Federal Register, Volume 59 Issue 181 (Tuesday, September 20, 1994)

[Federal Register Volume 59, Number 181 (Tuesday, September 20, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-22343]

[[Page Unknown]]

[Federal Register: September 20, 1994]

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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 60

[AD-FRL-5068-6]

Emission Guidelines: Municipal Waste Combustors

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed guidelines and notice of public hearing.

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SUMMARY: The EPA is proposing new subpart Cb ``emission guidelines'' to
be used by States in developing State regulations to control emissions
from existing municipal waste combustors (MWC's). Today's proposed
guidelines would apply to MWC's for which construction, modification,
or reconstruction began on or before September 20, 1994.
Today's proposal would implement sections 111 and 129 of the Clean
Air Act (Act). The proposed guidelines would apply to existing MWC
units at facilities with capacities to combust greater than 35
megagrams per day (Mg/day; a megagram is a metric ton, and one megagram
is equal to 2,204 pounds or about 1.1 short tons) of municipal solid
waste (MSW) and would require sources to achieve emission levels
reflecting the maximum degree of reduction in emissions of air
pollutants that the Administrator determines is achievable, taking into
consideration the costs, non-air-quality health and environmental
impacts, and energy impacts. The proposed guidelines would establish
emission limits for MWC acid gases (sulfur dioxide (SO2) and
hydrogen chloride (HCl)), MWC metals (particulate matter (PM), opacity,
cadmium (Cd), lead (Pb), and mercury (Hg)), MWC organics (dioxins/
furans), nitrogen oxides (NOX), and MWC fugitive fly ash/bottom
ash emissions. The proposed guidelines would also establish
requirements for MWC operating practices (carbon monoxide (CO), load,
and flue gas temperature), and operator training and certification.

DATES: Comments. Comments must be received on or before November 21,
1994.
Public Hearing. A public hearing will be held about 15 days
following proposal. See SUPPLEMENTARY INFORMATION for additional
information regarding the public hearing.

ADDRESSES: Comments. Comments on the proposal should be submitted (in
duplicate, if possible) to: Air and Radiation Docket and Information
Center (Mail Code 6102), ATTN: Docket No. A-90-45, Room M1500, U.S.
Environmental Protection Agency, 401 M Street, SW, Washington, DC
20460. See SUPPLEMENTARY INFORMATION for additional information
regarding submittal of comments.
Background Information. Key background information for the proposal
includes: (1) A document entitled ``FACT SHEET: Existing Municipal
Waste Combustors--Proposed Subpart Cb Emission Guidelines,'' which
succinctly summarizes the proposal, and (2) several technical documents
listed under SUPPLEMENTARY INFORMATION, including all of the background
information documents that supported the proposal and promulgation of
the subpart Ca emission guidelines. See SUPPLEMENTARY INFORMATION for
instructions for obtaining these documents.
Docket. Docket Nos. A-90-45 and A-89-08, containing supporting
information used in developing the proposed emission guidelines, are
located at the EPA's Air and Radiation Docket and Information Center,
Waterside Mall, Room M1500, Central Mall, 401 M Street, SW, Washington,
DC 20460. The docket may also be accessed by calling (202) 260-7548.
See SUPPLEMENTARY INFORMATION for further information regarding the
docket.

FOR FURTHER INFORMATION CONTACT: Mr. Walter Stevenson at (919) 541-5264
or Mr. Fred Porter at (919) 541-5251, Standards Development Branch,
Emission Standards Division (MD-13), U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina 27711.

SUPPLEMENTARY INFORMATION:

Background Information

On December 20, 1989, the EPA proposed emission guidelines for
existing MWC's in subpart Ca of 40 CFR part 60. The subpart Ca emission
guidelines were promulgated on February 11, 1991 and were developed
under authority of section 111 of the Act of 1977. The Act of 1990
requires the EPA to review and revise, as necessary, the subpart Ca
guidelines. The EPA has reviewed the subpart Ca emission guidelines and
has concluded that they are not adequate to comply with the
requirements of section 129 of the Act of 1990. In a separate notice in
today's Federal Register, the EPA is proposing to withdraw the subpart
Ca emission guidelines that were promulgated on February 11, 1991.
Today's proposed subpart Cb guidelines would fully comply with the
requirements of section 129 of the Act of 1990.
The Federal Register notices for the proposed emission guidelines,
withdrawal of the subpart Ca emission guidelines, and a proposed EPA
test method that is associated with the proposed guidelines, and the
economic impacts analysis associated with the proposed emission
guidelines are listed below and are available on the EPA's Technology
Transfer Network (TTN) electronic bulletin board. Also listed below and
available on the EPA's TTN is a FACT SHEET, which succinctly summarizes
the proposal and is suggested reading for persons requiring a limited
overview of the proposal. The TTN contains 18 electronic bulletin
boards, and the items listed below are included in the Clean Air Act
Amendments (CAAA) bulletin board and the Emissions Measurement
Technical Information Center (EMTIC) bulletin board. The FACT SHEET can
also be obtained by calling Ms. Cassie Posey at (919) 541-0069.

MWC Items in the CAAA Electronic Bulletin Board

(1) ``FACT SHEET: Existing Municipal Waste Combustors--Proposed
Subpart Cb Emission Guidelines.''
(2) Federal Register notice for this proposal: ``Emission
Guidelines: Municipal Waste Combustors'' (this document).
(3) Federal Register notice: ``Withdrawal of the 1991 Emission
Guidelines for Municipal Waste Combustors.''
(4) ``Economic Impact Analysis for Proposed Emission Standards and
Guidelines for Municipal Waste Combustors,'' EPA-450/3-91-029, March
1994.

MWC Items in the EMTIC Electronic Bulletin Board

(1) ``Emissions Test Method 29: Determination of Metals Emissions
from Stationary Sources (1994 Proposal),'' EPA-454/R-94-016, April
1994, (which includes both the Federal Register proposal notice
(chapter 1) and the full text of the rationale and test method for the
proposal (chapter 2)).
The TTN is accessible 24 hours per day, 7 days per week, except
Monday morning from 8 a.m. to 12 p.m., when the system is updated. The
service is free, except for the cost of the phone call. Dial (919) 541-
5742 to access the TTN. The TTN is compatible with up to a 14,400 bits-
per-second (bps) modem. Further instructions for accessing the TTN can
be obtained by calling the help desk at (919) 541-5384.
The background information for today's proposal includes all of the
documents that supported the proposal and promulgation of the subpart
Ca emission guidelines (Docket No. A-89-08), as well as information in
Docket No. A-90-45. Key background information documents used in
developing the subpart Ca emission guidelines as well as today's
proposed guidelines are as follows:
(1) ``Municipal Waste Combustors--Background Information for
Proposed Guidelines for Existing Facilities,'' EPA-450/3-89-27e, August
1989;
(2) ``Municipal Waste Combustors--Background Information for
Proposed Standards: Post-Combustion Technology Performance,'' EPA-450/
3-89-27c, August 1989;
(3) ``Municipal Waste Combustion Assessment: Combustion Control at
Existing Facilities,'' EPA-600/8-89-057, August 1989;
(4) ``Municipal Waste Combustion Assessment, Technical Basis for
Good Combustion Practices,'' EPA-600/8-89-063, August 1989;
(5) ``Municipal Waste Combustors--Background Information for
Proposed Standards: Cost Procedures,'' EPA-450/3-89-27a, August 1989;
and
(6) ``Economic Impact Analysis for Proposed Emissions Standards and
Guidelines for Municipal Waste Combustors,'' EPA-450/3-91-029, March
1994.
Docket Nos. A-90-45 and A-89-08 are available for public inspection
and copying between 8:00 a.m. and 4:00 p.m., Monday through Friday, at
the location specified in the ADDRESSES section of this preamble. A
reasonable fee may be charged for copying. Additionally, the docket may
be accessed by telephone, as specified in the ADDRESSES section.
Comments. Today's action is a proposal and comments are requested.
The MWC regulations are complex, and the EPA expects to receive
numerous comments on this proposal. The EPA has specifically requested
comments on items fundamental to the proposal, including but not
limited to the MACT floor, MACT performance levels, and a consideration
of materials separation requirements for existing MWC's. The EPA seeks
full public participation in arriving at its final decisions, and
strongly encourages comments on all aspects of this proposal from all
interested parties. Whenever applicable, full supporting data and
detailed analyses should be submitted with all comments to allow the
EPA to respond to the comments.
Commenters wishing to submit proprietary information for
consideration should clearly distinguish such information from other
comments, and clearly label it ``Confidential Business Information.''
Submissions containing such proprietary information should be sent
directly to the following address, and not to the public docket, to
ensure that proprietary information is not inadvertently placed in the
docket: Attention: Mr. Walter Stevenson, c/o Ms. Melva Toomer, U.S. EPA
Confidential Business Manager, 411 W. Chapel Hill Street, Room 944,
Durham, North Carolina 27701. Information covered by such a claim of
confidentiality will be disclosed by the EPA only to the extent allowed
and by the procedures set forth in 40 CFR part 2. If no claim of
confidentiality accompanies a submission when it is received by the
EPA, it may be made available to the public without further notice to
the commenter.
Public Hearing. The public hearing will be held to provide
interested parties an opportunity for oral presentation of data, views,
or arguments concerning the proposed guidelines (see DATES for the
hearing schedule). The public hearing will be held at Research Triangle
Park, North Carolina, and will start at about 9 a.m. Persons wishing to
present oral testimony at the public hearing should call Ms. Julia
Latta at (919) 541-5578 at least 2 days in advance of the public
hearing. Persons interested in attending the hearing should also call
Ms. Latta to verify the time, date, and location of the hearing.
Persons may call (919) 541-5264 to hear a recorded message that
provides current information on the status of the public hearing.
Preamble Outline. The following outline is provided to aid in
locating information in this preamble.

I. Introduction
A. Summary of Regulatory History
B. Emission Guidelines--General Goals
C. Overview of this Preamble
II. Summary of the Proposed Subpart Cb MWC Emission Guidelines
A. Source Category to be Regulated
B. Pollutants to be Regulated
C. Format for the Proposed Guidelines
D. Proposed Emission Guidelines
E. Comparison of the 1991 Guidelines and Today's Proposal
F. Performance Testing and Monitoring Requirements
G. Reporting, Recordkeeping, and Compliance Schedule Guidelines
III. Impacts of the Proposed Emission Guidelines
A. Air Impacts
B. Water and Solid Waste Impacts
C. Energy Impacts
D. Cost and Economic Impacts
IV. Rationale for the Proposed Guidelines for MWC Emissions
A. Background
B. Selection of Source Category
C. Modification or Reconstruction of Existing MWC's
D. Selection of Designated Pollutants
E. Selection of Designated Facilities
F. Selection of Maximum Achievable Control Technology
G. Selection of Format for the Proposed Guidelines
H. Performance Test Methods and Monitoring Requirements
I. Reporting, Recordkeeping, and Compliance Schedule
Requirements
V. Rationale for the Proposed Guidelines for Fugitive Fly Ash/Bottom
Ash Emissions
A. Background
B. Fugitive Emission Control Techniques
C. Proposed Fugitive Emissions Guidelines
VI. Proposed Guidelines for Air Curtain Incinerators
VII. Comparison of the Proposal and European Emission Limits
VIII. Miscellaneous
IX. Administrative Requirements
A. Public Hearing
B. Docket
C. Clean Air Act Procedural Requirements
D. Executive Order 12866 Review
E. Regulatory Flexibility Act Compliance

I. Introduction

This section provides an introduction to the proposed rule by: (1)
Summarizing the history of the development of emission guidelines for
existing MWC's over the past 7 years; (2) summarizing the general goals
of the proposed rule that are specified by sections 111(d) and 129 of
the Act of 1990; and (3) providing a brief overview of the major issues
discussed in this preamble.

A. Summary of Regulatory History

Today's proposal is a result of a series of regulatory decisions
that were initiated in 1987. During the early and mid-1980's, studies
were performed to determine whether MWC emissions should be regulated
and, if so, under what section of the Act. As set forth in the advance
notice of proposed rulemaking (52 FR 25399, July 7, 1987), the EPA
decided to regulate air emissions from MWC's under section 111 of the
Act as it existed prior to the 1990 Amendments. Section 111 of the Act
required that the regulations be based on best demonstrated technology
(BDT). On December 20, 1989, the EPA proposed new source performance
standards (NSPS) for new MWC's and emission guidelines for existing
MWC's (54 FR 52251 and 54 FR 52209, respectively). On November 15,
1990, the Act Amendments of 1990 were enacted and added section 129 to
the Act. Section 129 of the Act specifies that revised NSPS and
emission guidelines must be developed for MWC's in accordance with the
requirements of sections 111 and 129. Section 129 further specifies
that revised NSPS and emission guidelines be developed for both large
and small MWC's and that the NSPS and emission guidelines must reflect
certain standards of performance. Section 129 includes a schedule for
revising the 1991 emission guidelines. When the EPA did not comply with
that schedule, the Sierra Club and the Natural Resources Defense
Council (NRDC) filed a complaint with the U.S. District Court for the
Eastern District of New York. The resulting consent decree requires the
EPA Administrator to sign a notice of proposed rulemaking not later
than September 1, 1994 and a notice of promulgation not later than
September 1, 1995 (Nos. CV-92-2093 and CV-93-0284).
The NSPS and guidelines promulgated on February 11, 1991 (56 FR
5488 and 56 FR 5514, respectively) apply to MWC's with unit capacities
above 225 Mg/day and reflect BDT as determined by the Administrator at
the time those guidelines were issued. Today's notice therefore
proposes to create new emission guidelines to be fully consistent with
sections 111 and 129 of the Act and to extend coverage of the
guidelines to existing MWC units located at MWC facilities with
aggregate plant capacity above 35 Mg/day. In a separate notice in
today's Federal Register, the EPA is proposing to withdraw the subpart
Ca emission guidelines that were promulgated on February 11, 1991.
Under a separate regulatory action in today's Federal Register, a
new subpart Eb NSPS for new MWC plants with aggregate capacities above
35 Mg/day of MSW that are constructed after September 20, 1994 is being
proposed pursuant to sections 111(b) and 129 of the Act. Even though a
new subpart Eb NSPS is being proposed, the February 11, 1991 subpart Ea
NSPS will remain in effect. Municipal waste combustors constructed,
modified, or reconstructed after December 20, 1989 but on or before
September 20, 1994 would be subject to both subpart Ea (NSPS)
requirements and today's proposed subpart Cb (guideline) requirements.
In most cases, the control technologies being used to meet the 1991
subpart Ea NSPS emission limits would be able to comply with the
proposed subpart Cb guidelines, except that additional controls would
be required to reduce Hg emissions, dioxin/furan emissions, and
fugitive fly ash/bottom ash emissions.

B. Emission Guidelines--General Goals

The Act requires the promulgation of performance standards under
section 111 for categories of new and existing stationary sources that
may contribute to air pollution that may reasonably be anticipated to
endanger public health or welfare. Section 129 of the Act specifies
that NSPS and emission guidelines must be developed for MWC's in
accordance with the requirements of sections 111 and 129. Section
129(a)(2) provides that emission guidelines for existing MWC's reflect
the maximum degree of reduction in emissions of designated air
pollutants, taking into consideration the cost of achieving such
emission reduction, and any non-air-quality health and environmental
impacts and energy requirements that Administrator determines is
achievable for a particular category of sources (this standard is
commonly referred to as ``maximum achievable control technology, or
``MACT''). Additionally, section 129 provides that the emissions
limitations in the guidelines for existing MWC's may not be less
stringent than the average emissions limitation achieved by the best
performing 12 percent of units in the category. This is referred to as
the ``MACT floor.''
According to sections 111(d) and 129(b), States must submit to the
Administrator, within 1 year of the EPA's promulgation of the
guidelines, a plan that accomplishes the following: (1) Establishes for
existing sources emission standards for designated pollutants; and (2)
provides for implementation and enforcement of the emission standards.
Section 129(b) provides that a State plan for existing MWC's be at
least as protective as the emission guidelines.
As specified in section 129 of the Act, States are required to
submit to the Administrator a plan implementing the emission guidelines
within 1 year after the promulgation of the guidelines. This proposal
further requires that a State plan shall provide that each unit subject
to the guidelines shall be in compliance with all requirements of the
State plan within 3 years following issuance of a revised construction
or operation permit, if a permit modification is required, or within 3
years following approval of the State plan, if a permit modification is
not required. Section 60.24(e)(1) of subpart B of part 60 requires that
any compliance schedule extending more than 1 year from adoption of a
State plan shall include legally enforceable increments of progress to
achieve compliance for each designated facility. The proposed emission
guidelines include this requirement. This proposed compliance schedule
is more comprehensive than the compliance schedule and timetable
specified in the subpart Ca emission guidelines promulgated on February
11, 1991 (56 FR 5514). The Act specifies that the procedure for State
submission of a plan shall be similar to the procedure for submission
of State implementation plans under section 110. Section 129 specifies
that the EPA, in reviewing State plans for any variation from the
emission guidelines, must ensure that State plans and their resulting
MWC control requirements are at least as protective as the EPA
guidelines, including incorporation of the compliance scheduling
requirements established by the guidelines. The Act also provides that
the EPA shall prescribe a plan according to procedures similar to those
in section 110(c) if a State fails to submit a ``satisfactory plan.''
Moreover, States that believe additional control is desirable may
require more extensive controls, which might have the effect of closing
otherwise marginal facilities or banning a particular category of
sources outright.

C. Overview of This Preamble

This preamble will:
(1) Summarize the proposed guidelines by discussing the conclusions
reached with respect to each of the elements in the decision summary;
(2) describe the environmental, energy, and economic impacts of
these proposed guidelines;
(3) present a rationale for each of the decisions associated with
this proposal;
(4) present a regulatory flexibility analysis; and
(5) discuss administrative requirements relevant to this action.

II. Summary of the Proposed Subpart Cb MWC Emission Guidelines

This section presents a summary of the proposed emission
guidelines, including identification of the source category and
pollutants that would be regulated under the proposal, discussion of
the format of the proposed guidelines, and presentation of the proposed
guidelines and their associated performance testing, monitoring,
recordkeeping, and reporting requirements. This section also provides a
comparison of the emission guidelines in this proposed subpart Cb
versus the 1991 emission guidelines (subpart Ca).

A. Source Category To Be Regulated

Today's proposed emission guidelines would require States to
develop emission regulations limiting air emissions from each existing
MWC unit located at an MWC facility that has an aggregate existing
plant capacity to combust over 35 Mg/day of MSW, for which
construction, modification, or reconstruction commenced on or before
September 20, 1994. The proposed guidelines would apply to more than 99
percent of all existing MWC capacity. Additionally, plants with an
aggregate capacity to combust between 25 and 35 Mg/day would be
required to submit an initial report of their location and facility
capacities, but would not be subject to any provisions of the
guidelines.
The aggregate design capacity of all existing MWC's at an MWC plant
would be considered in determining: (1) Whether a plant is subject to
the guidelines; and (2) what control levels are applicable. The
capacity of new MWC's (i.e., those that commenced construction,
modification, or reconstruction after September 20, 1994) that are
located at the MWC plant would not be considered in determining
applicability of the emission guidelines to existing MWC's, but would
be considered in determining the applicability of the subpart Eb NSPS.
Only MWC units constructed, modified, or reconstructed on or before
September 20, 1994 would be used for determining the applicability of
subpart Cb guidelines. Modification of an existing MWC to comply with
the emission guidelines would not bring an existing MWC under the NSPS
for new MWC's.
An MWC is defined as any setting or equipment that combusts MSW.
Municipal waste combustion includes the burning (or pyrolysis) of MSW
in any type of setting or equipment, including combustion equipment
with and without heat recovery. This definition has been slightly
modified from the February 11, 1991 guidelines and is discussed below.
Municipal solid waste is defined as either a mixture or a single-
item stream of household, commercial, and/or institutional discards.
This would include discards such as paper, wood, yard wastes, tree
trimmings, plastics, leather, rubber, glass, metals, and other
combustible and noncombustible materials. The MSW definition includes
household discards as well as discards from institutional and
commercial sources, but does not include industrial process or
manufacturing discards. The MSW definition also includes refuse-derived
fuel (RDF), which is made from MSW that is shredded (or pelletized) and
classified by size before combustion. Municipal solid waste does not,
however, include wastes that are solely segregated medical wastes.
However, if segregated medical wastes are mixed with MSW, the resulting
mixture is considered to be MSW, and the proposed guidelines would
apply if the aggregate plant capacity exceeded 35 Mg/day. Minor editing
is proposed in the definition of MSW to clarify this point.
Air curtain incinerators that combust MSW are MWC's. However, air
curtain incinerators that burn only yard wastes, tree trimmings, and
clean untreated lumber would be covered under a separate set of
proposed opacity emission levels, and no other part of the proposal
would apply. Air curtain incinerator opacity requirements are discussed
in section VI of this preamble.

B. Pollutants To Be Regulated

Section 129 of the Act requires the EPA to establish numerical
emission limits specifically for SO2, HCl, PM, opacity, Cd, Pb,
Hg, dioxins/furans, CO, and NOX. Section 129 specifies that the
EPA may also:

* * * promulgate numerical emission limitations or provide for
the monitoring of post-combustion concentrations of surrogate
substances, parameters, or periods of residence times in excess of
stated temperatures with respect to pollutants other than those
listed [above] * * *.

Therefore, the EPA is proposing guidelines for load and flue gas
temperature at the PM control device inlet as additional indicators of
MWC operating practices. The EPA is also proposing a guideline emission
level for fly ash/bottom ash fugitive emissions because these emissions
include Cd, Pb, Hg, and dioxins/furans (see section V of this preamble
for further discussion of the EPA's decision to regulate fugitive
emissions from MWC's).
The February 11, 1991 guidelines include emission limitations for
all of the pollutants listed above except Cd, Pb, Hg, NOX, and fly
ash/bottom ash fugitive emissions. The proposed guidelines would
establish guidelines for all of the pollutants listed above. The
proposed guidelines for the same pollutants regulated by the February
11, 1991 guidelines (i.e., SO2, HCl, PM, opacity, dioxins/furans,
CO, load, and flue gas temperature at the PM control device inlet) have
been revised to reflect the requirements of section 129.

C. Format for the Proposed Guidelines

The format of the proposed emission guidelines is similar to the
format of the February 11, 1991 guidelines. In most cases, the format
is in the form of an emission level (concentration).
The format of the dioxin/furan guideline would be revised in
today's proposal. In the 1991 guidelines, dioxin/furan emissions were
reported as a concentration (nanograms per dry standard cubic meter
(ng/dscm), corrected to 7 percent oxygen (O2), dry basis) on a
total mass basis (i.e., the mass of all tetra- through octa-congeners
were added together). In today's proposal, dioxin/furan emissions could
be reported in units of either ng/dscm total mass or ng/dscm toxic
equivalency (TEQ). Reporting in TEQ units is done by first measuring
the total mass of dioxin/furan congeners and then adjusting the results
to account for the varying toxicity of each congener. The same test
method (Method 23) is used in either case. See section II.F of this
preamble for further discussion of the proposed method of reporting
dioxin/furan emissions in terms of TEQ.
The February 11, 1991 guidelines specify guideline emission levels
for PM and opacity. Particulate matter is measured as a concentration
(milligrams per dry standard cubic meter (mg/dscm)) and is corrected to
7 percent O2, and opacity is measured on a percentage basis. The
format for the PM and opacity guidelines would not change, but Cd, Pb,
and Hg emission guideline limits would be added. Emissions of Cd, Pb,
and Hg would be calculated as a concentration (mg/dscm) corrected to 7
percent O2. For Hg, the proposed emission guidelines would also
establish an alternative percentage reduction requirement. A new method
(Method 29) that would measure these pollutants is being proposed in a
separate part of today's Federal Register.
The February 11, 1991 guidelines establish control requirements for
SO2 and HCl (MWC acid gases) by specifying both numerical emission
levels, calculated as parts per million by volume (ppmv) corrected to 7
percent O2, dry basis, and percentage reduction requirements for
both SO2 and HCl. Today's proposed guidelines would also be based
on the same format.
Today's proposal would also establish a guideline emission level
(ppmv) for NOX emissions. The NOX guideline emission level
would apply to MWC units at MWC plants with capacities to combust
greater than 225 Mg/day.
In addition to controlling stack emissions, the February 11, 1991
emission guidelines establish combustion operating guidelines for
MWC's. These operating guidelines are part of good combustion practices
(GCP) and ensure that emissions of MWC organics (dioxins/furans) are
minimized on a continuous basis. The GCP requirements are included in
today's proposal, but they are being extended to apply to MWC's at
plants of 35 Mg/day aggregate capacity or larger. Additionally, some
minor revisions are being proposed. The proposed revisions would
include: (1) A requirement that all shift supervisors and chief
facility operators obtain full (as opposed to provisional) operator
certification; (2) ``stand in'' authority for MWC control room
operators; and (3) required training of MWC shift supervisors. These
items are discussed below.
The February 11, 1991 emission guidelines require provisional
certification of the chief facility operator and shift supervisors by
the American Society of Mechanical Engineers (ASME) or a State
certification program. Development of a site-specific training manual
to be used for training other MWC personnel is also required. Today's
proposal would require that the chief facility operator and shift
supervisor obtain both provisional and then full operator
certification.
Today's proposal would allow for the optional certification of one
or more control room operators. Under the February 11, 1991 guidelines,
all chief facility operators and shift supervisors must be certified,
and one of these individuals must be onsite during all periods of MWC
operation. Under today's proposal, a provisionally certified control
room operator may ``stand in'' for the chief facility operator or shift
supervisor during periods in which the certified chief facility
operator or certified shift supervisor is offsite, in order to fulfill
the requirement that a certified individual be on site during all
periods of MWC operation. This would provide additional operating
flexibility. Today's proposal would also require that all chief
facility operators, shift supervisors, and control room operators
complete the MWC training program developed by the EPA or a State
program. The EPA has developed a model training program that has been
distributed to State air pollution control agencies, EPA Regional
Offices, and MWC industry groups. The EPA believes that operator
training is an integral part of the implementation of GCP.
Today's proposed guidelines also establish guidelines for fugitive
fly ash/bottom ash emissions from ash handling facilities. These
guidelines would establish a no visible emissions level, and would
apply to all buildings, external ash transfer equipment, and ash
handling areas at the MWC facility.

D. Proposed Emission Guidelines

Today's proposal would establish emission guidelines for MWC
organics (dioxins/furans), MWC metals (PM, opacity, Cd, Pb, and Hg),
MWC acid gases (SO2 and HCl), and NOX. The guidelines also
propose requirements for fly ash/bottom ash fugitive handling, MWC
operating practices (CO, load, and flue gas temperature), and operator
training and certification.
The proposed guidelines would divide the MWC population into two
subcategories: The first would be for MWC units located at small MWC
plants (i.e., those with aggregate capacities to combust greater than
35 Mg/day of MSW but equal to or less than 225 Mg/day), and the second
would be for MWC units at large plants (i.e., those with aggregate
capacities to combust more than 225 Mg/day of MSW). The aggregate
capacity of all existing MWC units at one site would be added together
to define aggregate MWC plant capacity for the purposes of the emission
guidelines. The proposed emission guidelines for each subcategory and
subclass of MWC's are summarized in table 1.

Table 1.--Summary of Proposed Emission Guidelines for Existing MWC's
[Subpart Cb]^{a
------------------------------------------------------------------------
Plant size (MSW combustion
capacity) Requirement
------------------------------------------------------------------------
Applicability

The proposed guidelines would apply to existing MWC's located at plants
with capacities to combust greater than 25 Mg/day of residential,
commercial, and/or institutional discards.^{b Industrial discards are not
covered by the proposed guidelines.

25 Mg/day.......... Not covered by guidelines.
> 25 Mg/day but 35 Initial report of MWC design
Mg/day. capacity and startup date.
> 35 Mg/day but 225 Subject to provisions listed below.
Mg/day (referred to as small
MWC plants).
> 225 Mg/day (referred to as Subject to provisions listed below.
large MWC plants).
------------------------------------------------------------------------

Good Combustion Practices
Applies to large and small MWC plants.
A site-specific operator training manual would be required to
be developed and made available for MWC personnel. The EPA or a State
MWC operator training course would be required to be completed by the
MWC chief facility operator, shift supervisors, and control room
operators.
The ASME or a State MWC operator certification would be
required to be obtained by the MWC chief facility operator
(mandatory), shift supervisors (mandatory), and control room
operators (optional).
The MWC load level would be required to be measured and not to
exceed the maximum load level as demonstrated during the most recent
dioxin/furan performance test.
The maximum PM control device inlet flue gas temperature would
be required to be measured and not to exceed the level demonstrated
during the most recent dioxin/furan performance test.
The CO level would be required to be measured using a CEMS,
and the concentration in the flue gas would be required not to exceed
the following:
------------------------------------------------------------------------

MWC type CO level^{c Averaging time
Modular starved-air and excess-air...... 50 ppmv 4-hour.
Mass burn waterwall and refractory...... 100 ppmv 4-hour.
Mass burn rotary refractory............. 100 ppmv 24-hour.
Fluidized-bed combustion................ 100 ppmv 4-hour.
Coal/RDF mixed fuel-fired............... 150 ppmv 4-hour.
RDF stokers............................. 200 ppmv 24-hour.
Mass burn rotary waterwall.............. 250 ppmv 24-hour.

MWC Organic Emissions (measured as dioxin/furan)^{c,d

Dioxins/furans (compliance test by EPA Reference Method 23)

Large MWC plants............... 30 ng/dscm total mass or 0.5 ng/
dscm dioxin/furan TEQ.
Small MWC plants............... 60 ng/dscm total mass or 1.0 ng/
dscm dioxin/furan TEQ.
Basis for dioxin/furan guideline

Large MWC plants............... GCP and SD/ESP/CI or GCP and SD/FF/
CI.
Small MWC plants............... GCP and DSI/ESP/CI.

MWC Metal Emissions^{c

PM (compliance test by EPA Reference Method 5)

Large MWC plants............... 27 mg/dscm (0.012 gr/dscf).
Small MWC plants............... 69 mg/dscm (0.030 gr/dscf).
Opacity (compliance test by EPA Reference Method 9)

Large and small MWC plants..... 10 percent (6-minute average).
Cd (compliance test by EPA Reference Method 29)^{e

Large MWC plants............... 0.040 mg/dscm (18 gr/million dscf).
Small MWC plants............... 0.10 mg/dscm (44 gr/million dscf).

Pb (compliance test by EPA Reference Method 29)^{e

Large MWC plants............... 0.50 mg/dscm (200 gr/million dscf).
Small MWC plants............... 1.6 mg/dscm (700 gr/million dscf).
Hg (compliance test by EPA Reference Method 29)^{e

Large and small MWC plants..... 0.080 mg/dscm (35 gr/million dscf)
or 85-percent reduction in Hg
emissions.

Basis for PM, opacity, Cd, Pb, and Hg guidelines

Large and small MWC plants..... See basis for dioxin/furan
guidelines.

MWC Acid Gas Emissions^{c

SO2 (compliance test by CEMS)

Large MWC plants............... 35 ppmv or 75-percent reduction in
SO2 emissions (24-hour).
Small MWC plants............... 80 ppmv or 50-percent reduction in
SO2 emissions (24-hour).

HCl (compliance test by EPA Reference Method 26)

Large MWC plants............... 35 ppmv or 95-percent reduction in
HCl emissions.
Small MWC plants............... 250 ppmv or 50-percent reduction in
HCl emissions.

Basis for SO2 and HCl guidelines

Large and small MWC plants..... See basis for dioxin/furan
guidelines.

Nitrogen Oxides Emissions^{c

NOX (compliance test by CEMS)

Large MWC plants............... 180 ppmv (except mass burn/
refractory MWC's).
Mass burn refractory MWC plants No NOX control requirement.
Small MWC plants............... No NOX control requirement.

Basis for NOX guideline

Large MWC plants............... SNCR.
Mass burn refractory MWC plants No NOX control requirement.
Small MWC plants............... No NOX control requirement.

Fly Ash/Bottom Ash Fugitive Emissions

Fly Ash/Bottom Ash (compliance test by EPA Reference Method 22)

Large and small plants......... No visible emissions from
buildings, ash transfer points, or
ash handling areas.
Basis for fugitive emission Wet ash handling or enclosed ash
guideline. handling.

Compliance Testing/Monitoring Requirements

Load, flue gas Continuous monitoring systems, 4-
temperature. hour arithmetic average.
CO..................... CEMS, 4- or 24-hour arithmetic
average, as applicable.
Dioxins/Furans,^{d PM, Cd, Pb, Hg, and HCl

Large MWC plants............... Annual stack test.
Small MWC plants............... Annual or third year stack test^{f.
Opacity................ COMS (6-minute average) and annual
stack test.
SO2.................... CEMS, 24-hour geometric mean.
NOX (large MWC plants CEMS, 24-hour arithmetic average.
only).
Fly ash/bottom ash Annual test.
fugitive emissions.

Compliance Schedule:

State plans would be required to include one of the following
two schedules for compliance with regulatory requirements: (1) Full
compliance within 1 year following approval of the State plan; or (2)
full compliance within 3 years following issuance of a revised
construction or operation permit, if a permit modification is
required, or within 3 years following approval of the State plan, if
a permit modification is not required, provided the State plan
includes measurable and enforceable incremental steps of progress
toward compliance.
State plans would be required to specify that all MWC's at
large MWC plants for which construction, modification, or
reconstruction is commenced after June 26, 1987 comply with the
emission guidelines for Hg and dioxins/furans within 1 year following
issuance of a revised construction or operation permit, if a permit
modification is required, or within 1 year following approval of the
State plan, if a permit modification is not required.
State plans would be required to require compliance with the
MWC operator training and certification requirements by 1 year after
promulgation of the guidelines.

^{aDefinition of abbreviations used in table:
ASME=American Society of Mechanical Engineers
Cd=cadmium
CEMS=continuous emission monitoring system
CO=carbon monoxide
COMS=continuous opacity monitoring system
DSI/ESP/CI=dry sorbent injection/electrostatic precipitator/activated
carbon injection
GCP=good combustion practices
gr/dscf=grains per dry standard cubic foot
gr/million dscf=grains per million dry standard cubic feet
HCl=hydrogen chloride
Hg=mercury
mg/dscm=milligrams per dry standard cubic meter (100 mg/dscm=0.044 gr/
dscf)
Mg/day=megagrams per day (1 Mg/day=1.1 short tons/day (2,204 pounds/
day))
MSW=municipal solid waste
MWC=municipal waste combustor
ng/dscm=nanograms per dry standard cubic meter (1,000,000 ng=1 mg)
NOX=nitrogen oxides
Pb=lead
PM=particulate matter
ppmv=parts per million by volume
RDF=refuse-derived fuel
SD/ESP/CI=spray dryer/electrostatic precipitator/activated carbon
injection system
SD/FF/CI=spray dryer/fabric filter/activated carbon injection system
SNCR=selective noncatalytic reduction
SO2=sulfur dioxide
TEQ=toxic equivalency of 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (1989
North Atlantic Treaty Organization (NATO) international criteria)
Total mass=total mass of tetra- through octa-chlorinated dibenzo-p-
dioxins and dibenzofurans.

^{bAir curtain incinerators that combust only yard waste, tree trimmings,
and/or clean untreated lumber would be subject to an opacity
guideline, but to no other parts of the proposed emission guidelines.
Air curtain incinerators that combust other MSW are subject to all
requirements under the proposed emission guidelines.
^{cAll concentration levels in the table are converted to 7 percent O2,
dry basis.
^{dDioxins/furans are measured as tetra- through octa-chlorinated dibenzo-
p-dioxins and dibenzofurans. For plants complying with the TEQ format,
TEQ is determined using 1989 international toxicity equivalency
factors.
^{eMethod 29 is being proposed in a separate notice in today's Federal
Register.
^{fThe proposed guidelines include provisions that would allow small MWC
plants to conduct performance tests for dioxin/furans, PM, Cd, Pb, Hg,
and HCl every third year if the MWC meets certain specified criteria,
as discussed in section II.F of this preamble.

The proposed guideline limits are summarized below.

1. Municipal Waste Combustor Organics

The proposed guidelines would require existing MWC's at large MWC
plants to meet a dioxin/furan emission level of 0.50 ng/dscm TEQ or 30
ng/dscm total dioxins/furans, corrected to 7 percent O2. Existing
MWC's located at small MWC plants would be required to meet a dioxin/
furan level of 1.0 ng/dscm TEQ or 60 ng/dscm total dioxins/furans,
corrected to 7 percent O2. The TEQ emission levels would be
calculated using the 1989 North Atlantic Treaty Organization (NATO)
international toxic equivalency factors (TEF's), using the methods
described in section II.F of this preamble and section 60.58b of
subpart Eb of today's proposed NSPS.

2. Municipal Waste Combustor Metals

The proposed emission guidelines would require MWC's at large
plants to control PM to a level of 27 mg/dscm corrected to 7 percent
O2. The emission guideline PM level proposed for MWC's at small
plants is 69 mg/dscm, corrected to 7 percent O2. Municipal waste
combustors at both small and large existing MWC plants would be
required to meet an opacity level of 10 percent using a 6-minute
averaging period.
The proposed emission guidelines would also establish specific
emission levels for Cd, Pb, and Hg. The proposed guidelines would
require existing MWC's at large plants to meet a Cd emission level of
0.040 mg/dscm, a Pb emission level of 0.50 mg/dscm, and an Hg emission
level of 0.080 mg/dscm or an 85-percent reduction in Hg emissions.
For existing MWC's at small plants, the emission guidelines would
be 0.10 mg/dscm for Cd, 1.6 mg/dscm for Pb, and 0.080 mg/dscm or an 85-
percent reduction in Hg emissions.

3. Municipal Waste Combustor Acid Gases

The proposed emission guidelines for acid gases would require all
existing MWC's located at large plants to control SO2 emissions to
a level of either 35 ppmv or 75-percent reduction (at 7 percent
O2, dry basis) on a 24-hour geometric mean basis and HCl emissions
to a level of either 35 ppmv or 95-percent reduction (at 7 percent
O2, dry basis). All existing MWC's located at small plants would
be required to meet an SO2 emission level of either 80 ppmv or 50-
percent reduction (at 7 percent O2, dry basis) on a 24-hour
geometric mean basis and an HCl emission level of either 250 ppmv or
50-percent reduction (at 7 percent O2, dry basis).

4. Good Combustion Practices

Today's proposed emission guidelines would require all existing
MWC's at plants with capacities above 35 Mg/day to comply with
specified operating practices that reflect GCP. These operating
practices include CO levels, combustor load levels, and flue gas
temperatures and are specified below.
The GCP levels remain unchanged from the February 11, 1991
guidelines. For modular starved-air and modular excess-air types of
MWC's, the CO emission limit would be 50 ppmv (at 7 percent O2,
dry basis) on a 4-hour block average basis. For mass burn waterwall,
mass burn fixed-wall refractory, and fluidized-bed types of MWC's, the
CO emission limit would be 100 ppmv (at 7 percent O2, dry basis)
on a 4-hour block average basis. For mass burn rotary refractory MWC's,
the CO emission limit would be 100 ppmv (at 7 percent O2, dry
basis) on a 24-hour block average basis. For mass burn rotary waterwall
MWC's, the CO emission limit would be 250 ppmv (at 7 percent O2,
dry basis) on a 24-hour block average basis. For RDF-stoker MWC's, the
CO limit would be 200 ppmv (at 7 percent O2, dry basis) on a 24-
hour block average basis. For coal/RDF mixed fuel-fired MWC's, the CO
limit would be 150 ppmv (at 7 percent O2, dry basis) on a 4-hour
block average basis.
Municipal waste combustors would be allowed to operate up to 110
percent of the maximum capacity, as achieved during the most recent
dioxin/furan compliance test. Maximum capacity would be based on the
steam flow rate, which would be continuously monitored according to the
ASME Power Test Code (PTC) for Steam Generating Units (PTC4.1 and
PTC19.5). This requirement is unchanged from the February 11, 1991
emission guidelines. The EPA requests comments on this method of
measuring load for steam-generating MWC's. Specifically, the EPA has
questions regarding the requirement for calibration of the measuring
device (e.g., orifice plate) before and after each dioxin/furan
compliance test. The EPA is concerned that this calibration requirement
may be overly burdensome because the main steam line that contains the
orifice plate may need to be cut in order to access the orifice plate
for recalibration. Also, the EPA requests comments on whether the ASME
PTC adequately addresses the need for calibrating the signal from the
flow meter.
Additionally, the EPA requests comments on the use of boiler feed
water flow as an alternative method for continuously monitoring load
for steam-generating MWC's.
Furthermore, the EPA is considering allowing the use of the
continuous flue gas volumetric flow rate to measure maximum capacity
for both steam-generating MWC's, as well as those MWC's that do not
generate steam. These types of monitors are based on ultrasonic,
thermal, or differential pressure methods, and are now being required
as part of the EPA's Acid Rain Program (40 CFR part 75). The EPA
requests comments on whether continuous flue gas volumetric flow rate
monitors are adequately demonstrated and accurate methods for
determining compliance with the load level requirements, and if they
should be allowed as an alternative to the use of the ASME PTC.
Under the guidelines, MWC's would establish a site-specific maximum
flue gas temperature at the final PM control device inlet demonstrated
during their most recent dioxin/furan compliance test. Similar to the
provisions for establishing a maximum load level measurement, the
maximum demonstrated PM control device inlet temperature is established
as the maximum 4-hour block average temperature measured during the
most recent dioxin/furan compliance test. The MWC must then be operated
so that the temperature at the final PM control device inlet does not
exceed this level by more than 17 deg.C (30 deg.F) (4-hour block
average basis).

5. Operator Certification and Training

The proposed emission guidelines would require full certification
of all MWC shift supervisors and MWC chief facility operators by the
ASME or a State program. The proposed guidelines would also require
that at least one of the following persons be on duty at the MWC at all
times during which the MWC is combusting waste: A fully certified MWC
chief facility operator, a fully certified shift supervisor, or a
provisionally certified control room operator. A provisionally
certified control room operator would be allowed to ``stand in'' during
times that a fully certified chief facility operator or shift
supervisor is offsite.
In addition, the proposed emission guidelines would require each
owner or operator of an MWC with an aggregate capacity greater than 35
Mg/day to develop and maintain a site-specific training manual and to
review it with all employees associated with the operation of the MWC
(including MWC maintenance personnel, crane/load operators, and ash
handlers). The manual and training would be updated annually.
Section 129 of the Act of 1990 requires the EPA to develop and
promote a model State program for the training and certification of MWC
operators. Section 129 specifies that ``any person with control over
processes affecting emissions from a unit'' must successfully complete
an acceptable training program. Consistent with section 129, today's
proposed emission guidelines would require all MWC chief facility
operators, shift supervisors, and control room operators at MWC plants
with capacities above 35 Mg/day to complete the MWC operator training
course developed by the EPA or a State program. The EPA has developed a
model training program and has distributed it to State air pollution
control agencies, EPA regional offices, and MWC industry groups. This
model training program could be used to fulfill this requirement and
prepare for the ASME certification.

6. Nitrogen Oxides Emissions

The proposed emission guidelines would require MWC's at large
plants, except refractory MWC's, to control NOX emissions to a
level of 180 ppmv (corrected to 7 percent O2, dry basis, on a 24-
hour daily average basis). A ``no control'' NOX emission guideline
level for MWC's at small plants and refractory MWC's at large plants is
proposed and discussed in section VIII of this preamble.

7. Fly Ash or Bottom Ash Fugitive Emissions

The proposed guidelines for fly ash/bottom ash fugitive dust
emissions would establish a guideline of no visible emissions for fly
ash or bottom ash emissions from an MWC facility.
The visible emissions guidelines would apply to buildings and
external ash handling or transfer activities (e.g., loading), and any
other area at the designated facility that is a potential source of fly
ash or bottom ash fugitive emissions.

E. Comparison of the 1991 Guidelines and Today's Proposal

The subpart Ca emission guidelines promulgated on February 11, 1991
and today's proposed subpart Cb emission guidelines both contain
guideline emission levels for dioxins/furans, PM, SO2, and HCl at
large MWC's; however, today's proposed guidelines for most of these
pollutants are more stringent than the guidelines promulgated on
February 11, 1991. The February 11, 1991 guidelines did not address Cd,
Pb, Hg, NOX, or fly ash/bottom ash fugitive emissions, but each of
these is included in today's proposal. Also, today's proposal covers
all MWC units at plants with aggregate capacities above 35 Mg/day,
whereas the February 11, 1991 guidelines only covered MWC units with
unit capacities above 225 Mg/day. A comparison of the 1991 guidelines
and proposed guideline emission levels is provided in table 2.

Table 2.--Comparison of The Proposed Guidelines (Subpart Cb) and The 1991 Guidelines (Subpart Ca)
----------------------------------------------------------------------------------------------------------------
Guideline emission level^{a
----------------------------------------------------------------------------------------
Proposed subpart Cb 1991 guidelines (subpart Ca)
Pollutant guidelines^{b ----------------------------------------------------------
------------------------------ MWC's > 225 Mg/day but <
MWC plants > 225 Mg/day^{c 1000 Mg/day^{c MWC's > 1000 Mg/day^{c
----------------------------------------------------------------------------------------------------------------
Dioxins/furans......... 0.5 ng/dscm toxic 125 ng/dscm, total mass 60 ng/dscm, total mass
equivalence or 30 ng/dscm (equivalent to 2.0 ng/dscm (equivalent to 1.0 ng/dscm
total mass. toxic equivalence). toxic equivalence).
SO2.................... 35 ppmv or 75-percent 30 ppmv or 50-percent 30 ppmv or 70-percent
reduction^{d. reduction^{d. reduction^{d.
HCl.................... 35 ppmv or 95-percent 25 ppmv or 50-percent 25 ppmv or 90-percent
reduction^{d. reduction^{d. reduction^{d.
PM..................... 27 mg/dscm.................. 69 mg/dscm.................. 34 mg/dscm.
Opacity................ 10 percent.................. 10 percent.................. 10 percent.
Cd..................... 0.040 mg/dscm............... None........................ None.
Pb..................... 0.50 mg/dscm................ None........................ None.
Hg..................... 0.080 mg/dscm (or 85-percent None........................ None.
reduction)^{d.
NOX.................... 180 ppmv.................... None........................ None.
Fly ash/bottom ash No visible emissions from None........................ None.
fugitive emissions. buildings, ash transfer
points, or ash handling
areas.
----------------------------------------------------------------------------------------------------------------
^{a All emission levels are corrected to 7 percent O2, dry basis.
^{b Separate guideline levels are also proposed for MWC plants with aggregate plant capacities between 35 and 225
Mg/day.
^{c The February 11, 1991 guidelines were based on MWC unit capacity, and today's proposed guidelines are based on
aggregate plant capacity.
^{d Whichever is less stringent.

The MWC operating guidelines (GCP) included in today's proposal are
the same as those in the February 11, 1991 guidelines. The training and
certification requirements have changed somewhat. The February 11, 1991
guidelines required only provisional certification of MWC chief
facility operators and shift supervisors, but today's proposed
guidelines would require both provisional and then full certification.
This change is being proposed because the full operator certification
program is now widely available. In 1991, the program was not widely
available.
Today's proposal also adds a provision to allow provisionally
certified MWC control room operators to stand in for the MWC chief
facility operators or shift supervisors in their temporary absence from
the MWC. Additionally, today's proposal would require all MWC chief
facility operators, shift supervisors, and control room operators to
complete the EPA or a State MWC training course. This training course
requirement was not included in the February 11, 1991 guidelines.

F. Performance Testing and Monitoring Requirements

Information related to the performance testing and monitoring
requirements for MWC acid gases (SO2 and HCl), MWC organics
(dioxins/furans), PM, and MWC operating practices was published in the
February 11 and 13, 1991 Federal Register notices (56 FR 5514 and 56 FR
5758). These same requirements would be adopted by today's proposed
guidelines and would be extended to apply to all MWC's at plants with
aggregate capacities above 35 Mg/day. Because the proposed guidelines
allow compliance with either a dioxin/furan limit in terms of TEQ or a
dioxin/furan limit on a total mass basis, procedures are being proposed
for determining dioxin/furan emissions on a TEQ basis. The mass of each
tetra- through octa- chlorinated dibenzo-p-dioxin and dibenzofuran
congener would be measured by EPA Reference Method 23. Each congener
mass would then be adjusted by the corresponding toxic equivalency
factor (TEF; the 1989 NATO international TEF's). Finally, the adjusted
congener masses would be added together to determine dioxins/furans in
ng/dscm TEQ. Furthermore, today's proposal would require both large and
small MWC facilities to conduct annual opacity tests using EPA
Reference Method 9. This testing would be in addition to the continuous
monitoring of opacity levels. Also, today's proposal allows small MWC
facilities to conduct less frequent testing for dioxin/furan, HCl, and
PM emissions if the small facility consistently demonstrates
compliance. More specifically, under today's proposed emission
guidelines, if three consecutive annual compliance tests for an MWC at
a small MWC plant indicate compliance with the emission guideline for a
pollutant (i.e., PM, HCl, or dioxins/furans), the MWC would be allowed
to wait 3 years before retesting for the pollutant. If the next test
conducted in the third year shows compliance with the emission
guideline for that pollutant, then the facility could again wait 3
years to test for the pollutant. If noncompliance with the emission
guideline for the pollutant occurs, corrective actions would be
required to be undertaken and annual testing would be required to be
conducted until 3 consecutive years of compliance with the emission
guideline is established. At a minimum, performance tests for dioxins/
furans, HCl, and PM would be required to be performed for each MWC at a
small MWC plant every 3 years. This provision is included to minimize
costs for small MWC plants, while still retaining periodic testing to
ensure compliance. All large MWC plants would continue to be required
to conduct annual compliance tests.
Annual performance tests to determine compliance with the Cd, Pb,
and Hg emission guidelines would be based on EPA Reference Method 29.
The average emission rates of three or more test runs using this
methodology would be used to determine compliance. The EPA considered
the use of EPA Reference Method 101A for Hg testing; however, based on
available data, the EPA has concluded that Method 29 is a better
measure of Cd, Pb, and Hg emissions than Method 101A and has therefore
proposed Method 29 for testing MWC's. Also, as discussed above for
dioxins/furans, PM, and HCl, if small plants demonstrate compliance
with the Cd, Pb, and Hg emission guidelines for 3 consecutive years,
they would be allowed to begin testing for these three pollutants every
third year.
The EPA Reference Method 29 is proposed in a separate part of
today's Federal Register. Method 29 is very similar to the method that
has been used by the EPA's Office of Solid Waste to measure metal
emissions from boilers cofiring hazardous waste, commonly referred to
as the EPA multimetals method. The proposed Method 29 is discussed in
section IV.H of this preamble.
The proposed emission guidelines for NOX would require
continuous monitoring of NOX emissions for MWC's at large plants,
except refractory units for which a ``no control'' emission guideline
is proposed. Compliance with the NOX emission guideline level for
nonrefractory MWC's at large plants would be determined by calculating
the arithmetic average of the hourly emission rates, as measured by the
continuous emission monitoring system (CEMS), for a 24-hour period that
the MWC operates, using EPA Reference Method 19. Quality assurance
would be maintained in accordance with appendix F of 40 CFR part 60.
Annual performance tests to determine compliance with proposed fly
ash/bottom ash visible emissions guidelines would be based on EPA
Reference Method 22 (3-hour continuous visual observation). The limits
would apply at all times, and tests would be conducted during periods
of time when fly ash/bottom ash is transferred from the combustor or
from the air pollution control device to the ash loading area, and when
ash is loaded for transportation or is being transported onsite.
The data availability requirement for CEMS (SO2, NOX, CO,
and O2 (or CO2)) has been changed from the 1991 NSPS.
Today's proposal would require that valid paired CEMS hourly
averages (i.e., SO2 and O2 (or CO2), NOX and
O2 (or CO2), and CO and O2 (or CO2)) be obtained
for 75 percent of the hours per day for 90 percent of the days per
calendar quarter that the designated facility is operated and
combusting MSW.

G. Reporting, Recordkeeping, and Compliance Schedule Guidelines

The MWC emission guidelines promulgated on February 11, 1991 for
MWC's with unit capacities above 225 Mg/day established reporting and
recordkeeping requirements for MWC organics (dioxins/furans), MWC
metals (PM and opacity), MWC acid gases (SO2 and HCl), and
operating practices (CO, load, flue gas temperature, and operator
training/certification). These reporting and recordkeeping requirements
are discussed in the February 11, 1991 Federal Register notice (56 FR
5514). These same reporting and recordkeeping requirements would be
adopted under the proposed guidelines, except that dioxin/furan
emissions would be recorded and reported on either a total mass basis
or a TEQ basis. Furthermore, if small MWC's meet the criteria in
today's proposal allowing them to conduct performance tests for
dioxins/furans, HCl, and PM every third year, they would submit a
simplified annual report for years in which a full compliance test was
not required.
Today's proposal also would add reporting and recordkeeping
requirements for Cd, Pb, Hg, and NOX. The proposed emission
guidelines would require that initial and annual compliance reports be
submitted for Cd, Pb, and Hg for MWC's at plants with capacities above
35 Mg/day. If small MWC's meet the criteria allowing them to conduct
performance tests for Cd, Pb, or Hg every third year, they would be
allowed to submit a simplified annual report for years when a full
compliance test was not required. The proposed guidelines would also
require that the amount of activated carbon injected for Hg control at
small and large plants be recorded during MWC operation.
The NSPS for MWC's promulgated on February 11, 1991 (56 FR 5488)
establishes reporting and recordkeeping requirements for NOX for
new MWC's; however, no NOX requirements were established for
existing MWC's. These NSPS reporting and recordkeeping requirements
would now apply to MWC's only at large plants under today's proposed
emission guidelines. Submittal of initial and quarterly reports for all
CEMS data and accuracy determinations for NOX emissions would be
required. Quality assurance would be required in accordance with
appendix F in 40 CFR part 60.
Initial and annual compliance reports for fly ash/bottom ash
visible emissions testing would be required under today's proposal for
both small and large plants.
The proposed emission guidelines include revised compliance
scheduling requirements. The proposed guidelines require State plans to
require both small and large MWC plants to meet one of the following
two compliance schedules: (1) Full compliance with the State plan
within 1 year after approval of the State plan, or (2) full compliance
with the State plan within 3 years following issuance of a revised
construction or operation permit, if a permit modification is required,
or within 3 years following approval of the State plan, if a permit
modification is not required, provided the State plan includes
measurable and enforceable incremental steps of progress toward
compliance with the State plan (see section IV.I of this preamble for
further discussion of this requirement).
The proposed emission guidelines also include an accelerated
compliance schedule for compliance with the proposed dioxin/furan and
Hg emission limits for certain MWC's. Under the accelerated schedule,
MWC units for which construction commenced after June 26, 1987 and that
are located at large MWC plants would be required to be in compliance
with the proposed dioxin/furan and Hg emission guidelines within 1 year
following issuance of a revised construction or operation permit, if a
permit modification is required, or within 1 year following approval of
the State plan, if a permit modification is not required (these units
are already equipped with acid gas/PM control systems). The rationale
for requiring this accelerated schedule is provided in section IV.I of
this preamble.
Additionally, the proposal requires compliance with both the
operator training and certification requirements by 1 year after the
date of promulgation of the emission guidelines.
Records of all data, including results of emission tests and
compliance reports would be maintained for 5 years following the date
of submission of the data.

III. Impacts of the Proposed Emission Guidelines

This section describes the impacts (i.e., air, water, solid waste,
energy, control cost, and economic impacts) of the proposed emission
guidelines for small and large MWC facilities. The impacts are
summarized in table 3. Table 3 presents: (1) The impact of these
proposed subpart Cb guidelines over a pre-1989 baseline (i.e., baseline
prior to the effective date of the subpart Ca guidelines); and (2) the
incremental impact of these proposed subpart Cb guidelines over the
subpart Ca guidelines. The following discussion focuses only on the
impacts of today's proposal based on a pre-1989 baseline, since the
emission guidelines promulgated in 1991 have not been implemented. For
further information on the impacts of the proposed emission guidelines,
refer to the document entitled ``Economic Impact Analysis for Proposed
Emission Standards and Guidelines for Municipal Waste Combustors'' that
is included in the list of items under Supplementary Information at the
beginning of this preamble.

Table 3.--Impacts of the 1991 Subpart Ca and Proposed Subpart Cb
Guidelines
------------------------------------------------------------------------
Increment
of proposed
Proposed 1994
1991 1994 subpart Cb
Parameter subpart Ca subpart Cb guidelines
guidelines^{a guidelines^{a over the
1991
subpart Ca
guidelines^{b
------------------------------------------------------------------------
Characteristics of Existing
MWC's:
Combustion capacity (10^{6 Mg/yr) 35.9 39.0 3.1
Number of MWC plants........... 158 179 21
Cost (1990 Dollars):
Capital cost ($10^{6)............ 888 2,100 1,212
Annualized cost ($10^{6/yr)...... 168 445 277
Average cost increase ($/Mg MSW
combusted).................... 6.40 13.60 7.20
Annual Emissions Reduction (Mg/
yr):
SO2............................ 25,000 43,000 18,000
HCl............................ 36,000 56,000 20,000
PM............................. 1,100 3,100 2,000
Cd............................. 2 5 3
Pb............................. 30 83 53
Hg............................. 11 47 36
NOX............................ 0 19,000 19,000
Total dioxins/furans (kg/yr)^{c.. 117 157 40
Dioxin/furan TEQ (g/yr)^{d....... 1,950 2,620 670
------------------------------------------------------------------------
^{a The impacts are based on a pre-1989 baseline (i.e., a baseline prior
to the effective date of the subpart Ca guidelines).
^{b The impacts are calculated by subtracting the impacts of the 1991
subpart Ca guidelines from the impacts of the proposed 1994 subpart Cb
guidelines (based on a pre-1989 baseline).
^{c kg/yr = kilograms per year.
^{d g/yr = grams per year.

A. Air Impacts

The air emission reductions discussed below, as well as all other
impacts discussed in today's proposal, are nationwide impacts that
would result from full implementation of the guidelines and are
relative to the current baseline MWC population, considering in-place
air pollution control devices. These are not incremental impacts
relative to the February 11, 1991 emission guidelines. The total
impacts are presented because the February 11, 1991 guidelines have not
been implemented and are being significantly altered by today's
proposal.
Under today's proposed emission guidelines, nationwide emissions of
total dioxins/furans would be reduced by about 157 kilograms per year
(kg/yr) compared with emissions in the absence of nationwide
guidelines. Emissions of dioxins/furans on a TEQ basis would be reduced
by about 2,620 grams per year (g/yr). This represents a nationwide
reduction of about 99 percent compared to baseline levels in the
absence of the guidelines. Remaining nationwide dioxin/furan emissions
would be about 42 g/yr TEQ.
Nationwide emissions of PM would be decreased by about 3,100
megagrams per year (Mg/yr) compared with levels in the absence of
emission guidelines. This represents a reduction of just under 50
percent compared to baseline levels in the absence of nationwide
guidelines. In combination with baseline control, this would represent
greater than 99-percent PM control. Emissions of Cd would be reduced by
about 6 Mg/yr, Pb would be reduced by about 91 Mg/yr, and Hg would be
reduced by about 48 Mg/yr. These emission reductions represent
decreases of about 70 to 80 percent for each of these three metals. In
combination with baseline control, this would represent greater than
99-percent control for Cd and Pb and greater than 80-percent control
for Hg.
Nationwide emissions of SO2 and HCl would be decreased by
43,000 Mg/yr and 56,000 Mg/yr, respectively, relative to current
baseline levels. This represents about 87-percent control of acid gases
compared to baseline levels in the absence of emission guidelines. In
combination with baseline control, this would represent about 95-
percent control of these acid gases.
The proposed emission guidelines would reduce nationwide emissions
of NOX by 19,000 Mg/yr, representing an overall nationwide
emission reduction of over 30 percent compared to baseline levels that
would be emitted without the proposed guidelines.

B. Water and Solid Waste Impacts

Water and solid waste impacts that would result from today's
proposal were determined not to be significant. No water pollution
impacts are projected because the control technologies considered would
not produce a wastewater stream.
The EPA believes that MWC ash disposal is adequately addressed by
current waste management standards, so that considerations of ash
quality need not play a role in this rulemaking.

C. Energy Impacts

The energy impacts of applying add-on pollutant emission controls
required as part of today's proposal would not result in significant
energy impacts. Today's proposal for MWC acid gases, MWC organics, MWC
metals, and NOX would affect an estimated 179 MWC plants and would
result in energy requirements of 400 to 500 gigawatt-hours per year
(GW-hr/yr) of electricity to operate the air pollution control devices,
and about 780 terajoules per year (TJ/yr) of natural gas to maintain
combustor operating conditions that reflect GCP.
Most of the MWC's that would be affected by the proposed guidelines
generate electricity for sale. For example, a large mass burn/waterwall
MWC plant would generate about 500 GW-hr/yr of electricity. The energy
to operate its air pollution control equipment would represent only
about 4 percent of generation. Additionally, natural gas that is fired
for GCP requirements represents less than 0.2 percent of the annual
heat input to MWC's. Considering that a large percentage of new power
plant capacity to be constructed in the next 10 years will fire natural
gas, the firing of small amounts of natural gas for GCP (while
generating electricity) actually reallocates natural gas use rather
than just increasing consumption.

D. Cost and Economic Impacts

1. National Overview

The EPA projects that about 33 million Mg of MSW will be combusted
in the year 2000 in existing MWC plants subject to the guidelines being
proposed today. The EPA estimates that there would be 179 existing MWC
plants in operation that would be subject to the subpart Cb guidelines:
60 in the 35- to 225-Mg/day capacity range and 119 in the larger than
225-Mg/day capacity range. The typical plant has two or three MWC
units.
The cost estimates given below are in 1990 dollars and are for
emission control and compliance testing. The estimates do not include
costs for such things as permitting and enforcement. To estimate the
costs of the guidelines being proposed today, the EPA has taken into
account all existing control equipment. Cost estimates are incremental
over costs associated with the control equipment in current use and
include retrofit premiums. Cost estimates are total costs for the
revised MWC guidelines and are not incremental to the February 11, 1991
guidelines.
The nationwide annual cost of the guidelines including testing,
reporting, and recordkeeping for acid gas, PM, Hg, and NOX control
would be about $445 million. The national average annual cost of the
guidelines per unit of MSW combusted would be about $14/Mg.
The above costs for the guidelines are overall national costs
spread over the entire existing MWC population. However, about one half
of the affected waste flow from existing MWC's larger than 225 Mg/day
already is combusted in facilities equipped with spray dryer/
electrostatic precipitator (SD/ESP) or spray dryer/fabric filter (SD/
FF) systems, and these MWC's would incur only a minor compliance cost
(about $3/Mg) as a result of the proposed guidelines. The average
annual cost of acid gas, PM, and Hg control per unit of MSW combusted
at large plants that do not already have SD/ESP or SD/FF systems would
be about $20/Mg.
The average annual cost per unit of MSW combusted at small plants
using dry sorbent injection/electrostatic precipitator (DSI/ESP)
systems and Hg control would be about $36/Mg.
The guidelines will have a wide range of impacts on the price of
combustion services. To study these potential impacts, the EPA first
applied a cost accounting procedure that approximates the one that
would be used by an individual publicly owned MWC. Then, using a 1993
average tipping fee of $57/Mg of MSW combusted (1990 dollars) of waste
combusted and assuming the full cost of meeting acid gas, PM, Hg, and
NOX requirements is passed directly to MWC customers, the EPA
found that the lowest and highest tipping fee increases for the model
plants used in the EPA's economic analysis would be $9 and $56,
respectively, per megagram of MSW combusted. The majority of tipping
fee increases would be in the $17 to $28/Mg range. (These estimates
apply only to MWC's at small plants that do not already have DSI/ESP,
SD/ESP, or SD/FF systems or large plants that do not currently have SD/
ESP or SD/FF systems.)
The EPA projects that, regardless of how the regulatory costs are
financed, most of the burden will find its way directly or indirectly
to households served by MWC's. Costs that are directly assessed to
households are likely to be in the form of increased collection fees
and/or increased taxes. Indirect household costs are price increases
charged by businesses that similarly are faced with increases in
collection fees and/or taxes. For the guidelines being proposed today,
the EPA projects an increase in the average annual household cost of
waste disposal of about $25 for communities that have MWC's. The actual
cost per household will depend on local conditions, including the
extent to which recycling and landfilling are also used within the
affected community. Approximately 62 percent of the total average
household cost is a direct cost, thus the annual direct household cost
would be approximately $15. The EPA estimates that the average annual
household cost breaks down to $26 per year for communities over 250,000
in population; $24 for communities with populations between 100,000 and
250,000; $24 for communities with populations between 50,000 and
100,000; and $22 for communities with populations under 50,000. This
range represents less than 1 percent of household income. The actual
cost per household will depend on local conditions.
The EPA identified 39 private firms each of which owns one or more
MWC's. Detailed financial data are published for only 17 of the firms
projected to incur costs, none of which is small (under $6 million in
annual sales). (Firms for which annual sales data are not available are
assumed to be small.) The total annual cost of the guidelines as a
percentage of sales averages less than 1 percent and ranges from less
than 1 percent to about 80 percent for these 17 firms. Potential
tipping fee increases, based on an assumed full cost pass-through
(i.e., passing all control costs to consumers via the tipping fee) and
an average tipping fee of $57/Mg, are about 18 percent for MWC's owned
by small firms and about 14 percent for MWC's owned by large firms.
Some of the benefits of the emission guidelines have been
quantified. The absence of sufficient exposure-response and valuation
information precludes a comprehensive benefits analysis for many of the
MWC pollutants. The EPA expects partial benefits for reduction of PM
and SO2, including benefits from reductions in morbidity and
mortality, to total about $106 million annually. The total benefits
would be higher if benefits from reductions of other pollutants were
valuated. In addition, recent evidence suggests the mortality reduction
benefits of particulate mater controls may be higher than is assumed in
this analysis.

2. Control Costs for Typical MWC Plants

The previous section presented costs of the proposal on a national
basis. This section presents examples of typical retrofit costs that
would be experienced at both a large MWC plant and a small MWC plant.
These are typical costs. Lower costs will be experienced at MWC plants
that have already installed the air pollution control components
required by the proposal. Higher costs will be experienced for MWC
plants with more difficult retrofit applications.
The costing data presented in this section are provided in the
following formats: capital cost, annualized cost, and cost per Mg of
municipal waste combusted. The costing information is subcategorized by
air pollution control components (i.e., GCP upgrade, acid gas scrubber,
activated carbon injection application, and NOX control). For
perspective, the estimated cost of combustion units is also displayed.
Since the actual MWC unit cost for an existing combustion unit is
sensitive to past funding practices, the EPA could not provide this
cost. Instead, the EPA has provided the cost of combustion units for a
new MWC plant for reference. This costing information has been derived
from 1989 background information documents that were used in developing
the 1991 NSPS and emission guidelines (see SUPPLEMENTARY INFORMATION
for more information about these documents), and is presented in 1987
dollars (the escalation factor for converting to mid-1990 dollars is
1.111).
From table 3A, it can be noted that the capital cost for retrofit
at a large existing MWC plant (980 Mg/day capacity) would be about
$16.8 million of which $13.6 million would be for the acid gas control,
2.9 million for NOX control, and less than one million for
activated carbon injection and GCP. On an annualized basis, the cost
would be about $5.1 million/yr or about $16/Mg of waste combusted. This
would increase baseline combustor cost from about $60/Mg combusted
(based on the baseline combustor cost for a new large MWC plant
presented in table 3B) to about $76/Mg combusted. Large MWC plants
represent about 94 percent of the existing MWC combustion capacity.

Table 3A.--Capital and Annualized Costs of Air Pollution Control for Typical Existing Large and Small MWC
Plants^{a
----------------------------------------------------------------------------------------------------------------
Air pollution control device cost^{a
Baseline ------------------------------------------------ Total
Parameter combustor GCP^{b Acid gas/ Total APCD combustor and
PM CI^{c NOX cost^{d APCD cost
----------------------------------------------------------------------------------------------------------------
Existing large MWC
plant (980 Mg/day MB/
WW retrofitted with
GCP, SD/ESP, CI, and
SNCR)^{e,f,g,h:
Capital cost NA^{i 0.086 13.6 0.279 2.9 16.8 NA
($10\6\).
Annualized cost NA 0.148 3.8 0.498 0.844 5.14 NA
($10\6\/yr).
Average cost NA 0.45 11.7 1.52 2.53 15.7 NA
increase ($/Mg
MSW combusted).
Existing small MWC
plant (135 Mg/day MOD/
SA retrofitted with
GCP, DSI/ESP and
CI)^{j,k,l:
Capital cost NA 0.27 2.5 0.055 0 2.55 NA
($10\6\).
Annualized cost NA 0.182 0.726 0.041 0 0.77 NA
($10\6\/yr).
Average cost NA 4.01 16.0 0.90 0 16.9 NA
increase ($/Mg
MSW combusted).
----------------------------------------------------------------------------------------------------------------
^{aThe costs presented are in 1987 dollars. To calculate mid-1990 dollars, multiply 1987 dollars by a factor of
1.111. Total cost values may not add due to rounding.
^{bGCP = good combustion practices.
^{cCI = activated carbon injection.
^{dAPCD = air pollution control device.
^{eMB/WW = mass burn waterwall combustor.
^{fSNCR = selective noncatalytic reduction.
^{gSD/ESP = spray dryer and electrostatic precipitator.
^{hThe costs presented are based on the assumption that an existing ESP was upgraded and retrofitted with a spray
dryer system.
^{iNA = not available. Because the capital cost of the existing combustor was not available, the total costs could
not be calculated. Refer to the baseline combustor cost in table 3B for new facilities, which is similar to
the cost for existing facilities.
^{jMOD/SA = modular starved-air combustor.
^{kDSI/ESP = dry sorbent injection and electrostatic precipitator.
^{lThe costs presented are based on the assumption that an existing ESP was upgraded and retrofitted with a dry
sorbent injection system.

Table 3B.--Capital and Annualized Costs of Air Pollution Control for Typical New Large and Small MWC Plants^{a
----------------------------------------------------------------------------------------------------------------
Air pollution control device cost^{a Total
Baseline ------------------------------------------------ combustor
Parameter combustor GCP^{b Acid gas/ Total APCD and APCD
PM CI^{c NOX cost^{d cost
----------------------------------------------------------------------------------------------------------------
New large MWC plant (730 Mg/
day MB/WW with SD/FF, CI,
and SNCR)^{e,f,g:
Capital cost ($10^{6)...... 50 0 12 0.150 2.0 14.2 64.2
Percent of total capital
cost (%)^{h............... 78 0 19 0.2 3 22 100
Annualized cost ($10^{6/yr) 14.4 0 3.56 0.091 0.582 4.23 18.6
Average cost increase ($/
Mg MSW combusted)....... 59.5 0 14.8 0.37 2.39 17.5 77.05
New small MWC plant (90 Mg/
day MOD/SA with SD/FF and
CI)^{i:
Capital cost ($10^{6)...... 5.5 0 3.1 0.043 0 3.14 8.64
Percent of total capital
cost (%)^{h............... 64 0 36 0.5 0 36 100
Annualized cost ($10^{6/yr) 1.83 0 0.91 0.014 0 0.92 2.76
Average cost increase ($/
Mg MSW combusted)....... 60.5 0 30.2 0.46 0 30.7 91.2
----------------------------------------------------------------------------------------------------------------
A^{aThe costs presented are in 1987 dollars. To calculate mid-1990 dollars, multiply 1987 dollars by a factor of
1.111. Total cost values may not add due to rounding.
A^{bGCP = good combustion practices. Costs for GCP are included in combustor design (no cost).
A^{cCI = activated carbon injection.
A^{dAPCD = air pollution control device.
A^{eMB/WW = mass burn waterwall combustor.
A^{fSD/FF = spray dryer and fabric filter.
A^{gSNCR = selective noncatalytic reduction.
A^{hDoes not add to 100 percent due to rounding.
A^{iMOD/SA = modular starved-air combustor.

For a small existing MWC plant (135 Mg/day capacity), table 3A
shows a capital cost for retrofit of about $2.6 million of which $2.5
million would be for the acid gas control system and the remaining for
activated carbon injection and GCP. On an annualized basis, the cost
would be about $770,000/yr or about $17/Mg of waste combusted. This
would increase baseline combustor cost from about $61/Mg combusted
(based on the baseline combustor cost for a new small MWC plant
presented in table 3B) to about $78/Mg combusted. Small MWC plants
represent about 6 percent of the existing MWC combustion capacity.

IV. Rationale for the Proposed Guidelines for MWC Emissions

This section addresses the legal, technical, and economic basis for
the proposed emission guidelines. The basis for regulating MWC's, for
regulating the specified pollutants, and for regulating MWC's according
to the specified size categories are discussed. The section also
presents the EPA's approach in establishing the MACT floor and
selecting MACT. Additionally, the section discusses the selected format
of the proposed guidelines, the proposed performance testing and
monitoring requirements, and the proposed reporting and recordkeeping
requirements.

A. Background

On November 15, 1990, the Act was amended. The Act of 1990 includes
a new section 129 that applies to a range of solid waste incinerators
including MWC's, medical waste incinerators (MWI's), infectious waste
incinerators, and industrial waste incinerators.
Under authority of sections 111 and 129 of the Act of 1990, the EPA
was directed to promulgate MACT-based guidelines for MWC's. However,
section 129 also includes a clause directing the EPA to issue emission
guidelines based on BDT under the terms imposed in the consent decree
issued from State of New York et al. v. Reilly (No. 89-1729 D.D.C.),
but limiting applicability of those emission guidelines to MWC's with
unit capacities greater than 225 Mg/day. Emission guidelines that were
signed by the Administrator on January 11, 1991 and published in the
Federal Register on February 11, 1991 (56 FR 5514) complied with this
component of the section 129 requirements.
Regarding the MACT-based guidelines, section 129 directs the EPA to
promulgate MACT-based guidelines for MWC units located at plants with
capacities greater than 225 Mg/day and at plants with capacities less
than 225 Mg/day. The MACT-based guidelines are to include numerical
emission limits for Cd, Pb, Hg, and NOX, and are to address
operator training requirements.
Today's proposal complies with all requirements of section 129
described above. This has been done by: (1) Proposing MACT-based
guidelines that cover MWC units at plants with capacities above 35 Mg/
day; (2) proposing numerical emission limits for Cd, Pb, Hg, and
NOX; (3) proposing operator training requirements; and (4)
proposing opacity limits for air curtain incinerators firing specific
``clean'' fuels.
The subpart Eb NSPS that is proposed in a separate notice in
today's Federal Register would apply to new facilities constructed
after September 20, 1994. However, the February 11, 1991 subpart Ea
NSPS will remain in effect. Therefore, those existing facilities
subject to the February 11, 1991 NSPS that were constructed on or prior
to September 20, 1994 would be subject to both the subpart Ea NSPS and
the proposed subpart Cb emission guidelines.

B. Selection of Source Category

The MWC guidelines adopted on February 11, 1991 provided the
rationale for the selection of MWC's as a source category to be
regulated (56 FR 5514). Moreover, section 129 of the Act directs the
EPA to issue guidelines for this source category, and thereby confirms
the EPA's earlier decision.
Today's proposed emission guidelines (subpart Cb) would apply to
existing MWC's, defined as those MWC's for which construction,
modification, or reconstruction commenced on or before September 20,
1994. Municipal waste combustors for which construction, modification,
or reconstruction commenced after September 20, 1994 would be covered
by the subpart Eb NSPS proposed in a separate notice in today's Federal
Register.
Also, as required by section 129 of the Act, today's proposed
guidelines would establish opacity limits for certain existing air
curtain incinerators, for which construction, modification, or
reconstruction commenced on or before September 20, 1994. Under the
proposed guidelines, air curtain incinerators that burn only yard
wastes, tree trimmings, and clean untreated lumber would be required to
meet an opacity limit, and no other requirements would apply. The
proposed guidelines for these air curtain incinerators are presented in
section VI of this preamble.

C. Modification or Reconstruction of Existing MWC's

The subpart Ea NSPS proposal published in the Federal Register on
December 20, 1989 (54 FR 52251) provided a discussion of the terms and
conditions associated with construction, modification, and
reconstruction for MWC's. One change is being proposed. Previously, the
terms ``modification'' and ``reconstruction'' were defined under
sections 60.14 and 60.15 of subpart A of part 60. Section 129 of the
Act has specified a new definition of ``modified solid waste
incineration unit'' that combines and revises the previous definitions
of ``modification'' and ``reconstruction.'' Specifically, ``modified
solid waste incineration unit'' refers to: (1) Modifications for which
the

* * * cumulative costs of the modifications, over the life of
the unit, exceed 50 per centum of the original cost of the
construction and installation of the unit (not including the cost of
any land purchased in connection with such construction or
installation) updated to current costs. * * *

or (2) modifications involving

* * * a physical change in or change in the method of operation
of the unit which increases the amount of any air pollutant emitted
by the unit for which standards have been established under [section
129] or section 111 * * *.

D. Selection of Designated Pollutants

A complete discussion of the rationale for selecting ``MWC
emissions'' as the designated pollutants under sections 111(b) and
111(d) of the Act is provided in the December 20, 1989 proposal
preamble for the 1991 emission guidelines (54 FR 52209). Additionally,
section 129 of the Act specifies that emission guidelines be developed
for PM, opacity, SO2, HCl, NOX, CO, Cd, Pb, Hg, and dioxins/
furans. Emission guidelines for all but four of these pollutants (Cd,
Pb, Hg, and NOX) were established in the February 11, 1991
emission guidelines (56 FR 5514). Section 129 specifies that emission
limits be set for each of the metals (Cd, Pb, and Hg).
Emission guidelines for fugitive MWC fly ash/bottom ash emissions
are proposed today because these emissions also contain PM, Cd, Pb, Hg,
and dioxins/furans.

E. Selection of Designated Facilities

For the proposed emission guidelines, the designated facility, an
MWC unit, is defined as any setting or equipment chamber or pit used to
burn MSW (including RDF) and extends to and includes MWC fly ash/bottom
ash emission points, including ash storage areas, conveyor transfer
points, and ash loading areas for hauling trucks at the MWC site. This
does not extend to ash handling outside of the MWC property boundary or
at ash fill sites.
Municipal waste combustion includes the burning (or pyrolysis) of
MSW in any type of equipment, chamber, or pit including equipment with
and without heat recovery. Municipal solid waste is defined as either a
mixture or a single-item stream of household, commercial, and/or
institutional discards. This would include discards such as paper,
wood, yard wastes, tree trimmings, plastics, leather, rubber, glass,
metals, and other combustible and noncombustible materials. The MSW
definition includes household discards as well as discards from
institutional and commercial sources, but does not include industrial
process or manufacturing discards. The MSW definition also includes
RDF, which is a type of MSW that is shredded (or pelletized) and
classified by size before combustion. Municipal solid waste does not
include wastes that are solely segregated medical wastes. However, any
mixtures of medical waste with nonmedical hospital waste or with
household, commercial, or institutional waste is considered to be MSW.
Minor editing has been done to the definition of MSW to clarify this
point.
Cofired combustors are those that fire MSW with non-MSW fuel such
as coal. Cofired combustors that combust a fuel feed stream comprised,
in aggregate, of equal to or less than 30 percent MSW or RDF (by
weight, based on a 24-hour average), would not be subject to the
emission guidelines and would be required only to submit reports of the
amount of MSW and other fuels combusted. The exclusion of cofired
combustors from the guidelines is consistent with the Act of 1990. This
exclusion is unchanged from the February 11, 1991 guidelines.
Waste-fuel power generation facilities that combust a single-item
waste stream of tires, fuel derived solely from tires, or used oil
would be subject only to an initial report and to no other provisions
in today's proposal or to the emission guidelines that were promulgated
on February 11, 1991 (56 FR 5514). This exclusion is unchanged from the
February 11, 1991 guidelines.
Air curtain incinerators with unit capacities to combust greater
than 35 Mg/day of MSW are subject to the proposal; however, air curtain
incinerators that combust only tree trimmings, yard wastes, and clean
untreated lumber (these are a subset of MSW) would be subject to an
opacity standard and its associated testing, recordkeeping, and
reporting included in today's proposal, but would not be subject to
other parts of today's proposal. This exclusion does not apply to air
curtain incinerators that combust other MSW materials.
Today's proposed guidelines for MWC's would apply to MWC units at
plants with capacities above 35 Mg/day. The lower size cutoff of 35 Mg/
day aggregate plant capacity for controlling MWC emissions under the
proposed emission guidelines was selected after reviewing the
population distributions of MWI's and MWC's. Most incinerators at
medical waste facilities are smaller incinerators that fire segregated
medical waste with general hospital discards (MSW), and these
incinerators would have the potential to be covered by today's
proposal. The population distribution of MWI's is distinctly different
from the population distribution of traditional MWC plants that are the
target of today's proposal. The existing distribution of MWC's is
composed of about 372 units (about 179 plants), with an average plant
size of about 600 Mg/day combustion capacity, with two or three MWC
units at each plant. The potential nationwide combustion capacity of
existing MWC's is about 107,000 Mg/day, assuming continuous operation.
The MWI distribution is quite different and includes about 7,000
combustors with a single combustion unit per facility and an average
unit size of less than 3 Mg/day combustion capacity. The total U.S.
capacity of MWI's is about 20,000 Mg/day. This population is being
addressed under a separate rulemaking. Clearly, the MWC population
represents a smaller number of comparatively larger units, and MWI's
represent a much larger number of smaller units. The lower size cutoff
of 35 Mg/day aggregate plant capacity that is included in today's
proposed emission guidelines would exclude less than 1 percent of the
total nationwide combustion capacity of MWC's and would result in over
99 percent of total MWC capacity being covered by this proposal. The
same lower size cutoff would prevent significant dual coverage under
this proposal by excluding more than 99 percent of MWI units and about
97 percent of nationwide MWI capacity from today's proposed revisions.
As mentioned above, the proposed emission guidelines with a 35 Mg/
day cutoff would cover the great majority of MWC's, and may also cover
a few of the largest MWI's (nine units at three sites are known to
cofire medical waste with MSW and are above the 35 Mg/day of MSW total
plant capacity cutoff). Section 129 of the Act requires that
regulations for MWI's be developed in a separate rulemaking. For these
reasons, it is appropriate that today's proposed guidelines focus on
MWC's and that a separate regulation focus on MWI's. The NSPS and
guidelines for MWI's are scheduled to be proposed in 1995.
Municipal waste combustor plants with aggregate capacities below 35
Mg/day would not be subject to the emission limits under today's
proposed emission guidelines. However, those facilities with aggregate
plant capacities between 25 and 35 Mg/day would be required to report
(one time) their location, startup date, and aggregate plant capacity.
They would also be required to provide supporting information,
including calculations used to determine plant capacity. This one-time
report would allow the EPA or State agency to enforce the lower size
cutoff for applicability to the proposed guidelines. Plants with
aggregate capacities of 25 Mg/day or below would not be subject to any
provisions under this proposal.
The proposed emission guidelines for MWC's are subdivided into two
subcategories of air emissions requirements: The first for MWC's
located at MWC plants with aggregate capacities to combust more than 35
Mg/day but less than or equal to 225 Mg/day of MSW (referred to as
small MWC plants), and the second for MWC's located at MWC plants with
aggregate capacities to combust greater than 225 Mg/day of MSW
(referred to as large MWC plants). The 225 Mg/day dividing point was
established because this size break represents a transition point
between field-erected waterwall MWC's and modular MWC's.
In the subcategory of existing plants with capacities greater than
225 Mg/day, there are about 119 MWC plants with 235 MWC units. In the
subcategory of existing plants with capacities greater than 35 Mg/day
but equal to or less than 225 Mg/day, there are about 60 plants with
137 units. The large plant subcategory accounts for about 94 percent of
the total combustion capacity whereas the smaller subcategory accounts
for about 5 percent of total capacity.

F. Selection of Maximum Achievable Control Technology

The following discussion addresses the EPA's selection of MACT. The
existing technologies for controlling emissions of the designated
pollutants from MWC's are reviewed, followed by a summary of the EPA's
approach for establishing the MACT floor. Finally, the discussion
presents the EPA's selection of MACT for MWC's at small and large MWC
plants.
1. Summary of MWC Control Technologies
The following discussion reviews the existing technologies for
controlling emissions of acid gases, dioxins/furans, PM, Cd, Pb, Hg,
and NOx from MWC's.
a. Acid Gas/PM Control Technologies. Municipal waste combustor acid
gas/PM control is a general term that refers to a group of MWC air
pollution control technology combinations. These combinations control a
wide range of pollutants, such as acid gases (including SO2 and
HCl), organics (including dioxins/furans), and PM and metals (including
Cd, Pb, and a number of other metals except Hg). The three acid gas/PM
controls most commonly used in the United States for existing MWC's
are: (1) GCP plus DSI followed by an ESP; (2) GCP plus an SD followed
by an ESP; and (3) GCP plus an SD followed by an FF. Discussions of
each of these control systems were presented in the December 20, 1989
proposal preamble for the acid gas and PM emission guidelines in
subpart Ca (54 FR 52209). Control of Cd, Pb, and Hg were not discussed
in detail in the 1989 preamble.
Since 1991, the performance of the acid gas/PM control systems for
removal of Cd, Pb, and Hg has been investigated in more depth. Cadmium
and Pb are both volatile at temperatures present in combustion systems,
but condense onto PM in the flue gas at temperatures associated with
the operation of most PM control systems. As a result, the control of
Cd and Pb is generally related to the control of PM emissions. Much of
the PM in the flue gas from an MWC is fine PM; from 20 to 70 percent of
the PM in the flue gas from an MWC has an aerodynamic diameter of less
than 1 micrometer (1 micron). Because of the potential for adsorption
of Cd and Pb onto fine PM that is less readily collected by control
devices than larger PM, the control of fine PM is especially important
in controlling these metals.
Both FF-equipped systems (i.e., DSI/FF's and SD/FF's) and
electrostatic precipitator (ESP)-equipped systems (e.g., ESP's, DSI/
ESP's, and SD/ESP's) can achieve efficient control of PM, and the
efficiency of total PM and fine PM control achieved by these systems
depends on their design. However, FF-equipped systems are generally
more effective in capturing fine PM than ESP-equipped systems.
Therefore, the control of Cd and Pb achieved by FF-equipped systems is
typically better than that of ESP-equipped systems.
For DSI/FF and SD/FF systems, data for controlled Cd emissions
range from 0.001 to 0.0100 mg/dscm. Emissions of Pb from MWC's with
these systems are less than 0.10 mg/dscm. For SD/ESP systems, the data
for Cd and Pb emissions are variable, showing emission levels from
0.005 to 0.040 mg/dscm for Cd, and levels of less than 0.10 to 0.50 mg/
dscm for Pb. For DSI/ESP and ESP-only systems, there is no indication
of a difference in the level of Cd and Pb control between these control
systems. For both of these systems, Cd emission levels range up to 0.10
mg/dscm, and Pb emission levels range up to 1.6 mg/dscm.
Although the above combinations of acid gas/PM controls are
effective at removing Cd, Pb, and other metals, they do not
consistently remove Hg without integrating some other form of Hg
control. A discussion of Hg control is presented below.
b. Mercury Control Technologies. The EPA estimates that typical
uncontrolled Hg levels for MWC's in the United States range from 0.20
to 1.4 mg/dscm at 7 percent O2. Unlike other metals, Hg has a high
vapor pressure at typical operating temperatures of air pollution
control devices. As a result, collection of Hg by the PM control device
is highly variable. The EPA collected test data from more than 30 MWC's
with various air pollution controls that indicate a wide range of Hg
control. High-efficiency PM control, lower flue gas temperatures in the
air pollution control system, and a sufficient level of carbon in the
fly ash facilitate Hg control. Higher levels of carbon in the fly ash
and reduced flue gas temperatures enhance Hg adsorption onto the
carbon, which is removed by the PM control device. To promote Hg
adsorption, it is important to operate the control systems at
temperatures less than about 150 to 200 deg.C. Low flue gas
temperature is inherent to acid gas control.
Municipal waste combustors having high combustion efficiency will
have effective carbon burnout and, therefore, will have low fly ash
carbon content. These units may achieve little or no Hg control even
when equipped with acid gas/PM control systems, and the control may be
highly variable even at the same site.
Three techniques for Hg control are currently being used at MWC's:
Activated carbon injection, sodium sulfide (Na2S) injection, and
wet scrubbing. Activated carbon injection and Na2S injection are
used in conjunction with an existing acid gas control device. Brief
discussions of these three Hg control technologies and their
capabilities are presented below.
Injection of powdered activated carbon into the flue gas prior to
the acid gas/PM control device has been tested at U.S. MWC's. The
removal mechanism is not fully understood, but it is believed that
activated carbon is a catalyst for the oxidation of elemental Hg to
mercuric oxide and mercuric chloride, which can more readily be
captured in the air pollution control device. This technology has been
applied commercially to MWC's in Europe equipped with SD/ESP's and
during test programs in Europe and Canada to MWC's with SD/FF's and
DSI/FF's. The EPA also tested activated carbon injection at the
Stanislaus County MWC in California and the Camden County MWC in New
Jersey. The Stanislaus County MWC is equipped with an SD/FF, and the
Camden County MWC is equipped with an SD/ESP. Test results show Hg
reductions greater than 85 percent when injecting activated carbon.
A second Hg control technology is Na2S injection. Sodium
sulfide is a crystalline solid that dissolves in water. The resulting
Na2S solution is sprayed into the flue gas prior to the acid gas/
PM control device. The reaction of Na2S and Hg precipitates solid
mercuric sulfide (HgS) that is collected in the PM control device.
Three MWC's in Sweden, two in Germany, and one in Canada have used
Na2S injection to control Hg emissions. All of these facilities
use DSI/FF systems for acid gas/PM control, and injection of Na2S
occurs prior to the DSI/FF system at flue gas temperatures of 130 to
250 deg.C. In addition, Hg emission tests were conducted at the
Stanislaus County MWC in California while using Na2S injection.
Results from tests at European, Canadian, and U.S. MWC's have shown Hg
removal efficiencies of 40 to 90 percent when using Na2S
injection.
Wet scrubbing is a form of acid gas control that also controls Hg
without use of an add-on Hg control system. It has been used primarily
in Europe and Japan. Typically, the flue gas is first directed through
an ESP to reduce PM, followed by wet scrubbing, which involves passing
the flue gas through a one- or two-stage absorber system where the gas
stream is saturated with an alkaline solution. During this process,
flue gas temperatures are reduced to as low as 55 deg.C. The low
absorber operating temperature promotes Hg condensation, resulting in
an Hg reduction of 80 percent or better. The alkaline solution used in
the wet scrubbing process, typically containing calcium hydroxide,
reacts with the acid gas to form salts, which are generally insoluble
and may be removed by sequential clarifying, thickening, and vacuum
filtering. The dewatered salts or sludges are then sent to a landfill.
The disadvantages of wet scrubbing include the quantity of water
required, potential difficulties with waste handling, and undefined
performance at MWC units firing domestic (U.S.) MSW streams.
c. Nitrogen Oxides Control Technologies. During the combustion
process, NOX are formed through two mechanisms: (1) Oxidation of
fuel-bound nitrogen (N2) contained in MSW to NOX; and (2)
fixation and oxidation of atmospheric N2. In MWC's, the conversion
of fuel-bound N2 accounts for most (75 to 80 percent) of the
NOX production.
Controlling NOX emissions from MWC's can be accomplished
through: (1) Combustion modifications to reduce NOX formation; (2)
postcombustion control, which reduces NOX in the flue gas to
elemental N2; or (3) use of ``low-NOX'' combustors to reduce
NOX formation. Combustion modifications include staged combustion,
low excess air, and flue gas recirculation. Combustion modification
retrofit at existing MWC's has had limited application and its retrofit
potential must be evaluated on a case-by-case basis.
Postcombustion NOX control using selective noncatalytic
reduction (SNCR) is more flexible and has been more commonly used for
MWC NOX control. The SNCR control technology reduces NOX to
N2 without the use of catalysts. Techniques include Thermal
DeNOX^{TM, which injects ammonia into the combustor as a
reducing agent; the NOXOUT^{TM process, which injects urea with
chemical additives; and a two-stage urea/methanol injection process. A
discussion of SNCR NOX control was presented in the December 20,
1989 proposal preamble (54 FR 52251) for the 1991 NSPS for new MWC's.
The use of SNCR at existing MWC's results in NOX emission
reductions of about 45 percent.
However, for existing mass burn/refractory MWC's, SNCR retrofit
problems exist. Mass burn/refractory MWC's are generally older and
operate with greater fluctuations in combustor flue gas temperature
profiles than is typical for other types of MWC's. The fluctuating
temperature profiles create SNCR applicability and performance
problems. The SNCR control has not been used nor is expected to be used
at mass burn/refractory MWC's or other specialized combustors.
The SNCR technology has also never been applied to a modular
combustor, and the performance of such a system on a modular combustor
is questionable. Performance questions arise because of the potential
for temperature fluctuations resulting from batch-feed operations along
with the inability of the refractory-lined furnace to dampen
temperature spikes. The EPA requests comment on the applicability of
SNCR and other NOX control techniques to MWC's at small plants.
The EPA requests that comments address the cost, technical performance,
and reliability of application of SNCR or other NOX control
techniques specifically to modular starved-air MWC's and modular
excess-air MWC's. Based on the comments and information received, the
EPA will reconsider requiring NOX control on MWC's at small
plants.
Three types of MWC's, mass burn/rotary combustors, fluidized-bed
combustors, and modular/excess-air combustors, are considered ``low
NOX'' combustors. Available data show that these types of MWC's
consistently show NOX levels below 150 ppmv without the use of
SNCR.
2. MACT Floor and MACT Requirements of the Act
Section 129 of the Act, as amended in 1990, directs the EPA to
review and revise the February 11, 1991 guidelines to reflect MACT.
Section 129 also establishes a minimum ``floor'' for the guidelines, in
terms of their stringency; specifically:

* * * emission standards for existing units * * * shall not be
less stringent than the average emission limitation achieved by the
best performing 12 percent of units in the category * * *.

The intent of this MACT floor is to ensure that the guidelines
reflect the performance of the best emission control technologies
currently operating at existing MWC units. A large portion of the
existing MWC population is represented by relatively new and relatively
well-controlled MWC units (the average age of an MWC unit is less than
10 years). This results in a large percentage of existing MWC units
being operated with the best emission control technologies. This subset
constitutes about 45 percent of existing MWC units at large MWC plants,
and, based on EPA's current information, these units are all well
maintained and operated. Based on the examination and analysis of the
emission data available from these units, the EPA has not found a basis
for separating the top 12 percent of these units from the remaining
units in the subset of those units that are well-equipped, maintained,
and operated. Consequently, to determine the MACT floor, the EPA
utilized emission limitations included in Federal/State permits.
Emission limitations for existing MWC units at large plants were
determined by examining the air quality permits for those units
obtained from the EPA Regional Offices and by examining responses to
section 114 information requests, which included a section regarding
permitted emission limits. Emission limitations for MWC units at small
plants were determined only by examining the responses to section 114
information requests.
The emission limitations for each pollutant were then converted to
common units so that they could be compared. The emission limitations
for each pollutant were ranked separately for the small and large
categories of MWC plants. From those rankings, the average of the top
12 percent of emission limitations (i.e., the average of the most
stringent limitations) for each pollutant in the small and large plant
categories were calculated to determine the MACT floors.
The MACT floor defines the minimum level of emission control that
may be considered in defining MACT, regardless of cost or other
considerations. In considering control alternatives beyond the MACT
floor, the EPA must consider the cost of achieving such emission
reductions and any nonair quality health and environmental impacts and
energy requirements. Therefore, the level of control that represents
MACT may be more stringent than the MACT floor.
In the proposed regulations, subcategorization of existing MWC
units was limited only to size (units at large and small MWC plants).
Since the MACT floors may be sensitive to subcategorization, it is
possible that further or alternative means of subcategorization may
affect the determination of the MACT floor (i.e., the minimum level of
control requirements under section 129). The Act provides that ``the
Administrator may distinguish among classes, types (including mass-
burn, refuse-derived fuel, modular, and other types of units), and
sizes of units within a category'' in establishing MACT standards. In
examining various ways of subcategorization, the EPA found that
subcategorization uniformly across all emission standards could result
in more stringent standards for one pollutant and somewhat less
stringent standards for other pollutants. For example,
subcategorization by MWC technology generally results in a less
stringent MACT floor for NOX and a more stringent floor for PM.
Depending upon the approach used for subcategorization, the NOX
MACT floor for some units could be considerably higher than the 215
ppmv floor in the proposed rule. For example, the NOX MACT floor
for mass burn/waterwall units could be 230 ppmv, and the NOX MACT
floor for refuse-derived fuel units could be 275 ppmv.
The EPA is soliciting comments on whether subcategorization (beyond
size) should be used in the final rule and on the basis that one would
support for such further subcategorization (e.g., the inapplicability
of SNCR for mass burn/refractory combustors, and the inherently ``low-
NOX'' emission characteristics of mass burn/rotary combustors,
fluidized bed combustors, and modular/excess-air combustors.) In
addition, the EPA is seeking comment on the appropriateness of using
different subcategorization approaches for different pollutants. For
example, in setting standards under section 111 of the Act for
industrial boilers, the EPA established different emission standards
based on different fuel type inputs.
The following section presents the EPA's rationale for establishing
the MACT floor and MACT for MWC's.
3. MACT Floor and MACT for Large MWC Plants
This section summarizes the MACT floor and presents the EPA's
rationale for establishing MACT for each pollutant for MWC's at large
MWC facilities.
a. Summary of MACT Floor for Large MWC Plants. This proposal
determines the MACT floor for existing MWC's based on permit limits.
The population of MWC's at large plants consists of about 235 combustor
units. Therefore, the top 29 combustor units with the most stringent
permit limitations would represent the top 12 percent of emission
limitations for determining the MACT floor. An average of the top 29
permit limits was calculated to determine the floor for each pollutant.
The MACT floor emission levels for each pollutant for large MWC plants
is shown in table 4.

Table 4.--Mact Floor Emission Levels for Existing MWC's at Large MWC
Plants
------------------------------------------------------------------------
Pollutant MACT floor emission level^{a,b
------------------------------------------------------------------------
SO2................................ 35 ppmv.
HCl................................ 35 ppmv.
PM................................. 27 mg/dscm.
Cd................................. 0.25 mg/dscm.
Pb................................. 0.53 mg/dscm.
Hg................................. 0.36 mg/dscm.
Dioxins/furans..................... 100 ng/dscm total mass or about 1.7
ng/dscm TEQ.
NOX................................ 215 ppmv.
------------------------------------------------------------------------
^{aAll emission levels are corrected to 7 percent O2, dry basis.
^{bMost of the MACT floor requirements for large MWC plants are more
stringent than the 1991 subpart Ca guidelines. See table 2.

The top 12 percent MACT floor for the emission guidelines could be
constructed in a number of different ways including a permit basis
(this proposal), a technology basis, or an emissions data basis. Under
a technology basis, MWC's would be ranked by their control technology
to determine the technology used by the average or median of the top 12
percent of the MWC population, and the floor would be based on the
performance of that technology. Under an emission data basis, data on
the best top 12 percent of available test runs would be averaged to
calculate the floor. Other approaches are also possible. The different
approaches would result in noticeably different MACT floor performance
levels. The EPA specifically requests comments on what approach is most
appropriate and the rationale for that approach. Based on the EPA's
review of comments received on this issue, as well as reanalysis of any
data submitted, the MACT floor for the promulgated guidelines may be
noticeably higher or lower than the floor included in the proposal.
b. Discussion of the Selection of MACT for Large MWC Plants. After
establishing the MACT floor for each pollutant based on permit limits,
the EPA considered the cost, health and environmental impacts, and
energy requirements of selecting MACT for each pollutant at a control
level more stringent than the MACT floor. In selecting MACT for each
pollutant for large plants, the EPA used principally the data base
created for establishing the emission guidelines for MWC's proposed in
1989 and promulgated in 1991 under subpart Ca. For a few pollutants in
this proposal, the EPA utilized more recent test data to supplement the
1989 data base. Because most of the test data used for this proposal
are more than 4 years old, and in consideration of the fact that most
MWC's retest at least once per year, the EPA requests submittal of the
most recent MWC emissions test data.
The EPA requests comment on which MWC emissions test data would be
the most appropriate to use for establishing MACT for existing MWC's.
For example, if the EPA has multiple emission tests for a given MWC
over its operating history (which is common), should the EPA utilize
the data from all of the emission tests performed for the unit or from
only the most recent emission test, in determining the performance of
the unit? Additionally, the EPA requests comment on suggestions of
analytical methods to use for analyzing the data (e.g., analytical
methods that could be used to address emissions variability, including
methods for analyzing variable test data for one MWC collected over
multiple years and methods of adjusting the best 12 percent of the
emissions data to account for variability). The appropriate treatment
of variability will be related to the format chosen for the standards
(see discussion of alternative formats below).
Based on the new data submitted and on the final choice of which
test data and what analysis methods to use, the EPA may promulgate
final emission guidelines that are more or less stringent than those
proposed today. The following sections IV.F.3.c through IV.F.3.j
present the EPA's rationale for selecting MACT for each pollutant for
MWC's at large MWC facilities.
c. MACT for Sulfur Dioxide for Large MWC Plants. Uncontrolled
levels of SO2 for MWC's are typically about 160 ppmv. The MACT
floor for SO2 at large plants is 35 ppmv. Therefore, acid gas
control would be needed to achieve the MACT floor level of control.
Both SD/ESP's and SD/FF's can meet the MACT floor level of control.
Tests of many SD/FF's have demonstrated SO2 control to levels
below 35 ppmv.
Although SD/FF systems can generally achieve slightly better
SO2 control than SD/ESP systems, the cost of requiring existing
SD/ESP systems to retrofit an SD/FF to meet SO2 control levels
more stringent than the MACT floor would be prohibitively expensive and
is considered unreasonable. For example, at a typical 1,400 Mg/day MWC
plant already equipped with an SD/ESP, the capital cost to remove the
ESP and retrofit a new FF (as part of an SD/FF system) would be about
$14 million. This cost would be in addition to paying the remaining
debt for the relatively new ESP (about $5 million including interest
payments) and would result in a relatively small increase in control
device efficiency. The incremental cost of control for requiring a
retrofit from an SD/ESP to an SD/FF would be greater than $10,000/Mg of
acid gas reduction and would increase SO2 removal efficiency by
only about 6 percent. Therefore, the EPA is proposing that the MACT
guideline level for SO2 remain at the MACT floor level of 35 ppmv.
Additionally, the EPA is proposing an alternative SO2 guideline
level of 75-percent reduction to address SO2 emissions
variability. Therefore, the proposed MACT floor guideline level for
SO2 is either 35 ppmv or 75-percent reduction (24-hour averaging
period), whichever is less stringent.
d. MACT for Hydrogen Chloride for Large MWC Plants. Acid gas
control would also be needed for large MWC's to reduce HCl emissions
from uncontrolled levels of about 500 ppmv to the HCl MACT floor level
of 35 ppmv. The same types of acid gas control systems needed to
achieve the MACT control level for SO2 will also meet the MACT
floor levels of HCl. While it is expected that SD/FF systems could
achieve slightly lower HCl levels than SD/ESP systems, it has not been
demonstrated that existing SD/FF or SD/ESP systems can consistently
meet HCl levels below the MACT floor. Therefore, the EPA is proposing
that the MACT guideline level for HCl remain at the MACT floor level of
35 ppmv. Additionally, the EPA is proposing an alternative HCl
guideline level of 95-percent reduction to address HCl emissions
variability. Therefore, the proposed MACT floor guideline level for HCl
is either 35 ppmv or 95-percent reduction, whichever is less stringent.
e. MACT for Particulate Matter for Large MWC Plants. On average,
uncontrolled levels of PM from MWC's are about 3,700 mg/dscm. The MACT
floor for PM at large MWC plants is 27 mg/dscm. The MACT floor will
require greater than a 99-percent reduction in PM emissions. The EPA's
analysis of data from existing MWC's showed that both SD/FF and SD/ESP
systems can meet MACT floor PM levels. Although the newest SD/FF
systems can meet levels of less than 15 mg/dscm, SD/ESP systems and
many existing SD/FF systems cannot achieve such levels. Therefore, the
proposed MACT for PM at large MWC's is the MACT floor level of 27 mg/
dscm.
f. MACT for Cadmium for Large MWC Plants. Average uncontrolled
levels of Cd are about 1.2 mg/dscm from MWC's. The MACT floor for Cd
for large MWC plants is 0.25 mg/dscm. Therefore, the MACT floor will
require about 80-percent Cd reduction. As with Pb, Cd control is
associated with PM control. The EPA's analysis of Cd control showed
that SD/FF systems can generally achieve Cd levels of less than 0.010
mg/dscm and that SD/ESP systems can achieve less than 0.040 mg/dscm.
The Cd removal efficiency achievable with an SD/FF is only about 1.2
percent better than an SD/ESP (99.5-percent reduction versus 98.3-
percent reduction, respectively). Again, the high cost of retrofit to
an SD/FF is considered unreasonable for such a small incremental
reduction in emissions. Because a level of 0.040 mg/dscm is achievable
with both SD/ESP and SD/FF systems, and these technologies would
already be needed to meet MACT for acid gas control, the proposed MACT
for Cd is more stringent than the MACT floor, at a level of 0.040 mg/
dscm.
g. MACT for Lead for Large MWC Plants. Uncontrolled Pb emissions
from MWC's are about 25 mg/dscm, and the MACT floor for large MWC's is
0.53 mg/dscm. A reduction of about 98 percent would be needed to
achieve the MACT floor. The SD/ESP or SD/FF systems needed to meet MACT
for acid gases will also meet the MACT floor for Pb. The EPA's analysis
of Pb control showed that SD/FF systems can meet Pb levels of 0.20 mg/
dscm, and SD/ESP systems can meet Pb levels of 0.50 mg/dscm. The Pb
removal efficiency achievable with an SD/FF is only about 0.8 percent
better than an SD/ESP (reductions of about 99.8 versus 99.0 percent,
respectively). As explained above, the cost of replacing an SD/ESP with
an SD/FF would be unreasonable considering the small difference in
control efficiency. Because both SD/FF and SD/ESP systems can achieve
Pb levels of 0.50 mg/dscm, the proposed MACT for Pb is more stringent
than the MACT floor, at a level of 0.50 mg/dscm.
h. MACT for Mercury for Large MWC Plants. Uncontrolled levels of Hg
from MWC's are about 0.65 mg/dscm on average. The MACT floor for Hg for
large plants is 0.36 mg/dscm. The MACT floor, therefore, will require
about 40-percent reduction in Hg emissions. As described in section
IV.F.1.b of this preamble, Hg control can be achieved by using
activated carbon injection in combination with an acid gas/PM control
system (and the associated low flue gas temperatures). Recent tests at
the MWC's at Camden County, New Jersey (SD/ESP), and Stanislaus County,
California (SD/FF), demonstrate that both SD/ESP and SD/FF systems with
activated carbon injection can achieve an 85-percent emission reduction
in Hg emissions or an Hg emission level of 0.080 mg/dscm, corrected to
7 percent O2. Data from individual test runs show occasional
spikes of high inlet Hg emissions due to the variability in the waste
feed composition. In cases where Hg levels are temporarily elevated, a
0.080 mg/dscm level may not be consistently achievable; however,
activated carbon injection could achieve an 85-percent reduction during
such episodes. Based on the data from MWC's using activated carbon
injection, Hg control to these levels is achievable by properly
operated systems on all types of MWC's.
Although the MACT floor requires Hg control, the control levels
achievable using SD/ESP or SD/FF systems and activated carbon injection
are more stringent than the MACT floor. The incremental cost of
reducing Hg emissions from the MACT floor level of 0.36 mg/dscm to the
demonstrated level of 0.080 is less than about $1.00/Mg of MSW
combusted. This incremental cost is considered reasonable given the
toxicity and bioaccumulation potential of Hg. Therefore, the proposed
MACT guidelines for Hg are 0.080 mg/dscm or an 85-percent reduction,
whichever is least stringent.
The EPA has selected activated carbon injection as the basis for
achieving MACT for Hg, although facilities may use any technology
capable of meeting the proposed guideline. Of the three Hg control
technologies discussed in section IV.F.1.b of this preamble, the EPA
has determined that activated carbon injection is the most widely
tested of the three Hg control technologies in the United States.
i. MACT for Dioxins/Furans for Large MWC Plants. The average level
of dioxins/furans from an uncontrolled MWC is about 1,000 ng/dscm total
mass. The MACT floor for total dioxins/furans of 100 ng/dscm would
require about a 90-percent reduction.
Dioxins/furans are controlled by GCP and acid gas/PM control. Good
combustion practices alone can achieve total dioxin/furan levels of
about 500 ng/dscm. In combination with GCP, SD/FF systems can achieve
total dioxin/furan levels less than 30 ng/dscm, and SD/ESP systems can
achieve total dioxin/furan levels of less than 60 ng/dscm. Therefore,
the MACT floor (i.e., 100 ng/dscm) can be achieved with either SD/ESP
or SD/FF systems, and these systems would already be the basis for
meeting MACT for acid gas and PM emissions.
As discussed above, the MACT for Hg would be based on activated
carbon injection. Recent tests at the Camden County, New Jersey, MWC
showed that the injection of activated carbon into the flue gas of an
SD/ESP system provides further removal of dioxins/furans (greater than
50-percent reduction over levels achieved by the SD/ESP systems). The
greater than 50-percent reduction of the 60 ng/dscm level achieved by
an SD/ESP would equate to total dioxin/furan emission levels below 30
ng/dscm (0.5 ng/dscm dioxin/furan TEQ) for SD/ESP systems with
activated carbon injection.
As noted, SD/ESP or SD/FF systems with activated carbon injection
would already be needed to achieve MACT for acid gas, PM, and Hg.
Because both of these control systems in combination with activated
carbon injection can achieve a dioxin/furan emission level of 30 ng/
dscm or less, and because of the high cost for retrofitting an SD/FF,
the proposed guideline for dioxin/furan at large MWC's is based on GCP
and SD/ESP systems plus activated carbon injection. The EPA is
proposing MACT for dioxins/furans on both a TEQ and a total mass basis.
The 30 ng/dscm of total dioxins/furans is equivalent to 0.50 ng/dscm of
dioxin/furan TEQ; therefore, the proposed guideline level for large MWC
plants is 30 ng/dscm total dioxins/furans or 0.50 ng/dscm of dioxin/
furan TEQ. Comments are requested on whether lower dioxin/furan
guideline levels, which would require SD/FF's, should be incorporated
into the final guidelines.
j. MACT for Nitrogen Oxides for Large MWC Plants. The average level
of NOX emissions from MWC's without postcombustion NOX
control is about 225 ppmv. The MACT floor, however, is 215 ppmv.
Therefore, postcombustion NOX controls will be needed by most
existing MWC's at large plants to meet the MACT floor.
Selective noncatalytic reduction is currently used by 16 existing
MWC units at large plants. Tests conducted by the EPA at the Stanislaus
County, California, MWC showed that existing SNCR systems achieve
NOX levels of 180 ppmv on a 24-hour average basis.
Because postcombustion NOX control is required by the MACT
floor, and there is only a small incremental cost to operate an SNCR
system to achieve 180 ppmv versus the MACT floor level of 215 ppmv, the
proposed guideline level for NOX for large plants (excluding mass
burn/refractory MWC's) is 180 ppmv.
As discussed in section IV.F.1.c of this preamble, SNCR may not be
effective on mass burn/refractory MWC's. Therefore, postcombustion
NOX control is not being considered for this type of MWC. The MACT
guideline for NOX for mass burn/refractory MWC's at large MWC
plants is based on no control. Section VIII of this preamble discusses
``no control'' emission limits for NOX.
The EPA recognizes that costs associated with the proposed NOX
control requirements for large existing MWC plants are not
insignificant. Under the proposal, about 73 percent of current MWC
capacity would be expected to retrofit NOX control. On a national
basis, the retrofit of NOX controls to existing MWC plants would
cost about $56 million/yr and would represent about 13 percent of the
$445 million annual cost of the entire proposal.
As discussed above, the MACT floor for large MWC plants is 215 ppmv
and would require less than 20-percent NOX control (reduction).
This could be achieved by application of SNCR technology at a low
performance level or, perhaps, by using combustion modification (e.g.,
excess air) or materials management. The proposal, however, goes beyond
MACT floor requirements and would establish MACT at 180 ppmv or about
30- to 40-percent NOX reduction based on the full application of
SNCR at an MWC with average baseline emissions of 225 ppmv.
The EPA requests comment on the alternative of establishing
NOX standards at the level of the MACT floor (215 ppmv) based on
the above approach. The EPA also requests comment and data supporting
the achievability of a MACT floor level (24-hour arithmetic average,
corrected to 7 percent O2) without the use of an SNCR system.
Additionally, the EPA requests data and information on alternative
NOX control technologies including but not limited to the
application of combustion modification techniques to existing MWC's or
of other management measures (perhaps separation of yard waste) to
comply with either the proposed level or a floor level at a lower cost
than an SNCR system.
4. MACT Floor and MACT for Small MWC Plants
This section summarizes the MACT floor and presents the EPA's
rationale for establishing MACT for each pollutant for MWC's at small
MWC facilities.
a. Summary of MACT Floor for Small MWC Plants. The proposal
determines the MACT floor for existing MWC's based on permit limits.
The population of MWC units at small MWC plants consists of about 137
combustor units. Only 88 of the 137 units are facilities that have
federally enforceable permit limitations. Therefore, for determining
the MACT floor, the emission limitations achieved by the top 11 units
in the small MWC plant category represent the top 12 percent of units
with federally enforced permit limitations. Many of the smallest MWC's
with unit capabilities below 45 Mg/day (i.e., those MWC's not subject
to the 1971 subpart E NSPS) do not have federally enforceable permit
limitations. For some pollutants, less than 11 permits were identified
for the category of small MWC plants (i.e., many small plants with
permits have emission limits for only some of the pollutants covered by
the proposed guidelines.) In such cases, typical uncontrolled emission
levels for that pollutant were used for determining the average of the
top 12 percent of emission limitations. Table 5 provides a summary of
the MACT floor emission levels for each pollutant for small MWC plants.

Table 5.--MACT Floor Emission Levels for Existing MWC's at Small MWC
Plants
------------------------------------------------------------------------
Pollutant MACT floor emission level^{a
------------------------------------------------------------------------
SO2................................ 120 ppmv.
HCl................................ 660 ppmv.
PM................................. 85 mg/dscm.
Cd................................. 1.1 mg/dscm.
Pb................................. 15 mg/dscm.
Hg................................. 1.2 mg/dscm.
Dioxins/furans..................... 1,700 ng/dscm total mass or about
28 ng/dscm TEQ.
NOX................................ Uncontrolled.
------------------------------------------------------------------------
^{aAll emission levels are corrected to 7 percent O2, dry basis.

As discussed in Section IV.F.3.a. for large plants, the MACT floor
could be constructed in a number of different ways including a permit
basis (this proposal), a technology basis, or an emission data basis.
Comments are requested on what approach is most appropriate and the
rationalization for the approach. Based on the EPA's review of the
comments received and reanalysis of the data, the MACT floor for the
promulgated guidelines may be noticeably higher or lower than the floor
included in the proposal.
b. Discussion of the Selection of MACT for Small MWC Plants. After
establishing the MACT floor for each pollutant based on permit limits,
the EPA considered the cost, health and environmental impacts, and
energy requirements of selecting MACT for each pollutant at a control
level more stringent than the MACT floor. As discussed above for large
MWC plants in section IV.F.3.b, in selecting MACT for each pollutant
for small plants, the EPA used principally the data base created for
establishing the emission guidelines for MWC's proposed in 1989 and
promulgated in 1991 under subpart Ca. As discussed, the EPA
specifically requests submittal of the most recent MWC emissions test
data. Additionally, as discussed, the EPA requests comment on which MWC
emissions test data would be the most appropriate to use for
establishing MACT for existing MWC's (e.g., if the EPA has multiple
emission tests for a given MWC over its operating history, should the
EPA utilize the data from all of the emission tests performed for the
unit or from only the most recent emission test) and comment on
suggestions of analytical methods to use for analyzing the data (e.g.,
analytical methods that could be used to address emissions variability,
including methods for analyzing variable test data for one MWC
collected over multiple years and methods of adjusting the best 12
percent of the emissions data to account for variability). The
appropriate treatment of variability will be related to the format
chosen for the standards (see discussion of alternative formats below).
Based on the new data submitted and on the final choice of which
test data to utilize, the EPA may promulgate final emission guidelines
that are more or less stringent than those proposed today. The
following sections IV.F.4.c through IV.F.4.j present the EPA's
rationale for selecting MACT for each pollutant for MWC's at small MWC
facilities.
c. MACT for Sulfur Dioxide for Small MWC Plants. Uncontrolled
SO2 emissions from MWC's are typically about 160 ppmv, and the
MACT floor for SO2 for small MWC plants is 120 ppmv. Therefore,
MACT will require SO2 reduction of about 35 percent compared to
uncontrolled levels. Dry sorbent injection/ESP systems can achieve
greater than 50-percent reductions in SO2, and can satisfy the
MACT floor requirements. Retrofitting a new SD/FF system would achieve
greater acid gas control and small additional reductions in other MWC
pollutants, but the associated costs of such retrofits at small MWC's
would be prohibitively high (greater than $10,000/Mg of acid gas
reduction).
Although the MACT floor requires SO2 control to only 120 ppmv,
the incremental cost of operating a DSI/ESP system to achieve 80 ppmv
(about a 50-percent reduction) versus 120 ppmv is small and results in
improved cost effectiveness. Therefore, the MACT guideline proposed for
SO2 is more stringent than the MACT floor and is proposed at a
level of either 80 ppmv or 50-percent reduction (24-hour averaging
period), whichever is less stringent.
The EPA recognizes that costs associated with the proposed acid gas
control retrofit requirements for small MWC plants are not
insignificant. Small MWC plants represent about 10 percent of the
national MWC capacity to be retrofitted with acid gas control systems,
and their associated cost burden would be about 15 percent of the
national cost of the proposal. On a national basis, the retrofit of
acid gas controls to small MWC plants would cost about $60 million
annually and the retrofit of acid gas controls to large MWC plants
would be about $340 million annually.
As discussed above, the MACT floor for small MWC plants is 120 ppmv
and would require about 35-percent SO2 control (reduction). This
could be achieved by application of a DSI/ESP scrubbing system. The
proposal, however, goes beyond the MACT floor requirements and would
establish MACT at 80 ppmv or 50-percent SO2 reduction based on the
application of a DSI/ESP at its full optimal capability. Even at
optimal conditions, acid gas scrubbing on MWC units at small plants has
a higher control cost ($/Mg acid gas removed) than for MWC units at
large plants. In fact, acid gas control costs for small plants ($/Mg
acid gas removed) are more than twice those for large plants.
In the final regulations, the EPA is considering the alternative of
establishing acid gas control requirements for small MWC plants at the
level required by the MACT floor (120 ppmv or 35-percent reduction).
The EPA requests comment and data supporting the achievability of a 120
ppmv MACT floor level (24-hour geometric average, corrected to 7
percent O2) without the use of a scrubbing system. Additionally,
the EPA requests data and information on alternative acid gas control
technologies that could be applied to MWC units at small plants to
comply with a 120 ppmv floor level at a lower cost than a DSI/ESP
system.
Because some MWC units at small existing MWC plants are operated at
a low annual capacity factor and because the cost effectiveness of acid
gas control is sensitive to annual capacity factor, the EPA requests
comment on the appropriateness of subcategorizing MWC units at small
plants by annual capacity factor before determining the MACT floor. The
reanalysis after subcategorizing by annual capacity factor may conclude
that MACT for low capacity MWC units is less restrictive than MACT for
high capacity MWC units at small existing plants.
If the final guidelines establish different control requirements
for low capacity MWC units than high capacity MWC units, the guidelines
would include operational restrictions for low capacity units. That is,
each low capacity MWC unit located at a small MWC plant would be
required to have a federally enforceable operating permit that limits
the annual capacity factor of the unit to a specified capacity level,
and records would have to be maintained to document the amount of waste
fired in the unit on an annual basis. The annual capacity factor would
be calculated on a unit basis and not on a plant basis. This would
assure that obsolete and inoperable MWC units at an MWC site (i.e.,
with a 0-percent annual capacity factor) are not averaged together with
replacement high capacity units to calculate the annual capacity
factor, with the possible effect of circumvention of emission control
requirements for high capacity factor units. Additionally, if a
decision was made to switch a unit from a low capacity operational
designation to a high capacity designation, the unit would have to be
retrofitted with emission control equipment to comply with the emission
guideline requirements for high capacity MWC's.
d. MACT for Hydrogen Chloride for Small MWC Plants. The MACT floor
for HCl for small MWC plants is 660 ppmv, which is above the typical
uncontrolled level of about 500 ppmv. The MACT floor for HCl would not
require acid gas control, but MACT for SO2 would already require
acid gas control based on DSI/ESP systems. Dry sorbent injection/ESP
systems used for SO2 control can achieve greater than 50-percent
reductions in HCl emissions. As discussed above, the cost to retrofit
an SD/ESP or SD/FF system on a small MWC plant would be unreasonably
expensive.
Because a DSI/ESP system operating in a manner that achieves the
MACT for SO2 would also achieve a 50-percent reduction in HCl, the
proposed MACT guideline for HCl at small MWC plants is either 250 ppmv
or 50-percent reduction, whichever is less stringent.
The EPA recognizes that costs associated with the proposed acid gas
control retrofit requirements for small MWC plants are not
insignificant. The same acid gas control system used to control
SO2 emissions controls HCl emissions, and similar issues exist. As
discussed under the MACT SO2 section, small MWC plants represent
about 10 percent of the national MWC capacity to be retrofitted with
acid gas control systems, and the associated cost burden for this acid
gas retrofit would be about 15 percent of the national cost of the
proposal. On a national basis, the retrofit of SO2/HCl acid gas
control systems to small MWC plants would cost about $60 million/yr and
the retrofit of acid gas controls to large MWC plants would be about
$340 million/yr.
As discussed above, the HCl MACT floor for small MWC plants is 660
ppmv and would not require any HCl control. The proposal, however, goes
beyond the MACT floor requirement and would establish MACT at 250 ppmv
or 50-percent HCl reduction based on the DSI/ESP acid gas control
system installed for SO2 control. The EPA is soliciting comments
on the alternative of establishing HCl control requirements for small
MWC plants at the level required by the MACT floor (i.e., 660 ppmv,
which requires no control). The EPA requests comment and data
supporting the achievability of a 660 ppmv MACT floor level (24-hour
geometric average, corrected to 7 percent O2) without the use of a
scrubbing system.
e. MACT for Particulate Matter for Small MWC Plants. Average
uncontrolled PM emissions from MWC's are about 1,500 mg/dscm. The MACT
floor for PM is 85 mg/dscm, which would require about a 95-percent
reduction in PM over uncontrolled levels.
The MACT floor for PM can be achieved with the same DSI/ESP system
needed to meet MACT for the other pollutants. A DSI/ESP system can
achieve PM emissions of less than 69 mg/dscm. The cost to operate a
DSI/ESP system to achieve 69 mg/dscm versus the MACT floor level of 85
mg/dscm is negligible. Therefore, the proposed MACT guideline for PM
for small MWC plants is below the MACT floor at a level of 69 mg/dscm.
f. MACT for Cadmium for Small MWC Plants. Typical uncontrolled
levels of Cd from MWC's are about 1.2 mg/dscm. The MACT floor is also
1.1 mg/dscm, thus the MACT floor requires less than 10-percent Cd
control. However, the DSI/ESP systems that would already be needed to
achieve the MACT floor for SO2 can achieve Cd levels of 0.10 mg/
dscm. The proposed Cd MACT guideline, therefore, is 0.10 mg/dscm based
on DSI/ESP control.
g. MACT for Lead for Small MWC Plants. The average uncontrolled
emission level of Pb from MWC's is about 25 mg/dscm, and the MACT floor
for Pb for small plants is 15 mg/dscm. The MACT floor requires a 40-
percent reduction in Pb. The DSI/ESP systems needed to meet MACT for
acid gases can achieve Pb levels of 1.6 mg/dscm. The proposed MACT for
Pb is based on DSI/ESP control, and the proposed MACT guideline Pb
level is 1.6 mg/dscm.
h. MACT for Mercury for Small MWC Plants. The MACT floor for Hg for
small MWC plants is 1.2 mg/dscm, which is above typical uncontrolled Hg
emission levels for MWC's. Therefore, no Hg control is needed to meet
the MACT floor.
Because acid gas/PM control systems (DSI/ESP) will be needed at
small plants to meet other MACT requirements, activated carbon
injection could be added to the acid gas/PM control system to achieve
Hg control. The incremental cost to add activated carbon injection to
control Hg at small MWC plants already equipped with acid gas/PM
control is about $1.40/Mg of MSW combusted. The EPA believes that this
cost is reasonable given the concerns over the bioaccumulation of Hg in
the environment.
In addition to the EPA's test programs to study Hg removal using
SD-based scrubbing systems with activated carbon injection, the EPA has
also conducted Hg performance tests of DSI-based scrubbing systems with
activated carbon injection at small MWI's (Borgess, Michigan, MWI). The
use of activated carbon injection with either SD-based scrubbing
systems or DSI-based scrubbing systems has demonstrated greater than
85-percent Hg control.
In combination, DSI/ESP systems with activated carbon injection can
achieve Hg emission levels of 0.080 mg/dscm or an 85-percent reduction
in Hg emissions. Therefore, the proposed MACT guideline for Hg for
small MWC plants is 0.080 mg/dscm or an 85-percent reduction, whichever
is less stringent.
i. MACT for Dioxins/Furans for Small MWC Plants. The MACT floor for
total dioxins/furans is 1,700 ng/dscm, which is above typical
uncontrolled levels of about 1,000 ng/dscm. Although the MACT floor for
dioxins/furans would be based on no control, DSI/ESP is already needed
to meet MACT for other pollutants, and GCP are needed to meet MWC
operational and CO requirements. The combination of GCP and DSI/ESP can
achieve total dioxin/furan levels of less than 125 ng/dscm.
As discussed above, MACT for Hg for small plants would be based on
using activated carbon injection. Activated carbon injection provides
additional removal of dioxins/furans beyond that achieved by the acid
gas/PM control system, as discussed in the rationale for MACT for
dioxins/furans for large plants. Recent tests at small MWI's using DSI
systems with activated carbon injection have also shown that additional
dioxin/furan removal is achieved with activated carbon injection
(greater than a 50-percent reduction over levels achieved by the acid
gas/PM control system). Based on the use of activated carbon injection
with GCP and DSI/ESP systems, a level of 60 ng/dscm would be
achievable. The EPA is proposing MACT for dioxins/furans on both a TEQ
basis and a total mass basis. Based on EPA's analysis, a total dioxin/
furan level of 60 ng/dscm is equivalent to 1.0 ng/dscm of dioxin/furan
TEQ. Therefore, the proposed MACT guideline for MWC's at small plants
is 1.0 ng/dscm of dioxin/furan TEQ or 60 ng/dscm total mass dioxins/
furans.
j. MACT for Nitrogen Oxides for Small MWC Plants. Uncontrolled
NOX emissions from MWC's are about 225 ppmv on average. The MACT
floor is no control. The addition of SNCR postcombustion NOX
control has not been demonstrated on any modular starved-air MWC's, and
the performance of such a system on a modular starved-air MWC is in
question. Since NOX control is not required by the MACT floor and
SNCR has not been demonstrated on modular starved-air MWC's,
postcombustion NOX control is not being proposed for small MWC's.
The MACT guideline for NOX for MWC's at small MWC plants is based
on no control. Section VIII of this preamble discusses ``no control''
emission limits for NOX.

G. Selection of Format for the Proposed Guidelines

The February 11, 1991 emission guidelines described a format for
MWC acid gases (SO2 and HCl), MWC metals (PM and opacity), MWC
organics (dioxins/furans), and MWC operating practices (CO, load, and
flue gas temperature), and that same format is being adopted by today's
proposed guidelines, except for dioxins/furans. The selection of the
format for the emission guidelines for the above pollutants is
described in previous Federal Register notices (54 FR 52209, December
20, 1989 and 56 FR 5514, February 11, 1991). For dioxins/furans, the
proposed guidelines establish dioxin/furan guideline emission levels on
both a total mass dioxins/furans basis and a TEQ basis. The format for
the proposed emission guidelines for NOX is the same as the format
of the 1991 NSPS (56 FR 5488, February 11, 1991) and today's proposed
subpart Eb NSPS. The selection of the format for the 1991 NOX
standard is in previous Federal Register notices (54 FR 52251, December
20, 1989 and 56 FR 5488, February 11, 1991). The same format will apply
under the emission guidelines for NOX proposed today for MWC's at
large plants. The specific formats of the proposed emission guidelines
for Cd, Pb, and Hg are discussed below.
As required by section 129(a)(4) of the Act, the proposed emission
guidelines would establish numerical emission limitations for Cd, Pb,
and Hg. For the purpose of regulating Cd and Pb, the format selected in
the proposed emission guidelines for the numerical emission limitations
would be a numerical concentration limit (mg/dscm) corrected to 7
percent O2. For the purpose of regulating Hg, the format selected
in the proposed emissions guidelines would be both a numerical
concentration limit (mg/dscm) and an alternative percentage reduction
requirement. The numerical Hg emission limit reflects the emission
level that can be achieved based on activated carbon injection in
combination with acid gas/PM control. An alternative percentage
reduction requirement may be met instead of the numerical emission
level because emissions of Hg can be highly variable and dependent on
the Hg input level. Even at the same MWC, test data show occasional
spikes of high Hg emissions due to variability in the waste feed. In
cases where Hg levels are temporarily elevated, the 0.080 mg/dscm level
may not be consistently achievable. However, the control devices could
achieve an 85-percent reduction during such episodes. Therefore, a
combination of a concentration level and an optional percentage
reduction format best assures the maximum achievable Hg control while
accommodating potential spikes in Hg emission levels.
As discussed above, the proposed emission guidelines for SO2,
HCl, and Hg include two formats: (1) A percent reduction format, and
(2) an emission limit (concentration) format. The EPA requests comment
on and test data supporting the appropriateness of promulgating final
guidelines for SO2, HCl, and Hg which include only the emission
limit format. For each pollutant, the commenter should specify an
appropriate emission limit (without an associated alternative percent
reduction format) and provide rationale for the limit. Based on the
comments received, the EPA may promulgate final emission guidelines for
SO2, HCl, and Hg in the form of emission limits that are higher or
lower than the proposed emission limits.
The EPA has proposed emission guidelines that reflect the
performance levels achieved by MWC's equipped with properly designed,
constructed, and operated air pollution control systems. The proposed
emission guideline levels would apply during all periods of MWC
operation. To comply with the proposed guideline levels, the air
pollution control system would be designed and operated such that
actual emissions are less than the proposed guideline levels. Where
continuous monitoring systems are available, such as for SO2 and
NOX, the proposal would require their use to determine compliance
on a continuous basis. For other pollutants, an annual stack test would
be required. The EPA requests comment on whether continuous monitoring
methods exist for any additional pollutants.
The EPA also seeks comments on alternate formats of the guidelines
that would encourage optimal control system operation and optimal
performance, thus minimizing emissions. For example, the guidelines
could provide incentives, such as reduced testing and reporting, for
MWC's that operate well below the guideline emission levels. One
approach would be to structure the guideline such that, for an MWC with
three units, if all units demonstrated emissions at least 30 percent
less than the limit, then only one of the units would be tested each
year. The unit selected for testing would be rotated such that each
unit would be tested once every three years.
Another potential regulatory approach to assure optimal performance
would be to supplement the current emission guidelines (which must be
demonstrated by annual stack tests) with more stringent emission
guidelines calculated for each pollutant based on long-term average
emission levels. Compliance with this supplemental emission level would
be determined by continuous monitoring, where applicable, or by the
average of the annual tests from the current year and one or more
preceding years. The current guideline emission levels account for
variability from one emissions test to another, whereas the composite
average emission levels would reflect the mean performance level. This
may be a preferable measure of environmental performance for some of
the pollutants because it is their long term or cumulative emissions
that are of most concern. Other formats of the guidelines that
encourage optimal performance would also be possible. Comments and
suggestions are requested. Based on the information and comments
received, the EPA may change the form of the rule to include a long
term emissions average, and alternative compliance testing schedule, or
other alternative format to encourage optimal performance of the air
pollution control system.
Additionally, the EPA requests comment and suggestions on specific
work practice requirements or equipment requirements that would assure
optimal operation of the air pollution control system and minimize
emissions. Such operating practices or equipment practices would be
most beneficial for minimizing emissions of those pollutants for which
annual stack testing is the proposed compliance test method. Comments
are specifically requested on work practices or equipment requirements
that would minimize dioxin/furan, Hg, Cd, and PM emissions. Based on
the information received, the EPA may require specific work practices
or equipment to supplement the emission limits included in the final
guidelines.

H. Performance Test Methods and Monitoring Requirements

The emission guidelines promulgated on February 11, 1991 (56 FR
5514) for MWC's with unit capacities above 225 Mg/day established
performance testing and monitoring requirements for MWC acid gases
(SO2 and HCl), MWC metals (PM and opacity), MWC organics (dioxins/
furans), and MWC operating practices (CO, load, and flue gas
temperature). These same requirements would be adopted under today's
proposed emission guidelines, except that: (1) Procedures are being
proposed for determining dioxin/furan emissions on a TEQ basis; (2)
testing schedule provisions have been incorporated for annual
compliance testing for PM (opacity not included), HCl, and dioxins/
furans at small MWC plants; and (3) annual opacity tests using EPA
Reference Method 9 (in combination with continuous monitoring of
opacity levels) would be required for both large and small MWC plants.
Furthermore, today's proposal includes new data availability
requirements for CEMS. Today's proposal requires that valid paired CEMS
hourly averages (i.e., SO2 and O2 (or CO2), NOX and
O2 (or CO2), and CO and O2 (or CO2)) be obtained
for 75 percent of the hours per day for 90 percent of the days per
calendar quarter that the MWC is operating and combusting MSW.
Because the proposed NSPS allows compliance with a dioxin/furan
limit either on a TEQ basis or on a total mass basis, procedures are
being proposed for determining dioxin/furan emissions on a TEQ basis.
For measuring dioxins/furans on a TEQ basis, the mass of each dioxin/
furan tetra- through octa- congener would be measured by EPA Reference
Method 23. Each congener mass would then be adjusted by the
corresponding TEF's, which are listed in the proposed NSPS. Finally,
the adjusted congener masses would be added together to determine
dioxins/furans in terms of nanograms per dry standard cubic meter TEQ.
As required by the 1991 subpart Ca emission guidelines, following
the initial performance test for PM, HCl, and dioxins/furans,
subsequent annual performance tests would be required for all MWC's to
demonstrate compliance with the PM, HCl, and dioxin/furan emission
limits. Under today's proposed emission guidelines, if three
consecutive annual compliance tests for an MWC at a small MWC plant
indicate compliance with the emission limit for a pollutant (i.e., PM,
HCl, or dioxins/furans), the MWC would be allowed to wait 3 years
before retesting for the pollutant. If the next test conducted in the
third year shows compliance with the emission limit for that pollutant,
then the facility could again wait 3 years to test for the pollutant.
If noncompliance with the emission limit for the pollutant occurs,
corrective actions would be required to be undertaken and annual
testing would be required to be conducted until 3 consecutive years of
compliance with the emission limit is established. At a minimum,
performance tests for dioxins/furans, HCl, and PM would be required to
be performed for each MWC at a small MWC plant every 3 years. This
provision is included to minimize costs for small MWC plants, while
still retaining periodic testing to ensure compliance.
Testing and monitoring requirements are being proposed in today's
emission guidelines for NOX, Cd, Pb, and Hg emissions. The 1991
NSPS for MWC's includes performance testing and monitoring requirements
for NOX. These testing and monitoring requirements are described
in the NSPS promulgated on February 11, 1991 (56 FR 5488). These same
testing and monitoring requirements would apply to MWC's only at large
plants under today's proposed emission guidelines.
For Cd, Pb, and Hg, annual performance tests would be required for
MWC's subject to the proposed emission guidelines. The performance test
for all three metals would be conducted in accordance with EPA
Reference Method 29. The EPA Reference Method 1 would be used for
determining the number and location of sampling points. The EPA
Reference Method 3 would be used for flue gas analysis. All performance
tests would consist of a minimum of three test runs conducted under
representative operating conditions (i.e., at full load). The average
Cd, Pb, and Hg emission rates of the three runs or more would be used
to determine compliance.
Also, as discussed above for dioxins/furans, PM, and HCl, if small
plants demonstrate compliance with the Cd, Pb, and Hg emission limits
for 3 consecutive years, they would be allowed to begin testing for
these three pollutants every third year. At a minimum, performance
tests for Cd, Pb, and Hg would be required to be performed by small MWC
plants every 3 years. Large plants must test for each of these
pollutants annually. These annual testing requirements are consistent
with those for other pollutants, and MWC plants can reduce testing
expenses by testing for multiple pollutants during the same test
period.
Studies conducted by the EPA have shown EPA Reference Method 29 to
be a more reliable method for measuring Hg from MWC's than EPA
Reference Method 101A. Recent refinements have been made to Method
101A, but the EPA has concluded that Method 29 is a superior method.
In a separate notice in today's Federal Register, EPA Reference
Method 29 is being proposed for determining emissions of Hg and other
metals from MWC's, MWI's, and power plants. Method 29 consists of a
particulate filter followed in series by two nitric acid/hydrogen
peroxide (HNO3/H2O2) impingers and two acidified potassium
permangenate (KMnO4/H2SO4) impingers. The method is
identical to the EPA's Office of Solid Waste multimetals method, except
that Method 29 requires filtration and analysis of the impinger
solution collected in the KMnO4/H2SO4 impingers. These
filtration and analysis requirements are being added to the method for
quality assurance purposes to protect against the loss of Hg in the
manganese oxide (MnO2) precipitate that can form in this solution.
This additional step will result in similar sample preparation and
analysis requirements for EPA Reference Methods 29 and 101A.
The EPA does not believe that addition of this filtration and
analysis step will change the achievable Hg emission rates for MWC's
and MWI's. Because of the significant amount of chlorine in MWC and MWI
flue gas, most of the Hg in these flue gases occurs as water-soluble
ionic Hg. As a result, use of Method 29 collects most of the Hg in
these flue gases on the filter and in the HNO3/H2O2
impingers, with the remainder collected in the KMnO4/
H2SO4 impingers. Flue gases emitted from processes having
lower chlorine levels and/or higher sulfur levels (e.g., coal-fired
power plants) have a higher fraction of their Hg emissions present as
water-insoluble elemental Hg that is collected in the KMnO4/
H2SO4 impingers.
In testing conducted by the EPA at an MWC during which Method 101A
KMnO4/H2SO4 impinger solutions were filtered and the
filters analyzed (with Method 101A, all of the Hg in the flue gas is
collected by the KMnO4/H2SO4 impingers), results showed
that less than 3 percent of the total Hg collected by the sampling
train was associated with precipitated MnO2.
Based on review of analytical procedures used with multimetal train
samples collected during several other EPA-sponsored test programs, the
EPA believes the potential loss of Hg in precipitated MnO2 during
these tests was less than 3 percent (during these tests, the
KMnO4/H2SO4 impingers were shaken prior to removal of a
representative analytical sample and, thus, a portion of any
precipitated MnO2 was likely to have been included in the
analytical sample).
Because the analytical filter only makes a negligible difference in
the Hg test results for MWC's and because it is desirable to use a
uniform Hg test method for all source categories, the EPA is proposing
that the full Method 29 test procedures (including the analytical
filter analysis) be used for measuring Hg emissions from MWC's.
Overall, the proposed guidelines would require that CEMS be used as
the compliance test method for those pollutants for which CEMS are
available (i.e., SO2, NOX, CO, CO2 (or O2),
opacity, MWC load level, and air pollution control device temperature).
For those pollutants for which CEMS are not available (i.e., HCl, Hg,
Cd, Pb, PM, and dioxins/furans), the proposed guidelines would require
that stack test methods be used on an annual basis to determine
compliance. Progress continues to be made on the development of new and
improved CEMS. The EPA requests comment on the availability of CEMS to
replace stack testing for any of the pollutants listed above. The EPA
specifically requests comment on the availability, precision, accuracy,
and cost of CEMS for HCl and Hg. Based on the information received, the
EPA will reconsider CEMS requirements and may increase the number of
pollutants monitored by CEMS.

I. Reporting, Recordkeeping, and Compliance Schedule Requirements

The proposed emission guidelines would require owners and operators
of all designated facilities to submit notifications of the anticipated
date of startup and initial performance test and performance evaluation
of the CEMS (where applicable).
The February 11, 1991 emission guidelines for MWC's established
reporting and recordkeeping requirements for MWC acid gases, MWC
organics (dioxins/furans), MWC metals (PM and opacity), and MWC
operating practices. These reporting and recordkeeping requirements are
summarized in the previous Federal Register notice promulgating the
February 11, 1991 emission guidelines (56 FR 5514). These same
reporting and recordkeeping requirements would be adopted under today's
proposed guidelines with the following exceptions: (1) Dioxin/furan
emissions would be recorded and reported either in terms of dioxin/
furan TEQ or as total mass of dioxins/furans; (2) if MWC's at small
plants have met the criteria allowing them to conduct compliance tests
for PM, HCl, or dioxins/furans every third year (see section IV.H of
this preamble), they would submit a simplified annual report for years
where testing for those pollutants was not required; and (3) both small
and large MWC plants would be required to report the results of annual
EPA Reference Method 9 opacity tests.
Recordkeeping and reporting requirements are being proposed in
today's emission guidelines for NOX, Cd, Pb, and Hg emissions. The
reporting and recordkeeping requirements for NOX are described in
the NSPS promulgated on February 11, 1991 (56 FR 5488). Under today's
proposed emission guidelines, these reporting and recordkeeping
requirements would apply only to MWC's at large plants.
After an initial performance test has been completed, the proposed
emission guidelines would additionally require the submission of annual
compliance reports for Cd, Pb, and Hg. However, if MWC's at small
plants have met the criteria allowing them to conduct compliance tests
for Cd, Pb, or Hg every third year (see section IV.H of this preamble),
they would submit a simplified annual report for years where testing
for those pollutants was not required.
The proposed emission guidelines would require that certain types
of records be maintained. If an activated carbon injection system is
used for Hg control, MWC plants would be required to keep records of
the quantity of activated carbon used for each 8-hour period of MWC
operation. These records would provide documentation that these systems
continue to be operated properly between compliance tests. Initial and
annual compliance reports for fly ash/bottom ash fugitive emissions
testing would be required for MWC's at both small and large MWC plants.
The proposed guidelines would also require that records be kept
regarding the training and certification status of individuals involved
in the operation of the MWC. The proposed guidelines would specify that
all training and certification requirements be met within 1 year after
the date of promulgation of the guidelines.
The proposed emission guidelines include revised compliance
scheduling requirements. The proposed guidelines require State plans to
require both small and large MWC plants to meet one of the following
two compliance schedules: (1) Full compliance with the State plan by no
later than 1 year after the approval of the State plan; or (2) full
compliance with the State plan by no later than 3 years following
issuance of a revised construction or operation permit, if a permit
modification is required, or within 3 years following approval of the
State plan, if a permit modification is not required, provided the
State plan includes measurable and enforceable incremental steps of
progress toward compliance with the State plan. Suggested items for
specification in the State plan would be as follows:
(1) Date for obtaining the services of an architectural and
engineering firm;
(2) Date for obtaining design drawings of the pollution control
device(s);
(3) Date of for submittal of permit modifications, if necessary;
(4) Date for ordering the pollution control device(s);
(5) Date for delivery of the major components of the air pollution
control device(s);
(6) Date of initial site preparation for installing the pollution
control device(s);
(7) Date for commencing installation of the pollution control
device(s);
(8) Date of initial startup of the air pollution control device(s);
and
(9) Date for the initial compliance test(s) of the air pollution
control device(s).
The date associated with each of these incremental steps in a
compliance schedule would be established on a site-specific basis, by
the State air pollution control agency. Furthermore, submittal of the
State plan would be required to include performance test results for
dioxin/furan emissions for those MWC units with a compliance schedule
longer than 1 year from the date of approval of the State plan. These
tests results would be required to have been measured no earlier than
1990 and would be considered by a State in developing a facility's
compliance schedule.
In the event no plan for implementing the emission guidelines is
adopted, all MWC units covered by the guidelines would be required to
be in compliance with the guidelines no later than the date 5 years
after the date of promulgation of these guidelines.
Because of recent concern about dioxin/furan and Hg emissions, the
proposed emission guidelines require State plans to include an
accelerated compliance schedule for compliance with the emission limits
for these two pollutants for one subset of MWC's. Under the accelerated
schedule, existing MWC units for which construction, modification, or
reconstruction commenced after June 26, 1987 and that are located at
large MWC plants would be required to be in compliance with the
proposed dioxin/furan and Hg emission guidelines within 1 year
following issuance of a revised construction or operation permit, if a
permit modification is required, or within 1 year following approval of
the State plan, if a permit modification is not required. On June 26,
1987, the EPA issued operational guidance to State and local agencies
for best available control technology (BACT) determinations for
permitting of both new and modified MWC's, pursuant to the new source
review (NSR) provisions of the Act. This operational guidance has
resulted in all new MWC's at large MWC plants permitted since June 26,
1987 being constructed with an SD/ESP or SD/FF control system. As
discussed in section IV.F.1 of this preamble, control of dioxins/furans
and Hg is based on the combination of an acid gas/PM control system and
a carbon injection system. Since all MWC units at large MWC plants
permitted since June 26, 1987 have been subject to NSR and are,
therefore, already equipped with the appropriate acid gas/PM control
devices for dioxin/furan and Hg control (i.e., SD/ESP or SD/FF), the
EPA concluded that it would be reasonable to require that carbon
injection be retrofitted to these MWC units according to an accelerated
schedule in order to achieve additional dioxin/furan and Hg emission
reductions as soon as possible.
Additionally, compliance with all operator training and
certification guidelines would be required by 1 year after the date of
promulgation of the emission guidelines.
All reports submitted under this rulemaking would also be required
to be maintained as part of these records. All the information
contained in these records would be made available to enforcement
personnel upon request. All required records would be required to be
maintained for 5 years following the date of such records.
The reporting and recordkeeping requirements in the proposed
emission guidelines are necessary to inform enforcement personnel of
the compliance status of existing MWC's. In addition, the records would
provide the data and information necessary to ensure continued
compliance of these MWC's with the emission guidelines. At the same
time, these requirements have been structured so as not to impose an
unreasonable burden on MWC owners or operators.

V. Rationale for the Proposed Guidelines for Fugitive Fly Ash/Bottom
Ash Emissions

The following discussion addresses the basis for EPA's decision to
regulate fugitive fly ash/bottom ash emissions from MWC facilities. The
available technologies for controlling these fugitive emissions and the
EPA's selection of MACT for these emissions are presented.

A. Background

Fugitive emissions from MWC's are emissions of dust from fly ash
and bottom ash handling that are not confined (i.e., emissions that are
not contained within a fully enclosed ash handling system). The fly
ash/bottom ash dust consists of PM and various associated pollutants
adsorbed to the PM such as Cd, Pb, Hg, and organic compounds (e.g.,
dioxins/furans). A study of MWC ash handling and storage facilities has
shown that such facilities, when improperly controlled, can be sources
of these pollutants through fugitive fly ash/bottom ash emissions.
Therefore, visible emission guidelines for fugitive fly ash/bottom ash
emissions are being proposed to ensure that control equipment and
operating practices are implemented to eliminate such emissions.
Currently, more than 12 percent of existing MWC's use control systems
to eliminate fugitive fly ash/bottom ash emissions.

B. Fugitive Emission Control Techniques

Sources of MWC fugitive bottom ash/fly ash emissions include the
ash storage facilities (including ash storage bins or piles), fly ash
and bottom ash conveyors and conveyor transfer points, and truck or
container loading facilities.
Fugitive fly ash/bottom ash emissions from conveyors can be
controlled by totally enclosing the conveyors when they are not already
inside an enclosed structure. Emissions from conveyor transfer points
can be controlled by totally enclosing the transfer point and
ventilating it to a control device if the transfer point is not inside
an enclosed structure. Alternatively, maintaining adequate moisture in
the fly ash and bottom ash can be used to control fugitive emissions
from conveyors or transfer points.
Fugitive fly ash/bottom ash emissions from the ash storage
facilities at an MWC plant can be controlled by totally enclosing the
ash storage areas and by ensuring that the fly ash and bottom ash have
an adequate moisture content to prevent dust. Chemical stabilizers and
binders may also be used in addition to or in place of moisture to
prevent dust emissions from MWC ash for nearly all the activities
described in this section.
Fugitive fly ash/bottom ash emissions from truck or container
loading facilities at the MWC can be controlled primarily by the
moisture content of the ash. Fly ash or bottom ash can be passed
through a water-filled quench tank to wet the ash. Fugitive fly ash/
bottom ash emissions from the ash loading facility at the MWC may also
be controlled by enclosing the ash loading facility, fitting the truck
bays with doors that can be closed, and discharging the vent air to a
control device. Emissions can also be controlled by reducing ash spills
during loading and by recovering any spilled ash through sweeping,
vacuuming, or washing before the spilled ash can dry or be tracked out
of the loading facility.
Fugitive fly ash/bottom ash emissions from moving trucks used for
hauling ash from the MWC can be controlled by ensuring that the ash is
moist and that the truck or container is properly sealed and covered
during transit. Trucks can be covered with tarps, and truck tires can
be washed prior to leaving the ash handling facility to prevent ash
from being tracked onto roadways where it can later become airborne as
fugitive dust emissions.
Data collected at several MWC's indicate that when the control
methods described above are applied in a consistent and conscientious
manner, fugitive fly ash/bottom ash emissions can be controlled so that
no visible emissions are observed from the ash storage facilities or
from ash transfer points such as conveyors, trucks or container loading
facilities, and trucks hauling MWC ash.

C. Proposed Fugitive Emissions Guidelines

An emission guideline level of no visible emissions of fugitive fly
ash/bottom ash emissions from ash storage facilities and transfer
points is consistent with the determination that the controls described
above represent MACT.
Therefore, the following MACT guidelines are being proposed.
Fugitive fly ash/bottom ash emissions from any MWC ash storage facility
or any ash transfer point at an MWC plant with aggregate capacity to
combust greater than 35 Mg/day of MSW would be required to be
controlled so that no visible emissions are detected.
The fly ash/bottom ash visible emissions guidelines would be
determined using EPA Reference Method 22 (3-hour continuous visual
observation). Compliance with the visible emissions guidelines would be
determined by an annual performance test. Reports of initial and annual
performance tests would be required.
Any technology may be used to meet these standards. The fly ash/
bottom ash fugitive emissions guidelines would apply to ash handling
facilities within the property boundary of the MWC including trucks
moving away from the MWC, but would not apply to offsite transport of
ash.

VI. Proposed Guidelines for Air Curtain Incinerators

Air curtain incinerators operate by forcefully projecting a curtain
of air across the top of an open chamber or pit. The air curtain
reduces emissions during operation by promoting better combustion.
Incinerators of this type are built either above or below ground and
typically have refractory walls and a floor. Section 129 of the Act
exempts air curtain incinerators firing MSW from the definition of
``municipal waste combustion unit'' provided that the air curtain
incinerator burns only tree trimmings, yard wastes, and clean untreated
lumber and that it complies with an opacity limit that would be
established by the EPA. As clarified under the proposed guidelines,
``untreated lumber'' means that the lumber has not been painted,
pigment-stained, or ``pressure treated.''
Today's proposed guidelines include guideline opacity levels
specifically for air curtain incinerators that would combust greater
than 35 Mg/day of only yard wastes, tree trimmings, or clean untreated
lumber. The proposed opacity levels are 10-percent opacity (6-minute
average), except that a level of up to 35 percent (6-minute average)
would be allowed during the first 30 minutes of operation of the unit.
The proposed opacity levels are based on levels achieved by well-
designed and operated air curtain incinerators. Compliance with the air
curtain incinerator opacity guidelines would be demonstrated by
conducting an annual compliance test in accordance with EPA Reference
Method 9.
Air curtain incinerators with unit capacities above 35 Mg/day that
burn MSW other than yard wastes, tree trimmings, or clean untreated
lumber are covered by the emission guidelines for MWC's. Air curtain
incinerators with unit capacities above 35 Mg/day that burn only yard
wastes, tree trimmings, or clean untreated lumber would be subject to
the proposed opacity guideline and its associated testing, reporting,
and recordkeeping requirements, but would not be subject to any other
parts of the proposed emission guidelines.

VII. Comparison of the Proposal and European Emission Limits

Europe is more densely populated than the United States and the
combustion of MSW became increasingly common after World War II.
Because European countries have more experience combusting MSW, it is
interesting to compare the emission control requirements for MWC's
located in the Member States of the European Union (EU) to those for
MWC's in the United States. In addition to comparing emission
requirements, the EPA also compared the prevalence of waste combustion
in the United States and the EU.
In general, MSW combustion is more common in the EU than in the
United States. There are 12 members of the EU: Belgium, Denmark,
France, Germany, Great Britain, Greece, Ireland, Italy, Luxembourg, The
Netherlands, Spain, and Portugal. The percentage of waste combusted in
many of the EU countries is over 30 percent, with Denmark, Luxembourg,
and The Netherlands, combusting 60, 60, and 40 percent of their waste,
respectively. As a national average for the United States, 16 percent
of the waste generated is combusted. In the Eastern United States,
where the majority of MWC's are located, the rate of waste combustion
is higher, averaging 25 to 30 percent. In the New England region, the
rate of waste combustion approaches 60 percent. Therefore, although the
United States as a whole has a much lower rate of waste combustion than
does the EU, certain regions of the United States have combustion rates
similar to those of the EU.
Factors such as population density, percentage of urbanization,
land availability, and topography/geology influence the method of waste
disposal for a country or a region. In the EU, the majority of the
countries have population densities that range from 200 to 600 people
per square mile and urban population percentages of 60 to 90 percent.
The United States, in comparison, has a much lower average population
density of approximately 70 people per square mile, and the percentage
of the population living in urban areas is approximately 75 percent. In
the Eastern United States, the population density and percentage of
urban population are higher than national levels, at around 200 people
per square mile with over 80 percent of the population living in urban
areas, which is comparable to most of Europe. As noted above, other
factors contribute to the use of MWC technology. For example, in
Florida, the geology is such that in some cases landfilling waste is
not a desirable option. Similarly, the mountainous regions in parts of
Europe restrict the use of landfilling, and the increased usage of
MWC's is common.
Regarding regulatory development in the EU, the EU sets uniform
environmental guidelines, and individual EU countries may adopt those
guidelines or more stringent requirements. This is similar to the role
the EPA plays with the individual States. Table 6 presents: (1) The
proposed EPA emission guidelines for existing MWC plants with
capacities above 35 and 225 Mg/day; and (2) the EU limits that apply to
new and existing plants. Existing MWC plants in the EU with capacities
greater than 144 Mg/day must meet these requirements by December 1,
1996. All other existing plants with capacities between 24 and 144 Mg/
day must meet these requirements by December 1, 2000.

Table 6.--Comparison of the EPA's Proposed Guidelines and the EU Requirements for Existing MWC's
----------------------------------------------------------------------------------------------------------------
Proposed EPA emission
guidelines^{b EU
Pollutant Units^{a (@ 7% O2) -------------------------------- Guidelines^{d
Small plants^{b Large plants^{c
----------------------------------------------------------------------------------------------------------------
PM.............................. mg/dscm........................ 69 27 39
Cd.............................. mg/dscm........................ 0.10 0.040 (^{e)
Pb.............................. mg/dscm........................ 1.6 0.50 (^{e)
Hg.............................. mg/dscm........................ 0.080^{f 0.080^{f (^{e)
Hg and Cd....................... mg/dscm........................ 0.18^{g 0.12^{g 0.26^{h
Pb+Cr+Cu+Mn^{i.................... mg/dscm........................ (^{j) (^{j) 6.5^{h
HCl............................. ppmv........................... 250^{k, ^{l 35G5k, m 43G5n
SO2............................. ppmv........................... 80^{l, ^{o 35^{o, ^{p 147^{h
NO^{X............................. ppmv........................... 500 180 (^{q)
CO.............................. ppmv........................... 100^{r 100^{r 112^{s
Dioxins/furans.................. ng/dscm TEQ.................... 1.0 0.50 (^{q)
total mass..................... 60 30 (^{q)
----------------------------------------------------------------------------------------------------------------
^{aAll limits are presented on a dry basis, at standard conditions (20 \C, 101 kilopascals) corrected to 7 percent
O2 dry basis.
^{bApplies to plants that commenced construction, modification, or reconstruction on or before September 20, 1994
and have capacities greater than 35 Mg/day and less than or equal to 225 Mg/day.
^{cApplies to plants that commenced construction, modification, or reconstruction on or before September 20, 1994
and have capacities greater than 225 Mg/day.
^{dApplies to all existing plants with capacities greater than 24 Mg/day.
^{eNo individual limit specified. See combined limit.
^{fOr 85-percent reduction.
^{gThe proposed emission guidelines do not include a combined limit for Hg and Cd; however, based on the
individual limits, a combined limit is shown for comparison.
^{hBased on periodic determination.
^{iCr, Cu, and Mn are abbreviations for chromium, copper, and manganese, respectively.
^{jNo combined limit specified. See individual Pb limit.
^{kMeasured by an annual stack test.
^{lOr 50-percent reduction, whichever is less stringent.
^{mOr 95-percent reduction, whichever is less stringent.
^{nBased on a 7-day rolling average, measured continuously.
^{oBased on a 24-hour average, measured continuously.
^{pOr 75-percent reduction, whichever is less stringent.
^{qNo limit specified.
^{rFor mass burn/waterwall combustors. Based on a 4-hour average, measured continuously.
^{sBased on an hourly average, measured continuously.

As shown in table 6, the EU guidelines cover many of the same
pollutants as the EPA emission guidelines proposed in today's notice.
There are differences between the EPA and the EU guidelines with regard
to regulatory flexibility for demonstrating compliance, as well as the
test methods used to measure emissions. Factors like these should be
considered when comparing emission requirements. The EPA and EU both
have set standards for PM, HCl, SO2, and CO. For these pollutants,
the allowable emission levels proposed by the EPA for large MWC plants
are more restrictive than the EU guidelines. For small MWC plants, the
proposed EPA emission guidelines are more restrictive for CO. No EU
limits exist for NOx or dioxins/furans, and the EU metals emission
limits are for combined metals (e.g., Hg+Cd). As shown in table 6, the
proposed EPA guidelines for both large and small plants for Hg and Cd,
if combined, are lower than the EU Hg+Cd limit.
Some of the EU countries have adopted limits that are more
stringent than the general EU guidelines. For example, The Netherlands
has recently adopted standards for new and existing MWC's that are
considered to be some of the most stringent in the world. For example,
the Dutch Hg limit of 0.065 mg/dscm for existing MWC's (corrected to 7
percent O2) is lower than both the EU limit and the EPA's proposed
Hg guidelines of 0.080 mg/dscm. The Dutch dioxin/furan limit for
existing MWC's ranges from 0.13 to 0.52 ng/dscm TEQ (the limit varies
depending on site-specific economics of the MWC). These limits are more
restrictive than the EPA's proposed guidelines (0.5 ng/dscm TEQ or 30
ng/dscm total dioxins/furans for large MWC plants and 1.0 ng/dscm TEQ
or 60 ng/dscm total dioxins/furans for small MWC plants). As noted, the
EU has no dioxin/furan guideline.
It is difficult to compare the Dutch standards directly to the EPA
emission guidelines or to the performance of U.S. MWC's because the
test methods used in The Netherlands to measure emissions are different
from those used in the United States. Also, many Dutch MWC's are
currently completing retrofits in order to meet the Dutch standards by
January 1995. The actual performance level of the MWC units will be
unknown until that time.
As with some of the EU countries, some of the individual States are
establishing more stringent emissions standards than those in today's
proposed guidelines. Brief descriptions of the regulations under
consideration in Florida, Minnesota, and New Jersey are presented
below.
The State of Florida has promulgated a regulation that would set an
Hg emission limit of 0.070 mg/dscm (corrected to 7 percent O2), or
an 80-percent Hg reduction, for facilities that install Hg control
equipment (e.g., activated carbon injection) and that are equipped with
acid gas control equipment. This limit must be met by July 1, 1995, and
compliance must be demonstrated annually using EPA Reference Method
101A. For facilities equipped with acid gas control equipment that
choose to control Hg exclusively through the use of an Hg waste
separation program, Hg emissions would be limited to 0.14 mg/dscm after
July 1, 1995 and to 0.070 mg/dscm after July 1, 1997. Compliance must
be demonstrated semiannually using EPA Reference Method 101A.
Facilities not currently equipped with acid gas controls will be
required to meet the proposed Hg emission limits when the facility is
required to demonstrate compliance with the acid gas limits included in
the EPA's proposal. Florida's rulemaking procedures to develop SO2
and HCl emission limits will be initiated by December 1, 1994 unless
the Federal emission guidelines (today's action) have been proposed by
that date.
The State of Minnesota has also promulgated Hg requirements for
MWC's. For mass burn MWC's with acid gas control, the quarterly Hg
emission limit (one three-test run average) is 0.10 mg/dscm (corrected
to 7 percent O2). However, the annual average Hg emissions limit
(average of the four most recent quarterly tests) is 0.060 mg/dscm.
Measurements must be made using EPA Reference Method 29. The Minnesota
requirement also allows MWC's to demonstrate compliance with the
quarterly and annual limits by achieving an alternative 85-percent
reduction in Hg emissions.
Similar to the Florida regulations, the Minnesota regulation
provides less stringent standards for MWC's without acid gas control
until the time that acid gas control is required.
The State of New Jersey will be proposing an Hg standard for MWC's
of 0.028 mg/dscm (corrected to 7 percent O2), which would be
effective as of January 1, 2000, and an interim standard of 0.065 mg/
dscm or an 80-percent reduction, which would be effective as of
December 31, 1995. The 0.028 mg/dscm limit is based on reducing the
uncontrolled Hg emission level (assumed to be 0.70 mg/dscm) by 80
percent through reduction of Hg in the waste burned, and another 80-
percent reduction from Hg in the flue gas. These limits are annual
averages based on quarterly 3-run testing (i.e., a total of 12 runs),
using EPA Reference Method 29.

VIII. Miscellaneous

This section addresses the four following issues: (1) The selection
of a ``no control'' limit for NOX for MWC's at small MWC plants,
(2) the July 14, 1992 remand of the issue of lead-acid vehicle battery
combustion, (3) request for comments about requiring a materials
separation plan for existing MWC plants, and (4) general request for
comment on the proposal.
Regarding the first issue, section 129 of the Act specifies that
standards and guidelines for MWC's must include emission limits for PM,
opacity, SO2, HCl, NOX, CO, Pb, Cd, Hg, and dioxins/furans.
This means that emission limits for these pollutants must be specified
even if the MACT selected for a subcategory of facilities does not
control that particular pollutant. In particular, MACT requirements for
small MWC plants are based on usage of GCP, DSI/ESP, and activated
carbon injection, but NOX control is not required. Also, MACT
requirements for mass burn/refractory MWC's at large MWC plants are
based on usage of GCP, SD/ESP, and activated carbon injection, but
NOX control is not required under today's proposal (see section
IV.F.1.c for additional discussion). Therefore, a ``no control''
NOX limit is proposed for MWC's at small MWC plants and for mass
burn/refractory MWC's at large MWC plants. The proposed ``no control''
limit for NOX for these MWC's is 500 ppmv. The proposed guidelines
do not include any testing, reporting, or recordkeeping associated with
the ``no control'' emission limit. The 500 ppmv limit represents an
emission level higher than any of the test data and allows an adequate
margin to accommodate the variability in NOX emission levels. The
EPA expects that this ``no control'' limit will not be exceeded. The
EPA requests public comments on whether it is appropriate to include
such a ``no control'' emission limit in the final emission guidelines
or whether such a limit is not necessary.
Regarding the second issue, on December 20, 1989, the EPA proposed
NSPS and emission guidelines for new and existing MWC's under section
111 of the Act. The proposed NSPS and emission guidelines included a
prohibition on the combustion of lead-acid vehicle batteries in MWC's.
On February 11, 1991, the EPA promulgated standards and guidelines for
new and existing MWC that did not prohibit the combustion of lead-acid
vehicle batteries. The decision not to prohibit the combustion of lead-
acid vehicle batteries was challenged in the U.S. Court of Appeals for
the District of Columbia Circuit by NRDC, the State of New York, and
the State of Florida. In 1992, the U.S. Court of Appeals for the
District of Columbia Circuit concluded that the EPA had not adequately
explained its decision not to require a lead acid battery separation as
part of the 1991 NSPS and emission guidelines, when it had included
such a requirement in its proposed rule (State of New York v. Reilly,
969 F.2d 1147, 1153 (D.C.Cir. 1992)). The EPA is not addressing the
lead acid battery issue in this notice, but will publish a separate
notice in the Federal Register in the near future.
Regarding the third issue, unlike the NSPS for new MWC's proposed
in a separate part of today's Federal Register, the proposed emission
guidelines do not include any requirement for existing MWC's to prepare
a materials separation plan. However, the EPA is considering the option
of adding this type of requirement to the emission guidelines at
promulgation. As defined in section 69.51b of the proposed NSPS
(subpart Eb) included in a separate part of today's Federal Register, a
materials separation plan would be a plan that identifies both a goal
and an approach for a given MWC to separate certain components of MSW
for its service area in order to make the separated materials available
for recycling. While the current NSPS proposal does not require the
adoption of any particular approach, various types of approaches that
the owner or operator of an MWC may choose to include in their
materials separation plan are drop-off facilities, buy-back or deposit-
return incentives, curbside pick-up programs, or centralized mechanical
separation. Refer to the proposed NSPS in a separate part of today's
Federal Register for further discussion of the proposed material
separation plan for new MWC's.
As part of development of a materials separation plan, the owner or
operator of an existing MWC would be required to hold two public
hearings for presentation of preliminary and final draft materials
separation plans. The first public meeting would present the
opportunity for the existing facility and interested public from the
service area to discuss, among other issues, the types of materials
separation approaches suited to the service area of the MWC. The second
public meeting would present the opportunity for the existing facility
to present a plan to integrate approaches discussed at the initial
public meeting into the operation of the MWC (i.e., to discuss the
effects of different types of materials separation on the performance
of the combustor). After each public meeting, the owner or operator
would be required to prepare and distribute documents responding to the
public comments received at the public meetings. The final materials
separation plan would be submitted along with the report documenting
the results of the initial compliance test. Additionally, the owner or
operator may be required to submit some form of annual report
summarizing the effectiveness of the materials separation plan and
identifying any modifications made to the plan after implementation.
This last requirement has not yet been incorporated into the proposed
NSPS materials separation requirements included in a separate part of
today's Federal Register; however, the EPA has specifically requested
comment in that notice on the usefulness of this type of subsequent
reporting for assuring efficient application of the plan.
The EPA requests comments on the appropriateness of including
materials separation plan requirements in the emission guidelines for
existing MWC's.
Regarding the fourth issue, the MWC regulations are complex, and
the EPA expects to receive numerous comments on this proposal. The EPA
has specifically requested comments on items fundamental to the
proposal, including but not limited to the MACT floor, MACT performance
levels, and a consideration of materials separation requirements for
existing MWC's.

IX. Administrative Requirements

This section addresses the following administrative requirements:
Public hearing, docket, procedural requirements of the Act, Executive
Order 12866 review, and Regulatory Flexibility Act compliance.

A. Public Hearing

A public hearing will be held 15 days following proposal. The
hearing will be held at Research Triangle Park, North Carolina, and
will start about 9:00 a.m. At the public hearing, the proposed
standards will be discussed in accordance with section 307(d)(5) of the
Act. Persons wishing to make oral presentations at the public hearing
should contact the EPA at the address given in the ADDRESSES section of
this preamble. Oral presentations will be limited to 15 minutes each.
Any member of the public may file a written statement before, during,
or within 30 days after the hearing. Written statements should be
mailed to the Air and Radiation Docket and Information Center at the
address given in the ADDRESSES section of this preamble.
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 Air and Radiation Docket and Information Center in
Washington, DC (see ADDRESSES section of this preamble).

B. Docket

The docket is an organized and complete file of all the information
submitted to or otherwise considered in the development of this
proposed rulemaking. The principal purposes of the docket are: (1) To
allow interested parties to identify and locate documents so that they
can effectively participate in the rulemaking process; and (2) to serve
as the official record in case of judicial review, except for
interagency review material (section 307(d)(7)(A)). The docket number
for this rulemaking is A-90-45. Docket No. A-89-08 also includes
background information for this rulemaking that supported the proposal
and promulgation of the subpart Ca emission guidelines.

C. Clean Air Act Procedural Requirements

The following procedural requirements of the Act are addressed:
Administrative listing, periodic review, external participation, and
economic impact assessment.
1. Administrative Listing--Sections 111 and 129 of the Act
As prescribed by section 111 of the Act, establishment of emission
guidelines for MWC's is based on the Administrator's determination (52
FR 25399, July 7, 1987) that these sources contribute significantly to
air pollution that may reasonably be anticipated to endanger public
health or welfare. Additionally, section 129 of the Act of 1990 directs
the Administrator to promulgate guidelines for existing MWC's.
2. Periodic Review--Sections 111 and 129 of the Act
Sections 111 and 129 of the Act require that the guidelines be
reviewed no later than 5 years following the initial promulgation. At
that time and at 5-year intervals thereafter, the Administrator shall
review the guidelines in accordance with sections 111 and 129 of the
Act and revise them if necessary. This review will include an
assessment of such factors as the need for integration with other
programs, the existence of alternative methods, enforceability,
improvements in emission control technology, and reporting
requirements.
3. External Participation
In accordance with section 117 of the Act, publication of this
proposal was preceded by consultation with appropriate advisory
committees, independent experts, and Federal departments and agencies.
The Administrator welcomes comments on all aspects of the proposed
guidelines, including economic and technological issues.

4. Economic Impact Assessment

Section 317A of the Act requires the EPA to prepare an economic
impact assessment for any emission guidelines promulgated under section
111(d) of the Act. An economic impact assessment was prepared for the
proposed emission guidelines. In the manner described in sections III,
IV, and V of this preamble regarding the impacts of and rationale for
the proposed emission guidelines, the EPA considered all aspects of the
economic impact assessment in proposing the emission guidelines. The
economic impact assessment is included in the list of key technical
documents at the beginning of today's notice under SUPPLEMENTARY
INFORMATION.

D. Executive Order 12866 Review

Under Executive Order 12866 (58 FR 51735, October 4, 1993), the EPA
must determine whether the regulatory action is ``significant'' and,
therefore, subject to the Office of Management and Budget (OMB) review
and the requirements of the Executive Order. The Order defines a
``significant'' regulatory action as one that is likely to lead to a
rule that may:
(1) Have an annual effect on the economy of $100 million or more,
or adversely affect in a material way the economy, a sector of the
economy, productivity, competition, jobs, the environment, public
health or safety, or State, local, or tribal governments or
communities;
(2) create a serious inconsistency or otherwise interfere with an
action taken or planned by another agency;
(3) materially alter the budgetary impact of entitlements, grants,
users fees, or loan programs, or the rights and obligations of
recipients thereof; or
(4) raise novel legal or policy issues arising out of legal
mandates, the President's priorities, or the principles set forth in
the Executive Order.
Pursuant to the terms of Executive Order 12866, the EPA considers
these proposed guidelines to be ``significant'' because their annual
effect on the economy would be expected to exceed $100 million. As
such, this action was submitted to OMB for review. Changes made in
response to OMB suggestions or recommendations will be documented in
the public docket for this rulemaking.

E. Regulatory Flexibility Act Compliance

Section 605 of the Regulatory Flexibility Act (RFA) of 1980 (5
U.S.C. 601 et seq.) requires Federal agencies to give special
consideration to the impacts of regulations on small entities, which
are small businesses, small organizations, and small governments. The
major purpose of the RFA is to keep paperwork and regulatory
requirements from getting out of proportion to the scale of the
entities being regulated, without compromising the objectives of, in
this case, the Act.
If a regulation is likely to have significant economic impacts on a
substantial number of small entities, the EPA may give special
consideration to those small entities when analyzing regulatory
alternatives and drafting the regulation. In the case at hand, the EPA
considers that a regulation that is likely to affect 20 percent or more
of small entities with MWC's is a regulation that will affect a
substantial number of small entities.
Definitions of small entities are flexible. For analysis of the
guidelines being proposed today, the EPA considers a small business in
this industry to be one with gross annual revenue less than $6 million,
and a small government to be one that serves a population of less than
50,000. (A typical city of 50,000 generates about 90 Mg/day of MSW.)
Most small governments dispose of their MSW by landfilling and,
therefore, will not be affected by regulation of MWC emissions. In
regard to small organizations such as independent not-for-profit
enterprises, the EPA finds that they have no more than a very minor
involvement with MWC's, and for that reason the EPA has not found it
necessary to study potential direct impacts on small organizations.
A limited number of MWC units exist that range in size upward from
a capacity to combust less than 1 Mg/day of MSW to those capable of
combusting 35 Mg/day. The EPA estimates that MWC's under 35 Mg/day in
capacity except for MWI's, which will be regulated under a separate
action, contribute a negligible fraction of total MWC emissions. Many
MWC's under 35 Mg/day in capacity, and a few larger ones, are owned or
operated by small entities. The EPA estimates that considerably fewer
than 20 percent of small-entity MWC's will be affected by the emission
guidelines being proposed today.
Thus, the number of affected small entities is not expected to be
substantial, and a regulatory flexibility analysis is not required.
Nevertheless, the EPA has conducted an extensive analysis of potential
regulatory impacts on households, small governments, and small
businesses. The full analysis is included in the economic impact
assessment in the docket and listed at the beginning of today's notice
under SUPPLEMENTARY INFORMATION.
On December 20, 1989, the EPA proposed standards and emission
guidelines that applied to all sizes of MWC's. The proposal had no
lower size cutoff. Small businesses, small governments, and groups
representing small-entity interests commented extensively on the need
to lighten the potential regulatory burden on small entities. Most
commenters suggested a small size cutoff considerably smaller than the
one now being proposed. The most frequently suggested levels were 5 to
11 Mg/day, 18 Mg/day, 23 Mg/day, and 45 Mg/day. The EPA has used these
suggestions and the information submitted by these commenters, as well
as information from other sources, to fulfill the intent of the RFA.
The EPA has incorporated into the guidelines being proposed today
several features that will mitigate, and in most cases eliminate, any
potentially adverse economic impacts on small entities. These features
are as follows:
(1) The emission guidelines will apply only to MWC's with a plant
capacity of greater than 35 Mg/day. This cutoff eliminates from the
purview of the guidelines the overwhelming majority of existing very
small MWC's (There will be a one-time requirement for MWC plants in the
25 to 35 Mg/day range to report for verification the capacities and
locations of the plants, but this paperwork will impose a very minor
economic burden.);
(2) The guidelines are ``tiered'' so that the stringency (and
therefore potential economic burden) of the emission guidelines
increases as the size of the MWC plant increases. Plants with
capacities of 25 to 35 Mg/day would have only the one-time reporting of
capacity and location. Plants with capacities of 35 to 225 Mg/day would
have guidelines for PM, opacity, dioxins/furans, SO2, HCl, Cd, Pb,
Hg, operating practices, and operator training and certification.
Additionally, small MWC plants would be required to perform compliance
testing, but the guidelines and compliance testing requirements would
not be as stringent as those for plants larger than 225 Mg/day.
Furthermore, the plants would not be required to control NOX.
Plants with capacities above 225 Mg/day would be subject to guidelines
for NOX in addition to all other pollutants, and compliance
testing would be required more frequently;
(3) The emission guidelines consist of emission limits, as opposed
to design, equipment, work practice, or operational standards. Emission
limits give MWC owners and operators the freedom to select the most
economical means of reducing emissions; and
(4) The emission guidelines are not the usual type of regulation
governed by the RFA. The guidelines will not apply directly to any
MWC's, but will be used as a guide by individual State air pollution
control agencies in developing site-specific regulations for MWC's.
States are allowed some flexibility in implementing the guidelines.
Pursuant to the provisions of 5 U.S.C. 605(b), the EPA certifies that
these proposed emission guidelines, if promulgated, will not have a
significant economic impact on a substantial number of small entities,
because the number of small entities affected is not substantial.

F. Executive Order 12875

Under Executive Order 12875, the EPA is required to consult with
representatives of affected State, local, and tribal governments, and
keep these affected parties informed about the content and effect of
the proposed standards. The following discussion provides a brief
summary of the content, need for, and cost of the proposal, as well as
the actions that the EPA has taken to communicate and consult with the
affected parties.
1. Summary of the Proposed Guidelines
The proposed emission guidelines would establish emission
limitations for existing MWC units located at MWC plants with plant
capacities to combust greater than 35 Mg/day of MSW. The proposed
guidelines do not specify which type of air pollution control equipment
must be used at MWC's to meet the proposed emission limitations. The
EPA expects, however, that, as a result of the proposal, most large MWC
plants (plants with greater than 225 Mg/day capacity) would retrofit
scrubbing systems (SD/ESP) for dioxins/furans, metals, and acid gas
control and SNCR for NOX control. Small MWC plants (plants with 35
to 225 Mg/day capacity) would be expected to install scrubbing systems
(DSI/ESP), but SNCR technology would not be necessary. Refer to section
II of this preamble for a more detailed discussion of the proposed
guidelines.
2. Need for the Proposed Guidelines
Under the Act Amendments of 1990, section 129 includes a schedule
that requires the EPA to adopt the emission guidelines for large and
small MWC plants by the end of 1991 and 1992, respectively. The EPA did
not comply with that schedule and is now under court order to propose
the emission guidelines by September 1, 1994 and promulgate the
emission guidelines by September 1, 1995. As required by section 129,
the proposed emission guidelines would establish guideline emission
levels for MWC organics (dioxins/furans), MWC metals (Cd, Pb, Hg, PM,
and opacity), MWC acid gases (HCl and SO2), and NOX. See
section I of this preamble for further discussion of the regulatory
history and general goals of the proposed guidelines.
3. Cost of the Proposal
The national cost of the proposed guidelines would be about $445
million per year. More than 40 percent of all existing MWC capacity
subject to this proposal has already installed acid gas/PM control
systems. The retrofit cost of the air pollution control system for an
individual combustor subject to the proposed guidelines will vary
depending on the plant size and difficulty of the retrofit. The average
annualized retrofit cost of the proposed guidelines for a typical large
MWC plant requiring retrofit would be about $4.1 million per year. The
average annualized retrofit cost of the proposed guidelines for a
typical small MWC plant requiring retrofit would be about $0.9 million
per year. Tipping fees at combustors currently average about $57/Mg of
MSW combusted. For those MWC plants that would require an air pollution
control retrofit as a result of the proposal, the tipping fees would
typically increase by $17 to $28/Mg, with the lower cost being for
large MWC plants and the higher cost being for small MWC plants.
Regarding the impact of the proposed guidelines directly or indirectly
on households, the EPA projects an increase in the household cost of
waste disposal of about $22 to $26 per year or about $2 per month for
communities that have MWC's. Refer to section III.D of this preamble
for a more complete summary of the cost and economic impacts of the
proposed guidelines, on both national and plant-specific bases.
4. Communication With Affected Parties
As previously mentioned, Executive Order 12875 requires the EPA to
consult with representatives of affected State, local, and tribal
governments, and prior to promulgation of final standards, summarize
concerns of the governmental entities and respond to their comments.
The EPA has already initiated consultations with numerous governmental
entities including, but not limited to, the U.S. Conference of Mayors,
the National League of Cities, the National Association of Counties,
the Municipal Waste Management Association, and the Solid Waste
Association of North America. These groups have been informed of the
content of the proposal and the estimated impacts. In drafting the
proposal, the EPA has considered the concerns expressed by these
groups, and discussions with these groups will continue following
proposal. Following proposal, the EPA will mail a copy of this proposal
to all owners/operators of MWC's and their associated local
governmental official. The EPA awaits their comments on the proposal
and will respond to their comments.

List of Subjects in 40 CFR Part 60

Air pollution control, Incorporation by reference,
Intergovernmental relations, Reporting and recordkeeping.

Dated: September 1, 1994.
Jonathan Z. Cannon,
Acting Administrator.
[FR Doc. 94-22343 Filed 9-19-94; 8:45 am]
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