence level is the second most commonly used confidence level
and is generally used when it is very important that you be sure that
you are right (i.e., where you can only accept the risk of being wrong
1 time out of 100) before you classify the populations (in this case
subcategories) as different. Occasionally, but much less frequently,
confidence levels of 90% or less are used. But, we note that these
situations are so infrequent that some statistics books provide tables
for the ANOVA F-statistic only at the 95% and 99% confidence levels.
For these reasons, we believe that the 95% confidence level is an
appropriate level among those we could have reasonably selected.
VI. Emission Standards
A. Incinerators
Comment: A commenter states that EPA's subcategorization (and
assignment of differing dioxin/furan standards as a result) between
incinerators with wet or no air pollution control device and
incinerators equipped with dry air pollution control devices or waste
heat boilers is unlawful because incinerators equipped with a given
type of pollution control equipment are not different ``classes,''
``types,'' or ``sizes'' of source. The commenter implies that EPA
justifies this subcategorization by stating that these sources have
different emission characteristics, which is no less unlawful and
arbitrary than subcategorizing based on the pollution control devices
they use.
Response: We agree that it would not be appropriate to
subcategorize source categories based on a given air pollution control
technique. See 69 FR at 403 (Jan. 4, 2004). As stated at proposal, we
do not subcategorize incinerators with respect to dioxin/furans based
on the type of air pollution control device used. 69 FR at 21214. For
example, with respect to dioxin/furans, it would not be appropriate
subcategorize based on whether a source is using: (1) Good combustion
practices; (2) a carbon bed; (3) an activated carbon injection system;
or (4) temperature control at the inlet to its dry air pollution
control device. These devices and practices are what control dioxin/
furan emissions. Today's final rule does not subcategorize based on
these control devices and practices. Instead, our subcategorization
approach recognizes the potential of some emission control equipment to
create pollutant emissions that subsequently must be addressed.\152\
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\152\ Although we subcategorize between incinerators with wet or
no air pollution control device and incinerators equipped with dry
air pollution control devices or waste heat boilers for the floor
analysis, the calculated dioxin furan floors for both subcategories
for existing sources were determined to be less stringent than the
current interim standard. Subsequently, the final rule emission
limitations for both subcategories are, for the most part,
identical, and equivalent to the interim standard. See USEPA,
``Technical Support Document for the HWC MACT Standards, Volume III:
Selection of MACT Standards,'' September 2005, Section 10.1, for
further discussion.
---------------------------------------------------------------------------
Dioxin/furans are unique in that these pollutants are not typically
present in the process inputs, but rather are formed in the combustor
or in post combustion equipment. The primary cause of dioxin/furan
emissions from incinerators not equipped with waste heat boilers is
post combustion formation by surface-catalyzed reactions that occur
within the dry air pollution system.\153\ This is evidenced by the
statistically significant higher dioxin furan emissions for
incinerators with dry air pollution control systems compared to those
without dry systems.
---------------------------------------------------------------------------
\153\ See USEPA, ``Technical Support Document for the HWC MACT
Standards, Volume IV: Selection of MACT Standards,'' September 2005,
Section 3, for further discussion.
---------------------------------------------------------------------------
Incinerators with dry air pollution systems are designed to
effectively control metal and particulate matter emissions through use
of baghouses, electrostatic precipitators, etc. Incinerators that are
designed in this manner have the potential for elevated dioxin/furan
emissions because dry air pollution control systems provide locations
where surface-catalyzed reactions can occur (e.g., on particles on
fabric filter bags or electrostatic precipitator plates). Thus, for
purposes of dioxin/furan formation and control, incinerators equipped
with dry air pollution systems are in fact different ``types'' of
incinerators because of their unique pollutant generation characteristics.
On the other hand, incinerators with wet air pollution control
systems are generally designed to effectively reduce total chlorine
emissions (with the use of wet scrubbers) and metals and particulate
matter emissions. There generally is a tradeoff, however, in that these
types of incinerators may not be as efficient in reducing particulate
matter and metal emissions compared to incinerators that are equipped
with baghouses and dry electrostatic precipitators. These types of
incinerators generally do not have the potential to have elevated
dioxin/furan emissions because they do not provide locations where
surface catalyzed reactions can occur. For purposes of dioxin/furan
emission formation and control, sources with wet air pollution control
systems are thus likewise different types of incinerators.\154\
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\154\ A similar analogy applies to incinerators that are not
equipped with air pollution systems. These incinerators are not
designed to control emissions of metals, chlorine, and particulate
matter (perhaps because emission levels are low due to low HAP feed
levels). Similar to incinerator types with wet systems, this design
does not provide the locations for surface catalyzed reactions to
occur, which leads us to conclude that these are different types of
incinerator with respect to dioxin/furan control.
---------------------------------------------------------------------------
Subcategorizing dry air pollution systems and wet air pollution
control systems for purposes of establishing a dioxin/furan standard is
no different than subcategorizing incinerators equipped with waste heat
boilers. The waste heat boiler is the origin of the dioxin/furan that
is generated. These incinerators are designed to efficiently recover
heat from the flue gas to produce useful energy. A result of this type
of incinerator design, however, is that it also provides a location
where surface catalyzed reactions can occur (i.e., the boiler tubes),
potentially resulting in elevated dioxin/furan formation (and emissions
if not properly controlled).
An alternative approach that does not subcategorize these sources,
but rather identifies best performing sources as those sources with the
lowest emissions irrespective of whether they have a wet
[[Page 59468]]
or dry air pollution control device, would yield floors that would not
be achievable unless all the sources, including the best performers,
adopted beyond-the-floor technology. The calculated dioxin/furan floor
for existing incinerators and liquid fuel boilers using such an
approach would be 0.008 and 0.009 ng TEQ/dscm, respectively.\155\ All
of the best performing sources for these calculated floors had either
wet air pollution systems or no air pollution control systems. The
floor technology used by these sources is good combustion practices. As
a result, these floor levels would not be replicable by these best
performing sources nor duplicable by other sources through use of the
same good combustion practices because of the uncertainties associated
with dioxin/furan generation mechanisms and rates that can vary both
within sources and across sources, potentially leading to significant
variability in emission levels.\156\ Sources equipped with wet or no
air pollution systems would thus likely be required to install carbon
systems to comply with these standards, a technology used by only four
incinerators (none of which were best performers in the above discussed
floor analysis). Such an outcome should be viewed as a beyond-the-floor
technology and therefore assessed pursuant to the factors enumerated in
section 112(d)(2). Furthermore, it is unclear, and perhaps doubtful,
that these floors would be achievable by these sources even if they
were to install beyond-the-floor controls such as activated carbon
systems because no sources using activated carbon are currently
achieving those floor levels. We therefore conclude that it is
appropriate, and necessary, to subcategorize these types of
incinerators for purposes of calculating dioxin/furan floor standards.
---------------------------------------------------------------------------
\155\ See USEPA, ``Technical Support Document for the HWC MACT
Standards, Volume III: Selection of MACT Standards,'' September
2005, Section 20 and Appendix C, tables labeled ``E-INC-all-DF'' and
``E-LFB-all-DF''.
\156\ Dioxin/furan formation mechanisms are complex. Sources
equipped with wet or no air pollution control systems cannot rely on
good combustion practices alone to achieve these floor levels
because they cannot ``dial in'' to a specific emission level, as is
the case with typical back-end control systems that control
particulate matter and metals, for example. See Part Four, Section IV.B.
---------------------------------------------------------------------------
B. Cement Kilns
1. Hg Standard
Comment: Several commenters recommend that EPA use a commenter-
submitted dataset, which includes three years of data documenting day-
to-day levels of mercury in hazardous waste fuels fired to all
hazardous waste burning cement kilns, to identify a MACT floor for
existing and new cement kilns. Several commenters state that existing
cement kilns should have the option to comply with either of the
following mercury standards: (1) A hazardous waste feed concentration
limit, expressed in ppmw, based on an evaluation of the five best
performing sources within the commenter-submitted dataset (documenting
day-to-day levels of mercury in the hazardous waste over a three year
period); or (2) a hazardous waste maximum theoretical emissions
concentration (MTEC), expressed in units of [mu]g/dscm, developed by
projecting emissions of the best performing sources assuming mercury
concentrations in the hazardous waste were at the source's 99th
percentile level in the commenter-submitted dataset. To identify the
best performing sources, the commenter suggests selecting the five
sources with the lowest median mercury concentrations in the dataset.
For existing sources, the commenters' evaluation yields a hazardous
waste feed concentration limit of 3.3 ppmw and a stack concentration
emission limit of 150 [mu]g/dscm (rounded to two significant figures
and considering mercury contributions only from the hazardous waste).
For new cement kilns, the commenters recommend a mercury standard in
the format of a hazardous waste feed concentration limit only,
expressed in ppmw, based on the single source with the lowest 99th
percentile level of mercury in hazardous waste. The commenters
recommend a mercury standard of 1.9 ppmw for new sources.
Response: We agree with commenters that the commenter-submitted
dataset documenting the day-to-day levels of mercury in hazardous waste
fuels fired to all hazardous waste burning cement kilns is the best
available data to identify floor levels for existing and new cement
kilns. See discussion in Part Four, Section I.D. However, we disagree
with the commenters' suggested format of the mercury standard for
existing sources. Establishing the mercury standard as the commenters'
suggest (i.e., 3.3 ppmw in the hazardous waste feed or 150 [mu]g/dscm
as a hazardous waste MTEC) fails to consider the interim mercury
standards. As discussed in Part Four, Section III.E, there can be no
backsliding from the levels of performance established in the interim
standards. While not every source feeding hazardous waste with a
maximum mercury concentration of 3.3 ppmw would exceed the interim
standard, most sources using more than 50 percent hazardous waste as
fuel (i.e., replacing at least half its fossil fuel with hazardous
waste) would exceed the interim standard, emitting mercury higher than
the levels allowed under Sec. Sec. 63.1204(a)(2) and 63.1206(b)(15) of
the interim standards.\157\ The hazardous waste MTEC of 150 [mu]g/dscm
calculated by the commenters is also higher than the level currently
allowed under Sec. 63.1206(b)(15) of the interim standards. Since
sources cannot backslide from the levels of the interim standards, if
we were to accept the commenters' floor analysis results as presented
(which we are not), then we would ``cap'' each calculated standard
(i.e., 3.3 ppmw hazardous waste feed concentration and 150 [mu]g/dscm
in stack emissions) at the interim standard level. This would result in
a mercury standard for existing sources of 3.3 ppmw hazardous waste
feed and a hazardous waste feed MTEC of 120 [mu]g/dscm or 120 [mu]g/
dscm as a stack gas concentration limit. We note this is similar to the
mercury standard adopted today: a hazardous waste feed concentration
limit of 3.0 ppmw and a hazardous waste feed MTEC of 120 [mu]g/dscm or
120 [mu]g/dscm as a stack gas concentration limit. For an explanation
of why we derived a level of 3.0 ppmw from the data, see Section 7.5.3
of Volume III of the Technical Support Document.
---------------------------------------------------------------------------
\157\ USEPA, ``Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards,'' Section 23.4,
September 2005.
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The commenters' suggested new source mercury standard of 1.9 ppmw
in the hazardous waste has the same deficiency. New sources with a
hazardous waste fuel replacement rate of approximately 75% could emit
mercury at levels higher than currently allowed under the interim
standards. After capping the calculated standard at the interim
standard level, we would identify the mercury standard for new sources
as a hazardous waste concentration limit of 1.9 ppmw in the hazardous
waste and a hazardous waste feed MTEC of 120 [mu]g/dscm or 120 [mu]g/
dscm as a stack gas concentration limit. For reasons discussed in
Section 7.5.3 of Volume III of the Technical Support Document, this is
indeed the mercury standard we are promulgating for new cement kilns.
The commenters also suggest that the best performing sources should
be identified as those with the lowest three-year median concentration
of mercury in hazardous waste. Although this approach would be
permissible, we conclude that it is more appropriate to identify the
best performers (or single best performer for new sources) by
[[Page 59469]]
selecting those with the lowest 99th percentile upper level mercury
concentrations. (This is not a statistically determined upper
prediction limit; there is sufficient data for an arithmetically
calculated 99th percentile to reliably reflect sources' performance.)
We believe that this approach best accounts for the variability
experienced by best performing sources over time.
A detailed discussion of the MACT floor analysis for existing and
new cement kilns is presented in Section 7.5.3 of Volume III of the
Technical Support Document. In summary, the mercury standard for
existing cement kilns is 3.0 ppmw in the hazardous waste feed and 120
[mu]g/dscm as a hazardous waste maximum theoretical emission
concentration feed limit or 120 [mu]g/dscm as a stack gas concentration
limit. For new sources the mercury standard is 1.9 ppmw in the
hazardous waste feed and 120 [mu]g/dscm as a hazardous waste maximum
theoretical emission concentration feed limit or 120 [mu]g/dscm as a
stack gas concentration limit.\158\
---------------------------------------------------------------------------
\158\ Please note that we do not regard this standard as a work
practice standard under section 112(h)(1) of the Act, because part
of the standard includes an emission limit which is measured at the
stack. EPA believes the special requirements of section 112(h)(1)
apply when a work practice is the exclusive standard.
---------------------------------------------------------------------------
Comment: Two commenters oppose EPA's proposed approach to base
compliance with the mercury standard on averaged annual emissions. The
commenters state an annual average would allow mercury emissions to
exceed the interim standard because a source could burn high
concentrations of mercury waste over a short period and still comply
with an annual limit by burning low concentration wastes at other
times. These commenters support the concept of a 12-hour rolling
average feedrate limit (i.e., the current requirement under the interim
standards) in conjunction with an emission standard no less stringent
than the interim standard.
Response: We agree with these comments. Cement kilns must establish
a 12-hour rolling average feedrate limit of mercury to comply with
these standards. The mercury standards for cement kilns are ``capped''
at the interim standard level to prevent backsliding from the current
level of performance. This is accomplished by expressing the standard
as a limit on the mercury concentration in the hazardous waste (with
the rolling average) and either an emission concentration limit or
hazardous waste maximum theoretical emission concentration feed limit.
See Sec. 63.1209(l)(1)(iii).
2. Total Chlorine
Comment: One commenter states that the proposed MACT floor approach
is inconsistent with the statutory definition of MACT because EPA's
selection of a routinely achievable system removal efficiency (SRE) was
arbitrary and not representative of the best performing sources.
Instead, the commenter suggests EPA identify a MACT SRE based on the
five sources with the best SREs and apply that SRE to the MACT chlorine
feed level. Later, in supplemental comments, the same commenter
suggests two alternative approaches to identify a floor level. One
approach applies a ranking methodology based on emissions and chlorine
feed, and the second suggested approach applies a triple ranking method
based on emissions, feed, and chlorine SRE. Other commenters, however,
supported EPA's proposed approach.
Response: We are adopting the same approach we proposed at 69 FR at
21259. As we explained, this is a variant of the SRE/Feed approach, the
variant involving the degree of system removal efficiency achieved by
the best performing sources. In summary, to determine the floor level
we first identify the best performing sources according to their
hazardous waste chlorine feedrate. The best performing sources are
those that have the lowest maximum theoretical emissions concentration
(MTEC), considering variability. We then apply an SRE of 90 percent
(the specific point in contention) to the best performing sources'
total MTEC (i.e., thus evaluating removal of total chlorine across the
entire system, including chlorine contributions to emissions from all
feedstreams such as raw materials and fossil fuels) to identify the
MACT floor, which is expressed as a stack gas emissions concentration
in parts per million by volume. This approach defines the MACT floor as
an emission level that the best performing sources could achieve if the
source limits the feedrate of chlorine in the hazardous waste to the
MACT level (i.e., the level achieved by the average of the best
performing five sources) while also achieving an SRE that accounts for
the inherent variability in raw material alkalinity and (to a lesser
degree) cement kiln dust recycle rates, and production requirements. 69
FR at 21259.
Under this approach, we are evaluating hazardous waste feed control
as we do for other sources. One commenter objects to our determination
that an SRE of 90 percent is representative of the best performing
sources because we have not established a MACT SRE--the average SRE
achieved by the best performing sources.
There is no doubt that the cement manufacturing process is capable
of capturing significant quantities of chlorine when favorable
conditions exist within the kiln system. Our usual approach of
establishing an SRE by ranking the most efficient SREs taken from
individual compliance tests, however, would result in a standard that
would not be achievable because it may not be duplicable by the best
performers or certainly would not be replicable by others, given that
it is a function of various highly variable parameters, especially
levels of alkali metals (e.g., sodium and potassium) and volatile
compounds (e.g., chlorine and sulfur) in the raw materials. Alkalis and
volatiles vary at a given best performer facility (in fact, at all
facilities) as different strata are mined in the quarry, and across
facilities due to different sources of raw materials. Raw material
substitution is infeasible and counter to the objective of producing
quality product (i.e., a product with low alkali content).
Cement kilns thus are not able to design or operate to achieve a
specific SRE at the high (most efficient) end of the range of test
conditions. This is demonstrated by our calculations of system removal
efficiency data, which is essentially a collection of performance
``snapshots.'' See SRE data summarized in Table 1 at the end of this
response; see also Mossville, 370 F. 3d at 1242 (maximum emission
variability associated with raw material variability needs to be
accounted for in MACT floor determination since the standard must be
met at all times under all operating conditions). The performance data
of the ``apparent'' best performers--upwards of 99 percent--identified
by the commenter are simply a snapshot in the possible range of
performance and are not replicable in the future due to factors which
are uncontrollable by the source, as just explained. In confirmation,
cement kilns achieving this level of removal in one test proved
incapable of replicating their own result in other tests even though
individual sources each have their own proprietary source of raw
materials. See results in table for Giant (SC), Essroc (IN), Holcim
(MO), Giant (PA), and LaFarge (KS) all
[[Page 59470]]
of whom would violate a 99 + percent standard based on their own
operating results.
Table 1.--Summary of System Removal Efficiency Data for Wet Process Cement Kilns \159\
----------------------------------------------------------------------------------------------------------------
Number Runs in Low SRE Run High SRE Run Average SRE of
Facility Data Base (%) (%) All Runs (%)
----------------------------------------------------------------------------------------------------------------
LaFarge (OH).................................... 3 99.1 99.4 99.3
Giant (SC)...................................... 24 95.5 99.8 99.0
Essroc (IN)..................................... 13 97.3 99.9 98.7
Holcim (MO)..................................... 6 96.4 99.9 98.4
LaFarge (KS).................................... 12 95.7 99.3 98.1
Giant (PA)...................................... 17 87.7 99.4 97.1
Continental (MO)................................ 3 95.7 97.0 96.5
Ash Grove (AR).................................. 37 85.1 98.8 95.1
Texas Industries (TX)........................... 6 88.8 97.0 93.6
Holcim (MS)..................................... 9 76.5 99.2 90.0
----------------------------------------------------------------------------------------------------------------
\159\ See Section 3.6 of Volume II (Specific MACT Standards) of Comment Response Document, September 2005.
However, the data indicate that SRE is reasonably quantifiable to a
point. Based on our data base of system removal efficiency information
from 130 test conditions where total chlorine was evaluated, we
conclude that a system removal efficiency of 90 percent is a reasonable
estimate of MACT SRE.\160\
---------------------------------------------------------------------------
\160\ As discussed a number of times earlier, we are not basing
any standards on feed control of HAP in raw material and fossil fuel
input. We instead are controlling HAP attributable to those inputs
by means of end-of-stack emission standards which reflect removal of
HAP by some type of control device. This approach is consistent with
the discussion above, since we are not basing the cement kiln
chlorine standard on control of any raw material input, but rather
on some type of back-end removal efficiency.
---------------------------------------------------------------------------
We also reject the commenter's three suggested alternative
approaches to identify a MACT SRE to apply to the MACT feed level. The
commenter's methods all suffer a common flaw: They fail to recognize
and take into account the limitations of the total chlorine SRE data.
For example, as just demonstrated, available data show that considering
the SRE data associated with the most recent compliance test as a
ranking factor will result in unachievable standards due to the varying
effectiveness of chlorine capture (which impacts emissions) depending
on the raw material mix characteristics. Considering only the most
recent compliance test data as suggested yields results that are
unachievable because the best performer's SRE data are likely biased
high (e.g., sources that happen to test under favorable conditions are
likely to be identified as best performers), which would not be
replicable by even that source on a day-to-day basis.
3. Semivolatile and Low Volatile Metals
Comment: Commenters oppose EPA's proposed approach to treat each
kiln as a separate and unique source in the SRE/Feed MACT floor
analysis for cement kilns.\161\ Commenters state that the approach is
an improper way to perform a statistical analysis and reduces the
variability in emissions that otherwise would be observed in a MACT
pool of five unique sources. Variability is reduced because co-located
kilns at the same plant share many of the factors that comprise front-
end and back-end controls. As a result, the calculated MACT floors for
SVMs and LVMs for cement kilns are too stringent. The commenters'
recommended solution (in instances where co-located kilns are among the
top five performers) is to use only the data from the best performing
co-located kiln, exclude any lesser performing kilns at the plant site,
and then include the next-best performing non-co-located kiln in the
MACT pool. Implementing their recommendation, the commenters state that
the MACT floor for SVMs increases from 4.0 x 10-4 to 7.4 x
10-4 lbs/MMBtu and the floor for LVMs increases from 1.4 x
10-5 to 1.8 x 10-5 lbs/MMBtu. Another commenter
generally supports EPA's approach noting that the variability factor
applied to the emissions data already accounts for variability.
---------------------------------------------------------------------------
\161\ It is common for cement manufacturing plants to operate
multiple cement kilns at the same plant.
---------------------------------------------------------------------------
Response: We consider sources that are not identical as unique
sources and emissions data and information from unique sources are
considered separate sources in the floor analyses. An example of an
``identical'' source in our data base is compliance test data from a
similar on-site combustion unit used in place of a compliance test for
another unit (i.e., emissions testing of an identical unit was not
conducted). These sources and their associated data are called ``data
in lieu of'' sources in our data based on the RCRA provisions under
Sec. 266.103(c)(3)(i). We acknowledge that co-located sources may in
fact share certain similar operation features (e.g., use of raw
material from the same quarry, use of the same coal and hazardous waste
burn tank to fire the kilns); however, given that the co-located
sources (except those designated as data in lieu of) are not designed
identically, and given their hazardous waste feed control levels were
not identical during testing, we conclude we must consider each source
as a unique source in the floor analyses.\162\
---------------------------------------------------------------------------
\162\ Nonetheless, we analyzed the SVM and LVM floors for cement
kilns as suggested by the commenter. Results of the analysis are
presented in ``Technical Support Document for HWC MACT Standards,
Volume III: Selection of MACT Standards,'' Section 8.8, September 2005.
---------------------------------------------------------------------------
Comment: Commenter states that EPA's proposed standards for new
cement kilns are unachievable due to problems with its accounting for
variability, in part because EPA did not consider geographic
differences when assessing feed control levels. The concentrations of
hazardous constituents in the waste in a particular region are likely
to be different than in the waste from another geographical region due
to types of industrial sectors located within each region. Sources
cannot reasonably arrange for transportation of lower HAP wastes
generated across the country and cannot treat the hazardous waste to
remove or reduce HAP concentrations. The commenter cites several court
decisions that support their assertions. Commenter believes that while
this represents a problem for developing both the new and existing
source floors, it is a greater predicament for the new
[[Page 59471]]
source floor because this floor level is based on test data for only
one source.
Response: We are not obligated to account for varying hazardous
waste feed control levels occurring because of differing HAP generation
rates in different locations (for commercial sources), or because
different production process types generate higher or lower levels HAP
concentration wastes. Hazardous waste feed control is a legitimate
control technology. The commenter seems to suggest that we should
subcategorize low feeding sources and high feeding sources based on
their hazardous waste feed control level. This would inappropriately
subcategorize sources based on differing levels of controls, which we
do not do. See 69 FR at 403 (January 5, 2004). Nonetheless, as
previously discussed, the SRE/Feed methodology lessens the impact of
feed control variations across commercial units because it results in
fewer situations where best performing back-end controlled sources
(from a particulate matter emissions perspective) cannot achieve the
semivolatile and low volatile metal design levels and floors.
For new source standards, the single best performing cement kiln
sources for semivolatile metals and low volatile metals were not the
lowest hazardous waste feed controlled source (both floors were based
on sources with the fourth best, (i.e., lowest, hazardous waste feed
control level). We therefore do not believe these sources are
atypically low hazardous waste feeders relative to the other best
performing sources in the existing source MACT pools.
C. Lightweight Aggregate Kilns
1. Mercury Standard
Comment: One commenter, an operator of lightweight aggregate kilns
subject to this rule, recommends that EPA establish the mercury
standard for lightweight aggregate kilns at a hazardous waste feed
concentration limit of 3.3 ppmw for existing sources and 1.9 ppmw for
new sources, which is the same standard suggested in public comments by
a trade organization representing hazardous waste burning cement kilns.
The commenter notes that these mercury limits are appropriate for
lightweight aggregate kilns because the commenter's two lightweight
aggregate manufacturing facilities participate in the same hazardous
waste fuel market as the majority of cement kilns. Moreover, the
commenter maintains that its parent company also owns and operates two
cement kilns and that its lightweight aggregate kilns receive hazardous
waste from many of the same generators that provide hazardous waste
fuel to the cement kilns. Consequently, the commenter states that the
cement industry's data set of actual mercury feed concentrations in the
hazardous waste best represents the full range of hazardous waste fuel
concentrations that exist in the waste fuel market (see also Part Four,
Sections I.D and E).
Response: We disagree with the commenter. Although the cement
industry's set of mercury feed concentration data in the hazardous
waste may represent the full range of concentrations for the cement
kiln source category, we cannot conclude the same for lightweight
aggregate kilns because the commenter states that the mercury dataset
are only applicable to its kilns.\163\ Further, the commenter provides
no specific information or data to support the conclusion that its
suggested approach is justified for the other lightweight aggregate
kiln facility.
---------------------------------------------------------------------------
\163\ We note that the commenter-submitted dataset is not
amenable for use in establishing standards expressed in a thermal
emission format because sufficient information on the
characteristics of the hazardous waste (e.g., heating value of
hazardous waste) were not provided.
---------------------------------------------------------------------------
We also disagree with the commenter as to the appropriateness of
establishing the mercury standard in the format of a hazardous waste
feed concentration (i.e., 3.3 ppmw for existing sources and 1.9 ppmw
for new sources) for lightweight aggregate kilns. A hazardous waste
feed concentration standard is improper for this source category
because one lightweight aggregate kiln facility's sources (although not
the commenter's) controls mercury emissions using wet scrubbing. Thus,
a hazardous waste feed concentration standard would inappropriately
limit the mercury concentration in hazardous waste for sources that use
control equipment capable of capturing mercury. A source with control
equipment should not be restricted to a hazardous waste feed
concentration standard that is based on sources that can only control
mercury emissions through limiting the amount of mercury in the
hazardous waste.
In any case, as explained earlier in our discussion of cement kiln
mercury standard, we believe that it is preferable to establish an
emission standard to assure that the actual amount of mercury emitted
by these sources is controlled by means of a numerical standard for
stack emissions.
Comment: One commenter agrees that a source may not be able to
achieve the mercury standard due to raw material contributions that
might cause an exceedance of the emission standard in spite of a source
using properly designed and operated MACT floor control technologies,
including controlling the levels of metals in the hazardous waste. The
commenter opposes the proposed alternative standard of 42 [mu]g/dscm,
which is expressed as a hazardous waste maximum theoretical emissions
concentration. Instead, the commenter suggests that EPA maintain the
alternative standard options of Sec. Sec. 63.1206(b)(15) or 63.1206(b)(9).
Response: We agree with the commenter that the mercury standard
should address the concern of raw material contributions causing an
exceedance of the emission standard. We also agree that the proposed
alternative standard of a hazardous waste maximum theoretical emissions
concentration of 42 [mu]g/dscm is an improper standard because the
underlying data are unrepresentative. See discussion in Part Four,
Section I.E. We note that the mercury standard promulgated today is 120
[mu]g/dscm as a stack gas concentration limit or 120 [mu]g/dscm as a
hazardous waste maximum theoretical emission concentration feed limit.
The alternative mercury standard sought by the commenter under Sec.
63.1206(b)(15) is a limit of 120 [mu]g/dscm as a hazardous waste
maximum theoretical emission concentration, which is included in the
mercury standard promulgated today. This should address the commenter's
concern.
Comment: One commenter supports a mercury standard with short-term
compliance limits (e.g., 12-hour rolling average feedrate limits) as
opposed to the annual limit proposed.
Response: For reasons discussed in Part Four, Section I.E, we are
using a different mercury dataset than at proposal. We solicited
comment on a floor approach using these data in a notice \164\ sent
directly to certain commenters. We are adopting that approach today.
The monitoring requirements of the mercury standard for lightweight
aggregate kilns includes short-term averaging periods (i.e., not to
exceed a 12-hour rolling average), as recommended by the commenter.
---------------------------------------------------------------------------
\164\ See docket item OAR-2004-0022-0370.
---------------------------------------------------------------------------
2. Total Chlorine Standard
Comment: One commenter supports excluding from the floor analysis
all lightweight aggregate kiln sources that lack air pollution control
devices for chlorine, such as scrubbing technology. The floor analysis
should simply exclude sources without back-end controls according to
the commenter.
[[Page 59472]]
Response: We disagree. For the final rule, we are using the SRE/
Feed MACT floor approach which defines best performers as those sources
with the best combined front-end hazardous waste feed control and back-
end air pollution control efficiency. The commenter's suggestion would
exclude emissions data from two of the three facilities in this source
category even though valid emissions data from these sources are
available (and therefore ordinarily to be used, see CKRC, 255 F. 3d at
867), and these sources achieved the best front-end hazardous waste
feed control in the category. We note that the best feedrate controlled
sources have hazardous waste thermal feed levels that are approximately
one-fifth the level of the source's with back-end controls. These data
describe the level of performance of sources in the category and must
be evaluated in the MACT floor analysis. We also note that even if we
were to implement the commenter's suggestion, the MACT floor results
would not change for existing and new lightweight aggregate kilns
because the total chlorine emissions data of the source with back-end
air pollution controls (after considering variability) are higher than
the standards promulgated today. Thus, the commenter's suggestion also
would result in a standard that would be capped by the interim standard.
3. Beyond-the-Floor Standards
Comment: One commenter opposes EPA's proposed decision to
promulgate a beyond-the-floor standard for dioxin/furans for existing
and new lightweight aggregate kilns based on performance of activated
carbon injection.
Response: For the final rule, we conclude that a beyond-the-floor
standard for lightweight aggregate kilns is not warranted. The Clean
Air Act requires us to consider costs and non-air quality impacts and
energy requirements when considering more stringent requirements than
the MACT floor. In the proposed rule, we estimated that the incremental
annualized compliance costs for lightweight aggregate kilns to achieve
the beyond-the-floor standard would be approximately $1.8 million and
would provide an incremental reduction in dioxin/furan emissions of 1.9
grams TEQ per year (see 69 FR at 21262). At proposal we judged costs of
approximately $950,000 per additional gram of dioxin/furan TEQ removed
as justified, and, therefore, we proposed a beyond-the-floor standard.
Since proposal, we made several changes to the dioxin/furan data base
as the result of public comments. One implication of these changes is a
lower national emissions estimate for dioxin/furans for lightweight
aggregate kilns. We now estimate an incremental reduction in dioxin/
furan emissions of 1.06 grams TEQ per year with costs ranging between
$1.6 and $2.2 million per additional gram of dioxin/furan TEQ removed.
Based on these costs and consideration of the non-air quality impacts
and energy requirements (including more waste generated in the form of
spent activated carbon, and more energy consumed), we conclude that a
beyond-the-floor standard for existing and new lightweight aggregate
kilns is no longer justified. For an explanation of the beyond-the-
floor analysis, see Section 12.1.2 of Volume III of the Technical
Support Document. We note that EPA also retains its authority under
RCRA section 3005(c) (the so-called omnibus permitting authority) by
which permit writers can adopt more stringent emission standards in
RCRA permits if they determine that today's standards are not
protective of human health and the environment.
D. Liquid Fuel Boilers
1. Mercury Standard Not Achievable When Burning Legacy Mixed Waste
Comment: One commenter states that the proposed liquid fuel boiler
mercury standard is not achievable by a commercial boiler, DSSI
(Diversified Scientific Services, Inc.) that burns mercury-bearing low
level radioactive waste that is also a hazardous waste (so-called
`mixed waste') that was generated years ago (so-called, legacy waste).
The waste is an organic liquid containing high concentrations of
mercury. The boiler is equipped with a wet scrubber which provides good
mercury control--93%, system removal efficiency according to the commenter.
The commenter states that the proposed liquid fuel boiler mercury
standard is not achievable using feedrate control and/or additional
back-end control. Waste minimization is not an option because the waste
has already been generated. Further, available national treatment
capacity for mercury-bearing, low-level radioactive organic hazardous
waste is very limited. The only other hazardous waste combustion
facility authorized to treat such waste is the Department of Energy
incinerator at Oak Ridge, Tennessee. Waste treatment volumes at that
facility are restricted by the mercury feed rate limitation for the
incinerator. In addition, the feedrate of the waste cannot be
practicably reduced because of the large back-log of waste that must be
treated.
The commenter suggests that their boiler be subject to the
incinerator mercury standard because the mixed waste has far higher
concentrations of mercury than wastes burned by other boilers and, as a
consequence, the boiler is more incinerator-like with respect to the
feedrate of mercury.
Response. We agree with the commenter's suggestion. The final rule
subjects this commercial liquid fuel boiler to the mercury standard for
incinerators. We are classifying this source as a separate type of
source for purposes of the mercury standard, because the type of
mercury-containing waste it processes is dramatically different from
that processed by other liquid fuel boilers, effectively making this a
different type of source for purposes of a mercury standard \165\. The
source thus feeds mercury at concentrations exceeding that of any
boiler but at concentrations within the range processed by hazardous
waste incinerators. The maximum test condition average MTEC \166\ for
mercury for the remaining liquid fuel boilers is 20 [mu]g/dscm. All the
liquid fuel boiler mercury data represent ``normal'' data, i.e., data
that were not spiked. (The lack of spiked data in the liquid fuel
boiler data base, in and of itself, indicates that these sources do not
process mercury-bearing waste and do not need the operational
flexibility gained by spiking to account for occasional higher
concentration mercury wastes.) DSSI's 2002 mercury test condition
average MTEC was spiked to 3500 [mu]g/dscm. In other words, DSSI needs
the operational flexibility to feed 175 times more mercury than any
other liquid fuel boiler. Incinerators, on the other hand, had mercury
MTECs that ranged to 110,000 [mu]g/dscm in 2002. In fact, DSSI's
mercury feed rate is the eighth highest of the 40 incinerators,
including DSSI, for which we have 2002 mercury feed rate data. DSSI's
process feed is thus within the upper range of mercury feed found at
incinerators.
---------------------------------------------------------------------------
\165\ See CAA section 112 (d) (1)), authorizing EPA to
distinguish among different ``types * * * of sources within a
category or subcategory'' in developing MACT standards.
\166\ Maximum theoretical emission concentration is the feedrate
normalized by gas flowrate assuming zero system removal efficiency.
---------------------------------------------------------------------------
We believe it is well within the broad discretion accorded us in
section 112(d)(1) to subcategorize among ``types'' and ``classes'' of
sources within a category. See also Weyerhaeuser v. Costle, 590 F. 2d
at 254, n. 70 (D.C. Cir. 1978) (similar raw waste characteristics
justify common classification) and Chemical Manufacturers Ass'n v. EPA,
870 F. 2d 177, 253-54 and n. 340 (5th
[[Page 59473]]
Cir. 1989) (same). We note that this boiler will be subject to the
liquid fuel boiler standards for all HAP other than mercury (the only
HAP where the issue of appropriate classification arises).
Not surprisingly, given the disparity in waste concentration
levels, the DSSI boiler, even though equipped with back end control
comparable to best performing commercial incinerators, achieves mercury
emission levels less than an order of magnitude higher than the other
hazardous waste-burning liquid fuel boilers, few of which use back end
control that is effective for mercury.\167\ This emission disparity
likewise indicates that DSSI is treating a different type of waste than
other liquid fuel boilers.
---------------------------------------------------------------------------
\167\ USEPA, ``Technical Support Document for HWC MACT
Standards, Volume I: Description of Source Categories,'' September
2004, Section 2.4.4.
---------------------------------------------------------------------------
The nature of the mercury-bearing waste further confirms that it is
of a different type than that processed by other hazardous waste
burning liquid fuel boilers. The waste is a remediation waste, a type
of waste burned routinely by commercial hazardous waste incinerators
but almost never by a liquid fuel boiler.
Moreover, the waste is a legacy, mixed waste generated decades ago
in support of the United States' strategic nuclear arsenal. It is not
amenable to the types of control all other liquid fuel boilers use to
reduce mercury emissions--some type of feed control or other
minimization technique. We investigated whether any waste minimization
options are feasible for this waste, and find that they are not.
Normally, waste minimization is accomplished by one of three means:
eliminating the use of mercury in the process to prevent it from being
in the waste; pretreating the waste before burning to remove the
mercury; or sending it to another facility better suited to handle the
waste. Changing the production process to eliminate or reduce the
mercury content of the waste is not an option because this waste has
already been generated. Pretreatment is already practiced to the
maximum extent feasible by settling out and separating the heavier
mercury from the liquid components after thermal desorbtion. The
remaining organic liquid that is burned by the mixed waste boiler
contains concentrations of mercury (in organo-mercury and other organic
soluble forms) that are orders of magnitude higher than burned by other
liquid fuel boilers. Much of the waste cannot be feasibly pretreated to
remove mercury because this legacy, mixed waste comes from many highly
diverse sources. It is not practical or feasible to investigate how to
remove the mercury from wastes of such varied and unique origins.
Only one other facility could potentially treat this mixed waste,
DOE's incinerator at Oak Ridge, Tennessee, whose permit allows the
incinerator to manage mixed waste. However, waste treatment volumes for
mercury-bearing wastes at that facility are restricted by the mercury
feed rate limitation in the incinerator's permit. The DOE incinerator
alone cannot assure national capacity for mercury-bearing, low-level
radioactive organic hazardous waste. In addition, the back-end emission
controls of the mixed waste boiler are superior to those used by most
incinerators, including the Oak Ridge incinerator. This boiler uses a
highly effective wet scrubbing system--the principal MACT floor back-
end control for mercury used by incinerators--that achieves over 93%
system removal efficiency. This is superior control compared to most
incinerators, including the one at Oak Ridge which achieves 75 to 85%
removal.\168\
---------------------------------------------------------------------------
\168\ For more explanation concerning mixed waste sources,
limitations on the concentrations of mercury fed to these sources,
and the system removal efficiency achieved, see USEPA, ``Technical
Support Document for HWC MACT Standards, Volume III: Selection of
Standards,'' September 2005, Section 8.7.
---------------------------------------------------------------------------
Thus, this mixed waste boiler is reasonably classified a different
type of source with respect to mercury waste than other hazardous
waste-burning liquid fuel boilers, based on the nature of the waste
burned and confirmed by the source's mercury emissions. We note that,
although the final rule subjects only the DSSI mixed waste boiler to
the incinerator mercury standard, we would conclude that any other
liquid fuel boiler with the same fact pattern (i.e., that met the same
criteria as the DSSI boiler as discussed above) should also be subject
to the incinerator mercury standard rather than the liquid fuel boiler
mercury standard.
Comment. One commenter states that EPA's standards for all sources
must reflect the actual emission levels achieved by the relevant best
sources. If EPA wishes to subject the boiler source and incinerators to
the same emission standards, however, it is entirely within the
Agency's power to do so.
Response. We agree. There is no functional difference between this
boiler and incinerators with respect to mercury feed rate and the type
of waste processed (incinerators often treat remediation wastes).
Therefore, the most relevant sources for the purposes of clarification
in this case are incinerators, not liquid fuel boilers.
Accordingly, we have classified DSSI as an incinerator for purposes
of a mercury standard (i.e., made it subject to the mercury standard
for incinerators), and have included the DSSI mercury data with the
incinerator data when assessing mercury standards for incinerators.
Comment. In something of a contradiction, the same commenter argues
that the mixed waste boiler source (DSSI) does not claim that it cannot
meet the relevant mercury standard for liquid fuel boilers, but only
that it cannot do so ``using either feedrate control or MACT floor back
end emission control.'' Floors must reflect the emission levels that
the relevant best sources actually achieve, not what is achievable
through the use of a chosen emission control technology. It is flatly
unlawful--and essentially contemptuous of court--for EPA even to
entertain the source's argument that the source should be subject to a
less stringent emission standard based on the levels they believe would
be achievable through the use of one chosen control technology.
The commenter also states that the source acknowledges that it
could achieve a better emission level, and apparently meet the relevant
standards, by using activated carbon. Their argument that doing so
would generate large quantities of spent radioactive carbon does not
support its attempt to avoid Clean Air Act requirements; the
alternative to the source accumulating large quantities of radioactive
carbon is releasing large quantities of radioactive and toxic pollution
into the environment.
Response. DSSI cannot meet the liquid boiler mercury standard
because it burns a unique waste that resembles wastes processed by
hazardous waste incinerators (in terms of mercury concentration and
provenance) and is unlike any mercury-containing waste burned by the
remaining liquid fuel boilers. See the earlier discussion showing that
DSSI needs the operational flexibility to feed 175 times more mercury
than any other liquid fuel boiler, but that DSSI's process feed is
within the upper range of mercury feed found at incinerators.
We agree that DSSI is processing different types of mercury-bearing
wastes than those combusted by all other liquid fuel boilers. We
believe that establishing a different mercury standard for DSSI is
warranted, as it would for any source with demonstrably unique,
unalterable feedstock which is
[[Page 59474]]
more difficult to treat than that processed by other sources otherwise
in the same category.
How DSSI chooses to comply with the incinerator mercury standard
(for example, whether it must use some other type of emissions control
technology) is not germane to this decision. We note that today's
mercury standard for incinerators will force this source to lower its
mercury emissions, since it is unlikely that it can meet today's 120
[mu]g/dscm standard at all times without some changes in operations.
Comment. The source argues that waste minimization is not feasible
for legacy mixed waste that has already been generated. It is not
possible to travel back in time and unmake mixed legacy waste that
already has been created. That obvious fact, however, lends no support
to their argument that it should be allowed to burn mixed legacy waste
with less stringent emission standards, according to one commenter.
Response. As discussed above, the mercury standard for liquid fuel
boilers is not achievable for this source because it is a different
type and class of boiler, based on the type of mercury-containing
hazardous waste it processes. Because this boiler has mercury feed
rates that resemble those of incinerators--not liquid fuel boilers--and
waste minimization is not possible, subjecting the boiler to the
mercury incinerator standard is a reasonable means of sub-
categorization pursuant to the discretionary authority provided us by
section 112(d)(1) of the Clean Air Act.
Comment. The commenter states that it is entirely possible to
dispose of mixed legacy waste without burning it. Specifically,
currently available technologies such as chemical oxidation and
precipitation can be used to treat mixed legacy waste without burning
it--and without releasing mercury into the air. Therefore, mixed legacy
waste should not be burned at all; it should be disposed of safely
through the application of one of these more advanced technologies.
Response. First, these wastes must be treated before they can be
land disposed. RCRA sections 3004(d), (g)(5), and (m). They also must
meet a standard of 0.025 mg/l measured by the Toxicity Characteristic
Leaching Procedure before land disposal is permissible. 40 CFR 268.40
(standard for ``all other nonwastewaters that exhibit the
characteristic of toxicity for mercury'').\169\ EPA's technical
judgment is that it would be very difficult to meet this standard by
any means other than combustion. Moreover, as an organic liquid, the
waste is readily amenable to treatment by combustion. In addition,
combustion is a legal form of treatment for the waste. EPA did not
propose to change or otherwise reconsider these treatment standards in
this rulemaking, and is not doing so here. We note, however, that 40
CFR 268.42 and 268.44 provide means by which generators and treatment
facilities can petition the Agency to seek different treatment
standards from those specified by rule, and set out requirements for
evaluating such petitions.
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\169\ Although the legacy waste that DSSI is burning is
nominally classified as a nonwastewater due to its high organic
content, it is in fact a liquid matrix, meaning that the treatment
standard of 0.025 [mu]g/l is effectively a total standard.
---------------------------------------------------------------------------
We note further that, because this waste is radioactive,
exceptional precautions need to be taken in its handling. The
nonthermal treatment alternatives mentioned by the commenter ignore the
potential for radiation exposure if nonthermal treatment is used.
Concerns (some of which are mentioned in DSSI's comment) include:
Nonthermal treatment would (or could) increase worker exposure; desire
to reduce handling of radioactive materials in general; need to avoid
contaminating equipment that subsequently requires decontamination or
handling as radioactive material; minimizing the generation of
additional radioactive waste residues; reducing the amount of analysis
of radioactive materials, which causes potential exposure, generation
of radioactive wastes and equipment; wastes are varied and often of
small volumes, which makes it difficult to develop routine procedures.
Nonthermal treatment alternatives are also not currently available to
DOE to manage the diversity and volume of DOE mixed waste. It is thus
our belief that the commenter has not fully explored the implications
of its position, especially with regard to radiation exposure.
If the commenter wishes to pursue this issue, EPA believes the
appropriate context is through the Land Disposal Restriction mechanisms
described above.
Comment. The commenter states that the source argues that feedrate
control is not ``practical.'' There appears to be no record evidence
indicating what would make feedrate control impractical and why any
such obstacle could not be overcome.
Response. Feedrate control to the extent necessary to achieve the
liquid fuel boiler standards is not practical for reasons just
discussed. This source is one of two available sources that is
authorized to treat mixed waste, and the other source is not likely to
have the ability to burn mercury-bearing organic waste in the future
due to permit limitations and size constraints.
Comment. The commenter states that mixed legacy waste should not be
burned at all. If there are truly no other facilities that are
currently permitted to dispose of mixed legacy waste, such waste should
be stored until a facility that can treat such waste safely--e.g.,
through chemical oxidation--can be permitted.
Response. The commenter's suggestion is beyond the scope of today's
rulemaking. The suggestion is also illegal, since RCRA prohibits the
storage of hazardous waste for extended periods. See RCRA section
3004(j); and Edison Electric Inst. v. EPA, 996 F. 2d 326, 335-37 (DC
Cir. 1993) (illegal under RCRA section 3004(j) to store hazardous waste
pending development of a treatment technology). EPA also notes that it
retains authority under RCRA section 3005(c) (the so-called omnibus
permitting authority) by which permit writers can adopt more stringent
emission standards in RCRA permits if they determine that today's
standards are not protective of human health and the environment.
2. Different Mercury, Semivolatile Metals, Chromium, and Total Chlorine
Standards for Liquid Fuel Boilers Depending on the Heating Value of the
Hazardous Waste Burned
Comment. Several commenters state that liquid fuel boilers should
have an alternative concentration-based standard in addition to the
thermal emission-based standard. Liquid fuel boilers are typically
``captive'' units that burn waste fuels generated from on-site or
nearby manufacturing operations, rather than accepting wastes from a
wide variety of other sources. Because they have captive fuel sources,
operators generally do not have fuel blending capabilities. Liquid fuel
boilers ``burn what they have,'' and as such have very limited
operational flexibility. EPA should not penalize boilers that have the
same mass concentrations of metals or chlorine in their waste compared
to other boilers, but which wastes have a lower heating value than
wastes burned by other boilers. (The ``penalty'' is that emissions
limits that are normalized by the heating value of the hazardous waste
require that less volume of lower heating value waste can be burned
compared to higher heating value fuel.) This problem is made worse by
the limited data base for liquid fuel boilers,
[[Page 59475]]
the lack of historical data to verify that these standards are
achievable over time, and having most or all of the measured emissions
below detection limits. In addition, most of the mercury and
semivolatile metal data EPA has in the data base were obtained during
normal operations and while the source demonstrated compliance with
RCRA's chromium standard--the other metals data were available only
because stack method Method 29 reports data for all RCRA metals, even
ones that are not at issue for the compliance test. (Sources generally
elected to comply with the BIF Tier I metals emissions levels, but Tier
III for chromium. Thus, the Method 29 test for chromium will give
emissions results for all the metals--even those not subjected to stack
testing--not just chromium.)
Response. As explained earlier in Part Four, Section V.A., EPA has
selected normalizing parameters that best fit the input to the
combustion device. A thermal normalizing parameter (i.e., expressing
the standards in terms of amount of HAP contributed by hazardous waste
per thermal content of hazardous waste) is appropriate where hazardous
waste is being used in energy-recovery devices as a fuel, since the
waste serves as a type of fuel. Using a thermal normalizing parameter
in such instances avoids the necessity of subcategorizing based on unit
size.
The commenters raise the other side of the same issue. As the
commenters point out, some liquid fuel boilers burn lower Btu hazardous
waste because that is the waste available to them, and those with waste
that has a low heating value are, in their words, ``penalized,''
compared to those with a high(-er) heating value. Also, since these are
not commercial combustion units, they normally lack the opportunity to
blend wastes of different heating values to result in as-fired high
heating value fuels. If boiler standards are normalized by hazardous
waste heating value, sources with lower heating value waste must either
reduce the mass concentration of HAP or increase the waste fuel heating
value (or increase the system removal efficiency) compared to sources
with wastes having the same mass concentration of HAP but higher
heating value.
Moreover, the thermal normalizing parameter is not well suited for
a hazardous waste that is not burned entirely for its fuel value. In
cases where the lower heating value waste is burned, the boiler is
serving--at least in part--as a treatment device for the lower heating
value hazardous waste. When this occurs, the better normalizing
parameter is the unit's gas flow (a different means of accounting for
sources of different size), where the standard is expressed as amount
of HAP per volume of gas flow (the same normalizing parameter used for
most of the other standards promulgated in today's final rule.)
The commenters requested that liquid fuel boilers be able to select
the applicable standard (i.e., to choose between normalizing
parameters) and further requested that we assess the performance of
these units (for the purpose of establishing concentration-based MACT
floor levels) by using the same MACT pool of best performing sources
expressed on a thermal emissions basis.
Neither of these suggestions is appropriate. Choice of normalizing
parameter is not a matter of election, but rather reflects an objective
determination of what parameter is reasonably related to the activity
conducted by the source. Moreover, the commenter's suggestion to use
thermal emissions to measure best performance for a concentration-based
standard does not make sense. It arbitrarily assumes that the best
performers with respect to low and high heating value wastes are identical.
Instead, we have established two subcategories among the liquid
fuel boilers: those burning high and those burning low heating value
hazardous waste. The normalizing parameter for sources burning lower
energy hazardous waste is that used for the other hazardous waste
treatment devices, gas flow rate, so that the standard is expressed as
concentration of HAP per volume of gas flow (a concentration-based form
of the standard.) The normalizing parameter for sources burning higher
energy content hazardous waste is the thermal parameter used for energy
recovery devices, such as cement kilns and lightweight aggregate kilns.
For the purposes of calculating MACT floors, the best performers are
then drawn from those liquid fuel boilers burning lower energy
hazardous waste for the lower heating value subcategory, and from those
liquid fuel boilers burning higher energy hazardous waste for the
higher heating value subcategory \170\. (See Section 23.2 of Volume III
of the Technical Support Document for more information.)
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\170\ We also agree that liquid fuel boilers present several
unique circumstances, namely: they are often unable to blend fuel
and have limited operational flexibility as a result; our data base
on these sources' performance is relatively small; much of our
mercury and semivolatile metals data is at or near detection limits;
and much of the mercury and semivolatile metals data was obtained
for other purposes, namely from risk burns or as a result of Method
29 testing to demonstrate compliance with a RCRA chromium standard.
While not immediately important to the topic at hand--namely that
not all liquid fuel boilers burn for energy recovery--they are
secondary issues that we need to closely consider to make sure we do
not estimate what the best performing 12% of sources are achieving
in an unreasonable manner.
---------------------------------------------------------------------------
Moreover, liquid fuel boilers are not irrevocably placed in one or
the other of these subcategories. Rather, the source is subject to the
standard for one or the other of these subcategories based on the as-
fired heating value of the hazardous waste it burns at a given time.
Thus, when the source is burning for energy recovery, then the thermal
emissions-based standard would apply. When the source is burning at
least in part for thermal destruction, then the concentration based
standard would apply. This approach is similar to how we have addressed
the issue of normalization in other rules where single sources switch
back and forth among inputs which are sufficiently different to warrant
separate classification. \171\
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\171\ See NESHAP for Stationary Combustion Turbines, 40 CFR
section 63.6175 (definitions of ``diffusion flame gas-fired
stationary combustion turbine'', ``diffusion flame oil-fired
stationary combustion turbine'', ``lean pre-mix gas-fired stationary
combustion turbine'' and ``lean premix oil-fired stationary
combustion turbine'').
---------------------------------------------------------------------------
We next considered what an appropriate as-fired heating value would
be for each liquid fuel boiler subcategory. Although we have used 5000
Btu/lb (the heating value of lowest grade fuels such as scrap wood) in
past RCRA actions as a presumptive measure of when hazardous waste is
burned for destruction (see, e.g. 48 FR 11159 (March 16, 1983)), we do
not think that measure is appropriate here. We used the 5,000 Btu/lb
level to delineate burning for destruction from burning for energy
recovery at a time when that determination meant the difference between
regulation and nonregulation. See 50 FR 49166-167 (Nov. 29, 1985). This
is a different issue from choosing the most reasonable normalizing
parameter for regulated units (i.e., units which will be subject to a
standard in either case).
Instead, we are adopting a value of 10,000 Btu/lb as the threshold
for subcategorization. This is approximately the heating value of
commercial liquid fossil fuels. 63 FR 33782, 33788 (June 19, 1998) It
is also typical of current hazardous waste burned for energy recovery.
Id. Moreover, EPA has used this value in its comparable fuel
specification as a means of differentiating fuels from waste. See id.
and Table 1 to 40 CFR section 261.38, showing that EPA normalizes all
[[Page 59476]]
constituent concentrations to a 10,000 Btu/lb level in its
specification for differentiating fuels from wastes.
We next examined the waste fuel being burned at cement kilns and
lightweight aggregate kilns, which burn hazardous waste fuels to drive
the process chemistry to produce products\172\, to cross-check whether
10,000 Btu/lb is a reasonable demarcation value for subcategorizing.
10,000 Btu/lb is the minimum heating value found in burn tank and test
report data we have for cement kilns and lightweight aggregate kilns
\173\. We believe the cement kiln and light weight aggregate kiln data
confirm that this is an appropriate cutpoint, since these sources are
energy recovery devices that blend hazardous wastes into a consistent,
high heating value fuel for energy recovery in their manufacturing process.
---------------------------------------------------------------------------
\172\ The Norlite light-weight aggregate kiln was not included
in this analysis because they claim they are not burning for energy
recovery. The waste Norlite burns is 4,860 Btu/lb or lower. This is
indicative of a source burning solely for thermal treatment of the
waste and not, at least in part, for energy recovery. See 40 CFR
266.100(d)(2)(ii).
\173\ The cement kiln burn tank data and test report data shows
the minimum heating values of 9,900 and 10,000 Btu/lb, respectively,
for the hazardous waste. The minimum lightweight aggregate kiln
heating values for hazardous waste was 10,000 Btu/lb, excluding the
Norlite source.
---------------------------------------------------------------------------
We then separated the liquid fuel boiler emissions data we had into
two groups, sources burning hazardous waste fuel with less than 10,000
Btu/lb and all other liquid fuel boilers, and performed separate MACT
floor analyses. (See Sections 13.4, 13.6, 13.7, 13.8, and 22 of Volume
III of the Technical Support Document.) We calculated concentration-
based MACT standards for these sources from their respective mercury,
semivolatile metals, chromium, and total chlorine data.
Liquid fuel boilers will need to determine which of the two
subcategories the source belongs in at any point in time. Thus, you
must determine the as-fired heating value of each batch of hazardous
waste fired so that you know the heating value of the hazardous waste
fired at all times.\174\ If the as-fired heating value of hazardous
wastes varies above and below the cutpoint (i.e., 10,000 Btu/lb) at
times, you are subject to the thermal emissions standards when the
heating value is not less than 10,000 Btu/lb and the mass concentration
standards when the heating value is less than 10,000 Btu/lb. To avoid
the administrative burden of frequently switching applicable operating
requirements between the subcategories, you may elect to comply with
the more stringent operating requirements that ensure compliance with
the standards for both subcategories.
---------------------------------------------------------------------------
\174\ If you burn hazardous waste in more than one firing
nozzle, you must determine the mass-weighted average heating value
of the as-fired hazardous waste across all firing nozzles.
---------------------------------------------------------------------------
Comment: EPA's attempt to give actual performance two different
meanings within a single floor approach is unlawful, unexplained,
internally inconsistent, and arbitrary. If EPA believes that mass-based
emissions constitute sources' actual performance, the best performing
sources must be those with the best mass based emissions--not thermal
emissions.
Response: As just explained, we agree with this comment, and have
developed MACT floors independently for the two subcategories of liquid
fuel boilers. Thus, we have defined two separate MACT pools based on
the thermal input of the waste fuel and derived two separate and
consistent MACT standards for sources when they burn solely for energy
recovery, and when they do not.
We also note that a source cannot ``pick and choose'' the less
stringent of the two standards and comply with those. The source must
be in compliance with the set of standards that apply.
3. Alternative Particulate Matter Standard for Liquid Fuel Boilers
Comment: A commenter requested that EPA establish standards that
allow boilers the option to comply with either a concentration-based
particulate matter standard or thermal emissions-based particulate
matter standard.
Response: We determined that it is appropriate to express the
particulate matter emission standard as a concentration-based standard
consistently across source categories and not to give boilers the
option to comply with a thermal emissions-based particulate matter
standard. As discussed in Part Four, Section III.D as well as the
preceding section, metal and chlorine concentration-based emission
standards can be biased against sources that process more hazardous
waste (from an energy demand perspective), in part because the SRE/Feed
methodology assesses feed control of each source when identifying the
best performing sources; the ranking procedure thus favors sources with
lower percentage hazardous waste firing rates (keeping all other
assessment factors equal). The thermal emission standard format
eliminates this firing rate bias, which amounts to a limitation on the
amount of raw material (hazardous waste fuel to an energy recovery
device) that may be processed, when identifying best performing sources.
The methodology we use to identify best performing sources for
particulate matter emissions is not affected by the firing rate bias in
the manner that metal and chlorine emissions are. This is primarily
because we define best performing sources as those with the best back-
end air pollution control technology; feed control is not assessed
(specifically ash feed control) for raw materials, fossil fuel, or
unenumerated HAP metal in the hazardous waste. The hazardous waste
firing rate bias is therefore not present when we identify the best
performing particulate matter sources because a source's hazardous
waste firing rate is not a direct factor in the ranking procedure.
We also note that four of the nine best performing liquid fuel
boilers for particulate matter are equipped with fabric filters.
Particulate matter emissions from sources equipped with fabric filters
are not significantly affected by ash inlet loading. This is not true
for metals and chlorine, given metal and chlorine emissions from fabric
filters tend to increase at increased feed rates. See Volume III of the
Technical Support Document, Sections 5.3 and 7.4. We conclude that the
hazardous waste firing rate issue is not a concern for these sources
given their particulate matter emissions would not be significantly
affected by increased hazardous waste firing rates.
4. Long-term, Annual Averaging Is Impermissible
Comment: Standards expressed as long-term limits are legally
impermissible because those levels, by definition, would sometimes be
greater than the average emission levels achieved by the best
performing sources. Compliance also must be measured on a continuous
basis, under section 302(k) of the Act. Thus, floor levels (and
standards) for mercury expressed as long-term limits are illegal.
Response: The commenter maintains that the statutory command in
section 112(d)(3)(A) to base floor standards for existing sources on
``the average emission limitation achieved by the best performing 12
percent of * * * existing sources'' precludes establishing standards
expressed as long term averages because certain daily values could be
higher. We do not accept this position. The statute does not state what
type of ``average'' performance EPA must assess. Long term, i.e.,
annual, averaging of performance is quite evidently a type of average,
and so is permissible under the statutory text. Moreover, it is
reasonable to establish
[[Page 59477]]
standards on this basis (the standards being the average of the best
performing sources, expressed as a long-term average), where sufficient
data exist. Indeed, since the principal health concern posed by the
emitted HAP is from chronic exposure (i.e. cumulative exposure over
time), long-term standards (which reduce the long-term distribution of
emitted HAP) arguably would be preferable in addressing the chief risks
posed by these sources' emissions.
We establish standards with long-term averaging limits whenever we
use normal data to estimate long-term performance. We do this in the
few instances where there are insufficient data (whether normal data or
compliance test data) to estimate each source's short term emission
levels (e.g., mercury and semivolatile metal standards for liquid fuel
boilers).\175\ One or two snapshot data based on normal operations are
not likely to reflect a source's short-term operating levels in part
because feed control levels can vary over time.\176\ See Mossville, 370
F. 3d at 1242 (varying feed rates lead to different emission levels,
and this variability must be encompassed within the floor standard
because the standard must be met at all times). As a result, snapshot
normal emissions, when averaged together, better reflect a source's
long term average emissions. An emission standard based on normal data
that is averaged together, but expressed as a short-term limit, would
not be achievable by the best performing sources because it would not
adequately account for their emissions variability. See National
Wildlife Federation v. EPA, 286 F. 3d at 572-73 (``[c]ontinuous
operation at or near the daily maximum would in fact result in
discharges that exceed the long-term average. Likewise, setting monthly
limitations at the 99th percentile would not insure that the long-term
average is met''). Long-term limits better account for this variability
because such limits allow sources to average their varying feed control
levels over time while still assuring average emissions over this
period are below the levels demonstrated by the best performing sources.
---------------------------------------------------------------------------
\175\ Two emission standards in this rulemaking are based on
normal data but are expressed as short term limits (the mercury
standards for lightweight aggregate and cement kilns). However, in
these instances we had enough normal data to reasonably estimate
each source's maximum emissions, thus allowing us to express the
standard as a short term limit. See USEPA, ``Technical Support
Document for HWC MACT Standards, Volume III: Selection of MACT
Standards,'' September 2005, Sections 11.2 and 12.2.
\176\ This is not the case for floors that are based on
compliance tests because sources spiked their hazardous wastes to
account for variability in hazardous waste feedrate. See Part Four,
Section III.C above. Normal data, however, are a snapshot of what
occurred on that day and are not likely to be representative over
the long term, especially for mercury and semivolatile metals for
liquid fuel boilers, where these limited data were almost entirely
below the analytic detection limit.
---------------------------------------------------------------------------
Indeed, under the commenter's approach where no averaging of intra-
source data would be allowed, sources would not be in compliance with
the standards during the performance tests themselves. The tests
consist of the average of three data runs, so half of the emissions-
weighted data points would be impermissibly higher than the average
during the test used to derive today's emission standards.
EPA also does not see that section 302(f) of the Act, cited by the
commenter, supports its position. That provision indicates that the
emission standards EPA establishes must limit the quantity, rate, or
concentration of air pollutants on a continuous basis. A standard
expressed as a long-term average does so by constraining the overall
distribution of emissions to meet a long-term average. Also, long term
limits result in emission standards that are lower than those that
otherwise would be implemented on a short-term basis. The short-term
limit would have to reflect the best performing sources' short term
emissions variability (i.e., the maximum amount of variability a source
could experience during a single test period). National Wildlife
Federation, 286 F. 3d at 571-73.
Comment: Other commenters argued the opposite point, that ERA has
no data to show that an annual average is achievable, and EPA should
establish a longer averaging period.
Response: We believe that all sources can achieve the mercury and
semivolatile metals standards for liquid fuel boilers on an annual
basis using some combination of MACT controls, i.e., feed control, back
end control, or some combination of both. We agree that we have a small
data set for these standards, but also believe that it is intuitive
that a liquid fuel boiler can meet these standards on an annual basis,
because one year is sufficiently more than any seasonal (i.e., several
month long) production of certain items that may not be represented by
the tests we have.
This informs us that an average of less than a year may not be
achievable. It does not inform us that averaging of more than a year is
required, since variations that occur with a year are averaged
together. An annual average is sufficient for a source to determine
whether an individual waste stream impacts negatively on the compliance
of the liquid fuel boiler and take measures to address the issue.
5. Gas Fuel Boilers
Comment: How can a boiler burning only gaseous waste also be
burning hazardous waste? Uncontained gases are not considered hazardous
waste under RCRA. Why are boilers that burn only gasses part of the
liquid fuel boiler subcategory?
Response: We agree with the commenter that boilers that burn gasses
are unlikely to burn hazardous wastes. However, gas fuel hazardous
waste boilers have existed in the past,\177\ and we believe we need to
define a MACT standard for them. Therefore, we included gas fuel
boilers in the liquid fuel boiler subcategory for reasons cited in the
proposed rule. See 69 FR at 21216.
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\177\ For example, sources 2014 and 2015 owned by Environmental
Purification Industries in Toledo, Ohio, were considered hazardous
waste boilers at the time the Phase II data base was noticed in the
June 27, 2000, despite the fact that these boilers burned only
gasses. These boilers have since stopped burning hazardous waste.
---------------------------------------------------------------------------
E. General
1. Alternative to the Particulate Matter Standards
Comment: Commenters state that some incinerators are currently
complying with the alternative to the particulate matter standard
provision pursuant to the interim standards. See Sec. 63.1206(b)(14).
The eligibility and operating requirements for the alternative to the
particulate matter standard in the Interim Standards are different than
the proposed alternative to the particulate matter standard in the
replacement rule. Specifically, the proposed alternative to the
particulate matter standard would no longer require sources to
demonstrate a 90% system removal efficiency or a minimum hazardous
waste metal feed control level to be eligible for the alternative.
Commenters request that EPA clarify in the final rule that the proposed
alternative to the particulate matter standard supersedes the
requirements in the Interim Standards.
Response: We are finalizing the alternative to the particulate
matter standard for incinerators as proposed, with the exception that
the alternative metal emission limitations have been revised as a
result of database changes since proposal. See Sec. 1219(e) and part
three, section II.A. We considered superseding the interim standard
alternative to the particulate matter standard requirements
(63.1206(b)(14)) immediately (upon promulgation) by replacing it with
the revised alternative
[[Page 59478]]
standard provisions finalized in today's rule. Although the eligibility
requirements for the alternative to the particulate matter standard
finalized today are less stringent than the interim standard
requirements, the metal emission limitations that are also required by
the alternative finalized today are by definition equivalent to or more
stringent than the metal limitations in the interim standard
alternative. We therefore cannot completely supersede the interim
standard provisions immediately (upon promulgation) because sources
have three years to comply with more stringent standards. We are
instead revising the interim standard provisions of Sec.
63.1206(b)(14) to only reflect the revised alternative standard
eligibility criteria (specifically, we have removed the requirements to
achieve a given system removal efficiency and hazardous waste metal HAP
feed control level).\178\ These eligibility criteria revisions become
effective immediately with respect to the interim standards because
they are less stringent than the current requirements. Sources should
modify existing Notifications of Compliance and permit requirements as
necessary prior to implementing these revised procedures.
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\178\ Sources can only use Sec. 63.1206(b)(14) for purposes of
complying with the interim standards. After the compliance date for
today's rule, incinerators electing to comply with the alternative
to the particulate matter standard must comply with the provisions
found in Sec. 63.1219(e).
---------------------------------------------------------------------------
Comment: One commenter is opposed to the alternative to the
particulate matter standard because it ignores the health effects/
benefits that are attributable to particulate matter.
Response: Particulate matter is not defined as a hazardous air
pollutant pursuant the NESHAP program. See CAA 112(b)(1). We control
particulate matter as a surrogate for metal HAP. See part four, section
IV.A. As a result, a particulate matter standard is not necessary in
instances where metal HAP emission standards can alternatively and
effectively control the nonmercury metal HAP that is intended be
controlled with the surrogate particulate matter standard. The
alternative to the particulate matter standard in the final rule
accomplishes this. We acknowledge that particulate matter emission
reductions result in health benefits. That in itself does not give EPA
the authority under Sec. 112(d)(2) to directly regulate particulate
matter, however.
2. Assessing Risk as Part of Consideration of Nonair Environmental Impacts
Comment: Commenter states that EPA has inappropriately failed to
consider emissions of persistent bioaccumulative pollutants in its
beyond-the-floor analysis despite EPA's acknowledgment that these HAPs
have non-air quality health and environmental impacts.
Response: EPA has taken the consistent position that considerations
of risk from air emissions have no place when setting MACT standards,
but rather are to be considered as part of the residual risk
determination and standard-setting process made under section 112 (f)
of the statute. EPA thus interprets the requirement in section 112 (d)
(2) that we consider ``non-air quality health and environmental
impacts'' as applying to the by-product outputs from utilization of the
pollution control technology, such as additional amount of waste
generated, and water discharged.\179\ EPA's interpretation was upheld
as reasonable in Sierra Club v. EPA, 353 F. 3d 976, 990 (D.C. Cir.
2004) (Roberts, J.).
---------------------------------------------------------------------------
\179\ See USEPA, ``Technical Support Document for the HWC MACT
Standards, Volume V: Emission Estimates and Engineering Costs,''
September 2005, Section 6, for a discussion of the non-air impact
that were assessed for this final rule.
---------------------------------------------------------------------------
VII. Health-Based Compliance Alternative for Total Chlorine
A. Authority for Health-Based Compliance Alternatives
Comment: One commenter states there is no established health
threshold for either HCl or chlorine.
Response: Although EPA has not developed a formal evaluation of the
potential for HCl or chlorine carcinogenicity (e.g., for IRIS), the
evaluation by the International Agency for Research on Cancer stated
that there was inadequate evidence for carcinogenicity in humans or
experimental animals and thus concluded that HCl and chlorine are not
classifiable as to their carcinogenicity to humans (Group 3 in their
categorization method). Therefore, for the purposes of this rule, we
have evaluated HCl and chlorine only with regard to non-cancer effects.
In the absence of specific scientific evidence to the contrary, it has
been our policy to classify non-carcinogenic effects as threshold
effects. RfC development is the default approach for threshold (or
nonlinear) effects.
Comment: One commenter states that the proposal is an inappropriate
forum for bringing forward such a significant change in the way that
MACT standards are established under Section 112(d) of the Clean Air
Act. A precedent-setting change of the magnitude that EPA has raised
should be discussed openly and carefully with all affected parties,
rather than being buried in several individual proposed standards.
Response: Including health-based compliance alternatives for
hazardous waste combustors does not mean that EPA will automatically
provide such alternatives for other source categories. Rather, as has
been the case throughout the MACT rule development process, EPA will
undertake in each individual rule to determine whether it is
appropriate to exercise its discretion to use its authority under CAA
section 112(d)(4) in developing applicable emission standards.
Stakeholders for those affected rules will have ample opportunity to
comment on the Agency's proposals.
Comment: One commenter states that the proposed approach is
contrary to the intent of the CAA which explicitly calls for a general
reduction in HAP emissions from all major sources nationwide through
the establishment of MACT standards based on technology, rather than
risk, as a first step.
Response: For pollutants for which a health threshold has been
established, CAA section 112(d)(4) allows the Administrator to consider
such threshold level, with an ample margin of safety, to establish
emission standards.
Comment: One commenter states that the proposed approach would take
the national air toxics program back to the time-consuming NESHAP
process that existed prior to the Clean Air Act Amendments of 1990.
Response: We disagree that allowing a health-based compliance
alternative in the final rule will alter the MACT program or affect the
schedule for promulgation of the remaining MACT standards. Today's rule
is the last MACT rule to be promulgated, and the health-based
compliance alternative did not delay promulgation of the rule.
Comment: A commenter is concerned that the proposal would remove
the benefit of the ``level-playing field'' that would result from the
proper implementation of technology-based MACT standards.
Response: Providing health-based compliance alternatives in the
final rule for sources that can meet them will assure the application
of a uniform set of requirements across the nation. The final rule and
its criteria for demonstrating eligibility for the health-based
compliance alternatives apply uniformly to all hazardous waste
combustors except hydrochloric acid
[[Page 59479]]
production furnaces. The final rule establishes two baseline levels of
emission reduction for total chlorine, one based on a traditional MACT
analysis and the other based on EPA's evaluation of the health threat
posed by emissions of HCl and chlorine. All hazardous waste combustor
facilities must meet one of these baseline levels, and all facilities
have the same opportunity to demonstrate that they can meet the
alternative health-based emission standards. We also note that
additional uniformity is provided by limiting the health-based
compliance alternatives for incinerators, cement kilns, and lightweight
aggregate kilns to the emission levels allowed by the Interim Standards.
Comment: Several commenters state that site-specific emission
limits are inappropriate under section 112(d)(4) because they are not
emission standards. One commenter asserts that the Agency's position
that the limits are based on uniform procedures is flawed because the
process allows ``any scientifically-accepted, peer-reviewed risk
assessment methodology for your site-specific compliance
demonstration.'' This is not a ``uniform'' procedure, according to the
commenter. There are a host of variables that influence the results of
an accepted methodology. The commenter reasons that, without some
standardization of those variables, there is no uniform or standard
analysis. Each permitting authority could establish its view of
appropriate variables; there would be no national consistency.
Several other commenters assert that EPA has the authority to
establish an exposure-based emission limit for total chlorine. One
commenter notes that one issue that often arises when considering risk-
based standards is whether EPA has authority under section 112 to
establish an exposure-based emission limit. The commenter states that
the concern seems to be that some stakeholders construe the Act's
statutory provisions as requiring uniform emission limitations at all
facilities, rather than emissions that are measured at places away from
the source and that vary from facility to facility. The commenter does
not see any legal impediment to establishing exposure-based limits.
The commenter notes that, first, under section 112, EPA has
authority to establish ``emission standards.'' Emission standards are
defined to be a requirement established by the State or the
Administrator which limits the quantity, rate or concentration of
emissions of air pollutants on a continuous basis * * * to assure
continuous emission reduction, and any design, equipment, work practice
or operational standard promulgated under this chapter. EPA's alternate
risk-based emission standard will limit the quantity, rate or
concentration of the emissions. The commenter states that there is no
requirement in the definition that specifies where the emission
standard is to be measured, nor is there such a requirement anywhere in
the statute.
Second, the commenter notes that EPA's proposed exposure-based
limit will result in facilities establishing operating parameter
limitations, or OPLs. These OPLs qualify as emission limitations
because they are ``operational standards'' being promulgated under
section 112, according to the commenter. They will be measured at the
facility, not at the point of exposure. Finally, the commenter reasons
that the limitations EPA is establishing are uniform. They uniformly
protect the individual most exposed to emission levels no higher than a
hazard index of 1.0. Consequently, the commenter believes that there is
nothing in the statute that prevents the Agency from promulgating
exposure-based emission standards.
Response: We agree with the commenters who believe the Agency has
the authority to establish health-based compliance alternatives under a
national exposure standard. In particular, we agree with the commenter
that the health-based compliance alternatives are national standards
since they provide a uniform and national measure of risk control, and
also that the health-based compliance alternatives are ``emission
standards'' because they limit the quantity, rate or concentration of
total chlorine emissions.
Section 112(d)(4) authorizes EPA to bypass the mandate in section
112(d)(3) in appropriate circumstances. Those circumstances are present
for hazardous waste combustors other than hydrochloric acid production
furnaces. Section 112(d)(4) provides EPA with authority, at its
discretion, to develop health-based compliance alternatives for HAP
``for which a health threshold has been established,'' provided that
the standard reflects the health threshold ``with an ample margin of
safety.''
Both the plain language of section 112(d)(4) and the legislative
history indicate that EPA has the discretion under section 112(d)(4) to
develop health-based compliance alternatives for some source categories
emitting threshold pollutants, and that those standards may be less
stringent than the corresponding MACT standard (including floor
standards) would be.\180\ EPA's use of such standards is not limited to
situations where every source in the category or subcategory can comply
with them. As with technology-based standards, a particular source's
ability to comply with a health-based standard will depend on its
individual circumstances, as will what it must do to achieve compliance.
---------------------------------------------------------------------------
\180\ See also Legislative History at 876 (section 112(d)(4)
standard may be less stringent than MACT).
---------------------------------------------------------------------------
In developing health-based compliance alternatives under section
112(d)(4), EPA seeks to ensure that the concentration of the particular
HAP to which an individual exposed at the upper end of the exposure
distribution is exposed does not exceed the health threshold. The upper
end of the exposure distribution is calculated using the ``high end
exposure estimate,'' defined as ``a plausible estimate of individual
exposure for those persons at the upper end of the exposure
distribution, conceptually above the 90th percentile, but not higher
than the individual in the population who has the highest exposure''
(EPA Exposure Assessment Guidelines, 57 FR 22888, May 29, 1992).
Assuring protection to persons at the upper end of the exposure
distribution is consistent with the ``ample margin of safety''
requirement in section 112(d)(4).
We agree with the view of several commenters that section 112(d)(4)
is appropriate for establishing health-based compliance alternatives
for total chlorine for hazardous waste combustors other than
hydrochloric acid production furnaces. Therefore, we have established
such compliance alternatives for affected sources in those categories.
Affected sources which believe that they can demonstrate compliance
with the health-based compliance alternatives may choose to comply with
those compliance alternatives in lieu of the otherwise applicable MACT-
based standard.
Comment: One commenter states that the risk assessments would not
provide an ample margin of safety because background exposures are not
taken into account. There is no accounting for other chlorine compounds
from other sources at the facility, or from other neighboring
facilities. The commenter believes that there is no evidence in the
section 112(f) residual risk assessments produced thus far that
emissions from collocated sources will actually be pursued by EPA. The
commenter also notes that the Urban Air Toxics program cannot be relied
upon to address ambient background. This program,
[[Page 59480]]
required under section 112(k), was to be completed by 1999. However,
the strategy has not been finalized and the small amount of activity in
this area is focused on voluntary emission reductions rather than
federal requirements. Finally, the commenter notes that control of
criteria pollutants via State Implementation Plans to achieve
compliance with the NAAQS is problematic. For particulate matter (PM)
and ozone, new NAAQS were set in 1997 and seven years later the
nonattainment designations are still being determined. The designation
process will be followed by a 3 year period to prepare State
Implementation Plans and several more years to carry out those plans.
In the meantime, there will be high levels of PM and ozone in the air
near many hazardous waste combustors in New Jersey which will
exacerbate exposures to chlorine and hydrogen chloride.
Response: Total chlorine missions from collocated hazardous waste
combustors must be considered in establishing health-based compliance
alternatives under Sec. 63.1215. Ambient levels of HCl or chlorine
attributable to other on-site sources, as well as off-site sources, are
not considered, however. As we indicated in the Residual Risk Report to
Congress and in the recent residual risk rule for Coke Ovens, the
Agency intends to consider facility-wide HAP emissions as part of the
ample margin of safety determination for CAA section 112(f) residual
risk actions. 70 FR at 19996-998 (April 15, 2005); see also, 54 FR at
38059 (Sept. 14, 1989) (benzene NESHAP).
Comment: Several commenters state that acute exposure guideline
levels (AEGLs) are once-in-a-lifetime exposure levels. They assert
that, because short term exposures at a Hazard Index greater than 1.0
may occur more than once in a lifetime, using AEGLs for the purpose of
setting risk-based short-term limits for HCl and chlorine does not
provide an ``ample margin of safety.''
Response: To assess acute exposure, we proposed to use acute
exposure guideline levels for 1-hour exposures (AEGL-1) as health
thresholds. We have investigated commenters' concerns, however, and
conclude that AEGLs are not likely to be protective of human health
because individuals may be subject to multiple acute exposures at a
Hazard Index greater than 1.0 from hazardous waste combustors.
Consequently, we use acute Reference Exposure Levels (aRELs) rather
than acute exposure guideline levels (AEGLs) as acute exposure
thresholds for the final rule. See also Part Two, Section IX.D above.
Acute RELs are health thresholds below which there would be no adverse
health effects while AEGL-1 values are health thresholds below which
there may be mild adverse effects.
Acute exposures are relevant (in addition to chronic exposures) and
the acute exposure hazard index of 1.0 could be exceeded multiple times
over an individual's lifetime. Although we concluded at proposal that
the chronic exposure Hazard Index would always be higher than the acute
exposure Hazard Index, and thus would be the basis for the total
chlorine emission rate limit, this conclusion relates to acute versus
chronic exposure to a constant, maximum average emission rate of total
chlorine from a hazardous waste combustor. See 69 FR at 21300. We
explained that acute exposure must nonetheless be considered when
establishing operating requirements to ensure that short-term emissions
do not result in an acute exposure Hazard Index of greater than 1.0.
This is because total chlorine and chloride feedrates to a hazardous
waste combustor (e.g., commercial incinerator) can vary substantially
over time. Although a source may remain in compliance with a feedrate
limit with a long-term averaging period (e.g., 12-hour, monthly, or
annual) based on the chronic Hazard Index, the source could feed
chlorine during short periods of time that substantially exceed the
long-term feedrate limit. This could result potentially in emissions
that exceed the one-hour (i.e., acute exposure) Hazard Index.
Consequently, we discussed at proposal the need to establish both
short-term and long-term total chlorine and chloride feedrate limits to
ensure that neither the chronic exposure nor the acute exposure Hazard
Index exceeds 1.0.\181\
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\181\ Note that we conclude for the final rule that most sources
are not likely to exceed the acute Hazard Index because they will
establish a 12-hour rolling average chlorine feedrate limit and
their chlorine feedrates are not likely to vary substantially over
that averaging period. Thus, we believe that most sources will not
be required to establish an hourly rolling average chlorine feedrate
limit. The owner/operator must determine whether the hourly rolling
average chloride feedrate limit can be waived under Sec. 63.1215(d).
---------------------------------------------------------------------------
We conclude that 1-hour Reference Exposure Levels (aRELs) are a
more appropriate health threshold metric than AEGL-1 values for
hazardous waste combustors given that the acute Hazard Index limit of
1.0 may be exceeded multiple times over an individual's lifetime,
albeit resulting from uncontrollable factors. The California Office of
Health Hazard Assessment has developed acute health threshold levels
that are intended to be protective for greater than once in a lifetime
exposures. The acute exposure levels are called acute Reference
Exposure Levels and are available at
http://www.oehha.ca.gov/air/acute_rels/acuterel.html. 
The 1-hour REL values for hydrogen chloride and chlorine are 2.1
mg/m3 and 0.21 mg/m3, respectively. The AEGL-1
values for hydrogen chloride and chlorine are 2.7 mg/m3 and
1.4 mg/m3, respectively. Although there is little difference
between the 1-hour REL and AEGL-1 values for hydrogen chloride, the 1-
hour REL for chlorine is substantially lower than the AEGL-1 value.
In summary, we believe that aRELs are a more appropriate health
threshold metric than AEGL-1 values for establishing health-based
compliance alternatives for hazardous waste combustors because aRELs
are ``no adverse effect'' threshold levels that are intended to be
protective for multiple exposures.
Comment: One commenter states that the health-based compliance
alternative is unlawful because the proposal does not address
ecological risks that may result from uncontrolled HAP emissions,
including risks posed to those areas where few people currently live,
but sensitive habitats exist.
Response: An ecological assessment is normally required under CAA
section 112(d)(4) to assess the presence or absence of ``adverse
environmental effects'' as that term is defined in CAA section
112(a)(7). To identify potential multimedia and/or environmental
concerns, EPA has identified HAP with significant potential to persist
in the environment and to bioaccumulate. This list does not include
hydrogen chloride or chlorine.
We also note that health-based total chlorine emission limits for
incinerators, cement kilns, and lightweight aggregate kilns cannot be
higher than the current Interim Standards. See Sec. 63.1215(b)(7).
Thus, the ecological risk from total chlorine emissions from these
sources will not be increased under the health-based limits.
In addition, we note that only 2 of 12 solid fuel boilers have
total chlorine emissions higher than 180 ppmv, and only 1 liquid fuel
boiler has emissions higher than 170 ppmv. Thus, boilers generally have
low total chlorine emissions which would minimize ecological risk.
Consequently, we do not believe that emissions of hydrogen chloride
or chlorine from hazardous waste boilers will pose a significant risk
to the environment, and facilities attempting to comply with the
health-based
[[Page 59481]]
alternatives for these HAP are not required to perform an ecological
assessment.
B. Implementation of the Health-Based Standards
Comment: Several commenters are concerned that the health-based
compliance alternative will place an intensive resource demand on state
and local agencies to review and approve facilities' eligibility
demonstrations, and State and local agencies may not have adequate
expertise to review and approve the demonstrations. One commenter
states that permitting authorities do not have the expertise to review
eligibility demonstrations that are based on procedures other than
those included in EPA's Reference Library, as would be allowed. The
commenter also states that, if the health-based compliance alternative
is promulgated, EPA should establish one standard method for the
analyses so there is consistency nationwide. If EPA offers more than
one method, EPA should do all of the risk assessment reviews, instead
of passing the responsibility, without clear direction, to the
permitting authorities, according to the commenter.
Response: The health-based compliance alternatives for total
chlorine that EPA has adopted in the final rule should not impose
significant resource burdens on states. The required compliance
demonstration methodology is structured in such a way as to avoid the
need for states to have significant expertise in risk assessment
methodology. We have considered the commenters' concerns in developing
the criteria defining eligibility for these compliance alternatives,
and the approach that is included in the final rule provides clear,
flexible requirements and enforceable compliance parameters. The final
rule provides two ways that a facility may demonstrate eligibility for
complying with the health-based compliance alternatives. First, look-up
tables allow facilities to determine, using a limited number of site-
specific input parameters, whether emissions from their sources might
cause the Hazard Index limit to be exceeded. Second, if a facility
cannot demonstrate eligibility using a look-up table, a modeling
approach can be followed. The final rule presents the criteria for
performing this modeling.
Only a portion of hazardous waste combustors will submit
eligibility demonstrations for the health-based compliance
alternatives. Of these sources, several should be able to demonstrate
eligibility based on simple analyses--using the look-up tables.
However, some facilities will require more detailed modeling. The
criteria for demonstrating eligibility for the compliance alternatives
are clearly defined in the final rule. Moreover, under authority of
RCRA section 3005(c)(3), multi-pathway risk assessments will typically
have already been completed for many hazardous waste combustors to
document that emissions of toxic compounds, including total chlorine,
do not pose a hazard to human health and the environment. Thus, state
permitting officials have already reviewed and approved detailed
modeling studies for many hazardous waste combustors. The results of
these studies could be applied to the eligibility demonstration
required by this final rule.
Because these requirements are clearly defined, and because any
standards or requirements created under CAA section 112 are considered
applicable requirements under 40 CFR part 70, the compliance
alternatives would be incorporated into title V programs, and states
would not have to overhaul existing permitting programs.
Finally, with respect to the burden associated with ongoing
assurance that facilities that opt to do so continue to comply with the
health-based compliance alternatives, the burden to states will be
minimal. In accordance with the provisions of title V of the CAA and
part 70 of 40 CFR (collectively ``title V''), the owner or operator of
any affected source opting to comply with the health-based compliance
alternatives is required to certify compliance with those standards
every five years on the anniversary of the comprehensive performance
test. In addition, if the facility has reason to know of changes over
which the facility does not have control, and these changes could
decrease the allowable HCl-equivalent emission rate limit, the facility
must submit a revised eligibility demonstration. Further, before
changing key parameters that may impact an affected source's ability to
continue to meet the health-based emission standards, the source is
required to evaluate its ability to continue to comply with the health-
based compliance alternatives and submit documentation to the
permitting authority supporting continued eligibility for the
compliance alternative. Thus, compliance requirements are largely self-
implementing and the burden on states will be minimal.
Comment: One commenter suggests that the look-up tables would have
more utility if EPA developed tables for each source category to ensure
the HCl-equivalent emission rate limits reflected stack parameters
representative of each source category. Similarly, another commenter
notes that a look-up table designed to be applicable to all hazardous
waste combustors is very conservative and will have limited utility.
This commenter does not suggest that EPA develop look-up tables for
each class of hazardous waste combustors, however. Rather, the
commenter suggests that since look-up tables have already been
developed for industrial boilers that do not burn hazardous waste \182\
hazardous waste combustors should be allowed to use those look-up
tables instead of the look-up tables proposed for hazardous waste
combustors.
---------------------------------------------------------------------------
\182\ See Table 2 of Appendix A to Subpart DDDDD, Part 63.
---------------------------------------------------------------------------
Response: We noted at proposal that the emission rates provided in
the look-up table for hazardous waste combustors are more stringent
than those promulgated for solid fuel industrial boilers that do not
burn hazardous waste. This is because the key parameters used by the
SCREEN3 atmospheric dispersion model (i.e., stack diameter, stack exit
gas velocity, and stack exit gas temperature) to predict the normalized
air concentrations that EPA used to establish HCl-equivalent emission
rates for solid fuel industrial boilers that do not burn hazardous
waste are substantially different for hazardous waste combustors. Thus,
the maximum HCl-equivalent emission rates for hazardous waste
combustors would generally be lower than those EPA established for
solid fuel industrial boilers that do not burn hazardous waste.
Nonetheless, we agree with the commenter's concerns that the look-
up tables would have more utility if they better reflected the range of
stack properties representative of hazardous waste combustors.
Accordingly, we examined the stack parameters for all hazardous waste-
burning sources in our data base (except for hydrochloric acid
production furnaces that are not eligible for the health-based emission
standards). After analyzing the relationships among the various stack
parameters (i.e., stack height, stack diameter, stack gas exhaust
volume, and exit temperature), we concluded that the look-up table
should be modified to treat both stack diameter and stack height as
independent variables rather than relying on stack height alone.
We developed separate tables for short-term (i.e., 1-hour) HCl-
equivalent
[[Page 59482]]
emissions limits to protect against acute health effects and long-term
(i.e., annual) emission limits to protect against chronic effects from
exposures to chlorine and hydrogen chloride. As discussed above, we
used the acute Reference Exposure Level (aREL) developed by Cal-EPA as
the benchmark for acute health effects. We used EPA's Reference
Concentrations (RfC) as the benchmark for chronic health effects from
exposures occurring over a lifetime.
Emission limits in the look-up table are expressed in terms of HCl-
toxicity equivalent emission rates (lbs/hr). To convert your total
chlorine emission rate (lb/hr) to an HCl-equivalent emission rate, you
must adjust your chlorine emission rate by a multiplicative factor
representing the ratio of the HCl health risk benchmark to the chlorine
health risk benchmark. For 1-hour average HCl-equivalent emission
rates, the ratio is the ratio of the aREL for HCl (2100 micrograms per
cubic meter) to the aREL for chlorine (210 micrograms per cubic meter),
or a factor of 10.\183\ For annual average emissions, the ratio is the
ratio of the RfC for HCl (20 micrograms per cubic meter) to the RfC of
chlorine (0.2 micrograms per cubic meter), or a factor of 100. See
Sec. 63.1215(b).
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\183\ We note that this factor of 10 ratio of the aRELs of HCl
to chlorine is based on current aREL values and is subject to
change. You must use current aREL (and RfC) values when you conduct
your eligibility demonstration. See Sec. 63.1215(b)(4 and 5).
---------------------------------------------------------------------------
We used the SCREEN3 air dispersion model to develop the emission
limits in the look-up tables. SCREEN3 is a screening model that
estimates air concentrations under a wide variety of meteorological
conditions in order to identify the meteorological conditions under
which the highest ambient air concentrations are likely to occur and
what the magnitude of the ambient air concentrations are likely to be.
The SCREEN3 model implements the procedures in EPA's ``Screening
Procedures for Estimating the Air Quality Impact of Stationary Sources,
Revised'' (EPA-454/R-92-019, U.S. Environmental Protection Agency,
Office of Air Quality Planning and Standards, Research Triangle Park,
NC, October 1992). Included are options for estimating ambient air
concentrations in simple elevated terrain and complex terrain. Simple
elevated terrain refers to terrain elevations below stack top. We did
not use the complex terrain option in the development of the look-up
tables because of the site-specific nature of plume impacts in areas of
complex terrain. Therefore, the look-up tables cannot be used in areas
of complex terrain (which we define generally as terrain that rises
above stack top). Sources located in complex terrain (i.e., as a
practical matter, sources other than those that are located in flat or
simple elevated terrain as discussed below and thus cannot use the
look-up tables) must use site-specific modeling procedures to establish
HCl-equivalent emission rates.
We looked at two generic terrain scenarios for purposes of the
look-up table. In one we assumed the terrain rises at a rate of 5
meters for every 100 meter run (i.e., a slope of 5 percent) and that
terrain is ``chopped off'' above stack top (following the convention
for such analyses in simple elevated terrain). In the other we assumed
flat terrain. As can be seen from the tables in Sec. 63.1215, the
emission limits with flat terrain are significantly higher than those
with simple elevated terrain. To reasonably ensure that the emission
limits are not substantially over-stated (e.g., by a factor of 2), the
simple elevated terrain table must be used whenever terrain rises to an
elevation of one half (\1/2\) the stack height within a distance of 50
stack heights.
For both the simple elevated terrain and flat terrain scenarios, we
performed model runs for urban and rural dispersion conditions, with
and without building downwash. We selected the highest (ambient air
concentration) values at each distance from among the four runs for
each of the terrain scenarios.
As can be seen from the tables in Sec. 63.1215, the HCl-equivalent
emission rate limits range from 0.13 pounds per hour on an annual
average (for a 0.3 meter diameter stack that is 5 meters tall that lies
within 30 meters of the property boundary) to 340 pounds per hour (for
a 4.0 meter diameter stack that is 100 meters tall that lies 5000
meters from the property boundary) when located in simple elevated
terrain. In flat terrain, the range is from 0.37 to 1100 pounds per
hour on an annual average. This contrasts with the look-up table at
proposal, where the comparable range was from 0.0612 pounds per hour
(for a 5 meter stack height at a distance of 30 meters) to a maximum of
18 pounds per hour (for stack heights of 50 meters or greater, at
distances of 500 meters or greater).
If you have more than one hazardous waste combustor on site, the
sum of the ratios for all combustors of the HCl-equivalent emission
rate to the HCl-equivalent emission rate limit cannot exceed 1.0. See
Sec. 63.1215 (c)(3)(v). This will ensure that the Hazard Index of 1.0
is not exceeded considering emissions from all on-site combustors.
Comment: Several commenters state that facilities should be allowed
to establish an averaging period for the total chlorine and chloride
feedrate limit that is shorter than an annual rolling average.
Commenters are referring to the feedrate limit to ensure compliance
with the annual average HCl-equivalent emission rate limit. Commenters
are concerned with the data handling issues that could arise from
calculating, recording, and reporting an annual rolling average
feedrate level that is updated hourly, and note that a shorter
averaging period would make the limit more stringent.
Response: We agree with commenters, and conclude, moreover, that a
12-hour averaging period rather than an annual averaging period will be
imposed on the vast majority of sources as a practical matter. This is
because sources must establish a limit on the feedrate of total
chlorine and chloride to ensure compliance with the semivolatile metals
emission standards. See Sec. 63.1209(n). The feedrate limit for total
chlorine and chloride is established under Sec. 63.1209(n) as the
average of the hourly rolling averages for each test run, and the
averaging period is 12 hours. Thus, the averaging period for the
feedrate limit for semivolatile metals--12-hour rolling average updated
hourly--trumps the annual rolling average averaging period that would
otherwise apply here.\184\
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\184\ To also ensure compliance with the annual average HCl-
equivalent emission rate limit, however, the numerical value of the
feedrate limit established during the semivolatile metals
performance test cannot exceed the value calculated as the annual
average HCl-equivalent emission rate limit divided by [1 - system
removal efficiency], where you demonstrate the total chlorine system
removal efficiency during the comprehensive performance test.
---------------------------------------------------------------------------
Sources may also demonstrate compliance with the semivolatile
metals standard by assuming all semivolatile metals in feedstreams are
emitted. See Sec. 63.1207(m)(2). Sources that do not have emission
control equipment, such as most liquid fuel boilers, are particularly
likely to use this approach. Under this approach, there is no concern
regarding increased volatility of metals as chlorine feedrates
increase, and such sources are not subject to a feedrate limit for
chlorine for compliance assurance with the semivolatile metal standard.
These sources may establish an averaging period for the feedrate of
total chlorine and chloride for compliance with the health-based
compliance alternative for total chlorine of not to exceed one year.\185\
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\185\ We note that we have also applied this ``not-to-exceed''
approach to establishing the duration of averaging periods for the
limits on all operating parameters established under Sec. 63.1209.
See new Sec. 63.1209(r) and USEPA, ``Final Technical Support
Document for HWC MACT Standards, Volume IV: Compliance with HWC MACT
Standards, September 2005, Section 2.4.6.
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[[Page 59483]]
Comment: Several commenters offered suggestions on whether a short-
term feedrate limit was needed for total chlorine and chloride (i.e.,
chlorine) as EPA suggested, and if EPA continues to consider it
necessary, how the limit should be established.
One commenter states that it is not necessary to set short-term
limits for chlorine feedrates. If EPA concludes that short-term limits
are necessary, however, the commenter recommended these options: (1)
Cap the feedrate at a level that is extrapolated up to the feedrate
associated with Interim Standard for incinerators; (2) if the facility
uses the site-specific option to set emission limits, the dispersion
models can easily be used to set a 1-hour (or longer) limit; and (3) if
the facility uses the look up table (which at proposal provided only
annual average HCl-equivalent emission rate limits), a short-term limit
can be set based on a multiplier of the annual limit'10 times the
annual limit as recommended by documents in EPA's Air Toxics Risk
Assessment Reference Library.
Another commenter states that, if EPA were to promulgate a short-
term feedrate limit, the EPA-endorsed factor of 0.08 employed to
translate maximum hourly concentrations to annual concentrations could
be used to identify the maximum hourly feedrate limit.
Finally, another commenter states that extrapolation of the
chlorine feedrate (from the level during the comprehensive performance
test when the source documents compliance with the annual average HCl-
equivalent emission rate limit) should be allowed to 100% of the 1-hour
average HCl-equivalent emission rate limit because numerous safety
factors have already been included in the health risk threshold values,
look-up tables, and modeling demonstration.
Response: At proposal, we explained that sources would establish an
annual average feedrate limit on chlorine as the feedrate level during
the comprehensive performance test demonstrating compliance with the
annual average HCl-equivalent emission rate limit. \186\ Only long-term
exposures--maximum annual average exposures--need be considered when
confirming that the chlorine feedrate during the comprehensive
performance test (i.e., average of the hourly rolling averages for each
run) is acceptable because the annual exposure Hazard Index limit
(i.e., not to exceed 1.0) would always be exceeded before the 1-hour
Hazard Index limit (i.e., not to exceed 1.0). Thus, the feedrate limit
associated with annual exposures would always be more stringent than
the feedrate limit associated with 1-hour exposures. See 69 FR at 21299.
---------------------------------------------------------------------------
\186\ We discussed at proposal that the feedrate limit to ensure
compliance with the long-term Hazard Index limit of not to exceed
1.0 would be the average of the hourly rolling averages for each
test run, with compliance based on an annual average. Note that,
under the final rule however, the long-term chlorine feedrate limit
is established as the annual average HCl-equivalent emission rate
limit divided by [1 - system removal efficiency]. See Sec. 63.1215(g)(2).
---------------------------------------------------------------------------
We further explained at proposal, however, the need to establish a
short-term feedrate limit for chlorine to ensure that the 1-hour HCl-
equivalent emission rate did not exceed the 1-hour average HCl-
equivalent emission rate limit due to variability in the chlorine
feedrate during the annual averaging period for the feedrate limit. We
requested comment on approaches to establish this 1-hour chlorine
feedrate limit, including extrapolating feedrates to 100% of the 1-hour
average HCl-equivalent emission rate limit. See 69 FR at 21304.
In the final rule we have corrected and refined these procedures.
The final rule requires you to establish a long-term chlorine feedrate
limit to maintain compliance with the annual average HCl-equivalent
emission rate limit as either: (1) The chlorine feedrate during the
comprehensive performance test if you demonstrate compliance with the
semivolatile metals emission standard during the test (see Sec.
63.1209(o)); or (2) if you comply with the semivolatile metals emission
standard under Sec. 63.1207(m)(2) by assuming all metals in the feed
to the combustor are emitted, the annual average HCl-equivalent
emission rate limit divided by [1 - system removal efficiency]
where
you demonstrate the system removal efficiency during the comprehensive
performance test. See discussion in Part Two, Section IX.H, of this
preamble. If you establish the chlorine feedrate limit based on the
feedrate during the performance test to demonstrate compliance with the
semivolatile metals emission standard, the averaging period for the
feedrate limit is a 12-hour rolling average. If you establish the
chlorine feedrate limit based on the system removal efficiency during
the performance test, the averaging period is up to an annual rolling
average.
The final rule also requires you to establish an hourly rolling
average chlorine feedrate limit if you determine under Sec.
63.1215(d)(3) that the 1-hour average HCl-equivalent emission rate
limit may be exceeded. That feedrate limit is established as the 1-hour
HCl-equivalent emission rate limit divided by [1 - system removal
efficiency].
Under Sec. 63.1215(d)(3), you must establish an hourly rolling
average chlorine feedrate limit unless you determine considering
specified criteria that your chlorine feedrates will not increase over
the averaging period for the long-term chlorine feedrate limit (i.e.,
12-hour rolling average or (up to) annual rolling average) to a level
that may result in an exceedance of the 1-hour average HCl-equivalent
emission rate limit. The criteria that you must consider are: (1) The
ratio of the 1-hour average HCl-equivalent emission rate based on the
total chlorine emission rate you select for each combustor to the 1-
hour average HCl-equivalent emission rate limit for the combustor; and
(2) the potential for the source to vary chlorine feedrates
substantially over the averaging period for the long-term chlorine
feedrate limit.
For example, if a source's primary chlorine-bearing feedstreams
have a relatively constant chlorine concentration over the averaging
period for the chlorine feedrate limit to ensure compliance with the
annual average HCl-equivalent emission rate limit (e.g., generally 12-
hours), as may be the case for commercial sources feeding from large
burn tanks or on-site sources where chlorine levels in wastes are
fairly constant, you may conclude that there is little probability that
1-hour feedrates would vary substantially over the averaging period.
Thus, a 1-hour rolling average chlorine feedrate limit may not be
warranted. Even if chlorine feedrates could vary substantially over the
long-term feedrate averaging period, however, an hourly rolling average
feedrate limit still may not be warranted if the source's 1-hour
average HCl-equivalent emission rate is well below the 1-hour HCl-
equivalent emission rate limit. See Part Two, Section IX.H, of this
preamble for a discussion of the relationship between emission rates,
emission rate limits, and feedrate limits.
We disagree with the commenter who states that short-term chlorine
feedrate limits are not necessary. The 1-hour average HCl-equivalent
emission rate limit could potentially be exceeded for sources with
highly variable chlorine feedrates and where the 1-hour HCl-equivalent
emission rate is relatively high compared to the 1-hour HCl-equivalent
emission rate limit. The 1-hour average HCl-equivalent emission rate
limit could be exceeded even though the source remains in compliance
with the annual average HCl-equivalent emission rate limit (and,
[[Page 59484]]
moreover, the 12-hour rolling average or (up to) annual rolling average
chlorine feedrate limit).
We agree with commenters that suggest that the hourly rolling
average chlorine feedrate limit should be extrapolated from performance
test feedrates up to 100% of the 1-hour average HCl-equivalent emission
rate limit. The final rule requires you to establish the hourly rolling
average feedrate limit (if a limit is required under Sec.
63.1215(d)(3)) as the 1-hour HCl-equivalent emission rate limit divided
by [1 - system removal efficiency]. Establishing the hourly rolling
average feedrate in this manner ensures that the 1-hour HCl-equivalent
emission rate limit is not exceeded, and thus that the aREL-based
Hazard Index of 1.0 is not exceeded.
We also agree in principle with commenters that suggest that the
hourly rolling average feedrate limit be based on the 1-hour average
HCl-equivalent emission rate limit which is based on emissions
modeling. These commenters suggested that we use a multiplier of 10 or
12.5 (i.e., 1/0.08) to project 1-hour average HCl-equivalent emission
rate limits from the annual average HCl-equivalent emission rate
limits. Rather than use these approaches to project 1-hour average
emissions from annual average emissions, however, we use emissions
modeling to develop look-up tables for both 1-hour average HCl-
equivalent emission rate limits and annual average HCl-equivalent
emission rate limits. For sources that use site-specific risk
assessment to demonstrate eligibility, they will use the same models to
estimate 1-hour average maximum ambient concentrations. Thus, the final
rule uses modeling to establish directly 1-hour average HCl-equivalent
emission rate limits rather than approximating those limits from annual
average HCl-equivalent emission rate limits as commenters suggest. In
summary, the final rule requires you to establish the 1-hour average
HCl-equivalent emission rate limit by either using Tables 3 or 4 in
Sec. 63.1215 to look-up the limit, or conducting a site-specific risk
analysis. Under the site-specific risk analysis option, the 1-hour
average HCl-equivalent emission rate limit would be the highest
emission rate that the risk assessment estimates would result in an
aREL-based Hazard Index not exceeding 1.0 at any off-site receptor
location.
We do not agree that the short-term feedrate limit should be capped
at the level corresponding to the Interim Standards for incinerators,
cement kilns, and lightweight aggregate kilns. The final rule caps the
total chlorine emission rate and the annual average HCl-equivalent
emission rate limit at the level equivalent to the Interim Standard for
total chlorine. Thus, the long-term chlorine feedrate limit (12-hour
rolling average or (up to) an annual rolling average) is capped at the
level corresponding to the Interim Standards for incinerators, cement
kilns, and lightweight aggregate kilns. The hourly rolling average
feedrate limit to maintain compliance with the 1-hour average HCl-
equivalent emission rate limit, however, can exceed the numerical value
of the long-term chlorine feedrate limit because the 1-hour average
HCl-equivalent emission rate limit is substantially higher than the
annual average HCl-equivalent emission rate limit. Thus, capping at the
interim standard level is inappropriate unless the interim standard
were somehow re-expressed as a 1-hour limit.
Comment: Many commenters state that requiring prior approval of the
eligibility demonstration would be unworkable. Commenters are concerned
that the permitting authority may not approve the demonstration prior
to the compliance date even though the source has submitted complete
and accurate information and has responded to any requests for
additional information in good faith. Commenters are also concerned
that the permitting authority may disapprove the demonstration too late
for the source to take other measures to comply with the total chlorine
MACT standard. Once commenter recommends the following alternative
approach: (1) If the regulatory agency does not act on a risk
demonstration within the 6-month period, it is conditionally deemed
approved; and (2) if a risk demonstration is disapproved, the source
would have to comply with the MACT emission standards no later than
three years after notice of disapproval and, in the interim, sources
would comply with current emission limits for total chlorine.
Another commenter suggests that, if the permitting authority has
neither approved nor disapproved the eligibility demonstration by the
compliance date, the source may begin complying on the compliance date
with the alternative health-based limits specified in the eligibility
demonstration.
Finally, another commenter states that facilities should be granted
a three-year extension of the compliance date if the Agency denies a
good-faith eligibility demonstration. The commenter is concerned that
sources will not have time to install additional controls or take other
measures after a denial is issued but prior to the compliance date.
Response: We agree with commenters that requiring prior approval of
the eligibility demonstration may be unworkable for the reasons
commenters suggest. We also agree with commenters that sources who make
a good-faith eligibility demonstration but whose demonstration is
denied by the permitting authority may need additional time to install
controls or take other measures to comply with the MACT emission standards.
Accordingly, the final rule does not require prior approval of the
eligibility demonstration for existing sources. If your permitting
authority has not approved your eligibility demonstration by the
compliance date, and has not issued a notice of intent to disapprove
your demonstration, you may nonetheless begin complying, on the
compliance date, with the HCl-equivalent emission rate limits and
associated chlorine feedrate limits you present in your eligibility
demonstration.
In addition, the final rule states that the permitting authority
should notify you of approval or intent to disapprove your eligibility
demonstration within 6 months after receipt of the original
demonstration, and within 3 months after receipt of any supplemental
information that you submit. A notice of intent to disapprove your
eligibility demonstration, whether before or after the compliance date,
will identify incomplete or inaccurate information or noncompliance
with prescribed procedures and specify how much time you will have to
submit additional information or comply with the total chlorine MACT
standards. The permitting authority may extend the compliance date of
the total chlorine MACT standards to allow you to make changes to the
design or operation of the combustor or related systems as quickly as
practicable to enable you to achieve compliance with the total chlorine
MACT standards.
Comment: One commenter states that proposed Sec. 63.1215(f)(1)(A)
should have required sources to conduct a new comprehensive performance
test only if there are changes that would decrease the HCl-equivalent
emission rate limit below the HCl-equivalent emission rate demonstrated
during the comprehensive performance test. Similarly, the commenter
suggests that a retest should not be required if a change increases the
HCl-equivalent emission rate limit but the source elects to maintain
the current feedrate limit.
Another commenter states that the Agency should clarify that if
there are any changes that are not controlled by the facility owner/
operator, and the
[[Page 59485]]
facility is required to change its design or operation to lower
chlorine emissions to address the changes, the facility may request up
to three years to make such changes.
Response: We generally agree with the commenters and have revised
the rule as follows: (1) A new comprehensive performance test is
required to reestablish the system removal efficiency for total
chlorine only if you change the design, operation, or maintenance of
the source in a manner that may decrease the system removal efficiency
(e.g., the emission control system is modified in a manner than may
decrease total chlorine removal efficiency); and (2) if you use the
site-specific risk analysis option for your eligibility demonstration
and changes beyond your control (e.g., off-site receptors newly
residing or congregating at locations exposed to higher ambient levels
than originally estimated) dictate a lower HCl-equivalent emission rate
limit and you must make changes to the design, operation, or
maintenance of the combustor or related systems to comply with the
lower limit, you may request that the permitting authority grant you
additional time to make those changes as quickly as practicable.
Comment: Several commenters state that the proposed approach for
calculating chlorine emissions to address the potential bias using
Method 26/26A attributable to high bromine or sulfur levels in
feedstreams is not statistically valid. They indicate that the approach
could lead to collection of total chlorine, hydrogen chloride and
chlorine data that are contradictory and difficult to apply in a
compliance situation. One commenter suggests that using Method 26/26A
results for sources with bromine and sulfur dioxide, while recognizing
that there is bias in the sampling method, will result in a valid
compliance approach.
Response: We agree with commenters that the proposed approach to
avoid the bias when feedstreams contain high levels of bromine or
sulfur (bromine/chlorine ratio in feedstreams of greater than 5
percent, or sulfur/chlorine ratio in feedstreams of greater than 50
percent) during the comprehensive performance test may be problematic.
The proposed approach would have required you to use Method 320/321 or
ASTM D 6735-01 for hydrogen chloride measurements, to use Method 26/26A
for total chlorine (i.e., hydrogen chloride and chlorine combined)
measurements, and to calculate chlorine levels by difference. The
potential problem is that chlorine emission levels are generally a very
small portion of total chlorine measurements, and variability in the
hydrogen chloride or total chlorine measurements due to method
imprecision or other factors could result in inaccurate estimations of
chlorine emission levels.
We do not agree, however, that using Method 26/26A for chlorine
measurements for combustors feeding high levels of bromine or sulfur is
acceptable-the chlorine measurement may be biased low. Chlorine
emission levels must be determined as accurately as possible given that
the long-term health threshold for chlorine is 100 times the threshold
for HCl, and the short-term health threshold for chlorine is 10 times
the threshold for HCl (i.e., using current RfCs and aRELs). To ensure
that a conservative estimate of the chlorine emission rate is used to
establish the alternative health-based emission limits and to address
commenters' concerns, the final rule requires that you determine
chlorine emissions to be the higher of: (1) The chlorine value measured
by Method 26/26A, or an equivalent method; or (2) the chlorine value
calculated by difference between the combined hydrogen chloride and
chlorine levels measured by Method 26/26A, or an equivalent method, and
the hydrogen chloride measurement from EPA Method 320/321 or ASTM D
6735-01, or an equivalent method.
Comment: Several commenters state the procedures for calculating
HCl-equivalent emission rates cannot merely reference an outside
source, such as a Web site, unless that reference specifies that the
contents of the source are as of a date certain. To specify use of
health threshold values that can change over time provides inadequate
opportunity for notice and comment on the regulation.
Response: We believe that the best available sources of health
effects information should be used for risk or hazard determinations.
To assist us in identifying the most scientifically appropriate
toxicity values for our analyses and decisions, the Web site to be used
for RfCs identifies pertinent toxicity values using a default hierarchy
of sources, with EPA's Integrated Risk Information System (IRIS) being
the preferred source. The IRIS process contains internal and external
peer review steps and IRIS toxicity values represent EPA consensus
values. When adequate toxicity information is not available in IRIS,
however, we consult other sources in a default hierarchy that
recognizes the desirability of these qualities in ensuring that we have
consistent and scientifically sound assessments. Furthermore, where the
IRIS assessment substantially lags the current scientific knowledge, we
have committed to consider alternative credible and readily available
assessments (e.g., the acute Relative Exposure Levels established by
the California Office of Health Hazard Assessment). For our use, these
alternatives need to be grounded in publicly available, peer-reviewed
information. We agree with the commenter that the issue of changing
toxicity values is a general challenge in setting health-based
regulations. However, we are committed to establishing such regulations
that reflect current scientific understanding, to the extent feasible.
C. National Health-Based Standards for Cement Kilns
Comment: One commenter states that our suggestion at proposal that
it would be appropriate to establish a single national emission rate
type standard applicable to all cement kilns based on the worst-case
scenario cement kiln is unduly burdensome as it discounts the benefits
of improved dispersion realized by facilities that have invested in
taller stacks that minimize downwash effects. The commenter recommends
a dual limit for cement kilns such that the HCl equivalent emission
rate is limited to both: (1) A 130 ppmv total chlorine emission
standard (the Interim Standard) coupled with a chlorine feedrate limit
based on a 12-hour rolling average; and (2) a Hazard Index of 1.0.
Response: We have decided not to include a separate national
standard for cement kilns in the final rule for several reasons: (1) We
have no assurance that the Cl2/HCl volumetric ratio
exhibited during the most recent compliance test, and that was the
basis for the commenter documenting in a study \187\ that the Hazard
Index of 1.0\188\ was not exceeded, is representative of ratios in the
past or future; (2) the commenter's recommended emission standard for
cement kilns--130 ppmv total chlorine emission limit and a Hazard Index
of 1.0--is equivalent to the requirements under Sec. 63.1215
applicable to other hazardous waste combustors to establish site-
specific emission limits; (3) the MACT standard for total chlorine for
cement kilns is 120 ppmv such that the health-based standard that the
commenter recommends--130 ppmv,
[[Page 59486]]
the Interim Standard--would provide little compliance relief; and (4)
even though the final rule does not provide a separate national health-
based standard for cement kilns, cement kilns may apply for the health-
based compliance alternatives applicable to other hazardous waste
combustors.
---------------------------------------------------------------------------
\187\ See Trinity Consultants, ``Analysis of HCl/Cl2 Emissions
from Cement Kilns for 112(d)(4) Consideration in the HWC MACT
Replacement Standards,'' September 17, 2003.
\188\ The HCl/Cl2 ratio for the total chlorine
measurement is important because the current RfC for chlorine is 0.2
[mu]g/m\3\ while the current RfC for HCl is 20 [mu]g/m\3\. Thus,
when calculating HCl-equivalent emission rate limits, chlorine
emissions are currently multiplied by a factor of 100.
---------------------------------------------------------------------------
Prior to publication of the proposed rule, the commenter submitted
results of site-specific risk assessments for all cement kiln
facilities showing that both the long-term and short term Hazard Index
of 1.0 would not be exceeded at any facility assuming: (1) Sources emit
total chlorine at the Interim Standard level of 130 ppmv; and (2) total
chlorine emissions are apportioned between HCl and chlorine according
to the apportionment exhibited during the most recent compliance test.
At proposal, we requested comment on how to ensure that the 130
ppmv concentration-based standard would ensure that total chlorine
emission rates (lb/hr) would not increase to levels that may exceed the
Hazard Index limit of 1.0 given that: (1) The partitioning ratio
between HCl and chlorine could change over time such that a larger
fraction of total chlorine could be emitted as chlorine, which has a
much lower health risk threshold; and (2) the mass emission rate of
total chlorine could increase. See 69 FR at 21306.
The commenter has addressed the concern about the mass emission
rate of total chlorine potentially increasing by suggesting that the
health-based standard include a limit on the feedrate of total chlorine
and chloride at the level used in their risk assessment supporting a
separate national standard for cement kilns. The commenter has also
addressed the concern about the HCl and chlorine apportionment ratio
changing over time by suggesting that the standard also include a
requirement that the Hazard Index of 1.0 not be exceeded. We agree that
sources need to account for variability in the chlorine to HCl ratio
(see Sec. 63.1215(b)(6)) and that periodic checks to ensure that the
Hazard Index of 1.0 is not exceeded are needed. We believe the best way
to ensure that the health-based compliance alternatives for total
chlorine for cement kilns are protective with an ample margin of safety
is through the procedures of Sec. 63.1215 where site-specific emission
rate limits are established rather than under a separate national
standard for cement kilns.
VIII. Implementation and Compliance
A. Compliance Assurance Issues for both Fabric Filters and
Electrostatic Precipitators (and Ionizing Wet Scrubbers)
1. Implementation Issues
Comment: Several commenters state that design and performance
specifications and explicit detailed test procedures to determine
conformance with the specifications are needed so that manufacturers
can certify that their bag leak detection systems and particulate
matter detection systems meet applicable criteria. Absent design and
performance specifications and test procedures, commenters assert that
the ``manufacturer's certification'' cannot ensure the performance
capabilities of the devices.
Response: In general, we believe adherence to manufacturer's
written specifications and recommendations is an appropriate approach
to reasonably ensure performance of a bag leak detection system or
particulate matter detection system, and we have retained that
provision in the final rule. We agree, however, that there may be cases
where other procedures are more appropriate than the manufacturer's
recommendations to ensure performance of a bag leak detection system or
particulate matter detection system. Consequently, the rule allows you
to request approval for alternative monitoring procedures under Sec.
63.1209(g)(1).\189\ We note that you may use references other than
EPA's Guidance Document, ``Fabric Filter Bag Leak Detection Guidance,''
September 1997 to identify appropriate performance specifications for
the bag leak detection system or particulate matter detection system,
including: PS-11 for PM CEMS; PS-1 for opacity monitors; and CPS-001
for opacity monitoring below 10% opacity. You may use these references
to support your request for additions to, or deviations from,
manufacturer's specifications.
---------------------------------------------------------------------------
\189\ See discussion in Part Five, Section III.C, for an
explanation of how the alternative monitoring provisions of Sec.
63.1209(g)(1) relate to those of Sec. 63.8(f).
---------------------------------------------------------------------------
Comment: One commenter states that bag leak detection systems and
particulate matter detection systems should have a detection limit of
1.0 mg/acm to ensure peak performance is maintained rather than
explicitly allowing sources to request approval for a detection limit
on a site-specific basis as the rule currently allows. Several other
commenters state that the bag leak detection system or particulate
matter detection system need not have a detection limit as low as 1.0
mg/acm to detect increases in normal emissions. One commenter believes
that bag leak detection systems installed on cement kilns should be
allowed to have a detection limit of 10 mg/acm because: (1) A detection
limit requirement of 10 mg/acm is more than sufficient to protect the
particulate matter emission limit and to detect increases in
particulate matter concentration given that the current particulate
matter emission limit for existing kilns is 63 mg/dscm; (2) a detection
limit requirement of 10 mg/acm is consistent with the requirement for
bag leak detection systems in Subpart LLL, Part 63, for cement plants
that choose to install bag leak detection systems on finish mills and
raw mills, for bag leak detection systems and particulate matter
detection systems installed on lime kilns under Subpart AAAAAA, and for
industrial boilers under Subpart DDDDD; (3) a 10 mg/acm detection limit
is achievable using state-of-the-art transmissometers (the actual
instrument used in a continuous opacity monitoring system (COMS) at
cement plants having kiln stack diameters of 2-3 meters, or greater;
and (4) it is unclear if any bag leak detection system device can
actually be demonstrated to achieve a 1.0 mg/acm detection limit except
by extrapolation from tests conducted at higher dust loadings and
theoretical arguments based on signal-to-noise ratios or other
parameters. This commenter also recommends that EPA establish a 10 mg/
am\3\ detection limit for all cement kilns rather than provide for
site-specific determinations because allowing site-specific
determinations is likely to create confusion in the selection of
monitoring devices and further complicate the manufacturer's
certification of performance requirements.
Response: The current requirement for the bag leak detection system
sensitivity/detection limit applicable to incinerators and lightweight
aggregate kilns is 1.0 mg/acm unless you demonstrate under Sec.
63.1209(g)(1) that a lower sensitivity (i.e., higher detection limit)
would detect bag leaks. We proposed to apply the bag leak detection
system requirements to all hazardous waste combustors equipped with
fabric filters and promulgate that requirement today. Although we also
requested comment whether detection limits higher than 1.0 mg/acm
should be allowed, none of the comments has convinced us to alter our
view that the rule should allow higher detection limits on a site-
specific basis. Similarly,
[[Page 59487]]
we believe that the same detection limit requirement should apply to
particulate matter detection systems that you may elect to use for
compliance monitoring for your electrostatic precipitator or ionizing
wet scrubber in lieu of site-specific operating parameter limits.
Both bag leak detection systems and particulate matter detection
systems must be able to detect particulate emission in the range of
normal concentrations. For example, to establish the alarm level for
the bag leak detection system, you must first adjust detector gain/
sensitivity and response time based on normal operations. Although the
alarm level for particulate matter detection systems will be
established based on operations during the comprehensive performance
test or higher (see discussion below), the detector must be responsive
within the range of normal operations for you to effectively minimize
exceedances of the alarm level.
The range of normal emission concentrations will generally be well
below both the particulate matter standard and emissions during the
comprehensive performance test. Consequently, we disagree with
commenters that believe the detection limit need only be within the
range of emissions at the particulate matter emission standard. On the
other hand, normal emissions may be well above 1.0 mg/acm such that a
higher detection limit (e.g., 10 mg/acm) may be appropriate on a site-
specific basis.
We also disagree with the comment that bag leak detection systems
(or particulate matter detection systems) may not be able actually to
achieve a 1.0 mg/acm detection limit. EPA is aware of bag leak
detection system instruments certified to meet levels of 0.2 mg/m\3\
and particulate matter detection systems can readily achieve detection
limits well below 1.0 mg/acm.\190\
---------------------------------------------------------------------------
\190\ USEPA, ``Technical Support Document for HWC MACT
Standards, Volume IV: Compliance with the HWC MACT Standards,''
September 2005, Appendix C, Section 4.0.
---------------------------------------------------------------------------
Comment: One commenter states that a continuous opacity monitoring
system (COMS) that can achieve a detection level of 10 mg/acm or less
can be used to monitor electrostatic precipitator performance. The
commenter believes that allowing a COMS for compliance under Subpart
EEE is also appropriate because cement kilns will be operating under
the requirements of Subpart LLL (for cement kilns that do not burn
hazardous waste) at times, which requires compliance with an opacity
standard using a COMS.
Response: You may use a COMS (i.e., transmissometer) that meets the
detection limit requirement as discussed above (i.e., 1.0 mg/acm or a
higher detection limit that you document under an alternative
monitoring petition under Sec. 63.1209(g)(1) would routinely detect
particulate matter loadings during normal operations) as the detector
for your bag leak detection system or particulate matter detection system.
2. Compliance Issues
Comment: One commenter states that, if the bag leak detection
system or particulate matter detection system exceeds the alarm level
or an operating parameter limit (OPL) is exceeded, the automatic waste
feed cutoff (AWFCO) system must be initiated. Allowing a source to
exceed the alarm level for 5% of the time in a 6-month period does not
ensure continuous compliance.
Response: Although the AWFCO system must be initiated if an OPL is
exceeded, we believe that allowing exceedances of the bag leak
detection system or particulate matter detection system alarm level up
to 5% of the time in a 6-month period is reasonable. Requiring
initiation of the AWFCO for an exceedance of an OPL is reasonable
because sources generally can control directly the parameter that is
limited. Examples are the feedrate of metals or chlorine, or pressure
drop across a wet scrubber. Bag leak detection systems and particulate
matter detection systems, however, measure mass emissions of
particulate matter, a parameter that is affected by many interrelated
factors and that is not directly controllable. We believe that the 5
percent alarm rate is a reasonable allowance for sources due to
difficult-to-control variations in particulate matter emissions. More
important, although the bag leak detection system and particulate
matter detection system measure mass emissions of particulate matter,
the detector response is not correlated to particulate matter emission
concentrations to the extent necessary for compliance monitoring.\191\
Thus, triggering the alarm level is not evidence that the particulate
matter emission standard has been exceeded.
---------------------------------------------------------------------------
\191\ Actually, the BLDS is not correlated at all to PM
concentrations, and the alarm level for a PMDS may or may not be
approximately correlated to PM concentrations. See Sec. 63.1206(c)(9).
---------------------------------------------------------------------------
The purpose of a BLDS or PMDS is to alert the operator that the PM
control device is not functioning properly and that corrective measures
must be undertaken. We believe that using a BLDS or PMDS for compliance
assurance better minimizes emissions of PM (and metal HAP) than use of
operating parameter limits (which are linked to the automatic waste
feed cutoff system). APCD operating parameters often have an uncertain
relationship to PM emissions while the BLDS and PMDS provide real-time
information on actual PM mass emission levels.\192\
---------------------------------------------------------------------------
\192\ Moreover, for FFs, we are not aware of any APCD operating
parameters that correlate well with PM emissions. Thus, sources must
use a BLDS or PMDS for compliance assurance. For ESPs and IWSs, we
are not aware of generic APCD parameters that correlate well with PM
emissions. See discussion below in Section VIII.C of the text.
Consequently, although the rule allows sources with ESPs and IWSs to
establish site-specific operating parameter limits, sources are
encouraged to use a PMDS.
---------------------------------------------------------------------------
Comment: One commenter states that requiring a notification if the
bag leak detection system or particulate matter detection system set
point is exceeded more than 5% of the time in a 6-month period is not
cost-effective. Sources using bag leak detection systems have not
linked exceedances to the data logging system and would incur an
expense to do so.
Response: We continue to believe that limiting the aggregate
duration of exceedances in a 6-month period is a reasonable approach to
gage the effectiveness of the operation and maintenance procedures for
the combustor. We note that recent MACT standards for several other
source categories use this approach, including standards for industrial
boilers and process heaters and standards for lime kilns.
Comment: One commenter states that EPA did not present a rationale
for requiring a notification within 5 working days if the bag leak
detection system or particulate matter detection system set point is
exceeded more than 5% of the time during a 6-month period. The
commenter notes that this notice is not required under the Subpart
DDDDD boiler and process heater MACT. The commenter also notes that the
source is required to take corrective measures under both the operation
and maintenance plan and bag leak detection systems and particulate
matter detection systems requirements. The commenter believes that
requiring a report to the permitting authority is duplicative,
unnecessary, and increases the burden on regulated facilities without
providing additional protection to human health or the environment.
Response: If a source exceeds the alarm set point more than 5% of
the time in a 6-month period, it is an indication that the operation
and maintenance plan may need to be revised. Requiring the source to
report the excess exceedances to the permitting
[[Page 59488]]
authority serves as a notification that the authority may need to
review the operation and maintenance plan with the source to determine
if changes are warranted.
We agree with the commenter, however, that it is not necessary to
require that the report be submitted within five working days of the
end of the 6-month block period. Consequently, the final rule requires
you to submit the report within 30 days of the end of the 6-month block
period. Allowing 30 days to submit the report rather than 5 days as
proposed is reasonable. We are concerned that 5 days may not be enough
time to complete the report given that several exceedances toward the
end of the 6-month block period may cause you to exceed the 5% time
limit and that there may be many individual exceedances that need to be
included in the report. We acknowledge that it may take some time to
prepare the report given that you must describe the causes of each
exceedance and the revisions to the operation and maintenance plan you
have made to mitigate the exceedances.
Comment: One commenter notes that there is no guidance on how to
calculate when the set-point has been exceeded more than 5 percent of
the operating time within a 6 month period. The commenter notes that
the MACT for industrial boilers and process heaters provides minimal
instruction on how this is to be done, but it is not specific enough to
enable facilities to ensure that they are in compliance with this
requirement.
Response: For the final rule, we have adopted the procedures
specified in the industrial boiler and process heater MACT for
calculating the duration of exceedances of the set point. Those
procedures are as follows:
1. You must keep records of the date, time, and duration of each
alarm, the time corrective action was initiated and completed, and a
brief description of the cause of the alarm and the corrective action
taken.
2. You must record the percent of the operating time during each 6-
month period that the alarm sounds.
3. In calculating the operating time percentage, if inspection of
the fabric filter, electrostatic precipitator, or ionizing wet scrubber
demonstrates that no corrective action is required, no alarm time is
counted.
4. If corrective action is required, each alarm shall be counted as
a minimum of 1 hour.
Although the commenter indicates that these procedures are not
specific enough to ensure that sources are in compliance with the
requirements, the commenter did not indicate the deficiencies or
suggest additional requirements. If you need additional guidance on
compliance with this provision, you should contact the permitting
authority.
Comment: One commenter supports the approach of listing the
shutting down of the combustor as a potential--but not mandatory--
corrective measure in response to exceeding an alarm set point. Several
commenters suggest, however, that EPA should specify that corrective
measures could include shutting off the hazardous waste feed rather
than shutting down the combustor. Other commenters state that it is
inappropriate to imply that shutting down the combustor must be part of
a corrective measures program for responding to exceedance of a set
point. These commenters believe that the requirement to take corrective
action upon the alarm is sufficiently protective. The facility should
determine if shutting down the combustor is a necessary response to
avoid noncompliance with a standard.
Response: You must operate and maintain the fabric filter,
electrostatic precipitator, or ionizing wet scrubber to ensure
continuous compliance with the particulate matter, semivolatile metals,
and low volatile metals emission standards. Your response to exceeding
the alarm set point should depend on whether you may be close to
exceeding an operating parameter limit (e.g., ash feedrate limit for an
incinerator or liquid fuel boiler equipped with an electrostatic
precipitator) or an emission standard. If so, corrective measures
should include, as commenters suggest, cutting off the hazardous waste
feed. Corrective measures could also include, however, shutting down
the combustor as the ultimate immediate corrective measure if an
emission standard may otherwise be exceeded. Consequently, the final
rule continues to require you to alleviate the cause of the alarm by
taking the necessary corrective measure(s) which may include shutting
down the combustor. This provision does not imply that shutting down
the combustor is the default corrective measure. Rather, it implies
that the ultimate immediate response, absent other effective corrective
measures, would be to shut down the combustor.
Comment: One commenter states that periods of time when the
combustor is operating but the bag leak detection system or particulate
matter detection system is malfunctioning should not be considered
exceedances of the set-point.
Response: If the bag leak detection system or particulate matter
detection system is malfunctioning, the source cannot determine whether
it is operating within the alarm set point. Accordingly, it is
reasonable to consider periods when the bag leak detection system or
particulate matter detection system is malfunctioning as exceedances of
the set point.
B. Compliance Assurance Issues for Fabric Filters
Comment: One commenter states that establishing the set point for
the bag leak detection system at twice the detector response achieved
during bag cleaning as recommended by EPA guidance would not be
sensitive enough to detect gradual degradation of the fabric filter,
nor would it be low enough to require the operator of the source to
take corrective measures that would ensure effective operation of the
baghouse over time.
Response: The commenter expresses the same concern that EPA raised
at proposal. See 69 FR at 21347. We have concluded, however, that it
may be problematic to establish an alarm set point for fabric filters
based on operations during the comprehensive performance test. This is
because, as noted in earlier responses and at 69 FR at 21233, it is
much more difficult to ``detune'' a fabric filter than an electrostatic
precipitator to maximize emissions during the performance test.\193\
Consequently, emissions from fabric filters that have not been detuned
during the performance test may not be representative of the range of
normal emissions caused by factors such as bag aging. Baghouse
performance degrades over time as bags age. In addition, establishing
the alarm set point based on operations during the performance test for
baghouses that have not been detuned would establish more stringent
compliance requirements on sources that perform the best--the lower the
emissions, the lower the alarm set point. This would unfairly penalize
the best performing sources.
---------------------------------------------------------------------------
\193\ One approach to detune a fabric filter to simulate the
extreme high range of normal operations would be to install a
butterfly valve that allows a portion of the combustion gas to by-
pass a section of the baghouse.
---------------------------------------------------------------------------
For these reasons, the final rule requires you to establish the
alarm set-point for bag house detection systems using principles
provided in USEPA, ``Fabric Filter Bag Leak Detection Guidance,'' (EPA-
454/R-98-015, September 1997).
Comment: One commenter states that the bag leak detection system
requirement should not apply to the coal mill baghouse for cement kilns
with indirect-fired coal mill systems where a fraction of kiln gas is taken
[[Page 59489]]
from the preheater and routed to the coal mill and subsequently to a
baghouse before entering the stack. The commenter notes that the PM in
this gas is nearly exclusively coal dust, and the baghouse is
substantially smaller than the baghouse for the kiln.
Response: We believe that a bag leak detection system is a
reasonable approach to monitor emissions for the coal mill baghouse to
ensure compliance with the particulate matter (and semivolatile and low
volatile metals) emission standards. These systems are inexpensive to
install and operate. Annualized costs are approximately $24,000.\194\
Although the commenter did not suggest an alternative monitoring
approach, and we are not aware of a less expensive and effective
approach, we note that sources may petition the permitting authority
under Sec. 63.1209(g)(1) to request an alternative monitoring approach.
---------------------------------------------------------------------------
\194\ USEPA, ``Technical Support Document for HWC MACT
Standards, Volume IV: Compliance with the HWC MACT Standards,''
September 2005, Appendix C.
---------------------------------------------------------------------------
C. Compliance Issues for Electrostatic Precipitators and Ionizing Wet
Scrubbers
Comment: Several commenters believe that a particulate matter
detection system may not be necessary for monitoring of electrostatic
precipitators and ionizing wet scrubbers. Commenters state that site-
specific operating parameter limits linked to the automatic waste feed
cutoff system can effectively monitor and ensure the performance of
electrostatic precipitators and ionizing wet scrubbers. Particulate
matter detection systems on cement kilns would have to operate in a
high moisture stack environment (all kilns burning hazardous waste that
are equipped with electrostatic precipitators are wet process kilns),
with the potential for condensation and/or water droplet interference.
Commenters state that when water droplets are present, many of these
devices are not applicable.
Response: The final rule provides sources equipped with
electrostatic precipitators or ionizing wet scrubbers the alternative
of using a particulate matter detection system or establishing site-
specific operating parameter limits for compliance assurance. If a
particulate matter detection system is used, corrective measures must
be taken if the alarm set point is exceeded. If the source elects to
establish site-specific operating parameter limits, the limits must be
linked to the automatic waste feed cutoff system.
In response to commenters' concern that high moisture stack gas may
be problematic for particulate matter detection systems, we note that
extractive light-scattering detectors and beta gauge detectors can
effectively operate in high moisture environments. We acknowledge,
however, that the cost of these extractive detector systems is
substantially higher than transmissometers or in situ light-scattering
detectors.
Comment: One commenter states that EPA must set minimum total power
requirements for both ionizing wet scrubbers and electrostatic
precipitators because allowing permit officials to establish compliance
operating parameters on a site-specific basis frustrates the intention
of the CAA by obviating the requirements for federal standards. The
commenter asserts that a minimum total power requirement is
monitorable, recordable, and reportable, three requirements that are
necessary for these facilities to come into, and remain in compliance
with, their Title V operating permits.
Other commenters state that electrostatic devices are not easily
characterized by operating parameters in a ``one-size-fits-all''
fashion. The significant operating parameters for electrostatic devices
are secondary voltage, secondary current, and secondary power (the
product of the first two items). The relationship between these
parameters and performance of the unit differ between applications and
unit types. For example, inlet field power can increase as unit
performance appears to decrease. In this case, an operating parameter
other than secondary power by field would be more appropriate. The
commenter notes that, in its various proposals over the years, EPA has
discussed a number of approaches to establish operating parameter
limits for electrostatic devices, including: Minimum total secondary
power; minimum secondary power by field; pattern of increasing power
from inlet to outlet field; and minimum secondary power of the last \1/
3\ of fields (or the last field). Commenters have also proposed:
minimum specific power (secondary power divided by flue gas flow rate);
minimum secondary voltage and/or secondary current; and total secondary
voltage and/or secondary current. The commenter concludes that it is
not surprising that there is so little agreement on the right approach,
because different units and applications respond differently. EPA's
proposal to let facilities and local regulators determine the best
approach is far wiser than regulating from a distance.
Response: We agree with the commenters that state that it is not
practicable to establish operating parameter limits that would
effectively ensure performance of all electrostatic devices.
Accordingly, the final rule continues to allow sources to establish
site-specific operating parameter limits for these devices.
We disagree with the commenter's assertion that site-specific
operating parameter limits obviate the requirements for federal
standards. The site-specific operating parameter limits merely reflect
the truism that no two sources are identical and so what each needs to
do to comply with the uniform standards may differ. The final rule
provides consistent, federally-enforceable emission standards.
Necessary flexibility in compliance assurance for those emission
standards does not undermine the uniformity of those standards. In
addition, we disagree with the commenter's concern that without a
minimum power limit, there will be no monitorable, recordable, and
reportable Title V permit limits for electrostatic devices. To the
contrary, site-specific operating parameter limits can and will be
monitored, recorded, reported, and linked to the automatic waste feed
cut-off system. And, if a source elects to use a particulate matter
detection system in lieu of establishing site-specific operating
parameter limits, the detector response will be monitored, recorded,
reported, and linked to requirements to take corrective measures if the
alarm set point is exceeded.
Comment: One commenter asserts that the use of electrostatic
precipitator total power input data (sum of the product of kilovolts
times milliamps for each electrostatic precipitator field) is one
acceptable approach as a site-specific parameter to monitor
electrostatic precipitator performance. Limits on power input for each
field (or particular fields) are not warranted.
Response: A limit on total power input to a multifield
electrostatic device is generally not an acceptable operating parameter
for compliance assurance. We have documented that when total power
input was held constant for a four-field electrostatic precipitator
while the power input to the fourth field was decreased, emissions of
particulate matter doubled from 0.06 gr/dscf to 0.12 gr/dscf. See 66 FR
at 35143 (July 3, 2001). Thus, if the total power input during the
comprehensive performance test were used as the operating parameter
limit, particulate matter emissions could exceed the emission
[[Page 59490]]
standard because of changes in other parameters that were not limited
even though total power input did not exceed the parametric limit.
Notwithstanding our concern that a limit on total power input to a
multifield electrostatic device is generally not an effective operating
parameter for compliance assurance, this does not preclude you from
documenting to the permitting authority that total power input is an
effective compliance assurance parameter for your source. See Sec.
63.1209(m)(1)(iv).
Comment: Several commenters suggest that the rule should offer
various approaches to establish an achievable particulate matter
detection system alarm level on a site-specific basis in lieu of the
approach we proposed (i.e., average detector response during the
comprehensive performance test): (1) Use the 2 times the maximum peak
height or 3 times the baseline concepts developed in EPA's bag leak
detection guidance documents; (2) allow spiking to set the alarm set
point given that PS 11 allows for spiking as a way to calibrate PM
CEMs; (3) establish the limit as the 99th percentile upper prediction
limit of the average response during each performance test run instead
of the average of the test run averages; (4) allow upward extrapolation
from the average of the test run averages to some percentage of the
particulate matter emissions standard (fraction could be variable
depending upon how close to the standard the facility is during the
compliance test); or (5) set the alarm point at the maximum test run.
Response: We agree with several of the commenters' suggestions:
explicitly allowing spiking (and emission control device detuning)
during the comprehensive performance test to maximize controllable
operating parameters to simulate the full range of normal operations;
and upward extrapolation of the detector response. See discussion below.
The final rule is consistent with commenters' suggestion to
establish the alarm level for particulate matter detection systems on
fabric filters based on the concepts in the Agency's guidance document
on bag leak detection systems. Commenters made this suggestion in
response to our request for comments on requiring particulate matter
detection systems on fabric filters and establishing the alarm level
based on the detector response during the comprehensive performance
test. See 69 FR at 21347. The final rule requires bag leak detection
systems on all fabric filters and suggests that you establish the alarm
level using concepts in the bag leak detection system guidance. \195\
---------------------------------------------------------------------------
\195\ Note that a bag leak detection system is a type of
particulate matter detection system for purposes of this discussion.
A triboelectric detector is normally used for a bag leak detector
system because it is very inexpensive and has a low detection limit.
A triboelectric detector meets the criterion for a particulate
matter detector in a particulate matter detection system in that it
detects relative mass emissions of particulate matter within the
range of normal emission concentrations. (Note further, however,
that a triboelectric detector cannot be correlated to particulate
matter concentrations and thus cannot be used as a particulate
matter CEMS. Note also that a triboelectric detector cannot be used
on sources equipped with electronic control devices.) The alarm
level for a bag leak detection system would be established using the
concepts discussed in the Agency's guidance document on bag leak
detection systems. The alarm level for a particulate matter
detection system used on a fabric filter, however, (preferable with
a detector other than a tribolectric device that could be correlated
to PM concentrations) would be established based on the detector
response during the comprehensive performance test.
---------------------------------------------------------------------------
Neither the suggestion to establish the alarm level at the 99th
percentile upper prediction limit (UPL99) based on the average response
during the comprehensive performance test runs nor the suggestion to
establish the alarm level at the maximum test run response would
control PM emissions at the level achieved during the performance test
or provide some assurance that the PM standard was not being exceeded,
unless the detector response is correlated to PM concentrations. For
example, if the detector response does not relate linearly to PM
concentration (or if the response changes w/changes in particulate
characteristics), the UPL99 detector response could relate to a much
higher (e.g., 99.9th percentile) PM concentration. In addition, even if
the detector response were correlated to PM concentration, there is no
assurance that the correlation would be consistent over the range of
the average detector response during the performance test to the UPL99
detector response. Note that under PS-11 for PM CEMS, even after
complying with rigorous procedures to correlate the detector response
to PM concentrations, the detector response may be extrapolated only to
125% of the highest PM concentration used for the correlation. Thus,
the final rule does not use these approaches to establish the alarm level.
If you elect to use a particulate matter detection system in lieu
of site-specific operating parameters for your electrostatic
precipitator or ionizing wet scrubber, you must establish the alarm
level using either of two approaches. See Appendix C of USEPA,
``Technical Support Document for HWC MACT Standards, Volume IV:
Compliance with the HWV MACT Standards,'' September 2005. Under either
approach, you may maximize controllable operating parameters during the
comprehensive performance test to simulate the full range of normal
operations (e.g., by spiking the ash feedrate and/or detuning the
electrostatic device).\196\
---------------------------------------------------------------------------
\196\ Note, however, that bypassing or detuning an emission
control system could cause PM stratification and could make it
difficult to pass the PS-11 performance criteria you use as
guidelines for a PMDS.)
---------------------------------------------------------------------------
You may establish the alarm set-point as the average detector
response of the test condition averages during the comprehensive
performance test.
Alternatively, you may establish the alarm set point by
extrapolating the detector response. Under the extrapolation approach,
you must approximate the correlation between the detector response and
particulate matter emission concentrations during an initial
correlation test. You may extrapolate the detector response achieved
during the comprehensive performance test (i.e., average of the test
condition averages) to the higher of: (1) A response that corresponds
to 50% of the particulate matter emission standard; or (2) a response
that correlates to 125% of the highest particulate matter concentration
used to develop the correlation.
To establish an approximate correlation of the detector response to
particulate matter emission concentrations, you should use as guidance
Performance Specification-11 for PM CEMS (40 CFR Part 60, Appendix B),
except that you need only conduct only 5 runs to establish the initial
correlation rather than a minimum of 15 runs required by PS-11. In
addition, the final rule requires you to conduct an annual Relative
Response Audit (RRA) for quality assurance as required by Procedure 2--
Quality Assurance Requirements for Particulate Matter Continuous
Emission Monitoring Systems at Stationary Sources, Appendix F, Part
60.\197\ The RRA is required on only a 3-year interval, however, after
you pass two sequential annual RRAs.
---------------------------------------------------------------------------
\197\ You perform an RRA by collecting three simultaneous
reference method PM concentration measurements and PM CEMS measurements
at the as-found source operating conditions and PM concentration.
---------------------------------------------------------------------------
The rule requires only minimal correlation testing because the
particulate matter detection system is used for compliance assurance
only--as an indicator for reasonable assurance that an emission
standard is not exceeded. The particulate matter detection system is
not used for compliance monitoring--as an indicator of continuous
compliance with an
[[Page 59491]]
emission standard. Because particulate matter detection system
correlation testing and quality assurance is much less rigorous than
the requirements of PS-11 for a PM CEMS, the particulate matter
detection system response cannot be used as credible evidence of
exceedance of the emission standard.
D. Fugitive Emissions
Comment: A commenter does not support EPA's proposed approach to
allow alternative techniques that can be demonstrated to prevent
fugitive emissions without the use of instantaneous pressure limits
given that the CAA requires continuous compliance with the standards
and given positive pressure events can result in fugitive emissions,
irrespective of facility design.
Response: Rotary kilns can be designed to prevent fugitive
emissions during positive pressure events. As stated in the February
14, 2002 final rule, and subsequently in the April 20, 2004 proposed
rule, there are state-of-the-art rotary kiln seal designs (such as
those with shrouded and pressurized seals) which are capable of
handling positive pressures without fugitive releases. See 67 FR at
6973 and 69 FR at 21340. We have included documentation of such kiln
designs in the docket.\198\ Instantaneous combustion zone pressure
limits thus may not be necessary to assure continuous compliance with
these fugitive emission control requirements. Our approach to allow
alternative techniques that have been demonstrated to prevent fugitive
emissions is therefore reasonable and appropriate. We note that these
alternative techniques must be reviewed and approved by the appropriate
delegated regulatory official.\199\
---------------------------------------------------------------------------
\198\ See USEPA, ``Technical Support Document for the HWC MACT
Standards, Volume IV: Compliance With the HWC MACT Standards,''
September 2005, Section 10.
\199\ See Sec. 63.1206(c)(5)(i)(C) and (D).
---------------------------------------------------------------------------
Comment: A commenter disagrees with EPA's clarification that
fugitive emission control requirements apply only to fugitives
attributable to the hazardous waste, given that the CAA does not
distinguish between HAP emissions that come from hazardous waste
streams and other HAP emissions.
Response: The fugitive emission control requirements in today's
final rule originated from the RCRA hazardous waste combustion fugitive
emission control requirements for incinerators and boilers and
industrial furnaces.\200\ The primary focus of these RCRA requirements
is to ensure hazardous waste treatment operations are conducted in a
manner protective of human health and the environment.\201\ It is
therefore appropriate to clarify that the intent of this requirement is
to control fugitive emission releases from the combustion of hazardous
waste.
---------------------------------------------------------------------------
\200\ See Sec. 266.102(e)(7) and Sec. 264.345(d).
\201\ Section 3004(a) of RCRA requires the Agency to promulgate
standards for hazardous waste treatment, storage, and disposal
facilities as necessary to protect human health and the environment.
The standards for hazardous waste incinerators generally rest on
this authority. Sec. 3004(q) of RCRA requires the Agency to
promulgate standards for emissions from facilities that burn
hazardous waste fuels (e.g., cement and lightweight aggregate kilns,
boilers, and hydrochloric acid production furnaces) as necessary to
protect human health and the environment.
---------------------------------------------------------------------------
Furthermore, MACT requirements for source categories that do not
combust hazardous waste (e.g., industrial boilers, Portland cement
kilns, and commercial and industrial solid waste incinerators) do not
have combustion chamber fugitive emission control requirements for the
non-hazardous waste inputs or outputs (e.g., clinker product for cement
kilns or coal and natural gas fuels for industrial boilers). We have
previously taken the position that emissions not affected by the
combustion of hazardous waste (e.g., clinker coolers, raw material
handling operations, etc.) are regulated pursuant to the applicable
nonazardous waste MACT rules.\202\, \203\ We conclude the clarification
that the fugitive emission control requirements applies only to
fugitive emissions that result from the combustion of hazardous waste
is appropriate because it regulates emissions attributable to
nonhazardous waste streams to the same level of stringency that
otherwise would apply if the source did not combust hazardous waste.\204\
---------------------------------------------------------------------------
\202\ See 69 FR at 21203 and 64 FR at 52871, and Sec.
63.1206(b)(1)(ii).
\203\ Portland cement manufacturing facilities that combust
hazardous waste are subject to both Subpart EEE and Subpart LLL, and
hydrochloric acid production facilities that combust hazardous waste
may be subject to both Subpart EEE and Subpart NNNNN. In these
instances Subpart EEE controls HAP emissions from the cement kiln
and hydrochloric acid production furnace stack (and also fugitive
emissions from the combustion chamber), while Subparts LLL and NNNNN
would control HAP emissions from other operations that are not
directly related to the combustion of hazardous waste (e.g., clinker
cooler emissions for cement production facilities, and hydrochloric
acid product transportation and storage for hydrochloric acid
production facilities).
\204\ This issue has little relevance given that the measures
taken to control the fugitive emissions from the combustion of
hazardous waste will also control the fugitive emission associated
with other feedstreams.
---------------------------------------------------------------------------
Comment: A commenter states that the instantaneous monitoring
requirements are inappropriate because (1) EPA has not demonstrated
that the average of the top 12% of boilers are capable of operating
with no instantaneous deviations from the negative pressure
requirements; and (2) these requirements, though not standards
themselves, effectively increase the stringency of the standard itself
beyond what even the best available technology can achieve.
Response: As previously discussed, the fugitive emission control
requirements included in today's rule originated from the RCRA
hazardous waste combustion chamber fugitive emission control
requirements. These provisions allow sources to control fugitive
emissions by ``maintaining the combustion zone pressure lower than
atmospheric pressure, or an alternative means of control equivalent to
maintenance of combustion zone pressure lower than atmospheric
pressure.'' All sources that must comply with the provisions of this
rule are, or were, required to control fugitive emissions from the
combustion unit pursuant to RCRA.
The monitoring requirements in today's rule do not increase the
stringency of the standard beyond what the best available technology
can achieve. Although we do not have data that confirm negative
pressure is being maintained on an instantaneous basis (as we define
it)\205\ for at least 12 percent of the boilers, we believe this is
current practice and readily achievable by most sources.\206\ These
requirements have been in force for many years, and there is no basis
for stating that they are unachievable (EPA is not aware of
industrywide noncompliance with these provisions, the necessary premise
of the comment). First, maintaining negative pressure is the option
that most boilers elect to implement to demonstrate compliance with the
RCRA fugitive emission control requirements. Second, negative pressure
is readily achieved on an instantaneous basis in boilers through use of
induced draft fans. Third, the requirements we are finalizing today for
boilers are identical to the fugitive emission control requirements
that hazardous waste incinerators, cement kilns, and lightweight
aggregate kilns are currently complying with pursuant to the EEE
interim standard regulations. See Sec. 63.1206(c)(5). Most of these
sources maintain negative combustion chamber pressure through use of
induced draft fans, providing further evidence that continuously
maintaining combustion
[[Page 59492]]
zone pressure lower than ambient pressure is readily achievable by well
designed and operated boilers.\207\
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\205\ The February 14, 2002 Final Amendments Rule clarifies that
that a reasonable pressure monitoring frequency that could meet the
intent of ``instantaneous'' would be once every second. See 67 FR at 6974.
\206\ Commenters did not provide data to the contrary.
\207\ The commenter did not provide information that would lead
us to conclude that these requirements are harder to implement for
boilers than for incinerators, cement kilns, and lightweight
aggregate kilns.
---------------------------------------------------------------------------
We note that use of instantaneous pressure monitoring is not a
requirement. A source can elect to implement any of the four compliance
options to control combustion system leaks as well as request to use
alternative monitoring approaches. See Sec. Sec. 63.1206(c)(5) and
63.1209(g). The instantaneous pressure monitoring option offers sources
a method that satisfies the intent of the rule that can be applied at
numerous sources. The inclusion of this requirement in today's rule is
thus an attempt to simplify the review process for both regulators and
affected sources; the absence of prescriptive compliance options in
this case may likely result in time-consuming site-specific
negotiations that would prolong the review and approval of
comprehensive performance test workplans.
Comment: A commenter believes that requiring an instantaneous
waste-feed cutoff when these pressure excursions occur is short-sighted
and will result in greater HAP emissions. The commenter recommends EPA
instead allow the use of reasonable pressure averaging periods in lieu
of instantaneous pressure requirements.
Response: As discussed in the February 14, 2002 Final Amendments
Rule, automatic waste feed cutoffs are appropriate non-compliance
deterrents, and are necessary whenever an operating limit is exceeded.
See 67 FR at 6973. Pressure excursions that result in combustion system
leaks (and subsequently lead to automatic waste feed cutoffs) should be
prevented by maintaining negative pressure in the combustion zone. We
agree that needless triggering of automatic waste feed cutoffs due to
short term pressure fluctuations that do not result in combustion
system leaks would provide less environmental protection, not more.
Today's rule offers three alternative options that do not require the
use of instantaneous pressure monitoring to control combustion system
leaks. See Sec. 63.1206(c)(5). The use of averaging periods in these
alternatives is not prohibited. Sources that elect to use an
alternative compliance option must demonstrate that the alternative
method is equivalent to maintaining combustion zone pressure lower than
ambient pressure or, that the alternative approach prevents fugitive
emissions.
E. Notification of Intent To Comply and Compliance Progress Report
1. Notice of Intent To Comply
In the NPRM, we proposed to re-institute the Notification of Intent
to Comply (NIC) because we felt that it offered many benefits in the
early stages of MACT compliance. As discussed in the 1998 ``fast
track'' rule (63 FR 33782) and in the proposal, the NIC serves several
purposes: as a planning and communication tool in the early
implementation stages, to compensate for lost public participation
opportunities when using the RCRA streamlined permit modification
procedure to make upgrades for MACT compliance, and as a means to share
information and provide public participation opportunities that would
be lost when new units are not required to comply with certain RCRA
permit requirements and performance standards. Please refer to the
proposal at 69 FR 21313-21316 for additional discussion of the
regulatory history, purpose, and implementation of the NIC provisions.
Overall, most commenters supported our decision to finalize NIC
provisions. However, they also feel that the NIC should only be
required for sources that have not completed a NIC previously (i.e.,
Phase 2 sources or Phase 1 sources that did not meet the previous NIC
deadline) and for sources that need to make upgrades to comply with the
final standards (i.e., either Phase 1 or Phase 2). They suggest that if
sources do not need to make upgrades, then they should not be required
to complete the NIC process, if they had done so previously. To require
a second NIC would only add to the administrative burden and is not in
line with Agency efforts to reduce reporting burdens. We agree that if
Phase 1 sources do not need to make upgrades to comply with the
Replacement Standards and if they completed the NIC process before,
then it is not necessary to do so again.
In addition to the comment discussed above, a few commenters
proposed that for sources who must still comply with the NIC because
they wish to make upgrades, that the NIC public notice be combined with
the Title V re-opening or renewal public notice. They point out that
sources with existing Title V permits will have their permits re-opened
or renewed to incorporate the new applicable requirements (i.e., Phase
1 Replacement or even Phase 2 Standards) shortly after the NIC public
notice and meeting are to occur. Title V permit re-openings and
renewals require: public notice, a minimum of 30 days for comment, and
an opportunity to request a hearing.
While we do agree that the Title V re-opening and renewal
requirements provide adequate information to the public and an
opportunity for the public to comment and request a hearing, we are
concerned that the timing requirements for the NIC may not correspond
with the timing requirements for title V permit reopenings, revisions,
and renewals. The public review of the draft NIC and subsequent public
meeting are scheduled to occur 9 and 10 months, respectively, after the
rule's effective date. On the other hand, Title V permits for major
sources that have a remaining permit term of greater than 3 years from
the rule's promulgation date will need to be re-opened, but this re-
opening may not occur until 18 months beyond the promulgation date of
the rule. Also, Title V permits that have a remaining permit term of
less than 3 years from the rule's promulgation date will need to be
renewed, but the timing of the renewal is contingent upon the
individual permit term, not the timing requirements for public review
of the draft NIC and public meeting. Thus, we do not believe there is
ample opportunity to combine the requirements of the NIC and Title V
process for the vast majority of sources.\208\ Also, those sources that
need to make upgrades to comply with the final standards and that need
to modify any applicable conditions in their RCRA permit will not be
able to request the streamlined modification procedure (see 40 CFR
270.42(j)) until they meet the NIC requirements. So the earlier they
comply with the NIC requirements, the earlier they can begin upgrading
their combustion units.
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\208\ We recognize that there may be instances when states can
coordinate the Title V permit re-opening, revision, and renewal
process with the NIC timeframe requirements. Where this is possible,
we encourage states (or other permitting authorities) to coordinate
the two processes. By coordinating the two, duplication with respect
to material content and public participation would be eliminated for
both sources and states.
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Another commenter suggested a change to the regulations at Sec.
63.1210(c)(1) to account for sources that will cease burning hazardous
waste prior to or on the compliance date. The regulations, as proposed,
require sources to hold an informal public meeting to discuss
anticipated activities described in the draft NIC even if they plan to
cease burning hazardous waste. The commenter also suggested a similar
change to Sec. 63.1210(b)(2) that requires the draft NIC be made
available for public review no later than 30 days
[[Page 59493]]
prior to the public meeting. We agree with the commenter that it does
not make sense to require sources that intend to cease burning
hazardous waste to submit a NIC that discusses anticipated activities
that will allow them to achieve compliance with the standards. We also
agree that it is not necessary for those sources to hold an informal
public meeting, since there are no MACT compliance activities to
discuss. However, we believe that the public should be provided notice
of the draft NIC so that they are aware of the source's intentions to
cease burning and the steps (and key dates) the source will undertake
to stop hazardous waste combustion activities.
With regard to Phase 2 sources, we had proposed that all Phase 2
sources comply with the same NIC requirements as the Phase 1 sources.
Commenters did not express opinions in favor or against the NIC for
Phase 2 sources. We believe that the NIC is beneficial in several
respects. As mentioned previously, it serves as a planning and
communication tool in the early implementation stages, it compensates
for lost public participation opportunities when using the RCRA
streamlined permit modification procedure to make upgrades for MACT
compliance, and it is a tool to share information and provide public
participation opportunities that would be lost when new units are not
required to comply with certain RCRA permit requirements and
performance standards. Ultimately, it creates more public confidence in
the permitting process and so promotes a more stable regulatory environment.
For today's rule, we are finalizing our decision to re-institute
the NIC provisions for Phase 1 and Phase 2 sources. We are including a
few minor changes and clarifications to improve the proposed regulatory
language based on commenters' suggestions. Section 63.1210(b) is
revised so that Phase 1 sources that previously complied with the NIC
requirements, and that do not need to make upgrades to comply with the
Replacement Standards, are not required to comply with the NIC again.
Sections 63.1210(b)(1)(iv) and (b)(2) have been revised and (c)(5) has
been added so that sources that intend to cease burning hazardous waste
prior to or on the compliance date are only required to prepare a
(draft) NIC, make a draft of the NIC available for public review no
later than 9 months after the effective date of the rule, and submit a
final NIC to the Administrator no later than one year following the
effective date of the rule. Last, we have revised language in Sec.
63.1210(b) based upon a commenter's concerns that the term you ``will''
implies that sources are required meet their ``estimated'' dates for
achieving key activities. We have removed ``will'' and replaced it with
``anticipate'' to more accurately represent the objective of the NIC,
which is for sources to communicate their plans for complying with the
standards in two years.
2. Compliance Progress Report
In the proposal, we explained why we thought a compliance progress
report would be beneficial. In short, we believed it would help
regulatory agencies determine whether Phase 1 and Phase 2 sources were
making sufficient headway in their efforts to meet the compliance date.
The progress report would be due to the regulatory agency at the midway
point of the 3 year compliance period and would serve to update the
information the source provided in its NIC. However, because we do not
have any experience to draw upon regarding the value of the progress
report, we requested comment on whether or not it should be required.
In response to our request for comment, all commenters were opposed
to the progress report. They cited several reasons, with the most
consistent one being that the progress report serves no useful purpose
and imposes unnecessary additional burdens on sources. As we discussed
above, sources and regulatory agencies will be focusing on the NIC as
well as initial Title V applications, re-openings, revisions, and
renewals during this three year compliance period. We agree with the
commenter who noted that there is already significant interaction
between sources and regulatory authorities during this period.
Furthermore, we learned through implementation of the Interim Standards
that some regulatory agencies found it difficult to manage the notices,
applications, requests, and test plans that were due prior to the
compliance date. Therefore, we have decided not to finalize any
compliance progress report requirements for today's rule.
F. Startup, Shutdown, and Malfunction Plan
Comment: One commenter states that an exceedance of a standard or
operating requirement during a malfunction should be a violation not
only because source owners and operators need an incentive to minimize
exceedances caused by malfunctions, but also because an exemption for
malfunction periods would violate the plain language of the CAA. The
commenter notes that an emission standard is defined by 42 U.S.C. Sec.
7602(k) as a standard that ``limits the quantity, rate, or
concentration of emissions of air pollutants on a continuous basis,
including any requirement relating to the operation of maintenance of a
source to assure continuous emission reduction, and any design,
equipment, work practice or operational standard * * *.'' The commenter
concludes that a standard that contains a malfunction exemption does
not apply ``on a continuous basis'' as required by the statute.
Likewise, the commenter concludes that an exemption for startup and
shutdown periods would also violate this unambiguous statutory language.
The commenter also notes that, although some courts have held that
a technology-based standard must provide some kind of an exemption for
unavoidable technology failures, the rationale for such an exemption is
that the underlying standard is based on the performance of a
particular control technology that cannot be expected to function
properly all of the time. The commenter believes that neither the
rationale nor the exemption apply to section 112(d) standards, which
are not based on the performance of any particular technology but
instead must reflect the ``maximum degree of reduction'' that can be
achieved, irrespective of the measures used by a source to achieve that
reduction. CAA Sec. 112(d)(2).
The commenter states that, even assuming for the sake of argument
that EPA has authority to depart from the statutory language and carve
out a startup, shutdown, and malfunction exemption, any such exemption
must be narrowly drafted to apply only where a source demonstrates that
a violation was unavoidable. See, e.g., Marathon Oil, 564 F.2d at 1272-
73. As EPA recognizes, emission exceedances that occur during SSM
events are frequently avoidable. See 69 FR at 21339/3 (noting that
``proper operation and maintenance of equipment'' helps avoid
exceedances during startup, shutdown, and malfunction events), 69 FR at
21339/2 (describing the industry view that ``some'' exceedances that
occur due to malfunctions are unavoidable). Thus, the commenter
concludes that, even if a Marathon Oil-type exemption applies to a
Sec. 112(d) standard, it would be unlawful and arbitrary for EPA to
exempt sources from liability for all emission exceedances occurring
during startup, shutdown, and malfunction events. Rather, such an
exemption could only apply where a source demonstrates that a given
exceedance was unavoidable.
[[Page 59494]]
Many other commenters state that it would be illegal to require
compliance with the emission standards and operating requirements
during startup, shutdown, and malfunction events. The commenters note
that EPA and the courts have long recognized that technology fails at
times, despite a source's best efforts to maintain compliance. For this
reason, the courts have recognized that technology-based standards such
as EPA's Sec. 112(d)(2) MACT standards must account for such
unavoidable technology failures if the standards are to be truly
``achievable.'' Thus, the standards must excuse noncompliance with the
actual emission standards during startup, shutdown, and malfunction events.
These commenters also note that EPA took the position in the
September 1999 final MACT rule for hazardous waste combustors that
exceedance of an operating requirement during startup, shutdown, or
malfunction events was a violation if hazardous waste remained in the
combustion chamber. The commenters note that industry groups challenged
the rule, and while the D.C. Circuit did not reach this issue because
it vacated the emission standards, it pointed out that ``industry
petitioners may be correct that EPA should have exempted HWCs from
regulatory limits during periods of startup, shutdown, and malfunction,
permitting sources to return to compliance by following the steps of a
startup, shutdown, and malfunction plan filed with the Agency.'' CKRC
v. EPA, 255 F.3d 855, 872 (2001). Commenters conclude that, after
reading this language, EPA officials wisely decided that hazardous
waste combustors should not be required to meet the MACT emission
standards and operating limits during startup, shutdown, and
malfunction events.
Response: We agree with commenters who state that sources must be
exempt from technology-based emission standards and operating limits
during startup, shutdown, and malfunction events. Technology is
imperfect and can malfunction for reasons that are not reasonably
preventable. The regulations must provide relief for such situations.
We believe that existing case law supports this position. See, e.g.,
Chemical Mfr's Ass'n v. EPA, 870 F. 2d at 228-230 (daily maximum
limitations established at 99th percentile reasonable because rules
also provide for upset defense for unavoidable exceedances); Marathon
Oil v. EPA, 541 F. 2d at 1272-73 (acknowledged by commenter). As
commenters noted, the D.C. Circuit also intimated in CKRC that some
type of exception from compliance with standards during startup,
shutdown and malfunction periods was required.
We do not agree with the commenter who contends that the Sec.
112(d) MACT standards are not technology-based standards because they
are not based on the performance of any particular technology but
instead must reflect the ``maximum degree of reduction'' that can be
achieved, irrespective of the measures used by a source to achieve that
reduction. On the contrary, the standards must reflect the average
performance of the best performing sources, which performance is
achieved using technical controls--air pollution control devices, and
for some pollutants, hazardous waste feedrate control. Those controls
can fail for reasons that are not reasonably preventable. We note
further that the situation was the same in the Clean Water Act cases
which the commenter seeks to distinguish. Like section 112(d)
standards, Clean Water Act standards are technology-based (reflecting
Best Practicable Technology or Best Available Technology, see CWA
sections 304 (b) and 301 (b)) and do not require use of any particular
type of technology. See also Mossville, 370 F. 3d at 1242 (EPA must
account for foreseeable variability in establishing MACT floor standards).
We agree with the commenter who states that any exemption from the
emission standards and operating requirements during malfunctions must
apply only where a source demonstrates that a violation was
unavoidable. We note that the term malfunction is defined in Sec. 63.2
as ``any sudden, infrequent, and not reasonably preventable failure of
air pollution control and monitoring equipment, process equipment, or a
process to operate in a normal or usual manner which causes, or has the
potential to cause, the emission limitations in an applicable standard
to be exceeded. Failures that are caused in part by poor maintenance or
careless operation are not malfunctions.'' We believe this definition
largely addresses the commenter's concern.
We acknowledge, however, that emissions can increase during
malfunctions and potentially exceed the standards and agree that
exceedances must be minimized. Accordingly, the final rule (and the
current rule for incinerators, cement kilns, and lightweight aggregate
kilns) requires that sources maintain compliance with the automatic
hazardous waste feed cutoff system during malfunctions and notify the
permitting authority if they have 10 or more exceedances of an emission
standard or operating limit during a 6-month block period when
hazardous waste is in the combustion chamber. See Sec.
63.1206(c)(2)(v). This will alert the permitting authority that the
source's operation and maintenance plan may not be adequate to maintain
compliance with the emission standards and that the authority may need
to direct the source to revise the plan under Sec. 63.6(e)(3)(vi).
Finally, we note that sources must report all excess emissions
semiannually under Sec. 63.10(e)(3) if an emission standard or
operating limit is exceeded, including during malfunctions.
Comment: One commenter states that any exemption for emission
exceedances during startup, shutdown, or malfunction events would
violate the RCRA mandate for standards necessary ``to protect human
health and the environment.'' 42 U.S.C. 6924(a). The commenter reasons
that, because EPA's RCRA standards are health-based rather than
technology-based, no unavoidability defense is available. Given that
EPA concludes that the hazardous waste combustor MACT rule satisfies
both its CAA and RCRA mandates, the emission standards and operating
requirements cannot be waived during startup, shutdown, and malfunction
events.
Response: We agree that the RCRA mandate to ensure protection of
human health and the environment applies at all times, including during
startup, shutdown, and malfunction events. Accordingly, the existing
MACT requirements for incinerators, cement kilns, and lightweight
aggregate kilns give sources the option of continuing to comply with
RCRA permit requirements to control emission during these events, or to
comply with special MACT requirements that are designed to be proactive
and reactive and intended to be equivalent to the incentive to minimize
emissions during these events provided by the RCRA requirements. See
existing Sec. 63.1206(c)(2)(ii). The special MACT requirements require
sources to include proactive measures in the startup, shutdown, and
malfunction plan to minimize the frequency and severity of malfunctions
and to submit the startup, shutdown, and malfunction plan to the
permitting authority for review and approval. We proposed to require
boilers and hydrochloric acid production furnaces to comply with those
same provisions providing for equivalence between the two sets of
requirements, and promulgate those provisions today.
Comment: One commenter states that the rule should clarify the
definitions of startup, shutdown, and malfunctions to preclude sources
from improperly
[[Page 59495]]
classifying as unavoidable exceedances those exceedances that could
have been avoided had the source implemented an appropriate operation
and maintenance plan. Many other commenters state that the current
definitions in Sec. 63.2 clearly define these terms.
Response: We believe the definitions of startup, shutdown, and
malfunction are clearly defined in Sec. 63.2, and combined with the
startup, shutdown, and malfunction plan requirements, will preclude
sources from improperly classifying as malfunctions events that could
have been reasonably prevented by following appropriate procedures in
the operation and maintenance plan. As discussed above, the definition
of malfunction clearly states that failures that are caused in part by
poor maintenance or careless operation are not malfunctions.
Comment: One commenter states that all stack bypasses, automatic
waste feed cutoffs, and excursions from the operating parameter limits
should be considered malfunctions.
Response: All failures resulting in stack bypasses, automatic waste
feed cutoff, and excursions from the operating parameter limits are not
malfunctions. As discussed above, failures caused in part by poor
maintenance or careless operation are not malfunctions.
Comment: One commenter states that the rule should require sources
to expand the startup, shutdown, and malfunction plan to address
specific proactive measures that the source has considered and is
taking to minimize the frequency and severity of malfunctions. Many
other commenters believe that it is not necessary to expand the scope
of the startup, shutdown, and malfunction plan beyond that required
under Sec. 63.6(e)(3) for other MACT source categories.
Response: We do not believe that it is necessary to expand the
scope of the startup, shutdown, and malfunction plan generically for
all hazardous waste combustors to address specific proactive measures
that the source has considered and is taking to minimize the frequency
and severity of malfunctions. Imposing additional requirements in
particular situations is appropriate, however. For example, as
discussed above, this expanded plan is required for sources that elect
to meet the RCRA mandate using provisions of the startup, shutdown, and
malfunction plan. See Sec. 63.1206(c)(2)(ii). In addition, the plan
with expanded scope may be appropriate for sources that have
demonstrated an inability to minimize malfunctions. Consequently, the
permitting authority should consider expanding the scope of the
startup, shutdown, and malfunction plan on a site-specific basis under
authority of Sec. 63.6(e)(3)(vii) if the source has excessive
exceedances during malfunctions. See Sec. 63.1206(c)(2)(v)(A)(3)
defining excessive exceedances during malfunctions and requiring
reporting of the exceedances in the excess emissions report required
under Sec. 63.10(e)(3).
Comment: Two commenters state that all startup, shutdown, and
malfunction plans should be submitted for review and approval by the
delegated authority and made available for a 60-day public review
period. Review and approval of the plans is needed in light of EPA's
acknowledgment that most excess emissions would occur during startup,
shutdown, and malfunctions. One of these commenters also believes that
the regulations should provide for the public review period to be
extended as necessary to accommodate a thorough public review. The
reviewing authority should be required to provide a written response to
public comments explaining any decision to reject a public comment
suggesting ways for a facility to limit emissions during startup,
shutdown, and malfunction events.
Many other commenters have concerns with requiring review and
approval of startup, shutdown, and malfunction plans, except as
required under Sec. 63.1206(c)(2)(ii) for sources that elect to meet
the RCRA mandate using provisions of the startup, shutdown, and
malfunction plan as discussed above.
Response: Commenters express the same views here that they
expressed under the rulemaking the Agency recently completed to revise
the startup, shutdown, and malfunction plan requirements of the General
Provisions applicable to all MACT source categories. See 68 FR at
32589-93 (May 30, 2003).
EPA concluded in that final rule that the Administrator may at any
time request in writing that the owner or operator submit a copy of any
startup, shutdown, and malfunction plan (or a portion thereof). Upon
receipt of such a request, the owner or operator must promptly submit a
copy of the requested plan (or a portion thereof) to the Administrator.
In addition, the Administrator must request that the owner or operator
submit a particular startup, shutdown, or malfunction plan (or a
portion thereof) whenever a member of the public submits a specific and
reasonable request to examine or to receive a copy of that plan or
portion of a plan.
These provisions to provide the Administrator and the public with
access to startup, shutdown, and malfunction plans, coupled with the
provisions of Sec. 63.6(e)(3)(vii) under which the Administrator must
require the source to make changes to a deficient plan, should ensure
that startup, shutdown, and malfunction plans are complete and
accurate. We note that under Sec. 63.6(e)(3)(vii) the Administrator
must require the source to revise the plan if the plan: (1) does not
address a startup, shutdown, or malfunction event that has occurred;
(2) fails to operate the source (including associated air pollution
control and monitoring equipment) during a startup, shutdown, or
malfunction event in a manner consistent with the general duty to
minimize emissions; (3) does not provide adequate procedures for
correcting malfunctioning process and/or air pollution control and
monitoring equipment as quickly as practicable; or (4) includes an
event that does not meet the definition of startup, shutdown, or
malfunction listed in Sec. 63.2.
The commenter advocating that all hazardous waste combustors should
be required to submit their startup, shutdown, and malfunction plans
for review and approval did not explain why the concerns the Agency
expressed in the General Provisions rulemaking (see 68 FR at 32589-93)
are not valid for hazardous waste combustors. Accordingly, we do not
believe it is appropriate to deviate from the General Provisions to
require that all hazardous waste combustors submit their startup,
shutdown, and malfunction plans for review.
G. Public Notice of Test Plans
1. What Are the Revised Public Notice Requirements for Test Plans?
Prior to the proposal, it was brought to our attention that the
Agency did not provide any direction in the 1999 final rule regarding
how and when sources should notify the public, what the notification
should include, or where and for how long performance test plans should
be made available. Consequently, we proposed to add clarifying language
to the Sec. 63.1207(e)(2) public notification requirement for approved
performance test and CMS performance evaluation test plans because we
believe that providing opportunities for timely and adequate public
notice is necessary to fully inform nearby communities of a source's
plans to initiate important waste management activities. The proposed
clarifications are based upon the RCRA Expanded Public Participation
Rule (60 FR 63417, December 11, 1995) requirements for
[[Page 59496]]
public notification of an impending trial burn test. As a result, we
did not feel that the clarifications imposed any new or additional
requirements upon sources that will conduct a MACT comprehensive
performance test or confirmatory performance test.
Commenters generally supported the clarifications to the public
notice.\209\ However, they suggested a change to the proposed
requirement to provide notice of test plan approval no later than 60
days prior to conducting the test. The basis for suggesting a change is
that many sources had not received approval of their test plans 60 days
prior to the deadline for initiating their test under the Interim
Standards. Moreover, several sources did not receive approval until
well after the deadline for initiating the test. The problem created
for these sources is that the required 60 day notification of the
approved test plan effectively determines when the source will be able
to begin its test. In other words, its test would need to be postponed
until the approved test plan had been noticed for 60 days. Thus,
commenters provided several possible alternatives.
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\209\ See 69 FR 21347-21349.
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One alternative that would avoid causing delays to testing is to
require the public notice when the source submits its test plan.
Although this fulfills the notification requirement, this alternative
has a shortfall: The notice would occur at least one year (barring any
extensions) in advance of the test and given this long period of time,
the test plan is likely to be modified prior to approval. A second
alternative is to provide notice of the test plan 60 days before the
test as before, but regardless of approval status. This alternative is
improved over the first, but still faces the same problem of
potentially not offering the public an opportunity to view a final
approved plan. A third alternative is to issue notice of the test plan
as soon as it is approved. With this alternative, the public will have
the most up-to-date information; however, it may not be until a few
days prior to commencement of the test. Ideally, the second and third
alternatives could be combined to provide the best possible chance of
providing the public with an approved test plan in a reasonable period
of time prior to the test. On the other hand, that would potentially
require the facility to issue two notices if the test plan is not
approved 60 days prior to the test. We do not believe this would be
reasonable given that sources will be focused on activities associated
with the impending test.
In consideration of practicality, we believe that the second
alternative provides an adequate solution. As we mentioned, the
drawback is that the public may not have the opportunity to view an
approved test plan. However, we believe it is more important that the
public be aware of a source's plans (i.e., how and when) for conducting
the performance test.\210\ This way, if they have questions, there will
be 60 days in which they may contact the regulatory authority or the
source before the test is scheduled to begin. This alternative will
also eliminate the conflict associated with the confirmatory
performance test. The regulations at Sec. 63.1207(e)(1)(ii) specify
that a source must submit to the regulatory authority its notice of
intent to conduct a confirmatory performance test and the applicable
test plans at least 60 calendar days prior to the date the test is to
begin. Since we are no longer requiring that the test plans be approved
before issuing public notice, sources would then provide notice of
their confirmatory performance test plan to the public at the same time
they submit their notice of intent and test plans to the regulatory
authority. Therefore, we are requiring that sources issue the public
notice of test plans 60 days in advance of commencing the performance
test, whether their test plans have been approved or not. The
regulations at Sec. 63.1207(e)(2) have been revised accordingly.
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\210\ We expect that some source's test plans may be modified
after notice is issued and prior to approval or commencement of
their test. However, even under the previous regulations, test plans
could be modified after they had been approved and public noticed.
It is often a necessary consequence as sources continue to prepare
the combustion unit for the test.
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One last concern related to the public notice of approved test
plans involves sources that choose to conduct a performance test
without an approved test plan (e.g., both time extensions provided by
Sec. Sec. 63.7(h) and 63.1207(e)(3) have expired or due to other
circumstances, the source has elected to begin the test without
approval). Because we did not believe any sources would choose or need
to do so, we did not propose any guidance or regulations specific to
issuing notice to the public of their test plans. Nevertheless, a few
commenters raised this possibility indirectly in their discussion of
the problematic 60 day notice of approved test plan requirement. The
revised proposal addresses this concern by no longer requiring that
test plans be approved before issuing public notice. Thus, sources that
choose to begin their test without an approved plan will have complied
with the requirement to issue public notice. Irrespective of the public
notice requirements for noticing test plans, we expect that sources
will notify their regulatory authority of their decision to proceed
with their test in the absence of plan approval.
2. What Are the Revised Public Notice Requirements for the Petition To
Waive a Performance Test?
In the Final Amendments Rule (67 FR 6968, February 14, 2002), the
Agency did not provide direction regarding how, when, where, and what
should be included in the public notice for a petition for time
extension if the Administrator fails to approve or deny test
plans.\211\ In the proposal, we believed it important to provide
clarification regarding when the notice must be issued and what it
should contain. Thus, we proposed to revise paragraph Sec.
63.1207(e)(3)(iv).
---------------------------------------------------------------------------
\211\ Sections 63.1207(e)(2) and (e)(3) each require public
notice, but neither had provided any direction on how, when, where,
and what should be included in their respective notices until
today's final rule.
---------------------------------------------------------------------------
We received only one comment in response to the proposed
requirements. The commenter did not express any concern over the
requirements themselves, but rather suggested a change to terminology
used. The commenter feels that the terms ``to waive a performance
test'' or ``waiver'' as used in Sec. 63.1207(e)(3)(iv) could be
confusing to readers when we are actually referring to a time extension
for commencing the test. Although we agree the terminology could be
confusing, 40 CFR 63.1207(e)(3) clearly uses the term ``waiver'' in the
context of an extension of time to conduct the performance test at a
later date, implying that the deadline can be waived in this specific
situation. The use of the term waiver is derived from the General
Provisions requirements for requesting a waiver of performance tests
(Sec. 63.7(h)). Thus, Sec. 63.7(h)(3) provides the basis by which
sources may petition, in the form of a waiver, for a time extension
under Sec. 63.1207(e)(3). In consideration of the above and that the
existing regulations of Sec. 63.1207(e)(3)(i)-(iii) consistently use
the term waiver, we do not feel that a change to Sec.
63.1207(e)(3)(iv) is warranted.
H. Using Method 23 Instead of Method 0023A
Comment. Most commenters support our proposal to allow the use of
Method 23 instead of Method 0023A if a source includes this request in
the comprehensive test plan to the permitting authority. Some
commenters believe that Method 23 should be
[[Page 59497]]
allowed in all cases without prior approval or on a source category basis.
Response. We proposed to allow sources to use Method 23 for dioxin
and furan testing instead of SW-846 Method 0023A in situations where
the enhanced procedures found in Method 0023A would not increase
measurement accuracy. We proposed this change in the July 3, 2001,
proposed rule, and again in the April 20, 2004, proposal. See 66 FR at
35137 and 69 FR at 21342.
The final rule promulgates this change as proposed. See Sec.
63.1208(b)(1)(i). You may use Method 23 in lieu of Method 0023A after
justifying use of Method 23 as part of your performance test plan that
must be reviewed and approved the delegated permitting authority. You
may be approved to use Method 23 considering factors including whether
previous Method 0023A analyses document that dioxin/furan are not
detected, are detected at low levels in the front half of Method 0023A,
or are detected at levels well below the emission standard, and the
design and operation of the combustor has not changed in a manner that
could increase dioxin/furan emissions. We note that coal-fired boilers
and combustors equipped with activated carbon injection systems may not
be able to support use of Method 23, however, because these sources'
stack gas is likely to contain carbonaceous particulate. Thus, these
sources are likely to benefit the most from using Method 0023A.
The final rule does not automatically allow use of Method 23 for
particular source categories because we cannot assess whether all
sources in a category meet the conditions for use of Method 23--
generally that quality assurance may not be improved--such as those
listed above. These determinations can only be made on a site specific
basis by the permitting authority most familiar with the particular source.
Comment: Commenters do not believe that an additional petition
process (i.e., under Sec. 63.1209(g)(1)) is necessary before allowing
use of Method 23. Instead, EPA should require that the use of Method 23
should be submitted with the test plan to the regulatory agency for approval.
Response: We agree that a separate petition is unnecessary. Sources
should include a justification to use Method 23 in the performance test
plan that is submitted for review and approval. This will allow the
permitting authority to determine whether use of Method 23 is
appropriate for the source.
Comment: Two commenters state that ``the justification of the use
of Method 23 will not be by the existing system of a petition to EPA,
but will be included as a part of the performance test plan that is
submitted to the delegated regulatory authority for review and
approval. This means that the expertise, training, and decision-making
will not be consistent across the country. This is especially a problem
because of the severe resource, training and staff reductions among the
delegated regulatory authorities across the country and from region to
region. The decision to allow or disallow use of Method 23 should come
specifically, for each case, from EPA consideration of the submitted
justification, based on the knowledge and expertise of trained and
experienced EPA staff. This is important for uniformly applying the
testing requirements all across the country.''
Response: We disagree, and we believe the responses to comments in
today's rule make clear when Method 23 is an acceptable substitute for
Method 0023A. If the source has carbon in the flue gas, as is the case
with coal-fired boilers, boilers with carbon injection, and other
sources likely to have a substantial amount of carbonaceous particulate
matter in the flue gas, Method 0023A will generally be preferable
because it includes procedures to account for dioxin and furan bound to
carbonaceous particulate matter found in the probe and filter. In other
situations, Method 23 will generally give the same results at a lower cost.
I. Extrapolating Feedrate Limits for Compliance With the Liquid Fuel
Boiler Mercury and Semivolatile Metal Standards
Comment: One commenter questions whether allowing sources to
extrapolate metal feedrates downward from the levels achieved during
the comprehensive performance test to establish a metal feedrate limit
will ensure compliance with the emission standards.
Response: The mercury and semivolatile metals standards for liquid
fuel boilers are annual average emission limits where compliance is
established by a rolling average mercury feedrate limit with an
averaging period not to exceed an annual rolling average (updated
hourly).\212\ We use this approach because the emissions data used to
establish the standards are more representative of normal emissions
than compliance test emissions.\213\
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\212\ If you select an averaging period for the feedrate limit
that is greater than a 12-hour rolling average, you must calculate
the initial rolling average as though you had selected a 12-hour
rolling average, as provided by Sec. 63.1209 (b)(5)(i). This is
reasonable because allowing a longer period of time before
calculating the initial rolling average would not effectively ensure
compliance with the feedrate limit. You must calculate rolling
averages thereafter as the average of the available one-minute
values until enough one-minute values are available to calculate the
rolling average period you select. We note that this is an approach
allowed for calculating rolling averages under different modes of
operation at Sec. 63.1209(q)(2)(ii). At that time and thereafter,
you update the rolling average feedrate each hour with a 60-minute
average feedrate.
\213\ See USEPA, ``Technical Support Document for HWC MACT
Standards, Volume III: Selection of HWC MACT Standards,'' September
2005, Section 13.
---------------------------------------------------------------------------
As we explained at proposal, to ensure compliance with the mercury
and semivolatile metal emission standards for liquid fuel boilers, you
must document during the comprehensive performance test a system
removal efficiency for the metals and back-calculate from the emission
standard a maximum metal feedrate limit that must not be exceeded on an
(not to exceed) annual rolling average. See 69 FR at 21311-12. If your
source is not equipped with an emission control system (such as
activated carbon to control mercury) for the metals in question,
however, you must assume zero system removal efficiency. This is
because, although a source that is not equipped with an emission
control system may be able to document a positive system removal
efficiency in a single test, that removal efficiency is not likely to
be reproducible. Rather, it is likely to be an artifact of the
calculation of emissions and feeds rather than a removal efficiency
that can reliably be repeated.
To ensure that you can calculate a valid, reproducible system
removal efficiency for sources equipped with a control system that
effectively controls the metal in question, you may need to spike
metals in the feed during the comprehensive performance test at levels
that may result in emissions that are higher than the standard. This is
appropriate because compliance with an emission standard derived from
normal emissions data is based on compliance with an (not to exceed)
annual average feedrate limit calculated as prescribed here, rather
than compliance with the emission standard during the comprehensive
performance test.\214\
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\214\ The emission standard accounts for long-term variability
by incorporating an (not to exceed) annual averaging period that is
implemented by an (not to exceed) annual average chlorine feedrate
limit. Thus, because the emission level achieved during the
performance test relates to daily (or hourly) variability, an
exceedance of the emission standard during the test is not a violation.
---------------------------------------------------------------------------
The commenter is concerned that downward extrapolation from the
levels achieved during the comprehensive performance test to establish
a metal feedrate limit may not ensure
[[Page 59498]]
compliance with the standard because system removal efficiency may be
lower at lower feedrates.
This is a valid concern, and we have investigated it since
proposal. We conclude that downward extrapolation of feedrates for the
purpose of complying with the mercury and semivolatile metals emission
standards for liquid fuel boilers will ensure compliance with the
emission standards under the conditions discussed below.
We investigated the theoretical relationship between stack gas
emissions and feedrate considering vapor phase metal equilibrium, the
chlorine, mercury, and semivolatile metal feedrates for liquid fuel
boilers in our data base, and the mercury and semivolatile emission
standards for liquid fuel boilers.\215\ We considered sources equipped
with dry particulate matter controls and sources equipped with wet
particulate matter controls.
---------------------------------------------------------------------------
\215\ USEPA, ``Technical Support Document for HWC MACT
Standards, Volume IV: Compliance with the HWC MACT Standards,''
September 2005, Section 2.5 and Appendix B.
---------------------------------------------------------------------------
Sources Equipped with Dry Controls. For sources equipped with dry
controls other than activated carbon, mercury is not controlled. Thus,
you must assume zero system removal efficiency. Consequently, if you
are in the low Btu subcategory and comply with the mercury standard
expressed as a mass concentration ([mu]g/dscm), the mercury feedrate
limit expressed as an MTEC (maximum theoretical emission concentration,
[mu]g/dscm) is equivalent to the emission standard.\216\ If you are in
the high Btu subcategory and comply with the mercury standard expressed
as a hazardous waste thermal emission concentration (lb/MM Btu), the
mercury feedrate limit expressed as a hazardous waste thermal feed
concentration (lb/MM Btu) is also equivalent to the emission standard.
---------------------------------------------------------------------------
\216\ Note, however, that you convert the MTEC ([mu]g/dscm) to a
mass feedrate (lb/hr) by considering the average gas flowrate of the
test run averages during the comprehensive performance test to
simply implementation and compliance.
---------------------------------------------------------------------------
For semivolatile metals, the theoretical relationship between
emissions and feedrate indicates that downward extrapolation introduces
only a trivial error'0.17% at an emission rate 100 times the standard
irrespective of the level of chlorine present. Id. Nonetheless, to
ensure the error is minimal and to be practicable, you should limit
semivolatile emissions during the comprehensive performance test to
five times the emission standard.
Sources Equipped with Wet Scrubbers. For sources equipped with wet
scrubbers, we conclude that the approach we use for semivolatile metals
for dry scrubbers will also be appropriate to extrapolate a
semivolatile metal feedrate limit for wet scrubbers. To ensure that
downward extrapolation of the feedrate limit is conservative and to be
practicable, you should limit semivolatile metal emissions during the
comprehensive performance test to five times the emission standard.
For mercury, ensuring control with wet systems is more complicated
because the level of chlorine present affects the formation of mercuric
chloride which is soluble in water and easily controlled by wet
scrubbers. Elemental mercury has very low solubility in scrubber water
and is not controlled. The worst-case situation for conversion of
elemental mercury to soluble mercuric chloride would be when the
chlorine MTEC is lowest and the mercury MTEC is highest. We conclude
that downward extrapolation of mercury feedrates is conservative for
feedstreams that contain virtually no chlorine, e.g., below an MTEC of
100 [mu]g/dscm. In addition, we conclude that downward extrapolation is
appropriate \217\ for boilers feeding chlorinated feedstreams provided
that during the performance test: (1) Scrubber blowdown has been
minimized and the scrubber water has reached steady-state levels of
mercury prior to the test (e.g., by spiking the scrubber water); (2)
scrubber water pH is minimized (i.e., you establish a minimum pH
operating limit based on the performance test as though you were
establishing a compliance parameter for the total chlorine emission
standard); and (3) temperature of the scrubber water is maximized
(i.e., you establish a maximum scrubber water temperature limit).
---------------------------------------------------------------------------
\217\ Mercury SRE is constant as the mercury feedrate decreases.
---------------------------------------------------------------------------
J. Temporary Compliance With Alternative, Otherwise Applicable MACT
Standards
Comment: One commenter requests clarification on the requirements
applicable to a source that switches to an alternative mode of
operation when hazardous waste is no longer in the combustion chamber
under the provisions of Sec. 63.1206(b)(1)(ii). The commenter suggests
that Sec. 63.1206(b)(1)(ii) can imply that the complete compliance
strategy needs to be switched over to the alternative section 112 or
129 requirements, even though compliance with the Subpart EEE
requirements for monitoring, notification, reporting, and recordkeeping
remains environmentally protective under Subpart EEE. For example, the
commenter notes that Sec. 63.1206(b)(1)(ii) could be incorrectly
interpreted to require a source to comply with illogical requirements
when the source temporarily switches to alternative, otherwise
applicable standards, including standards testing and opacity
monitoring under the alternative section 112 or 129 requirements. The
commenter states that this interpretation makes little sense because a
source that temporarily changes its mode of operation will continue to
do testing under Subpart EEE, Part 63, or, in the case of opacity, the
alternative section 112 requirements for cement kilns would necessarily
require duplicate systems and compliance with redundant limits because
a source may already be using a bag leak detection system or a
particulate matter detection system. The commenter suggests only
requiring sources to comply with the otherwise applicable emission
standards under the alternative section 112 or 129 requirements while
still operating under the various associated compliance requirements of
Subpart EEE, part 63.
Response: The commenter requests clarification of Sec.
63.1206(b)(1)(ii), which states that if a source is not feeding
hazardous waste to the combustor and the hazardous waste residence time
has expired (i.e., the hazardous waste feed to the combustor has been
cut off for a period of time not less than the hazardous waste
residence time), then the source may elect to comply temporarily with
alternative, otherwise applicable standards promulgated under the
authority of sections 112 and 129 of the Clean Air Act.\218\ As we have
explained in previous notices,\219\ sources that elect to invoke Sec.
63.1206(b)(1)(ii) to become temporarily exempt from the emission
standards and operating requirements of Subpart EEE, Part 63, remain an
affected source under Subpart EEE (and only Subpart EEE) until the
source is no longer an affected source by meeting the requirements
specified in Table 1 of Sec. 63.1200. Of course, a source can elect
not to use the alternative requirements for compliance during periods when
[[Page 59499]]
they are not feeding hazardous waste, but, if so, the source must
comply with all of the operating and monitoring requirements and
emission standards of Subpart EEE at all times.\220\ To implement Sec.
63.1206(b)(1)(ii) a source defines the period of compliance with the
otherwise applicable sections 112 and 129 requirements as an
alternative mode of operation under Sec. 63.1209(q). In order to be
exempt from the emission standards and operating requirements of
Subpart EEE, a source documents in the operating record that they are
complying with the otherwise applicable Section 112 and 129
requirements specified under Sec. 63.1209(q).
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\218\ Examples include 40 CFR part 60, subparts CCCC and DDDD
for commercial and industrial solid waste incinerators, 40 CFR part
63, subpart LLL for Portland cement manufacturing facilities, 40 CFR
part 63, subpart DDDDD for industrial/commercial/institutional
boilers and process heaters, and 40 CFR part 63, subpart NNNNN for
hydrochloric acid production facilities.
\219\ This provision has been discussed in several Federal
Register notices including 64 FR at 52904 (September 30, 1999), 66
FR at 35090, 35145 (July 3, 2001), 67 FR at 6979 (February 14,
2002), and 69 FR at 21203 (April 20, 2004).
\220\ However, the operating requirements do not apply during
startup, shutdown, or malfunction provided that hazardous waste is
not in the combustion chamber. See Sec. 63.1206(b)(1)(i).
---------------------------------------------------------------------------
The commenter recommends that the complete compliance strategy need
not be switched over to the alternative section 112 and 129
requirements when temporarily switching to the alternative standards.
In general, we disagree. The intent of Sec. 63.1206(b)(1)(ii) is to
ensure that a source is complying with all requirements of sections 112
and 129 as an alternative mode of operation in lieu of the requirements
under Subpart EEE. In the 1999 final rule we stated that the source
must comply with all otherwise applicable standards under the authority
of sections 112 and 129. Specifically, the source must comply with all
of the applicable notification requirements of the alternative
regulation, comply with all of the monitoring, recordkeeping, and
testing requirements of the alternative regulation, modify the Notice
of Compliance (or Documentation of Compliance) to include the
alternative mode(s) of operation, and note in the operating record the
beginning and end of each period when complying with the alternative
regulation. See 64 FR at 52904. A source that elects to comply with
otherwise applicable standards under Sec. 63.1206(b)(1)(ii) must
specify all requirements of those standards, not only the emission
standards applicable under the sections 112 and 129 standards, but also
the associated monitoring and compliance requirements and notification,
reporting, and recordkeeping requirements in the operating record under
Sec. 63.1209(q).
The commenter suggests that a source should be able to comply with
the otherwise applicable emission standards, while continuing to
operate under the associated compliance requirements for the HAP under
Subpart EEE. An example would be a cement kiln source complying with
the dioxin and furan monitoring requirements under Sec. 63.1209(k) of
Subpart EEE for the dioxin and furan standards under Sec. 63.1343(d)
under Subpart LLL. We did not determine, when promulgating the
provisions of Sec. Sec. 63.1206(b)(1)(ii) and 63.1209(q)(1), that the
monitoring provisions under Subpart EEE are equivalent to the
associated monitoring requirements under the otherwise applicable 112
and 129 standards, or indeed, whether they are even well-matched. Such
a determination would require notice and opportunity for comment, which
we have not provided. However, this should not be interpreted to mean
that a similar determination could not be made on a site-specific basis
given that the MACT general provisions allow a source to request
alternative monitoring procedures under Sec. 63.8(f)(4). Certainly, a
source can apply under this provision that the compliance requirements
under Subpart EEE satisfy the associated monitoring requirements under
the otherwise applicable 112 and 129 standards.
We also disagree with the commenter that emissions testing under
the alternative standards of sections 112 and 129 is an example of an
illogical requirement under Sec. 63.1206(b)(1)(ii). Performance
testing generally is required to demonstrate compliance with the
emission standards and to establish limits on specified operating
parameters to ensure compliance is maintained. In order to take
advantage of the alternative under Sec. 63.1206(b)(1)(ii), a source
needs to show that compliance with and establish operating parameter
limits for the otherwise applicable standards of sections 112 and 129.
Thus, testing in order to establish operating parameter limits will be
necessary. However, this does not mean that a separate performance test
with the alternative sections 112 or 129 standards is necessarily
required. We note that a source can make use of the performance test
waiver provision under Sec. 63.7(h) of the general provisions to
request that the performance test under the alternative sections 112
and 129 standards be waived because the source is meeting the relevant
standard(s) on a continuous basis by continuing to comply with Subpart
EEE for the relevant HAP. This approach may be practicable for sources
that can demonstrate that their level of performance during testing
under Subpart EEE, including the associated operating and monitoring
limits, will undoubtedly ensure continuous compliance with the
emissions standards and the associated operating limits of alternative
sections 112 and 129 standards.
Finally, the commenter notes that Subpart LLL (the alternative
section 112 standards for cement kilns) includes opacity monitoring
while Subpart EEE may not. The commenter states that this unnecessarily
would require duplicate systems and compliance with redundant limits
because of the bag leak detection and particulate matter detection
system requirements under Subpart EEE. We respond that Subpart LLL
specifies opacity as a standard (see Sec. 63.1343(b)(2)), and,
therefore, cement kilns subject to Subpart EEE must comply with the
opacity standard when electing to comply temporarily with the
requirements of Subpart LLL. We note that the opacity standard under
Subpart EEE does not apply to cement kilns that are equipped with a bag
leak detection system under Sec. 63.1206(c)(8) and to sources using a
particulate matter detection system under Sec. 63.1206(c)(9). However,
a cement kiln may use an opacity monitor that meets the detection limit
requirements as the detector for a bag leak detection system or
particulate matter detection system. See Part Four, Section VIII.A-C of
the preamble.
K. Periodic DRE Testing and Limits on Minimum Combustion Chamber
Temperature for Cement Kilns
Comment: Several commenters oppose the need for cement kilns that
burn at locations other than the normal flame zone to demonstrate
compliance with the destruction and removal efficiency (DRE) standard
during each comprehensive performance test. These commenters recommend
that EPA remove the requirement of Sec. 63.1206(b)(7)(ii) for cement
kilns citing that existing rule provisions (i.e., the requirements
under Sec. 63.1206(b)(5) pertaining to changes that may adversely
affect compliance) are sufficient to require additional DRE testing
after changes are made that may adversely affect combustion efficiency.
Commenters question EPA's position that cement kilns that burn
hazardous waste at locations other than the normal flame zone
demonstrate a variability in DRE sufficient to justify the expense of
re-testing for DRE with each performance test. Commenters point to
EPA's data base that includes DRE results from over 30 tests with
nearly 250 runs showing consistent DRE results, including sources
burning hazardous waste at locations other than the normal flame zone,
being achieved by cement kilns. The commenters note several burdens
associated with DRE
[[Page 59500]]
testing that do not result in improved environmental benefit including
the purchase of expensive exotic virgin chemicals for performance
testing, the risks to workers and contractors associated with the
handling of these chemicals, and increasing the length of operation at
stressful kiln operating conditions necessary to conduct DRE testing at
minimum combustion chamber temperatures. Alternatively, commenters
recommend that EPA revise the DRE requirements such that periodic
testing is no longer required for cement kilns (that burn at locations
other than the normal flame zone) after they have successfully achieved
the DRE standard over multiple testing cycles (e.g., two or three)
under similar testing regimes. That is, the source should only be
required to demonstrate compliance with the DRE standard a maximum of
two or three times until the source (that burns at locations other than
the normal flame zone) modifies the system in a manner that could
affect the ability of it to achieve the DRE standard.
Response: We are revising the requirements of Sec.
63.1206(b)(7)(ii) such that cement kilns that feed hazardous waste at
locations other than the normal flame zone need only demonstrate
compliance with the DRE standard during three consecutive comprehensive
performance tests provided that the source has successfully
demonstrated compliance with the DRE standard in each test and that the
design, operation, and maintenance features of each of the three tests
are similar. These revisions do not affect sources that burn hazardous
waste only in the normal flame zone.\221\
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\221\ The DRE demonstration for these sources need be made only
once during the operational life of a source, either before or
during the initial comprehensive performance test, provided that the
design, operation, or maintenance features do not change in a manner
that could reasonably be expected to affect the ability to meet the
DRE standard. See Sec. Sec. 63.1206(b)(7) and 63.1207(c)(2)(ii).
The source would ensure continued compliance by operating under the
operating parameter limits established during this DRE test.
---------------------------------------------------------------------------
Prior to today's change, we required sources that feed hazardous
waste in locations other than the flame zone to perform periodic DRE
testing every 5 years to ensure that the DRE standard continues to be
achieved over the life of the unit. See Sec. 63.1206(b)(7)(ii). We
justified this requirement because of concerns that sources that feed
hazardous waste at locations other than the flame zone have a greater
potential of varying DRE performance due to their hazardous waste
firing practices. As we stated in the 1999 rule, we were concerned that
the DRE may vary over time due to the design and operation of the
hazardous waste firing system, and that those variations may not be
identical or limited through operating limits set during a single DRE
test (similar to what we concluded for sources that burn hazardous
waste only in the normal flame zone). See 64 FR at 52850.
Commenters now question the need for subsequent DRE testing at
cement kilns that feed hazardous waste at locations other than the
normal flame zone once a cement kiln demonstrates compliance with the
MACT DRE standard. The regulatory requirement for the destruction and
removal efficiency standard has proved to be an effective method to
determine appropriate process controls necessary for the combustion of
hazardous waste. We are not convinced that only one DRE test is
sufficient to ensure that a cement kiln that burns hazardous waste at
locations other than the normal flame zone will continue to meet the
DRE standard because temperatures are lower and gas residence times are
shorter at the other firing locations. This is especially true given
the industry trend to convert to the more thermally efficient
preheater/precalciner kiln manufacturing process.\222\ Precalciner
kilns use a secondary firing system (i.e., flash furnace) at the base
of the preheater tower to calcine the raw material feed outside the
rotary kiln. This results in two separate combustion processes that
must be controlled `` one in the kiln and the other in the flash
furnace. The gas temperature necessary for calcining the limestone raw
material in the flash furnace is lower than the temperature required
making the clinker product. We conclude, therefore, that it is
necessary, in spite of the concerns raised by commenters, to retain
periodic DRE testing to ensure continued compliance with the DRE
standard necessary for the control of nondioxin/furan organic HAP.
---------------------------------------------------------------------------
\222\ For example, Ash Grove Cement in Chanute, KS replaced
their two wet process cement kilns with one preheater/precalciner
kiln in 2001. Holcim Inc in Holly Hill, SC has also recently
constructed a new preheater/precalciner kiln to replace two wet
process cement kilns. Keystone Cement Company in Bath, PA is
considering replacing their two wet process cement kilns with a new
preheater/precalciner kiln. See docket item OAR-2004-0022-0384.
---------------------------------------------------------------------------
We also acknowledge, however, the concerns raised by the
commenters. Our DRE data base of operating cement kilns includes
results from approximately 25 DRE tests and nearly 200 runs.\223\ All
data show compliance with the DRE standard. Of these, approximately
one-quarter of the data are from cement kilns that burned hazardous
waste at locations other than the normal flame zone (e.g., injecting
waste at midkiln in a wet process kiln), but we do not have DRE results
from every operating cement kiln. Considering available DRE data and
the concerns of the commenters, we believe that DRE testing during
three consecutive comprehensive performance tests is sufficient to
provide needed certainty about DRE performance while reducing the
overall costs and toxic chemical handling concerns to the regulated
source. Thus, we are revising the requirements of Sec.
63.1206(b)(7)(ii) such that cement kilns that feed hazardous waste at
locations other than the normal flame zone need only demonstrate
compliance with the DRE standard during three consecutive comprehensive
performance tests provided that the source has successfully
demonstrated compliance with the DRE standard in each test and that the
design, operation, and maintenance features of each of the three tests
are similar. If a facility wishes to operate under new operating
parameter limits that could be expected to affect the ability to meet
the DRE standard, then the source would need to conduct another DRE
test. Once the facility has conducted another three DRE tests under the
new operating limits, then subsequent DRE testing would not be
required. Accordingly, we are revising the requirements of Sec.
63.1206(b)(7)(ii).
---------------------------------------------------------------------------
\223\ U.S. EPA, ``Final Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards and
Technologies,'' Section 23.4, September 2005.
---------------------------------------------------------------------------
Comment: Several commenters support EPA's proposal to delete the
requirement to establish an operating limit on the minimum combustion
chamber temperature for dioxin/furans under Sec. 63.1209(k)(1) for
cement kilns. These commenters point to the high temperatures of
approximately 2500[deg]F required to make the clinker product. These
high temperatures are fixed by the reaction kinetics and thermodynamics
occurring in the burning zone and cannot be reduced below minimum
values at the whim of the operator and still make a marketable product.
In addition to deleting the minimum combustion chamber temperature
limit for dioxin/furans, commenters also recommend, for similar
reasons, that EPA delete the minimum combustion chamber temperature
requirement under Sec. 63.1209(j)(1) associated with the destruction
and removal efficiency standand. Commenters note that demonstrating the
minimum temperature requires operating under stressful operating
conditions that can
[[Continued on page 59501]]
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