NESHAPS: Final Standards for Hazardous Air Pollutants for Hazardous Waste Combustors

[Federal Register: September 30, 1999 (Volume 64, Number 189)]
[Rules and Regulations]
[Page 52827-52876]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr30se99-24]

[[Page 52827]]

_______________________________________________________________________

Part II

Environmental Protection Agency

_______________________________________________________________________

40 CFR Part 60, et al.

NESHAPS: Final Standards for Hazardous Air Pollutants for Hazardous
Waste Combustors; Final Rule

[[Page 52828]]

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 60, 63, 260, 261, 264, 265, 266, 270, and 271

[FRL-6413-3]
RIN 2050-AEO1

NESHAPS: Final Standards for Hazardous Air Pollutants for
Hazardous Waste Combustors

ACTION: Final rule.

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

SUMMARY: We are promulgating revised standards for hazardous waste
incinerators, hazardous waste burning cement kilns, and hazardous waste
burning lightweight aggregate kilns. These standards are being
promulgated under joint authority of the Clean Air Act (CAA) and
Resource Conservation and Recovery Act (RCRA). The standards limit
emissions of chlorinated dioxins and furans, other toxic organic
compounds, toxic metals, hydrochloric acid, chlorine gas, and
particulate matter. These standards reflect the performance of Maximum
Achievable Control Technologies (MACT) as specified by the Clean Air
Act. These MACT standards also will result in increased protection to
human health and the environment over existing RCRA standards.

DATES: This final rule is in effect on September 30, 1999. You are
required to be in compliance with these promulgated standards 3 years
following the effective date of the final rule (i.e., September 30,
2002). You are provided with the possibility of a site-specific one
year extension for the installation of controls to comply with the
final standards or for waste minimization reductions. The incorporation
by reference of certain publications listed in the rule was approved by
the Director of the Federal Register as of September 30, 1999.

ADDRESSES: The official record (i.e., public docket) for this
rulemaking is identified as Docket Numbers: F-96-RCSP-FFFFF, F-97-CS2A-
FFFFF, F-97-CS3A-FFFFF, F-97-CS4A-FFFFF, F-97-CS5A-FFFFF, F-97-CS6A-
FFFFF, F-98-RCSF-FFFFF, and F-1999-RC2F-FFFFF. The official record is
located in the RCRA Information Center (RIC), located at Crystal
Gateway One, 1235 Jefferson Davis Highway, First Floor, Arlington,
Virginia. The mailing address for the official record is RCRA
Information Center, Office of Solid Waste (5305W), U.S. Environmental
Protection Agency Headquarters, 401 M Street, SW, Washington, DC 20460.
Public comments and supporting materials are available for viewing
in the RIC. The RIC is open from 9 a.m. to 4 p.m., Monday through
Friday, excluding federal holidays. To review docket materials, you
must make an appointment by calling 703-603-9230 or by sending a
message via e-mail to: RCRA-Docket@epamail.epa.gov. You may copy a
maximum of 100 pages from any regulatory docket at no charge.
Additional copies cost 15 cent/page. The index for the official record
and some supporting materials are available electronically. See the
``Supplementary Information'' section of this Federal Register notice
for information on accessing the index and these supporting materials.

FOR FURTHER INFORMATION CONTACT: For general information, you can
contact the RCRA Hotline at 1-800-424-9346 or TDD 1-800-553-7672
(hearing impaired). In the Washington metropolitan area, call 703-412-
9810 or TDD 703-412-3323. For additional information on the Hazardous
Waste Combustion MACT rulemaking and to access available electronic
documents, please go to our Web page: www.epa.gov/hwcmact. Any
questions or comments on this rule can also be sent to EPA via our Web
page.
For more detailed information on technical requirements of this
rulemaking, you can contact Mr. David Hockey, 703-308-8846, electronic
mail: Hockey.David@epamail.epa.gov. For more detailed information on
permitting associated with this rulemaking, you can contact Ms.
Patricia Buzzell, 703-308-8632, electronic mail:
Buzzell.Tricia@epamail.epa.gov. For more detailed information on
compliance issues associated with this rulemaking, you can contact Mr.
Larry Gonzalez, 703-308-8468, electronic mail:
Gonzalez.Larry@epamail.epa.gov. For more detailed information on the
assessment of potential costs, benefits and other impacts associated
with this rulemaking, you can contact Mr. Lyn Luben, 703-308-0508,
electronic mail: Luben.Lyn@epamail.epa.gov. For more detailed
information on risk analyses associated with this rulemaking, you can
contact Mr. David Layland, 703-308-0482, electronic mail:
Layland.David@epamail.epa.gov.

SUPPLEMENTARY INFORMATION:
Official Record. The official record is the paper record maintained
at the address in ADDRESSES above. All comments that were received
electronically were converted into paper form and placed in the
official record, which also includes all comments submitted directly in
writing. Our responses to comments, whether the comments are written or
electronic, are located in the response to comments document in the
official record for this rulemaking.
Supporting Materials Availability on the Internet. The index for
the official record and the following supporting materials are
available on the Internet as:
--Technical Support Documents for HWC MACT Standards:
--Volume I: Description of Source Categories
--Volume II: HWC Emissions Database
--Volume III: Selection of MACT Standards and Technologies
--Volume IV: Compliance with the MACT Standards
--Volume V: Emission Estimates and Engineering Costs
--Assessment of the Potential Costs, Benefits and Other Impacts of the
Hazardous Waste Combustion MACT Standards--Final Rule
--Risk Assessment Support to the Development of Technical Standards for
Emissions from Combustion Units Burning Hazardous Wastes: Background
Information Document
--Response to Comments for the HWC MACT Standards Document

To access the information electronically from the World Wide Web
(WWW), type: www.epa.gov/hwcmact

Outline

Acronyms Used in the Rule

acfm--Actual cubic feet per minute
BIF--Boilers and industrial furnaces
CAA--Clean Air Act
CEMS--Continuous emissions monitors/monitoring system
CFR--Code of Federal Regulations
DOC--Documentation of Compliance
DRE--Destruction and Removal Efficiency
dscf--Dry standard cubic foot
dscm--Dry standard cubic meter
EPA/USEPA--United States Environmental Protection Agency gr--Grains
HSWA--Hazardous and Solid Waste Amendments
kg--Kilogram
MACT--Maximum Achievable Control Technology
mg--Milligrams
Mg--Megagrams (metric tons)
NOC--Notification of Compliance
NESHAP--National Emission Standards for HAPs
ng--Nanograms
NODA--Notice of Data Availability
NPRM--Notice of Proposed Rulemaking
POHC--Principal Organic Hazardous Constituent

[[Page 52829]]

ppmv--Parts per million by volume
ppmw--Parts per million by weight
RCRA--Resource Conservation and Recovery Act
R & D--Research and Development
SSRA--Site specific risk assessment
TEQ--Toxicity equivalence
g--Micrograms

Outline

Part One: Overview and Background for This Rule
I. What Is the Purpose of This Rule?
II. In Brief, What Are the Major Features of Today's Rule?
A. Which Source Categories Are Affected By This Rule?
B. How Are Area Sources Affected By This Rule?
C. What Emission Standards Are Established In This Rule?
D. What Are the Procedures for Complying with This Rule?
E. What Subsequent Performance Testing Must Be Performed?
F. What Is the Time Line for Complying with This Rule?
G. How Does This Rule Coordinate With the Existing RCRA
Regulatory Program?
III. What Is the Basis of Today's Rule?
IV. What Was the Rulemaking Process for Development of This
Rule?
Part Two: Which Devices Are Subject to Regulation?
I. Hazardous Waste Incinerators
II. Hazardous Waste Burning Cement Kilns
III. Hazardous Waste Burning Lightweight Aggregate Kilns
Part Three: How Were the National Emission Standards for Hazardous
Air Pollutants (NESHAP) in This Rule Determined?
I. What Authority Does EPA Have to Develop a NESHAP?
II. What Are the Procedures and Criteria for Development of
NESHAPs?
A. Why Are NESHAPs Needed?
B. What Is a MACT Floor?
C. How Are NESHAPs Developed?
III. How Are Area Sources and Research, Development, and
Demonstration Sources Treated in this Rule?
A. Positive Area Source Finding for Hazardous Waste Combustors
1. How Are Area Sources Treated in this Rule?
2. What Is an Area Source?
3. What Is the Basis for Today's Positive Area Source Finding?
B. How Are Research, Development, and Demonstration (RD&D)
Sources Treated in this Rule?
1. Why Does the CAA Give Special Consideration to Research and
Development (R&D) Sources?
2. When Did EPA Notice Its Intent to List R&D Facilities?
3. What Requirements Apply to Research, Development, and
Demonstration Hazardous Waste Combustor Sources?
IV. How Is RCRA's Site-Specific Risk Assessment Decision Process
Impacted by this Rule?
A. What Is the RCRA Omnibus Authority?
B. How Will the SSRA Policy Be Applied and Implemented in Light
of this Mandate?
1. Is There a Continuing Need for Site-Specific Risk
Assessments?
2. How Will the SSRA Policy Be Implemented?
C. What Is the Difference Between the RCRA SSRA Policy and the
CAA Residual Risk Requirement?
Part Four: What Is The Rationale for Today's Final Standards?
I. Emissions Data and Information Data Base
A. How Did We Develop the Data Base for this Rule?
B. How Are Data Quality and Data Handling Issues Addressed?
1. How Are Data from Sources No Longer Burning Hazardous Waste
Handled?
2. How Are Nondetect Data Handled?
3. How Are Normal Versus Worst-Case Emissions Data Handled?
4. What Approach Was Used to Fill In Missing or Unavailable
Data?
II. How Did We Select the Pollutants Regulated by This Rule?
A. Which Toxic Metals Are Regulated by This Rule?
1. Semivolatile and Low Volatile Metals
2. How Are the Five Other Metal Hazardous Air Pollutants
Regulated?
B. How Are Toxic Organic Compounds Regulated By This Rule?
1. Dioxins/Furans
2. Carbon Monoxide and Hydrocarbons
3. Destruction and Removal Efficiency
C. How Are Hydrochloric Acid and Chlorine Gas Regulated By This
Rule?
III. How Are the Standards Formatted In This Rule?
A. What Are the Units of the Standards?
B. Why Are the Standards Corrected for Oxygen and Temperature?
C. How Does the Rule Treat Significant Figures and Rounding?
IV. How Are Nondioxin/Furan Organic Hazardous Air Pollutants
Controlled?
A. What Is the Rationale for DRE as a MACT Standard?
1. MACT DRE Standard
2. How Can Previous Successful Demonstrations of DRE Be Used To
Demonstrate Compliance?
3. DRE for Sources that Feed Waste at Locations Other Than the
Flame Zone
4. Sources that Feed Dioxin Wastes
B. What Is the Rationale for Carbon Monoxide or Hydrocarbon
Standards as Surrogate Control of Organic Hazardous Air Pollutants?
V. What Methodology Is Used to Identify MACT Floors?
A. What Is the CAA Statutory Requirement to Identify MACT
Floors?
B. What Is the Final Rule Floor Methodology?
1. What Is the General Approach Used in this Final Rule?
2. What MACT Floor Approach Is Used for Each Standard?
C. What Other Floor Methodologies Were Considered?
1. April 19, 1996 Proposal
2. May 1997 NODA.
D. How Is Emissions Variability Accounted for in Development of
Standards?
1. How Is Within-Test Condition Emissions Variability Addressed?
2. How Is Waste Imprecision in the Stack Test Method Addressed?
3. How Is Source-to-Source Emissions Variability Addressed?
VI. What Are the Standards for Existing and New Incinerators?
A. To Which Incinerators Do Today's Standards Apply?
B. What Subcategorization Options Did We Evaluate?
C. What Are the Standards for New and Existing Incinerators?
1. What Are the Standards for Incinerators?
2. What Are the Standards for Dioxins and Furans?
3. What Are the Standards for Mercury?
4. What Are the Standards for Particulate Matter?
5. What Are the Standards for Semivolatile Metals?
6. What Are the Standards for Low Volatile Metals?
7. What Are the Standards for Hydrochloric Acid and Chlorine
Gas?
8. What Are the Standards for Carbon Monoxide?
9. What Are the Standards for Hydrocarbon?
10. What Are the Standards for Destruction and Removal
Efficiency?
VII. What Are the Standards for Hazardous Waste Burning Cement
Kilns?
A. To Which Cement Kilns Do Today's Standards Apply?
B. How Did EPA Initially Classify Cement Kilns?
1. What Is the Basis for a Separate Class Based on Hazardous
Waste Burning?
2. What Is the Basis for Differences in Standards for Hazardous
Waste and Nonhazardous Waste Burning Cement Kilns?
C. What Further Subcategorization Considerations Are Made?
D. What Are The Standards for Existing and New Cement Kilns?
1. What Are the Standards for Cement Kilns?
2. What Are the Dioxin and Furan Standards?
3. What Are the Mercury Standards?
4. What Are the Particulate Matter Standards?
5. What Are the Semivolatile Metals Standards?
6. What Are the Low Volatile Metals Standards?
7. What Are the Hydrochloric Acid and Chlorine Gas Standards?
8. What Are the Hydrocarbon and Carbon Monoxide Standards for
Kilns Without By-Pass Sampling Systems?
9. What Are the Carbon Monoxide and Hydrocarbon Standards for
Kilns With By-Pass Sampling Systems?
10. What Are the Destruction and Removal Efficiency Standards?
VIII. What Are the Standards for Existing and New Hazardous
Waste Burning Lightweight Aggregate Kilns?
A. To Which Lightweight Aggregate Kilns Do Today's Standards
Apply?
B. What Are the Standards for New and Existing Hazardous Waste
Burning Lightweight Aggregate Kilns?
1. What Are the Standards for Lightweight Aggregate Kilns?

[[Page 52830]]

2. What Are the Dioxin and Furan Standards?
3. What Are the Mercury Standards?
4. What Are the Particulate Matter Standards?
5. What Are the Semivolatile Metals Standards?
6. What Are the Low Volatile Metals Standards?
7. What Are the Hydrochloric Acid and Chlorine Gas Standards?
8. What Are the Hydrocarbon and Carbon Monoxide Standards?
9. What Are the Standards for Destruction and Removal
Efficiency?
Part Five: Implementation
I. How Do I Demonstrate Compliance with Today's Requirements?
A. What Sources Are Subject to Today's Rules?
1. What Is an Existing Source?
2. What Is a New Source?
B. How Do I Cease Being Subject to Today's Rule?
C. What Requirements Apply If I Temporarily Cease Burning
Hazardous Waste?
1. What Must I Do to Comply with Alternative Compliance
Requirements?
2. What Requirements Apply If I Do Not Use Alternative
Compliance Requirements?
D. What Are the Requirements for Startup, Shutdown and
Malfunction Plans?
E. What Are the Requirements for Automatic Waste Feed Cutoffs?
F. What Are the Requirements of the Excess Exceedance Report?
G. What Are the Requirements for Emergency Safety Vent Openings?
H. What Are the Requirements for Combustion System Leaks?
I. What Are the Requirements for an Operation and Maintenance
Plan?
II. What Are the Compliance Dates for this Rule?
A. How Are Compliance Dates Determined?
B. What Is the Compliance Date for Sources Affected on April 19,
1996?
C. What Is the Compliance Date for Sources That Become Affected
After April 19, 1996?
III. What Are the Requirements for the Notification of Intent to
Comply?
IV. What Are the Requirements for Documentation of Compliance?
A. What Is the Purpose of the Documentation of Compliance?
B. What Is the Rationale for the DOC?
C. What Must Be in the DOC?
V. What Are the Requirements for MACT Performance Testing?
A. What Are the Compliance Testing Requirements?
1. What Are the Testing and Notification of Compliance
Schedules?
2. What Are the Procedures for Review and Approval of Test Plans
and Requirements for Notification of Testing?
3. What Is the Provision for Time Extensions for Subsequent
Performance Tests?
4. What Are the Provisions for Waiving Operating Parameter
Limits During Subsequent Performance Tests?
B. What Is the Purpose of Comprehensive Performance Testing?
1. What Is the Rationale for the Five Year Testing Frequency?
2. What Operations Are Allowed During a Comprehensive
Performance Test?
3. What Is the Consequence of Failing a Comprehensive
Performance Test?
C. What Is the Rationale for Confirmatory Performance Testing?
1. Do the Comprehensive Testing Requirements Apply to
Confirmatory Testing?
2. What Is the Testing Frequency for Confirmatory Testing?
3. What Operations Are Allowed During Confirmatory Performance
Testing?
4. What Are the Consequences of Failing a Confirmatory
Performance Test?
D. What Is the Relationship Between the Risk Burn and
Comprehensive Performance Test?
1. Is Coordinated Testing Allowed?
2. What Is Required for Risk Burn Testing?
E. What Is a Change in Design, Operation, and Maintenance?
F. What are the Data In Lieu Allowances?
VI. What Is the Notification of Compliance?
A. What Are the Requirements for the Notification of Compliance?
B. What Is Required in the NOC?
C. What Are the Consequences of Not Submitting a NOC?
D. What Are the Consequences of an Incomplete Notification of
Compliance?
E. Is There a Finding of Compliance?
VII. What Are the Monitoring Requirements?
A. What Is the Compliance Monitoring Hierarchy?
B. How Are Comprehensive Performance Test Data Used to Establish
Operating Limits?
1. What Are the Definitions of Terms Related to Monitoring and
Averaging Periods?
2. What Is the Rationale for the Averaging Periods for the
Operating Parameter Limits?
3. How Are Performance Test Data Averaged to Calculate Operating
Parameter Limits?
4. How Are the Various Types of Operating Parameters Monitored
or Established?
5. How Are Rolling Averages Calculated Initially, Upon
Intermittent Operations, and When the Hazardous Waste Feed Is Cut
Off?
6. How Are Nondetect Performance Test Feedstream Data Handled?
C. Which Continuous Emissions Monitoring Systems Are Required in
the Rule?
1. What Are the Requirements and Deferred Actions for
Particulate Matter CEMS?
2. What Are the Test Methods, Specifications, and Procedures?
3. What Is the Status of Total Mercury CEMS?
4. What Is the Status of the Proposed Performance Specifications
for Multimetal, Hydrochloric Acid, and Chlorine Gas CEMS?
5. How Have We Addressed Other Issues: Continuous Samplers as
CEMS, Averaging Periods for CEMS, and Incentives for Using CEMS?
D. What Are the Compliance Monitoring Requirements?
1. What Are the Operating Parameter Limits for Dioxin/Furan?
2. What Are the Operating Parameter Limits for Mercury?
3. What Are the Operating Parameter Limits for Semivolatile and
Low Volatile Metals?
4. What Are the Monitoring Requirements for Carbon Monoxide and
Hydrocarbon?
5. What Are the Operating Parameter Limits for Hydrochloric
Acid/Chlorine Gas?
6. What Are the Operating Parameter Limits for Particulate
Matter?
7. What Are the Operating Parameter Limits for Destruction and
Removal Efficiency?
VIII. Which Methods Should Be Used for Manual Stack Tests and
Feedstream Sampling and Analysis?
A. Manual Stack Sampling Test Methods
B. Sampling and Analysis of Feedstreams
IX. What Are the Reporting and Recordkeeping Requirements?
A. What Are the Reporting Requirements?
B. What Are the Recordkeeping Requirements?
C. How Can You Receive Approval to Use Data Compression
Techniques?
X. What Special Provisions Are Included in Today's Rule?
A. What Are the Alternative Standards for Cement Kilns and
Lightweight Aggregate Kilns?
1. What Are the Alternative Standards When Raw Materials Cause
an Exceedance of an Emission Standard?
2. What Special Provisions Exist for an Alternative Mercury
Standard for Kilns?
B. Under What Conditions Can the Performance Testing
Requirements Be Waived?
1. How Is This Waiver Implemented?
2. How Are Detection Limits Handled Under This Provision?
C. What Other Waiver Was Proposed, But Not Adopted?
D. What Equivalency Determinations Were Considered, But Not
Adopted?
E. What are the Special Compliance Provisions and Performance
Testing Requirements for Cement Kilns with In-line Raw Mills and
Dual Stacks?
F. Is Emission Averaging Allowable for Cement Kilns with Dual
Stacks and In-line Raw Mills?
1. What Are the Emission Averaging Provisions for Cement Kilns
with In-line Raw Mills?
2. What Emission Averaging Is Allowed for Preheater or
Preheater-Precalciner Kilns with Dual Stacks?
G. What Are the Special Regulatory Provisions for Cement Kilns
and Lightweight Aggregate Kilns that Feed Hazardous Waste at a
Location Other Than the End Where Products Are Normally Discharged
and Where Fuels Are Normally Fired?
H. What is the Alternative Particulate Matter Standard for
Incinerators?

[[Page 52831]]

1. Why is this Alternative Particulate Matter Standard
Appropriate under MACT?
2. How Do I Demonstrate Eligibility for the Alternative
Standard?
3. What is the Process for the Alternative Standard Petition?
XI. What Are the Permitting Requirements for Sources Subject to
this Rule?
A. What Is the Approach to Permitting in this Rule?
1. In General What Was Proposed and What Was Commenters'
Reaction?
2. What Permitting Approach Is Adopted in Today's Rule?
3. What Considerations Were Made for Ease of Implementation?
B. What Is the Applicability of the Title V and RCRA Permitting
Requirements?
1. How Are the Title V Permitting Requirements Applicable?
2. What Is the Relationship Between the Notification of
Compliance and the Title V Permit?
3. Which RCRA Permitting Requirements Are Applicable?
4. What Is the Relationship of Permit Revisions to RCRA
Combustion Permitting Procedures?
5. What is the Relationship to the RCRA Preapplication Meeting
Requirements?
C. Is Title V Permitting Applicable to Area Sources?
D. How will Sources Transfer from RCRA to MACT Compliance and
Title V Permitting?
1. In General, How Will this Work?
2. How Will I Make the Transition to CAA Permits?
3. When Should RCRA Permits Be Modified?
4. How Should RCRA Permits Be Modified?
5. How Should Sources in the Process of Obtaining RCRA Permits
be Switched Over to Title V?
E. What is Meant by Certain Definitions?
1. Prior Approval
2. 50 Percent Benchmark
3. Facility Definition
4. No New Eligibility for Interim Status
5. What Constitutes Construction Requiring Approval?
XII. State Authorization
A. What is the Authority for Today's Rule?
B. How is the Program Delegated Under the Clean Air Act?
C. How are States Authorized Under RCRA?
Part Six: Miscellaneous Provisions and Issues
I. Does the Waiver of the Particulate Matter Standard or the
Destruction and Removal Efficiency Standard Under the Low Risk Waste
Exemption of the BIF Rule Apply?
II. What is the Status of the ``Low Risk Waste'' Exemption?
III. What Concerns Have Been Considered for Shakedown?
IV. What Are the Management Requirements Prior to Burning?
V. Are There Any Conforming Changes to Subpart X?
VI. What Are the Requirements for Bevill Residues?
A. Dioxin Testing of Bevill Residues
B. Applicability of Part 266 Appendix VIII Products of
Incomplete Combustion List
VII. Have There Been Any Changes in Reporting Requirements for
Secondary Lead Smelters?
VIII. What Are the Operator Training and Certification
Requirements?
IX. Why Did the Agency Redesignate Existing Regulations
Pertaining to the Notification of Intent to Comply and Extension of
the Compliance Date?
Part Seven: National Assessment of Exposures and Risks
I. What Changes Were Made to the Risk Methodology?
A. How Were Facilities Selected for Analysis?
B. How Were Facility Emissions Estimated?
C. What Receptor Populations Were Evaluated?
D. How Were Exposure Factors Determined?
E. How Were Risks from Mercury Evaluated?
F. How Were Risks from Dioxins Evaluated?
G. How Were Risks from Lead Evaluated?
H. What Analytical Framework Was Used to Assess Human Exposures
and Risk?
I. What Analytical Framework Was Used to Assess Ecological Risk?
II. How Were Human Health Risks Characterized?
A. What Potential Health Hazards Were Evaluated?
1. Dioxins
2. Mercury
3. Lead
4. Other Metals
5. Hydrogen Chloride
6. Chlorine
B. What are the Health Risks to Individuals Residing Near HWC
Facilities?
1. Dioxins
2. Mercury
3. Lead
4. Other Metals
5. Inhalation Carcinogens
6. Other Inhalation Exposures
C. What are the Potential Health Risks to Highly Exposed
Individuals?
1. Dioxins
2. Metals
3. Mercury
D. What is the Incidence of Adverse Health Effects in the
Population?
1. Cancer Risk in the General Population
2. Cancer Risk in the Local Population
3. Risks from Lead Emissions
4. Risks from Emissions of Particulate Matter
III. What is the Potential for Adverse Ecological Effects?
A. Dioxins
B. Mercury
Part Eight: Analytical and Regulatory Requirements
I. Executive Order 12866: Regulatory Planning and Review (58 FR
51735)
II. What Activities Have Led to Today's Rule?
A. What Analyses Were Completed for the Proposal?
1. Costs
2. Benefits
3. Other Regulatory Issues
4. Small Entity Impacts
B. What Major Comments Were Received on the Proposal RIA?
1. Public Comments
2. Peer Review
III. Why is Today's Rule Needed?
IV. What Were the Regulatory Options?
V. What Are the Potential Costs and Benefits of Today's Rule?
A. Introduction
B. Combustion Market Overview
C. Baseline Specification
D. Analytical Methodology and Findings--Engineering Compliance
Cost Analysis
E. Analytical Methodology and Findings--Social Cost Analysis
F. Analytical Methodology and Findings--Economic Impact Analysis
1. Market Exit Estimates
2. Quantity of Waste Reallocated
3. Employment Impacts
4. Combustion Price Increases
5. Industry Profits
6. National-Level Joint Economic Impacts
G. Analytical Methodology and Findings--Benefits Assessment
1. Human Health and Ecological Benefits
2. Waste Minimization Benefits
VI. What Considerations Were Given to Issues Like Equity and
Children's Health?
A. Executive Order 12898, ``Federal Actions to Address
Environmental Justice in Minority Populations and Low-Income
Populations'' (February 11, 1994)
B. Executive Order 13045: Protection of Children from
Environmental Health Risks and Safety Risks (62 FR 19885, April 23,
1997)
C. Unfunded Mandates Reform Act of 1995 (URMA) (Pub. Law 104-4)
VII. Is Today's Rule Cost Effective?
VIII. How Do the Costs of Today's Rule Compare to the Benefits?
IX. What Consideration Was Given to Small Businesses?
A. Regulatory Flexibility Act (RFA) as amended by the Small
Business Regulatory Enforcement Fairness Act of 1996 (SBREFA), 5
U.S.C. 601 et seq.
B. Analytical Methodology
C. Results--Direct Impacts
D. Results--Indirect Impacts
E. Key Assumptions and Limitations
X. Were Derived Air Quality and Non-Air Impacts Considered?
XI. The Congressional Review Act (5 U.S.C. 801 et seq., as added
by the Small Business Regulatory Enforcement Fairness Act of 1996)
XII. Paperwork Reduction Act (PRA), 5 U.S.C. 3501-3520
XIII. National Technology Transfer and Advancement Act of 1995
(Pub L. 104-113, section 12(d)) (15 U.S.C. 272 note)
XIV. Executive Order 13084: Consultation and Coordination With
Indian Tribal Governments (63 FR 27655)
Part Nine: Technical Amendments to Previous Regulations
I. Changes to the June 19, 1998 ``Fast-track'' Rule
A. Permit Streamlining Section
B. Comparable Fuels Section

[[Page 52832]]

Part One: Overview and Background for This Rule

I. What Is the Purpose of This Rule?

In this final rule, we adopt hallmark standards to more rigorously
control toxic emissions from burning hazardous waste in incinerators,
cement kilns, and lightweight aggregate kilns. These emission standards
and continuation of our RCRA risk policy create a national cap for
emissions that assures that combustion of hazardous waste in these
devices is properly controlled.
The standards themselves implement section 112 of the Clean Air Act
(CAA) and apply to the three major categories of hazardous waste
burners--incinerators, cement kilns, and lightweight aggregate kilns.
For purposes of today's rule, we refer to these three categories
collectively as hazardous waste combustors. Hazardous waste combustors
burn about 80% of the hazardous waste combusted annually within the
United States. As a result, we project that today's standards will
achieve highly significant reductions in the amount of hazardous air
pollutants being emitted each year by hazardous waste combustors. For
example, we estimate that 70 percent of the annual dioxin and furan
emissions from hazardous waste combustors will be eliminated. Mercury
emissions already controlled to some degree under existing regulations
will be further reduced by about 55 percent.
Section 112 of the CAA requires emissions standards for hazardous
air pollutants to be based on the performance of the Maximum Achievable
Control Technology (MACT). The emission standards in this final rule
are commonly referred to as MACT standards because we use the MACT
concept to determine the levels of emission control under section
112(d) of the CAA.¹ At the same time, these emissions
standards satisfy our obligation under the main statute regulating
hazardous waste management, the Resource Conservation Recovery Act
(RCRA), to ensure that hazardous waste combustion is conducted in a
manner adequately protective of human health and the environment. Our
use of both authorities as the legal basis for today's rule and details
of the MACT standard-setting process are explained more fully in later
sections of this preamble. Most significantly, by using both
authorities in a harmonized fashion, we consolidate regulatory control
of hazardous waste combustion into a single set of regulations, thereby
eliminating the potential for conflicting or duplicative federal
requirements.
---------------------------------------------------------------------------

\1\ The MACT standards reflect the ``maximum degree of reduction
in emissions of * * * hazardous air pollutants'' that the
Administrator determines is achievable, taking into account the cost
of achieving such emission reduction and any nonair quality health
and environmental impacts and energy requirements. Section
112(d)(2).
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Today's rule also has other important features in terms of our
legal obligations and public commitments. First, promulgation of these
standards fulfills our legal obligations under the CAA to control
emissions of hazardous air pollutants from hazardous-waste burning
incinerators and Portland cement kilns.² Second, today's
rule fulfills our 1993 and 1994 public commitments to upgrade emission
standards for hazardous waste combustors. These commitments are the
centerpiece of our Hazardous Waste Minimization and Combustion
Strategy.³ Finally, today's rulemaking satisfies key terms
of a litigation settlement agreement entered into in 1993 with a number
of groups that had challenged our previous rule addressing emissions
from hazardous waste boilers and industrial furnaces.⁴
---------------------------------------------------------------------------

\2\ In a 1992 Federal Register notice, we published the inital
list of categories of major and area sources of hazardous air
pollutants including hazardous waste incinerators and Portland
cement plants. See 57 FR 31576 (July 16, 1992). Today's rule meets
our obligation to issue MACT standards for hazardous waste
incinerators. Today's rule also partially meets our obligation to
issue MACT standards for Portland cement plants. To complete the
obligation, we have finalized, in a separate rulemaking, MACT
standards for the portland cement industry source category. Those
standards apply to all cement kilns except those kilns that burn
hazardous waste. See 64 FR 31898 (June 14, 1999). Those standards
also apply to other HAP emitting sources at a cement plant (such as
clinker coolers, raw mills, finish mills, and materials handling
operations) regardless of whether the plant has hazardous waste
burning cement kilns.
\3\ EPA Document Number 530-R-94-044, Office of Solid Waste and
Emergency Response, November 1994.
\4\ ``Burning of Hazardous Waste in Boilers and Industrial
Furnaces'' (56 FR 7134, February 21, 1991). These groups include the
Natural Resources Defense Council, Sierra Club, Environmental
Technology Council, National Solid Waste Management Association, and
a number of local citizens' groups.
---------------------------------------------------------------------------

II. In Brief, What Are the Major Features of Today's Rule?

The major features of today's final rule are summarized below.
A. Which Source Categories Are Affected by This Rule?
This rule establishes MACT standards for three source categories,
namely: Hazardous waste burning incinerators, hazardous waste burning
cement kilns, and hazardous waste burning lightweight aggregate kilns.
As mentioned earlier, we refer to these three source categories
collectively as hazardous waste combustors.
B. How Are Area Sources Affected by This Rule?
This rule establishes that MACT standards apply to both major
sources--sources that emit or have the potential to emit 10 tons or
greater per year of any single hazardous air pollutant or 25 tons per
year or greater of hazardous air pollutants in the aggregate--and area
sources, all others. Area sources may be regulated under MACT standards
if we find that the category of area sources ``presents a threat of
adverse effects to human health or the environment * * * warranting
regulation (under the MACT standards).'' We choose to regulate area
sources in today's rule and, as a result, all hazardous waste burning
incinerators, cement kilns, and lightweight aggregate kilns will be
regulated under standards reflecting MACT.
C. What Emission Standards Are Established in This Rule?
This rule establishes emission standards for: Chlorinated dioxins
and furans; mercury; particulate matter (as a surrogate for antimony,
cobalt, manganese, nickel, and selenium); semivolatile metals (lead and
cadmium); low volatile metals (arsenic, beryllium, and chromium);
hydrogen chloride and chlorine gas (combined). This rule also
establishes standards for carbon monoxide, hydrocarbons, and
destruction and removal efficiency as surrogates in lieu of individual
standards for nondioxin/furan organic hazardous air pollutants.
D. What Are the Procedures for Complying With This Rule?
This rule establishes standards that apply at all times (including
during startup, shutdown, or malfunction), except if hazardous waste is
not being burned or is not in the combustion chamber. When not burning
hazardous waste (and when hazardous waste does not remain in the
combustion chamber), you may either follow the hazardous waste burning
standards in this rule or emission standards we promulgate, if any, for
other relevant nonhazardous waste source categories.
Initial compliance is documented by stack performance testing. To
document continued compliance with the carbon monoxide or hydrocarbon
standards, you must use continuous emissions monitoring systems. For
the remaining standards, you must document continued compliance by
monitoring limits on specified operating parameters. These operating
parameter

[[Page 52833]]

limits ⁵ are calculated based on performance test conditions
using specified procedures intended to ensure that the operating
conditions (and by correlation the actual emissions) do not exceed
performance test levels at any time. You must also install an automatic
waste feed cutoff system that immediately stops the flow of hazardous
waste feed to the combustor if a continuous emissions monitoring system
records a value exceeding the standard or if an operating parameter
limit is exceeded (considering the averaging period for the standard or
operating parameter). The standards and operating parameter limits
apply when hazardous waste is being fed or remains in the combustion
chamber irrespective of whether you institute the corrective measures
prescribed in the startup, shutdown, and malfunction plan.
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\5\ The term ``operating parameter limit'' and ``operating
limit'' have the same meaning and are used interchangeably in the
preamble and rule language.
---------------------------------------------------------------------------

E. What Subsequent Performance Testing Must Be Performed?
You must conduct comprehensive performance testing every five
years. This testing regime is referred to as ``subsequent performance
testing.'' You must revise the operating parameter limits as necessary
based on the levels achieved during the subsequent performance test. In
addition, you must conduct confirmatory performance testing of dioxins/
furans emissions under normal operating conditions midway between
subsequent performance tests.
F. What Is the Time Line for Complying With This Rule?
The compliance date of the standards promulgated in today's rule is
three years after the date of publication of the rule in the Federal
Register, or September 30, 2002 (See CAA section 112(i)(3)(A)
indicating that the Environmental Protection Agency (EPA) may establish
a compliance date no later than three years from the date of
promulgation.) A one-year extension of the compliance date may be
requested if you cannot complete system retrofits by the compliance
date despite a good faith effort to do so.⁶ CAA section
112(i)(3)(B).
Continuous emissions monitoring systems and other continuous monitoring
systems for the specified operating parameters must be fully
operational by the compliance date. You must demonstrate compliance by
conducting a performance test no later than 6 months after the
compliance date (i.e., three and one-half years from the date of
publication of today's rule in the Federal Register).
---------------------------------------------------------------------------

\6\ In June 1998, we promulgated a rule to allow hazardous waste
combustors also to request a one-year extension to the MACT
compliance date in cases where additional time will be needed to
install pollution prevention and waste minimization measures to
significantly reduce the amount or toxicity of hazardous waste
entering combustion feedstreams. See 63 FR at 43501 (June 19, 1998).
This provision is recodified in today's rule as 40 CFR 63.1213.
---------------------------------------------------------------------------

To ensure timely compliance with the standards, by the compliance
date you must place in the operating record a Documentation of
Compliance identifying limits on the specified operating parameters you
believe are necessary and sufficient to comply with the emission
standards. These operating parameter limits (and the carbon monoxide or
hydrocarbon standards monitored with continuous monitoring systems) are
enforceable until you submit to the Administrator a Notification of
Compliance within 90 days of completion of the performance test.
The Notification of Compliance must document: (1) Compliance with
the emission standards during the performance test; (2) the revised
operating parameter limits calculated from the performance test; and
(3) conformance of the carbon monoxide or hydrocarbon continuous
emissions monitoring systems and the other continuous monitoring
systems with performance specifications. You must comply with the
revised operating parameter limits upon submittal of the Notification
of Compliance.
G. How Does This Rule Coordinate With the Existing RCRA Regulatory
Program?
You must have a RCRA permit for stack air emissions (or RCRA
interim status) until you demonstrate compliance with the MACT
standards. You do so by conducting a comprehensive performance test and
submitting a Notification of Compliance to the Administrator, as
explained above.⁷ Hazardous waste combustors with RCRA
permits remain subject to RCRA stack air emission permit conditions
until the RCRA permit is modified to delete those conditions. (As
discussed later in more detail, we recommend requesting modification of
the RCRA permit at the time you submit the Notification of Compliance.)
Only those provisions of the RCRA permit that are less stringent than
the MACT requirements specified in the Notification of Compliance will
be approved for deletion.⁸ Hazardous waste combustors still
in interim status without a full RCRA permit are no longer subject to
the RCRA stack air emissions standards for hazardous waste combustors
in Subpart O of Part 265 and subpart H of part 266 once compliance with
the MACT standards has been demonstrated and a Notification of
Compliance has been submitted to the Administrator.
---------------------------------------------------------------------------

\7\ Hazardous waste combustors, of course, also continue to be
subject to applicable RCRA requirements for all other aspects of
their hazardous waste management activities that are separate from
the requirements being deferred to the CAA by this rule.
\8\ RCRA permit requirements that may be less stringent than
applicable MACT standards are nonetheless enforceable until the RCRA
permit is modified.
---------------------------------------------------------------------------

You must satisfy both sets of requirements during the relatively
short period when both RCRA and MACT stack air emissions standards and
associated requirements in the RCRA permit or in RCRA interim status
regulations are effective.
You also may have existing site-specific permit conditions. On a
case-by-case basis during RCRA permit issuance or renewal, we determine
whether further regulatory control of emissions is needed to protect
human health and the environment, notwithstanding compliance with
existing regulatory standards. Additional conditions may be included in
the permit in addition to those derived from the RCRA emission
standards as necessary to ensure that facility operations are
protective of human health and the environment. Any of these risk-based
permit provisions more stringent than today's MACT standards (or that
address other emission hazards) will remain in the RCRA permit.
After the MACT compliance date, hazardous waste combustors must
continue to comply with the RCRA permit issuance process to address
nonMACT provisions (e.g., general facility standards) and potentially
conduct a risk review under Sec. 270.32(b)(2) to determine if
additional requirements pertaining to stack or other emissions are
warranted to ensure protection of human health and the environment.

III. What Is the Basis of Today's Rule?

As stated previously, this rule issues final National Emissions
Standards for Hazardous Air Pollutants (NESHAPS) under authority of
section 112 of the Clean Air Act for three source categories of
combustors: Hazardous waste burning incinerators, hazardous waste
burning cement kilns, and hazardous waste burning lightweight aggregate
kilns. The main purposes of the CAA are to protect and enhance the
quality of our Nation's

[[Page 52834]]

air resources, and to promote the public health and welfare and the
productive capacity of the population. CAA section 101(b)(1). To this
end, sections 112(a) and (d) of the CAA direct EPA to set standards for
stationary sources emitting (or having the potential to emit) ten tons
or greater of any one hazardous air pollutant or 25 tons or greater of
total hazardous air pollutants annually. Such sources are referred to
as ``major sources.''
Today's rule establishes MACT emission standards for the following
hazardous air pollutants emitted by hazardous waste burning
incinerators, hazardous waste burning cement kilns, and hazardous waste
burning lightweight aggregate kilns: Chlorinated dioxins and furans,
mercury, two semivolatile metals (lead and cadmium), three low
volatility metals (arsenic, beryllium, and chromium), and hydrochloric
acid/chlorine gas. This rule also establishes MACT control for the
other hazardous air pollutants identified in CAA section 112(b)(1)
through the adoption of standards using surrogates. For example, we
adopt a standard for particulate matter as a surrogate to control five
metals that do not have specific emission standards established in
today's rule. These five metals are antimony, cobalt, manganese,
nickel, and selenium. Also, we adopt standards for carbon monoxide,
hydrocarbons, and destruction and removal efficiency to control the
other organic hazardous air pollutants listed in section 112(b)(1) that
do not have specific emission standards established in this rule.
Today's standards meet our commitment under the Hazardous Waste
Minimization and Combustion Strategy, first announced in May 1993, to
upgrade the emission standards for hazardous waste burning facilities.
EPA's Strategy has eight goals: (1) Ensure public outreach and EPA-
State coordination; (2) pursue aggressive use of waste minimization
measures; (3) continue to ensure that combustion and alternative and
innovative technologies are safe and effective; (4) develop and impose
more rigorous controls on combustion facilities; (5) continue
aggressive compliance and enforcement efforts; (6) enhance public
involvement opportunities in the permitting process for combustion
facilities; (7) give higher priority to permitting those facilities
where a final permit decision would result in the greatest
environmental benefit or the greatest reduction in risk; and (8)
advance scientific understanding on combustion issues and risk
assessment and ensure that permits are issued in a manner that provides
proper protection of human health and the environment.
We have made significant progress in implementing the Strategy.
Today's rule meets the Strategy goal of developing and implementing
rigorous state-of-the-art safety controls on hazardous waste combustors
by using the best available technologies and the most current
science.⁹ We also developed a software tool (i.e., the Waste
Minimization Prioritization Tool) that allows users to access relative
persistent, bioaccumulative and toxic hazard scores for any of 2,900
chemicals that may be present in RCRA waste streams. We also committed
to the reduction of the generation of the most persistent,
bioaccumulative and toxic chemicals by 50 percent by 2005. To
facilitate this reduction we are developing a list of the persistent,
bioaccumulative and toxic chemicals of greatest concern and a plan for
working with the regulated community to reduce these chemicals. In
addition, we promulgated new requirements to enhance public involvement
in the permitting process ¹⁰ and performed risk evaluations
during the permitting process for high priority facilities. We also
made allowances for one-year extensions to the MACT compliance period
as incentives designed to promote the installation of cost-effective
pollution prevention technologies to replace or supplement emission
control technologies for meeting MACT standards.
---------------------------------------------------------------------------

\9\ The three source categories covered by today's final rule
burn more than 80 percent of the total amount of hazardous waste
being combusted each year. The remaining 15-20 percent is burned in
industrial boilers and other types of industrial furnaces, which
will be addressed in a future NESHAPS rulemaking for hazardous waste
burning sources.
\10\ See 60 FR 63417 (December 11, 1995).
---------------------------------------------------------------------------

Finally, with regard to the regulatory framework that will result
from today's rule, we are eliminating the existing RCRA stack emissions
national standards for hazardous waste incinerators, cement kilns, and
lightweight aggregate kilns. That is, after submittal of the
Notification of Compliance established by today's rule (and, where
applicable, RCRA permit modifications at individual facilities), RCRA
national stack emission standards will no longer apply to these
hazardous waste combustors. We originally issued air emission standards
under the authority of section 3004(a) of RCRA, which calls for EPA to
promulgate standards ``as may be necessary to protect human health and
the environment.'' In light of today's new MACT standards, we have
determined that RCRA emissions standards for these sources would only
be duplicative and so are no longer necessary to protect human health
and the environment. Under the authority of section 3004(a), it is
appropriate to eliminate such duplicative standards.
Emission standards for hazardous waste burning incinerators and
other sources burning hazardous wastes as fuel must be protective of
human health and the environment under RCRA. We conducted a
multipathway risk assessment to assess the ecological and human health
risks that are projected to occur under the MACT standards. We have
concluded that the MACT standards are generally protective of human
health and the environment and that separate RCRA emission standards
are not needed. Please see a full discussion of the national assessment
of exposures and risk in Part VIII of this preamble.
Additionally, RCRA section 1006(b) directs EPA to integrate the
provisions of RCRA for purposes of administration and enforcement and
to avoid duplication, to the maximum extent practicable, with the
appropriate provisions of the Clean Air Act and other federal statutes.
This integration must be done in a way that is consistent with the
goals and policies of these statutes. Therefore, section 1006(b)
provides further authority for EPA to eliminate the existing RCRA stack
emissions standards to avoid duplication with the new MACT standards.
Nevertheless, under the authority of RCRA's ``omnibus'' clause (section
3005(c)(3); see 40 CFR 270.32(b)(2)), RCRA permit writers may still
impose additional terms and conditions on a site-specific basis as may
be necessary to protect human health and the environment.

IV. What Was the Rulemaking Process for Development of This Rule?

We proposed MACT standards for hazardous waste burning
incinerators, hazardous waste burning cement kilns, and hazardous waste
burning lightweight aggregate kilns on April 19, 1996. (61 FR 17358) In
addition, we published five notices of data availability (NODAs):
1. August 23, 1996 (61 FR 43501), inviting comment on information
pertaining to a peer review of three aspects of the proposed rule and
information pertaining to the since-promulgated ``Comparable Fuels''
rule (see 63 FR 43501 (June 19, 1998));
2. January 7, 1997 (62 FR 960), inviting comment on an updated
hazardous waste combustor data base containing the emissions and
ancillary

[[Page 52835]]

data that the Agency used to develop the final rule;
3. March 21, 1997 (62 FR 13775), inviting comment on our approach
to demonstrate the technical feasibility of monitoring particulate
matter emissions from hazardous waste combustors using continuous
emissions monitoring systems;
4. May 2, 1997 (62 FR 24212), inviting comment on several topics
including the status of establishing MACT standards for hazardous waste
combustors using a revised emissions data base and the status of
various implementation issues, including compliance dates, compliance
requirements, performance testing, and notification and reporting
requirements; and
5. December 30, 1997 (62 FR 67788), inviting comment on several
status reports pertaining to particulate matter continuous emissions
monitoring systems.
Finally, we have had many formal and informal meetings with
stakeholders, representing an on-going dialogue on various aspects of
the rulemaking.
We carefully considered information and comments submitted by
stakeholders on these rulemaking actions and during meetings. We
address their comments in our Response to Comments documents, which can
be found in the public docket supporting this rulemaking. In addition,
we addressed certain significant comments at appropriate places in this
preamble.

Part Two: Which Devices Are Subject to Regulation?

I. Hazardous Waste Incinerators

Hazardous waste incinerators are enclosed, controlled flame
combustion devices, as defined in 40 CFR 260.10. These devices may be
fixed or transportable. Major incinerator designs used in the United
States are rotary kilns, fluidized beds, liquid injection and fixed
hearth, while newer designs and technologies are also coming into
operation. Detailed descriptions of the designs, types of facilities
and typical air pollution control devices were presented in the April
1996 NPRM and in the technical background document prepared to support
the NPRM. (See 61 FR 17361, April 19, 1996.) In 1997, there were 149
hazardous waste incinerator facilities operating 189 individual units
in the U.S. Of these 149 facilities, 20 facilities (26 units) were
commercial hazardous waste incinerators, while the remaining 129
facilities (163 units) were on-site hazardous waste incinerators.

II. Hazardous Waste Burning Cement Kilns

Cement kilns are horizontally inclined rotating cylinders, lined
with refractory-brick, and internally fired. Cement kilns are designed
to calcine, or drive carbon dioxide out of, a blend of raw materials
such as limestone, shale, clay, or sand to produce Portland cement.
When combined with sand, gravel, water, and other materials, Portland
cement forms concrete, a material used widely in many building and
construction applications.
Generally, there are two different processes used to produce
Portland cement: a wet process and a dry process. In the wet process,
raw materials are ground, wetted, and fed into the kiln as a slurry. In
the dry process, raw materials are ground and fed dry into the kiln.
Wet process kilns are typically longer in length than dry process kilns
to facilitate water evaporation from the slurried raw material. Dry
kilns use less energy (heat) and also can use preheaters or
precalciners to begin the calcining process before the raw materials
are fed into the kiln.
A number of cement kilns burn hazardous waste-derived fuels to
replace some or all of normal fossil fuels such as coal. Most kilns
burn liquid waste; however, cement kilns also may burn bulk solids and
small containers containing viscous or solid hazardous waste fuels.
Containers are introduced either at the upper, raw material end of the
kiln or at the midpoint of the kiln.
All existing hazardous waste burning cement kilns use particulate
matter control devices. These cement plants either use fabric filters
(baghouses) or electrostatic precipitators to control particulate
matter.
In 1997, there were 18 Portland cement plants operating 38
hazardous waste burning kilns. Of these 38 kilns, 27 kilns use the wet
process to manufacture cement and 11 kilns use the dry process. Of the
dry process kilns, one kiln uses a preheater and another kiln used a
preheater and precalciner. Detailed descriptions of the design types of
facilities and typical air pollution control devices are presented in
the technical background document.\11\
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\11\ USEPA, ``Final Technical Support Document for HWC MACT
Standards, Volume I: Description of Source Categories,'' July 1999.
---------------------------------------------------------------------------

In developing standards, the Agency considered the appropriateness
of distinguishing among the different types of cement kilns burning
hazardous waste. We determined that distinguishing subcategories of
hazardous waste burning cement kilns was not needed to develop uniform,
achievable MACT standards. (See Part Four, Section VII of the preamble
for a discussion of subcategory considerations.)

III. Hazardous Waste Burning Lightweight Aggregate Kilns

The term ``lightweight aggregate'' refers to a wide variety of raw
materials (such as clay, shale, or slate) that, after thermal
processing, can be combined with cement to form concrete products.
Lightweight aggregate concrete is produced either for structural
purposes or for thermal insulation purposes. A lightweight aggregate
plant is typically composed of a quarry, a raw material preparation
area, a kiln, a cooler, and a product storage area. The material is
taken from the quarry to the raw material preparation area and from
there is fed into the rotary kiln.
A rotary kiln consists of a long steel cylinder, lined internally
with refractory bricks, which is capable of rotating about its axis and
is inclined horizontally. The prepared raw material is fed into the
kiln at the higher end, while firing takes place at the lower end. As
the raw material is heated, it melts into a semiplastic state and
begins to generate gases that serve as the bloating or expanding agent.
As temperatures reach their maximum, the semiplastic raw material
becomes viscous and entraps the expanding gases. This bloating action
produces small, unconnected gas cells, which remain in the material
after it cools and solidifies. The product exits the kiln and enters a
section of the process where it is cooled with cold air and then
conveyed to the discharge. Kiln operating parameters such as flame
temperature, excess air, feed size, material flow, and speed of
rotation vary from plant to plant and are determined by the
characteristics of the raw material.
In 1997, there were five lightweight aggregate kiln facilities in
the United States operating 10 hazardous waste-fired kilns. Detailed
descriptions of the lightweight aggregate process and air pollution
control techniques are presented in the technical support document.\12\
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\12\ USEPA, ``Final Technical Support Document for HWC MACT
Standards, Volume I: Description of Source Categories,'' July 1999.

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[[Page 52836]]

Part Three: How Were the National Emission Standards for Hazardous
Air Pollutants (NESHAP) in This Rule Determined?

I. What Authority Does EPA Have To Develop a NESHAP?

The 1990 Amendments to the Clean Air Act (CAA) significantly
revised the requirements for controlling emissions of hazardous air
pollutants. EPA is required to develop a list of categories of major
and area sources of the hazardous air pollutants identified in section
112 and to develop, over specified time periods, technology-based
performance standards for sources of these hazardous air pollutants.
See CAA sections 112(c) and 112(d). These source categories and
subcategories are to be listed pursuant to section 112(c)(1). We
published an initial list of 174 categories of such major and area
sources in the Federal Register on July 16, 1992 (57 FR 31576), which
was later amended at 61 FR 28197 (June 4, 1996) \13\ and 63 FR 7155
(February 12, 1998). That list includes the Hazardous Waste
Incineration, Portland Cement Manufacturing, and Clay Products
Manufacturing source categories.
---------------------------------------------------------------------------

\13\ A subsequent Notice was published on July 18, 1996 (61 FR
37542) which corrected typographical errors in the June 4, 1996
Notice.
---------------------------------------------------------------------------

Promulgation of technology-based standards for these listed source
categories is not necessarily the final step in the process. CAA
section 112(f) requires the Agency to report to Congress on the
estimated risk remaining after imposition of technology-based standards
and make recommendations as to additional legislation needed to address
such risk. If Congress does not act on any recommendation presented in
this report, we are required to impose additional controls if such
controls are needed to protect public health with an ample margin of
safety or (taking into account costs, energy, safety, and other
relevant factors) to prevent adverse environmental effects. In
addition, if the technology-based standards for carcinogens do not
reduce the lifetime excess cancer risk for the most exposed individual
to less than one in a million (1 x 10^-6), then we must
promulgate additional standards.
We prepared the Draft Residual Risk Report to Congress and
announced its release on April 22, 1998 (63 FR 19914-19916). In that
report, we did not propose any legislative recommendation to Congress.
In section 4.2.4 of the report, we state that: ``The legislative
strategy embodied in the 1990 CAA Amendments adequately maintains the
goal of protecting the public health and the environment and provides a
complete strategy for dealing with a variety of risk problems. The
strategy recognizes that not all problems are national problems or have
a single solution. National emission standards will be promulgated to
decrease the emissions of as many hazardous air pollutants as possible
from major sources.''

II. What Are the Procedures and Criteria for Development of NESHAPs?

A. Why Are NESHAPs Needed?
NESHAPs are developed to control hazardous air pollutant emissions
from both new and existing sources. The statute requires a NESHAP to
reflect the maximum degree of reduction of hazardous air pollutant
emissions that is achievable taking into consideration the cost of
achieving the emission reduction, any nonair quality health and
environmental impacts, and energy requirements. NESHAPs are often
referred to as maximum achievable control technology (or MACT)
standards.
We are required to develop MACT emission standards based on
performance of the best control technologies for categories or sub-
categories of major sources of hazardous air pollutants. We also can
establish lower thresholds for determining which sources are major
where appropriate. In addition, we may require sources emitting
particularly dangerous hazardous air pollutants such as particular
dioxins and furans to control those pollutants under the MACT standards
for major sources.
In addition, we regulate area sources by technology-based standards
if we find that these sources (individually or in the aggregate)
present a threat of adverse effects to human health or the environment
warranting regulation. After such a determination, we have a further
choice whether to require technology-based standards based on MACT or
on generally achievable control technology.
B. What Is a MACT Floor?
The CAA directs EPA to establish minimum emission standards,
usually referred to as MACT floors. For existing sources in a category
or subcategory with 30 or more sources, the MACT floor cannot be less
stringent than the ``average emission limitation achieved by the best
performing 12 percent of the existing sources. * * *'' For existing
sources in a category or subcategory with less than 30 sources, the
MACT floor cannot be less stringent than the ``average emission
limitation achieved by the best performing 5 sources. * * *'' For new
sources, the MACT floor cannot be ``less stringent than the emission
control that is achieved by the best controlled similar source. * * *''
We must consider in a NESHAP rulemaking whether to develop
standards that are more stringent than the floor, which are referred to
as ``beyond-the-floor'' standards. To do so, we must consider statutory
criteria, such as the cost of achieving emission reduction, cost
effectiveness, energy requirements, and nonair environmental
implications.
Section 112(d)(2) specifies that emission reductions may be
accomplished through the application of measures, processes, methods,
systems, or techniques, including, but not limited to: (1) Reducing the
volume of, or eliminating emissions of, such pollutants through process
changes, substitution of materials, or other modifications; (2)
enclosing systems or processes to eliminate emissions; (3) collecting,
capturing, or treating such pollutants when released from a process,
stack, storage, or fugitive emissions point; (4) design, equipment,
work practice, or operational standards (including requirements for
operator training or certification); or (5) any combination of the
above. See section 112(d)(2).
Application of techniques (1) and (2) are consistent with the
definitions of pollution prevention under the Pollution Prevention Act
and the definition of waste minimization under RCRA. In addition, these
definitions are in harmony with our Hazardous Waste Minimization and
Combustion Strategy. These terms have particular applicability in the
discussion of pollution prevention/waste minimization incentives, which
were finalized at 63 FR 33782 (June 19, 1998) and which are summarized
in the permitting and compliance sections of this final rule.
C. How Are NESHAPs Developed?
To develop a NESHAP, we compile available information and in some
cases collect additional information about the industry, including
information on emission source quantities, types and characteristics of
hazardous air pollutants, pollution control technologies, data from
emissions tests (e.g., compliance tests, trial burn tests) at
controlled and uncontrolled facilities, and information on the costs
and other energy and environmental impacts of emission control
techniques. We use this information in analyzing and developing
possible regulatory

[[Page 52837]]

approaches. Of course, we are not always able to assemble the same
amount of information per industry and typically base the NESHAP on
information practically available.
NESHAPs are normally structured in terms of numerical emission
limits. However, alternative approaches are sometimes necessary and
appropriate. Section 112(h) authorizes the Administrator to promulgate
a design, equipment, work practice, or operational standard, or a
standard that is a combination of these alternatives.

III. How Are Area Sources and Research, Development, and Demonstration
Sources Treated in This Rule?

A. Positive Area Source Finding for Hazardous Waste Combustors
1. How Are Area Sources Treated in This Rule?
In today's final rule, we make a positive area source finding
pursuant to CAA section 112(c)(3) for hazardous waste burning
incinerators, hazardous waste burning cement kilns, and hazardous waste
burning lightweight aggregate kilns. This rule subjects both major and
area sources in these three source categories to the same standards--
the section 112(d) MACT standards. We make this positive area source
determination because emissions from area sources subject to today's
rule present a threat of adverse effects to human health and the
environment. These threats warrant regulation under the section 112
MACT standards.
2. What Is an Area Source?
Area sources are sources emitting (or having the potential to emit)
less than 10 tons per year of an individual hazardous air pollutant,
and less than 25 tons per year of hazardous air pollutants in the
aggregate. These sources may be regulated under MACT standards if we
find that the sources ``presen[t] a threat of adverse effects to human
health or the environment (by such sources individually or in the
aggregate) warranting regulation under this section.'' Section
112(c)(3).
As part of our analysis, we estimate that all hazardous waste
burning lightweight aggregate kilns are major sources, principally due
to their hydrochloric acid emissions. We also estimate that
approximately 80 percent of hazardous waste burning cement kilns are
major sources, again due to hydrochloric acid emissions. Only
approximately 30 percent of hazardous waste burning incinerators appear
to be major sources, considering only the stack emissions from the
incinerator. However, major and area source status is determined by the
entire facility's hazardous air pollutant emissions, so that many on-
site hazardous waste incinerators are major sources because they are
but one contributing source of emissions among others (sometimes many
others at large manufacturing complexes) at the same facility.
3. What Is the Basis for Today's Positive Area Source Finding?
The consequences of us not making a positive area source finding in
this rule would result in an undesirable bifurcated regulation. First,
the CAA provides independent authority to regulate certain hazardous
air pollutant emissions under MACT standards, even if the emissions are
from area sources. These are the hazardous air pollutants enumerated in
section 112(c)(6), and include 2,3,7,8 dichlorobenzo-p-dioxins and
furans, mercury, and some specific polycyclic organic hazardous air
pollutants--hazardous air pollutants regulated under this rule. See 62
FR at 24213-24214. Thus, all sources covered by today's rule would have
to control these hazardous air pollutants to MACT levels, even if we
were not to make a positive area source determination. Second, because
all hazardous air pollutants are fully regulated under RCRA, area
source hazardous waste combustors would have not only a full RCRA
permit, but also (as just explained) a CAA title V permit for the
section 112(c)(6) hazardous air pollutants. One purpose of this rule is
to avoid the administrative burden to sources resulting from this type
of dual permitting, and these burdensome consequences of not making a
positive area source finding have influenced our decision that area
source hazardous waste combustors ``warrant regulation'' under section
112(d)(2).
a. Health and Environmental Factors. Our positive area source
finding is based on the threats presented by emissions of hazardous air
pollutants from area sources. We find that these threats warrant
regulation under the MACT standards given the evident Congressional
intent for uniform regulation of hazardous waste combustion sources, as
well as the common emission characteristics of these sources and
amenability to the same emission control mechanisms.
As discussed in both the April 1996 proposal and May 1997 NODA, all
hazardous waste combustion sources, including those that may be area
sources, have the potential to pose a threat of adverse effects to
human health or the environment, although some commenters disagree with
this point. These sources emit some of the most toxic, bioaccumulative
and persistent hazardous air pollutants--among them dioxins, furans,
mercury, and organic hazardous air pollutants. As discussed in these
Federal Register notices and elsewhere in today's final rule, potential
hazardous waste combustor area sources can be significant contributors
to national emissions of these hazardous air pollutants. (See 62 FR
17365 and 62 FR 24213.)
Our positive area source finding also is based on the threat posed
by products of incomplete combustion. The risks posed by these
hazardous air pollutants cannot be directly quantified on a national
basis, because each unit emits different products of incomplete
combustion in different concentrations. However, among the products of
incomplete combustion emitted from these sources are potential
carcinogens.\14\ The potential threat posed by emissions of these
hazardous air pollutants is manifest and, for several reasons, we do
not believe that control of these products of incomplete combustion
should be left to the RCRA omnibus permitting process. First, we are
minimizing the administrative burden on sources from duplicative
permitting in this rule by minimizing the extent of RCRA permitting and
hence minimizing our reliance on the omnibus process. Second, we are
dealing with hazardous air pollutant emissions from these sources on a
national rather than a case-by-case basis. We conclude that the control
of products of incomplete combustion from all hazardous waste
combustors through state-of-the art organic pollution control is the
best way to do so from an implementation standpoint. Finally, a basic
premise of the CAA is that there are so many uncertainties and
difficulties in developing effective risk-based regulation of hazardous
air pollutants that the first step should be technology-based standards
based on Maximum Available Control Technology. See generally S. Rep.
No. 228, 101st Cong. 1st Sess. 128-32 (1990). The positive area source
finding and consequent MACT controls is consistent with this primary
legislative objective.
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\14\ E.g., benzene, methylene chloride, hexachlorobenzene,
carbon tetrachloride, vinal chloride, benzo(a)pyrene, and
chlorinated dioxins and furans. Energy and Environmental Research
Corp., surrogate Evaluation for Thermal Treatment Systems, Draft
Report, October 1994. Also see: USEPA, ``Final technical Support
Document for HWC MACT Standards, Volume III: Section of MACT
Standards and Technologies,'' July 1999.
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The quantitative risk assessment for the final rule did not find
risk from

[[Page 52838]]

mercury emissions from hazardous waste burning area source cement kilns
to be above levels we generally consider acceptable. However, the
uncertainties underlying the analysis are such that only qualitative
judgments can be made. We do not believe our analysis can be relied
upon to make a definitive quantitative finding about the precise
magnitude of the risk. See Part Five, Section XIII for a discussion of
uncertainty. Background exposures, which can be quite variable, were
not considered in the quantitative assessment and are likely to
increase the risk from incremental exposures to mercury from area
source cement kilns. Commenters, on the other hand, believed that
cement kilns did not pose significant risk and questioned our risk
estimates made in the April 1996 NPRM and May 1997 NODA. However,
taking into account the uncertainty of our mercury analysis and the
likelihood of background exposures, a potential for risk from mercury
may exist. Furthermore, the information available concerning the
adverse human health effects of mercury, along with the magnitude of
the emissions of mercury from area source cement kilns, also indicate
that a threat of adverse effects is presumptive and that a positive
area source finding is warranted.
b. Other Reasons Warranting Regulation under Section 112. Other
special factors indicate that MACT standards are warranted for these
sources.
The first reason is Congress's, our, and the public's strong
preference for similar, if not identical, regulation of all hazardous
waste combustors. Area sources are currently regulated uniformly under
RCRA, with no distinction being made between smaller and larger
emitters. This same desire for uniformity is reflected in the CAA. CAA
section 112(n)(7) directs the Agency, in its regulation of HWCs under
RCRA, to ``take into account any regulations of such emissions which
are promulgated under such subtitle (i.e., RCRA) and shall, to the
maximum extent practicable and consistent with the provisions of this
section, ensure that the requirements of such subtitle and this section
are consistent.'' Congress also dealt with these sources as a single
class by excluding hazardous waste combustion units regulated by RCRA
permits from regulation as municipal waste combustors under CAA section
129(g)(1). Thus, a strong framework in both statutes indicates that air
emissions from all hazardous waste combustors should be regulated under
a uniform approach. Failure to adopt such a uniform approach would
therefore be inconsistent with Congressional intent as expressed in
both the language and the structure of RCRA and the CAA. Although many
disagree, several commenters support the approach to apply uniform
regulations for all hazardous waste combustors and assert that it is
therefore appropriate and necessary to make the positive area source
finding.
Second, a significant number of hazardous waste combustors could
plausibly qualify as area sources by the compliance date through
emissions reductions of one or more less dangerous hazardous air
pollutants, such as total chlorine. We conclude it would be
inappropriate to exclude from CAA 112(d) regulation and title V
permitting a significant portion of the sources contributing to
hazardous air pollutant emissions, particularly nondioxin products of
incomplete combustion should this occur.
Third, the MACT controls identified for major sources are
reasonable and appropriate for potential area sources. The emissions
control equipment (and where applicable, feedrate control) defined as
floor or beyond-the-floor control for each source category is
appropriate and can be installed and operated at potential area
sources. There is nothing unique about the types and concentrations of
emissions of hazardous air pollutants from any class of hazardous waste
combustors that would make MACT controls inappropriate for that
particular class of hazardous waste combustors, but not the others.
Commenters also raised the issue of applying generally available
control technologies (GACT), in lieu of MACT, to area sources.
Consideration of GACT lead us to the conclusion that GACT would likely
involve the same types and levels of control as we identified for MACT.
We believe GACT would be the same as MACT because the standards of this
rule, based on MACT, are readily achievable, and therefore would also
be determined to be generally achievable, i.e., GACT.
Finally, we note that the determination here is unique to these
RCRA sources, and should not be viewed as precedential for other CAA
sources. In the language of the statute, there are special reasons that
these RCRA sources warrant regulation under section 112(d)(2)--and so
warrant a positive area source finding--that are not present for usual
CAA sources. These reasons are discussed above--the Congressional
desire for uniform regulation and our desire (consistent with this
Congressional objective) to avoid duplicative permitting of these
sources wherever possible. We repeat, however, that the positive area
source determination here is not meant as a precedent outside the dual
RCRA/CAA context.
B. How Are Research, Development, and Demonstration (RD&D) Sources
Treated in This Rule?
Today's rule excludes research, development, and demonstration
sources from the hazardous waste burning incinerator, cement kiln, and
lightweight aggregate kiln source categories. We discuss below the
statutory mandate to give special consideration to research and
development (R&D) sources, an Advanced Notice of Proposed Rulemaking to
list R&D facilities that we published in 1997, and qualifications for
exclusion of R&D sources from the hazardous waste combustor source
categories.
1. Why Does the CAA Give Special Consideration to Research and
Development (R&D) Sources?
Section 112(c)(7) of the Clean Air Act requires EPA to ``establish
a separate category covering research or laboratory facilities, as
necessary to assure the equitable treatment of such facilities.''
Congress included such language in the Act because it was concerned
that research and laboratory facilities should not arbitrarily be
included in regulations that cover manufacturing operations. The Act
defines a research or laboratory facility as ``any stationary source
whose primary purpose is to conduct research and development into new
processes and products, where such source is operated under the close
supervision of technically trained personnel and is not engaged in the
manufacture of products for commercial sale in commerce, except in a de
minimis manner.''
We interpret the Act as requiring the listing of R&D major sources
as a separate category to ensure equitable treatment of such
facilities. Language in the Act specifying special treatment of R&D
facilities (section 112(c)(7)), along with language in the legislative
history of the Act, suggests that Congress considered it inequitable to
subject the R&D facilities of an industry to a standard designed for
the commercial production processes of that industry. The application
of such a standard may be inappropriate because the wide range of
operations and sizes of R&D facilities. Further, the frequent changes
in R&D operations may be significantly different from the typically
large and continuous production processes.
We have no information indicating that there are R&D sources, major
or

[[Page 52839]]

area, that are required to be listed and regulated, other than those
associated with sources already included in listed source categories
listed today. Although we are not aware of other R&D sources that need
to be added to the source category list, such sources may exist, and we
requested information about them in an Advance Notice of Proposed
Rulemaking, as discussed in the next section.
2. When Did EPA Notice Its Intent To List R&D Facilities?
In May 1997 (62 FR 25877), we provided advanced notice that we were
considering whether to list R&D facilities. We requested public
comments and information on the best way to list and regulate such
sources. Comment letters were received from industry, academic
representatives, and governmental entities. After we compile additional
data, we will respond to these comments in that separate docket. As a
result we are not deciding how to address the issue in today's rule.
The summary of comments and responses will be one part of the basis for
our future decision whether to list R&D facilities as a source category
of hazardous air pollutants.
3. What Requirements Apply to Research, Development, and Demonstration
Hazardous Waste Combustor Sources?
This rule excludes research, development, and demonstration sources
from the hazardous waste incinerator, cement kiln, or lightweight
aggregate kiln source categories and therefore from compliance with
today's regulations. We are excluding research, development, and
demonstration sources from those source categories because the emission
standards and compliance assurance requirements for those source
categories may not be appropriate. The operations and size of a
research, development, and demonstration source may be significantly
different from the typical hazardous waste incinerator that is
providing ongoing waste treatment service or hazardous waste cement
kiln or hazardous waste lightweight aggregate kiln that is producing a
commercial product as well as providing ongoing waste treatment.
We also are applying the exclusion to demonstration sources because
demonstration sources are operated more like research and development
sources than production sources. Thus, the standards and requirements
finalized today for production sources may not be appropriate for
demonstration sources. Including demonstration sources in the exclusion
is consistent with our current regulations for hazardous waste
management facilities. See Sec. 270.65 providing opportunity for
special operating permits for research, development, and demonstration
sources that use an innovative and experimental hazardous waste
treatment technology or process.
To ensure that research, development, and demonstration sources are
distinguished from production sources, we have drawn from the language
in section 112(c)(7) to define a research, development, and
demonstration source. Specifically, these are sources engaged in
laboratory, pilot plant, or prototype demonstration operations: (1)
Whose primary purpose is to conduct research, development, or short-
term demonstration of an innovative and experimental hazardous waste
treatment technology or process; and (2) where the operations are under
the close supervision of technically-trained personnel.¹⁵
---------------------------------------------------------------------------

\15\The statute also qualifies that research and development
sources do not engage in the manufacture of products for commercial
sale except in a de minimis manner. Although this qualification is
appropriate for research and development sources, engaged in short-
term demonstration of an innovative or experimental treatment
technology or process may produce products for use in commerce. For
example, a cement kiln engaged in a short-term demonstration of an
innovative process may nonetheless produce marketable clinker in
other than de minimis quantities. Consequently, we are not including
this qualification in the definition of a research, development, and
demonstration source.
---------------------------------------------------------------------------

In addition, today's rule limits the exclusion to research,
development, and demonstration sources that operate for not longer than
one year after first processing hazardous waste, unless the
Administrator grants a time extension based on documentation that
additional time is needed to perform research development, and
demonstration operations. We believe that this time restriction will
help distinguish between research, development, and demonstration
sources and production sources. This time restriction draws from the
one-year time restriction (unless extended on a case-by-case basis)
currently applicable to hazardous waste research, development, and
demonstration sources under Sec. 270.65.
The exclusion of research, development, and demonstration sources
applies regardless of whether the sources are located at the same site
as a production hazardous waste combustor that is subject to the MACT
standards finalized today. A research, development, and demonstration
source that is co-located at a site with a production source still
qualifies for the exclusion. A research, development, and demonstration
source co-located with a production source is nonetheless expected to
experience the type and range of operations and be of the size typical
for other research, development, and demonstration sources.
Finally, hazardous waste research, development, and demonstration
sources remain subject to RCRA permit requirements under Sec. 270.65,
which direct the Administrator to establish permit terms and conditions
that will assure protection of human health and the environment.
Although we did not propose this exclusion specifically for
hazardous waste combustor research, development, and demonstration
sources, the exclusion is an outgrowth of the May 1997 notice discussed
above. In that notice we explain that we interpret the CAA as requiring
the listing of research and development major sources as a separate
category to ensure equitable treatment of such facilities. A commenter
on the April 1996 hazardous waste combustor NPRM questioned whether we
intended to apply the proposed regulations to research and development
sources. We did not have that intent, and in response are finalizing
today an exclusion of research, development, and demonstration sources
from the hazardous waste incinerator, hazardous waste burning cement
kiln, and hazardous waste burning lightweight aggregate kiln source
categories.

IV. How Is RCRA's Site-Specific Risk Assessment Decision Process
Impacted by This Rule?

RCRA Sections 3004(a) and (q) mandate that standards governing the
operation of hazardous waste combustion facilities be protective of
human health and the environment. To meet this mandate, we developed
national combustion standards under RCRA, taking into account the
potential risk posed by direct inhalation of the emissions from these
sources.¹⁶ With advancements in the assessment of risk since
promulgation of the original national standards (i.e., 1981 for
incinerators and 1991 for boilers and industrial furnaces), we
recognized in the 1993 Hazardous Waste Minimization and Combustion
Strategy that additional risk analysis was appropriate. Specifically,
we noted that the risk posed by indirect exposure (e.g., ingestion of
contamination in the food chain) to long-term deposition of metals,

[[Page 52840]]

dioxin/furans and other organic compounds onto soils and surface waters
should be assessed in addition to the risk posed by direct inhalation
exposure to these contaminants. We also recognized that the national
assessments performed in support of the original hazardous waste
combustor standards did not take into account unique and site-specific
considerations which might influence the risk posed by a particular
source. Therefore, to ensure the RCRA mandate was met on a facility-
specific level for all hazardous waste combustors, we strongly
recommended in the Strategy that site-specific risk assessments
(SSRAs), including evaluations of risk resulting from both direct and
indirect exposure pathways, be conducted as part of the RCRA permitting
process. In those situations where the results of a SSRA showed that a
facility's operations could pose an unacceptable risk (even after
compliance with the RCRA national regulatory standards), additional
risk-based, site-specific permit conditions could be imposed pursuant
to RCRA's omnibus authority (section 3005(c)(3)).
---------------------------------------------------------------------------

\16\ See No CFR part 264, subpart O for incinerator standards
and 40 CFR part 266, subpart H for BIF standards.
---------------------------------------------------------------------------

Today's MACT standards were developed pursuant to section 112(d) of
the CAA, which does not require a concurrent risk evaluation of those
standards. To determine if the MACT standards would satisfy the RCRA
protectiveness mandate in addition to the requirements of the CAA, we
conducted a national RCRA evaluation of both direct and indirect risk
as part of this rulemaking. If we found the MACT standards to be
sufficiently protective so as to meet the RCRA mandate as well, we
could consider modifying our general recommendation that SSRAs be
conducted for all hazardous waste combustors, thereby lessening the
regulatory burden to both permitting authorities and facilities.
In this section, we discuss: The applicability of both the RCRA
omnibus authority and the SSRA policy to hazardous waste combustors
subject to today's rulemaking; the implementation of the SSRA policy;
the relationship of the SSRA policy to the residual risk requirement of
section 112(f) of the CAA; and public comments received on these
topics. A discussion of the national risk characterization methodology
and results is provided in Part Five, Section XIII of today's notice.
A. What Is the RCRA Omnibus Authority?
Section 3005(c)(3) of RCRA (codified at 40 CFR 270.32(b)(2))
requires that each hazardous waste facility permit contain the terms
and conditions necessary to protect human health and the environment.
This provision is commonly referred to as the ``omnibus authority'' or
``omnibus provision.'' It is the means by which additional site-
specific permit conditions may be incorporated into RCRA permits should
such conditions be necessary to protect human health and the
environment.¹⁷ SSRAs have come to be used by permitting
authorities as a quantitative basis for making omnibus determinations
for hazardous waste combustors.
---------------------------------------------------------------------------

\17\ The risk-based permit conditions are in addition to those
conditions required by the RCRA national regulatory standards for
hazardous waste combustors (e.g., general facility requirements).
---------------------------------------------------------------------------

In the April 1996 NPRM and May 1997 NODA, we discussed the RCRA
omnibus provision and its relation to the new MACT standards.
Commenters question whether the MACT standards supersede the omnibus
authority with respect to hazardous waste combustor air emissions.
Other commenters agree in principle with the continued applicability of
the omnibus authority after promulgation of the MACT standards. These
commenters recognize that there may be unique conditions at a given
site that may warrant additional controls to those specified in today's
notice. For those sources, the commenters acknowledge that permit
writers must retain the legal authority to place additional operating
limitations in a source's permit.
As noted above, the omnibus provision is a RCRA statutory
requirement and does not have a CAA counterpart. The CAA does not
override RCRA. Each statute continues to apply to hazardous waste
combustors unless we determine there is duplication and use the RCRA
section 1006(b) deferral authority to create a specific regulatory
exemption.¹⁸ Promulgation of the MACT standards, therefore,
does not duplicate, supersede, or otherwise modify the omnibus
provision or its applicability to sources subject to today's
rulemaking. As indicated in the April 1996 NPRM, a RCRA permitting
authority (such as a state agency) has the responsibility to supplement
the national MACT standards as necessary, on a site-specific basis, to
ensure adequate protection under RCRA. We recognize that this could
result in a situation in which a source may be subject to emission
standards and operating conditions under two regulatory authorities
(i.e., CAA and RCRA). Although our intent, consistent with the
integration provision of RCRA section 1006(b), is to avoid regulatory
duplication to the maximum extent practicable, we may not eliminate
RCRA requirements if a source's emissions are not protective of human
health and the environment when complying with the MACT
standards.¹⁹
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\18\ The risk-based permit conditions are in addition to those
conditions required by the RCRA national regulatory standards for
hazardous waste combustors (e.g., general facility requirements).
\19\ RCRA section 1006(b) authorizes deferral of RCRA provisions
to other EPA-implemented authorities provided, among other things,
that key RCRA policies and protections are not sacrificed. See
Chemical Waste Management v. EPA, 976 F. 2d 2, 23, 25 (D.C. Cir.
1992).
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B. How Will the SSPA Policy Be Applied and Implemented in Light of This
Mandate?
1. Is There a Continuing Need for Site-Specific Risk Assessments?
As stated previously, EPA's Hazardous Waste Minimization and
Combustion Strategy recommended that SSRAs be conducted as part of the
RCRA permitting process for hazardous waste combustors where necessary
to protect human health and the environment. We intended to reevaluate
this policy once the national hazardous waste combustion standards had
been updated. We view today's MACT standards as more stringent than
those earlier standards for incinerators, cement kilns and lightweight
aggregate kilns. To determine if the MACT standards as proposed in the
April 1996 NPRM would satisfy the RCRA mandate to protect human health
and the environment, we conducted a national evaluation of both human
health and ecological risk. That evaluation, however, did not
quantitatively assess the proposed standards with respect to mercury
and nondioxin products of incomplete combustion. This was due to a lack
of adequate information regarding the behavior of mercury in the
environment and a lack of sufficient emissions data and parameter
values (e.g., bioaccumulation values) for nondioxin products of
incomplete combustion. Since it was not possible to suitably evaluate
the proposed standards for the potential risk posed by mercury and
nondioxin products of incomplete combustion, we elected in the April
1996 NPRM to continue recommending that SSRAs be conducted as part of
the permitting process until we could conduct a further assessment once
final MACT standards are promulgated and implemented.
Although some commenters agree with this approach, a number of
other commenters question the necessity of a quantitative nondioxin
product of incomplete combustion assessment to demonstrate RCRA
protectiveness of the MACT standards. These commenters

[[Page 52841]]

assert that existing site-specific assessments demonstrate that
emissions of nondioxin products of incomplete combustion are unlikely
to produce significant adverse human health effects. However, we do not
agree that sufficient SSRA information exists to conclude that
emissions from these compounds are unlikely to produce significant
adverse effects on human health and the environment on a national
basis. First, only a limited number of completed SSRAs are available
from which broader conclusions can be drawn. Second, nondioxin products
of incomplete combustion emissions can vary widely depending on the
type of combustion unit, hazardous waste feed and air pollution control
device used. Third, a significant amount of uncertainty exists with
respect to identifying and quantifying these compounds. Many nondioxin
products of incomplete combustion cannot be characterized by standard
analytical methodologies and are unaccounted for by standard emissions
testing.²⁰ (On a site-specific basis, uncharacterized
nondioxin products of incomplete combustion are typically addressed by
evaluating the total organic emissions.) Fourth, nondioxin products of
incomplete combustion can significantly contribute to the overall risk
posed by a particular facility. For example, in the Waste Technologies
Industries incinerator's SSRA, nondioxin organics were estimated to
contribute approximately 30% of the total cancer risk to the most
sensitive receptor located in the nearest subarea to the
facility.²¹ Fifth, national risk management decisions
concerning the protectiveness of the MACT standards must be based on
data that are representative of the hazardous waste combustors subject
to today's rulemaking. We do not believe that the information afforded
by the limited number of SSRAs now available is sufficiently complete
or representative to render a national decision.²²
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\20\ USEPA, ``Development of a Hazardous Waste Incinerator
Target Analyte List of Products of Incomplete Combustion'' EPA-600/
R-98-076. 1998.
\21\ The total cancer risk for this receptor was 1 x 10E-6. The
results derived for the Waste Technologies Industries incinerator's
SSRA are a combination of measurements and conservative estimates of
stack and fugitive emissions, which were developed in tandem with an
independent external peer review. USEPA, ``Risk Assessment for the
Waste Technologies Industries Hazardous Waste Incineration Facility
(East Livepool, Ohio)'' EPA-905-R97-002.
\22\ Since publication of the April 1996 NPRM, we have expanded
our national risk evaluation of the other hazardous waste combustor
emissions (e.g., metals) from 11 facilities to 76 facilities
assessed for today's final rulemaking. The 76 facilities were
selected using a stratified random sampling approach that allowed
for a 90 percent probability of including at least one ``high risk''
facility. However, this larger set of facility assessments does not
include an evaluation nondioxin products of incomplete combustion.
See Part Five, Section XIII for further discussion.
---------------------------------------------------------------------------

Some commenters recommend discontinuing conducting SSRAs
altogether. Other commenters, however, advocate continuing to conduct
SSRAs, where warranted, as a means of addressing uncertainties inherent
in the national risk evaluation and of addressing unique, site-specific
circumstances not considered in the assessment.
In developing the national risk assessment for the final MAC
standards, we expanded our original analysis to include a quantitative
assessment of mercury patterned after the recently published Mercury
Study Report to Congress.²³ We were unable to perform a
similar assessment of nondioxin products of incomplete combustion
emissions because of continuing data limitations for these compounds,
despite efforts to collect additional data since publication of the
April 1996 NPRM . Thus, we conclude that sufficient data are not
available to quantitatively assess the potential risk from these
constituents on a national level as part of today's rulemaking.
---------------------------------------------------------------------------

\23\ USEPA, ``Mercury Study Report to Congress, Volume III: Fate
and Transport of Mercury in the Environment,'' EPA 452/R-97-005,
December 1997.
---------------------------------------------------------------------------

Given the results of the final national risk assessment for other
hazardous air pollutants, we generally anticipate that sources
complying with the MACT standards will not pose an unacceptable risk to
human health or the environment. However, we cannot make a definitive
finding in this regard for all hazardous waste combustors subject to
today's MACT standards for the reasons discussed.
First, as discussed above, the national risk evaluation did not
include an assessment of the risk posed by nondioxin products of
incomplete combustion. As reflected in the Waste Technologies
Industries SSRA, these compounds can significantly contribute to the
overall risk posed by a hazardous waste combustor. Without a
quantitative evaluation of these compounds, we cannot reliably predict
whether the additional risk contributed by nondioxin products of
incomplete combustion would or would not result in an unacceptable
increase in the overall risk posed by hazardous waste combustors
nationally.
Second, the quantitative mercury risk analysis conducted for
today's rulemaking contains significant uncertainties. These
uncertainties limit the use of the analysis for drawing quantitative
conclusions regarding the risks associated with the national mercury
MACT standard. Among others, the uncertainties include an incomplete
understanding of the fate and transport of mercury in the environment
and the biological significance of exposures to mercury in fish. (See
Part Five, Section XIII.) Given these uncertainties, we believe that
conducting a SSRA, which will assist a permit writer to reduce
uncertainty on a site-specific basis, may be still warranted in some
cases.²⁴ As the science regarding mercury fate and transport
in the environment and exposure improves, and greater certainty is
achieved in the future, we may be in a better position from which to
draw national risk management conclusions regarding mercury risk.
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\24\ An example of the possible reduction in uncertainty which
may be derived through the performance of a SSRA includes the degree
of conversion of mercury to methyl mercury in water bodies. Due to
the wide range of chemical and physical properties associated with
surface water bodies, there appears to be a great deal of
variability concerning mercury methylation. In conducting a SSRA, a
risk assessor may choose to use a default value to represent the
percentage of mercury assumed to convert to methyl mercury.
Conversely, the risk assessor may choose to reduce the uncertainty
in the analysis by deriving a site-specific value using actual
surface water data. Chemical and physical properties that may
influence mercury methylation include, but are not limited to:
dissolved oxygen content, pH, dissolved organic content, salinity,
nutrient concentrations, and temperature. See USEPA, ``Human Health
Risk Assessment Protocol for Hazardous Waste Combustion
Facilities,'' EPA-530-D-98-001A, External Peer Review Draft, 1998.
---------------------------------------------------------------------------

Third, we agree with commenters who indicated that, by its very
nature, the national risk assessment, while comprehensive, cannot
address unique, site-specific risk considerations \25\ As a result of
these considerations, a separate analysis or ``risk check'' may be
necessary to verify that the MACT standards will be adequately
protective under RCRA for a given hazardous waste combustor.
---------------------------------------------------------------------------

\25\ Including for example, unusual terrain or dispersion
features, particularly sensitive ecosystems, unusually high
contaminant background concentrations, and mercury methylation rates
in surface water.
---------------------------------------------------------------------------

Thus, we are recommending that for hazardous waste combustors
subject to the Phase I final MACT standards, permitting authorities
should evaluate the need for a SSRA on a case-by-case
basis.²⁶ SSRAs are not anticipated to be necessary for every
facility, but should be conducted for facilities where there is some
reason to believe that operation

[[Page 52842]]

in accordance with the MACT standards alone may not be protective of
human health and the environment. If a SSRA does demonstrate that
operation in accordance with the MACT standards may not be protective
of human health and the environment, permitting authorities may require
additional conditions as necessary. We consider this an appropriate
course of action to ensure protection of human health and the
environment under RCRA, given current limits to our scientific
knowledge and risk assessment tools.
---------------------------------------------------------------------------

\26\ We continue to recommend that for those HWCs not subject to
the Phase I final MACT standards, as SSRA should be conducted as
part of the RCRA permitting process.
---------------------------------------------------------------------------

2. How Will the SSRA Policy Be Implemented?
Some commenters suggest that EPA provide regulatory language
specifically requiring SSRAs. Adequate authority and direction already
exists to require SSRAs on a case-by-case basis through current
regulations and guidance (none of which are being reconsidered, revised
or otherwise reopened in today's rulemaking). The omnibus provision
(codified in 40 CFR 270.32(b)(2)) directs the RCRA permitting authority
to include terms and conditions in the RCRA permit as necessary to
ensure protection of human health and the environment. Under 40 CFR
270.10(k), the permitting authority may require a permittee or permit
applicant to submit information where the permitting authority has
reason to believe that additional permit conditions may be warranted
under Sec. 270.32(b)(2). Performance of a SSRA is a primary, although
not exclusive mechanism by which the permitting authority may develop
the information necessary to make the determination regarding what, if
any, additional permit conditions are needed for a particular hazardous
waste combustor. Thus, for hazardous waste combustors, the information
required to establish permit conditions could include a SSRA, or the
necessary information required to conduct a SSRA.
In 1994, we provided guidance concerning the appropriate
methodologies for conducting hazardous waste combustor
SSRAs.²⁷ This guidance was updated in 1998 and released for
publication as an external peer review draft.²⁸ We
anticipate that use of the updated and more detailed guidance will
result in a more standardized assessments for hazardous waste
combustors.
---------------------------------------------------------------------------

\27\ USEPA. ``Guidance for Performing Screening Level Risk
Analyses at Combustion Facilities Burning Hazardous Wastes'' Draft,
April 1994; USEPA. ``Implementation of Exposure Assessment Guidance
for RCRA Hazardous Waste Combustion Facilities'' Draft, 1994.
\28\ USEPA. ``Human Health Risk Assessment Protocol for
Hazardous Waste Combustion Facilities'' EPA-520-D-98-001A, B&C.
External Peer Review Draft, 1998.
---------------------------------------------------------------------------

To implement the RCRA SSRA policy, we expect permitting authorities
to continue evaluating the need for an individual hazardous waste
combustor risk assessment on a case-by-case basis. We provided a list
of qualitative guiding factors in the April 1996 NPRM to assist in this
determination. One commenter is concerned that the subjectivity
inherent in the list of guiding factors might lead to inconsistencies
when determining if a SSRA is necessary and suggested that we provide
additional guidance on how the factors should be used. We continue to
believe that the factors provided, although qualitative, generally are
relevant to the risk potential of hazardous waste combustors and
therefore should be considered when deciding whether or not a SSRA is
necessary. However, as a practical matter, the complexity of the
multipathway risk assessment methodology precludes conversion of these
qualitative factors into more definitive criteria. We will continue to
compile data from SSRAs to determine if there are any trends which
would assist in developing more quantitative or objective criteria for
deciding on the need for a SSRA at any given site. In the interim,
SSRAs provide the most credible basis for comparisons between risk-
based emission limits and the MACT standards.
The commenter further suggests that EPA emphasize that the factors
should be considered collectively due to their complex interplay (e.g.,
exposure is dependent on fate and transport which is dependent on
facility characteristics, terrain, meteorological conditions, etc.). We
agree with the commenter. The elements comprising multipathway risk
assessments are highly integrated. Thus, the considerations used in
determining if a SSRA is necessary are similarly interconnected and
should be evaluated collectively.
The guiding factors as presented in the April 1996 NPRM contained
several references to the proposed MACT standards. As a result, we
modified and updated the list to reflect promulgation of the final
standards and to re-focus the factors to specifically address the types
of considerations inherent in determining if a SSRA is necessary. The
revised guiding factors are: (1) Particular site-specific
considerations such as proximity to receptors, unique dispersion
patterns, etc.; (2) identities and quantities of nondioxin products of
incomplete combustion most likely to be emitted and to pose significant
risk based on known toxicities (confirmation of which should be made
through emissions testing); (3) presence or absence of other off-site
sources of pollutants in sufficient proximity so as to significantly
influence interpretation of a facility-specific risk assessment; (4)
presence or absence of significant ecological considerations, such as
high background levels of a particular contaminant or proximity of a
particularly sensitive ecological area; (5) volume and types of wastes
being burned, for example wastes containing highly toxic constituents
both from an acute and chronic perspective; (6) proximity of schools,
hospitals, nursing homes, day care centers, parks, community activity
centers that would indicate the presence of potentially sensitive
receptors; (7) presence or absence of other on-site sources of
hazardous air pollutants so as to significantly influence
interpretation of the risk posed by the operation of the source in
question; and (8) concerns raised by the public. The above list of
qualitative guiding factors is not intended to be all-inclusive; we
recognize that there may be other factors equally relevant to the
decision of whether or not a SSRA is warranted in particular
situations.
With respect to existing hazardous waste combustion sources, we do
not anticipate a large number of SSRAs will need to be performed after
the compliance date of the MACT standards. SSRAs already have been
initiated for many of these sources. We strongly encourage facilities
and permitting authorities to ensure that the majority of those risk
assessments planned or currently in progress be completed prior to the
compliance date of the MACT standards. The results of these assessments
can be used to provide a numerical baseline for emission limits. This
baseline then can be compared to the MACT limits to determine if site-
specific risk-based limits are appropriate in addition to the MACT
limits for a particular source.
Several commenters suggest that completed risk assessments should
not have to be repeated. We do not anticipate repeating many risk
assessments. It should be emphasized that changes to comply with the
MACT standards should not cause an increase in risk for the vast
majority of the facilities given that the changes, in all probability,
will be the addition of pollution control equipment or a reduction in
the hazardous waste being burned. For those few situations in which the
MACT requirements might result in increased potential risk for a
particular facility due to unique site-specific considerations, the
RCRA permit writer, however, may determine

[[Page 52843]]

that a risk check of the projected MACT emission rates is in
order.²⁹ Should the results of the risk check demonstrate
that compliance with the MACT requirements does not satisfy the RCRA
protectiveness mandate, the permitting authority should invoke the
omnibus provision to impose more stringent, site-specific, risk-based
permit conditions as necessary to protect human health and the
environment.
---------------------------------------------------------------------------

\29\ For example, hazardous waste burning cement kilns that
previously monitored hydrocarbons in the main stack may elect to
install a mid-kiln sampling port for carbon monoxide or hydrocarbon
monitoring to avoid restrictions on hydrocarbon levels in the main
stack. Thus, their stack hydrocarbon emissions may increase.
---------------------------------------------------------------------------

With respect to new hazardous waste combustors and existing
combustors for which a SSRA has never been conducted, we recommend that
the decision of whether or not a SSRA is necessary be made prior to the
approval of the MACT comprehensive performance test protocol, thereby
allowing for the collection of risk emission data at the same time as
the MACT performance testing, if appropriate (see Part Five, Section
V). In those instances where it has been determined a SSRA is
appropriate, the assessment should take into account both the MACT
standards and any relevant site-specific considerations.
We emphasize that the incorporation of site-specific, risk-based
permit conditions into a permit is not anticipated to be necessary for
the vast majority of hazardous waste combustors. Rather, such
conditions would be necessary only if compliance with the MACT
requirements is insufficient to protect human health and the
environment pursuant to the RCRA mandate and if the resulting risk-
based conditions are more stringent than those required under the CAA.
Risk-based permit conditions could include, but are not limited to,
more stringent emission limits, additional operating parameter limits,
waste characterization and waste tracking requirements.
C. What Is the Difference Between the RCRA SSRA Policy and the CAA
Residual Risk Requirement?
Section 112(f) of the CAA requires the Agency to conduct an
evaluation of the risk remaining for a particular source category after
compliance with the MACT standards. This evaluation of residual risk
must occur within eight years of the promulgation of the MACT standards
for each source category. If it is determined that the residual risk is
unacceptable, we must impose additional controls on that source
category to protect public health with an ample margin of safety and to
prevent adverse environmental effects.
Our SSRA policy is intended to address the requirements of the RCRA
protectiveness mandate, which are different from those provided in the
CAA. For example, the omnibus provision of RCRA requires that the
protectiveness determination be made on a permit-by-permit or site-
specific basis. The CAA residual risk requirement, conversely, requires
a determination be made on a source category basis. Further, the time
frame under which the RCRA omnibus determination is made is more
immediate; the SSRA is generally conducted prior to final permit
issuance. The CAA residual risk determination, on the other hand, is
made at any time within the eight-year time period after promulgation
of the MACT standards for a source category. Thus, the possibility of a
future section 112(f) residual risk determination does not relieve RCRA
permit writers of the present obligation to determine whether the RCRA
protectiveness requirement is satisfied. Finally, nothing in the RCRA
national risk evaluation for this rule should be taken as establishing
a precedent for the nature or scope of any residual risk procedure
under the CAA.

Part Four: What Is the Rationale for Today's Final Standards?

I. Emissions Data and Information Data Base

A. How Did We Develop the Data Base for This Rule?
To support the emissions standards in today's rule, we use a
``fourth generation'' data base that considers and incorporates public
comments on previous versions of the data base. This final data base
²⁴ summarizes emissions data and ancillary information on
hazardous waste combustors that was primarily extracted from
incinerator trial burn reports and cement and lightweight aggregate
kiln Certification of Compliance test reports prepared as part of the
compliance process for the current regulatory standards. Ancillary
information in the data base includes general facility information
(e.g., location) process operating data (e.g., waste, fuel, raw
material compositions, feed rates), and facility equipment design and
operational information (e.g., air pollution control device
temperatures).
---------------------------------------------------------------------------

\24\ USEPA, ``Final Technical Support Document for HWC MACT
Standards, Volume II: HWC Emissions Database,'' July 1999.
---------------------------------------------------------------------------

The data base supporting the April 1996 proposal was the initial
data base released for public comment.²⁵ We received a
substantial number of public comments on this data base including
identification of data errors and submission of many new trial burn and
compliance test reports not already in the data base. Subsequently, we
developed a ``second generation'' data base addressing these comments
and, on January 7, 1997, published a NODA soliciting public comment on
the updated data base. Numerous industry stakeholders submitted
comments on the second generation data base. The data base was revised
again to accommodate these public comments resulting in a ``third
generation'' data base. We also published for comment a document
indicating how specific public comments submitted in response to the
January NODA were addressed.²⁶ In the May 1997 NODA, we used
this third generation data base to re-evaluate the MACT standards.
Since the completion of the third generation data base, we have
incorporated additional data base comments and new test reports
resulting in the ``fourth generation'' data base. This final data base
is used to support all MACT analyses discussed in today's rule.
Compared to the changes made to develop the third generation data base,
those changes made in the fourth generation are relatively minor. The
majority of these changes (e.g., incorporating a few trial burn reports
and incorporating suggested revisions to the third generation data
base) were in response to public comments received to May 1997 NODA.
---------------------------------------------------------------------------

\25\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards, Volume II: HWC Emissions Database,'' February 1996.
\26\ See USEPA, ``Draft Report of Revisions to Hazardous Waste
Combustor Database Based on Public Comments Submitted in Response to
the January 7, 1997 Notice of Data Availability (NODA),'' May 1997.
---------------------------------------------------------------------------

B. How Are Data Quality and Data Handling Issues Addressed?
We selected approaches to resolve several data quality and handling
issues regarding: (1) Data from sources no longer burning hazardous
waste; (2) assigning values to reported nondetect measurements; (3)
data generated under normal conditions versus worst-case compliance
conditions; and (4) use of imputation techniques to fill in missing or
unavailable data. This section discusses our selected approaches to
these four issues.

[[Page 52844]]

1. How Are Data From Sources No Longer Burning Hazardous Waste Handled?
Data and information from sources no longer burning hazardous waste
are not considered in the MACT standards evaluations promulgated today.
We note that some facilities have recently announced plans to cease
burning hazardous waste. Because we cannot continually adjust our data
base and still finalize this rulemaking, we concluded revisions to the
data base in early 1998. Announcements or actual facility changes after
that date simply could not be incorporated.
Numerous commenters responded to our request for comment on the
appropriate approach to handle emissions data from sources no longer
burning hazardous waste. In the April 1996 proposal, we considered all
available data, including data from sources that had since ceased waste
burning operations. However, in response to comments to the April 1996
NPRM, in the May 1997 NODA we excluded data from sources no longer
burning hazardous waste and reevaluated the MACT floors with the
revised data base. Of the data included in the fourth generation data
base, the number of sources that have ceased waste burning operations
include 18 incineration facilities comprising 18 sources; eight cement
kiln facilities comprising 12 sources; and one lightweight aggregate
kiln facility comprising one source.
Several commenters support the inclusion in the MACT analyses of
data from sources no longer burning hazardous waste. They believe the
performance data from these sources are representative of emissions
control achievable when burning hazardous waste because the data were
generated under compliance testing conditions. Other commenters suggest
that data from sources no longer burning hazardous waste should be
excluded from consideration when conducting MACT floor analyses to
ensure that the identified MACT floor levels are achievable.
The approach we adopt today is identical to the one we used for the
May 1997 NODA. Rather than becoming embroiled in a controversy over
continued achievability of the MACT standards, we exercise our
discretion and use a data base consisting of only facilities now
operating (at least as of the data base finalization date). Ample data
exist to support setting the MACT standards without using data from
facilities that no longer burn hazardous waste. To the extent that some
previous data from facilities not now burning hazardous waste still
remain in the data base, we ascribe to the view that these data are
representative of achievable emissions control and can be used.
2. How Are Nondetect Data Handled?
In today's rule, as in the May 1997 NODA, we evaluated nondetect
values, extracted from compliance test reports and typically associated
with feedstream input measurements rather than emissions
concentrations, as concentrations that are present at one-half the
detection limit. In the proposal, we assumed that nondetect analyses
were present at the value of the full detection limit.
Some commenters support our approach to assume that nondetect
values are present at one-half the detection limit. The commenter
states that this approach is consistent with the data analysis
techniques used in other EPA environmental programs such as in the
evaluation of groundwater monitoring data. Other commenters oppose
treating nondetect values at one-half the detection limit, especially
for dioxins/furans because Method 23 for quantitating stack emissions
states that nondetect values for congeners be treated as zero when
calculating total congeners and the toxicity equivalence quotient for
dioxins/furans. As explained in the NODA, the assumption that nondetect
measurements are present at one-half the reported detection limit is
more technically and environmentally conservative and increases our
confidence that standards and risk findings are appropriate. Further,
we considered assuming that nondetect values were present at the full
detection limit, but found that there were no significant differences
in the MACT data analysis results.²⁷ Therefore, in today's
rule, we assume nondetect measurements are present at one-half the
detection limit.
---------------------------------------------------------------------------

\27\ Using dioxins and furans as an example, for those sources
using MACT control, this difference is no more than approximately 10
percent of the standard. USEPA, ``Final Technical Support Document
for HWC MACT Standards, Volume III: Selection of MACT Standards and
Technologies,'' July 1999.
---------------------------------------------------------------------------

3. How Are Normal Versus Worst-Case Emissions Data Handled?
The majority of the available emissions data for all of the
hazardous air pollutants except mercury can be considered worst-case
because they were generated during RCRA compliance testing. Because
limits on operating parameters are established based on compliance test
operations, sources generally operate during compliance testing under
worst-case conditions to account for variability in operations and
emissions. However, the data base also contains some normal data for
these hazardous air pollutants. Normal data include those where
hazardous waste was burned, but neither spiking of the hazardous waste
with metals or chlorine nor operation of the combustion unit and
emission control equipment under detuned conditions occurred.
In the MACT analyses supporting today's rule, normal data were not
used to identify or define MACT floor control, with the exception of
mercury, as discussed below. This approach is identical to the one used
in the May 1997 NODA. 62 FR 24216.
Several commenters support the use of normal emissions data in
defining MACT controls because the effect of ignoring the potentially
lower emitters from these sources would skew the analysis to higher
floor results. Other commenters oppose the use of normal data because
they would not be representative of emissions under compliance test
conditions--the conditions these same sources will need to operate
under during MACT performance tests to establish limits on operating
conditions.²⁸
---------------------------------------------------------------------------

\28\ These commenters are concerned that, if the standards were
based on normal emissions data, sources would be inappropriately
constrained to emissions that are well below what is currently
normal. This is because of the double ratcheting effect of the
compliance regime whereby a source must first operate below the
standard during compliance testing, and then again operate below
compliance testing levels (and associated operating parameters) to
maintain day-to-day compliance.
---------------------------------------------------------------------------

We conclude that it is inappropriate to perform the MACT floor
analysis for a particular hazardous air pollutant using emissions data
that are a mixture of normal and worst-case data. The few normal
emissions data would tend to dominate the identification of best
performing sources while not necessarily being representative of the
range of normal emissions. Because the vast majority of our data is
based on worst-case compliance testing, the definition of floor control
is based on worst-case data.²⁹ Using worst-case emissions
data to establish a MACT

[[Page 52845]]

floor also helps account for emissions variability, as discussed in
Section V.D. below.
---------------------------------------------------------------------------

\29\ We considered adjusting the emissions data to account for
spiking to develop a projected normal emissions data base. However,
we conclude that this is problematic and have not done so. For
example, it is difficult to project (lower) emissions from
semivolatile metal-spiked emissions data given that system removal
efficiency does not correlate linearly with semivolatile metal
feedrate. In addition, we did not know for certain whether some data
were spiked. Thus, we would have to use either a truncated data base
of despiked data or a mixed data base of potentially spiked data and
despiked data, neither of which would be fully satisfactory.
---------------------------------------------------------------------------

Sources did not generally spike mercury emissions during RCRA
compliance testing because they normally feed mercury at levels
resulting in emissions well below current limits.³⁰
Consequently, sources are generally complying with generic,
conservative feedrate limits established under RCRA rather than
feedrate limits established during compliance testing. Because our data
base is comprised essentially of normal emissions, we believe this is
one instance where use of normal data to identify MACT floor is
appropriate. See discussion in Section V.D. below of how emissions
variability is addressed for the mercury floors.
---------------------------------------------------------------------------

\30\ Three of 23 incinerators used to define MACT floor (i.e.,
sources for which mercury feedrate data are available) are known to
have spiked mercury. No cement kilns used to define MACT floor
(e.g., excluding sources that have stopped burning hazardous waste)
are known to have spiked mercury. Only one of ten lightweight
aggregate kilns used to define MACT floor is known to have spiked
mercury.
---------------------------------------------------------------------------

4. What Approach Was Used To Fill In Missing or Unavailable Data?
With respect to today's rule, the term ``imputation'' refers to a
data handling technique where a value is filled-in for a missing or
unavailable data point. We only applied this technique to hazardous air
pollutants that are comprised of more than one pollutant (i.e.,
semivolatile metals, low volatile metals, total chlorine). We used
imputation techniques in both the proposal and May 1997 NODA; however,
we decided not to use imputation procedures in the development of
today's promulgated standards. We used only complete data sets in our
MACT determinations. Several commenters to the proposal and May 1997
NODA oppose the use of imputation techniques. Commenters express
concern that the imputation approach used in the proposal did not
preserve the statistical characteristics (average and standard
deviation) of the entire data set. Thus, commenters suggest that
subsequent MACT analyses were flawed. We reevaluated the data base and
determined that a sufficient number of data sets are complete without
the use of an imputation technique.³¹ A complete discussion
of various data handling conventions is presented in the technical
support document.³²
---------------------------------------------------------------------------

\31\ This is especially true because antimony is no longer
included in the low volatile metal standard.
\32\ See USEPA, ``Final Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards and
Technologies,'' July 1999.
---------------------------------------------------------------------------

II. How Did We Select the Pollutants Regulated by This Rule?

Section 112(b) of the Clean Air Act, as amended, provides a list of
188 ³³ hazardous air pollutants for which the Administrator
must promulgate emission standards for designated major and area
sources. The list is comprised of metal, organic, and inorganic
compounds.
---------------------------------------------------------------------------

\33\ The initial list consisted of 189 HAPs, but we have removed
caprolactam (CAS number 105602) from the list of hazardous air
pollutants. See Sec. 63.60.
---------------------------------------------------------------------------

Hazardous waste combustors emit many of the hazardous air
pollutants. In particular, hazardous waste combustors can emit high
levels of dioxins and furans, mercury, lead, chromium, antimony, and
hydrogen chloride. In addition, hazardous waste combustors can emit a
wide range of nondioxin/furan organic hazardous air pollutants,
including benzene, chloroform, and methylene chloride.
In today's rule, we establish nine emission standards to control
hazardous air pollutants emitted by hazardous waste combustors.
Specifically, we establish emission standards for the following
hazardous air pollutants: Chlorinated dioxins and furans, mercury, two
semivolatile metals (i.e., lead and cadmium), three low volatility
metals (i.e., arsenic, beryllium, chromium), and hydrochloric acid/
chlorine gas. In addition, MACT control is provided for other hazardous
air pollutants via standards for surrogates: (1) A standard for
particulate matter will control five metal hazardous air pollutants--
antimony, cobalt, manganese, nickel, and selenium; and (2) standards
for carbon monoxide, hydrocarbons, and destruction and removal
efficiency will control nondioxin/furan organic hazardous air
pollutants.
A. Which Toxic Metals Are Regulated by This Rule? ³⁴
---------------------------------------------------------------------------

\34\ RCRA standards currently control emissions of three toxic
metals that have not been designated as Clean Air Act hazardous air
pollutants: Barium, silver, and thallium. These RCRA metals are
incidentally controlled by today's MACT controls for metal hazardous
air pollutants in two ways. First, the RCRA metals are semivolatile
or nonvolatile and will, in part, be controlled by the air pollution
control systems used to meet the semivolatile metal and low volatile
metal standards in today's rule. Second, these RCRA metals will be
controlled by the measures used to meet today's MACT participate
matter standard. See text that follows.
---------------------------------------------------------------------------

1. Semivolatile and Low Volatile Metals
The Section 112(b) list of hazardous air pollutants includes 11
metals: antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead,
manganese, mercury, nickel, and selenium. To establish an implementable
approach for controlling these metal hazardous air pollutants, we
proposed to group the metals by their relative volatility and
established emission standards for each volatility group. We placed six
of the eleven metals in volatility groups. The high-volatile group is
comprised of mercury, the semivolatile group is comprised of lead and
cadmium, and the low volatile group is comprised of arsenic, beryllium,
and chromium.³⁵ We refer to these six metals for which we
have established standards based on volatility group as ``enumerated
metals.'' We have chosen to control the remaining five metals using
particulate matter as a surrogate as discussed in the next section.
---------------------------------------------------------------------------

\35\ Antimony was included in the low volatile group at
proposal, but we subsequently determined that the MACT particulate
matter standard serves as an adequate surrogate for this metal. See
the May 1997 NODA (62 FR at 24216). In making this determination, we
noted that antimony is an noncarcinogen with relatively low toxicity
compared with the other five nonmercury metals that were placed in
volatility groups. To be of particular concern, antimony would have
to be present in hazardous waste at several orders of magnitude
higher than shown in the available data.
---------------------------------------------------------------------------

Grouping metals by volatility is reasonable given that emission
control strategies are governed primarily by a metal's volatility. For
example, while semivolatile metals and low volatile metals are in
particulate form in the emission control train and can be removed as
particulate matter, mercury species are generally emitted from
hazardous waste combustors in the vapor phase and cannot be controlled
by controlling particulate matter unless a sorbent, such as activated
carbon, is injected into the combustion gas. In addition, low volatile
metals are easier to control than semivolatile metals because
semivolatile metals volatilize in the combustion chamber and condense
on fine particulate matter, which is somewhat more difficult to
control. Low volatile metals do not volatilize significantly in
hazardous waste combustors and are emitted as larger, easier to remove,
particles entrained in the combustion gas.³⁶
---------------------------------------------------------------------------

\36\ The dynamics associated with the fate of metals in a
hazardous waste combustor are much more complex than presented here.
For more information, see USEPA, ``Draft Technical Support Document
for HWC MACT Standards, Volume VII: Miscellaneous Technical
Issues,'' February 1996.
---------------------------------------------------------------------------

Commenters agree with our proposal to group metals by their
relative volatility. We adopt these groupings for the final rule.
We note that the final rule does not require a source to control
its particulate matter below the particulate matter standard to control
semivolatile and low

[[Page 52846]]

volatile metals. It is true that when we were determining the
semivolatile and low volatile metal floor standards, we did examine the
feedrates from only those facilities that were meeting the numerical
particulate standard. See Part Four, Section V.B.2.c. This is because
we believe that facilities, in practice, use both feedrate and
particulate matter air pollution control devices in a complementary
manner to address metals emissions (except mercury). However, our
setting of the semivolatile and low volatile metal floor standards does
not require MACT particulate matter control to be installed, either
directly or indirectly, as a matter of CAA compliance. We do not think
it is necessary to require compliance with a particulate matter
standard as an additional express element of the semivolatile/low
volatile metal emission standards because the particulate matter
standard is already required to control the nonenumerated metals, as
discussed below. However, we could have required compliance with a
particulate matter standard as part of the semivolatile or low volatile
metal emission standard because of the practice of using particulate
matter control as at least part of a facility's strategy to control or
minimize metal emissions (other than mercury).
2. How Are the Five Other Metal Hazardous Air Pollutants Regulated?
We did not include five metal hazardous air pollutants (i.e.,
antimony, cobalt, manganese, nickel, selenium) in the volatility groups
because of: (1) Inadequate emissions data for these metals
³⁷; (2) relatively low toxicity of antimony, cobalt, and
manganese; and (3) the ability to achieve control, as explained below,
by means of surrogates. Instead, we chose the particulate matter
standard as a surrogate control for antimony, cobalt, manganese,
nickel, and selenium. We refer to these five metals as ``nonenumerated
metals'' because standards specific to each metal have not been
established. We conclude that emissions of these metals is effectively
controlled by the same air pollution control devices and systems used
to control particulate matter.
---------------------------------------------------------------------------

\37\ USEPA, ``Final Technical Support Document for HWC MACT
Standards, Volume II: HWC Emissions Database,'' July 1999.
---------------------------------------------------------------------------

Some commenters suggest that particulate matter is not a surrogate
for the five nonenumerated metals. Commenters also note that our own
study, as well as investigations by commenters, did not show a
relationship between particulate matter and semivolatile metals and low
volatile metals when emissions from multiple sources were considered.
However, we conclude that such a relationship is not expected when
multiple sources are considered because wide variations in source
operations can affect: (1) Metals and particulate matter loadings at
the inlet to the particulate matter control device; (2) metals and
particulate matter collection efficiency; and (3) metals and
particulate matter emissions. Factors that can contribute to
variability in source operations include metal feed rates, ash levels,
waste types and physical properties (i.e., liquid vs. solid),
combustion temperatures, and particulate matter device design,
operation, and maintenance.
Conversely, emissions of semivolatile metals and low volatile
metals are directly related to emissions of particulate matter at a
given source when other operating conditions are held constant (i.e.,
as particulate matter emissions increase, emissions of these metals
also increase) because semivolatile metals and low volatile metals are
present as particulate matter at the typical air pollution control
device temperatures of 200 to 400 deg.F that are required under today's
rule.³⁸ A strong relationship between particulate matter and
semivolatile/low volatile metal emissions is evident from our emissions
data base of trial burn emissions at individual sources where
particulate matter varies and metals feedrates and other conditions
that may affect metals emissions were held fairly constant. Other work
also has clearly demonstrated that improvement in particulate control
leads to improved metals control.³⁹
---------------------------------------------------------------------------

\38\ The dioxin/furan emission standard requires that gas
temperatures at the inlet to electrostatic precipitators and fabric
filters not exceed 400 deg.F. Wet particulate matter control devices
reduce gas temperatures to below 400 deg.F by virtue of their design
and operation. The vapor phase contribution (i.e., nonparticulate
form that will not be controlled by a particulate matter control
device) of semivolatile metal and low volatile metal at these
temperatures is negligible.
\39\ USEPA, ``Final Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards and
Technologies,'' July 1999.
---------------------------------------------------------------------------

We also requested comment on whether particulate matter could be
used as a surrogate for all semivolatile and low volatile metal
hazardous air pollutants (i.e., all metal hazardous air pollutants
except mercury). See the May 1997 NODA. This approach is strongly
recommended by the cement industry. In that Notice, we concluded that,
because of varying and high levels of metals concentrations in
hazardous waste, use of particulate matter control alone may not
provide MACT control for metal hazardous air pollutants.⁴⁰
Our conclusion is the same today. Without metal-specific MACT emission
standards or MACT feedrate standards, sources could feed high levels of
one or more metal hazardous air pollutant metals. This practice could
result in high metal emissions, even though the source's particulate
matter is controlled to the emission standard (i.e., a large fraction
of emitted particulate matter could be comprised of metal hazardous air
pollutants). Thus, the use of particulate matter control alone would
not constitute MACT control of that metal and would be particularly
troublesome for the enumerated semivolatile and low volatile metal
because of their toxicity.⁴¹
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\40\ However, for sources not burning hazardous waste and
without a significant potential for extreme variability in metals
feedrates, particulate matter is an adequate surrogate for metal
hazardous air pollutants (e.g., for nonhazardous waste burning
cement kilns).
\41\ Using particulate matter as a surrogate for metals is,
however, the approach we used in the final rule for five metals:
Antimony, cobalt, manganese, nickel, selenium. Technical and
practical reasons unique to these metals support this approach.
First, these metals exhibit relatively low toxicity. Second, for
some of these metals, we did not have emissions data adequate to
establish specific standards. Therefore, the best strategy for these
particular metals, at this time, is to rely on particulate matter as
a surrogate.
---------------------------------------------------------------------------

Many commenters suggest that particulate matter is an adequate
surrogate for all metal hazardous air pollutants. They suggest that,
given current metal feedrates and emission rates, particularly in the
cement industry, a particulate matter standard is sufficient to ensure
that metal hazardous air pollutants (other than mercury) are controlled
to levels that would not pose a risk to human health or the
environment. While this may be true in some cases as a theoretical
matter, it may not be in all cases. Data demonstrating this
conclusively were not available for all cement kilns. Moreover, this
approach may not ensure MACT control of the potentially problematic
(i.e., high potential risk) metals for reasons discussed above (i.e.,
higher metal feedrates will result in higher metals emissions even
though particulate matter capture efficiency remains constant).
Consequently, we conclude that semi-volatile metals and low volatile
metals standards are appropriate in addition to the particulate matter
standard.
Finally, several commenters suggest that a particulate matter
standard is not needed to control the five nonenumerated metals because
the standards for the enumerated semivolatile and low volatile metals
would serve as surrogates for those

[[Page 52847]]

metals. Their rationale is that because the nonenumerated metals can be
classified as either semivolatile or nonvolatile ⁴², they
would be controlled along with the enumerated semivolatile and low
volatile metals. However, MACT control would not be assured for the
five nonenumerated metals even though they would be controlled by the
same emission control device as the enumerated semivolatile and low
volatile metals. For example, a source with high particulate matter
emissions could achieve the semivolatile and low volatile metal
emission standards (i.e., MACT control) by feeding low levels of
enumerated semivolatile and low volatile metals. But, if that source
also fed high levels of nonenumerated metals, MACT control for those
metals would not be achieved unless the source was subject to a
particulate matter MACT standard. Consequently, we do not agree that
the semivolatile and low volatile metal standards alone can serve as
surrogates for the nonenumerated metals.
---------------------------------------------------------------------------

\42\ As a factual matter, selenium can be classified as a
semivolatile metal and the remaining four nonenumerated metals can
be classified as low volatile metals.
---------------------------------------------------------------------------

We also proposed to use particulate matter as a supplemental
control for nondioxin/furan organic hazardous air pollutants that are
adsorbed onto the particulate matter. Commenters state, however, that
the Agency had not presented data showing that particulate matter in
fact contains significant levels of adsorbed nondioxin/furan organic
hazardous air pollutants. We now concur with commenters that, for
cement kiln and lightweight aggregate kiln particulate matter,
particulate matter emissions have not been shown to contain significant
levels of adsorbed organic compounds. This is likely because cement
kiln and lightweight aggregate kiln particulate matter is primarily
inert process dust (i.e., entrained raw material). Although particulate
matter emissions from incinerators could contain higher levels of
carbon that may adsorb some organic compounds, this is not likely a
significant means of control for those organic hazardous air
pollutants.⁴³
---------------------------------------------------------------------------

\43\ We recognize that sorbent (e.g., activated carbon) may be
injected into the combustion system to control mercury or dioxin/
furan. In these cases, particulate matter would be controlled as a
site-specific compliance parameter for these organics. See the
discussion in Part Five of this preamble.
---------------------------------------------------------------------------

B. How Are Toxic Organic Compounds Regulated by This Rule?
1. Dioxins/Furans
We proposed that dioxin/furan emissions be controlled directly with
a dioxin/furan emission standard based on toxicity equivalents. The
final rule adopts a TEQ approach for dioxin/furans. In terms of a
source determining compliance, we expect sources to use accepted TEQ
references.⁴⁴
---------------------------------------------------------------------------

\44\ For example, USEPA, ``Interim Procedure for Estimating
Risks Associated With Exposures to Mixtures of Chlorinated Dibenzo-
p-Dioxin and -Dibenzofurans (CDDs and CDFs) and 1989 Update'', March
1989; Van den Berg, M., et al. ``Toxic Equivalency Factors (TEFs)
for PCBs, PCDDs, PCDFs for Humans and Wildlife'' Environmental
Health Perspectives, Volume 106, Number 12, December 1998.
---------------------------------------------------------------------------

2. Carbon Monoxide and Hydrocarbons
We proposed that emissions of nondioxin/furan organic hazardous air
pollutants be controlled by compliance with continuously monitored
emission standards for either of two surrogates: carbon monoxide or
hydrocarbons. Carbon monoxide and hydrocarbons are widely accepted
indicators of combustion conditions. The current RCRA regulations for
hazardous waste combustors use emissions limits on carbon monoxide and
hydrocarbons to control emissions of nondioxin/furan toxic organic
emissions. See 56 FR 7150 (February 21, 1991) documenting the
relationship between carbon monoxide, combustion efficiency, and
emissions of organic compounds. In addition, Clean Air Act emission
standards for municipal waste combustors and medical waste incinerators
limit emissions of carbon monoxide to control nondioxin/furan organic
hazardous air pollutants. Finally, hydrocarbon emissions are an
indicator of organic hazardous air pollutants because hydrocarbons are
a direct measure of organic compounds.
Nonetheless, many commenters state that EPA's own surrogate
evaluation ⁴⁵ did not demonstrate a relationship between
carbon monoxide or hydrocarbons and nondioxin/furan organic hazardous
air pollutants at the carbon monoxide and hydrocarbon levels evaluated.
Several commenters note that this should not have been a surprise given
that the carbon monoxide and hydrocarbon emissions data evaluated were
generally from hazardous waste combustors operating under good
combustion conditions (and thus, relatively low carbon monoxide and
hydrocarbon levels). Under these conditions, emissions of nondioxin/
furan organic hazardous air pollutants were generally low, which made
the demonstration of a relationship more difficult. These commenters
note that there may be a correlation between carbon monoxide and
hydrocarbons and nondioxin/furan organic hazardous air pollutants, but
it would be evident primarily when actual carbon monoxide and
hydrocarbon levels are higher than the regulatory levels. We agree, and
conclude that carbon monoxide and hydrocarbon levels higher than those
we establish as emission standards are indicative of poor combustion
conditions and the potential for increased emissions of nondioxin/furan
organic hazardous air pollutants. Consequently, we have adopted our
proposed approach for today's final rule.⁴⁶
---------------------------------------------------------------------------

\45\ See Energy and Environmental Research Corporation,
``Surrogate Evaluation of Thermal Treatment Systems,'' Draft Report,
October 17, 1994.
\46\ As discussed at proposal, however, this relationship does
not hold for certain types of cement kilns where carbon monoxide and
hydrocarbons emissions evolve from raw materials. See discussion in
Section VII of Part Four.
---------------------------------------------------------------------------

3. Destruction and Removal Efficiency
We have determined that a destruction and removal efficiency (DRE)
standard is needed to ensure MACT control of nondioxin/furan organic
hazardous air pollutants.⁴⁷ We adopt the implementation
procedures from the current RCRA requirements for DRE (see
Secs. 264.342, 264.343, and 266.104) in today's final rule. The
rationale for adopting destruction and removal efficiency as a MACT
standard is discussed later in Section IV of the preamble.
---------------------------------------------------------------------------

\47\ Under this standard, several difficult to combust organic
compounds would be identified and destroyed or removed by the
combustor to at least a 99.99% (or 99.9999%, as applicable)
efficiency.
---------------------------------------------------------------------------

C. How Are Hydrochloric Acid and Chlorine Gas Regulated by This Rule?
We proposed that hydrochloric acid and chlorine gas emissions be
controlled by a combined total chlorine MACT standard because: (1) The
test method used to determine hydrochloric acid and chlorine gas
emissions may not be able to distinguish between the compounds in all
situations; ⁴⁸ and (2) both of these hazardous air
pollutants can be controlled by limiting feedrate of chlorine in
hazardous waste and wet scrubbing. We have adopted this approach in
today's final rule.
---------------------------------------------------------------------------

\48\ See the proposed rule, 61 FR at 17376.
---------------------------------------------------------------------------

One commenter questions whether it is appropriate to establish a
combined standard for hydrochloric acid and chlorine gas because the
removal efficiency of emission control equipment is substantially
different for the two pollutants. Although we agree that the efficiency
of emission control equipment is substantially different for the two
pollutants, we conclude that the MACT control techniques will readily

[[Page 52848]]

enable sources to achieve the hydrochloric acid/chlorine gas emission
standard. As discussed in Sections VI, VII, and VIII below, MACT
control for all hazardous waste combustors is control of the hazardous
waste chlorine feedrate. This control technique is equally effective
for hydrochloric acid and chlorine gas and represents MACT control for
cement kilns. MACT control for incinerators also includes wet
scrubbing. Although wet scrubbing is more efficient for controlling
hydrochloric acid, it also provides some control of chlorine gas. MACT
control for lightweight aggregate kilns also includes wet or dry
scrubbing. Although dry scrubbing does not control chlorine gas,
chlorine feedrate control combined with dry scrubbing to remove
hydrochloric acid will enable lightweight aggregate kilns to achieve
the emission standard for hydrochloric acid/chlorine gas.

III. How Are the Standards Formatted in This Rule?

A. What Are the Units of the Standards?
With one exception, the final rule expresses the emission standards
on a concentration basis as proposed, with all standards expressed as
mass per dry standard cubic meter (e.g., g/dscm), with
hydrochloric acid/chlorine gas, carbon monoxide, and hydrocarbon
standards being expressed at parts per million by volume (ppmv). The
exception is the particulate matter standard for hazardous waste
burning cement kilns where the standard is expressed as kilograms of
particulate matter per Mg of dry feed to the kiln.
Several commenters suggest that the standards should be expressed
on a mass emission basis (e.g., mg/hour) because of equity concerns
across source categories and environmental loading concerns. They are
concerned that expressing the standards on a concentration basis allows
large gas flow rate sources such as cement kilns to emit a much greater
mass of hazardous air pollutants per unit time than smaller sources
such as some on-site incinerators. Concomitantly, small sources would
incur a higher cost/lb of pollutant removed, they contend, than a large
source.⁴⁹ Further, they reason that the larger sources would
pose a much greater risk to human health and the environment because
risk is a function of mass emissions of pollutants per unit of time.
---------------------------------------------------------------------------

\49\ This result is not evident given that the cost of an
emission control device is generally directly proportional to the
gas flow rate, not the mass emission rate of pollutants per unit
time.
---------------------------------------------------------------------------

Although we agree with commenters' point about differential
environmental loadings attributable to small versus large sources with
a concentration-based standard, we note that the mass-based standard
urged here is inherently incompatible with technology-based MACT
standards for several reasons.⁵⁰ A mass-based standard does
not ensure MACT control at small sources. Small sources have lower flow
rates and thus would be allowed to emit hazardous air pollutants at
high concentrations. They could meet the standard with no or minimal
control. In addition, this inequity between small and large sources
would create an incentive to divert hazardous waste from large sources
to small sources (existing and new), causing an increase in emissions
nationally.
---------------------------------------------------------------------------

\50\ Although the particulate matter standard for hazardous
waste burning cement kilns in today's rule is the New Source
Performance Standard expressed as on a mass basis (i.e., kg of
particulate matter per megagram of dry feed to the kiln), this
standard is not based on a ``mass of particulate matter emissions
per unit of time'' that commenters suggest. Rather, the cement kiln
standard can be equated to a concentration basis given that cement
kilns emit a given quantity of combustion gas per unit of dry feed
to the kiln. In fact, we proposed the cement kiln particulate matter
standard on a concentration basis, 0.03 gr/dscf, that was calculated
from the New Source Performance Standard when applied to a typical
wet process cement kiln.
---------------------------------------------------------------------------

B. Why Are the Standards Corrected for Oxygen and Temperature?
As proposed, the final standards are corrected to 7 percent oxygen
and 20 deg.C because the data we use to establish the standards are
corrected in this manner and because the current RCRA regulations for
these sources require this correction. These corrections normalize the
emissions data to a common base, recognizing the variation among the
different combustors and modes of operation.
Several commenters note that the proposed oxygen correction
equation does not appropriately address hazardous waste combustors that
use oxygen enrichment systems. They recommend that the Agency
promulgate the oxygen correction factor equation proposed in 1990 for
RCRA hazardous waste incinerators. See 55 FR at 17918 (April 27, 1990).
We concur, and adopt the revised oxygen correction factor equation.
C. How Does the Rule Treat Significant Figures and Rounding?
As proposed, the final rule establishes standards and limits based
on two significant figures. One commenter notes that a minimum of three
significant figures must be used for all intermediate calculations when
rounding the results to two significant figures. We concur. Sources
should use standard procedures, such as ASTM procedure E-29-90, to
round final emission levels to two significant figures.

IV. How Are Nondioxin/Furan Organic Hazardous Air Pollutants
Controlled?

Nondioxin/furan organic hazardous air pollutants are controlled by
a destruction and removal efficiency (DRE) standard and the carbon
monoxide and hydrocarbon standards. Previous DRE tests demonstrating
compliance with the 99.99% requirement under current RCRA regulations
may be used to document compliance with the DRE standard provided that
operations have not been changed in a way that could reasonably be
expected to affect ability to meet the standard. However, if waste is
fed at a point other than the flame zone, then compliance with the
99.99% DRE standard must be demonstrated during each comprehensive
performance test, and new operating parameter limits must be
established to ensure that DRE is maintained. A 99.9999% DRE is
required for those hazardous waste combustors burning dioxin-listed
wastes. These requirements are discussed in Section IV.A. below.
In addition, the rule establishes carbon monoxide and hydrocarbons
emission standards as surrogates to ensure good combustion and control
of nondioxin/furan organic hazardous air pollutants. Continuous
monitoring and compliance with either the carbon monoxide or
hydrocarbon emissions standard is required. If you choose to
continuously monitor and comply with the carbon monoxide standard, you
must also demonstrate during the comprehensive performance test
compliance with the hydrocarbon emission standard. Additionally, you
must also set operating limits on key parameters that affect combustion
conditions to ensure continued compliance with the hydrocarbon emission
standard. Alternatively, continuous monitoring and compliance with the
hydrocarbon emissions standard eliminates the need to monitor carbon
monoxide emissions because hydrocarbon emissions are a more direct
surrogate of nondioxin/furan organic hazardous air pollutant emissions.
These requirements are discussed in Section IV.B below.
A. What Is the Rationale for DRE as a MACT Standard?
All sources must demonstrate the ability to destroy or remove 99.99

[[Page 52849]]

percent of selected principal organic hazardous compounds in the waste
feed as a MACT standard. This requirement, commonly referred to as
four-nines DRE, is a current RCRA requirement. We are promulgating the
DRE requirement as a MACT floor standard to control the emissions of
nondioxin organic hazardous air pollutants. The rule also requires
sources to establish limits on specified operating parameters to ensure
compliance with the DRE standard. See Part Five Section VII(B).
In the April 1996 NPRM, we proposed that the four-nines DRE test
requirement be retained under RCRA and be performed as part of a RCRA
approved trial burn because we did not believe that the DRE test could
be adequately implemented using the generally self-implementing MACT
performance test and notification process.⁵¹ See 61 FR
17447.
---------------------------------------------------------------------------

\51\ Historically, under RCRA regulations, the permittiing
authority and hazardous waste combustion source found it necessary
to go through lengthy negotiations to develop a RCRA trial burn plan
that adequately demonstrates the unit's ability to achieve four-
nines DRE.
---------------------------------------------------------------------------

In response to the April proposal, however, we received comments
that suggest the MACT comprehensive performance test and RCRA DRE trial
burn could and should be combined, and that we should combine all stack
air emission requirements for hazardous waste combustors into a single
permit. Commenters are concerned that our proposed approach required
sources to obtain two permits for air emissions and potentially be
unnecessarily subject to dual enforcement.
We investigated approaches that would achieve the goals of a single
air emission permit and inclusion of DRE in MACT. We determined that
the 40 CFR part 63 general provisions, applicable to all MACT regulated
sources unless superseded, includes a process similar to the process to
develop a RCRA trial burn test plan and allows permitting authorities
to review and approve MACT performance test plans. See 40 CFR 63.7.
Additionally, we determined that, because all hazardous waste
combustors are currently required to achieve four-nines DRE, the DRE
requirement could be included as a MACT floor standard rather than a
RCRA requirement. In the May 1997 NODA, we discussed an alternative
approach that used a modified form of the general provision's
performance test plan and approval process. The approach would allow
combination of the DRE test with the comprehensive performance test
and, therefore, facilitate implementation of DRE as a MACT standard. We
also discussed modifying the general approach to extend the performance
test plan review period to one year in advance of the date a source
plans to perform the comprehensive performance test. This extended
review period would provide sufficient time for negotiations between
permitting authorities and sources to develop and approve comprehensive
performance test plans. These test plans would identify operating
parameter limits necessary to ensure compliance with all the proposed
MACT standards, as well as, implement the four-nines DRE test as a MACT
floor standard. See 62 FR at 24241. Commenters support the process to
combine the applicable stack emission requirements into a single
permit. As for making the DRE test a MACT standard, we received no
negative comments. Many commenters, however, question the need for
subsequent DRE testing once a unit demonstrates four-nines DRE. See
discussion and our response in Subsection 2 below.
We believe that requiring the DRE test as a MACT standard is
appropriate. As we previously noted, the four-nines DRE is firmly
grounded statutory and regulatory requirement that has proven to be an
effective method to determine appropriate process controls necessary
for the combustion of hazardous waste. Specifically, RCRA requires that
all hazardous waste incinerators must demonstrate the minimum
technology requirement of four-nines DRE (RCRA section 3004(o)(1)(B)).
Additionally, the current RCRA BIF regulations require that all boiler
and industrial furnaces meet the four-nines DRE standard. Moreover,
current RCRA regulations require all sources incinerating certain
dioxin-listed contaminated wastes (F020-023 and F026-27) to achieve
99.9999% (six-nines) DRE. See Secs. 264.343(a)(2) and 266.104(a)(3).
The statutory requirement for incinerators to meet four-nines DRE
can be satisfied if the associated MACT requirements ensure that
incinerators will continue to meet the four-nines DRE minimum
technology requirement, i.e., that MACT standards provide at least the
``minimum'' RCRA section 3004(o)(1) level of control. To determine if
the RCRA statutory requirements could be satisfied, we investigated
whether DRE could be replaced with universal standards for key
operating parameters based on previous DRE demonstrations (i.e.,
standards for carbon monoxide and hydrocarbon emissions). We found
that, in the vast majority of DRE test conditions, if a unit operated
with carbon monoxide levels of less than 100 ppmv and hydrocarbon
emissions of less than 10 ppmv, the unit met or surpassed four-nines
DRE. In a small number of test conditions, units emitted carbon
monoxide and hydrocarbons at levels less than 100 and 10 ppmv
respectively, but failed to meet four-nines DRE. Most failed test
conditions were either due to questionable test results or faulty test
design.⁵² See U.S. EPA, ``Draft Technical Support Document
for HWC MACT Standards (NODA), Volume II: Evaluation of CO/HC and DRE
Database,'' April 1997. Even though we could potentially explain the
reasons these units failed to achieve four-nines DRE, we determined
that universal carbon monoxide and hydrocarbon emissions limits may not
ensure that all units achieve four-nines DRE because carbon monoxide
and hydrocarbon emissions may not be representative of good combustion
for all operating conditions that facilities may desire to operate. In
addition, we could not identify a better method than the DRE test to
limit combustion failures modes.
---------------------------------------------------------------------------

\52\ In many of the failed test conditions that we investigated,
the facility fed a low concentration of organic compound on which
the DRE was being calculated. As has been observed many times,
organic compounds can be reformed in the post combustion gas stream
at concentrations sufficient to fail DRE. This is not indicative of
a failure in the systems ability to destroy the compound, but is
more likely the result of a poorly designed test. If the facility
had fed a higher concentration of organic compound in the waste to
the combustor, the unit would have been more likely to meet four-
nines DRE with no change in the operating conditions used during the
test. In other cases, poor test design (i.e., firing aqueous organic
waste into an unfired secondary combustion chamber) is considered to
be the cause.
---------------------------------------------------------------------------

Commenters state that the test conditions under which the DRE
failures occurred involved feeding practices that were not common in
the hazardous waste combustion industry. They further state that, if it
could be ensured that hazardous waste ignited, hydrocarbon and carbon
monoxide limits would be sufficient to ensure four-nines DRE is
achieved continuously. Therefore, a DRE demonstration would not be
warranted. Although we might agree in theory, the fact that tests were
performed under these test conditions indicates that a source desired
to operate in that fashion. Only the DRE test identified that the
combustion failure occurred and was not susceptible to control via
carbon monoxide and hydrocarbon emissions. This and other similar
failures can lead to increased emissions of products of incomplete
combustion and organic hazardous air pollutants. Also, as commenters
acknowledge, carbon monoxide and hydrocarbon emissions were effective
surrogates to ensure four-nines DRE only when

[[Page 52850]]

hazardous waste ignited. However, as we identified in the May 1997
NODA, there are a number of hazardous waste combustion sources that
operate in a manner that does not ensure ignition of hazardous waste.
As a result of the DRE test investigation, we determined that a
successful DRE demonstration is an effective, appropriate, and
necessary method to identify operating parameter limits that ensure
proper and achievable combustion of hazardous waste and to limit the
emissions of organic hazardous air pollutants. Additionally, the DRE
standard is a direct measure to ensure that the RCRA section 3004(o)(1)
mandate and its protectiveness goals are being met, and also serves to
maintain a consistent test protocol for sources combusting hazardous
waste. The DRE demonstration requirement is also reasonable, provides a
sound means to allow deferral of a RCRA mandate to the CAA, and
simplifies implementation by having all stack emissions-related testing
and compliance requirements promulgated under one statute, the CAA.
Therefore, we retain the DRE demonstration as part of the MACT
comprehensive performance test unless a DRE test has already been
performed with no relevant changes.
1. MACT DRE Standard
In today's rule, all affected sources are required to meet 99.99%
DRE of selected Principal Organic Hazardous Constituents (POCs) that
are as or more difficult to destroy than any organic hazardous
pollutant fed to the unit. With one exception discussed in subsection 3
below, this demonstration need be made only once during the operational
life of a source, either before or during the initial comprehensive
performance test, provided that the design, operation, and maintenance
features do not change in a manner that could reasonably be expected to
affect the ability to meet the DRE standard.
The DRE demonstration involves feeding a known mass of POHC(s) to a
combustion unit, and then measuring for that POHC(s) in stack
emissions. If the POHC(s) is emitted at a level that exceeds 0.01% of
the mass of the individual POHC(s) fed to the unit, the unit fails to
demonstrate sufficient DRE.
Operating limits for key combustion parameters are used to ensure
four-nines DRE is maintained. The operating parameter limits are
established based on operations during the DRE test. Examples of
combustion parameters that are used to set operating limits include
minimum combustion chamber temperature, minimum gas residence time, and
maximum hazardous waste feedrate by mass. See Sec. 63.1209(j).
Today's MACT DRE requirement is essentially the same as that
currently required under RCRA. The main difference is that the vast
majority of the MACT DRE demonstrations would not have to be repeated
as often as currently required under RCRA, as discussed in section 3
below.
2. How Can Previous Successful Demonstrations of DRE Be Used To
Demonstrate Compliance?
Except as discussed below, today's rule requires that, at least
once during the operational life of a source during or before the
initial comprehensive performance test, the source must demonstrate the
ability to achieve 99.99% DRE and must set operating parameter limits
to ensure that DRE is maintained. However, we recognize that many
sources have already undergone approved DRE testing. Further, many
facilities do not intend to modify their units design or operations in
such a way that DRE performance or parameters would be adversely
affected. Therefore, the Agency is allowing sources to use results from
previous EPA or State-approved DRE demonstrations to fulfill the MACT
four-nines DRE requirement, as well as to set the necessary operating
limits on parameters that ensure continued compliance.
If a facility wishes to operate under new operating parameter
limits that could reasonably be expected to affect the ability to meet
the standard, a new DRE demonstration must be performed before or
concurrent with the comprehensive performance test. If the DRE
operating limits conflict with operating parameter limits that are set
to ensure compliance with other MACT standards, the unit must comply
with the more stringent limits. Additionally, if a source is modified
in such a way that its DRE operating limits are no longer applicable or
valid, the source must perform a new DRE test. Moreover, if a source is
modified in any way such that DRE performance or parameters are
affected adversely, the source must perform a new DRE test.
3. DRE for Sources That Feed Waste at Locations Other Than the Flame
Zone
Today's rule requires sources that feed hazardous waste in
locations other than the flame zone to perform periodic DRE tests to
ensure that four-nines DRE continues to be achieved over the life of
the unit. As indicated in the May 1997 NODA at 62 FR 25877, the Agency
is concerned that these types of sources have a greater potential of
varying DRE performance due to their waste firing practices. That is,
due to the unique design and operation of the waste firing system, the
DRE may vary over time, and those variations cannot be identified or
limited through operating limits set during a single DRE test. For
these units, we are requiring that DRE be verified during each
comprehensive performance test and that new operating parameter limits
be established to ensure continued compliance.
4. Sources That Feed Dioxin Wastes
In today's rule, we are requiring all sources that feed certain
dioxin-listed wastes (i.e., F020-F023, F026, F027) to demonstrate the
ability to achieve 99.9999 percent (six-nines) DRE as a MACT standard.
This requirement will serve to achieve a number of goals associated
with today's regulations. First, under RCRA, six-nines DRE is required
when burning certain dioxin-listed wastes. If we did not promulgate
this requirement as a MACT standard, sources that feed dioxin-listed
waste would be required to maintain two permits to manage their air
emissions. Thus, by including this requirement as a MACT standard, we
eliminate any unnecessary duplication. That outcome is contrary to our
goal which is to limit, to the greatest extent possible, the need for
sources to obtain two permits governing air emissions under different
statutory authorities. Second, six-nines DRE helps to improve control
of nondioxin organic hazardous air pollutants as well. Finally, this
requirement properly reflects floor control for sources that feed
dioxin-listed wastes. Currently, all sources that feed dioxin listed
wastes must achieve six-nines DRE. Before making the decision to
include six-nines DRE as a MACT standard, we considered whether the
requirements could be eliminated given that we are issuing dioxin/furan
emission standards with today's rule. We concluded, first, that we had
not provided sufficient notice and comment to depart from the current
regulations applicable to these sources. Second, we also decided that
because we currently require other similar highly toxic bioaccumulative
and persistent compounds (e.g., PCB wastes) to be fed to units that
demonstrate six-nines DRE, a departure from that policy for RCRA dioxin
wastes would be inconsistent. Finally, we are in discussions that may
cause us to reevaluate our overall approach to dioxin-listed wastes,
with the potential to impact this rule and the land disposal
restrictions program. Any changes to our approach will be included in a
single rulemaking that would be proposed later.

[[Page 52851]]

B. What Is the Rationale for Carbon Monoxide or Hydrocarbon Standards
as Surrogate Control of Organic Hazardous Air Pollutants?
Today's rule adopts limits on emissions of carbon monoxide and
hydrocarbons as surrogates to ensure good combustion and control of
nondioxin organic hazardous air pollutants. We require continuous
emissions monitoring and compliance with either the carbon monoxide or
hydrocarbon emissions standard. Sources can choose which of these two
standards it wishes to continuously monitor for compliance. If a source
chooses the carbon monoxide standard, it must also demonstrate during
the comprehensive performance test compliance with the hydrocarbon
emission standard. During this test the source also must set operating
limits on key parameters that affect combustion conditions to ensure
continued compliance with the hydrocarbon emission standard. These
parameters relate to good combustion practices and are identical to
those for which you must establish limits under the DRE standard. See
Sec. 63.109(a)(7) and 63.1209(j). However, this source need not install
and use a continuous hydrocarbon monitor to ensure continued compliance
with the hydrocarbon standard. As discussed previously, the limits
established for DRE are identical. If a source elects to use the
hydrocarbon limit for compliance, then it must continuously monitor and
comply with the hydrocarbon emissions standard. However, this type of
source need not monitor carbon monoxide emissions or carbon monoxide
operating parameters because hydrocarbon emissions are a more direct
surrogate of nondioxin organic hazardous air pollutant emissions.
The April 1996 NPRM proposed MACT emission standards for both
carbon monoxide and hydrocarbon as surrogates to control emissions of
nondioxin organic hazardous air pollutants. We also proposed that
cement kilns comply with either a carbon monoxide or hydrocarbons
standard due to raw material considerations.⁵³ See 61 FR at
17375-6. Our reliance on only carbon monoxide or only hydrocarbon has
drawbacks, and therefore we proposed that incinerators and lightweight
aggregate kilns comply with emissions standards for both. Nonetheless,
we also acknowledged that requiring compliance with both carbon
monoxide and hydrocarbon standards may be redundant, and requested
comment on: (1) Giving sources the option of complying with either
carbon monoxide or hydrocarbon emission standards; or (2) establishing
a MACT standard for either carbon monoxide or hydrocarbon, but not
both.
---------------------------------------------------------------------------

\53\ See discussion regarding cement kilns compliance with the
carbon monoxide and/or hydrocarbon standards in Part Four, Section
VII.D.
---------------------------------------------------------------------------

Comments to our proposed approach question the necessity of two
related surrogates to control organic hazardous air pollutants. Many
commenters assert they are capable of controlling hydrocarbon emissions
effectively, but due to their system's unique design, they could not
comply continuously with the carbon monoxide emission standard. In
general, commenters prefer an approach that would afford them maximum
flexibility in demonstrating compliance with organic control standards,
i.e., more like option (1) in the NPRM.
The May 1997 NODA included a refined version of the option that
commenters prefer that allowed sources to monitor and comply with
either a carbon monoxide or hydrocarbon emission standard. In response
to the May 1997 NODA, commenters nearly unanimously support the option
that allowed facilities to monitor and comply with either the carbon
monoxide or hydrocarbon standard as surrogates to limit emissions of
nondioxin organic hazardous air pollutants. However, a few commenters
suggest that compliance with carbon monoxide or hydrocarbons in
combination with DRE testing is redundant and unnecessary. However, in
their comments, they do not address the issue of DRE failures
associated with low carbon monoxide or hydrocarbon emissions, other
than to state that if ignition failure was avoided, emissions of carbon
monoxide or hydrocarbons would be good indicators of combustion
efficiency and four-nines DRE. This does not address our concerns,
which reflect cases in which ignition failures did not occur and in
which destruction and removal efficiencies were not met.
In the May 1997 NODA, we discussed another option that required
sources to comply with the hydrocarbon emission standard and establish
a site-specific carbon monoxide limit higher than 100 ppmv. This option
was developed because compliance with the hydrocarbon standard assures
control of nondioxin organic hazardous air pollutants, and a site-
specific carbon monoxide limit aids compliance by providing advanced
information regarding combustion efficiency. However, we conclude that
this option may be best applied as a site-specific remedy in situations
where a source has trouble maintaining compliance with the hydrocarbon
standard.
Today's final rule modifies the May 1997 NODA approach slightly.
Complying with the carbon monoxide standard now requires documentation
that hydrocarbon emissions during the performance test are lower than
the standard, and requires operating limits on parameters that affect
hydrocarbon emissions. We adopt this modification because some data
show that high hydrocarbon emissions are possible while simultaneously
low carbon monoxide emissions are found.⁵⁴
---------------------------------------------------------------------------

\54\ In a number of instances, RCRA compliance test records
showed that sources emitting carbon monoxide at less than 100 ppmv
emitted hydrocarbons in excess of 10 ppmv.
---------------------------------------------------------------------------

In the BIF rule (56 FR at 7149-50), we found that both monitoring
and compliance with either carbon monoxide or hydrocarbon limits and
achieving four-nines DRE is needed to ensure control of products of
incomplete combustion (including nondioxin organic hazardous air
pollutants) that are a result of hazardous waste combustion. DRE,
although sensitive to identifying combustion failure modes, cannot
independently ensure that emissions of products of incomplete
combustion or organic hazardous air pollutants are being controlled.
DRE can only provide the assurance that, if a hazardous waste combustor
is operating normally, the source has the capability to transform
hazardous and toxic organic compounds into different compounds through
oxidation. These other compounds can include carbon dioxide, water, and
other organic hazardous air pollutants. Because carbon monoxide
provides immediate information regarding combustion efficiency
potentially leading to emissions of organic hazardous air pollutants
and hydrocarbon provides a direct measure of organic emissions, these
two parameters individually or in combination provide additional
control that would not be realized with the DRE operating parameter
limits alone.⁵⁵ Neither our data nor data supplied by
commenters show that only monitoring

[[Page 52852]]

carbon monoxide, hydrocarbons, or DRE by itself can adequately ensure
control of nondioxin organics. Therefore, the approach used in the BIF
rule still provides the best regulatory model. We conclude in today's
rule that hydrocarbons and carbon monoxide monitoring are not redundant
with the DRE testing requirement to control emissions of organic
hazardous air pollutants and require both standards. For an additional
discussion regarding the use of hydrocarbons and carbon monoxide to
control emissions of organic hazardous air pollutants, see USEPA,
``Technical Support Document for HWC MACT Standards, Volume III:
Selection of MACT Standards and Technologies,'' July 1999.
---------------------------------------------------------------------------

\55\ We acknowledge that although hydrocarbon emissions are a
direct measure of organic emissions, they are measured with a
continuous emissions monitoring system known as a flame ionization
detector. Some data suggest hydrocarbon flame ionization detectors
do not respond with the same sensitivity to the full spectrum of
organic compounds that may be present in the combustion gas.
Additionally, combustion gas conditions also may affect the
sensitivity and accuracy of the monitor. Nonetheless, monitoring
hydrocarbons with these detectors appears to be the best method
reasonably available to provide real-time monitoring of organic
emissions from a hazardous waste combustor.
---------------------------------------------------------------------------

V. What Methodology Is Used To Identify MACT Floors?

This section discusses: (1) Methods used to identify MACT floor
controls and emission levels for the final rule; (2) the rationale for
using hazardous waste feedrate control as part of MACT floor control
for the metals and total chlorine standards; (3) alternative methods
for establishing floor levels considered at proposal and in the May
1997 NODA; and (4) our consideration of emissions variability in
identifying MACT floor levels.
A. What Is the CAA Statutory Requirement To Identify MACT Floors?
We identify hazardous waste incinerators, hazardous waste burning
cement kilns, and hazardous waste burning lightweight aggregate kilns
as source categories to be regulated under section 112. We must,
therefore, develop MACT standards for each category to control
emissions of hazardous air pollutants. Under CAA section 112, we may
distinguish among classes, types and sizes of sources within a category
in establishing such standards.
Section 112 prescribes a minimum baseline or ``floor'' for
standards. For new sources, the standards for a source category cannot
be less stringent than the emission control that is achieved in
practice by the best-controlled similar source. Section 112(d)(3). The
standards for existing sources may be less stringent than standards for
new sources, but cannot be less stringent than ``(A) * * * the average
emissions limitation achieved by the best performing 12 percent of the
existing sources (for which the Administrator has emissions
information) * * *, in the category or subcategory for categories and
subcategories with 30 or more sources, or (B) the average emissions
limitation achieved by the best performing 5 sources (for which the
Administrator has or could reasonably obtain emissions information) in
the category or subcategory for categories and subcategories with fewer
than 30 sources.'' Id.
We also must consider a more stringent standard than the floor,
referred to in today's rule as a ``beyond-the-floor'' standard. For
each beyond-the-floor analysis, we evaluate the maximum degree in
reduction of hazardous air pollutants determined to be achievable,
taking into account the cost of achieving those reductions, nonair
quality health and environmental impacts, and energy costs. Section
112(d)(2). The object of a beyond-the-floor standard is to achieve the
maximum degree of emission reduction without unreasonable economic,
energy, or secondary environmental impacts.
B. What Is the Final Rule Floor Methodology?
Today's rule establishes MACT standards for the following hazardous
air pollutants, hazardous air pollutant groups or hazardous air
pollutant surrogates: dioxin/furans, mercury, two semivolatile metals
(lead and cadmium), three low volatile metals (arsenic, beryllium, and
chromium), particulate matter, total chlorine (hydrochloric acid and
chlorine gas), carbon monoxide, hydrocarbons, and destruction and
removal efficiency. This subsection discusses the overall engineering
evaluation and data analysis methods we used to establish MACT floors
for these standards. Additional detail on the specific application of
these methods for each source category and standard is presented in
Part Four, Sections VI-VIII, of the preamble and in the technical
support document.⁵⁶
---------------------------------------------------------------------------

\56\ USEPA, ``Final Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards and
Technologies,'' July 1999.
---------------------------------------------------------------------------

1. What Is the General Approach Used in This Final Rule?
The starting point in developing standards is to determine a MACT
floor emission level, the most lenient level at which a standard can be
set. To identify the floor level, we first identified the control
techniques used by the best performing sources. We designate these best
performing sources the ``MACT pool'' and the emission control
technologies they use we call ``MACT floor controls.''
After identifying the MACT pool and MACT floor controls, we
determine the emission level that the MACT floor controls are routinely
achieving--that is, an achievable emission level taking into account
normal operating variability (i.e., variability inherent in a properly
designed and operated control system). This is called the floor
emission level. To ensure that the floor emission level is being
achieved by all sources using floor controls (i.e., not just the MACT
pool sources), we generally consider emissions data from all sources in
a source category that use well-designed and properly operated MACT
floor controls. (We call the data set of all sources using floor
controls the ``expanded MACT pool.'') Floor levels in this rule are
generally established as the level achieved by the source in the
expanded MACT pool with the highest emissions average ⁵⁷
using well-designed and properly operated MACT floor controls.
---------------------------------------------------------------------------

\57\ Each source's emissions usually are expressed as an average
of three or more emission measurements at the same set of operating
parameters. This is because compliance is based on the average of
three or more runs.
---------------------------------------------------------------------------

Several commenters oppose considering emissions data from all
sources using MACT floor controls (i.e., the expanded MACT pool)
because they assert the expansion of the MACT pool results in inflated
floors. If we adopt these commenters' recommendation, then many sources
using MACT controls would not meet the standard, even though they were
using MACT floor control. (Indeed, in some cases, other test conditions
from the very system used to establish the MACT pool would not meet the
standard, notwithstanding no significant change in the system's design
and operation.) This result is inappropriate in that all sources using
properly designed and operated MACT floor controls should achieve the
floor emission level if the technology is well designed and operated.
In the absence of data indicating a design or operation problem, we
assume the floor emission level based on an expanded MACT pool reflects
an emission level consistently achievable by MACT floor technology. Our
resulting limits account for the fact that sources and emissions
controls will experience normal operating variability even when
properly designed and operated.
The MACT floor methodology in this rule does not use a single
uniform data analysis approach consistently across all three source
categories and standards. Our data analysis methods vary due to: (1)
Limitations of our emissions data and ancillary information; (2)
emissions of some hazardous air pollutants being related to the
feedrate of the hazardous air pollutant (e.g., semivolatile metal
emissions are affected by semivolatile metal feedrates) while emissions
of

[[Page 52853]]

other hazardous air pollutants are not (e.g., dioxin/furan emissions
are related to postcombustion dioxin/furan formation rather than
dioxin/furan feedrates); (3) the various types of emissions controls
currently in use which do not lend themselves to one type of MACT
analysis; and (4) consideration of existing regulations as themselves
establishing floor levels.
Finally, as discussed in Section D, the MACT floor levels
established through our data analysis approaches account for emissions
variability without the separate addition of a statistically-derived
emissions variability factor.
2. What MACT Floor Approach Is Used for Each Standard?
a. Dioxins and Furans. For dioxins and furans, we adopt the MACT
floor methodology discussed in the May 1997 NODA. Based on engineering
information and principles, we identify temperature of combustion gas
at the particulate matter control device of 400 deg.F or less as MACT
floor control of dioxin/furan. This technology and level of control has
been selected because postcombustion formation of dioxin/furan is
suppressed by lowering postcombustion gas temperatures, and formation
is reasonably minimized at gas temperatures of 400 deg.F or below.
Sources controlling gas temperatures to 400 deg.F or less at the
particulate matter control device represent the level achieved by the
median of the best performing 12 percent of sources where the source
category has more than 30 sources (or the median of the best performing
five sources where the source category has fewer than 30 sources).
The next step is to identify an emissions level that MACT floor
control achieved on a routine basis. We analyzed the emissions data
from all sources (within each source category) using MACT floor control
and establish the floor level equal to the highest test condition
average.
As discussed in greater detail in Part Four, Section VI,
incinerators with waste heat recovery boilers present a unique
situation for dioxin/furan control. Our data base shows that
incinerators equipped with waste heat recovery boilers have
significantly higher dioxin/furan emissions compared to other
incinerators. In the waste heat recovery boiler, combustion gas is
exposed to particles on boiler tubes within the temperature window of
450 deg. F to 650 deg. F, which promotes surface-catalyzed formation of
dioxin/furan. Therefore, we establish separate dioxin/furan standards
for incinerators with waste heat boilers and incinerators without waste
heat boilers.⁵⁸ The specified floor control for both waste
heat boilers and nonwaste heat boilers is combustion gas temperature
control to 400 deg.F or less at the particulate matter control
device.⁵⁹ Floor levels for waste heat boiler incinerators
are much higher, however, because of the dioxin/furan formation during
the relatively slow temperature quench in the boiler. See the
incinerator dioxin/furan discussion in Part Four, Section VI, of
today's rule for more details.
---------------------------------------------------------------------------

\58\ We concluded that separate standards to control other
hazardous air pollutants were not needed for waste heat boiler-
equipped incinerators versus other incinerators. That is, whether or
not the incinerator is equipped with a waste heat recovery boiler is
only of concern for dioxin/furan emissions, not the other hazardous
air pollutants.
\59\ Wet particulate matter control devices (e.g., venturi
scrubbers) inherently preclude dioxin/furan formation because: (1)
They do not suspend particulate matter in the combustion gas flow as
do fabric filters and electrostatic precipitators, and (2) gas
temperatures are below 400 deg.F in the scrubber. Given this, floor
control is use of a wet particulate matter control device or control
of combustion gas temperature to 400 deg.F or below at the inlet to
a dry particulate matter control device.
---------------------------------------------------------------------------

b. What MACT Floor Methodology Is Used for Particulate Matter? We
adopt a final MACT floor methodology for particulate matter based on
the approaches discussed in the May 1997 NODA. For incinerators, the
final MACT floor is determined through engineering principles and
information, coupled with analysis of the emissions data base. For
cement kilns, we base final MACT on the existing requirements of the
New Source Performance Standard applicable to Portland cement kilns.
Finally, for lightweight aggregate kilns, the final floor level is
derived directly from the emissions data base (i.e., the highest test
condition average for sources using properly designed and operated
floor control).
i. Incinerators. Today's rule identifies MACT floor control as
either a well-designed, operated, and maintained fabric filter,
ionizing wet scrubber, or electrostatic precipitator, based on
engineering information and an evaluation of the particulate matter
control equipment used by at least the median of the best performing 12
percent of sources and the emission levels achieved. These types of
particulate matter control equipment routinely and consistently achieve
superior particulate matter performance relative to other controls used
by the incinerator source category and thus represent MACT. Using
generally accepted engineering information and principles, we then
identify an emission level that well-designed, operated and maintained
fabric filters, ionizing wet scrubbers, and electrostatic precipitators
routinely achieve.
The floor level is not directly identified from the emissions data
base as the highest test condition average for sources using a fabric
filter, ionizing wet scrubber, or electrostatic precipitator. The
hazardous waste combustor incinerator data base, however, was used as a
tool to determine if the identified floor level, established on
generally accepted engineering information and principles, is in
general agreement with available particulate matter data. This is
because we do not have adequate data on the features of the control
devices to accurately distinguish only those devices that are well-
designed, operated, and maintained and thus representative of MACT.
Several sources in the emissions data base that are equipped with
fabric filters, ionizing wet scrubbers, or electrostatic precipitators
have emission levels well above the emission levels of other sources
equipped with those devices. This strongly suggests that the higher
levels are not representative of those achieved by well-designed,
operated, and maintained units, even when normal operating variability
is considered. We accordingly did not use these data in establishing
the standard. See Kennecott v. EPA, 780 F.2d 445, 458 (4th Cir. 1985)
(EPA ``can reject data it reasonably believes to be unreliable
including performance data that is higher than other plants operating
the same control technology.'')
ii. Cement Kilns. As discussed in the May 1997 NODA and in more
detail in the standards section for cement kilns in Part Four, Section
VII, we base the MACT floor emission level on use of a fabric filter or
electrostatic precipitator to achieve the New Source Performance
Standard for Portland cement kilns. The MACT floor is equivalent to and
expressed as the current New Source Performance Standard of 0.15 kg/Mg
dry feed (0.30 lb/ton dry feed). In the NPRM and the May 1997 NODA, we
proposed to express the particulate matter standard on a concentration
basis. However, because we are not yet requiring sources to document
compliance with the particulate matter standard by using a particulate
matter continuous emissions monitoring system in this final rule, we
establish and express the floor emission level equivalent to the New
Source Performance Standard. Commenters' concerns about separate MACT
pools for particulate matter, semivolatile metals, and low volatile
metals are discussed in Part Four, Section VII.
iii. Lightweight Aggregate Kilns. All lightweight aggregate kilns
burning

[[Page 52854]]

hazardous waste are equipped with fabric filters. We could not
distinguish only those sources with fabric filters better designed,
operated, and maintained than others, and thus represent MACT control.
Because we could not independently use engineering information and
principles to otherwise distinguish which well-designed, operated, and
maintained fabric filters are routinely achieving levels below the
highest test condition average in the emissions data base (i.e.,
considering the high inlet grain loadings for lightweight aggregate
kilns), we establish the floor level as that highest test condition
average emission level. Commenters concerns about a high floor level
and separate MACT pools for particulate matter, semivolatile metals,
and low volatile metals are discussed in Part Four, Section VIII.
c. Metals and Total Chlorine. This rule establishes MACT standards
for mercury; semivolatile metals comprised of combined emissions of
lead and cadmium; low volatility metals comprised of combined emissions
of arsenic, beryllium, and chromium; and total chlorine comprised of
combined emissions of hydrogen chloride and chlorine gas. As shown by
the following analysis, these hazardous air pollutants are all
controlled by the best performing sources, at least in part, by
feedrate control of the metal or chlorine in the hazardous waste. In
addition to hazardous waste feedrate control, some of the hazardous air
pollutants also are controlled by air pollution control equipment. Both
semivolatile metals and low volatile metals are controlled by a
combination of hazardous waste metal feedrate control and by
particulate matter control equipment. Total chlorine is controlled by a
combination of feedrate control and, for hazardous waste incinerators,
scrubbing equipment designed to remove acid gases.
i. How Are the Metals and Chlorine Floor Control(s) Identified? We
follow the language of CAA section 112(d)(3) to identify the control
techniques used by the best performing sources. The hazardous waste
incinerator and hazardous waste cement kiln source categories are
comprised of 186 and 33 sources, respectively. From the statutory
language, we conclude that for this analysis the control techniques
used by the best performing 6% of sources represents the average of the
best performing 12% of the sources in those categories. It follows,
therefore, that floor control for metals and chlorine is the
technique(s) used by the best performing 12 incinerators and two cement
kilns.
Because the hazardous waste lightweight aggregate kiln source
category is comprised of only 10 sources, we follow the language of
section 112(d)(3)(B) to identify the control technique(s) used by the
three best performing sources, which represents the median of the best
performing five sources.
Our floor control analysis indicates that the best performing 12
incinerators, two cement kilns, and three lightweight aggregate kilns
all use hazardous waste feedrate control to limit emissions of mercury,
semivolatile metal, low volatile metal, and total chlorine. For the
semivolatile and low volatile metals, the best performing sources also
use particulate matter control as part of the floor control technique.
In addition, the best performing incinerator sources also control total
chlorine and mercury with wet scrubbing. Accordingly, we identify floor
control for semivolatile metal and low volatile metal as hazardous
waste feedrate control plus particulate matter control, and floor
control for incinerators for total chlorine and mercury as hazardous
waste feedrate control plus wet scrubbing.
ii. What is the Rationale for Using Hazardous Waste Feedrate
Control as MACT Floor Control Technique? As discussed above, MACT floor
control for mercury, semivolatile metals, low volatile metals, and
total chlorine is based on, or at least partially based on, feedrate
control of metal and chlorine in the hazardous waste. The feedrate of
metal hazardous air pollutants will affect emissions of those
pollutants, and the feedrate of chlorine will affect emissions of total
chlorine (i.e., hydrochloric acid and chlorine gas) because metals and
chlorine are elements and are not destroyed during combustion.
Emissions controls, if any, control only a percentage of the metal or
total chlorine fed. Therefore, as concentrations of metals and total
chlorine in the inlet to the control device increase, emissions
increase.
At proposal, we identified hazardous waste feedrates as part of the
technology basis for the proposed floor emission
standards.⁶⁰ MACT maximum theoretical emission
concentrations ⁶¹ (MTECs) were established individually for
mercury, semivolatile metals, low volatile metals, and total chlorine
at a level equal to the highest MTEC of the average of the best
performing 12% of sources. For some hazardous air pollutants, hazardous
waste feedrate control of metals and chlorine was identified as the
sole component of floor control (i.e., where the best performing
existing sources do not use pollution control equipment to remove the
hazardous air pollutant). Examples include mercury and total chlorine
from cement kilns. For other hazardous air pollutants, we identified
hazardous waste feedrate control of metals and chlorine as a partial
component of MACT floor control (e.g., floor control for semivolatile
metals include good particulate matter control in addition to feedrate
control of semivolatile metals in hazardous waste).
---------------------------------------------------------------------------

\60\ See 61 FR at 17366.
\61\ We developed a term, Maximum Theoretical Emissions
Concentration, to compare metals and chlorine feedrates across
sources of different sizes. MTEC is defined as the metals or
chlorine feedrate divided by the gas flow rate, and is expressed in
g/dscm.
---------------------------------------------------------------------------

In the May 1997 NODA, we continued to consider hazardous waste
feedrate control of metals and chlorine as a valid floor control
technology. However, rather than defining a specific MACT control
feedrate level (expressed as a MTEC), we instead relied on another
analysis tool, an emissions breakpoint analysis, to identify sources
feeding metals and/or chlorine at high (and not MACT) levels. At the
time, we believed that the breakpoint analysis was a less problematic
approach to identify sources using MACT floor control than the
approaches proposed initially.⁶²
---------------------------------------------------------------------------

\62\ Comments had objected to our proposed approach of defining
MTECs as too reliant on engineering inspection of the data.
---------------------------------------------------------------------------

Given commenters' subsequent concerns with the emissions breakpoint
analysis as well (see discussion in Section C below), we conclude that
specifying MTECs as MACT control (partially or solely) is necessary to
properly reflect the feedrate component of MACT control.
Notwithstanding how the MACT floor MTEC is defined, many commenters
suggest that our consideration of hazardous waste feedrate as a floor
control technique is inappropriate in a technology-based rulemaking and
not permissible under the CAA. Commenters also state that hazardous
waste feedrate control is not a control technique due to the wide
variations in metals and chlorine in the hazardous waste generated at a
single facility location. Further, they believe even greater variations
occur in metals and chlorine levels in the hazardous waste generated at
multiple production sites representing different industrial sectors.
Thus, commenters suggest that basing a floor emission level on data
from sources that feed hazardous waste with low levels of metals or
chlorine is tantamount to declaring that wastes with higher levels of
metals or chlorine are not to be generated. Other

[[Page 52855]]

commenters note, however, that hazardous waste feedrate control must be
considered as a floor control technique because feedrate control is
being used as a control means to comply with existing RCRA regulations
for these combustors. Still other commenters recommend that we
establish uniform hazardous waste feedrate limits (i.e., base the
standard on an emission concentration coupled with a hazardous waste
feedrate limit on metals and chlorine) across all three hazardous waste
combustor source categories. Please refer to Part Five, Section
VII.D.3.c.iv of today's preamble and the Comment Response Document for
detailed responses to these comments.
We do not accept the argument that control of hazardous waste
metals and chlorine levels in hazardous waste cannot be part of the
floor technology. First, control of hazardous air pollutants in
hazardous waste feedstock(s) can be part of a MACT standard under
section 112(d)(2)(A), which clearly indicates that material
substitution can be part of MACT. Second, hazardous waste combustors
are presently controlling the level of metal hazardous air pollutants
and chlorine in the hazardous waste combusted because of RCRA
regulatory requirements. (See Sec. 266.103(c)(1) and (j) where metal
and chlorine feedrate controls are required, and where monitoring of
feedrates are required.) Simply because these existing controls are
risk-based, rather than technology-based, does not mean that they are
not means of controlling air emissions cognizable under the CAA. Floor
standards are to be based on ``emission limitation[s]'' achieved by the
best existing sources. An ``emission limitation'' includes ``a
requirement established by the * * * Administrator which limits the
quantity, rate, or concentration of emissions. * * * including any
requirement relating to the operation * * * of a source. * * *'' CAA
section 302(k). This is precisely what current regulations require to
control metal and chlorine levels in hazardous waste feed.
Commenters also note that contemplated floor levels were lower than
the feed limits specified in current regulations for boilers and
industrial furnaces. This is true, but not an impediment to identifying
achievable MACT floor levels. Actual performance levels can serve as a
basis for a floor. An analogy would be where a group of facilities
achieve better capture efficiency from air pollution control devices
than required by existing rule. That level of performance (if generally
achievable) can serve as the basis for a floor standard. Accordingly,
we use hazardous waste feedrate, entirely or partially, to determine
floor levels and beyond-the-floor levels for mercury, semivolatile
metals, low volatile metals, and total chlorine.
iii. How Are Feedrate and Emissions Levels Representative of MACT
Floor Control Identified? After identifying feedrate control as floor
control, we use a data analysis method called the ``aggregate feedrate
approach'' to establish floor control hazardous waste feedrate levels
and emission levels for mercury, semivolatile metals, low volatile
metals, and total chlorine. The first step in the aggregate feedrate
approach is to identify an appropriate level of aggregated mercury,
semivolatile metals, low volatile metals, and total chlorine feedrate
control, expressed as a MTEC, being achieved in practice by the best
performing incinerator, cement kiln and lightweight aggregate kiln
sources. This aggregate MTEC level is derived only from the sources
using MACT floor emission controls.
The aggregate feedrate approach involves four steps: (1)
Identifying test conditions in the data base where data are available
to calculate hazardous waste feedrate MTECs for all three metal
hazardous air pollutant groups and total chlorine; (2) screening out
test conditions where a source was not using the MACT floor emission
control device for hazardous air pollutants that are cocontrolled by an
air pollution control device ⁶³; (3) ranking the individual
hazardous air pollutant MTECs, from the different source test
conditions, from lowest to highest and assigning each a numerical rank,
with a rank of one being the lowest MTEC; and (4) summing, for each
test condition, the individual ranking for each of the hazardous air
pollutants to determine a composite ranking. The total sum is used to
provide an overall assessment of the aggregate level of hazardous air
pollutants in the hazardous waste for each test condition. The
hazardous waste feed streams with lower total sums (i.e., hazardous air
pollutant levels) are ``cleaner'' in aggregate than those with higher
total sums.⁶⁴ (See the technical support document for more
details on this procedure.⁶⁵)
---------------------------------------------------------------------------

\63\ For example, to potentially be considered a MACT-controlled
incinerator with respect to both the emissions control device and
hazardous waste metals and chlorine feedrate, the incinerator must
use a wet scrubber for hydrochloric acid and mercury control and
must use either a fabric filter, ionizing wet scrubber, or
electrostatic precipitator and achieve the floor particulate matter
level of 0.015 gr/dscf. Similarly, cement kilns must achieve the
particulate matter MACT floor (for this analysis only, the New
Source Performance Standard was converted to an estimated equivalent
stack gas concentration of 0.03 gr/dscf) and lightweight aggregate
kilns must meet the particulate matter MACT floor of 0.025 gr/dscf.
There is no MACT floor hydrochloric acid emissions control device
for cement kilns and lightweight aggregate kilns.
\64\ This aggregate hazardous waste MTEC ranking is done
separately for each of the three combustor source categories.
\65\ USEPA, ``Final Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards and
Technologies,'' July 1999.
---------------------------------------------------------------------------

The aggregate MTEC ranking process results in aggregate feedrate
data from nine incinerators, 10 cement kilns, and 10 lightweight
aggregate kilns from which to select an appropriate level of feedrate
control representative of MACT floor control.⁶⁶ We
considered selecting the source with either the highest or lowest
aggregate MTEC in each source category to represent MACT floor control,
but did not believe this was appropriate based on concerns about
representativeness and achievability. We conclude that it is
reasonable, however, to consider the best 50% of the sources for which
we have data in each source category as the best performing sources.
This is because, for incinerators and cement kilns, we have only a few
sources with complete aggregate MTEC data relative to the size of the
source category. The best 50% of the sources for these categories
equates to five sources, given that we have aggregate MTEC data for
nine incinerators and 10 cement kilns. For lightweight aggregate kilns,
this equates also to five sources given that we have aggregate MTEC
data for 10 lightweight aggregate kiln sources.
---------------------------------------------------------------------------

\66\ Only nine incinerators were ultimately used because (1) We
have complete metal emissions data on relatively few sources, and
(2) many sources do not use particulate matter floor control, a
major means of controlling semivolatile metals and low volatile
metals.
---------------------------------------------------------------------------

Additionally, we conclude it is appropriate to identify a feedrate
MTEC representative of floor control based on the median of the best
performing five sources. In selecting a representative sample and
identifying the appropriate MTEC floor control level, we draw guidance
from section 112(d)(3)(B), in which Congress requires the Agency to use
the average of the best performing five sources when faced with small
source categories (i.e., less than 30 sources), and therefore limited
data, to establish a MACT floor. In addition, this methodology is
reasonable and appropriate because it allows consideration of a number
of best performing sources (i.e., five), which is within the range of
reasonable values we could have selected.
We considered an approach that selected both the control technique
and level of control as the average of the best performing 12% of
incinerator and

[[Page 52856]]

cement kiln sources for which we have aggregate MTEC data. This
approach resulted in using only the best single source as
representative of MACT floor control for all existing sources because
there are only nine incinerators and 10 cement kilns for which we have
adequate aggregate data. However, the level of feedrate control
achieved by the single best performing existing source is likely not
representative of the range of higher feedrate levels achieved by the
best performing existing sources and, indeed, would inappropriately
establish as a floor what amounts to a new source standard.
The final step of the aggregate feedrate approach is to determine
an emission level that is routinely achieved by sources using MACT
floor control(s). Similar to the April 1996 NPRM and May 1997 NODA, we
evaluated all available data for each test condition to determine if a
hazardous air pollutant is fed at levels at or below the MACT floor
control MTEC. If so, the test condition is added to the expanded MACT
pool for that hazardous air pollutant.⁶⁷ We then define the
floor emission level for the hazardous air pollutant/hazardous air
pollutant group as the level achieved by the source with the highest
emissions average in the MACT expanded pool.
---------------------------------------------------------------------------

\67\ The expanded MACT pool for each hazardous air pollutant is
comprised of test conditions from sources equipped with the
prescribed MACT floor emission control device, if any, and feeding
hazardous waste at an MTEC not exceeding the MACT floor MTEC for
that hazardous air pollutant.
---------------------------------------------------------------------------

The aggregate feedrate approach is a logical and reasonable
outgrowth of the aggregate hazardous air pollutant approach to
establish floor emission levels that we discussed in the April 1996
NPRM. The initial proposal determined MACT floors separately for each
hazardous air pollutant controlled by a different control technology,
but we also proposed an alternative whereby floors would be set on the
basis of a source's performance for all hazardous air pollutants.
Many commenters prefer the total aggregate hazardous air pollutant
approach over the individual hazardous air pollutant approach because
it better ensures that floor levels would be simultaneously achievable.
However, we reject the total aggregate approach because it tends to
result in floors that are likely to be artificially high, reflective of
limited emissions data for all hazardous air pollutants at each
facility. These floor levels, therefore, would not reflect performances
of the best performing sources for particular hazardous air pollutants.
We are assured of simultaneous achievability in our final methodology
by: (1) Establishing the MACT floor feedrate control levels on an
aggregate basis for metals and chlorine, as discussed above, rather
than for each individual hazardous air pollutant; (2) using the
particulate matter MACT pool to establish floor levels for particulate
matter, semivolatile metals, and low volatile metals; and (3) ensuring
that floor controls are not technically incompatible. In fact, our
resulting floor emission levels are already achieved in practice by 9
to 40 percent of sources in each of the three source categories,
clearly indicating simultaneously achievable standards.⁶⁸
---------------------------------------------------------------------------

\68\ Our analysis shows that approximately nine percent of
incinerators, 27 percent of cement kilns, and 40 percent of
lightweight aggregate kilns currently operating can meet all of the
floor levels simultaneously. See USEPA, ``Final Technical Support
Document For HWC MACT Standards, Volume V: Emissions Estimates and
Engineering Costs,'' July 1999.
---------------------------------------------------------------------------

C. What Other Floor Methodologies Were Considered?
This is a brief overview of the major features of the MACT floor
methodologies that we proposed in the April 1996 NPRM or discussed in
the May 1997 NODA, accompanied by our rationale for not pursuing those
methodologies in this final rule.
1. April 19, 1996 Proposal
We proposed the same general approach to identify floor control and
floor emission levels as used in today's final rule. The proposal
contained an approach to identify the controls used by the best
performing sources (i.e., the MACT pool) and then identify an emission
level that those controls are achieving. To identify the floor emission
level, we considered emissions from all sources using properly designed
and operated controls (i.e., the expanded MACT pool) and established a
preliminary floor level as the highest test condition average for those
sources.
There are three major differences between the proposed approach and
today's final approach, however:
a. Emissions Variability. At proposal, we added a statistically-
derived emissions variability factor to the highest test condition
average in the expanded MACT pool. Today we conclude that emissions
variability is considered inherently in the floor methodology. (See
discussion in section D below for our rationale for not using a
statistically-derived variability factor.)
b. MACT Pool for Particulate Matter, Semivolatile Metals, and Low
Volatile Metals. At proposal, we identified separate and different MACT
pools (and associated MACT controls) for particulate matter,
semivolatile metals, and low volatile metals, even though all three are
controlled by a particulate matter control device. Commenters said this
is inappropriate and we concur. Specifying the MACT floor particulate
matter emission control device individually for these pollutants is
likely to result in three different definitions of floor control. Thus,
the same particulate matter control device would need to meet three
different design specifications. As a practical matter, the more
stringent specification would prevail. But, this highlights the
impracticability of evaluating floor emission control for these
standards individually rather than in the aggregate.
As discussed in the May 1997 NODA, today's approach uses the same
initial MACT pool to establish the floor levels for particulate matter,
semivolatile metals, and low volatile metals. The initial MACT pool is
comprised of those sources meeting the emission control component of
MACT control. To establish the semivolatile metal and low volatile
metal floor levels, the particulate matter MACT pool is then analyzed
to consider MACT hazardous waste feedrate control first for
semivolatile metals and then for low volatile metals, using the
aggregate feedrate approach discussed above.
c. Definition of MACT Control. At proposal, we defined MACT
emissions control by specifying the design of the emissions control
device. Commenters suggested that this was problematic because: (1) Our
data base had limited data on design of the control device; (2) some of
our available data were incorrect; and (3) the parameters the Agency
was using to characterize MACT control did not adequately correlate
with control efficiency. Given these concerns, our May 1997 NODA
contained an emissions breakpoint approach to identify those sources
that appeared to have anomalously higher emissions than other sources
in the potential MACT pool. Our rationale was that given the
anomalously high emissions, those sources were not, in fact, using MACT
control.
Commenters express serious concerns about the validity of the
nonstatistical approach used to identify the breakpoint. After
considering various statistical approaches to identify an emissions
breakpoint, we conclude that the emissions breakpoint approach is
problematic.⁶⁹ For these reasons, we are

[[Page 52857]]

not defining MACT emissions control by design parameters or using an
emissions breakpoint approach to identify MACT emissions or feedrate
control. Rather, the MACT floor emission control equipment, where
applicable, is defined generically (e.g., electrostatic precipitator,
fabric filter), and the aggregate feedrate approach is used to define
MACT floor feedrates. We believe the aggregate feedrate approach
addresses the concerns that commenters raise on the proposed approach
because it more clearly defines MACT control and relies less on
engineering judgment.
---------------------------------------------------------------------------

\69\ To improve the rigor of our breakpoint approach, we
investigated a modified Rosner ``outlier'' test that: (1) Uses a
single tailed test to consider only high ``outliers'' (i.e., test
conditions that anomalously high emissions, not necessarily true
outliers in the statistical sense); (2) presumes that any potential
``outliers'' are at the 80th percentile value or higher; and (3) has
a confidence level of 90 percent. We abandoned this statistical
approach because: (1) Although modifications to the standard Rosner
test were supportable, the modified test has not been peer-reviewed;
(2) although the target confidence level was 90 percent, the true
significance level of the test, as revised, is inappropriately low--
approximately 80 percent; and (3) the ``outlier'' test does not
identify MACT-like test conditions because it only identifies
anomalously high test conditions rather than the best performing
test conditions.
---------------------------------------------------------------------------

2. May 1997 NODA
We have incorporated into the final rule several of the procedures
discussed in the May 1997 NODA. The NODA explained why it is
inappropriate to add a statistically-derived emissions variability
factor to the highest test condition average of the expanded MACT pool.
Despite comments to the contrary, we conclude that emissions
variability is inherently considered in the floor methodology. See
discussion in section D below.
In addition, the NODA discussed using the same initial MACT pool to
establish the floor levels for particulate matter, semivolatile metals,
and low volatile metals. We use this same approach in this final rule.
Commenters generally concurred with that approach.
As discussed above, we considered using an emissions breakpoint
technique, but conclude that this approach is problematic and did not
use the approach for this rule.
D. How Is Emissions Variability Accounted for in Development of
Standards?
The methodology we use to establish the final MACT emission
standards intrinsically accounts for emissions variability without
adding statistically-derived emissions variability factors. Many
commenters strongly suggest that statistically-derived emissions
variability factors must be added to the emission levels we identify
from the data base as floor emission levels to ensure that the
standards are routinely achievable.⁷⁰ Other commenters
suggest that our floor methodology inherently accounts for emissions
variability. We discuss below the types of emissions variability and
why we conclude that emissions variability is inherently accounted for
by our methodology.
---------------------------------------------------------------------------

\70\ One commenter recommends specific statistical approaches to
calculate variability factors and provides examples of how the
statistical methods should be applied to our emissions data base.
See comment number CS4A-00041.
---------------------------------------------------------------------------

We account for three types of emissions variability in establishing
MACT standards: (1) Within test condition variability among test runs
(a test condition is comprised of at least three runs that are
averaged); (2) imprecision in the stack test method; and (3) source-to-
source emissions variability attributable to source-specific factors
affecting the performance of the same MACT control device. (See, e.g.
FMC Corp. v. Train, 539 F.2d 973, 985-86 (4th Cir. 1976), holding that
variability in performance must be considered when ascertaining whether
a technology-based standard is achievable.) The following sections
discuss the way in which we account for these types of variability in
the final rule.
1. How Is Within-Test Condition Emissions Variability Addressed?
Inherent process variability will cause emissions to vary from run-
to-run within a test condition, even if the stack method is 100 percent
precise and even though the source is attempting to maintain constant
operating conditions. This is caused by many factors including: Minor
changes in the feedrate of feedstreams; combustion perturbations (e.g.,
uncontrollable, minor fluctuations in combustion temperature or fan
velocity); changes in the collection efficiency of the emission control
device caused by fluctuations in key parameters (e.g., power input to
an electrostatic precipitator); and changes in emissions of materials
(e.g., sulfur dioxide) that may cause test method interferences.
At proposal, we used a statistical approach to account for
emissions variability. See 61 FR at 17366. The statistical approach
identified an emissions variability factor, which was added to the log-
mean of the emission level being achieved based on the available
``short-term'' compliance test data. We called this emission level the
``design level.'' The variability factor was calculated to ensure that
the design level could be achieved 99 percent of the time, assuming
average within-test condition emissions variability for the source
using MACT control.
In the May 1997 NODA, we discussed alternative emission standards
developed without using a statistically-derived variability factor.
Adding such a variability factor was determined inappropriate because
it sometimes resulted in nonsensical results. For example, the
particulate matter MACT floor level for incinerators under one floor
methodology would have been higher than the current RCRA standard
allows, simply due to the impact of an added variability factor. In
other cases, the floor levels would have been much higher than our
experience would indicate are routinely being achieved using MACT
control. We reasoned that these inappropriate and illogical results may
flow from either the data base used to derive the variability factor
(e.g., we did not have adequate information to screen out potentially
outlier runs on a technical basis) or selecting an inappropriate floor-
setting test condition as the design level (e.g., we did not have
adequate information on design, operation, and maintenance of emissions
control equipment used by sources in the emissions data base to
definitively specify MACT control).
Consequently, we reasoned that adequately accounting for within
test condition emissions variability is achieved where relatively large
data sets are available to evaluate for identifying the floor level.
Large sets of emissions data from MACT sources, which have emissions
below the floor level, are likely to represent the range of emissions
variability. For small data sets (e.g., dioxin/furan emissions for
waste heat recovery boiler equipped incinerators; dioxin/furan
emissions data for lightweight aggregate kilns), we acknowledged that
the same logic would not apply. For these small data sets, the floor
level was set at the highest run for the MACT source with the highest
test condition average emissions. Many commenters suggest that our
logic was flawed. Commenters say that, if we desire the floor level to
be achievable 99 percent of the time (i.e., the basis for the
statistically-derived variability factor at proposal), the emissions
data base is far too small to identify the floor level as the highest
test condition average for sources using MACT control.
We conclude, however, that the final floor levels identified, using
the procedures discussed above (i.e., without adding a statistically-
derived emissions variability factor), are levels that can be
consistently achieved by well designed, operated, and maintained MACT
sources. We

[[Page 52858]]

conclude this because our emissions data base is comprised of
compliance test data generated when sources have an incentive to
operate under worst case conditions (e.g., spiking metals and chlorine
in the waste feed; detuning the emissions control equipment). Sources
choose to operate under worst case conditions during compliance testing
because the current RCRA regulations require that limits on key
operating parameters not exceed the values occurring during the trial
burn. Therefore, these sources conduct tests in a manner that will
establish a wide envelope for their operating parameter limits in order
to accommodate the expected variability (e.g., variability in types of
wastes, combustion system parameters, and emission control parameters).
See 56 FR at 7146 where EPA likewise noted that certain RCRA operating
permit test conditions are to be ``representative of worst-case
operating conditions'' to achieve needed operating flexibility. One
company that operates several hazardous waste incinerators at three
locations comments that, because of the current RCRA compliance regime,
which is virtually identical to the compliance procedures of today's
MACT rule, ``the result is that units must be tested at rates which are
at least three standard deviations harsher than normal operations and
normal variability in order to simulate most of the statistical
likelihood of allowable emission rates.'' ⁷¹ The commenter
also states that because of the consequences of exceeding an operating
parameter limit under MACT, ``* * * clearly a source will test under
the worst possible operating conditions in order to minimize future
(exceedances of the limits).'' Finally, the commenter says that
``Because of variability and the stiff consequences of exceeding these
limits, operators do not in fact operate their units anywhere near the
limits for sustained periods of time, but instead tend to operate
several standard deviations below them, or at about 33 to 50% of the
limits.'' ⁷²
---------------------------------------------------------------------------

\71\ See Comment No. CS4A-00029.A, dated August 16, 1996.
\72\ To estimate the compliance cost of today's rule, we assumed
that sources would design their systems to meet an emission level
that is 70% of the standard, herein after called the ``design
level.''
---------------------------------------------------------------------------

We conclude from these comments, which are consistent with
engineering principles and with many discussions with experts from the
regulated community, that MACT sources with compliance test emissions
at or below the selected floor level are achieving those levels
routinely because these test conditions are worst-case and are defined
by the source itself to ensure 100 percent compliance with the relevant
standard.
We acknowledge, however, that mercury is a special case because our
mercury emission data may not be representative of worst-case
conditions. As discussed in Section I.B.3 above, sources did not
generally spike mercury emissions during RCRA compliance testing
because they normally feed mercury at levels resulting in emissions
well below current limits.⁷³ Although our data base for
mercury is comprised essentially of normal emissions, emissions
variability is adequately accounted for in setting floor levels. First,
mercury emissions variability is minimal because the source can readily
control emissions by controlling the feedrate of mercury.⁷⁴
For cement and lightweight aggregate kilns, mercury is controlled
solely by controlling feedrate. Given that there is no emission control
device that could have perturbations affecting emission rates,
emissions variability at a given level of mercury feedrate control is
relatively minor. Any variability is attributable to variability in
feedrate levels due to feedstream sampling and analysis imprecision,
and stack method imprecision (see discussion below).
---------------------------------------------------------------------------

\73\ Three of 23 incenerators used to define MACT floor (i.e.,
sources for which mercury feedrate data are available) are known to
have spiked mercury. No cement kilns used to define MACT floor
(e.g., excluding sources that have stopped burning hazardous waste)
are known to have spiked mercury. Only one of ten lightweight
aggregate kilns used to define MACT floor is known to have spiked
mercury.
\74\ Although incenerators are generally equipped with wet
scrubbers that can have a mercury removal efficiency of 15 to 60
percent, feedrate control is nonetheless the primary means of
mercury emissions control because of the relatively low removal
efficiency provided by wet scrubbers.
---------------------------------------------------------------------------

Second, our emissions data indicate that the mercury floor levels
are being achieved by a wide margin, which is a strong indication that
a variability factor is not needed. Only one of the 15 incinerators
using MACT floor control exceeds the design level for the floor
emission level.⁷⁵ In addition, only seven of 45 incinerators
for which we have mercury emissions data exceed the design level, and
two of those eight are know to have spiked mercury in the hazardous
waste feed during compliance testing. Only six of the 45 incinerators
exceed the floor emission level.
---------------------------------------------------------------------------

\75\ Commenters note that the mercury levels fed during RCRA
compliance testing may not represent the normal range of feedrates,
and thus the compliance test emission levels may not be
representative of emission levels achieved in practice. Given that
only one of 15 incinerators using floor control exceeds the design
level, it appears that the floor emission level is, in fact, being
achieved in practice. Some of these 15 sources were likely feeding
mercury at the high end of their normal range, even though others
may have been feeding mercury at normal or below normal levels. This
is also the situation of cement kilns where only two of 2 kilns
using floor control exceed the design level, and for lightweight
aggregate kilns where only one of nine kilns using floor exceeds the
design level.
---------------------------------------------------------------------------

The situation is similar for cement kilns and lightweight aggregate
kilns. Only two of 22 cement kilns using floor control exceed the
design level, only five of the 33 kilns in the source category exceed
the design level, and only one of the 33 kilns exceeds the floor
emission level. Only one of nine lightweight aggregate kilns using
floor control exceeds the design level, and only two of the 10 kilns in
the source category exceed the design level (and one of those kilns is
known to have spiked mercury in the hazardous waste feed during
compliance testing). Only one of the 10 kilns exceeds the floor
emission level, and that kiln spiked mercury.
We conclude from this analysis that the mercury floor emission
levels in this rule are readily achieved in practice even though our
mercury emissions data were not spiked (i.e., they may not represent
worst-case emissions), and therefore a separate variability factor is
not needed.
2. How Is Waste Imprecision in the Stack Test Method Addressed?
Method precision is a measure of how closely emissions data are
grouped together when measuring the same level of stack emissions
(e.g., using a paired or quad test train). Method imprecision is
largely a function of the ability of the sampling crew and analytical
laboratory to routinely follow best practices. Precision can be
affected by: (1) Measurement of ancillary parameters including gas flow
rate, pressure, and temperature; (2) recovery of materials from the
sampling train; and (3) cleaning, concentrating, and quantitating the
analyte.
Several commenters state that we must add a factor to the selected
floor level to account for method imprecision in addition to a factor
to account for within-test condition emissions variability. We
investigated the imprecision for the stack methods used to document
compliance with today's rule and determined that method imprecision may
be significant for some hazardous air pollutant/method
combinations.⁷⁶ Our results indicate, however, that method
precision is much better than commenters claim, and that as additional
data sets become available,

[[Page 52859]]

the statistically-derived precision bars for certain pollutants are
reasonably expected to be reduced significantly. This is mainly because
data should become available over a wider range of emission levels thus
reducing the uncertainty that currently results in large precision bar
projections for some hazardous air pollutants at emission levels that
are not close to the currently available paired and quad-train
emissions data.
---------------------------------------------------------------------------

\76\ USEPA, ``Final Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards and
Technologies,'' July 1999.
---------------------------------------------------------------------------

We conclude that method imprecision, in selecting the floor levels
for hazardous waste combustors, is adequately addressed for the same
reasons that we accounted for within-test condition emissions
variability. Method precision is simply a factor that contributes to
within-test condition variability. As discussed above, sources consider
emissions variability when defining their compliance test operating
conditions to balance emissions standards compliance demonstrations
with the need to obtain a wide operating envelope of operating
parameter limits.
3. How Is Source-to-Source Emissions Variability Addressed?
If the same MACT control device (i.e., same design, operating, and
maintenance features) were used at several sources within a source
category, emissions of hazardous air pollutants from the sources could
vary. This is because factors that affect the performance of the
control device could vary from source to source. Even though a device
has the same nominal design, operating, and maintenance features, those
features could never be duplicated exactly. Thus, emissions could vary
from source to source.
We agree that this type of emissions variability must be accounted
for in the standards to ensure the standards are achieved in practice.
Source-to-source emissions variability is addressed by identifying the
floor emission level as the highest test condition average for sources
in the expanded MACT pool, as discussed above.⁷⁷
---------------------------------------------------------------------------

\77\ Because of the need to account for this type of
variability, we disagree with those commenters recommending that:
(1) The floor emission level be identified as the average emission
level achieved by the 12 percent of source with the lowest
emissions; and (2) it is inappropriate to base the floor emission
level on sources using floor control but that are not within the 12
percent of sources with the lowest emissions (i.e., the expanded
MACT pool should not be used to identify floor emission levels). The
floor emission level must be achieved in practice by sources using
the appropriately designed and operated floor control. Thus,
emission levels being achieved by all sources using the
appropriately designed and operated floor control (i.e., including
sources using floor control but having emission levels greater than
the average of the emissions achieved by the 12 percent of sources
with the lowest emissions) must be considered when identifying the
floor emission level.
---------------------------------------------------------------------------

The test condition average emissions for sources in the expanded
MACT pool for most standards often vary over several orders of
magnitude. That variability is attributable partially to the type of
source-to-source emissions variability addressed here as well as the
inclusion of sources with varying levels of MACT control in the pool.
Sources are included in the expanded MACT pool if they have controls
equivalent to or better than MACT floor controls. We are unable to
identify true source-to-source emissions variability for sources that
actually have the same MACT controls because we are unable to specify
in sufficient detail the design, operating, and maintenance
characteristics of MACT control. Such information is not readily
available. Therefore, we define MACT control only in general terms.
This problem (and others) are addressed in today's rule by selecting
the MACT floor level based on the highest test condition average in the
expanded MACT pool, which accounts for source-to-source variability.
We also conclude that the characteristics of the emissions data
base coupled with the methodology used to identify the floor emission
level adequately accounts for emissions variability so that the floor
level is routinely achieved in practice by sources using floor control.
As further evidence, we note that a large fraction--50 to 100 percent--
of sources in the data base currently meet the floor levels regardless
of whether they currently use floor control.⁷⁸
---------------------------------------------------------------------------

\78\ USEPA, ``Final Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards and
Technologies,'' July 1999.
---------------------------------------------------------------------------

VI. What Are the Standards for Existing and New Incinerators?

A. To Which Incinerators Do Today's Standards Apply?
The standards promulgated today apply to each existing,
reconstructed, and newly constructed incinerator (as defined in 40 CFR
260.10) burning hazardous waste. These standards apply to all major
source and area source incinerator units and to all units whether they
are transportable or fixed sources. These standards also apply to
incinerators now exempt from RCRA stack emission standards under
Secs. 264.340(b) and (c).\79\ Additionally, these standards apply to
thermal desorbers that meet the definition of a RCRA incinerator, and
therefore, are not regulated under subpart X of part 264.
---------------------------------------------------------------------------

\79\ Sections 264.340(b) and (c) exempt from stack emission
standards incinerators (a) burning solely ignitable, corrosive or
reactive wastes under certain conditions, and (b) if the waste
contains no or insignificant levels of hazardous constituents.
---------------------------------------------------------------------------

B. What Subcategorization Options Did We Evaluate?
We considered whether it would be appropriate to subcategorize
incinerators based on several factors discussed below and conclude that
subcategorization is not necessary. However, for waste heat recovery
boiler-equipped incinerators, we establish a separate emission standard
solely for dioxin/furan. We explained our rationale for separate
dioxin/furan standards for waste heat recovery boilers in the May 1997
NODA (62 FR 24220). We said that waste heat recovery boilers emit
significantly higher dioxin/furan emissions than other incinerators,
probably because the heat recovery boiler precludes rapid temperature
quench of the combustion gases to below 400 deg.F, therefore warranting
separate standards for dioxin/furan only (i.e., the waste heat boiler
does not affect achievability of the other emission standards).
We considered several options for subcategorizing the hazardous
waste incinerator source category based on: (1) Size of the unit (e.g.,
small and large incinerators); (2) method of use of the hazardous waste
incinerator (e.g., commercial hazardous waste incinerator, captive (on-
site) unit); (3) facility design (e.g., rotary kiln, liquid injection,
fluidized bed, waste heat boiler), and (4) type of waste fed (e.g.,
hazardous waste mixed with radioactive waste, munitions, liquid, solid
or aqueous wastes). Subcategorization would be appropriate if one or
more of these factors affected achievability of emission standards that
were established without subcategorization. In the May 1997 NODA (62 FR
24219), we stated that subdividing the hazardous waste incinerator
source category by size or method of use (such as commercial or on-
site) would be inappropriate because it would not result in standards
that are more achievable. Many of the standards would be the same for
the subcategories while the remainder would be more stringent. That
conclusion is not altered by any of the changes in today's final rule.
Therefore, subcategorization would add complexity without any tangible
achievability benefits.
In the same notice, we also requested comment on subcategorization
and/or a deferral of standards for mixed waste incinerators based on a
comment from the Department of Energy that this type of incinerator has
several unique features that warrant subcategorization.

[[Page 52860]]

There are three Department of Energy mixed waste incinerators. Each
mixed waste incinerator has a different type of operation and different
air pollution control devices, and two of the sources have high dioxin/
furan and mercury emissions (several times the dioxin/furan standards
adopted in today's rule). We received several comments on the mixed
waste incinerator issue. These commenters contend that, because of the
radioactive component of the wastes, mixed waste incinerators pose
greater than average risk, and regulating these facilities should not
be deferred. These commenters also note that the MACT controls are not
incompatible with mixed waste incinerators and thus these incinerators
can readily achieve the emission standards. We agree that MACT controls
are compatible with mixed waste incinerators, with one exception
discussed below, and do not establish a mixed waste incinerator
subcategory.
The standards promulgated today are generally achievable by all
types and sizes of incinerators when using MACT controls. We recognize,
however, that each of the possible subcategories considered has some
unique features. At the same time, upon consideration of each
individual issue, we conclude that unique features of a particular
hazardous waste incinerator can be better dealt with on an individual
basis (through the permit process or through petitions) instead of
through extensive subcategorization. As an example, we agree with the
Department of Energy's contentions that feedstream testing for metals
is problematic for mixed waste incinerators due to radioactivity of the
waste and because risk from metal emissions is minimal in mixed waste
incinerators that use HEPA filters to prevent radioactive emissions.
Section 63.1209(g)(1) of today's rule provides a mechanism for
petitioning the Administrator for use of an alternative monitoring
method.⁸⁰ This petition process appears to be an appropriate
vehicle for addressing the concerns expressed by the Department of
Energy about feedstream testing for metals and use of HEPA filters at
its mixed waste incinerators.
---------------------------------------------------------------------------

\80\ The petition for an alternative monitoring method should be
included in the comprehensive performances test plan submitted for
review and approval.
---------------------------------------------------------------------------

In summary, our decision not to subcategorize hazardous waste
incinerators is based on four reasons:
(1) Size differences among hazardous waste incinerators do not
necessarily reflect process, equipment or emissions differences among
the incinerators. Many small size hazardous waste incinerators have
emissions lower than those promulgated today even though they are not
regulated to those low levels.
(2) Types and concentrations of uncontrolled hazardous air
pollutants are similar for all suggested subcategories of hazardous
waste incinerators.
(3) The same type of control devices, such as electrostatic
precipitators, fabric filters, and scrubbers, are used by all hazardous
waste incinerators to control emissions of particular hazardous air
pollutants.
(4) The standards are achievable by all types and sizes of well
designed and operated incinerators using MACT controls.
C. What Are the Standards for New and Existing Incinerators?
1. What Are the Standards for Incinerators?
We discuss in this section the basis for the emissions standards
for incinerators. The emissions standards are summarized below:

Standards for Existing and New Incinerators
----------------------------------------------------------------------------------------------------------------
Emissions standard \1\
Hazardous air pollutant or ------------------------------------------------------------------------------
hazardous air pollutant surrogate Existing sources New sources
----------------------------------------------------------------------------------------------------------------
Dioxin /Furan.................... 0.20 ng TEQ \2\/ 0.20 ng TEQ/dscm.
dscm; or 0.40 ng
TEQ/dscm and
temperature at
inlet to the
initial
particulate matter
control device 400 deg.F.
Mercury.......................... 130 g/dscm 45 g/dscm.
Particulate Matter............... 34mg/dscm (0.015gr/ 34mg/dscm (0.015gr/dscf).
dscf).
Semivolatile Metals.............. 240 g/dscm 24 g/dscm.
Low Volatile Metals.............. 97 g/dscm. 97 g/dscm.
Hydrochloric Acid/Chlorine Gas... 77 ppmv............ 21 ppmv.
Hydrocarbons ^3, ⁴................ 10 ppmv (or 100 10 ppmv (or 100 ppmv carbon monoxide).
ppmv carbon
monoxide).
Destruction and Removal 99.99% for each Same as for existing incinerators.
Efficiency. specific principal
organic hazardous
constituent,
except 99.9999%
for specified
dioxin-listed
wastes.
----------------------------------------------------------------------------------------------------------------
\1\ All emission levels are corrected to 7 percent oxygen.
\2\ Toxicity equivalent quotient, the international method of relating the toxicity of various dioxin/furan
congeners to the toxicity of 2,3,7,8-TCDD.
\3\ Hourly rolling average. Hydrocarbons reported as propane.
\4\ Incinerators that elect to continuously comply with the carbon monoxide standard must demonstrate compliance
with the hydrocarbon standard of 10ppmv during the comprehensive performance test.

2. What Are the Standards for Dioxins and Furans?
We establish a dioxin/furan standard for existing incinerators of
either 0.20 ng TEQ/dscm, or a combination of dioxin/furan emissions up
to 0.40 ng TEQ/dscm and temperature at the inlet to the initial dry
particulate matter control device not to exceed 400 deg.F.⁸¹
Expressing the standard as a temperature limit as well as a dioxin/
furan concentration limit provides better control of dioxin/furan,
because sources operating at temperatures below 400 deg.F generally
have lower emissions and is consistent with the current practice of
many sources. Further, without the lower alternative TEQ limit of 0.20
ng/dscm, sources that may be operating dry particulate matter control
devices at temperatures higher than 400 deg.F while achieving dioxin/
furan emissions below 0.20 ng TEQ/dscm would nonetheless be required to
incur costs to lower gas temperatures. This would not be appropriate
because lowering gas temperatures in this case would likely

[[Page 52861]]

achieve limited reductions in dioxin/furan emissions (i.e., because
emissions are already below 0.20 ng TEQ).
---------------------------------------------------------------------------

\81\ Incinerators that use wet scrubbers as the initial
particulate matter control device are presumed to meet the 400 deg.F
temperature requirement. Consequently, as a practical matter, the
standard for such incinerators is simply 0.4 ng TEQ/dscm.
---------------------------------------------------------------------------

For new incinerators, the dioxin/furan standard is 0.20 ng TEQ/
dscm. We discuss below the rationale for these standards.
a. What is the MACT Floor for Existing Sources? We establish the
same MACT floor control, as was evaluated in the May 1997 NODA, based
on the revised data base and the refinements to the analytical
approaches. This floor control is based on quenching of combustion
gases to 400 deg.F or below at the dry particulate matter control
device.⁸² We selected a temperature of 400 deg.F because
that temperature is below the temperature range for optimum surface-
catalyzed dioxin/furan formation reactions--450 deg.F to 650 deg.F--and
most sources operate their particulate matter control device below that
temperature. In addition, temperature is an important control parameter
because dioxin/furan emissions increase exponentially as combustion gas
temperatures at the dry particulate matter control device increase
above 400 deg.F.
---------------------------------------------------------------------------

\82\ The temperature limit applies at the inlet to a dry
particulate matter control device that suspends particulate matter
in the combustion gas stream (e.g., electrostatic precipitator,
fabric filter) such that surface-catalyzed formation of dioxin/furan
is enhanced. The temperature limit does not apply to a cyclone
control device, for example.
---------------------------------------------------------------------------

We identify a MACT floor level of 0.40 ng TEQ/dscm for incinerators
other than those equipped with waste heat recovery boilers. As
discussed in the May 1997 NODA, the floor level of 0.40 ng TEQ/dscm is
based on the highest nonoutlier test condition for sources equipped
with dry particulate matter control devices operated at temperatures of
400 deg.F or below or wet particulate matter control devices. We
screened out four test conditions from three facilities because they
have anomalously high dioxin/furan emissions and are not representative
of MACT control practices.⁸³ Three of these test conditions
are from sources that had other test conditions with emission averages
well below 0.40 ng TEQ/dscm, indicating that the same facilities can
achieve lower emission levels in different operating modes.
---------------------------------------------------------------------------

\83\ USEPA, ``Technical Support Document for HWC MACT Standards,
Volume III: Selection of MACT Standards and Technologies,'' July
1999, Section 3.1.1.
---------------------------------------------------------------------------

We identify a MACT floor level for waste heat boiler-equipped
hazardous waste incinerators of 12 ng TEQ/dscm based on the highest
emitting individual run for sources equipped with dry particulate
matter control devices operated at temperatures of 400 deg.F or below
or wet particulate matter control devices. We use the highest run to
set the floor level rather than the average of the runs for the test
condition to address emissions variability concerns given that we have
a very small data set for waste heat boilers. All waste heat boiler-
equipped hazardous waste incinerators meet this floor level, except for
a new test conducted after the publication of the May 1997 NODA at high
temperature conditions that resulted in dioxin/furan emission levels of
47 ng TEQ/dscm. This source is not using MACT control, however, because
the temperature at the particulate matter control device exceeded
400 deg.F. Thus, we do not consider emissions from this source in
identifying the floor level.
We received numerous and diverse comments on the April 1996
proposal and the May 1997 NODA. While some commenters consider the
dioxin/furan standards too high, a large number comment that the
standards are too stringent. Many comment that the methodology used for
calculating the dioxin/furan MACT floor level is inappropriate and that
the cost-effectiveness of the standards is not reasonable. In
particular, some commenters suggest separating ``fast quench'' and
``slow quench'' units. We have fully addressed this latter concern
because we now establish separate dioxin/furan standards for waste heat
boilers given that they are a fundamentally different type of process
and that they have higher dioxin/furan emissions because of the slow
quench across the boiler. We address the other comments elsewhere in
the preamble and in the comment response document.
Approximately 65% of all test conditions at all incinerator sources
are achieving the 0.40 ng TEQ/dscm level, and over 50% of all test
conditions achieve the 0.20 ng TEQ/dscm level. We estimate that
approximately 60 percent of incinerators currently meet the TEQ limit
as well as the temperature limit. Under the statute, compliance costs
are not to be considered in MACT floor determinations. For purposes of
compliance with Executive Order 12866 and the Regulatory Flexibility
Act, we calculated the annualized cost for hazardous waste incinerators
to achieve the dioxin/furan MACT floor levels. Assuming that no
hazardous waste incinerator exits the market due to MACT standards, the
annual cost is estimated to be $3 million, and the standards will
reduce dioxin/furan emissions nationally by 3.4 g TEQ per year from the
baseline emissions level of 24.8 g TEQ per year.
b. What Are Our Beyond-the-Floor Considerations for Existing
Sources? We investigated the use of activated carbon injection, along
with limiting temperatures at the inlet to the initial dry particulate
matter control device to 400 deg.F,⁸⁴ to achieve two
alternative beyond-the-floor emission levels: (1) 0.40 ng TEQ/dscm for
waste heat boiler-equipped incinerators (i.e., slow quench) to reduce
their emissions to the floor level for other incinerators; and (2) 0.20
ng TEQ/dscm for all incinerators. Activated carbon injection technology
is feasible and proven to reduce dioxin/furan emissions by 99 percent
or greater.⁸⁵ It is currently used by one waste heat boiler-
equipped hazardous waste incinerator (Waste Technologies Industries in
East Liverpool, Ohio) and many municipal waste combustors.⁸⁶
The removal efficiency of an activated carbon injection system is
affected by several factors including carbon injection rate and
adsorption quality of the carbon. Thus, activated carbon injection
systems can be used by waste heat boiler-equipped incinerators to
achieve alternative beyond-the-floor emissions of either 0.40 ng TEQ/
dscm or 0.20 ng TEQ/dscm.
---------------------------------------------------------------------------

\84\ Limiting the temperature at the dry particulate matter
control device reduces surface-catalyzed formation of dioxin/furan
and enhances the adsorption of dioxin/furan on the activated carbon.
\85\ USEPA, ``Technical Support Document for HWC MACT Standards,
Volume III: Selection of MACT Standards and Technologies,'' July
1999.
\86\ We have established in a separate rulemaking that activated
carbon injection is MACT floor control for municipal waste
combustors.
---------------------------------------------------------------------------

We conclude that a beyond-the-floor emission level of 0.40 ng TEQ/
dscm for waste heat boiler-equipped incinerators is cost-effective but
a 0.20 ng TEQ/dscm emission level for all incinerators is not cost-
effective. We estimate that 23 waste heat boiler-equipped incinerators
will need to install activated carbon injection systems at an
annualized cost of approximately $6.6 million. This will result in a
sizable reduction of 17.9 g TEQ dioxin/furan emissions per year and
will provide an 84 percent reduction in emissions from the floor
emission level (21.4 g TEQ per year) for all hazardous waste
incinerators. This represents a cost-effectiveness of $370,000 per gram
TEQ removed.
When we evaluated the alternative beyond-the-floor emission level
of 0.20 ng TEQ/dscm for all incinerators, we determined that 80
hazardous waste incinerators would incur costs to reduce dioxin/furan
emissions by 19.5 g TEQ from the floor level (21.4 g TEQ) at an
annualized cost of $16.1 million. The cost-effectiveness would be
$827,000 per gram of TEQ removed. In addition,

[[Page 52862]]

we determined that the vast majority of these emissions reductions
would be provided by waste heat boiler-equipped incinerators, and would
be provided by the beyond-the-floor emission level of 0.40 ng TEQ/dscm
discussed above. The incremental annualized cost of the 0.20 ng TEQ/
dscm option for incinerators other than waste heat boiler-equipped
incinerators would be $9.5 million, and would result in an incremental
reduction of only 1.6 g TEQ per year. This represents a high cost for a
very small additional emission reduction from the floor, or a cost-
effectiveness of $6.0 million per additional gram of TEQ dioxin/furan
removed. Accordingly, we conclude that the 0.20 ng TEQ/dscm beyond-the-
floor option is not cost-effective.
We note that dioxin/furan are some of the most toxic compounds
known due to their bioaccumulative potential and wide range of adverse
health effects, including carcinogenesis, at exceedingly low doses. We
consider beyond-the-floor reduction of dioxin/furan emissions a prime
environmental and human health consideration. As discussed above, our
data base indicates that a small subset of incinerators--those equipped
with waste heat recovery boilers--can emit high levels of dioxin/furan,
up to 12 ng TEQ/dscm, even when operating the dry particulate matter
control device at 400 deg.F. We are concerned that such high
dioxin/furan emission levels are not protective of human health and the
environment, as mandated by RCRA. If dioxin/furan emissions from waste
heat boiler-equipped incinerators are not reduced by a beyond-the-floor
emission standard, omnibus RCRA permit conditions would likely be
needed in many cases. This would defeat our objective of having only
one permitting framework for stack air emissions at hazardous waste
incinerators (except in unusual cases). Thus, the beyond-the-floor
standard promulgated today for waste heat boiler-equipped incinerators
is not only cost-effective, but also an efficient approach to meed the
Agency's RCRA mandate.
Some commenters suggest that the standard for waste heat boiler-
equipped hazardous waste incinerators, which is based on activated
carbon injection, be set at levels achieved by activated carbon
injection at the Waste Technologies Industries facility--an average of
0.07 ng TEQ/dscm. We determined that this would not be appropriate
because of concerns that such a low emission level may not be routinely
achievable. An emission level of 0.07 ng TEQ/dscm represents a 99.4
percent reduction in emissions from the floor level of 12 ng TEQ/dscm.
Although activated carbon injection can achieve dioxin/furan emissions
reductions of 99 percent and higher, we are concerned that removal
efficiency may decrease at low dioxin/furan emission levels. We noted
our uncertainty about how much activated carbon injection control
efficiency may be reduced at low dioxin/furan concentrations in the May
1997 NODA (62 FR at 24220). Several commenters agree with our concern,
including Waste Technologies Industries.⁸⁷ No commenters
provide data or information to the contrary. Because we have data from
only one hazardous waste incinerator documenting that an emission level
of 0.07 ng TEQ can be achieved, we are concerned that an emission level
that low may not be routinely achievable by all sources.
---------------------------------------------------------------------------

\87\ Waste Technologies Industries suggested, however, that
after experience with activated carbon injection systems has been
attained by several hazardous waste incinerators, the Agency could
then determine whether an emission level of 0.07 ng TEQ/dscm is
routinely achievable. See comment number 064 in Docket F-97-CS4A-
FFFFF.
---------------------------------------------------------------------------

c. What Is the MACT Floor for New Sources? For new sources, the CAA
requires that the MACT floor be the level of control used by the best
controlled single source. As discussed above, one source, the Waste
Technologies Industries (WTI) incinerator in Liverpool, Ohio, uses
activated carbon injection. Therefore, we identify activated carbon
injection as MACT floor control for new sources. To establish the MACT
floor emission level that is being achieved in practice for sources
using activated carbon injection, data are available from only WTI. WTI
is achieving an emission level of 0.07 ng TEQ/dscm. As discussed above,
we are concerned that emission level may not be routinely achievable
because the removal efficiency of activated carbon injection may be
reduced at such low emission levels. An emission level of 0.20 ng TEQ/
dscm is routinely achievable, however. We note that activated carbon
injection is MACT floor control for dioxin/furan at new large municipal
waste combustors. We established a standard of 13 ng/dscm total mass
``equal to about 0.1 to 0.3 ng/dscm TEQ'' for these sources (60 FR
65396 (December 19, 1995)), equivalent to approximately 0.20 ng TEQ/
dscm. We conclude, therefore, that a floor level of 0.20 ng TEQ/dscm is
achievable for new sources using activated carbon injection and
accordingly set this as the standard.
d. What Are Our Beyond-the-Floor Considerations for New Sources? As
discussed in the May 1997 NODA, a beyond-the-floor standard below 0.20
ng TEQ/dscm would not be appropriate. Although installation of carbon
beds would enable new hazardous waste incinerators to achieve lower
dioxin/furan levels, we do not consider the technology to be cost-
effective. The reduction in dioxin/furan emissions would be very small,
while the costs of carbon beds would be prohibitively high. In
addition, due to the very small dioxin/furan reduction, the benefit in
terms of cancer risks reduced also will be very small. Therefore, we
conclude that a beyond-the-floor standard for dioxin/furan is not
appropriate.
3. What Are the Standards for Mercury?
We establish a mercury standard for existing and new incinerators
of 130 and 45 g/dscm respectively. We discuss below the
rationale for these standards.
a. What Is the MACT Floor for Existing Sources? We are establishing
the same MACT floor level as proposed, 130 g/dscm although, as
discussed below, the methodology underlying this standard has changed
from proposal. At proposal, the floor standard was based on the
performance of either: (1) Feedrate control of mercury at a maximum
theoretical emission concentration not exceeding 19 g/dscm; or
(2) wet scrubbing in combination with feedrate control of mercury at a
level equivalent to a maximum theoretical emission concentration not
exceeding 51 g/dscm. In the May 1997 NODA, we reevaluated the
revised data base and defined MACT control as based on performance of
wet scrubbing in combination with feedrate control of mercury at a
level equivalent to a maximum theoretical emission concentration of 50
g/dscm and discussed a floor level of 40 g/dscm.
Several commenters object to our revised methodology and are
concerned that we use low mercury feedrates to define floor control.
These commenters state that standards should not be based on sources
feeding very small amounts of a particular metal, but rather on their
ability to minimize the emissions by removing the hazardous air
pollutant. As discussed previously, we maintain that hazardous waste
feedrate is an appropriate MACT control technique. We agree with
commenters' concerns, however, that previous methodologies to define
floor feedrate control may have identified sources feeding anomalously
low levels of a metal (or chlorine). To address this concern, we have
revised the floor determination methodology for mercury, semivolatile
metals, low volatile metals and total chlorine. A

[[Page 52863]]

detailed description of this methodology--the aggregate feedrate
approach--is presented in Part Four, Section V of this preamble.
Adopting this aggregate feedrate approach, we identify a mercury
feedrate level that is approximately five times higher than the May
1997 NODA level and higher than approximately 70% of the test
conditions in our data base.
Wet scrubbers also provide control of mercury (particularly mercury
chlorides). Given that virtually all incinerators are equipped with wet
scrubbers (for control of particulate matter or acid gases), we
continue to define floor control as both hazardous waste feedrate
control of mercury and wet scrubbing. The MACT floor based on the use
of wet scrubbing and feedrate control of mercury is 130 g/
dscm.\88\
---------------------------------------------------------------------------

\88\ This is coincidentally the same floor level as proposed,
notwithstanding the use of a different methodology.
---------------------------------------------------------------------------

The floor level is being achieved by 80% of the test conditions in
our data base of 30 hazardous waste incinerators. As already discussed
above, consideration of costs to achieve MACT floor standards play no
part in our MACT floor determinations, but we nevertheless estimate
costs to the hazardous waste incinerator universe for administrative
purposes. We estimate that 35 hazardous waste incinerators, assuming no
market exit by any facility, will need to adopt measures to reduce
mercury emissions at their facilities by 3.46 Mg from the current
baseline of 4.4 Mg at an estimated annualized cost $12.2 million,
yielding a cost-effectiveness of $3.6 million per Mg of mercury
reduced.
b. What Are Our Beyond-the-Floor Considerations for Existing
Sources? As required by statute, we evaluated more stringent beyond-
the-floor controls for further reduction of mercury emissions from the
floor level. Activated carbon injection systems can achieve mercury
emission reductions of over 85 percent and we proposed them as beyond-
the-floor control in the April 1996 NPRM. In the May 1997 NODA, we
reevaluated the use of activated carbon injection ⁸⁹ as
beyond-the-floor control, but cited significant cost-effectiveness
concerns. We reiterate these concerns here. Our technical support
document ⁹⁰ provides details of annualized costs and
reductions that can be achieved.
---------------------------------------------------------------------------

\89\ Flue gas temperatures would be limited to 400 deg.F at the
point of carbon injection to enhance mercury removal.
\90\ USEPA, ``Technical Support Document for HWC MACT Standards,
Volume V: Emission Estimates and Engineering Costs,'' July 1999.
---------------------------------------------------------------------------

In addition, we considered a beyond-the-floor level of 50
g/dscm based on limiting the feedrate of mercury in the
hazardous waste (i.e., additional feedrate control beyond floor
control), and conducted an evaluation of the cost of achieving this
reduction to determine if this beyond-the-floor level would be
appropriate. The national incremental annualized compliance cost to
meet this beyond-the-floor level, rather than comply with the floor
controls, would be approximately $4.2 million for the entire hazardous
waste incinerator industry and would provide an incremental reduction
in mercury emissions nationally beyond the MACT floor controls of 0.7
Mg/yr, yielding a cost-effectiveness of $10 million per additional Mg
of mercury reduced. Thus, potential benefits in relation to costs are
disproportionately low, and we conclude that beyond-the-floor mercury
controls for hazardous waste incinerators are not warranted. Therefore,
we are not adopting a mercury beyond-the-floor standard.
Many commenters object to our beyond-the-floor standards as
proposed, citing high costs for achieving relatively small mercury
emission reductions, and compare the cost-effectiveness numbers with
regulations of other sources (electric utilities, municipal and medical
waste incinerators). Although comparison between rules for different
sources is not directly relevant (see, e.g., Portland Cement
Association v. Ruckelshaus 486 F.2d 375, 389 (D.C. Cir. 1973)), we
nevertheless agree that the cost of a mercury beyond-the-floor standard
in relation to benefits is substantial. Some commenters, as well as the
peer review panel, state that beyond-the-floor levels are not supported
by a need based on risk. Although the issue of residual risk can be
deferred under the CAA, an immediate question must be addressed if RCRA
regulation of air emissions is to be deferred. Our analysis \91\
indicates that mercury emissions at the floor level do not pose a
serious threat to the human health and environment and that these
standards are adequately protective to satisfy RCRA requirements as a
matter of national policy, subject, of course, to the possibility of
omnibus permit conditions for individual facilities in appropriate
cases.
---------------------------------------------------------------------------

\91\ USEPA, ``Risk Assessment Support to the Development of
Technical Standards for Emissions from Combustion Units Burning
Hazardous Wastes: Background Information Document,'' July 1999.
---------------------------------------------------------------------------

Some commenters state that the technical performance of activated
carbon injection for mercury control is not adequately proven.
Activated carbon injection performance has been adequately demonstrated
at several hazardous waste incinerators, municipal waste combustors,
and other devices.\92\ Our peer review panel also states that activated
carbon injection can achieve 85% reduction of mercury emissions.\93\
Some commenters also state that we underestimate the cost and
complexities of retrofitting incinerators to install activated carbon
injection systems (e.g., air reheaters would be required in many
cases). We reevaluated the modifications needed for retrofits of
activated carbon injection systems and have revised the costs of
installation.
---------------------------------------------------------------------------

\92\ USEPA, ``Technical Support Document for HWC MACT Standards,
Volume III: Selection of Proposed MACT Standards and Technologies,''
July 1999.
\93\ Memo from Mr. Shiva Garg, EPA to Docket No. F-96-RCSP-FFFFF
entitled ``Peer Review Panel Report in support of proposed rule for
revised standards for hazardous waste combustors'', dated August 5,
1996.
---------------------------------------------------------------------------

c. What Is the MACT Floor for New Sources? Floor control must be
based on the level of control used by the best controlled single
source. The best controlled source in our data base uses wet scrubbing
and hazardous waste feedrate control of mercury at a feedrate
corresponding to a maximum theoretical emission concentration of 0.072
g/dscm. We conclude that this feedrate is atypically low,
however, given that the next lowest mercury feedrates in our data base
are 63, 79, 110, and 130 g/dscm, expressed as maximum
theoretical emission concentrations. Accordingly, we select the mercury
feedrate for the second best controlled source under the aggregate
feedrate approach to represent the floor control mercury feedrate for
new sources. That feedrate is 110 g/dscm \94\ expressed as a
maximum theoretical emission concentration, and corresponds to an
emission level of 45 g/dscm after considering the expanded
MACT pool (i.e., the highest emission level from all sources using
floor control). Therefore, we establish a MACT floor level for mercury
for new sources of 45 g/dscm.\95\ We note that, at proposal
and in

[[Page 52864]]

the May 1997 NODA, mercury standards of 50 and 40 g/dscm
respectively were proposed for new sources. Today's final rule is in
the same range as those proposed emission levels.
---------------------------------------------------------------------------

\94\ The test conditions with mercury feedrates of 63 and 79
g/dscm do not have complete data sets for all metals and
chlorine. Thus, these conditions cannot be used under the aggregate
feedrate approach to define the floor level of feedrate control.
Mercury emissions from those test conditions are used, however, to
identify a floor emission level that is being achieved.
\95\ In addition, this floor emission level may be readily
achievable for new sources using activated carbon injection as floor
control for dioxiin/furan without the need for feedrate control of
mercury. Activated carbon injection can achieve mercury emissions
reductions of 85 percent. Given that the upper bound mercury
feedrate for ``normal'' wastes (i.e., without mercury spiking) in
our data base corresponds to a maximum theoretical emission
concentration of 300 g/dscm, such sources could achieve the
mercury floor emission level of 45 g/dscm using activated
carbon injection alone.
---------------------------------------------------------------------------

d. What Are Our Beyond-the-Floor Considerations for New Sources? We
evaluated the use of activated carbon injection as beyond-the-floor
control for new sources to achieve emission levels lower than floor
levels. In the April 1996 NPRM and May 1997 NODA, we stated that new
sources could achieve a beyond-the-floor level of 4 g/dscm
based on use of activated carbon injection. We cited significant cost-
effectiveness concerns at that level, however. We reiterate those
concerns today.
Many commenters object to our beyond-the-floor standards as
proposed, citing high costs for achieving relatively small mercury
emission reductions. They compare the proposed standards unfavorably
with other sources' regulations (e.g., electric utilities, municipal
and medical waste incinerators), where the cost-effectiveness values
are much lower. As stated earlier, comparison between rules for
different sources is not directly relevant. Nonetheless, we conclude
that use of activated carbon injection as a beyond-the-floor control
for mercury for new sources would not be cost-effective. We also note
that the floor levels are adequately protective to satisfy RCRA
requirements.
We also considered additional feedrate control of mercury as
beyond-the-floor control. We conclude, however, that significant
emission reductions using feedrate control may be problematic because
the detection limit of routine feedstream analysis procedures for
mercury is such that a beyond-the-floor mercury emission limit could be
exceeded even though mercury is not present in feedstreams at
detectable levels. Although sources could potentially perform more
sophisticated mercury analyses, cost-effectiveness considerations would
likely come into play and suggest that a beyond-the-floor standard is
not warranted.
4. What Are the Standards for Particulate Matter?
We establish standards for existing and new incinerators which
limit particulate matter emissions to 0.015 grains/dry standard cubic
foot (gr/dscf) or 34 milligrams per dry standard cubic meter (mg/
dscm).\96\ We chose the particulate matter standard as a surrogate
control for the metals antimony, cobalt, manganese, nickel, and
selenium. We refer to these five metals as ``nonenumerated metals''
because standards specific to each metal have not been established. We
discuss below the rationale for adopting these standards.
---------------------------------------------------------------------------

\96\ Particulate matter is a surrogate for the metal hazardous
air pollutants for which we are not establishing metal emission
standards: Antimony, cobalt, manganese, nickel, and selenium.
---------------------------------------------------------------------------

a. What Is the MACT Floor for Existing Sources? Our data base
consists of particulate matter emissions from 75 hazardous waste
incinerators that range from 0.0002 gr/dscf to 1.9 gr/dscf. Particle
size distribution greatly affects the uncontrolled particulate matter
emissions from hazardous waste incinerators, which, in turn, is
affected by incinerator type and design, particulate matter entrainment
rates, waste ash content, waste sooting potential and waste chlorine
content. Final emissions from the stacks of hazardous waste
incinerators are affected by the degree of control provided to
uncontrolled particulate matter emissions by the air pollution control
devices. Dry collection devices include fabric filters or electrostatic
precipitators, while wet collection devices include conventional wet
scrubbers (venturi type) or the newer patented scrubbers like
hydrosonic, free jet, or the collision type. Newer hazardous waste
incinerators now commonly use ionizing wet scrubbers or wet
electrostatic precipitators or a combination of both dry and wet
devices.
The MACT floor setting procedure involves defining MACT level of
control based on air pollution control devices used by the best
performing sources. Control devices used by these best performing
sources can be expected to routinely and consistently achieve superior
performance. Then, we identify an emissions level that well designed,
well-operated and well-maintained MACT controls can achieve based on
demonstrated performance, and engineering information and principles.
The average of the best performing 12 percent of hazardous waste
incinerators use either fabric filters, electrostatic precipitators
(dry or wet), or ionizing wet scrubbers (sometimes in combination with
venturi, packed bed, or spray tower scrubbers). As explained in Part
Four, Section V, we define floor control for particulate matter for
incinerators as the use of a well-designed, operated, and maintained
fabric filter, electrostatic precipitator, or ionizing wet scrubber.
Sources using certain wet scrubbing techniques such as high energy
venturi scrubbers, and novel condensation, free-jet, and collision
scrubbers can also have very low particulate matter emission levels. We
do not consider these devices to be MACT control, however, because, in
general, a fabric filter, electrostatic precipitator, or ionizing wet
scrubber will provide superior particulate matter control. In some
cases, sources using medium or low energy wet scrubbers are achieving
very low particulate matter emissions, but only for liquid waste
incinerators, which typically have low ash content waste. Thus, this
control technology demonstrates high effectiveness only under atypical
conditions, and we do not consider it to be MACT floor control for
particulate matter.
We conclude that fabric filters, electrostatic precipitators, and
ionizing wet scrubbers are routinely achieving an emission level of
0.015 gr/dscf based upon the following considerations:
i. Sources in our data base are achieving this emission level. Over
75 percent of the sources in the expanded MACT pool are achieving an
emission level of 0.015 gr/dscf. We investigated several sources in our
data base using floor control but failing to achieve this level, and we
found that the control devices do not appear to be well-designed,
operated, and maintained. Some of these sources are not using superior
fabric filter bags (e.g., Gore-tex, Nomex felt, or tri-lift
fabrics), some exhibit salt carry-over and entrainment from a poorly
operated wet scrubber located downstream of the fabric filter, and some
are poorly maintained in critical aspects (such as fabric cleaning
cycle or bag replacements). \97\
---------------------------------------------------------------------------

\97\ USEPA, ``Technical Support Document for HWC, MACT
Standards, Volume III: Selection of MACT Standards and
Technologies,'' July 1999.
---------------------------------------------------------------------------

ii. Well-designed, operated, and maintained fabric filters and
electrostatic precipitators can routinely achieve particulate matter
levels lower than the floor level of 0.015 gr/dscf. Levels less than
0.005 gr/dscf were demonstrated on hazardous waste incinerators and
municipal waste combustors in many cases. Well-designed fabric filters
have a surface collection area of over 0.5 ft²/acfm and high
performance filter fabrics such as Nomex and Gore-tex. Well-designed
electrostatic precipitators have advanced power system controls (with
intermittent or pulse energization), internal plate and electrode
geometry to

[[Page 52865]]

allow for high voltage potential, flue gas conditioning by addition of
water or reagents such as sulfur trioxide or ammonia to condition
particulate matter for lower resistivity, and optimized gas
distribution within the electrostatic precipitator. The technical
support document identifies many hazardous waste incinerators using
such well designed control equipment.
iii. The 0.015 gr/dscf level is well within the accepted
capabilities of today's particulate matter control devices in the
market place. Vendors typically guarantee emission levels for the
particulate matter floor control devices at less than 0.015 gr/dscf and
in some cases, as low as 0.005 gr/dscf.
iv. The 0.015 gr/dscf level is consistent with standards
promulgated for other incinerator source categories burning municipal
solid waste and medical waste, both of which are based on performance
of fabric filters or electrostatic precipitators as MACT. Comparison of
hazardous waste incinerator floor level to these standards is
appropriate because particulate matter characteristics such as particle
size distribution, loading and particulate matter type are comparable
within the above three types of waste burning source categories.
v. Hazardous waste incinerators that meet the 0.015 gr/dscf
particulate matter level also generally achieve semivolatile metal
system removal efficiencies of over 99% and low volatile metal system
removal efficiencies over 99.9%. This indicates superior particulate
matter collection efficiency because these metals are controlled by
controlling fine and medium-sized particulate matter.
vi. Over 50 percent of all test conditions in the data base,
regardless of the type of air pollution control device used, design of
the hazardous waste incinerator, or the type of waste burned, currently
meet the 0.015 gr/dscf level. This includes hazardous waste
incinerators with high particulate matter entrainment rates (such as
fluidized bed and rotary kilns) as well as those with wastes that
generate difficult to capture fine particulate matter, such as certain
liquid injection facilities.
vii. Many incinerators conducted several tests to develop the most
flexible operating envelope for day-to-day operations, keeping in view
the existing RCRA particulate matter standard of 0.08 gr/dscf. In many
test conditions, they elected to meet (and be limited to) the 0.015 gr/
dscf level, although they were only required to meet a 0.08 gr/dscf
standard.
Many commenters object to the use of engineering information and
principles in the selection of the MACT floor level. Some consider
engineering information and principles highly subjective and dependent
on reviewers' interpretation of the data, while others suggest the use
of accepted statistical methods for handling the data. We performed
analyses based on available statistical tools for outlier analysis and
variability, as discussed previously, but conclude that those
approaches are not appropriate. We continue to believe that the use of
engineering information and principles is a valid approach to establish
the MACT floor (i.e., to determine the level of performance
consistently achievable by properly designed and operated floor control
technology).
Some commenters object to the use of ``well-designed, operated and
maintained'' MACT controls. They consider the term too vague and want
specific parameters and features (e.g., air to cloth ratio for fabric
filters and power input for electrostatic precipitators) identified. We
understand commenters' concerns but such information is simply not
readily available. Further, many parameters work in relation with
several others making it problematic to quantify optimum values
separate from the other values. The system as a whole needs to be
optimized for best control efficiency on a case-by-case basis.
Some commenters object to our justification of particulate matter
achievability on the basis of vendors' claims. They contend that: (1)
Vendors' claims lack quality control and are driven by an incentive for
sales; (2) vendors' claims are based on normal operating conditions,
not on trial burn type conditions; and (3) MACT floor should not be
based on theoretical performance of state-of-the-art technology. We
would agree with the comments if the vendor information were from
advertising literature, but instead, our analysis was based on
warranties. The financial consequences of vendors' warranties require
those warranties to be conservative and based on proven performance
records, both during normal operations and during trial burn
conditions. In any case, we are using vendor information as
corroboration, not to establish a level of performance.
In the May 1997 NODA (62 FR at 24222), we requested comments on the
alternative MACT evaluation method based on defining medium and low
energy venturi-scrubbers burning low ash wastes as an additional MACT
control, but screening out facilities from the expanded MACT floor
universe that have poor semivolatile metal system removal efficiency.
The resulting MACT floor emission level under this approach would be
0.029 gr/dscf. Many commenters agree with the Agency that this
technique is unacceptable because it ignores a majority (over 75
percent) of the available particulate matter data in identifying the
MACT standard. This result is driven by the fact that corresponding
semivolatile metal data are not available from those sources. Other
commenters, however, suggest that venturi scrubbers should be
designated as MACT particulate matter control. These commenters suggest
that sources using venturi scrubbers are within the average of the best
performing 12 percent of sources, and there is no technical basis for
their exclusion. As stated above, we agree that well-designed and
operated venturi scrubbers can achieve the MACT floor level of 0.015gr/
dscf under some conditions (as when burning low ash wastes), but their
performance is generally not comparable to that of a fabric filter,
electrostatic precipitator, or ionizing wet scrubber. Thus, we conclude
that sources equipped with venturi scrubbers may not be able to achieve
the floor emission level in all cases, and the floor level would have
to be inappropriately increased to accommodate unrestricted use of
those units.
Some commenters state that we must demonstrate health or
environmental benefits if the rule were to require sources to replace
existing, less efficient air pollution control devices (e.g., venturi
scrubbers incapable of meeting the standard) with a better performing
device, particularly because particulate matter is not a hazardous air
pollutant under the CAA. These comments are not persuasive and are
misplaced as a matter of law. The MACT floor process was established
precisely to obviate such issues and to establish a minimum level of
control based on performance of superior air pollution control
technologies. Indeed, the chief motivation for adopting the technology-
based standards to control emissions of hazardous air pollutants in the
first instance was the evident failure of the very type of risk-based
approach to controlling air toxics as is suggested by the commenters.
(See, e.g., H. Rep. No. 490, 101st Cong. 2d Sess., at 318-19.) Inherent
in technology-based standard setting, of course, is the possibility
that some technologies will have to be replaced if they cannot achieve
the same level of performance as the best performing technologies.
Finally, with regard to the commenters' points regarding particulate
matter not being a hazardous air pollutant, we explain

[[Page 52866]]

above why particulate matter is a valid surrogate for certain hazardous
air pollutants, and can be used as a means of controlling hazardous air
pollutant emissions. In addition, the legislative history appears to
contemplate regulation of particulate matter as part of the MACT
process. (See S. Rep. No. 228, 101st Cong. 1st Sess., at
170.⁹⁸)
---------------------------------------------------------------------------

\98\ Control of particulate matter also helps assure that the
standards are sufficiently protective to make RCRA regulation of
these sources' air emissions unnecessary (except potentially on a
site-specific basis through the omnibus permitting process). See
Technical Support Document on Risk Assessment.
---------------------------------------------------------------------------

We do not consider cost in selecting MACT floor levels.
Nevertheless, for purposes of administrative compliance with the
Regulatory Flexibility Act and various Executive Orders, we estimate
the cost burden on the hazardous waste incinerator universe to achieve
compliance. Approximately 38 percent of hazardous waste incinerators
currently meet the floor level of 0.015 gr/dscf. The annualized cost
for the remaining 115 incinerators to meet the floor level, assuming no
market exits, is estimated to be $17.4 million. Nonenumerated metals
and particulate matter emissions will be reduced nationally by 5.1 Mg/
yr and 1345 Mg/yr, respectively, or over 50 percent from current
baseline emissions.
b. What Are Our Beyond-the-Floor Considerations for Existing
Sources? In the NPRM, we proposed a beyond-the-floor emission level of
69 mg/dscm (0.030 gr/dscf) and solicited comment on an alternative
beyond-the-floor emission level of 34 mg/dscm (0.015 gr/dscf) based on
improved particulate matter control. (61 FR at 17383.) In the May 1997
NODA, we concluded that a beyond-the-floor standard may not be
warranted due to significant cost-effectiveness considerations. (62 FR
at 24222.)
In the final rule, we considered more stringent beyond-the-floor
controls that would provide additional reductions of particulate matter
emissions using fabric filters, electrostatic precipitators, and wet
ionizing scrubbers that are designed, operated, and maintained to have
improved collection efficiency. We considered a beyond-the-floor level
of 16 mg/dscm (0.007 gr/dscf), approximately one-half the floor
emission level, for existing incinerators based on improved particulate
matter control. We then determined the cost of achieving this reduction
in particulate matter, with corresponding reductions in the
nonenumerated metals for which particulate matter is a surrogate, to
determine if this beyond-the-floor level would be appropriate. The
national incremental annualized compliance cost for incinerators to
meet this beyond-the-floor level, rather than comply with the floor
controls, would be approximately $6.8 million for the entire hazardous
waste incinerator industry and would provide an incremental reduction
in nonenumerated metals emissions nationally beyond the MACT floor
controls of 1.7 Mg/yr. Based on these costs of approximately $4.1
million per additional Mg of nonenumerated metals emissions removed, we
conclude that this beyond-the-floor option for incinerators is not
acceptably cost-effective nor otherwise justified. Therefore, we do not
adopt this beyond-the-floor standard. Poor cost-effectiveness would be
particularly unacceptable here considering that these metals also have
relatively low toxicity. Thus, the particulate matter standard for new
incinerators is 34 mg/dscm. Therefore, the cost-effectiveness threshold
we would select would be less than for more toxic pollutants such as
dioxin, mercury or other metals.
c. What Is the MACT Floor for New Sources? We proposed a floor
level of 0.030 gr/dscf for new sources based on the best performing
source in the data base, which used a fabric filter with an air-to-
cloth ratio of 3.8 acfm/ft\2\. In the May 1997 NODA, we reevaluated the
particulate matter floor level and indicated that floor control for
existing sources would also appear to be appropriate for new sources.
We are finalizing the approach discussed in the May 1997 NODA whereby
floor control is a well-designed, operated, and maintained fabric
filter, electrostatic precipitator, or ionizing wet scrubber, and the
floor emission level is 0.015 gr/dscf.
d. What Are Our Beyond-the-Floor Considerations for New Sources? We
considered more stringent beyond-the-floor controls that would provide
additional reductions of particulate matter emissions using fabric
filters, electrostatic precipitators, and wet ionizing scrubbers that
are designed, operated, and maintained to have improved collection
efficiency. We considered a beyond-the-floor level of 16 mg/dscm (0.007
gr/dscf), approximately one-half the emissions level for existing
sources, for new incinerators based on improved particulate matter
control. For analysis purposes, improved particulate matter control
assumes the use of higher quality fabric filter bag material. We then
determined the cost of achieving this reduction in particulate matter,
with corresponding reductions in the nonenumerated metals for which
particulate matter is a surrogate, to determine if this beyond-the-
floor level would be appropriate. The incremental annualized compliance
cost for one new large incinerator to meet this beyond-the-floor level,
rather than comply with floor controls, would be approximately $39,000
and would provide an incremental reduction in nonenumerated metals
emissions of approximately 0.05 Mg/yr.⁹⁹ For a new small
incinerator, the incremental annualized compliance cost would be
approximately $7,500 and would provide an incremental reduction in
nonenumerated metals emissions of approximately 0.008 Mg/yr. Based on
these costs of approximately $0.8-1.0 million per additional Mg of
nonenumerated metals removed, we conclude that a beyond-the-floor
standard of 16 mg/dscm is not warranted due to the high cost of
compliance and relatively small nonenumerated metals emission
reductions. Poor cost-effectiveness would be particularly unacceptable
here considering that these metals also have relatively low toxicity.
Thus, the particulate matter standard for new incinerators is 34 mg/
dscm.
---------------------------------------------------------------------------

\99\ Based on the data available, the average emissions in sum
of the five nonenumerated metals from incinerators using MACT
particulate matter control is approximately 229 g/dscm. To
estimate emission reductions of the nonenumerated metals for
specific test conditions, we assume a linear relationship between a
reduction in particulate matter and these metals.
---------------------------------------------------------------------------

5. What Are the Standards for Semivolatile Metals?
Semivolatile metals are comprised of lead and cadmium. We establish
standards which limit semivolatile metal emissions to 240 g/
dscm for existing sources and 24 g/dscm for new sources. We
discuss below the rationale for adopting these standards.
a. What Is the MACT Floor for Existing Sources? As discussed in
Part Four, Section V of the preamble, floor control for semivolatile
metals is hazardous waste feedrate control of semivolatile metals plus
MACT floor particulate matter control. We use the aggregate feedrate
approach to define the level of semivolatile metal feedrate control. We
have aggregate feedrate data for 20 test conditions from nine hazardous
waste incinerators that are using MACT floor control for particulate
matter. The semivolatile metal feedrate levels, expressed as maximum
theoretical emission concentrations, for these sources range from 100
g/dscm to 1.5 g/dscm while the semivolatile emissions range
from 1 to 6,000 g/dscm. The MACT-defining maximum theoretical
emission concentration is

[[Page 52867]]

5,300 g/dscm. Upon expanding the MACT pool, only the highest
emissions test condition of 6,000 g/dscm was screened out
because the semivolatile metal maximum theoretical emission
concentration for this test condition was higher than the MACT-defining
maximum theoretical emission concentration. The highest emission test
condition in the remaining expanded MACT pool identifies a MACT floor
emission level of 240 g/dscm.
We originally proposed a semivolatile metal floor standard of 270
g/dscm based on semivolatile metal feedrate control. We
subsequently refined the emissions data base and reevaluated the floor
methodology, and discussed in the May 1997 NODA a semivolatile metal
floor level of 100 g/dscm. Commenters express serious concerns
with the May 1997 NODA approach in two areas. First, they note that the
MACT-defining best performing sources have very low emissions, not
entirely due to the performance of MACT control, but also due to
atypically low semivolatile metal feedrates. Second, they object to our
use of a ``breakpoint'' analysis to screen out the outliers from the
expanded MACT pool (which was already small due to the screening
process to define the feedrate level representative of MACT control).
Our final methodology makes adjustments to address these concerns.
Under the aggregate feedrate approach, sources with atypically low
feedrates of semivolatile metals would not necessarily drive the floor
control feedrate level. This is because the aggregate feedrate approach
identifies as the best performing sources (relative to feedrate
control) those with low feedrates in the aggregate for all metals and
chlorine. In addition, the floor methodology no longer uses the
breakpoint approach to identify sources not using floor control. These
issues are discussed above in detail in Part Four, Section V, of the
preamble.
Although cost-effectiveness of floor emission levels is not a
factor in defining floor control or emission levels, we have estimated
compliance costs and emissions reductions at the floor for
administrative purposes. Approximately 66 percent of sources currently
meet the semivolatile metal floor level of 240 g/dscm. The
annualized cost for the remaining 64 incinerators to meet the floor
level, assuming no market exits, is estimated to be $1.8 million.
Semivolatile metal emissions will be reduced nationally by 55.9 Mg per
year from the baseline emissions level of 58.5 Mg per year, a reduction
of 95.5%.
b. What Are Our Beyond-the-Floor Considerations for Existing
Sources? We considered more stringent semivolatile metal feedrate
control as a beyond-the-floor control to provide additional reductions
in emissions. Cost effectiveness considerations would likely come into
play, however, and suggest that a beyond-the-floor standard is not
warranted. Therefore, we conclude that a beyond-the-floor standard for
semivolatile metals for existing sources is not appropriate. We note
that a beyond-the-floor standard is not needed to meet our RCRA
protectiveness mandate.
c. What Is the MACT Floor for New Sources? Floor control for new
sources is: (1) The level of semivolatile metal feedrate control used
by the source with the lowest aggregate feedrate for all metals and
chlorine;¹⁰⁰ and (2) use of MACT floor particulate matter
control for new sources (i.e., a fabric filter, electrostatic
precipitator, or wet ionizing scrubber achieving a particulate matter
emission level of 0.015 gr/dscf). Three sources in our data base are
currently using the floor control selected for all new sources and are
achieving semivolatile emissions ranging from 2 g/dscm to 24
g/dscm. To ensure that the floor level is achievable by all
sources using floor control, we are establishing the floor level for
semivolatile metals for new sources at 24 g/dscm.
---------------------------------------------------------------------------

\100\ I.e., a semivolatile metal feedrate equivalent to a
maximum theoretical emission concentration of 3,500 g/dscm.
---------------------------------------------------------------------------

d. What Are Our Beyond-the-Floor Considerations for New Sources? We
considered more stringent beyond-the-floor controls (i.e., a more
restrictive semivolatile metal feedrate) to provide additional
reduction in emissions. We determined that cost-effectiveness
considerations would likely be unacceptable due to the relatively low
concentrations achieved at the floor. This suggests that a beyond-the-
floor standard is not warranted. We note that a beyond-the-floor
standard is not needed to meet our RCRA protectiveness mandate.
6. What Are the Standards for Low Volatile Metals?
Low volatile metals are comprised of arsenic, beryllium, and total
chromium. We establish standards that limit emissions of these metals
to 97 g/dscm for both existing and new incinerators. We
discuss below the rationale for adopting these standards.
a. What Is the MACT Floor for Existing Sources? We are using the
same approach for low volatile metals as we did for semivolatile metals
to define floor control. Floor control for low volatile metals is use
of particulate matter floor control and control of the feedrate of low
volatile metals to a level identified by the aggregate feedrate
approach.
The low volatile metal feedrates for sources using particulate
matter floor control range from 300 g/dscm to 1.4 g/dscm when
expressed as maximum theoretical emission concentrations. Emission
levels for these sources range from 1 to 803 g/dscm.
Approximately 60 percent of sources using particulate matter floor
control have low volatile metal feedrates below the MACT floor
feedrate--24,000 g/dscm, expressed as a maximum theoretical
emission concentration.
Upon expanding the MACT pool, the source using floor control with
the highest emissions is achieving an emission level of 97 g/
dscm. Accordingly, we are establishing the floor level for low volatile
metals for existing sources at 97 g/dscm to ensure that the
floor level is achievable by all sources using floor control.
We identified a low volatile metal floor level of 210 g/
dscm in the April 1996 proposal. The refined data analysis in the May
1997 NODA, based on the revised data base, reduced the low volatile
metal floor level to 55 g/dscm. As with semivolatile metals,
commenters express serious concerns with the May 1997 NODA approach,
including selection of the breakpoint ``outlier'' screening approach
and use of hazardous waste incinerator data with atypically low
feedrates for low volatile metals. We acknowledge those concerns and
adjusted our methodology accordingly. See discussions above in Part
Four, Section V.
We estimated compliance costs to the hazardous waste incinerator
universe for administrative purposes. Approximately 63 percent of
incinerators currently meet the 97 g/dscm floor level. The
annualized cost for the remaining 69 incinerators to meet the floor
level, assuming no market exits, is estimated to be $1.9 million, and
would reduce low volatile metal emissions nationally by 6.9 Mg per year
from the baseline emissions level of 8 Mg per year.
b. What Are Our Beyond-the-Floor Considerations for Existing
Sources? We considered more stringent beyond-the-floor controls (i.e.,
a more restrictive low volatile metal feedrate) to provide additional
reduction in emissions. Due to the relatively low concentrations
achieved at the floor, we determined that cost-effectiveness
considerations would likely be unacceptable. Therefore, we conclude
that a beyond-the-floor standard for low volatile metals for existing
sources is not

[[Page 52868]]

appropriate. We note that a beyond-the-floor standard is not needed to
meet our RCRA protectiveness mandate.
c. What Is the MACT Floor for New Sources? We identified a floor
level of 260 g/dscm for new sources at proposal based on the
best performing source in the data base. That source uses a venturi
scrubber with a low volatile metal feedrate equivalent to a maximum
theoretical emission concentration of 1,000 g/dscm. Our
reevaluation of the data base in the May 1997 NODA identified a floor
level of 55 g/dscm based on use of floor control for
particulate matter and feedrate control of low volatile metals. Other
than the comments on the two issues of low feedrate and the
inappropriate use of a breakpoint analysis discussed above, no other
significant comments challenged this floor level.
Floor control for new sources is the same as discussed in the May
1997 NODA (i.e., use of particulate matter floor control and feedrate
control of low volatile metals), except the floor feedrate level under
the aggregate feedrate approach used for today's final rule is 13,000
g/dscm. Upon expanding the MACT pool, the source using floor
control with the highest emissions is achieving an emission level of 97
g/dscm.¹⁰¹ Accordingly, we are establishing the
floor level for low volatile metals for new sources at 97 g/
dscm to ensure that the floor level is achievable by all sources using
floor control.
---------------------------------------------------------------------------

\101\ The emission level for new sources achieving a feedrate
control of 13,000 g/dscm (expressed as a maximum
theoretical emission concentration) is the same as the emission
level for existing sources achieving a feedrate control of 24,000
g/dscm because sources feeding low volatile metals in the
range of 13,000 to 24,000 g/dscm have emission levels at or
below 97 g/dscm. Although these sources feel low volatile
metals at higher levels than the single best feedrate-controlled
source, their emission control devices apparently are more
efficient. Thus, they achieved lower emissions than the single best
feedrate-controlled source.
---------------------------------------------------------------------------

d. What Are Our Beyond-the-Floor Considerations for New Sources? We
considered more stringent beyond-the-floor controls (i.e., a more
restrictive low volatile metal feedrate) to provide additional
reduction in emissions. Because of the relatively low concentrations
achieved, we determined that cost-effectiveness considerations would
likely be unacceptable. Therefore, we conclude that a beyond-the-floor
standard for low volatile metals for new sources is not appropriate. We
note that a beyond-the-floor standard is not needed to meet our RCRA
protectiveness mandate.
7. What Are the Standards for Hydrochloric Acid and Chlorine Gas?
We establish standards for hydrochloric acid and chlorine gas,
combined, for existing and new incinerators of 77 and 21 ppmv
respectively. We discuss below the rationale for adopting these
standards.
a. What Is the MACT Floor for Existing Sources? Almost all
hazardous waste incinerators currently use some type of add-on stack
gas wet scrubbing system, in combination with control of the feedrate
of chlorine, to control emissions of hydrochloric acid and chlorine
gas. A few sources use dry or semi-dry scrubbing, alone or in
combination with wet scrubbing, while a few rely upon feedrate control
only. Wet scrubbing consistently provides a system removal efficiency
of over 99 percent for various scrubber types and configurations.
Current RCRA regulations require 99% removal efficiency and most
sources are achieving greater than 99.9 percent removal efficiency.
Accordingly, floor control is defined as wet scrubbing achieving a
system removal efficiency of 99 percent or greater combined with
feedrate control of chlorine.
The floor feedrate control level for chlorine is 22 g/
dscm, expressed as a maximum theoretical emission concentration, based
on the aggregate feedrate approach. The source in the expanded MACT
pool (i.e., all sources using floor control) with the highest emission
levels of hydrogen chloride and chlorine gas is achieving an emission
level of 77 ppmv. Thus, MACT floor for existing sources is 77 ppmv.
At proposal, we also defined floor control as wet scrubbing
combined with feedrate control of chlorine. We proposed a floor
emission level of 280 ppmv based on a chlorine feedrate control level
of 21 g/dscm, expressed as a maximum theoretical emission
concentration. The best performing sources relative to emission levels
all use wet scrubbing and feed chlorine at that feedrate or lower. We
identified a floor level of 280 ppmv based on all sources in our data
base using floor control and after applying a statistically-derived
emissions variability factor. In the May 1997 NODA, we again defined
floor control as wet (or dry) scrubbing with feedrate control of
chlorine. We discussed a floor emission level of 75 ppmv based on the
revised data base and break-point floor methodology. Rather than using
a break-point analysis in the final rule, we use a floor methodology
that identifies floor control as an aggregate chlorine feedrate
combined with scrubbing that achieves a removal efficiency of at least
99 percent.
We estimated compliance costs to the hazardous waste incinerator
universe for administrative purposes. Approximately 70 percent of
incinerators currently meet the hydrochloric acid and chlorine gas
floor level of 77 ppmv. The annualized cost for the remaining 57
incinerators to meet that level, assuming no market exits, is estimated
to be $4.75 million and would reduce emissions of hydrochloric acid and
chlorine gas nationally by 2,670 Mg per year from the baseline
emissions level of 3410 Mg per year, a reduction of 78%.
b. What Are Our Beyond-the-Floor Considerations for Existing
Sources? We considered more stringent beyond-the-floor controls to
provide additional reduction in emissions. Due to the relatively low
concentrations achieved at the floor, we determined that cost-
effectiveness considerations would likely be unacceptable. Therefore,
we conclude that a beyond-the-floor standard for hydrochloric acid and
chlorine gas for existing sources is not appropriate. We note that a
beyond-the-floor standard is not needed to meet our RCRA protectiveness
mandate.
c. What Is the MACT Floor for New Sources? We identified a floor
level of 280 ppmv at proposal based on the best performing source in
the data base. That source uses wet scrubbing and a chlorine feedrate
of 17 g/dscm, expressed as a maximum theoretical emission
concentration. Our reevaluation of the revised data base in the May
1997 NODA defined a floor level of 75 ppmv. Based on the aggregate
feedrate approach used for today's final rule, we are establishing a
floor level of 21 ppmv, based on a chlorine feedrate of 4.7 g/
dscm expressed as a maximum theoretical emission concentration.
d. What Are Our Beyond-the-Floor Considerations for New Sources? We
considered more stringent beyond-the-floor controls to provide
additional reduction in emissions. Due to the relatively low
concentrations achieved at the floor, we determined that cost-
effectiveness considerations would likely be unacceptable. Therefore,
we conclude that a beyond-the-floor standard for hydrochloric acid and
chlorine gas for new sources is not appropriate. We note that a beyond-
the-floor standard is not needed to meet our RCRA protectiveness
mandate.
8. What Are the Standards for Carbon Monoxide?
We use carbon monoxide as a surrogate for organic hazardous air
pollutants. Low carbon monoxide

[[Page 52869]]

concentrations in stack gas are an indicator of good control of organic
hazardous air pollutants and are achieved by operating under good
combustion practices.
We establish carbon monoxide standards of 100 ppmv for both
existing and new sources based on the rationale discussed below.
Sources have the option to comply with either the carbon monoxide or
the hydrocarbon emission standard. Sources that elect to comply with
the carbon monoxide standard must also document compliance with the
hydrocarbon standard during the performance test to ensure control of
organic hazardous air pollutants. See discussion in Part Four, Section
IV.B.
a. What Is the MACT Floor for Existing Sources? As proposed, floor
control for existing sources is operating under good combustion
practices (e.g., providing adequate excess oxygen; providing adequate
fuel (waste) and air mixing; maintaining high temperatures and adequate
combustion gas residence time at those temperatures).¹⁰²
Given that there are many interdependent parameters that affect
combustion efficiency and thus carbon monoxide emissions, we were not
able to quantify ``good combustion practices.''
---------------------------------------------------------------------------

\102\ USEPA, ``Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards and
Technologies,'' July 1999.
---------------------------------------------------------------------------

We are identifying a floor level of 100 ppmv on an hourly rolling
average, as proposed, because it is being achieved by sources using
good combustion practices. More than 80 percent of test conditions in
our data base have carbon monoxide levels below 100 ppmv, and more than
60 percent have levels below 20 ppmv. Of approximately 20 test
conditions with carbon monoxide levels exceeding 100 ppmv, we know the
characteristics of many of these sources are not representative of good
combustion practices (e.g., use of rotary kilns without afterburners;
liquid injection incinerators with rapid combustion gas quenching). In
addition, we currently limit carbon monoxide concentrations for
hazardous waste burning boilers and industrial furnaces to 100 ppmv to
ensure good combustion conditions and control of organic toxic
compounds. Finally, we have established carbon monoxide limits in the
range of 50 to 150 ppmv on other waste incineration sources (i.e.,
municipal waste combustors, medical waste incinerators) to ensure good
combustion conditions. We are not aware of reasons why it may be more
difficult for a hazardous waste incinerator to achieve carbon monoxide
levels of 100 ppmv.
We estimated compliance costs to the hazardous waste incinerator
universe for administrative purposes. Because carbon monoxide emissions
from these sources are already regulated under RCRA, approximately 97
percent of incinerators currently meet the floor level of 100 ppmv. The
annualized cost for the remaining six incinerators to meet the floor
level, assuming no market exits, is estimated to be $0.9 million and
would reduce carbon monoxide emissions nationally by 45 Mg per year
from the baseline emissions level of 9170 Mg per year.¹⁰³
Although we cannot quantify a corresponding reduction of organic
hazardous air pollutant emissions, we estimate these reductions would
be significant based on the carbon monoxide reductions.
---------------------------------------------------------------------------

\103\ As discussed previously in the text, you have the option
of complying with the hydrocarbon emission standard rather than the
carbon monoxide standard. This is because carbon monoxide is a
conservative indicator of the potential for emissions of organic
compounds while hydrocarbon concentrations in stack gas are a direct
measure of emissions of organic compounds.
---------------------------------------------------------------------------

b. What Are Our Beyond-the-Floor Considerations for Existing
Sources? We considered more stringent beyond-the-floor controls (i.e.,
better combustion practices resulting in lower carbon monoxide levels)
to provide additional reduction in emissions. Although it is difficult
to quantify the reduction in emissions of organic hazardous air
pollutants that would be associated with a lower carbon monoxide limit,
we concluded that cost-effectiveness considerations would likely come
into play, and suggest that a beyond-the-floor standard is not
warranted. Therefore, we conclude that a beyond-the-floor standard for
carbon monoxide for existing sources is not appropriate. We note that,
although control of carbon monoxide (or hydrocarbon) is not an absolute
guarantee that nondioxin/furan products of incomplete combustion will
not be emitted at levels of concern, this problem (where it may exist)
can be addressed through the RCRA omnibus permitting process.
c. What Is the MACT Floor for New Sources? At proposal and in the
May 1997 NODA, we stated that operating under good combustion practices
defines MACT floor control for new (and existing)
sources,¹⁰⁴ and the preponderance of data indicate that a
floor level of 100 ppmv over an hourly rolling average is readily
achievable. For reasons set forth in the proposal, and absent data to
the contrary, we conclude that this floor level is appropriate.
---------------------------------------------------------------------------

\104\ Because we cannot quantify good combustion practices,
floor control for the single best controlled source is the same as
for existing sources (i.e., that combination of design, operation,
and maintenance that achieves good combustion as evidenced by carbon
monoxide levels of 100 ppmv or less on an hourly rolling average).
---------------------------------------------------------------------------

d. What Are Our Beyond-the-Floor Considerations for New Sources? We
considered more stringent beyond-the-floor controls (i.e., better
combustion practices resulting in lower carbon monoxide levels) to
provide additional reduction in emissions. For the reasons discussed
above in the context of beyond-the-floor controls for existing sources,
however, we conclude that a beyond-the-floor standard for carbon
monoxide for new sources is not appropriate.
9. What Are the Standards for Hydrocarbon?
Hydrocarbon concentrations in stack gas are a direct surrogate for
emissions of organic hazardous pollutants. We establish hydrocarbon
standards of 10 ppmv for both existing and new sources based on the
rationale discussed below. Sources have the option to comply with
either the carbon monoxide or the hydrocarbon emission standard.
Sources that elect to comply with the carbon monoxide standard,
however, must nonetheless document compliance with the hydrocarbon
standard during the comprehensive performance test.
a. What Is the MACT Floor for Existing Sources? We proposed a
hydrocarbon emission standard of 12 ppmv ¹⁰⁵ based on good
combustion practices, but revised it in the May 1997 NODA to 10 ppmv
based on refinements of analysis and the corrected data base.
---------------------------------------------------------------------------

\105\ Based on an hourly rolling average, reported as propane,
corrected to 7 percent oxygen, dry basis.
---------------------------------------------------------------------------

As proposed, floor control for existing sources is operating under
good combustion practices (e.g., providing adequate excess oxygen;
providing adequate fuel (waste) and air mixing; maintaining high
temperatures and adequate combustion gas residence time at those
temperatures). Given that there are many interdependent parameters that
affect combustion efficiency and thus hydrocarbon emissions, we are not
able to quantify good combustion practices.
We are identifying a floor level for the final rule of 10 ppmv on
an hourly rolling average because it is being achieved using good
combustion practices. More than 85 percent of test conditions in our
data base have hydrocarbon levels below 10 ppmv, and nearly 75 percent
have levels below 5 ppmv. Although 13 test conditions in our data base
representing 7 sources have hydrocarbon levels higher than 10 ppmv, we
conclude that these sources

[[Page 52870]]

are not operating under good combustion practices. For example, one
source is a rotary kiln without an afterburner. Another source is a
fluidized bed type incinerator that operates at lower than typical
combustion temperatures without an afterburner while another source is
operating at high carbon monoxide levels, indicative of poor combustion
efficiency.¹⁰⁶
---------------------------------------------------------------------------

\106\ USEPA, ``Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards and
Technologies,'' July 1999.
---------------------------------------------------------------------------

Some commenters on the May 1997 NODA object to the 10 ppmv level
and suggest adopting a level of 20 ppmv based on the BIF rule
(Sec. 266.104(c)), and an earlier hazardous waste incinerator proposal
(55 FR 17862 (April 27, 1990)). These commenters cite sufficient
protectiveness at the 20 ppmv level. We conclude that this comment is
not on point because the MACT standards are technology rather than
risk-based. The MACT standards must reflect the level of control that
is not less stringent than the level of control achieved by the best
performing sources. Because hazardous waste incinerators are readily
achieving a hydrocarbon level of 10 ppmv using good combustion
practices, that floor level is appropriate.
Some commenters also object to the requirement to use heated flame
ionization hydrocarbon detectors ¹⁰⁷ in hazardous waste
incinerators that use wet scrubbers. The commenters state that these
sources have a very high moisture content in the flue gas that hinders
proper functioning of the specified hydrocarbon detectors. We agree
that hydrocarbon monitors may be hindered in these situations. For this
and other reasons (e.g., some sources can have high carbon monoxide but
low hydrocarbon levels), the final rule gives sources the option of:
(1) Continuous hydrocarbon monitoring; or (2) continuous carbon
monoxide monitoring and demonstration of compliance with the
hydrocarbon standard only during the performance test.
---------------------------------------------------------------------------

\107\ See Performance Specification 8A, appendix B, part 60,
``Specifications and test procedures for carbon monoxide and oxygen
continuous monitoring systems in stationary sources.''
---------------------------------------------------------------------------

We estimated compliance costs to the hazardous waste incinerator
universe for administrative purposes. Approximately 97 percent of
incinerators currently meet the hydrocarbon floor level of 10 ppmv. The
annualized cost for the remaining six incinerators to meet the floor
level, assuming no market exits, is estimated to be $0.35 million, and
would reduce hydrocarbon emissions nationally by 28 Mg per year from
the baseline emissions level of 292 Mg per year. Although the
corresponding reduction of organic hazardous air pollutant emissions
cannot be quantified, these reductions are qualitatively assessed as
significant.
b. What Are Our Beyond-the-Floor Considerations for Existing
Sources? We considered more stringent beyond-the-floor controls (i.e.,
better combustion practices resulting in lower hydrocarbon levels) to
provide additional reduction in emissions. Although it is difficult to
quantify the reduction in emissions of organic hazardous air pollutants
that would be associated with a lower hydrocarbon limit, cost-
effectiveness considerations would likely come into play, however, and
suggest that a beyond-the-floor standard is not warranted. Therefore,
we conclude that a beyond-the-floor standard for hydrocarbon emissions
for existing sources is not appropriate. We note further that, although
control of hydrocarbon emissions is not an absolute guarantee that
nondioxin products of incomplete combustion will not be emitted at
levels of concern, this problem (where it may exist) can be addressed
through the RCRA omnibus permitting process.
c. What Is the MACT Floor for New Sources? At proposal and in the
May 1997 NODA, we stated that operation under good combustion practices
at new (and existing) hazardous waste incinerators defines the MACT
control.¹⁰⁸ As discussed above, sources using good
combustion practices are achieving hydrocarbon levels of 10 ppmv or
below. Comments on this subject were minor and did not identify any
problems in achieving the 10 ppmv level by new sources. Thus, we
conclude that a floor level of 10 ppmv on hourly rolling average is
appropriate for new sources.
---------------------------------------------------------------------------

\108\ Because we cannot quantify good combustion practices,
floor control for the single best controlled soruce is the same as
for existing sources (i.e., that combination of design, operation,
and maintenance that achieves good combustion as evidenced by
hydrocarbon levels of 10 ppmv or less on an hourly rolling average).
---------------------------------------------------------------------------

d. What Are Beyond-the-Floor Considerations for New Sources? We
considered more stringent beyond-the-floor controls (i.e., better
combustion practices) to provide additional reduction in emissions. For
the reasons discussed above in the context of beyond-the-floor controls
for existing sources, however, we conclude that a beyond-the-floor
standard for hydrocarbons for new sources is not appropriate.
10. What Are the Standards for Destruction and Removal Efficiency?
We establish a destruction and removal efficiency (DRE) standard
for existing and new incinerators to control emissions of organic
hazardous air pollutants other than dioxins and furans. Dioxins and
furans are controlled by separate emission standards. See discussion in
Part Four, Section IV.A. The DRE standard is necessary, as previously
discussed, to complement the carbon monoxide and hydrocarbon emission
standards, which also control these hazardous air pollutants.
The standard requires 99.99 percent DRE for each principal organic
hazardous constituent (POHC), except that 99.9999 percent DRE is
required if specified dioxin-listed hazardous wastes are burned. These
wastes are listed as--F020, F021, F022, F023, F026, and F027--RCRA
hazardous wastes under Part 261 because they contain high
concentrations of dioxins.
a. What Is the MACT Floor for Existing Sources? Existing sources
are currently subject to DRE standards under Sec. 264.342 and
Sec. 264.343(a) that require 99.99 percent DRE for each POHC, except
that 99.9999 percent DRE is required if specified dioxin-listed
hazardous wastes are burned. Accordingly, these standards represent
MACT floor. Since all hazardous waste incinerators are currently
subject to these DRE standards, they represent floor control, i.e.,
greater than 12 percent of existing sources are achieving these
controls.
b. What Are Our Beyond-the-Floor Considerations for Existing
Sources? Beyond-the-floor control would be a requirement to achieve a
higher percentage DRE, for example, 99.9999 percent DRE for POHCs for
all hazardous wastes. A higher DRE could be achieved by improving the
design, operation, or maintenance of the combustion system to achieve
greater combustion efficiency.
Sources will not incur costs to achieve the 99.99 percent DRE floor
because it is an existing RCRA standard. A substantial number of
existing incinerators are not likely to be routinely achieving 99.999
percent DRE, however, and most are not likely to be achieving 99.9999
percent DRE. Improvements in combustion efficiency will be required to
meet these beyond-the-floor DREs. Improved combustion efficiency is
accomplished through better mixing, higher temperatures, and longer
residence times. As a practical matter, most combustors are mixing-
limited. Thus, improved mixing is

[[Page 52871]]

necessary for improved DREs. For a less-than-optimum burner, a certain
amount of improvement may typically be accomplished by minor,
relatively inexpensive combustor modifications--burner tuning
operations such as a change in burner angle or an adjustment of swirl--
to enhance mixing on the macro-scale. To achieve higher and higher
DREs, however, improved mixing on the micro-scale may be necessary
requiring significant, energy intensive and expensive modifications
such as burner redesign and higher combustion air pressures. In
addition, measurement of such DREs may require increased spiking of
POHCs and more sensitive stack sampling and analysis methods at added
expense.
Although we have not quantified the cost-effectiveness of a beyond-
the-floor DRE standard, we do not believe that it would be cost-
effective. For reasons discussed above, we believe that the cost of
achieving each successive order-of-magnitude improvement in DRE will be
at least constant, and more likely increasing. Emissions reductions
diminish substantially, however, with each order of magnitude
improvement in DRE. For example, if a source were to emit 100 gm/hr of
organic hazardous air pollutants assuming zero DRE, it would emit 10
gm/hr at 90 percent DRE, 1 gm/hr at 99 percent DRE, 0.1 gm/hr at 99.9
percent DRE, 0.01 gm/hr at 99.99 percent DRE, and 0.001 gm/hr at 99.999
percent DRE. If the cost to achieve each order of magnitude improvement
in DRE is roughly constant, the cost-effectiveness of DRE decreases
with each order of magnitude improvement in DRE. Consequently, we
conclude that this relationship between compliance cost and diminished
emissions reductions associated with a more stringent DRE standard
suggests that a beyond-the-floor standard is not warranted.
c. What Is the MACT Floor for New Sources? The single best
controlled source, and all other hazardous waste incinerators, are
subject to the existing RCRA DRE standard under Sec. 264.342 and
Sec. 264.343(a). Accordingly, we adopt this standard as the MACT floor
for new sources.
d. What Are Our Beyond-the-Floor Considerations for New Sources? As
discussed above, although we have not quantified the cost-effectiveness
of a more stringent DRE standard, diminishing emissions reductions with
each order of magnitude improvement in DRE suggests that cost-
effectiveness considerations would likely come into play. We conclude
that a beyond-the-floor standard is not warranted.

VII. What Are the Standards for Hazardous Waste Burning Cement Kilns?

A. To Which Cement Kilns Do Today's Standards Apply?
The standards promulgated today apply to each existing,
reconstructed, and newly constructed Portland cement manufacturing kiln
that burns hazardous waste. These standards apply to all hazardous
waste burning cement kilns (both major source and area source cement
plants). Portland cement kilns that do not engage in hazardous waste
burning operations are not subject to this NESHAP. However, these
hazardous waste burning kilns would be subject to the NESHAP for other
sources of hazardous air pollutants at the facility (e.g., clinker
cooler stack) that we finalized in June 1999.¹⁰⁹
---------------------------------------------------------------------------

\109\ On June 14, 1999, we promulgated regulations for kiln
stack emissions for nonhazardous waste burning cement kilns and
other sources of hazardous air pollutants at all Portland
manufacturing plants. (See 64 FR 31898.)
---------------------------------------------------------------------------

B. How Did EPA Initially Classify Cement Kilns?
1. What Is the Basis for a Separate Class Based on Hazardous Waste
Burning?
Portland cement manufacturing is one of the initial 174 categories
of major and area sources of hazardous air pollutants listed pursuant
to section 112(c)(1) for which section 112(d) standards are to be
established.¹¹⁰ We divided the Portland cement manufacturing
source category into two different classes based on whether the cement
kiln combusts hazardous waste. This action was taken for two principal
reasons: If hazardous wastes are burned in the kiln, emissions of
hazardous air pollutants can be different for the two types of kilns in
terms of both types and concentrations of hazardous air pollutants
emitted, and metals and chlorine emissions are controlled in a
significantly different manner.
---------------------------------------------------------------------------

\110\ EPA published an initial list of 174 categories of area
and major sources in the Federal Register on July 16, 1992. (See 57
FR at 31576.)
---------------------------------------------------------------------------

A comparison of metals levels in coal and in hazardous waste fuel
burned in lieu of coal on a heat input basis reveals that hazardous
waste frequently contains higher concentrations of hazardous air
pollutant metals (i.e., mercury, semivolatile metals, low volatile
metals) than coal. Hazardous waste contains higher levels of
semivolatile metals than coal by more than an order of magnitude at
every cement kiln in our data base.¹¹¹ In addition, coal
concentrations of mercury and low volatile metals were less than
hazardous waste by approximately an order of magnitude at every
facility except one. Thus, a cement kiln feeding a hazardous waste fuel
is likely to emit more metal hazardous air pollutants than a
nonhazardous waste burning cement kiln. Given this difference in
emissions characteristics, we divided the Portland cement manufacturing
source category into two classes based on whether hazardous waste is
burned in the cement kiln.
---------------------------------------------------------------------------

\111\ USEPA, ``Final Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards and
Technologies,'' July 1999.
---------------------------------------------------------------------------

Today's rule does not establish hazardous air pollutant emissions
limits for other hazardous air pollutant-emitting sources at a
hazardous waste burning cement plant. These other sources of hazardous
air pollutants may include materials handling operations, conveyor
system transfer points, raw material dryers, and clinker coolers.
Emissions from these sources are subject to the requirements
promulgated in the June 14, 1999 Portland cement manufacturing NESHAP.
See 64 FR 31898. These standards are applicable to these other sources
of hazardous air pollutants at all Portland cement plants, both for
nonhazardous waste burners and hazardous waste burners.
In addition, this regulation does not establish standards for
cement kiln dust management facilities (e.g., cement kiln dust piles or
landfills). We are developing cement kiln dust storage and disposal
requirements in a separate rulemaking.
2. What Is the Basis for Differences in Standards for Hazardous Waste
and Nonhazardous Waste Burning Cement Kilns?
Today's final standards for hazardous waste burning cement kilns
are identical in some respects to those finalized for nonhazardous
waste burning cement kilns on June 14, 1999. The standards differ,
however, in several important aspects. A comparison of the major
features of the two sets of standards and the basis for major
differences is discussed below.
a. How Does the Regulation of Area Sources Differ? As discussed
earlier, this rule makes a positive area source finding under section
112(c)(3) of the CAA (i.e., a finding that hazardous air pollutant
emissions from an area source can pose potential risk to human health
and the environment) for existing hazardous waste burning cement kilns
and subjects area sources to the same standards that apply to major
sources. (See Part Three, Section III.B of today's preamble.) For
nonhazardous waste burning cement kilns, however, we regulate area
sources under authority of

[[Page 52872]]

section 112(c)(6) of the CAA, and so apply MACT standards only to the
section 112(c)(6) hazardous air pollutants emitted from such sources.
The positive finding for hazardous waste burning cement kilns is
based on several factors and, in particular, on concern about potential
health risk from emissions of mercury and nondioxin/furan organic
hazardous air pollutants which are products of incomplete combustion.
However, we do not have this same level of concern with hazardous
air pollutant emissions from nonhazardous waste burning cement kilns
located at area source cement plants, and so did not make a positive
area source finding. As discussed above, mercury emissions from
hazardous waste burning cement kilns are generally higher than those
from nonhazardous waste burning cement kilns. Also, nondioxin and
nonfuran organic hazardous air pollutants emitted from hazardous waste
burning cement kilns have the potential to be greater than those from
nonhazardous waste burning cement kilns because hazardous waste can
contain high concentrations of a wide-variety of organic hazardous air
pollutants. In addition, some hazardous waste burning cement kilns feed
containers of hazardous waste at locations (e.g., midkiln, raw material
end of the kiln) other than the normal coal combustion zone. If such
firing systems are poorly designed, operated, or maintained, emissions
of nondioxin and furan organic hazardous air pollutants could be
substantial (and, again, significantly greater than comparable
emissions from nonhazardous waste Portland cement plants). Finally,
hazardous air pollutant emissions from nonhazardous waste burning
cement kilns currently are not regulated uniformly under another
statute as is the case for hazardous waste burning cement kilns which
affects which pollutants are controlled at the floor for each class.
Under the June 1999 final rule, existing and new nonhazardous waste
burning cement kilns at area source plants are subject to dioxin and
furan emission standards, and a hydrocarbon ¹¹² standard for
new nonhazardous waste burning cement kilns that are area sources.
These standards are promulgated under the authority of section
112(c)(6). That section requires the Agency to establish MACT standards
for source categories contributing significantly in the aggregate to
emissions of identified, particularly hazardous air pollutants. The
MACT process was also applied to the control of mercury, although the
result was a standard of no control.
---------------------------------------------------------------------------

\112\ Hydrocarbon emissions would be limited as a surrogate for
polycyclic organic matter, a category of organic hazardous air
pollutants identified in section 112(c)(6).
---------------------------------------------------------------------------

b. How Do the Emission Standards Differ? The dioxin, furan and
particulate matter emission standards for nonhazardous waste burning
cement kilns are identical to today's final standard for hazardous
waste burning cement kilns. The standards for both classes of kilns are
floor standards and are identical because hazardous waste burning is
not likely to affect emissions of either dioxin/furan ¹¹³ or
particulate matter. We also conclude that beyond-the-floor standards
for these pollutants would not be cost-effective for either class of
cement kilns.
---------------------------------------------------------------------------

\113\ Later in the text, however, we discuss how hazardous waste
burning may potentially affect dioxin and furan emissions and the
additional requirements for hazardous waste burning cement kilns
that address this concern.
---------------------------------------------------------------------------

Under today's rule, hazardous waste burning cement kilns are
subject to emission standards for mercury, semivolatile metals, low
volatile metals, and hydrochloric acid/chlorine gas, but we did not
finalize such standards for nonhazardous waste burning cement kilns.
Currently, emissions of these hazardous air pollutants from hazardous
waste burning cement kilns are regulated under RCRA. Therefore, we
could establish floor levels for each pollutant under the CAA. These
hazardous air pollutants, however, currently are not controlled for
nonhazardous waste burning cement kilns and floor levels would be
uncontrolled levels (i.e., the highest emissions currently
achieved).¹¹⁴ We considered beyond-the-floor controls and
emission standards for mercury and hydrochloric acid for nonhazardous
waste burning cement kilns, but conclude that beyond-the-floor
standards are not cost-effective, especially considering the lower
rates of current emissions for nonhazardous waste burning plants.
---------------------------------------------------------------------------

\114\ Although semivolatile metal and low volatile metal are
controlled by nonhazardous waste burning cement kilns, along with
other metallic hazardous air pollutants, by controlling particulate
matter. These metals are not individually controlled by nonhazardous
waste burning cement kilns as they are for hazardous waste burning
cement kilns by virtue of individual metal feedrate limits
established under existing RCRA regulations.
---------------------------------------------------------------------------

Finally, under today's rule, hazardous waste burning cement kilns
are subject to emission limits on carbon monoxide and hydrocarbon and a
destruction and removal efficiency standard to control nondioxin/furan
organic hazardous air pollutants. We identified these controls as floor
controls because carbon monoxide and hydrocarbon emissions are
controlled for these sources under RCRA regulations, as is destruction
and removal efficiency.¹¹⁵ For nonhazardous waste burning
cement kilns, carbon monoxide and hydrocarbon emissions currently are
not controlled, and the destruction and removal efficiency standard,
established under RCRA, does not apply. Therefore, carbon monoxide,
hydrocarbon control and the destruction and removal efficiency standard
are not floor controls for this second group of cement kilns. We
considered beyond-the-floor controls for hydrocarbon from nonhazardous
waste burning cement kilns and determined that beyond-the-floor
controls for existing sources are not cost-effective. The basis of this
conclusion is discussed in the proposed rule for nonhazardous waste
burning cement kilns (see 63 FR at 14202). We proposed and finalized,
however, a hydrocarbon emission standard for new source nonhazardous
waste cement kilns based on feeding raw materials without an excessive
organic content.¹¹⁶ See 63 FR at 14202 and 64 FR 31898.
---------------------------------------------------------------------------

\115\ For hazardous waste burning cement kilns, existing RCRA
carbon monoxide and hydrocarbon standards do not apply to the main
stack of a kiln equipped with a by-pass or other means of measuring
carbon monoxide or hydrocarbon at mid kiln to ensure good combustion
of hazardous waste. Therefore, there is no carbon monoxide or
hydrocarbon floor control for such stacks, and we conclude that
beyond-the-floor controls would not be cost-effective.
\116\ Consistent with the nonhazardous waste burnign cement kiln
proposal, however, we subject the main stack of such new source
hazardous waste burning cemen tkilns to a hydrocarbon standard.
---------------------------------------------------------------------------

We did not consider a destruction and removal efficiency standard
as a beyond-the-floor control for nonhazardous waste burning cement
kilns because, based historically on a unique RCRA statutory provision,
the DRE standard is designed to ensure destruction of organic hazardous
air pollutants in hazardous waste fed to hazardous waste combustors.
The underlying rationale for such a standard is absent for nonhazardous
waste burning cement kilns that do not combust hazardous waste and that
feed materials (e.g., limestone, coal) that contain only incidental
levels of organic hazardous air pollutants.
c. How Do the Compliance Procedures Differ? We finalized compliance
procedures for nonhazardous waste burning cement kilns that are similar
to those finalized today for hazardous waste burning cement kilns. For
particulate matter, we are implementing a coordinated program to
document the feasibility of particulate matter continuous emissions
monitoring

[[Page 52873]]

systems on both nonhazardous waste and hazardous waste burning cement
kilns. We plan to establish a continuous emissions monitoring systems-
based emission level through future rulemaking that is achievable by
sources equipped with MACT control (i.e., an electrostatic precipitator
or fabric filter designed, operated, and maintained to meet the New
Source Performance Standard particulate matter standard). In the
interim, we use the opacity standard as required by the New Source
Performance Standard for Portland cement plants under Sec. 60.62 to
ensure compliance with the particulate matter standard for both
hazardous waste and nonhazardous waste burning cement kilns.
For dioxin/furan, the key compliance parameter will be identical
for both hazardous waste and nonhazardous waste burning cement kilns--
control of temperature at the inlet to the particulate matter control
device. Other factors that could contribute to the formation of dioxins
and furans, however, are not completely understood. As a result,
hazardous waste burning cement kilns have additional compliance
requirements to ensure that hazardous waste is burned under good
combustion conditions. These additional controls are necessary because
of the dioxin and furan precursors that can be formed from improper
combustion of hazardous waste, given the hazardous waste firing systems
used by some hazardous waste burning cement kilns and the potential for
hazardous waste to contain high concentrations of many organic
hazardous air pollutants not found in conventional fuels or cement kiln
raw materials.
We also require both hazardous waste and nonhazardous waste burning
cement kilns to conduct performance testing midway between the five-
year periodic comprehensive performance testing to confirm that dioxin/
furan emissions do not exceed the standard when the source operates
under normal conditions.
C. What Further Subcategorization Considerations Are Made?
We also fully considered further subdividing the class of hazardous
waste burning cement kilns itself. For the reasons discussed below, we
decided that subcategorization is not needed to determine achievable
MACT standards for all hazardous waste burning cement kilns.
We considered, but rejected, subdividing the hazardous waste
burning cement kiln source category on the basis of raw material feed
preparation, more specifically wet process versus dry process. In the
wet process, raw materials are ground, wetted, and fed into the kiln as
a slurry. Approximately 70 percent of the hazardous waste burning
cement kilns in operation use a wet process. In the dry process, raw
materials are ground dry and fed into the kiln dry. Within the dry
process there are three variations: Long kiln dry process, preheater
process, and preheater-precalciner process. We decided not to
subcategorize the hazardous waste burning cement kiln category based on
raw material feed preparation because: (1) The wet process kilns and
all variations of the dry process kilns use similar raw materials,
fossil fuels, and hazardous waste fuels; (2) the types and
concentrations of uncontrolled hazardous air pollutant emissions are
similar for both process types;¹¹⁷ (3) the same types of
particulate matter pollution control equipment, specifically either
fabric filters or electrostatic precipitators, are used by both process
types, and the devices achieve the same level of performance when used
by both process types; and (4) the MACT controls we identify are
applicable to both process types of cement kilns. For example, MACT
floor controls for metals and chlorine include good particulate matter
control and hazardous waste feedrate control, as discussed below, the
particulate matter standard promulgated today is based on the New
Source Performance Standard, which applies to all cement kilns
irrespective of process type. Further, a cement kiln operator has great
discretion in the types of hazardous waste they accept including the
content of metals and chlorine in the waste. These basic control
techniques--particulate matter control and feedrate control of metals
and chlorine--clearly show that subcategorization based on process type
is not appropriate.
---------------------------------------------------------------------------

\117\ Although dry process kilns with a separate by-pass stack
can have higher metals emissions from that stack compared to the
main stack of other kilns, today's rule allows such kilns to
flowrate-average its emissions between the main and by-pass stack.
The average emissions are similar to the emissions from dry and wet
kilns that have only one stack. Similarly, kilns with in-line raw
mills have higher mercury emissions when the raw mill is off.
Today's rule allows such kilns to time-weight average their
emissions, however, and the time-weighted emissions for those kilns
are similar to emissions from other hazardous waste burning cement
kilns.
---------------------------------------------------------------------------

Some commenters stated that it is not feasible for wet process
cement kilns to use fabric filters, especially in cold climates, and
thus subcategorization based on process type is appropriate. The
problem, commenters contend, is that the high moisture content of the
flue gas will clog the fabric if the cement-like particulate is wetted
and subsequently dried, resulting in reduced performance and early
replacement of the fabric filter bags. Other commenters disagreed with
these assertions and stated that fabric filter technology can be
readily applied to wet process kilns given the exit temperatures of the
combustion gases and the ease of insulating fabric filter systems to
minimize cold spots in the baghouse to avoid dew point problems and
minimize corrosion. These commenters pointed to numerous wet process
applications currently in use at cement kilns with fabric filter
systems located in cold climates to support their claims.¹¹⁸
In light of the number of wet process kilns already using fabric
filters and their various locations, we conclude that wet process
cement kilns can be equipped with fabric filter systems and that
subdividing by process type on this basis is not necessary or
warranted. A review of the particulate matter emissions data for one
wet hazardous waste burning cement kiln using a fabric filter shows
that it is achieving the particulate matter standard. We do not have
data in our data base from the only other wet hazardous waste burning
cement kiln using a fabric filter; however, this cement kiln recently
installed and upgraded to a new fabric filter system.
---------------------------------------------------------------------------

\118\ We are aware of four wet process cement kiln facilities
operating with fabric filters: Dragon (Thomaston, ME), Giant
(Harleyville, SC), Holnam (Dundee, MI), and LaFarge (Paulding, OH).
Commenters also identified kilns in Canada operating with fabric
filters.
---------------------------------------------------------------------------

We also fully considered, but ultimately rejected, subdividing the
hazardous waste burning cement kiln source category between long kilns
and short kilns (preheater and preheater-precalciner) technologies, and
those with in-line kiln raw mills. This subcategorization approach was
recommended by many individual cement manufacturing member companies
and a cement manufacturing trade organization. Based on information on
the types of cement kilns that are currently burning hazardous waste,
these three subcategories consist of the following four subdivisions:
(1) Short kilns with separate by-pass and main stacks; (2) short kilns
with a single stack that handles both by-pass and preheater or
precalciner emissions; (3) long dry kilns that use kiln gas to dry raw
meal in the raw mill; and (4) others wet kilns, and long dry kilns not
using in-line kiln raw mill drying. Currently, each of the first three
categories consists of only one cement kiln facility while

[[Page 52874]]

the kilns at the remaining 15 facilities are in the fourth category:
wet kilns or long dry kilns that do not use in-line kiln raw mill
drying.
Commenters state that these subcategories should be considered
because the unique design or operating features of the different types
of kilns could have a significant impact on emissions of one or more
hazardous air pollutants that we proposed to regulate. Specifically,
commenters noted the potential flue gas characteristic differences for
cement kilns using alkali bypasses on short kilns and in-line kiln raw
mills. For example, kilns with alkali bypasses are designed to divert a
portion of the flue gas, approximately 10-30%, to remove the
problematic alkalis, such as potassium and sodium oxides, that can
react with other compounds in the cool end of the kiln resulting in
operation problems. Thus, bypasses allow evacuation of the undesirable
alkali metals and salts, including semivolatile metals and chlorides,
entrained in the kiln exit gases before they reach the preheater
cyclones. As a result, the commenters stated that the emission
concentration of semivolatile metals in the bypass stack is greater
than in the main stack, and therefore the difference in emissions
supports subcategorization.
We agree, in theory, that the emissions profile for some hazardous
air pollutants can be different for the three kilns types--short kilns
with and without separate bypass stacks, long kilns with in-line kiln
raw mills. To consider this issue further, we analyzed floor control
and floor emissions levels based only on the data and information from
the other long wet kilns and long dry kilns not using raw mill drying.
We then considered whether the remaining three kiln types could apply
the same MACT controls and achieve the resulting emission standards. We
conclude that these three types of kilns at issue can use the MACT
controls and achieve the corresponding emission levels identified in
today's rule for the wet kilns and long dry kilns not using raw mill
drying.¹¹⁹ As a result, we conclude that there is no
practical necessity driving a subcategorization approach even though
one would be theoretically possible. Further, to ensure that today's
standards are achievable by all cement kilns, we establish a provision
that allows cement kilns operating in-line kiln raw mills to average
their emissions based on a time-weighted average concentration that
considers the length of time the in-line raw mill is on-line and off
line. We also adopt a provision that allows short cement kilns with
dual stacks to average emissions on a flow-weighted basis to
demonstrate compliance with the emissions standards. (See Part Five,
Section X--Special Provisions for a discussion of these provisions.)
---------------------------------------------------------------------------

\119\ USEPA, ``Final Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards and
Technologies,'' July 1999.
---------------------------------------------------------------------------

In the case of hydrocarbons and carbon monoxide, we developed final
standards that reflect the concerns raised by several commenters. We
determined that this approach best accommodated the unique design and
operating differences between long wet and long dry process and short
kilns using either a preheater or a preheater and precalciner.
Existing hazardous waste preheater and preheater-precalciner cement
kilns, one of each type is burning hazardous waste, are equipped with
bypass ducts that divert a portion of the kiln off-gas through a
separate particulate matter control device to remove problematic alkali
metals. Long cement kilns do not use bypasses designed to remove alkali
metals. The significance of this operational difference is that
hydrocarbon and carbon monoxide levels in the bypass gas of short kilns
is more representative of the combustion efficiency of burning
hazardous waste and other fuels in the kiln than the measurements made
in the main stack. Main stack gas measurements of hydrocarbons and
carbon monoxide, regardless of process type, also include contributions
from trace levels of organic matter volatilized from the raw materials,
which can mask the level of combustion efficiency achieved in the kiln.
Today's tailored standards require cement kilns to monitor
hydrocarbons and carbon monoxide at the location best indicative of
good combustion. For short kilns with bypasses, the final rule requires
monitoring of hydrocarbons and carbon monoxide in the bypass. Long
kilns are required to comply with the hydrocarbon and carbon monoxide
standards in the main stack. However, long kilns that operate a mid-
kiln sampling system, for the purpose of removing a representative
portion of the kiln off-gas to measure combustion efficiency, can
comply with the hydrocarbon and carbon monoxide standards at the
midkiln sampling point.
In addition, establishing separate hydrocarbon and carbon monoxide
standards reflects the long and short kiln subcategorization approach
recommended by some commenters. The standards differ because MACT floor
control for hydrocarbons and carbon monoxide is based primarily on the
existing requirements of the Boiler and Industrial Furnace rule. In
that rule, the unique design and operating features of long and short
kilns were considered in establishing type specific emission limits for
hydrocarbons and carbon monoxide. Thus, MACT floor control for long and
short kilns is different. However, we note these same unique design and
operating features were not a factor in establishing standards for
other pollutants, including mercury, semivolatile and low volatile
metals, and hydrochloric acid/chlorine gas, in the Boiler and
Industrial Furnace rule.
For the reasons discussed above, subcategorization would not appear
to be needed to establish uniform, achievable MACT standards for all
cement kilns burning hazardous waste. Thus, because the differences
among kiln types ``does not affect the feasibility and effectiveness of
air pollution control technology,'' subcategorization is not
appropriate. S. Rep. No. 228, 101st Cong. 1st sess. 166.
D. What Are The Standards for Existing and New Cement Kilns?
1. What Are the Standards for Cement Kilns?
In this section, the basis for the emissions standards for cement
kilns is discussed. The kiln emission limits apply to the kiln stack
gases, in-line kiln raw mill stack gases if combustion gases pass
through the in-line raw mill, and kiln alkali bypass stack gases if
discharged through a separate stack from cement plants that burn
hazardous waste in the kiln. The emissions standards are summarized
below:

[[Page 52875]]

Standards for Existing and New Cement Kilns
------------------------------------------------------------------------
Hazardous air pollutant or Emissions standard ¹
hazardous air pollutant -------------------------------------------
surrogate Existing sources New sources
------------------------------------------------------------------------
Dioxin and furan............ 0.20 ng TEQ/dscm; or 0.20 ng TEQ/dscm; or
0.40 ng TEQ/dscm 0.40 ng TEQ/dscm
and control of flue and control of flue
gas temperature not gas temperature not
to exceed 400 deg.F to exceed 400 deg.F
at the inlet to the at the inlet to the
particulate matter particulate matter
control device. control device.
Mercury..................... 120 g/dscm. 56 g/dscm.
Particulate matter ²........ 0.15 kg/Mg dry feed 0.15 kg/Mg dry feed
and 20% opacity. and 20% opacity.
Semivolatile metals......... 240 g/dscm. 180 g/dscm.
Low volatile metals......... 56 g/dscm.. 54 g/dscm.
Hydrochloric acid and 130 ppmv............ 86 ppmv.
chlorine gas.
Hydrocarbons: kilns without 20 ppmv (or 100 ppmv Greenfield kilns: 20
by-pass ^3, ⁶. carbon monoxide) ³. ppmv (or 100 ppmv
carbon monoxide and
50 ppmv ⁵
hydrocarbons).
.................... All others: 20 ppmv
(or 100 ppmv carbon
monoxide) ³.
Hydrocarbons: kilns with by- No main stack 50 ppmv ⁵.
pass; main stack ^4, ⁶. standard.
Hydrocarbons: kilns with by- 10 ppmv (or 100 ppmv 10 ppmv (or 100 ppmv
pass; by-pass duct and carbon monoxide). carbon monoxide).
stack ^3, ^4, ⁶.
Destruction and removal For existing and new sources, 99.99% for
efficiency. each principal organic hazardous
constituent (POHC) designated. For
sources burning hazardous wastes F020,
F021, F022, F023, F026, or F027, 99.9999%
for each POHC designated.
------------------------------------------------------------------------
\1\ All emission levels are corrected to 7% O2, dry basis.
\2\ If there is an alkali by-pass stack associated with the kiln or in-
line kiln raw mill, the combined particulate matter emissions from the
kiln or in-line kiln raw mill and the alkali by-pass must be less than
the particulate matter emissions standard.
\3\ Cement kilns that elect to comply with the carbon monoxide standard
must demonstrate compliance with the hydrocarbon standard during the
comprehensive performance test.
\4\ Measurement made in the by-pass sampling system of any kiln (e.g.,
alkali by-pass of a preheater and/or precalciner kiln; midkiln
sampling system of a long kiln).
\5\ Applicable only to newly-constructed cement kilns at greenfield
sites (see discussion in Part Four, Section VII.D.9). 50 ppmv standard
is a 30-day block average limit. Hydrocarbons reported as propane.
\6\ Hourly rolling average. Hydrocarbons are reported as propane.

2. What Are the Dioxin and Furan Standards?
In today's rule, we establish a standard for new and existing
cement kilns that limits dioxin/furan emissions to either 0.20 ng TEQ/
dscm; or 0.40 ng TEQ/dscm and temperature at the inlet to the
particulate matter control device not to exceed
400 deg.F.¹²⁰ Our rationale for these standards is discussed
below.
---------------------------------------------------------------------------

\120\ The temperature limit applies at the inlet to a dry
particulate matter control device that suspends particulate matter
in the combustion gas stream (e.g., electrostatic precipitator,
fabric filter) such that surface-catalyzed formation of dioxin/furan
is enhanced. The temperature limit does not apply to a cyclone
control device, for example.
---------------------------------------------------------------------------

a. What Is the MACT Floor for Existing Sources? In the April 1996
proposal, we identified floor control as either temperature control at
the inlet to the particulate matter control device of less than
418 deg.F, or achieving a specific level of dioxin/furan emissions
based upon levels achievable using proper temperature control. (61 FR
at 17391.) The proposed floor emission level was 0.20 ng TEQ/dscm, or
temperature at the inlet to the electrostatic precipitator or fabric
filter not to exceed 418 deg.F. In the May 1997 NODA, we identified an
alternative data analysis method to identify floor control and the
floor emission level. Floor control for dioxin/furan was defined as
temperature control at the inlet to the electrostatic precipitator or
fabric filter at 400 deg.F, which was based on further engineering
evaluation of the emissions data and other available information. That
analysis resulted in a floor emission level of 0.20 ng TEQ/dscm, or
0.40 ng TEQ/dscm and temperature at the inlet to the electrostatic
precipitator or fabric filter not to exceed 400 deg.F. (62 FR at
24226.) The 0.40 ng TEQ/dscm standard is the level that all cement
kilns, including data from nonhazardous waste burning cement kilns, are
achieving when operating at the MACT floor control level or better. We
considered a data set that included dioxin/furan emissions from
nonhazardous waste burning cement kilns because these data are
adequately representative of general dioxin/furan behavior and control
in either type of kiln. The impacts of hazardous waste constituents
(HAPs) on the emissions of those HAPs prevent us from expanding our
database for other HAPs in a similar way.
We conclude that the floor methodology discussed in the May 1997
NODA is appropriate and we adopt this approach in today's final rule.
We identified two technologies for control of dioxin/furan emissions
from cement kilns in the May 1997 NODA. The first technology achieves
low dioxin/furan emissions by quenching kiln gas temperatures at the
exit of the kiln so that gas temperatures at the inlet to the
particulate matter control device are below the temperature range of
optimum dioxin/furan formation. For example, we are aware of several
cement kilns that have recently added flue gas quenching units upstream
of the particulate matter control device to reduce the inlet
particulate matter control device temperature resulting in
significantly reduced dioxin/furan levels.¹²¹ The other
technology is activated carbon injected into the kiln exhaust gas.
Since activated carbon injection is not currently used by any hazardous
waste burning cement kilns, this technology was evaluated only as part
of a beyond-the-floor analysis.
---------------------------------------------------------------------------

\121\ USEPA, ``Final Technical Support Document for HWC MACT
Standards. Volume III: Selection of Proposed MACT Standards and
Technologies'', July 1999. See Section 3.2.1.
---------------------------------------------------------------------------

As discussed in the May 1997 NODA, specifying a temperature
limitation of 400 deg.F or lower is appropriate for floor control
because, from an engineering perspective, it is within the range of

[[Page 52876]]

reasonable values that could have been selected considering that: (1)
The optimum temperature window for surface-catalyzed dioxin/furan
formation is approximately 450-750 deg.F; and (2) temperature levels
below 350 deg.F can cause dew point condensation problems resulting in
particulate matter control device corrosion, filter cake cementing
problems, increased dust handling problems, and reduced performance of
the control device. (62 FR at 24226.)
Several commenters disagreed with our selection of 400 deg.F as the
particulate matter control device temperature limitation and stated
that other higher temperature limitations were equally appropriate as
MACT floor control. Based on these NODA comments, we considered
selecting a temperature limitation of 450 deg.F, generally regarded to
be the lower end of the temperature range of optimum dioxin/furan
formation. However, available data indicate that dioxin/furan formation
can be accelerated at kilns operating their particulate matter control
device at temperatures between 400-450 deg.F. Data from several kilns
show dioxin/furan emissions as high as 1.76 ng TEQ/dscm when operating
in the range of 400-450 deg.F. Identifying a higher temperature limit
such as 450 deg.F is not consistent with other sources achieving much
lower emissions at 400 deg.F, and thus identifying a higher temperature
limit would not be MACT floor control.
Some commenters also state that EPA has failed to demonstrate that
the best performing 12 percent of existing sources currently use
temperature control to reduce dioxin/furan emissions, and therefore,
temperature control is more appropriately considered in subsequent
beyond-the-floor analyses. However, particulate matter control device
operating temperatures associated with the emissions data used to
establish the dioxin/furan standard are based on the maximum operating
limits set during compliance certification testing required by the
Boiler and Industrial Furnace rule. See 40 CFR 266.103(c)(1)(viii). As
such, cement kilns currently must comply with these temperature limits
on a continuous basis during day-to-day operations, and therefore,
these temperature limits are properly assessed during an analysis of
MACT floors.
Several commenters also oppose consideration of dioxin/furan
emissions data from nonhazardous waste burning cement kilns in
establishing the floor standard. Commenters state that pooling the
available emissions data from hazardous waste burning cement kiln with
data from nonhazardous waste burning cement kilns to determine the MACT
floor violates the separate category approach that EPA decided upon for
the two classes of cement kilns. Notwithstanding our decision to divide
the Portland cement manufacturing source category based on the kiln's
hazardous waste burning status, we considered both hazardous waste
burning cement kiln and nonhazardous waste burning cement kiln data
together because both data sets are adequately representative of
general dioxin/furan behavior and control in either type of kiln. This
similarity is based on our engineering judgement that hazardous waste
burning does not have an impact on dioxin/furan formation, dioxin/furan
is formed post-combustion. Though the highest dioxin/furan emissions
data point from MACT (i.e., operating control device less than
400 deg.F) hazardous waste and nonhazardous waste burning cement kiln
sources varies somewhat (0.28 vs 0.37 ng TEQ/dscm respectively), it is
our judgment that additional emissions data, irrespective of hazardous
waste burning status, would continue to point to a floor of within the
range of 0.28 to 0.37 ng TEQ/dscm. This approach ensures that the floor
levels for hazardous waste burning cement kilns are based on the
maximum amount of relevant data, thereby ensuring that our judgment on
what floor level is achievable is as comprehensive as possible.
We estimate that approximately 70 percent of test condition data
from hazardous waste burning cement kilns are currently emitting less
than 0.40 ng TEQ/dscm (irrespective of the inlet temperature to the
particulate matter control device). In addition, approximately 50
percent of all test condition data are less than 0.20 ng TEQ/dscm. The
national annualized compliance cost for cement kilns to reduce dioxin/
furan emissions to comply with the floor standard is $4.8 million for
the entire hazardous waste burning cement industry and will reduce
dioxin/furan emissions by 5.4 g TEQ/yr or 40 percent from current
baseline emissions.
b. What Are Our Beyond-the-Floor Considerations for Existing
Sources? We considered in the April 1996 proposal and May 1997 NODA a
beyond-the-floor standard of 0.20 ng TEQ/dscm based on activated carbon
injection at a temperature of less than 400 deg.F. We continue to
believe that a beyond-the-floor standard 0.20 ng TEQ/dscm based on
activated carbon injection is the appropriate beyond-the-floor standard
to evaluate given the risks posed by dioxin/furan emissions.
Carbon injection is routinely effective at removing 99 percent of
dioxin/furans for numerous municipal waste combustor and mixed waste
incinerator applications and one hazardous waste incinerator
application. However, currently no hazardous waste burning cement kilns
use activated carbon injection for dioxin/furan removal. For cement
kilns, we believe that it is conservative to assume only 95 percent is
achievable given that the floor level is already low at 0.40 ng/dscm.
As dioxin/furans decrease, activated carbon injection efficiency is
expected to decrease. In addition, we assumed for cost-effectiveness
calculations that cement kilns needing activated carbon injection to
achieve the beyond-the-floor standard would install the activated
carbon injection system after the normal particulate matter control
device and add a new, smaller fabric filter to remove the injected
carbon with the absorbed dioxin/furan and mercury.¹²² The
costing approach addresses commenter's concerns that injected carbon
may interfere with cement kiln dust recycling practices.
---------------------------------------------------------------------------

\122\ We received many comments on the use of activated carbon
injection as a beyond-the-floor control techniques at cement kilns.
Since we do not adopt a beyond-the-floor standard based on activated
carbon injection in the final rule, these comments and our responses
to them are only discussed in our document that responds to public
comments.
---------------------------------------------------------------------------

The national incremental annualized compliance cost for the
remaining cement kilns to meet this beyond-the-floor level, rather than
comply with the floor controls, would be approximately $2.5 million for
the entire hazardous waste burning cement industry and would provide an
incremental reduction in dioxin/furan emissions nationally beyond the
MACT floor controls of 3.7 g TEQ/yr. Based on these costs,
approximately $0.66 million per g dioxin/furan removed, we determined
that this dioxin/furan beyond-the-floor option for cement kilns is not
justified. Therefore, we are not adopting a beyond-the-floor standard
of 0.2 ng TEQ/dscm.
We note that one possible explanation of high cost-effectiveness of
the beyond-the-floor standard may be due to the significant reduction
in national dioxin/furan emissions achieved over the past several years
by hazardous waste burning cement kilns due to emissions improving
modifications. The hazardous waste burning cement kiln national dioxin/
furan emissions estimate for 1997 decreased by nearly

[[Continued on page 52877]]

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