United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research.Triangle Park, NC 27711
EPA-452/R-94-008
February 1994
Air
f> EPA SO2 GUIDELINE DOCUMENT
-------
DISCLAIMER
This report has been reviewed by the Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency, and
approved for publication. Any mention of trade names or
commercial products is not intended to constitute endorsement or
recommendation for use.
Publication No. EPA-452/R-94-008
ii February 1994
-------
CONTENTS
Disclaimer ii
Appendices viii
Tables ix
1. Introduction 1-1
1.1 Overview of the Manual 1-1
1.2 Provisions for Updating the Manual 1-2
1.3 Additional Information Sources 1-2
2. Determining Air Quality Status 2-1
2.1 Section 107 Attainment Demonstration Redesignations. . 2-1
2.1.1 General 2-1
2.1.2 Designating Areas as Nonattainment 2-1
2.1.3 Redesignating Areas to Attainment 2-2
2.1.4 Monitoring Data and Modeling Results 2-5
2.1.5 Control Strategy Demonstration 2-6
2.1.6 Future SIP Violations 2-7
2.1.7 Area Boundaries 2-7
References for Section 2.1 2-9
2.2 Ambient Air 2-17
2.2.1 General 2-17
2.2.2 Location Aspects 2-17
2.2.3 Time Aspects 2-18
2.2.4 Public Access 2-18
2.2.5 PSD Considerations * 2-18
2.2.6 Land Acquisition 2-19
References for Section 2.2 2-20
3. Ambient Air Quality Monitoring and Data Usage 3-1
3.1 General 3-1
References for Section 3.1 3-4
3.2 Quality Assurance 3-6
References for Section 3.2 3-8
3.3 Ambient Monitoring Methodology 3-9
3.3.1 General 3-9
3.3.2 Sampling Interval 3-9
3.3.3 Data Completeness 3-9
References for Section 3.3 3-10
3.4 Network Design 3-12
References for Section 3.4 3-14
3.5 Probe Siting Criteria 3-16
References for Section 3.5 3-17
3.6 Episode Monitoring 3-18
3.7 Ambient Air Quality Data Reporting 3-19
3.7.1 General 3-19
3.7.2 Air Pollution Index 3-20
References for Section 3.7 3-21
iii February 1994
-------
3.8 Ambient Air Monitoring Network for Model
Evaluation 3-^
References for Section 3.8 3-
4. Air Quality Modeling 4-1
4.1 General 4-1
4.2 Guidance on Air Quality Models 4-1
References for Sections 4.1 and 4.2 4-4
4.3 Model Selection 4-6
References for Section 4.3 4-8
4.4 Meteorological Input 4-10
References for Section 4.4 4-12
4.5 Source Input 4-14
4.5.1 General 4-14
4.5.2 Allowable Versus Actual Emissions 4-14
4.5.3 Background Concentration 4-15
4.5.4 Stack Height Input to Air Quality Modeling. . .4-16
4.5.5 Stack Downwash and Building Wake Effects. . . .4-18
References for Section 4.5 4-19
4.6 Receptor Grid 4-21
References for Section 4.6 4-22
4.7 Other Model Requirements 4-23
References for Section 4.7 4-25
5. Stack Height Regulations 5-1
5.1 General Regulations 5-1
References for Section 5.1 5-2
5.2 Good Engineering Practice Stack Height 5-3
5.2.1 General 5-:-
5.2.2 Definition of Nearby for GEP 5-4
5.2.3 Definition of Excessive Concentration 5-4
References for Section 5.2 '• 5-6
5.3 Dispersion Techniques 5-7
5.3.1 General 5-7
5.3.2 Prohibitions 5-7
5.3.3 Exceptions 5-7
References for Section 5.3 5-8
5.4 Remanded Regulations 5-9
References for Section 5.4 5-10
5.5 Specific Stack Height Policies 5-11
5.5.1 Definition of "In Existence" 5-11
5.5.2 Tie-Ins to Existing Stacks 5-12
References for Section 5.5 5-13
5.6 Demonstrations by Fluid Modeling, Field Studies or
Nuisance 5-14
5.6.1 Applicability 5-14
5.6.2 Field Studies 5-14
5.6.3 Fluid Modeling 5-15
5.6.3.1 Credit for Height Above GEP Formula . 5-15
5.6.3.2 Credit for Height Less than or Equal
to GEP Formula 5-15
5.6.4 Emission Rate for Physical Demonstrations . . . 5-16
5.6.5 Not in Ambient Air 5-16
5.6.6 Additional Guidance 5
iv February 199T
-------
References for Section 5.6 5-18
5.7 Merged Stacks 5-21
5.7.1 General 5-21
5.7.2 Exceptions 5-21
References for Section 5.7 5-23
5.8 Stack Height Negative Declarations 5-25
5.8.1 General 5-25
5.8.2 Information Needed 5-25
5.8.3 Modeling Needed 5-25
References for Section 5.8 5-27
5.9 Emissions Balancing 5-28
References for Section 5.9 5-29
6. General Provisions 6-1
6.1 General 6-1
6.2 Current NAAQS and PSD Increments 6-3
6.2.1 General 6-3
6.2.2 National Ambient Air Quality Standards 6-3
6.2.3 Prevention of Significant Deterioration
Increments 6-3
References for Section 6.2 6-6
6.3 Nonattainment Area Time Frames 6-7
6.3.1 Title I of the Clean Air Act Amendments of 1990 6-7
6.3.2 Plan Submittal 6-8
6.3.2.1 Primary SIP Deadlines 6-8
6.3.2.2 Secondary SIP Deadlines 6-8
6.3.2.3 Combined Secondary and Primary SIP
Deadlines 6-9
6.3.3 Attainment Schedule 6-9
6.3.3.1 Primary NAAQS Attainment Dates . . . .6-9
6.3.3.2 Secondary NAAQS Attainment Dates . . . 6-10
References for Section 6.3 6-11
6.4 Establishing Emission Limitations 6-14
6.4.1 Design Concentration 6-14
6.4.2 Averaging Periods 6-14
6.4.3 Compliance Methods 6-15
6.4.4 Multipoint Rollback Modeling 6-16
References for Section 6.4 6-15
6.5 SIP Revisions 6-19
6.5.1 General 6-19
6.5.2 SIP Completeness 6-19
6.5.3 Approval Options 6-20
6.5.4 Grandfathering 6-23
6.5.5 SIP Relaxations 6-24
6.5.6 SIP Tightening 6-24
References for Section 6.5 6-25
6.6 Sanctions and FIP Reqiuirements 6-31
6.6.1 Actions Triggering Sanctions & FIP Requirements 6-31
6.6.2 Sanctions and FIP Clocks 6-31
6.6.3 Available Sanctions 6-32
References for Section 6.6 6-34
6.7 Interim Control Strategies 6-36
References for Section 6.7 6-37
v February 1994
-------
6.8 SIP Calls 6-38
6.9 Nonattainment Area Control Requirements for S02 Sources 6-
6.9.1 RACT 6-'
6.9.2 RFP 6-39
6.9.3 Contingency Measures 6-40
References for Section 6.9 6-42
7. Permits 7-1
7.1 Permit Programs 7-1
References for Section 7.1 7-2
7.2 Permit Requirements 7-3
7.2.1 General 7-3
7.2.2 Nonattainment Areas 7-3
7.2.2.1 Applicability 7-3
7.2.2.2 Control Technology Requirements .... 7-3
7.2.2.3 Emission Offsets 7-4
7.2.2.4 Net Air Quality Benefit 7-4
7.2.2.5 Other Requirements 7-5
7.2.3 NSR Transition 7-7
7.2.4 PSD Areas 7-9
7.2.4.1 Applicability 7-9
7.2.4.2 Control Technology Requirements .... 7-10
7.2.4.3 Air Quality Analysis 7-11
7.2.4.4 Other Impacts 7-12
7.2.4.5 Class I Areas 7-13
7.2.5 SIP Permit Requirements 7-14
7.2.6 Visibility 7-15
References for Section 7.2 7-
7.3 Emissions Trading 7-
7.3.1 General Policy Aspects 7-
7.3.1.1 Bubbling .- 7-23
7.3.1.2 Netting 7-23
7.3.1.3 Offsets 7-24
7.3.1.4 Banking 7-24
7.3.1.5 Emission Reduction Credits 7-24
7.3.2 SO2-Specific Policy Aspects 7-24
References for 7.3 7-27
8. Compliance and Enforcement 8-1
8.1 General 8-1
8.2 Enforceability Criteria 8-1
References for Section 8.2 8-4
8.3 Continuous Compliance 8-6
8.3.1 General 8-6
8.3.2 Enforcement Discretion Approach 8-7
8.3.3 Malfunctions and Unusual Start-up or
Shutdown 8-8
8.3.4 Fuel Shortage 8-9
References for Section 8.3 8-10
8.4 Compliance Monitoring Requirements 8-12
References for Section 8.4 8-15
8.5 Compliance Plans/Schedules 8-16
References for Section 8.5 8-18
vi February 19:
-------
9. New Source Performance Standards 9-1
9.1 General 9-1
References for Section 9.1 9-3
9.2 NSPS Provisions for S02 9-4
9.2.1 Subpart D--Fossil-Fuel-Fired Steam Generators .9-4
9.2.2 Subpart Da--Electric Utility Steam
Generating Units 9-4
9.2.3 Subpart Db--Industrial, Commercial, and
Institutional Steam Generators 9-5
9.2.4 Subpart Dc--Small-Commercial-Institutional Steam
Generating Units 9-6
9.2.5 Subpart Ea--Municipal Waste Combustors. ... 9-7
9.2.6 Subpart GG--Stationary Gas Turines 9-7
9.2.7 Subpart H--Sulfuric Acid Plants 9-7
9.2.8 Subpart J--Petroleum Refineries 9-8
9.2.9 Subparts P, Q, and R--Smelters 9-8
References for Section 9.2 9-9
9.3 EG Provisions for S02 9-11
9.3.1 Subpart Ca--Municipal Waste Combustors. ... 9-11
Reference for Section 9.3 9-12
9.4 Modification/Reconstruction Provisions 9-13
References for Section 9.4 9-15
vii February 1994
-------
Appendices
A. S02 Checklist A-l
B. SO, Guideline References B-l
viii February 19
-------
TABLES
Number Page
6-1 Current PSD Increments for S02 6-5
9-1 Summary of NSPS SO2 Regulations 9-16
ix February 1994
-------
1. INTRODUCTION
1.1 OVERVIEW OF THE MANUAL
The Sulfur Dioxide (S02) Guideline is an integration
and clarification of policy and guidance information
available for S02 programs. The Guideline is divided into
nine chapters as follows:
1. Introduction,
2. Determining Air Quality Status,
3. Ambient Air Quality Monitoring and Data Usage,
4. Air Quality Modeling,
5. Stack Height Regulations,
6. General Provisions,
7. Permits,
8. Compliance and Enforcement, and..
9. New Source Performance Standards.
Emissions inventory guidance is discussed primarily in
conjunction with the air quality modeling guidance, which is
presented in Chapter 4.
Each chapter summarizes relevant policy and guidance
and provides detailed references to guide the user to more
complete sources. References include statutory and
regulatory sources [Clean Air Act and Code of Federal
Regulations (CFR)], Federal Register notices, U.S.
Environmental Protection Agency (EPA) guideline documents,
EPA policy, questions and answers (Q & A's), and guidance
memoranda. Where appropriate, quotations are provided from
the applicable reference materials to be used as a quick
reference. Citations to the CFR should be checked regularly
as it is updated annually, which may not be reflected in
1-1 February 1994
-------
this document.
This guideline is intended to provide a guide to policy
and guidance ,in.effect at the time of its preparation. The
SO2 guideline should not be cited in regulatory actions
because any regulatory decisions should be based on the
original sources, rather than the summaries in each chapter.
In addition, in some instances, it is possible that only
part of a document still represents current EPA policy.
Therefore, before citing a document section excerpted in the
references at the end of each chapter, please consult EPA to
assure the information is still current.
Appendix A contains a checklist for preparing and
reviewing S02 SIP revisions. Appendix B to this document
contains copies of the memoranda cited in the reference
sections.
1.2 PROVISIONS FOR UPDATING THE MANUAL
The guideline will be updated periodically by adding
new pages or replacing existing pages. Revised pages will
be dated and copies will be provided by the EPA's Office of
Air Quality Planning and Standards (OAQPS) to the EPA
Regional Office SO2 contacts. Citations of the CFR are to
the most current version at the time of preparation of this
guideline. Users of the guideline should refer to later
versions of the CFR since it is updated on a regular basis.
The CFR is published annually including changes for that
year. However, new/revised regulations can be promulgated
at any time and States should be aware of those prior to
publication in the bound CFR.
1.3 ADDITIONAL INFORMATION SOURCES
This guideline is intended to be used in conjunction
with other guidance documents and policy statements
including the following:
• General Preamble (see 57 FR 13598, April 16, 1992 and
1-2 February 1994
-------
57 FR 18070, April 29, 1992).
• Air Programs Policy and Guidance Notebook. Many
references cited in this guideline are found in this
notebook and are cross referenced by PN number from the
notebook.
• New Source Review/Prevention of Significant
Deterioration and Nonattainment Area Guidance Notebook:
contains comprehensive NSR/PSD guidance.
• New Source Review Workshop Manual: describes in
general terms, and illustrates by examples, the
requirements of the NSR regulations and existing
policies.
• Clean Air Act Compliance/Enforcement Policy Compendium:
contains comprehensive compliance guidance.
• Guideline for Review of State implementation plan (SIP)
Revisions by EPA Regional Offices: contains references
on SIP processing.
• Processing procedures for SIP revisions for part 52,
part 62-III(d) Plans, and part 82 Redesignations.
• Guideline on Air Quality Models: contains
comprehensive modeling guidance.
Where existing guidance is insufficient, State and
local agencies should seek clarification from their Regional
Office contact. Regional Offices are encouraged to solicit
additional guidance when needed from EPA Headquarters
personnel. Contact the S02/Particulate Matter Programs
Branch, AQMD, OAQPS at 919/541-5628.
1-3 February 1994
-------
2. DETERMINING AIR QUALITY STATUS
2.1 SECTION 1.07 ATTAINMENT DEMONSTRATION AND REDESIGNATIONS
2.1.1 General. Section 107 of the Clean Air Act requires
the EPA to identify the air quality status for every air
quality control region (AQCR) within each State. Current
attainment status of section 107 areas for S02 is listed
under subpart C of 40 CFR part 81 as either attainment,
nonattainment, or unclassifiable. The EPA considers
revisions to this list upon request from the State, and was
also given authority under the CAA amendments of 1990 to
initiate and promulgate designations itself.1
An assessment of the attainment status of an area
should involve a review of all available information.
Typically, such information would include the most recent
eight quarters of ambient monitoring data, air quality
modeling results, and evidence of an implemented control
strategy that meets EPA requirements.2 Attainment
determinations for S02 will generally not -rely on ambient
monitoring data alone, but instead will be supported by an
acceptable modeling analysis which quantifies that the SIP
strategy is sound and that enforceable emission limits are
responsible for attainment.3 An area may be designated
nonattainment based on two or more exceedances of the
National Ambient Air Quality Standards (NAAQS), either
modeled at the same receptor or measured at the same monitor
(i.e., two exceedances per year equal one violation).4
2.1.2 Designating Areas as Nonattainment. The amended Act,
in accordance with section 107(d)(3)(A), authorizes EPA to
promulgate the designation of new areas as nonattainment for
S02 on the basis of air quality data, planning and control
considerations, or any other air quality-related
consideration that the Administrator deems appropriate. As
2-1 February 1994
-------
part of the designation process, EPA notifies the governors
of those States with areas that EPA believes should be
redesignated as -nonattainment [section 107(d)(3)(A)].
Governors of affected States must then submit to EPA the
designation they consider appropriate for each area in
question within 120 days. No later than 120 days [section
107(d)(3)(B)] after a Governor's response, if any, EPA must
promulgate those redesignations which EPA deems necessary
and appropriate [section 107(d) (3) (C) ] .5
2.1.3 Redesignating Areas to Attainment. The 1990
amendments to the CAA included specific criteria which
govern the redesignation of an area from nonattainment to
attainment, including: (1) EPA determines that the area has
attained the NAAQS; (2) the area has a fully-approved
implementation plan; (3) EPA determines that the improvement
in air quality is attributable to permanent and enforceable
emissions reductions; (4) the area has a fully-approved
maintenance plan meeting the requirements of section 175A;
and (5) the area meets all applicable requirements of
section 110 and part D.€
The following is an expanded discussion of the criteria
which must be met before an area can be redesignated from
nonattainment to attainment. It is suggested that the
reader refer to the memorandum dated September 4, 1992 from
John Calcagni to the Regional Air Divisions Directors
entitled Procedures for Processing Requests to Redesignate
Areas to Attainment for an extended discussion of these
criteria.7
• Attainment of the NAAQS:
The State must show that the area is attaining the S02
NAAQS. There are two components involved in making
this demonstration which should be considered
interdependently. The first component relies on air
quality data. For S02/ the area may be considered
2-2 February 1994
-------
attaining the NAAQS if, according to 40 CFR 50.4, an
area shows no more than one exceedance annually.8
The second component relies on supplemental air quality
modeling. Modeling may be necessary to determine the
representativeness of the monitored data. For SO2,
dispersion modeling will generally be necessary to
evaluate comprehensively a source's impacts and to
determine the areas of expected high concentrations
based upon current conditions. Regions should consult
with OAQPS for further guidance addressing the need for
modeling in specific circumstances.9
Approved 110(k) SIP for the area
The SIP for the area must be fully approved under
section 110(k) of the Act and must satisfy all
requirements that apply to the area. "An area cannot
be redesignated if a required element of its plan is
the subject of a disapproval; a finding of failure to
submit or to implement the SIP; or partial,
conditional, or limited approval. However, this does
not mean that earlier issues with regard to the SIP
will be reopened."10
Permanent and enforceable improvement in air quality
The State must be able to reasonably attribute the
improvement in air quality to emission reductions which
are permanent and enforceable. In making this showing,
the State should estimate the percent reduction
achieved from Federal measures.11
Section 110 and Part D Requirements
For the purposes of redesignation, a State must meet
all requirements of section 110 and title I, part D of
the Act that were applicable prior to submittal of the
complete redesignation request. Section 110(a)(2)
contains general requirements for nonattainment plans.
part D consists of general requirements applicable to
all areas designated nonattainment and specific
2-3 February 1994
-------
requirements applicable to certain NAAQS.12
• Fully approved maintenance plan
Before an area can be redesignated to attainment, EPA
must approve a maintenance plan which meets the
requirements Of section 175A.13 The maintenance plan
will constitute a SIP revision and must provide for
maintenance of the SO2 NAAQS in the area for at least
10 years after redesignation.14 In addition, the
maintenance plan shall contain such contingency
measures necessary to ensure prompt correction of any
violation of the S02 NAAQS. At a minimum, these
measures must include a requirement that the State will
implement all measures contained in the nonattainment
SIP prior to redesignation.15
The following is a list of the provisions that should
be included in a maintenance plan:
Attainment inventory: The State should develop an
attainment emissions inventory to identify the level of
emissions in the area which is sufficient to attain the
SO2 NAAQS.16
Maintenance demonstration: A State may generally
demonstrate maintenance of the NAAQS by either showing
that future emissions of S02 will not exceed the level
of the attainment inventory, or by modeling to show
that the future mix of sources and emission rates will
not cause a violation of the SO2 NAAQS.17 In either
case, the State should project emissions for the 10-
year period following redesignation.18
Monitoring network: Once an area has been
redesignated, the State should continue to operate an
appropriate air quality monitoring network to verify
the attainment status of the area.19
Verification of continued attainment: Each State
should ensure that it has the legal authority to
2-4 February 1994
-------
implement and enforce all measures necessary to attain
and to maintain the S02 NAAQS. The State submittal
should indicate how the State will track the progress
of the maintenance plan.20
Contingency plan: The maintenance plan must contain
contingency provisions that will promptly correct any
violation of the S02 NAAQS that occurs after
redesignation. For the purposes of section 175A, a
State is not required to have fully adopted contingency
measures that will take effect without further action
by the State in order for the maintenance plan to be
approved. However, the contingency plan is considered
to be an enforceable part of the SIP and should ensure
that contingency measures are adopted expediently once
they are triggered. The plan should clearly identify
the measures to be adopted, a schedule and procedure
for adoption and implementation, and a specific time
limit for action by the State.21 The EPA will review
what constitutes a contingency plan on a case-by-case
basis. At a minimum, it must require that the State
will implement all measures contained in the part D
nonattainment plan for the area prior to redesignation.
This language suggests that a State may submit a SIP
revision at the time of its redesignation request to
remove or reduce the stringency of control measures.
The EPA can approve such a revision if it provides for
compensating equivalent reductions. Alternatively, a
State might be able to demonstrate that the measures
are not necessary for maintenance of its standard.22
2.1.4 Monitoring Data and Modeling Results. For S02
attainment demonstrations, monitoring data alone will
generally not be adequate. A small number of ambient S02
monitors usually is not representative of the air quality
for an entire area. Typically, modeling estimates of
2-5 February 1994
-------
maximum ambient concentration are based on a fairly
infrequent combination of meteorological and source
operating conditions. To capture such results on a monitor
would normally require a prohibitively large and expensive
network. Therefore, dispersion modeling will generally be
necessary to evaluate comprehensively a source's impacts and
to determine the areas of expected high concentrations.23
Air quality modeling results would be especially important
if sources were not emitting at their maximum level during
the monitoring period or if the monitoring period did not
coincide with potentially worst-case meteorological
conditions. Further, monitoring data is not adequate if
sources are using stacks with heights greater than good
engineering practice or other prohibited dispersion
techniques.
Ambient monitoring data and air quality modeling data
for a particular area can sometimes appear to conflict.
This is primarily due to the fact that modeling results may
predict maximum S02 concentrations at receptors where no
monitors are located. Where ambient monitoring data are
determined to be "adequate", the ambient monitoring data
should be used in designating an area.24 Ambient monitors
should be located in areas of expected maximum air quality
concentrations .25
With respect to receptor locations for modeling and
ambient air purposes, the EPA does not consider whether such
sites could meet standard siting criteria for monitors.
Although siting criteria may preclude the placement of
ambient monitors at certain locations, this does not
preclude the placement of model receptors at these sites.
The placement of the receptor at such sites will enhance the
basis for the attainment demonstration.26
2.1.5 Control Strategy Demonstration. A control strategy
that has not been approved by EPA as part of the SIP cannot
2-6 February 1994
-------
be used to support a redesignation unless physical
circumstances and/or long term economic factors with the
same weight as a SIP have occurred. For example, the
permanent closing of the main sources contributing to
nonattainment could be used to support a redesignation if
new permits were required prior to any reopening of the
sources.27
The General Preamble for the implementation of Title I
of the Clean Air Act Amendments provided that States seeking
to establish such sources as permanently closed must: (l)
demonstrate that the source has been inoperative for at
least the preceding 2 years; (2) that the source is
precluded from resuming operations and has been withdrawn
from the State's emissions inventory; and (3) have
2 8
fully-approved NSR and PSD programs in place.
Redesignations can have an effect on the overall
stringency of the SIP. If there is one set of control
requirements for nonattainment areas and a less stringent
set for attainment areas, then a redesignation could lead to
a relaxation of the SIP. In such cases, the redesignation
should also be treated as a SIP revision and the Agency
should respond with criteria on the requirements for SIP
relaxation and attainment demonstrations.29
2.1.6 Future SIP Violations. Projected future violations
of the SO2 NAAQS can provide the basis for continuing
nonattainment designations. For example, a period of
attainment that is attributable to a temporary economic
downturn cannot be used to support a redesignation.
Therefore, information used to support any attainment
determination must reflect anticipated future operating
rates.30 Modeling using maximum allowable emission rates
can satisfy this criterion.
2.1.7 Area Boundaries. Section 107 areas for S02 may be
2-7 February 1994
-------
established according to political boundaries such as cities
or counties.31
2-8 February 1994
-------
REFERENCES FOR SECTION 2.1
1. "Although State Governors continue to have authority to
initiate the designation process [section
107(d)(3)(D)], the 1990 CAAA also give EPA the
authority to initiate and to promulgate designations
[sections 107(d) (1) (3)] ." General Preamble for the
Implementation of Title I of the Clean Air Act
Amendments of 1990. Federal Register 57:13545.
April 16, 1992.
2. "In general, all available information relative to the
attainment status of an area should be reviewed. These
data include the most recent eight quarters of quality-
assured, representative ambient air quality data plus
evidence of an implemented control strategy EPA had
fully approved. Supplemental information, including
air quality modeling data, etc., should be used to
determine if the monitoring data accurately
characterize the worst case air quality in the area."
Memorandum from Myers, S., OAQPS, to Director of Air
and Waste Management Division, Regions II-IV, VI-VIII,
X, and Director of Air Management Division, Regions I,
V, IX. April 21, 1983. PN 107-83-04-21-008.
3. "Where only the most recent four quarters of data
showing attainment are available, a state-of-the-art
modeling analysis must be provided which quantifies
that the SIP strategy is sound and that actual
enforceable emission reductions are responsible for the
air quality improvement." Memorandum from Helms, G.T.,
OAQPS, to Air Branch Chief, Regions I-X. December 23,
1983.
4. U. S. Environmental Protection Agency. Guideline on
Air Quality Models (Revised). Office of Air Quality
Planning and Standards, Research Triangle Park, N.C.
EPA Publication No. EPA-450/12-78-027R. July 1986.
p. 11-7.
5. Federal Register 56:16274-7, Volume 56, No. 77. April
22, 1991. Preparation, Adoption, and Submittal of
State Implementation Plans; PM-10, Sulfur Dioxide, and
Lead Nonattainment and Unclassifiable Area
Designations; Background for PM-10.
6. Reference 1. "The particular criteria for
redesignating nonattainment areas to attainment
[section 107(d)(3)(E)] include the following: The area
has attained the NAAQS, the area has a fully approved
[section 110(k)] implementation plan, the improvement
in air quality is due to permanent and enforceable
2-9 February 1994
-------
emissions reductions, the area has a maintenance plan
meeting the requirements of section 175A, and the area
meets all applicable requirements under section 110 and
part D. "
7. Memorandum from Calcagni, John, Director, Air Quality
Management Division, OAQPS, U.S. EPA, Research Triangle
Park, NC, to Director, Air, Pesticides and Toxics
Management Division, Regions I and IV; Director, Air
and Waste Management Division, Region II; Director,
Air, Radiation and Toxics Division, Region III;
Director, Air and Radiation Division, Region V;
Director, Air, Pesticides, and Toxics Division, Region
VI; and Director, Air and Toxics Division, Regions VII,
VIII, IX, and X. Procedures for Processing Requests to
Redesignate Areas to Attainment. September 4, 1992.
8. Reference 7. "The State must show that the area is
attaining the applicable NAAQS. There are two
components involved in making this demonstration which
should be considered interdependently. The first
component relies on air quality data. The data that
are used to demonstrate attainment should be the
product of ambient monitoring that is representative of
the area of highest concentration. These monitors
should remain at the same location for the duration of
the monitoring period required for demonstrating
attainment . . . For S02, according to 40 CFR 50.9, an
area must show no more than one exceedence annually..."
9. Reference 7. "The second component relies on
supplemental EPA-approved air quality modeling.
Modeling may be necessary to determine the
representativeness of the monitored data. When dealing
with SO2, Pb, PM-10 (except for a limited number of
initial moderate nonattainment areas), dispersion
modeling will generally be necessary to evaluate
comprehensively sources' impacts and to determine the
areas of expected high concentrations based upon
current conditions. Areas which were designated
nonattainment based on modeling will generally not be
redesignated to attainment unless an acceptable
modeling analysis indicates attainment. Regions should
consult with OAQPS for further guidance addressing the
need for modeling in specific circumstances."
10. Reference 7. "The SIP for the area must be fully
approved under section 110(k), and must satisfy all
requirements that apply to the area. It should be
noted that approval action on SIP elements and the
redesignation request may occur simultaneously. An
2-10 February 1994
-------
area cannot be redesignated if a required element of
its plan is the subject of a disapproval; a finding of
failure to submit or to implement the SIP; or partial,
conditional, or limited approval. However, this does
not mean that earlier issues with regard to the SIP
will be reopened. Regions should not reconsider those
things that have already been approved and for which
the Clean Air Act Amendments did not alter what is
required. In contrast, to the extent the amendments
add a requirement or alter an existing requirement so
that it adds something more, Regions should consider
those issues. In addition, requests from areas known
to be affected by dispersion techniques which are
inconsistent with EPA guidance will continue to be
considered unapprovable under section 110 and will not
qualify for redesignation."
11. Reference 7. "The State must be able to reasonably
attribute the improvement in air quality to emission
reductions which are permanent and enforceable.
Attainment resulting from temporary reductions in
emission rates or usually favorable meteorology would
not qualify as an air quality improvement due to
permanent and enforceable emission reductions. In
making this showing, the State would estimate the
percent reduction achieved from Federal measures."
12. Reference 7. "For the purposes of redesignation, a
State must meet all requirements of section 110 and
part D of the Act that were applicable prior to
submittal of the complete redesignation request.'. When'.
evaluating a redesignation request Regions should not
consider whether the State has met requirements that
come due under the Act after submittal of a complete
redesignation request. However, any requirements that
came due prior to submittal of the redesignation
request must be fully approved into the plan at or
before the time EPA redesignates the area. Section
110(a)(2) contains general requirements for
nonattainment plans. Most of the provisions of this
section are the same as those contained in the pre-
amended Act. Part D consists of general requirements
applicable to all areas which are designated
nonattainment based on a violation of the NAAQS. The
general requirements are followed by a series of
subparts specific to each pollutant. The general
requirements appear in subpart 1. The requirements
relating to 03, CO, PM-10, SO2, N02, and Pb appear in
subparts 2 through 5. In those instances where an area
is subject to both the general nonattainment provisions
in subpart 1 as well as one of the pollutant-specific
subparts, the general provisions may be subsumed
2-11 February 1994
-------
within, or superseded by, the more specific
requirements [that] are found in subpart 5."
13. Reference 7. "Section 107(d)(3)(E) of the amended Act
stipulates that for an area to be redesignated, EPA
uust fully approve a maintenance plan which meets the
requirements of section 175A. A State may submit both
the redesignation request and the maintenance plan at
the same time and rulemaking on both may proceed on a
parallel track. Maintenance plans may, of course, be
submitted and approved by EPA before a redesignation is
requested. However, according to section 175A(c),
pending approval of the maintenance plan and
redesignation request, all applicable nonattainment
area requirements shall remain in place."
14. Reference 7. "Section 175A defines the general
framework of a maintenance plan. The maintenance plan
will constitute a SIP revision and must provide for
maintenance of the relevant NAAQS in the area for at
least 10 years after redesignation. Section 175A
further states that the plan shall contain such
additional measures, if any, as may be necessary to
ensure such maintenance. Because the Act requires a
demonstration of maintenance for 10 years after an area
is redesignated, the State should plan for some lead
time for EPA action on the request... In determining the
amount of lead time to allow, States should consider
that section 170(d)(3)(D) grants the Administrator up
to 18 months from receipt of a complete submittal to
process a redesignation request."
15. Reference 7. "In addition, the maintenance plan shall
contain such contingency measures necessary to ensure
prompt correction of any violation of the NAAQS [see
section 175A(d)]. The Act provides that, at a minimum,
the contingency measures must include a requirement
that the State will implement all measures contained in
the nonattainment SIP prior to redesignation. Failure
to maintain the NAAQS and triggering of the contingency
plan will not necessitate a revision of the SIP unless
required by the Administrator, as stated in section
175A(d) . "
16. Reference 7. "The State should develop an attainment
emissions inventory to identify the level of emissions
in the area which is sufficient to attain the NAAQS.
This inventory should be consistent with EPA's most
recent guidance on emission inventories for
nonattainment areas available at the time and should
include the emissions during the time period associated
with the monitoring data showing attainment. Source
2-12 February 1994
-------
size thresholds are 100 tons/year for S02/ N02, and PM-
10 areas, and 5 tons/year for Pb based upon 40 CFR
51.100(k) and 51.322, as well as established practice
for AIRS 'data. The source size threshold for serious
PM-10 areas is 70 tons/year according to Clean Air Act
section 189(b)(3)."
17. Reference 7. "A State may generally demonstrate
maintenance of the NAAQS by either showing that future
emissions of a pollutant or its precursors will not
exceed the level of the attainment inventory, or by
modeling to show that the future mix of sources and
emission rates will not cause a violation of the NAAQS.
Under the Clean Air Act, many areas are required to
submit modeled attainment demonstrations to show that
proposed reductions in emissions will be sufficient to
attain the applicable NAAQS. For these areas, the
maintenance demonstration should be based upon the same
level of modeling. In areas where no such modeling was
required, the State should be able to rely on the
attainment inventory approach. In both instances, the
demonstration should be for a period of 10 years
following the redesignation."
18. Reference 7. "In either case, to satisfy the
demonstration requirement the State should project
emissions for the 10-year period following
redesignation, either for the purpose of showing that
emissions will not increase over the attainment
inventory or for conducting modeling". The projected
inventory should consider future growth, including
population and industry, should be consistent with the
attainment inventory, and should document data inputs
and assumptions. All elements of the demonstration
should be consistent with current EPA modeling
guidance."
19. Reference 7. "Once an area has been redesignated, the
State should continue to operate an appropriate air
quality monitoring network, in accordance with 40 CFR
part 58, to verify the attainment status of the area.
The maintenance plan should contain provisions for
continued operation of air quality monitors that will
provide such verification. In cases where measured
mobile source parameters have changed over time, the
State may also need to perform a saturation monitoring
study to determine the need for, and location of,
additional permanent monitors."
20. Reference 7. "Each State should ensure that it has the
legal authority to implement and enforce all measures
necessary to attain and to maintain the NAAQS. Section
2-13 February 1994
-------
110(a)(2)(b) and (F) of the Clean Air Act, as amended,
and regulations promulgated at 40 CFR 51.110(k),
suggest that one such measure is the acquisition of
ambient and source emission data to demonstrate
attainment and maintenance. Regardless of whether the
maintenance demonstration is based on a showing that
future emission inventories will not exceed the
attainment inventory or on modeling, the State
submittal should indicate how the State will track the
progress of the maintenance plan. This is necessary
due to the fact that the emission projections made for
the maintenance demonstration depend on assumptions of
point and area source growth."
21. Reference 7. "Section 175A of the Act also requires
that a maintenance plan include contingency provisions,
as necessary, to promptly correct any violation of the
NAAQS that occurs after redesignation of the area. For
the purposes of section 175A, a State is not required
to have fully adopted contingency measures that will
take effect without further action by the State in
order for the maintenance plan to be approved.
However, the contingency plan is considered to be an
enforceable part of the SIP and should ensure that the
contingency measures are adopted expediently once they
are triggered. The plan should clearly identify the
measures to be adopted, a schedule and procedure for
adoption and implementation, and a specific time limit
for action by the State. As a necessary part of the
plan, the State should also identify -specific
indicators, or triggers, which will be used to
determine when the contingency measures need to be
implemented."
22. Reference 7. "The EPA will review what constitutes a
contingency plan on a case-by-case basis. At a
minimum, it must require that the State will implement
all measures contained in the part D nonattainment plan
for the area prior to redesignation [see section
175A(d)]. This language suggests that a State may
submit a SIP revision at the time of its redesignation
request to remove or reduce the stringency of control
measures. Such a revision can be approved by EPA if it
provides for compensating equivalent reductions. A
demonstration that measures are equivalent would have
to include appropriate modeling or an adequate
justification. Alternatively, a State might be able to
demonstrate (through EPA-approved modeling) that the
measures are not necessary for maintenance of the
standard. In either case, the contingency plan would
have to provide for implementation of any measures that
were reduced or removed after redesignation of the
2-14 February 1994
-------
area." -
23. Reference 2. "In most S02 cases, monitoring data alone
will not be sufficient for areas dominated by point
sources. A small number of ambient monitors usually is
not representative of the air quality for the entire
area. Dispersion modeling employing legally
enforceable S02 SIP limits will generally be necessary
to evaluate comprehensively the source's impacts as
well as identify the areas of highest concentrations."
24. "I am in agreement with your position that, when
available, adequate ambient monitoring data should be
given preference over modeling results in designating
areas as attainment/nonattainment under section 107 of
the Clean Air Act (CAA)." Memorandum from
Barber, W.C., OAQPS, to R.C. Pickard, Indiana Air
Pollution Control Board. September 3, 1981.
25. Memorandum from Myers, S., OAQPS, to D. Kee, Air
Management Division, Region V. September 16, 1982. PN
107-82-09-16-007.
26. "All receptor locations that may affect control
strategy requirements, and meet the definition of
'ambient air,' must be included in regulatory modeling
applications. ambient air is defined in 40 CFR part
50.1(e) as 'that portion of the atmosphere, external to
buildings, to which the general public has access.'
Receptor points 180 and 197 are adjacent to a roadway
to which the public clearly has access; thus, they
must be included in the SIP modeling analysis.
Although siting criteria may preclude placement of
ambient monitors at these receptors, as was discussed
by Asarco, this does not preclude the placement of
model receptors at these sites." Letter from Skie,
D.M., Region VIII, to Jeffrey T. Chaffee, Montana
Department of Health and Environmental Sciences. March
13, 1992.
27. Reference 3. "However, an exception will be made if
the physical circumstances and long-term economic
factors are such that the implemented measures have the
same weight as a SIP; for example, the permanent
closing of the major emitting sources, road paving to
eliminate fugitive emissions, or other irreversible
measures."
28. Reference 1. "A minimum of two actions are required
for States wishing to establish that these areas are
inoperative for SIP purposes.
2-15 February 1994
-------
The first action is that the State must provide EPA
with sufficient evidence to establish that the source
has in fact been permanently shut down. Three criteria
exist for establishing permanent source shutdown.
These criteria require proof that the source has been
inoperative for at least the 2 preceding years, that
the source is precluded from resuming operations, and
that the source has been withdrawn from the State's
emissions inventory.
The second action is that the State must establish that
fully-approved NSR and PSD programs are in place so
that the source would be required to undergo NSR prior
to start-up if it were reactivated." Page 13547.
29. "The redesignation would have relaxed the relevant SIP
because the SIP specified one set of control
requirements for nonattainment areas and a less
stringent set for attainment areas." Memorandum from
Tyler, D.D.,OAQPS, to P.H. Wyckoff, Office of General
Counsel (OGC). February 2, 1985.
30. Reference 2. "Projections of future violations can
provide the basis for continuing nonattainment
designations. This concept is particularly important
because of the current economic downturn. Information
submitted to support attainment redesignations must
adequately and accurately reflect anticipated operating
rates."
1
31. Reference 2. "Current policies on appropriate
boundaries for designation of nonattainment areas by
EPA remain in effect, i.e., generally political
boundaries such as city or county for TSP and S02..."
2-16 February 1994
-------
2.2 AMBIENT AIR
2.2.1 General. Ambient air is defined at 40 CFR 50.1(e) as
"that portion of the atmosphere, external to buildings, to
which the general public has access." Generally, this
definition signifies that ambient air would constitute any
air to which the public could be exposed, even for a short
period of time. The only exemption from the ambient air
provision is the atmosphere over land that is owned or
controlled by the source and to which public access (and,
therefore, exposure) is precluded by a fence or other
physical barrier.1 It should be noted that for sources
operating on leased property, ambient air is considered to
exclude only the atmosphere over that land leased and
controlled by the source.2
2.2.2 Location Aspects. Ambient air includes such areas as
elevated building sites and parking lots for public arenas.
Although it may not be practical to analyze the air quality
at every such location, the State should evaluate the air
quality impact at these sites if it deems this necessary to"
protect health and welfare.3'4
For modeling purposes, ambient air is considered to be
air everywhere outside of contiguous plant property to which
public access is precluded by an effective physical barrier.
Therefore, modeling receptors should be placed anywhere
outside of inaccessible plant property, including over
bodies of water, unfenced plant property, on buildings, over
roadways, and over property owned by other sources.5'6 As
discussed in section 2.1.4, although siting criteria may
preclude the placement of ambient monitors at certain
locations, modeling receptors should be placed at areas of
anticipated worst-case impacts.7
A few examples should clarify potential uncertainties
regarding receptor location. In the case of waterways,
2-17 February 1994
-------
receptors should be placed over any body of water not
privately owned or which allow public access. Even where
public recreational traffic is limited, the air above a body
of water should be considered ambient air as long as the
potential for public exposure exists.8 With respect to
roadways dividing plant property, the air above the road
should have a receptor, even if the road separates otherwise
inaccessible private property owned by a single source.9-10
Regarding property owned by other sources, current policy
requires that receptors be placed over neighboring property
regardless of public accessibility. In other words, the
atmosphere above neighboring property is considered "ambient
air" in relation to emissions from a given source.11
2.2.3 Time Aspects. Even if public access to a given site
is time-limited, the site should not be excluded from the
ambient air definition as long as the other conditions
apply. Regardless of the period of exposure at a given site
(or receptor), ambient air is defined in terms of public
access not frequency of access, length of _. stay, age of the
person or other factors.12
2.2.4 Public Access. If an area is owned or leased by the
source and public access is prevented, the area is not
ambient air with respect to the source's own emissions.
However, there should be sufficient barriers to prevent
public access. Barriers considered sufficient to prevent
public access are generally limited to fences. However, a
clearly posted area alongside a river that is regularly
patrolled by security guards would qualify as sufficient
protection.13 The EPA has accepted other equally effective
means of preventing access where the use of a fence or other
physical barrier is impractical.14
2.2.5 PSD Considerations. Unlike the NAAQS, PSD increments
2-18 February 1994
-------
do not apply to building rooftops, but only to the ground
level. The PSD system, unlike the NAAQS system, does not
aim at achieving one single goal. Rather, it represents a
balance determined by Congress between economic growth and
deterioration of air quality. If building rooftops were
included in PSD permitting strategy, the PSD system would be
appreciably more stringent than Congress had contemplated.15
Because air over neighboring property is considered
ambient air regardless of public accessibility (see section
2.2.2), receptors should be placed over neighboring property
when modeling PSD increments. However, the S02
concentration contributed by the neighboring property can be
subtracted from the total concentrations.16
2.2.6 Land Acquisition. Land acquisition and removal of
the area from ambient air is not automatically considered a
dispersion technique prohibited by section 123; this
situation is reviewed on a case-by-case basis. (Also see
discussion on stack height regulations, section 5.) In only
a few instances has the EPA tolerated land acquisition to
contain modeled violations of the NAAQS.17
2-19 February 1994
-------
REFERENCES FOR SECTION 2.2
1. "We are retaining the policy that the exemption from
ambient air is available only for the atmosphere over
land owned or controlled by the source and to which
public access is precluded by a fence or other physical
barriers." Letter from Costle, D.M., EPA Administrator
to Honorable J. Randolph, U.S. Senate. December 19,
1980. PN 123-80-12-19-001.
2. "We agree with your position that all property outside
of-' the property leased and controlled by EFRI would be
considered ambient air." Memorandum from Helms, G.T.,
OAQPS, to W.S. Baker, Air Branch Chief, Region II.
July 27, 1987.
3. "While EPA considers ambient air to include elevated
building receptor sites, it is not practical to analyze
the air quality at every such existing location."
Letter from Bennett, K.M., Office of Air Noise and
Radiation (OANR), to H. Hovey, New York Department of
Environmental Conservation. March 18, 1983. PN 110-
83-03-18-063.
4. "There is no basis for excluding ambient air above a
public parking lot from coverage by the SIP."
Memorandum from James, M.A., OGC, to C. Simon, Air
Programs Branch Chief, Region II. September 27, 1972.
5. "The Regional Meteorologists propose1'that for modeling
purposes the air everywhere outside of contiguous plant
property to which public access is precluded by a fence
or other effective physical barrier should be
considered in locating receptors. Specifically, for
stationary source modeling, receptors should be placed
anywhere outside inaccessible plant property. For
example, receptors should be included over bodies of
water, over unfenced plant property, on buildings, over
roadways, and over property owned by other sources."
Memorandum from Koerber, M., Region V, to J. Tikvart,
OAQPS. May 16, 1985.
6. "The Regional Meteorologists' memorandum to which you
refer does not imply any change in [the] national
policy and simply harmonizes modeling procedures with
our long-standing policy. It is intended to ensure
consistent Regional implementation of that policy and
to dispel any questions about pollutant concentrations
at locations where the general public has access."
Letter from Emison, G.A., OAQPS, to W.F. O'Keefe,
American Petroleum Institute, January 22, 1986.
2-20 February 1994
-------
7. "All receptor locations that may affect control
strategy requirements, and meet the definition of
'ambient air,' must be included in regulatory modeling
applications. Ambient air is defined in 40 CFR part
50.1(e) as 'that portion of the atmosphere, external to
buildings, to which the general public has access.'
Receptor points 180 and 197 are adjacent to a roadway
to which the public clearly has access; thus, they
must be included in the SIP modeling analysis.
Although siting criteria may preclude placement of
ambient monitors at these receptors, as was discussed
by Asarco, this does not preclude the placement of
model receptors at these sites." Letter from Skie,
D.M., Region VIII, to Jeffrey T. Chaffee, Montana
Department of Health and Environmental Sciences. March
13, 1992.
8. "Case 3 (Wayne County, MI): This case involves the air
over the Detroit River, the Rouge River, and the Short-
cut Canal. We agree that the air over all three of
these is ambient air, since none of the companies owns
them or controls public access to them." Memorandum
from Helms, G.T., OAQPS, to S. Rothblatt, Region V.
April 30, 1987. PN 110-87-04-30-083.
9. Reference 7. "Case 1 (Dakota County, MN): This case
involves two noncontiguous pieces of fenced property
owned by the same source, divided by a public road. We
agree that the road is clearly ambient air and that
both fenced pieces of plant property'are not."
10. "Scenario One: We agree with you that the road and the
unfenced property are ambient air and could be
locations for the controlling receptor." Memorandum
from Helms, G.T., OAQPS, to B. Miller, Air Programs
Branch, Region IV. April 30, 1987. PN 110-87-04-30-
082.
11. Reference 7. "Case 5 (involves the placement of
receptors on another source's fenced property): As
mentioned in Case 2, we feel that present policy does
require that receptors be placed over another source's
property to measure the contribution of the outside
source to its neighbor's ambient air."
12. "Regardless of whether any member of the public is
expected to remain at a particular place for a specific
period of time, ambient air is defined in terms of
public access, not frequency of access, length of stay,
age of the person or other limitations." Memorandum
from Tyler, D.D., OAQPS, to A. Davis, Region VI. May
26, 1983.
2-21 February 1994
-------
13. Reference 9. "We do not think that any of the barriers
mentioned are sufficient to preclude public access so
as to allow the source to dispense with a fence. An
example .of .an unfenced boundary that would qualify is a
property line along a river that is clearly posted and
regularly patrolled by security guards."'
14. "In summary, if ARCO can certify to EPA that an
exclusionary safety zone exists and that reasonable and
routine measures are undertaken to control the boundary
of this zone, EPA will consider it to be the area
controlled by the source and therefore, excluded from
being considered ambient air." Memorandum from Phil
Millam, Air and Radiation Branch, Region X to Randy
Poteet, ARCO, Alaska, Inc. March 1, 1993.
15. "However, the PSD system, unlike the NAAQS system, does
not aim at achieving one single goal." Memorandum from
Cannon, J.A., OAR, to C.R. Jeter, Region IV.
June 11, 1984. PN 165-84-06-11-014.
16. "3. Where a receptor is located on Plant B's
nonambient air property, the contribution from Plant B
(only) may be subtracted from the total concentration."
Memorandum from Bauman, R. D., OAQPS, to G. Fontenot,
Air Programs Branch, Region VI, October 17, 1989.
17. "We have never either flatly stated that land
acquisition in general is acceptable or unacceptable
under section 123 of the Clear Air Act...we will review
individual situations on a case-by-case basis."
Memorandum from Tyler, D., OAQPS, to I. Dickstein,
Region VIII. April 7, 1987.
2-22 February 1994
-------
submission specifically excludes S02/ the SIP must provide
the necessary information on S02 monitoring.2 Further
information on what the SIP itself must contain is provided
in Guidelines for Implementation of the Ambient Air
Monitoring Regulations, EPA-450/4-79-038.
Any ambient air quality station other than a SLAMS or
PSD station from which a State intends to use data for
demonstrating attainment or nonattainment or for computing a
design value for control purposes must meet the requirements
for SLAMS as described in 40 CFR parts 58.13 and 58.22 as
well as the requirements of appendices A and E of part 58.3
In addition, any ambient air quality station other than a
SLAMS or PSD station from which a State intends to use data
for SIP-related functions other than as part of an
attainment or nonattainment demonstration or for computing a
design value for NAAQS control purposes, need not
necessarily satisfy the requirements for a SLAMS station,
but must be operated in accordance with specifications
approved by the Regional Administrator.4
Measurement of meteorological variables at the location
of an air quality monitoring station provides a basis for
correlating air pollutant levels with local weather
patterns. Meteorological monitoring data are also required
for the purposes of air quality modeling. Meteorological
inputs to modeling are discussed in section 4.4 of this
document.5
Finally, guidelines for sources required to monitor
ambient air quality under PSD regulations are contained in
the Ambient Monitoring Guidelines for Prevention of
Significant Deterioration (PSD) and general considerations
for requiring ambient air monitoring under PSD regulations
are contained in the New Source Review Workshop Manual
(draft). Section 165 (e) (2) of the Clean Air Act (CAA)
requires conducting preconstruction air quality monitoring
to determine whether emissions of new sources or source
3-2 February 1994
-------
3. AMBIENT AIR QUALITY MONITORING AND DATA USAGE
3.1 GENERAL
According to the regulations established in 40 CFR part
58, States are required to establish and maintain an air
quality surveillance system for the purpose of measuring
ambient air concentrations of those pollutants for which
national ambient air quality standards (NAAQS) have been
defined. The network of monitoring stations that is to be
provided for in State implementation plans is designated as
the State and Local Air Monitoring Stations (SLAMS) network.
The general SIP monitoring requirements are contained in 40
CFR 58.20 and include the following:1
I. Requirements in appendices A, C, D, and E of 40
CFR part 58 which pertain to quality assurance for
monitoring stations, monitoring methodology,
monitoring network design, and probe siting
criteria, respectively.
2. An annual review of the monitoring network to
assure that the monitoring objectives as defined
in appendix D of part 58 are satisfied.
3. Operate at least one station of the SLAMS network
per pollutant during any stage of an air pollution
episode.
4. Provide a SLAMS network description for public
review and submission to the EPA Administrator.
The SIP itself does not have to contain the network
description; however, these must be kept on file at the
State agency's office, made available for public inspection,
and submitted to the Administrator upon request. A State's
prior SIP submission that covers air quality monitoring in
general may meet the requirements for S02 SIP's. The
Regional Office should determine whether the State's prior
monitoring submission includes S02. If the monitoring
3-1 February 1994
-------
modifications located in attainment or unclassifiable areas
will result in exceedance of the NAAQS.6 Section 165(a)(7)
of the CAA giy.es EPA the discretion to require
postconstruction air quality monitoring to determine the
ambient air quality impacts from emissions of new sources or
source modifications on such areas.7
Under PSD regulations, source applicants are generally
required to collect ambient air quality data for 1 year, but
EPA has the discretion to allow a shorter collecting period
(not less than 4 months) if the resulting data can
demonstrate a complete analysis of the ambient air quality
impacts the source will have on the area. Source applicants
must also use quality assurance procedures pursuant to
appendix B of 40 CFR part 58 in order to ensure accuracy and
precision of the data collected.8 EPA requirements for
incorporating PSD provisions in SIP's are contained in 40
CFR part 51.166.
3-3 February 1994
-------
REFERENCES FOR SECTION 3.1
1. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
58.20.
2. "The State shall adopt and submit to the Administrator
a revision to the plan which will: . . . (e) Provide
having a SLAMS network description available for public
inspection and submission to the Administrator upon
request." U.S. EPA. Code of Federal Regulations.
Title.40, chapter I, subchapter C, part 58.20(e).
3. "Any ambient air quality monitoring station other than
a SLAMS or PSD station from which the State intends to
use the data as part of a demonstration of attainment
or nonattainment or in computing a design value for
control purposes of the National Ambient Air Quality
Standards (NAAQS) must meet the requirements for SLAMS
described in section 58.22 and, after January 1, 1983,
must also meet the requirements for SLAMS as described
in section 58.13 and appendices A and E to this part."
U.S. EPA. Code of Federal Regulations. Title 40,
chapter I, subchapter C, part 58.14 (a).
4. "Any ambient air quality monitoring station other than
a SLAMS or PSD station from which the State intends to
use data for SIP-related functions other than described
in paragraph (a) of this section in not necessarily
required to comply with the requirements of a SLAMS
station under paragraph (a) but must be operated in
accordance with a monitoring schedule, methodology,
quality assurance procedures, and probe or instrument-
siting specifications approved by the Regional
Administrator." U.S. EPA. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
58.14 (b).
5. U.S. Environmental Protection Agency. On-site
Meteorological Program Guidance for Regulatory Modeling
Applications. PB87-227542. June 1987.
6. "The court ruled that section 165(e)(2) of the Clean
Air Act requires that continuous preconstruction air
quality monitoring data must be collected to determine
whether emissions from a source will result in
exceeding the National Ambient Air Quality Standards
(NAAQS) . . ." U.S. EPA. Ambient Monitoring
Guidelines for Prevention of Significant Deterioration
(PSD). Office of Air Quality Planning and Standards,
Research Triangle Park, NC. EPA Publication No. EPA-
450/4-87-007. May 1987. page 3.
3-4 February 1994
-------
7. U.S. Environmental Protection Agency. New Source
Review Workshop Manual. Draft document. Office of Air
Quality Planning and Standards, Research Triangle Park,
North Carolina. October 1990. page C.21.
8. "(m)(1)(iv) The plan shall provide that, in general,
the continuous air monitoring data that is required
shall have been gathered over a period of one year . .
. except that, if the reviewing authority determines
that a complete and adequate analysis can be
accomplished with monitoring data gathered over a
period shorter than one year (but not to be less than
four months) . . . (m)(3) The plan shall provide that
the owner or operator of a major stationary source or
major modification shall meet the requirements of
appendix B to part 58 of this chapter . . ." U.S. EPA,
Code of Federal Regulations. Title 40 chapter I,
subchapter C, part 51.166.
3-5 February 1994
-------
3 . 2 QUALITY ASSURANCE
Quality Assurance requirements for SLAMS networks are
contained in .appendix A of 40 CFR part 58, and requirements
for PSD monitoring are contained in appendix B of 40 CFR
part 58. The requirements in appendix A are general in
nature in order to allow each State the opportunity to
develop the most efficient and effective quality assurance
system for its specific circumstances.1 Accuracy and
precision tests for S02 sampling are the essence of the
quality assurance system established. The results of all
valid precision and accuracy tests must be reported on a
quarterly basis to the Atmospheric Research and Exposure
Assessment Laboratory (AREAL) (formerly the Environmental
Monitoring Systems Laboratory (EMSL)). A list of all S02
monitoring sites and their Aerometric Information Retrieval
System (AIRS) site identification codes shall be kept
updated and on file with the appropriate EPA Regional Office
and with AREAL.2 AIRS was formerly, known as the Storage and
Retrieval of Aerometric Data (SAROAD) system.
Primary guidance for developing the quality assurance
program for ambient air monitoring is provided in the
Quality Assurance Handbook for Air Pollution Measurement
Systems, Volume I - Principles (EPA-600/9-76-005), and in
the Quality Assurance Handbook for Air Pollution Measurement
Systems, Volume II - Ambient Air Specific Methods (EPA-
600/4-77-027a). These documents contain suggested
procedures, checks, and control specifications. As a
minimum, each quality assurance program must include
operational procedures for the following activities:3
1. Selection of methods, analyzers, or samplers.
2. Training.
3. Equipment installation.
4. Selection and control of calibration standards.
5. Calibration procedures and frequency.
6. Zero/span checks and adjustments of automated
3-6 February 1994
-------
analyzers.
7. Control checks and their frequency.
8. Control limits for zero, span, and other control
checks, and respective corrective actions when
such limits are surpassed.
9. Calibration and zero/span checks for multiple
range analyzers.
10. Preventive and remedial maintenance.
11. Quality control procedures for air pollution
episode monitoring.
12. Recording and validating data.
13. Data quality assessment (precision and accuracy).
14. Documentation of quality control information.
Generally, standards used for ambient air monitoring
quality assurance must be traceable to standards or devices
certified by the National Institute of Standards Technology
(NIST), or other approved reference material. Gaseous
pollutant concentration standards used to obtain test
concentrations for S02 must be traceable to the NIST.4 NIST
was formerly the National Bureau of Standards (NBS) . •'
Agencies operating SLAMS network stations are subject
to annual EPA systems audits of their ambient air monitoring
program and are required to participate in EPA's National
Performance Audit Program.5 Audit procedures are described
in section 1.4.16 of the Quality Assurance Handbook for Air
Pollution Measurement Systems, Volume I - Principles (EPA-
600/9-76-005). The EPA's National Performance Audit Program
is described in section 2.0.10 of the Quality Assurance
Handbook for Air Pollution Measurement Systems, Volume II -
Ambient Air Specific Method. Systems audit criteria and
procedures are given in section 2.0.11 of the same document.
3-7 February 1994
-------
REFERENCES FOR SECTION 3.2
1. "General Information...The selection and extent of the
quality control activities - as well as additional
quality assessment activities - used by a monitoring
agency depend on a number of local factors such as the
field and laboratory conditions, the objectives of the
monitoring, the level of the data quality needed, the
expertise of assigned personnel, the cost of control
procedures, pollutant concentration levels, etc.
Therefore, the quality assurance requirements, in
section 2 of this appendix, are specified in general
terms to allow each State to develop a quality
assurance system that is most efficient and effective
for its own circumstances." U.S. Environmental
Protection Agency. Quality Assurance Requirements for
State and Local Air Monitoring Stations (SLAMS) Code of
Federal Regulations. Title 40, chapter I, subchapter
C, part 58, appendix A. Washington, D.C. Office of
the Federal Register.
2. "4. Reporting Requirements... For each pollutant,
prepare a list of all monitoring sites and their SAROAD
site identification codes in each reporting
organization and submit the list to the appropriate EPA
Regional Office, with a copy to the Environmental
Monitoring Systems Laboratory (MD-75), U.S.
Environmental Protection Agency, Research Triangle
Park, North Carolina 27711 (AREAL/RTP). Whenever there
is a change in this list of monitoring sites in a
reporting organization, report this' change to the
Regional Office and to AREAL/RTP." U.S. Environmental
Protection Agency. Quality Assurance Requirements for
State and Local Air Monitoring Stations (SLAMS) Code of
Federal Regulations. Title 40, chapter I, subchapter
C, part 58, appendix A. Washington, D.C. Office of
the Federal Register.
3. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
58, appendix A. Section 2.2.
4. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
58, appendix A. Section 2.3.
5. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
58, appendix A. Section 2.4.
3-8 February 1994
-------
3.3 AMBIENT MONITORING METHODOLOGY
3.3.1 General. Monitoring methods used in SLAMS networks
must be reference or equivalent methods as defined in 40 CFR
50.1. The reference method used for measuring ambient
levels of sulfur dioxide to determine compliance with the
primary and secondary NAAQS is the pararosaniline method.1
The air quality monitoring regulations allow the use,
for a period of time determined by the Administrator, of any
manual method or analyzer purchased prior to cancellation of
its reference or equivalent method designation in 40 CFR
53.11 or 40 CFR 53.16.2 NAMS sites must use continuous
analyzers.5 Certain allowances are also made for use, in
specific geographical areas, of methods with higher,
nonconforming measurement ranges.3 No reference or
equivalent method that has been modified in a manner that
will, or might, significantly alter the performance
characteristics of the method, may be used in a SLAMS
without prior approval of the Administrator.4
3.3.2 Sampling Interval. Sulfur dioxide data collected at
any SLAMS must be consecutive hourly averages, for
continuous analyzers and at least one 24-hour sample every
6 days, for manual methods. NAMS sites must use continuous
analyzers.5 Certain periods or seasons may be exempted from
sampling by the Regional Administrator (e.g., in the case of
continuous analyzers, periods of routine maintenance and
instrument calibration are exempt).6
3.3.3 Data Completeness. A minimum of 75 percent of the
individual hourly values for continuous analyzers should be
reported in any sampling period for monitors in the
SLAMS/NAMS network.5 A minimum of 80 percent of the
individual hourly values for continuous analyzers should be
reported for monitors in the PSD network.7
3-9 February 1994
-------
REFERENCES FOR SECTION 3.3
1. "1.1 This method provides a measurement of the
concentration of sulfur dioxide (S02) in ambient air
for determining compliance with the primary and
secondary national ambient air quality standards for
sulfur oxides (sulfur dioxide) as specified in 50.4 and
50.5 of this chapter." U.S. Environmental Protection
Agency. Reference Method for the Determination of
Sulfur Dioxide in the Atmosphere (Pararosaniline
Method). Code of Federal Regulations. Title 40,
chapter I, subchapter C, part 50, appendix A.
Washington, D.C. Office of the Federal Register.
2. "2.3 Any manual method or analyzer purchased prior to
cancellation of its reference or equivalent method
designation under 53.11 or 53.16 of this chapter may be
used in a SLAMS following cancellation for a reasonable
period of time to be determined by the Administrator."
U.S. Environmental Protection Agency. Ambient Air
Quality Monitoring Methodology. Code of Federal
Regulations. Title 40, chapter I, subchapter C,
part 58, appendix A. Washington, D.C. Office of the
Federal Register.
3. "2.6 Use of Methods With Higher, Nonconforming Ranges
in Certain Geographical Areas ... 2.6.2 Nonconforming
ranges. An analyzer may be used (indefinitely) on a
range which extends to concentration-'higher than two
times the upper limit specified in Table B-l of part 53
of this chapter if ..." U.S. Environmental Protection
Agency. Ambient Air Quality Monitoring Methodology.
Code of Federal Regulations. Title 40, chapter I,
subchapter C, part 58, appendix A. Washington, D.C.
Office of the Federal Register.
4. "2.8 Modifications of Methods by Users. 2.8.1 Except
as otherwise provided in this section (2.8), no
reference method, equivalent method, or alternative
method may be used in a SLAMS if it has been modified
in a manner that will, or might, significantly alter
the performance characteristics of the method without
prior approval by the Administrator." U.S.
Environmental Protection Agency. Ambient Air Quality
Monitoring Methodology. Code of Federal Regulations.
Title 40, chapter I, subchapter C, part 58, appendix A.
Washington, D.C. Office of the Federal Register.
5. "Methods used in those SLAMS which are also designated
as NAMS to measure S02, CO, N02, or 03 must be automated
reference or equivalent methods (continuous
3-10 February 1994
-------
analyzers)." U.S. Environmental Protection Agency.
Code of Federal Regulations. Title 40, chapter I,
subchapter B, part 58, appendix C, section 3.0
National Ambient Monitoring Stations (NAMS).
6. "Ambient air quality data collected at any SLAMS must
be collected as follows: (a) For continuous analyzers-
consecutive hourly averages except during: (l) Periods
of routine maintenance, (2) Periods of instrument
calibration, or (3) Periods or seasons exempted by the
Regional Administrator. (b) For manual methods
(excluding PM-10 samplers)-at least one 24 hour sample
every six days except during periods or seasons
exempted by the Regional Administrator." U.S.
Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter B,
part 58.13. Washington, D.C. Office of the Federal
Register.
7. "For continuous analyzers, at least 80 percent of the
individual hourly values should be reported by the
source in any sampling period." U.S. Environmental
Protection Agency. Ambient Monitoring Guidelines for
Prevention of Significant Deterioration (PSD). Office
of Air Quality Planning and Standards, Research
Triangle Park, NC. EPA Publication No. EPA-450/4-87-
007. May 1987.
3-11 February 1994
-------
3.4 NETWORK DESIGN
General criteria for the establishment of the SLAMS
network and for the selection of new monitoring stations is
provided in appendix D of 40 CFR 58.1 These criteria are
employed by EPA in evaluating the adequacy of SLAMS
networks.
A network of SLAMS should be designed to comply with
four basic monitoring objectives:2
o to determine the highest concentrations expected
to occur in the area encompassed by the network;
o to determine representative concentrations in
areas of high population density;
o to determine the impact on ambient pollution
levels of significant sources or source
categories; and
o to determine general background concentration
levels.
Proper siting of a monitoring station requires exact
specification of the monitoring objective and commonly
involves a definition of a spatial scale of
t
representativeness.3 As stated in appendix D, the goal in
siting stations is to correctly match the spatial scale that
the sample of monitored air represents with the spatial
scale most appropriate for the monitoring objective of the
station.4 The spatial scales designated for S02 SLAMS
monitoring are the middle, neighborhood, urban and regional
scales, the definitions of which are provided in appendix D.
Additional information on monitoring network design may
be found in the documents "Optimum Site Exposure Criteria
for S02 Monitoring" and "Ambient Monitoring Guidelines for
Prevention of Significant Deterioration (PSD)."5-6
In designing ambient monitoring networks under PSD
regulations, such factors as topography, climatology,
population, and existing emission sources must be
considered; therefore, the ultimate design of the network
3-12 February 1994
-------
will be determined on a case-by-case basis by the permitting
authority.7 In general, ambient networks under PSD are
designed during a preconstruction phase and a post-
construction phase. For both the preconstruction phase and
the post-construction phase, the number and location of
monitors will be determined through appropriate dispersion
modeling techniques. In addition, the number of monitors
will depend on the expected spatial variability of the
pollutant in the area being studied (i.e., the higher the
spatial variability of the pollutant under study, the
greater the number of monitors needed in that area).8
During the preconstruction phase, the monitors should
be (1) located in the area of maximum concentration increase
expected from the proposed source or modification; (2)
located in the area of the maximum expected concentrations
from emissions of existing sources; and (3) located in the
area of maximum impact of the pollutant from the combination
effect of existing sources and the proposed source or
modification. In most rnultisource settings, one to four
sites would be sufficient. For remote settings (i.e., in
areas with no significant existing sources), a minimum
number of monitors would need to be located (i.e., one or
two at the most).9
For the postconstruction phase, two or three sites
would probably be sufficient for most situations involving
multi-source areas. For remote areas, one or two sites
would be sufficient.10
3-13 February 1994
-------
REFERENCES FOR SECTION 3.4
1. U.S. Environmental Protection Agency. Network Design
for State and Local Air Monitoring Stations (SLAMS) and
National Air Monitoring Stations (NAMS). Code of
Federal Regulations. Title 40, chapter I,
subchapter C, part 58, appendix D. Washington, B.C.
Office of the Federal Register.
2. Reference 1. "The network of stations which comprise
SLAMS should be designed to meet a minimum of four
basic monitoring objectives. These basic monitoring
objectives are: (1) To determine highest concentrations
expected to occur in the area covered by the network;
(2) to determine representative concentrations in areas
of high population density; (3) to determine the impact
on ambient pollution levels of significant sources or
source categories; and (4) to determine general
background concentration levels."
3. "Proper siting of a monitoring station requires precise
specification of the monitoring objective which usually
includes a desired spatial scale of
representativeness." U.S. Environmental Protection
Agency. Network Design for State and Local Air
Monitoring Stations (SLAMS) and National Air Monitoring
Stations (NAMS). Code of Federal Regulations.
Title 40, chapter I, subchapter C, part 58, appendix D.
Washington, D.C. Office of the Federal Register.
4. "The goal in siting stations is to correctly match the
spatial scale represented by the sample of monitored
air with the spatial scale most appropriate for the
monitoring objective of the station."
U.S. Environmental Protection Agency. Network Design
for State and Local Air Monitoring Stations (SLAMS) and
National Air Monitoring Stations (NAMS). Code of
Federal Regulations. Title 40, chapter I,
subchapter C, part 58, appendix D. Washington, D.C.
Office of the Federal Register.
5. U.S. Environmental Protection Agency. Optimum Site
Exposure Criteria for S02 Monitoring. Research
Triangle Park, NC. EPA Publication
No. EPA-450/3-77-013. April 1977.
6. U.S. Environmental Protection Agency. Ambient
Monitoring Guidelines for Prevention of Significant
Deterioration (PSD). Office of Air Quality Planning
and Standards. Research Triangle Park, NC. EPA
Publication No. EPA-450/4-87-007. May 1987.
3-14 February 1994
-------
7. Reference 6. "3.1 Network Design. The design of a
network for criteria and noncriteria pollutants will be
affected by many factors such as topography,
climatology, population, and existing sources.
Therefore, the ultimate design of a network for PSD
purposes must be decided on a case-by-case basis by the
permit granting authority."
8. Reference 6. "3.2.2. As discussed above for
preconstruction monitoring, appropriate dispersion
modeling techniques are used to estimate the location
of the air quality impact of the new source or
modification. Monitors should then be placed at (a)
the expected area of the maximum concentrations from
the new source or modification, and (b) the maximum
impact area(s), i.e., where the maximum pollutant
concentration will occur based on the combined effect
of existing sources and the new source or modification
. . . 3.2 Number and Location of Monitors . . .
Generally, the number of monitors will be higher where
the expected spatial variability of the pollutant in
the area(s) of study is higher."
9. Reference 6. "3.2.1 Preconstruction Phase . . . This
would provide sufficient information for the applicant
to place a monitor at (a) the location(s) of the
maximum concentration increase expected from the
proposed source or modification, (b) the location(s) of
the maximum air pollutant concentration from existing
sources of emissions, and (c) the location(s) of the
maximum impact area, i.e., where the-maximum pollutant
concentration would hypothetically occur based on the
combination effect of existing sources and the proposed
new source or modification . . . Generally, one to
four sites would cover most situations in multisource
settings. For remote areas in which the permit
granting authority has determined that there are no
significant existing sources, a minimum number of
monitors would be needed, i.e., one or probably two at
the most . . . When industrial process fugitive
particulate emissions are involved, the applicant
should locate a monitor at the proposed source site.
If stack emissions are also involved, a downwind
location should also be selected."
10. Reference 6. "3.2.2 Postconstruction Phase . . .
Generally, two or three sites would be sufficient for
most situations in multisource areas. In remote areas
where there are no significant existing sources, one or
two sites would be sufficient."
3-15 February 1994
-------
3.5 PROBE SITING CRITERIA
Criteria for determining the correct siting of S02
samplers is provided in appendix E of 40 CFR 58 and in the
"Ambient Monitoring Guidelines for Prevention of Significant
Deterioration (PSD).Ml These criteria must be adhered to as
strictly as possible. In the event that the siting criteria
cannot be met, a written request must be made justifying the
differences in the proposed siting criteria.2
3-16 February 1994
-------
REFERENCES FOR SECTION 3.5
1. U.S. Environmental Protection Agency. Ambient
Monitoring Guidelines for Prevention of Significant
Deterioration (PSD). Office of Air Quality Planning
and Standards, Research Triangle Park, NC. EPA
Publication No. EPA-450/4-87-007. May 1987.
2. "The probe siting criteria as discussed below must be
followed to the maximum extent possible. It is
recognized that there may be situations when the probe
siting criteria cannot be followed. If the siting
criteria cannot be met, this must be thoroughly
documented with a written request for a waiver which
describes how and why the siting criteria differ."
U.S. Environmental Protection Agency. Probe Siting
Criteria for Ambient Air Quality Monitoring. Code of
Federal Regulations. Title 40, chapter I,
subchapter C, part 58, appendix E. Washington, D.C.
Office of the Federal Register.
3-17 February 1994
-------
3.7 AMBIENT AIR QUALITY DATA REPORTING
3.7.1 General. On an annual basis States shall submit a
summary report of all the ambient air quality monitoring
data from their SLAMS (40 CFR 58.26). These annual
summaries must contain the following statistics:1
o the annual arithmetic mean (ppm);
o the highest and second highest 24-hour averages
and dates of occurrence;
o the highest and second highest 3-hour averages and
dates and ending hours of occurrence;
o the number of exceedances of the 24-hour primary
NAAQS;
o the number of exceedances of the 3-hour secondary
NAAQS;
o the number of 24-hour average concentrations in
the ranges as specified in appendix F;
o the location, date, pollution source and duration
of each air pollution incident during which
ambient SO2 levels reached or exceeded the
significant harm level specified by 40 CFR 51.151;
and
o a certification of accuracy by the State's senior
air pollution control officer or that officer's
designee.
It is important to note that EPA policy permits the use of
block averages in implementing the 3-hour and 24-hour
NAAQS.2 This policy does not preclude States from
developing more stringent requirements such as requiring
running averages.3 Part 58.26 requires that the annual
report be submitted by July 1 of each year for data
collected from January 1 to December 31 of the previous
year. In addition, the States are required to submit, upon
Regional Administrator request, all or part of SLAMS data.4
As a subset of the SLAMS network, NAMS data are required,
3-19 February 1994
-------
3.6 EPISODE MONITORING
Classification of regions required to have air
pollution episode contingency plans is provided in 40 CFR 51
subpart H. The definition of an air pollution emergency and
the level of sulfur dioxide associated with it are defined
in 40 CFR 51 appendix L. As stated in 40 CFR 51.152, each
State contingency plan must satisfy the following:
o specify two or more stages of episode criteria, as
set forth in appendix L, or their equivalent;
o provide for public announcement whenever any
episode stage has been determined to exist; and
o specify adequate emission control actions to
implement at each episode stage.
3-18 February 1994
-------
under part 58.35, to be reported quarterly and within 120
days of the end of a quarter.5
In addition to the annual SLAMS reporting requirements,
section 4.1 of .appendix A of 40 CFR part 58 requires that
the results of all valid precision and accuracy tests be
reported to AIRS via the appropriate EPA Regional Office
within 120 calendar days after the end of each calendar
quarter. The report should include the results of all
collocated measurements including those falling below 45
^g/m3 for SO2 as specified in section 5.3.1 of appendix A.
Data from invalid tests, from tests performed during a
period of time for which ambient data immediately prior or
subsequent to the tests were invalidated for appropriate
reasons, and from tests of methods or analyzers not approved
for SLAMS network use under appendix C of part 58, should
not be reported.6
3.7.2 Air Pollution Index. States are required to report
to the public, through a prominent notice (such as radio,
television, newspapers), an air quality index in accordance
with the requirements outlined in appendix G of 40 CFR 58.
This index provides the general public with an idea of how
healthy the ambient air is on a particular day. Reporting
of the air quality index is required for all urban areas
with populations exceeding 200,000 (based on the most
current decennial U.S. Census of Population Report).7
3-20 February 1994
-------
REFERENCES FOR SECTION 3.7
1. "The annual summary report must contain: (1) The
information specified in appendix F, (2) The location,
date, pollution source, and duration of each incident of
air pollution during which ambient levels of a pollutant
reached or exceeded the level specified by 51.16(a)
[redesignated as 51.151] of this chapter as a level which
could cause significant harm to the health of persons.
(c) The senior air pollution control officer in the State
or his designee shall certify that the annual summary
report is accurate to the best of his knowledge." U.S.
Environmental Protection Agency. Code of Federal
Regulations title 40, chapter I, subchapter C,
part 58.26(b) and (c). Washington, B.C. Office of the
Federal Register.
2. Memorandum from Bauman, R.D., OAQPS to Air Branch Chief,
Regions I-X. Boilerplates for Block Averaging and
Grandfathering Modeling Analyses. July 12, 1989.
3. "The question has arisen whether block averages are
indeed the proper interpretation of the NAAQS. We have
investigated this issue, and concluded that block
averages are the proper interpretation. Thus, we will
continue to use block averages in actions implementing
the 3-hour and 24-hour NAAQS." Memorandum from Emison,
G.A., to Director, Air Divisions, Regions I-X. March 28,
1986. Block Averages in Implementing S02 NAAQS.
4. "The State shall submit all or a portion of the SLAMS
data to the Regional Administrator upon his request. U.S.
EPA. Code of Federal Regulations. Title 40. part 58.28.
"Regional Office SLAMS data Acquisition."
5. "(b) The State shall report quarterly to the
Administrator (through the appropriate Regional Office)
all ambient air quality data and information...(c) The
quarterly report must: (1) Be received by the National
Aerometric Data Bank within 120 days of the end of each
reporting period, after being submitted by the States to
the Regional Offices for review; (2) Contain all data and
information gathered during the reporting period." U.S.
EPA. Code of Federal Regulations. Title 40, chapter I,
subchapter C, part 58.35. "NAMS Data Submittal."
6. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part 58,
appendix A 4.1.
7. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part 58,
3-21 February 1994
-------
subpart E. Washington, B.C. Office of the Federal
Register.
3-22 February 1994
-------
3.8 AMBIENT AIR MONITORING NETWORK FOR MODEL EVALUATION
While it is generally not feasible to base point source
emission limits solely on monitoring data, such data may be
used to determine, through an evaluation study, the best
available model for a particular application.1 A difficult
aspect of implementing this approach is the determination of
the appropriate network size. A network too small would
provide inadequate data and hence an invalid evaluation. A
network too large would be prohibitively expensive to
operate.2 Based on experience with previously conducted
model evaluation studies, the operation of approximately
15 monitors for a period of one year is considered the
minimum network size to obtain a valid data base under
normal (e.g., not complex terrain) circumstances.3'4 The
protocol and data base requirements for conducting a model
performance evaluation study are described in the EPA report
"Interim Procedures for Evaluating Air Quality Models
(Revised)."5
3-23 February 1994
-------
4. AIR QUALITY MODELING
4 .1 GENERAL
Air quality modeling analyses are performed to
demonstrate that a proposed control strategy can adequately
attain and maintain the National Ambient Air Quality
Standards (NAAQS) (40 CFR 51.112) and protect the Prevention
of Significant Deterioration (PSD) increments. State
Implementation Plan (SIP) submittals must include a
description of how the modeling analysis was conducted by
providing, in a Technical Support Document, information on:
the models used; the justification of model selection; the
modes of models used; assumptions involved in model
application; the meteorological data; ambient monitoring
data used; the justification of off-site data, if used; the
model input data; and the model output data.1
4.2 GUIDANCE ON AIR QUALITY MODELS
Air quality modeling techniques appropriate for use in
SIP, New Source Review (NSR) and PSD analyses are specified
in the "Guideline on Air Quality Models (Revised)"
("Guideline"), Supplement A2'3, and Supplement B4 which was
promulgated on July 20, 1993 (58 FR 38816). The Guideline
is a primary source of information on the proper selection
and regulatory application of air quality models.
Recommendations are made in the Guideline concerning air
quality models, data bases, requirements for concentration
estimates, the use of measured data in lieu of model
estimates and model evaluation procedures.
The Federal Register notice in which Supplement B was
promulgated did several things. It added new models and
improved existing models to the Guideline, it gave
regulatory status to long-standing EPA policy regarding the
4-1 February 1994
-------
REFERENCES FOR SECTION 3.8
1. "It is generally not feasible to establish emission
limits for point sources based solely on monitoring
data. [A] n alternative approach is to establish a
monitoring network of reasonable size, use the
resulting monitored data to evaluate the models for
applicability to those particular conditions, and to
use the resulting 'best available' model to establish
the emission limitation." Memorandum from
Rhoads, R.G., OAQPS, to R.C. Campbel1, OAQPS.
September 1, 1981.
2. Reference 1. "One problem with this approach is
defining the "network of reasonably size" which would
be used to evaluate the models. If the network is too
small, the data would be inadequate to distinguish
between models and the evaluation would have no
validity. If the network is too large, the cost would
be excessive."
3. Reference 1. "Based on our experience with these
programs (all of which were reasonable successful, but
with the exception of EPRI, none of which were 'data
rich'), I believe that approximately 15 monitors
operating for one year is probably the minimum network
size to obtain a valid data base under normal
circumstances."
4. "Although our experience with networks for this purpose
is limited, we believe that an appropriate balance
between the technical requirements of the analyses and
the costs would result in approximately 15 monitors,
depending upon the type of terrain, meteorological
conditions, prior knowledge of air quality in the area,
etc." Memorandum from Rhoads, R.G., OAQPS, to D. Kee,
Region V. August 7, 1981.
5. U.S. Environmental Protection Agency. Interim
Procedures for Evaluating Air Quality Models (Revised).
Monitoring and Data Analysis Division, Office of Air
Quality Planning and Standards, Research Triangle Park,
NC.' EPA Publication No. EPA-450/4-84-023 .
September 1984.
3-24 February 1994
-------
use of air quality models for other regulatory programs, and
it codified the Guideline by adding Appendix W to 40 CFR
part 51. Appendix W will be published in the 1993 edition
of the CFR, which is updated each July. However, CFR
volumes are not generally available until at least the
following December. Therefore, the reader is advised to
refer to the Federal Register (op. cit.) in the interim.
As was done with Supplement B, announcements of
proposed and final revisions to the Guideline are made in
the Federal Register as needed. Clarifications and
interpretations of modeling procedures become official EPA
guidance through several courses of action: 1) the
procedures are published as regulations or guidelines;
2) the procedures are formally transmitted as guidance to
Regional Office managers; 3) the procedures are formally
transmitted as guidance to Regional Modeling Contacts as a
result of a Regional consensus on technical issues; or
4) the procedures are a result of decisions by the Model
Clearinghouse that effectively establish a national
precedent.5 Formally located in the Source Receptor
Analysis Branch (SRAB) of the OAQPS, the Model Clearinghouse
is the single EPA focal point for the review of criteria
pollutant modeling techniques for specific regulatory
applications.6 The Clearinghouse serves a major role in
promoting fairness and consistency in modeling decisions
that deviate from the established modeling guidance.7 Model
Clearinghouse memoranda involving significant decisions with
respect to interpretation of modeling guidance are available
on the Support Center for Regulatory Air Models Electronic
Bulletin Board.8
The time at which changes in modeling guidance affect
modeling analyses in progress will depend on the type of
agreement under which those analyses are being conducted.9
Normally, on-going analyses will be grandfathered if there
is a written protocol with a legal or regulatory basis or if
4-2 February 1994
-------
the analysis is complete and regulatory action is imminent
or underway.10
4-3 February 1994
-------
applications." Memorandum from Tikvart, J.A., OAQPS,
to Regional Chiefs, Air Branch Region VII, Technical
Support Branch Region I, Air and Radiation Branch
Region V, Air Programs Branch Regions II, III, IV, VI,
VIII, IX, X. June 7, 1988.
7. Reference 5. "However, there is also a need to provide
for a mechanism that promotes fairness and consistency
in modeling decisions among the various Regional
Offices and the States."
8. The Support Center for Regulatory Air Models (SCRAM)
Electronic Bulletin Board, Office of Air Quality
Planning and Standards, Research Triangle Park, NC
27711.
9. Reference 4. "(T)he time at which changes in modeling
guidance affect on-going modeling analyses is a
function of the type of agreement under which those
analyses are being conducted."
10. Reference 4. "On-going analyses should normally be
"grandfathered" if (1) there is a written protocol with
a legal or regulatory basis (such as the Lovett Power
Plant) or (2) the analysis is complete and regulatory
action is imminent or underway."
4-5 February 1994
-------
REFERENCES FOR SECTIONS 4.1 and 4.2
1. "(e) Modeling information required to support the
proposed revision, including input data, output data,
models used, justification of model selections, ambient
monitoring data used, meteorological data used,
justification for use of offsite data (where used),
modes of models used, assumptions, and other
information relevant to the determination of adequacy
of the modeling analysis." Appendix V - Criteria for
Determining the Completeness of Plan Submissions.
Proposed Amendment to 40 CFR Part 51. Federal Register
54:2141. January 19, 1989.
2. "This guideline recommends air quality modeling
techniques that should be applied to State
Implementation Plan (SIP) revisions for existing
sources and to new source reviews, including prevention
of significant deterioration (PSD)." U.S. Environmental
Protection Agency. Guideline on Air Quality Models
(Revised), Office of Air Quality Planning and
Standards, Research Triangle Park, NC. EPA Publication
No. EPA-450/2-78-027R. July 1986. p. 1-1.
3. U.S. Environmental Protection Agency. Supplement A to
the Guideline on Air Quality Models (Revised). Office
of Air Quality Planning and Standards, Research
Triangle Park, NC. EPA Publication No.
EPA-450/2-78-027R-A. July 1987.
4. U.S. Environmental Protection Agency'. Supplement B to
the Guideline on Air Quality Models (Revised). Office
of Air Quality Planning and Standards, Research
Triangle Park, NC. EPA Publication No.
EPA-450/2-78-027R-B. February 1993.
5. "(C)hanges in EPA modeling procedures become official
Agency guidance when: (1) they are published as
regulations or guidelines, (2) they are formally
transmitted as guidance to Regional Office managers,
(3) they are formally transmitted as guidance to
Regional Modeling Contacts as the result of a Regional
consensus on technical issues, or (4) they are a result
of decisions by the Model Clearinghouse that
effectively establish a national precedent."
Attachment 2 of memorandum from Tikvart, J.A., OAQPS,
to Regional Modeling Contacts. January 2, 1985.
PN 110-85-01-02-070.
6. "The Model Clearinghouse is the single EPA focal point
for reviewing the use of modeling techniques for
criteria pollutants in specific regulatory
4-4 February 1994
-------
4.3 MODEL SELECTION
Air quality, modeling techniques recommended for
application to SIP revisions for existing sources and to now
source reviews, including PSD are provided in the
Guideline.1-2 Each SIP revision must identify and describe
the air quality model selected.3
The model selected for application should in all
situations be the one which most accurately represents
atmospheric transport, dispersion, and chemical
transformations in the area under analysis.4 For example,
models have been developed for both simple and complex
terrain situations; some are designed for urban applications
while others are designed for rural applications.
The acceptability of using an alternative model for a
given regulatory application may be justified in certain
situations.5 Procedures for objectively evaluating
alternative techniques are discussed in the EPA documents:
"Interim Procedures for Evaluation Air Quality Models
(Revised)" and "Interim Procedures for Evaluating Air
Quality Models: Experience with Implementation."6-7 A third
document to refer to when evaluating an alternative model,
is the "Protocol for Determining the Best Performing
Model."8
Two levels of model sophistication exist: screening and
refined. Screening techniques are used initially to
eliminate more extensive modeling if it is clearly
established, through their application, that the proposed
source or control strategy will not cause or contribute to
ambient concentrations in excess of either the NAAQS or the
allowable PSD increments.9 Refined air quality models
require more detailed and precise input data and
consequently provide more accurate estimates of source
impact. These refined models are used if a screening
technique indicates that a concentration resulting from the
4-6 February 1994
-------
source causes or contributes to an exceedance of the PSD
increment or the NAAQS .10
As noted above, the Guideline should be consulted on
specific requirements for model selection. The most current
versions of regulatory, air quality model computer code may
be obtained from the Support Center for Regulatory Air
Models Electronic Bulletin Board.11
4-7 February 1994
-------
REFERENCES FOR SECTION 4.3
1. "This guideline recommends air quality modeling
techniques that should be applied to State
Implementation Plan (SIP) revisions for existing
sources and to new source reviews, including prevention
of significant deterioration (PSD)." Introduction;
Guideline on Air Quality Models (Revised) and its
Supplements (see section 4.2), codified as appendix W
of title 40, part 51, Code of Federal Regulations.
Office of the Federal Register.
2. "(1) All applications of air quality modeling involved
in this subpart shall be based on the applicable
models, data bases, and other requirements specified in
the appendix W of this part ('Guideline on Air Quality
Models (Revised)' (1986), supplement A (1987) and
supplement B (1993))." Federal Register 58:38822.
July 20, 1993.
3. "(4) A description of the dispersion models used to
project air quality and to evaluate control
strategies." U.S. Environmental Protection Agency.
Code of Federal Regulations. Title 40, chapter I,
subchapter C, part 51.112(b). Washington, B.C. Office
of the Federal Register.
4. Reference 1. "In all cases, the model applied to a
given situation should be the one that provides the
most accurate representation of atmospheric transport,
dispersion, and chemical transformations in the area of
interest."
5. Reference 1, section 3.2 Use of Alternative Models.
"An EPA document, 'Interim Procedures for Evaluation
Air Quality Models,' has been prepared to assist in
developing a consistent approach when justifying the
use of other than the preferred modeling techniques
recommended in this guide."
6. U.S. Environmental Protection Agency. Interim
Procedures for Evaluating Air Quality Models (Revised).
Office of Air Quality Planning and Standards, Research
Triangle Park, NC. EPA Publication No. EPA-450/4-84-
023. September 1984.
7. U.S. Environmental Protection Agency. Interim
Procedures for Evaluating Air Quality Models:
Experience with Implementation. Office of Air Quality
Planning and Standards. Research Triangle Park, EPA
Publication No. EPA-450/4-85-006. July 1985.
4-8 February 1994
-------
8. Environmental Protection Agency, 1992. Protocol for
Determining the Best Performing Model. EPA Publication
No. EPA-454/R-92-025. U.S. Environmental Protection
Agency, Research Triangle Park, NC.
9. Reference l, Section 2.3 Levels of Sophistication of
Models. "The purpose of such techniques is to
eliminate the need of further more, detailed modeling
for those sources that clearly will not cause or
contribute to ambient concentrations in excess of
either the National Ambient Air Quality Standards or
the allowable prevention of significant deterioration
concentration increments."
10. Reference 9. "If a screening technique indicates that
the concentration contributed by the source exceeds the
PSD increment or the increment remaining to just meet
the NAAQS, then the second level of more sophisticated
models should be applied."
11. The Support Center for Regulatory Air Models (SCRAM)
Electronic Bulletin Board. Access through the
Technology Transfer Network (TTN) Bulletin Board
System, Office of Air Quality Planning and Standards,
Research Triangle Park, NC 27711. Communications
Software Parameters: 8-N-l; 1200-2400 baude, (919)541-
5742; 9600 baude, (919)541-1447. SYSOP (919)541-5384.
4-9 February 1994
-------
4.4 METEOROLOGICAL INPUT
Meteorological data utilized in air quality modeling
should be spatially and climatolcgically ^(temporally)
representative of the area of interest.1 Use of site-
specific data is preferred for air quality analyses provided
one year or more of quality-assured data are available.2
Suggestions for the collection and use of on-site data are
provided in the Guideline and in the EPA documents: "On-Site
Meteorological Program Guidance for Regulatory Modeling
Applications," "Ambient Monitoring Guidelines for Prevention
of Significant Deterioration (PSD)" and "Quality Assurance
Handbook for Air Pollution Measurement Systems: Volume IV.
Meteorological Measurements. "3~5
If one year of site-specific data is not available,
five years of other representative meteorological data can
be used in the modeling analysis. These five years should
be the most recent, readily available consecutive five years
of data.6 The five year period is defined to ensure that
the model results adequately represent meteorological
conditions conducive to the prediction of maximum ambient
concentrations. Potential sources of representative
meteorological data include the National Weather Service,
local universities, the Federal Aviation Administration,
military stations and air pollution control agencies.
Meteorological data collected by the National Weather
Service may be obtained from the Support Center for
Regulatory Air Models Electronic Bulletin Board.7
When modeling previously permitted sources whose
emission limitations are based on a specific year of
meteorological data, that year of data should be added to
any longer period involved in the modeling analysis.7
Hours of calm wind should not be included in Gaussian
model calculations of ambient concentrations.8 Proper
procedures for calculating average concentrations during
4-10 February 1994
-------
calm wind conditions are provided in the Guideline. Some
air quality models recommended in the Guideline include
algorithms to automatically recalculate concentrations
during periods of calm wind.
As mentioned earlier, meteorological data collected on-
site must be quality-assured prior to its application in air
quality modeling analyses. At sites with collocated,
continuous air quality monitors, the inspection, maintenance
and calibration of each meteorological instrument operated
must be conducted to guarantee a minimum of 90 percent data
retrieval (80 percent for remote sites).9 At the initiation
of the monitoring program and at least every six months
thereafter, routine system calibrations and audits should be
performed.10
Meteorological audits, performed independently of the
organization responsible for data collection and system
maintenance, should be scheduled on a semiannual basis.11
Aside from providing for on-site calibration of instruments,
these independent evaluations should address network
installation; inspection, maintenance and'.calibration
procedures; data reduction procedures; and data logging and
tabulation procedures.12
As recommended in the Quality Assurance Handbook,
meteorological data validation can be conducted using a
three-fold approach of initial hardcopy audit of the data
followed by screening of the data through a program designed
to note and flag questionable values and finally passing of
the data through a comparison program which evaluates how
well the data fit the synoptic conditions prevalent in the
area of on-site measurement.
4-11 February 1994
-------
REFERENCES FOR SECTION 4.4
1. "The meteorological data used as input to a dispersion
model should be selected on the basis of spatial and
climatological (temporal) representativeness as well as
the ability of the individual parameters selected to
characterize the transport and dispersion conditions in
the area of concern." Section 9.3 Meteorological
Input Data; Guideline on Air Quality Models (Revised)
and its Supplements (see section 4.2), codified as
appendix W of title 40, part 51, Code of Federal
Regulations. Office of the Federal Register.
2. Reference 1, Section 9.3.1.2 Recommendations. "If one
year or more, up to five years, of site-specific data
is available, these data are preferred for use in air
quality analyses."
3. U.S. Environmental Protection Agency. On-Site
Meteorological Program Guidance for Regulatory Modeling
Applications. Office of Air Quality Planning and
Standards, Research Triangle Park, NC. EPA Publication
No. EPA-450/4-87-013. June 1987.
4. U.S. Environmental Protection Agency. Ambient
Monitoring Guidelines for Prevention of Significant
Deterioration (PSD). Office of Air Quality Planning
and Standards, Research Triangle Park, NC. EPA
Publication No. EPA-450/4-87-007. May 1987.
5. U.S. Environmental Protection Agency. Quality
Assurance Handbook for Air Pollution Measurement
Systems: Volume IV. Meteorological Measurements.
Environmental Monitoring Systems Laboratory, Research
Triangle Park, NC. EPA Publication No. EPA-600/4-90-
003. August 1989.
6. Reference 2. "Five years of representative
meteorological data should be used when estimating
concentrations with an air quality model. Consecutive
years from the most recent, readily available 5-year
period are preferred."
7. The Support Center for Regulatory Air Models (SCRAM)•
Electronic Bulletin Board, Office of Air Quality
Planning and Standards, Research Triangle Park, NC
27711.
4-12 February 1994
-------
8. Reference 2. "For permitted sources whose emission
limitations are based on a specific year of
meteorological data that year should be added to any
longer period being used (e.g., 5 years of NWS data)
when modeling the facility at a later time."
9. Reference 1, Section 9.3.4.2 Recommendations. "Hourly
concentrations calculated with Gaussian models using
calms should not be considered valid; the wind and
concentration estimates for these hours should be
disregarded and considered to be missing."
10. Reference 4, p. 55. "Inspection, servicing, and
calibration of equipment must be scheduled throughout
the measurement program at appropriate intervals to
assure at least 90 percent data retrieval for each
variable measured at sites where continuous air quality
monitors are being operated. At remote sites, data
retrieval for measured variables should not fall below
80 percent."
11. Reference 3, p. 8-38. "Routine system calibrations and
system audits should be performed at the initiation of
a monitoring program and at least every six months
thereafter. More frequent calibrations and audits may
be needed in the early stages of the program if
problems are encountered, or if valid data retrieval
rates are unacceptably low."
12. Reference 4, p. 55. "An independent•meteorological
audit (by other than one who conducts the routine
calibration and operation of the network) should be
performed to provide an on-site calibration of
instruments as well as an evaluation of (a) the network
installation, (b) inspection, maintenance, and
calibration procedures, and logging thereof, (c) data
reduction procedures, including spot checking of data,
and (d) data logging and tabulation procedures. [S]uch
independent meteorological audit-evaluations should be
performed about each 6 months."
4-13 February 1994
-------
4.5 SOURCE INPUT
4.5.1 General. Emission input data to be used to evaluate
SIPs and PSD analyses for compliance with both the annual
and short-term ambient standards are described in Table 9-1
of the "Guideline On Air Quality Models (Revised)."1 The
model input data requirements in this table apply to
stationary point source control strategies.2 Other model
input criteria may apply with regard to emissions trading or
new source review. Determination of emission limits for
these purposes is discussed in section 7.
4.5.2 Allowable Versus Actual Emissions. Annual and short-
term average concentrations estimated from stationary point
sources undergoing a SIP emission limit review must reflect
the maximum allowable emission limit or federally
enforceable permit limit of the source.3 A source's total
emissions reflected in modeling analyses are determined as
the product of the source's emission limit, operating level
and operating factor. The operating level used must be the
actual or design capacity (whichever is greater) or the
federally enforceable permit condition. Operating levels
less than 100 percent of capacity should also be modeled for
those cases in which the source operates at a capacity
substantially less than design and in which changes in stack
parameters associated with the operating conditions could
result in higher ground level concentrations.4 In the case
of large power plants, for example, loads such as 50 and
75 percent of capacity should also be modeled. If a source
operates at greater than 100 percent load for periods during
normal operation that could result in violations of the
NAAQS or PSD increments, this load should be modeled.
The operating factor (e.g., hours/year or hours/day) to
be used in the case of annual averages should be the actual
operating factor averaged over the most recent two years
4-14 February 1994
-------
(unless it is determined that this period is not
representative).5 In the case of short-term averages,
operation should be assumed to occur for all hours of the
time period under consideration (i.e, continuous operation).
Appropriate adjustment of the modeled emission rate may be
made if operation does not occur continuously and the
operation is constrained by a federally enforceable permit
condition (i.e., modeling may only be performed for those
hours during which the source is operating).6
Identical input requirements apply to sources defined
as "nearby" background sources (here the term "nearby"
refers to those sources expected to cause a significant
concentration gradient in the vicinity of the source or
sources under consideration).7 If other background sources
are modeled, the maximum allowable emission limit or
federally enforceable permit limit should be used in
estimating both annual and short-term average
concentrations. The operating level used for estimating
both annual and short-term concentrations from these sources
should be the annual level when actually operating, averaged
over the most recent two years (unless this period is deemed
unrepresentative). The operating factors used for other
background sources are identical to those indicated
previously in this section.
4.5.3 Background Concentration. Background concentrations
are an essential element of the total air quality
concentration to be considered in the determination of
source impacts for State Implementation Plans.8 These
concentrations may include contributions from natural
sources, nearby sources other than those currently under
consideration, and unidentified sources. Recommendations
for determining background concentrations are provided in
the Guideline.9
In the case of isolated sources, air quality data
4-15 February 1994
-------
monitored in the vicinity of the source(s) under
consideration should be used to determine the background
concentration for the averaging times of concern.10
Concentrations recorded while the source in question is
impacting the monitor should not be used in determining the
background concentration.11 Use of monitored air quality
data is recommended for determining that portion of the
background attributable to sources other than those nearby
(e.g., natural sources, minor sources, and distant major
sources) ,12
In multi-source areas, nearby sources that are
anticipated to cause a concentration gradient in the
vicinity of the source or sources under consideration for
emission limit (s) should be explicitly modeled.13-14 The
impact of nearby sources should be examined at those
locations where interaction exists between the plume of the
source under consideration and those of the nearby sources
(including natural background).
4.5.4 Stack Height Input to Air Quality Modeling.
Specification of stack height is an important consideration
in the development of source input for an air quality
modeling analysis. Generally, the lesser of the actual
stack height or Good Engineering Practice (GEP) stack height
is used for air quality modeling (refer to section 5 for
definition of GEP). Guidance on a number of particular
modeling questions has been provided by EPA, as follows:15
o If the actual stack height is greater than GEP
height and where it is necessary to reduce stack
height credit below that which exists:
Use existing stack gas exit parameters--
temperature, flow rate and stack top diameter
--and model the stack at GEP height.
o If the actual stack height is less than GEP height
and dispersion techniques are employed:
4-16 February 1994
-------
- • Two cases should be modeled in order to
establish an appropriate emission limitation
for the situation in which it is desired to
construct a source at less than GEP height
and use dispersion techniques to make up the
difference in plume rise. First conduct a
modeling analysis using the GEP stack height
without enhanced dispersion parameters.
Secondly, conduct a modeling analysis using
the less than GEP stack height with the
increased plume rise. The more stringent
emission limitation resulting from each of
the two model runs should be the one
specified as the enforceable limitation.
Stack height input for point sources modeled for
the purpose of demonstrating protection of the
NAAQS or PSD increments:
The GEP stack height should be used as input.
If a source is operating at a height less
than GEP, then the actual stack height should
be input to the model.
Stack height for background sources:
The GEP stack height should be used for each
background source. If a background source is
operating with less than a GEP stack height,
then the actual stack height should be input
to the model.
Excluding the effects of prohibited dispersion
techniques for modeling purposes:
Modeling to exclude the effects of prohibited
dispersion techniques on the emission
limitations will be accomplished by using the
temperature and flow rates as the gas stream
enters the stack, and recalculating stack
parameters to exclude the use of prohibited
techniques.
If single flued, merged stacks or multiflued
stacks are involved in a modeling analysis refer
to section 5.7 to determine if this merging is
creditable.
If plume merging from multiflued stacks is not
allowed, then each flue/liner must be modeled as a
separate source and the combined impact
determined. For single flued, merged stacks where
4-17 February 1994
-------
credit is not allowed, each unit should be modeled
as a separate stack located at the same point.
The stack exit velocity and temperature would be
the. same as for the existing merged stack
conditions and the volume flow rate based on an
apportionment of the flow from the individual
units.
4.5.5 Stack Downwash and Building Wake Effects. Air
quality modeling of sources with stacks which are less than
GEP should consider the impacts associated with building
wake effects both for the source in question and for nearby
sources.16 In determining which background sources
constitute "nearby" sources, the reviewing agency must
exercise judgement. Exercising judgement in these cases can
minimize the resource burden associated with collecting
building dimension data.17
4-18 February 1994
-------
REFERENCES FOR SECTION 4.5
1. Table 9-1 (section 9.1.2); Guideline on Air Quality
Models (Revised) and its Supplements (see section 4.2),
codified as appendix W of title 40, part 51, Code of
Federal Regulations. Office of the Federal Register.
2. "The EPA's policy for demonstrating stationary point
source compliance with the NAAQS for SIP purposes
clearly requires the use of emissions which are more
closely tied to allowable emissions. The model
emission input data requirements for such SIP
demonstrations are contained in Table 9-1 of the
'Guideline for Air Quality Models (Revised)' ..."
Memorandum from Calcagni, J., and Laxton, W., OAQPS, to
T.J. Maslany, Air Management Division, Region III, and
W.B. Hathaway, Air Pesticides, and Toxics Division
Region VI. March 16, 1989.
3. Reference 1.
4. Reference 1, section 9.1.2 Recommendations. "Where a
source operates at substantially less than design
capacity, and the changes in the stack parameters
associated with the operating conditions could lead to
higher ground level concentrations, loads such as 50
percent and 75 percent of capacity should also be
modeled."
5. Reference 1. \.
6. Reference 1.
7. Reference 1, section 9.2.3 Recommendations (Multi-
Source Areas). "Nearby Sources: All sources expected
to cause a significant concentration gradient in the
vicinity of the source or sources under consideration
for emission limit(s) should be explicitly modeled."
8. Reference 1, section 9.2.1 Discussion. "Background
concentrations are an essential part of the total air
quality concentration to be considered in determining
source impacts."
9. Reference 8.
10. Reference 1, 9.2.2 Recommendations (Isolated Single
Source). "Use air quality data collected in the
vicinity of the source to determine the background
concentration for the averaging times of concern."
4-19 February 1994
-------
11. Reference 10. "Determine the mean background
concentration at each monitor by excluding values when
the source in question is impacting the monitor."
12. Reference 7. "Other Sources: That portion of the
background attributable to all other sources (e.g.,
natural sources, minor sources and distant major
sources) should be determined either by the procedures
found in section 9.2.2 or by application of a model
using Table 9-1."
13. Reference 7.
14. "Nearby sources which are expected to cause a
significant concentration gradient in the vicinity of
the source under consideration should be explicitly
modeled (as 'background' sources)." Memorandum from
Calcagni, J., OAQPS, to W. Laxton, OAQPS. May 3, 1989.
15. Memorandum from Helms, G.T., OAQPS, to Air Branch
Chief, Regions I-X. October 10, 1985. (PN 123-85-10-
10-007).
1.6. Reference 1, section 7.2.5 Good Engineering Practice
Stack Height. "If stacks for new or existing major
sources are found to be less than the height defined by
EPA's refined formula [H + 1.5L] for determining GEP
height, then air quality impacts associated with cavity
or wake effects due to the nearby building structures
should be determined."
17. "This guidance provides considerable flexibility and
requires judgement to be exercised by the reviewing
agency in identifying which background sources should
be fully modeled. The burden collecting building
dimension data may be mitigated somewhat by application
of this judgement." Memorandum from Calcagni, J.,
OAQPS, to W.B. Hathaway, Air Pesticides, and Toxics
Division, Region VI. March 31, 1989.
4-20 February 1994
-------
4.6 RECEPTOR GRID
Definition of the receptor network used for air quality
analyses in support of SIP revisions should be made on a
case-by-case basis, taking into consideration the
topography, the climatology, existing monitor locations, and
results of the initial screening procedure.1 Receptor sites
for any analysis should be assigned in sufficient detail to
estimate the highest concentrations and potential violations
of the NAAQS or the PSD increment.2
A modeling analysis performed for the purpose of
redesignating an area to attainment must follow the
Guideline with respect to the scope of the receptor network
and not necessarily address only the area to be
redesignated.3
4-21 February 1994
-------
REFERENCES FOR SECTION 4.6
1. "The selection of receptor sites should be a case-by-
case determination taking into consideration the
topography, the climatology, monitor sites, and the
results of the initial screening procedure." Section
8.2.2 Critical Receptor Sites; Guideline on Air
Quality Models (Revised) and its Supplements (see
section 4.2), codified as appendix W of title 40, part
51, Code of Federal Regulations. Office of the Federal
Register.
2. Reference 1. "Receptor sites for refined modeling
should be utilized in sufficient detail to estimate the
highest concentrations and possible violations of a
NAAQS or a PSD increment."
3. "If a modeling analysis is required for any reason,
that analysis must meet the requirements of the
Guideline." Memorandum from Bauman, R.D., OAQPS, to
J. Tikvart, OAQPS. February 15, 1989.
4-22 February 1994
-------
4.7 OTHER MODEL REQUIREMENTS
The "Guideline on Air Quality Models (Revised)"
provides discussion and guidance relative to a number of
special modeling considerations that may occur from time to
time. The special considerations most often associated with
SO2 are as follows.
Comparison of short term estimates and measurements of
air quality on an event-by-event basis with the intent of
calibrating.a model is unacceptable given the uncertainties
in both source and meteorological data.1 In the case of
long term estimates, model calibration may be the best
alternative for improving the accuracy of estimated
concentrations, provided a more accurate model for the
particular situation is not available.2
Air quality modeling of SO2 emissions involves some
designation of the pollutant's chemical transformation. In
rural areas this transformation is generally considered
insignificant when the travel time is a few hours or less.
Specification of the chemical transformation rate is more
critical when modeling urban areas, where synergistic-
effects among pollutants are observed to occur. A half-life
of four hours may be applied to the analysis of S02
emissions in urban areas.3
Issues that may arise in modeling analyses of SO2
emissions are treatment of stagnation, fumigation and long
range transport. Stagnation events, characterized by both
long and short term periods of very light winds, and plume
fumigation, an important phenomenon on and near shorelines,
are not adequately addressed in current Guideline models.
Determining the long range transport of S02 emissions may be
significant in the analysis of source impacts on PSD Class I
areas.4 Assistance on the appropriate techniques to utilize
in these modeling situations should be obtained from the EPA
Regional Office.
4-23 February 1994
-------
While modeling is the preferred method for determining
emission limitations for both new and existing sources,
there may be circumstances in which no applicable model to
the situation at hand exists (e.g., complex terrain,
land/water interface areas). The Guideline provides criteria
for determining the acceptability of measured data to be
used in these instances.5
4-24 February 1994
-------
REFERENCES FOR SECTION 4.7
1. "Calibration of short term models is not common
practice -and is subject to much greater error and
misunderstanding. There have been attempts by some to
compare short term estimates and measurements on an
event-by-event basis and then to calibrate a model with
results of that comparison. This approach is severely
limited by uncertainties in both source and
meteorological data and therefore it is difficult to
precisely estimate the concentration at an exact
location for a specific increment of time. Such
uncertainties make calibration of short term models of
questionable benefit. Therefore, short term model
calibration is unacceptable." Section 8.2.11
Calibration of Models; and its Supplements (see section
4.2), codified as appendix W of title 40, part 51, Code
of Federal Regulations. Office of the Federal
Register.
2. Reference 1. "Calibration of long term multi-source
models has been a widely used procedure even though the
limitations imposed by statistical theory on the
reliability of the calibration process for long term
estimates are well known. In some cases, where a more
accurate model is not available, calibration may be the
best alternative for improving the accuracy of the
estimated concentrations needed for control strategy
evaluations."
3. Reference 1, Section 8.2.6 Chemical Transformation.
"The chemical transformation of S02 emitted from point
sources or single industrial plants in rural areas is
generally assumed to be relatively unimportant to the
estimation of maximum concentrations when travel time
is limited to a few hours. However, in urban areas,
where synergistic effects among pollutants are of
considerable consequence, chemical transformation rates
may be of concern. In urban area applications, a half-
life of 4 hours may be applied to the analysis of S02
emissions."
4. Reference 1, Section 7.2.6 Long Range Transport
(LRT)(i.e., beyond 50 km). "However, 50 km is the
useful distance to which most Gaussian models are
considered accurate for setting emission limits. Since
in many cases PSD analyses may show that Class I areas
may be threatened at distances greater that 50 km from
new sources, some procedure is needed to (1) determine
if a significant impact will occur, and (2) identify
the model to be used in setting an emission limit if
the Class I increments are threatened..."
4-25 February 1994
-------
Reference 1, section 11.2.2 Use of Measured Data in
Lieu of Model Estimates. "Modeling is the preferred
method for determining emission limitations for both
new and existing sources. ...[T]here are circumstances
where there is no applicable model, and measured data
may need to be used. Examples of such situations are:
(1) complex terrain locations; (2) land/water interface
areas; and (3) urban locations with a large fraction of
particulate emissions from nontraditional sources."
4-26 February 1994
-------
5. STACK HEIGHT REGULATIONS
5.1 GENERAL REGULATIONS
Revised stack height regulations were promulgated on
July 8, 1985 and implement provisions of section 123 of the
Clean Air Act which dictate that the degree of emission
limitation required for pollutant control under an
applicable State Implementation Plan shall not be affected
by stacks in excess of good engineering practice (GEP) stack
height or by any other dispersion technique.1'2 Stacks in
existence or dispersion techniques implemented before
December 31, 1970 are exempt from these provisions (see
section 5.5.1 for definition of "in existence").3 Sources
defined in section 110(a)(3) of the Clean Air Act which were
constructed, reconstructed or for which major modifications
were performed after December 31, 1970 are not exempt from
these provisions, however.4
A comprehensive overview of stack height policy is
contained in the "Workshop on Implementing the Stack Height
Regulations (Revised)."5 This document includes a
discussion of SIP stack height requirements and
documentation in outline format and presents several
checklists for GEP stack height review.
5-1 February 1994
-------
REFERENCES FOR SECTION 5 . 1
1. "Section 123, which was added to the Clean Air Act by
the 1977 Amendments, regulates the manner in which
techniques for dispersion of pollutants from a source
may be considered in setting emission limitations.
Specifically, section 123 requires that the degree of
emission limitation shall not be affected by that
portion of a stack which exceeds GEP or by 'any other
dispersion technique.'" Federal Register 50:27892.
July 8, 1985.
2. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, parts
51.118, 51.164, and 52.21{h). Washington, B.C. Office
of the Federal Register.
3. United States Congress. U.S. Congress. Clean Air Act
as Amended November 1990. 42 U.S.C. 7401 et. seq.
section 123(a). Washington, D.C. U.S. Government
Printing Office.
4. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
51.118(b). Washington, D.C. Office of the Federal
Register.
5. U.S. Environmental Protection Agency. Workshop on
Implementing the Stack Height Regulations (Revised).
Office of Air Quality Planning and Standards, Research
Triangle Park, NC. October 1985.
5-2 February 1994
-------
5.2 GOOD ENGINEERING PRACTICE STACK HEIGHT
5.2.1 General. Discussion of the technical basis and
procedures for determining GEP stack height are provided in
the "Guideline for Determination of Good Engineering
Practice Stack Height (Revised)."1 Good Engineering
Practice (GEP), with respect to stack height, is defined by
section 123 of the Clean Air Act as: "the height necessary
to insure that emissions from the stack do not result in
excessive concentrations of any air pollutant in the
immediate vicinity of the source as a result of atmospheric
downwash, eddies or wakes which may be created by the source
itself, nearby structures or nearby terrain obstacles."
According to 40 CFR 51.100(ii), GEP stack height is
determined, quantitatively, as the greatest of the
following:
o De Minimis
65 meters, measured from the ground-level
elevation at the base of the stack;
o Formula Height
Hg = H + 1.5L
where:
Hg = good engineering practice stack height, measured
from the ground-level elevation at the base of the
stack,
H = height of nearby structure(s) measured from the
ground-level elevation at the base of the stack,
L = lesser dimension, height or projected width, of
nearby structure(s).
Provided that the EPA, State or local control
agency may require the use of a field study
or fluid model to verify GEP stack height for
the source.
For stacks in existence on January 12, 1979 and
for which the owner or operator had obtained all
5-3 February 1994
-------
applicable permits or approvals required under 40
CFR Parts 51 and 52:
Hg = 2.5H
Provided the owner or operator furnishes
evidence that this equation was actually
relied on in establishing an emission
limitation.
o Physical Demonstrations
The height demonstrated by a fluid modeling or field
study approved by the EPA, State or local control
agency, which ensures that the stack emissions do not
result in excessive concentrations of any air pollutant
as a result of atmospheric downwash, wakes, or eddy
effects created by the source itself, nearby structures
or nearby terrain features (see section 5.6).
Sources in existence prior to 1971 are not subject to the
stack height regulation.
5.2.2 Definition of Nearby for GEP. For the purpose of
determining GEP stack height, "nearby" is limited to five
times the structure height or width, whichever is less (a
distance not to exceed one-half mile) and in the case of a
fluid model or field study is limited to one-half mile.
This range may be extended, for the portion of a terrain
feature which exists within a distance of up to 10 times the
maximum height of the feature (not to exceed two miles), if
such feature reaches a height, at one-half mile from the
stack, that is at least 40 percent of the GEP stack height
determined by Formula (2) above or 26 meters, whichever is
greater/ as measured from the ground level elevation at the
base of the stack.2
5.2.3 Definition of Excessive Concentration. The term
"excessive concentration," as it applies to a physical
(fluid or field) demonstration of GEP stack height, is
defined in 40 CFR 51.100(kk) for several situations, all of
5-4 February 1994
-------
which require showing a 40 percent increase in the maximum,
ground-level concentration relative to the maximum
concentration observed in the absence of downwash, wakes, or
eddy effects. Certain situations also require a showing
that the stack contributes to a total concentration, due to
emissions from all sources, that exceeds the NAAQS or PSD
increment. The stack emission rate in some cases must be
based on a presumptive NSPS emission rate. (See section
5.6.4 for more detailed discussion).
5-5 February 1994
-------
REFERENCES FOR SECTION 5.2
1. U.S. Environmental Protection Agency. Guideline for
Determination of Good Engineering Practice Stack Height
(Technical Support Document For the Stack Height
Regulations) (Revised). Office of Air Quality Planning
and Standards, Research Triangle Park, NC. EPA
Publication No. EPA-450/4-80-023R. June 1985.
2. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
51,100(jj). Washington, D.C. Office of the Federal
Register.
5-6 February 1994
-------
5.3 DISPERSION TECHNIQUES
5.3.1 General. The revised, EPA stack height regulations
generally prohibit stationary sources from taking credit for
dispersion techniques in determining allowable emission
limitations.
5.3.2 Prohibitions. As stated in 40 CFR 51.100(hh)(1), the
prohibited dispersion techniques are:
o using that portion of a stack in excess of good
engineering practice stack height;
o varying the pollutant emission rate according to
atmospheric conditions or ambient concentrations
of that pollutant (referred to as intermittent or
supplemental control systems - ICS or SCS); or
o increasing final exhaust gas plume rise by
manipulating source process parameters, exhaust
gas parameters, stack parameters or combining
exhaust gases from several existing stacks into
one stack, or other selective handling of exhaust
gas streams so as to increase the exhaust gas
plume rise.
5.3.3 Exceptions. Although credit for selective handling
of exhaust gas streams to increase the exhaust gas plume
rise is generally prohibited, in certain circumstances
credit is allowed for:
o merging of gas streams in original design and
construction (also see section 5.4);
o utilizing techniques which increase final, exhaust gas
plume rise, provided facility-wide allowable emissions
of S02 are less than 5,000 tons per year (see section
5.7.2);
o smoke management techniques involved in agricultural or
silvicultural programs;
o episodic restrictions on residential wood burning and
open burning; and
o reheating after a pollution control system.1
5-7 February 1994
-------
REFERENCES FOR SECTION 5.3
1. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
51.100(hh)(2). Washington, B.C. Office of the Federal
Register.
5-8 February 1994
-------
5.4 REMANDED REGULATIONS
Three portions of the revised, EPA stack height
regulations, promulgated on July 8, 1985, were remanded to
EPA for review:1
o Under the definition of excessive concentration -
Grandfathering pre-October 11, 1983 within-formula
stack height increases from demonstration
requirements [40 CFR 51.100(kk)(2)];
o Under the definition of dispersion technique -
Dispersion credit for sources originally designed
and constructed with merged or multiflue stacks
[40 CFR 51.100(hh)(2)(ii)(A)]; and
o Under the definition of good engineering practice stack
height -
Grandfathering of pre-1979 use of the refined "H +
1.5i" formula [40 CFR 51.100(ii)(2)].
As a result of the remand, an interim policy on stack height
regulatory actions is in effect. This policy provides that
most actions affected by the remand may proceed, provided
appropriate caveat language is incorporated indicating that
the action is subject to review and modification on
completion of EPA's response to the court decision.2
5-9 February 1994
-------
REFERENCES FOR SECTION 5.4
1. "Although the court upheld most provisions of the
rules, three portions were remanded to EPA for review:
1. Grandfathering pre-October 11, 1983 within-formula
stack height increases from demonstration requirements
[40 CFR 51.100(kk) (2)]; 2. Dispersion credit for
sources originally designed and constructed with merged
or multiflue stacks [40 CFR 51.100(hh)(2)(ii)(A)]; and
3. Grandfathering of pre-1979 use of the refined H +
1.5L formula [40 CFR 51.100(ii) (2) ]." Memorandum from
Potter, J.C., O£R, to Air Management Division Director,
Regions I, III, and IX, Air and Waste Management
Division Director, Region II, Air, Pesticides, and
Toxics Management Division Director, Regions IV, and
VI, Air and Radiation Division Director, Region V, Air
and Toxics Division Director, Regions VII, VIII, and X.
April 22, 1988.
2. "In general, actions taken at this time to approve or
disapprove statewide stack height rules which are
affected by the remand must include the qualification
that they are subject to review and modification on
completion of EPA's response to the court decision."
Memorandum from Calcagni, J., OAQPS, to Air Branch
Chief, Regions I-X. May 17, 1988. (PN
123-88-05-17-016).
5-10 February 1994
-------
5.5 SPECIFIC STACK HEIGHT POLICIES
5.5.1 Definition of "In Existence". In promulgating the
1982 stack height regulations, EPA adopted a definition of
"stack heights in existence before December 31, 1970.Ml
This definition allowed the grandfathering of stacks either:
a) physically completed; b) for which continuous
construction had begun; or c) for which construction had not
yet commenced, but for which binding contracts had been
signed that could not be cancelled without substantial loss
to the source owner or operator. The revised stack height
regulation promulgated on July 8, 1985 does not modify this
definition except to restrict its applicability to
facilities that have not undertaken major modifications or
reconstruction and have not ducted effluent gas streams from
post-1970 units into pre-1971 stacks.2
o Grandfathering exemptions may be supported in one of
three ways:3
In the case of stacks physically completed prior
to December 31, 1970 - proof of -stack completion
must be documented (an acceptable form of
documentation, for example, would be a copy of the
1970 Federal Power Commission Report Form 67,
which includes information on stack height);
Evidence submitted to support the commencement
date of stack construction can include any
contemporaneous documentation such as building
inspection records, delivery receipts of
construction materials or news clippings that
clearly indicate that construction activities were
under way before December 31, 1970; or
Date of signature on a contract for stack
construction is acceptable for applying
grandfathering exemptions provided the "binding
contract" is one that commits the source owner or
operator to financially undertake stack
construction and that did not have an "escape"
provision in effect on December 31, 1970 allowing
cancellation by the owner or operator without
penalty. If a contract contains provisions for
5-11 February 1994
-------
assessing penalties for modification or
cancellation that were in effect before December
31, 1970, then the provisions must be reviewed to
determine whether the penalties and other costs of
cancellation would have imposed a "substantial
loss" on the owner or operator. In general, EPA
will presume a substantial loss would have
resulted in those situations in which penalties
exceed ten percent of the project cost.
Documentation supporting any of these grandfathering
exemptions must be made available for public review by the
State or source owner or operator.4
5.5.2 Tie-Ins to Existing Stacks. The definition of
"source" that should be used in determining whether tie-ins
to grandfathered stacks should be permitted or prohibited is
that meaning a single emission unit. Hence, credit for
tying a single, post-1970 unit(s) into a grandfathered stack
serving a number of old units is prohibited under the
revised stack height regulations.5
5-12 February 1994
-------
REFERENCES FOR SECTION 5.5
1. "3. Grandfathered Stack Height. The 1970 Clean Air Act
became effective on December 31, 1970. Prior to that
date some sources had constructed stacks taller than
their GEP height. In Section 123, Congress recognized
this and exempted those sources' stack heights.
Section 123 allows credit for stack height in existence
on December 31, 1970. A source's stack is considered
to be 'in existence' if that stack was part of the
design of a facility on which construction commenced
prior to December 31, 1970." Federal Register 47:5865.
February 8, 1982, p. 5865.
2. "The EPA's definition was upheld by the U.S. Court of
Appeals for the D.C. circuit in Sierra Club v. EPA. 719
F.2d 436, and has not been modified in any way by the
rule revisions promulgated on July 8, 1985, except to
restrict its applicability to facilities that have not
undertaken major modifications or reconstruction, and
have not ducted the effluent gas streams from post-1970
units into pre-1971 stacks. Memorandum from D.D.,
Tyler, OAQPS, to Regional Air Management Division
Director, Regions I-X. Determining Stack Heights "In
Existence" Before December 31, 1970. October 28, 1985.
(PN 123-85-10-28-010) .
3. Reference 2.
4. Reference 2. "The burden of proof for showing that a
stack is eligible for grandfathering exemption lies
with either the State or the source owner or operator,
as appropriate, and documentation in support of
exemptions must be made available for public review
during the rulemaking process."
5. "Q: What 'source' definition should be used in
determining whether tie-ins to grandfathered stacks
should be permitted or prohibited? A: The term
'source' in this instance means a single emitting unit.
Thus, credit for tying a single post-1970 unit(s) into
a grandfathered stack serving a number of old units is
prohibited under the regulation." Memorandum from
Helms, G.T., OAQPS, to Air Branch Chief, Regions I-X.
October 10, 1985. (PN 123-85-10-10-007).
5-13 February 1994
-------
5.6 DEMONSTRATIONS BY FLUID MODELING, FIELD STUDIES OR
NUISANCE
5.6.1 Applicability.
o Sources seeking credit for stack height above GEP
formula height must demonstrate by a field study
or fluid modeling analysis that this height is
necessary to avoid excessive pollutant
concentrations as a result of downwash, wakes or
eddy effects created by the source itself, nearby
structures or nearby terrain (refer to section 5.2
for definitions of "excessive concentration" and
"nearby")-1
o Sources seeking credit within formula height may
also need to conduct such demonstrations: a) in
those cases where it is believed that the formula
may significantly overstate the appropriate stack
height credit and b) to justify certain increases
in stack height.2
o Sources seeking credit for increases in stack
heights up to formula GEP may justify the increase
by demonstating the actual presence of a local
nuisance caused by the existing stack, as
determined by the authority administering the
SIP.3
5.6.2 Field Studies. A field demonstration of GEP height
involves the installation and operation of a monitoring
network designed to clearly identify maximum downwind
concentrations. Concentration patterns from two release
points must be determined: one near the source in the
presence of structure(s) and/or terrain and the other in the
absence of such features. Except for differences due to
structure(s) and/or terrain, the atmospheric flow at the
latter location must be similar to that near the source, as
5-14 February 1994
-------
verified by meteorological observations upwind of both
sites .4
5.6.3 Fluid Modeling.
5.6.3.1 Credit for Height Above GEP Formula. In performing
fluid modeling demonstrations, sources seeking credit for
stacks greater than formula height must use the appropriate
emission rate for the source category (see section 5.6.4)
and the background air quality as determined by procedures
described in section 4.5.3. The following "excessive
concentration" criteria must be met: a) exceedance of the
NAAQS or PSD increment and b) a concentration at least 40
percent in excess of the maximum concentration experienced
in the absence of downwash, wakes or eddy effects. After
these criteria are met, the source must use the lowest stack
height necessary to meet the more restrictive of the two
excessive concentration criteria in order to set emission
limitations. This lowest height becomes the new GEP
height.5
5.6.3.2. Credit for Height Less than or Equal to GEP
Formula. For sources seeking credit after October 11, 1983
for increases in existing stack height up to GEP formula
height, the excessive concentration criteria (a) and (b)
given above generally apply. For sources seeking credit
after January 12, 1979 for a stack height less than or equal
to formula height; for sources seeking credit after November
9, 1984 based on the aerodynamic influence of cooling
towers; and for sources seeking credit after December 31,
1970 based on the aerodynamic influence of structures not
adequately represented by GEP formula, the 40 percent excess
concentration is the only criterion needed to demonstrate
equivalence to formula height.6
5-15 February 1994
-------
5.6.4 Emission Rate for Physical Demonstrations. For
sources seeking credit above formula GEP height, the stack
height regulations require that a presumptive emission rate
equivalent to the NSPS be established for the source in
question before fluid modeling is initiated to determine the
stack height necessary to avoid excessive concentrations due
to downwash.7 The NSPS emission rate is "presumptive" in
that EPA presumes that all sources seeking to justify stack
heights in excess of those established by GEP formulae are
capable of controlling their emissions to NSPS levels. If
it is infeasible for a source to control its emissions to
NSPS levels, then an alternative emission limit representing
the lowest feasible emission limit must be met before credit
for stack height in excess of GEP formula height can be
obtained. These alternative emission rates will be reviewed
by EPA based on the Best Available Retrofit Technology
(BART) guidelines.8'9'10 Unless the source owner or operator
demonstrates that the emission rate prescribed by the NSPS
applicable to the source category is infeasible, the
allowable emission rate to be used in conducting the field
study or fluid modeling demonstrations must be the NSPS
emission rate.11
For certain sources seeking credit for increases in
existing stack heights up to GEP formula height, the
emission rate used in the demonstration shall be the
emission rate specified by the applicable State
Implementation Plan, or, in the case of no established
limit, the actual emission rate shall be used.12 For other
sources 'for which verification of correct GEP height is
requested, the satisfying 40 percent excess concentration
criterion is sufficient demonstration.13
5.6.5 Not in Ambient Air. For the purpose of the physical
demonstration, the exceedance of the NAAQS or PSD increment
need not occur at a location meeting the definition of
5-16 February 1994
-------
ambient air.14
5.6.6 Additional Guidance. Sources of guidance on
conducting fluid modeling demonstrations have been
identified by EPA.15 Documents which form the basis of
information include: "Guideline for Use of Fluid Modeling to
Determine Good Engineering Stack Height"/16 "Determination
of Good Engineering Practice Stack Height - A Fluid Model
Demonstration Study for a Power Plant";17 "Guideline for
Fluid Modeling of Atmospheric Diffusion";18 and "Fluid
Modeling Demonstration of Good Engineering Practice Stack
Height in Complex Terrain."19
5-17 February 1994
-------
REFERENCES FOR SECTION 5.6
1. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
51.100 (ii) (3) . Washington, B.C. Office of the Federal
Register.
2. "Nevertheless, in response to the court's remand, EPA
is including in this final rule a provision for the
authority administering these rules to require field
studies or fluid modeling demonstrations, even for
stacks built to formula height, in cases where it
believes that the formula may significantly overstate
the appropriate stack height credit. (Quite apart from
any such regulatory provision, States have authority to
require such demonstrations, on the terms outlined or
on stricter or more lenient terms, under the savings
provision of section 116 of the Clean Air Act)."
Federal Register 50:27900. Monday, July 8, 1985.
3. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
51.100(kk)(2). Washington, B.C. Office of the Federal
Register.
4. "A field demonstration of GEP stack height requires
experiments to determine the concentration patterns
from two release points -- one with the structure(s)
and/or terrain; the other in the absence of
structure(s) and/or terrain. [A] monitoring array must
be arranged to clearly identify the maximum
concentrations downwind of similar releases at both
sites." U.S. Environmental Protection Agency.
Guideline for Betermination of Good Engineering
Practice Stack Height (Technical Support Bocument For
the Stack Height Regulations) (Revised). Office of Air
Quality Planning and Standards, Research Triangle Park,
NC. EPA Publication No. EPA-450/4-80-023R, June 1985.
p. 47.
5. Reference 4, p. 52. "After demonstrating that both
excessive concentration criteria are met as defined in
Section 1, the source must determine the lowest stack
height necessary to meet the more restrictive of the
two excessive concentration criteria. This lower
height is the new GEP height."
6. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
51.100(kk)(3). Washington, B.C. Office of the Federal
Register.
5-18 February 1994
-------
7. "The regulations require that a presumptive emission
rate equivalent to the new source performance standards
(NSPS) be established for the source in question before
modeling may be conducted to determine stack height
needed to avoid excessive concentrations due to
downwash (where the NSPS has been subject to revision,
and the source in question is not subject to the
revised NSPS, the earliest standard will be applied;
e.g., for power plants a rate of 1.2 Ib/MM Btu would be
used)." Memorandum from Tyler, D.D., OAQPS, to
Regional Air Management Division Director, Regions I-X.
Implementation of Stack Height Regulations -
Presumptive NSPS Emission Limit for Fluid Modeling
Stacks Above Formula GEP Height. Memo dated October
28, 1985. (PN 123-85-10-28-009).
8. Reference 7. "This emission rate is described as
'presumptive' because it is EPA's presumption that all
sources seeking to justify stack heights exceeding
those provided by the GEP formulae are capable of
controlling their emissions to NSPS levels. However,
the regulations also allow source owners or operators
to rebut this presumption, establishing an alternative
emission rate that represents the most stringent level
of control that can feasibly be met by that source in
excess of the NSPS level. In the preamble to the
regulations, EPA indicated that it will rely on the
'Guidelines for Determination of Best Available
Retrofit Technology for Coal Fired Power Plants and
other Existing Stationary Facilities-' EPA-450/3-80-009b'
(BART Guidelines) when reviewing these rebuttals."
9. "In conclusion, we are in full agreement with the
position taken by Region III that sources seeking
credit above formula height must meet an emission rate
consistent with BART/NSPS." Letter from Gerald A.
Emison, G.A., OAQPS, to J.P. Proctor. April 20, 1989.
10. Memorandum from Calcagni,J., OAQPS to I. Dickstein,
Region VIII. November 27, 1990.
11. "Q: Can new or modified sources who have agreed to a
case-by case best available control technology (BACT)
emission rate be required to use this rate for fluid
modeling rather than a less stringent new source
performance standard (NSPS) emission rate? A: As set
forth in 40 CFR 51.1(kk), the allowable emission rate
to be used in making demonstrations under this part
shall be prescribed by the NSPS that is applicable to
the source category unless the owner or operator
demonstrates that this emission rate is infeasible."
Memorandum from Helms, G.T., OAQPS, to Air Branch
5-19 February 1994
-------
Chief, Regions I-X. October 10, 1985. (PN
123-85-10-10-007}.
12. Reference 3.
13. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
51.100(kk)(3). Washington, D.C. Office of the Federal
Register.
14. Reference 11. "Q: Must the exceedance of NAAQS or PSD
increment due to downwash, wakes or eddies occur at a
location meeting the definition of ambient air? A:
No, the exceedance may occur at any location, including
that to which the general public does not have access."
15. Memorandum from Tikvart, J.A., OAQPS, to D. Stonefield,
OAQPS. September 19, 1985. (PN 123-85-09-19-006).
16. U.S. Environmental Protection Agency. Guideline for
Use of Fluid Modeling to Determine Good Engineering
Stack Height. Office of Air Quality Planning and
Standards, Research Triangle Park, NC. EPA Publication
No. EPA-450/4-81-003. July 198i.
17. U.S. Environmental Protection Agency. Determination of
Good Engineering Practice Stack Height - A Fluid Model
Demonstration Study for a Power Plant. Environmental
Science Research Laboratory. EPA Publication No.
EPA-600/3-83-024. April 1983.
18. U.S. Environmental Protection Agency. Guideline for
Fluid Modeling of Atmospheric Diffusion. Environmental
Science Research Laboratory. EPA Publication No.
EPA-600/8-81-009.
19. U.S. Environmental Protection Agency. Fluid Modeling
Demonstration of Good Engineering Practice Stack Height
in Complex Terrain. Atmospheric Sciences Research
Laboratory, EPA Publication No. EPA-600/3-85-022.
April 1985.
5-20 February 1994
-------
5.7 MERGED STACKS
5.7.1 General. Dispersion credit for the retrofit
combining or merging of gas streams is generally not allowed
under the stack height regulations.1 Originally designed
and constructed merged streams are creditable at this time
[40 CFR 51.100(hh)(2)]; however, this provision is affected
by the stack height remand (see section 5.4).
5.7.2 Exceptions. Credit for retrofit merging is allowed
under circumstances where:2
o after July 8, 1985 such merging is part of a change in
facility operation that includes the installation of
pollution controls and is accompanied by a net
reduction in the allowable emissions of a pollutant.
This exclusion from the definition of "dispersion
techniques" shall only apply to the emission limitation
for the pollutant affected by such change in operation;
o before July 8, 1985 such merging: 1),. was part of a
change in operation at the facility that included the
installation of emission control equipment, 2) was
conducted for sound economic or engineering reasons3,
or 3) was not "significantly motivated by an intent to
obtain emissions credit for increased dispersion."4
Such a demonstration could be made by submitting
evidence showing that consideration of dispersion
advantages was conspicuously absent in the intent of
the source owner or operator;s or
o the total, facility-wide allowable SO2 emissions from
the source do not exceed 5,000 tons per year.6 This
exception applies only to S02 and not to other
pollutants.
In addition, exemption from prohibitions on gas stream
merging is provided for sources which constructed their
5-21 February 1994
-------
stacks before December 31, 1970.
It is incumbent on the State or source owner or
operator to demonstrate that any retrofit merging was not
motivated by an intent to avoid emission controls.
Information indicating that merging was specifically carried
out to increase final exhaust gas plume rise serves as a
demonstration of dispersion intent that justifies denial of
credit for merged gas streams.7
5-22 February 1994
-------
REFERENCES FOR SECTION 5.7
1. Memorandum from Tyler, D.D., OAQPS, to Air Management
Division Directors, Regions I-X. Implementation of
Stack Height Regulations - Exceptions From Restrictions
on Credit for Merged Stacks. October 28, 1985. (PN
123-85-10-28-008).
2. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
51.100(hh)(2)(ii). Washington, D.C. Office of the
Federal Register.
3. Reference 1. "Sources that are not covered under these
criteria may still qualify for exemption if they can
show that merging was conducted for sound economic or
engineering reasons."
4. Reference 1. "In some instances, a State or emission
source owner may not be able to make a demonstration as
described above, or believe that sound economic reasons
existed for merging stacks, regardless of the
relationship between financial savings attributable to
reduced emission control requirements versus lower
stack construction costs. In such cases, an
opportunity should be provided to affirmatively
demonstrate that merged stacks'were not significantly
motivated by an intent to obtain emissions credit for
increased dispersion."
5. Reference 1. "For instance, such a demonstration could
be made by submitting documentary or other evidence
(e.g., internal company memoranda presenting the
alternative construction opportunities available to the
company) that indicates the intent of the source owner
or operator and shows that consideration of dispersion
advantages was conspicuously absent."
6. Reference 1. "Several exemptions from prohibitions on
gas stream merging are provided for existing sources
in the stack height regulations: 1- where sources
constructed their stacks before December 31, 1970, 2-
where the total facility-wide emissions from the source
do not exceed 5,000 tons per year, 3- where the
facility was originally designed and constructed with
merged gas streams, and 4- where the merging was part
of a change in facility operation that included the
installation of pollution control equipment and
resulted in no increase in the allowable emissions of
any pollutant (where there was no federally-approved
emission limit prior to merging gas stream, there must
be no increase in the actual emissions of any
5-23 February 1994
-------
pollutant. Moreover, it is incumbent on the State to
demonstrate that there was a logical relationship
between the merging of existing gas streams and the
installation of controls). Where there was an increase
in emission in conjunction with the merging and
installation of control equipment, the regulations
require that source owners also make an affirmative
demonstration that the merging was not motivated by
dispersive intent."
7. Reference 1. "Because merged gas streams are generally
regarded as prohibited dispersion techniques under the
regulations, it is incumbent on the State or the source
owner or operator to demonstrate that such merging was
conducted for sound economic or engineering reasons,
and was not significantly motivated by an intent to
avoid emission controls. Consequently, the first step
should entail a review of State and EPA files to
determine the existence of any evidence of intent on
the part of the source owner or operator. Information
showing that merging was conducted specifically to
increase final exhaust gas plume rise serves as a
demonstration of dispersion intent that justifies a
denial of credit for merged gas streams."
5-24 February 1994
-------
5.8 STACK HEIGHT NEGATIVE DECLARATIONS
5.8.1 General. Following promulgation of the revised stack
height regulations on July 8, 1985, each State was required
to review its SIP and determine if any sources were credited
with stack heights or dispersion techniques not in
accordance with the revised regulations.1 Where sources are
found in compliance with the revised regulations, a
"negative declaration" is issued in the Federal Register for
that State. A Federal Register notice of negative
declaration for the stack height requirements does not need
to be incorporated into the State Implementation Plan since
it is not required under section 110 of the Act.
5.8.2 In f ormation Needed. There are three primary ways to
declare a source as unaffected by the stack height rules:2
o source was constructed prior to December 31, 1970;
o source stack height is less than GEP formula height;
and
o source emission limitation was not affected by stack
height or by any other dispersion technique.
The simplest way to approach the negative declaration
is to set up 2 tables, one for stack heights greater than 65
meters, and the other for sources with S02 emissions greater
than 5,000 tons per year. The lists at the end of this
section provide examples of the information that should be
contained in the negative declaration.3
It is very important that a description of the
grandfathering documentation is provided along with the date
of documentation, so that proof of the grandfathering can be
easily traced back to a specific document.4
5.8.3 Modeling Needed. Source remodeling would be required
in those situations in which credit for excess stack height
5-25 February 1994
-------
or dispersion techniques has been taken. Any remodeling
must follow the "Guideline on Air Quality Models (Revised)."
If a source has never been analyzed for dispersion, then no
modeling 'is required.5
EXAMPLE INFORMATION TO BE CONTAINED IN A NEGATIVE DECLARATION
Stacks Greater
than 65 Meters
Name
Plant Location
Unit ID Number
Stack ID Number
Actual/GEP Height (ft)
Construction Date
Grandfather
Documentation:
Description & Date
2.5H
H + 1.5L
Modeled
Need for Stricter Control
Source Emissions Greater than
5.000 tons per year
Name
Plant Location
Unit ID Number
Stack ID Number
Actual Height (ft)
Merged
Other Dispersion Techniques
Documentation of Dispersion
Techniques
Grandfather
Documentation and Date
Need for Stricter Control
5-26
February 1994
-------
REFERENCES FOR SECTION 5.8
1. "Nine months after date of promulgation ..." United
States Congress. Clean Air Act, as amended August
1977. 42 U.S.C. 1857 et. seq. Section 406(d)(2)(B).
Washington, D.C. U.S. Government Printing Office.
November 1977.
2. U.S. Environmental Protection Agency. Workshop on
Implementing the Stack Height Regulations (Revised).
Control Programs Development Division, Office of Air
Quality Planning and Standards, Research Triangle Park,
NC. October 1985.
3. From tables attached to the memorandum from Helms,
G.T., OAQPS, to Air Branch Chief, Regions I-X. October
9, 1987.- (PN 123-87-10-09-014) .
4. "For grandfathering documentation, the date the source
was built is not essential, but the type and date of
the documentation that the source was built prior to
December 31, 1970, must be listed." Memorandum from
Helms, G.T., OAQPS, to Air Branch Chief, Region I-X.
October 9, 1987. (PN 123-87-10-09-014) .
5. "If a source has never been analyzed for dispersion,
then it is not necessary to conduct a dispersion
analysis now." Memorandum from Tyler, D.D., OAQPS, to
Air Division Director, Regions I-X. February 11, 1986.
(PN 123-86-02-11-012).
5-27 February 1994
-------
5.9 EMISSIONS BALANCING
Emissions balancing refers to the procedure whereby a
source subject to the stack height regulations ("affected
source") may obtain the required emission reduction from
another source or set of sources ("providing sources").1
Emissions balancing may be used to comply with the stack
height regulations only if certain conditions are met.2
These conditions include:
o an approvable emissions balance must require that the
providing source(s) reduce emissions of the same
pollutant, calculated on an annual average basis, to an
extent 1.2 times the emission reduction required of the
affected source by application of the stack height
regulation. That is, 1.2 times that portion of the
required reduction for which the affected source is
seeking an emissions balance);
o an emissions balance must take place entirely within
the boundaries of a single State or single interstate
AQCR ;
o emission reductions from the providing source(s) must
be stack emissions, not fugitive emissions;
o both the affected and providing sources must be in
compliance with federally-approved SIP requirements,
including protection of the NAAQS, PSD increments and
air quality related values of any Class I area; and
o an enforceable means of monitoring compliance should be
included in the emissions balance SIP revision.
Additional details on the conditions necessary for an
acceptable emissions balance, methodology for determining
baseline emissions from which an emissions balance is
credited and other procedural requirements are listed in
Reference 2. A summary of major comments on the proposed
emissions balancing policy and EPA response to these
comments are contained in Reference 1.
5-28 February 1994
-------
REFERENCES FOR SECTION 5.9
1. "Today's final policy has been developed in
consideration of the fact that emission reductions
mandated by the stack height regulation may be
obtained at (an)other source(s), in lieu of reducing
emissions at its own facility. For the purposes of
this policy, the source which is subject to more
stringent emission limits is called the 'affected
source;' the source which provides the emission
reductions needed to satisfy such limits is called the
'providing source.' This joint satisfaction of an
emission reduction obligation is referred to as an
'emissions balance.'" Stack Height Emissions
Balancing: Final Policy. Federal Register 53:480.
January 7, 1988.
2. Memorandum from Thomas, L.M., EPA Administrator, to
Regional Administrators Regions I-X. December 23,
1987. (See Federal Register 53:483. January 7, 1988.)
5-29 February 1994
-------
6. GENERAL PROVISIONS
6.1 GENERAL •
National Ambient Air Quality Standards (NAAQS) are
necessary to protect the public health and welfare. The
amount of time that nonattainment areas are given within the
CAA to reach the SO2 NAAQS can depend upon whether the
standard is a primary standard (health based) or a secondary
standard (welfare based). For areas that are in attainment
or are designated unclassifiable, Prevention of Significant
Deterioration (PSD) increments are set to prevent relative
deterioration in air quality for different classes of air
quality.
SIP's and SIP revisions provide for the implementation,
maintenance, and enforcement of measures needed to attain
and maintain-NAAQS. If the provisions in a SIP are found to
be inadequate, a SIP call may be issued by the federal
agency. If a state does not correct the deficiencies after
a SIP call, the federal agency may impose .sanctions or
develop a Federal Implementation Plan (FIP).
Each SIP must contain an enforceable pollution control
strategy to ensure attainment and maintenance of all the
NAAQS. According to 40 CFR 51.110(a), a control strategy
must be selected "that provides the degree of emission
reductions necessary for attainment and maintenance of the
national ambient air quality standards. The emission
reductions must be sufficient to offset any increases in air
quality concentrations that are expected to result from
emission increases due to projected growth of population,
industrial activity, motor vehicle traffic, or other
factors."
In general, a control strategy will consist of a set of
emission limitations applicable to all sources within
specified classes. The emission limit is the level of
6-1 February 1994
-------
emissions that is demonstrated to be the level that must not
be exceeded in order to attain or maintain the NAAQS. With
respect to SO2 regulations, different emission limitations
may apply depending on such parameters *as facility size,
fuel type, geographical location, and age of source.
6-2 February 1994
-------
6.2 CURRENT NAAQS AND PSD INCREMENTS
6.2.1 General. The authority for developing NAAQS is
provided under section 109 of the CAA. Part C of the CAA
(sections 160-169) establishes the basis for the prevention
of significant deterioration (PSD) program.
6.2.2 National Ambient Air Quality Standards. The EPA is
required, under section 109 of the CAA, to establish NAAQS
for each pollutant for which air quality criteria are
established (under section 108 of the CAA). There are two
types of NAAQS: primary and secondary. The primary NAAQS
are established to protect public health with an adequate
margin of safety. The secondary NAAQS protects public
welfare (soil, crops, vegetation, animals, visibility,
building materials, etc.) from known or anticipated effects.
The current primary S02 NAAQS are as follows: 80 ug/m3
(0.03 ppm) based on an annual arithmetic mean and 365 ug/m3
(0.14 ppm) based on the maximum 24-hour concentration not to
be exceeded more than once per year. The-.current secondary
NAAQS is 1,300 ug/m3 (0.5 ppm) based on the maximum 3-hour •
concentration not to be exceeded more than once per year.1
For any ambient standard that cannot be exceeded more than
once per year, a violation occurs if an exceedance is
recorded twice at the same monitor or is predicted through
modeling to occur twice at the same receptor in 1 year.2
6.2.3 Prevention of Significant Deterioration Increments.
The PSD program mandated by Congress is required to balance
three primary goals as specified in section 160 of the CAA.
The first of these goals is to protect public health and
welfare. This goal includes avoiding air quality
degradation in all areas that are attaining the NAAQS. The
second goal emphasizes the protection of air quality in
national parks, wilderness areas, and similar areas of
6-3 February 1994
-------
special concern where air quality is considered particularly
important. The third goal is to ensure that economic growth
which causes environmental degradation in clean areas occurs
only after careful deliberation by State and local
communities.
The PSD requirements (see section 7.2.4 for additional
detail) apply to areas that are classified as attainment or
unclassifiable pursuant to section 107 of the CAA.3 The
program is implemented largely through the use of increments
and area classifications that effectively define
"significant deterioration" for individual pollutants.
Numerical increments for S02 are defined in the CAA as the
maximum allowable increase, above a baseline concentration,
in the ambient concentration of S02 allowed in a PSD area.
These increments limit the change in the ambient
concentration of sulfur dioxide in any area that is in
compliance with ths NAAQS. The area classification scheme
establishes three classes of geographic areas and applies
increments of different stringency to each class. The most
restrictive increments apply in Class I areas, which are
regions of special national environmental concern. Less
restrictive increments apply in Class II and Class III
areas. Class II areas are all PSD areas that are designated
as attainment or unclassifiable and that were not identified
in the CAA as Class I areas. There are no Class III areas
as of yet; however, these areas would permit more
deterioration of air quality and higher industrial growth
than Class II areas. The current PSD increments for SO2 are
shown in Table 6-1.
6-4 February 1994
-------
TABLE 6-1. PSD INCREMENTS FOR S024
Area Maximum
classification Allowable increase
(ug/m3)*
I 2 (annual arithmetic mean)
5 (24-hour maximum)
25 (3-hour maximum)
II 20 (annual arithmetic mean)
91 (24-hour maximum)
512 (3-hour maximum)
III 40 (annual arithmetic mean)
182 (24-hour maximum)
700 (3-hour maximum)
*For any period other than an annual period, the
applicable maximum allowable increase may be
exceeded during one such period per year at any
one location.4
6-5 February 1994
-------
REFERENCES FOR SECTION 6.2
1. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C,
sections 50.4 and 50.5. Washington, D.C. Office of
the Federal Register.
2. U.S. Environmental Protection Agency. Guideline of Air
Quality Models (Revised). Office of Air quality
Planning and Standards, Research Triangle Park, N.C.
EPA Publication No. EPA-450/2-78-027R. July 1986. p.
11-7.. (See also "Guidelines for Interpretation of Air
Quality Standards (Revised). OAQPS No. 1.2-008. 1977)
3. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C,
sections 51.166 and 52.21. Washington, D.C. Office of
the Federal Register.
4. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C,
section 51.16S(c) and 52.21(c). Washington, D.C.
Office of the Federal Register.
6-6 February 1994
-------
6.3 NONATTAINMENT AREA TIME FRAMES
Section 110(a) of the Clean Air Act (CAA) requires each
State to submit a plan for attainment and maintenance of the
national ambient air quality standards (NAAQS) to EPA. The
plan must provide for attainment and maintenance of the
NAAQS within the State. The schedules for SIP plan or plan
revision and attainment of the primary S02 NAAQS were
revised by the Clean Air Act Amendments of 1990 (CAAA).
6.3.1 Title I of the Clean Air Act Amendments of 1990.
Title I (Air Pollution Prevention and Control) of the CAAA
revamped the requirements for areas that have not attained
the NAAQS for S02, and made numerous changes in the
requirements for SIP's and SIP revisions, as well as the
repercussions of State failures to meet the various SIP
requirements-1 The EPA has already and will continue to
initiate rulemaking that will incorporate the provisions of
the CAAA into the Code of Federal Regulations (CFR) in the
near future. In order to provide States with early guidance
on the EPA's interpretation of these provisions, a General
Preamble for the implementation of title I was published on
April 16, 1992 in the Federal .Register.2 The preamble
focuses primarily on the SIP submissions required for
nonattainment areas under part D of the amended Act.
The General Preamble discussed EPA's intended
interpretation of the minimum changes all States must make
in their SIP's in order to comply with the amended CAA
provisions. Not only did the CAAA revise many provisions
applicable to nonattainment areas and provide deadlines for
submittal of SIP revisions, some areas were designated
nonattainment "by operation of law" upon enactment of the
CAAA pursuant to section 107(d)(1)(C). These areas are
currently listed in 40 CFR part 81.3
Additionally, the CAAA added a new subpart 5 to
6-7 February 1994
-------
title I, which provides SIP submittal dates and attainment
dates for areas designated as nonattainment by operation of
law as part of the CAAA or subsequent to them. The dates
provided in subpart 5 are discussed in the following
sections.
6.3.2 Plan Submittal. The CAAA provided specific
submission deadlines for States to submit SIP'S for areas
which violate the primary NAAQS in section 191'. Plan
requirements for nonattainment areas are found in part D of
title I of the CAA. Part D is divided into 6 subparts
containing sections 171 through 193 of the CAA.
6.3.2.1 Primary SIP Deadlines. Section 191 provides
18 months for submittal of a SIP plan meeting the
requirements of subpart 1 of part D. Section 191(a)
provides that States with areas which are redesignated as
nonattainment after the enactment of the CAAA must submit
implementation plans meeting the requirements of part D
within 18 months of the redesignation. Section 191(b)
provides that States with existing nonattainment areas
lacking fully approved SIP's prior to the enactment of the
1990 amendments to the CAA must also submit SIP's within
18 months of the enactment of the CAAA (i.e., by May 15,
1992) .4
6.3.2.2 Secondary SIP Deadlines. One result of the CAAA
was that discretion was given to the EPA to establish, at
the time of designation or redesignation as nonattainment, a
schedule for submittal of a secondary plan or revision.
Although the law allows up to 3 years for submittal of a
secondary nonattainment plan, the EPA has established
18 months as the schedule for these submittals. Because the
level of control necessary to attain the secondary NAAQS for
S02 is no more difficult to establish than for the primary
6-8 February 1994
-------
NAAQS, the EPA will require SIP submittals for secondary
nonattainment areas within 18 months of nonattainment
designation, absent compelling justification by a State for
an extended schedule.5
6.3.2.3 Combined Secondary and Primary SIP Deadlines.
Although explicit plan submission deadlines were not given
in section 191 for nonattainment areas violating both the
primary and secondary SO2 NAAQS, the EPA considers allowing
separate submittals schedules to unnecessarily complicate
plan processing and implementation.6 Therefore, the EPA
expects plans for attaining the secondary NAAQS to be
submitted on the same schedule as plans for attaining the
primary NAAQS for these areas.7
6.. 3.3 Attainment Schedule. The CAA requires the attainment
of both the primary and the secondary NAAQS as expeditiously
as practicable in section 172(a)(2). However, in the case
of the primary NAAQS, the CAAA added a maximum attainment
deadline as established in section 192 of ;no later than 5
years after designation.
6.3.3.1 Primary NAAQS Attainment Dates. There are three
cases in which a State plan must be developed or revised to
provide for attainment of the primary S02 NAAQS: (1) when a
state contains an area that was designated nonattainment at
the time of enactment of the CAAA; (2) when a state contains
an area which is redesignated as nonattainment subsequent to
the CAAA; and (3) when an approved plan addressing an area
designated nonattainment is found to be substantially
inadequate to attain or maintain the NAAQS. This last case
is referred to as a SIP call and is allowed under section
110(k)(5). Section 192 established an attainment schedule
of no more than 5 years for each of these cases, as
specified below.
6-9 February 1994
-------
State plans for areas designated as nonattainment by
operation of law at the time of enactment of the CAAA (i.e.,
initial nonattainment areas) must provide for attainment of
the primary NAAQS as expeditiously as practicable
[section 172(a) (2)1 but no later than November 15, 1995.8
Areas designated (or redesignated) as nonattainment
subsequent to enactment of the CAAA also must attain the
primary S02 NAAQS as expeditiously as practicable, but not
later than 5 years after the designation.9 In the case of a
State whose approved plan for attaining the primary S02
NAAQS is found to be substantially inadequate, the revised
plan must provide for attainment of the NAAQS by 5 years
from the date of the finding of inadequacy.10
6.3.3.2 Secondary NAAQS Attainment Dates. As stated in
section 6.3.3, although Congress retained the requirement to
attain the secondary NAAQS as expeditiously as practicable
in section 172(a)(2), a specific deadline for attainment of
the secondary NAAQS was not provided in section 192.il In
the General Preamble for the Implementation of Title I of
the CAAA, the EPA announced plans to allow attainment with
the secondary NAAQS to be scheduled on what is expeditious
for the actual area. The EPA also advised that the
provisions included in subpart R (40 CFR 51.340) would be
consulted in determining expeditiousness. In the case of
areas which are nonattainment for both primary and secondary
SO2 NAAQS, States may be allowed additional time beyond the
5-year deadline for the primary NAAQS to attain the
secondary NAAQS, provided that the State can demonstrate
that the secondary NAAQS cannot be attained within the same
timeframe as the primary NAAQS.
6-10 February 1994
-------
REFERENCES FOR SECTION 6.3
1. "Title I of the Clean Air Act Amendments (CAAA) of 1990
revamped the requirements for areas that have not
attained the national ambient air quality standards
(NAAQS) for ozone, carbon monoxide (CO), particulate
matter (PM-10), sulfur dioxide (SO2) , nitrogen dioxide
(N02), and lead. In addition, title I made numerous
changes in the requires for State implementation plans
(SIP's) in general, including the provisions governing
EPA's processing of SIP revisions, as well as the
repercussions of State failures to meet the various SIP
requirements." General Preamble for the Implementation
of Title I of the Clean Air Act Amendments of 1990.
Federal Register 57:13498. April 16, 1992.
2. Reference 1. "This General Preamble principally
describes EPA's preliminary views on how EPA should
interpret various provisions of title I, primarily
those concerning SIP revisions required for
nonattainment areas."
3. Reference 1. "Some areas were designated 'by operation
of law' upon enactment of the 1990 CAAA based upon
their status immediately before enactment. Areas which
were designated nonattainment by operation of law
[section 107(d)(1)(C)] are listed in 40 CFR part 81."
Page 13545.
4. Reference 1. "States with existing nonattainment areas
for the primary S02 NAAQS where those areas lack -fully •
approved SIP's, including part D plans, must submit
implementation plans [section 191(b)]. These
implementation plans must meet the requirements of
subpart 1 of part D, and they must be submitted within
18 months after enactment of the 1990 CAAA (i.e., by
May 15, 1992). Page 13545.
5. Reference 1. "As a result of the 1990 CAAA, EPA has
the authority to establish a schedule for submittal of
a secondary NAAQS plan or plan revision
[section 172(b)]. The EPA must establish this schedule
at the time of the nonattainment designation. The SIP
must be submitted no later than 3 years from the date
of the nonattainment designation. Although the law
allows up to 3 years for SIP submittal, because the
level of control is no more difficult to establish than
for the primary NAAQS, and absent compelling
justification by a State, EPA will require SIP's for
these areas within 18 months of nonattainment
designation." Page 13546.
6-11 February 1994
-------
6. Reference 1. "Explicit plan submission deadlines are
given for nonattainment areas which violate the primary
SO2 NAAQS (section 191). Explicit plan submission
deadlines are not given for nonattainment areas that
violate only the secondary or both the primary and
secondary S02 ITAAQS, however." Page 13545.
7. Reference 1. "For areas which violate both primary and
secondary NAAQS, allowing separate schedules for
secondary and primary plans unnecessarily complicates
the plan implementation and processing. Therefore, EPA
expects secondary NAAQS attainment plans to be
submitted on the same schedule as plans for the primary
NAAQS for these areas." Page 13546.
8. Reference 1. "Areas which were designated
nonattainment at the time of enactment (i.e., areas
which are nonattainment by operation of law), must
attain the primary NAAQS as expeditiously as
practicable but not later than 5 years after enactment
of the 1990 CAAA (i.e., by November 15, 1995)
[section 192(b)]." Page 13546.
9. Reference 1. "Areas which are redesignated as
nonattainment, subsequent to the November 15, 1990
date of enactment, must attain the primary NAAQS 'as
expeditiously as practicable,' but not later than
5 years after the nonattainment designation
[section 192(a)]." Page 13546.
10. Reference 1. "Some nonattainment areas have plans
which were approved by EPA before enactment of the 1990
CAAA. If, subsequent to the plan's approval, EPA finds
that such a plan is substantially inadequate, the plan
must be revised to provide for attainment. The revised
plan must provide attainment of the primary NAAQS
within 5 years from the finding of inadequacy
[section 192 (c)] ." Page 13546.
11. Reference 1. "In the 1990 CAAA, Congress provided for
attainment "as expeditiously as practicable" in both
primary and secondary nonattainment areas
[section 172(a)(2)]. Congress set a specific
attainment date of 5 years for primary NAAQS (see
above) but did not set a specific deadline for
attainment of secondary NAAQS (section 192).
Page 13546.
12. Reference 1. "...EPA plans to allow attainment with
the secondary NAAQS to be scheduled on the basis of
what is expeditious for the area (section 193). Areas
which are nonattainment for the secondary SO2 NAAQS may
6-12 February 1994
-------
be allowed additional time for attainment beyond the
deadlines mandated for the primary NAAQS. In general,
EPA will rely on the substantive provisions of
40 CFR 5i.340 (subpart R) to determine expeditiousness.
Areas which are nonattainment for both the primary
and secondary NAAQS may split their attainment dates,
i.e., attain the primary NAAQS within 5 years and
attain the secondary NAAQS as expeditiously as
practicable. This will be acceptable provided that the
State can demonstrate that the secondary NAAQS cannot
be attained within the same timeframe as the primary
NAAQS." Page 13546.
6-13 February 1994
-------
6.4 ESTABLISHING EMISSION LIMITATIONS
6.4.1 Design Concentration. The general approach for
determining S02 SIP emission limitations for an isolated
point source is to use a dispersion model to identify the
emission levels that provide attainment of the NAAQS. The
averaging time for the emission limitation should be
consistent with the modeling and reflect the period which
results in the most stringent control requirements.
When short-term standards are most restrictive, it may
be necessary to consider a broader range of concentrations
than the highest value. For pollutants such as S02, the
highest, second high concentration is the design
concentration. Thus, a violation of the short-term standard
occurs when the standard is exceeded a second time at the
same site.1
6.4.2 Averaging Periods. The EPA policy regarding
averaging periods for S02 SIP emission limitations is to
require enforceable limits that protect the short-term
(3-hour and 24-hour) NAAQS as well as the annual NAAQS.
These emission limitations must be protective with maximum
emission scenarios and worst-case meteorological conditions.
Every emissions limit should clearly indicate the
appropriate averaging time for that limit. The EPA will not
approve an S02 SIP with emission limitations based on 30-day
averaging, unless the SIP also contains short-term limits
established by an approved dispersion modeling analysis.2
This point is especially important for S02 sources that are
complying with an NSPS (e.g., subpart Da). Although
subpart Da allows 30-day averaging, parameters for
evaluating the control system on a short-term basis must
also be established for compliance with the NAAQS and PSD
increments.3
6-14 February 1994
-------
6.4.3 Compliance Methods. Each SIP must identify methods
for determining compliance with the emission limitations.4
(See chapter 8 also.) The compliance methods should be
consistent with the averaging periods for the emission
limitations selected. For many sources, Continuous Emission
Monitoring Systems (CEMS) should be used as the compliance
test method. If a State adopts an S02 emission limitation
without a stated averaging period, EPA accepts Method 6
(40 CFR 60 Appendix A) stack gas testing as the S02
compliance test method. In some situations, as an
alternative to Method 6 (or equivalent) testing, the SIP may
require short-term (3-hour, 24-hour) fuel sampling as S02
compliance test methods. A SIP may contain separate
compliance test methods for each emission averaging period.5
6-. 4.4 Multipoint Rollback Modeling. Multipoint rollback
modeling addresses the problem of inherently variable S02
emissions from smelting operations by correlating the
frequency of emissions at various levels with the
probability of violating the SIP. Essentially, the
technique "rolls back" an entire yearly emission profile
(frequency distribution) to protect the standards. The EPA
has accepted this modeling technique in very few cases.
Although multipoint rollback modeling has been accepted
for setting emission limitations for certain copper
smelters, EPA does not believe the technique is appropriate
for most situations. The EPA believes that in most
situations the rollback approach is technically less sound
than approved modeling methods. Multipoint rollback
modeling was approved because of the unusual nature of
smelter emission problems and the associated difficulty of
using standard modeling techniques on these sources.6 This
technique was judged to be inappropriate for the Indiana
SIP. Rejection of the technique was due to the fact that
Indiana S02 emissions are dominated by large industrial
6-15 February 1994
-------
boilers and utility power plants, which have emissions that
do not vary nearly so much as smelters and which do not have
large fugitive emissions and complex terrain. Also, the EPA
believes that other approved models already exist for
establishing emission limitations for these sources.7
6-16 February 1994
-------
REFERENCES FOR SECTION 6.4
1. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
51, appendix W, section 11.2.3.1 Design Concentrations.
Washington, B.C. Office of the Federal Register.
2. "As you know, the current National Ambient Air Quality
Standard (NAAQS) for S02 has both short-term (i.e.,
3-hour and 24-hour averages) as well as annual average
components. Because under the Clean Air Act, State
Implementation Plans (SIPs) must demonstrate attainment
of those short-term standards, EPA has a long standing
policy to require emission limitations to be
enforceable on a short-term basis to protect the short-
term standard." Letter from Potter, J.C., to
Ms. N. Maloley, Indiana Department of Environmental
Management. May 23, 1986. (PN 110-86-05-23-075).
3. "The PSD regulations clearly require that the
application of BACT conform with any applicable
standard of performance under 40 CFR part 60 at a
minimum. However, this should not be taken to
supersede any additional limitations as needed to
enable the source to demonstrate compliance with the
NAAQS and PSD increments. In the case of sulfur
dioxide (S02) , source compliance with the 30-day
rolling average emission limit under subpart Da does
not adequately demonstrate compliance with the
short-term NAAQS and PSD increments. •• Memorandum from
Emison, G.A., OAQPS, to D. Kee, Region V-Air Management
Division. November 24, 1986. (PN 165-86-11-24-016).
4. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C,
part 51.111(d). Washington, D.C. Office of the
Federal Register. July 1, 1992
5. "...EPA has accepted Method 6 as the SIP compliance
test method. The EPA also accepts continuous emissions
monitoring and short-term fuel sampling and analysis
(3-hour and 24-hour) as SO2 SIP test methods."
Memorandum from Emison, G.A., OAQPS, to Air Management
Division Directors, Regions I, III, V, and IX, Air and
Waste Management Division Director, Region II, Air,
Pesticides, and Toxics Division Directors, Region IV,
and VI, and Air and Toxics Division Directors,
Region VII, VIII, and X. July 29, 1987.
(PN 110-87-07-29-084).
6. Reference 2. "Although in most circumstances EPA
considers the rollback approach to be technically less
6-17 February 1994
-------
sound than approved modeling methods, the Agency
finally approved that approach for Arizona as a result
of a wide range of factors stemming from the very
unusual nature of the smelter emission problems. As
you know, the problems of smelters have proven
particularly difficult, as demonstrated by Congress'
own special treatment of smelters in section 119 of the
Clean Air Act."
7. Reference 2. "My understanding is that the Indiana SIP
for S02, in contrast, is dominated by utility power
plants and large industrial boilers, whose emissions do
not vary nearly so much as smelters and which do not
have large associated fugitive emissions sources or
complex terrain. Approved models already exist and
have been used nationally to account for multiple
source interactions and stack height adjustments (where
stack heights greater than GEP must be discounted).
The existing air quality modeling methods for
establishing emission limitations have been used
successfully in different state SIPs which have sources
similar to Indiana."
6-18 February 1994
-------
6.5 SIP REVISIONS
6.5.1 General. All SIP revisions must include a
demonstration that the NAAQS and PSD increments are not
violated in the area. Specific requirements for SIP
processing are contained in Guidelines for the Review of SIP
Revisions by EPA Regional Offices.1
6.5.2 SIP Completeness. In accordance with the
requirements of section 110(k)(1) of the amended Act, EPA
has promulgated minimum completeness criteria that any SIP
submittal must meet [see 56 FR 23826 and 56 FR 42216] . The
minimum completeness criteria serve as a tool for EPA to
assess whether a SIP submittal is complete and, therefore,
adequate to trigger an EPA review and action on the
submittal. The completeness criteria provide criteria and
procedures that can be used by States to prepare adequate
SIP submittals.2
Two categories of criteria have been developed in order
to determine whether a submittal by a State is complete:
(1) administrative information and (2) technical support
information. Administrative information includes the
documentation necessary to demonstrate that the State has
adhered to basic administrative procedures during the rule
adoption process. Technical support information includes
the documentation that adequately identifies all of the
required technical components of the plan submission. If a
submittal is determined to be complete, EPA will inform the
State by letter of its determination and then begin the
formal review for approvability. If a submittal is
determined to be incomplete, EPA will return it to the State
with a letter listing the deficiencies. EPA will attempt to
make completeness determinations within 60 days of receiving
a submittal in accordance with section 110(k)(1)(B) of the
amended Act. However, if a completeness determination is
6-19 February 1994
-------
not made by EPA within 6 months of its receipt of the
submittal, the submittal will be deemed complete.2
6.5.3 Approval Options. In the processing of SIP
submittals, there are three general situations that can
occur related to each required submittal: (1) the State may
fail to submit the required plan; (2) the State may make a
submittal that is deemed incomplete; or (3) the State may
make a complete submittal. If the State fails to make a
required submittal or makes a submittal that is determined
by EPA to be incomplete, sanctions and FIP provisions of
sections 179 and 110 (c) will be triggered. If EPA
determines that a submittal is complete, it must either
approve or disapprove the submittal within 12 months of the
date EPA determines the submittal is complete.3 However, in
some instances a State's complete Sip submission may include
provisions that do not comply with applicable requirements
of the Act. In those instances, EPA may issue a partial
approval, a limited approval, or a conditional approval.4'5
Section 110 (k) (3) of the amended Act .-addresses the
situation in which a separable portion of a submittal meets
all applicable requirements of the Act. If the disapproved
portions of a SIP submittal are separable (i.e., disapproval
of a provision does not affect the stringency of other
portions of the SIP) , EPA will grant a partial approval of
the SIP submittal.5 The disapproval of any part of a SIP
submittal starts the clocks for sanctions and FIP's
requirements.6
In some instances, inseparable portions of a SIP
submittal may be disapproved. However, if the submittal as
a whole has a strengthening effect on the SIP, EPA may grant
a limited approval of the SIP submittal.5'7 The amended Act
does not address situations requiring limited approval.
Rather, EPA is using its "gap-filling" authority under
sections 301(a) and 110(k)(3) to interpret the Act to
6-20 February 1994
-------
provide for such actions.8
Limited approval is not considered a complete action on
the SIP submittal. It may be used where a submittal as a
whole serves to improve air quality by providing progress
toward attainment, RFP, and/or RACT, but fails to comply
with all of the Act's requirements. For the action on a SIP
submittal to be considered complete, EPA must issue, in
addition to the limited approval, a limited disapproval that
disapproves the SIP revision request as a whole for failing
to meet one or more requirements of the Act.5
Limited approval differs from partial approval in that
under limited approval, EPA approves the entire rule since
that rule strengthens the SIP, although parts of it do not
meet the requirements of the Act. Likewise, a limited
disapproval applies to the entire rule, but the rule remains
a part of the SIP because the rule strengthens the SIP.9
Limited appr6val should not be used in situations where a
rule is unenforceable for all situations or where it has no
strengthening effects on the SIP; however, limited approval
can be used when the rule is unenforceable in a limited
number of situations and the rule has a strengthening- effect
on the SIP. Disapproval coinciding with (or following) the
limited approval also starts the sanctions and FIP clocks.10
Under section 110(k)(4) of the amended Act, EPA may
conditionally approve a plan based on a commitment of the
State to adopt specific enforceable measures by a specified
date within I year from the date of approval of the plan
revision that incorporated that commitment.11-12 If EPA
determines that the State fails to meet the commitment
within that year, the conditional approval would
automatically become a disapproval. The sanctions and FIP
clocks do not begin to run until the conditional approval
becomes a disapproval.12
EPA's policy is to award conditional approvals only in
rare situations that merit special consideration and after
6-21 February 1994
-------
evaluating specific types of SIP submittals. To ensure
consistency, EPA's policy is to urge the Regions not to use
conditional approvals without input from Headquarters as to
whether such an approach is appropriate.13 In general, the
greater the extent to which a submittal is lacking in
important plan elements, the less appropriate is the use of
conditional approval. In some cases, EPA may accept a SIP
revision consisting of a commitment only (with no
specifically adopted rules) as a candidate for conditional
approval. In such instances, the commitment should be
accompanied by a work plan detailing specific measures to be
adopted, steps that will be taken to adopt those measures,
and a schedule for adoption. Such a submittal will be
considered a SIP revision and is subject to State procedures
for submitting SIP revisions.14 Where the submittal
contains specifically adopted rules that need some revisions
to be fully approvable, the commitment should be explicit in
describing the measures to be adopted and the corresponding
schedule for implementation.15
Because conditional approval relies on a commitment
from the State, EPA needs to make a determination of whether
the State can reasonably be expected to meet its commitment.
This determination would be based on consideration of a
number of factors including, but not limited to, (1) the
amount of technical work necessary for the measures to be
adopted; (2) whether the measures are controversial; (3) the
average length of the State adoption process and how far
along in the process the State is; and (4) the State's past
track record.16
For conditional approvals, sanctions and FIP clocks
start if and when the approval is converted to a
disapproval. This occurs in at least two situations. In
the first case, the State fails to adopt and submit the
specified measures by the end of one year. In this case,
EPA will issue a finding of disapproval and the sanctions
6-22 February 1994
-------
and FIP clocks start on the date of issuance of the finding
of disapproval.17 The second situation is where an approval
is converted to a disapproval when a State makes a complete
submittal by the end of the 1-year period, but EPA concludes
that the submittal does not adequately address the
deficiencies that were the subject of the conditional
approval. In this case, EPA will have to go through notice-
and-comment rulemaking to disapprove the submittal, and the
sanctions and FIP clocks start on the date of final
disapproval.18
In a Federal Register notice published on October 1,
1993, the EPA has proposed that sanctions be applied in a
specific order. The EPA has proposed that the offset
sanction apply in an area 18 months after the date on which
the EPA makes a finding and that the highway sanction apply
in that area six months following application of the offset
sanction.19
When the EPA finds that a State has failed to submit a
plan or complete plan, the sanction and FIP clocks start on
the date of the finding. If the EPA subsequently finds the
late plan submittal complete, the sanction clock will.
permanently stop. If the EPA then takes final rulemaking
action to conditionally approve the same plan, the FIP clock
will temporarily stop. If the conditional approval converts
to a disapproval, the FIP clock resumes where it stopped and
a new sanction clock starts. The FIP clock will stop
permanently if the State fulfills its commitment and the EPA
takes final action fully approving the plan.20
6.5.4 Grandfathering. Generally, all SIP revisions are
evaluated based on the requirements in existence at the time
of EPA's rulemaking. However, EPA does have the flexibility
to grandfather certain provisions in new regulations if the
following conditions are met: (1) the new rule would
represent an abrupt departure from existing practice; (2)
affected parties must have relied on the old rule; (3) the
6-23 February 1994
-------
new rule would impose a large burden on those affected; and
(4) there would be little statutory interest in applying the
new rule.21 (For grandfathering of modeling analyses, see
section 4.2.)
Grandfathering is neither mandatory nor automatic. In
determining whether to grandfather a State-submitted rule,
the decision-maker should focus on whether good-faith
efforts were made to comply with the existing rules.
Grandfathering should not allow sources to circumvent
tighter requirements or agencies to avoid difficult
decisions.22
Exceptions to the allowance of grandfathering
provisions include the following:
• If a court ruling has explicitly changed a current
Federal requirement
• If the old regulation or policy was ill-founded
• If it would have substantial adverse environmental
impact
• If lack of compliance with the new requirements renders
the SIP inadequate for NAAQS attainment23
6.5.5 SIP Relaxations. All SIP relaxations should contain
the following information in a Federal Register notice
and/or technical support document: (1) plant name and
location; (2) facility size (including number of units); (3)
revised SO2 emission limit, existing SIP limit, and
corresponding averaging times; and (4) actual and "paper"
(allowable) emissions decrease or increase.24
6.5.6 SIP Tightening. In general, where a SIP revision
will result in an emissions decrease at a specific source
and there is no other change in the stack parameters, a new
control strategy demonstration will not be required.
6-24 February 1994
-------
REFERENCES FOR SECTION 6.5
1. U.S. Environmental Protection Agency, Guidelines for
the Review of SIP Revisions by EPA Regional Offices.
EPA-450/2-89-005, Research Triangle Park, NC, February
1989.
2. U.S. Environmental Protection Agency. General Preamble
for the Implementation of Title I of the Clean Air Act
Amendments of 1990; Proposed Rule. Federal Register.
57:13565, Volume 57, No. 74. April 16, 1992. EPA
Requirements; SIP Processing Requirements;
Completeness.
3. "In general, there are three situations that can occur
related to each required submittal: the State may fail
to submit the required plan, the State may make a
submittal that is not complete, or the State may make a
complete submittal. Once a State submits a SIP and EPA
has determined that the submittal is complete, EPA must
either approve or disapprove the submittal within a
specified time period. However, if the State fails to
make a required submittal or makes a submittal that is
determiried to be incomplete, the sanctions and FIP
provisions of section 179 and 110 (c), respectively,
will be triggered." Memorandum from Calcagni, John,
Director, Air Quality Management Division, OAQPS,
U.S. EPA, Research Triangle Park, NC,, to Director, Air,
Pesticides, and Toxics Management Division, Regions I
and IV; Director, Air and Waste Management Division,
Region II; Director, Air, Radiation, and Toxics
Division, Region III; Director, Air and Radiation
Division, Region V; Director, Air, Pesticides and
Toxics Division, Region VI; Director, Air and Toxics
Division, Regions VII, VIII,IX, and X. Processing of
State Implementation Plan (SIP) Submittals. July 9,
1992.
4. Reference 3, p. 1. "There are, however, three
alternatives to full approval or full disapproval of a
complete SIP submittal: partial approval, limited
approval, and conditional approval."
5. Reference 2, p. 13565. EPA Requirements; SIP
Processing Requirements; Partial Approvals; Full,
Partial, and Limited Approval and Disapproval.
6. Reference 3, p. 2. "In the case where a separable
portion of the submittal meets all of the applicable
requirements, partial approval may be used to approve
that part of the submittal and disapprove the
6-25 February 1994
-------
remainder. It is important that the two parts of the
submittal be separable. The EPA can approve some of
the rules and disapprove the rest as long as the rules
that are disapproved do not affect those that are
approved. The disapproval of any part of a required
SIP submittal starts the clocks discussed above for
sanctions and FIP's."
7. Reference 3, p. 2. "In some cases, a submittal may
contain certain provisions that meet the applicable
requirements of the Act along with other provisions
that do not meet the requirements, and the provisions
are not separable. Although a submittal may not meet
all of the applicable requirements, EPA may want to
consider whether the submittal as a whole has
strengthening effect on the SIP. If this is the case,
limited approval may be used to approve a rule that
strengthens the existing SIP as representing an
improvement over what is currently in the SIP and as
meeting some of the applicable requirements of the
Act. "
8. Reference 3, p. 2. "The Act does not expressly provide
for limited approvals. Rather, EPA is using its 'gap-
filling' authority under section 301(a) of the Act in
conjunction with section 110(k)(3) approval provision
to interpret the Act to provide for this type of
approval action."
9. Reference 3, p. 3. "A key distinction between the
limited approval and a partial approval is that under a
limited approval EPA's approval action goes to the
entire rule. In other words, although portions of a
rule prevent EPA from finding that the rule meets a
certain requirement of the Act, EPA believes that the
rule, as a whole, strengthens the SIP. Therefore, EPA
approves the entire rule--even those portions that
prohibit full approval. Likewise, when EPA issues the
limited disapproval, the disapproval applies to the
entire rule as failing to meet a specific requirement
of the Act. The rule remains a part of the SIP,
however, under the limited disapproval, because the
rule strengthens the SIP."
10. Reference 3, p. 3. "The primary advantage of using the
limited approval approach is to make the State
submittal federally enforceable and to increase the
SIP's potential to achieve additional reductions.
Therefore, limited approval should not be used to
approve any rule that is unenforceable for all
situations. These rules and any other rules that do
not have an overall strengthening effect on the SIP
6-26 February 1994
-------
should be disapproved. Limited approval can be used,
however, where the rule is unenforceable for some
limited number of situations but is enforceable for the
majority of situations, if the rule, as a whole,
strengthens the SIP . . . The disapproval coinciding
with (or following) the limited approval also starts
the sanctions and FIP clocks discussed above."
11. Reference 3, p. 4. "Under section 110(k)(4) of the Act
EPA may conditionally approve a plan based on a
commitment from the State to adopt specific enforceable
measures within 1 year from the date of approval."
12. Reference 2, p. 13566. EPA Requirements; SIP
Processing Requirements; Partial Approvals; Conditional
Approval.
13. Reference 3, p. 4. "We will evaluate specific types of
SIP submittals [e.g., reasonable available control
technology (RACT) catch-ups, particles with aerodynamic
diameter less than or equal to a nominal 10 micrometers
(PM-10) SIP's] to determine whether certain elements of
that type of submittal, or that type of submittal as a
whole, merit conditional approval. For this reason and
to ensure consistency, Regions should not use
conditional approvals without input from Headquarters
as to whether such an approach is appropriate."
14. Reference 3, p. 5. "As a general matter, the greater
the extent to which a submittal is lacking in important
plan elements, the less appropriate the use of
conditional approval may be. It should be noted
however, that there may be circumstances under which
EPA would accept a SIP revision consisting of a
commitment only (without specifically adopted rules) as
a candidate for conditional approval. In such cases,
the commitment should also be accompanied by a work
plan detailing any specific measures to be adopted, the
steps that will be taken to adopt the measures, and the
schedule for adoption of those measures. As stated
earlier, a submittal that consists entirely of a
commitment will be considered a SIP revision that is
subject to the State process for submitting SIP
revisions."
15. Reference 3, p. 5. "Where the submittal contains
specifically adopted rules that need some revisions or
corrections to be fully-approvable, the commitment may
not need to be as comprehensive. The commitment
should, however, be as explicit as possible concerning
the measures that will be adopted, the steps that will
be taken to adopt the measures, and the schedule for
6-27 February 1994
-------
adoption of those measures."
16. Reference 3, p. 6. "Because the conditional approval
relies on a commitment from the State, EPA would need
some level of confidence that the State would be able
to meet such a commitment. In making a determination
as to whether a State could reasonably be expected to
meet its commitment, EPA would need to consider a
number of factors such as: the amount of technical work
necessary for measures to be adopted; whether adoption
of the measures is expected to be controversial; the
average length of the State adoption process; how far
along in the process the State is; and the State's past
track record. It should be noted that these are only
some of the factors that should be considered. Each
Region, in making a determination regarding the
credibility of the State's commitment, may have to look
at a number of other factors."
17. Reference 3, p. 6. "Unlike the limited
approval/disapproval, the conditional approval does not
immediately start the sanctions and FIP clocks. These
clocks start if and when the approval is converted to a
disapproval. There are at least two ways that the
conditional approval may be converted to a disapproval.
There are at least two ways that the conditional
approval may be converted to a disapproval. First, if
the State fails to adopt and submit the specified
measures by the end of 1 year (from the final
conditional approval), or fails to submit anything at
all, EPA will have to issue a finding of disapproval
but will not have to propose the disapproval . . .
Therefore, at the end of 1 year from the conditional
approval, the Regional Administrator (RA) will send a
letter to the State finding that it had failed to meet
its commitment and that the SIP submittal is
disapproved. The 18-month clock for sanctions and the
2-year clock for FIP start as of the date of the
letter. Subsequently, a notice to that effect will be
published in the Federal Register, and appropriate
language will be inserted in the Code of Federal
Regulations. Similarly, if EPA receives a submittal
addressing the commitment but determines that the
submittal is incomplete, the RA will send a letter to
the State making such a finding. As with the failure
to submit, the sanctions and FIP clocks will begin as
of the date of the finding letter."
18. Reference 3, p. 7. "Second, where the State does make
a complete submittal by the end of the 1-year period,
EPA will have to evaluate that submittal to determine
if it may be approved and take final action on the
6-28 February 1994
-------
submittal within 12 months after the date EPA
determines the submittal is complete. If the submittal
does not adequately address the deficiencies that were
the subject of the conditional approval, and is
therefore not approvable, EPA will have to go through
notice-and-comment rulemaking to disapprove the
submittal. The 18-month clock for sanctions and the 2-
year clock for a FTP start as of the date of final
disapproval."
19. U.S. Environmental Protection Agency. Application
Sequence for Clean Air Act Section 179 Sanctions.
Federal Register 58:51270. October 1, 1993.
20. Memorandum from Berry, K.D., OAQPS to Director, Air,
Pesticides, and Toxics Management Division, Regions I
and IV; Director, Air and Waste Management Division,
Region II; Director, Air, Radiation, and Toxics
Division, Region III; Director, Air and Radiation
Division, Region V; Director, Air, Pesticides and
Toxics Division, Region VI; Director, Air and Toxics
Division, Regions VII, VIII,IX, and X. Impact of
Conditional Approvals on Sanction and Federal
Implementation Plan (FIP) Clocks. July 14, 1993.
21. "However, an agency does have some flexibility to
provide grandfathering provisions in new regulations.
Generally, such provisions are appropriate where they
meet a four-part test. First, the new rule represents
an abrupt departure from well-established practice.
Second, affected parties have relied on the old rule.
Third, the new rule imposes a large burden on those
affected. Fourth, there is no strong statutory
interest in applying the new rule." Memorandum from
Emison, G.A., OAQPS, to Director, Air Management
Division Regions I, III, and IX; Director, Air, and
Waste Management Division, Region II; Director, Air
Pesticides and Toxics Division Region IV and VI;
Director, Air and Radiation Division Region V; and
Director Air and Toxics Division, Regions VII, VIII,
and X. June 27, 1988. (PN 110-88-06-27-095).
22. Reference 21. "Grandfathering is not to be considered
mandatory or automatic. In determining whether
grandfathering should apply, and what the appropriate
date should be, the decision maker should keep in mind
the thrust of this guidance, i.e., to honor good faith
effort on the part of the State/local agency submitting
the revision, balancing equity with other
considerations. This guidance expressly is not
intended as a vehicle to allow circumvention of tighter
requirements or to facilitate the avoidance of
6-29 February 1994
-------
difficult decisions."
23. Reference 21. "B. There are certain exceptions to the
general grandfathering guidance:" Items 2,3,4 and 6.
24. "In order to allow us to assess the relative impact of
each S02 relaxation more accurately, I ask that the
following information be included in each action memo.
1. Plant name and location.
2.- Size of the facility (including the number of
boilers) expressed in megawatts or Btu/hour firing
capacity (design).
3. Amount, type, and sulfur content of actual fuel
combusted during the previous year.
4. The revised S02 emission limit, the existing SIP
limit, and the corresponding averaging times for
these limits.
5. The "paper" as well as actual increase or decrease
in emissions.
Memorandum from Rhoads, R.G., OAQPS, to Director, Air
and Hazardous Materials Division, Regions I-V and VIII.
Information Required in Federal Register Packages.
June 12, 1980.
6-30 February 1994
-------
6.6 SANCTIONS AND FIP REQUIREMENTS
Section 179 (a) of the amended Act sets forth specific
criteria for EPA to determine when to apply sanctions. Two
types of sanctions are specified under section 179(b): (1)
highway funding restrictions, and (2) increased emissions
offset ratios for new and modified sources. A third type of
sanction, restrictions on air grant funding, is provided for
under section 179(a). The construction ban provisions of
section 110(a)(2)(I) of the 1977 Clean Air Act Amendments
were largely repealed with the passage of the amended Act in
1990.*
6.6.1 Actions Triggering Sanctions and FIP Requirements.
Section 179 (a) of the amended Act sets forth four types of
findings which may trigger sanctions. The first is a
finding that-a State has failed to submit a SIP or an
element of a SIP, or that the submittal fails to meet the
completeness criteria. The second is a finding that a SIP
submission for a nonattainment area fails >to meet one or
more elements of the plan required by the Act. The third is
a finding that the State has not made any other submission
required by the Act that meets the completeness criteria or
has made a required submission that is disapproved by EPA
for not meeting the Act's requirements. The fourth is a
finding that a requirement of an approved plan is not being
implemented.1'2
Section 110(c) sets forth two types of findings that
trigger FIP requirements: (1) a finding that a State fails
to make a required submittal or that a submittal does not
satisfy the minimum completeness criteria under section
110(k)(1)(A), and (2) a disapproval of a SIP submittal in
whole or in part.3
6.6.2 Sanctions and FIP Clocks. The amended Act provides a
6-31 February 1994
-------
"clock" for imposing sanctions and FIP requirements.
Section 179(a) allows up to 18 months for the State to
Correct the deficiency that triggered EPA's disapproval
before EPA can impose sanctions. Section 110(c) (1) gives
the State two years to correct a deficiency and EPA to
approve a new submittal before EPA is obligated to
promulgate a FIP.4
The sanctions clock, triggered under section 179(a),
can be stopped when the State corrects the deficiency
prompting the finding. The EPA must apply one of the two
sanctions specified under section 179(b) within 18 months
after the date of the finding. If the deficiency persists,
EPA must apply both sanctions at 24 months. Under section
179(a), EPA need not wait 24 months to apply both sanctions.
EPA may apply both sanctions at 18 months if it determines a
lack of good faith on the part of the State.5 The FIP clock
can be stopped only when EPA issues a final approval of the
State submittal. Where the sanctions and FIP clocks were
started by EPA disapproval of a plan, the sanctions and FIP
clocks will run concurrently.6
6.6.3 Available Sanctions. The two sanctions available for
EPA are provided under section 179 (b) and include
restriction of highway funding, and application of emission
offset requirements. As part of the highway funding
sanctions, EPA may prohibit approval by the Secretary of
Transportation of projects or grants in the affected
nonattainment area.7 However, section 179(b)(1) of the
amended Act provides exemptions for certain projects and
grants that are intended to minimize air pollution
problems .8
The emission offset sanction refers to the application
of the emission offset requirements of section 173 and
applies to new or modified sources. Under this sanction,
the ratio of emissions reductions that must be obtained to
6-32 February 1994
-------
offset increased emissions (caused by the new or modified
source) in the sanctioned area must be at least 2 to I.8'9
6-33 February 1994
-------
REFERENCES FOR SECTION 6.6
1. U.S. Environmental Protection Agency. General Preamble
for the Implementation of Title I of the Clean Air Act
Amendments of 1990; Proposed Rule. Federal _Reqister.
57:13566, Volume 57, No. 74. April 16, 1992. EPA
Requirements; Sanctions and Other Safeguards; Available
Measures Under 1990 CAAA.
2. "The Act in section 179 requires EPA to impose
sanctions based on four types of actions (findings)
provided in section 179(a): (1) a finding that the
State has failed to submit a SIP, a SIP element, or has
submitted a SIP or SIP element that does not satisfy
the completeness criteria; (2) that EPA disapproval of
a SIP submission for a nonattainment area based on its
failure to meet one or more elements required by the
Act; (3) a determination that the State has not made
any other submission, has made an inadequate submission
(as required by the Act), or that EPA disapproves such
submission; or (4) a finding that a requirement of an
approved plan is not being implemented." Memorandum
from Calcagni, John, Director, Air Quality Management
Division, OAQPS, U.S. EPA, Research Triangle Park, NC,
to Director, Air, Pesticides, and Toxics Management
Division, Regions I and IV; Director, Air and Waste
Management Division, Region II; Director, Air,
Radiation, and Toxics Division, Region III; Director,
Air and Radiation Division, Region V; Director, Air,
Pesticides and Toxics Division, Region VI; Director,
Air and Toxics Division, Regions VII, VIII,IX, and X.
Processing of State Implementation Plan (SIP)
Submittals. July 9, 1992.
3. Reference 2, p. 9. "Under section 110(c)(1) , EPA is
required to promulgate a FIP based on two types of
findings: (1) a finding that a State has failed to make
a required submittal or that a submittal does not
satisfy the minimum completeness criteria under section
110(k)(1)(A), or the EPA disapproval of a SIP submittal
in whole or in part."
4. Reference 2, p. 9. "For plan submittals required under
part D or in response to a SIP call, section 179(a)
allows for up to 18 months for the State to correct the
deficiency that is the subject of a finding or
disapproval before EPA is required to impose sanctions.
Section 110(c)(1) provides for up to 2 years for the
State to correct the deficiency and for EPA to approve
a new submittal before EPA is obligated to promulgated
a FIP."
6-34 February 1994
-------
5. Reference 2, p. 10. "Under section 179(a), in order to
stop the sanctions clock, the State must correct the
1 deficiency' prompting the finding. The EPA must apply
one of the two sanctions available under section 179(b)
within 18 months after the date of the finding and both
sanctions at 24 months, unless the deficiency has been
corrected. Section 179 (a) also requires EPA to apply
both sanctions after 18 months if EPA finds a lack of
good faith on the part of the State."
6. Reference 2, p. 10. "In other words, EPA must approve
the State submittal in order to stop the FIP clock.
Where the sanctions and FIP clocks were started by EPA
disapproval of a plan, the clocks will run
concurrently. In this case, to correct the deficiency
for purposes of the sanctions clock, the State must
make a submittal which EPA finds approvable. Such a
determination is not made until EPA issues a final
approval of the plan. Final approval of a plan is also
what is needed to stop the FIP clock."
7. Reference 2, p. 11. "For plan submittals required
under part D or in response to a SIP call, if the State
does not correct the specific deficiency within the 18-
month period allowed under section 179(a), EPA must
apply at least one of the two sanctions available under
section 179(b) as described: (1) Highway funding
sanctions: The EPA may impose a prohibition on the
approval by the Secretary of Transportation of certain
projects, or the awarding of certain'-grants."
8. Reference 1, p. 13566. EPA Requirements,- Sanctions and
Other Safeguards; Available Measures Under 1990 CAAA;
Highway Funding Sanctions.
9. Reference 2, p. 11. "(2) Offset sanctions. A ratio
of at least 2-to-l will be required for emissions
reductions within the nonattainment area to offset
emissions from new or modified major facilities (as
required under section 173)."
6-35 February 1994
-------
6.7 INTERIM CONTROL STRATEGIES
In certain .situations, air pollution control equipment
may need to be repaired, upgraded or replaced to meet the
applicable emission limitations in a revised SIP. During
the period until new or upgraded control equipment is
operational and the source is in compliance, emissions from
the source must not be allowed to increase. The existing
control equipment must remain operational to the maximum
extent possible, with appropriate maintenance and repair,
until construction or linking of new equipment requires its
shutdown or removal. A source may choose to implement
interim controls that offer a higher degree of emission
reduction instead of maintaining existing equipment.
However, the use of such interim controls should not be
allowed to unnecessarily delay the installation of final
control equipment.1
Additional interim controls or other interim measures
are required to prevent excess emissions during periods when
existing control equipment must be taken 'off line to link or
complete construction of new or upgraded equipment. Such
measures may include installing additional temporary control
equipment or operational controls (such as curtailing
production rates, relocating production to complying process
lines, "purchasing power or product elsewhere," or temporary
shutdown).2
The source should also be required to implement an
interim continuous emissions monitoring program. This will
enable the agency to monitor emissions from the source
during the interim period.3
6-36 February 1994
-------
REFERENCES FOR SECTION 6.7
1. "During the interim period until the new or upgraded
control equipment is operational and the source is in
compliance, emissions from the source must not be
allowed to increase. The existing though inadequate
control equipment must remain operational to the
maximum extent possible, including being maintained and
repaired, until such time that construction or tie-in
of new equipment requires its shut down or removal. In
lieu of maintaining the existing though inadequate
control equipment, interim controls which offer a
higher degree of emission reduction and are readily and
reasonably available may be installed. The use of such
interim controls shall not unduly delay the
installation of final control equipment." Memorandum.
Seitz, John S., Director, Stationary Source Compliance
Division, OAQPS, U.S. EPA, Washington, DC, to Air
Management Division Directors, Regions I, III, and IX;
Air and Waste Management Division Director, Region II;
Air, Pesticides and Toxics Management Division
Directors, Regions IV and VI; Air and Toxics Division
Directors, Regions VII, VIII and X; and Air and
Radiation Division Director, Region V. Transmittal of
OAQPS Interim Control Policy Statement. March 31, 1988.
PN-113-88-03-31-047.
2. Reference 1. "When existing control.equipment must be
taken off line to tie in or complete-construction of
new or upgraded equipment, additional interim controls
or other interim measures are required to ensure no
increase in excess emissions occurs during the tie in
period. Such measures may include installation of
additional temporary control equipment or operational
controls, e.g., curtailment of production rates,
relocation of production to complying process lines or
facilities, purchase of power or product elsewhere as
needed, or temporary shutdown."
3. Reference 1. "The source should also be required to
implement an interim continuous emissions monitoring
program, to enable the agency to monitor the emissions
performance of the source during the interim period."
6-37 February 1994
-------
6.8 SIP CALLS
In accordance with section 110(k)(5) of the amended
Act, the Administrator shall require the State to revise the
SIP as necessary if the Administrator determines that the
applicable implementation plan for any area is substantially
inadequate to attain or maintain the relevant NAAQS. The
Administrator shall establish deadlines (18 months maximum
after date of notice) for the submittal of revised plans.
Inadequate plan findings and notice shall be public.
Section 110 (a) (2) (H) requires that SIP'S provide for
plan revisions as necessary to take account of NAAQS
revisions or the availability of improved or more
expeditious methods for attaining the standards. Such
revisions should also be provided for should the
Administrator find that the plan is subtantially inadequate
to attain the applicable NAAQS, or to otherwise comply with
any additional requirements of the Act. Relevant exceptions
to these requirements for plan revisions are set forth in
section 110 (a) (3) (C) .
Plan revisions for nonattainment areas are addressed in
part D of title I of the Act. Any plan revision for a
nonattainment area that is required in response to a section
110(k) (5) finding must correct the plan deficiency and meet
all other applicable plan requirements under sections
110(a)(2) and part D of the Act. EPA may reasonably adjust
the applicable deadlines to achieve a consistent application
of plan requirements if the applicable attainment date has
elapsed. EPA will issue written guidelines, as necessary,
to facilitate submittal of adequate and approval plans.
6-38 February 1994
-------
6.9 NONATTAINMENT AREA CONTROL REQUIREMENTS FOR SO2
SOURCES1
6.9.1 RACT. For most criteria pollutants, RACT is control
technology that is reasonably available considering
technological and economic feasibility (see memorandum from
R. Strelow, December 9, 1976). The definition of RACT for
S02 is that control technology which is necessary to achieve
the NAAQS [40 CFR part 51.100 (o)]. Since S02 RACT is
already defined as the technology necessary to achieve
NAAQS, control technology which failed to achieve the S02
NAAQS would, by definition, fail to be S02 RACT.
The EPA intends to continue defining RACT for SO2 as
that control technology which will achieve the NAAQS within
statutory timeframes.
6.9.2 RFP. Section 171(1) of the amended Act defines RFP
as "such annual incremental reductions in emissions of the
relevant air pollutant as are required by--this part [part D]
or may reasonably be required by EPA for the purpose of
ensuring attainment of the applicable national ambient air
quality standard by the applicable date." This definition
is most appropriate for pollutants which are emitted by
numerous and diverse sources, where the relationship between
any individual source and the overall air quality is not
explicitly quantified, and where the emission reductions
necessary to attain the NAAQS are inventory-wide. The
definition is generally less pertinent to pollutants such as
SO2 which usually have a limited number of sources,
relationships between individual sources and air quality
which are relatively well defined, and emissions control
measures which result in swift and dramatic improvement in
air quality. That is, for S02, there is usually a single
"step" between pre-control nonattainment and post-control
6-39 February 1994
-------
attainment.
Therefore, for S02, with its discernible relationship
between emissions and air quality and significant and
immediate air quality improvements, RFP will continue to be
construed as "adherence to an ambitious compliance
schedule."2
6.9.3 Contingency Measures. Section 172 (c) (9) of the
amended Act defines contingency measures as measures in a
SIP which are to be implemented if an area fails to make RFP
or fails to attain the NAAQS by the applicable attainment
date. Contingency measures become effective without further
action by the State or EPA, upon determination by EPA that
the area has failed to (1) make reasonable further progress
or (2) attain the S02 NAAQS by the applicable statutory
deadline. These contingency measures shall consist of other
available control measures that are not included in the
control strategy.
The EPA interprets the contingency measure provisions
as primarily directed at general programs-which can be
undertaken on an areawide basis. Again, S02 presents
special considerations. First, for some of the other
criteria pollutants, the analytical tools for quantifying
the relationship between reductions in precursor emissions
and resulting air quality improvements remain subject to
significant uncertainties, in contrast with procedures for
pollutants such as S02. Second, emission estimates and
attainment analyses can be strongly influenced by overly-
optimistic assumptions about control efficiency and rates of
compliance for many small sources. In contrast, controls
for S02 are well understood and are far less prone to
uncertainty. Since S02 control measures are by definition
based upon what is directly and quantifiably necessary to
attain the SO2 NAAQS, it would be unlikely for an area to
implement the necessary emissions control yet fail to attain
6-40 February 1994
-------
the NAAQS. Therefore, for S02 programs, EPA interprets
"contingency measures" to mean that the State agency has a
comprehensive program to identify sources of violations of
the S02 NAAQS and to undertake an aggressive follow-up for
compliance and enforcement, including expedited procedures
for establishing enforceable consent agreements pending the
adoption of revised SIP's.
This definition of minimum contingency measures for SO2
does not preclude a State from requiring additional
contingency measures that are enforceable and appropriate
for a particular source or source category.
A contingency measure for an S02 SIP might be a consent
agreement between the State and EPA to reduce emissions from
the source further in the event that contingencies are
triggered. Alternatively, the source might adopt a
contingency measure such as switching to low sulfur coal or
reducing load until more permanent measures can be put into
place to correct the problem. In either case, the
contingency measure must be a fully adopted provision in the
SIP in order for it to become effective at the time the
Administrator determines that the area fails to meet RFP or.
fails to attain the standard by the statutory attainment
date.
6-41 February 1994
-------
REFERENCES FOR SECTION 6.9
1. General Preamble for the Implementation of Title I of
the Clean Air Act Amendments of 1990. Federal Register
57:13547. April 16, 1992.
2. U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards, "Guidance Document for
Correction of Part D SIP's for Nonattainment Areas,"
(Research Triangle Park, North Carolina: January 27,
1984), page 25.
6-42 February 1994
-------
7. PERMITS
7.1 PERMIT PROGRAMS
The discussion below pertains to permit requirements
for construction and operation of major new or modified
sources. Title V of the Clean Air Act of 1990, however,
does include provisions for establishing State-administered
operating permit programs. The EPA has promulgated
regulations containing the minimum elements necessary for
federally enforceable operating permit programs,1 while EPA
has not reached a final determination about the relationship
between SIP's and title V permits.2 Operating permits may,
among other things, largely codify present SIP regulations.
For this reason, it is important that SIP's are adequate and
enforceable before operating permits are in place. The
operating permit program is not discussed in this guideline.
7-1 February 1994
-------
REFERENCES FOR SECTION 7.1
1. 57 Federal Register 32,250 (July 21, 1992), Operating
Permit Program.
2. 57 Federal Register 13,567-9 (April 16, 1992), General
Preamble for the Implementation of Title I of the Clean
Air Act Amendments of 1990; Proposed Rule;
Miscellaneous.
7-2 February 1994
-------
7.2 PERMIT REQUIREMENTS
7.2.1 General. Major new sources and existing sources that
have undergone major modifications are generally required to
obtain air pollution permits prior to
construction/modification and operation. Permits are
required to assure that emissions from sources are minimized
via the application of good control technology, and that the
resulting emissions do not cause or contribute to violation
of any NAAQS or PSD increment. The requirements for these
permits vary depending on the size and location of the
proposed source. For a complete compendium of new source
review and permitting guidance see: "New Source
Review/Prevention of Significant Deterioration and
Nonattainment Area Guidance Notebook." Additional
information is available on the New Source Review Electronic
Bulletin Board and the "New Source Review Workshop
Manual. "1-2
7.2.2 Nonattainment Areas.
7.2.2.1 Applicability. Major new or modified major
stationary sources of S02 located within an area designated
nonattainment for S02 pursuant to section 107 of the CAAA
are required to obtain construction permits which
satisfy the requirements of part D of title I of the CAA.
Major SO2 sources have the potential to emit at least 100
tons of S02 per year; major modifications occur if the net
increase in S02 emissions at a major SO2 source is at least
40 tons per year.3
7.2.2.2 Control Technology Requirements. All major sources
subject to nonattainment area new source review requirements
are required to control emissions to a degree that reflects
the lowest achievable emission rate (LAER) .4 LAER is the
7-3 February 1994
-------
most stringent emission control demonstrated in any major
source permit review or in any SIP regulations.5 These
control techniques must be applied to the proposed new
source unless they are demonstrated to be technically
infeasible, site-specific cost considerations
notwithstanding.
7.2.2.3 Emission Offsets. Major new and modified sources
are required to offset net increases in allowable S02
emissions that result after the application of LAER.6 The
degree of emission offset may vary by State but in general,
the emission offset reductions must exceed the proposed net
increase from the proposed source so that reasonable
progress toward attainment of the NAAQS continues.
Consistent with provisions of 40 CFR 51.165(a), new sources
for which emission offsets are required must also comply
with procedures relating to the permissible location of
offsetting emissions, which are equivalent or more stringent
than those set out in 40 CFR part 51, appendix S, section
(IV) (D) .
7.2.2.4 Net Air Quality Benefit. In order to satisfy the
location requirements for SO2 emission offsets as specified
in 40 CFR part 51, appendix S, section (IV)(A), it may be
necessary to demonstrate that a net air quality benefit will
result. No specific net air quality benefit test exists.
However, one way in which this demonstration may be made is
with a modeling analysis that predicts that the proposed
emissions increase and proposed emission offsets will not
increase the concentration at an agreed upon number of
receptors and will not significantly increase the
concentration at all other receptors. A significant
concentration increase for SO2 is defined as an increase in
ambient S02 concentrations that exceeds: 25 /ig/m3 for a
3-hour average; 5 ^g/m3 for a 24-hour average; and, 1 M9/™3
7-4 February 1994
-------
for an annual average (see Table 7-1).
7.2.2.5 Other Requirements. In addition to the above
requirements, any applicant for a new source permit within a
nonattainment area must certify that other sources owned or
operated by the applicant are in compliance with applicable
air quality regulations. Compliance includes being on an
approved compliance schedule.7 The permit applicant must
conduct an analysis of alternative sites, sizes, production
processes, and environmental control techniques to
demonstrate that the benefits of the proposed source
outweigh the environmental and social costs imposed as a
result of its location, construction, and modification.8
7-5 February 1994
-------
TABLE 7-1. SULFUR DIOXIDE CONCENTRATIONS
Averaging Time
(micrograms per cubic meter)
3-Hour 24-Hour Annual
NAAQS 1,300 365 80
PSD Increments Class I 25 5 2
II 512 91 20
III 700 182 40
PSD significant ambient 25 5 1
impact concentrations.
PSD significant monitoring -- 13
concentration
7-6 February 1994
-------
7.2.3 NSR Transition. The amended Act makes numerous
changes to the NSR requirements for nonattainment and PSD
programs. These include creation of new and expanded
nonattainment areas, extension of PSD coverage to Class I
area boundaries, and a mandate for a PSD exemption for
certain hazardous air pollutants. The EPA has provided its
interpretation of the new or revised NSR nonattainment
permit program requirements contained in part D of the
amended Act within the General Preamble, New Source Review
Nonattainment Permit Requirements. The EPA intends to issue
regulations setting forth specific requirements for an
approvable NSR program.9 EPA has published transitional
guidance on the most important issues involving the NSR
program to be used in preparing SIP revisions in the interim
between passage of the amended Act and adoption of the
Agency's final regulations. This guidance appeared in a
March 11, 1991 memorandum and is published in Appendix D of
the General Preamble. The transitional guidance is not
intended to replace existing State regulations or approved
SIP's; however, it calls upon States to implement their NSR
programs consistent with provisions of the amended Act that
are applicable immediately.10 The transitional guidance,
since it does not represent final EPA action, has not been
subject to judicial review and is not intended, and cannot
be relied upon, to create any rights enforceable in
litigation with the United States. The EPA may decide to
follow the transitional guidance, or to act at variance with
it based on specific circumstances. The Agency may also
change the guidance at any time without public notice.11
Major issues relating to NSR S02 nonattainment dealt
with in the transitional guidance include the following:
• NSR construction permit requirements in nonattainment
areas. In States where the existing part D permit
7-7 February 1994
-------
program covers all designated nonattainment areas in
the State, the program will automatically cover any new
or expanded areas under the amended Act and States
should apply the requirements of their existing
programs. In other States, where a part D program may
be limited to specific areas and does not apply to new
or expanded areas, States must implement a transitional
permit program until their existing programs are
revised to meet the requirements of the amended Act,
and expanded to cover all nonattainment areas in the
State.12
Status of construction bans. An existing construction
ban that was imposed due to the absence of approved
part D NSR rules remains in effect until a revised NSR
SIP is approved. Specific construction bans may be
lifted where appropriate. The status of construction
bans in general will be published in the Federal
Register. If a construction ban is lifted in a
nonattainment area, and the area lacks an approved part
D NSR rule, the State should meet the requirements of
appendix S to 40 CFR part 51 in issuing permits for
major new sources or major modifications until NSR
rules meeting the requirements of the amended Act are
adopted.13
Federal implementation plans. The NSR permitting
program in an existing FIP remains in effect until a
SIP is approved or a revised FIP is adopted.14
Use of previously approved growth allowances. Growth
allowances in existing SIP's are invalidated [pursuant
to section 173 (b) of the amended Act] in areas where a
SIP call has been received either before or after
enactment of the amended Act. In such areas,
previously approved growth allowances cannot be used
for NSR permits issued on or after November 15, 1990.
Construction permits that rely on previously approved
7-8 February 1994
-------
growth allowances cannot be issued in SIP call areas
under existing, approved part D programs. Emission
offsets must be obtained on a case by case basis for
any such permits, and any other existing part D
requirements must be met.15
In a September 3, 1992 memorandum, the EPA provided a
supplement to the transitional guidance in order to clarify
EPA's position regarding the NSR permitting when a State
does not submit a SIP revision implementing the additional
part D NSR provisions of the amended Act by the applicable
statutory deadline. For S02, the statutory submittal
deadline for such revisions was May 15, 1992. This
supplemental guidance is nonbinding in the same sense as the
initial transition guidance and does not affect EPA's
interpretations of NSR provisions in the amended Act as
published in the General Preamble.16
The supplemental guidance addresses conditions under
which permits may be issued to sources and obtain EPA
recognition as being in compliance with the Act. In
general, sources that have submitted complete permit
applications by the submittal deadline may receive permits
and be recognized as complying with the Act, provided that
specific conditions are met. These conditions are spelled
out in the guidance.17 Submitted applications by the
submittal deadline may be considered as complying with the
Act provided that the source obtains from the State a permit
which is consistent with the substantive new NSR part D
provisions. Those NSR provisions applicable to S02 include
section 173 offset requirements.16 This guidance does not
overrule any State rules or transitional guidance that may
be more stringent.19
7.2.4 PSD Areas
7.2.4.1 Applicability. Major new stationary sources
7-9 February 1994
-------
located within areas designated as attainment or
unclassifiable pursuant to section 107 of the CAA are
required to undergo preconstruction review in accordance
with regulations for the prevention of significant
deterioration (PSD) .20-21 A major stationary source for PSD
purposes is any stationary source which has the potential to
emit 250 tons per year (tpy) or more (or 100 tpy or more, if
the source category is one of the 28 categories specifically
listed in the PSD regulations) of any pollutant subject to
regulation under the CAA. Note that hazardous air
pollutants initially or subsequently listed in
section 112(b)(1) of the Clean Air Act are no longer subject
to PSD review as individual pollutants. Therefore,
emissions of arsenic, asbestos, benzene (including benzene
from gasoline), beryllium, mercury, radionuclides (including
radon and polonium), and vinyl chloride, which had
previously been subject to review once a source became
subject to PSD review, are now exempt. Such emissions are
still regulated under PSD if they are one component of a
more general pollutant subject to regulation under Clean Air
Act provisions other than section 112.22 An additional
note: Hydrogen sulfide, which was initially included on the
section 112 list, has been removed by act of Congress, and
is, therefore, still a regulated pollutant subject to PSD
review.23'24 Any new major stationary source that also has
the potential to emit 40 tpy or more of S02 in an area
designated attainment or unclassifiable for S02 must undergo
PSD review with respect to those SO2 emissions. Similarly,
any existing major stationary source that proposes a
physical or operational charge that would increase emissions
of SO2 by 40 tpy or more is also subject to PSD for S02.
7.2.4.2 Control Technology Requirements. Major sources
subject to PSD review for S02 are required to control their
potential S02 emissions to a degree that reflects the best
7-10 February 1994
-------
available control technology (BACT) ,25-26 BACT is the maximum
degree of reduction for each pollutant which the permitting
authority determines is achievable. A BACT analysis is done
on a case-by-case basis, and considers energy,
environmental, and economic impacts in determining the
maximum degree of reduction achievable for the proposed
source or modification. In no event can the determination
of BACT result in an emission limitation which would not
meet any applicable standard of performance under 40 CFR
parts 60 and 61.
7.2.4.3 Air Quality Analysis. The applicant for a PSD
permit is required to demonstrate via a modeling analysis
that the proposed new emissions will not cause or contribute
to a violation of any NAAQS or PSD increment.27'28 The NAAQS
impose a ceiling on total ambient concentrations.
Increments impose a ceiling on the amount of increase in
ambient concentrations relative to a baseline concentration
(see Table 7-1). Both NAAQS and increments for S02 are
expressed for annual, 24-hour, and 3-hour-periods.
Guidance for preparing a demonstration of compliance
with the NAAQS and the S02 increment is provided in the
EPA's New Source Review Workshop Manual.2 As part of this
demonstration, a modeling analysis must be carried out in a
manner that is consistent with the "Guideline on Air Quality
Modeling (Revised)" (see Chapter 4 for more detail).
The emissions increment inventory contains data for
determining changes in actual emissions for sources which
affect the PSD increments. That is, (1) major sources at
which construction occurred since the major source baseline
data, and (2) any source at which an actual emission
increase or decrease occurred after the minor source
baseline date. Monitoring data may need to be provided by
the applicant to meet preconstruction monitoring
requirements under the PSD program. When monitoring data is
7-11 February 1994
-------
required, guidance is available in the "Ambient Monitoring
Guidelines for Prevention of Significant Deterioration
(PSD) . "29
The air quality analysis should also be used as a basis
for establishing S02 emission limits if BACT-derived limits
are not sufficient. In either case, the limits must be
sufficient to protect both long-term and short-term S02
NAAQS and increments Thus, PSD emission limits that
reflect the air quality analysis will need to be specified
<*
on a 3-hour and 24-hour basis as well as on an annual
basis.30
An air quality analysis for PSD purposes occasionally
reveals a violation of the S02 NAAQS due to background
sources. In these situations, the State must take action to
resolve the air quality problems. Depending upon whether
the new source would be a significant contributor, the
source may need to obtain emission reductions from existing
sources as offset credit to mitigate its own contribution to
a NAAQS violation.31
7.2.4.4 Other Impacts. Pursuant to 40 CFR part 51.166(o),'
the applicant must prepare additional impact analyses for
each pollutant subject to regulation under the Act which
will be emitted by the proposed new source or
modification.2'32 The analysis assesses the impacts of air,
ground, and water pollution on soils, vegetation, and
visibility caused by any increase in emissions of any
regulated pollutant from the source or modification under
review, and from associated growth.
Other impact analysis requirements may also be imposed
on a permit applicant under local, State, or Federal laws
which are outside the PSD permitting process. Receipt of a
PSD permit does not relieve an applicant from the
responsibility to comply fully with such requirements. For
example, two Federal laws which may apply on occasions are
7-12 February 1994
-------
the Endangered Species Act and the National Historic
Preservation Act. Such legislation may require additional
analyses (although not as part of the PSD permit) if any
federally-listed rare or endangered species, or any sites
that are included (or are eligible to be included) in the
National Register of Historic Sites, are identified in the
source's impact area. Secondary emissions (i.e., emissions
not caused by the new source itself, but from associated
growth) must be included in the impact analyses, e.g.,
emissions caused by the new construction itself.
An analysis of visibility impairment is conducted using
a three-level screening technique. The analysis method is
described in the EPA document entitled, Workbook for
Estimating Visibility Impairment.33
7.2.4.5 Class I Areas. The PSD program is designed to
provide the greatest degree of protection to Class I areas.
For the most part, Class I areas are those specified by the
CAA. They are protected by (I) a stringent Class I PSD
increment and (2) air quality-related values (AQRV's) that
the Federal Land Manager (FLM) has an affirmative duty to
protect. AQRV's are those attributes of a Class I area that
are dependent on the maintenance of a high level of ambient
air quality. These may include acid deposition effects and
visibility impairment in Class I areas.
Major stationary sources located within 100 kilometers
of a designated Class I area are required to notify the FLM,
who may require that the applicant conduct a Class I area
impact assessment. Certain large major sources located more
than 100 kilometers away may also be required to conduct a
Class I assessment depending on their potential for
adversely impacting a Class I area. A Class I impact
analysis must show that the source will not cause or
contribute to a violation of the Class I increment.
Otherwise, the applicant must demonstrate to the
7-13 February 1994
-------
satisfaction of the FLM that no AQRV is adversely affected.
If no violations of the increment are shown to occur, the
FLM may still call for a denial of the PSD permit, based on
demonstrable adverse impacts on any AQRV.
Procedures for Class I review, involving
responsibilities for both the FLM and the reviewing agency,
are contained in the New Source Review Workshop Manual, and
in guidance documents produced by the National Parks
Service, Forest Service, and Fish and Wildlife Service.
The Clean Air Act amendments of 1990 specify that the
boundaries of areas designated as Class I must now conform
to all boundary changes made at such parks or wilderness
areas made since August 7, 1977 or in the future. Guidance
for implementing this change is provided in a March 11, 1991
memorandum, "New Source Review (NSR) Transitional
Guidance. "34
7.2.5 SIP Permit Requirements. In addition to the special
major source permit requirements listed above, SIP permit
requirements are specified in 40 CFR part .51.165(b). These
requirements govern the permitting of sources in areas where
modeled or measured violations of the S02 NAAQS are
discovered as part of the permitting analysis. Essentially,
what is required is that a source demonstrate that its
ambient impact would be less than the air quality
significance levels for S02 in all areas and for all time
periods where NAAQS violations will occur.35 It is not
necessary to demonstrate an insignificant impact everywhere
in the impact area.
The 40 CFR part 165(b)(3) requirements also provide for
sources that demonstrate significant air quality impacts at
noncomplying receptors. In such situations, sources may
obtain emission reductions (which must be federally
enforceable) to offset their ambient impacts. The
particular ambient criteria that must be satisfied to
7-14 February 1994
-------
conform to SIP provisions developed pursuant to 40 CFR part
51.165(b) must be discussed with each reviewing agency and
reflect local plans for maintenance and attainment of the
NAAQS.
7.2.6 Visibility. With respect to visibility protection,
PSD permit reviews for new or modified major stationary
sources.must provide for:
o written notification (including the visibility
analysis) of Federal Land Managers of any affected
Federal Class I areas within 30 days of receipt of and
at least 60 days prior to public hearing or, in cases
where the reviewing agency receives advance
notification (e.g., early consultation with the source
prior to submission of the application), written
notification shall be provided to the affected Federal
Land Manager(s) within 30 days of such advance
notification; and
o consideration of any analysis performed by the Federal
Land Manager that is provided within', 30 days of written
notification as specified above and concludes that the
proposed new major stationary source or major
modification may have an adverse impact on visibility
in any Federal Class I area. Where the reviewing
agency finds that such an analysis does not demonstrate
to the satisfaction of the State that an adverse impact
will result in the Federal Class I area, the State
must, in the notice of public hearing, either explain
its decision or give notice as to where the explanation
can be obtained.
New source review with respect to visibility protection
must provide for review of any new major stationary source
or major modification that:
7-15 February 1994
-------
o has an impact on any integral vista of a Federal Class
I area, if the vista is identified in accordance with
40 CFR part 51.304 by the Federal Land Manager at least
12 months before submission of a complete permit
application (or within 6 months if the Federal Land
Manager has provided notice and opportunity for public
comment); or
o proposes to locate in an area classified as
nonattainment under section 107(d)(1)(A)(B)(C) of the
Clean Air Act but which may have an impact on
visibility in any Federal Class I area.
States may also require monitoring of visibility in any
Federal Class I area near the proposed new stationary source
or major modification.
New source reviews with respect to visibility generally
shall be performed in accordance with State rules which meet
the minimum requirements set forth at 40 CFR part 51.320.
Where the State plan has been disapproved with respect to
protection of visibility, the requirements at 40 CFR 52.27
and 52.28 apply to protect visibility in attainment areas
and nonattainment areas, respectively. In any case, the
reviewing agency must ensure that the source's emissions
will be consistent with making reasonable progress toward
the national visibility goal referred to in 40 CFR part
51.300 (a) .
7-16 February 1994
-------
REFERENCES FOR SECTION 7.2
1. The New Source Review Electronic Bulletin Board.
Access through the Technology Transfer Network (TTN)
Bulletin Board System, Office of Air Quality Planning
and Standards, Research Triangle Park, NC 27711.
Communications Software Parameters: 8-N-l; 1200-2400
bps, (919)541-5742; 9600 bps, (919)541-1447. SYSOP
(919)541-5384.
2. U.S. Environmental Protection Agency. New Source
Review Workshop Manual, Draft, New Source Review
Section, OAQPS. October 1990.
3. United States Congress. Clean Air Act, as amended Nov.
1990. 42 U.S.C. 7401 et. seq. section 172(c)(5).
Washington, D.C. U.S. Government Printing Office. (See
also U.S. Environmental Protection Agency. Code of
Federal Regulations. Title 40, chapter I, subchapter
C, part 51.165(a). Washington, D.C. Office of the
Federal Register.)
4. United States Congress. Clean Air Act, as amended Nov.
1990. 42 U.S.C. 7401 et. seq. section 173(a)(2).
Washington, D.C. U.S. Government Printing Office.
(See also U.S. Environmental Protection Agency. Code
of Federal Regulations. Title 40, chapter I,
subchapter C, part 51. Appendix S. section (IV)(A).
Washington, D.C. Office of the Federal Register.)
5. United States Congress. Clean Air Act, as amended Nov.
1990. 42 U.S.C. 7401 et. seq. section 171(3).
Washington, D.C. U.S. Government Printing Office.
6. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
51. Appendix S. Washington, D.C. Office of the
Federal Register.
7. United States Congress. Clean Air Act, as amended
November 1990. 42 U.S.C. 7401 et. seq. section
173(a)(3). Washington, D.C. U.S. Government Printing
Office.
8. United States Congress. Clean Air Act, as amended
November 1990. 42 U.S.C. 7401 et. seq. section
173(a)(5). Washington, D.C. U.S. Government Printing
Office.
9. "The Clean Air Act Amendments of 1990 (1990 Amendments)
make numerous changes to the NSR requirements of the
prevention of significant deterioration (PSD) and
7-17 February 1994
-------
nonattainment area programs. The 1990 Amendments
create new and expanded nonattainment areas, extend PSD
coverage to current Class I area boundaries, and
mandate a PSD exemption for certain hazardous air
pollutants. The Environmental Protection Agency (EPA)
intends to propose by September of this year a
regulatory package that will implement these and other
changes to the NSR provisions. Final adoption of these
revised regulations is projected for August 1992. In
the interim period between passage of the 1990
Amendments and adoption of the Agency's final
regulations EPA expects that numerous issues regarding
the 1990 Amendments will arise." Federal Register
57:18074, Volume 57, No. 82. April 28, 1992. Appendix
D - New Source Review (NSR) Program Transitional
Guidance.
10. "This guidance document does not supersede existing
State regulations or approved State implementation
plans. However, in some cases, it calls upon States to
implement their NSR programs in a manner consistent
with provisions of the 1990 Amendments that are
applicable immediately and with the requirements that
flow directly from these provisions." Memorandum from
Seitz, John S., Director, OAQPS, U.S. EPA, Research
Triangle Park, NC, to Addressees. New Source Review
(NSR) Program Transitional Guidance. March 11, 1991.
11. Reference 10. "Nonetheless, the policies set out in
the transition memorandum are intended solely as
guidance and do not represent final Agency action.
They are not ripe for judicial review for this reason.
Moreover, they are not intended, nor can they be relied
upon, to create any rights enforceable by any party in
litigation with the United States. The EPA officials
may decide to follow the guidance provided in this
memorandum, or to act at variance with the guidance,
based on an analysis of specific circumstances. The
Agency also may change this guidance at any time
without public notice."
12. Reference 9, p. 18076. "In many States, the existing
approved part D permit program by its terms covers all
designated nonattainment areas in the State, so part D
permit program will automatically apply to the new and
expanded nonattainment areas which are established
under provisions of Title I of the 1990 Amendments.
Thus, until new rules are adopted for these new or
expanded nonattainment areas, States should apply the
requirements of their existing approved part D permit
program. However, in other States part D program may
be limited to specified areas and does not apply to new
7-18 February 1994
-------
or expanded areas. In these cases, States must
implement a transitional permitting program until their
existing part D programs are revised to meet the
requirements of the 1990 Amendments and expanded to
cover all nonattainment areas in the State. Otherwise,
both the goals of part D and Congress' intent in
creating new or expanded nonattainment areas will be
frustrated."
13. Reference 9, p. 18076-7. "Pursuant to section
110(n)(3), an existing construction ban that was
imposed due to the absence of approved part D NSR rules
remains in effect until a revised NSR SIP is approved.
Existing construction bans imposed due to disapproval
of primary sulfur dioxide NAAQS attainment plans also
remain in effect. A Federal Register notice will be
published soon announcing the status of construction
bans in general and also lifting specific bans where
appropriate. Should a construction ban be lifted in
any area designated as nonattainment, and the area
lacks an approved part D NSR rule, the State should
meet the requirements of 40 CFR part 51, appendix S, in
issuing permits to major new sources or major
modifications prior to the adoption of NSR rules
meeting the requirements of the 1990 Amendments."
14. Reference 9, p. 18077. "The NSR permitting program in
an existing FIP remains in effect until a SIP is
approved or a revised FIP is adopted." Federal
Register 57:18077, Volume 57, No. 82.- April 28, 1992.
Appendix D - New Source Review (NSR) Program
Transitional Guidance.
15. Reference 9, p. 18077. "Section 173(b) invalidates
growth allowances in existing SIP's in areas that
received a SIP call prior to enactment of the 1990
Amendments, or that received one thereafter. For NSR
permits issued on or after November 15, 1990,
previously-approved growth allowances cannot be used in
these areas. Construction permits cannot be issued in
SIP-call areas under existing EPA-approved part D •
programs to the extent that such permits rely on
previously-approved growth allowances. Case-by-case
emission offsets must be obtained for any such permits,
and other existing part D requirements must be met."
16. "To address some immediate concerns generated by the
1990 CAAA, the Environmental Protection Agency (EPA)
issued an initial NSR transitional memorandum on March
11, 1991, entitled 'New Source Review Program
Transitional Guidance.' This memorandum supplements
that effort by clarifying EPA guidance regarding the
7-19 February 1994
-------
permitting of new or modified sources in situations
where a State does not submit a State implementation
plan (SIP) revision implementing the augmented part D
NSR provisions of the 1990 CAAA by the applicable
statutory deadline. The statutory deadlines for
submission of revised NSR SIP's are listed in the
attachment. Moreover, as more fully set forth in the
March 11, 1991 transitional memorandum, this
supplemental memorandum sets forth nonbinding guidance
that does not create any rights or otherwise
predetermine the outcome of any procedures. Also, many
of EPA's interpretations of the new part D NSR
requirements are in the 'General Preamble for the
Implementation of Title I of the Clean Air Act
Amendments of 1990' (General Preamble) (see 57 FR 1398,
13552-556, April 16, 1992). These interpretations are
not affected by this memorandum." Memorandum from
Seitz, John S., Director, OAQPS, U.S. EPA, Research
Triangle Park, NC, to Addressees. New Source Review
(NSR) Program Supplemental Transitional Guidance on
Applicability of New Part D NSR Permit Requirements.
September 3, 1992.
17. Reference 16. "Where States do not submit the part D
NSR SIP by the applicable statutory deadline ...
sources submitted complete permit applications ... by
the submittal deadline may receive final permits under
existing State NSR rules. In this situation, such
sources will be considered by EPA to be in compliance
with the Act without meeting the amended part D NSR
provisions of the 1990 CAAA, provided they meet the
following conditions:
1. The State and source move expeditiously towards
final permit issuance.
2. Construction begins no later than 18 months from
the date of permit issuance unless an earlier time
is required under the applicable SIP.
3. Construction is not discontinued for a period of
18 months or more.
4. Construction is completed within a reasonable
time. States may not grant permit extensions
beyond these time periods unless the permittee is
required in a federally-enforceable manner to meet
the new part D NSR provision."
18. Reference 16. "Also, under today's guidance, where
States miss the statutory deadline for part D NSR SIP
submittal, for sources that have not submitted complete
7-20 February 1994
-------
permit applications by the SIP submittal deadline, EPA
will also consider the source to be in compliance with
the Act where the source obtains from the State a
permit that is consistent with the substantive new NSR
part D provisions in the 1990 CAAA. The substantive
new provisions are the new applicability thresholds,
the new offset ratios, the offset requirements of
section 173, and the NOX requirements of section 182 (f)
for most O3 nonattainment areas and the NOTR."
19. Reference 16. "Please note that the Act allows States
tO'implement the new part D NSR provisions prior to the
statutory deadlines and in a manner more stringent than
EPA guidance or rules. Thus, today's guidance does not
apply in any State to the extent that the State's own
rules or transitional guidance is more stringent."
20. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
51.166(b)(1)(i). (See also appendix S. Washington,
D.C. Office of the Federal Register.)
21. Reference 2.
22. Reference 10.
23. "Resolved by the Senate and House of Representatives of
the United States of America in Congress assembled,
That in section 112 (b) (1) of the Clean Air Act, as
amended by section 301 of Public Law-'101-549, strike
out the term '7783064 Hydrogen Sulfide' in the
list of pollutants." Congressional Record -- Senate.
August 1, 1991. p. S11799.
24. Congressional Record -- House. November 25, 1991.
pp. H11217 - H11219.
25. United States Congress. Clean Air Act, as amended Nov.
1990. 42 U.S.C. 7401 et. seq. section 165(i)(5).
Washington, D.C. U.S. Government Printing Office.
26. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
51.166 (j) (2) . Washington, D.C. Office of the Federal
Register.
27. United States Congress. Clean Air Act, as amended Nov.
1990. 42 U.S.C. 7401 et. seq. section 165(i)(5).
Washington, D.C. U.S. Government Printing Office.
28. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
7-21 February 1994
-------
51.166(k) and (1).
29. U.S. Environmental Protection Agency. Ambient
Monitoring guidelines for Prevention of Significant
Deterioration (PSD). Office of Air Quality Planning
and Standards, Research Triangle Park, NC. EPA
Publication No. EPA-450/4-87-007. May 1987.
30. "This is in response to your November 17, 1986
memorandum in which you requested comment on Region V's
belief that PSD permits must contain short-term
emission limits to ensure protection of the NAAQS and
PSD increments. I concur with your position and
emphasize that this position reflects our national
policy." Memo from Emison, G., OAQPS, to D. Kee.,
Region V. November 24, 1986.
31. Letter from Spink, M.L., Air Programs Branch, Region
III, to Daniel, J.M., Department of Air Pollution
Control, Virginia. April 25, 1990.
32. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
51.166(o). Washington, D.C. Office of the Federal
Register.
33. U.S. Environmental Protection Agency. Workbook for
Estimating Visibility Impairment. Office of Air
Quality Planning and Standards, Research Triangle Park,
NC. EPA Publication No. EPA-450/4-87-031. November
1980.
34. Attachment to Reference 10. Page 4.
35. "I believe the most appropriate course of action to
follow is the second approach which considers the
significant impact of the source in a way that is
spatially and temporally consistent with the predicted
violations." Memorandum from Emison, G.A., OAQPS, to
T.S. Maslany, Air Management Division, Region III.
July 5, 1988.
7-22 February 1994
-------
7.3 EMISSIONS TRADING
7.3.1 General Policy Aspects. Emissions trading consists
of bubbles, netting, offsets, and emission reduction
banking. These trading alternatives do not alter existing
air quality requirements, e.g., this policy and guidance
does not affect the applicable NSR/PSD rules for offsetting
and netting. Still, these trading alternatives may provide
flexibility to States and industry in meeting their
requirements. Emission trading can result in reduced costs
and faster compliance with applicable regulations. Any use
of bubbles, banking, or similar emissions trading provisions
must be approved by the EPA as a SIP revision or it must be
approved by the state under an EPA approved generic bubble
rule. A summary of emissions trading alternatives follows.1
7.3.1.1 Bubbling. The EPA's bubbling of emissions lets
existing plants (or groups of plants) increase emissions at
one or more emission sources in exchange for compensating
extra decreases in emissions at other emission sources. To
be approvable, each bubble must produce results which are
equivalent to or better than the baseline emission levels
in terms of ambient impact and enforceability. Thus,
bubbles should not jeopardize compliance with ambient
standards, applicable PSD increments or visibility
requirements. Under EPA's policy for bubbling, emissions
reductions from existing sources can not be used to meet
technology-based requirements applicable to new or modified
stationary sources.2
7.3.1.2 Netting. The netting of emissions may enable a
physical change or change in the method of operation of a
major stationary source to avoid preconstruction permit
requirements under New Source Review (NSR). An exemption is
allowed when the netting results in no significant net
7-23 February 1994
-------
emissions increase at the major source. By "netting out,"
the modification is not considered "major" and is therefore
not subject to associated preconstruction permit
requirements for major modifications under 40 CFR 51.165(a)
and (b) , 51.166, 52.21, 52.24, 52.27, or 52.28. The
modification must nevertheless meet applicable NSPS,
NESHAPs, State preconstruction applicability review
requirements added pursuant to 40 CFR 51.160, and SIP
requirements.3
7.3.1.3 Offsets. Where it is determined that a source will
cause or contribute to a violation of a NAAQS or a PSD
increment, new and modified major stationary sources may be
required to obtain surplus emission reductions to more than
"offset" their increased emissions and air quality impact.
This requirement is designed to permit industrial growth in
an area without interfering with the existing air quality
maintenance plan or a demonstration of attainment.
7.3.1.4 Banking. Emission reduction banking lets firms
store qualified emission reductions for later use in bubble,
netting, or offset transactions. Banked emission reduction
credits can also be sold to firms seeking alternative ways
to meet regulatory requirements.
7.3.1.5 Emission Reduction Credits. Emission reduction
credits are the common currency of all trading activity. To
ensure that emission trades do not contravene relevant
requirements of the Clean Air Act, only reductions which are
surplus, enforceable, permanent, and quantifiable can
qualify as emission reduction credits and be banked or used
in an emissions trade.
7.3.2 SO2-Specific Policy Aspects. For S02, certain
aspects of the emissions trading policy are especially worth
7-24 February 1994
-------
noting. Generally, an emissions trading applicant must
demonstrate that the proposed trades will not cause an
increase in .baseline emissions. The baseline emission
depends upon the type of area the source operates in.
Usually, an air quality demonstration for SO2 via ambient
dispersion modeling is required.4
The emissions trading policy offers four alternatives
States can evaluate for approval of any bubble or offset.
These include5:
(1) De Minimis. In general, no modeling is needed to
determine the ambient equivalence to trades in which
applicable net baseline emissions do not increase or whose-
gross sum totals less than 40 tpy for sulfur dioxide.
(2) Level I. In general no modeling is needed to
determine ambient equivalence if:
(a) The trade does not result in an increase in
applicable net baseline emissions;
(b) The relevant sources are located in the same
vicinity (within 250 meters of each other);
(c) No increase in baseline emissions occurs in the
source with the lower effective plume height as determined
under EPA's Guidelines on Air Quality Models; and
(d) No complex terrain is within the area of
significant impact of the trade or 50 kilometers, whichever
is less;
(e) Stacks with increasing baseline emissions are tall
enough to avoid possible downwash situations, as determined
by the formula at 50 FR 27892 (July 8, 1985) (to be codified
at 40 CFR part 51).
(3) Level II. Bubble trades which are neither de
minimis nor Level I may nevertheless be evaluated for
approval based on modeling to determine ambient equivalence
limited solely to the impacts of the specific emission
sources involved in the trade, 1) if there is no increase in
applicable net baseline emissions, 2) if the potential
7-25 February 1994
-------
change in emissions before and after the trade will not
cause a significant increase in pollutant concentrations at
any receptor for any averaging time specified in an
applicable ambient air quality standard, and 3) if such an
analysis does not predict any increase in ambient
concentrations in a mandatory Federal Class I area. The
definition of "significant" as used above can be found in
the Emission Trading Policy Federal Register Notice, 51 FR
43845 (December 4, 1986) footnote 38.
(4) Level III. Full dispersion modeling considering
all sources affecting the trade's area of impact is required
to determine ambient equivalence if applicable net baseline
emissions will increase as a result of the trade, or if the
trade cannot meet criteria for approval under de minimis,
Level I or Level II.
For discussion on stack height emissions balancing
policy see section 5.9.
7-26 February 1994
-------
REFERENCES FOR SECTION 7.3
1. Federal Register 51:43832. Emissions Trading Policy
Statement; General Principles for Creation, Banking and
Use of Emission Reduction Credits; Final Policy
Statements and Accompanying Technical Issues Document.
2. Reference 1, p. 43830. Introduction: Basic Elements of
Emissions Trading; The Bubble.
3. Reference 1, p. 43830. Introduction: Basic Elements of
Emissions Trading; Netting.
4. Reference 1, p. 43826. Final Policy Statements and
Accompanying Technical Issues Document. "Bubble
applicants must show that their proposed trades are at
least equivalent in ambient effect to the SIP emission
limits the bubble would replace. For some criteria
pollutants (e.g., VOC or NOx (this test may generally
be met by showing equal reduction in emissions. For
other pollutants (e.g., S02, TSP, or CO) it was
traditionally met, prior to the 1982 policy, through
dispersion modeling."
5. Reference 1, p. 438444-5. Final Policy Statements and
Accompanying Technical Issues Document.
7-27 February 1994
-------
8. COMPLIANCE AND ENFORCEMENT
8 .1 GENERAL
Implementation and enforcement provisions must be included
in a SIP to show how the requirements of the plan will be put
into effect and how sources that are in violation of the plan's
requirements will be brought into compliance. Therefore, the
emission limits and other requirements (1) must be written so
that they are enforceable, (2) must require continuous
compliance with the SIP provisions and with the NAAQS, (3) must
include provisions for monitoring and testing to determine
compliance, and (4) must include provisions for compliance
schedules to address violations of the SIP requirements. A
compendium of EPA's enforcement guidance is contained in, "The
Clean Air Act Compliance/Enforcement Policy Compendium."
8.2 ENFORCEABILITY CRITERIA
To be enforceable, the wording of SIP regulations must
unambiguously describe what facilities are affected by the rule
and what they are required to do to be in compliance. The
requirements should be within the statutory authority of the
regulatory agency and, in all cases, the owner or operator of a
source should be aware of the standard of conduct required by
the regulation. A SIP regulation should explicitly set forth:
o who must comply with the regulation1, including a
description of the facilities covered by the
regulation2;
o quantity of emissions which cannot be exceeded (e.g.,
the emission limit);
o period over which compliance is determined (e.g., the
averaging time)3 which is consistent with air quality
modeling and otherwise sufficient to protect all S02
NAAQS4 ;
o date by which compliance is expected (or the date on
which noncompliance will be considered a violation
8-1 February 1994
-------
of the rule)5, and the important dates required in
any compliance schedule which the source is required
to submit to the state6;
o recordkeeping and reporting requirements;
o requirement of continuous compliance; and
o methods to be used to determine compliance7
(including the method for determining the level of
emissions prior to implementing the controls for
regulations expressed as a percentage reduction
requirement)8.
In addition, any exemptions to the regulation should also be
clearly stated in the text of the regulation. For example,
exemptions based on the size of the facility or on the emission
levels from a source should state explicitly how the owner or
operator of the source is to determine size and emission
level (e.g., whether emissions are actual or design emissions,
how actual emissions are calculated). Provisions of a
regulation that allow for variations in the normal mode of
compliance should be clearly specified. These variance
provisions require prior EPA approval for a .general variance or
EPA approval on a case-by-case basis.9'10
If the SIP regulation includes provisions of Federal
regulations that are incorporated by reference, those Federal
regulations should be examined to check that they are
appropriate and relevant.11 To allow for future changes to the
referenced Federal regulations, the SIP regulation could
reference the current version of the Federal regulation or any
subsequent, version promulgated by EPA.
The SIP regulations should explicitly state recordkeeping
and reporting requirements. They should describe the records
that are to be kept to demonstrate compliance, how long and
where the records are to be maintained, accessibility for
inspection, and schedules and content requirements for any
required reports. Whenever possible, the SIP should specify
the form and format of reports or it should give an example of
8-2 February 1994
-------
an acceptable report. The SIP regulations should be written so
that failure to submit a required report is itself a violation
of the regulations.
8-3 February 1994
-------
REFERENCES FOR'SECTION 8.2
1. "Your review should ensure that the rules in question are
clearly worded and explicit in their applicability to the
regulated sources." Memorandum and attachment from
Potter, J.C., OAR, Adams, T.L., Jr., OECM, and Blake,
F.S., General Counsel to Regional Administrators, Regions
I - X, et al. September 23, 1987. Review of State
Implementation Plans and Revisions for Enforceability and
Legal Sufficiency. (PN 113-87-09-23-041).
2. "The SIPs should include a description of the types of
affected facilities." Memorandum and attachment from
Alushin, M.S., Associate Enforcement Counsel for Air
Enforcement, et al. to Regional Administrators, Regions I
- X, et al. September 23, 1987. Review of State
Implementation Plans and Revisions for Enforceability and
Legal Sufficiency. (PN 113-87-09-23-041).
3. Reference 1. "The period over which compliance is
determined and the relevant test method to be used should
be explicitly noted."
4. Memorandum and attachment from Baumen, R., AQMD, and
Biondi, R., SSCD, to Air Branch Chiefs, Regions I-X.
November 28, 1990. S02 SIP Deficiency Checklist.
5. Reference 1. "The rule should be clear as to who must
comply and by what date."
6. Reference 2. "Also, the regulation should specify the
important dates required of any compliance schedule which
is required to be submitted by the source to the state."
7. Reference 3.
8. Reference 2. "Also, some regulations might require a
certain percentage reduction from sources. The regulation
should be clear as to how the baseline from which such a
reduction is to be accomplished is set."
9. Reference 1. "Also provisions which allow for "alternate
equivalent techniques" or "bubbles" or any other sort of
variation of the normal mode of compliance must be
completely and explicitly defined and must make clear
whether or not EPA case-by-case approval is required to
make such a method of compliance federally effective."
10. Reference 2. "These provisions must make it clear as to
whether EPA approval of state granted alterative
compliance techniques is required on a case-by-case basis
in order for the changed mode of compliance to replace the
8-4 February 1994
-------
existing federally enforceable requirement."
11. Reference 2. "Some federal regulations are inappropriate
for adoption by reference."
8-5 February 1994
-------
8.3 CONTINUOUS COMPLIANCE
8.3.1 General. As a general rule, sources are required to
meet all applicable emission limitations and other control
requirements incorporated into a SIP regulation at all times.
Emission limitations and other control requirements are
established to prevent concentrations of pollutants in the
ambient air from exceeding National Ambient Air Quality
Standards (NAAQS). Ambient air should meet NAAQS at all times.
An exceedance of the SIP emission limits and other requirements
might result in an exceedance of the NAAQS, therefore,
compliance with the SIP regulations must be continuous.
Continuous compliance means that excess emissions should be
avoided by proper design, operation, and maintenance of air
pollution sources. It also means that excess emissions, that
occur as a result of a malfunction or other emergency
situation, are minimized and quickly terminated.1
All periods of excess emissions are violations of the
standard. However, enforcement action might not be appropriate
in all situations.2 Even with proper design', operation, and
maintenance of equipment, malfunctions might occur. Unusual
start-up and shut-down episodes might also cause exceedances to
occur. A third situation during which exceedances might not
require enforcement action is an emergency situation of fossil
fuel shortages.
If a malfunction occurs such that bypassing pollution
control equipment will prevent death, personal injury, or
severe property damage, the pollution control agency can
consider specific circumstances before choosing to take
enforcement action.3 During such a malfunction or emergency
situation, the owner or operator of the pollution source is
expected to minimize and eliminate emission limit exceedances
as quickly as possible. When an emission exceedance occurs in
emergency situations, the source operator or owner is
responsible for proving that the excess emissions resulted from
8-6 February 1994
-------
a true malfunction (e.g. unpreventable, unavoidable).
Exceptions to the continuous compliance requirement for
malfunctions, unusual start-up or shut-down, or fossil fuel
shortages, can be included in a SIP. If they are included in a
SIP, such regulations must be narrowly drafted. Since it might
be difficult to write an unambiguous regulation which
differentiates between a true malfunction and a malfunction
which could have been prevented, a preferred approach is the
enforcement discretion approach.4 For the enforcement
discretion approach, rather than write exceptions into the
regulation, the enforcement agency uses its discretion to
determine when the enforcement action is inappropriate,
although a violation did occur.
8.3.2 Enforcement Discretion Approach. The enforcement
discretion approach allows the enforcing agency to determine
whether emission limit violations are cases which do not
require enforcement actions. In these situations, the source
is responsible for proving that enforcement action would be
inappropriate. An advantage to this approach is that by using
the enforcement discretion, an agency encourages sources to
establish and follow proper operating and maintenance
procedures. Proper procedures help to minimize periods of
excess emissions. To demonstrate that enforcement action is
inappropriate, a source must prove that it has an active
continuous compliance program and it must demonstrate that
excess emissions were due to an unavoidable malfunction.
Components' of an active continuous compliance program might
include a self-monitoring of emissions and/or surrogate
operating parameters, maintenance of spare parts inventories,
and establishing procedures for correcting types of violations
that are likely to occur.5 Criteria that the enforcing agency
should consider in determining whether enforcement actions are
appropriate include:
o equipment was properly sized, designed, and
8-7 February 1994
-------
installed;
o equipment and processes were maintained and operated
to minimize emissions;
o repairs were made quickly;
o the amount and duration of the excess emissions were
minimized to the extent possible;
o all possible steps were taken to minimize the impact
of excess emissions on ambient air quality;
o excess emissions were not part of a recurring pattern
which would indicate the source was inadequately
designed, operated, or maintained.6
Unless the above criteria are met, enforcement action should be
taken for the violation.
8•3.3 Malfunctions and Unusual Start-up or Shut-down. Al1
excess emissions are violations of the applicable standard. A
SIP may not allow "automatic exemptions" for malfunctions that
sources allege have occurred. Instead, a SIP should provide
for proceedings to determine whether enforcement actions should
be taken. For such proceedings the burden of proof, that an
actual malfunction occurred, is upon the source. A malfunction
is defined as a sudden and unavoidable breakdown of process or
control equipment."7
Start-up and shut-down are part of normal process
operations. Excess emissions during these periods should be
avoided through careful planning. Likewise, excess emissions
should not take place during scheduled maintenance periods
because these periods can also be planned.8 It is reasonable
to expect that careful planning and proper equipment design and
operation and maintenance will eliminate violations of emission
limitations during such periods.
In rare cases, excess emissions during start-up or shut-
down can not be avoided. An example of such a situation is
when a process starts up only once or twice a year and the
condition of the emissions during a few hours is such that the
8-8 February 1994
-------
effluent gas would severely damage the control equipment. For
all such situations, the source must adequately show that
excess emissions could not be prevented.9
8.3.4 Fuel Shortage Emergencies. The exemption from the
continuous compliance requirement for periods of fuel shortage
were enacted into the Clean Air Act by Congress at section
110 (f). Under section 110 (f), a Governor may petition the
President to declare that an energy emergency exists. To
request such a declaration, the Governor must find that an
energy emergency exists in the vicinity of a source (such as a
natural gas curtailment) that could lead to high levels of
unemployment or loss of necessary energy supplies to
residences, and that suspension of SIP requirements would
alleviate the emergency. Under such a declaration, the
requirements of any part of the SIP can be suspended for up to
4 months. The EPA administrator may disapprove any SIP
suspension which does not comply with section 110(f).1C Any
energy emergency claim should be based on adequate
documentation, including the identities of the affected'
parties, the amount and duration of the expected shortage,
current inventories of energy supplies, the availability of
alternative supplies, and actions taken to mitigate the
impacts of the emergency. The source(s) and the State are
responsible for providing sufficient information and for
meeting other requirements of section 110 (f) before an energy
emergency will be declared.11
8-9 February 1994
-------
REFERENCES FOR SECTION 8.3
1. "In the strict legal sense, sources are required to meet,
without interruption, all applicable emission limitations
and control requirements, unless such limitations
specifically provide otherwise." Memorandum from Bennett,
K.M., OANR, to Directors, Air and Waste Management
Divisions and Air Management Divisions, Regions I - X.
June 21, 1982. Definition of "Continuous Compliance" and
Enforcement of 0 & M Violations.
2. "States can, of course, consider any demonstration by the
source that the excess emissions were due to an
unavoidable occurrence in determining whether any
enforcement action is required." Memorandum and
attachment from Bennett, K.M., OANR, to Regional
Administrators, Regions I - X. September 28, 1982.
Policy on Excess Emissions During Startup, Shutdown,
Maintenance, and Malfunctions. (PN 113-83-02-15-017)
3. "Therefore, during this latter situation, if effluent
gases are bypassed which cause an emission limitation to
be exceeded, this excess need not be treated as a
violation if the source can show that the excesses could
not have been prevented through careful and prudent
planning and design and that bypassing was unavoidable to
prevent loss of life, personal injury, or severe property
damage." Memorandum and attachment from Bennett, K.M.,
OANR, to Regional Administrators, Regions I - X. February
15, 1983. Policy on Excess Emissions During Startup,
Shutdown, Maintenance, and Malfunctions.
(PN 113-83-02-15-017).
4. Reference 2. "EPA can approve SIP revisions which
incorporate the "'enforcement discretion approach.'"
5. Reference 1. "Such a program would normally involve one
or more of the following elements: continuous or periodic
self-monitoring of emissions; monitoring of operating
parameters such as scrubber pressure drop, incinerator
combustion temperature or flow rates; maintenance of spare
parts inventory; maintenance of spare control device
modules; and procedures designed to correct the types of
violations that are most likely to occur."
6. Reference 2. "The excess emissions are not part of a
recurring pattern indicative of inadequate design,
operation, or maintenance."
7. Reference 2. "'Malfunction' means a sudden and
unavoidable breakdown of process or control equipment."
8-10 February 1994
-------
8. Referenced. "Consequently, excess emissions during
periods of scheduled maintenance should be treated as a
violation unless a source can demonstrate that such
emissions could not have been avoided through better
scheduling for maintenance, or through better operation
and maintenance practices."
9. Reference 3.
10. "EPA Administrator may review the Governors suspension and
disapprove it if he determines that it does not satisfy
the criteria set forth in (3) above." Memorandum from
Burning, M.B., Assistant Administrator for Enforcement,
and Hawkins, D.G., Assistant Administrator for Air Noise,
and Radiation, to The Administrator. March 6, 1979.
Energy Emergency Task Force; Implementation of
section 110(f) of the Clean Air Act.
11. "Although EPA should provide assistance in developing the
state's record, the responsibility of providing this
information rests with the state and the source."
Memorandum from Hawkins, D., Assistant Administrator for
Air Noise, and Radiation, and Burning, M.B., Assistant
Administration for Enforcement, to The Administrator.
June 19, 1979. Supplemental Guidance Regarding
Implementation of section 110(f) of the Clean Air Act.
8-11 February 1994
-------
8.4 COMPLIANCE MONITORING REQUIREMENTS
The EPA regulations require SIPs to contain legally
enforceable procedures to require stationary sources to install
and operate equipment for continuously monitoring, recording
and reporting emissions [40 CFR 51.214(a)3. The SIP should
identify the types of sources (by source category and capacity)
that must install, maintain, and operate the equipment; the
planned use of the data; calculations, recordkeeping,
reporting, and quality assurance procedures; and the pollutants
that must be monitored [40 CFR 51.214(b)].
Industries and control agencies benefit from routinely
monitoring emissions, keeping records, and periodically
reporting. The benefits include increased cost effectiveness
by increasing the sources' energy efficiency and through
pollution prevention and better targeting of "problem sources".
For SO2 emissions, continuous emission monitoring systems
(CEMS) provide the best means for directly determining source
compliance with emission regulations. In sqme situations, CEMS
technology might not be feasible so alternative methods of
compliance might be necessary. These alternative technologies
might include instrumental monitoring of process parameters
such as temperature, pressure, and voltage, and manual
monitoring of process information.1
Wherever technologically feasible, CEMS should be the
required method for monitoring emissions from a source. This
is particularly true for major sources and for sources located
in nonattainment areas. CEMS should be used to monitor the
continuous compliance of NSPS and PSD sources in attainment
areas.2 Wherever it is technically feasible CEMS requirements
should also be incorporated into NSR preconstruction reviews,
operating permits, and resolution of enforcement actions. If
S02, TRS, or H2S CEMS are not technically feasible, the
regulation should require monitoring of process and control
system parameters sufficient to ensure continuous compliance.3
8-12 February 1994
-------
CEMS data should also be used to identify significant violators
of a SIP regulations.4'5
EPA regulations require SIP revisions to require source
continuous monitoring to determine compliance for some types of
sources(40 CFR part 51, appendix P). These sources include
power plants, sulfuric acid plants, and FBC catalytic cracking
unit regenerators at petroleum refineries that exceed size
thresholds'. If a State does not have plants that meet these
qualifications, these provisions need not be included in the
SIP. The State, however, should submit a certification with
the SIP that there are no plants meeting these specifications.6
Many States require CEMS on major sources such as pulp and
paper plants and smelters.
Further, the operating permit rule requires that all
sources' permits contain periodic monitoring and testing.
Section 70.6(a)(3)(i)(B) of the permit rule requires that where
the underlying standard (e.g., SIP) does not contain a periodic
monitoring or testing method, the permit must provide one.
Where the underlying regulation does provide periodic
monitoring or testing, that method simply needs to be
incorporated into the operating permit. Periodic monitoring
must be representatives of the source's compliance with the
underlying emission standard, consistent with the averaging
time of the standard, result in accurate and reliable data, be
consistent with approved testing and/or monitoring
requirements, be directly comparable to an applicable
requirement, and reported at least semiannually. This method
must be used in the compliance certifications required by the
permit rule, as evidence of continuous or intermitent
compliance. As such, the periodic monitoring method is
directly enforceable evidence of compliance with the emission
limit. EPA is developing guidance on the criteria for periodic
monitoring and testing under the operating permit program.
Likewise, any emission units subject to enhanced
monitoring would need to incorporate directly enforceable
8-13 February 1994
-------
enhanced monitoring requirements into the operating permit.
Enhanced monitoring is at least as stringent as periodic
monitoring, therefore, compliance with enhanced monitoring
requirements are deemed to meet the minimum criteria for
periodic monitoring. These enhanced or periodic monitoring
requirements should be considered when making SIP revisions, so
such revisions will be consistent with what will otherwise be
separately required by the operating permit.
The primary purposes of requiring such monitoring are to
assure that the source (1) has timely and accurate compliance
data; (2) has a quantitative basis to monitor emissions changes
which are caused by process or control equipment changes (e.g.,
so the source is able to modify maintenance procedures); and
(3) can minimize energy and raw product use rates by using
information made available by the CEMS. Such monitoring
measurably helps agencies ensure continuous compliance and
allows them to target resources for the sources which violate
their emission limits.
8-14 February 1994
-------
REFERENCES FOR SECTION 8.4
1. "While EPA considers continuous emission monitoring
systems (CEMS) to be the most useful means of directly
determining source compliance with emission regulations,
the agency also recognizes the need to rely on the
application of other means of continuous monitoring.
These include instrumental monitoring of process
parameters such as temperature, pressure, and voltage, and
manual monitoring of process information such as the
number of gallons and chemical analysis of specific paints
used to coat automobiles." Letter from Riley, William,
Administrator, Environmental Protection Agency, to
Congressman John Dingell. April 10, 1991.
2. "CEMS should be used to assure continuous compliance of
sources in both attainment and nonattainment areas."
Memorandum and attachment from Emison, G.A., OAQPS, to Air
Management Division Director, Regions I, III, and IX, Air
and Waste Management Division Director, Region II, Air,
Pesticides and Toxics Management Division Director,
Regions VII, VIII and X, Air and Radiation Division
Director, Region V. March 31, 1988. Transmittal of
Reissued OAQPS CEMS Policy.
3. Reference 2. "OAQPS is committed to promoting,
encouraging and utilizing CEMS data as a compliance
assessment measure."
t
4. Reference 2. "Where CEMS is the compliance method,' CEMS
data should be used to identify significant violators."
5. Reference 1. "CEMS may be used most efficiently and
effectively in the... detection and documentation of a
violation of an emission standard and an operation and
maintenance (0 & M) requirement..."
6. Reference 2. "The second type of CEMS data is where CEMS
is not the compliance method."
8-15 February 1994
-------
8.5 COMPLIANCE PLANS/SCHEDULES
The EPA regulations require each SIP to contain legally
enforceable compliance schedules that set forth the dates by
which all stationary and mobile sources or categories must be
in compliance with the SIP [40 CFR 51.260(a)3. Compliance
plans/schedules should include:
o enforceable milestones;
o stipulated penalties;
o final compliance dates; and
o compliance test method.
The compliance schedules contained in the SIP must provide
for attainment of compliance with the primary standards as soon
as practicable, or no later than a specified date [40 CFR
51.261(a)]. Section 192 of the CAAA requires SIPs to provide
for the attainment of primary S02 NAAQS as expeditiously as
possible, but in no case later than five years after
designation of the area to nonattainment.
The 172(a)(2)(B) also requires SIPs to provide for the
attainment of secondary NAAQS as expeditiously as practicable..
In general, EPA will rely on the substantive provisions of 40
CFR 51.340 (subpart R) to determine expeditiousness.
To determine whether the secondary NAAQS will be attained
as expeditiously as practicable, the EPA will consider:
o the time required to modify the process or to design
and construct control equipment;
o the time required to investigate alternative control
or pollution reduction technologies;
o contractual obligations, such as long-term fuel
contracts, that may constrain fuel switching; and
o the need to phase in costs of control over a
reasonable period of time.1
If a SIP revision provides for the extension of the
compliance date for a source, the State must demonstrate that
the extension will not interfere with timely attainment and
8-16 February 1994
-------
maintenance of the standards and, where relevant, that the
source will make continued reasonable further progress towards
attainment [40 CFR 51.262]. This will entail an analysis of
the effect that changes in other sources' emissions will have
on the attainment status of the area. Second, the proposed
time extension must also be consistent with the requirement
that nonattainment area SIPs provide for "implementation of
all reasonably available control measures as expeditiously as
practicable."2
8-17 February 1994
-------
REFERENCES FOR SECTION 8.5
1. "State Justification. The compliance schedule and cost
estimates recognize that PSI's existing coal contracts
limit their ability to rapidly substitute lower sulfur
coal for their existing supply." Memorandum and
attachment from Bauman, B., OAQPS, to Emison, G.A., OAQPS.
August 25, 1988. Gibson County, Indiana, S02 Plan.
2. "Second, time extensions also must be consistent with the
requirement that nonattainment area SIPs provide for
implementation of all reasonably control measures as
expeditiously as practicable' [§172(b)(2)]." Memorandum
and attachment from Potter, J.C., OAR, to Regional
Administrators, Regions I - X. August 7, 1986. Policy on
SIP Revisions Requesting Compliance Date Extensions for
VOC Sources. (PN 110-86-07-076).
8-18 February 1994
-------
9. NEW SOURCE PERFORMANCE STANDARDS AND EMISSION GUIDELINES
9 .1 GENERAL ..
Under section 111 of the Clean Air Act (CAA), EPA is
required to develop emission regulations for a category of
sources which "...causes, or contributes significantly to,
air pollution which may reasonably be anticipated to
endanger public health or welfare."1 These regulations,
referred to as new source performance standards (NSPS), are
to reflect the degree of emission reduction achievable
through technology that has been adequately demonstrated,
taking into consideration the cost of the emission
reductions and any environmental, and energy impacts of
meeting the standard.2 Under section 111 of the CAA, the
EPA is also required to develop emission guidelines (EG) to
require States to submit plans for the control of existing
emissions of certain air pollutants for which NSPS have been
established.3
This chapter does not provide a comprehensive overview
of the section 111 program, but it does summarize relevant
NSPS and EG provisions (including emission limits,
compliance testing, and monitoring procedures) for several
source categories that are significant emitters of S02.
These source categories (presented in sections 9.2 and 9.3)
include: (1) steam generators; (2) municipal waste
combustors; (3) stationary gas turbines; (4) sulfuric acid
plants; (5) petroleum refineries; and (6) smelters (this is
not an exhaustive list for S02 sources) . Detailed summaries
of the relevant NSPS and EG provisions are included in
Tables 9-1 through 9-12, while each NSPS and EG is discussed
briefly in the text. Section 9.4 clarifies aspects of the
provisions for modifications and reconstructions.
Most existing NSPS subparts concentrate on determining
initial compliance through the performance of reference
9-1 February 1994
-------
method tests. That approach documents that a source is
capable of complying using its installed control technology
but does not necessarily assure that the source will remain
in compliance over time. Generally, the NSPS standards also
include monitoring provisions, but those monitoring
provisions are separate from the compliance determination
process. Most existing monitoring is intended to serve as
an indicator of compliance, not a determination of
compliance.
Please note that continuous compliance does not
necessarily mean continuous monitoring. Although the term
"continuous" generally means at all times, the Agency has
determined that less frequent measurements or determinations
of compliance can ensure continuous compliance. For S02
continuous monitoring means use of CEMS.
9-2 February 1994
-------
REFERENCES FOR SECTION 9.1
1. United States Congress. Clean Air Act as amended
November 1990. 42 U.S.C. 7401 et. seq. Section
lll(b)(1)(A). Washington, B.C. U.S. Government
Printing Office.
2. United States Congress. Clean Air Act as amended
November 15, 1990. 42 U.S.C. 7401 et. seq. Section
111(a)(1). Washington, D.C. U.S. Government Printing
Office.
3. United States Congress. Clean Air Act as amended
November 15, 1990. 42 U.S.C. 7401 et. seq. Section
lll(d)(l). Washington, D.C. Government Institutes,
Inc.
9-3
February 1994
-------
9.2 NSPS PROVISIONS FOR S02
9-2.1 Subpart- D--Fossil-Fuel-Fired Steam Generators1. This
subpart applies to fossil-fuel-fired steam generating units
that commenced construction after August 17, 1971, and that
have a heat input capacity greater than 250 million British
thermal units per hour (MM Btu/hr). A fossil-fuel-fired
steam generating unit is defined as a furnace or boiler used
in the process of burning fossil fuel (coal, oil, and
natural gas) for the purpose of producing steam by heat
transfer.
For this source category, SO2 emissions are limited to
0.80 pounds (Ib) of pollutant per MM Btu heat input for
liquid fuel and 1.2 Ib/MM Btu heat input for solid fuel.
Excess emissions is determined by continuously
.monitoring the S02 concentration in the flue gas and
calculating 3-hour averages [CFR 60.45(g)(2)]. However,
compliance is determined by a Method 6 stack test [CFR
60.46(b)(4)]. See Table 9-1 for details.
9.2.2 Subpart Da--Electric Utility Steam Generating Units2..
This subpart applies to electric utility steam generating
units that commenced construction after September 18, 1978,
and that have a design heat input capacity greater than
250 MM Btu/hr. An electric utility steam generating unit is
defined as a steam electric generating unit that supplies
more than one-third of its potential electric output and
more than 25 MW electrical output to any utility power
distribution system for sale. This NSPS applies to both the
traditional utility power plants and to the independent
power producers (IPP) .
For units in this source category that combust liquid
or gaseous fuels, subpart Da limits S02 emissions to either:
(1) 0.80 Ib/MM Btu heat input and 90 percent S02 reduction
from the potential combustion concentration or (2) to
9-4 February 1994
-------
0.20 Ib/MM Btu heat input (without any percent SO2 reduction
required).
For those units combusting solid fuels, S02 emissions
are limited to either: (1) 1.2 Ib/MM Btu heat input and
90 percent reduction or (2) 0.6 Ibs/MM Btu and 70 percent
S02 reduction.
Compliance with this regulation is determined by
continuously monitoring the SO2 concentration in the flue
gas [CFR 60.48a(c)(5)] and calculating 30-day averages [CFR
60.43a(g) ] .
It should be noted that even though Subpart Da
specifies continuous compliance based on a 30-day rolling
average emission rate, SIP emission limits must be based on
a short-term (e.g., 3-hour or 24-hour) average to show
compliance with the short-term NAAQS. This requirement is
discussed in sections 6.1 and 6.2. See Table 9-2 for
details.
9.2.3 Subpart Db--Industrial. Commercial, and Institutional
Steam Generators3. This subpart applies to industrial,
commercial, and institutional steam generating units that
commenced construction after June 19, 1984, and that have a
heat input capacity greater than 100 MM Btu/hr and that are
not covered by subpart Da. The steam generating unit in
this source category is defined as a device that combusts
any fuel or by-product/waste to produce steam or to heat
water or any other transfer medium. Note that this subpart
does not apply to process dryers or kilns.4 Subpart Db
requires an S02 emission reduction of 90 percent or
compliance with an SO2 emission limit as specified by an
equation in the regulation (see Table 9-3). There are,
however, a few exceptions to this general rule. For units
combusting only coal refuse in a fluidized bed combustion
unit, subpart Db requires an 80 percent S02 emission
reduction and compliance with an S02 emission limit of
9-5 February 1994
-------
1.2 Ib/MM Btu heat input. For units combusting coal and/or
oil using an emerging technology, subpart Db requires a
50 percent S02 emission reduction and compliance with an
emission limit specified by an equation in the regulation.
For certain intermittently-used (low-capacity factor) steam
generating units, subpart Db requires emission limits of
1.2 Ib/MM Btu heat input (for coal-fired units) and
0.5 Ib/MM Btu heat input (for oil-fired units) without any
percent reduction requirement.
Compliance with subpart Db is determined by
continuously monitoring the flue gas and calculating 30-day
rolling averages. As discussed above, compliance with a
30-day rolling average for the NSPS does not necessarily
guarantee compliance with the short-term (e.g., 3-hour or
24-hour) NAAQS. Thus, compliance with subpart Db does not
negate the responsibility of the source to comply with SIP
emission limits. See Table 9-3 for details.
9.2.4 Subpart DC--Small Industrial-Commercial-Institutional
Steam Generating Units5. This subpart app.lies to small
industrial- commercial-institutional steam generating units
that commenced construction after June 9, 1989, and that
have a heat input capacity of less than 100 MM Btu/hr, but
greater than or equal to 10 MM Btu/hr. A steam generating
unit is defined as all devices that combust fuel and produce
steam, heat water, or heat other fluids which are used as
heat transfer media. Note that this subpart does not apply
to process dryers or kilns.4 For units in this source
category, subpart DC requires an SO2 emission reduction of
90 percent for coal-fired units that have a heat input
capacity greater than 75 million Btu/hr and greater than
55 percent annual capacity factor, limit S02 emissions to
1.2 ib/MM Btu for all coal-fired units, and limit S02
emissions from oil-fired units to 0.5 Ib/MM Btu heat input.
Compliance with subpart DC is based on calculated
9-6 February 1994
-------
30-day rolling averages of continuous monitoring data, fuel
sampling, Method 6B, or in some cases, fuel supplier
certification. See Table 9-4 for details.
9.2.5 Subpart Ea--Municipal Waste Combustors6. This
subpart applies to municipal waste combustors (MWC's) that
commenced construction after December 20, 1989 and that have
a capacity to combust over 250 tons per day (tpd) of
municipal solid waste (MSW) which is composed of
residential, commercial, and/or institutional discards. An
MWC unit is defined as any facility that combusts any MSW.
The MWC emissions are a composite pollutant, comprised of
MWC organics, MWC acid gases, and MWC metals emissions. The
MWC acid gas emissions require an SC>2 emission reduction of
80 percent or 30 parts per million by volume (ppmv).
Compliance with subpart Ea is determined by continuously
monitoring on a 24-hour geometric mean basis. See Table 9-5
for details.
9.2.6 Subpart GG--Stationary Gas Turbines7. This NSPS
applies to stationary gas turbines that commenced
construction after October 3, 1977, and that have a heat
input capacity greater than 100 MM Btu/hr. The emission
limits include a restriction on the S02 concentration in the
exhaust gas (less than or equal to 0.015 percent, by
volume), or a limit in the fuel sulfur content (less than
0.8 percent, by weight). Compliance with this NSPS is
determined by daily monitoring of the fuel sulfur content
after an initial performance test demonstrates that the
outlet concentration limit has been met. See Table 9-6 for
details.
9.2.7 Subpart H--Sulfuric Acid Plants6. This NSPS applies
to sulfur acid production units that commenced construction
after August 17, 1971. Sulfur dioxide emission are limited
9-7 February 1994
-------
to 4 Ib S02/ton of acid produced. Compliance is determined
by continuously monitoring exhaust gases and calculating
average S02 emission rates for three consecutive 1-hour
periods. See Table 9-7 for details.
9.2.8 Subpart J--Petroleum Refineries9. This NSPS applies
to petroleum refineries with fuel combustion devices that
commenced construction after June 11, 1973, and with Glaus
sulfur recovery plants (>20 long tons/day capacity) that
commenced construction after October 4, 1976. Sulfur
dioxide emission limits apply only to Claus sulfur recovery
plants and are 0.25 percent in the exhaust gas. Compliance
with the emission limit is determined by continuously
monitoring exhaust gases and calculating 6-hour averages of
the exhaust gas S02 concentration. See Table 9-8 for
details.
9.2.9 Subpart s P, Q, and R--Smelters10'11'12. There are three
NSPS that apply to certain categories of smelting
operations. These NSPS include subpart P-(Primary Copper
Smelters), subpart Q (Primary Zinc Smelters), and subpart R'
(Primary Lead Smelters). These three standards all limit the
concentration of SO: in smelter exhaust gases to
0.065 percent (by volume). Exemptions from the emission
limit are listed in the respective regulations. Compliance
with the emission limits is determined by continuously
monitoring the exhaust gas and calculating 6-hour, 2-hour,
and 2-hour averages for the copper smelter, zinc smelter,
and lead smelter standards, respectively. See Tables 9-9
through 9-11 for details.
9-8 February 1994
-------
REFERENCES FOR SECTION 9.2
1. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
60, subpart D. Washington, D.C. Office of the Federal
Register.
2. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
60, subpart Da. Washington, D.C. Office of the
Federal Register.
3. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
60, subpart Db. Washington, D.C. Office of the Federal
Register.
4. "Subparts Db and DC does not apply to process dryers or
kilns." Memorandum from Jordan, B., OAQPS, to
Addressees. Applicability of NSPS subparts Db/Dc to
Process Dryers. November 17, 1992.
5. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C,
part 60, subpart DC. Washington, D.C. Office of the
Federal Register.
6. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C,
part 60, subpart Ea. Washington, D.C. Office of the
Federal Register.
7. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
60, subpart GG. Washington, D.C. Office of the
Federal Register.
8. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
60, subpart H. Washington, D.C. Office of the Federal
Register.
9. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
60, subpart J. Washington, D.C. Office of the Federal
Register.
10. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
60, subpart P. Washington, D.C. Office of the Federal
Register.
9-9 February 1994
-------
11. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
60, subpart Q. Washington, B.C. Office of the Federal
Register.
12. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
60, subpart R. Washington, D.C. Office of the Federal
Register.
9-10 February 1994
-------
9.3 EG PROVISIONS FOR S02
9.3.1 Subpart Ca--Municipal Waste Combustors1. This
subpart applies to existing MWC's at commenced construction
on or before December 20, 1989, and that have a capacity to
combust over 250 tpd of MSW. An MWC unit is defined as any
facility that combusts any MSW, The MWC plants are
classified as large MWC plants, which have a plant capacity
greater than 250 tpd but less than or equal to 1,100 tpd of
MSW, and very large MWC plants, which have a plant capacity
greater than 1,100 tpd of MSW. For MWC units in this source
category, subpart Ca regulates MWC emissions and nitrogen
oxides (NOX) . The MWC emissions are a composite pollutant,
comprised of MWC organics, MWC acid gases, and MWC metals
emissions. The MWC acid gas emissions require an SO2
emission reduction of 70 percent or 30 ppmv for very large
MWC plants and 50 percent or 30 ppmv for large MWC plants.
Compliance with subpart Ca is determined by continuously
monitoring on a 24-hour geometric mean basis. See
Table 9-12 for details.
9-11 February 1994
-------
REFERENCE FOR SECTION 9.3
1. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C,
part 60, subpart Ca. Washington, B.C. Office of the
Federal Register.
9-12 February 1994
-------
9.4 MODIFICATION/RECONSTRUCTION PROVISIONS
"Modification" refers to "any physical or operational
change to an existing facility which results in an increase
in the emission rate to the atmosphere of any pollutant to
which a standard applies..." as described in the NSPS
general provisions. Some of the possible changes that do
not qualify as modifications include: (1) routine
maintenance, repair, and replacement, (2) increases in
production rate not accompanied by capital expenditures,
(3) increased capacity utilization, (4) fuel switching,
provided that facility was originally designed to handle the
new fuel, (5) addition of air pollution control and related
equipment, and (6) the change in ownership of an existing
facility.1 The key factor here is that if emissions
increase then it is considered a modification. If the
emission increase is offset with control of that emission
then it is not considered a modification.
"Reconstruction" generally includes "the replacement of
components of an existing facility to such an extent that:
(1) the fixed capital cost of the new components exceeds
50 percent of the fixed capital cost that would be required
to construct a comparable new facility, and (2) it is
technologically feasible to meet the applicable
standards..."2
New source performance standards apply to any facility
that has been modified or reconstructed as defined above.
In light of the modification and reconstruction provisions,
it is important to point out that "repowered" sources may be
subject to the applicable NSPS. Emission units that have
reduced capacity due to physical deterioration are treated
as though they have an actual capacity that is smaller than
the original design. Physical capacity restoration to those
units, even if they only restore the units to the original
design capacity, result in an emission increase and, if they
9-13 February 1994
-------
include substantial capital outlay, may subject the emission
units to the NSPS.3
9-14 February 1994
-------
REFERENCES FOR SECTION 9.4
1. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
60.14. Washington, D.C. Office of the Federal
Register.
2. U.S. Environmental Protection Agency. Code of Federal
Regulations. Title 40, chapter I, subchapter C, part
60.15. Washington, D.C. Office of the Federal
Register.
3. Letter from Clay, D.R., OAR, to J.W. Boston, Wisconsin
Electric Power Company. February 15, 1989.
9-15 February 1994
-------
TABLE 9-1. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.40
Subpart D--Standards of Performance for
Fossil-Fuel-Fired Steam Generators
Affected facility
Applicable time frame
Emission limits
Fossil-fuel-fired steam generating
unit >73 MW heat input rate
(250 MMBtu/hour); or fossil-fuel and
wood-residue-fired steam generating
unit capable of firing at >73 MW
(250 MMBtu/hour).
After 8/17/71
340 ng/J (0.80 Ib/MMBtu) heat input
derived from liquid fossil fuel and
wood residue.
520 r>fl/J (1.2 lb/MMBtu> heat input
(1.2 Ib/MMBtu) derived from solid
fossil fuel and wood residue (except
units at the Newton Power Station
owned or operated by the Illinois
Public Service Co.)
When different fossil fuels burned
simultaneously, limit determined by
proration using the formula:
PS(S02) = [y(340) + z(520)J/(y «• z)
(See Section 60.43.)
9-16
February 1994
-------
TABLE 9-1. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.40 (CONCLUDED)
Subpart D--Standards of Performance for.
Fossil-Fuel-Fired Steam Generators
Initial performance testing
Monitoring
Definition of
Noncompliance
Performance test in accordance with
Section 60.8. Performance
Specification 2 (Appendix B) used in
evaluating acceptability of OEMS at
time of installation (i.e., for
preparing calibration mixtures).
Span (liquid fossil fuel) ='
1,000 ppm.
Span (solid fossil fuel) = 1,500 ppm
Span (combination of fuels) =
(I.OOOy + 1,500z) ppm.
where:
y = the fraction of total heat input
derived from gaseous fossil fuel; and
z = the fraction of total heat input
derived from solid fossil fuel. All
span values rounded to nearest 500
ppm.
Continuous monitoring system (to
measure SOj and either CO or 02)
required except for: (1) a steam
generating unit that burns only
gaseous fossil fuel and (2) a unit
without an FGD system if the
owner/operator monitors S02 by fuel
sampling and analysis.
If no continuous monitoring system
used for S02, then none required for
02 or C02. Methods 3, 3A, 6, 6A, 6B,
or 6C. Method 1 for selection of
sampling site and sampling traverses.
For Method 6, Method 3 for gas
analysis. Method 6 or 6C for
concentration of S02. Method 6A may
be used whenever Methods 6 or 6C and
3 or 3A data are used to determine
the SO? emission rate in ng. Method
6C shall be used only at the sole
discretion of the source owner or
operator.
Min. sampling time for Method 6,
20 min.; and min. sample vol. = 0.02
dscm (0.71 dscf) for each sample.
Arithmetic average of 2 samples = 1
run. Samples taken -30 min. For
Methods 6 and 6C, the 02 sample shall
be obtained simultaneously at the
same point in the duct.
Method 6 stack test. Excess
emissions is any 3-hour period during
which the average emissions
(arithmetic average of 3 contiguous
1-hour periods) of S02 as measured by
a continuous monitoring system exceed
the standards.
9-17
February 1994
-------
TABLE 9-2. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.40a
Subpart Da—Standards of Performance for
Electric Utility Steam Generators
Affected facility
Applicable time frame
Emission limits
Electric utility steam generating
unit capable of combusting >73 MU
heat input (250 MMBtu/hour) of fossil
fuel (either alone or in confcination
with any other fuel)
After 9/18/78
When combusting solid or
solid-derived fuel:
(1) 520 ng/J (1.20 Ib/MMBtu) heat
input and 10X of the potential
combustion cone. (90%) or
(2) 30% of the potential combustion
cone. (70X reduction) when emissions
are <260 ng/J (0.60 Ib/MMBtu) heat
input.
When combusting liquid or gaseous
fuels (except those derived from
solid fuels):
(1) 340 ng/J (0.80 Ib/MM Btu) heat
input and 10% of the potential
combustion cone. (90%) or
(2) 100% of the potential combustion
cone. (0% reduction) when emissions
are < 86 ng/J (0.20 Ib/MMBtu) heat
input.
Uhen combusting solid solvent refined
coal (SCR-1):
520 ng/J (1.20 Ib/MMBtu) heat input'
and 15% of the potential combustion
cone. (85%)
9-18
February 1994
-------
TABLE 9-2. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.40a (CONCLUDED)
Subpart Da--Standards of Performance for
Electric Utility Steam Generators
Initial performance testing
Monitoring
Definition of
Noncompliance
Performance test in accordance with
Section 60.8. Performance
Specification 2 used in evaluating
acceptability of CEMS at time of
installation (i.e., used in preparing
calibration gas mixtures).
Span = 125X of max. estimated hourly
potential emissions of the fuel fired
(at the inlet) and SOX (at the
outlet).
Performance test based on average
emission rates for the first 30 days
within 60 days after achieving the
max. production rate. (Not later
than 180 days after date of initial
startup.) Calculated as arithmetic
average of all hourly emission rates
for the 30 successive boiler
operating days except for data
obtained during emergency conditions.
Compliance with X reduction is based
on average inlet and outlet emission
rates. Standards, use 30-day rolling
average basis. Compliance with %
reduction determined on a 24-hour
basis.
Continuous monitoring system for S02
(both inlet and outlet of control
device). Alternatively, an as-fired
fuel monitoring system (upstream of
coal pulverizers) meeting the
requirements of Method 19
(Appendix A) may be used. Continuous
monitoring system for 02 or CO?. 1
hour averages must contain at least 2
data points.
Methods 3 or 3A, 6 or 6C. Method 6A
or 66 may be used whenever Methods 6
and 3 data are required to determine
the SOj emission rate in ng/J.
Methods 6A and 6C are used solely at
the discretion of the owner/operator.
Min. sampling time for Method 6, 20
min.; and min. sample vol. = 0.02
dscm (0.71 dscf) for each sample.
Samples collected -every 60 min.
Each sample = 1 hour average.
Method 6B operated for 24 hours per
sample. Min. sample vol. = 0.02
dscnr (0.71 dscf) for each sample.
Each Method 6B sample = 24 1-hour
averages.
Any 30-hour period during which the
average (rolling) emissions of S02 as
measured by a continuous monitoring
system (i.e., CEMS) exceed the
standards.
9-19
February 1994
-------
TABLE 9-3. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.40b
Subpart Db--Standards of Performance for
Industriat-Comroercial-Institutional Steam Generators
Affected facility
Applicable time frame
Emission limits
Steam generating unit with input
capacity from fuels combusted of
>Z9 MW (100 MMBtu/hour) heat input
After 6/19/84
Steam generating unit with input
capacity from fuels combusted of
>29 MW (100 MMBtu/hour) heat input
(1) with annual capacity factor <30%;
(2) located in a noncontinental area;
(3) combusting coal or oil alone or
in combination with another fuel, in
a duct burner as part of a combined
cycle system where 30X or less of
heat input is from coal or oil in the
duct burner and >70% is from exhaust
gases entering the duct burner;
(4) combusting very low sulfur oil.
When combusting coal or oil:
10X of the potential combustion cone.
(90X reduction) and an emission limit
determined by the following formula:
(K, Ha
H6)
where:
CH, + Hb)
Es = S02 emission limit,
(ng/J [Ib/MM Btu] )
Ka = 520 ng/J (1.2 Ib/MMBtu)
Kt = 340 ng/J (0.80 Ib/MMBtu)
Hs = heat input from combusting
coal, J (MMBtu)
HD = heat input from combusting
oil, J (MMBtu)
When combusting coal refuse alone in
an FBC:
20% of the potential combustion cone.
(80% reduction) with SOj emissions
<520 ng/J (1.2 Ib/MMBtu) heat input.^
When combusting coal or oil (alone or
in combination) and using an emerging
•technology:
50% of the potential combustion cone.
(50% reduction) and' emission limit
calculated using the following
formula:
(Kc Hc
Kc Hc)
(H,
where:
E,, = SO? emission limit,
(ng/J [Ib/MM Btu])
Kc = 260 ng/J (0.60 Ib/MMBtu)
Ka = 170 ng/J (0.40 Ib/MMBtu)
Hc = heat input from combusting
real, J (MMBtu)
H(, = heat input from combusting
oil, J (MMBtu)
When combusting coal:
520 ng/J (1.2 Ib/MMBtu) heat input
When combusting oil:
215 ng/J (0.50 Ib/MMBtu) heat input
No % reduction here.
9-20
February 1994
-------
TABLE 9-3. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.40b (CONCLUDED)
Subpart Db--Standards of Performance for
Industrial-Commercial-Institutional Steam Generators
Initial performance testing
Monitoring
Definition of
Noncofflpliance
Performance test in accordance with
Section 60.8. Conducted over first
30 consecutive operating days.
30 day average. First day of test
scheduled within 30 days of achieving
max. production rate (but no later
than 180 days after startup).
Performance Specification 2
(Appendix B) used in evaluating
acceptability of CEMS at time of
installation (i.e., preparing
calibration gas mixtures). Quarterly
accuracy determinations and daily
calibration drift tests according to
Procedure 1, Appendix F.
Span = 125% of max. estimated hourly
potential emissions of fuel combusted
(at the inlet); 50% (at the outlet).
Continuous monitoring system for SOj,
and Oj or COj (at inlet and outlet).
30-day rolling average basis except
if (1) annual capacity factor for oil
limited to 10X or less; (2) only oil
which emits <215 ng/J is combusted;
and (3) no other fuel is combusted.
Alternative methods:
(1) Collect coal or oil samples at
inlet and analyze for S and heat
content (Method 19);
(2) Method 6B;
(3) Daily emission rate determined by
Method 6A;
(4) Mean 30-day emission rate
(Equation 19-20 of Method 19).
Any 30-day period during which the
average (rolling) emissions of S02 as
measured by a continuous monitoring
system (i.e., CEMS) exceed the
standards.
9-21
February 1994
-------
TABLE 9-4. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.40c
Subpart Dc--Standards of Performance for Small
Industrial-Commercial-Institutional Steam Generating Units
Affected facility
Applicable time frame
Emission limits
Industrial-commercial-institutional
steam generating unit <29 MW (100 MM
Btu/hr) and > 2.9 MW (10 MM Btu/hr)
heat input capacity.
After 6/9/89
When combusting coal:
520 ng/J (1.2 Ib/MM Btu) heat input.
When comubsting coal in a unit having
a heat input capacity >22 MW (75 MM
Btu/hr) and operating at greater than
a 55X annual capacity factor:
520 ng/J (1.2 Ib/MM Btu) heat input
and 10X of the potential combustion
cone. (90%).
When combusting oil:
215 ng/J (0.50 Ib/MM Btu) heat input;
or firing oil with a sulfur content
of 0.5 wt. % or less.
9-22
February 1994
-------
TABLE 9-4. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.40c (CONCLUDED)
Subpart DC--Standards of Performance for Small
Industrial-Commercial-Institutionat Steam Generating Units
Initial performance testing
Monitoring
Definition of
Noncompliance
Performance test in accordance with
Section 60.8. Conducted over first
30 consecutive operating days.
30 day average. First day of test
scheduled within 30 days of achieving
max. production rate (but no later
than 180 days after startup).
Performance specifications 1, 2, and
3 (Appendix B) provide applicable
procedures for operation of CEMS.
Quarterly accuracy determinations and
daily calibration drift tests
according to Procedure 1, Appendix F.
Span = 125% of max. estimated hourly
potential emissions of fuel combusted
(at the inlet); 50% (at the outlet).
Coal-fired units subject to
percent-reduction may use continuous
monitoring system, as-fired fuel
sampling, or emission measurements
using Method 6B, at inlet and outlet
30-day rolling average basis.
Units subject to emission limits may
use CEMS, Method 6B emission
measurements, daily fuel sampling and
analysis, or shipment fuel sampling
analysis.
Residual-oil and coal-fired units
with heat input capacities between
2.9 and 8.7 MW (10 and 30 MM Btu/hr)
and all distillate oil-fired units
may use supplier certification in
lieu of monitoring, measurement, or
analysis.
Any 30-hour period during which the
average (rolling) emissions of S02 as
measured by a continuous monitoring
system (i.e., CEMS) or calculated
using manual data or fuel analysis
exceed the standards.
9-23
February 1994
-------
TABLE 9-5. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.50a
Subpart Ea--Standards of Performance for Municipal Waste Combustors
Affected facility
Applicable time frame
Emission limits
Municipal waste combustor combusting
>225 Mg/day (250 tpd) of municipal
solid waste (residential, commercial
and/or institutional discards).
After 12/20/89
When combusting acid gases:
80% reduction in 803 emissions or a
30 ppm S02 emission limit on a daily
(block average) 24-hour geometric
mean basis measured continuously.
9-24
February 1994
-------
TABLE 9-5. SUMMARY OF SOg REGULATIONS IN 40 CFR 60.50a (CONCLUDED)
Subpart Ea--Standards of Performance for Municipal Waste Combustors
Definition of
Initial compliance testing • Monitoring Noncompliance
Compliance test in accordance with Continuous monitoring system for S02, Any 24-hour period during which the
Section 60.8. Procedures under or Oj or CO? from acid gases on a average (rolling) emissions of SOj as
Section 60.13 for installation, daily (block) 24-hour geometric mean measured by a continuous monitoring
evaluation, and operation. basis. system (i.e, CEMS) exceed the
standards.
Performance specifications 1, 2, and
3 (Appendix B) provide applicable
procedures for operation of CEMS.
Quarterly accuracy determinations and
daily calibration drift tests shall
be performed in accordance with
procedure 1, Appendix F.
Span = 125% of max. estimated hourly
potential sulfur dioxide emissions of
the MWC unit combusted (at the
inlet); 50% (at the outlet).
9-25 February 1994
-------
TABLE 9-6. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.330
Subpart GG--Standards of Performance for Stationary Gas Turbines
Affected facility
Applicable time frame
Emission limits
Stationary gas turbine with a heat
input at peak load >10.7 GJ/hour,
based on the lower heating value of
the fuel fired.
After 10/3/77
One of the following conditions must
be met:
(1) < 0.015X by vol. of S02 from
gases discharged to the atmosphere at
15X 02 (dry basis);
(2) <0.8% by weight S content of fuel
burned.
9-26
February 1994
-------
TABLE 9-6. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.330 (CONCLUDED)
Subpart GG--Standards of Performance for Stationary Gas Turbines
Definition of
Initial performance testing Monitoring Noncompliance
Performance test in accordance with Reference Method 20 for the Any daily period during which the S
Section 60.8. concentration of SO?. content of the fuel fired exceeds
0.8X.
S02 content of fuel fired must be
monitored. If fuel is from a bulk
storage tank, values shall be
determined each time fuel is
transferred to the storage tank. If
fuel does not undergo bulk storage,
values shall be determined and
recorded daily. For S content, use
ASTM D-2880-71 for liquid fuels: use
ASTM D-1072-80, D-3031-81, D-4084-82,
or D-3246-81 for gaseous fuels.
9-27 February 1994
-------
TABLE 9-7. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.80
Subpart H--Standards of Performance for Sulfuric Acid Plants
Affected facility
Applicable time frame
Emission limits
Sulfuric acid production unit (any
facility producing sulfuric acid by
the contact process burning
elemental S, alkylation acid, HjS,
organic sulfides end mercaptans, or
acid sludge).
After 8/17/71
<2 kg S02/metric ton of acid produced
(4 Ib/ton), production being
expressed as 100X
A source that processes elemental S
or an ore that contains elemental S
and uses air to supply oxygen.
9-28
February 1994
-------
TABLE 9-7. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.80 (CONCLUDED)
Subpart H--Standards of Performance for Sulfuric Acid Plants
Initial performance testing
Monitoring
Definition of
Noncompliance
Performance test in accordance with
Section 60.8.
Performance Specification 2 used to
evaluate the acceptability of CEMS at
time of installation (i.e., used in
preparing calibration gas nixtures).
Performance Specifications 2 and 3
used to evaluate the acceptability of
CEMS at time of installation (i.e.,
used in preparing calibration gas
mixtures).
Continuous monitoring system.
Determine conversion factor 3 times
daily by measuring the cone, of SOj
entering the converter.
Span = 1,000 ppm of S02.
Reference Method 8 (only the S02
portion).
An alternative method (not required)
would be to continuously monitor SC^,
CO, and C02 (if required).
All 3-hour periods (or the arithmetic
average of 3 consecutive 1-hour
periods) during which the integrated
average S02 emissions exceed the
applicable emission limits.
Span for C02 (if required)
Span for 02 = 20.9%.
10%.
No S0j> conversion factor needed.
Method in reg. to calculate S02
emission rate. Reference Method 8
for S02 and acid mist; reference
Method 3 for 02 and C02. No
production rate or total gas flow
rate needed.
9-29
February 1994
-------
TABLE 9-8. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.100
Subpart J--Standards of Performance for Petroleum Refineries
Affected facility
Applicable time frame
Emission limits
Fuel gas combustion device
After 6/11/73
<230 mg/dscm (0.10 gr/dscf) H2S
(unless it can be demonstrated to the
Administrator that the method for
treating combustion gases is equally
effective in controlling S02
emissions).
All Claus sulfur recovery plants
>20 long tons/day
After 10/4/76
<0.025% vol. S02 at OX 02 (dry basis)
("if an oxidation control system or a
reduction control system followed by
incineration is used).
<0.030% vol. reduced S compounds a
0.0010% vol. of H2S calculated as S02
at 0% 02 (dry basis).
9-30
February 1994
-------
TABLE 9-8. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.100 (CONCLUDED)
Subpart .I—Standards of Performance for Petroleum Refineries
Initial performance testing
Monitoring
Definition of
Noncompliance
Performance test in accordance with
Section 60.8.
Performance Specification 2 used to
evaluate the acceptability of CEMS at
time of installation (i.e., used in
preparing calibration gas nixtures).
Span = 100 ppm.
Reference Method 6 for S02.
Reference Method 11 for H2S.
Performance test in accordance with
Section 60.8. Performance Spec. 2
used in evaluating acceptability of
CEMS at time of installation (i.e.,
used in preparing calibration gas
mixtures).
Span = 500 ppm. Reference Method 6.
Performance test in accordance with
Section 60.8. Continuous monitoring
system for H2S.
Span = 20 ppm for monitoring H2S.
Span = 600 ppm for monitoring reduced
S compounds.
Reference Method 15 (or Reference
Method 15a for reduced S compounds).
Continuous monitoring system (except
if continuous monitor for H2S is
used). Performance Spec. 2 used in
preparing calibration gas mixtures.
Span - 100 ppm.
If Reference Method 6 for S02,
Method 1 for velocity traverse and
Method 2 for determining velocity and
volumetric flow rate. Reference
Method 11 for H2S (for both methods,
min. sampling time = 10 min; min.
sample vol. = 0.01 dscm (0.35 dscf).
Arithmetic average of 2 samples = 1
run. Sampling at -1 hour intervals.
Continuous monitoring system.
Span = 500 ppm.
Reference Method 6. Method 1 for
velocity traverses and Method 2 for
determining velocity and volumetric
flow rate. Min. average of
4 consecutive hours of continuous
sampling = 1 run.
Continuous monitoring system for H2S.
Span = 20 ppm for monitoring H2S.
Span = 600 ppm for monitoring reduced
S compounds.
Reference Method 15 (or Reference
Method 15a for reduced S compounds).
For Method 15, each run = 16 samples
taken over min. of 3 hours. Method 4
used to determine moisture content of
gases. For Method 15a, each run = 1
3-hour sample or 3 1-hour samples.
All 3-hour period when the average
MoS cone, exceeds 230 mg/dscm
(0.10 gr/dscf), if H2S is removed
from the fuel gas before it is
burned; or any 3-hour period when the
average cone. S02 level exceeds the
specified limits if compliance is
achieved by removing S02 from the
combusted fuel gases.
Any 12-hour period when the average
cone. SOp in the discharged gases
exceeds 250 ppm at 0% 02 (dry basis).
Any 6-hour period during which the
average emission (arithmetic average
of 6 contiguous 1-hour periods) of
S02 as measured by a continuous
monitoring system exceed the
specified emission limits.
Any 12-hour period when the average
cone, of H2S, or reduced sulfur
compounds in the discharged gases,
-.exceeds 10 ppm or 300 ppm,
'respectively, at 0% 02 (dry basis).
Any 6-hour period during which the
average emissions (arithmetic average
of 6 contiguous 1-hour periods) of
S02 as measured by a continuous
monitoring system exceed the
specified emission limits.
9-31
February 1994
-------
TABLE 9-9. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.160
Subpart P--Standards of Performance for Primary Copper Smelters
Affected facility
Applicable time frame
Emission limits
Primary cooper smelter (drver,
roaster, smelting furnace, and copper
converter)
After 10/16/74
<0.065X by vol. of S02 from gases
discharged to the atmosphere.
(Reverbertory smelting furnaces are
exempted during periods when the
total smelter charge at the primary
copper smelter contains a high level
of volatile impurities. A change in
fuel combusted in a reverbertory
smelting furnace is not considered a
modification.)
9-32
February 1994
-------
TABLE 9-9. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.160 (CONCLUDED)
Subpart P--Stendards of Performance for Primary Copper Smelters
Initial performance testing
Monitoring
Definition of
Noncompliance
Performance test in accordance with
Section 60.8. Performance
Specification 2 (Appendix B) used to
evaluate acceptability of CEMS at
time of installation (i.e., used to
prepare calibration gases and for
calibration checks).
Span of continuous monitoring system
may = 0.15X SOj by vol. if necessary
to maintain system output between 20%
and 90% of full scale.
Reference Method 6.
Maintain a monthly record of the
total smelter charge and weight %
(dry basis) as As, Sb, Pb, and Zn in
this charge. Approved methods must
be accurate to +10X. Continuous
monitoring system.
Span = 0.20X S02 by vol.
One 6-hour average shall constitute
1 run.
Monitoring drift not to exceed 2X of
span.
All 6-hour periods during which the
average emissions of SOj, as measured
by the continuous monitoring system,
exceed the specified standards.
Excess emissions for <1.5X of the
6-hour periods during a quarter will
not be considered as potential
violation.
9-33
February 1994
-------
TABLE 9-10. SUHMARY OF S02 REGULATIONS IN 40 CFR 60.170
Subpart Q--Standards of Performance for Primary Zinc Smelters
Affected facility
Applicable time frame
Emission limits
Primary zinc smelter (roaster and
sintering machine)
After 10/16/74
<0.065X by vol. of S02 from gases
discharged to the atmosphere. (Any
sintering machine which eliminates
more than 10% of the S initially
contained in the zinc sulfide ore
will be considered as a roaster.)
9-34
February 1994
-------
TABLE 9-10. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.170 (CONCLUDED)
Subpart (I—Standards of Performance for Primary Zinc Smelters
Initial performance testing
Monitoring
Definition of
Noncompliance
Performance test in accordance with
Section 60.8. Performance
Specification 2 (Appendix B) used to
evaluate acceptability of CEMS at
time of installation (i.e., used to
prepare calibration gases and for
calibration checks).
Span of continuous monitoring system
may = 0.15X SOj by vol. ff necessary
to maintain system.
Continuous monitoring system.
Span = 0.20X SOj by vol.
One 2-hour average shall constitute 1
run.
The 2-hour average SOj cones, shall
be calculated and recorded daily for
the 12 consecutive 2-hour periods of
each operating day (to be the
arithmetic mean of the appropriate 2
contiguous 1-hour average SOj cones.
provided by the CEMS).
Monitoring drift not to exceed 2% of
span.
Any 2-hour period during which
average S02 emissions exceed the
standard.
9-35
February 1994
-------
TABLE 9-11. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.180
Subpart R--Standards of Performance for Primary Lead Smelters
Affected facility • Applicable time frame Emission limits
Primary lead smelter (sintering After 10/16/74 <0.065% by vol. of SOj from gases
machine, electric smelting furnace, discharged to the atmosphere.
and converter)
9-36 February 1994
-------
TABLE 9-11. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.180 (CONCLUDED)
Subpart R--Standards of Performance for Primary Lead Smelters
Initial performance testing
Monitoring
Definition of
Noncompliance
Performance test in accordance with
Section 60.8. Performance
Specification 2 of Appendix B used to
evaluate acceptability of CEMS at
time of installation (i.e., used to
prepare calibration gases and for
calibration checks). Span of
continuous monitoring system
may = 0.15X S02 by vo^* '* necessary
to maintain system.
Continuous monitoring system.
Span = 0.20X S02 by vol.
One 2-hour average shall constitute
1 run.
The 2-hour average S02 cones, shall
be calculated and recorded daily for
the 12 consecutive 2-hour periods of
each operating day (to be the
arithmetic mean of the appropriate
2 contiguous 1-hour average S02
cones, provided by the CEMS).
Monitoring drift not to exceed 2% of
span.
Any 2-hour period during which
average S02 emissions exceed the
standard.
9-37
February 1994
-------
TABLE 9-12. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.30a
Subpart Ca--Emissions Guidelines and Compliance Times
for Municipal Waste Combustors
Affected facility
Applicable time frame
Emission limits
Municipal waste combostor combusting
between 225 Mg/day (250 tpd)
1,000 Mg/day and (1,100 tpd) of
municipal solid waste (residential,
commercial and/or institutional
discards).
Municipal waste combustor combusting
>1,000 Mg/day (1,100 tpd) of
municipal solid waste (residential,
commercial and/or institutional
discards).
Before 12/20/89
70X reduction in S02 emissions or a
30 ppm S02 emission limit on a daily
(block average) 24-hour geometric
mean basis measured continuously.
SOX reduction in S02 emissions or a
30 ppm S02 emission limit on a daily
(block average) 24-hour geometric
mean basis measured continuously.
9-38
February 1994
-------
TABLE 9-12. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.30a (CONCLUDED)
Subpart Ca--Emissions Guidelines and Compliance Times
for Municipal Waste Combustors
Definition of
Initial compliance testing Monitoring Noncompliance
Compliance test in accordance with Continuous monitoring system for S02, Any 24-hour period during which the
Section 60.8. Procedures under or Oj or CO? from acid gases on a average (rolling) emissions of SOg as
Section 60.13 for installation, daily (block) 24-hour geometric mean measured by a continuous monitoring
evaluation, and operation. basis. system exceed the standards.
Performance specifications 1, 2, and
3 (Appendix B). Provide applicable
procedures for operation of CEMS.
Quarterly accuracy determinations and
daily calibration drift tests
according to Procedure 1, Appendix F.
Span = 125 of max. estimated hourly
potential emissions of fuel combusted
(at the inlet); 50% (at the outlet).
9-39 February 1994
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-452/R-94-008
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
SO, Guideline Document
5. REPORT DATE
February 1994-Date of Preoarat
on
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S)
Andrew M. Smith
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards (MD-15)
Research Triangle Park, NC 27711
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Same as 9
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
Supersedes S02 Guideline EPA-450/2-89-019
16. ABSTRACT
The S02 (sulfur dioxide) guideline document is a compilation of currently available
policy and guidance for S02 programs. It* is intended only to provide a guide to
S02 policy and guidance in effect at the time of the document's preparation and does
not present any new policy or guidance. Each chapter summarizes relevant policy and
guidance and provides detailed references to guide the user to more complete sources
found in the appendix and elsewhere. References include statutory and regulatory
sources (Clean Air Act and Code of Federal Regulations), Federal Register notices, -.
and U.S. Environmental Protection Agency (EPA) guidance documents and memoranda, and
questions and answers. The guideline covers topics such as air quality status, air
quality monitoring and modeling, and control strategies.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATl Field/Group
Sulfur dioxide, S02, State implementation
plan, air quality status, ambient
monitoring, air quality modeling,
emission inventories, stack height
regulations, control strategies, permit
regulations, compliance and enforcement,
new source performance standards
18. DISTRIBUTION STATEMENT
Release unlimited
19. SECURITY CLASS (This Report)
21. NO. OF PAGES
235
20. SECURITY CLASS (Tins page)
22. PRICE
PA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
------- |