Revised Standards for Hazardous Waste Combustors

SUMMARY: The Agency is proposing revised standards for hazardous waste

incinerators, hazardous waste-burning cement kilns, and hazardous

waste-burning lightweight aggregate kilns. These standards are being

proposed 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. The MACT

standards also should result in increased protection to human health

and the environment over existing RCRA standards. The nature of this

proposal requires that the following actions also be proposed:

proposing the addition of hazardous waste-burning lightweight aggregate

kilns to the list of source categories in accordance with 112(c)(5) of

the Act; exempting from RCRA emission controls secondary lead

facilities subject to MACT; considering an exclusion for certain

``comparable fuels''; and revising the small quantity burner exemption

under the BIF rule.

DATES: EPA will accept public comments on this proposed rule until June

18, 1996.

ADDRESSES: Commenters must send an original and two copies of their

comments referencing docket number F-96-RCSP-FFFFF to: RCRA Docket

Information Center, Office of Solid Waste (5305W), U.S. Environmental

Protection Agency Headquarters (EPA, HQ), 401 M Street, SW.,

Washington, DC 20460. Deliveries of comments should be made to the

Arlington, VA, address listed below. Comments may also be submitted

electronically through the Internet to: RCRA-D[email protected].

Comments in electronic format should also be identified by the docket

number F-96-RCSP-FFFFF. All electronic comments must be submitted as an

ASCII file avoiding the use of special characters and any form of

encryption.

Commenters should not submit electronically any Confidential

Business Information (CBI). An original and two copies of CBI must be

submitted under separate cover to: RCRA CBI Document Control Officer,

Office of Solid Waste (5305W), U.S. EPA, 401 M Street, SW, Washington,

DC 20460.

Public comments and supporting materials are available for viewing

in the RCRA Information Center (RIC), located at Crystal Gateway One,

1235 Jefferson Davis Highway, First Floor, Arlington, VA. The RIC is

open from 9 a.m. to 4 p.m., Monday through Friday, excluding federal

holidays. To review docket materials, the public must make an

appointment by calling (703) 603-9230. The public may copy a maximum of

100 pages from any regulatory docket at no charge. Additional copies

cost $.15/page. The index and some supporting materials are available

electronically. See the ``Supplementary Information'' section for

information on accessing them.

A public hearing will be held, if requested, to discuss the

proposed standards for hazardous waste combustors, in accordance with

section 307(d)(5) of the Act. Persons wishing to make an oral

presentation at a public hearing should contact the EPA at the address

given in the ADDRESSES section of this preamble. Oral presentations

will be limited to 5 minutes each, unless additional time is feasible.

Any member of the public may file a written statement before, during,

or within 30 days after the hearing. Written statements should be

addressed to the RCRA Docket Section address given in the ADDRESSES

section of this preamble and should refer to Docket No. F-96-RCSP-

FFFFF. A verbatim transcript of the hearing and written statements will

be available for public inspection and copying during normal working

hours at the EPA's RCRA Docket Section in Washington, D.C. (see

ADDRESSES section of this preamble).

FOR FURTHER INFORMATION CONTACT: For general information, 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 more detailed information on specific aspects of this

rulemaking, contact Larry Denyer, Office of Solid Waste (5302W), U.S.

Environmental Protection Agency, 401 M Street, SW., Washington, DC

20460, (703) 308-8770, electronic mail: Denyer.L[email protected].

For more detailed information on implementation of this rulemaking,

contact Val de la Fuente, Office of Solid Waste (5303W), U.S.

Environmental Protection Agency, 401 M Street, SW., Washington, DC

20460, (703) 308-7245, electronic mail: DeLaFuente.V[email protected].

For more detailed information on regulatory impact assessment of this

rulemaking, contact Gary Ballard, Office of Solid Waste (5305), U.S.

Environmental Protection Agency, 401 M Street, SW., Washington, DC

20460, (202) 260-2429, electronic mail: Ballard.G[email protected].

For more detailed information on risk analyses of this rulemaking,

contact David Layland, Office of Solid Waste (5304), U.S. Environmental

Protection Agency, 401 M Street, SW., Washington, DC 20460, (202) 260-

4796, electronic mail: Layland.D[email protected].

SUPPLEMENTARY INFORMATION: The index and the following supporting

materials are available on the Internet: (List documents) Follow these

instructions to access the information electronically:

Gopher: gopher.epa.gov

WWW: http://www.epa.gov

Dial-up: (919) 558-0335.

This report can be accessed off the main EPA Gopher menu, in the

directory: EPA Offices and Regions/Office of Solid Waste and Emergency

Response (OSWER)/Office of Solid Waste (RCRA)/(consult with

Communication Strategist for precise subject heading)

FTP: ftp.epa.gov

Login: anonymous

Password: Your Internet address

Files are located in /pub/gopher/OSWRCRA

The official record for this action will be kept in paper form.

Accordingly, EPA will transfer all comments received electronically

into paper form and place them in the official record, which will also

include all comments submitted directly in writing. The official record

is the paper record maintained at the address in ADDRESSES at the

beginning of this document.

EPA responses to comments, whether the comments are written or

electronic, will be in a notice in the Federal Register or in a

response to comments document placed in the official record for this

rulemaking. EPA will not immediately reply to commenters electronically

other than to seek clarification of electronic comments that may be

garbled in transmission or during conversion to paper form, as

discussed above.

Glossary of Acronyms

APCD--Air Pollution Control Device

[[Page 17359]]

BDAT--Best Demonstrated Available Technology

BIFs--Boilers and Industrial Furnaces

BTF--Beyond-the-Floor

CAA--Clean Air Act

Cl2--Chlorine

CO--Carbon Monoxide

D/F--Dioxins/Furans

D/O/M--Design/Operation/Maintenance

ESP--Electrostatic Precipitator

EU--European Union

FF--Fabric Filter

HAP--Hazardous Air Pollutant

HC--Hydrocarbons

HCl--Hydrochloric acid

Hg--Mercury

HHE--Human Health and the Environment

HON--Hazardous Organic NESHAPs

HSWA--Hazardous and Solid Waste Amendments

HWC--Hazardous Waste Combustion/Combustor

ICR--Information Collection Request

LDR--Land Disposal Restrictions

LVM--Low-volatile Metals

LWAK--Lightweight Aggregate Kiln

MACT--Maximum Achievable Control Technology

MTEC--Maximum Theoretical Emission Concentration

NESHAPs--National Emission Standards for Hazardous Air Pollutants

PM--Particulate Matter

PICs--Products of Incomplete Combustion

RCRA--Resource Conservation and Recovery Act

RIA--Regulatory Impact Assessment

SVM--Semivolatile Metals

TCLP--Toxicity Characteristic Leaching Procedure

UTS--Universal Treatment Standards

Part One: Background

I. Overview

II. Relationship of Today's Proposal to EPA's Waste Minimization

National Plan

Part Two: Devices That Would Be Subject To The Proposed Emission

Standards

I. Hazardous Waste Incinerators

A. Overview

B. Summary of Major Incinerator Designs

C. Number of Incinerator Facilities

D. Typical Emission Control Devices For Incinerators

II. Hazardous Waste-Burning Cement Kilns

A. Overview of Cement Manufacturing

B. Summary of Major Design and Operating Features of Cement

Kilns

C. Number of Facilities

D. Emissions Control Devices

III. Hazardous Waste-Burning Lightweight Aggregate Kilns

A. Overview of Lightweight Aggregate Kilns (LWAKs)

B. Major Design and Operating Features

C. Number of Facilities

D. Air Pollution Control Devices

Part Three: Decision Process for Setting National Emission Standards

for Hazardous Air Pollutants (NESHAPs)

I. Source of Authority for NESHAP Development

II. Procedures and Criteria for Development of NESHAPs

III. List of Categories of Major and Area Sources

A. Clean Air Act Requirements

B. Hazardous Waste Incinerators

C. Cement Kilns

D. Lightweight Aggregate Kilns

IV. Proposal to Subject Area Sources to the NESHAPs under

Authority of Section 112(c)(6)

V. Selection of MACT Floor for Existing Sources

A. Proposed Approach: Combined Technology-Statistical Approach

B. Another Approach Considered But Not Used

C. Identifying Floors as Proposed in CETRED

D. Establishing Floors One HAP or HAP Group at a Time

VI. Selection of Beyond-the-Floor Levels for Existing Sources

VII. Selection of MACT for New Sources

VIII. RCRA Decision Process

A. RCRA and CAA Mandates to Protect Human Health and the

Environment

B. Evaluation of Protectiveness

C. Use of Site-Specific Risk Assessments under RCRA

Part Four: Rationale for Selecting the Proposed Standards

I. Selection of Source Categories and Pollutants

A. Selection of Sources and Source Categories

B. Selection of Pollutants

C. Applicability of the Standards Under Special Circumstances

II. Selection of Format for the Proposed Standards

A. Format of the Standard

B. Averaging Periods

III. Incinerators: Basis and Level for the Proposed NESHAP

Standards for New and Existing Sources

A. Summary of MACT Standards for Existing Incinerators

B. Summary of MACT Standards For New Incinerators

C. Evaluation of Protectiveness

IV. Cement Kilns: Basis and Level for the Proposed NESHAP

Standards for New and Existing Sources

A. Summary of Standards for Existing Cement Kilns

B. MACT for New Hazardous Waste-Burning Cement Kilns

C. Evaluation of Protectiveness

V. Lightweight Aggregate Kilns: Basis and Level for the Proposed

NESHAP Standards for New and Existing Sources

A. Summary of MACT Standards for Existing LWAKs

B. MACT for New Sources

C. Evaluation of Protectiveness

VI. Achievability of the Floor Levels

VII. Comparison of the Proposed Emission Standards With Emission

Standards for Other Combustion Devices

VIII. Alternative Floor (12 Percent) Option Results

A. Summary of Results of 12 Percent Analysis

B. Summary of MACT Floor Cost Impacts and Emissions Reductions

C. Alternative Floor Option: Percent Reduction Refinement

IX. Additional Data for Comment

Part Five: Implementation

I. Selection of Compliance Dates

A. Existing Sources

B. New Sources

C. One year extensions for Pollution Prevention/Waste

Minimization

II. Selection of Proposed Monitoring Requirements

A. Monitoring Hierarchy

B. Use of Comprehensive Performance Test Data to Establish

Operating Limits

C. Compliance Monitoring Requirements

D. Combustion Fugitive Emissions

E. Automatic Waste Feed Cutoff (AWFCO) Requirements and

Emergency Safety Vent (ESV) Openings

F. Quality Assurance for Continuous Monitoring Systems

III. MACT Performance Testing and Related Issues

A. MACT Performance Testing

B. RCRA Trial Burns

C. Waiver of MACT Performance Testing for HWCs Feeding De

Minimis Levels of Metals or Chlorine

D. Relative Accuracy Tests for CEMS

IV. Selection of Manual Stack Sampling Methods

V. Notification, Recordkeeping, Reporting, and Operator

Certification Requirements

A. Notification Requirements

B. Reporting Requirements

C. Recordkeeping Requirements

VI. Permit Requirements

A. Coordination of RCRA and CAA Permitting Processes

B. Permit Application Requirements

C. Clarifications on Definitions and Permit Process Issues

D. Pollution Prevention/Waste Minimization Options

E. Permit Modifications Necessary to Come Into Compliance With

MACT Standards

VII. State Authorization

A. Authority for Today's Rule

B. Program Delegation Under the Clean Air Act

C. RCRA State Authorization

VIII. Definitions

A. Definitions Proposed in Sec. 63.1201

B. Conforming Definitions Proposed in Secs. 260.10 and 270.2

C. Clarification of RCRA Definition of Industrial Furnace

Part Six: Miscellaneous Provisions and Issues

I. Comparable Fuel Exclusion

A. EPA's Approach to Establishing Benchmark Constituent Levels

B. Sampling, Analysis, and Statistical Protocols Used

C. Options for the Benchmark Approach

D. Comparable Fuel Specification

E. Exclusion of Synthesis Gas Fuel

F. Implementation of the Exclusion

G. Transportation and Storage

H. Speculative Accumulation

I. Regulatory Impacts

II. Miscellaneous Revisions to the Existing Rules

A. Revisions to the Small Quantity Burner Exemption under the

BIF Rule

B. The Waiver of the PM Standard under the Low Risk Waste

Exemption of the

[[Page 17360]]

BIF Rule Would Not Be Applicable to HWCs

C. The ``Low Risk Waste'' Exemption from the Emission Standards

Provided by the Existing Incinerator Standards Would Be Superseded

by the MACT Rules

D. Bevill Residues

E. Applicability of Regulations to Cyanide Wastes

F. Shakedown Concerns

G. Extensions of Time Under Certification of Compliance

H. Technical Amendments to the BIF Rule

I. Clarification of Regulatory Status of Fuel Blenders

J. Change in Reporting Requirements for Secondary Lead Smelters

Subject to MACT

Part Seven: Analytical and Regulatory Requirements

I. Executive Order 12866

II. Regulatory Options

III. Assessment of Potential Costs and Benefits

A. Introduction

B. Analysis and Findings

C. Total Incremental Cost per Incremental Reduction in HAP

Emissions

D. Human Health Benefits

E. Other Benefits

IV. Other Regulatory Issues

A. Environmental Justice

B. Unfunded Federal Mandates

C. Regulatory Takings

D. Incentives for Waste Minimization and Pollution Prevention

V. Regulatory Flexibility Analysis

VI. Paperwork Reduction Act

VII. Request for Data

Appendix--Comparable Fuel Constituent and Physical Specifications

PART 60--STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES

PART 63--NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS

FOR SOURCE CATEGORIES

PART 260--HAZARDOUS WASTE MANAGEMENT SYSTEM: GENERAL

PART 261--IDENTIFICATION AND LISTING OF HAZARDOUS WASTE

PART 264--STANDARDS FOR OWNERS AND OPERATORS OF HAZARDOUS WASTE

TREATMENT, STORAGE, AND DISPOSAL FACILITIES

PART 265--INTERIM STATUS STANDARDS FOR OWNERS AND OPERATORS OF

HAZARDOUS WASTE TREATMENT, STORAGE, AND DISPOSAL FACILITIES

PART 266--STANDARDS FOR THE MANAGEMENT OF SPECIFIC HAZARDOUS WASTES

AND SPECIFIC TYPES OF HAZARDOUS WASTE MANAGEMENT FACILITIES

PART 270--EPA ADMINISTERED PERMIT PROGRAMS: THE HAZARDOUS WASTE

PERMIT PROGRAM

PART 271--REQUIREMENTS FOR AUTHORIZATION OF STATE HAZARDOUS WASTE

PROGRAMS

PART ONE: BACKGROUND

I. Overview

The U.S. Environmental Protection Agency (EPA) is proposing to

revise standards for hazardous waste incinerators and hazardous waste-

burning cement kilns and lightweight aggregate kilns (LWAKs) under

joint authority of the Clean Air Act, as amended, (CAA) and the

Resource Conservation and Recovery Act, as amended (RCRA). The emission

standards in today's proposal have been developed under the CAA

provisions concerning the maximum level of achievable control over

hazardous air pollutants (HAPs), taking into consideration the cost of

achieving the emission reduction, any non-air quality health and

environmental impacts, and energy requirements. These maximum

achievable control technology (MACT) standards, also referred to as

National Emission Standards for Hazardous Air Pollutants (NESHAPs), are

proposed in today's rule for the following HAPs: dioxins/furans,

mercury, two semivolatile metals (lead and cadmium), four low

volatility metals (antimony, arsenic, beryllium, and chromium),

particulate matter, and hydrochloric acid/chlorine gas. Other toxic

organic emissions are addressed by standards for carbon monoxide (CO)

and hydrocarbons (HC).

This action is being taken for several reasons. First, this

proposal is consistent with the terms of the 1993 settlement agreement

between the Agency and a number of groups who challenged EPA's final

RCRA rule entitled ``Burning of Hazardous Waste in Boilers and

Industrial Furnaces'' (56 FR 7134, Feb. 21, 1991). These groups include

the Natural Resources Defense Council, Sierra Club, Inc., Hazardous

Waste Treatment Council (now the Environmental Technology Council),

National Solid Waste Management Association, and a number of local

citizens' groups. Under this settlement agreement, the Agency is to

propose this rulemaking by September-November, 1995, and finalize it by

December 1996.

Second, EPA has scheduled rulemakings to develop maximum achievable

control technology (MACT) standards for hazardous waste incinerators

and cement kilns. To minimize the burden on the Agency and the

regulated community, the Agency has combined its efforts under the CAA

and RCRA into one rulemaking to establish MACT standards, which also

would satisfy the RCRA settlement agreement obligations.

Third, the Agency's Hazardous Waste Minimization and Combustion

Strategy, first announced in May 1993, in addition to stressing waste

minimization, also made a commitment to upgrade the emission standards

for hazardous waste-burning facilities. The three categories of

facilities covered in this proposal burn over 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 are to be addressed in the next rulemaking

for which a proposal is to be issued by December 1998 or sooner.]

Finally, as relates to the development of revised standards under

concurrent Clean Air Act and RCRA authority, most of these hazardous

waste combustion facilities are major sources of HAP emissions. They

therefore must be regulated under section 112(d) of the Clean Air Act.

In addition, EPA noted, when promulgating the RCRA rules for boilers

and industrial furnaces in 1991 and in a proposal to revise the

incinerator rules, that existing standards did not fully consider the

possibility of exposure via indirect (non-inhalation) exposure

pathways. 56 FR at 7150, 7167, 7169-70 (Feb. 21, 1991); 54 FR at 43720-

21, 43723, 43757 (Oct. 26, 1989). The Agency reiterated these concerns

in the Combustion Strategy announced in 1993 as one of the major

factors leading to its decision to undertake revisions to the standards

for hazardous waste combustors. As also noted in the Combustion

Strategy and elsewhere, site-specific RCRA omnibus authority, whereby

permit writers can impose additional conditions as are necessary to

protect human health and the environment, can be used to buttress the

existing regulations. See, e.g., 56 FR 7145, at n.8. Nevertheless, this

process is expensive, time-consuming, and not always sufficiently

certain in result. The Agency thus indicated, in the Combustion

Strategy, that technology-based standards could provide a superior

means of control by providing certainty of operating performance.

Because of the joint authorities under which this rule is being

proposed, the proposal also contains an implementation scheme that is

intended to harmonize the RCRA and CAA programs to the maximum extent

permissible by law. In pursuing a common-sense approach towards this

objective, the proposal seeks to establish a framework that: (1)

Provides for combined (or at least coordinated) CAA and RCRA permitting

of these facilities; (2) allows maximum flexibility for regional,

state, and local agencies to determine which of their resources will be

used for permitting, compliance, and enforcement efforts; and (3)

integrates the monitoring, compliance testing, and recordkeeping

requirements of the CAA and RCRA so that facilities will be able

[[Page 17361]]

to avoid two potentially different regulatory compliance schemes.

In addition, this proposal addresses the variety of issues, to the

extent appropriate at this time, raised in several petitions filed with

the Agency. These petitions are from the Cement Kiln Recycling

Coalition (Jan. 18, 1994), the Hazardous Waste Treatment Council (May

18, 1994), and the Chemical Manufacturers Association (Oct. 14, 1994).

II. Relationship of Today's Proposal to EPA's Waste Minimization

National Plan

EPA believes that today's proposed rule will create significant

incentives for source reduction and recycling by waste generators that

would, in turn, help facilities achieve compliance with the MACT

standards. RCRA, as well as the Pollution Prevention Act of 1990 (PPA),

encourage pollution prevention at the source, and the Clean Air Act

mentions pollution prevention as a specific means of achieving MACT. In

Sec. 112(d)(2) of the CAA, Congress expressly defined MACT as the

``application of measures, processes, methods, systems, or techniques

including, but not limited to, measures which reduce the volume of, or

eliminate emissions of, such pollutants through process changes,

substitution of materials and other modifications.''

In addition, in the Hazardous and Solid Waste Amendments of 1984

(HSWA) to RCRA, Congress established a national policy for waste

minimization. Section 1003 of RCRA states that, whenever feasible, the

generation of hazardous waste is to be reduced or eliminated as

expeditiously as possible. Section 8002(r) requires EPA to explore the

desirability and feasibility of establishing regulations or other

incentives or disincentives for reducing or eliminating the generation

of hazardous waste. In 1990, the PPA reinforced these policies by

declaring it ``to be the national policy of the United States that

pollution should be prevented at the source whenever feasible'' and,

when not feasible, waste should be recycled, treated, or disposed of--

in that order of preference.

Although the Agency has devoted significant effort to evaluation

and promotion of waste minimization in the past 1, the Hazardous

Waste Minimization and Combustion Strategy, first announced in May

1993, recently provided a new impetus to this effort. The Strategy had

several components, among which was reducing the amount and toxicity of

hazardous waste generated in the United States. Other components of the

Strategy included strengthening controls on emissions from hazardous

waste combustion units; enhancing public participation in facility

permitting; establishing risk assessment policies with respect to

facility permitting; and continued emphasis on strong compliance and

enforcement.

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\1\ For example, EPA prepared a report to Congress,

``Minimization of Hazardous Wastes'' (October 1986), that summarized

existing waste minimization activities and evaluated options for

promoting waste minimization.

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EPA held a National Roundtable and four Regional Roundtables

throughout the nation in 1993-94 to facilitate a broad dialogue on the

spectrum of waste minimization and combustion issues. The major

messages from these Roundtables became the building blocks for EPA's

further efforts to promote source reduction and recycling and

specifically for EPA's Waste Minimization National Plan, released in

November 1994.

The Waste Minimization National Plan focuses on the goal of

reducing persistent, bioaccumulative, and toxic constituents in

hazardous waste nationally by 25 percent by the year 2000 and 50

percent by the year 2005. The central themes of the National Plan are:

(1) Developing a framework for setting national priorities for the

minimization of hazardous waste; (2) promoting multimedia environmental

benefits and preventing cross-media transfers; (3) demonstrating a

strong preference for source reduction by shifting attention to

hazardous waste generators to reduce generation at its source; (4)

defining and tracking progress in minimizing the generation of wastes;

and (5) involving citizens in waste minimization implementation

decisions. The Agency intends to continue its pursuit of hazardous

waste minimization under the National Plan and other Agency initiatives

in concert with the actions proposed in today's rule.

Of the 3.0 million tons of hazardous waste combusted in 1991,

approximately two-thirds of that amount were combusted at on-site

facilities (i.e., the same facilities at which the waste was

generated). Combustion at an on-site facility therefore presents a

situation in which the same facility owners and operators may have some

measure of control over generation of wastes at its source and its

ultimate disposition. Although close to 400 industries generated wastes

destined for combustion in 1991, much of the quantity was concentrated

in a few sectors. As a companion to this proposed rule, EPA is focusing

its waste minimization efforts on reducing the generation and

subsequent release to the environment of the most persistent,

bioaccumulative, and toxic constituents in hazardous wastes (i.e.,

metals, halogenated organics).

Analysis of waste minimization potential suggests that generators

currently burning wastes may have a number of options for eliminating

or reducing these wastes. We believe that roughly 15 percent of all

combusted wastes may be amenable to waste minimization. Three waste

generating processes appear to have the most potential in terms of

tonnage reduction: (1) Solvent and product recovery/distillation

procedures, primarily in the organic chemicals industry, (2) product

processing wastes, and (3) process waste removal and cleaning. In

addition, preliminary analyses of Toxics Release Inventory and

hazardous waste stream data indicate that over 3 million pounds of

hazardous metals are contained in waste streams being combusted. The

top 5 ranking metals (with respect to health risk considering

persistence, bioaccumulation, and toxicity) are mercury, cadmium, lead,

copper, and selenium. Additional analyses are underway to identify the

industry sectors and production processes that are chief sources of

these and other high priority hazardous constituents.2

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\2\ USEPA, Office of Solid Waste, ``Setting Priorities for

Hazardous Waste Minimization'', July 1994.

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In today's rule, EPA is soliciting comment on two options to

promote the use of pollution prevention/waste minimization measures as

methods for helping meet MACT standards. These options (regarding feed

stream analysis and permitting requirements) are described in Part

Five, Section VI, Subsection D of this preamble. EPA is also seeking

comment on a proposal to consider, on a case-by-case basis, extending

the compliance deadlines for this rule by one year if a facility can

show that extra time is needed to implement pollution prevention/waste

minimization measures in order for the facility to meet the MACT

standards and that implementation cannot be practically achieved within

the allotted three-year period after promulgation of this rule (see

Part V, Section 1, Subsection C).

PART TWO: DEVICES THAT WOULD BE SUBJECT TO THE PROPOSED EMISSION

STANDARDS

I. Hazardous Waste Incinerators

A. Overview

A hazardous waste incinerator is an enclosed, controlled flame

combustion

[[Page 17362]]

device, as defined in 40 CFR 260.10, and is used to treat primarily

organic and/or aqueous wastes. These devices may be in situ (fixed), or

consist of mobile units (such as those used for site remediation and

superfund clean-ups) or may consist of units burning spent or unusable

ammunition and/or chemical agents that meet the incinerator definition.

B. Summary of Major Incinerator Designs

The following is a brief description of the typical incinerator

designs used in the United States.3

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\3\ For a more detailed description of incineration technology,

see ``Combustion Emissions Technical Resource Document (CETRED)'',

USEPA EPA530-R-94-014, May 1994.

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1. Rotary Kilns

Rotary kiln systems typically contain two incineration chambers:

the rotary kiln and an afterburner. The kiln itself is a cylindrical

refractory-lined steel shell 10-20 feet in diameter, with a length-to-

diameter ratio of 2 to 10. The shell is supported by steel trundles

that ride on rollers, allowing the kiln to rotate around its horizontal

axis at a rate of 1-2 revolutions per minute. Wastes are fed directly

at one end of the kiln and heated by primary fuels. Waste continues to

heat and burn as it travels down the inclined kiln. Combustion air is

provided through ports on the face of the kiln. The kiln typically

operates at 50-200 percent excess air and temperatures of 1600-

1800 deg.F. Flue gas from the kiln is routed to an afterburner

operating at 2000-2500 deg.F and 100-200 percent excess air where

unburnt components of the kiln flue gas are more completely combusted.

Auxiliary fuel and/or pumpable liquid wastes are typically used to

maintain the afterburner temperature.

Some rotary kiln incinerators, known as slagging kilns, operate at

high enough temperatures such that residual materials leave the kiln in

a molten slag form. The molten residue is then water-quenched. Another

kiln, an ashing kiln, operates at a lower temperature, producing a

residual ash, which leaves as a dry material.

2. Liquid Injection Incinerators

A liquid injection incinerator system consists of an incineration

chamber, waste burner and auxiliary fuel system. The combustion chamber

is a cylindrical steel shell lined with refractory material and mounted

horizontally or vertically. Liquid wastes are atomized as they are fed

into the combustion chamber through waste burner nozzles. Typical

combustion chamber temperatures are 1300-3000 deg.F and residence times

are from 0.5 to 3 seconds.

3. Fluidized Bed Incinerators

A fluidized bed system is essentially a vertical cylinder

containing a bed of granular material at the bottom. Combustion air is

introduced at the bottom of the cylinder and flows up through the bed

material, suspending the granular particles. Waste and auxiliary fuels

are injected into the bed, where they mix with combustion air and burn

at temperatures from 840-1500 deg.F. Further reaction occurs in the

volume above the bed at temperatures up to 1800 deg.F.

4. Fixed Hearth Incinerators

Fixed hearth incinerators typically contain two furnace chambers: a

primary and a secondary chamber. Some designs have two or three step

hearths on which ash and waste are pushed with rams through the system.

A controlled flow `underfire' combustion air is introduced up through

the hearths. The primary chamber operates in ``starved air'' mode and

the temperatures are around 1000 deg.F. The unburnt hydrocarbons reach

the secondary chamber where 140-200 percent excess air is supplied and

temperatures of 1400-2000 deg.F are achieved for more complete

combustion.

C. Number of Incinerator Facilities

Currently, 162 permitted or interim status incinerator facilities,

having 190 units, are in operation in the U.S. Another 26 facilities

are proposed 4 (i.e., new facilities under construction or

permitting). Of the above 162 facilities, 21 facilities are commercial

facilities that burn about 700,000 tons of hazardous waste annually.

The remaining 141 are on-site or captive facilities and burn about

800,000 tons of waste annually.

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\4\ USEPA ``List of hazardous waste incinerators,'' November

1994.

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D. Typical Emission Control Devices for Incinerators

Incinerators are equipped with a wide variety of air pollution

control devices (APCDs), which range from no control (for devices

burning low ash and low chlorine wastes) to sophisticated state-of-the-

art units providing control for several pollutants. Hot flue gases from

the incinerators are cooled and cleaned of the air pollutants before

they exit the stack. Cooling is mostly done by water quenching, wherein

atomized water is sprayed directly into the hot gases. The cooled gases

are passed through various pollution control devices to control PM,

metals and organic emissions to desired or required levels. Most

incinerators use wet APCDs to scrub acid emissions (3 facilities use

dry scrubbers). Typical APCDs used include packed towers, spray dryers,

or dry scrubbers for acid gas (e.g., HCl, Cl2) control, and

venturi-scrubbers, wet or dry electrostatic precipitators (ESPs) or

fabric filters for particulate control.

Activated carbon injection for controlling dioxin and mercury is

being used at only one incinerator. Newer APC technologies (such as

catalytic oxidizers and dioxin/furan inhibitors) have recently emerged,

but have not been used on any full scale facilities in the U.S. For

detailed description of APCDs, see Appendix A of ``Combustion Emissions

Technical Resource Document (CETRED),'' US EPA Document #EPA530-R-94-

014, May 1994.

II. Hazardous Waste-Burning Cement Kilns

A. Overview of Cement Manufacturing

Cement refers to the commodities that are produced by heating

mixtures of limestone and other minerals or additives at high

temperature in a rotary kiln, followed by cooling, grinding, and finish

mixing. This is the manner in which the vast majority of commercially-

important cementitious materials are produced in the United States.

Cements are used to chemically bind different materials together. The

most commonly produced cement type is ``Portland'' cement, though other

standard cement types are also produced on a limited basis (e.g.,

sulfate-resisting, high-early-strength, masonry, waterproofed).

Portland cement is a hydraulic cement, meaning that it sets and hardens

by chemical interaction with water. When combined with sand, gravel,

water, and other materials, Portland cement forms concrete, one of the

most widely used building and construction materials in the world.

Cement produced and sold in the U.S. must meet specifications

established by the American Society for Testing and Materials (ASTM).

Each type requires specific additives or changes in the proportions of

the raw material mix to make products for specific applications.

B. Summary of Major Design and Operating Features of Cement Kilns

Cement kilns are horizontally inclined rotating cylinders,

refractory-brick lined, and internally-fired, that calcine a blend of

raw materials

[[Page 17363]]

containing calcium (typically limestone), silica and alumina (typically

clay, shale, slate, and/or sand), and iron (typically steel mill scale

or iron ore) to produce Portland cement. Generally, there is a wet

process and a dry process for producing cement. In the wet process, the

limestone and shale are ground up, wetted and fed into the kiln as a

slurry. In the dry process, raw materials are ground dry and fed into

the kiln dry. Wet process kilns are typically longer than dry process

kilns in order to facilitate water evaporation from the slurried raw

material. Wet kilns can be more than 450 feet in length. Dry kilns are

more thermally efficient and frequently use preheaters or precalciners

to begin the calcining process (i.e., the essential function of driving

CO2 from raw materials) before the raw materials are fed into the

kiln.

Combustion gases and raw materials move in a counterflow direction,

with respect to each other, inside a cement kiln. The kiln is inclined,

and raw materials are fed into the upper end (i.e., the ``cold'' end)

while fuels are normally fired into the lower end (i.e., the ``hot''

end). Combustion gases move up the kiln counter to the flow of raw

materials. The raw materials get progressively hotter as they travel

down the length of the kiln. The raw materials eventually begin to

soften and fuse at temperatures between 2,250 and 2,700 deg.F to form

the clinker product. Clinker is then cooled, ground, and mixed with

other materials, such as gypsum, to form cement.

Combustion gases leaving the kiln typically contain from 6 to 30

percent of the free solids as dust, which are often recycled to the

kiln feed system, though the extent of recycling varies greatly among

cement kilns.

Dry kilns with a preheater (PH) or precalciner (PC) often use a by-

pass duct to remove from 5 to 30 percent of the kiln off-gases from the

main duct. The by-pass gas is passed through a separate air pollution

control system to remove particulate matter. Collected by-pass dust is

not reintroduced into the kiln system to avoid a build-up of metal

salts that can affect product quality.

Some cement kilns burn hazardous waste-derived fuels to replace

from 25 to 100 percent of normal fossil fuels (e.g., coal). Most kilns

burn liquid waste fuels but several also burn bulk solids and small

(e.g., six gallon) containers of 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. EPA has also found that

hazardous waste-fired precalciners can still be considered part of the

cement kiln and, thus, would be part of an industrial furnace (per the

definition in 40 CFR 260.10). See 56 FR at 7184-85 (February 21, 1991).

This finding is codified at Sec. 266.103(a)(5)(I)(c). This is the only

time (and the only rulemaking) in which the Agency found that a device

not enumerated in the list of industrial furnaces in Sec. 260.10 can be

considered part of the industrial furnace when it burns hazardous

wastes separate from those burned in the main combustion device.

C. Number of Facilities

The Agency has emissions data from 26 facilities representing 49

cement kilns in the U.S. It should be noted that some facilities no

longer burn or process hazardous waste since they were required to

certify compliance with the BIF regulations in August 1992.

Of the hazardous waste-burning kilns for which we have emissions

data, 14 facilities use a wet process, 5 facilities use a dry process,

and the remaining 7 facilities employ either preheaters or preheater/

precalciners in the cement manufacturing process.

D. Emissions Control Devices

All hazardous waste-burning cement kilns either use fabric filters

(baghouses) or electrostatic precipitators (ESPs) as air pollution

control devices. ESPs have traditionally been employed in the cement

industry and are currently used at 17 of the facilities. Nine

facilities use fabric filters. A detailed description of these and

other air pollution control devices is contained in the technical

support document. 5

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\5\ USEPA, ``Draft Technical Support Document for HWC MACT

Standards, Volume I: Description of Source Categories'', February

1996.

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III. Hazardous Waste-Burning Lightweight Aggregate Kilns

A. Overview of Lightweight Aggregate Kilns (LWAKs)

The term lightweight aggregate refers to a wide variety of raw

materials (such as clay, shale, or slate) which 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.

B. Major Design and Operating Features

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 at an angle of about 5 degrees to the horizontal. The

length of the kiln depends in part upon the composition of the raw

material to be processed but is usually 30 to 60 meters. The prepared

raw material is fed into the kiln at the higher end, while firing takes

place at the lower end. The dry raw material fed into the kiln is

initially preheated by hot combustion gases. Once the material is

preheated, it passes into a second furnace zone where it melts to a

semiplastic state and begins to generate gases which serve as the

bloating or expanding agent. In this zone, specific compounds begin to

decompose and form gases such as SO2, CO2, SO3, and

O2 that eventually trigger the desired bloating action within the

material. As temperatures reach their maximum (approximately

2100 deg.F), 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.

Maximum temperature in the rotary kiln varies from 2050 deg.F to 2300

deg.F, depending on the type of raw material being processed and its

moisture content. Exit temperatures may range from 300 deg.F to 1200

deg.F, again depending on the raw material and on the kiln's internal

design. Approximately 80 to 100 percent excess air is forced into the

kiln to aid in expanding the raw material.

C. Number of Facilities

EPA has identified 36 lightweight aggregate kiln locations in the

United States. Of these, EPA has identified seven facilities that are

currently burning hazardous waste in a total of 15 kilns.

D. Air Pollution Control Devices

Lightweight aggregate kilns use one or a combination of air

pollution control devices, including fabric filters, venturi scrubbers,

spray dryers, cyclones and wet scrubbers. All of the facilities utilize

fabric filters as the main type of emissions control, although one

facility uses a spray dryer, venturi scrubber and

[[Page 17364]]

wet scrubber in addition to a fabric filter. For detailed descriptions

of these and other air pollution control devices, please see Appendix A

of the draft EPA document Combustion Emissions Technical Resource

Document (CETRED). 6

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\6\ USEPA, ``Draft Combustion Emission Technical Resource

Document (CETRED)'', EPA 530-R-94-014, May 1994.

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PART THREE: DECISION PROCESS FOR SETTING NATIONAL EMISSION STANDARDS

FOR HAZARDOUS AIR POLLUTANTS (NESHAPs)

I. Source of Authority for NESHAP Development

The 1990 Amendments to the Clean Air Act significantly revised the

requirements for controlling emissions of hazardous air pollutants. EPA

is now required to develop a list 7 of categories of major and

area sources 8 of the hazardous air pollutants (HAPs) enumerated

in section 112 and to develop technology-based performance standards

for such sources over specified time periods. See Clean Air Act (the

Act or CAA) Secs. 112(c) and 112(d). Section 112 of the Act replaces

the previous system of pollutant-by-pollutant health-based regulation

that proved ineffective at controlling the high volumes,

concentrations, and threats to human health and the environment posed

by HAPs in air emissions. See generally S. Rep. No. 228, 101st Cong.

1st Sess. 128-32 (1990).

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\7\ The Agency published an initial list of categories of major

and area sources of HAPs on July 16, 1992. See 57 FR 31576.

\8\ See Part Three, Section III of today's proposal for a

discussion of major and area sources. Generally, a major source is a

stationary source that emits, or has the potential to emit

considering controls, 10 tons per year of a HAP or 25 tons per year

of a combination of HAPs. CAA Sec. 112(a)(1). An area source is

generally a stationary source that is not a major source. Id.

Sec. 112(a)(2).

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Section 112(f) also requires the Agency to report to Congress by

the end of 1996 on estimated risk remaining after imposition of

technology-based standards and to make recommendations as to

legislation to address such risk. CAA Sec. 112(f)(1). If Congress does

not act on the recommendation, then EPA must address any significant

remaining residual risks posed by sources subject to the section 112(d)

technology-based standards within 8 years after promulgation of these

standards. See Sec. 112(f)(2). The Agency is required to impose

additional controls if such controls are needed to protect public

health with an ample margin of safety, or to prevent adverse

environmental effects. Id. 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 the Agency must promulgate additional standards.

See Sec. 112(f)(2)(A).

II. Procedures and Criteria for Development of NESHAPs

NESHAPs are developed in order to control HAP emissions from both

new and existing sources according to the statutory directives set out

in Sec. 112. The statute requires a NESHAP to reflect the maximum

degree of reduction of HAP emissions that is achievable taking into

consideration the cost of achieving the emission reduction, any non-air

quality health and environmental impacts, and energy requirements.

Sec. 112(d)(2). In regulatory parlance, these are often referred to as

maximum achievable control technology (or MACT) standards.

The Clean Air Act establishes minimum levels, usually referred to

as MACT floors, for the emission standards. Section 112(d)(3) requires

that MACT floors be determined as follows: for existing sources in a

category or sub-category 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 sub-category with less than 30

sources, then 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 * * *''. See Sec. 112(d)(3) (A) and (B).

EPA must, of course, consider in all cases whether to develop

standards that are more stringent than the floor (``beyond the floor''

standards). To do so, however, EPA must consider the enumerated

statutory criteria such as cost, energy, and non-air environmental

implications.

Emission reductions may be accomplished through 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 Sec. 112(d)(2).

Application of techniques (1) and (2) of the previous paragraph are

consistent with the definitions of pollution prevention under the

Pollution Prevention Act and the definition of waste minimization under

RCRA/HSWA. These terms have particular applicability in the discussion

of pollution prevention/waste minimization options presented in the

permitting and compliance sections of today's proposal.

To develop a NESHAP, the EPA compiles available information and in

some cases collects additional information about the industry,

including information on emission source quantities, types and

characteristics of HAPs, pollution control technologies, data from HAP

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. EPA uses this information in analyzing and developing

possible regulatory approaches. EPA, of course, does not always have or

collect the same amount of information per industry, but rather bases

the standard on information practically available.

Although NESHAPs are normally structured in terms of numerical

emission limits--the preferred means of establishing standards--

alternative approaches are sometimes necessary and appropriate. In some

cases, for example, physically measuring emissions from a source may be

impossible, or at least impractical, because of technological and

economic limitations. Section 112(h) authorizes the Administrator to

promulgate a design, equipment, work practice, or operational standard,

or a combination thereof, in those cases where it is not feasible to

prescribe or enforce an emissions standard.

EPA is required to develop emission standards based on performance

of maximum achievable control technology for categories or sub-

categories of major sources of hazardous air pollutants.

Sec. 112(d)(1). As explained more fully in the following section, a

major source emits, or has the potential to emit considering controls,

either 10 tons per year of any hazardous air pollutant or 25 tons or

more of any combination of those pollutants. Sec. 112(a)(1). EPA also

can establish lower thresholds where appropriate. Id. EPA

[[Page 17365]]

may in addition require sources emitting particularly dangerous

hazardous air pollutants (such as particular chlorinated dioxins and

furans) to be regulated under the MACT standards for major sources.

Sec. 112(c)(6).

Area sources are any source which is not a major source. Such

sources must be regulated by technology-based standards if they are

listed, pursuant to Sec. 112(c)(3), based on the Agency's finding 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, the Agency has a further choice

as to require technology-based standards based on MACT or on generally

achievable control technology (GACT). Sec. 112(d)(5).

In this rulemaking, EPA is proceeding pursuant to Sec. 112(c)(6)

(i.e., imposing MACT controls on area sources), because these hazardous

waste combustion units emit a number of the HAPs singled out in that

provision, including the enumerated dioxins and furans, mercury, and

polycyclic organic matter. (See discussion below.)

III. List of Categories of Major and Area Sources

A. Clean Air Act Requirements

As just discussed, Section 112 of the CAA requires that the EPA

promulgate regulations requiring the control of hazardous air

pollutants emissions associated with categories or subcategories of

major and area sources. These source categories and subcategories are

to be listed pursuant to Sec. 112(c)(1). EPA published an initial list

of 174 categories of such major and area sources in the Federal

Register on July 16, 1992 (57 FR 31576).

B. Hazardous Waste Incinerators

``Hazardous waste incinerators'' is one of the 174 categories of

sources listed. The category consists of commercial and on-site

(including captive) incinerating facilities. The listing was based on

the Administrator's determination that at least one hazardous waste

incinerator may reasonably be anticipated to emit several of the 189

listed HAPs in quantities sufficient to designate them as major

sources. EPA used two emission rate values to evaluate the available

hazardous waste incinerator emissions data: the maximum emission rate

measured during the compliance test, and the average emission rate. The

data indicate that approximately 30 percent of the facilities meet the

major source criteria when using the maximum emissions rate value. When

using the average emissions rate value approximately 15 percent of

facilities meet the major source criteria.9 Those facilities

meeting the major source criteria do so for HCl and Cl2 emissions,

and one facility is also a major source for antimony emissions.

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\9\ For further details see USEPA, ``Draft Technical Support

Document for HWC MACT Standards, Volume I: Description of Source

Categories'', February 1996.

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

It should be noted that a major source and boundary for considering

whether a source is a major includes all potential emission points of

HAPs at that contiguous facility, including storage tanks, equipment

leaks, and other hazardous waste handling facilities. The above

calculations for incinerators on whether a source is a major source

under Sec. 112 do not reflect these potential emission points.

Notwithstanding the fact that most HW incinerators are not likely

to meet the HAP emission thresholds for major sources, the Agency is

proposing to subject all HWCs to regulation under MACT as major

sources, under the authority of Sec. 112(c)(6). See Section IV below.

C. Cement Kilns

Another of the 174 categories of major and area sources of HAPs is

Portland Cement Manufacturing (cement kilns). In evaluating the

emissions data for the hazardous waste-burning cement kilns, 85 percent

of the cement kilns were determined to meet the major source criteria

when using the maximum emission rate value. Using the average emission

rate value, just over 80 percent of the hazardous waste-burning cement

kilns meet the major source criteria.10 Those facilities meeting

the major source criteria do so for HCl and Cl2 emissions, and one

facility is also a major source for organic emissions. It should be

noted that the calculation on whether a cement kiln is a major source

did not include potential emission points of HAPs at that contiguous

facility.

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

\10\ Ibid.

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

Notwithstanding the fact that some hazardous waste-burning cement

kilns may not meet the definition of major source, the Agency is

proposing to subject all HWCs to regulation under MACT, as major

sources, under the authority of Sec. 112(c)(6). See Section IV below.

D. Lightweight Aggregate Kilns

Section 112(c)(5) authorizes EPA to amend the source category list

at any time to add categories or subcategories that meet the listing

criteria. EPA is proposing to exercise that authority by adding HW-

burning lightweight aggregate kilns to the list of source categories.

In analyzing the emissions data, EPA found that all hazardous

waste-burning LWAKs met the major source criteria for two HAPs, HCl and

Cl2, using either the average or maximum emission rate

value.11 It should be noted that the calculation on whether a LWAK

is a major source did not include potential emission points of HAPs at

that contiguous facility. EPA is therefore proposing today the addition

of hazardous waste-burning LWAKs as a source category in accordance

with section 112(c)(5) of the Act. In addition, as discussed below,

even if a LWAK would otherwise be an area source, EPA is proposing to

subject it to the same NESHAPS as major LWAK sources.

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\11\ Ibid.

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IV. Proposal To Subject Area Sources to the NESHAPs Under Authority of

Section 112(c)(6)

EPA is today proposing to subject all hazardous waste incinerators,

hazardous waste-burning cement kilns, and hazardous waste-burning

lightweight aggregate kilns (i.e., both area and major sources) to

regulation as major sources pursuant to CAA Sec. 112(c)(6). That

provision states that, by November 15, 2000, EPA must list and

promulgate Sec. 112 (d)(2) or (d)(4) standards (i.e., standards

reflecting MACT) for categories (and subcategories) of sources emitting

specific pollutants, including the following HAPs emitted by HWCs:

polycyclic organic matter, mercury, 2,3,7,8-tetrachlorodibenzofuran,

and 2,3,7,8-tetrachlorodibenzo-p-dioxin. (Although the Agency has not

prepared the list, it is the Agency's intention to include hazardous

waste combustors.) EPA must assure that sources accounting for not less

than 90 percent of the aggregate emissions of each enumerated pollutant

are subject to MACT standards.

The chief practical effect of invoking Sec. 112(c)(6) for this

rulemaking is to subject area sources that emit 112(c)(6) pollutants to

the same MACT standards as major sources, rather than to the

potentially less stringent 112(d)(5) or ``GACT'' (``generally

achievable control technology'') standards.12 Today's proposal

constitutes one of many EPA actions to assure that sources accounting

for at least 90 percent of

[[Page 17366]]

emissions of Sec. 112(c)(6) pollutants are subject to MACT standards.

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\12\ EPA also solicits comment on an alternative reading of

Sec. 112(c)(6), whereby the provision would require MACT control for

the enumerated pollutants but not necessarily for other HAPs emitted

by the source, which HAPs are not enumerated in Sec. 112(c)(6).

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

Although Sec. 112(c)(6) requires the Agency to regulate source

categories that emit not less than 90 percent of the aggregate

emissions of the high priority HAPs, the Agency will use its discretion

to avoid regulating area source categories with trivial aggregate

emissions of specific Sec. 112(c)(6) HAPs. However, as an example of

the emissions that are possible from the HWC source categories, it is

estimated that HWCs presently emit in aggregate 11.1 tons of mercury

per year. Of this quantity, 4.6 tons per year can be attributed to

hazardous waste incinerators and 6.5 tons per year to hazardous waste-

burning cement and lightweight aggregate kilns. Also, it is estimated

that HWCs presently emit in aggregate 122 pounds of dioxins/furans (or

2.15 pounds TEQ) per year. Of this quantity, 9 pounds (or 0.2 pounds

TEQ) per year can be attributed to hazardous waste incinerators and 113

pounds (or 1.95 pounds TEQ) per year to hazardous waste-burning cement

and lightweight aggregate kilns. To show an example of how today's

proposal constitutes an action to assure that sources accounting for at

least 90 percent of emissions of Sec. 112(c)(6) pollutants are subject

to MACT standards, the document Estimating Exposure to Dioxin-Like

Compounds, Vol. II: Properties, Sources, Occurrence and Background

Exposures (EPA, 1994) estimates (on p. 29) that national emissions of

dioxins and furans (D/F) total 4.18 pounds TEQ per year. Based on this

estimation, HWCs account for 51 percent of the annual national

emissions of D/F. (Consequently, EPA expects these source categories to

be included in the list of sources to be controlled to achieve the

requisite 90 percent reduction in aggregate emissions of section

112(c)(6) pollutants.)

Congress singled out the HAPs enumerated in Sec. 112(c)(6) as being

of ``specific concern'' not just because of their toxicity but because

of their propensity to cause substantial harm to human health and the

environment via indirect exposure pathways (i.e., from the air through

other media, such as water, soil, food uptake, etc.). S. Rep. No. 228,

101st Cong. 1st Sess., pp. 155, 166. These pollutants have exhibited

special potential to bioaccumulate, causing pervasive environmental

harm in biota (and, ultimately, human health risks). Id. Indeed, as

discussed later, the data appear to show that much of the human health

risk from emissions of these HAPs from HWCs comes from these indirect

exposure pathways. Id. at p. 166. Congress' express intention was to

assure that sources emitting significant quantities of Sec. 112(c)(6)

pollutants received a stricter level of control. Id.

V. Selection of MACT Floor for Existing Sources

The starting point in developing MACT standards is determining

floor levels, i.e. the minimum (least stringent) level at which the

standard can be set.

All of the hazardous waste combustion units subject to this

proposed rule are already subject to RCRA regulation under 40 CFR Parts

264, 265, or 266. As a result, the Agency has a substantial amount of

data reflecting performance of these devices. These data consist

largely of trial burn data for hazardous waste incinerators and data

from certifications of compliance for hazardous waste-burning cement

kilns and LWAKs obtained pursuant to 266.103(c). These data consist of

at least three runs for any given test condition.

In using these ``short term'' test data to establish a MACT floor,

the Agency has developed an approach that ensures the standards are

achievable, i.e. reflect the performance over time of properly designed

and operated air pollution control devices (or operating practices)

taking into account intrinsic operating variability.

In addition, the Agency notes that the floor calculations were

performed on individual HAPs or, in the case of metals, in two groups

of HAPs that behave similarly (i.e., separate floor levels for each

hazardous air pollutant or group of metal pollutants). However, for

HAPs that are controlled by the same type of air pollution control

device (APCD), EPA has ensured that all HAP floors are simultaneously

achievable by identifying the APCD and APCD treatment train that can be

used to meet all floor levels. The ultimate floor levels thus derived

can be achieved using the identified technology. This approach is

consistent with methods used by EPA in other rules to calculate MACT

requirements where the HAP species present must be treated by a

treatment train. See, e.g., MACT Rules for Secondary Lead Smelters. 60

FR 32589 (June 23, 1995).

The Agency is not, however, treating hazardous waste-burning

incinerators, cement kilns, and LWAKs as a single source category for

purposes of developing the MACT floor (or for any other purpose). The

Agency's initial view is that there are technical differences in

performance for particular HAPs among the three source categories, and

therefore that the technology-based floors must reflect these operating

differences.

A. Proposed Approach: Combined Technology-Statistical Approach

This analysis first identified the best performing control

technology(ies) for each source category (i.e., incinerators, cement

kilns, and lightweight aggregate kilns) and each HAP of concern by

arraying from lowest to highest all the particular HAP emissions data

from existing units within the source category by test condition

averages. These technologies comprise MACT floor. In cases where a

source had emissions data for a HAP from several different test

conditions of a compliance test, the Agency arrayed each test condition

separately. The Agency then identified the emission control technology

or technologies (and normalized feedrate of metals and chlorine in

hazardous waste) used by sources with emissions levels at or below the

level emitted by the median of the best performing 12 percent of

sources. The sources are termed ``the best performing 6 percent'' of

the sources, or ``MACT pool'', and the controls they use comprise MACT

floor.

The next step was to identify an emissions level that MACT floor

control could achieve. Thus, emissions data from all sources (in the

source category) that use MACT floor control were arrayed in ascending

order by average emissions. [This is referred to as the ``expanded MACT

pool'' or ``expanded universe''.] The Agency evaluated the control

technologies used by the additional sources within the ``expanded

universe'' as available data allowed to ensure that they were in fact

equivalent in design to MACT floor. The Agency then selected the test

condition in the expanded MACT pool with the highest mean emissions to

identify the emission level that MACT floor could achieve.

Because the emissions database was comprised of ``short-term'' test

data, the Agency used a statistical approach to identify an emission

level that MACT floor could achieve routinely. The Agency then

identified the test condition in the expanded MACT pool with the

highest mean emissions to statistically calculate a ``design level''

and a floor standard. The design level was calculated as the log mean

of the emissions for the test condition. The standard was calculated as

a level that a source (that is designed and operated to routinely meet

the design level) could meet 99 percent of the time if it has the

average within-test-condition emissions variability of the expanded

MACT pool. Although the Agency evaluated 90th and 95th percentile

limits, the 99th

[[Page 17367]]

percentile limit was chosen to: (1) More accurately reflect the

variability that could be present in emissions data, and (2)

appropriately characterize this variability in light of the consequence

of failing to achieve the emissions standards. Additional information

on how MACT floor levels were identified is provided in the ``Draft

Technical Support Document for HWC MACT Standards, Volume III:

Selection of Proposed MACT Standards and Technologies''.

In accounting for operating variability, the Agency solicits

comment on whether it may have overcompensated so that the identified

floor levels are unduly lenient. The test data on which the proposal is

based to some extent reflect worst-case performance conditions because

RCRA sources try to obtain maximum operating flexibility by conducting

test burns at extreme operating conditions. For example, many sources

spike wastes with excess metals and chlorine during compliance testing.

In addition, sources operate their emissions control devices under low

efficiency conditions (while still meeting emission standards) to

ensure lenient operating limits. It thus may be that the Agency's

emissions database is so inflated that separate consideration of

emissions variability may not be warranted. A floor level could be the

highest mean of the test conditions in the expanded MACT pool.

The Agency emphasizes that it would be preferable, for purposes of

setting these MACT standards, to have operational and emissions data

that better reflect long-term, more routine day-to-day facility

operations from all of the source categories. We believe that this type

of data would enable the MACT process to articulate a set of HAP

standards that would not create some of the issues raised in subsequent

sections of this preamble (such as the most appropriate resolution of a

variability factor, the optimum approach for considering the

contribution of cement and lightweight aggregate kiln raw material feed

to HAP emissions, and better identification among sources that are now

in an expanded MACT pool but which, with better data, would be

determined not to be employing the identified floor controls). As noted

in these subsequent sections, the Agency urges commenters to submit

these types of data.

B. Another Approach Considered but not Used

Although the Agency believes the proposed approach reflects a

reasonable interpretation of the statute, there are other possible

interpretations. One of these interpretations, termed the ``12 percent

approach'', was raised and, in fact, evaluated during the process

already outlined. This approach is presented here, along with the

results of the process in Part Four, Section VIII, for public

inspection.

This ``12 percent approach'' was evaluated in a like manner to the

Agency's preferred approach just described. Again, the best performing

control technology(ies) for each source category and each HAP were

identified by arraying the data by test condition averages. However,

the Agency identified the technology or technologies used by the best

performing 12 percent of the sources. After arraying emissions data

from all facilities in the source category that use the identified MACT

floor technology(ies) (i.e., the expanded MACT pool), the Agency

selected an emissions floor level based on the statistical average of

the 12 percent MACT pool, to which was added the average within-test

condition variability within the expanded MACT pool. The emissions

floor was then calculated at a level that a source with average

emissions variability would be expected to achieve 99 percent of the

time. The approach was not proposed because it could not be

demonstrated that sources within the expanded MACT pool using MACT

floor controls could achieve the floor levels. Again, the details of

the statistical methods employed are presented in the ``Draft Technical

Support Document for HWC MACT Standards, Volume III: Selection of

Proposed MACT Standards and Technologies''.

C. Identifying Floors as Proposed in CETRED

The discussion in the Draft Combustion Emissions Technical Resource

Document (CETRED) (U.S. EPA, EPA530-R-94-014, May 1994) presented one

methodology for establishing particulate matter (PM) and dioxin/furan

(D/F) technology-based emission levels for hazardous waste combustors

(HWCs). The document presented a procedure for establishing numerical

levels which took into account the natural variability that was present

in the Agency's PM and D/F emissions data. EPA received numerous

comments on the document.

The approaches outlined in CETRED were an initial and preliminary

attempt to apply the process by which the NESHAPs are to be established

for the existing types of hazardous waste combustors. The approaches in

CETRED focused solely on the performance of MACT and how to establish

the ``floor'' emission level under the MACT process.

In CETRED, determination of the MACT floor involved: (1) screening

unrepresentative data; (2) ranking all HWC sources based on the data

average, considering variability; (3) identifying the top 12 percent of

sources as the MACT pool; and (4) statistically evaluating the MACT

pool to set the MACT floor. These elements and considerations are

described in further detail in CETRED and the ``Draft Technical Support

Document for HWC MACT Standards, Volume III: Selection of Proposed MACT

Standards and Technologies''. The Agency specifically indicated the

preliminary nature of the CETRED approaches and, in light of further

deliberations and comments received, has considered and adopted other

approaches for this proposal. The comments received are found in the

docket.

In considering the use of a purely statistical approach to setting

MACT floors, the Agency recognized that whether sources could actually

achieve a statistically-derived MACT floor level on a regular basis was

significant in determining whether a purely statistical approach could

be appropriate or not. The Agency encountered difficulties in

identifying an appropriate purely statistical model for the combined

source category (HW incinerators, HW-burning cement kilns, and HW-

burning lightweight aggregate kilns) emissions database. Consequently,

the Agency abandoned a purely statistical approach and examined an

approach--referred to here as the ``technology approach''--that used

demonstrated technological capabilities as a key factor in selecting

MACT floor levels.

D. Establishing Floors One HAP or HAP Group at a Time

EPA believes it is permissible to establish MACT floors separately

for individual HAPs or group of HAPs that behave the same from a

technical standpoint (i.e., based on separate MACT pools and floor

controls), provided the various MACT floors are simultaneously

achievable. As set out below, Congress has not spoken to this precise

issue. An interpretation that allows this approach is consistent with

statutory goals and policies, as well as established EPA practice in

developing MACT standards.

As described earlier, Congress specified in section 112(d)(3) the

minimum level of emission reduction that could satisfy the requirement

to adopt MACT. For new sources, this floor level is to be ``the

emission control that is achieved in practice by the best

[[Page 17368]]

controlled similar source''. For existing sources, the floor level is

to be ``the average emission limitation achieved by the best performing

12 percent of the existing sources'' for categories and subcategories

with 30 or more sources, or ``the average emission limitation achieved

by the best performing 5 sources'' for categories and subcategories

with fewer than 30 sources. An ``emission limitation'' is ``a

requirement * * * which limits the quantity, rate, or concentration of

emissions of air pollutants'' (section 302 (k)) (although the extent,

if any, the section 302 definitions need to apply to the terms used in

section 112 is not clear).

This language does not expressly address whether floor levels can

be established HAP-by-HAP. The existing source MACT floor achieved by

the average of the best performing 12 percent can reasonably be read as

referring to the source as a whole or performance as to a particular

HAP. The statutory definition of ``emission limitation'' (assuming it

applies) likewise is ambiguous, since ``requirements limiting quantity,

rate, or concentration of pollutants'' could apply to particular HAPs

or all HAPs. The reference in the new source MACT floor to ``emission

control achieved by the best controlled similar source'' can mean

emission control as to a particular HAP or achieved by a source as a

whole.

Here, Congress has not spoken to the precise question at issue, and

the Agency's interpretation effectuates statutory goals and policies in

a reasonable manner. See Chevron v. NRDC, 467 U.S. 837 (1984)

(indicating that such interpretations must be upheld). The central

purpose of the amended air toxics provisions was to apply strict

technology-based emission controls on HAPs. See, e.g., H. Rep. No. 952,

101st Cong. 2d sess. 338. The floor's specific purpose was to assure

that consideration of economic and other impacts not be used to ``gut

the standards''. While costs are by no means irrelevant, they should by

no means be the determining factors. There needs to be a minimum degree

of control in relation to the control technologies that have already

been attained by the best existing sources. Legislative History of the

Clean Air Act Vol. II at 2897 (statement of Rep. Collins).

Furthermore, an alternative interpretation would tend to result in

least common denominator floors where multiple HAPs are emitted,

whereby floors would no longer be reflecting performance of the best

performing sources. For example, if the best performing 12 percent of

facilities for HAP metals did not control organics as well as a

different 12 percent of facilities, the floor for organics and metals

would end up not reflecting best performance. Indeed, under this

reading, the floor would be no control, because no plant is controlling

both types of HAPs.

EPA is convinced that this result is not compelled by the statutory

text, and does not effectuate the evident statutory purpose of having

floor levels reflect performance of an average of a group of best-

performing sources. Conversely, using a HAP-by-HAP approach (or an

approach that groups HAPs based on technical factors) to identify

separate floors for metals and organics in this example promotes the

stated purpose of the floor to provide a minimum level of control

reflecting what best performing existing sources have already

demonstrated an ability to do.

EPA notes, however, that if optimized performance for different

HAPs is not technologically possible due to mutually inconsistent

control technologies (for example, metals performance decreases if

organics reduction is optimized), then this would have to be taken into

account in establishing a floor (or floors). (Optimized controls for

both types of HAPS would not be MACT in any case, since the standards

would not be mutually achievable.) The Senate Report indicates that in

such a circumstance, EPA is to optimize the part of the standard

providing the most environmental protection. S. Rep. No. 228, 101st

Cong. 1st sess. 168. It should be emphasized, however, that ``the fact

that no plant has been shown to be able to meet all of the limitations

does not demonstrate that all the limitations are not achievable''.

Chemical Manufacturers Association v. EPA, 885 F. 2d at 264 (upholding

technology-based standards based on best performance for each pollutant

by different plants, where at least one plant met each of the

limitations but no single plant met all of them).

All available data for HWCs indicate that there is no technical

problem achieving the floor levels for each HAP or HAP metal group

simultaneously, using the MACT floor technology. In the case of metals

and PM, the characteristics of the MACT floor technology associated

with the hardest-to-meet floor (e.g., the fabric filter with lowest

air-to-cloth ratio) would define the MACT floor technology for purposes

of determining achievability of floors and for purposes of costing out

the impact of the standards. Existing data show that approximately 9

percent of existing hazardous waste incinerators, approximately 8

percent of hazardous waste-burning cement kilns, and approximately 25

percent of hazardous waste-burning LWAKs are already achieving the

proposed floor standards for all HAPs.

Finally, EPA notes that the HAP-by-HAP or HAP group approach to

establishing MACT floor levels is not unique to this rule. For example,

the Agency has adopted it for the NESHAP for the secondary lead source

category (60 FR 32589 (June 23, 1995)) and proposed the same approach

for municipal waste combustors (59 FR 48198 (September 20, 1994)).

As discussed above, EPA has the authority to establish MACT floors

on a HAP group by HAP group basis and has done so in this case. In

doing so, EPA will ensure that such floors, taken as a whole, are

reasonably achievable for facilities subject to the MACT standards.

VI. Selection of Beyond-the-Floor Levels for Existing Sources

As discussed in Section V above, the MACT floor defines the minimum

level of emission control for existing sources, regardless of cost or

other considerations. The process of considering emissions levels more

stringent than the MACT floor for existing sources is called a

``beyond-the-floor'' (BTF) analysis and involves consideration of

certain additional factors, including cost, any non-air quality health

and environmental impacts and energy requirements, technologies

currently in use within these industry sectors, and also other more

efficient and appropriate technologies that have been demonstrated and

are available on the market (e.g., carbon bed for dioxin/furan

control).

Because there are virtually unlimited BTF emissions levels that the

Agency could consider, the Agency used several criteria in this

proposal to identify when to examine a particular beyond-the-floor

emissions level in detail, and also whether to propose a MACT standard

based on the beyond-the-floor emissions levels for existing sources.

The primary factor is the cost-effectiveness of setting MACT

standards based upon a more efficient technology than the MACT floor

technology(ies). If the Agency's economic analysis suggested that BTF

levels could be cost-effectively achieved (particularly if significant

health benefits would result from a lower emission level), then an

applicable BTF emission level control technology was identified to

achieve that level. The associated costs were then weighed along with

the other criteria. Dioxin/furans is an example

[[Page 17369]]

where the Agency considered a BTF level because a beyond-the-floor

emission level can be achieved in a cost-effective manner, achieving,

in addition, significant non-air quality environmental benefits.

VII. Selection of MACT for New Sources

For new sources, the standards for a source category (or sub-

category) cannot be less stringent than the emission control that is

achieved in practice by the best-controlled similar source. See

Sec. 112(d)(3). The following discussion summarizes the methodology

used by the Agency in developing today's proposed emissions standards

for new HWC sources.

The approach used to identify MACT for new sources parallels in

most ways the approach used to determine the MACT floor for existing

sources. For each HAP, the Agency identified the technology associated

with the single best performing source (for each source category). The

Agency used this best performing technology then looked at all

facilities operating the control technology, and determined the

achievable emission levels that represent ``the emission control that

is achieved in practice by the best controlled similar source'' by

using the maximum value achieved by properly-operated technology

(adjusted upwards by a statistically derived variability factor). For

further details, see the technical background documents \13\ supporting

today's proposal.

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

\13\ USEPA, ``Draft Technical Support Document for HWC MACT

Standards, Volume III: Selection of Proposed MACT Standards and

Technologies'', February 1996.

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

Since MACT for new sources is to reflect optimized achievable

performance and is not necessarily limited to performance levels

currently achieved, the Agency also considered several other factors in

selecting the MACT new emissions limit. These factors included: (1)

Comparisons to other emissions standards which may indicate that a

technology is demonstrated and its level of performance (e.g., proposed

municipal waste combustors and medical waste incinerators regulations

and the European Union waste incineration standards); and (2) test

condition emissions variability.

As mentioned earlier, the Agency believes that it is appropriate to

compare the proposed emissions standards for new sources to other

existing or recently proposed standards applicable to hazardous waste

combustors or similar devices as a type of ``reality check'' that we

are developing the most rigorous emissions limits for new sources based

upon the best technologies available today.

The extracted data and data plots are presented in the background

document \14\ located in the docket.

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

\14\ USEPA, ``Draft Technical Support Document for HWC MACT

Standards, Volume III: Selection of Proposed MACT Standards and

Technologies'', February 1996.

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

VIII. RCRA Decision Process

It is EPA's intention to eliminate duplicative or potentially

duplicative regulation wherever possible. In this section, we discuss:

(1) The RCRA mandate to ensure protection of human health and the

environment and how that mandate relates to the CAA technology-based

MACT standards; (2) how, for RCRA purposes, we evaluated the

protectiveness of the proposed MACT standards; (3) how, for RCRA

purposes, the Agency intends to continue its policies with respect to

site-specific risk assessments and permitting so that, in appropriate

situations, additional RCRA permit conditions can be developed as

necessary to protect human health and the environment; and (4) how

waste minimization opportunities may be considered at individual

facilities during the permitting process.

A. RCRA and CAA Mandates To Protect Human Health and the Environment

The Agency is proposing emission standards for HWCs under joint

authority of the Clean Air Act Amendments of 1990 and the Resource

Conservation and Recovery Act (RCRA). As noted earlier, section 3004(a)

of RCRA requires the Agency to promulgate standards for hazardous waste

treatment, storage, and disposal facilities as necessary to protect

human health and the environment. The standards for incinerators

generally rest on this authority. In addition, Sec. 3004(q) requires

the Agency to promulgate standards as necessary to protect human health

and the environment specifically for facilities that burn hazardous

waste fuels (e.g., cement and light-weight aggregate kilns). Using RCRA

authority, the Agency has historically established emission (and other)

standards for HWCs that are either entirely risk-based (e.g., site-

specific standards for metals under the BIF rule), or are technology-

based but determined by a generic risk assessment to be protective

(e.g., the DRE standard for incinerators and BIFs).

The MACT standards proposed today implement the technology-based

regime of CAA Sec. 112. There is, however, a residual risk component to

air toxics standards. Section 112(f) of the Clean Air Act requires the

Agency to impose, within eight years after promulgation of the

technology-based standards promulgated under Sec. 112(d) (i.e., the

authority for today's proposed standards), additional controls if

needed to protect public health with an ample margin of safety or to

prevent adverse environmental effect. (Cost, energy, and other relevant

factors must be considered in determining whether regulation is

appropriate in the case of environmental effects.)

As noted earlier, EPA's express intent is to avoid regulatory

duplication. RCRA Sec. 1006 directs that EPA ``integrate all provisions

of [RCRA] for purposes of administration and enforcement and * * *

avoid duplication, to the maximum extent possible, with the appropriate

provisions of the Clean Air Act * * *.'' The overall thrust of the

proposed rule is to have the CAA standards supplant independent RCRA

standards wherever possible (i.e., to have the CAA standards, wherever

possible, also serve to satisfy the RCRA mandate so that additional

RCRA regulation is unnecessary).

Under RCRA, EPA must promulgate standards ``as may be necessary to

protect human health and the environment.'' RCRA Sec. 3004(a) and (q).

Technology-based standards developed under CAA Sec. 112 do not

automatically satisfy this requirement, but may do so in fact. See 59

FR at 29776 (June 6, 1994) and 60 FR at 32593 (June 23, 1995) (RCRA

regulation of secondary lead smelter emissions unnecessary at this time

given stringency of technology-based standard and pendency of

Sec. 112(f) determination). If the MACT standards, as a factual matter,

are sufficiently protective to also satisfy the RCRA mandate, then no

independent RCRA standards are required. Conversely, if MACT standards

are inadequate, the RCRA authorities would have to be used to fill the

gap.

It should be noted that this RCRA risk evaluation can inform the

MACT decision process as well. For example, the RCRA risk evaluations

indicate the potential for significant risk via indirect pathways from

dioxins and furans originating in today's baseline air emissions for

HWCs. EPA is explicitly authorized to consider non-air environmental

impacts (such as exposure to HAPS which, after emission, enter into the

food chain and are eventually consumed by humans and other biota) in

determining whether to adopt standards more stringent than the MACT

floor. Thus, EPA can consider benefits from curbing these

[[Page 17370]]

indirect exposures as part of its beyond-the-floor determinations.

As discussed below, the Agency has conducted an evaluation, for the

purposes of satisfying the RCRA statutory mandates, of the degree of

protection afforded by the MACT standards being proposed today.

However, the Agency's current RCRA evaluation is not intended to have

any bearing on what we may or may not determine is necessary in several

years to satisfy the Sec. 112(f) provisions.

B. Evaluation of Protectiveness

To determine whether the MACT standards are consistent with the

Agency's mandate under RCRA to establish standards for hazardous waste

management facilities and to issue permits that are protective of human

health and the environment, the Agency conducted two types of analyses

to assess the extent to which potential risks from current hazardous

waste combustion emissions would be reduced through implementation of

MACT standards.

The first of these analyses was designed to assess the potential

risks to individuals living near hazardous waste combustion facilities

and to nearby aquatic ecosystems. The procedures used in this analysis

are discussed in detail in the background document contained in the

docket for today's proposal.15 The results are summarized in Part

Four of today's notice, ``Rationale for Selecting Proposed Standards''.

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

\15\ ``Risk Assessment Support to the Development of Technical

Standards for Emissions from Combustion Units Burning Hazardous

Wastes: Background Information Document,'' February 20, 1996.

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

The second analysis of potential risk reduction was a more

qualitative evaluation of risks at the national level for those two

constituents (dioxins and mercury) which the Agency believes pose

significant health risks at the national level and which are found at

significant concentrations in hazardous waste combustor emissions. The

results of this analysis are presented in Section Seven, ``Regulatory

and Administrative Requirements'', as part of the discussion of

potential costs and benefits required under Executive Order 12866.

1. Individual Risk Analysis

The Agency assessed potential risks to individuals from both direct

inhalation of emissions (after dispersion in the ambient air) and

indirect exposure to emissions through deposition onto soils and

vegetation and subsequent uptake through the food chain. The analysis

focussed primarily on dioxins and related compounds since these have

been of major concern to the Agency from a risk perspective and because

there is enough information about the properties of these constituents

to allow for a quantitative analysis. The individual risk analysis did

also include risks from inhalation of metals, hydrogen chloride, and

chlorine (Cl2).

The Agency conducted an evaluation of risks from metals through

indirect exposure routes. With the exception of mercury, most of the

metals are not expected to accumulate significantly in the food chain,

and the risks from other indirect exposure routes (such as deposition

on soil and incidental ingestion of the soil) are not projected to be

significant, even with conservative assumptions.

With respect to mercury, the Agency suspects that there may be

significant individual risks near hazardous waste combustion

facilities, primarily through deposition, erosion to surface waters,

and accumulation in fish which are then consumed. However, the current

state of knowledge concerning the behavior of mercury in the

environment does not allow for a meaningful quantitative risk

assessment of emission sources which is precise enough to support

regulatory decisions at the national level. Specifically, there is

insufficient information with respect to speciation of the mercury into

various forms in emissions and with respect to the deposition and

cycling of mercury species in the environment to conduct a defensible

national quantitative assessment of mercury deposition, erosion to

surface waters, and bioaccumulation in fish. The Agency solicits

comment and information on the issue of the risks posed by mercury

emissions from hazardous waste combustion facilities.

The Agency also considered potential risks from emissions of non-

dioxin semi-volatile organics that are products of incomplete

combustion (PICs). However, the Agency was not able to conduct an

appropriate analysis for several reasons. First, the limited emissions

data now available to the Agency on non-dioxin PICs are not

sufficiently reliable to conduct an adequate assessment of risk.

Second, there is not a universally accepted set of parameter values for

some non-dioxin PICs with which to assess potential exposures (e.g.,

the use of octanol-water partition coefficients (Kow) to predict

bioaccumulation versus the use of empirical data and the extent to

which bioaccumulation of compounds such as phthalates and polycyclic

aromatic hydrocarbons (PAHs) occurs in domestic animals). The Agency

solicits comment on these issues and, in particular, requests data on

bioaccumulation of PAHs, phthalates, and other non-dioxin PICs in farm

animals used for food production and in other mammals and birds. The

Agency also intends to obtain a better set of data relating to the non-

dioxin PIC emissions from hazardous waste combustion facilities.

2. Individual Risks From Dioxins

In order to evaluate potential risks from dioxins to individuals

living near hazardous waste combustion facilities, the Agency selected

eleven example facility locations, consisting of areas in which five

actual cement kilns, four incinerators, and two lightweight aggregate

kilns are located. The example facility locations represent a variety

of environmental settings and facility characteristics. The purpose of

using example facilities was to incorporate as much realism as possible

into the Agency's risk assessment and to reduce the reliance on

hypothetical, conservative assumptions about either location or source

type characteristics. Site-specific characteristics considered in the

analysis include meteorological conditions, topography, and land use as

well as stack height and gas flow rates. However, the stack gas

concentrations used in the modeling of the example facilities were

derived from national emissions data. Therefore, while the example

facility analyses are useful for providing information to evaluate

national standards on a generic basis, they are not site-specific

assessments of any individual facility and cannot be regarded as such.

The Agency has identified a number of indirect exposure pathways

which are most likely to present significant risks. These include:

consumption of locally-produced meat, eggs, and dairy products and

consumption of fish from local waterways. Contamination of food occurs

from deposition of toxic emissions onto plants and soil with subsequent

ingestion by farm animals or, in the case of fish contamination, from

deposition directly into water bodies or onto soil and runoff into

surface waters with subsequent uptake in fish.

In assessing risks to the more highly exposed individuals, the

Agency assumed that certain segments of the population subsisted in

part on home-produced foods or fish obtained from nearby lakes or

streams. In addition, the Agency assumed that these individuals were

exposed in the farming and fishing areas most affected by the example

facilities' emissions. In its analysis of the eleven example

facilities, the

[[Page 17371]]

Agency attempted to identify the actual location of farms and water

bodies where subsistence activities might be expected to occur. For

dioxins, the highest exposures are expected to occur for individuals

whose diets include significant amounts of home-produced meat and eggs

or locally caught fish. Individuals likely to have high exposures

include subsistence farmers that raise beef cattle, dairy cows, or

chickens along with their families as well as subsistence fishers and

recreational anglers and their families.

In evaluating individual risks, the Agency projected both ``high

end'' and ``central tendency'' estimates of risks to the individuals of

concern in the analysis. The central tendency estimates were derived by

setting all emission rates, fate and transport parameters, and exposure

assumptions at central tendency values, as described in the risk

assessment background document. To derive high end risk estimates, the

Agency set the emission levels at the 90th percentile of the

distribution of available dioxin concentrations and, for most exposure

scenarios, set one exposure parameter to a high end value while keeping

all other parameters at central tendency values. For purposes of

evaluating the protectiveness of the standards, the Agency used a

target risk level of 10-5 for the high end individual risk, which is

consistent with the approach taken in the 1991 BIF rule.

3. Uncertainties in the Individual Dioxin Risk Estimates

Much of the information used to derive the individual risk

estimates for dioxins was taken from the Agency's draft Dioxin

Reassessment documents \16\ \17\ \18\. Those documents discuss in

considerable detail a number of the uncertainties associated with both

the cancer slope factor (the dose-response descriptor) and the many

parameters used in the exposure assessment. Some of these uncertainties

are also discussed in the risk assessment background document for

today's proposal.

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

\16\ ``Health Assessment Document for 2,3,7,8-

Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds Volume I

and II'', Office of Research and Development, June 1994.

\17\ ``Health Assessment Document for 2,3,7,8-

Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds Volume

III'', Office of Research and Development, August 1994.

\18\ ``Estimating Exposure to Dioxin-Like Compounds Volume I,

II, and III'', Office of Research and Development, June 1994.

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

In addition, there have been a large number of public comments on

the Dioxin Reassessment, which the Agency is now considering. If the

Agency decides to revise its assessment of either the toxicity or

exposure associated with dioxins prior to the final promulgation of

this rule, those revisions will be considered in the development of the

final rule.

The Agency is also conducting an external peer review of its risk

analysis supporting today's proposal. The results of this peer review,

which are expected during the comment period, will be available in the

public record for this rule and will be considered in developing the

final rule.

4. Qualitative Assessments of National Risks

While the individual risk assessment discussed above provides a

quantitative measure of the protectiveness of the proposed MACT

standard, there are other ways of evaluating potential impacts of

reducing emissions of hazardous constituents. One approach taken by the

Agency is to describe to the extent practicable what is known about the

national extent of risks from constituents such as dioxins and mercury.

To put that information in context with respect to this rule, the

relative contribution of hazardous waste combustion to other known air

releases of these constituents to the environment is then presented.

The Agency recognizes that it is not appropriate to quantitatively

correlate emissions with risk on a national scale; nevertheless, this

type of information is useful for qualitatively evaluating the

potential impact of the proposed MACT rule.

C. Use of Site-Specific Risk Assessments Under RCRA

As part of the Agency's Hazardous Waste Minimization and Combustion

Strategy, EPA currently has a national RCRA policy of strongly

recommending to all federal and state RCRA permit writers that, under

the omnibus permit provisions of RCRA Sec. 3005(c)(3), site-specific

risk assessments be performed as part of the RCRA permitting process if

necessary to protect human health and the environment. Regions and

authorized states have been implementing this national policy since

mid-1993 under the aegis of the omnibus and other applicable

authorities.

The Combustion Strategy announced this policy encouraging site-

specific risk assessments as part of the overall effort to ensure that,

under appropriate legal authorities, all RCRA combustion permits being

issued are sufficiently protective. Specifically, these site-specific

risk assessments were intended to address potential concerns about a

suite of hazardous air pollutants, among them dioxins, furans, metals,

and non-dioxin PICs, during the time it took for the Agency to upgrade

the technical standards for hazardous waste incinerators, boilers, and

industrial furnaces. This proposal is the first rulemaking that the

Agency has issued in the upgrading effort.

The question has arisen as to the status of the Agency's current

policy with respect to site-specific risk assessments, particularly

with respect to the HAPs for which standards are being proposed today

as well as for other non-dioxin PICs. As noted above, the Agency has

conducted a risk evaluation under RCRA of the degree of protection

afforded by the proposed MACT standards for the HAPs addressed in

today's rule. However, with respect to mercury and non-dioxin PICs, the

Agency does not at this time have sufficient reliable data to be able

to assess, on a national basis, the magnitude of the risks that can

routinely be expected from burning hazardous waste in HWCs. Although

the Agency has plans to obtain extensive and detailed PIC emissions

data from hazardous waste combustors in the coming months, it may be

some time before the Agency is in a proper position to make any type of

regulatory and policy judgment about the need, if any, for additional

national standards for these toxic organics. Indeed, at several sites,

the levels of some non-dioxin PICs have not previously been shown to be

of concern, at least to the extent that site-specific testing revealed

their presence and to the extent evaluated in site-specific risk

assessments.

The Agency is continuing its policy of recommending that, if

necessary to protect human health and the environment, site-specific

risk assessments be conducted as part of RCRA permitting for all

hazardous waste combustors (incinerators, boilers, and industrial

furnaces alike) until national standards for HAPs of concern are in

place. We expect that, in most situations prior to actual

implementation of facility measures to appropriately control the HAPs

addressed in this rule, the EPA regional and authorized state

permitting officials will find there is a necessity to conduct site-

specific risk assessments prior to final permit determinations. We also

note that the remaining uncertainties about the risks from non-dioxin

PICs and mercury would likely bear upon implementation of the national

policy. However, small on-site facilities are not likely to present the

same level of potential risk as other facilities. This industry segment

may not warrant site specific risk assessments with the same frequency

as the large on-site or

[[Page 17372]]

commercial facilities. Among the factors that the regions and states

should consider in their evaluation of the necessity for a site-

specific risk assessment are: (1) The current level of HAPs being

emitted by a facility, particularly in comparison to the MACT standards

being proposed and in comparison to the emissions assumptions and

exposure scenarios used in the RCRA risk evaluation of the proposed

MACT standards (detailed in the Background Document); (2) whether the

facility is exceeding the proposed HAP standards, particularly for

dioxins/furans and mercury, what immediate measures could be instituted

to reduce those emissions; (3) the scope of waste minimization efforts

at the facility with respect to the HAPs of concern and the status of

implementation of any facility waste minimization plan; (4) particular

site-specific considerations such as proximity to receptors, unique

dispersion patterns, etc.; (5) the PICs most likely to be found and

those most likely to pose significant risk; (6) the presence or absence

of other sources of HAPs in sufficient proximity as to exert a

significant influence on interpretation of a facility-specific risk

assessment; (7) the presence or absence of significant ecological

considerations, including for example high background levels of a

particular contaminant or proximity of a particularly sensitive

ecological area; and (8) the volume and types of wastes being burned.

This list is by no means exhaustive, but is meant only to suggest

significant factors that have thus far been identified. Others may be

equally or more important.

Continuation of the site-specific risk assessment policy rests

primarily on the RCRA requirement to ensure that all permits are

protective of human health and the environment. Until the Agency is in

a position to determine, on a national basis, whether additional

standards are needed to address toxic emissions, we anticipate this

policy will remain in effect. EPA's intention is to make that

determination, if sufficient data is in hand, by the time of the final

rule, now scheduled for issuance in December 1996. In that respect, we

emphasize the importance of the submission of detailed data on non-

dioxin PICs from commenters.

In the meantime, the omnibus provision in Sec. 3005(c)(3) provides

the regions and authorized states with the proper site-by-site

authority to ensure that these risk assessments are completed as part

of the permitting process. Other RCRA statutory and regulatory

provisions may apply as well. Furthermore, we encourage individual

facilities to work with their local communities in designing these risk

assessments and in carrying out the testing and analysis, so that the

confidence of local communities is maximized.

In addition, EPA strongly urges companies to explore waste

minimization opportunities as a means to reduce risks from combustion

emissions, particularly with respect to the HAPs of concern. Nearly

every state provides free pollution prevention/waste minimization

technical assistance. Further information on how to obtain this

assistance can be furnished by state permitting agencies or by

contacting the National Pollution Prevention Roundtable at (202) 466-

7272. Other sources of information include Enviro$ense, an electronic

library on pollution prevention, technical assistance, and

environmental compliance. Access is via a system operator (703) 908-

2007, via modem at (703) 908-2092, or via Internet at http://

wastenot.inel.gov/enviro-sense.

PART FOUR: RATIONALE FOR SELECTING THE PROPOSED STANDARDS

This part describes the Agency's rationale for today's proposed

standards and other options under consideration.

I. Selection of Source Categories and Pollutants

A. Selection of Sources and Source Categories

The Agency is proposing emissions standards for three source

categories: hazardous waste incinerators, hazardous waste-burning

cement kilns, and hazardous waste-burning lightweight aggregate kilns.

The Agency is not proposing to regulate emissions from CKs (in this

notice) or LWAKs that do not burn hazardous waste.

In this section, we discuss the Agency's analysis of subdividing

incinerators by size (i.e., small and large sources) and subdividing

cement kilns by process type (i.e., wet and dry). We also discuss the

scope of the MACT standards for cement kilns, and the existing RCRA

standards that control emissions of HAPs from equipment leaks and tanks

which are used to manage hazardous waste.

1. Consideration of Subdividing Incinerators by Size

Section 112(d) allows the Administrator to distinguish among

classes, types, and sizes of sources within a source category in

establishing MACT floor levels. Given that the size of incinerators, as

measured by gas flow rate in actual cubic feet per minute (acfm),

varies substantially (i.e., from 1,000 acfm to 180,000 acfm), the

Agency considered subdividing incinerators by size.

The basis for distinguishing between small and large incinerators

as well as the preliminary estimates of the resultant floor levels for

each category are presented in the docket and summarized below. The

Agency is not proposing separate standards (at the floor) 19 for

incinerators because: (1) the types and concentrations of uncontrolled

HAP emissions are similar for large and small incinerators; (2) the

same types of emission control devices are applicable to both small and

large incinerators; and (3) the floor levels would be generally

unchanged 20 (several floor levels would decrease somewhat), with

the exception that the LVM standard for large incinerators would

increase by more than a factor of four. We believe that the higher LVM

floor level for large incinerators would not be appropriate given that

approximately 80 percent of incinerators already are meeting the LVM

floor without subdividing.

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\19\ Note that we discuss in Part Four, Section III in the text

whether beyond-the-floor standards for D/F, Hg, and PM (as currently

proposed for all incinerators) are appropriate for small

incinerators.

\20\ And therefore, a level of complexity would be added to the

rule without substantial benefit.

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The Agency invites comment on its determination that subdividing

incinerators by size would not be warranted. We also invite comment on

whether subdividing incinerators by other classifications (e.g.,

commercial versus on-site units) would be appropriate for establishing

MACT floor levels. Commenters should provide data and information on,

in particular: (1) how the types and concentrations of uncontrolled HAP

emissions are different for the suggested categorization of sources;

(2) whether and why MACT emission control technology would not be

applicable to a category of sources; and (3) other appropriate factors.

To investigate the effect on MACT floor levels of subdividing

incinerators by size, the Agency identified a gas flow rate of 23,127

acfm as a reasonable and appropriate demarcation between small and

large incinerators. This value was determined using a slope analysis

approach whereby gas flow rates for each source (for which the Agency

had data) were plotted in ascending order. The Agency chose the point

at which the slope markedly changed as the point of demarcation between

small and large incinerators. Approximately 57 percent of incinerators

for which we have gas flow rate data would be classified as small using

this approach.

[[Page 17373]]

Projected MACT floor levels for small and large incinerators are

compared to floor levels for combined incinerators (i.e., without

subdividing) in the table below:

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

Small incinerators Large incinerators

------------------------------------------------------------------------------ Floor levels for all incinerators

Floor level Floor level combined

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

D/F (ng/dscm)....................... 0.2 TEQ or g/dscm)................ 110.................................. 130.................................. 130

SVM (g/dscm)............... 230.................................. 270.................................. 270

LVM (g/dscm)............... 160.................................. 880.................................. 210

HCl + Cl2 (ppmv).................... 280.................................. 260.................................. 280

CO (ppmv)........................... 100.................................. 100.................................. 100

HC (ppmv)........................... 12................................... 12................................... 12

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

2. Consideration of Subdividing Cement Kilns by Manufacturing Process

The Agency also considered whether to subdivide the cement kiln

source category into wet and dry process kilns given that these types

of kilns are designed and operated differently. (See discussion in Part

Two, Section II.) MACT floor levels for wet and dry kilns are compared

to floor levels for combined cement kilns (i.e., without subdividing)

in the table below:

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

Wet process kilns Dry process kilns

Pollutant ------------------------------------------------------------------------------ Floor levels for all kilns combined

Floor level Floor level

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

D/F (ng/dscm)....................... 0.2 TEQ or 418 deg.F................ 0.2 TEQ or 547 deg.F................ 0.2 TEQ or 418 deg.F.

PM (mg/dscm)........................ 69................................... 69................................... 69

Hg (g/dscm)................ 83................................... 150.................................. 130

SVM (g/dscm)............... 870.................................. 57................................... 57

LVM (g/dscm)............... 220.................................. 49................................... 130

HCl + Cl2 (ppmv).................... 460.................................. 340.................................. 640

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

Subdividing cement kilns by process type would result in a mix of

impacts with varying degrees of significance. For wet kilns, the main

impact would be an increase in the SVM floor from 57 to 870 g/

dscm. The mercury floor, on the other hand, would drop from 130 to 83

g/dscm. The remainder of the floors would remain roughly the

same. For dry cement kilns, the main impact would be that the LVM floor

drops from 130 to 49 g/dscm. The dioxin/furan floor would

change by allowing a higher APCD temperature--547 deg.F rather than

418 deg.F.

The Agency is not proposing separate standards for wet and dry

process kilns because: (1) The types and concentrations of uncontrolled

HAP emissions are similar for both types of kilns; (2) the same types

of emission control devices are applicable to both types of kilns; (3)

for dry process kilns, the LVM floor level would drop to an extremely

low level that may be difficult for many kilns to achieve because of

the presence of these metals in raw materials; and (4) for wet kilns,

the SVM floor would increase to 870 g/dscm, a level much

higher than the industry can achieve.21 There may also be other

factors that should be considered, and the Agency invites comment on

those in addition to the factors noted above.

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\21\ See letter from Craig Campbell, CKRC, to James Berlow,

USEPA, undated but received February 20, 1996. We note that,

although the Agency is proposing a SVM standard of 57 g/

dscm, we invite comment on an alternative (and potentially

preferable) approach to identify MACT floor technology which would

result in a floor-based standard of 160 g/dscm. See Part

Four, Section IV in the text. Because we identified the alternative

approach late in the rule development process, we are inviting

comment on the higher standard rather than proposing it.

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

We note that the cement industry has asserted that it is not

feasible to use a FF on wet kilns in cold climates because the ``high

moisture content of the gas will clog the fabric with cement-like dust

and ice.'' 22 This is not consistent with the Agency's

understanding. Although wet kilns located in cold climates that operate

at low flue gas temperatures (e.g., 350-400 deg.F) in order to

minimize formation of D/F and improve performance of activated carbon

injection systems may be required to improve insulation or take other

measures to minimize cold spots in the baghouse to limit corrosion, we

believe that appropriate measures can be readily taken. The Agency is

aware of two wet kilns that currently operate fabric filters in cold

climates (Thomaston, Maine, and Dundee, Michigan) at flue gas

temperatures below 400 deg.F. \23\ In addition, a wet kiln

burning hazardous waste in Paulding, Ohio, is currently upgrading its

PM control system to replace an ESP with a FF.

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\22\ See letter from Micheal O'Bannon, EOP Group, to Elliot

Laws, USEPA, dated February 14, 1996, p. 3 of Attachment.

\23\ See USEPA, ``Draft Technical Support Document For HWC MACT

Standards, Volume III: Selection of Proposed MACT Standards and

Technologies'', February, 1996, for further information.

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

The Agency invites comment on the appropriate criteria to be used

and upon its determination that subdividing cement kilns by process

type is not warranted. Commenters should provide data and information

on, in particular: (1) Whether the types and concentrations of

uncontrolled HAP emissions are different for wet and dry kilns; (2)

whether and why MACT emission control technology(ies) would not be

applicable to a wet or dry kiln; and (3) other appropriate factors.

3. Scope of the MACT Standards for Cement Kilns

The proposed NESHAP for cement kilns addresses only exhaust

combustion gas emissions from main stack(s), bypass stack(s), and

fugitive combustion emissions (e.g., leaks from kiln seals). The cement

kiln standards would not apply to process or fugitive emissions that

are not affected

[[Page 17374]]

by burning hazardous waste (such as emissions from raw material

processing or clinker cooler emissions). 24

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\24\ Today's proposal applies only to those kilns that burn or

process hazardous waste irrespective of the purpose of burning or

processing. The term ``burn'' means burning for energy recovery or

destruction, or processing as an ingredient. The Agency is

developing a NESHAP for cement kilns that do not process hazardous

waste in a separate rulemaking. That NESHAP will also regulate those

hazardous waste-burning cement kiln process and fugitive emissions

that would not be subject to today's rule (i.e., emission sources

other than the main or by-pass stack).

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

4. Current RCRA Controls on Equipment Leaks and Tanks

We note that the Agency has promulgated air emission standards

regulating fugitive emissions from equipment leaks (e.g., pumps,

compressors, valves) and tanks which are used to manage hazardous

waste. Accordingly, these devices are not addressed by today's

proposal. (Tanks and equipment leaks from HW management activities at

HWCs are regulated under RCRA standards. See, e.g., 40 CFR Parts 264

and 265, Subparts AA, BB, and CC. These controls are expected to be

consistent with MACT and are not being reevaluated here.)

B. Selection of Pollutants

As noted earlier, section 112(b) of the Clean Air Act contains a

list of 189 hazardous air pollutants for which the Administrator must

promulgate regulations establishing emissions standards for designated

major and area sources. The list of 189 HAPs is comprised of metallic,

organic, and inorganic compounds.

Hazardous waste incinerators and hazardous waste-burning cement

kilns and LWAKs emit many of the listed HAPs. Data available to the

Agency indicate that metal HAP emissions include antimony, arsenic,

beryllium, cadmium, chromium, lead, mercury, nickel, and selenium

compounds. Organic HAPs emitted include chlorinated dioxin and furan,

benzene, carbon disulfide, chloroform, chloromethane,

hexachlorobenzene, methylene chloride, naphthalene, phenol, toluene,

and xylene. Hydrochloric acid and chlorine gas are prevalent inorganic

compounds found in stack emissions because of high chlorine content of

many hazardous wastes.

Today, the Agency is proposing eight emissions standards for

individual HAPs, group of HAPs, or HAP surrogates. These emission

standards cover dioxin/furan, mercury, particulate matter, semivolatile

HAP metals (lead and cadmium), low-volatile HAP metals (antimony,

arsenic, beryllium, and chromium), carbon monoxide, hydrocarbons, and

total chlorides. The following discussion presents the Agency's

rationale for proposing NESHAPs for these individual HAPs, group of

HAPs, or HAP surrogates.

1. Toxic Metals

In developing today's proposed rule, the Agency considered 14 toxic

metals that may pose a hazard to human health and the environment when

they are components of emissions from hazardous waste combustion

sources. Section 112(b) of the Act contains a list of 11 metal HAPs:

antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead,

manganese, mercury, nickel, and selenium. The list of hazardous

constituents under RCRA 25 specifies three additional metals:

barium, silver, and thallium. Five of these metals (or their compounds)

are known or suspected carcinogens: arsenic, beryllium, cadmium,

hexavalent chromium, and nickel.

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

\25\ The list of hazardous constituents is contained in appendix

VIII of Part 261. Cobalt and manganese are not hazardous

constituents.

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

To develop an implementable approach for controlling the metal HAP

emission levels, the Agency grouped metal HAPs by their relative

volatility and is proposing an emissions limit for the each volatility

group (i.e., the sum of emissions from the metals in the group cannot

exceed the limit). We selected the following three groups: (1) A high-

volatile group comprised of only mercury, (2) a semivolatile group

comprised of lead and cadmium, and (3) a low-volatile group consisting

of antimony, arsenic, beryllium, and chromium. The Agency's proposal

not to include the remaining seven toxic metals in these volatility

groupings is discussed later in this section.

Our data indicate that mercury is generally in the vapor form in

and downstream of the combustion chamber, including at the air

pollution control device (APCD). Thus, the level of emissions is a

function of the feedrate of mercury and the use of APCDs that can

control Hg in the vapor form (e.g., carbon injection, wet scrubbers for

some control of soluble HgCl). The semivolatile group metals typically

vaporize at combustion temperatures, then condense onto fine

particulate before entering the APCD. Thus, emissions of semivolatile

metals are a function not only of the feedrate of the metal, but also

of the efficiency of the particulate matter (PM) control device. Low-

volatile metals are less apt to vaporize at combustion temperatures and

therefore partition primarily to the bottom ash, residue, or clinker

(in the case of cement kilns) or adsorb onto large, easy-to-control

particles in the combustion gas. Thus, low-volatile metal emissions are

more strongly related to the operation of the PM APCD than to the

feedrate.26

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

\26\ Although, at a given PM emission rate at a source,

emissions of LMV will be affected by LVM feedrate.

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

We note that the dynamics associated with the fate of metals in a

combustion device are much more complex than presented here. Numerous

factors impact metals' behavior such as the presence of chlorine

(higher metal volatility associated with metal chlorides than metal

oxides), combustion conditions within the device (e.g., temperature

profile), inter-metal relationships, physical and chemical form the

metal exhibits when introduced to the device (e.g., valence state and

solid versus liquid), type and efficiency of the particulate control

device, and differences in the design and operation of sources (e.g.,

cement kiln dust recycling rate). See the technical background document

supporting today's proposal for more details.27

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

\27\ USEPA, ``Draft Technical Support Document for HWC MACT

Standards, Volume VII: Miscellaneous Technical Issues'', February

1996.

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

Setting an emission level for a number of grouped metals has

several advantages and disadvantages. One advantage is that fewer

individual standards are involved, which helps implementability.

Moreover, grouping allows a facility more flexibility in complying with

an emissions standard based on facility-specific characteristics (e.g.,

special characteristic waste streams) and operation requirements (e.g.,

reduced spiking of numerous metals). On the other hand, a disadvantage

of a group emission limit is that it potentially allows higher

emissions of the more toxic metals within a group (than if an

individual metal limit were established).28

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

\28\ We note that, for the risk assessment used to determine if

RCRA concerns would be adequately addressed by the proposed MACT

standards, we assumed that each metal in a volatility was emitted in

turn at the emission limit for that volatility group.

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

The Agency is proposing not to regulate directly emissions of the

remaining four metal HAPs (i.e., cobalt, manganese, nickel, and

selenium).29 The

[[Page 17375]]

Agency's rationale is based upon a combination of factors: (1)

Inadequate emissions data for Co, Mg, Ni, and Se; and (2) relatively

low toxicity of Co and Mn. The Agency specifically requests comment on

whether these four metals would be adequately controlled under the MACT

standards that would be provided by today's proposal.

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

\29\ The Agency acknowledges that three metals (barium, silver

and thallium), currently regulated by the BIF rule, would not be

regulated under this MACT proposal. EPA notes that these three

metals are not HAPs. The Agency believes that the combination of the

proposed particulate and metals standards would adequately control

emissions of these three metals.

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

The Agency is aware of two other approaches to group toxic metals.

First, the European Union has established three groupings to control

metal emissions from hazardous waste incineration units. One ``group''

includes only mercury, a second group consists of cadmium and thallium,

and the third group includes antimony, arsenic, chromium, cobalt,

copper, lead, manganese, nickel, tin, and vanadium. Section VII of this

Part summarizes the European Union emission standards.

A rulemaking petition 30 submitted to the Agency by the Cement

Kiln Recycling Coalition (CKRC) contained a report 31 (appendix D

of the petition) prepared by a technical advisory board to the CKRC.

Their analysis of stack emissions and cement kiln dust data suggests

three volatility groupings based on metal volatility demonstrated in

cement kilns. The groupings are: (1) Volatile metals including mercury

and thallium; (2) semivolatile metals consisting of antimony, cadmium,

lead, and selenium; and (3) low-volatile metals comprising barium,

beryllium, chromium, arsenic, nickel, manganese, and silver. See the

technical background document for further discussion on grouping metals

by volatility.32 The Agency requests comments on the

appropriateness of grouping metals by volatility and requests

supporting information and data on the appropriate composition of metal

volatility groups (i.e., for the metals discussed above).

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

\30\ CKRC's rulemaking petition proposes to establish new

technology-based combustion emissions standards and was submitted to

EPA on January 18, 1994. CKRC's petition consists of four basic

components. First, the stringency of current BIF Rule toxic metal

limits should be increased by factors of 5 to 10 and applied to all

combustion devices (i.e., both BIFs and incinerators). Second, new

regulatory efforts for dioxin/furan standards should focus on a

toxic equivalency approach (TEQ) rather than on a total congener

approach. Third, the implementation of the new metals and dioxin/

furan standards should be applied uniformly to all types of

hazardous waste combustors (HWCs) and imposed at the same time.

Finally, EPA should conduct a rulemaking on indirect exposure risk

assessments before requiring their use. CKRC's petition has been

placed in the docket supporting today's proposal.

\31\ ``Scientific Advisory Board on Cement Kiln Recycling

(Process Technology Workgroup), Evaluation of the Origin, Emissions

and Control of Organic and Metal Compounds From Cement Kilns Co-

Fired With Hazardous Wastes,'' June 8, 1993.

\32\ USEPA, ``Draft Technical Support Document for HWC MACT

Standards, Volume VII: Miscellaneous Technical Issues,'' February

1996.

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2. Toxic Organic Compounds

Burning hazardous waste that contains toxic organic compounds under

poor combustion conditions can result in substantial emissions of HAPs

originally present in the waste as well as other compounds, due to the

partial but incomplete combustion of the constituents in the waste

(known as products of incomplete combustion, or PICs). PICs can be

unburned organic compounds that were present in the waste, thermal

decomposition products resulting from organic constituents in the

waste, or compounds synthesized during or immediately after combustion.

The quantity of toxic organic compounds emitted depends on such factors

as the combustion conditions under which the waste is burned (including

time, temperature, and turbulence), the concentrations of the toxic

compounds in the waste, and the waste firing rate.

Since the majority of the 189 enumerated HAPs are organics, the

Agency has concluded (for today's proposal) that establishing

individual emission limits for each of the organic HAP compounds

emitted from these combustion sources would be impractical and not

implementable. Measuring each compound would be very costly and would

pose unreasonable compliance and monitoring burden on the regulated

community while achieving little, if any, emission reduction from the

approach presented in today's proposal. In addition, EPA and state

compliance oversight and enforcement efforts would also be unreasonably

costly without concurrent benefits. Also, the Agency does not have

adequate emissions data to support development of individual organic

emission limits 33 at this time. Therefore, the Agency is

proposing a multi-faceted approach to control the toxic organic HAPs to

be addressed under Sec. 112: (1) Emissions limits for dioxin and furan

on a toxicity equivalents (TEQ) basis; (2) limits on flue gas

concentrations of hydrocarbons (HC) as a HAP surrogate; (3) limits on

flue gas concentrations of carbon monoxide (CO) also as a HAP

surrogate; and (4) emission limits for particulate matter (PM) to

control adsorbed semivolatile organic HAPs (see separate discussion on

PM below).

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

\33\ The number of organic HAPs measured at each facility varies

widely with some facilities reporting measurements for a large

number of HAPs while other facilities measuring only a few HAPs.

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

First, given the high toxicity of some dioxin and furan congeners

and the fact that standards ensuring good operating conditions alone

(i.e., temperature at the inlet of the APCD) will not always control

emissions of dioxin/furans

(D/F), the Agency has determined that proposing an emission standard

specifically for D/F is a necessary component to the multi-faceted

approach for toxic organics emissions control. The D/F standard

proposed today is based on TEQ (Toxicity Equivalents).34 TEQ is a

method for assessing the risks associated with exposures to complex

mixtures of chlorinated dibenzo-p-dioxin and dibenzofurans (CDDs and

CDFs). The method relates the toxicity of the 209 structurally related

chemical pollutants to the toxicity of 2,3,7,8-tetrachlorodibenzo-p-

dioxin (2,3,7,8-TCDD).

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

\34\ The TEQ approach used for today's proposal is the I-TEQ/89

approach defined in 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. For a discussion of establishing D/F limits based on TEQ

versus total congeners, see USEPA, ``Combustion Emissions Technical

Resource Document (CETRED),'' May 1994, pp. 4-21.

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

Second, the Agency is proposing to use carbon monoxide (CO) and

hydrocarbons (HC) as surrogates to control emissions of non-D/F organic

HAPs. We note that limiting CO and HC emissions to levels ensuring good

combustion conditions would also help minimize D/F precursors. CO and

HC emissions are both recognized indicators of combustion intensity and

completeness. Low CO flue gas levels are indicative of a combustion

device operating at high combustion efficiency (56 FR at 7149-54).

Operating at high combustion efficiency helps ensure minimum emissions

of unburned (or incompletely burned) organics. However, limiting CO may

not by itself absolutely minimize PIC emissions. This is because PICs

can result from small pockets within the combustion zone where adequate

time, temperature, turbulence, and oxygen have not been provided to

completely oxidize these organics.35 As combustion becomes less

efficient or less complete, at some point, the emissions of total

organics (measured as HC) will increase. A

[[Page 17376]]

portion of the HC emission is comprised of organic HAPs. Thus, CO

levels provide an indication of the potential for organic HAP emissions

and CO limits are therefore proposed as a measure to help prevent these

emissions. HC limits are proposed to document actual emissions of

organic HAPs.36

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\35\ We note that there are emissions data indicating that even

though CO levels are below 100 ppmv, HC emissions can exceed 5 ppmv

(measured as propane with a heated sampling system), the upper HC

level that is generally representative of operating under good

combustion conditions. See 56 FR 7154, note 26 (February 21, 1991),

and Energy and Environmental Research Corporation, ``Surrogate

Evaluation of Thermal Treatment Systems,'' Draft Report dated

October 17, 1994, Figure 2-1.

\36\ We note that virtually all HWCs are already equipped with a

CO monitor because of RCRA requirements. In addition, several

incinerators, cement kilns and lightweight aggregate kilns are also

equipped with a HC monitor because of RCRA or state requirements or

voluntary initiative.

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

Notwithstanding today's proposal to establish MACT standards for

both CO and HC emissions for HWIs and LWAKs (CKs would be required to

comply with either a CO or HC standard for technical reasons discussed

in Section IV below), the Agency invites comment on whether standards

for both CO and HC (coupled with the D/F and PM standards to also

control organic HAPs) are unnecessarily redundant. Commenters should

provide data and information on how either CO or HC alone (but in

conjunction with

D/F and PM standards) would ensure proper control of organic HAPs. In

particular, commenters should address the fact that the Agency's

database indicates that HC levels can exceed good combustion condition

levels when CO levels are below 100 ppmv (thus suggesting that controls

on both CO and HC are needed). In addition, commenters should address

how the MACT standards proposed today for HC would or could ensure that

sources operate under good combustion conditions and thus minimize

emissions of organic HAPs.

If based on review of comments and further analysis the Agency

determines that standards for both CO and HC are not warranted, we

would consider, among other potential options, the following

alternative regulatory approaches: (1) Give each source the option of

complying with either the CO or HC standard (as proposed today for

technical reasons for by-pass duct gas for cement kilns); or (2)

establish a national standard for either CO or HC, but not both (the

Agency would determine which parameter is more appropriate and

establish a standard for that parameter). The Agency invites comment on

these alternative regulatory approaches or others that would ensure

proper control of organic HAP emissions.

3. Hydrochloric Acid (HCl) and Chlorine (Cl2)

Both hydrochloric acid and chlorine are designated HAPs that are

present in HWC emissions. However, the test method used to determine

HCl and Cl2 emissions (BIF methods 0050, 0051, and 9057, commonly

referred to as ``Method 26A'') 37 may not be able to distinguish

between HCl and Cl2 in all situations.38 Therefore, EPA

proposes combining the two HAPs into a single HCl and Cl2

standard. We believe this is appropriate because emissions of both of

these HAPs can be controlled by limiting feedrate of chlorine in

hazardous waste and wet scrubbing.39

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\37\ We note that owners and operators of cement kilns have

argued that this method provides measurements that are biased high

because metallic salts penetrate the filter and the chloride is

incorrectly reported as HCl. EPA has considered this concern and

continues to believe that metallic salts do not significantly bias

the results. Nonetheless, we invite comment on this issue. If, in

fact, metallic salts can bias the results, we invite comment

particularly on how or whether the proposed MACT standards could be

adjusted given the inflated emissions database, and how compliance

with an adjusted standard could be demonstrated.

\38\ In the presence of other halogens (e.g., fluorine and

bromine) that are often constituents of hazardous waste, fossil

fuels or kiln raw materials, EPA is concerned that reactions can

occur in the impinger solutions used by the stack sampling method

that cause a portion of the Cl2 to be reported as HCl. Thus,

the HCl levels could be biased high, and the Cl2 levels could

be biased low. Nonetheless, the method does continue to give an

accurate determination of combined HCl and Cl2 levels in the

presence of other halogens.

\39\ We also note that, for purposes of determining whether the

proposed MACT standard would satisfy RCRA concerns, we evaluated the

level of protection that would be provided assuming (conservatively)

that 10 percent of the HCl/Cl2 standard would be emitted as the

more toxic Cl2.

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4. Particulate Matter (PM)

EPA is proposing to use particulate matter (PM) as a surrogate for

non-D/F organic HAPs (that are adsorbed onto the PM) and for the metal

HAPs which are not specified in the metals standards (i.e., Co, Mn, Ni,

and Se).40 More than 40 semivolatile organic HAPs can be adsorbed

onto PM and can, thus, be controlled by a MACT standard for PM.41

The metal HAPs that are not directly controlled by the MACT standards

for metals can also be controlled (at least partially) by a PM

standard. The low volatility metals are likely to be entrained in

larger particulates and the semivolatile metals are likely to be

condensed onto small particulates.

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\40\ We note that PM 10 is a criteria pollutant under the Clean

Air Act. PM can also have adverse effects on human health even if

toxics are not adsorbed on the PM. Although EPA cannot control PM in

and by itself under Sec. 112(d) (it must be a surrogate for HAP

control), EPA may consider reductions in criteria pollutants in

assessing cost-effectiveness of MACT controls. See S. Rep. No. 228,

101st Congress, 1st Session, p. 172.

\41\ See memo from Larry Gonzalez, EPA, to the docket for this

rule (F-96-RCSP-FFFFF), entitled ``Semi-volatile Organic HAPs that

Can Be Adsorbed onto PM'', dated February 22, 1996.

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The Agency notes that we are proposing to use PM also as a

compliance parameter to ensure compliance with the SVM, LVM, and D/F

standards. As discussed in Part V, Section II, of the preamble, a site-

specific PM operating limit would be established as a surrogate for the

PM control device collection efficiency. Given that we are also

proposing a PM MACT emission standard, the site-specific operating

limit for PM could not exceed the PM standard.

C. Applicability of the Standards Under Special Circumstances

In this section, we discuss the applicability of the proposed MACT

standards under the following circumstances: (1) When a regulated metal

or chlorine is not present in the hazardous waste at detectable levels;

(2) when the source temporarily ceases hazardous waste burning; and (3)

when the source terminates hazardous waste burning.

1. Nondetect Levels of Metals or Chlorine in All Feedstreams

If no feedstreams to a HWC (e.g., on-site incinerator) contain

detectable levels of Hg, SVM, LVM, or chlorine, the source would not be

subject to the emission standard associated with the metal or chlorine

(e.g., if no feedstreams contain detectable levels of chlorine, the

HCl/Cl2 standard would be waived). In addition, performance

testing, monitoring, notification, and recordkeeping requirements

ancillary to the waived standard would also be waived. We believe that

this waiver is appropriate because the source would be incompliance

with the emission standard by default if it was not feeding the metal

or chlorine.

To be eligible for the waiver, the source must develop and

implement a feedstream sampling and analysis plan to document that no

feedstream contains detectable levels of the metal or chlorine (for

which a waiver is claimed).

The Agency invites comment on whether it is necessary to specify

minimum detection levels (or to take other measures) to ensure that

appropriate analytical procedures are used to document levels of metal

or chlorine in feedstreams.

2. Nondetect Levels of Metals or Chlorine in the Hazardous Waste Feed

The proposed MACT standards for mercury, SVM, LVM, or chlorine

would apply even if these constituents are not present at detectable

levels in the

[[Page 17377]]

hazardous waste. This issue is relevant for cement kilns and light-

weight kilns because, if these sources were not burning hazardous

waste, the proposed MACT standards would not apply. Cement kilns (CKs)

that do not burn hazardous waste would be subject to separate MACT

standards that the Agency is developing for those sources, and light-

weight aggregate kilns (LWAKs) that do not burn hazardous waste would

not be subject to any MACT standards.

It could be argued that a CK or LWAK that burns hazardous waste

with nondetect levels of Hg, SVM, LVM, or chlorine is not burning

hazardous waste with respect to that metal or the HCl/Cl2

standard. Accordingly, regulation should revert to any applicable MACT

standard for the source when not burning hazardous waste. The Agency

rejects this argument, however. A source cannot be subject to

regulation under two MACT source categories. Further, such an approach

would be extremely difficult to implement and enforce for CKs given

that compliance procedures would be different for the two source

categories.

3. Sources That Temporarily Cease Burning Hazardous Waste

Sources that temporarily cease burning hazardous waste would remain

subject to today's proposed standards. Similar to the discussion above,

such sources could argue that in the interim when hazardous waste is

not burned, MACT regulation should revert to the MACT standards

applicable to CKs or LWAKs that do not burn hazardous waste.

The Agency rejects this argument as well and for the same reasons

discussed above: a source cannot be intermittently subject to MACT

regulation under two source categories, and implementation and

enforcement would be extremely complicated. See the discussion below

regarding how to define temporary interruptions in waste burning versus

termination of waste burning.

4. Sources That Terminate Hazardous Waste Burning

A source that terminates hazardous waste burning would no longer be

subject to today's proposed rules. A source has terminated hazardous

waste burning when it: (1) ceases burning hazardous waste (i.e.,

hazardous waste is not fed and hazardous waste does not remain in the

combustion chamber); and (2) stops complying with the proposed

standards and begins complying with other applicable MACT standards

(i.e., cement kilns must comply with the MACT standards, when

promulgated, for kilns that do not burn hazardous waste). In addition,

today's rule would require sources that terminate hazardous waste

burning to notify the Administrator in writing within 5 days of the

termination.

Such sources could begin burning hazardous waste again under the

following conditions: (1) The source must comply with the MACT

standards applicable to new sources; (2) the source must submit a

notification of compliance with the standards (based on a comprehensive

performance test); and (3) prior to submitting the notification of

compliance, the source cannot burn hazardous waste for more than a

total of 720 hours, and hazardous waste may be burned only for purposes

of emissions pretesting (i.e., in preparation for the comprehensive

performance test) or comprehensive performance testing.

We are taking this position regarding termination of waste burning

to avoid the implementation and enforcement complications that could

result if a source could claim that it was not subject to the proposed

regulations during those periods of time that it was not burning

hazardous waste. Without these requirements, a source could vacillate

at will between being regulated and unregulated (or for CKs, between

being subject to regulation as a hazardous waste-burning kiln versus a

non-hazardous waste-burning kiln). We invite comment on whether these

requirements are reasonable and appropriate to address the Agency's

implementation and enforcement concerns.

II. Selection of Format for the Proposed Standards

A. Format of the Standard

When EPA regulates a source, it must determine on a case-by-case

basis what format the standards are. This section explains the reasons

why EPA chose the format it did for this specific source category. Due

to differing situations in other cases, other formats may be chosen for

other source categories.

1. Units

EPA investigated four formats for use in expressing today's

proposed standards: mass-based emissions; calculated mass-based

emissions; percent reduction; and concentration-based. The Agency

ultimately selected concentration-based standards for the reasons

discussed below.

The mass-based approach would set a limit of mass emissions per

unit time, i.e., kg/hr, lb/hr, etc. This approach was rejected because

it is inherently incompatible with technology based standards for

several reasons. First, a mass-based standard does not assure good

control at small facilities. Small facilities have lower flow rates,

would be allowed higher concentration of emissions, and thus could meet

a standard with no or minimal technological control. Also, it produces

an undue burden on larger facilities in that they would have to install

controls and small facilities would not. One potential consequence is

that it would cause an incentive for more small facilities, causing an

increase in emissions nationally. For these reasons, this option was

not chosen.

An alternate to the mass-based approach is the calculated mass-

based approach. This would involve EPA determining some appropriately

low level of metals and chlorine feed, multiplying that by a system

removal efficiency factor, and issuing the result as a mass-based

limit. One concern with this approach is EPA does not know what

feedrate would be appropriate. Any feedrate could be construed as

arbitrary. Also, the approach would result in a mass-based limit which

does not address concerns described in the preceding paragraph. It also

does not address how to set the other standards: CO, HC, PM, and

dioxin/furans. For these reasons, this option was not chosen.

A third approach is to set the standards based on a specified

percent reduction. This comports well with a technology-based approach

because it deals directly with determining what technology performs

most efficiently. However, there are problems with this approach.

First, it is difficult to determine where the percent reduction should

be applied: feed to stack, across the APCD train, or across a specific

control device. Use of feed to stack percent reductions present a

difficulty due to the measurement variability of feed samples and stack

emissions. APCD train or device specific percent reductions would be

difficult to implement. Facilities are not configured to sample inlet

emissions to the APCD train or to a specific APCD. Thus, facilities

would have to be reconfigured to allow inlet sampling. Stack sampling

would be required at both the outlet and, possibly, multiple inlet

points. This would significantly increase the testing burden. In

addition, implementation of any approach based on percent reduction

would involve substantial and expensive monitoring of operating

parameters to ensure that the specified percent reduction occurs during

operation. For these reasons, this approach was not chosen.

[[Page 17378]]

The approach that was chosen for these source categories is to set

concentration-based standards. This approach is consistent with how EPA

has historically based air emission standards. It favorably addresses

the problems of the other options. However, it does allow larger

facilities to emit higher mass emissions of HAPs. But mass-based levels

would result in higher emissions nationally by encouraging more smaller

facilities (see previous paragraph). This tradeoff, having higher mass

emissions at larger facilities but lower emissions nationally, was

considered acceptable for this proposal. Concentration based approaches

are also easier to implement and do not necessarily rely on the setting

of operating limits. For this reason, concentration-based standards are

regarded as preferable to the other options, and was chosen on that

basis.

It is possible that other units could be chosen for other source

categories. As explained in the introductory paragraph this is

consistent because other units might be more appropriate for other

source categories.

2. Correction to 7 Percent Oxygen and 20 deg. C

All standards are corrected to 7 percent oxygen and 20 deg. C. This

is because the data EPA used to derive the standards were corrected in

this manner. This is also consistent with the correction used for BIFs,

hazardous waste incinerators, MWCs, and MWIs.

3. Significant Figures and Rounding

All standards proposed here are expressed to two significant

figures.

For the purposes of rounding, we propose to require the use of ASTM

procedure E-29-90 or its successor. This procedure is the American

standard for rounding. Rounding shall be avoided prior to rounding for

the reported result.

B. Averaging Periods

Averaging periods are the time periods over which emissions or

feedstream and operating parameters are set. These periods require

consideration because of the inherent variability associated with the

operation of complying (i.e., properly designed and operated) MACT

devices. As noted above, facilities normally operate within certain

limits but do have emissions above and below these normal levels due to

the natural variability associated with the operation of a facility.

EPA must account for this variability when promulgating technology-

based standards. See, e.g., FMC Corp. v. Train, 538 F.2d 973, 986 (4th

Cir. 1976). If EPA were to establish a ``not-to-be-exceeded'' limit,

that limit would invariably be higher than if the limit were expressed

as an average emission level. That would tend to encourage higher

emitting, but low variability devices since they could meet the not-to-

exceed standard.

For instance, say EPA is considering establishing a standard on: an

instantaneous basis; a one hour average; and a 12-hour average. Also,

assume that the complying MACT facility has average emissions of 5 and

short-term perturbations as high as 300. In this case equally stringent

emissions levels could be: 300 on an instantaneous basis; on the order

of 10 for an hourly average; or closer to 5 for the 12-hour average. If

the limit were established at 300 on an instantaneous basis, this could

significantly favor a facility that has high perturbations less than

300, but average emissions of 250 (assuming the facility with average

emissions of 250 could meet the instantaneous limit, 300, with fewer

controls.) This facility would emit 50 times more of that HAP than a

facility operating at an emission average of 5, but would still comply

with the standard. To address the problem of setting limits on an

instantaneous basis, emissions and feedstream and operating limits are

established on the average with specified averaging periods.

1. Manual Methods

The MACT standards for HWCs (except those for HC and CO) were based

on the average of data from three test runs during which emissions were

measured by manual methods. EPA thus proposes that compliance be based

on the average of three manual methods test runs to be consistent with

data used to establish the standards. Chemical Waste Management v. EPA,

976 F.2d 2, 34 (D.C. Cir. 1992) (Noting that this is an inherently

reasonable approach and is consistent with the standard approach for

compliance under the Part 63 MACT standards.)

The standard could be set in such a way as to require all three

runs to be less than the standard. Such a standard would be derived by

choosing the highest data point from three manual test runs and would

result in an emission level higher than those proposed. The ``not-to-

be-exceeded'' approach was considered problematic for reasons just

described, so averaging was chosen.

Manual methods sample facility exhaust emissions for a period of

time. The minimum length of time required to sample is specified

indirectly by the manual method in the form of collection or gas flow

specifications. The results of the manual method test are reported as

an average over the sampling period. Therefore for manual method test

runs, the averaging period is the sampling period over which the sample

was collected.

EPA proposes no specific averaging period here for manual method

test runs, with one caveat discussed below. Instead EPA proposes to

rely on the minimum sampling volumes or collected sample (whichever the

method requires) specified by the manual methods. EPA invites comment

on whether minimum sampling periods for manual methods should be

specified directly.

EPA is proposing a three hour minimum sampling time for method

0023A. Three hours is also the minimum sampling period stated in method

23 to Part 60, appendix A. EPA is proposing a minimum sampling time in

order to ensure that each D/F run samples long enough to obtain

adequate samples of the various congeners to determine compliance with

the TEQ standard. This issue is important here because there is an

inconsistency between air rules and RCRA rules regarding how to treat

nondetected congeners when calculating the TEQ.

The document which defines the TEQ calculation, ``Interim

Procedures for Estimating Risks Associated with Exposures to Mixtures

of Chlorinated Dibenzo-p-Dioxins (CDDs and CDFs) and 1989 Update''

(EPA/625/3-89/016, March 1989), uses in its examples the assumption

that all non-detects are zero. Also, Method 23 of Part 60 Appendix A,

the method used by air programs for determining total D/F congeners,

similarly states in Section 9, titled Calculations:

Any PCDD's or PCDF's that are reported as nondetected (below the

MDL) shall be counted as zero for the purpose of calculating the

total concentration of PCDD's and PCDF's in the sample.

Therefore, many assume that nondetects are zero for the purposes of

calculating site specific TEQs.

Unfortunately, RCRA programs in most instances use the nondetect

value, not zero, in the calculation of the TEQ. (See BIF method 23

found in Part 266, Appendix IX, section 3.4.) Since this rule would be

promulgated under both RCRA and CAA authority, this issue needs to be

resolved.

The Agency believes a facility will have to measure for 20 minutes

per run using SW-846 method 0023a to obtain enough sample to be useful

for the TEQ calculation. This leads EPA to believe that enough sample

will be collected during a three hour run to assure that

[[Page 17379]]

nondetected congeners are indeed not present. If a source complies with

the minimum sampling period and still has non-detects, then EPA

proposes allowing non-detects to be assumed to be zero.

This would also apply to other methods which have passed the Method

301 validation procedures and EPA has agreed are acceptable. In the

case of other methods, the facility would assume that non-detects are

zero if the method accumulates the same amount or more

This text is long and has been trimmed here. Open the source document for the complete record.