Approval, Exhaust Gas Monitoring, and Safety Requirements for the Use of Diesel-Powered Equipment in Underground Coal Mines; Final Rule

[Federal Register: October 25, 1996 (Volume 61, Number 208)]
[Rules and Regulations]               
[Page 55411-55461]


[[Page 55411]]


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Part III





Department of Labor





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Mine Safety and Health Administration



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30 CFR Parts 7, et al.



Approval, Exhaust Gas Monitoring, and Safety Requirements for the Use 
of Diesel-Powered Equipment in Underground Coal Mines; Final Rule


[[Page 55412]]



DEPARTMENT OF LABOR

Mine Safety and Health Administration

30 CFR Parts 7, 31, 32, 36, 70, and 75

RIN 1219-AA27

 
Approval, Exhaust Gas Monitoring, and Safety Requirements for the 
Use of Diesel-Powered Equipment in Underground Coal Mines

AGENCY: Mine Safety and Health Administration, Labor.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: This final rule establishes new requirements for the approval 
of diesel engines and other components used in underground coal mines; 
requirements for monitoring of gaseous diesel exhaust emissions by coal 
mine operators; and safety standards for the use of diesel-powered 
equipment in underground coal mines. The final rule is derived in part 
from existing MSHA regulations, and provides protection against 
explosion, fire, and other safety and health hazards related to the use 
of diesel-powered equipment in underground coal mines. The final rule 
also amends certain equipment safety standards in part 75 previously 
applicable only to electric-powered equipment to apply to diesel-
powered equipment. The new standards are consistent with advances in 
mining technology, address hazards not covered by existing standards, 
and impose minimal additional paperwork requirements.

EFFECTIVE DATES: This regulation is effective April 25, 1997, except 
for subparts E and F of part 7, the removal of part 31, the
amendments 
to part 36, and Sec. 75.1907 which are effective November 25, 1996. 
Incorporations by reference were approved by the Director of the 
Federal Register as of April 25, 1997.

FOR FURTHER INFORMATION CONTACT: Patricia W. Silvey, Director, Office 
of Standards, Regulations, and Variances, Mine Safety and Health 
Administration, 4015 Wilson Boulevard, Arlington, VA 22203-1984. Ms. 
Silvey can be reached at psilvey (Internet E-mail), 703-235-
1910 (voice), or 703-235-5551 (facsimile).

SUPPLEMENTARY INFORMATION:

I. Background

    Coal mine operators began to introduce diesel-powered equipment 
into underground mines in the early 1970's. The number of diesel units 
operating in underground coal mines has increased from approximately 
150 in 1974 to over 2,900 units operating in 173 mines in 1995. MSHA 
projects that the number of diesel units operating in underground coal 
mines could increase to approximately 4,000 in 250 underground coal 
mines by the year 2000.
    Although diesel-powered equipment does not have the inherent 
electrocution hazard of electric-powered equipment, it nonetheless 
presents a number of safety and health risks. By introducing an 
internal combustion engine into an environment where explosive levels 
of methane can be present, diesel-powered equipment brings with it 
risks of fire or explosion. Diesel engines also have high temperature 
exhaust components which, in the presence of coal and other 
combustibles in the underground mine environment, present a fire 
hazard. The handling and storage of diesel fuel underground also 
present potentially serious fire hazards. Finally, diesel engines 
produce exhaust gases containing carbon monoxide, oxides of nitrogen, 
and particulate matter, presenting potentially serious health risks to 
miners.
    Before publication of this final rule, MSHA's regulations contained 
limited safety and health and machine approval requirements that 
specifically addressed the use of diesel-powered equipment in 
underground coal mines. In the 1980's, the increase of the numbers of 
this equipment in underground coal mines, coupled with the health and 
safety risks associated with its use, highlighted the need for a 
regulatory approach specifically tailored to diesel-powered equipment 
operated in underground coal mines.
    In response to this need, the Secretary of Labor convened a Federal 
advisory committee in 1987 to evaluate and make recommendations for the 
safe and healthful use of diesel-powered equipment in underground coal 
mines. The Diesel Advisory Committee addressed approval issues--
covering equipment design and performance; use issues--addressing the 
safe use of diesel equipment in the mine environment; and health 
issues--concerning the evaluation and control of health hazards 
associated with diesel equipment. In July 1988, the Committee issued a 
report of its recommendations entitled ``Report of the Mine Safety and 
Health Advisory Committee on Standards and Regulations for Diesel-
Powered Equipment in Underground Coal Mines''. In its report the 
Committee concluded that MSHA should develop regulations to govern the 
approval and use of diesel-powered equipment in underground coal mines, 
and identified a number of specific areas to be addressed.
    On October 4, 1989, the Mine Safety and Health Administration 
published a Notice of Proposed Rulemaking in the Federal Register [54 
FR 40950] that included criteria for the approval of diesel engines and 
other related equipment; addressed exposure limits, monitoring, and 
recordkeeping requirements for certain diesel emissions; and provided 
corresponding safety standards for the use of diesel-powered equipment 
in underground coal mines, including the safe storage and transport of 
diesel fuel, and the training of persons performing work on diesel 
equipment. On the same day, MSHA also published an Advance Notice of 
Proposed Rulemaking [54 FR 40996] soliciting comment on the approach 
and scope of an MSHA approval program for diesel machines. MSHA held 
four public hearings on the proposed rule: in Salt Lake City, Utah; 
Pittsburgh, Pennsylvania; Chicago, Illinois; and Birmingham, Alabama.
    This final rule, which includes specifications for the approval of 
diesel engines as well as provisions for the safe and healthful use of 
such equipment in underground coal mines, is derived from the data, 
information, and public comments compiled during the rulemaking 
process. The final rule, like the proposal, takes an integrated 
approach to the control of diesel safety and health hazards, requiring 
clean-burning engines on diesel-powered machines, maintained by persons 
who have been adequately trained for the task. Sufficient ventilating 
air is required where diesel-powered equipment is operated to control 
the potential health hazards of diesel exhaust. Sampling every shift 
confirms the effectiveness of the mine ventilation system in addressing 
these hazards.

Part 7 Equipment Approval

    MSHA regulations require the Agency's approval of the design of 
electrical equipment to be used in the production areas of underground 
coal mines. This equipment must be designed to eliminate fire and 
explosion hazards. MSHA's approval program has been very successful in 
reducing the number of fires, explosions and other hazards associated 
with electric-powered equipment. The final rule establishes a similar 
approach for diesel-powered equipment used in areas of underground coal 
mines where permissible (explosion-proof) electric equipment is 
required, ensuring the same level of safety in mines where diesel-
powered equipment is used.

[[Page 55413]]

    The permissibility requirements for diesel-powered equipment used 
in gassy non-coal mines in MSHA's part 36 regulations
have been in 
place for a number of years. Although specific regulations did not 
exist for diesel-powered equipment operated in underground coal mines, 
MSHA has used the ventilation plan approval process to require the use 
of permissible diesel-powered equipment, approved under part 36, in 
those areas of underground coal mines where permissible electric 
equipment is required. However, mine ventilation plans have generally 
only addressed fire and explosion protection for equipment operating 
near the point of coal extraction (inby), and other locations where 
methane may be present, and have not addressed other possible safety 
hazards associated with the use of diesel-powered equipment in other 
(outby) areas. Additionally, mine ventilation plans have not dealt with 
such important concerns as the storage and handling of diesel fuel and 
regular maintenance of diesel equipment.
    The final rule requires that only approved engines be used in 
diesel-powered equipment in underground coal mines, and establishes 
approval requirements for diesel engines to be used in both permissible 
areas (inby) and nonpermissible areas (outby) under part 7, subpart E. 
The subpart E approval requirements are modeled after existing approval 
requirements in part 36 for engines used in gassy non-coal mines. 
Certain other safety features, such as flame arresters, spark 
arresters, and water scrubbers, must be added to the engines used in 
permissible areas to ensure that they can be operated safely in the 
coal mine environment. An engine in combination with these safety 
features is termed a diesel power package. A separate approval was 
established in the final rule for the power package because the power 
package manufacturer is normally a company other than the engine 
manufacturer and controls the assembly of the power package. In 
addition, approval requirements for power packages under part 7, 
subpart F, are incorporated into machines approved under existing part 
36. This is similar to the approach taken for electrical equipment 
where explosion-proof components are incorporated into machines 
approved under part 18.
    In order to protect miners from harmful contaminants emitted from 
diesel engines, the approval requirements in the final rule contain 
test procedures and limits on the concentrations of carbon monoxide and 
oxides of nitrogen. Based on commenters' recommendations, the final 
rule requires that the same test cycle be used for testing both the 
gaseous and particulate emissions. In response to commenters' 
recommendations, the final rule is based on ISO 8178, an international 
consensus standard, which establishes a common test cycle for the 
measurement of gaseous and particulate emissions. All equipment testing 
under part 7 is intended to be conducted at test sites other than MSHA 
facilities, such as manufacturers' laboratories, independent testing 
laboratories, or other government or university laboratories.

Part 70 Exhaust Gas Monitoring.

    The final rule addresses the monitoring and control of gaseous 
diesel exhaust emissions. The final rule requires area sampling as part 
of the onshift examination during every work shift. These monitoring 
provisions will ensure, in a reliable and systematic manner, that 
miners will be protected from exposure to harmful levels of gaseous 
contaminants.
    The final rule requires that mine operators take representative 
samples of carbon monoxide and nitrogen dioxide in strategic locations 
to determine concentrations of these contaminants in miners' 
workplaces. The sampling locations are based on knowledge of the 
specific operation of diesel equipment underground and the behavior of 
gaseous emissions generated by these machines. Samples exceeding an 
action level of 50 percent of the threshold limit values 
(TLV<Register>) for carbon monoxide and nitrogen dioxide trigger 
corrective action by the mine operator.

Part 75 Safety Requirements

    The final rule specifies minimum ventilating air quantities in 
areas where diesel equipment is operated, and requires that the 
quantities be incorporated into the mine operator's approved mine 
ventilation plan. As part of the equipment approval process in
part 7 
of the final rule, diesel engines used underground are tested for 
gaseous and particulate emissions. The required minimum ventilating air 
quantity is determined based on the results of these emission tests and 
is included on the approval plate for each unit of diesel-powered 
equipment. The approval plate quantity of ventilating air is the air 
quantity needed to dilute the exhaust gases to their permissible 
exposure limits. This air quantity should be used in ventilation system 
design by the mine operator and in the evaluation and approval of 
minimum air quantities in ventilation plans by MSHA.
    Under the final rule individual units of diesel equipment must be 
ventilated, as a general rule, with the air quantity specified on the 
equipment's approval name plate. The quantity of air required in areas 
where multiple units of equipment are operated is based on a simple 
addition of approval plate air quantities. The final rule also allows 
for adjustments in air quantities for multiple units of equipment, if 
sampling of contaminants indicates that lesser air quantities will 
result in dilution to the necessary levels. In addition, the final rule 
establishes specific locations where air quantities must be measured.
    Under the final rule, low sulfur fuel must be used to operate 
diesel-powered equipment underground. Low sulfur fuel, which is readily 
available and widely used throughout the United States, will lower 
gaseous and particulate emissions, helping to protect miners from 
exposure to harmful diesel exhaust contaminants. In addition, the final 
rule prohibits the use of flammable liquids as additives in diesel fuel 
used underground and requires that only additives registered with the 
Environmental Protection Agency in accordance with 40 CFR
Part 79 be 
used in diesel-powered equipment.
    The use of diesel fuel underground can present risks to miners' 
safety, because the spilling of fuel on hot surfaces or electric 
components, or the inadvertent ignition of stored diesel fuel, can 
result in fire. Additionally, a fire started with a combustible 
material other than diesel fuel that then spreads to diesel fuel stored 
underground could be catastrophic. Diesel fuel handling and storage are 
addressed in the final rule by specific requirements for diesel fuel 
storage and the transportation of fuel from one location to another.
    New design, installation, and maintenance requirements are 
established under the final rule for fire suppression systems installed 
on diesel-powered equipment and fuel transportation units. The 
requirements in the final rule address the risk of fire on diesel-
powered equipment caused by, for example, hot exhaust components, 
dragging brakes, and shorted electrical components igniting diesel 
fuel, hydraulic fluid, brake fluid, lube oil, and other combustible 
materials. The final rule also requires that automatic fire-suppression 
systems be listed or approved by a nationally recognized independent 
testing laboratory.
    The final rule recognizes that regular maintenance of diesel-
powered equipment is essential. Inadequate equipment maintenance can 
result in the creation of a fire or explosion

[[Page 55414]]

hazard, and the levels of harmful gaseous and particulate components in 
diesel exhaust can rise when equipment is not adequately maintained. In 
response, the final rule requires diesel-powered equipment to be 
examined on the same weekly basis as electric equipment. The rule 
specifically requires that air filters be changed and scrubbers be 
flushed regularly, and that weekly gaseous emission tests be conducted 
on certain diesel equipment while the engine is operating. The final 
rule also requires that persons performing certain work on diesel-
powered equipment be qualified. Commenters agreed that requiring 
diesel-powered equipment to be maintained in approved condition is 
necessary to ensure that features installed to reduce the risk of fire, 
explosion, and harmful emissions are operating properly. The final rule 
does not adopt the proposal that MSHA approve the training plans used 
for qualification. Under the final rule, training to establish 
qualification for persons performing maintenance may be obtained 
through the equipment manufacturer, community colleges, training 
schools, or other training providers.
Amendments to Existing Part 75 Requirements
    The final rule amends certain existing MSHA regulations in
part 75 
by extending their applicability to diesel-powered equipment. The final 
rule requires that certain types of diesel-powered equipment be 
equipped with methane monitors to detect dangerous levels of methane, 
and also with cabs or canopies to protect miners from roof falls. 
Additionally, the final rule clarifies that accumulation of coal dust 
and other combustible materials is prohibited on diesel-powered 
equipment. These safety features have been proven to save miners' 
lives.

II. Discussion of the Final Rule

A. General Discussion

Recordkeeping Requirements in the Final Rule
    Recordkeeping requirements in the final rule are found in 
Secs. 7.83 and 7.97, Application requirements; Secs. 7.90 and 7.105, 
Approval marking; Secs. 7.108, Power package checklist; Sec. 75.363, 
Hazardous condition; posting, correcting and recording; Sec. 75.371 
(r), (kk), (ll), (mm), (nn), (oo), and (pp), Mine ventilation plan, 
contents; Sec. 75.1901(a), Diesel fuel requirements; 
Sec. 75.1904(b)(4)(i), Underground diesel fuel tanks and safety cans; 
Sec. 75.1911(i) and (j), Fire suppression systems for diesel-powered 
equipment and fuel transportation units; Sec. 75.1912(h) and (i), Fire 
suppression systems for permanent underground diesel fuel storage 
facilities; Sec. 75.1914 (f)(1), (f)(2), (g)(5), (h)(1) and (h)(2), 
Maintenance of diesel-powered equipment; Sec. 75.1915(a), (b)(5), 
(c)(1), and (c)(2), Training and qualification of persons working on 
diesel-powered equipment.
    The paperwork burden imposed on manufacturers by the final rule 
totals 558, which is an increase of 790 burden hours for the transfer 
of hours from part 36 approval requirements, and a decrease of 232 
hours for the removal of parts 31 and 32. In the first year the final 
rule is in effect, the burden hours on mine operators will be 56,258, 
of which large and small mine operators will incur 54,774 and 1,484 
hours, respectively. After the first year, the burden hours to mine 
operators will be 52,228, of which large and small mine operators will 
incur 50,949 and 1,279 hours, respectively.
    In the first year that the final rule is in effect, the total new 
paperwork burden hours to mine operators and manufacturers will be 
56,816 [56,258 + (790-232)]. After the first year, the total new 
paperwork burden hours to mine operators and manufacturers will be 
52,786 [52,228 + (790-232)].
    MSHA solicited comments regarding the burden estimates or any other 
aspect of the collection of information in the proposed rule. Proposed 
paperwork requirements were submitted to the Office of Management and 
Budget (OMB) for review in accordance with section 3504(h) of the 
Paperwork Reduction Act of 1980 (PRA 80). Comments by OMB were filed 
under comment numbers 1219-0111, 1219-0112, and 1219-0114. Control 
number 1219-0100 was approved for proposed paperwork burden hours 
required by part 7.
    When proposed in 1989, the information collection requirements in 
the diesel equipment regulations were calculated under PRA 80. The 
final rule calculations are done in compliance with the Paperwork 
Reduction Act of 1995 (PRA 95). Generally, changes in the final rule 
burden hour and cost estimates from the proposed requirements result 
from the revision necessitated by PRA 95. When the change represents a 
regulatory change, it is so noted in the discussion of the appropriate 
section within the preamble. For details on the calculation of 
paperwork hours and costs see ``VII, Paperwork Reduction Act of 1995'' 
in the Regulatory Impact Analysis, which may be accessed electronically 
or may be requested from MSHA's Office of Standards, Regulations, and 
Variances.
    Information is to be recorded, maintained for the period specified, 
and made accessible, upon request, to authorized representatives of the 
Secretary and to miners' representatives. Records are to be stored in a 
manner that is secure and not susceptible to alteration, to preserve 
the integrity of records for review by interested parties. This may be 
done traditionally, by recording in a book, or electronically by 
computer.
    Examples of books that MSHA considers to be secure and not 
susceptible to alteration include, but are not limited to, record books 
that are currently approved by state mine safety agencies, and 
permanently bound books. Examples of books that would not be considered 
secure include loose-leaf binders and spiral notebooks.
    Recognizing the trend of electronic storage and retrieval of 
information through computers to be an increasingly common business 
practice, MSHA permits the use of electronically stored records, 
provided that they are secure and not susceptible to alteration, that 
they are able to capture the information and signatures required, and 
that information is accessible to authorized representatives of the 
Secretary and miners' representatives. ``Secure'' is intended to mean 
unalterable or unable to be modified. An example of acceptable storage 
would be a ``write once, read many'' drive. Electronic records meeting 
these criteria are practical and as reliable as traditional records. 
Although the final rule does not require backing up the data, some 
means is necessary to ensure that the condition and existence of 
electronically stored information is not compromised or lost.
    The 1995 Paperwork Reduction Act mandates agencies to encourage the 
use of electronic submission of responses to minimize the burden of the 
collection of information on respondents. Likewise, one of the major 
objectives of Executive Order No. 12866 is to make the regulatory 
process more accessible and open to the public as a means to reduce the 
duplication of information between agencies. Elsewhere in this 
preamble, MSHA announces the electronic availability of its rulemaking 
documents with access instructions. The mining community and other 
interested parties are encouraged to access on-line material as needed.

B. Section-by-Section Discussion

    The following section-by-section portion of the preamble discusses 
each provision affected. The text of the final

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rule is included at the end of the document.
General Discussion of Diesel Equipment Approvals and Safety 
Requirements
    One of the three major areas addressed by the Diesel Advisory 
Committee was the approval of diesel-powered equipment. Historically, 
MSHA and its predecessor agencies have approved equipment intended for 
use in areas of mines where methane and other substances pose the 
danger of a fire or explosion. Through the approval process, equipment 
is evaluated against technical requirements which, when met, will 
render the equipment safe for its intended use in the mine environment. 
In part as a result of this process, the approved equipment used in 
mines in the United States is recognized as among the safest in the 
world.
    The Advisory Committee recommended that diesel-powered equipment 
for use in underground mines be subject to MSHA approval in much the 
same way that electrical equipment has been regulated. Under existing 
standards, electrical equipment operated in the area of extraction and 
in return airways of underground coal mines and gassy metal and 
nonmetal mines, where methane may accumulate, must be approved as 
permissible (explosion-proof). Electrical equipment operated elsewhere 
in these mines is not required to be permissible, but is subject to 
certain safety requirements to protect against fire, shock, and other 
hazards of operation. The Advisory Committee further recommended:
    <bullet> Only diesel-powered equipment currently considered 
permissible should be permitted to continue to operate in areas of coal 
mines where permissible electrical equipment is required.
    <bullet> Separate specifications should be developed for diesel-
powered equipment used in areas where permissible equipment is required 
and elsewhere.
    <bullet> An approval program for diesel-powered equipment and 
portable, attended equipment should be established. This program should 
identify those equipment design features most readily addressed by the 
equipment manufacturers.
    <bullet> A time schedule should be developed to allow for 
conversion of outby equipment presently in use through retrofits, 
replacement, or additional interim safety features to meet the 
applicable new requirements.
    <bullet> Equipment newly introduced underground after a fixed date 
should meet the new standards.
    <bullet> Current safety requirements including those that are 
applicable to electric equipment should apply to diesel equipment as 
appropriate.
    <bullet> Only approved diesel engines should be used in underground 
equipment and the approval requirements should include measurements of 
exhaust gas pollutants and determination of a nameplate airflow 
quantity. Measurement of particulate generation should also be included 
in the engine approval process.
    In the proposed rule, MSHA outlined three new subparts for existing 
part 7, which set approval requirements for diesel engines and power 
packages to be used in underground coal mines. The Agency also gave 
notice of its intention to develop approval requirements for fully 
assembled diesel-powered machines under a proposed subpart H for 
permissible equipment and subpart I for large outby equipment. 
Requirements for a limited class of light-duty equipment and stationary 
unattended equipment were proposed in part 75. A special class of 
equipment consisting of ambulances and fire fighting equipment was 
proposed that could be used in emergency situations as part of the 
mine's evacuation plan. The proposal also included provisions to permit 
fire prevention features in lieu of surface temperature controls for 
diesel locomotives.
    Currently, MSHA approves diesel equipment under 30
CFR Part 36 for 
use in ``gassy noncoal mines''. In underground coal mines, ventilation 
plans specify the use of diesel-powered equipment approved as 
permissible under part 36 in areas where permissible electric equipment 
is required. In addition to the equipment approval under part 36, MSHA 
regulations address the approval of diesel mine locomotives in
30 CFR 
Part 31, and of mobile diesel-powered equipment for noncoal mines in
30 
CFR Part 32. The proposal suggested that parts 31, 32, and
36 could be 
revised or revoked, and solicited comment. Some commenters favored 
retaining all of the existing diesel approval regulations since they 
still could have some application for equipment used in metal and 
nonmetal mines. Commenters generally agreed that the proposed rules for 
part 7 should supersede any applicability these existing approval 
regulations have for diesel engines used in underground coal mines.
    The final rule for part 7 governs the approval of diesel engines 
intended for use in underground coal mines. As recommended by the 
Advisory Committee and as set forth in the proposed rule, the final 
rule requires that all diesel engines used in underground coal mines be 
approved.
    Part 7 was originally promulgated in 1988 to establish application 
procedures and requirements for MSHA approval of certain products for 
use in underground mines, with testing conducted by the applicant or a 
third party. Traditionally, MSHA's role in approving products for 
safety emphasized testing by the Agency. Under part 7, testing is 
performed by the applicant or by a third party selected by the 
applicant, with MSHA maintaining the right to observe product testing. 
This approach has permitted MSHA to focus on its product audit function 
and keep pace with technological improvements in mining products.
    As originally promulgated, part 7 applied to only two types of 
products: brattice cloth and ventilation tubing under subpart B, and 
battery assemblies under subpart C. Subsequently, three additional 
subparts were developed covering multiple-shot blasting units; electric 
motor assemblies; and electric cables, signaling cables, and cable 
splice kits. As designed, part 7 expedites the approval process, while 
providing greater assurance that the products are manufactured in 
accordance with safety specifications.
    The final rule for part 7 is organized into two subparts--E and F. 
Subpart E sets diesel engine performance and exhaust emission 
requirements. As more fully discussed elsewhere in the preamble, 
subpart E creates two classes of engine approvals--one for Category A 
engines and one for Category B engines. Engines intended for use where 
permissible electric equipment is required in underground coal mines 
must have a Category A approval; engines for use elsewhere in 
underground coal mines must meet the requirements for Category B 
engines.
    Subpart F of the final rule sets standards for safe design of 
diesel engines with respect to both fire and explosion hazards. The 
final rule establishes requirements for approval of diesel ``power 
packages'' on engines intended to be used where electric equipment is 
required to be permissible under existing standards. The term ``power 
packages'' refers to an approved engine and those components added to 
the engine, such as flame arresters, which prevent the ignition of 
methane, and surface temperature controls, which prevent the ignition 
of accumulations of combustible materials and combustible liquids. 
Permissible equipment is designed to be explosion-proof.
    Subpart G of the proposed rule would have established requirements 
for diesel

[[Page 55416]]

power packages intended for use in areas of underground coal mines 
where permissible electrical equipment is not required. As this 
equipment is not designed to be operated in a potentially explosive 
methane environment, the proposed rule would not have required these 
power packages to have explosion-proof features. However, these diesel 
engines do present fire hazards which must be controlled. Under the 
proposal, subpart G would have set standards for surface temperatures, 
exhaust cooling, and safety system controls. As discussed more fully 
below, the final rule does not retain subpart G, but addresses these 
hazards through new requirements in part 75.
    The proposed rule, responding to a recommendation of the Advisory 
Committee, also established a category of ``limited class of light-duty 
diesel-powered equipment.'' This category included machines with light-
duty cycles, such as pickup trucks and personnel carriers. This 
equipment, while light-duty as compared to production equipment, can, 
nevertheless, present a fire hazard. For this ``limited class'' of 
diesel-powered equipment, instead of requiring surface temperature 
controls, the proposal set standards for fire prevention features that 
would prevent fuel, hydraulic fluid, and lubricants from coming into 
contact with hot engine surfaces. Features such as special fuel system 
protection, fire suppression systems, safe electrical systems, and 
engine compartment sensors that shut down the engine in the event of 
overheating were specified in the proposal for additional fire 
protection. Other necessary safety features, such as braking systems, 
were also addressed by the proposal. As recommended by the Advisory 
Committee, these requirements were not made part of the approval 
process described above, but were set forth in the proposal as safety 
standards for underground coal mines, appearing in 30 CFR
Part 75.
    The final rule retains many of the provisions of the ``limited 
class'' concept in the proposal, but broadens the scope of the 
equipment subject to these requirements to include all equipment not 
required to be permissible (outby equipment). This change eliminates 
the need for formal approval of outby equipment, and simplifies the 
final rule. This aspect of the final rule, and the diesel-powered 
equipment approval requirements, are discussed in detail under the 
section-by-section analysis which follows.
    In the proposed rule MSHA notified the public of its intentions to 
develop two new approval regulations. Subpart H would have established 
requirements for the approval of fully assembled permissible diesel-
powered equipment, and subpart I would have established approval 
requirements for fully assembled nonpermissible diesel-powered 
equipment. These sections would have included machine features 
currently required by part 36 for permissible equipment and similar 
features, described above, for ``limited class'' equipment. These 
subparts would have required the incorporation of appropriate power 
packages as described in proposed subparts F and G.
    In the advance notice of proposed rulemaking, which accompanied the 
proposed rule, MSHA requested comments on this regulatory approach. 
Commenters objected to a formal approval program for nonpermissible 
equipment, but supported the incorporation of machine safety features 
in the use requirements specified in part 75. Commenters also supported 
the need for continuing the approval program for permissible equipment.
    In response to these comments, the final rule retains part 36 as 
the basis for the approval program for permissible diesel-powered 
equipment and adopts the machine safety features specified for the 
limited class of light-duty equipment in the proposal for all 
nonpermissible equipment. Subparts H and I are not further developed. 
Instead, the final rule adopts the fire prevention features specified 
for limited class equipment for all nonpermissible equipment. 
Additionally, the final rule enhances the fire prevention features that 
now apply to all nonpermissible equipment. This approach eliminates the 
need for subpart G of the proposal dealing with power packages for 
outby equipment.
    The final rule makes certain revisions to part 36 to update and 
make these existing requirements more flexible. The final rule revises 
part 36 to remove references to ``gassy noncoal mines and tunnels'', 
thus making these existing regulations applicable to equipment intended 
for use in coal as well as in metal and nonmetal mines. In addition, 
part 36 is amended to afford equipment manufacturers the option of 
incorporating in equipment submitted for approval either a part 7, 
subpart F power package, or engine and safety component systems that 
meet the existing requirements of part 36. Under the final rule,
part 
36-approved equipment with a part 7, subpart F power package will be 
suitable for use in underground coal mines where permissible electrical 
equipment is required. Part 36 equipment with engine and safety 
component systems certified under part 36 will continue to be 
recognized for use in metal and nonmetal mines where permissible 
equipment is required.
    These changes are responsive to commenters who recommended that 
part 36 continue to be utilized for approving diesel-powered equipment. 
The final rule revisions to part 36 also retain, as recommended by 
commenters, a distinction between approval requirements for equipment 
used in coal mines and approval requirements for metal and nonmetal 
mining equipment.
    The final rule revokes parts 31 and 32. MSHA previously identified 
these regulations for elimination in its response to the President's 
March 4, 1995, Regulatory Reform Initiative. Parts 31 and 32 are 
outdated and, with the final rule changes to parts 7 and 36, are 
obsolete. Only nine approvals have been issued under part 31 since its 
inception, and none have been issued since 1977. No other MSHA 
standards require part 31-approved equipment, and diesel mine 
locomotive manufacturers have submitted approval applications under 
part 36 for locomotives intended to be used where permissible equipment 
is required. With the revocation of part 31, diesel mine locomotive 
manufacturers may continue to acquire equipment approvals under part 
36.
    The part 32 approval requirements for mobile diesel-powered 
equipment used in noncoal mines are likewise unnecessary. No MSHA 
regulation requires the use of part 32 equipment, and no
part 32 
machine approval has been issued since 1981. Part 32 engine 
certifications have continued to be issued by MSHA, however, and some 
state and federal agencies' regulations make reference to
part 32. 
State and federal agencies that reference part 32 are directed to look 
to part 7, subpart E, which contains engine requirements, and to 
Secs. 75.1909 and 75.1910, which contain the requirements for other 
machine features. Together, these final standards cover the 
requirements previously found under part 32. These new sections of the 
final rule will continue to accommodate those government agencies that 
reference MSHA approval or certification regulations.
    Likewise, manufacturers seeking part 32 engine approvals will be 
able to acquire the requisite engine approval through the new part 7, 
subpart E. Existing part 32 engine approvals continue to be valid.
    A significant issue for the Advisory Committee and in the proposal 
was the schedule set for compliance with the new standards for diesel-
powered equipment. The Advisory Committee

[[Page 55417]]

recommended that MSHA require diesel equipment newly introduced 
underground to meet the new standards after a certain date. The 
Committee further recommended that MSHA set a schedule for existing 
diesel equipment to meet any new requirements.
    The proposal called for the part 7 approval requirements to be 
effective 60 days after publication of the final rule. The schedule for 
requiring in-mine use of diesel equipment meeting the new requirements 
was set by proposed Sec. 75.1907. Under these provisions, the new 
requirements would have been met over a schedule ranging from six 
months to five years after the effective date of the final rule.
    The final rule follows the approach of the proposal, setting 
effective dates for the new approval requirements, as well as the 
schedule for requiring in-mine use of diesel-powered equipment which 
meets the new requirements. In response to the comments and as a result 
of not adopting proposed subparts G, H, and I, the final rule sets a 
compliance schedule ranging from 60 days to three years after 
publication of the final rule. In order to facilitate implementation of 
the final rule, MSHA will begin accepting approval applications under 
revised parts 7 and 36 immediately. In addition, MSHA will continue 
power package testing until the Agency determines that a competitive 
capacity exists in the private sector. At that time, MSHA will 
discontinue power package testing and rely solely on the part 7 testing 
provisions.
Subpart E Overview
    Subpart E of the final rule is new and amends existing part 7. As 
an amendment to these existing regulations, the general administrative 
provisions of subpart A of part 7 apply to the new subpart E 
application requirements.
    Subpart E establishes engine performance and exhaust emission 
requirements for MSHA approval of diesel engines for use in underground 
coal mines. As discussed elsewhere in this preamble, diesel engines for 
use in metal and nonmetal mines are approved under part 36.
    The final rule, like the proposal, creates two classes of engine 
approvals--Category A and B--for diesel engines to be used in 
underground coal mines. Several commenters objected to the proposed 
approval of diesel engines for use in outby areas, noting that outby 
electrical equipment is not subject to approval under existing 
standards. However, other commenters stated, and the Diesel Advisory 
Committee acknowledged, that all diesel engines in underground coal 
mines should meet certain safety and performance specifications. In its 
report the Advisory Committee suggested that, depending on equipment 
location and use, different requirements would be appropriate for 
diesel engines. One commenter to the proposal recommended that all 
diesel engines be approved as permissible.
    For underground coal mines, MSHA believes that clean-burning 
engines are critically important. Unlike electrical equipment, diesel 
engines emit exhaust which contains toxic gases that can be harmful to 
miners. Inappropriately designed engines can pollute the mine 
atmosphere excessively, elevating toxic gases to levels that cannot be 
controlled with normal ventilation practices.
    To achieve the objective of clean-burning, appropriately designed 
engines in mines, the final rule sets performance standards for all 
diesel engines, whether they are operated in the face area or outby.
    The emission test requirements for Category A and B engines are the 
same, except that Category A engines are tested with methane injected 
into the intake system. Equipment operating at or near the point of 
coal extraction and in return air courses may encounter concentrations 
of methane gas, which is liberated during mining. Testing an engine 
with methane injected in its intake simulates operation of the engine 
in these areas of coal mines. Operation in methane atmospheres causes 
an increase in exhaust emissions, which requires higher ventilation 
rates.
    Under the final rule, diesel equipment used in areas where 
permissible electrical equipment is required by existing standards 
incorporate fire and explosion prevention features provided by a power 
package. Such a power package must include a Category A engine and 
components added to the engine to prevent the ignition of methane and 
accumulations of combustibles. Power packages intended for use with 
Category A diesel engines must be approved under part 7, subpart F of 
the final rule.
    Current safety standards require that intake air courses in areas 
away from or outby the mining face be maintained free of explosive 
concentrations of methane. Engines used on equipment operated in these 
outby areas must have a Category B approval under the final rule. 
Engines approved under Category B are emission tested without the 
injection of methane into the engine's intake system.
    The proposed technical requirements for diesel engines addressed 
the control of gaseous exhaust emissions and quantification of the 
engines' particulate matter generation. The proposed rule also set 
specifications for the equipment used and the standard laboratory test 
conditions for determining gaseous and particulate output for diesel 
engines. The proposed requirements for measuring gaseous emissions were 
derived from now-removed part 32 and existing part 36,
and the proposed 
requirements for measuring diesel particulate were based on the 
Environmental Protection Agency's requirements published in 40 CFR
Part 
86. In addition, the proposal specified the engine operating parameters 
as well as a method to calculate the ventilation rate and particulate 
index for the engine.
    Engine manufacturers do not manufacture engines specifically for 
mining. Typically, ``off-road'', heavy-duty diesel engines are utilized 
in mining equipment. Over-the-road utility vehicles and smaller general 
industry equipment are also used in mines. At the time of the proposed 
rule, the only certification test specifications designed for engines 
used in mining were the MSHA engine certification standards in now-
removed part 32 and in existing part 36.
    In the proposal, MSHA used its rules in now-removed part 32 and 
existing part 36 for the steady-state test for gaseous diesel exhaust 
emission. The test equipment specified in the proposal for diesel 
exhaust particulate measurement was modeled after the transient test 
equipment required in 40 CFR Part 86, subpart N.
    Commenters to the proposal stated that a correlation should not be 
made between MSHA's proposed rule and then-current EPA testing, because 
the proposal used a test with specific points in a ``steady state'', 
while EPA used a ``transient test.'' Commenters also recommended using 
the same test cycle for both gaseous and particulate matter. In 
addition, commenters generally recommended comparability of testing for 
similar types of tests and indicated a desire to use international 
standards whenever possible.
    The International Organization for Standardization (ISO) has 
prepared ``ISO 8178 Reciprocating Internal Combustion Engines--Exhaust 
Emission Measurement'', which includes test specifications for off-road 
diesel engines. The ISO is a recognized international standard-setting 
body. Equipment manufacturers, as well as other standard-setting 
bodies, make reference to and adopt the standards developed by the ISO.

[[Page 55418]]

    ISO 8178 is an international test standard for measuring off-road 
diesel engine emissions. It contains a detailed description of the test 
equipment requirements and standard procedures for conducting a steady-
state test to determine both gaseous and particulate emissions. The ISO 
8178 procedures also specify an 8-point test cycle for measuring both 
gaseous and particulate emissions. ISO 8178 does not set emission 
limits.
    The final rule is based on the ISO 8178 ``Reciprocating Combustion 
Engines--Exhaust Emission Measurement'', part 1 test procedures that 
apply to gaseous and particulate emission testing for diesel engines. 
This change from the proposal is responsive to commenters' concerns 
about correlating the proposed rule and EPA diesel engine tests, and 
simplifies the test procedures. For example, under the final rule the 
gaseous emission tests are reduced to 8 test points from 39 test points 
under the proposal. The particulate emission tests are also reduced 
from 10 to 8 test points. In addition, the final rule permits the tests 
for exhaust gaseous and particulate emission tests to be performed 
concurrently following the same test cycle, rather than independently 
following different cycles. A number of minor changes are made in 
Secs. 7.86, 7.87, 7.88, and 7.89 of the final rule, so that the tests 
performed under these sections conform to the ISO 8178 requirements. 
Substantive changes to these sections are discussed in this overview 
and in the section-by-section discussion that follows.
    The final rule adds one requirement to the ISO 8178 test 
procedures. Section 7.89(a)(5)(iii) requires that 1.0 percent of 
methane be added to the intake air for testing Category A engines. This 
addition to the ISO 8178 procedure should present no technical 
difficulties for manufacturers or third-party laboratories. MSHA, 
however, will provide technical assistance for setting up this aspect 
of the test procedure upon request. The final rule also requires a test 
to determine the maximum fuel-to-air ratio, and specifies requirements 
for determining the gaseous ventilation rate and particulate index for 
diesel engines.
    Basing the final rule on an international consensus standard 
enables diesel engine manufacturers to test with a single set of 
procedures common to both the United States and foreign markets. Also, 
existing test facilities established to perform tests to these 
international standards can be used to perform the tests prescribed by 
this final rule. In addition, use of the ISO 8178 test procedures leads 
to better comparability with international testing practices, and 
provides a more competitive posture for American products in foreign 
markets. Many off-road engine manufacturers are already complying with 
EPA and California Air Resources Board (CARB) requirements, which 
include testing in accordance with ISO 8178 procedures.
    One commenter to the proposal objected to permitting engine 
manufacturers or third-party laboratories to test diesel engines for 
conformance to approval standards, questioning the objectivity of such 
an approach. MSHA experience over eight years with manufacturers and 
third- party laboratory testing under existing part 7 and the Agency's 
program for off-site testing (POST) of diesel engines confirms that 
non-MSHA testing is performed competently and produces reliable 
results. In addition, MSHA will initially witness all tests conducted 
by manufacturers and third parties to ensure continued reliability of 
test results. In all cases, MSHA will accept only results of tests 
performed by manufacturers or third-party laboratories which have the 
capability to competently perform the required tests with properly 
calibrated instrumentation.
    Section 7.81  Purpose and effective date. The part 7, subpart E 
approval requirements are effective November 25, 1996. MSHA will begin 
accepting applications under subpart E immediately, but will complete 
any in-house part 32 applications, or evaluate such applications under 
the new part 7, subpart E, at the applicant's choice. As discussed 
elsewhere in this preamble, the requirements for the use of approved 
diesel engines in underground coal mines are effective in 3 years.
    Commenters to the proposal generally supported the approval 
requirements of subpart E for diesel-powered equipment to be used in 
underground coal mines. Several commenters suggested, however, that a 
phase-in period, up to three years, be established. According to these 
commenters, manufacturers would use the phase-in period to gain 
experience with the new test procedures, become familiar with new 
engine approval application procedures, and re-evaluate their existing 
approvals.
    The final rule does not incorporate a phase-in period for diesel 
engine approvals. Diesel engine manufacturers and third-party testing 
facilities are familiar with the ISO 8178 test procedures on which the 
final rule is based, and have the capability to perform these tests in 
their laboratories with minor changes. In fact, two engine 
manufacturers and a testing laboratory have tested diesel engines for 
MSHA approval using the ISO 8178 procedure.
    With this diesel engine testing experience and capability already 
present in the marketplace, MSHA finds no reason to provide an extended 
phase-in period for the approval standards for diesel-powered 
equipment, and anticipates that manufacturers and third-party testing 
laboratories can immediately begin testing engines under subpart E.
    Section 7.82  Definitions. In addition to the existing definitions 
in Sec. 7.2, Sec. 7.82 of the final rule sets out and clarifies the key 
terms which apply in subpart E. Commenters generally agreed with the 
proposed definitions, which were derived from definitions developed for 
ISO 8178 and the Society of Automotive Engineers (SAE) Recommended 
Practice J177.
    No comments were received on the proposed definitions for 
``Category A engines'', ``Category B engines'', ``corrosion-resistant 
material'', ``diesel engine'', ``exhaust emission'', ``percent load'', 
and ``steady-state condition''. These terms and their proposed 
definitions are adopted in the final rule.
    The definitions of the terms ``rated speed'' and ``intermediate 
speed'' in the proposed rule have been modified in the final rule in 
response to a commenter who recommended that MSHA's definitions of 
these terms conform to definitions contained in internationally 
accepted standards. The definitions of these terms in the final rule 
are conformed to the definitions in ISO 8178.
    The term ``peak torque speed'' in the proposed rule has been 
changed to ``maximum torque speed'' in the final rule to conform with 
ISO 8178. Both terms convey the same meaning.
    One commenter objected to the definition of ``diesel particulate 
matter'' as ``any material, with the exception of water, which is 
collected on a filter passed by an air diluted exhaust stream.'' 
According to this commenter the proposed definition was vague and too 
dependent on the filter used and method of sampling. The final rule 
does not include the proposed definition, adopting instead the 
definition for diesel particulates contained in ISO 8178. The ISO 
definition is more specific, providing that diesel particulates are 
``any material collected on a specified filter media after diluting 
diesel exhaust gases with clean filtered air at a temperature less than 
or equal to 325 K (52 deg. C) as measured at a point immediately 
upstream of the primary filter. This is primarily carbon, condensed 
hydrocarbons, and sulphates

[[Page 55419]]

and associated water.'' In addition, the filter and sampling methods, 
which are well detailed in ISO 8178, are included in the final rule. 
The objective of this definition is to facilitate accurate, repeatable 
tests for the diesel particulate matter in an engine's exhaust. Other 
definitions may be more appropriate for addressing health effects.
    The same commenter also objected to the proposed definition of 
``total oxides of nitrogen'' as focusing only on nitric oxide and 
nitrogen dioxide. The commenter suggested revisions to these 
definitions and offered definitions for several other terms used in the 
proposed rule, including ``gaseous ventilation'', ``particulate 
index'', ``threshold limit value'', ``permissible exposure limit'' and 
``recommended exposure limit.'' According to the commenter, these terms 
were not used consistently in the proposal. The final rule does not 
adopt these suggested changes. Many of these terms have accepted 
meanings that are well known. However, changes throughout the final 
rule have been made to be sure the terms are used consistently and 
appropriately.
    The proposed definition of rated horsepower is revised in the final 
rule to conform with current procedures for evaluating engines under 
existing part 36. This change will help define an engine's power output 
as it is related to performance testing. A definition for the term 
``operational range'' is added to also conform with current procedures 
for evaluating engines under existing part 36.
    Section 7.83  Application requirements. The proposed application 
requirements were derived from now-removed part 32 and existing
part 36 
and are largely unchanged in the final rule. The application procedures 
are designed to provide sufficient information to demonstrate 
compliance with the technical requirements of subpart E, and form the 
basis for approval of diesel engines.
    The final rule adopts the proposal to permit applicants to submit 
composite drawings in lieu of individual drawings. This approach 
reduces paperwork and affords applicants flexibility in the preparation 
of their drawings.
    The final rule also provides for certain information to be 
submitted after approval testing. This information includes the 
ventilation rate and particulate index for the engine, and the fuel 
deration chart, which provides guidance for how to adjust approved 
engines to compensate for altitude.
    Like existing part 7 and other MSHA approval standards, the 
documentation formulated in the application process forms the basis for 
MSHA's approval. Approved diesel engines must be manufactured in 
accordance with the specifications contained in the approval and, once 
put into service, approved engines must be maintained and operated 
within the parameters set in the MSHA approval.
    In general, commenters concurred with the proposed application 
requirements. One commenter suggested that a description of the design 
features which promote efficiency and control over production of toxic 
emissions specifically include fuel injection timing. MSHA agrees that 
specifications for the fuel injection system of diesel engines and the 
fuel injection timing are key in controlling exhaust emissions. The 
proposal included a requirement that the fuel injection system be 
detailed in approval applications. However, a requirement specifying 
the fuel injection timing was not included in the proposed rule.
    The final rule adopts the proposed requirement for a description of 
the fuel injection system, and adopts in paragraph (b)(6) the 
suggestion that fuel injection timing also be specified. This 
information had been required in now-removed part 32 and is required 
for part 36 engine approvals and to help ensure accurate measurement of 
the engine's emissions during the tests and proper maintenance of the 
engine's fuel injection timing.
    Although the Agency allows electronic record storage in other areas 
of this regulation, electronic computer submission of part 7 approval 
applications is not yet available. MSHA's Approval and Certification 
Center is developing a means for computer submission, and at present 
has pilot programs to facilitate the use of electronic reporting. 
However, the system is in the formative stage and is not yet available 
for public use.
    The paperwork hours in the approval application, including test 
requirements, are assigned OMB control number 1219-0100.
    Section 7.84 Technical requirements. This section of the final rule 
sets the specific technical requirements for Category A and Category B 
diesel engines. The objective of this aspect of the final rule is to 
set standards which, when met, will produce clean-burning diesel 
engines that are safe and appropriate for use in the confined 
environment of underground coal mines.
    Like the proposal, the final rule's requirements for the gaseous 
emissions of diesel engines are based on appropriate sections of 
existing part 36 approval regulations for diesel engines.
Experience 
confirms that compliance with these regulations, which address fuel 
injection adjustments and fuel-to-air ratios, produces engines that 
operate without excessive gaseous emissions that can be harmful to 
miners.
    One commenter to the proposal suggested that the fuel injection 
system on approved diesel engines be required to be fixed and sealed so 
that it could not be changed. According to the commenter, sealing the 
system would prevent unauthorized changes.
    The final rule does not adopt this suggested change, as adjustments 
to diesel engine fuel injection systems are necessary for maintenance 
and to compensate for altitude. Adjustments such as these permit the 
fuel-to-air ratio for diesel engines to be maintained at a level which 
minimizes exhaust emissions.
    The final rule does, however, adopt the proposed security 
requirements to prevent unauthorized fuel injection system adjustments. 
Fuel injection system adjustments are required to be changeable only 
after breaking a seal, or by altering the injection system's design. 
For example, a shim may be added or removed to change the fuel pump's 
performance. These parts are supplied by engine manufacturers and must 
be used in accordance with the engine's approval. For engines with 
electronic fuel injectors, specialized computer interface equipment is 
used to adjust the computer programming sequence. The programming 
sequence must be installed by the engine manufacturer and is listed 
with the engine approval documentation. After adjustments are made in a 
fuel injection system, any seal removed must be replaced. Failure to 
follow these procedures for adjusting a fuel injection system would 
result in the engine no longer being in approved condition. Under 
Sec. 75.1914(a) of the final rule, diesel engines used in underground 
coal mines are required to be maintained in approved condition.
    Consistent with a recommendation of the Diesel Advisory Committee, 
the technical requirements for diesel engines also include undiluted 
exhaust limits for carbon monoxide and oxides of nitrogen, both of 
which have toxic properties which can be harmful to miners. The limits 
set for these gases, which are determined when the engine is operated 
at its maximum fuel-to-air ratio, are derived from existing 
Sec. 36.26(b) and now-removed Sec. 32.4(f). As noted in the proposal, 
applying these exhaust gas limits to diesel engines for use in outby 
areas is new.
    One commenter questioned why the proposal set the same undiluted 
exhaust gas limits for Category A and B engines, except that the carbon 
monoxide limit

[[Page 55420]]

was 0.30 percent for Category A engines, while the carbon monoxide 
limit for Category B engines was set at 0.25 percent. This aspect of 
the proposal, which is adopted without change in the final rule, 
recognizes a difference in the test procedure between Category A and B 
engines. As noted above, Category A engines must be designed to operate 
safely in face areas and return air courses where methane may be 
present. Thus, Category A engine testing is performed with 1.0 percent 
methane injected into the intake air. The methane acts as additional 
fuel in the engine, which affects the fuel-to-air ratio. This change in 
fuel-to-air ratio increases emission levels, especially carbon monoxide 
and oxides of nitrogen. Thus, the final rule technical requirements 
permit a slightly elevated carbon monoxide level for Category A engines 
during testing so as to avoid imposing an unnecessarily strict test 
requirement for this class of diesel engines. The ventilating air 
requirement, however, is based on the actual emissions measured during 
testing.
    The final rule also defines procedures to establish the ventilating 
air quantities necessary to maintain the gaseous emissions of diesel 
engines within existing required ambient limits. Emissions from both 
Category A and Category B engines are diluted to the same ambient 
levels when their ventilating air requirements are calculated. Like the 
proposal and consistent with the recommendations of the Diesel Advisory 
Committee, the final rule addresses this issue by requiring that a 
ventilation rate be set for each engine model. Under the final rule, 
this ventilation rate must appear on the engine's approval plate. The 
ventilation rate, calculated under Sec. 7.88 of the final rule, 
indicates the amount of air necessary to dilute carbon dioxide, carbon 
monoxide, nitric oxide, and nitrogen dioxide to within allowable 
levels. For consistency, the levels specified in the final rule are 
those set by existing Sec. 75.322. These exposure standards are based 
on the 1972 threshold limit values set by the American Conference of 
Governmental Industrial Hygienists (ACGIH) and have applied to 
underground coal mines for nearly 25 years. This aspect of the final 
rule comports with the recommendation of the Diesel Advisory Committee 
that gaseous diesel exhaust components not be treated differently from 
contaminants generated by other mining sources. The final rule does not 
adopt updated exposure standards at this time because this issue 
remains in the rulemaking process for Air Quality standards.
    The exposure levels adopted by the final rule for purposes of 
calculating the ventilation rate for an engine will lead to lower 
required air quantities for ventilating subpart E-approved engines, as 
compared to engines approved under now-superseded part 36. This is 
because engines previously approved under part 36 were required to 
dilute oxides of nitrogen and carbon dioxide to levels lower than 
currently specified by the threshold limit values (TLV<Register>'s) in 
Sec. 75.322. The ventilation rates set for engines under the final rule 
will be more precisely related to current exposure standards. In 
addition, Sec. 75.325(g) of the final rule revises the percentage of 
the approval plate air quantity that is required when multiple units of 
diesel equipment operate in the same air current. Finally, as discussed 
elsewhere, the final rule is designed to produce an integrated system 
of controls to protect miners from overexposure to harmful diesel 
emissions.
    Commenters generally accepted the value and purpose of setting a 
ventilation rate for each diesel engine model. Knowledge of the 
ventilation rate needed to control gaseous emissions to safe levels 
will allow comparison of the efficiency and ventilation demands of 
different engine models, and facilitate evaluation of their general 
ventilation needs during use. One commenter, however, urged that the 
gaseous ventilation rate for control of diesel engine exhaust gases not 
be part of the approval process. According to this commenter, existing 
ventilation and air quality standards are adequate.
    The final rule adopts the requirements for determining the 
ventilation rate necessary to dilute diesel engine exhaust 
contaminants. Ventilation systems provide different quantities of air 
at different locations in the mine. Knowing the ventilating air 
quantities needed for diesel-powered equipment will allow the mine 
operator to make informed decisions about equipment selection and 
utilization and mine ventilation.
    Other commenters, who acknowledged the purpose of establishing 
ventilation rates for approved diesel engines, recommended for the sake 
of clarity that the levels set for the gases be specified in the final 
rule. In the proposal, MSHA had set these levels by reference to the 
time weighted average (TWA) concentrations for the gases. The final 
rule adopts this suggestion and the levels for carbon dioxide, carbon 
monoxide, nitric oxide and nitrogen dioxide are specified in the final 
rule. The levels in the final rule are identical to the levels in 
existing Sec. 75.322, and MSHA intends that the levels in the final 
rule conform with any levels that may ultimately be updated. 
Specifically, if any of the levels for any of these contaminants are 
revised as part of MSHA's Air Quality rulemaking, MSHA intends to 
conform the levels in this section to any revised levels.
    The proposed requirement for fuel deration received no comments. 
The purpose of this requirement, which is adopted without change from 
the proposal, is to ensure that the fuel-to-air ratio does not increase 
due to the lower density of air at higher altitudes. Not correcting the 
maximum fuel delivery on the engine for higher altitude operation 
results in increased emission levels. The fuel injection rate 
established during the approval may be required to be reduced when the 
engine is used at a higher altitude.
    Implementing a recommendation of the Diesel Advisory Committee, the 
proposed rule also called for a particulate index to be set for 
approved diesel engines. The particulate index specifies the quantity 
of air needed to dilute the particulate generated by the engine to 1 
milligram of diesel particulate matter per cubic meter of air. The 
control of particulate matter in diesel engine exhaust was a 
significant issue for the Advisory Committee. The Committee concluded 
that whole diesel exhaust represents a probable risk for causing human 
lung cancer, and recommended that MSHA develop a regulatory scheme to 
monitor and control diesel particulate underground. The Committee did 
not recommend an exposure level, but did urge that consideration be 
given to what level of exposure to diesel particulate presents a health 
risk to miners. MSHA is currently developing regulations, separate from 
this rule, to address this issue.
    The Diesel Advisory Committee also recommended that a particulate 
index be set for engines so that the mining industry and MSHA could 
compare the particulate levels generated by different engines in terms 
of a ventilating air quantity. For example, if the particulate indices 
for diesel engines of the same horsepower were established as 7,500 
cubic feet of air per minute (cfm) and 12,000 cfm respectively, an 
equipment manufacturer, mine operator, and MSHA personnel could use 
this information, along with consideration of the type of machine the 
engines would power and the area of the mine in which it would be used, 
to make certain decisions. For example, a mine operator could use this 
information when choosing an engine to roughly estimate an engine's 
contribution of diesel particulate to the mine's total respirable

[[Page 55421]]

dust. MSHA would use this information when evaluating mine dust control 
plans. Equipment manufacturers can use the particulate index to design 
and install exhaust after-treatments.
    The final rule retains the proposed requirement for a particulate 
index to be set for approved diesel engines. Unlike the ventilation 
rate set for each engine, the particulate index value will not appear 
on the engine's approval plate. The particulate index, calculated under 
Sec. 7.89 of the final rule, indicates what air quantity is necessary 
to dilute the diesel particulate in the engine exhaust to 1 milligram 
of diesel particulate matter per cubic meter of air. This information 
will be available to the mining industry from the engine manufacturer 
and MSHA.
    Some commenters to the proposal objected to the use of a 
particulate index to establish required ventilation air quantities for 
diesel engines. These commenters noted that a diesel particulate 
permissible exposure level has not yet been set and maintained that 
suitable monitoring technology is not available for widespread field 
use. These commenters also urged that control of diesel particulate in 
underground mines be accomplished through a combination of measures, 
including fuel requirements, equipment design, and controls such as 
ventilation and equipment maintenance. The commenters recommended that 
the particulate index not be part of the engine ventilation rate, and 
concluded that such an index should be viewed as a guideline providing 
useful information about diesel engines. The commenters further 
suggested that additional evaluation be undertaken to determine 
appropriate procedures for setting a particulate index.
    The overall approach of the final rule is to control diesel 
emissions in the underground mine environment through various 
established methods, including those suggested by commenters. The 
information provided by the particulate index is part of the multi-
level approach recommended by the Diesel Advisory Committee.
    As explained above, the particulate index value determined for a 
diesel engine is intended to provide useful information about diesel 
engines, as the commenters suggested. In addition, the particulate 
index value does not appear on the equipment's approval plate and 
therefore is not considered in setting the engine's required 
ventilation rate.
    Section 7.85  Critical characteristics. Critical characteristics, 
which are specified for all part 7-approved products, are those 
features or specifications which, because of their importance to proper 
operation of the equipment, must be inspected or tested on each unit 
manufactured. The proposal called for inspecting or testing each diesel 
engine to verify that the fuel rate is set to altitude, and the fuel 
injection pump adjustment is sealed, if applicable. No comments were 
received on this aspect of the proposal, and the final rule adopts the 
proposal without substantive change. Instead of requiring the fuel rate 
to be set to altitude, the final rule specifies that the fuel rate be 
properly set.
    As discussed elsewhere in this preamble, the rate of fuel delivery 
to a diesel engine significantly affects its gaseous and particulate 
emission. As noted earlier, correct adjustment of the fuel injection 
pump is essential to the efficient operation of diesel engines.
    Inspecting or testing the proposed critical characteristics for 
diesel engines approved under part 7, subpart E reasonably ensures that 
the performance and emission characteristics of production engines will 
be equivalent to those of the engine tested for approval. As a result, 
miners are protected against harmful exposure to diesel emissions.
    No comments were received on this aspect of the proposal, which is 
adopted by the final rule, with the change noted above.
    Section 7.86  Test equipment and specifications. This section 
adopts the measurement and evaluation methods for emissions from diesel 
engines as described in ISO 8178-1. The final rule describes the 
apparatus, or test cell, required for testing diesel engine 
performance, and sets the specifications for operating this testing 
equipment to perform steady-state tests for both gaseous and 
particulate emissions.
    The major components of a test cell are a dynamometer with engine 
operating controls, and gaseous and particulate emission measurement 
systems. This test cell is used to perform the test required by 
Secs. 7.87, 7.88, and 7.89 of the final rule. Most engine testing 
laboratories today have the equipment and meet the specifications 
called for by ISO 8178-1 and the final rule.
    The final rule's test cell requirements are substantially the same 
as the proposed requirements, except that the specifications for the 
testing apparatus and test conditions are revised to conform with ISO 
8178-1. Commenters to the proposal did not direct attention to these 
requirements, but did express concern about correlating the proposed 
rule test requirements and Environmental Protection Agency diesel 
engine tests, and recommended that the MSHA procedures conform to 
internationally accepted test procedures. The adoption of the ISO 8178-
1 provisions eliminates this issue and is responsive to commenters' 
concerns.
    Like the proposal, the final rule also sets specifications for the 
fuel to be used during testing of diesel engines. The proposed rule 
would have required No. 2D diesel fuel with certain properties. A 
uniform test fuel is important to obtaining repeatable test results and 
test data that can be compared. Commenters did not direct their 
attention to this aspect of the proposal, except that they generally 
encouraged adoption of international standards to the extent possible.
    The final rule revises the proposed requirements for diesel engine 
test fuel to conform with the fuel requirements in Sec. 75.1901. 
Section 75.1901 of the final rule specifies the use of diesel fuel 
containing no more than 0.05 percent sulfur. Under this section, diesel 
fuel used for engine testing must also be low in sulfur content. In 
addition, the properties specified for test fuel conform with the test 
fuel EPA requires for testing diesel engines that use low sulfur fuel. 
Thus, the final rule will not require testing laboratories to acquire 
special fuel to comply with the final rule.
    The final rule also adopts the proposal that Category A engines, 
which are intended for operation in areas of mines where concentrations 
of methane gas could be encountered, be tested with 1.0 percent of 
methane added to the engine's intake air. As noted above, this addition 
to the ISO 8178 test procedure adopted by the final rule should present 
no technical difficulties for manufacturers or third-party 
laboratories. MSHA, however, will provide technical assistance for 
setting up this aspect of the test procedure upon request.
    Metering in 1.0 percent of methane to the intake air of Category A 
engines replicates a foreseeable operating condition in underground 
mines. In addition, methane gas acts as a fuel when it is aspirated 
into a diesel engine, increasing its output of carbon monoxide and 
oxides of nitrogen. These emission effects need to be accounted for in 
determining the gaseous ventilation rate for Category A engines.
    Section 7.87  Test to determine the maximum fuel-to-air ratio. As 
noted earlier, the tests prescribed by this section are performed using 
the test cell meeting the requirements of Sec. 7.86. Determining the 
maximum fuel-to-air ratio for diesel engines is essential to 
controlling harmful diesel engine emissions. Too rich a fuel and air

[[Page 55422]]

mixture produces engine exhaust with elevated levels of carbon monoxide 
and oxides of nitrogen.
    Under this section, engines are required to be operated at several 
speed/torque conditions to determine the concentrations of carbon 
monoxide and the oxides of nitrogen. Acceptable performance is achieved 
when the levels of these exhaust gases do not exceed the limits set by 
Sec. 7.84(b) of the final rule throughout the operational range of the 
engine.
    Commenters did not address the proposed test to determine the 
maximum fuel-to-air ratio for diesel engines. The final rule adopts the 
proposal without change.
    Section 7.88  Test to determine the gaseous ventilation rate. The 
test to determine the gaseous ventilation rate for a diesel engine is 
required by the final rule to be performed using the test cell required 
by Sec. 7.86. This test may be performed together with the test to 
determine the particulate index required by Sec. 7.89.
    The test required by this section measures the undiluted exhaust 
gas concentrations of carbon monoxide, carbon dioxide, nitric oxide, 
and nitrogen dioxide in the exhaust. These constituent gases of diesel 
engine exhaust are potentially harmful to miners in the confined 
environment of underground mines.
    In accordance with Sec. 7.86, exhaust gas measurements must be made 
at 8 specified points while the engine is operated at each rated speed 
and horsepower requested by the approval applicant. For Category A 
engines, 1.0 percent methane is added to the engine's intake, as 
discussed above.
    Like the proposal, the final rule specifies the calculations to be 
performed using the results obtained from the test procedure. These 
calculations produce a gaseous ventilation rate for the diesel engine. 
As discussed above, the ventilation rate indicates the amount of 
ventilating air necessary to dilute carbon monoxide, carbon dioxide, 
nitric oxide and nitrogen dioxide to within permitted levels. The 
ventilation rate for each approved Category A or B diesel engine will 
appear on the engine's approval plate. Knowledge of the ventilation 
rate needed to control gaseous emissions to safe levels will allow 
comparison of the efficiency and ventilation demands of different 
engine models, and their general ventilation needs during use can be 
evaluated.
    As discussed above, commenters generally accepted the value and 
purpose of setting a ventilation rate for each diesel engine model. One 
commenter urged that the ventilation rate not be part of the approval 
process, while others supported the approach taken in the proposed and 
final rules. These commenters, however, suggested that the levels for 
the exhaust gases be stated in the final rule. The final rule adopts 
this suggestion in Sec. 7.84(c).
    Section 7.89  Test to determine the particulate index. Like the 
other engine tests prescribed by the final rule, the test to determine 
the particulate index for an engine is required by the final rule to be 
performed using the test cell required by Sec. 7.86. As noted above, 
this test may be performed concurrently with the test to determine an 
engine's gaseous ventilation rate required by Sec. 7.88.
    The test required by this section measures the amount of 
particulate in the engine's exhaust when it is operated at eight 
specified operating conditions. For Category A engines, 1.0 percent 
methane is added to the engine's intake, as discussed above.
    The proposed rule would have required that the particulate index be 
determined using a different set of test points than those used to 
determine the gaseous ventilation rate. The particulate index tests 
were based on a cycle of 10 test points. In response to commenters' 
suggestions that the particulate and gaseous emissions tests be 
conducted using the same test cycle and internationally accepted test 
procedures, the final rule adopts the same ISO 8178-4, 8-point test 
cycle for both the particulate and gaseous emissions tests.
    The Diesel Advisory Committee observed that whole diesel exhaust 
represents a probable risk for causing human lung cancer. While 
proposing no specific exposure level, the Diesel Advisory Committee 
recommended control of diesel particulate in engines used underground 
through a combination of measures, including equipment design.
    Like the proposal, the final rule does not set a particulate limit 
for engines. Instead, the final rule specifies the calculations to be 
performed using the results obtained from the test procedures in this 
section. From the calculations, a particulate index is derived. As 
discussed above, the particulate index for an engine does not appear on 
its MSHA approval plate. This information will be available, however, 
from MSHA and the engine manufacturer.
    Section 7.90  Approval markings. This section requires that each 
approved diesel engine be identified with a permanent approval plate 
containing certain information. Approval markings to identify equipment 
appropriate for use in mining have been used for more than 85 years, 
and are routinely relied upon by users of mining equipment as well as 
state and federal inspection authorities.
    The information required to be displayed on diesel engine approval 
plates includes the MSHA-assigned approval number, together with the 
engine's model number, ventilation rate, rated power, high idle 
setting, and the altitude above which the engine must be derated. 
Including these specifications on diesel engine approval plates gives 
engine users convenient, immediate access to information important to 
proper maintenance and operation of diesel engines.
    Commenters directed little attention to this aspect of the 
proposal, which is adopted without change in the final rule. Commenters 
who objected to setting a ventilation rate for diesel engines as part 
of the approval process repeated this concern with respect to the 
requirement for the ventilation rate to appear on engine approval 
plates. As discussed above, setting a gaseous ventilation rate for 
diesel engines comports with the recommendations of the Diesel Advisory 
Committee and provides diesel equipment users with information 
important to protecting miners. Knowledge of the rate of ventilation 
needed to control the gaseous exhaust emissions of a diesel engine 
facilitates comparison of the efficiency and ventilation demands of 
different engine models.
    The other information required by the final rule to appear on an 
engine's approval plate likewise provides engine users needed data. The 
high idle setting informs maintenance personnel of the engine speed 
appropriate for conducting several of the tests to be performed as part 
of the engine's permissibility checklist. Together, an engine's 
approval number, model number, and its rated power and speed facilitate 
use of the manufacturer's maintenance procedures. The maintenance 
procedures, along with the altitude above which the engine must be 
derated, specify the adjustments which must be made to ensure that an 
engine continues to operate in approved condition.
    Burden hours required to make and mount MSHA approval plates are 
assigned OMB control number 1219-0100.
    Section 7.91  Post-approval product audit. This section 
incorporates the standard audit requirement for part 7-approved 
equipment, specifying that approval holders must make a diesel engine 
available for audit by MSHA, at no cost to the Agency. The obligation 
to

[[Page 55423]]

supply an engine for audit under this section arises only upon request 
by MSHA, and is limited to no more frequently than once a year, except 
for cause. Under existing Sec. 7.8(b), the approval holder may observe 
any tests conducted under the audit.
    Post-approval audits are a critical part of MSHA's quality control 
program for approved equipment. By inspecting and testing an engine for 
continuing compliance with its approval specifications, potential 
problems can be detected and confidence in the approval process is 
maintained. Since the inception of post-approval product audits under 
part 7, MSHA has detected numerous discrepancies, which have been 
effectively corrected.
    Commenters directed no attention to this aspect of the proposal, 
which is adopted without change from the proposal.
    Section 7.92  New technology. This section is designed to 
facilitate the introduction of new technology or new applications of 
existing technology. It allows MSHA to approve a diesel engine that 
incorporates technology for which the requirements of subpart E are not 
applicable, provided that MSHA determines the engine is as safe as one 
which meets the requirements of subpart E. To make this determination, 
MSHA develops appropriate technical requirements and test procedures 
when novel designs are submitted for approval. Experience with this 
provision under existing regulations has shown that new innovations can 
be effectively evaluated and made available for use in a prompt 
fashion, thus serving the best interests of miners' safety and health.
    Commenters supported this aspect of the proposal, stressing that 
research and technological improvements in diesel engines can be 
expected. The final rule adopts the proposal without change.
Subpart F Overview
    Subpart F of the final rule amends existing part 7, which specifies 
testing by the approval applicant or a third party. As an amendment to 
the existing regulations, the general administrative provisions of 
subpart A of part 7 apply to these new subpart F application 
requirements.
    Subpart F establishes design and performance requirements for MSHA 
approval of ``diesel power packages'' for use in areas of underground 
coal mines where permissible electrical equipment is required by 
existing safety standards. A ``diesel power package'' is a diesel 
engine, together with the attached safety components, such as flame 
arresters, spark arresters, surface temperature controls, shut down 
systems, and the exhaust cooling system that make a diesel engine 
explosion-proof and reduce the engine's surface temperature to a safe 
level. Like the proposal, the final rule requirements for diesel power 
packages are largely derived from existing MSHA approval regulations in 
part 36, which apply to diesel engines for use in gassy underground 
mines. The final rule is also consistent with current MSHA practices 
for coal mines using diesel-powered equipment and with the 
recommendations of the Diesel Advisory Committee. The Advisory 
Committee specifically recommended an approval program for diesel power 
packages.
    Commenters generally accepted the proposal for MSHA approval of 
diesel power packages, recognizing the need for diesel-powered 
equipment used in underground coal mines to meet critical 
specifications and to be properly tested for safe operation in a 
potentially explosive atmosphere. Some commenters directed their 
attention to the effective date of subpart F, expressing concern about 
the availability of commercial testing facilities. For the reasons 
discussed below, the final rule does not adopt an extended phase-in 
period. However, accommodations are made in the final rule to simplify 
the implementation of testing in the private sector, and MSHA will 
continue to perform diesel power package testing to subpart F 
specifications for up to 3 years, pending the development of private 
sector resources.
    Other commenters recommended that diesel engine exhaust after-
treatment devices, such as particulate filters or catalytic converters, 
be required as part of diesel power packages. These commenters also 
suggested that the ventilation rate and particulate index set under 
Secs. 7.88 and 7.89 of the final rule credit the use of such devices.
    The final rule responds to these comments in part. Under the MSHA 
approval program in subpart E, MSHA will evaluate exhaust gas and 
particulate controls, provided these devices are integral to the engine 
design and are part of normal production engines. The effectiveness of 
such controls will also be considered in setting the engine's 
ventilation rate and particulate index. This approach will ensure that 
the controls are compatible with the engine and are effective. MSHA has 
already approved, under existing regulations, engines which incorporate 
techniques such as electronic fuel injection systems. Exhaust after-
treatment devices that are not part of an engine's design and 
production have been developed which can reduce the particulate matter 
in diesel engine exhaust. Also, catalytic converters are available 
which can be added to engines to reduce the levels of some harmful 
gaseous emissions. MSHA encourages the use of these devices, and under 
existing regulations has approved, as safe, several power packages that 
utilize catalytic converters and particulate filters. However, under 
the final rule MSHA will not evaluate the effectiveness of these 
exhaust after-treatment devices. Exhaust after-treatment devices 
encompass a wide range of concepts that have demonstrated varying 
degrees of effectiveness and reliability. The evaluation of these types 
of after-treatment devices is beyond the scope of a part 7 approval 
program.
    For the same reasons, the final rule does not adopt a commenter's 
suggestion that the particulate index for an engine be adjusted to 
reflect the use of a diesel particulate filter. Also, the particulate 
index for an engine is intended to be used by manufacturers and mine 
operators as an aid for, among other things, selecting appropriate 
after-treatment devices such as particulate filters. Therefore, under 
the final rule the particulate index for an engine will indicate the 
particulate contained in the raw engine exhaust.
    Other aspects of the final rule will, however, recognize exhaust 
after-treatment controls. The positive effects of catalytic converters 
in lowering levels of harmful exhaust gases may be considered under 
Sec. 75.325(i) for reducing the quantity of ventilating air required 
where multiple pieces of diesel-powered equipment are in use. Also, 
particulate filters can be effective in maintaining compliance with the 
respirable dust standard set by existing Sec. 70.100.
    During the course of this rulemaking, the question has been raised 
as to whether the final rule should require that some or all diesel 
engines be equipped with particulate filters. As noted above, MSHA 
encourages the use of such filters and other emission controls. 
However, the proposed rule did not raise this issue and MSHA received 
only limited comment regarding the appropriate role of diesel 
particulate filters. The final rule, therefore, does not require the 
use of these filters. However, MSHA is currently developing a proposed 
rule to address control of miners' exposure to diesel particulate. This 
rulemaking will afford an opportunity to fully develop this issue.
    Other commenters suggested that diesel engine cooling system

[[Page 55424]]

components, such as radiators, not be included as part of the approval 
of diesel power packages so as to permit changes in cooling system 
components to be made in the field without affecting the engine's 
approval. The final rule does not adopt this suggestion. The inter-
relationship of the components in the cooling system of a diesel engine 
is critically important to controlling power package surface 
temperatures, which, when elevated, can lead to a fire. Consequently, 
the engine cooling system components must be considered an integral 
part of a diesel power package. This aspect of the final rule does not 
prohibit field radiator changes, provided that the inter-relationship 
of the engine's cooling system components is maintained in approved 
condition.
    A number of minor changes are made in Secs. 7.97, 7.98, 7.100, 
7.101, 7.102, and 7.103 of the final rule to clarify the requirements 
of these sections. Substantive changes to these sections are discussed 
in the section-by-section discussion which follows.
    Section 7.95  Purpose and effective date. The final rule's part 7, 
subpart F approval requirements apply to diesel power packages intended 
for equipment used in areas of underground coal mines where this 
equipment is required to be permissible. The design, performance and 
testing requirements of this section are effective November 25, 1996. 
MSHA will begin accepting applications under new subpart F immediately. 
To accommodate all interests, the Agency also will complete any in-
house part 36 safety component certification applications, or evaluate 
such applications under new subpart F, at the applicant's choice. As 
noted elsewhere in this preamble, the requirements for approved diesel 
power packages in equipment used in underground coal mines become 
effective in 3 years.
    As noted above, several commenters urged that an extended phase-in 
period of several years be included in the final rule. According to the 
commenters, a phase-in period is needed to allow for the development of 
competent third- party testing facilities, particularly with respect to 
explosion-proof testing. Other commenters suggested that subpart F be 
made effective immediately, so as to accelerate conformance to the new 
requirements for the benefit of miners' safety.
    A number of the final rule's test requirements can be performed 
effectively with inexpensive, simple test equipment or facilities, or 
with the power package installed in the mining equipment. For example, 
the static pressure test required by Sec. 7.104 to evaluate the 
structural integrity of power package components can be performed using 
currently available hand pump devices. Likewise, explosion-proof 
testing can be performed in inexpensive test chambers of relatively 
simple design.
    Nonetheless, MSHA recognizes that some testing capabilities are not 
immediately available in the private sector, such as surface 
temperature testing and exhaust gas cooling efficiency testing with 
methane gas injection in the intake air. To facilitate the approval of 
power packages and accommodate the needs of applicants, MSHA may be 
consulted for simple alternative procedures which can be used to 
provide the same results. In addition, MSHA will perform the tests 
required by subpart F for diesel power package approval at its Approval 
and Certification Center upon request by applicants. MSHA anticipates 
providing these test services, for the fees set in accordance with 30 
CFR Part 5, for up to 3 years, or until private sector testing 
capability is available. MSHA reserves the right to determine when 
competent private sector testing capability is available and to 
discontinue MSHA testing.
    Section 7.96  Definitions. In addition to the existing definitions 
in Secs. 7.2 and 7.82, this section of the final rule sets out and 
clarifies the key terms used in subpart F.
    Commenters did not direct specific attention to this aspect of the 
proposal. The final rule adopts the proposed definitions, with five 
exceptions, adds two terms and definitions, and deletes three 
definitions from the proposal which now appear in subpart E. These 
changes are intended to add flexibility to the final rule and respond 
to confusion among some commenters with respect to the substantive 
requirements of subpart F.
    The definition for ``exhaust conditioner'' has been revised to 
remove the words ``corrosion-resistant.'' The requirement for the 
exhaust conditioner to be made of corrosion-resistant material is 
adopted from the proposal in Sec. 7.98(s)(4)(i). The definitions for 
``exhaust system'' and ``intake system'' are revised to include the 
phrase ``but is not limited to'', to recognize the use of components 
not otherwise mentioned in the definitions for these terms. The term 
``explosive mixture'' has been changed to ``flammable mixture'' to 
conform with part 36, and the definition for this term has been 
modified with the non-substantive change of removing the word 
``violently.'' The definition for ``fastening'' has been modified for 
the sake of clarity to remove the words ``device such as'' when 
referring to bolts, screws, or studs. The term ``high idle speed/no 
load'' has been revised to ``high idle speed.'' This is another non-
substantive change, since ``no load'' is specified in the definition of 
the term. New definitions for ``dry exhaust conditioner'' and ``wet 
exhaust conditioner'' are added to the final rule to more clearly 
differentiate between the requirements for these systems. Under the 
final rule, a dry exhaust conditioner is defined as a device which 
cools exhaust gases without direct contact with water, such as a heat 
exchanger. A wet exhaust conditioner is defined as a system which cools 
exhaust gases through direct contact with water. Minor changes to the 
definitions for ``step (rabbet) joint'' and ``threaded joint'' have 
been made for the sake of clarity. The terms ``corrosion-resistant 
material,'' ``idle speed/no load,'' and ``rated speed'' and their 
definitions are deleted from subpart F. These terms are common to both 
subparts E and F, and have already been defined in subpart E. Section 
7.96 has been modified to incorporate the definitions of subpart E, 
Sec. 7.82.
    Section 7.97  Application requirements. This section is derived 
from existing part 36 and requires that an application for approval of 
a diesel power package contain sufficient information to document 
compliance with the technical requirements of the final rule. The list 
of information specified for inclusion in the approval application, 
which is revised from the proposal in response to commenters and to 
fully identify the engine and the fan blade material, is intended to 
help applicants supply the data necessary for a prompt evaluation. The 
final rule permits applicants to submit composite drawings. This 
approach reduces paperwork, affords applicants flexibility in the 
preparations of their drawings, and has proven to be effective in other 
MSHA approval programs.
    Like existing part 7 and other MSHA approval standards, the 
documentation formulated in the application process under Sec. 7.97 
forms the basis for MSHA's approval of a diesel power package. Approved 
diesel power packages must be manufactured in accordance with the 
specifications contained in the approval and, once put into service, 
approved power packages must be maintained and operated within the 
parameters set in the MSHA approval.
    The paperwork hours in the approval application, including test 
requirements, are assigned OMB control number 1219-0100.
    Section 7.98  Technical requirements. This section of the final 
rule sets specific technical requirements

[[Page 55425]]

for diesel power packages. Diesel power packages are intended for use 
with Category A engines so that they can be operated safely and not 
create a fire or explosion hazard. Consistent with the Advisory 
Committee's recommendation that permissible diesel equipment be 
required in areas of underground coal mines where permissible electric 
equipment is required, the final rule's technical specifications 
introduce many of the safety features currently required for 
permissible electric-powered equipment.
    Like the proposal, the final rule is derived largely from existing 
technical requirements in part 36 for diesel-powered equipment intended 
for use in gassy non-coal mines. The final rule also addresses the 
hazard of combustible coal dust by specifying a maximum surface 
temperature of 302  deg.F (150  deg.C). This is the same technical 
requirement applied to permissible electric-powered equipment. Other 
aspects of the final rule set specifications necessary to control 
engine surface temperatures, sparking, and the passage of flame from 
the exhaust system or components to the external atmosphere. Any of 
these conditions could ignite an explosion or fire in the underground 
coal mine environment.
    Commenters generally accepted the proposed technical requirements, 
which, as noted above, are based on long-standing regulations which 
have been proven effective and workable. Commenters did, however, raise 
several issues.
    Some commenters sought wider tolerances for explosion-proof 
enclosures in diesel power packages, citing experience in the United 
States and Europe. These commenters directed their attention to the 
proposed specifications for joints in engine exhaust systems, and 
suggested that MSHA review the proposed specification of 0.004 inches 
for maximum clearance for joints all in one plane.
    The final rule retains this specification, which has proven to be 
effective for decades. Commenters offered no basis for the 
recommendation for a wider tolerance.
    Other commenters suggested that electric starting devices for 
diesel engines be prohibited. The proposed rule recognized the 
conventional use of hydraulic, pneumatic or other mechanically actuated 
starting mechanisms, but also retained the flexibility to evaluate 
other means of starting under Sec. 7.107 of the rule concerning new 
technology. This aspect of the proposal differs from the existing part 
36 regulations from which this proposal was derived.
    The final rule is intended to serve as a flexible set of 
regulations that will continue to be workable over a period of years. 
Throughout the final rule MSHA has adopted the more current practices 
and, where appropriate, provides that alternatives may be developed 
which are safe and effective. With this in mind, the final rule does 
not expressly prohibit the use of electric starting devices for diesel 
engines, adopting the proposal to permit MSHA to evaluate other 
starting mechanisms. Such alternatives are subject to evaluation under 
Sec. 7.107 and must be found by MSHA to be as safe as the pneumatic and 
hydraulic starting mechanisms presently in use.
    Some commenters asked for clarification of proposed paragraph (i) 
with respect to the safety shutdown system required for diesel power 
packages. The safety shutdown system is required to automatically shut 
off the fuel supply and stop the engine in response to certain 
dangerous engine conditions. MSHA intended in the proposal, and the 
final rule clarifies, that the shutdown system must respond to both 
high exhaust temperature and low water level in the engine's exhaust 
conditioner. Either of these conditions can rapidly lead to a fire or 
explosion hazard.
    In addition, the final rule has been revised from the proposal to 
cover other safety system shutdowns that may be installed by the 
applicant. Section 75.342 requires methane monitors on some permissible 
equipment, and the final rule requires permissible equipment to be 
provided with a fire suppression system meeting the requirements of 
Sec. 75.1911. Both of these standards specify that the diesel engine 
must shut down when either an elevated level of methane is encountered 
or when the fire suppression system is actuated. This requirement will 
most likely be satisfied by a connection to the safety shutdown system. 
The technical requirements of this rule now cover these additional 
sensors.
    Another commenter suggested that the safety shutdown system include 
automatic brake lock-up to prevent diesel-powered equipment from 
rolling. This aspect of a machine's safety is evaluated under the 
existing requirements of part 36 and is not part of a diesel
power-
package approval. Thus, the final rule does not adopt this suggestion.
    The final rule adopts clarifying revisions in addition to changes 
made in response to commenters. In several instances more precise 
language is adopted to differentiate between requirements for wet and 
dry exhaust conditioner systems. Proposed Sec. 7.98(d) has been revised 
in the final rule to refer to ``nonmetallic rotating parts'' instead of 
``fans'', to conform with other MSHA regulations. Paragraph (p)(2)(ix) 
has been revised to require that the minimum thread engagement of 
fastenings must meet the requirements of the explosion tests in 
Sec. 7.104. This is a correction. This change conforms to paragraph 
(p)(2)(viii), which requires both tests for acceptance of a minimum 
thread engagement of fastenings less than \3/8\ inch. In addition, 
paragraph (q)(7) of the final rule does not retain the proposed 
requirement that a ``minimum of four fastenings'' be used for 
explosion-proof joints. MSHA's experience shows that flange designs 
with fewer than four fastenings have proven to be effective. Paragraph 
(r)(5) has been revised to note that the opening for connection of a 
gage to measure the intake vacuum must be closed by a plug or other 
suitable device that is sealed or locked in place except when in use. 
This language conforms to the language of part 36, and closing of this 
opening is necessary to perform certain tests in this subpart. 
Paragraph (s)(1) has been revised to require that the flame arrester 
prevent the discharge of glowing particles, conforming it to the 
requirement in part 36. Finally, paragraph (s)(5) has been revised to 
note that the opening for connection of a gage to measure the 
backpressure must be closed by a plug or other suitable device that is 
sealed or locked in place except when in use. This language also 
conforms to part 36, and is needed to perform some of the tests under 
this subpart.
    Section 7.99  Critical characteristics. Critical characteristics, 
which are specified for all part 7-approved products, are those 
features or specifications which, because of their importance to proper 
operation of the equipment, must be inspected or tested on each unit 
manufactured. The proposal focused on power package features essential 
to preventing fires and explosions in the underground coal mine 
environment, such as flame-arresting path clearances and the explosion-
proof integrity of the power package. Commenters did not direct their 
attention to this aspect of the proposal, which is adopted without 
change in the final rule.
    Section 7.100  Explosion tests. This section describes the tests to 
be performed on diesel power packages to ascertain whether they are 
explosion-proof, as specified by the technical

[[Page 55426]]

requirements in Sec. 7.98. Like the proposal, the final rule is derived 
from existing Sec. 36.46. Using an explosive mixture of natural gas and 
air, or methane and air, the tests prescribed by the final rule 
determine the power package's integrity in the event of an explosion 
inside the intake or exhaust system. This could be caused by an engine 
backfire during starting or ingestion of methane into the engine while 
it is running. The prescribed tests determine whether flame arresters 
and joints are capable of preventing propagation of the internal 
explosion to the surrounding atmosphere. These tests also determine the 
lowest water level in the exhaust conditioner that will act effectively 
as a flame arrester, and the peak explosion pressures generated in each 
segment of the intake and exhaust system. Excessive pressures may be an 
indication of a design flaw.
    Commenters did not raise issues regarding the proposed explosion 
tests. However, the final rule includes one change from the proposal to 
better ensure the ability of a diesel power package to withstand an 
internal explosion, and another change to revise the speeds at which 
dynamic tests are to be conducted. The final rule also includes non-
substantive changes for clarification and to conform the final rule 
with existing MSHA regulations.
    Paragraphs (a)(2) (v) and (vi) of the final rule specify an 
internal peak pressure of 110 psig instead of the proposed 125 psig, 
during power package explosion-proof testing. Excessive internal 
pressures during explosion-proof testing indicate the potential for 
failure of the diesel power package in use, with potentially 
catastrophic results in the underground coal mine environment. Lowering 
the peak pressure expected during explosion-proof testing recognizes 
that diesel power package designs differ and that it is difficult to 
select the optimum location for pressure measurements. When pressures 
greater than 110 psig are measured during testing, the final rule 
specifies redesign of the system to reduce the pressure or more 
rigorous testing to verify the integrity of the system. Due to the 
critical nature of this test, MSHA has adopted the same approach in its 
explosion-proof test requirements for electric motors. The final rule 
conforms these like requirements.
    Paragraph (a)(2)(vii) of the final rule requires that dynamic tests 
be conducted at two speeds--1800<plus-minus>200 RPM and 
1000<plus-minus>200 RPM--instead of at rated speed and 50 percent of 
rated speed specified in the proposal. The speeds set by the final rule 
correspond to the speeds at which dynamic tests are performed 
successfully at MSHA facilities. Also some test facilities may not be 
capable of performing tests at the rated speed called for by the 
proposal. This change is also reflected in paragraphs (a)(3)(iii) (A) 
and (B).
    For clarification, the final rule also adopts more precise language 
to identify requirements which apply to wet exhaust conditioners, 
distinguishing them from dry systems. The final rule also defines 
natural gas that may be used in explosion-proof testing in a manner 
that better recognizes the variables in the make-up of the hydrocarbons 
found in natural gas. As a result, the final rule affords greater 
flexibility for manufacturers and testing laboratories.
    Section 7.101  Surface temperature tests. This section describes 
the tests necessary to ascertain that diesel power packages will not 
create a fire hazard in underground coal mines due to coal dust or 
other combustible materials contacting hot surfaces. Like the proposal, 
the final rule is derived from Sec. 36.48, and sets a maximum external 
surface temperature of 302  deg.F (150  deg.C). The test protocol 
simulates the operation of a diesel power package under heavy use 
conditions. A note has been added to this section to alert the 
applicant that this test may be done simultaneously with the exhaust 
gas cooling efficiency test described in Sec. 7.102 of the final rule.
    Commenters did not direct their attention to this aspect of the 
proposal. The final rule is unchanged from the proposal, except for a 
non-substantive clarifying change regarding wet exhaust conditioners 
and the elimination of the reference to the use of natural gas. A 
reference to natural gas, which consists primarily of methane, is 
redundant. Instead, the final rule specifies the percentage of methane 
to be added to the intake. Elimination of the reference to natural gas 
also conforms this section to similar tests, which also determine 
engine performance and which only specify methane, in subpart E of part 
7.
    Section 7.102  Exhaust gas cooling efficiency test. This section 
describes the test procedures for measuring the temperature of the 
exhaust gas at the discharge point from the exhaust conditioner. 
Acceptable performance under this test is exhaust gases that do not 
exceed 170  deg.F (76  deg.C) for power packages with a wet exhaust 
conditioner, and 302  deg.F (150  deg.C) for a dry system. The proposed 
and final rules are derived from existing Sec. 36.47 and address the 
hazard of hot exhaust gases creating a fire or explosion hazard.
    Commenters raised only one issue concerning this aspect of the 
proposal, suggesting clarification of the different performance 
requirements for wet and dry exhaust conditioners. The final rule 
adopts this suggestion.
    Section 7.103  Safety system controls test. This section is derived 
from Sec. 36.47 and describes tests to evaluate the performance of the 
safety shutdown systems required for diesel power packages. As 
discussed above, these systems automatically shut down a diesel engine 
in response to potentially dangerous conditions, such as overheating. 
The tests prescribed introduce failure modes, such as loss of engine 
coolant, and initiate the safety system. Acceptable performance is 
achieved when the safety system automatically shuts down the engine 
before the technical requirements for approval are exceeded.
    Commenters recommended that the final rule more clearly delineate 
the different requirements for wet and dry exhaust conditioners. The 
final rule adopts this suggestion in paragraphs (a)(3), (a)(4), (b)(2), 
and (b)(3).
    Commenters also suggested that paragraph (a)(7)(ii) be amended to 
include a caveat about the surface temperature of a turbocharger not 
exceeding 302 deg. F (150 deg. C). This comment is not adopted because 
the final rule addresses surface temperature control under Sec. 7.101 
and requires that all external surfaces of power packages, including 
turbochargers, not exceed 302  deg.F (150 deg. C). Paragraph (b)(7) has 
been revised to accept starting mechanisms constructed of nonsparking 
materials in addition to starting mechanisms that prevent the 
engagement of the starter while the engine is running. This revision 
conforms to Sec. 7.98(j)(1), which permits both options under the final 
rule, as it would have under the proposal.
    Section 7.104  Internal static pressure test. This section 
describes tests to determine if the design of the intake and exhaust 
system components of diesel power packages is structurally sound. The 
prescribed tests specify internally pressurizing each segment of the 
intake and exhaust system. The pressure required to be applied is four 
times the maximum pressure observed in the tests performed under 
Sec. 7.100, or 150 psig (<plus-minus>5 psig), whichever is less. 
Acceptable performance is based on an assessment of key points in the 
intake and exhaust system, such as joints and welds, for evidence of 
leakage or damage.
    Commenters raised no issues with respect to the proposal. Paragraph 
(b)(2)(vi) has been added to limit

[[Page 55427]]

permanent distortion of any planar surface of the diesel power package 
to 0.04-inches/linear foot or less. This change conforms this 
requirement to the same requirement applied to the explosion tests in 
Sec. 7.100(b)(7).
    Section 7.105  Approval markings. This section requires that each 
approved diesel power package be identified with a permanent approval 
plate inscribed with the MSHA approval number. If the power package 
includes a wet exhaust conditioner that functions as an exhaust flame 
arrester, the final rule requires that the approval plate also indicate 
the grade limitation for the power package. This information is 
important so that users are aware of the maximum grade on which the 
exhaust conditioner will be effective as a flame arrester.
    As noted elsewhere in this preamble, approval markings have been 
used for more than 85 years, and are routinely relied upon by users of 
mining equipment as well as state and federal authorities to identify 
equipment appropriate for use in mining.
    Another commenter suggested clarification of the proposal with 
respect to the grade limitation for certain diesel power packages. The 
final rule has been revised in response to this commenter to clarify 
that the grade limitation applies to systems which use a wet exhaust 
conditioner as a flame arrester. No grade limitation is appropriate for 
power packages with a dry exhaust conditioner.
    Burden hours required to make and mount MSHA approval plates are 
assigned OMB control number 1219-0100.
    Section 7.106  Post-approval product audit. This section 
incorporates the standard audit requirement for part 7-approved 
equipment, specifying that approval holders must make a diesel power 
package available for audit by MSHA, at no cost to the Agency. The 
obligation to supply a power package under this section arises only 
upon request by MSHA, and is limited to no more frequently than one a 
year, except for cause. Under existing Sec. 7.8(b), the approval holder 
may observe any tests conducted under the audit.
    Post-approval audits are a critical part of MSHA's quality control 
program for approved equipment. By inspecting and testing a diesel 
power package for continuing compliance with the specifications for its 
approval potential problems can be detected and confidence in the 
approval process is maintained. Since the inception of post-approval 
product audits under part 7, MSHA has detected numerous discrepancies 
which have been effectively corrected.
    Commenters directed no attention to this aspect of the proposal, 
which is adopted without change from the proposal.
    Section 7.107  New technology. This section is designed to 
facilitate the introduction of new technology or new applications of 
existing technology. It allows MSHA to approve a diesel power package 
that incorporates technology for which the requirements of subpart F 
are not applicable, provided that MSHA determines the power package is 
as safe as one which meets the requirements of subpart F. To make this 
determination, MSHA develops appropriate technical requirements and 
test procedures when applications for the approval of novel designs are 
submitted. To provide confidence in the adequacy of the design, such 
tests may be required to be performed by MSHA. Experience with this 
provision under existing regulations has shown that technological 
innovations can be effectively evaluated and made available for use in 
a prompt fashion, thus serving the best interests of miners' safety and 
health. Commenters generally supported this aspect of the proposal, and 
the final rule adopts the proposal without change.
    Section 7.108  Power package checklist. This section requires that 
approved diesel power packages be accompanied by a description of the 
features which must be checked and tests that must be performed to 
ascertain that the power package is in approved condition. These 
instructions, which are developed as part of the approval process, are 
intended to aid power package users in keeping this equipment in safe 
operating condition.
    Commenters did not direct specific attention to this aspect of the 
proposal, which is adopted without change in the final rule.
Part 7, Subparts G, H and I
    The final rule does not adopt proposed subpart G to part 7, nor 
further develops the advance notice of rulemaking published 
concurrently with the proposal concerning subparts H and I to part 7. 
Subpart G-approved power packages would have been required for 
nonpermissible, heavy-duty diesel-powered equipment used in underground 
coal mines. Subpart H would have established regulations for the 
approval of fully assembled permissible diesel-powered machines, and 
subpart I would have set requirements for the approval of fully 
assembled nonpermissible, heavy-duty diesel-powered equipment. In lieu 
of this approach, the final rule responds to the commenters who urged 
that safety and fire protection features for nonpermissible diesel-
powered equipment be addressed in the Agency's part 75 safety standards 
for underground coal mines. Existing part 36 is retained by the final 
rule and revised to specifically apply to permissible diesel-powered 
equipment for use in underground coal mines. Subpart H is not further 
developed by the final rule.
    In the proposal, subparts G and I were developed as an approach to 
several of the Advisory Committee's concerns. In its deliberations, the 
Advisory Committee considered the risk of fire on nonpermissible 
diesel-powered equipment caused by hot surfaces igniting combustibles 
such as hydraulic and lubricating oils, diesel fuel, and coal dust. To 
address this hazard, the Committee recommended limiting engine surface 
temperatures. Under the proposal, surface temperature controls and 
other machine safety features for heavy-duty nonpermissible diesel 
equipment would have been addressed in subparts G and I.
    The Committee, however, also recognized the difficulty of applying 
such controls to all nonpermissible diesel-powered equipment, 
especially light-duty, utility equipment. The Advisory Committee, 
therefore, recommended that a ``limited class'' of light-duty equipment 
be identified for which less complex fire prevention measures would be 
required, such as fire suppression systems which shut down the engine, 
guarded drive shafts to prevent damage of fuel and hydraulic lines in 
the event of a shaft failure, protection of the fuel tank and lines, 
and proper design of the electrical system to prevent electrical arcs. 
The proposal included these requirements for a ``limited class'' of 
light-duty equipment in the part 75 safety standards for underground 
coal mines.
    The Advisory Committee also examined what additional features 
should be included in the approval requirements for completely 
assembled units of diesel-powered equipment. The Committee recommended 
that MSHA develop an approval program that would emphasize other 
equipment safety features which could be readily addressed by equipment 
manufacturers. These features included safeguarding of the fuel system, 
an exhaust gas dilution system, a fire suppression system, and 
appropriate electrical and braking systems. As a completely assembled 
machine, the interrelationship of these systems would be evaluated as 
part of the approval process contemplated in the proposal under subpart 
H.
    A number of commenters objected to the approval of nonpermissible 
diesel-

[[Page 55428]]

powered equipment. These commenters maintained that such an expansion 
of MSHA's approval process would result in regulating diesel-powered 
equipment differently than electric-powered equipment without 
justification, and would present severe technical and economic 
difficulties in meeting certain proposed requirements. The commenters 
recommended that the final rule adhere to the long-standing regulatory 
approach for electric-powered equipment, which sets performance-
oriented safety requirements for nonpermissible equipment in the 
Agency's part 75 safety standards for underground coal mines. According 
to the commenters, this approach would be responsive to the hazards 
posed by diesel-powered equipment, and provide sufficient flexibility 
to facilitate the introduction of new and safer technology.
    In contrast, one commenter urged that all diesel-powered equipment 
be approved as permissible, without regard to the equipment's use in 
the mine. This commenter pointed out that diesel-powered equipment 
presents different hazards than electric equipment, inasmuch as it 
contains both a fuel source and an ignition source. The commenter 
further maintained that permissible diesel-powered equipment receives 
better maintenance than nonpermissible equipment, and explosive 
accumulations of methane can be encountered anywhere in an underground 
coal mine. This commenter noted that since 1969, 10 explosions occurred 
in areas where nonpermissible equipment is permitted, and seven of 
these explosions were caused by equipment that was not maintained in 
permissible condition.
    Another commenter agreed that heavy-duty nonpermissible equipment 
should have approved engines and power packages to limit harmful 
emissions from the engine and protect against the fire hazard presented 
by hot engine surfaces. This commenter, however, objected to MSHA 
approval of fully assembled nonpermissible machines as contemplated by 
subpart I.
    MSHA acknowledges that fire prevention and other machine safety 
features can be successfully introduced for nonpermissible equipment, 
without a formal approval program. This regulatory approach has been 
effectively implemented through MSHA's part 75 safety standards for 
underground coal mines as they apply to nonpermissible electric-powered 
equipment. For example Sec. 75.518 provides fire protection by 
requiring electrical system overload protection for nonpermissible 
electric-powered machines. Section 75.523-3 provides a machine safety 
feature by requiring automatic emergency parking brakes. Setting such 
performance-based requirements for nonpermissible equipment maximizes 
the flexibility afforded mine operators and manufacturers to minimize 
the hazards of this equipment, and facilitates the introduction of new 
technology for dealing with these hazards. For example, new heat 
insulating materials have been developed since the publication of the 
proposed rule, which can be used to control surface temperatures on 
diesel-powered equipment.
    To adapt this regulatory approach to nonpermissible diesel-powered 
equipment, the final rule extends the proposal's safety requirements 
for limited class equipment. Under the final rule, nonpermissible 
diesel-powered equipment is not required to be approved by MSHA. 
Instead, this equipment must comply with the final rule's safety 
requirements in Secs. 75.1909 and 75.1910. These standards include 
requirements for fire prevention and machine safety features such as 
protection of hydraulic, fuel and electrical systems and adequate 
brakes and operator controls.
Part 36
    Existing part 36, previously known as schedule 31, has been in 
effect since 1961. It sets approval requirements and specifications for 
diesel-powered equipment used in ``gassy noncoal mines and tunnels''. 
The final rule retains these existing regulations as the basis for 
approval of diesel-powered equipment and, in lieu of further developing 
subpart H, includes amendments which expand part 36 to apply to 
equipment used in underground coal mines. Specifically, part 36 is 
amended to afford manufacturers the option of incorporating into their 
equipment part 7-approved power packages. Diesel-powered equipment with 
approved power packages will be suitable for use in areas of 
underground coal mines where permissible equipment is required. The 
existing part 36 approval requirements for diesel-powered equipment 
used in metal and nonmetal mines are unchanged by the final rule. Part 
36-approved equipment with certified engines and safety component 
systems will continue to be recognized for use in metal and nonmetal 
mines where permissible equipment is required. MSHA will issue approval 
numbers that differentiate between equipment for use in coal mines and 
equipment for use in metal and nonmetal mines. Machines approved under 
revised part 36 specifically for use in underground coal mines will be 
identified with an MSHA approval number in a new sequence ``36c-''. 
This will indicate that the equipment has been approved for use in 
underground coal mines. A part 36 MSHA approval number in the sequence 
``31-'' will indicate that the equipment has been approved for use in 
metal and nonmetal mines.
    These changes are responsive to a number of commenters who urged 
that the existing part 36 regulations for the approval of
diesel-
powered equipment be retained and continue to apply to equipment for 
use in metal and nonmetal mines. In addition, the final rule expands 
the scope of part 36, eliminating the need for separate approval 
regulations for diesel-powered equipment for use in underground coal 
mines as contemplated by subpart H in the proposal.
    To retain part 36 and include the approval of diesel-powered 
equipment for use in underground coal mines, the final rule re-titles 
part 36 and eliminates references to ``gassy noncoal mines and 
tunnels'' and related definitions. In addition, the application 
requirements of Sec. 36.6 and design requirements of Sec. 36.20 are 
revised to recognize the use of part 7-approved power packages, which 
substitute for Secs. 36.21 through 36.26 (except Secs. 36.25(f) and 
36.43 through 36.48).
    The final rule also updates part 36 in several respects. Section 
36.20, concerning the quality of material, workmanship and design, is 
revised to eliminate an outdated reference to Sec. 18.24 of part 18, 
schedule 2F. In its place, the final rule requires compliance with 
Sec. 7.98 of the final rule, which provides structural and flame path 
requirements for explosion-proof enclosures. This aspect of the final 
rule reflects long-standing requirements for explosion-proof 
components.
    The definition of ``low-volatile hydrocarbon (diesel) fuel'' in 
Sec. 36.2(i) is deleted by the final rule. This definition is outdated 
and potentially confusing in context with Sec. 75.1901 of the final 
rule, which specifies requirements for diesel fuel.

C. 30 CFR Part 70
Discussion

Section 70.1900 Exhaust Gas Monitoring
    As outlined in the proposal, the Advisory Committee regarded the 
health effects of diesel exhaust as a key area of concern. In its final 
report, the Advisory Committee focused on two areas--exposure limits 
and a sampling strategy to monitor the concentration of diesel exhaust 
in miners' work environment.

[[Page 55429]]

    The Committee recommended further research to develop information 
about diesel particulate exposure levels at which health effects 
accrue. The Committee also addressed gaseous diesel exhaust components, 
concluding that suitable protection for miners would be achieved by 
relying on coal mine air quality standards, either as they currently 
exist or may be revised in the future. The Advisory Committee further 
concluded that exposure limits for gaseous contaminants of diesel 
exhaust should not be unique from the exposure limits set by the same 
contaminants generated by other mining sources, such as blasting. The 
Committee specifically recommended a periodic sampling strategy for 
carbon monoxide, nitric oxide and nitrogen dioxide and sampling for 
sulfur dioxide if diesel fuel containing more than 0.25 percent sulfur 
is used. In addition, the Advisory Committee recommended a sampling 
strategy which utilized return air course samples to trigger personal 
exposure sampling. The Advisory Committee's recommendations served as 
the basis for the proposed rule.
    The proposed rule did not contain a diesel particulate exposure 
standard. At the conclusion of their deliberations the Advisory 
Committee recommended that the Secretary of Labor set in motion a 
mechanism whereby a diesel particulate standard could be set, and that 
the Secretary work in concert with the Bureau of Mines (BOM) and the 
National Institute for Occupational Safety and Health (NIOSH) to 
develop a sampling strategy and a program for its implementation. 
Subsequent to those deliberations, MSHA has been working closely with 
the BOM and NIOSH to develop methods for measuring diesel particulate 
and for the development of criteria for reducing miners' exposure to 
diesel particulate. In 1991, MSHA issued an advance notice of proposed 
rulemaking seeking additional information for the development of a 
rule. MSHA also held three workshops in 1995 that provided a forum for 
mine operators, labor unions, trade organizations, engine 
manufacturers, fuel producers, exhaust after-treatment manufacturers, 
and academia, to present and discuss information about technologies and 
approaches that can be utilized to limit the exposure of miners to 
diesel particulate. MSHA is currently using the information obtained 
from the advance notice of proposed rulemaking and the workshops to 
develop a proposed rule for reducing miners' exposure to diesel 
particulate.
    The proposal generally followed the Advisory Committee 
recommendations for sampling and permissible exposure limits. Under the 
proposal, samples of carbon monoxide, nitric oxide and nitrogen dioxide 
would be taken weekly in the immediate return airways of each split of 
air where diesel equipment is used. When sampling results exceeded 50 
percent of any permissible exposure limit set by the proposal, personal 
exposure monitoring would have been required. If personal exposure 
samples showed concentrations which exceeded 75 percent of the 
permissible exposure standard, sampling would continue each operational 
shift until, with 95 percent confidence, it was established that 
exposure was at or below the permissible level.
    Commenters to the proposed rule generally accepted the need for 
regular sampling to evaluate miners' working conditions for the 
presence of potentially harmful gaseous diesel exhaust components. A 
number of commenters, however, noted that the proposed rule was too 
focused on sampling, and gave inadequate attention to requiring 
corrective action.
    Some commenters recommended an alternative to sampling in return 
air courses. These commenters suggested a personal sampling approach 
keyed to the person in each mechanized mining unit likely to experience 
the highest diesel exhaust exposure. This ``designated occupation'' 
would be identified in the mine's ventilation plan. According to the 
commenters, this approach would recognize differences in mine 
configuration and mining methods.
    Some commenters considered the proposed action level for area 
samples, set by the proposal at 50 percent of the permissible exposure 
limit values for the gaseous emission components being measured, to be 
reasonable. One commenter, in support of the action level concept, 
noted that sampling in the immediate return air course would measure 
the contribution of all diesel equipment on the mining section, thereby 
yielding readings that would give reasonable assurance that miners 
working on the section were protected.
    Other commenters considered the 50 percent action level possibly 
too low for mines with naturally occurring ambient levels of carbon 
monoxide near the action level. Some of these commenters also foresaw 
possible problems at mines operating near the 50 percent action level. 
These commenters were concerned that an unnecessarily burdensome cycle 
of area sampling followed by personal sampling could result. Commenters 
also noted that the 50 percent action level could be raised because the 
permissible exposure limits themselves include a safety factor. No 
commenters offered data or specific support for a particular action 
level.
    Commenters also expressed concern about how effectively the 
proposed sampling procedures would address variations in the 
concentration of diesel exhaust in miners' workplaces. A number of 
commenters suggested different strategies with more frequent samples to 
better monitor the presence of the gaseous components of diesel 
exhaust. Some commenters suggested special sampling to evaluate peak 
exposure when, for example, equipment was operated under load. Other 
commenters opposed such an approach, citing difficulties in determining 
when peak conditions might occur. Another commenter recommended, in 
addition to weekly samples in return air courses, weekly personal 
samples of each diesel equipment operator, and at the same time samples 
for at least two miners working inby all pieces of diesel equipment on 
the same split of air. According to this commenter, the suggested 
sampling strategy would yield better information about what diesel 
exhaust control measure modifications may be needed. Other commenters 
noted the dynamic nature of the underground mining environment, which 
varies the concentrations of diesel exhaust in miners' workplaces. 
These commenters recommended sampling be performed every shift in 
miners' work areas to timely detect the onset of elevated levels of 
diesel exhaust contaminants.
    A number of commenters also noted that, in addition to sampling in 
the immediate return air course, attention should be given to the area 
of the section loading point. According to these commenters, diesel 
exhaust contaminants are often elevated at this location due to high 
engine loads at a single stationary point. Commenters also noted the 
need to address situations when diesels are used in locations outby the 
working faces. According to these commenters, construction projects can 
involve significant diesel usage at some mines.
    The proposed rule did not specify sampling methods for evaluating 
the gaseous components of diesel exhaust. In the preamble discussion to 
the proposal, however, MSHA made reference to electrochemical analyzers 
and detector tubes as technology that could be used to determine 
concentrations of the gases to be measured. Commenters did not suggest 
specific sampling methods or object to those mentioned in the preamble 
discussion. Some commenters, however, emphasized that the methods 
chosen should not be highly technical in

[[Page 55430]]

nature. Several commenters urged that the task of sampling be something 
miners generally could perform with proper training.
    As discussed elsewhere in this preamble, the final rule as a whole 
is designed to lay a foundation for the safe and healthful operation of 
diesel equipment in the confined, potentially explosive underground 
coal mine environment. To accomplish this objective, the final rule 
sets standards for diesel engines, suitable for mining. For the 
operation of this equipment, the final rule sets practicable standards 
for the use of low sulfur fuel and for adequate ventilation and proper 
maintenance of diesel equipment. These standards are intended to work 
together as an operating system to create a more healthful and safe 
working environment for miners.
    Paragraph (a) of the final rule adopts a streamlined sampling 
strategy that is keyed to this operating system approach. The 
requirements of proposed Sec. 70.1900 have been revised in the final 
rule to integrate sampling for gaseous components of diesel exhaust 
with existing on-shift workplace examination requirements and to take 
advantage of modern sampling instrumentation. The final rule also 
incorporates by reference the threshold limit values (TLV<Register>'s) 
adopted by the American Conference of Governmental Industrial 
Hygienists (ACGIH). These TLV<Register>'s are also incorporated by 
reference in MSHA's existing standards for exposure limits in 
Sec. 75.322. The final rule retains the proposed action level concept 
with some modifications responsive to commenters. However, the final 
rule does not adopt the proposed requirement that area samples over the 
action level trigger personal sampling. Instead, paragraph (c) of the 
final rule requires corrective action to be taken immediately to reduce 
gaseous diesel exhaust concentrations to or below the action level. The 
final rule's sampling requirements are intended to provide a regular 
and timely check on how the total operating system of diesel exhaust 
control is working, with an emphasis on prompt corrective action.
    Although the final rule does not require personal sampling, 
existing standards regulate miners' exposure to harmful airborne 
contaminants. These standards do not permit miner exposures over the 
established TLV<Register>'s incorporated in this section of the final 
rule and in Sec. 75.322. MSHA enforces these standards during mine 
inspections through personal and other sampling methods.
    Like the proposal, paragraph (a) of the final rule specifies area 
samples in the ventilation return airways of each working section where 
diesel equipment is used, at a location which represents the 
contribution of all diesel equipment on the section. This approach was 
recommended by the Advisory Committee, and generally was supported by 
the commenters. In response to commenters, the final rule also requires 
samples in the area of the section loading point if diesel haulage 
equipment is operated on the working section, and at the point inby the 
last unit of diesel equipment on the longwall or shortwall face where 
mining equipment is being installed or removed. Depending on the mining 
system used, these are strategic locations in which to take area 
samples to evaluate the overall effectiveness of the control measures 
for diesel exhaust.
    In addition, the final rule authorizes the MSHA district manager to 
specify area samples at other strategic locations on a mine-by-mine 
basis in order to accommodate circumstances which can result in 
significant concentrations of diesel exhaust. This aspect of the final 
rule responds to commenters' concerns about situations which can 
involve significant diesel usage in areas outby the working face, such 
as construction projects. The paperwork aspect of this provision 
results in a minimally increased burden since existing Sec. 75.370 of 
this chapter requires that all underground coal mines have ventilation 
plans. Although this provision of the final rule is new, proposed 
Sec. 75.390(b) would have required that the mine operator include 
certain minimum ventilation quantities in the mine's ventilation plan. 
Under the proposal, these minimum air quantities would have been 
related to the number of diesel-powered units operating and the air 
quantity necessary to control gaseous diesel emissions. Thus, this 
final rule provision is consistent with proposed Sec. 75.390(b).
    Monitoring of gaseous diesel exhaust components during the on-shift 
examination required by existing Sec. 75.362 of this chapter makes 
checks for diesel exhaust concentrations part of the workplace 
examinations which have been historically conducted in the coal mining 
industry. On-shift examinations are designed to detect hazards which 
can develop during a working shift when normal mining operations are 
underway. Such examinations include tests for methane gas accumulations 
and oxygen deficiency, and determinations of air direction and 
velocity. Tests for diesel exhaust gases can be readily made during the 
on-shift examination by the same mine personnel. Currently, multi-gas 
detectors are available and in use in a significant number of mines in 
the industry which can sample simultaneously and directly read out 
results for methane, oxygen, carbon monoxide and nitrogen dioxide. 
Making checks of the mine's diesel exhaust control system part of the 
existing practice of on-shift examinations minimizes the burden of 
compliance with the final rule's sampling requirements. Under the final 
rule, special staff and a separate diesel exhaust sampling schedule 
should be unnecessary.
    Sampling as part of the on-shift examination also increases the 
frequency of diesel exhaust concentration monitoring from the proposed 
weekly schedule, and responds to commenters who questioned the adequacy 
of the proposal in this regard. The final rule's increased frequency of 
sampling affords more timely and meaningful information about the 
performance of the mine's overall diesel exhaust control system. Diesel 
equipment is highly mobile and the mining environment changes rapidly 
as mine development progresses. Monitoring each shift alerts the mine 
operator to emerging problems with the control of diesel exhaust, 
before miners are overexposed to harmful contaminants.
    Consistent with existing Sec. 75.362 of this chapter, the final 
rule also requires sampling to be performed by a certified person 
designated by the operator. This aspect of the final rule is generally 
consistent with the proposal as it requires that competent persons 
perform the sampling, the results of which form the basis for important 
decisions about miners' work environments.
    Under the final rule, sampling would be required for two gaseous 
components of diesel exhaust: carbon monoxide and nitrogen dioxide. The 
final rule does not retain the proposal for sampling sulfur dioxide 
when diesel fuel containing more than 0.25 percent sulfur is used. 
Section 75.1901 of the final rule requires the use of low-sulfur fuel 
at all times, rendering this aspect of the proposed rule unnecessary. 
The final rule also deletes the proposed requirement for sampling 
nitric oxide.
    Both carbon monoxide and nitric oxide are produced in significant 
quantities when diesel engines operate under load. Elevated carbon 
monoxide is also indicative of engine faults such as misadjusted fuel 
systems, failure to derate engines for altitude, or dirty air cleaners. 
Conditions of use such as prolonged diesel engine idling can also 
produce elevated levels of carbon monoxide. Catalytic converters, 
designed to remove carbon monoxide

[[Page 55431]]

from the exhaust, work poorly under these conditions due to lower 
equipment operating temperatures.
    Nitric oxide concentrations generally do not reflect engine faults. 
In addition, nitric oxide is readily converted to nitrogen dioxide in 
the mine atmosphere, making representative measurement difficult under 
the final rule's area sampling strategy. Also, in MSHA's experience the 
TLV<Register> for carbon monoxide will be exceeded before the 
TLV<Register> for nitric oxide. Sampling for nitric oxide, therefore, 
is not retained in the final rule.
    The final rule also requires sampling for nitrogen dioxide. 
Nitrogen dioxide is readily detectable and potentially harmful to 
miners. The TLV<Register> for nitrogen dioxide is 5 parts-per-million 
(ceiling), which cannot be exceeded at any time. Therefore, the final 
rule adopts the proposed requirement to sample for nitrogen dioxide.
    The final rule addresses the collection of carbon monoxide and 
nitrogen dioxide samples with performance-based requirements. In 
response to commenters, the task of sampling is significantly 
simplified. The sampling requirements also emphasize prompt 
availability of sample results, consistent with the final rule's 
emphasis on corrective action to protect miners from the risk of 
overexposure.
    Paragraph (b)(1) provides that monitoring of carbon monoxide and 
nitrogen dioxide is to be performed in a manner which makes the results 
available immediately to the person collecting the samples. This aspect 
of the final rule recognizes that direct-readout sampling instruments 
are now available that can measure carbon monoxide and nitrogen 
dioxide. Use of these hand-held instruments requires no specialized 
technical background so that persons may be easily trained to perform 
this task. Mine-wide monitoring systems, with properly located sensors, 
could also be employed to collect the required carbon monoxide and 
nitrogen dioxide samples.
    Paragraph (b)(2) of the final rule generally adopts the proposal, 
and specifies that samples are to be collected by appropriate 
instrumentation that has been maintained and calibrated in accordance 
with the manufacturer's recommendations. These provisions establish 
sound practices necessary for accurate sample results, while retaining 
the flexibility for new instrumentation that may be developed in the 
future.
    Paragraph (b)(3) requires that samples be collected during periods 
that are representative of conditions during normal operations. This 
aspect of the final rule is consistent with the proposal and serves the 
underlying purpose of the sampling requirements, which is to gauge the 
performance of the diesel exhaust control system under normal operating 
conditions. Like the proposal, the final rule does not prescribe 
special requirements to measure the performance of the diesel exhaust 
control system under peak load conditions. As some commenters noted, 
determining when peak load conditions occur would be difficult to 
predict. In addition, such an approach would increase the complexity of 
the final rule unnecessarily.
    Regular sampling during on-shift examinations will afford a 
realistic picture of the performance of the diesel operating system. To 
meet the requirement that samples be taken during periods that are 
``representative of conditions during normal operations,'' MSHA intends 
that tests for carbon monoxide and nitrogen dioxide be made when 
diesel-powered equipment is being used as it typically is in the mining 
process. Thus, for example, sampling is appropriate when diesel haulage 
equipment is moving coal or diesel-powered roof bolters are installing 
bolts.
    Some commenters noted the need to monitor exhaust concentrations 
during longwall moves with diesel-powered equipment, expressing concern 
that moving the component parts of a longwall to a new block of coal 
for mining can involve heavy usage of diesel equipment over the course 
of multiple shifts. As a result, miners could be exposed to elevated 
levels of diesel exhaust gases. The final rule addresses these comments 
through the increased frequency of samples to monitor diesel exhaust 
gases. On-shift examinations are required under Sec. 75.362 of this 
chapter when longwall moves are being performed and, under the final 
rule, tests of the concentrations of carbon monoxide and nitrogen 
dioxide are required at the point immediately inby the last piece of 
diesel equipment on the longwall or shortwall face. If these samples 
indicate carbon monoxide and/or nitrogen dioxide concentrations greater 
than the action level, immediate corrective action is required. This 
approach protects miners through early detection of elevated 
concentrations of diesel exhaust gases, and prompt adjustments to the 
mine's diesel exhaust controls.
    Paragraph (c) of the final rule is modeled after other MSHA 
standards for potentially hazardous gases, such as methane, and 
requires immediate corrective action when sample results indicate gas 
concentrations exceeding the action level. This change in the proposal 
is responsive to commenters who pointed out that the proposal gave 
inadequate attention to corrective action. The final rule retains the 
proposed action level concept tied to the TLV<Register>'s for carbon 
monoxide and nitrogen dioxide. The exposure limits incorporated are 
those already incorporated in existing Sec. 75.322 of this chapter. 
These exposure standards are based on the 1972 threshold limit values 
set by the American Conference of Governmental Industrial Hygienists 
(ACGIH) and have applied to underground coal mines for nearly 25 years. 
This aspect of the final rule comports with the recommendation of the 
Advisory Committee that gaseous diesel exhaust components not be 
treated differently from contaminants generated by other mining 
sources. The final rule does not adopt updated permissible exposure 
standards at this time, as referenced in the proposal, because this 
issue remains in the rulemaking process for Air Quality standards.
    Under paragraph (c) of the final rule, the action level is set at 
50 percent of the TLV<Register>'s for carbon monoxide and/or nitrogen 
dioxide for samples collected in the areas identified in paragraph (a). 
As noted in the proposed rule, an action level is used to minimize the 
risk that workers will be overexposed. An action level is not a 
compliance limit for miners' exposure. Instead, an action level is 
intended to provide a timely trigger for reviewing the mine's diesel 
exhaust control system. Exceeding an action level under the final rule 
is not, by itself, a violation.
    The 50 percent action level concept is well-recognized in 
industrial hygiene practice as an effective, practical screening tool 
for minimizing the risk of workers' overexposure. This approach, based 
largely on statistical considerations, was developed by the National 
Institute for Occupational Safety and Health (NIOSH) for regulations 
promulgated by the Occupational Safety and Health Administration 
(OSHA), ``Leidel et al., NIOSH Publication No. 77-173.''. It is 
designed to afford a single value trigger for simplicity of application 
and to reduce exposure monitoring burdens. ``Patty's Industrial Hygiene 
and Toxicology, 1994, p. 528.'' Based on the work of Nelson A. Leidel 
and others, the 50 percent action level is considered a reliable 
indicator that there is a low probability of worker exposures which 
exceed the TLV<Register> linked to the action level.
    The action level of 50 percent of the TLV<Register>'s for carbon 
monoxide and nitrogen dioxide is well-suited to the

[[Page 55432]]

purposes of this final rule, and will afford miners protection from 
overexposure to potentially harmful diesel exhaust emissions. Samples 
collected in accordance with paragraph (a) of this section will yield 
results showing the concentration of diesel exhaust emissions in key 
places under representative conditions on a regular basis. Applying the 
50 percent action level to these routine sample results will account 
for sources of variability affecting miners' exposure, such as the 
diesel activity level, ventilation rates, and duty cycles. The action 
level also provides a simple means of evaluating the status of the 
mine's overall diesel exhaust control system. As discussed elsewhere, 
this operating system approach to the control of diesel exhaust 
emissions is a key underpinning of the final rule.
    The final rule also permits adjustments to the 50 percent action 
level on a mine-by-mine basis. Under Sec. 75.325(j) of the final rule 
the MSHA district manager may approve an alternative action level in 
the mine's ventilation plan. Ventilation plans are required for all 
underground coal mines by existing standards under Sec. 75.370 of this 
chapter. Under the final rule, any change in the 50 percent action 
level must be based on the results of sampling which demonstrate that 
miners' personal exposure will not exceed the applicable TLV<Register>. 
Thus, a mine operator may show that a 60 percent action level, for 
example, is appropriate for the miners working on a section. To do 
this, the operator must demonstrate through sampling that miners 
working on the section are not overexposed to diesel exhaust gases when 
samples in the immediate return air course show that concentrations of 
carbon monoxide and/or nitrogen dioxide are maintained at 60 percent of 
the TLV<Register>. Based on this data, the 50 percent action level 
could be revised, with the approval of the district manager. The higher 
action level would be made part of the mine's approved ventilation plan 
and, thereby, become a compliance requirement at the mine. If, with 
experience, the revised action level was shown to be inappropriate, 
changes would be made through the mine ventilation plan approval 
process. Mine ventilation plans are required by existing standards to 
be reviewed at least every six months.
    The sampling necessary to demonstrate that the personal exposure of 
miners would not exceed the TLV<Register> is not specified by the final 
rule, recognizing that many approaches can be taken. For approval to 
revise an action level, however, MSHA will require clear evidence that 
a proposed change in an action level is appropriate. As discussed 
above, the purpose of an action level is to trigger a review of the 
mine's diesel exhaust control system before miners are overexposed to 
harmful gases. As the action level is raised closer to the 
TLV<Register>, the reliability of the action level as a timely warning 
diminishes. Thus, MSHA does not anticipate approval of action levels 
that provide a nominal margin of protection.
    The final rule does not specify what corrective action is required 
when an action level for carbon monoxide and/or nitrogen dioxide is 
exceeded. Instead, this determination is to be made by the mine 
operator, who is in the best position to implement changes appropriate 
to the situation and sufficient to promptly return carbon monoxide and/
or nitrogen dioxide concentrations to or below the applicable action 
level. Corrective action may involve addressing ventilation 
deficiencies, controlling the number of diesel machines operating in an 
area, or correcting engine faults. Elevated levels of carbon monoxide 
and/or nitrogen dioxide may indicate that appropriate corrective action 
is revision of the mine's ventilation plan. Modifying the mine's 
ventilation plan integrates needed controls into the operating system 
for the mine.
    The final rule does not retain the proposed requirement to conduct 
personal sampling when the action level for gaseous diesel exhaust 
components is exceeded. Proposed Sec. 70.1901 therefore is not included 
in the final rule. While the Advisory Committee recommended a two-
tiered approach of area sampling which could trigger personal sampling, 
MSHA believes that the final rule's sampling strategy will better 
protect miners. As discussed above, the sampling strategy adopted 
focuses on the performance of the mine's control system for diesel 
exhaust, rather than measurements of individuals' exposure levels. This 
approach safeguards miners from overexposure by frequent testing for 
gaseous diesel exhaust components in key areas, and establishing action 
levels for initiating corrective action that responds to emerging 
problems. In addition, MSHA mine inspections will include regular 
checks on miners' exposure to harmful airborne contaminants, including 
carbon monoxide and nitrogen dioxide, as part of determining compliance 
with the TLV<Register>'s in Sec. 75.322 of this chapter. MSHA's current 
practice is to sample, at least annually, all diesel equipment 
occupations on each mechanized mining unit. It is MSHA policy to also 
sample half of the diesel equipment occupations in areas outby the 
face. As a result, MSHA is confident that miners will be adequately 
protected.
    The final rule changes also respond to commenters who objected to 
the proposed personal monitoring requirements as fostering excessive 
sampling. In its guidance comments, the Office of Management and Budget 
counseled that the criteria for personal monitoring had the potential 
for an unnecessarily burdensome paperwork loop in which a mine would be 
required to conduct area sampling one week and personal sampling the 
next week. Other commenters also foresaw the potential for a cycle of 
area sampling followed by personal sampling, particularly at mines with 
naturally occurring high levels of carbon monoxide. These commenters 
also objected to the proposal that when personal exposure monitoring 
results indicate levels greater than 75 percent of the permissible 
exposure limit, such sampling would be required to continue on each 
operational shift until compliance was established with 95 percent 
confidence. By focusing the final rule's sampling requirements on 
monitoring the performance of the mine's diesel exhaust control system 
and taking timely corrective action, this potential problem is 
eliminated.
    The proposed rule recordkeeping requirements were tied to MSHA's 
proposed Air Quality standards in Secs. 72.200 (d), (e), (f) and (g) of 
this chapter. Commenters objected to the proposal's reference to MSHA's 
proposed Air Quality standards concerning exposure monitoring and 
referenced the comments they had submitted on those proposed rules. 
Under the proposal, the results of miners' personal samples were to be 
maintained for 5 years and include personal identification information 
as well as data about sampling location, duration, and results. The 
proposed requirements also required a record of the corrective action 
taken if miners' exposure readings exceeded the permissible limit. In 
addition, the proposed rule set requirements for access to miners' 
personal exposure records, provided miners or their representatives 
with the opportunity to observe monitoring, and called for notification 
of miners when samples indicate they have had exposures exceeding the 
permissible limit.
    In the Air Quality rulemaking, commenters objected to MSHA's 
proposal that adjustments to calculations of exposure be made for novel 
workshifts when a miner worked longer than eight hours. Commenters also 
objected to mine operators having to take corrective action to reduce

[[Page 55433]]

exposures based on one sample showing overexposure. In addition, 
commenters objected that it was burdensome to include the mine 
operator's corrective action in exposure monitoring records. Other 
commenters supported this requirement. These commenters further stated 
that the period for record retention should be 30 years for 
epidemiological purposes and to be consistent with the Occupational 
Safety and Health Administration's general industry requirements.
    For the reasons discussed above, the final rule re-focuses sampling 
for the gaseous components of diesel exhaust on early detection of 
diminishing performance of the mine's diesel exhaust control system. As 
a result, personal samples are not required. Certain limited 
recordkeeping is, however, necessary to support the final rule's 
objective of tracking the performance of the mine's diesel exhaust 
control system. To accomplish this objective with the least 
recordkeeping burden, paragraph (d) of the final rule revises the 
recordkeeping requirements of the proposal, conforming them to the 
existing requirements for on-shift examinations. Under the final rule, 
a record is required to be made of the results of samples taken under 
this section which exceed the applicable action level for carbon 
monoxide and/or nitrogen dioxide. Like the proposal, the data to be 
recorded under the final rule include the location where the sample was 
taken; the concentration of carbon monoxide and/or nitrogen dioxide 
measured; and the corrective action taken to reduce the concentration 
of carbon monoxide and/or nitrogen dioxide to below the applicable 
action level. A record of the instrumentation used, which would have 
been required under the proposal, has not been adopted in the final 
rule, because this is not essential information under the sampling 
scheme of the final rule.
    This aspect of the final rule is intended to minimize recordkeeping 
by requiring a record only when sample results are over the appropriate 
action level. This information is key to an effective monitoring system 
and provides essential data for assessing how the mine's diesel exhaust 
control system is functioning.
    For ease of administration by mine operators, the final rule 
specifies that recordkeeping under paragraph (d) follow the same 
requirements contained in existing Sec. 75.363 of this chapter. These 
standards prescribe the recordkeeping requirements for hazardous 
conditions found during a shift, including on-shift examinations. 
Section 75.363 of this chapter requires that the record be kept in a 
book maintained for the purpose on the surface of the mine, and that 
the record be completed by the end of the shift. Section 75.363 
requires that the record be made by the certified person who conducted 
the examination, or a person designated by the operator. In the latter 
case, the certified person must verify the record by the end of the 
shift. Records made under Sec. 75.363 also must be countersigned by the 
mine foreman or equivalent mine official by the end of the mine 
foreman's or equivalent mine official's next regularly scheduled 
working shift. These features of Sec. 75.363 emphasize the importance 
of mine management using and responding to data about working 
conditions in the mine.
    Section 75.363 also recognizes the use of electronic recordkeeping 
technology, provided it is made secure and not susceptible to 
alteration. MSHA encourages the use of such systems to ease 
recordkeeping burdens and facilitate analysis of this important 
information.
    The final rule does not retain certain proposed recordkeeping 
requirements which related to personal exposure monitoring. These 
include notification of miners if they are exposed over permissible 
limits, the opportunity for miners to observe personal monitoring being 
conducted, and access to personal exposure records by miners and their 
representatives. Since personal sampling is not required by the final 
rule, these provisions of the proposal are no longer appropriate.
    The final rule does, however, make results from area samples 
required by this section available for inspection by miners' 
representatives and MSHA inspectors through Sec. 75.363 of this 
chapter. This aspect of the final rule is consistent with the statutory 
role of miners' representatives and facilitates meaningful mine 
inspections. The retention period for the records required by paragraph 
(d) is at least one year, through the existing requirements of 
Sec. 75.363 of this chapter.
    Paragraph (e) of this section of the final rule provides that 
exhaust gas monitoring be conducted in accordance with Sec. 70.1900 as 
of 12 months after the publication date of the rule. This compliance 
deadline should provide mine operators with adequate time to implement 
the requirements of this section, and corresponds to the 12-month 
compliance deadline for the new ventilation requirements for diesel-
powered equipment in Sec. 75.325 of the final rule. Persons who are 
qualified to take the required gas measurements should be available at 
the mine, given the fact that air sampling for other gases, such as 
methane, is already required.

D. 30 CFR Part 75 Discussion.

Section 75.325  Air Quantity
    Diesel engines produce exhaust containing carbon monoxide, the 
oxides of nitrogen, and particulate matter, presenting potentially 
serious health risks to miners. Ventilation systems at underground coal 
mines where diesel-powered equipment is operated must be designed to 
dilute and carry away diesel exhaust contaminants, to ensure that 
miners' exposure to contaminants is maintained within acceptable 
limits. This portion of the final rule establishes minimum air quantity 
requirements in areas of underground coal mines where diesel-powered 
equipment is operated. These requirements recognize that effective mine 
ventilation is a key component in the control of miners' exposure to 
diesel exhaust contaminants.
    Air quantity requirements for diesel equipment were proposed in 
Sec. 75.390. Under the final rule these requirements have been 
consolidated with the other air quantity requirements for underground 
coal mines located in existing Sec. 75.325.
    The final rule provides that the minimum air quantity required to 
ventilate an individual unit of diesel-powered equipment is the 
quantity listed on the equipment approval plate. The approval plate 
quantity, which is calculated under Sec. 7.88 of the final rule for 
each engine model, is the amount of air necessary to dilute carbon 
monoxide (CO), carbon dioxide (CO<INF>2), nitric oxide (NO), and 
nitrogen dioxide (NO<INF>2) to the levels set by existing Sec. 75.322 
for those gaseous contaminants. This ventilation rate must be displayed 
on the engine's approval plate. The approval plate air quantity must be 
maintained: in any working place where an individual unit of diesel 
equipment is being operated; at the section loading point during any 
shift the equipment is being operated on the working section; in any 
entry where equipment is being operated outby the section loading point 
in areas of the mine developed on or after the effective date of the 
final rule; and in any air course with single or multiple entries where 
equipment is being operated outby the section loading point in areas of 
the mine developed prior to the effective date of the final rule. The 
district manager may also designate, in the ventilation plan, 
additional locations where minimum air quantities must be maintained 
for individual units of equipment.

[[Page 55434]]

    In areas of the mine where multiple units of diesel-powered 
equipment are operated, the final rule provides that the minimum air 
quantity will be the sum of the approval plate air quantities of all of 
the equipment. The air quantity must be maintained in the last open 
crosscut of each set of entries or rooms in each working section; in 
the intake, reaching the working face of each longwall; and at the 
intake end of any pillar line. The final rule allows certain types of 
equipment to be excluded from the multiple unit calculation for air 
quantity, based on the fact that the emissions from those types of 
equipment would not significantly affect the exposure of miners to 
contaminants. The final rule also authorizes the district manager to 
allow reduced air quantities in the ventilation plan for multiple units 
of diesel-powered equipment, if the mine operator presents evidence 
that justifies the reduction. Under this section mine operators are 
also permitted to obtain district manager approval for an action level 
other than the 50 percent level specified in Sec. 70.1900, if evidence 
submitted by the mine operator supports such a change.
    The Diesel Advisory Committee recommended that MSHA establish 
minimum ventilating air quantities for areas of the mine where diesel-
powered equipment operates, and that these minimum quantities be 
specified in the mine operator's ventilation plan. The Advisory 
Committee further recommended that required air quantities be based on 
the approval plate air quantities, with appropriate provisions made to 
address multiple units of equipment in the same air course. The 
Committee also concluded that allowances should be made for adjustment 
to minimum air quantities, if operating experience and workplace 
sampling indicate that such an adjustment is appropriate. Finally, the 
Committee recommended that a particulate index be developed for each 
piece of diesel-powered equipment and be reported on the engine 
approval plate.
    Under the proposed rule, the minimum quantity of air in any split 
of air where an individual unit of diesel-powered equipment was 
operated would have been the approval plate air quantity. The minimum 
air quantity on any split of air where multiple diesel units were 
operating would have been calculated using the sum of 100 percent of 
the highest approval plate air quantity, 75 percent of the second 
highest approval plate air quantity, and 50 percent of any additional 
approval plate air quantities. This was referred to as the ``100-75-
50'' approach during the public hearings and throughout the rulemaking 
process. Minimum air quantity requirements would also have applied when 
face equipment was being installed or removed.
    The proposed rule would also have established a minimum ventilation 
quantity based upon the particulate index determined for each type of 
diesel engine. The particulate index would have specified the quantity 
of air needed to dilute the diesel particulate matter generated by the 
specific engine to 1 milligram per cubic meter of air. In some cases 
the minimum air quantity derived from the particulate index would have 
been greater than the air quantity specified on the machine approval 
plate.
    A major concern of many commenters was the use of approval plate 
air quantities in establishing ventilation requirements for both 
individual and multiple units of diesel-powered equipment. A number of 
commenters stated that the air quantities specified on engine approval 
plates are not always necessary to dilute contaminants generated by the 
equipment to permissible levels. Several commenters expressed concern 
that the proposal represented a simplistic approach to complex issues, 
given the great variety of ventilation systems in underground coal 
mines.
    Some commenters stated that determining minimum air quantities on a 
mine-by-mine basis was more appropriate than the across-the-board 
approach taken in the proposal. Most of these commenters stated that if 
a mine's air quality is acceptable, air quantity should not be an 
issue, advocating a performance-based approach. These commenters 
believed that the final rule should give mine operators much more 
flexibility than the proposal would in designing their ventilation 
systems.
    A number of these commenters recommended that approval plate 
quantities be used only as a guideline for determining minimum air 
quantities for diesel equipment, and that a number of other variables 
be taken into account in determining the quantity of air needed to 
dilute exhaust contaminants. Commenters stated that such variables 
should include the minimum volume and velocity of air proposed by the 
mine operator; the number of diesel-powered units operating on the 
section; the equipment approval plate quantities; the duty cycles of 
the equipment; and the duty cycles of equipment that is not typically 
operating, such as equipment used for longwall moves.
    Some commenters recommended the exclusion of certain equipment, 
such as limited class equipment and equipment that is vented directly 
into return air courses, from minimum air quantity calculations. 
Commenters also suggested that administrative and engineering controls 
designed to maintain contaminant levels within acceptable limits, as 
well as respiratory protection practices implemented at the mine, 
should be taken into account in calculating minimum air quantities.
    One commenter pointed out that an engine's approval plate air 
quantity is based on the worst point of the operational range of the 
engine. The commenter further stated that this engine rating fails to 
take into account a number of factors that affect the gaseous emissions 
levels actually discharged into the mine environment, including the 
equipment power package; the engine duty cycle; the mine's elevation; 
the fuel used; and equipment maintenance.
    Other commenters stated that the proposal would give no credit to 
mine operators who used low emission technology, and that consideration 
should be given to calculating approval plate quantities after rather 
than before exhaust gases are treated. Other commenters stated that 
approval plate air quantities were well below average ventilation 
quantities currently provided in any given split of air.
    The final rule does not incorporate the approach advocated by 
several commenters for individual units of diesel-powered equipment. 
Instead, paragraph (f) adopts the proposed requirement and provides 
that the minimum ventilating air quantity where an individual unit of 
diesel- powered equipment is operated is the approval plate air 
quantity.
    Although commenters are correct in stating that the goal of air 
quantity requirements is to ensure that exhaust contaminants produced 
by the diesel engine are diluted to within acceptable limits, thereby 
preventing overexposure of miners, a pure performance-oriented 
approach, based on sampling to determine whether contaminants are 
within acceptable limits, is not the best way to achieve this goal. 
Elimination of minimum air quantities and adoption of the performance-
based scheme advocated by some commenters would by necessity demand an 
extensive and burdensome regimen of personal sampling to ensure that 
miners are not being overexposed. In contrast, the mandatory minimum 
ventilating air quantities in the final rule will give reasonable 
assurance that contaminant levels are being adequately controlled, 
while the sampling that an operator must perform has been minimized. 
The

[[Page 55435]]

amount of air required by the approval plate quantity to ventilate a 
diesel engine is a scientifically-based determination of the minimum 
air needed to maintain gaseous contaminants, particularly NO<INF>2, 
within acceptable limits and avoid overexposures of miners. The 
sampling under the final rule confirms that the integrated system of 
protections--diesel engines that are well maintained and effectively 
ventilated--continues to function as intended.
    The approach taken by the final rule is an effective method of 
minimizing miners' exposure to unhealthful diesel emissions. As 
explained above, the approval plate air quantity is derived from a 
mathematical determination of the amount of air that is needed to 
dilute CO, CO<INF>2, NO, and NO<INF>2 to the TLV<Register>'s 
established in existing Sec. 75.322, which have applied in underground 
coal mines for the last 25 years. The TLV<Register>'s for these 
contaminants, with the exception of NO<INF>2, are time-weighted 
averages, which means that the average concentration of the contaminant 
over an 8-hour period must be within allowable limits, although the 
levels of these contaminants may spike up significantly in excess of 
the TLV<Register> in short excursions over the measurement period. In 
contrast, the NO<INF>2 limit of 5 parts per million is a ceiling limit, 
which means that concentrations of NO<INF>2 must never exceed the 
TLV<Register>, even for a brief period of time. This is because 
elevated concentrations of NO<INF>2 can be very toxic, and even short 
exposure to high levels of NO<INF>2 can cause inflammation of the 
lungs, possibly resulting in pulmonary edema and lung hemorrhaging. The 
only external sign of NO<INF>2 poisoning is shortness of breath. 
Sufficient dilution by adequate quantities of air of all contaminants, 
and in particular of NO<INF>2, during the entire period that diesel-
powered equipment operates is therefore essential in protecting miners' 
health.
    It is important to note that the approval plate calculation assumes 
total mixing of the exhaust gases in the ventilating air, and that 
levels of exhaust gases that are higher than the TLV<Register>'s will 
likely occur close to the machine's exhaust, before the gases are fully 
dispersed and diluted by the ventilating air. Essentially, this means 
that the approval plate air quantity represents the best-case scenario 
for contaminant dilution. The approval plate air quantity is therefore 
the smallest amount of air that will ensure that contaminants are 
within acceptable levels at all points in the engine's duty cycle.
    It should also be noted that the oxides of nitrogen (NO and 
NO<INF>2) have been the controlling gases for engine approval plate 
quantities for the vast majority of diesel engines that have been 
approved in the past. This means the approval plate quantity is 
determined by the air needed to dilute those two gases; a lesser 
quantity of air is sufficient to dilute the other gaseous contaminants 
produced by the engine. Although NO does not have the same toxic 
effects as NO<INF>2, it does convert to NO<INF>2 over time. As 
mentioned above, sufficient dilution of NO<INF>2 is essential to 
protect miners from its potentially severe effects.
    The approval plate air quantity calculation takes into account the 
worst operating point of a properly maintained engine tested under 
laboratory conditions. Some commenters asserted that approval plate air 
quantities were unnecessarily high, because the quantities were 
calculated for the worst operating point of the machine, when the 
machine generated the highest levels of gaseous contaminants. Although 
commenters are correct in stating that the approval plate calculation 
represents the air quantity needed to dilute contaminants at the point 
where the engine produces the highest level of emissions, diesel engine 
emission levels are high over a range of operating points. See, Report 
of the Bureau of Mines, U.S. Department of the Interior, ``Relationship 
of Underground Diesel Engine Maintenance to Emissions'' (December 
1983). Contrary to the assertions of some commenters, the engine 
approval plate quantity does not represent an unrealistically high 
quantity of air, but is an accurate determination, based on testing, of 
the ventilating air quantity needed to protect miners working in the 
vicinity of the equipment over their working shift. Finally, as pointed 
out by one commenter, the approval plate air quantity is calculated 
using new engines, whose performance will likely degrade to some extent 
over time, with the potential for increased emission levels, even if 
the engines are well maintained.
    The performance-based approach advocated by several commenters 
could provide another method for determining minimum air quantities, 
but, for the reasons stated earlier, would substitute a rather 
intricate sampling process that would result in a determination that 
essentially the same minimum air quantities are needed to ventilate the 
equipment. Mandating approval plate quantities as the minimum air 
quantities is not the only approach to ventilation of diesel-powered 
equipment, but it is the most workable and practical.
    The final rule does not adopt the suggestion of commenters who 
advocated factoring in exhaust after-treatment in determining minimum 
air quantities. The after-treatment technology currently available is 
ineffective in reducing the oxides of nitrogen. Consequently, the gases 
used to determine the approval plate air quantities for the vast 
majority of diesel engines that have been approved cannot be controlled 
by existing exhaust after-treatment technology. This recommendation has 
therefore not been adopted in the final rule.
    The locations where minimum air quantities must be maintained for 
individual units of diesel equipment have been modified in the final 
rule from what would have been required under the proposal. The 
proposal would have required minimum air quantities for individual 
units of equipment to be maintained in any split of air where the 
equipment was being operated. A number of commenters disagreed with 
this provision, stating that the term ``split'' was vague and 
ambiguous, and did not adequately specify areas of the mine where 
individual units of equipment were likely to operate and generate high 
levels of diesel exhaust contaminants. Commenters also identified outby 
areas and section loading points as locations where diesel exhaust 
levels tended to be a particular problem and where additional 
ventilating air was needed. Several commenters stated that it was 
essential to have adequate ventilation across the mine's dumping points 
to ensure that diesel emissions are swept out of the area. These 
commenters stated that the rule should also address outby operation of 
diesel-powered equipment, because excessive diesel emissions occur in 
idled areas of the mine and during non-production times, when less air 
is typically required for ventilation because dangerous levels of 
methane tend to be less of a problem during those periods. Other 
commenters were of the opinion that the rule should not designate 
locations where minimum air quantities must be maintained, and 
supported determining these locations on a mine-by-mine basis.
    In response to commenters, the final rule does not adopt the 
proposed requirement that the air quantity for individual units of 
equipment be maintained in any ``split'' where the equipment was being 
operated. Instead, paragraphs (f)(1) through (f)(5) list the specific 
locations where the minimum air quantity must be maintained, and 
include those locations identified by commenters where diesel equipment 
is typically inadequately ventilated and

[[Page 55436]]

where levels of exhaust contaminants are likely to be high. These 
locations include any working place where the equipment is being 
operated; at the section loading point during any shift the equipment 
is being operated on the working section; in any entry where equipment 
is being operated outby the section loading point in areas of the mine 
developed on or after the effective date of the final rule; in any air 
course with single or multiple entries where the equipment is being 
operated outby the section loading point in areas of the mine developed 
prior to the effective date of the final rule; and at any other 
location required by the district manager and specified in the approved 
ventilation plan.
    Paragraph (f)(1) provides that the minimum ventilating air quantity 
for an individual unit of diesel-powered equipment must be maintained 
in any working place where the equipment is being operated. This 
responds to commenters' concerns and clarifies the intent of the 
proposal, which would have required that the minimum air quantity be 
maintained in the ``split'' where the equipment operates. As discussed 
above, a number of commenters did not consider the term ``split'' to be 
sufficiently descriptive, and the final rule has been revised in 
response. Under the final rule required air quantities must be 
maintained in the ``working place,'' which is defined in existing 
Sec. 75.2 as ``The area of a coal mine inby the last open crosscut.'' 
This location is designed to address ventilation of an individual unit 
of diesel-powered equipment that is working at an inby location, near 
the face.
    Paragraph (f)(2) adds the specific requirement that the minimum air 
quantity for an individual unit of equipment be maintained at the 
section loading point during any shift that the equipment is being 
operated on the working section. This provision responds to commenters 
who singled out loading points as one of the locations where excessive 
levels of diesel contaminants were a particular problem. Commenters 
pointed out that the ventilating air quantities at these locations were 
frequently insufficient to dilute exhaust contaminants and protect 
miners from unhealthful levels of exhaust gases. Because different 
types of equipment move in and out of a section loading point on a 
regular basis, the minimum required air quantity will be the greatest 
approval plate quantity among all of the diesel-powered equipment that 
is operated at the loading point during the shift. This will ensure 
that miners are protected from overexposure to contaminants at all 
times during the shift, regardless of which unit of diesel equipment is 
at the loading point.
    Paragraphs (f)(3) and (f)(4) have been added to the final rule to 
address the concerns of those commenters who stated that minimum 
ventilation requirements should apply to diesel-powered equipment that 
is being operated in outby areas. These two provisions, one of which 
applies to areas of the mine developed before the effective date of the 
final rule and the other which applies to areas developed on or after 
the effective date, recognizes that the ventilation system design at 
some mines with multiple common haulage entries would make it 
difficult, if not impossible, to maintain minimum air quantities in a 
single entry. Consequently, the final rule allows the minimum air 
quantity to be maintained in the air course rather than in a single 
entry, in areas of the mine developed before the effective date of the 
final rule. In areas of the mine developed on or after the effective 
date, the minimum air quantity must be maintained in a single entry. 
This means that mines with multiple common entries that use diesel 
equipment must alter their approach to future mine development no later 
than the effective date of the final rule.
    This two-pronged approach to ventilation of outby diesel equipment 
recognizes that the location and direction of required air quantities 
have an impact on how effectively the air will dilute diesel engine 
emissions. Air that is coursed directly over diesel equipment will 
dilute contaminants more effectively than air of the same volume and 
velocity that is dispersed over a wider area. Consequently, providing 
the air quantity in a single entry rather than over multiple entries is 
a more desirable method of ventilation. However, this approach also 
takes into account that a number of mines would be unable to comply 
with the location requirements of (f)(3) in areas that have already 
been developed, without significant capital expenditures and 
substantial disruption of mining operations. This aspect of the final 
rule therefore strikes a balance between the concerns of commenters 
regarding adequate ventilation of diesel equipment operated in outby 
areas, and the economic infeasibility of a complete overhaul of areas 
of the mine that have already been developed.
    It should be noted that Sec. 75.1907 of the final rule does not 
require diesel equipment used in outby areas to have an engine approved 
under subpart E of part 7 of the final rule until 3 years after the 
publication date of this rule. During this transitional period, 
equipment with unapproved engines that do not have an approval plate 
will not be subject to the minimum air quantity requirements of the 
final rule. However, mine operators are under a continuing obligation 
to ensure that air contaminants are maintained within the limits 
established in Sec. 75.322, and diesel-powered equipment must be 
ventilated with sufficient quantities of air to prevent overexposure of 
miners.
    Paragraph (f)(5) has been added to the final rule to give the 
district manager the authority to require other locations where minimum 
air quantities for individual units of equipment must be maintained. 
These locations must be specified in the ventilation plan. This 
provision has been added in response to commenters who were concerned 
about inadequate ventilation in areas where diesel-powered equipment 
was operating, other than those locations specified in paragraphs (f) 
(1) through (4). These locations could include, for example, 
underground repair shops, permanent fuel storage facilities or 
temporary fuel storage areas, or construction sites where diesel-
powered equipment is regularly operated and where minimum air 
quantities are needed to keep contaminant levels within acceptable 
limits.
    The final rule adopts the proposal's approach of using the engine 
approval plate air quantity to determine the minimum air quantity in 
areas where multiple units of diesel-powered equipment are being 
operated. Paragraph (g) provides that the minimum ventilating air 
quantity where multiple units of diesel-powered equipment are operated 
on working sections and in areas where mechanized mining equipment is 
being installed or removed, must be the sum of 100 percent of the 
approval plate quantities for all of the equipment. As mentioned 
earlier, this is a change from the 100-75-50 percent approach of the 
proposal.
    The final rule, like the proposal, also specifies certain equipment 
that may be excluded from the calculation of minimum air quantity, and 
also permits a mine operator to obtain a reduction in the required 
minimum air quantity for multiple units if sampling evidence 
establishes that a lesser ventilating air quantity will maintain 
continuous compliance with the TLV\'S in Sec. 75.322.
    Several commenters advocated that approval plate air quantities be 
used only as guidelines for ventilation of multiple units of equipment, 
for the same reasons outlined in the discussion of ventilating air 
quantities for individual units of equipment. These commenters stated 
that there were a

[[Page 55437]]

number of variables that must be considered in establishing ventilation 
for diesel equipment, and advocated determining minimum air quantities 
on a mine-by-mine basis.
    Some commenters were opposed to the 100-75-50 approach, stating 
that it would not adequately protect miners. These commenters took 
issue with the assumption that multiple units of diesel-powered 
equipment could not be operating at their worst point, i.e., generating 
the highest levels of emissions--simultaneously. Commenters also 
pointed out that the 100-75-50 approach assumed that engines perform at 
a consistent level from the day they are purchased until the end of 
their useful life, and advocated that the sum of 100 percent of the 
approval plate air quantities be used instead as the minimum 
ventilation quantity.
    The final rule, like the proposal, specifies that engine approval 
plate quantities are the minimum ventilating air quantity for diesel-
powered equipment. The approval plate quantity is required for multiple 
units for the same reasons that it is required for individual units: it 
is an accurate calculation of the amount of air that is needed to 
dilute gaseous diesel exhaust contaminants to acceptable levels. 
However, the final rule, like the proposal, allows mine operators to 
seek reductions in the required air quantities if they are able to 
demonstrate that contaminant levels will be kept within required limits 
at reduced ventilating air levels. This provision recognizes that, as 
stated by commenters, there may be variables of mine design, equipment 
operation, or ventilation in areas where multiple units operate that 
may result in less air being needed to keep air quality within 
healthful limits. For example, if the diesel machines on a section are 
not operated so that all machines are producing maximum emissions 
simultaneously, reduced minimum air quantities may be appropriate.
    The final rule does not adopt the 100-75-50 approach, in response 
to commenters' concerns that it would not provide adequate protection 
for miners, and for several other reasons. First, the 100-75-50 formula 
was designed to account for differences in duty cycles among the 
equipment, since the approval plate air quantity is based upon the 
worst point of the operating range of the equipment relative to gaseous 
emissions. The 100-75-50 approach assumed, as has been pointed out by 
commenters, that multiple units of equipment would not have been 
operating at their worst points at the same time. As discussed above, 
although the approval plate air quantity is calculated for a worst case 
engine operating point, research has shown that engines generate high 
levels of contaminants over a range of engine operating points. The air 
quantity available on the section should be sufficient to control the 
engine emissions under all conditions.
    The 100-100-100 approach also recognizes that approval plate air 
quantities will be calculated differently under part 7 than they have 
been under part 36, prior to the promulgation of this final rule. As 
discussed in the preamble to subpart E of part 7, an engine's approval 
plate air quantity under the final rule will be determined by the 
amount of air needed to dilute contaminants to the TLV<Register>'s in 
Sec. 75.322. Up until now, approval plate quantities have been 
determined under part 36 based on the amount of air needed to dilute 
contaminants to 50 percent of the TLV<Register>'s that were in effect 
when part 36 was first promulgated in 1961. Although the levels to 
which CO and NO<INF>2 must be diluted remain the same under the final 
rule, the dilution levels for NO and CO<INF>2 are twice as high. 
Consequently, less air will be needed to dilute these two gases to the 
higher levels, and the approval plate quantity will be lower for most 
if not all engines. However, the approval plate quantity will now 
directly correlate to existing TLV<Register>'s. It follows that 100 
percent of the approval plate quantity, rather than some fraction 
thereof, must be provided to adequately dilute the gaseous diesel 
engine contaminants.
    Approval plate quantities determined under the final rule may also 
be slightly lower than before under old part 36, as a result of the 
revision in part 36 that requires engines to be tested with 1.0 percent 
methane injected into the engine air intake, rather than the current 
1.5 percent. Because injection of methane into the engine increases 
engine emissions, the lower concentration of methane used under the 
final rule will result in lower emissions and will require a lower 
quantity of air to dilute.
    Because of these factors, the 100-100-100 calculation for multiple 
units of equipment will not result in minimum air quantities that are 
significantly greater than air quantities currently required in 
ventilation plans using the 100-75-50 method of calculation. In fact, 
in some cases, the air quantity required for multiple units may be less 
than what was required before, depending on the diesel equipment that 
is being operated.
    Under the proposal, air quantities in excess of the 100-75-50 
calculation for multiple units of equipment would have been required 
when the particulate index established for the equipment indicated that 
a greater air quantity was needed to maintain diesel particulate levels 
within acceptable limits. The particulate index indicates the quantity 
of air required to dilute particulate emissions from that specific 
engine to a concentration of 1 milligram per cubic meter of air. The 1 
milligram value was chosen to make the use of a diesel particulate 
permissible exposure limit with an engine's particulate index a matter 
of simple multiplication, and is not meant to be an indicator of the 
level of any diesel particulate standard that may be set by MSHA in the 
future.
    Under the proposal, MSHA intended to apply the particulate index in 
two phases, before and after the setting of a diesel particulate 
standard. Before the promulgation of a standard, MSHA intended to take 
an engine's particulate index into account in approving minimum air 
quantities in a mine operator's ventilation plan by estimating the 
contribution of diesel particulate to the total respirable coal mine 
dust concentration. After the promulgation of a diesel particulate 
standard, the minimum air quantity would be determined using the 
particulate index to calculate the air quantity needed to dilute the 
particulate concentration to whatever level was required.
    A number of commenters stated that, because MSHA has not yet 
established a permissible exposure limit for diesel particulate, a 
requirement for increased air quantities based upon a diesel 
particulate index was inappropriate. Other commenters supported the use 
of a particulate index as a point of comparison among different diesel-
powered engines, but they were strongly opposed to the use of the index 
to require minimum air quantities. Other commenters stated that 
accurate measurement of diesel particulate is not possible, because 
diesel particulate matter is indistinguishable from other respirable 
coal mine dust. One commenter stated that the particulate index fails 
to take into account that the diesel engine is itself only one factor 
in how cleanly the machine operates as a whole. This commenter 
recommended that other factors be considered, including the 
effectiveness of water scrubbers, dilutors, catalytic convertors, and 
particulate traps or filters, any one of which could significantly 
reduce diesel particulate emissions.
    Although MSHA is currently developing a proposed rule to control 
miners' exposure to diesel particulate, MSHA agrees with commenters who 
believe that the use of the particulate

[[Page 55438]]

index for determining minimum ventilation requirements would be 
premature in the absence of a standard for diesel particulate. The 
final rule therefore does not adopt the proposal's requirement for 
increased air quantities based on a diesel engine's particulate index. 
However, MSHA will still calculate an engine's particulate index as 
part of the approval process. As was true under the proposal, the 
particulate index will be determined under part 7 of the final rule. 
The particulate index for the engine will be reported in the approval 
letter that MSHA sends to the engine manufacturer notifying the 
manufacturer that the engine has been approved. A copy of this letter 
also accompanies the equipment when it is purchased by the mine 
operator. The particulate index for all MSHA-approved diesel engines 
will also be included on MSHA's list of approved products, which is 
issued on a regular basis to the individuals and companies on MSHA's 
mailing list. MSHA anticipates that, until a diesel particulate 
standard has been set, mine operators and machine manufacturers will 
use the engine particulate index in selecting and purchasing engines. 
During this time mine operators may also use an engine's particulate 
index to roughly estimate the engine's contribution to the mine's 
levels of total respirable coal mine dust.
    Under the proposal multiple units of equipment would have been 
required to be ventilated by specified minimum air quantities in the 
last open crosscut of each working section or in the intake splits of 
longwall sections. The proposed rule would also have required minimum 
air quantities to be maintained when face equipment was being installed 
or removed.
    One commenter stated that air on a dieselized section should be 
coursed throughout the section and should not be concentrated in the 
last open crosscut. This commenter recommended that the total intake 
air quantity going into the section intake and the total return air 
quantity leaving the section should be measured. Another commenter 
stated that air measurements are more accurate in the immediate return 
of each split, rather than at the last open crosscut.
    Several commenters pointed out that too much air across the face 
area was detrimental to the effective operation of respirable dust 
scrubbers on continuous miners. Several commenters identified longwall 
moves as periods when miners were exposed to high levels of diesel 
exhaust, due to the increased use of diesel-powered equipment on the 
sections during these periods and the increased diesel engine loads. 
These commenters stated that during longwall moves the exhaust from one 
diesel machine would be ``rebreathed'' by another diesel machine, 
resulting in a doubling of carbon monoxide levels.
    Paragraphs (g)(1) through (g)(3) of the final rule set forth the 
specific locations where minimum air quantities must be maintained 
where multiple units of diesel-powered equipment are operating. Under 
the proposal, as described above, minimum air quantities would have 
been required in the last open crosscut of each working section or in 
the intake splits of longwall sections.
    The final rule essentially adopts the approach of the proposal, 
although the term ``split'' used in the proposal has not been adopted 
in the final rule because, as explained in the discussion under 
paragraph (a) of this section, commenters considered the term ``split'' 
to be vague and ambiguous. The final rule provides more specific 
description of the locations where air quantities must be maintained, 
although the location requirements themselves are essentially the same 
as they would have been under the proposal. Paragraphs (g)(1) through 
(g)(3) of this section require the minimum air quantity in working 
sections to be maintained: in the last open crosscut of each set of 
entries or rooms in each working section; in the intake, reaching the 
working face of each longwall; and at the intake end of any pillar 
line.
    The final rule does not adopt the suggestion of commenters that air 
measurements be taken at locations other than those specified in the 
proposal. The recommendation that the total intake air quantity 
entering a section and the total return air quantity leaving a section 
be measured has not been adopted because this method of measurement 
will not provide an indication of the air quantity that is actually 
reaching the working section. The air could be short-circuited before 
it reaches the diesel machine, but still be measured as part of the 
return air quantity. Further, the recommendation that air measurements 
be taken in the immediate return of each split, rather than at the last 
open crosscut, has not been incorporated into the final rule because 
measurement at that location will give a less accurate indication of 
the air that is actually ventilating the diesel equipment. Finally, the 
measurement of air quantities at the last open crosscut under the final 
rule is also consistent with air measurement requirements currently in 
most underground coal mine ventilation plans.
    The final rule does not respond to commenters who stated that too 
much air across the face area could have a negative impact on the 
effectiveness of respirable dust scrubbers on continuous miners. While 
it is true that increased air quantities could in some cases have an 
adverse effect on dust scrubber effectiveness, this impact must be 
balanced against the need to control harmful diesel exhaust 
contaminants. There are other dust control technologies that are 
available to supplement dust scrubbers if the need arises.
    In response to the many commenters who expressed concern about 
exposure of miners to high levels of diesel exhaust contaminants during 
installation or removal of longwall equipment, the final rule adopts 
the proposed requirement that minimum air quantities be maintained in 
areas where mechanized equipment is being installed or removed.
    Paragraphs (h)(1) through (h)(4) of this section of the final rule, 
like the proposal, allow certain types of equipment to be excluded from 
the minimum air quantity calculation of paragraph (g). The rationale 
behind these exclusions is that the specified equipment is operated or 
ventilated in such a way that it does not significantly affect the 
exposure of miners to diesel exhaust contaminants. Commenters were 
generally in favor of allowing certain equipment to be excluded, such 
as equipment with light-duty cycles or equipment that is only used 
intermittently. One commenter stated, however, that MSHA should verify 
information submitted by the operator to support exclusion of 
equipment, and that the final rule should require mine operators to 
notify miners or their representatives to allow them to comment on the 
operator's request for exclusion of equipment from the air quantity 
calculation.
    In response to this comment the final rule, unlike the proposal, 
requires district manager approval of all exclusions and requires the 
exclusions to be specified in the ventilation plan. This will allow 
MSHA review of all equipment that will be excluded from the air 
quantity calculation, and responds to commenter concerns about MSHA 
verification of excluded equipment. Additionally, requiring excluded 
equipment to be specified in the ventilation plan will ensure that 
miners and their representatives, who are required under existing 
regulations to be provided with proposed revisions to an operator's 
ventilation plan, are notified of an operator's intention to exclude 
certain equipment. This

[[Page 55439]]

responds to commenters who advocated that miners' representatives be 
notified of and be given an opportunity to comment on such matters.
    Paragraph (h)(1) allows the exclusion of self-propelled equipment 
meeting the requirements of Sec. 75.1908(b) of the final rule. The 
proposal would have allowed the exclusion of the limited class of 
equipment meeting the requirements of proposed Sec. 75.1908, except 
diesel-powered air compressors that are regularly used. The 
requirements of proposed Sec. 75.1908 included specific objective 
criteria limiting equipment horsepower and weight. In response to 
commenters and for reasons explained in detail in the preamble to 
Sec. 75.1908, equipment categories are defined in the final rule by the 
equipment function rather than by weight or horsepower. Equipment that 
meets the requirements of Sec. 75.1908(b) is light-duty equipment that 
does not, among other things, cut or move rock or coal or move longwall 
components. Because the equipment is not operated under heavy load, it 
is not expected to produce high levels of exhaust emissions, and may 
therefore be excluded if specified in the mine operator's approved 
ventilation plan. Although the proposal did not explicitly limit the 
exclusion to self-propelled equipment, as does the final rule, the only 
portable equipment included in the proposed limited class was 
compressors and welders, and compressors were not eligible for 
exclusion under the proposal if they were regularly operated. The final 
rule takes a different approach and only includes self-propelled light-
duty equipment in the automatic exclusion under paragraph (h)(1), 
because some types of non-self-propelled light-duty equipment, such as 
compressors and generators, can produce high levels of exhaust 
emissions. However, light-duty equipment that is not self-propelled 
whose emissions would not significantly affect the exposure of miners 
may be excluded from the air quantity calculation if approved by the 
district manager under paragraph (h)(4).
    Also eligible for exclusion, under paragraphs (h)(2) and (h)(3), is 
equipment that discharges its exhaust into an intake air course that is 
vented directly into a return air course, or that discharges its 
exhaust directly into a return air course. Paragraph (h)(3), which 
exempts equipment vented directly into a return air course, has been 
adopted without change from the proposal. Paragraph (h)(2), which 
exempts equipment that discharges its exhaust into intake air that is 
coursed directly to a return air course, has been added to the final 
rule to be consistent with other MSHA regulations, which require 
certain equipment, such as electrical equipment, to be vented either 
directly into a return air course or into an intake air course that is 
coursed directly into a return air course. The rationale for both of 
these exceptions in the final rule is the same: that the diesel exhaust 
of equipment that discharges into a return air course or into an intake 
air course that goes directly into a return air course will not, in 
most cases, come into contact with miners because most of them will be 
working in intake air in the face area where production occurs. 
Commenters did not indicate any opposition to the reasoning behind 
these exceptions.
    Paragraph (h)(4), like the proposal, allows mine operators to 
obtain MSHA approval for the exclusion of other equipment from the air 
quantity calculation in paragraph (g). Equipment may be excluded under 
this paragraph if its duty cycle is such that the emissions would not 
significantly affect the exposure of miners. Mine operators who seek to 
exclude equipment must identify the equipment in the ventilation plan 
that is submitted to MSHA for approval. Equipment that may be eligible 
for exclusion under paragraph (h)(4) includes equipment with a very 
small engine (less than 10 horsepower) or heavy-duty equipment that is 
operated infrequently, for very short periods of time, or when other 
diesel equipment normally operated on the section is shut down or not 
operating. An example of equipment that could be considered for 
exclusion under this paragraph is a supply vehicle that is driven up to 
the section, shut down and unloaded, started up and immediately driven 
off of the section. Equipment that is operated in a location so that 
its exhaust does not pass over miners could also be eligible for this 
exclusion. All other equipment, such as nonpermissible heavy-duty 
equipment and face equipment which discharges its exhaust into an 
intake air course of the working section, must be included in the 
minimum air quantity calculation required by paragraph (g).
    Paragraph (i) of the final rule, like the proposal, allows the 
district manager to approve a lesser air quantity than what would 
otherwise be required under paragraph (g) for multiple units of diesel 
equipment. The final rule allows such a modification if sampling 
results demonstrate that miners exposure to diesel contaminants will 
not exceed applicable TLV<Register>'s at the modified ventilation 
quantity.
    The proposed rule would have allowed the district manager to 
approve lesser air quantities for multiple units of equipment if the 
results of a comprehensive personal monitoring program indicated that 
contaminant exposure levels were below 75 percent of the applicable 
contaminant standards with 95 percent confidence. The proposed rule 
also specified the information that mine operators would have been 
required to submit to MSHA for consideration in reducing minimum air 
quantities, including the actual sampling plan and an evaluation of the 
sampling results.
    Some commenters were opposed to requiring a 95 percent confidence 
level for the sampling used to support a reduction in air quantity, 
stating that this requirement was too technical and unrealistic for 
practical application. Some commenters strongly opposed allowing 
reduction of air quantities under the procedure set forth in the 
proposal, stating that miners and their representatives would not be 
given sufficient opportunity to participate in the process. One 
commenter advocated use of petition for modification procedures under 
section 101(c) of the Federal Mine Safety and Health Act when mine 
operators seek to revise their ventilation plans, stating that under 
these procedures miners and miners' representatives would have the 
right to review and comment on the proposed plan modifications.
    The final rule takes a more performance-oriented approach to 
reduction in minimum air quantities, and requires that samples of 
contaminants demonstrate that a lesser air quantity will maintain 
contaminant levels within permissible limits. This is consistent with 
the streamlined procedures for contaminant sampling in Sec. 70.1900 of 
the final rule, and also responds to commenters' recommendations that 
this aspect of the rule should be less technical.
    The objective of this aspect of the final rule is the same as that 
of the proposal: that reduction of minimum air quantities required by 
the final rule is permitted if a mine operator can establish that 
miners will not be overexposed to gaseous diesel exhaust contaminants 
at the lesser ventilating air quantities.
    The final rule does not adopt the suggestion of commenters that 
reductions in air quantity be granted only under the modification 
procedures of section 101(c) of the Mine Act. Since the time of the 
submission of these comments, MSHA has issued a final rule governing 
underground coal mine ventilation, which includes revisions to the 
existing ventilation plan submission and approval process [61 FR 9764] 
and addresses several of these commenters' concerns. The revised 
ventilation rules

[[Page 55440]]

provide an increased role for the representative of miners in the 
ventilation plan approval process. Mine operators are now required to 
notify the representative of miners at least 5 days before a 
ventilation plan or plan revision is submitted to MSHA for approval, 
and make a copy of the proposed plan or plan revision available for 
inspection to the miners' representative. The representative of miners 
is given the opportunity to submit written comments to MSHA for 
consideration during the plan review process. Under this process, 
operators seeking reduction in the minimum air quantities required 
under paragraph (g) are required to notify miners' representatives, who 
then have the opportunity to comment on the reduction. No provisions 
have therefore been made to address these comments in the final rule, 
because the comments have already been addressed appropriately in the 
revised ventilation rule.
    Paragraph (j) allows modification of the 50 percent action level 
specified in Sec. 70.1900(c) if sampling results demonstrate that 
miners will not be exposed to contaminants that exceed permissible 
limits at the modified action level. As described in detail in the 
preamble discussion for Sec. 70.1900, any change to the action level 
must be based on the results of sampling that demonstrate that miners' 
personal exposure will not exceed the applicable TLV<Register><SUP>.
    Paragraph (k) provides that, as of 12 months after the publication 
date of the final rule, the ventilating air quantity required where 
diesel-powered equipment is operated shall meet the requirements of 
paragraphs (f) through (j) of this section. Compliance with the 
ventilation requirements of the final rule will in some cases require 
modifications to the mine's ventilation system. These revisions, along 
with other information required to be specified in the mine ventilation 
plan under paragraphs (f) through (j) of this section, should be 
included in a revised ventilation plan submitted to MSHA for review and 
approval.
Section 75.371  Mine Ventilation Plan; Contents
    The requirements for diesel-powered equipment that are included by 
the final rule in existing Sec. 75.325 identify information that must 
be specified in the mine operator's ventilation plan. Existing 
Sec. 75.371, which lists the information that must be provided by mine 
operators in their mine ventilation plans, is amended by the final rule 
to conform to the new requirements in Sec. 75.325.
    As was true under the proposal, minimum air quantities for 
individual units of diesel-powered equipment are not required to be 
included in the ventilation plan, because individual units are required 
to be ventilated with at least the engine approval plate air quantity 
while they are operating. The final rule does require that the 
ventilation plan specify where air quantity will be maintained at the 
section loading point for individual units of equipment, as well as any 
additional locations required by the district manager where a minimum 
air quantity must be maintained for an individual unit of equipment.
    The final rule, like the proposal, requires the ventilation plan to 
specify ventilation quantities for multiple units of equipment, as well 
as to include a description of equipment that is excluded from the 
multiple unit calculation of Sec. 75.325(g).
    Existing Sec. 75.371(r) is revised by the final rule to include a 
cross-reference to Sec. 75.325 (d), (g), and (i). Paragraph (r) 
requires the ventilation plan to identify the minimum quantity and the 
location of air that will be provided during the installation and 
removal of mechanized mining equipment, as well as the ventilation 
controls that will be used. The addition of a cross-reference to 
Sec. 75.325 clarifies that minimum air quantity requirements for 
diesel-powered equipment must be considered when determining 
ventilation quantities during mechanized equipment installation and 
removal.
    New paragraph (kk) has been added to Sec. 75.371 and provides that 
the ventilation plan shall include any additional areas designated by 
the district manager under Sec. 70.1900(a)(4) of the final rule for CO 
and NO<INF>2 sampling. As explained in more detail in the preamble to 
Sec. 70.1900, the district manager is authorized under the final rule 
to require sampling in strategic locations on a mine-by-mine basis, in 
order to address situations involving significant concentrations of 
diesel exhaust. Paragraph (kk) conforms the content requirements for 
ventilation plans to this new provision.
    New paragraph (ll) provides that the ventilation plan must specify 
the location where the air quantity will be maintained at the section 
loading point.
    New paragraph (mm) provides that the ventilation plan include any 
additional locations required by the district manager, under 
Sec. 75.325(f)(5), where a minimum air quantity must be maintained for 
an individual unit of diesel-powered equipment.
    New paragraph (nn) provides that the ventilation plan must specify 
the minimum air quantities that will be provided where multiple units 
of diesel-powered equipment are operated. To comply with this 
requirement, mine operators should indicate the equipment that is being 
used in the normal mining cycle, and the minimum air quantities that 
must be provided to ventilate the specified equipment.
    New paragraph (oo) provides that the ventilation plan must specify 
the diesel-powered equipment excluded from the calculation under 
Sec. 75.325(g). MSHA does not intend that this provision require the 
itemization or the serial numbers of specific equipment. Instead, the 
mine operator should provide a general description that is sufficient 
to identify the types of equipment that are excluded from the 
calculation.
    New paragraph (pp) conforms ventilation plan content requirements 
to Secs. 70.1900(c) and 75.325(j), and provides that the ventilation 
plan shall identify any action levels that are higher than the 50 
percent level specified by Sec. 70.1900(c). As described in greater 
detail in the preamble discussion of Sec. 70.1900, mine operators may 
obtain a higher action level if they are able to demonstrate that 
miners will not be overexposed to contaminants at the higher level. If 
a higher action level is approved by the district manager under 
Sec. 75.325(j), it must be specified in the mine ventilation plan.
Section 75.1900  Definitions
    This section of the final rule contains definitions of terms used 
in subpart T of part 75. These definitions are provided to assist the 
mining community in understanding and complying with the requirements 
of the final rule. As a general matter, terms which are unique to the 
final rule are defined, while those terms that are commonly used and 
understood in the mining industry have not been included for 
definition.
    The proposed rule defined two terms: ``fixed underground diesel 
fuel storage facility'' and ``mobile underground diesel fuel storage 
facility''. The final rule adopts the proposed definition for ``fixed 
underground diesel fuel storage facility'', although the term itself 
has been slightly modified, with the substitution of the word 
``permanent'' for the word ``fixed'' to more accurately reflect the 
nature of the facility. A ``permanent underground diesel fuel storage 
facility'' is defined as a facility designed and constructed to remain 
at one location for the storage and dispensing of diesel fuel, and 
which does not move as mining progresses. Such facilities are designed 
to remain at

[[Page 55441]]

one location for an extended period of time. Additionally, the final 
rule also adopts, with slight modification, the proposed definition for 
``mobile underground diesel fuel storage facility'', although that term 
has been changed in the final rule to ``temporary underground diesel 
fuel storage area'' to be more accurately descriptive. A ``temporary 
underground diesel fuel storage area'' is defined as an area of the 
mine provided for the short-term storage of diesel fuel in a fuel 
transportation unit, which moves as mining progresses.
    The final rule also includes additional definitions for the terms 
``diesel fuel tank'', ``diesel fuel transportation unit'', 
``noncombustible material'', and ``safety can''.
    Several commenters believed that the definitions in the proposal 
were too narrow in scope and did not accurately reflect the different 
fuel storage facilities currently in use in underground coal mines or 
the different applications of mobile diesel-powered equipment. These 
commenters recommended the definition of two additional categories of 
underground diesel fuel storage facilities: ``temporary'' and ``self-
propelled.'' Commenters offered definitions for these two additional 
types of facilities, but they have not been adopted in the final rule, 
although, as mentioned above, the word ``temporary'' has been 
substituted for the word ``mobile'' in describing areas provided for 
short-term fuel storage that move as mining progresses. The suggested 
definition for ``self-propelled diesel fuel storage facility'' has not 
been included because it is similar in function and definition to a 
``diesel fuel transportation unit,'' which has been defined in the 
final rule.
    The definition offered by commenters for ``temporary diesel fuel 
storage facility'' reflected commenters' concerns that the proposed 
construction requirements for mobile fuel storage facilities were too 
extensive, and would make it difficult for the facility to move with 
the section and keep pace as mining progressed. Commenters therefore 
recommended the creation of a category of fuel storage facility with 
more flexibility than the mobile storage facilities under the proposal.
    In response to these comments, requirements for temporary fuel 
storage are addressed separately from those for permanent facilities in 
the final rule, and reflect a more practical approach to temporary fuel 
storage, which is explained in detail in the discussion of 
Sec. 75.1903, below. A definition for ``temporary fuel storage 
facility'' is consequently unnecessary and has therefore not been 
adopted in the final rule.
    One commenter recommended that several other terms be defined in 
the final rule, including ``container,'' ``safety can,'' ``tank,'' and 
``fuel transportation unit.'' This commenter pointed out that these 
terms are used throughout subpart T, and definition of these terms 
would enhance understanding of the requirements of the final rule.
    MSHA agrees that definition of certain terms will facilitate 
compliance with the requirements of subpart T, and has therefore 
included definitions for ``diesel fuel tank,'' ``diesel fuel 
transportation unit,'' ``noncombustible material,'' and ``safety can.'' 
Because the term ``fuel storage container'' is not used in the final 
rule, a definition for this term is not included in the final rule.
    The term ``diesel fuel tank'' is defined in the final rule as a 
closed metal vessel specifically designed for the storage or transport 
of diesel fuel. Metal tanks are required based on metal's demonstrated 
ability to contain diesel fuel in the event of a fire, documented by 
the Bureau of Mines in a 1985 Report of Investigation entitled ``Fire 
Tests of Five-Gallon Containers Used for Storage in Underground Coal 
Mines'' (RI 8946). This type of construction is also consistent with 
the National Fire Protection Association (NFPA) ``Standards for 
Portable Shipping Tanks for Flammable and Combustible Liquids'', (NFPA 
386).
    The term ``diesel fuel transportation unit'' is defined as a self-
propelled or portable, wheeled vehicle used to transport a diesel fuel 
tank. This definition includes diesel-powered vehicles such as lube 
units, maintenance trucks, tractors, and scoops. This definition also 
includes locomotives that pull rail-mounted, portable diesel fuel 
transportation units. Under the final rule fuel transportation units 
must be wheel-mounted, since skid-mounted units are more likely to be 
damaged during loading and unloading in a scoop bucket or while being 
dragged through the mine. Required safety features for these units are 
contained in Sec. 75.1902 and Secs. 75.1904 through 75.1906 of the 
final rule. Additionally, self-propelled fuel transportation units that 
are diesel-powered, and diesel-powered equipment used to tow portable 
fuel transportation units are considered heavy-duty equipment under 
Sec. 75.1908(a). Heavy-duty equipment must be provided with the safety 
features specified in Sec. 75.1909, including an automatic fire 
suppression system and additional specifications for the equipment's 
braking system.
    Under the final rule, permanent underground diesel fuel storage 
facilities must be constructed of ``noncombustible materials,'' and 
stationary tanks in those facilities must be placed on 12-inch supports 
constructed of ``noncombustible material.'' ``Noncombustible material'' 
is defined in the final rule as a material that will continue to serve 
its intended function for 1 hour when subjected to a fire test 
incorporating an ASTM E119-88 time/temperature heat input, or 
equivalent. This test, contained in the publication ``Standard Test 
Methods for Fire Tests of Building Construction and Materials'' of the 
American Society for Testing and Materials, is used to establish fire 
resistance ratings in minutes or hours for a particular building 
assembly such as a roof, wall, or beam. This means that a material 
maintains its integrity under a fire exposure test used by the building 
industry to classify assemblies for their ability to resist fire. This 
definition is consistent with the definition of ``noncombustible 
material'' in existing Sec. 75.301, which applies to the construction 
of ventilation controls in underground coal mines.
    One commenter who recommended that ``noncombustible material'' be 
defined in the final rule suggested that the definition specify a 2-
hour fire rating. The definition in the final rule specifies a 1-hour 
rating, which will provide protection in the event of a fire in 
underground fuel storage areas by confining the fire within the area 
for a sufficient period of time to allow miners to safely evacuate the 
mine. Additionally, the final rule requires automatic fire suppression 
systems and audible and visual alarms for permanent underground fuel 
storage facilities. For these reasons, adequate protection of miners 
against fire is provided, and a 2-hour fire rating has not been adopted 
in the final rule.
    The term ``safety can'' is defined in the final rule as a metal 
container with a nominal capacity of no more than 5 gallons used for 
storage, transport, or dispensing of diesel fuel that is listed or 
approved by a nationally recognized independent testing laboratory. 
Commenters supported the use of approved safety cans to transport small 
amounts of diesel fuel. This definition provides assurance that 
adequate construction and performance specifications for fire 
protection are met. The limitation on the capacity of safety cans to no 
more than 5 gallons will control the amount of diesel fuel being 
transported and minimize potential fuel

[[Page 55442]]

spillage. Such specifications and limitations are necessary in light of 
accident reports of 10 fires in Canadian mines that resulted from 
diesel fuel spillage during refueling.
    A safety can that meets this definition could be listed by 
Underwriters Laboratories or approved by Factory Mutual, Inc. Some 
nationally recognized independent testing laboratories have established 
specific construction specifications for the type and thickness of 
materials; material strength, stability and resistance to leakage; and 
standards for fire exposure that ensure that the can will safely vent 
if exposed to a heat source such as a fire.
    The final rule defines ``safety can'' as a metal container. Thus, a 
plastic safety can listed or approved by a nationally recognized 
independent testing laboratory would not be acceptable under the final 
rule. A metal container is specified because metal is superior to 
plastic in containing diesel fuel in the event of a fire. The safety 
advantage provided by metal cans has been documented in the 1985 Bureau 
of Mines' Report cited earlier. Specific design requirements for safety 
cans are addressed in Sec. 75.1904 of the final rule.
Section 75.1901  Diesel Fuel Requirements
    This section of the final rule establishes specifications for the 
fuel used in diesel-powered equipment in underground coal mines. 
Satisfying the requirements of this section will lower diesel engine 
gaseous and particulate emissions, and will reduce equipment 
maintenance by limiting the amount of sulfur in the fuel. The risk of 
fire in underground coal mines is also reduced by the minimum flash 
point for the fuel required by the final rule. The safety benefits that 
result from this aspect of the final rule are particularly important in 
the confined environment of an underground coal mine.
    Paragraph (a) of this section requires that diesel fuel used in 
underground coal mines contain no greater than 0.05 percent sulfur and 
have a flash point of 100 deg. F (38 deg. C) or greater. The final rule 
also requires the mine operator to provide an authorized representative 
of the Secretary, upon request, with evidence that the diesel fuel 
purchased for use in diesel-powered equipment underground meets these 
requirements.
    The proposed rule would have required ASTM D975 No. 2D diesel fuel, 
with a flash point of 125 deg. F or greater, at standard temperature 
and pressure. Many commenters objected to the requirement for ASTM D975 
No. 2D diesel fuel, stating that the reference to No. 2D fuel was a 
manufacturing classification, did not describe a type of diesel fuel 
that was commercially available, and would unnecessarily limit the use 
of diesel fuel in underground coal mines.
    MSHA agrees with commenters that the proposed fuel specifications 
do not describe a fuel that is commercially available, and the fuel 
specifications contained in the final rule respond to these comments. 
The reference to ASTM D975 No. 2D diesel fuel has been eliminated, and 
a minimum flash point and maximum sulfur content for diesel fuel have 
been specified. The fuel described by the final rule is in widespread 
use throughout the United States, and is easily obtained by mine 
operators. The fuel specifications in the final rule are based on 
Environmental Protection Agency on-highway fuel requirements for 
commercially available diesel fuel.
    A number of commenters were concerned that the required flash point 
of diesel fuel not be set too low, stating that any diesel fuel 
specifications must keep the fuel within the class of combustible 
liquids, ensuring that hazards associated with diesel fuel are no 
greater than those associated with other combustible liquids used 
underground. Some of these commenters recommended that the flash point 
for diesel fuel be set at 140 deg. F, stating that lower flash points 
would increase the risk of vaporization and increased aromatic content, 
especially at warmer mine temperatures. These commenters stated that 
increased aromatic content has an effect on particulate emissions.
    Other commenters stated that the proposed flash point of 125 deg. F 
was too high. Some commenters reported that the flash point of diesel 
fuel is intentionally lowered when fuel suppliers mix it for a winter 
blend, to depress the cloud point of the diesel fuel and reduce the 
temperature at which the fuel begins to jell. These commenters believed 
that a flash point of 125 deg. F would virtually eliminate their 
ability to use diesel-powered equipment in cold temperatures, unless 
the rule specifically allowed the use of winter blends of diesel fuel 
with flash points below 125 deg. F. These commenters pointed out that 
the ASTM 975 specification for diesel fuel is being changed to lower 
the minimum flash point of D1 diesel fuel to 100 deg. F (38 deg. C) 
when the cloud point is lower than 10 deg. F, and that a reduction of 
the flash point in the final rule was appropriate.
    Another commenter believed that the diesel fuel autoignition point 
does not change in the lower range of flash point for diesel-powered 
equipment, concluding that the safety of diesel fuel exposed to hot 
surfaces would not change with changing flash points.
    No demonstrated hazard exists to justify raising the flash point of 
diesel fuel above the proposed flash point of 125 deg. F. However, MSHA 
acknowledges commenters' concerns that the proposed flash point may 
unintentionally limit the use of diesel fuel during the winter. To 
address this issue, the flash point has been lowered in the final rule 
to 100 deg. F (38 deg. C) or greater.
    Several commenters suggested that the terms ``flash point'' and 
``combustible liquid'' be defined, with some commenters offering 
recommended language for the definitions. The final rule does not 
include definitions for these terms. The term ``flash point'' is 
commonly understood in the mining industry to mean the lowest 
temperature at which a liquid will give off sufficient vapor to ignite 
on application of a flame, and does not need to be defined in this 
rule. The suggested definition offered by commenters for the term 
``combustible liquid'' specifies a flash point temperature. Because the 
final rule sets a minimum flash point temperature for diesel fuel, such 
a definition is unnecessary.
    The proposal did not set a limit on sulfur content for diesel fuel, 
but would have required sampling for sulfur dioxide when diesel fuel 
was used that contained more than 0.25 percent sulfur. This approach 
was taken because, although the proposal recognized that use of low 
sulfur fuel was desirable, it was not readily available nationwide at 
the time the proposal was published in October 1989.
    Some commenters stated that the sulfur content of diesel fuel 
should be limited in all cases to 0.25 percent. Others stated that a 
sulfur content requirement should be phased in, ultimately reaching the 
Environmental Protection Agency's maximum sulfur level of 0.05 percent. 
One commenter stated that a requirement for low sulfur fuel would 
provide a health benefit to miners by reducing particulate emissions.
    MSHA agrees that the sulfur content of diesel fuel should be kept 
at a low level. Sulfur in diesel fuel contributes to diesel particulate 
emissions. Additionally, some types of exhaust after-treatment 
technology designed to lower hazardous diesel emissions work better 
when the sulfur content in the fuel is low. More effective strategies 
for after-treatment technology will result in reduced hydrocarbons and 
carbon monoxide levels. Low sulfur fuel also

[[Page 55443]]

greatly reduces the sulfate production from the catalytic converters 
currently in use in underground coal mines, thereby decreasing exhaust 
pollutants. Today, low sulfur fuel is readily available and widely used 
by on-road commercial vehicles. For these reasons, the final rule 
requires that diesel fuel contain no greater than 0.05 percent sulfur, 
which fuel is readily available nationwide.
    Under Sec. 70.1900 of the proposal, mine operators would have been 
required to provide MSHA with a certified statement if the sulfur 
content of the fuel used in their diesel equipment was 0.25 percent or 
less. This provision was included with exposure monitoring requirements 
because use of high sulfur fuel under the proposed rule would have 
triggered weekly area sampling requirements. Specifications for diesel 
fuel are now addressed in paragraph (a) of this section of the final 
rule, and the operator's obligation to verify the fuel's sulfur content 
has also been included in this section.
    The final rule requires the mine operator to provide to an 
authorized representative of the Secretary, upon request, evidence that 
the diesel fuel purchased for use in diesel-powered equipment 
underground meets the requirements of paragraph (a). This will not be a 
burdensome requirement. MSHA anticipates that the mine operator's 
contract with the mine's fuel supplier will document the type of fuel 
that is being purchased. The verification required under this paragraph 
may also be provided by a copy of a fuel analysis, which can be 
performed by a supplier's quality control laboratory or a private 
laboratory at minimal or no cost to the operator. MSHA recognizes that 
purchase orders and invoices may be kept at a mine's administrative 
office rather than at the mine site. Although the final rule does not 
specify a location or manner of recordkeeping for the document 
evidencing diesel fuel content, the mine operator may choose to keep an 
additional copy of the document to be easily accessible to a 
representative of the Secretary. A small recordkeeping burden is 
estimated for this requirement under the Paperwork Reduction Act of 
1995.
    Paragraphs (b) and (c) of this section of the final rule address 
additives for diesel fuel used in diesel-powered equipment in 
underground coal mines. The requirements of these two paragraphs were 
not part of the proposal but have been added to the final rule in 
response to commenters' concerns over the types of substances that 
could be safely added to diesel fuel.
    Paragraph (b) prohibits the addition of flammable liquids to diesel 
fuel. One commenter expressed concern that the proposed rule would not 
prohibit flammable liquids, such as gasoline, from being mixed with 
diesel fuel underground to assist in machine starting and operation 
during cold weather. Because gasoline is highly flammable, adding it to 
diesel fuel could cause the flash point of the fuel to drop below 
100 deg. F (38 deg. C) and transform the fuel into a flammable liquid. 
Further, use of gasoline as a diesel fuel additive could ruin an 
engine's fuel system by reducing the lubricating properties of the 
fuel. In response to these concerns, the final rule prohibits the 
addition of flammable liquids, such as gasoline, to diesel fuel. This 
restriction will promote the safe use of diesel fuel underground.
    Kerosene, on the other hand, is commonly used as a cutter stock for 
lowering the cloud point in diesel fuel. Because kerosene has a flash 
point above 100 deg. F (38 deg. C) it is classified as a combustible 
rather than a flammable liquid and therefore may be added to diesel 
fuel under the final rule.
    Paragraph (c) permits only diesel fuel additives that have been 
registered with the Environmental Protection Agency (EPA) under 40 CFR 
Part 79 [59 FR 33042] to be used in diesel-powered equipment 
underground. Because the proposed rule was silent on whether the use of 
diesel fuel additives would be permitted, a number of commenters raised 
additives as an issue and advocated that the final rule permit them to 
be used. These commenters stated that additives served to depress the 
cloud point of diesel fuel during cold weather to prevent jelling of 
the fuel. A cloud point depressant works by breaking down larger size 
crystals to smaller crystals, thus allowing the fuel to flow more 
freely. Several commenters expressed concern about the effect additives 
may have on diesel exhaust particulate emissions when mixed with diesel 
fuel. Other commenters wanted to be permitted to use additives, such as 
barium additives, with diesel fuel used to power equipment underground. 
One commenter stated that MSHA should encourage further research on the 
use of additives.
    The wide variety of diesel fuel additives currently on the market 
makes control of the use of these additives difficult. The final rule 
addresses this issue by limiting fuel additives used underground to 
those registered under specific EPA regulations.
    EPA regulations at 40 CFR Part 79 forbid manufacturers from
placing 
any fuel additive into commerce unless the additive has been registered 
with the EPA Administrator. The EPA registration process requires the 
submission of extensive test data for specific health effect endpoints, 
as well as a general systemic and organ toxicity literature search on 
the health and welfare effects of the fuel additive emissions, 
including the characteristics of the emissions. Registered fuel 
additives are maintained by the EPA on a list that is available to the 
public.
    The requirements of this paragraph do not place an undue burden on 
mine operators, because operators need only verify with their fuel 
supplier or distributer that the additive purchased is included on the 
EPA registration list.
Section 75.1902  Underground Diesel Fuel Storage--General Requirements
    This section of the final rule provides general requirements for 
the safe storage of diesel fuel underground. These requirements are 
intended to minimize risks associated with fire hazards in the areas 
where diesel fuel is stored. This section limits the receptacles that 
may be used for diesel fuel storage underground to diesel fuel tanks 
and safety cans; allows only one diesel fuel transportation unit in a 
temporary fuel storage area; places a 1000-gallon limit on the capacity 
of stationary diesel fuel tanks in permanent fuel storage facilities; 
and limits the location of permanent fuel storage facilities and 
temporary fuel storage areas underground.
    A number of commenters were concerned about the additional hazards 
that would be created by the storage of a combustible--diesel fuel--in 
underground coal mines. Some commenters opposed any type of fuel 
storage underground, while others believed that diesel fuel can be 
safely stored. Those commenters who opposed the storage of diesel fuel 
underground stated that it would present numerous safety hazards, 
including an increase in the probability of the fuel becoming involved 
in a mine fire and cutting off the avenue of escape for miners. These 
commenters recommended that language in existing MSHA regulations at 
Sec. 31.9 (c)(2) and (c)(3) be incorporated in the final rule. These 
regulations address refueling of diesel locomotives underground and 
provide that, whenever possible, locomotive fuel tanks be filled on the 
surface; contain specific requirements when locomotives are refueled 
underground; and prohibit underground fuel storage.
    Commenters opposed to allowing storage of diesel fuel underground 
suggested that mine operators could file a petition for modification 
under Section 101(c) of the Mine Act if they

[[Page 55444]]

had a compelling need to store diesel fuel underground. These 
commenters felt that a case-by-case approach would more effectively 
address hazards associated with diesel fuel storage.
    Commenters were also concerned with maintenance and upkeep of 
diesel fuel areas. These commenters stated that fuel spills and hose 
leakage could possibly contribute to fire hazards. Commenters expressed 
reservations about storage, transport, and dispensing of diesel fuel 
from 5-gallon cans, particularly during refueling, stating that 
temporary storage should not be allowed. These commenters wanted 
assurance that if diesel fuel storage were allowed underground, 
protections such as fireproof enclosures and pumps and other provisions 
that address fuel spillage would be provided.
    Some commenters suggested that diesel fuel storage should be 
allowed only if it is tightly controlled, and that fuel spills must not 
be tolerated in areas of the mine that cannot be cleaned. A number of 
commenters recommended setting limits on the maximum quantity of fuel 
allowed on a production section, ranging from a 24- to a 48-hour 
supply. Other commenters supported permitting diesel fuel storage 
underground, but raised a number of issues related to fuel storage, 
such as appropriate construction requirements for underground 
facilities; fire protection; and the logistics of transporting and 
dispensing fuel in an underground environment. One commenter cited 
years of positive industry experience with safe underground storage and 
transport of diesel fuel. He stated that his own experience in safely 
operating an underground coal mine, including diesel fuel delivery, 
storage, transport and transfer, countered the proposition that 
proliferation of diesel fuel storage facilities would occur in an 
uncontrolled manner, resulting in unlimited quantities of diesel fuel 
being stored in underground mines.
    MSHA has carefully reviewed all of the comments in determining how 
to address the storage of diesel fuel underground. Both MSHA and 
industry experience demonstrate that diesel fuel can be safely stored 
underground in limited quantities under controlled conditions. Allowing 
limited storage on the section will minimize other safety concerns 
cited by commenters, such as fuel leaks and spills. Underground fuel 
storage will also eliminate the need for frequent fuel trips, thus 
reducing hazards that are inherent in the transportation of diesel 
fuel. MSHA does not believe that it is useful or practical to restrict 
diesel fuel quantities based on projected use. The final rule instead 
sets specific gallon limits on the capacity of underground fuel storage 
tanks.
    The final rule establishes safety requirements, including design 
and performance specifications for storage tanks, transportation 
vehicles, and cans for fuel storage; a limitation on the number of fuel 
storage units that may be parked on a section; and a limitation on the 
capacity of underground fuel storage facilities. MSHA believes that 
these requirements will provide a significant measure of additional 
protection from the hazards associated with the storage and handling of 
diesel fuel, and permit efficient and safe transportation and refueling 
of diesel equipment in underground coal mines. Under the final rule, 
miners are afforded protections that are equal to or greater than the 
protections of existing standards.
    Paragraph (a) of this section provides that diesel fuel shall be 
stored in: (1) Diesel fuel tanks in permanent underground diesel fuel 
storage facilities; (2) diesel fuel tanks on diesel fuel transportation 
units in permanent diesel fuel storage facilities or temporary diesel 
fuel storage areas; or (3) safety cans. The proposal did not explicitly 
limit fuel storage underground to tanks and safety cans, and would have 
required that diesel fuel be transported in containers specifically 
designed for the transport of diesel fuel.
    MSHA recognizes that large quantities of diesel fuel must be used 
in some mines. However, to protect against fires, spills, and other 
hazards, large quantities can only be stored in permanent facilities 
under this final rule.
    The final rule permits fuel storage in tanks on fuel transportation 
units, but only under certain conditions and in limited quantities 
spelled out in other requirements in this section. A number of 
commenters recommended that the rule accommodate the need for fuel 
supplies to move as the production section moves. Other commenters 
expressed concerns that multiple mobile storage tanks might be located 
on the section at the same time, exposing miners to hazards, 
particularly from fire. The final rule also allows diesel fuel to be 
stored in safety cans.
    The restrictions contained in paragraph (a) respond to commenters' 
concerns that storage of diesel fuel underground would lead to 
prolific, uncontrolled storage practices, and strictly limit the 
locations and receptacles for diesel fuel storage.
    Paragraph (b) of this section limits the capacity of stationary 
diesel fuel tanks in permanent underground fuel storage facilities to 
1,000 gallons. It is important to note that, while the total capacity 
of the fixed tanks is set, there is no limit on the number of 
stationary tanks that may be located in the facility. This means that 
the 1,000 gallons may be stored, for example, in two 500-gallon tanks 
or four 250-gallon tanks.
    Like the final rule, the proposal prohibited storage of more than 
1,000 gallons of diesel fuel in a permanent facility. Commenters' 
opinions of this provision varied, from those who opposed any kind of 
fuel storage underground, those who recommended limited storage, to 
those who believed that diesel fuel could be safely stored underground. 
The final rule balances the concerns raised by those opposed to storage 
against the need to store fuel underground to minimize other fuel 
handling hazards. The fire protection and construction requirements for 
fixed storage tanks and permanent storage facilities in Secs. 75.1903 
and 75.1904 of the final rule appropriately and adequately address fire 
and other hazards involving diesel fuel, and, when satisfied, will 
afford safe storage of the fuel quantities allowed under this section.
    Under the final rule, the storage of safety cans and parking of 
fuel transportation units in permanent storage areas would also be 
permitted. The 1,000-gallon limit applies to the total capacity of 
stationary tanks in the fuel storage facility, and the quantity of fuel 
in safety cans stored or fuel transportation units parked in the 
facility would not be counted as part of the 1,000-gallon limitation 
under this paragraph.
    The final rule permits storage of diesel fuel on a working section 
or in an area of the mine where equipment is being installed or 
removed, but places specific restrictions on such storage in paragraphs 
(c)(1) through (c)(4) of this section.
    The proposal did not separately address storage of diesel fuel on a 
working section. MSHA received many comments both opposing and 
supporting section fuel storage. Those opposed stated that storage on 
the section would present fuel leakage and spillage hazards, creating 
fire and escape hazards for miners. Those supporting fuel storage on 
the section stated that, because the production section advances 
rapidly, the final rule must permit diesel fuel storage on the section. 
These commenters further stated that properly designed fuel 
transportation units should be allowed on mining sections, as long as 
they are parked within reasonable proximity to

[[Page 55445]]

the work area and comply with specific safety requirements.
    MSHA agrees with commenters who supported allowing mobile fuel 
storage on the section, which can move as mining progresses, but also 
agrees with commenters who believe that such storage must be carefully 
controlled. In response to these concerns, paragraph (c)(1) permits 
only one temporary diesel fuel storage area for each working section or 
in areas of the mine where equipment is being installed or removed. 
Paragraph (c)(2)(i)-(iii) requires that the temporary fuel storage area 
be located within 500 feet of the loading point; within 500 feet of the 
projected location of the future loading point where equipment is being 
installed; or within 500 feet of the location of the last loading point 
where equipment is being removed. This requirement will ensure that the 
fuel storage area will be located close enough to miners to allow any 
hazards that may develop to be quickly addressed. This provision is a 
logical outgrowth of the rulemaking because it addresses commenters' 
concerns that fuel storage be allowed in close proximity to the mining 
section, while at the same time recognizing that safety concerns 
dictate limitations on where fuel may be stored.
    Consistent with the final rule's approach of allowing limited 
storage on the section, paragraph (c)(3) prohibits more than one diesel 
fuel transportation unit at a time to be parked in a temporary diesel 
fuel storage area. This requirement is consistent with sound fire 
protection engineering principles for the storage and handling of 
diesel fuel, and is supported by experiences in the field and 
applicable NFPA standards. It should be noted, however, that a 
``parked'' diesel fuel transportation unit under this paragraph would 
not include a unit that is in the process of refueling equipment or 
that is itself being refueled. This means, for example, that a 
temporary fuel storage area could contain more than one diesel fuel 
transportation unit at one time, so long as only one unit is parked. 
Any other units in the area must be in use and attended.
    The proposal would have allowed fuel to be stored in free-standing 
tanks in mobile diesel fuel storage facilities. The final rule allows 
fuel to be stored in temporary fuel storage areas, but only in tanks on 
diesel fuel transportation units. These units are specially designed to 
provide both mobility and protection for the fuel tanks. Protection is 
provided by requiring the tank to be permanently affixed to the 
transportation unit. The construction and design requirements for fuel 
tanks are contained in Sec. 75.1904 of the final rule.
    Paragraph (d) of this section of the final rule imposes limitations 
on the location of permanent fuel storage facilities and temporary fuel 
storage areas, and has been revised from the proposal for clarity. This 
aspect of the final rule requires diesel fuel to be kept out of areas 
where the potential for fire is greatest. The final rule prohibits 
permanent storage facilities and temporary storage areas from being 
located within 100 feet of shafts, slopes, shops, or explosives 
magazines, or within 25 feet of trolley wires or power cables, or 
electric equipment not necessary for the operation of the storage 
facilities. The fuel storage facilities or areas must also be in a 
location protected from damage by other mobile equipment.
    Some commenters stated that the proposed requirement that diesel 
fuel storage facilities be located at least 100 feet away from shafts, 
slopes, or shops was not adequate in light of the amount of diesel fuel 
involved and the amount of spillage that could occur. Another commenter 
stated that requiring shops to be located at least 100 feet away from 
fuel storage facilities was inconsistent with proposed Sec. 75.1903(c), 
which would have prohibited welding and cutting within 50 feet of 
storage facilities. The commenter also noted that in some cases it may 
be best to locate the fuel storage facility within 100 feet of the shop 
near a return, because this would provide the best direct ventilation 
to the return for both the shop and storage facility, but that the 
proposed 100-foot requirement could prevent this. The final rule, like 
the proposal, adopts separation distances that are consistent with the 
National Fire Protection Association 123 Standard for Fire Prevention 
and Control in Bituminous Coal Mines. NFPA 123 requires fixed 
combustible liquid storage areas to be located a minimum of 100 feet 
from explosive magazines, electrical substations, shaft stations, and 
shops. MSHA disagrees with commenters who considered a 100-foot 
separation distance insufficient in light of the amount of diesel fuel 
that could be stored. The design, construction, and fire suppression 
system requirements in the final rule that apply to permanent fuel 
storage facilities provide adequate protection to miners with a 100-
foot separation distance.
    MSHA also disagrees with the commenter who believed that requiring 
shops to be located at least 100 feet away from fuel storage 
facilities, where cutting and welding are likely to occur, was 
inconsistent with a prohibition against welding and cutting within 50 
feet of storage facilities. The high volume of vehicle traffic in and 
out of the area of the shop warrants a greater separation distance than 
for cutting and welding alone.
    Finally, the final rule does not adopt the recommendation of the 
commenter who advocated allowing a permanent fuel storage facility 
closer to a shop than 100 feet, to allow better ventilation of both the 
shop and the storage facility. The fire protection afforded by the 100-
foot separation distance outweighs any advantage in ventilation that 
would result from allowing a lesser distance.
    Paragraph (d)(3) provides that permanent fuel storage facilities 
and temporary fuel storage areas must be in a location that is 
protected from damage from other mobile equipment. Under the proposal, 
fuel storage facilities would have been required to be at least 25 feet 
away from haulageways, which are entries where miners and materials are 
normally transported. The rationale for this requirement was that areas 
where diesel fuel is stored should be out of the line of mine traffic, 
where tanks would be exposed to damage from collision with other mine 
vehicles. Instead of adopting the proposed requirement, the final rule 
takes a performance-oriented approach by providing that storage 
facilities and areas be located where they are protected from damage. 
This responds to a commenter who indicated the importance of keeping 
fuel storage facilities out of the line of traffic.
    Paragraph (e) prohibits permanent fuel storage facilities from 
being located in the primary escapeway, which provides miners with a 
route of escape from the mine in the event of an emergency. This 
restriction was not included in the proposal, but has been added to 
this section of the final rule in response to commenters' concerns 
relative to diesel fuel storage facilities' impeding miners' ability to 
escape in the event of a mine fire, explosion, or other emergency. This 
prohibition recognizes that the primary escapeway should be kept clear 
of obstructions and potential hazards, to ensure that miners are able 
to safely evacuate the mine in the event of an emergency.
Section 75.1903  Diesel Fuel Storage Facilities And Areas; Construction 
And Safety Precautions
    This section of the final rule establishes construction and design 
requirements for permanent diesel fuel storage facilities and temporary 
diesel fuel storage areas. These requirements are intended to minimize 
fire hazards associated with storage of diesel fuel

[[Page 55446]]

underground, and provide safety protections for miners during the 
storage, transportation, and dispensing of diesel fuel.
    The proposal did not distinguish between construction and design 
requirements for those diesel fuel storage facilities that are fixed 
and remain in one location indefinitely, and those that move as the 
production section advances. A number of commenters stated that the 
proposed requirements were suitable for permanent facilities but were 
unnecessary and impractical for facilities that would be temporary. 
Some commenters were concerned that some mine operators would not be 
able to complete construction of the temporary facility before the 
facility would have to be moved to keep pace with the advancing 
section. In support of this position, commenters stated that compliance 
with the proposed requirements would be impractical and would force 
mine operators to transport fuel to the section to refuel equipment on 
a shift basis, creating increased hazards due to transportation.
    Another commenter voiced similar concerns, noting that the rapid 
advance of mining in modern underground coal mines makes it more 
practical for fuel stations to be advanced with mining activity, and 
that properly designed transportation units should be allowed on mining 
sections as long as they are parked in accordance with specific 
safeguards in reasonable proximity to the working area. The commenter 
stated that a specific parking requirement with proper safeguards would 
be much safer than the requirements in MSHA's proposal. Another 
commenter stated that the Diesel Advisory Committee made general 
recommendations for permanent and temporary storage facilities that 
were not intended to eliminate fuel trailers and their use. On the 
other hand, several commenters believed that the fact that the proposal 
would not have required mobile storage facilities to have a drain 
system and sump would provide no incentive for operators to construct 
fixed facilities, and that the construction of an unlimited number of 
mobile facilities would result.
    In response to the comments, the final rule reflects a clear 
distinction between construction and design requirements for permanent 
underground diesel fuel storage facilities and temporary underground 
diesel fuel storage areas. MSHA recognizes that temporary diesel fuel 
storage areas move frequently as mining advances, and that construction 
specifications must take this fact into account. Requirements for 
permanent storage facilities have therefore been addressed separately 
from those for temporary facilities in the final rule. The final rule 
provides a more practical approach for the construction and design of 
areas designated for temporary fuel storage, and eliminates several 
proposed construction requirements that are unnecessary from a fire 
protection engineering standpoint. Specifically, the final rule does 
not adopt the proposed requirements that temporary fuel storage areas 
be constructed of noncombustible material, be provided with a self-
closing door, and be provided with a fire suppression system. Because 
construction of temporary storage areas with these features would make 
it extremely difficult for these facilities to be built as fast as 
mining progressed, transportation of fuel between permanent storage 
facilities and the section would increase significantly. The risk of an 
accident involving a fuel transportation unit would also increase, and 
with it the risk of fuel spillage and the risk of fire. The final rule 
therefore reduces the construction requirements for temporary fuel 
storage areas, to provide better control of the fire hazards inherent 
in fuel transportation and storage.
    Paragraphs (a)(1) through (a)(7) of this section establish 
construction and design requirements for permanent underground diesel 
fuel storage facilities. Consistent with basic fire protection 
engineering principles, the final rule requires permanent storage 
facilities to be constructed of noncombustible materials; provided with 
self-closing doors or a means for automatic enclosure, and with a means 
for entry and exit after closure; ventilated with intake air; equipped 
with an automatic fire suppression system; and provided with a means to 
contain diesel fuel and with a concrete floor or equivalent to prevent 
spills from saturating the mine floor. These requirements are intended 
to reduce the fire hazards inherently present in areas where diesel 
fuel is stored and increase protection in the event of a fire.
    The proposal contained requirements similar to those in the final 
rule, but the final rule has been modified in response to commenters. 
Some commenters were generally opposed to the proposed requirements, 
stating that diesel fuel systems currently in use do not pose the 
degree of hazard that would warrant such extensive requirements. One 
commenter stated that the requirements of the proposal suggested that 
the hazards of diesel fuel storage exceed the hazards of the storage of 
explosives underground by several-fold. Other commenters stated that 
the proposed requirements for construction of storage facilities with 
noncombustible materials and with a means for automatic enclosure were 
too vague and not stringent enough. These commenters recommended that 
MSHA require at a minimum that diesel fuel be stored in an enclosure 
with at least a 2-hour fire-resistance rating.
    Paragraph (a)(1) provides that permanent underground fuel storage 
facilities shall be constructed of noncombustible materials, including 
floors, roofs, roof supports, doors, and door frames. Exposed coal 
within the fuel storage areas is required to be covered with 
noncombustible material. If they are used, bulkheads are required to be 
built of or covered with noncombustible material.
    The proposal would have required that the storage facility be 
constructed of noncombustible material, a term that was not 
specifically defined. As discussed above, the term ``noncombustible 
materials'' is defined in Sec. 75.1900 of the final rule as materials 
meeting the equivalent of a one-hour fire resistance rating test. 
Paragraph (a)(1) also incorporates NFPA 123 requirements. These 
requirements clarify which components of the facility must be 
noncombustible, including floors, roofs, roof supports and door frames, 
and specify that exposed coal must be covered with noncombustible 
material and bulkheads either built of or covered with noncombustible 
materials.
    MSHA's Approval and Certification Center has established guidelines 
to determine the suitability of trowelable or sprayable coatings for 
protecting coal surfaces against fire, which meet the requirements of 
paragraph (a)(1). In addition, textile-type thermal barriers may also 
be used to provide isolation of the combustible surfaces within the 
storage facility. Materials meeting the ``Performance Criteria for 
Materials used for Welding and Cutting Curtains and/or Thermal Barriers 
in Underground Coal Mines'' (Luzik, MSHA Report No. 01-098-92) may also 
be used. MSHA has also established guidelines for noncombustible doors. 
Additionally, MSHA has tested certain designs of high-temperature 
silica fabric curtains and published the results in Coal Magazine, June 
1993, pp. 102-104, ``MSHA Develops New Fire Resistant Check Curtains''. 
For purposes of the final rule, MSHA will accept as doors the curtain 
constructions described in this article. Facilities constructed to meet 
these requirements will afford protection to miners working in the 
production areas inby in the event of a fire and should provide ample 
time for miners to exit.

[[Page 55447]]

    Paragraph (a)(2) of the final rule requires that permanent fuel 
storage facilities be provided with either self-closing doors or a 
means for automatic enclosure. This paragraph provides mine operators 
with flexibility in the method used to comply with the final rule. The 
proposal would have required that the facility be provided with a means 
for automatic enclosure, which suggests that the door must be closed by 
powered means, such as electrically or pneumatically. The proposal did 
not specifically include non-powered self-closing doors as an 
alternative, although they were not intended to be excluded. Self-
closing doors serve the same function in containing a fire as 
automatic-closing doors, and the final rule clarifies that they are 
permitted.
    Paragraph (a)(3) requires that permanent fuel storage facilities be 
provided with a means for personnel to enter and exit the facility 
after closure. This provision has been added to the final rule to 
ensure that miners who are inside the fuel storage facility when the 
automatic enclosure activates will be able to exit from the facility. 
This requirement is also intended to allow miners to gain access to the 
facility to suppress an incipient fire that may develop. This paragraph 
also requires a means for exit and entrance when self-closing doors are 
used. Self-closing doors that are specifically designed to be manually 
opened would be in compliance with this paragraph. This aspect of the 
final rule is necessary to prevent miners from being trapped in the 
facility, and is a logical outgrowth of the rulemaking.
    Paragraph (a)(4) of this section of the final rule requires that 
permanent fuel storage facilities be ventilated with intake air that is 
coursed into a return air course or to the surface and that is not used 
to ventilate working places, using ventilation controls meeting the 
requirements of existing Sec. 75.333(e). The proposal would have 
required that both fixed and mobile fuel storage facilities be 
ventilated directly into a return air course using noncombustible 
materials for ventilation controls. Some commenters stated they were 
already venting fuel storage areas in their mines directly to the 
return.
    The final rule adopts the proposed requirement only for permanent 
fuel storage facilities, with some modification. The final rule 
requires that the facility be ventilated with intake air coursed to a 
return air course or to the surface that is not used to ventilate 
working places. This language, which is consistent both with existing 
requirements at Sec. 75.340 for the ventilation of underground 
electrical installations and with the current definition of ``return 
air'' in existing Sec. 75.301, is intended to eliminate the confusion 
caused by the phrase ``directly to a return air course''. The final 
rule clarifies that the intake air ventilating the fuel storage 
facility may not be used to also ventilate active working places. Thus, 
the air may be coursed into other entries before being coursed into a 
return, so long as the air is not used to ventilate a working place.
    Temporary underground diesel fuel storage areas are not required to 
be vented directly to the return in the final rule, in response to 
commenters who advocated more flexibility and less restrictive 
requirements for temporary fuel storage that moves as mining 
progresses.
    If the permanent facility is equipped with self-closing doors that 
would normally be closed, an opening will have to be provided in the 
doors to allow intake air to flow through the facility. This opening 
will prevent the build-up of diesel fuel vapors in the facility and 
prevent smoke generated during the incipient stages of a fire from 
entering the intake air courses. The opening is not intended to prevent 
smoke and other products of combustion from backing up into the intake 
airway if the fire is not extinguished in its incipient stages. For 
automatic closing doors, which would normally be open, a vent in the 
doors may not be needed since enclosure is required to seal the 
facility to cut off oxygen to the fire after the doors have closed.
    The requirements of paragraph (a)(4) are also intended to ensure 
that, if an enclosure has self-closing doors that are normally closed, 
precautions are taken to adequately vent diesel exhaust emissions from 
the facility. Such precautions could include the use of a regulator in 
the door to bring air into the facility that would then be vented to 
the return. In the case of a diesel fuel transportation unit that must 
have its engine running to dispense fuel, the unit's exhaust could be 
vented either directly to the return, if it incorporates a power 
package approved under subpart F of part 7, or into intake air which is 
coursed directly to a return air course. A fuel transportation unit 
that is equipped with a subpart F-approved power package will have fire 
and explosion prevention features that would permit the engine to 
exhaust directly into the potentially methane-rich atmosphere of the 
return. When the unit is exhausted into intake air, the fire and 
explosion prevention features of a subpart F power package are not 
required. However, the emissions from the engine must be vented 
directly to return air to prevent unnecessary exposure of miners to 
diesel exhaust.
    Paragraph (a)(5) adopts the requirements of the proposal and 
provides that permanent fuel storage facilities must be equipped with 
an automatic fire suppression system that meets the requirements of 
Sec. 75.1912 of the final rule. This paragraph also includes an 
additional requirement, not included in the proposal, that actuation of 
the automatic fire suppression system shall initiate the means for 
automatic enclosure. One commenter stated that the proposed requirement 
for automatic enclosure was not sufficiently stringent, that these 
storage facilities should be designed with fire containment capability, 
and that automatic enclosure should be triggered by actuation of the 
automatic fire suppression system. MSHA agrees, and the final rule 
enhances the capabilities of the automatic fire suppression system by 
requiring that initiation of the system will activate closure of the 
doors to the facility if self-closing doors are not used. Operation of 
the system in an environment with minimal air movement, which would 
exist when the doors are closed, will improve the effectiveness of fire 
suppressant agents in extinguishing a fire.
    Paragraph (a)(6) requires that permanent fuel storage facilities be 
provided with a means of containment capable of holding 150 percent of 
the maximum capacity of the fuel storage system. This provision is 
intended to address hazards associated with diesel fuel spillage and 
leakage--both slip and fall and fire hazards. The proposal would have 
required that permanent facilities be equipped with a drain system and 
a sump capable of holding 150 percent of the maximum capacity of the 
fuel storage system. Instead of requiring a drain system and sump, the 
final rule requires a ``means of containment''. This change 
acknowledges that a suitable drain system is generally considered 
overly difficult to design and install, and will also allow more 
flexibility in design of fuel containment systems. Additionally, 
spilled diesel fuel is best left confined in the facility where the 
fire suppression system is located. One commenter offered a case that 
illustrates this principle where the fuel escaped into the mine during 
a fuel spill because the drain valve at the bottom of the remote sump 
that serviced the storage area was left partially open.
    It is important to note that, in cases where fuel is piped from the 
surface to an underground fuel storage facility, the containment 
capacity must account for

[[Page 55448]]

the total fuel capacity. This means that the capacity of the 
containment must equal at least 150 percent of the surface tank's 
capacity, plus 150 percent of the underground tank's capacity, plus 150 
percent of the volume of the piping system connecting the surface tank 
to the underground tank. In cases where there is no underground tank, 
the maximum capacity includes the surface storage tank and the piping 
system from the surface. Where a stationary tank is located in a 
permanent facility and is not connected to a surface tank, the means of 
containment must account for 150 percent of the capacity of the largest 
stationary tank. If the underground fuel storage facility is not 
equipped with a stationary tank but is used for the storage of only 
diesel fuel transportation units, the single largest transportation 
unit tank would be counted in the maximum capacity for purposes of this 
paragraph. However, diesel fuel transportation units that may be parked 
in permanent fuel storage facility where a piping system from the 
surface terminates or where a larger stationary tank is housed would 
not be considered part of the ``fuel storage system'', and the capacity 
of the transportation unit tank would not be included. The rationale 
behind this is that only one component in a fuel storage facility would 
be expected to fail at one time, such as a burst piping system or a 
leak in a stationary tank or in a transportation unit tank.
    In support of the requirement of this paragraph, one commenter 
noted that a fuel spill occurred when valves in the piping system from 
the surface storage tank failed, allowing the static head pressure to 
be imparted on the dispensing hose which caused it to rupture and fuel 
to escape.
    Commenters stated that it is important that the storage location be 
designed to contain fuel spills and tank ruptures to stop the spread of 
fuel. The final rule's containment capacity requirement of 150 percent 
of the capacity of the fuel system will provide a prudent safety factor 
in view of the potential fire hazard created by the release of large 
amounts of diesel fuel into an underground mine.
    Paragraph (a)(7) has been added to the final rule and requires that 
permanent fuel storage facilities be provided with a competent concrete 
floor or equivalent to prevent fuel spills from saturating the mine 
floor. This provision is intended to ensure that spilled diesel fuel 
can be easily cleaned up and will not accumulate, creating a fire 
hazard. This requirement is added in the final rule in response to 
commenters who suggested that the floor of the storage facility should 
be noncombustible and impermeable to oil and diesel fuel. These 
commenters argued persuasively that a requirement for a concrete floor 
would preserve the integrity of a noncombustible facility.
    Under the requirements of this paragraph a permanent fuel storage 
facility must be provided with a competent floor made of concrete or an 
equivalent material. The term ``competent'' is used to make clear that 
a cracked concrete floor or a porous mine floor would not satisfy this 
requirement. A brattice-type lining or rubber membrane would not be 
considered equivalent because it could easily be torn during refueling 
of vehicles, and diesel fuel could leak through and accumulate 
underneath. This provision has been added to the final rule in direct 
response to commenters, many of whom testified at the Agency's public 
hearings on the proposal. MSHA believes that this provision constitutes 
a logical outgrowth of the proposal because of commenters' stated 
concerns in ensuring that spilled fuel will not saturate the mine floor 
and create a fire hazard.
    The requirements of paragraph (b) of this section of the final rule 
apply to both permanent underground fuel storage facilities and 
temporary underground fuel storage areas. This paragraph requires that 
these storage facilities or areas be: equipped with a 240 pounds of 
rock dust and at least two fire extinguishers, or, in the alternative, 
with at least three fire extinguishers; be conspicuously marked; and be 
maintained to prevent the accumulation of water. These basic 
requirements address potential fire hazards in these facilities and 
ensure that mine personnel are aware of the presence and location of 
such facilities.
    Paragraph (b)(1) requires that permanent fuel storage facilities 
and temporary fuel storage areas be equipped with at least 240 pounds 
of rock dust and provided with two portable multipurpose dry chemical 
type (ABC) fire extinguishers that are listed or approved by a 
nationally recognized independent testing laboratory and have a 
10A:60B:C or higher rating. Both extinguishers must be easily 
accessible to personnel, and at least one must be located outside of 
the facility or area, upwind of the facility in intake air. Paragraph 
(b)(2) provides, as an alternative to the requirement of paragraph 
(b)(1), that three fire extinguishers may be provided.
    The proposal would have required fixed and mobile fuel storage 
facilities to be equipped with at least two 20-pound multipurpose dry 
chemical type fire extinguishers, and would not have required that rock 
dust be provided. One commenter recommended that foam generating 
machines or fire extinguishers of 150 pounds or more be required. The 
final rule does not adopt the suggestion of this commenter, because 
MSHA considers it too hazardous to fight a diesel fire underground that 
cannot be extinguished in its incipient stages. The fire extinguishers 
and fire suppression equipment required by this section are intended to 
be used to extinguish small fires, such as could occur on equipment in 
the facility.
    The final rule redefines the type of dry chemical extinguishers 
that are required, based on specifications recommended by the National 
Fire Protection Association for the particular hazard involved. The 
rating of the fire extinguishers has been adopted from NFPA 123 and is 
in accordance with NFPA 10-Standard for Portable Fire Extinguishers. 
Also, extinguishers must be listed or approved by a nationally 
recognized independent testing laboratory, which provides assurance 
that the extinguishers will perform effectively in the event of a fire 
emergency. The final rule requires that the fire extinguishers be 
located so that miners will have quick access to them in the event of a 
fire. To allow flexibility in complying with the requirements of this 
paragraph, the final rule addresses the location of only one fire 
extinguisher. The location of the other extinguisher should be 
determined based on mine conditions and the particular usage of the 
facility. The final rule specifies that the fire extinguisher be 
located upwind of the facility, which has been added to ensure that if 
a fire occurs miners will be able to reach the fire extinguisher 
without being exposed to the heat or smoke of the fire.
    The final rule adds a requirement for 240 pounds of rock dust to be 
kept in the storage facility in response to comments concerning the 
effectiveness of rock dust in fighting diesel fuel fires and the 
ability of rock dust to contain spills. The requirement for 240 pounds 
of rock dust is consistent with Sec. 75.1100-2(f), which requires 240 
pounds of rock dust to be provided at permanent underground oil storage 
stations, and is included in the final rule as an added measure of fire 
protection in response to the concerns of commenters. However, 
paragraph (b)(2) allows an additional fire extinguisher to be 
substituted for the rock dust required under paragraph (b)(1), which is 
consistent with provisions in existing petitions for

[[Page 55449]]

modification for fire protection at electrical installations. The 
requirements of the final rule strike a balance between those 
commenters concerned about the need for additional fire protection 
provided by rock dust in locations where diesel fuel is stored, and 
those who were concerned that the storage of rock dust in those 
locations was inadvisable in mines that tended to be wet.
    Paragraph (b)(3) adopts the requirement of the proposal that 
permanent diesel fuel storage facilities and temporary fuel storage 
areas be identified with conspicuous markings designating diesel fuel 
storage. The proposal would have required the facilities to be 
designated as ``combustible liquid storage,'' but MSHA has concluded 
that precise identification as areas of diesel fuel storage is more 
appropriate, and will ensure that mine personnel are aware of the 
locations where diesel fuel is stored underground.
    Paragraph (b)(4) requires that fuel storage facilities or areas be 
maintained to prevent the accumulation of water. The proposal would 
have required that fixed and mobile underground storage facilities be 
located in an area as dry as practicable, a concept which several 
commenters considered to be vague and potentially difficult to comply 
with. This requirement has therefore been revised to require that 
permanent underground diesel fuel storage facilities and temporary fuel 
storage areas be maintained to prevent the accumulation of water. This 
provision recognizes that tanks or other components of the storage 
facility may corrode as a result of exposure to water. Additionally, 
accumulated water can increase the fire hazard present by a fuel spill, 
because diesel fuel will float on top of water and may be spread more 
easily throughout the storage facility. The requirement of this 
paragraph addresses these hazards.
    Paragraph (c) adopts the proposed prohibition on welding or 
cutting, except as provided in paragraph (d) of this section, from 
being performed within 50 feet of a diesel fuel storage facility or 
area. This requirement is intended to minimize fire hazards and is 
consistent with National Fire Protection Association requirements (NFPA 
123). No comments were received on this aspect of the proposal.
    Paragraphs (d)(1) and (d)(2) adopt the requirements of the proposal 
and set forth specific precautions to be followed when welding, 
cutting, or soldering pipelines, tanks, or other containers that might 
have contained diesel fuel. MSHA received only a few comments on this 
aspect of the proposal, which is consistent with NFPA requirements. A 
review of MSHA's accident data reveals that a fatal accident occurred 
when the victim was welding a diesel fuel storage tank. The victim had 
drained the tank, which had been filled with water, and attempted to 
repair a small leak which remained in the tank. Vapors from the 
residual fuel were ignited by the heat of welding, and the tank 
exploded. The requirements of this paragraph are intended to address 
such hazards, and recognize that welding can be performed safely 
underground as long as appropriate safeguards are followed. 
Additionally, the large size of certain vessels used for the storage of 
diesel fuel underground would make it impractical to restrict welding 
of such containers to the surface. The precautions in paragraph (d)(1) 
include thoroughly purging and cleaning or inerting the pipelines, 
containers, or tanks before welding or cutting, with a vent or opening 
provided in the container or tank to release pressure before heat is 
provided. The final rule also prohibits diesel fuel from entering 
pipelines, tanks, or other containers that have been welded, soldered, 
brazed, or cut until the metal has cooled to ambient temperature. A 
slight change has been made in the language of this requirement to 
conform the references to the diesel fuel containers that are the 
subject of these requirements. The phrase ``pipelines, tanks, or other 
containers'' is used throughout. Additionally, the reference in 
proposed paragraph (d)(1) to containers or tanks that ``have contained 
combustible or flammable materials'' has been changed in the final rule 
to pipelines, tanks or other containers ``that have contained diesel 
fuel,'' to eliminate the inconsistency that existed between this 
provision and other language in this paragraph and to clarify the scope 
of these requirements.
    One commenter recommended that a cleanup program be required for 
underground fuel storage facilities and areas. This recommendation has 
not been adopted in the final rule, because existing Sec. 75.400-2 
already requires mine operators to establish and maintain programs for 
regular cleanup of accumulations of coal and other combustibles. MSHA 
will require that underground diesel fuel storage facilities and areas 
be covered by the cleanup program under Sec. 75.400-2, which will 
ensure that these locations are kept clear of any combustible 
materials.
Section 75.1904  Underground Diesel Fuel Tanks And Safety Cans
    This section includes requirements for the design of diesel fuel 
tanks and safety cans and for emergency venting devices for diesel fuel 
tanks for venting vapors to protect against the buildup of pressure in 
the tank, which could lead to its rupture if the tank is exposed to 
fire. The requirements of this section are responsive to comments and 
are consistent with NFPA, Underwriters Laboratories, and American 
Petroleum Institute standards for storage tanks for combustible 
liquids. A number of commenters suggested restructuring and 
reorganizing the proposed design requirements for diesel fuel tanks, 
and the final rule is revised in response to these comments.
    Paragraph (a) of this section of the final rule contains 
construction and location requirements for underground diesel fuel 
tanks in permanent underground fuel storage facilities and temporary 
underground fuel storage areas. These requirements are intended to 
guard against leakage of diesel fuel and to minimize fire hazards.
    Paragraph (a)(1) requires that underground diesel fuel tanks have 
steel walls of a minimum \3/16\-inch thickness or walls made of other 
metal of a thickness that provides equivalent strength. This 
specification has been added to the final rule to ensure that diesel 
fuel storage tanks are properly designed for their intended purpose, 
and in response to commenters who were concerned that diesel fuel tanks 
be durably constructed. MSHA explored alternatives for an objective 
measurement of durable construction. The requirement of this paragraph 
is consistent with prevailing industry standards, and is intended to 
serve as a minimum design standard for substantially constructed tanks. 
This requirement is derived from Department of Transportation (DOT) 
Spec. 51 Section 178-245-2(b), and is consistent with DOT requirements 
for over-the-road vehicles that transport diesel fuel. This 
specification is also recognized by the National Fire Protection 
Association in many of its fire protection standards as a design 
guideline for tanks used for storage of combustible liquids. 
Manufacturers of fuel transportation units currently produce diesel 
fuel storage tanks with \3/16\-inch thick steel walls, and this 
specification will allow mine operators to buy diesel fuel tanks off-
the-shelf.
    Paragraph (a)(2) requires diesel fuel tanks to be protected from 
corrosion. The proposal would have required these tanks to be 
constructed of ``noncorrosive

[[Page 55450]]

material.'' The language of the final rule will allow mine operators 
the option of either using a tank that has been constructed of 
noncorrosive material, such as galvanized or stainless steel, or of 
protecting a tank from corrosion that has been constructed of an 
oxidizing material, such as common steel. Protection from corrosion can 
be achieved by applying a protective coating.
    Paragraph (a)(3) requires diesel fuel tanks to be of seamless 
construction or fabricated with liquid tight welded seams. MSHA has 
added this requirement to the final rule in response to comments 
raising concerns about the durability of fuel tanks in use underground, 
to provide an objective measurement of substantial construction. Bolted 
and crimped joints are not allowed under the final rule because they 
are prone to leakage. The requirement of this paragraph is consistent 
with DOT Spec. 51 Section 178-245-2(b), and is intended to ensure that 
diesel fuel tanks are well constructed and designed not to leak.
    Paragraph (a)(4) requires that diesel fuel tanks not leak, and has 
been added in the final rule in response to commenters' concerns that 
tanks not contribute to a fire. Under the final rule, all attachments 
to the tank, such as vents, caps, hoses, pumps, valves, and nozzles, 
must also be free from leaks. Many commenters were concerned with 
leakage hazards presented by the storage of diesel fuel underground. 
These commenters were particularly concerned about leakage in temporary 
diesel fuel storage areas. MSHA believes that the requirement of this 
paragraph, in conjunction with the other provisions in this final rule, 
will greatly minimize hazards associated with storage of diesel fuel 
underground.
    Paragraph (a)(5) requires stationary tanks in permanent underground 
diesel fuel storage facilities to be placed on noncombustible supports 
so that tanks are at least 12 inches above the floor. Under the 
proposal such tanks would have been required to be supported by 
concrete, masonry, protected steel, or equivalent supports. Steel 
supports, except for steel saddles less than 12 inches from the floor, 
would have been required to be protected by materials having a fire 
resistance rating of not less than two hours. The proposal did not 
specify the minimum distance the tank must be from the floor. 
Commenters stated that positioning tanks at least 12 inches off the 
floor would allow for proper cleaning, rock dusting and quick detection 
of leaks. MSHA agrees with these comments and has revised the final 
rule accordingly. Additionally, the final rule provides that the tank 
supports must be made of noncombustible material, which is defined in 
Sec. 75.1900 of the final rule, making unnecessary the reference in the 
proposal to ``concrete, masonry, protected steel, or equivalent 
supports''. The reference has therefore not been adopted in the final 
rule.
    Paragraph (b)(1) requires diesel fuel tanks to be provided with 
devices for emergency venting that are designed to open at a pressure 
that does not exceed 2.5 pounds per square inch. Under this 
requirement, the venting devices must also meet minimum size 
requirements based on the capacity of the tank. The rule provides 
minimum vent device specifications for two ranges of tank sizes: tanks 
with a capacity of 500 gallons or less and tanks with a capacity of 
more than 500 gallons. The requirements of this section are 
incorporated in NFPA standards for portable tanks for transporting and 
storage of combustible liquids, as well as in American Petroleum 
Institute design standards. These vents are designed to activate at a 
pressure which is below the expected yield point of the tank and to 
provide the necessary volumetric flow rate to maintain safe internal 
pressure if the tank shell were to heat up as a fire develops. Opening 
of the device will allow the vapors to be safely vented and will 
prevent the tank from rupturing under this condition. Some commercially 
available emergency vents have been listed or approved by nationally 
recognized independent testing laboratories and can be expected to 
provide adequate pressure relief in a fire situation. The vent sizes 
required in the final rule were determined by design calculations 
outlined in National Fire Protection Association, Underwriters 
Laboratories, and American Petroleum Institute standards for a range of 
tank sizes typical for underground diesel fuel storage. These 
calculations take into account the probable maximum rate of heat 
transfer per unit area; the size of the tank and the percentage of the 
area likely to be exposed; the time required to bring the tank contents 
to a boil; the time required to heat unwet portions of the tank shell 
or roof to a temperature where the metal will lose strength; and the 
effect of drainage, insulation and the application of water in reducing 
the fire exposure and heat transfer. MSHA believes that specifying the 
minimum size of vent for two ranges of tank sizes is preferable to a 
requirement that would require the operator to design vents for a given 
size. The types of emergency vents required under this paragraph are 
commercially available and relatively inexpensive. The requirement of 
this paragraph respond to concerns of commenters regarding the hazards 
of fuel storage underground.
    Paragraph (b)(2) requires tethered or self-closing caps for 
stationary tanks in permanent underground diesel fuel storage 
facilities, and self-closing caps for diesel fuel tanks on diesel fuel 
transportation units. The proposed rule would have required self-
closing caps for all diesel fuel storage tanks, and did not include the 
alternative of a tethered cap for stationary tanks. One commenter 
suggested that self-closing caps are not needed on fixed tanks since 
they are unlikely to incur fuel spillage. The final rule permits the 
optional use of a tethered cap for stationary tanks, which adds 
flexibility and provides the same degree of protection as a self-
closing cap.
    Paragraphs (b)(3), (b)(4), (b)(5), and (b)(6) are unchanged from 
the proposal, with the exception of paragraph (b)(6) which has been 
revised to reflect commenters' concerns with respect to the location of 
shutoff valves. Paragraph (b)(3) addresses the size of vents, and will 
permit the free flow of fuel out of the tank without creating a vacuum 
in the tank that could damage its shell. Paragraph (b)(4) addresses 
requirements for liquid tight connections, and will minimize the risk 
of leaks and the resulting risk of fire. Paragraph (b)(4)(i) requires 
that liquid tight connections for all tank openings be identified by 
conspicuous markings that specify the function. Because this provision 
is performance-oriented and allows the mine operator to choose the 
manner in which markings identify connections, MSHA anticipates the 
burden time under the Paperwork Reduction Act of 1995 to be minimal.
    Paragraph (b)(5) addresses requirements for vent pipes, and will 
minimize the possibility of fuel leaking from vent lines.
    Paragraph (b)(6) is derived from proposed Sec. 75.1906(c)(5) and 
requires that shutoff valves be located as close as practicable to the 
tank shell. The proposal would have required shutoff valves to be 
located within 1 inch of the tank shell. Because shutoff valves that 
extend for any distance from the fuel tank can be inadvertently damaged 
or broken off, making it impossible to shut off the flow of liquid from 
the fuel tank, the valves must be located close to the tank where they 
are protected from damage. However, one commenter was concerned that 
the proposal was too restrictive because it may not always be possible 
from a practical standpoint to locate the shutoff valve within 1 inch 
of

[[Page 55451]]

the tank shell. The final rule responds to this commenter's suggestion 
by allowing greater flexibility, and provides that the valve be located 
as close as practicable to the tank shell.
    Paragraph (b)(7) adopts the requirement of the proposal for an 
automatic closing, heat-actuated valve on each withdrawal connection 
below the liquid level. The final rule does not adopt the proposed 
exception for connections used for emergency disposal, because this 
exception is not relevant to underground coal mines. The proposed rule 
required the installation of heat-actuated shutoff valves only on tanks 
in fixed storage facilities. The final rule extends this requirements 
to all diesel fuel tanks used underground, which would include tanks on 
diesel fuel transportation units. Automatic closing, heat-actuated 
valves shut the flow of fuel off when exposed to high temperatures. 
These valves prevent additional fuel from being discharged from the 
tank in the event of a fire. This requirement has been extended to 
tanks on transportation units, and is warranted in light of the scaling 
back of construction requirements for temporary fuel storage areas in 
the final rule in response to commenters' concerns that the 
requirements were impractical.
    Paragraph (c) addresses tanks with openings for manual gauging, and 
requires that liquid tight, tethered or self-closing caps or covers be 
provided and be kept closed when not open for gauging. The alternative 
of tethered caps or covers has been added to the final rule for 
flexibility. MSHA believes the use of self-closing or tethered caps 
will provide necessary protection against overflow.
    Paragraph (d) requires that surfaces of the tank and its associated 
components be protected against collision. This provision has been 
added to the final rule in response to commenters who were concerned 
about protecting the tanks from moving equipment. MSHA agrees that it 
is essential that diesel fuel storage tanks be protected from damage by 
collision with other equipment. Stationary tanks in permanent fuel 
storage facilities may need guards or barricades, depending upon their 
location, to prevent moving equipment from colliding with the tank.
    Paragraph (e) sets forth requirements for leakage tests for tanks 
and their associated components, except that tanks and components 
connected directly to piping systems must be properly designed for the 
application. The final rule requires a leakage test at a pressure equal 
to the working pressure. The proposed rule would have required both a 
strength test and a leakage test, at a pressure equal to the static 
head, for diesel fuel storage tanks before the tanks were placed in 
service. Commenters recommended that tanks and their connections be 
tested at a pressure twice the working pressure.
    The final rule does not require testing at twice the working 
pressure, in light of the detailed construction and design requirements 
for diesel fuel storage tanks in the final rule. The term ``static 
head'' in the proposed rule has been replaced with the term ``working 
pressure'' in the final rule. Although the meanings are the same in 
this context, the term ``working pressure'' is more widely used and 
more commonly understood in the mining industry. Compliance with the 
requirement of this paragraph will provide protection from hazards 
associated with leakage of diesel fuel underground. Under the final 
rule, mine operators are expected to verify that no leaks exist after 
installing the tank underground and connecting all of the tank's 
associated components before placing the tank in service. All 
components must be rated for the working pressures in the system. Both 
the static head and the maximum pump pressure, if applicable, must be 
considered when designing and selecting tanks and associated components 
connected to a piping system. For tanks connected to a piping system 
from the surface, the static head pressure could easily exceed several 
hundred pounds per square inch (psi), either during normal operation or 
because of a fault in the system. For these systems, MSHA advises mine 
operators to plan for a worst-case (highest pressure) scenario and 
select a tank and tank components that are designed for use at this 
pressure.
    MSHA has concluded that the strength test for tanks that was 
included as part of the proposal is unnecessary, given the other 
specifications for tanks. This proposed requirement has therefore not 
been included in the final rule.
    The proposal would have imposed additional requirements on tanks in 
underground diesel storage facilities that were not located in ``dry 
areas.'' Such tanks would have been required under the proposal to be 
placed on noncombustible supports so that the tanks were at least 6 
inches above water or wet bottom, and such tanks would also have been 
required to be constructed of noncorrosive material. Commenters stated 
that the concept of ``dry areas'' was ambiguous and should not be 
adopted. MSHA agrees with these comments, and this aspect of the 
proposal has therefore not been included in the final rule. However, 
under the final rule, stationary tanks in permanent underground storage 
facilities must be placed on noncombustible supports at least 12 inches 
above the floor to allow for proper cleaning, rock dusting and quick 
detection of leaks. Tanks will also be protected by this requirement 
from wet floors. Further, the final rule requires all diesel fuel 
storage tanks to be protected from corrosion. These requirements will 
ensure that tanks are sufficiently shielded from water damage.
    Paragraph (f) establishes design and size requirements for safety 
cans. These requirements have been added to the final rule to ensure 
that small amounts of diesel fuel can be transported and stored in a 
safe manner. Although the proposed rule contemplated the use of safety 
cans to transport small amounts of diesel fuel underground, the 
proposal would not have set design requirements for safety cans. 
Commenters were concerned that widespread and uncontrolled use of 
safety cans underground would result in fuel spills and accumulations 
on mine equipment and mine floors. The provisions of this paragraph are 
intended to address commenters' concerns about the hazards presented by 
safety cans used to store and transport diesel fuel in the underground 
mine environment.
    The final rule establishes specific design requirements for safety 
cans. As indicated in the discussion of Sec. 75.1900, the term ``safety 
can'' is defined in the final rule as a metal container intended for 
storage, transport or dispensing of diesel fuel with a nominal capacity 
of no more than 5 gallons, listed or approved by a nationally 
recognized independent testing laboratory. Paragraph (f)(1) of this 
section reiterates the 5-gallon capacity limitation, and paragraph 
(f)(2) requires that safety cans be equipped with a flexible or rigid 
tubular nozzle attached to a valved spout. Paragraph (f)(3) requires 
that safety cans be provided with a vent valve designed to open and 
close simultaneously and automatically with the opening and closing of 
the pouring valve. Finally, paragraph (f)(4) requires that safety cans 
be designed so that they will safely relieve internal pressure when 
exposed to fire. These requirements will reduce the likelihood of 
diesel fuel spills and afford appropriate protection for miners, in 
response to commenters who were concerned about the use of safety cans 
to store and transport diesel fuel.

[[Page 55452]]

Section 75.1905  Dispensing of Diesel Fuel
    This section addresses the dispensing of diesel fuel, and has been 
revised from the proposal to clarify the various ways that diesel fuel 
may be safely dispensed. Paragraph (a) provides that diesel-powered 
equipment may be refueled only from safety cans, from tanks on diesel 
fuel transportation units, or from stationary tanks. These requirements 
are intended to control the circumstances under which diesel fuel is 
dispensed underground, minimizing the opportunities for spills or 
leakage, and in response to commenters who expressed concern about fuel 
spillage underground.
    Paragraph (b) contains requirements for the dispensing of diesel 
fuel from tanks, except for the dispensing of fuel from safety cans. 
Design specifications for safety cans are included in Sec. 75.1904(f) 
of the final rule, which requires nozzles, spouts, and vent valves on 
safety cans.
    The requirements of paragraph (b)(1) apply when gravity feed is 
used as a means of dispensing diesel fuel. Although in developing the 
proposed rule MSHA contemplated that gravity feed would be used as a 
method for dispensing fuel, the proposal did not specifically refer to 
it. Some commenters questioned whether this omission should be 
interpreted as a prohibition of gravity feed fuel dispensing. In 
response to these comments, MSHA has clarified that gravity feed is a 
permissible method of dispensing fuel. However, because gravity feed 
presents the same potential as a powered pump for a loss of fuel from 
an unattended hose, the final rule prohibits a latch-open device when 
gravity feed is the method of dispensing.
    Paragraph (b)(2) is identical to the proposal and requires that a 
manual pump used to dispense diesel fuel have a hose equipped with a 
nozzle containing a self-closing valve. No comments were received on 
this aspect of the proposal, and it has been adopted unchanged.
    Paragraphs (b)(3) (i) through (iii) require that, when a powered 
pump is used to dispense fuel, it be equipped with an accessible 
emergency shutoff switch for each nozzle, and that the hose be equipped 
with a self-closing valve without a latch-open device, and with an 
anti-siphoning device. These requirements have been adopted, with some 
minor changes, from the proposal. Specifically, the final rule 
clarifies that an accessible emergency shutoff switch be provided for 
``each nozzle'', and adds a requirement for an anti-siphoning device. 
These modifications recognize that fuel piping systems may be installed 
underground that do not transport fuel from the surface, but from one 
location to another in the mine itself. These additional requirements 
are intended to prevent the leakage or pumping of the contents of a 
tank into the mine in the event of a broken or leaking pipe or hose. An 
accessible emergency shutoff switch is required for each nozzle under 
the final rule to permit quick action by mine personnel in the case of 
a leaking pipe or hose or in the event of fire during refueling. An 
anti-siphoning device prevents the inadvertent siphoning of fuel from a 
tank connected to the piping system, and is responsive to commenters' 
concerns regarding the hazards of fuel leaks and spills underground.
    Commenters recommended that an inline fuse be required as near as 
possible to the pump's power source to deenergize the electrical system 
in the event of an electrical short circuit. This comment has not been 
adopted in the final rule, because the circuit protection specified in 
existing Sec. 75.518 is sufficient to prevent or detect a short 
circuit. In addition, other existing electrical safety requirements in 
part 75 apply to electrical components associated with diesel fuel 
handling and storage, and provide adequate protection from electrical 
hazards.
    Paragraph (c) prohibits the use of compressed gas in dispensing 
diesel fuel. This prohibition is identical to what was proposed and 
received no comments. The use of compressed gas to dispense diesel fuel 
would require not only a special tank but also an emergency venting 
system for pressurized tanks, and would still present a hazard. If a 
leak developed in the pressurized tank or its associated piping, 
relatively large amount of fuel could be spilled onto the mine floor, 
creating a serious fire hazard. This prohibition has therefore been 
retained in the final rule.
    Paragraph (d), like the proposal, prohibits diesel fuel from being 
dispensed to the fuel tank of diesel-powered equipment while the 
equipment engine is running. This prohibition is derived from MSHA's 
review of Canadian fire accident data, which reveals that 10 fires 
occurred during refueling. Failure to shut off the engine may have 
contributed to these fires. This prohibition is also consistent with 
Sec. 75.1916(d) of the final rule, which forbids unnecessary engine 
idling, and reduces exposure of miners to exhaust emissions.
    Several commenters recommended that permissible diesel equipment be 
excluded from this prohibition because it is designed to be explosion-
proof. These commenters also stated that shutting down the equipment 
should be avoided because of the difficulty in restarting it, and that 
in some cases a trained mechanic would be needed to restart the engine.
    MSHA does not agree that permissible equipment should be excluded 
from this requirement. Although permissible diesel equipment is 
equipped with engine surface temperature controls that would prevent 
the ignition of diesel fuel if it is spilled on the equipment, air 
quality considerations support the adoption of this requirement for 
permissible as well as nonpermissible equipment. Not shutting down a 
machine engine during refueling serves no purpose other than 
convenience, and the diesel exhaust produced contributes unnecessarily 
to contaminant levels. The fact that engines may be difficult to 
restart does not justify exempting permissible equipment from this 
requirement. Equipment that is difficult to restart is in need of 
service or repair. The final rule therefore does not exempt permissible 
equipment from the prohibition against refueling of diesel equipment 
while the equipment engine is running.
    Paragraph (e), which requires that powered pumps be shut off when 
fuel is not being dispensed, has been added to the final rule to 
address concerns about loss of fuel as a result of broken or leaking 
pipes. This requirement is intended to minimize the likelihood of fuel 
spills in the underground mine environment.
Section 75.1905-1  Diesel Fuel Piping Systems
    Section 75.1905-1 has been added to the final rule to address 
requirements for diesel fuel piping systems. The requirements in the 
proposal governing fuel piping systems were included in the same 
section as proposed requirements for fuel transfer. MSHA has concluded 
that dispensing requirements and design and construction requirements 
for piping systems are sufficiently unique that they are more 
appropriately addressed in a separate standard.
    Underground fuel piping systems can be very complex and may require 
specialized expertise for their design and installation. Mine operators 
should ensure that an engineering evaluation, including a fault 
analysis, is performed in developing a fuel piping system.
    One commenter recommended that piping of diesel fuel should be 
allowed only in shaft mines, from the surface vertically to permanent 
underground

[[Page 55453]]

storage areas, and that the piping should be contained in its own 
borehole to isolate it from ignition sources. Safety considerations do 
not warrant restricting fuel piping systems to shaft mines. MSHA and 
industry experience, including an analysis of accident reports, does 
not reveal any increased hazard with the use of piping systems in slope 
mines. In the final rule, MSHA has removed the reference to vertical 
pipelines to clarify that this section applies to all mines.
    Paragraph (a) of this section of the final rule adopts the proposed 
requirement that diesel fuel piping systems from the surface to be 
designed and operated as dry systems, unless an automatic shutdown is 
incorporated that prevents accidental loss or spillage of fuel and that 
activates an alarm system. The phrase ``from the surface'' has been 
added to the final rule to clarify that only piping systems from the 
surface are governed by the requirements of this paragraph. MSHA is 
aware that some mines have installed horizontal piping systems that do 
not originate at the surface. Because these horizontal systems 
typically cannot be operated as dry systems, the rule specifies that 
these systems would not be affected by this requirement. No location is 
specified for the alarm in the final rule, to allow mine operators 
flexibility in determining where the alarm will be most effective in 
alerting mine personnel.
    Compliance with the requirement of this paragraph mandates a well 
designed piping system, and may require a double wall system. Except 
for the comment suggesting that piping of diesel fuel underground be 
limited to shaft mines, MSHA received no other comments on this 
provision, and the proposed requirement has been adopted in the final 
rule without change.
    Paragraphs (b)(1) through (b)(4) address requirements for piping, 
valves, and fittings. These requirements are unchanged from the 
proposal, and constitute generally accepted design specifications. This 
standard requires that all piping, valves, and fittings be: (1) Capable 
of withstanding working pressures and stresses; (2) capable of 
withstanding four times the static pressure; (3) compatible with diesel 
fuel; and (4) maintained in a manner which prevents leakage.
    Paragraph (c) requires pipelines to have manual shutoff valves 
installed at the surface filling point, and at the underground 
discharge point. This requirement is the same as the proposal, except 
that the proposal used the term ``vertical'' to describe pipelines. For 
the reasons discussed in the introduction to this section, the term 
``vertical'' has been eliminated to clarify that this section applies 
to all underground coal mines.
    Paragraphs (d) and (e), like the proposal, include requirements for 
shutoff valves on fuel lines. Paragraph (d) provides that if fuel lines 
are not buried in the ground, shutoff valves must be located every 300 
feet. Paragraph (e) requires that shutoff valves be installed at each 
branch line where the branch line joins the main line. One commenter 
recommended that automatic shutoff valves be required in these two 
situations, stating that they provide for minimal loss of fuel and 
maximum safety in the case of a pipeline rupture or leak. MSHA does not 
believe that automatic shutoff valves are necessary when the additional 
benefits are balanced with other provisions in this final rule. The 
commenter's suggestion has therefore not been adopted in the final 
rule.
    Paragraph (f) is a new provision in the final rule and requires 
that an automatic means be provided to prevent unintentional transfer 
of fuel from the surface into the permanent underground diesel fuel 
storage facility. This requirement has been added to address the 
concerns of some commenters that were prompted by a specific diesel 
fuel spill caused by malfunctioning components in a diesel fuel piping 
system. Additionally, many commenters were generally concerned about 
possible fire and other hazards that could result from diesel fuel 
spills and leaks, particularly when piping systems are used. This 
paragraph responds to those comments by requiring a fail-safe piping 
system, ensuring that necessary protection is provided to miners.
    Paragraph (g) provides that diesel fuel piping systems from the 
surface can only be used to transport fuel directly to stationary tanks 
or diesel fuel transportation units in a permanent underground diesel 
fuel storage facility. This requirement has been renumbered and has 
been revised from the proposal to respond to commenters who recommended 
strict control of the use of safety cans and stated that dispensing 
fuel from a piping system directly into diesel equipment fuel tanks 
would create a fire hazard. This paragraph is intended to prohibit 
filling safety cans and equipment fuel tanks directly from a piping 
system and further minimize hazards associated with fuel spills.
    Under this paragraph a fuel piping system from the surface may 
terminate underground only in a permanent fuel storage facility, which 
must be equipped with features such as a fire suppression system and a 
means of containing a fuel spill. Because temporary fuel storage areas 
are not required to have these features, they would not provide 
adequate fire protection for a situation where a significant amount of 
fuel is lost in a spill from a piping system.
    Paragraph (h), like the proposal, requires that when boreholes are 
used the diesel fuel piping system cannot be located in a borehole with 
electric power cables. This will minimize the likelihood of fire by 
diesel fuel coming into contact with potential ignition sources.
    Paragraph (i) requires that diesel fuel piping systems located in 
entries not be located on the same side of the entry as electric cables 
or power lines. It also requires that guarding be provided when piping 
systems cross electric cables or power lines. The final rule has been 
modified from the proposal to acknowledge that, in some cases, a 
pipeline must cross over power lines, depending upon the mine's layout. 
The standard addresses any hazards presented by the intersection of 
pipelines and electric cables or power lines by requiring that guarding 
be provided.
    Paragraph (j) requires that piping systems be protected to prevent 
physical damage. Commenters supported this provision, and it is 
unchanged from the proposal.
Section 75.1906  Transport of Diesel Fuel
    This section of the final rule has been retitled and reorganized to 
reflect MSHA's approach to diesel fuel storage and handling in this 
final rule. The word ``containers'' is removed from the title to 
reflect that only two types of vessels are allowed to transport and 
dispense diesel fuel--safety cans and tanks. This section of the final 
rule is responsive to commenters who: expressed concerns about the wide 
and uncontrolled use of safety cans in underground coal mines; 
recommended limited section storage of diesel fuel; stated that fire 
suppression systems were not needed on the tank used to transport fuel; 
and noted the need for clarification of the requirement for portable 
fire extinguishers on diesel fuel transportation units.
    Several commenters stated that the proposed rule was vague and 
confusing. Their comments were directed to the use of the terms 
``containers,'' ``safety cans,'' ``tanks,'' and ``fuel transportation 
units.'' As indicated in the preamble discussion for Sec. 75.1900, MSHA 
has included definitions in the final rule for the terms ``safety 
cans,'' ``diesel fuel tank,'' and ``diesel fuel transportation unit'' 
to provide additional clarification

[[Page 55454]]

for the fuel handling and storage requirements in the final rule. The 
term ``container'' has not been defined because it has been eliminated 
from the final rule.
    Several commenters recommended that the use of small containers and 
cans be restricted because they are prone to leak when transported or 
used to dispense fuel. In support of their recommendation, these 
commenters cited instances of mine floors being saturated with fuel. 
Other commenters urged that safety cans be allowed for transport of 
small quantities of diesel fuel, and stated that prohibiting their use 
would be unwarranted. As stated earlier in the discussion for this 
section, the final rule has been revised to require that safety cans be 
listed or approved by a nationally recognized independent testing 
laboratory. This aspect of the final rule will provide miners with 
protection against leakage and spillage during dispensing operations, 
while recognizing the practical need to transport small quantities of 
diesel fuel.
    Paragraph (a) of this section of the final rule requires diesel 
fuel to be transported only by diesel fuel transportation units or in 
safety cans. This requirement is intended to ensure that diesel fuel is 
transported only in vessels designed for that purpose. The proposal 
would have required diesel fuel to be transported in specially designed 
containers. A commenter recommended substituting the term ``combustible 
liquid'' in place of the term ``diesel fuel'', stating that there are 
Department of Transportation specifications for containers that 
transport combustible liquids. The final rule responds to commenters by 
limiting the transport of diesel fuel to safety cans, which must be 
listed or approved by a nationally recognized independent testing 
laboratory, or by diesel fuel transportation units, which must be 
equipped with a tank designed for the transport of diesel fuel.
    MSHA recognizes that safety can use must be carefully controlled. 
Paragraph (b) of this section of the final rule allows only one safety 
can to be transported on a vehicle at any time, and the can must be 
protected from damage during transport. All other safety cans must be 
stored in permanent underground fuel storage facilities. This provision 
is revised from the proposal to be responsive to commenters who cited 
problems with misuse of small cans and recommended that they be 
strictly controlled. Commenters further stated that in some mines there 
was no designated area for storage of safety cans. The requirements 
that have been added to the final rule are intended to ensure safe 
transport of safety cans. The final rule does not require that single 
safety cans, which are secured and protected on a vehicle, be removed 
for storage in permanent facilities when the vehicle is left 
unattended. This aspect of the final rule will allow for emergency 
refueling, while at the same time provide a degree of control over the 
use of safety cans.
    Paragraphs (c) and (d) require that leaking safety cans be promptly 
removed from the mine, and that safety cans and tanks on diesel fuel 
transportation units be conspicuously marked. These marking 
requirements are consistent with marking requirements for permanent 
fuel storage facilities and temporary fuel storage areas in 
Sec. 75.1903(b)(3) of the final rule. The inclusion of marking 
requirements for safety cans and tanks in the final rule is responsive 
to several commenters who suggested that signs should be placed on 
mobile equipment identifying tanks and cans used for diesel fuel 
storage. This is also a prudent fire protection practice.
    Paragraphs (e) and (f) establish requirements for the 
transportation of tanks on fuel transportation units. As mentioned 
earlier, the final rule does not use the term ``container''. Paragraph 
(e) provides that diesel fuel transportation units must not transport 
more than 500 gallons of diesel fuel at one time. Paragraph (f) 
requires tanks on diesel fuel transportation units to be permanently 
fixed to the units and have a total capacity of no greater than 500 
gallons. Under the proposal, containers used for the transport of 
diesel fuel could not exceed a capacity of 500 gallons, and would have 
been required to be permanently fixed to the transportation unit. One 
commenter recommended that the maximum tank capacity be limited to 250 
gallons, reasoning that less fuel would reduce the fire hazard. The 
interrelated precautions of the final rule are designed to protect 
against a fire involving a diesel fuel transportation unit. Reducing 
the unit's fuel capacity to 250 gallons would not add significantly to 
the protection against fire, and would increase the frequency with 
which the unit would need to be refilled. However, paragraph (e) is 
intended to limit the amount of fuel transported by a single trip, 
either on rails or rubber tires, to 500 gallons. Paragraph (f) will 
ensure that the fuel tank is not removed from the vehicle for transport 
separately, thereby exposing the tank to possible damage, and also 
offers some protection for the tank from the vehicle frame.
    Paragraph (g) requires non-self-propelled diesel fuel 
transportation units equipped with electric components for dispensing 
fuel that are connected to a source of electrical power be provided 
with a fire suppression device that meets the requirements of existing 
Secs. 75.1107-3 through 75.1107-6, Secs. 75.1107-8, and Sec. 75.1107-
16. The proposed requirement would have required a fire suppression 
system meeting the requirements of proposed Sec. 75.1911 on all diesel 
fuel transportation units, not only on those with electrical 
components.
    Commenters were opposed to a requirement for fire suppression 
systems on all diesel fuel transportation units, stating that a 
trailer-mounted fuel tank did not need a fire suppression system since 
it had no ignition source, and should not be treated any differently 
than tanks transporting other combustible materials. These commenters 
believed that the fire extinguishers required under the proposal would 
provide adequate fire protection in temporary fuel storage areas.
    MSHA agrees with commenters that fuel tanks alone, without an 
ignition source, do not present a significant fire hazard. However, 
fire protection for fuel tanks must be provided when a potential 
ignition source exists. An ignition source is present on the diesel 
fuel transportation unit when electrical power is provided to the 
dispensing pump on the unit from either an electric-powered machine or 
the mine electrical system. The final rule therefore requires fire 
protection for non-self-propelled diesel fuel transportation units with 
electrical components for dispensing fuel that are connected to a 
source of electrical power. Diesel fuel transportation units with 
electrical devices other than those used for dispensing fuel, such as 
lights, do not present a significant fire hazard and do not need to be 
protected by a fire suppression system. This fire suppression device 
requirement would also apply when the transportation unit's dispensing 
pump is powered by its own batteries or an off-board generator.
    The final rule requires a fire suppression device meeting the 
requirements of existing Sec. 75.1107, instead of Sec. 75.1911 under 
the proposal, because the fire protection provided by Sec. 75.1107 is 
suitable for electrical installations, and therefore appropriate for 
electrical components of fuel transportation units. A fire suppression 
system under Sec. 75.1911 is designed to protect diesel-powered 
equipment, and,

[[Page 55455]]

unlike existing Sec. 75.1107, does not require that the mine electric 
power supply to the fuel transportation unit be shut off when the fire 
suppression system is actuated, an important safety feature that 
prevents reignition of the fire.
    Paragraph (h) requires diesel fuel transportation units and 
vehicles transporting safety cans to have at least two multipurpose, 
dry chemical type (ABC) fire extinguishers. The fire extinguishers must 
be listed or approved by a nationally recognized independent testing 
laboratory, and have a 10A:60B:C or higher rating. There must be at 
least one fire extinguisher located on each side of the vehicle. The 
proposal would have required that fire extinguishers be provided on 
each end of a fuel transportation unit when diesel fuel was transported 
in containers other than safety cans. Locating fire extinguishers on 
the side is consistent with the requirements of Sec. 75.1911(e) of the 
final rule for the location of fire suppression system actuators. The 
type and size of extinguisher are the same as required by 
Sec. 75.1903(b)(1) and (b)(2) for permanent underground diesel fuel 
storage facilities and temporary underground diesel fuel storage areas.
    Paragraph (i) requires that diesel fuel transportation units be 
parked in permanent underground diesel fuel storage facilities or 
temporary underground fuel storage areas when not in use. Under the 
proposal, ``unattended'' diesel fuel transportation units would have 
been required to be parked only in fixed or mobile fuel storage 
facilities. Some commenters objected to this requirement, and urged 
MSHA to provide a more workable rule that would allow transportation 
units to be parked, consistent with the Advisory Committee's 
recommendation that MSHA establish requirements for the temporary 
parking of diesel transportation vehicles. Some commenters also stated 
that ``unattended'' was an ambiguous term.
    The term ``unattended'' has been eliminated from the final rule. 
Instead, the final rule provides that diesel fuel transportation units 
that are ``not in use'' must be parked either in permanent storage 
facilities or temporary storage areas. The phrase ``not in use'' means 
that the unit is not being trammed or used to dispense fuel or 
lubricants or waiting to refuel another piece of equipment. It does not 
mean that the unit operator must be within 500 feet or within the line 
of sight of the fuel transportation unit, as long as the operator is 
performing an activity associated with the operation of the unit. This 
may occur, for example, while the operator is locating the next unit of 
equipment to be refueled. This requirement is intended to control the 
locations of diesel fuel transportation units to minimize fire hazards 
associated with their use.
    Paragraph (j), like the proposal, applies the requirements of 
existing Sec. 75.1003-2 when the distance between a diesel fuel 
transportation unit and an energized trolley wire at any location is 
less than 12 inches. Section 75.1003-2 sets forth specific precautions 
to be followed when off-track equipment is being moved in areas where 
energized trolley wires are present. MSHA received no comments on this 
aspect of the proposal and it has been adopted into the final rule 
unchanged. This requirement is intended to minimize the risk of 
ignition and fire when a diesel fuel transportation unit is in close 
proximity to a bare energized trolley wire. The sparks and heat from an 
electrical short circuit could ignite residual fuel on the 
transportation unit and fire may then spread to the larger volume of 
fuel stored on the transportation unit.
    Paragraph (k) prohibits the transport of diesel fuel on or with 
mantrips, or on conveyor belts. This requirement has been revised from 
the proposal, which would have prohibited transport of diesel fuel on 
conveyor belts, to include within the prohibition the transport of 
diesel fuel on mantrips, in response to several commenters who 
expressed concern about transportation of diesel fuel on personnel 
carriers because of the inherent hazards associated with that practice. 
This requirement applies to equipment being used as personnel carriers, 
but does not apply to such equipment when it is used for purposes other 
than transporting miners in the mine. This requirement also does not 
apply to diesel fuel contained in the fuel tank of a diesel-powered 
personnel carrier.
    Paragraph (l) requires that, as of 12 months after the publication 
date of the final rule, diesel fuel must be stored and handled in 
accordance with the requirements of Secs. 75.1902 through 75.1906 of 
this part. Twelve months will provide sufficient time for mine 
operators to make any necessary changes to their fuel handling, 
transportation, and storage practices underground, such as fuel tank 
retrofits or construction of fuel storage facilities. The requirements 
of Sec. 75.1903 (c) and (d) take effect sooner, because they address 
safe welding practices in or near diesel fuel storage areas, and mine 
operators should not need any additional time to come into compliance 
with these provisions.
 Section 75.1907  Diesel-Powered Equipment Intended For Use In 
Underground Coal Mines.
    This section establishes a schedule for compliance with the final 
rule's equipment-related requirements, including requirements for 
approved engines and power packages, fire suppression systems, and 
safety-related requirements for nonpermissible equipment in 
Secs. 75.1909 and 75.1910. The concept of a time schedule to allow for 
conversion or replacement of diesel-powered equipment currently in use 
to comply with the new requirements of the final rule was recommended 
by the Diesel Advisory Committee. The Committee also recommended that 
equipment newly introduced underground after a fixed date meet the new 
requirements.
    Under the compliance schedule of this section, 30 days after the 
rule's publication date all diesel-powered equipment used where 
permissible electric equipment is required must be approved under part 
36. This section also establishes a compliance schedule for Part 36-
approved equipment, to comply with certain surface temperature limits 
within 6 months, and be provided with a fire suppression system and 
brakes that meet certain standards within 36 months of the rule's 
publication. Part 36-approved equipment is also required to have a 
particulate index and a dilution air quantity determined under subpart 
E of part 7 within 12 months of the rule's publication date. 
Permissible diesel-powered equipment that is manufactured 3 years after 
the date of publication of the final rule or later and used in 
underground coal mines must incorporate a power package approved under 
subpart F of part 7 of the final rule. This section of the final rule 
also requires nonpermissible diesel-powered equipment, with the 
exception of the special category of ambulances and firefighting 
equipment under Sec. 75.1908(d), to be equipped with the machine safety 
features set forth in Secs. 75.1909 and 75.1910 within 36 months of the 
publication date of the final rule.
    The overall approach taken in the final rule for equipment safety 
features is different from that of the proposal, in response to 
commenters and for reasons explained in detail in the preamble for 
parts 7 and 36. The proposed rule would have required approval of fully 
assembled permissible equipment under subpart H of part 7, and approval 
of fully assembled nonpermissible

[[Page 55456]]

equipment under subpart I of part 7. A limited class of light-duty 
nonpermissible equipment would have been established that did not 
require fully assembled machine approval, but which would have been 
equipped with specific machine safety features set forth as mandatory 
standards in proposed Sec. 75.1909. Under proposed Sec. 75.1907, 
specific deadlines, up to 60 months after the rule's effective date, 
would have been set for compliance with the equipment-related 
requirements of the final rule for both permissible and nonpermissible 
equipment, including limited class and stationary unattended equipment. 
Additionally, the proposal would have allowed a mine operator to apply 
for MSHA approval for continued use of diesel-powered locomotives 
without required subpart F or G power packages. MSHA would have been 
authorized to grant such approval if approved power packages suitable 
for specific mine conditions and locomotive design were not available, 
recognizing that the current state of technology might make compliance 
difficult or impossible.
    The proposed rule took the approach of phasing in the different 
equipment-related requirements, depending on how long MSHA determined 
mine operators and manufacturers would need to obtain the necessary 
equipment or make the necessary retrofits, including time needed to 
obtain MSHA approval for the appropriate machine components. 
Specifically, the proposed rule would have allowed a longer period of 
time for equipment to be provided with approved engines and power 
packages than it would have allowed for other equipment-related 
requirements, for such features as brakes, fuel systems, and electrical 
components. Different time frames would have been allowed under the 
proposal to take into account the time needed for the MSHA approval 
process as well as the technical difficulties associated with 
retrofitting equipment with approved power packages and engines.
    As discussed in the preamble to part 7 of the final rule, the final 
rule does not adopt the approach of fully assembled machine approval 
under subparts H and I of part 7 contemplated by the proposal and 
addressed in the concurrent advance notice of proposed rulemaking. 
Instead, part 36 has been expanded to specifically provide for approval 
of diesel-powered equipment used in areas of underground coal mines 
where permissible electric equipment is required. Fully assembled 
machine approval is not required under the final rule for any category 
of nonpermissible equipment. The compliance time frames of this section 
of the final rule reflect this change in approach.
    The time frames in this section are based on an estimation of the 
useful life of existing diesel-powered equipment, the reasonable time 
needed to convert or retrofit existing equipment, and the commercial 
availability of suitable replacement equipment. The time frames in this 
section are intended to provide mine operators with a reasonable period 
of time to make determinations of the expected remaining useful life of 
diesel-powered machines in use in their mines and the cost of necessary 
machine modifications, and to compare this information with the 
replacement cost of equipment that complies with the requirements of 
the final rule.
    One commenter rebuilt a diesel-powered truck to convert it to a 
personnel carrier that met the equipment safety requirements of the 
proposed rule for self-propelled limited class nonpermissible 
equipment, and submitted a written summary documenting the conversion 
into the rulemaking record. This information generally demonstrated 
that compliance would be facilitated if equipment-related requirements 
were phased in by equipment type, rather than phasing in specific 
requirements across all equipment types. In short, once an equipment 
rebuild is initiated, it is easier to perform all machine feature 
modifications at the same time.
    One commenter asserted generally that mine operators and equipment 
manufacturers could bring diesel-powered equipment into compliance with 
the requirements of the final rule within 12 months. Although MSHA 
agrees, and the final rule reflects, that some requirements can be met 
within a year, compliance with other requirements, will reasonably 
involve more time.
    As explained in greater detail elsewhere in the preamble, the final 
rule requires specific safety features on both permissible and 
nonpermissible diesel-powered equipment. These requirements apply to 
nonpermissible diesel-powered equipment in Secs. 75.1909 and 75.1910, 
and will be applied to permissible diesel-powered equipment during the 
MSHA approval process under part 36.
    The final rule does not require nonpermissible equipment to be 
provided with power packages, which would have been required under the 
proposal. Neither does it require fully assembled machine approval for 
nonpermissible equipment. Power packages would have provided this 
equipment with, among other things, surface temperature controls for 
the equipment. As discussed elsewhere in the preamble, commenters were 
divided on this issue. Some commenters believed not only that 
temperature controls were necessary to adequately address the fire 
hazards presented by diesel-powered equipment underground, but also 
recommended that all diesel-powered equipment be approved under part 36 
as permissible, and provided with the explosion-proof features required 
on such equipment. Other commenters strenuously opposed a requirement 
for approved power packages on nonpermissible equipment, stating that 
surface temperature controls were not needed on equipment operated 
outby the face, and that fire protection features, such as fire 
suppression systems, in conjunction with other machine safety features 
would provide an appropriate margin of safety. These commenters stated 
that a power package requirement for nonpermissible equipment would 
have the effect of eliminating many useful pieces of equipment from 
mines that could not be retrofitted with power packages or would not be 
manufactured with them.
    The final rule does not require approved power packages on outby 
equipment, except when the equipment discharges its exhaust directly 
into a return air course, as provided under Sec. 75.1909. Proposed 
subpart G, which would have established an approval program for power 
packages for nonpermissible equipment, has not been adopted in the 
final rule. Instead, nonpermissible equipment is required under 
Sec. 75.1909(a)(10) to be provided with a means to prevent the spray 
from ruptured hydraulic or lubricating oil lines from being ignited by 
contact with engine exhaust system component surfaces. This requirement 
recognizes that the hazards of high surface temperatures on diesel-
powered equipment can be controlled in a number of ways in addition to 
the methods contemplated under proposed subpart G. MSHA has concluded 
that the requirement of paragraph (a)(10), along with the other safety 
features required for control of fuel sources on diesel-powered 
equipment, provides effective fire prevention on nonpermissible diesel-
powered equipment. The approach of the final rule allows mine operators 
and manufacturers the flexibility to improve existing methods and to 
develop new methods of meeting the performance goals of the final rule 
requirements.
    Paragraph (a) of this section of the final rule adopts the proposed 
requirement that within 30 days of the date of publication of the final 
rule, all

[[Page 55457]]

diesel-powered equipment used where permissible electrical equipment is 
required be approved under part 36. Part 36 approval ensures that the 
equipment is explosion-proof, and that equipment used in areas of the 
mine where methane is likely to accumulate and where there may be 
combustible quantities of coal dust and other materials will not cause 
a fire or an explosion. All underground coal mines using diesel 
equipment already have the approved equipment necessary to comply with 
this requirement, in most cases because the mine's ventilation plan 
specifically requires it. This requirement therefore goes into effect 
30 days after publication of the final rule, providing necessary 
protections for miners working underground.
    Paragraph (b) establishes a time schedule under which equipment 
approved under part 36 is required to be provided with additional 
safety features. Paragraph (b)(1) requires the equipment to be provided 
with a safety component system that limits surface temperatures to 
those specified in subpart F of part 7. This requirement is essentially 
identical to that of the proposal, which would have required that part 
36-approved equipment be provided with a power package that limits 
surface temperatures to those specified in subpart F. In the final 
rule, the equipment is required to have a ``safety component system'' 
that limits the surface temperatures rather than a ``power package'' 
specified under the proposal. Existing permissible equipment has been 
approved under the current version of part 36, which uses the term 
``safety component system'' to refer to those devices added to the 
engine to control surface temperatures of the exhaust system. The term 
``power package'' used in the final rule includes those devices, which, 
with the engine, comprises the ``power package.'' Power packages are 
approved under subpart F of part 7 of the final rule. As discussed 
elsewhere in this preamble, part 36 has been specifically revised to 
provide for approval of diesel-powered machines used in underground 
coal mines. Part 36 now references subparts E and F of part 7 of the 
final rule, and requires equipment approved under part 36 for use in 
coal mines to be equipped with a power package approved under subpart 
F. Subpart F limits the maximum surface temperature to less than 
302 deg. F (150 deg. C). Until promulgation of this final rule, the 
maximum surface temperature of the engine and exhaust system components 
under part 36 was 400 deg. F (204 deg. C). To date, only one engine and 
safety component system used in part 36-approved equipment has a 
surface temperature above 302 deg. F, and the equipment on which the 
system is installed is not used in coal mines. Consequently, compliance 
with this requirement within six months of the publication of the final 
rule should present no compliance difficulties for mine operators or 
manufacturers. This requirement will ensure that permissible equipment 
in underground coal mines will have surface temperatures below 302 deg. 
F, minimizing the chance that combustibles such as diesel fuel, float 
coal dust, and hydraulic fluid will be ignited by high surface 
temperatures.
    Paragraph (b)(2) requires that, as of 36 months after the final 
rule is published, equipment approved under part 36 be provided with an 
automatic or manual fire suppression system that meets the requirements 
of Sec. 75.1911, and be provided with a portable fire extinguisher. A 
fire suppression system is required on permissible equipment in 
addition to surface temperature controls to address fire hazards 
created by other machine system malfunctions. The fire suppression 
system on permissible equipment may be either manual or automatic. 
Under the proposal, part 36-approved equipment would have been required 
to have a fire suppression system that met the requirements of 
Sec. 75.1911. The requirements of proposed Sec. 75.1911 provided only 
for automatic fire suppressions systems. For reasons explained in 
greater detail in the preamble discussion to Sec. 75.1911, automatic 
fire suppression is not required on permissible diesel-powered 
equipment. This is because all equipment approved under part 36 is 
provided with surface temperature controls, which reduce the risk of 
fire. The final rule includes the additional requirement that the 
equipment be provided with at least one portable multipurpose dry 
chemical type ABC fire extinguisher having a 10A:60B:C rating or 
higher. The fire extinguisher must be located within easy reach of the 
equipment operator and be protected from damage by collision. This 
requirement has been added in response to the recommendation of a 
commenter. MSHA has concluded that requiring equipment to be provided 
with a portable fire extinguisher is a good fire prevention practice, 
and this recommendation has therefore been adopted in the final rule, 
superseding the requirement in part 36 for a fire extinguisher with a 
much lower firefighting rating. This requirement is consistent with the 
fire extinguisher requirements for nonpermissible equipment in the 
final rule.
    MSHA had proposed a 6-month compliance deadline for installation of 
fire suppression systems on part 36-approved equipment, but has 
concluded that a 36-month time frame is needed for mine operators to 
obtain MSHA approval of field modifications on approved equipment, and 
for equipment manufacturers to process approval applications to permit 
installation of fire suppression systems on permissible equipment. The 
Agency intends to promptly process approval applications for 
modification of machines to aid compliance with this requirement.
    Paragraph (b)(3) has been added to the final rule to require that, 
as of 36 months after the publication date of the final rule, equipment 
approved under part 36 be provided with brake systems that meet the 
requirements of Sec. 75.1909(b)(7), (b)(8), (b)(9), (c), (d), and (e). 
These brake requirements have been added to ensure that permissible 
equipment meets at least the same braking requirements as 
nonpermissible equipment under the final rule. All existing part 36 
equipment is already equipped with service brake systems that meet the 
requirements of Sec. 75.1909(b)(8), (b)(9), and (d). The requirements 
of Sec. 75.1909(c) have been developed from requirements for automatic 
emergency parking brakes on electric equipment in Sec. 75.523-3. A 
number of commenters supported the application of these requirements to 
diesel-powered equipment, and they have been applied to permissible 
equipment under the final rule. Some existing part 36-approved 
equipment will require minor modifications to comply with the 
requirements of Sec. 75.1909(c). Section 75.1909(b)(7) essentially 
requires independent service brake systems for the front and rear 
wheels of vehicles. This is a well-recognized safety feature that is 
warranted for part 36-approved diesel-powered equipment as well as for 
nonpermissible equipment covered by Sec. 75.1909. Although the majority 
of part 36-approved equipment is already provided with this feature, a 
limited number of machines will require modification. Because some mine 
operators will need to obtain field modifications and equipment 
manufacturers must obtain MSHA approval of design modifications, a 36-
month compliance time is appropriate and is provided for in the final 
rule.
    Section 75.1909 of the final rule requires that nonpermissible 
diesel-powered equipment be equipped with a supplemental brake system, 
which provides substantially the same features as would be provided by 
the automatic emergency parking brakes specified in

[[Page 55458]]

Sec. 75.523-3. Section 75.1909(e) requires setting of the supplemental 
brake system when the operator is not at the controls of the equipment, 
except during the movement of disabled equipment. Because part 36-
approved equipment is provided with a supplemental brake system under 
the final rule, the requirement for setting of the supplemental brake 
has also been applied to this equipment.
    Paragraph (b)(4) requires that equipment approved under part 36 
have a particulate index and a dilution air quantity determined in 
accordance with part 7, subpart E within 12 months of the publication 
date of the final rule. The types of engines that are affected by this 
requirement are installed in permissible face equipment that is 
currently approved under part 36. Because of where and how this 
equipment is used, it significantly affects the air quality where 
miners work and travel. Diesel-powered face equipment includes haulage 
equipment and roof bolters, which are typically used in the confined 
environment in the production area of the face and operated almost 
continuously over the course of a shift. The contribution of diesel 
exhaust from this equipment into the mine atmosphere can be significant 
and can adversely affect the health conditions for miners working in 
and around the area where the equipment is being operated. Under new 
requirements in Sec. 75.325 of the final rule, minimum ventilating air 
quantities are established for areas where diesel-powered equipment 
operates. These minimum quantities are derived from the approval plate 
ventilating air quantity for the equipment that is operating. 
Consequently, ventilating air quantities must be calculated for these 
engines so that the minimum air quantity requirements can be 
implemented. As mentioned elsewhere in this preamble, the particulate 
index will not be used to determine the minimum ventilating air 
quantity for the engine, but will be available for informational 
purposes.
    There are only four engines models used in the majority of part 36-
approved equipment used in underground coal mines. These engines are 
typically of older design, and it is uncertain whether the engine 
manufacturers will seek approval for their engine designs under subpart 
E of part 7. As a result, MSHA intends to determine dilution air 
quantities and particulate indices for these engines in accordance with 
part 7, subpart E, whether or not the manufacturers seek a subpart E 
approval for their engines. MSHA will make this information available 
to mine operators, which must be applied and implemented within 12 
months of the date of the final rule's publication. This time frame is 
consistent with the 12-month effective date for compliance with the 
ventilation requirements of Sec. 75.325(k) of the final rule that apply 
where diesel-powered equipment is operated.
    Paragraph (b)(5) requires that permissible diesel-powered equipment 
that is manufactured 36 months or more after the publication date of 
the final rule and used in an underground coal mine incorporate a power 
package approved under part 7, subpart F. Under the proposal, only 
``new'' diesel-powered equipment approved under subpart H or I or 
meeting the requirements of Secs. 75.1909 and 1910 could be introduced 
into underground coal mines 60 months after the effective date of 
Sec. 75.1907. This meant that both new permissible and nonpermissible 
equipment (that did not fall into the limited class or was not used as 
stationary unattended equipment) introduced in an underground coal mine 
after the deadline would have had to receive a full machine approval. 
One commenter recommended that the proposed 60-month delayed effective 
date be changed to 12 months. Another commenter suggested that the 
language be clarified to state that existing part 36 approvals remain 
valid.
    The time frame for compliance has been reduced to 36 months in 
recognition of the fact that the final rule does not require full 
machine approval of all permissible and nonpermissible equipment, as 
contemplated by the proposal. Three years should be sufficient for 
equipment manufacturers to obtain approval for and incorporate subpart 
F power packages into the permissible diesel-powered equipment they 
manufacture. Part 36-approved equipment manufactured before the 
relevant date may continue to be used in accordance with its approval 
indefinitely.
    Paragraph (c) requires nonpermissible diesel-powered equipment to 
comply with Secs. 75.1909 and 75.1910 within 36 months of the 
publication date of the rule. Under the final rule nonpermissible 
equipment, which is used in areas where permissible electric equipment 
is not required, does not need full machine approval by MSHA. However, 
under Sec. 75.1909(a)(1) nonpermissible equipment must be equipped with 
an engine approved under subpart E of part 7. The final rule did not 
adopt the proposed establishment of a limited class of nonpermissible 
light-duty equipment, for reasons explained in detail in the preamble 
to Sec. 75.1908. Instead, the final rule establishes two categories of 
nonpermissible equipment, heavy-duty and light-duty. Under paragraph 
(c) of this section of the final rule, equipment in both categories 
must be provided with the safety features set forth in Secs. 75.1909 
and 75.1910. These features include engines approved under subpart E of 
part 7, fire suppression systems, brakes, and electrical protections. 
Several commenters stated that approved engines, power packages, or 
surface temperature controls are unnecessary for nonpermissible 
equipment, while other commenters considered surface temperature 
controls necessary.
    The final rule's equipment safety requirements for nonpermissible 
diesel-powered equipment are intended to ensure that the equipment will 
not present a fire hazard and that gaseous diesel exhaust emissions and 
particulate emissions are addressed.
    A compliance time of 24 months was proposed, and one commenter 
recommended a 12-month compliance time. The final rule allows 36 months 
for nonpermissible equipment to comply with the requirements of 
Secs. 75.1909 and 75.1910. Included in these sections is a requirement 
that nonpermissible equipment be provided with an engine approved under 
subpart E of part 7. It is expected that this requirement will require 
the longest time period for compliance, as engine manufacturers must 
first obtain MSHA approval of appropriate engines. The 36-month time 
frame allows some models of nonpermissible equipment currently in use 
in underground coal mines to reach the end of its useful life and to be 
replaced with equipment that meets these requirements, rather than 
being retrofitted with a new engine and the other features required by 
Secs. 75.1909 and 75.1910.
    The final rule does not adopt the proposed provision allowing mine 
operators to seek MSHA approval for the extended use of diesel-powered 
locomotives because of the unavailability of approved power packages 
suitable for the mine conditions or for the locomotive's design. This 
provision recognized that certain types of diesel locomotives might not 
have been able to be retrofitted to meet all of the applicable 
equipment-related requirements. Because the final rule does not require 
approved power packages for nonpermissible equipment, a process for 
MSHA approval of extended use of nonpermissible locomotives without 
approved power packages is no longer

[[Page 55459]]

necessary, and has consequently not been adopted in the final rule.
Section 75.1908  Nonpermissible Diesel-Powered Equipment; Categories
    This section of the final rule establishes three categories of 
nonpermissible diesel-powered equipment: heavy-duty equipment, which is 
defined as equipment that is used for such tasks as cutting or moving 
rock or coal, drilling or bolting, or moving longwall components; 
light-duty equipment, which includes any other nonpermissible equipment 
that is not heavy-duty; and a special category for ambulances and fire 
fighting equipment. Because nonpermissible equipment is used in areas 
of the mine where methane is not likely to accumulate, it is not 
required to be explosion-proof. However, all nonpermissible equipment, 
with the exception of ambulances and other emergency equipment 
described under paragraph (d), is required to have an engine approved 
under subpart E of part 7, which sets engine performance and exhaust 
emissions requirements.
    The requirements that apply to nonpermissible equipment under the 
final rule vary according to the equipment's category. Most 
importantly, the equipment category determines which equipment safety 
features are required under Secs. 75.1909 and 75.1910 of the final 
rule. One of the most important distinctions between heavy-and light-
duty equipment under the final rule is that heavy-duty equipment is 
required to have an automatic fire suppression system under 
Sec. 75.1909, while light-duty equipment may be provided with either a 
manual or automatic system. Additionally, heavy-duty nonpermissible 
equipment is subject to the weekly undiluted exhaust emissions test 
under Sec. 75.1914(g) of the final rule, and must also be included in 
the air quantity calculation for multiple units of diesel-powered 
equipment under Sec. 75.325(g). These provisions do not apply to light-
duty equipment.
    The final rule is a significant departure from the proposal, in 
response to a majority of commenters who were opposed to the proposed 
criteria for the equipment categories. The proposal would have 
established a special category of nonpermissible ``limited class'' 
equipment. Limited class equipment under the proposal would have been 
equipment weighing less than 6,000 pounds and equipped with an engine 
of less than 90 horsepower. Equipment with a hydraulic system could not 
be included in the limited class, although MSHA stated in the preamble 
to the proposal that this restriction was not intended to apply to 
hydraulic systems used in brake units or automotive-style power assist 
units. Additionally, the equipment engine could not be turbocharged. 
Portable equipment that fell into this class was limited to welders and 
compressors. The proposal also allowed altitude compensation devices to 
be used with limited class equipment.
    Although limited class equipment under the proposal would have been 
required to have an engine approved under subpart E of part 7, the 
machine as a whole would not have been approved by MSHA. Instead, 
limited class equipment would have been required to be equipped with 
the safety features in proposed Sec. 75.1909. All other nonpermissible 
equipment would have been required to have a subpart F or G approved 
``power package,'' which would have included an approved engine with 
additional components to prevent the ignition of methane or combustible 
materials, such as surface temperature controls. Additionally, it was 
MSHA's intention, reflected in the advance notice of proposed 
rulemaking published with the proposal, to require whole machine 
approval of all nonpermissible equipment, except equipment that fell 
into the limited class defined under the proposal.
    The equipment categories in the proposed rule were based upon the 
Diesel Advisory Committee recommendation that fire prevention features, 
including surface temperature controls and fire suppression systems, be 
required on all outby equipment. However, the Committee recognized that 
much of the light-duty equipment in use in mines was not specifically 
designed for mining and might not be available with surface temperature 
controls. The Committee therefore concluded that a limited class of 
light-duty equipment could be safely operated if it was equipped with 
fire prevention and protection features in lieu of surface temperature 
controls, such as fire suppression devices, reduction of the potential 
for fuels to contact hot surfaces, and reduction of potential ignition 
sources. Equipment in this limited class would be expected to operate 
on a light-duty cycle, and would not reach high temperatures or would 
reach high temperatures for a limited period of time, with a 
significantly reduced potential for fire.
    Commenters expressed widely varying views on this aspect of the 
proposal. Most commenters supported the concept of a distinct class of 
equipment with less extensive safety requirements, but many stated that 
the criteria in the proposal for limited class equipment were 
unnecessarily restrictive, and that the class should be significantly 
broadened to include many more types of equipment, such as light-duty 
manned personnel and material haulage equipment. A number of commenters 
indicated that the equipment that they would consider light-duty 
equipment in their mines exceeded either the weight or horsepower 
restrictions of the proposal.
    Other commenters were of the opinion that fire suppression systems 
were an acceptable substitute for surface temperature controls, and 
strongly supported a significant expansion of the equipment falling 
into the limited class and therefore not required to have a power 
package that would provide such controls. A number of commenters also 
indicated that much of the equipment currently in use in mines that did 
not fall into the proposed limited class would have to be replaced, 
because it would be impossible to retrofit the equipment to provide the 
required surface temperature controls. Other commenters were concerned 
that limitations based on existing equipment designs could discourage 
the development of new technology.
    One commenter was generally opposed to the creation of a limited 
class that was not required to have surface temperature controls, 
because the commenter believed that this would present an unacceptable 
fire hazard. This commenter stated that heat sensors that triggered 
engine shutdown or fire suppression were not acceptable substitutes for 
surface temperature controls.
    A number of commenters were opposed to the limitation on equipment 
weight, stating that weight had no relationship to the hazards 
presented by the equipment, and that the 6,000-pound restriction was 
arbitrary. One commenter stated that although weight in some cases 
could be an indicator of duty cycle and the potential for higher 
equipment operating temperatures and resulting fires, requirements for 
fire suppression and automatic engine shutdown when engine temperature 
reaches a specified limit would adequately address these concerns. 
Another commenter stated that most diesel equipment that exceeds 6,000 
pounds is not used in heavy-duty applications such as coal production 
but is considered light-duty equipment.
    Some commenters were particularly concerned about the safety impact 
of the weight limitation on railmounted equipment, pointing out that 
weight is needed to provide traction. These commenters stated that 
although some

[[Page 55460]]

rail-mounted equipment would fall below the proposed horsepower 
limitation, the weight of most rail-mounted equipment significantly 
exceeds 6,000 pounds, and that it would be neither practical nor 
feasible to modify existing outby track equipment to meet the proposed 
limited class criteria. Because of this concern, one commenter 
suggested that outby rail-mounted equipment be addressed in a separate 
category, without a weight restriction.
    Several commenters also stated that the safety features that would 
be required on limited class equipment under proposed Sec. 75.1909 
would add to the vehicle weight, making the 6,000-pound restriction 
even more unrealistic in those commenters' opinion. One commenter 
estimated that equipment retrofits for safety features and for mine-
worthiness would increase equipment weight by at least 50 percent. 
Another commenter suggested that the proposed weight limitation would 
result in overloading equipment units because of light construction. 
Some suggested that the weight limitation for limited class equipment 
be increased to 7,500 or 8,500 pounds; others recommended that the 
limit be increased to 14,000 to 15,000 pounds, to permit units to be 
manufactured with heavy steel to withstand collisions. One commenter 
recommended that the weight limitation be reduced to 4,000 pounds for 
self-propelled equipment.
    A number of commenters were also opposed to the 90-horsepower 
limitation, stating that engine horsepower was no more an indication of 
whether equipment was heavy-duty or light-duty than was equipment 
weight. However, one commenter recommended that the limitation be 
reduced to less than 70 horsepower.
    Commenters were also concerned about the prohibition against 
hydraulic systems on limited class equipment. Several commenters stated 
that there was no basis for excluding equipment with hydraulic systems 
from the limited class, except for the fact that hydraulic fluid could 
present a fire hazard. These commenters suggested that equipment with 
hydraulic systems that utilized fire-resistant hydraulic fluid should 
be permitted. Some of these commenters also suggested that equipment 
with hydraulic systems should be eligible for the limited class 
category if the equipment is equipped with a fire-suppression system. 
Other commenters stated that equipment with hydraulic systems had not 
been shown to be less safe than equipment without such systems. Some 
pointed out that hydraulic systems facilitate the handling of supplies 
and materials, making the job easier and safer. These commenters also 
believed that prohibiting hydraulic systems on limited class equipment 
would preclude other equipment features that enhance safety, such as 
power take-offs, automatic transmissions, and hydrostatic drive units.
    Commenters were also opposed to the prohibition against 
turbocharged engines for limited class equipment. This restriction was 
included in the proposal because of the concern about the potential 
ignition of combustible materials on the hot exhaust system surfaces 
that are characteristic of turbocharged engines. Commenters stated that 
turbochargers have served as an effective means of yielding greater 
horsepower from smaller engines and should be allowed on limited class 
equipment, and that the exhaust components could be encased in 
protective insulating material to eliminate any fire hazard.
    A number of commenters expressed concern that manufacturers of 
equipment that was not specifically designed for use in mines would not 
seek MSHA approval for their equipment because the share of the market 
for mining applications was too small to warrant the expense of 
developing power packages.
    A number of commenters stated that inclusion of equipment in a 
limited class should depend on how the equipment is being used rather 
than on factors such as size and weight. Some of these commenters 
suggested that light- duty equipment include equipment that does not 
move rock, coal, or longwall shields. Other commenters advocated that 
all diesel-powered equipment, including limited class equipment, be 
designed to be explosion-proof and be approved by MSHA under part 7. 
These commenters felt that establishing a limited class of light-duty 
equipment would allow mine operators to use equipment with inferior 
means of fire prevention.
    One commenter recommended that a determination of the equipment 
included in the limited class should be based on MSHA's evaluation of 
diesel equipment fire experience in other industries and in other 
countries as to which types of equipment do and do not pose a 
significant fire hazard. In response to this comment, MSHA acquired 
accident reports from the Ministry of Labor, Province of Ontario, 
Canada, containing detailed information of fires on diesel-powered 
equipment in underground mines in Ontario for the years 1984 through 
1992. This information was carefully analyzed to determine which 
machine safety features and what type of equipment design are needed to 
prevent fires on diesel-powered equipment used in underground coal 
mines. An analysis of the Ontario fire data reveals that equipment used 
in heavy-duty type activities, such as hauling rock or coal or moving 
longwall components, presents a significant fire hazard and requires 
suitable fire prevention and protection features.
    Consistent with these conclusions and also with the recommendations 
of a number of commenters, paragraphs (a)(1) through (a)(5) of this 
section of the final rule specify what constitutes heavy-duty 
equipment. Heavy-duty nonpermissible equipment includes equipment that 
cuts or moves rock or coal; equipment that performs drilling or bolting 
functions; equipment that moves longwall components; self-propelled 
diesel fuel transportation units and lube units; and machines used to 
transport portable fuel transportation units or lube units. These 
machines are intended to move rock or coal or other heavy loads, such 
as longwall components, or move large quantities of combustible diesel 
fuel as a normal part of their duty cycle. Locomotives used to 
transport rock or coal and portable diesel fuel transportation units or 
lube units would also be in the heavy-duty equipment category under the 
final rule. Graders would also be considered heavy-duty equipment, 
because they are used to move rock or coal.
    Equipment falling within the heavy-duty equipment category under 
paragraph (a) is typically used for extended periods during a shift on 
a continuous, rather than intermittent, basis. This is in contrast to 
equipment that is used for limited periods during a shift, such as 
mantrips or supply vehicles. Heavy-duty equipment under the final rule 
also moves heavy loads or performs considerable work as in the case of 
drilling machines. Equipment used to haul longwall components is 
typically operated at a consistently accelerated pace under an 
extremely heavy load. Fuel transportation units and lube units 
generally are larger machines specially designed to transport and 
dispense diesel fuel, hydraulic fluid, grease, oil, and other 
combustible materials. This equipment also operates under a heavy load 
and typically moves constantly around a section during the course of a 
shift, refueling equipment as needed. Equipment that performs drilling 
and bolting functions generally has an engine that runs at a high rate 
of speed and powers large hydraulic systems. Under the final rule 
heavy-duty

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equipment must be provided with an automatic fire suppression system, 
addressing the additional fire risks resulting from the way this 
equipment is used. Heavy-duty equipment also produces greater levels of 
gaseous contaminants, and under the final rule is therefore subject to 
weekly undiluted exhaust emissions tests under Sec. 75.1914(g), and is 
included in the air quantity calculation for ventilation of diesel-
powered equipment under Sec. 75.325(g).
    Under paragraph (b) light-duty equipment is defined as any other 
diesel-powered equipment that does not meet the criteria of paragraph 
(a). This is in contrast to the approach taken in the proposed rule 
establishing a limited class of light-duty equipment. Light-duty 
equipment under the final rule may include, but is not limited to, 
forklifts used to carry supplies, rock dusting machines, tractors not 
used to move rock or coal, supply trucks, water trucks, personnel 
carriers, jeeps, scooters, golf carts, and pickup trucks. The equipment 
may be rubber-tired, crawler-mounted, or rail-mounted.
    Under the final rule two machines of the same model could fall into 
different equipment categories, depending on how they are used. For 
example, a load-haul-dump unit used to move rock or coal would be 
considered heavy-duty equipment, while an identical machine used 
exclusively to move supplies would be a light-duty machine, subject to 
different requirements. Although these machines are of the same design, 
they do not present the same risk of fire because of the way they are 
used. They also do not produce the same quantities of exhaust 
contaminants: machines that are operated for extended periods of time 
under heavy load generate more contaminants than machines that are not.
    Equipment that is classified as light-duty may not be used, even 
intermittently, to perform the functions listed in paragraphs (a)(1) 
through (a)(5). This is because equipment that performs heavy-duty 
functions poses an increased fire risk, resulting in the need for an 
automatic fire suppression system, as required under Sec. 75.1909 for 
heavy-duty equipment. On the other hand, heavy-duty equipment may be 
used to perform light-duty work.
    The proposed restriction of portable limited class equipment to 
compressors and welders has not been adopted in the final rule. 
Although one commenter did support this restriction, most commenters 
were opposed to it, stating that it was arbitrary and unjustified as 
well as impractical. One commenter stated that the proposed restriction 
would require major replacement of diesel-powered portable equipment, 
either by electric-powered machines or by diesel equipment furnished 
with power packages. Other commenters suggested that attended diesel 
generators be added to the limited class because they presented safety 
concerns that were no greater than for welders and compressors.
    In response to these comments, any type of attended portable 
diesel-powered equipment may be light-duty under the final rule, so 
long as it does not perform any of the functions listed in paragraph 
(a). As discussed more fully above, the distinction between light-duty 
and heavy-duty equipment has less significance under the final rule 
than it would have had under the proposal, since neither light-duty nor 
heavy-duty nonpermissible equipment will be required to have a surface 
temperature-controlled power package or be subject to fully assembled 
machine approval.
    One commenter suggested that the term ``attended'' be defined in 
the final rule, and paragraph (c) specifies that attended diesel-
powered equipment for purposes of subpart T includes: any machine or 
device that is operated by a miner; and any machine or device that is 
mounted in the direct line of sight of a job site located within 500 
feet of such machine or device, which job site is occupied by a miner.
    This definition of ``attended'' is largely derived from the 
definition of ``attended'' in existing Sec. 75.1107-1 applicable to 
electric-powered equipment, although it has been tailored to address 
safety concerns unique to diesel-powered equipment, such as the fact 
that fires on diesel-powered equipment, unlike fires on electrical 
equipment, do not smolder for a very long time and therefore are less 
likely to be discovered before flaming and spreading. For this reason 
and unlike equipment under Sec. 75.1107-1, attended equipment under 
paragraph (c) must be continuously attended while it is operating, 
regardless of whether it is during a production shift. Also unlike 
equipment under Sec. 75.1107-1, attended equipment under paragraph (c) 
does not need to be attended by the person assigned to operate it. The 
definition of ``attended'' in this section permits prompt operator 
action in the event of a fault or fire on a diesel-powered machine. As 
discussed elsewhere in this preamble, the category of ``stationary 
unattended'' equipment has not been adopted in the final rule, and 
under Sec. 75.1916(e) all diesel-powered equipment must be attended 
when operated.
    Paragraph (d) establishes a special equipment category for diesel-
powered ambulances and fire fighting equipment, which may be used 
underground only in accordance with the fire fighting and evacuation 
plan required under existing Sec. 75.1101-23. This special category was 
included in the proposal under Sec. 75.1907(b), but has been included 
in this section of the final rule with the other categories of 
nonpermissible equipment. Equipment that falls into this category is 
not required to have an approved engine or power package, or to comply 
with the requirements of Secs. 75.1909 and 75.1910. Instead, such 
equipment must be used in accordance with the fire fighting and 
evacuation plan required under existing Sec. 75.1101-23.
    This provision was addressed by only a few commenters, who 
supported the establishment of a special class of diesel-powered 
equipment for emergency use, and has been adopted essentially unchanged 
from the proposal. The equipment under this paragraph may be used only 
during emergencies and the fire drills specified in the fire-fighting 
and evacuation plan. Very little equipment that is currently in use 
falls into this category. Mines that do have such equipment must 
provide MSHA with revised fire fighting and evacuation plans that 
adequately address the use of this equipment.
Sections 75.1909 and 1910  Design and Performance Requirements for 
Nonpermissible Diesel-Powered Equipment
    Overview. Sections 75.1909 and 75.1910 of the final rule set forth 
the design and performance requirements that apply to nonpermissible 
diesel-powered equipment, except for the special category of emergency 
equipment established under Sec. 75.1908(d) of the final rule. Section 
75.1909 requires, among other things, nonpermissible diesel-powered 
equipment to be provided with engines approved under subpart F of part 
7, fire suppression systems, fuel systems, and brakes. For ease of 
reference, electrical system requirements, which were proposed under 
Sec. 75.1909, have been adopted in the final rule in Sec. 75.1910.
    As explained in greater detail in the preamble discussion for 
Sec. 75.1908 of the final rule, the proposal would have established a 
``limited class'' of light-duty equipment, which, although required to 
have an approved engine, was not otherwise subject to MSHA approval. 
Instead, limited class equipment would have been governed by the design 
and performance requirements set forth in proposed



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