• 

1" 

,~~EPA 

J r"", 

• 

• 

United States 

Environmental Protection 

Agency 

Air 

Office of Air Quality 

Planning and Standards 

Research. Triangle Park, NC 27711 

EPA-452/R-94-008 

February 1994 

S02 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 

Appendices 

Tables .. 

1. 

2. 

• 

3. 

Introduction . . . . . . . . . . . 

1.1 Overview of the Manual ..... . 

1.2 Provisions for Updating the Manual . 

1.3 Additional Information Sources .. 

Determining Air Quality Status ..... 

2.1 Section 107 Attainment Demonstration Redesignations. 

2.1.1 General ............. . 

2.1.2 Designating Areas as Nonattainment .. 

2.1.3 Redesignating Areas to Attainment .. 

2.1.4 Monitoring Data and Modeling Results 

2.1.5 Control Strategy Demonstration. 

2.1.6 Future SIP Violations 

2.1.7 Area Boundaries 

References for Section 2.1. 

2.2 Ambient Air .. 

2.2.1 General .... 

2.2.2 Location Aspects. 

2.2.3 Time Aspects .. 

2.2.4 Public Access . 

2.2.5 PSD Considerations. 

2.2.6 Land Acquisition .. 

References for Section 2.2. 

Ambient Air Quality Monitoring and Data Usage 

3.1 General ..... References for Section 3.1. 

3.2 Quality Assurance ... 

References for Section 3.2. 

3.3 Ambient Monitoring Methodology 

3.3.1 General ..... 3.3.2 Sampling Interval 

3.3.3 Data Completeness 

References for Section 3.3. 

3.4 Network Design .... 

References for Section 3.4. 

3.5 Probe Siting Criteria. 

References for Section 3.5. 

3.6 Episode Monitoring .. 

3.7 Ambient Air Quality Data Reporting 

3.7.1 General ..... 

3.7.2 Air Pollution Index 

References for Section 3.7 ... 

ii 

viii 

ix 

1-1 

1-1 

1-2 

1-2 

2-1 

2-1 

2-1 

2-1 

2-2 

2-5 

2-6 

. 2-7 

2-7 

2-9 

2-17 

2-17 

2-17 

2-18 

2-18 

2-18 

2-19 

2-20 

3-1 

3-1 

3-4 

3-6 

3-8 

3-9 

. 3-9 

3-9 

3-9 

3-10 

3-12 

3-14 

3-16 

3-17 

3-18 

3-19 

3-19 

3-20 

3-21 

• iii February 1994 
4 . 

5 . 

3.8 Ambient Air Monitoring Network for Model 

Evaluation . . . . . . 

References for Section 3.8. 

Air Quality Modeling ... . 

4.1 General ........ . 

4.2 Guidance on Air Quality Models 

References for Sections 4.1 and 4.2 

4.3 Model Selection .... 

References for Section 4.3. 

4.4 Meteorological Input . 

References for Section 4.4. 

4.5 Sourc~ Input .... . 

4.5.1 General ... . 

4.5.2 Allowable Versus Actual Emissions 

4.5.3 Background Concentration ..... 

4.5.4 Stack Height Input to Air Quality Modeling. 

4.5.5 Stack Downwash and Building Wake Effects. 

References for Section 4.5. 

4.6 Receptor Grid ..... . 

References for Section 4.6 .. 

4.7 Other Model Requirements 

References for Section 4.7. 

Stack Height Regulations .. . 

5.1 General Regulations .. . 

References for Section 5.1 .. 

5.2 Good Engineering Practice Stack Height 

5.2.1 General ........... . 

5.2.2 Definition of Nearby for GEP .. 

5.2.3 Definition of Excessive Concentration 

References for Section 5.2. 

5.3 Dispersion Techniques. 

5.3.1 General ... 

5.3.2 Prohibitions .. 

5.3.3 Exceptions ... References for Section 5.3. 

5.4 Remanded Regulations . 

References for Section 5.4. 

5.5 Specific Stack Height Policies 

5.5.1 Definition of "In Existence". 

5.5.2 Tie-Ins to Existing Stacks .. 

References for Section 5.5 ....... . 

5.6 Demonstrations by Fluid Modeling, Field Studies or 

Nuisance . . . . . . 

5.6.1 Applicability . 

5.6.2 Field Studies . 

5.6.3 Fluid Modeling. 

5.6.4 

5.6.5 

5.6.6 

5.6.3.1 Credit for Height Above GEP Formula 

5.6.3.2 Credit for Height Less than or Equal 

to GEP Formula . . . . . . . . . 

Emission Rate for Physical Demonstrations 

Not in Ambient Air. 

Additional Guidance . . . . . . . . . . 

~=~tt 4-1 

4-1 

. 4-1 

4-4 

4-6 

4-8 

4-10 

4-12 

4-14 

4-14 

4-14 

4-15 

4-16 

4-18 

4-19 

4-21 

4-22 

4-23 

4-25 

5-1 

5-1 

5-2 

5-3 

.;=~· 5-4 

5-6 

5-7 

5-7 

5-7 

5-7 

5-8 

5-9 

5-10 

5-11 

5-11 

5-12 

5-13 

5-14 

5-14 

5-14 

5-15 

5-15 

5-15 

5-16 

5-16 

iv 

5-l· 

February 1994 
• 

• 

• 

6 . 

References fqr Section 5.6. 

5.7 Merged Stacks .. . 

5.7.1 General ... . 

5.7.2 Exceptions .. . References for Section 5.7. 

5.8 Stack Height Negative Declarations . 

5.8.1 General ..... . 5.8.2 Information Needed. 

5.8.3 Modeling Needed 

References for Section 5.8. 

5.9 Emissions Balancing .. References for Section 5.9. 

General Provisions .... . 6.1 General ....... . 

6.2 Current NAAQS and PSD Increments 

6 . 2 . 1 General . . . . . . . . . . . . 6.2.2 National Ambient Air Quality Standards. 

6.2.3 Prevention of Significant Deterioration 

5-18 

5-21 

5-21 

5-21 

5-23 

5-25 

5-25 

5-25 

5-25 

5-27 

5-28 

5-29 

6-1 

6-1 

6-3 

6-3 

6-3 

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 Attai~ment 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 R.FP . . . . . . . . . . . . . . . . . . . . . . 6- 3 9 

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 -t 

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 

7.3.2 802 -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 
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 . . . . . . . . . . . 

9.2.3 Subpart Db--Industrial, Commercial, and 

Institutional Steam Generators . . . . . 

9.2.4 Subpart De--Small-Commercial-Institutional 

Generating Units . . . . . . . . . . 

9.2.5 Subpart Ea--Municipal Waste Combustors. 

9.2.6 Subpart GG--Stationary Gas Turines .. 

9.2.7 Subpart H--Sulfuric Acid Plants 

9.2.8 Subpart J--Petroleum Refineries .. 

9.2.9 Subparts P, Q, and R--Smelters .. . 

References for Section 9.2 ............ . 

9.3 EG Provisions for S02 •••••••••••• 

9.3.1 Subpart Ca--Municipal Waste Combustors. 

Reference for Section 9.3 ........ . 

9.4 Modification/Reconstruction Provisions 

References for Section 9.4 ...... . 

9-4 

9-5 

Steam 

9-6 

9-7 

9-7 

9-7 

9-8 

9-8 

9-9 

9-11 

9-11 

.9-12 

9-13 

.9-15 

vii February 1994 
Appendices 

A. 

B. 

S02 Checklist . . . . . . 

S02 Guideline References. 

viii 

. A-1 

B-1 

• 

• 

February 19. 
• 

TABLES 

Number 

6-1 Current PSD Increments for S02 • 

9-1 Summary of NSPS S02 Regulations. 

• 

• ix 

Page 

6-5 

9-16 

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.~ffec~ at the time of its preparation. The 

S02 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 S02 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 a·nd 

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 i07 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 ~ely 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. 6 

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 S02 , 

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 

wi 11 be reopened. 1110 

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 a~ea can be redesignated to attainment, EPA 

must approve a maintenance plan which meets the 

requirements of section 17SA. 13 The maintenance plan 

will constitute a SIP revision and must provide for 

maintenance of the S02 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 suffi~ient to attain the 

S02 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 S02 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 moni~oring 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 a$ 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: (1) 

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 

fully-approved NSR and PSD programs in place. 28 

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 S02 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 

initiate the designation process [section 

to 

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 qualityassured, 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 fr~m 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 exce~dence 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 S02 , 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 

• 

• 
• 

11. 

• 12. 

• 

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." 

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." 

Reference 7. "For the purposes of redesignation, a 

State must meet all requirements of section 110 and 

part D of the Act that were applicab1e 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 preamended 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, S02 , 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 

htust fully approve a maintenance plan which meets the 

requirements of section 1?5A. 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 • 
• 

• 

• 

17. 

size thresholds are 100 tons/year for 802 , N02 , and PM10 areas, and 5 tons/year for Pb based upon 40 CFR 

51.100(k) and 51.322, as well as established practice 

for AIRS~at~. The source size threshold for serious 

PM-10 are.as. is 70 tons/year according to Clean Air Act 

section 189 (b) (3) . " 

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 
21. 

22. 

110(a) (2) (b~ and (F) of the Clean Air Act, as amended, 

and regulat1ons 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 

th~ maintenance demonstration depend on assumptions of 

point and area source growth." 

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." 

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) . 11 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 fq_r 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." 

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 @Valuate the air 

quality impact at these sites if it deems this necess·ary 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. s, 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 11 ambient 

air 11 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 802 

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 lan9 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 propose·· 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 Shortcut 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 no.t." 

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 standarns (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 

1. 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 obje~tives 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 

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• 

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• 

• 

• 

modifications located in attainment or unclassifiable areas 

will result in exceedance of the NAAQS. 6 Section 165(a) (7) 

of the CAA giyes 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 requirem~nts of a SLAMS 

station under paragraph (a) but must be operated in 

accordance with a monitoring schedule, methodology, 

quality assurance procedures, and probe or instrumentsiting 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. EPA450/4-87-007. May 1987. page 3. 

3-4 February 1994 

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• 

• 
• 

• 

• 

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 ... 11 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 (EPA600/4-77-027a). 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. 

6. 

Calibration procedures and frequency. 

Zero/span checks and adjustments of automated 

3-6 February 1994 

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• 

7. 

8 . 

analyzers . 

Control checks and their frequency. 

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 ~o 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 (EPA600/9-76-005). 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. 11 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 

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• 

• 

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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 

Me,thod) . 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-1 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 0 3 must be automated 

reference or equivalent methods (continuous 

3-10 February 1994 • 
• 

• 

• 

6. 

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) . 

"Ambient air quality data collected at any SLAMS must 

be collected as follows: (a) For continuous analyzersconsecutive hourly averages except during: (1) 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 

• 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 • 
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• 

• 

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 postconstruction 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 multisource 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, D.C. 

Office of the Federal Register. 

2. Reference 1. "The network of stations which comprise 

SLA.~S 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 

represent::ativeness." 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." 

5. 

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. 

U.S. Environmental Protection Agency. 

Exposure Criteria for S02 Monitoring. 

Triangle Park, NC. EPA Publication 

No. EPA-450/3-77-013. April 1977. 

Optimum Site 

Research 

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 • 
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• 

• 

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 

9 . 

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. 11 

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) ." 1 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 

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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 ambien~ 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 numbeY of 24-hour average concentrations in 

the ranges as specified in appendix F; 

0 the location, date, pollution source and duration 

of each air pollution incident during which 

ambient 802 levels reached or e~ceeded the 

significant harm level specified by 40 CFR ?1.151; 

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 

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3.6 EPISODE MONITORING 

Classification of regions required to have air 

pollution ep~sod~ 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 S02 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 i~dex 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 

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• 

REFERENCES FOR SECTION 3.7 

1. "The annu,al 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, D.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 Implementins 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. 11 

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, D.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 

11 Interim Procedures for Evaluating Air Quality Models 

(Revised) . 115 

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)" 

( 11 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 tor point sources based solely on monitoring 

data. [A]~ 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. Campbell, 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. 11Based 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 networ~s for this purpose 

is limited, we believe that an appropriate balan~e 

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 4lt 

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 Sour~e 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 qual·ity, modeling techniques recommended for 

application to SIP revisions for existing sources and to naw 

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 

establi~hed, 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, inclujing 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, D.C. Office 

of the Federal Register. 

4. Reference 1. "In all cases, the model applied to a 

given situation should be the one th~t 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-1; 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 Jtemporally) 

representative of the area of interest. 1 Use of sitespecific data is preferred for air quality analyses provided 

one year or more of quality-assured data are available. 2 

Suggest~ons 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 onsite 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. M~y 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. 

concentrations calculated with Gaussian models 

calms should not be considered valid; the wind 

concentration estimates for these hours should 

disregarded and considered to be missing." 

"Hourly 

using 

and 

be 

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 ann 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) . 111 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 shortterm 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: 

0 

Use existing stack gas exit parameters--

temperature, flow rate and stack top diameter 

--and model the stack at GEP height. 

If the actual stack height is less than GEP height 

and dispersion techniques are employed: 

4-16 February 1994 

• 

• 

• 
• 

• 

• 

0 

0 

0 

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. 

o 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. 

o 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 

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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)' 11 

Memorandum from Calcagni, J., and Laxton, W., OAQPS, to 

T.J. Maslany, Air Management Division, Region III, and 

W.B. Hathaway, Air Pesticides, and Taxies 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 (MultiSource 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 iri question is impacting the monitor." 

1.2. 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, toW. 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). 

1E. Reference 1, section 7.2.5 Good Engineering Practice 

Stack H~ight. "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 structureq 

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 

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• 

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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-bycase determ.ination 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 

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• 

4.7 OTHER MODEL REQUIREMENTS 

The 11 Guideline on Air Quality Models (Revised) 11 

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 

S02 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 S02 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 transformat~on 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 802 

emissions in urban areas. 3 

Issues that may arise in modeling analyses of 802 

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 

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• 
• 

• 

• 

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. 

4. 

"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 halflife of 4 hours may be applied to the analysis of S02 

emissions." 

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 
5. Reference 1, section 11.2.2 Use of Measured Data in 

Lieu of Model Estimates. 11 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 

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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 11 in existence 11 ) • 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 11 Workshop on Implementins 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, D.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 

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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 

fpllowing: 

0 

0 

De Minimis 

65 meters, measured from the ground-level 

elevation at the base of the stack; 

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 furnish~s 

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. 

5.6.4 for more detailed discussion) . 

(See section 

5-5 Fe'bruary 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 

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• 

• 

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 - res or SCS) ; or 

0 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 

0 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, D.C. Office of the Federal 

Register. 

5-8 February 1994 

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• 

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• 

• 

• 

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. SL" 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 pr.oceed, 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.SL 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 

Taxies Management Division Director, Regions IV, and 

VI, Air and Radiation Division Director, Region V, Air 

and Taxies 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 

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• 

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." 1 

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 co~tracts 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 

0 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. 

Documen~~tion 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 

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• 

• 

• 

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 fo'r 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. 11 

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 incr~ases 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 maxi~um 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 

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• 

• 
• 

• 

• 

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 bac~ground 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 neces~ary 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 

equivale~t 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 1 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. 1119 

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, D.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, D.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 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. 

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. 11 

6. 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. 

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 lb/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 

2 8 I 19 8 5 . ( PN 12 3 - 8 5 -1 0 - 2 8 - 0 0 9 ) . 

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. 

123-85-10-10-007). 

12. Reference 3. 

(PN 

13. U.S. Environmental Protection Agency. Code of Feoeral 

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 PSn 

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 1981. 

• 

17. U.S. Environmental Protection Agency. Determination of • 

Good Engineering Practice Stack Height - A Fluid Model 

Demonstration Study for a Power Plant. Environmental 

18. 

Science Research Laboratory. EPA Puolication No. 

EPA-600/3-83-024. April 1983. 

U.S. Environmental Protection 

Fluid Modeling of Atmospheric 

Science Research Laboratory. 

EPA-600/8-81-009. 

Agency. Guideline for 

Diffusion. Environmental 

EPA Publication No. 

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 • 
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• 

• 

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 exalusion from the definition of "dispersion 

techniques" shall only apply to the emission limitation 

for the pollutant affected by such change in operation; 

0 before July 8, 1985 such merging: 1t. 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 reasons 3 , 

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; 5 or 

0 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 c0nstruction 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. 11 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 Information 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; 

0 source stack height is less than GEP formula height; 

and 

o source emission limitation was not af~ected 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 + l.SL 

Modeled 

Need for Stricter Control 

Source Emissions Greater than 

5,000 tons per year 

5-26 

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 

February 1994 

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• 

• 

• 

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 I 19 8 7 . ' ( PN 12 3 - 8 7 - 1 0 - 0 9 - 0 14 ) . 

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 12 3 - 8 6 - 0 2 - 11 - 0 12 ) . . 

5-27 February 1994 
5.9 EMISSIONS BALANCING 

Emissions balancing refers to the procedure whereby a 

source subject to the stack height regulations ("affected 

sour~e") 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; 

0 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 

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• 
• 

• 

• 

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 
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• 

• 

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 S02 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 S02 r~gulations, different emission limitations 

may apply depending on such parameters •as facility size, 

fuel type, geographical location, and age of source. 

6-2 February 1994 

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• 

• 
• 

• 

• 

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 lG0-169) 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 802 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 th2 ~~QS. The area classification schem~ 

establishes three classes of geographic areas and applies 

increments of different stringency to each class. The most 

restrictive increments apply in Class I a~~as, 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 802 are 

shown in.Tablc 6-1. 

6-4 February 1994 

• 

• 

• 
• 

• 

• 

TABLE 6-1. PSD INCREMENTS FOR 802 

4 

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 51.166(c) and 52.21(c). Washington, D.C. 

Office of the Federal Register. 

6-6 February 1994 

• 

• 

• 
• 

• 

• 

6.3 NONATTAINMENT AREA TIME FRAMES 

Section ~10(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. S~ction 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 nonattainrnent areas violating both the 

primary and secondary S02 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 802 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)] 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 requi=ement 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. 11 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 

S02 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 

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• 

• 
• 

• 

• 

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 {S02 ), 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 CPR part 81. 11 

Page 13545. 

4. Reference 1. "States with existing nonattainment areas 

for the primary 802 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 

802 NAAQS (section 191) . Explicit plan submission 

deadlines are not given for nonattainment areas that 

violate only the secondary or both the primary and 

secondary 802 r~AAQS, however. " Page 13 54 5 . 

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 802 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 Si.340 (subpart R) t9 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. Th~ general approach for 

determjning 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 \lith 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 compl~ance 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, D.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 shortterm 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 (802 ), 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 

6 . 

(3-hour and 24-hour) as 802 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 Taxies Division Directors, Region IV, 

and VI, and Air and Taxies Division Directors, 

Region VII, VIII, and X. July 29, 1987. 

(PN 110-87-07-29-084) . 

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 

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• 
• 

• 

• 

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 llO(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 

submitt~l 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 includP 

provisions that do not comply with applicable require,nents 

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 approval 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 llO{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 1 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 gn 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 noticeand-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 subs~quently 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 attainment 23 

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 S02 emission limit, existing SIP limit, and 

corresponding averaging times; and (4) actual and 11 paper 11 

(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 

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• 

• 
• 

• 

• 

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 

qetermirted to be incomplete, the sanctions and FIP 

provisions of section 179 and 110(c), respectively, 

will be triggered. 11 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 lim:.teci approvals. Rather, EPA is using its 'gapfilling' authority under section 30l(a) of the Act in 

conjunction with section llO(k) (3) approval provision 

to interpret the Act to provide for this type of 

approval action." 

9. Reference 3, p. 3. "A key distincti6n 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 
• 

• 

• 

11. 

12. 

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." 

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." 

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 mat:ter, 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 factvrs 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 dis~pproval . 

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 

• 
• 

• 

• 

19. 

20. 

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 FIP start as of the date of final 

disapproval." 

U.S. Environmental Protection Agency. Application 

Sequence for Clean Air Act Section 179 Sanctions. 

Federal Register 58:51270. October 1, 1993. 

Memorandum from Berry, K.D., OAQPS to Director, Air, 

Pesticides, and Taxies Management Division, Regions I 

and IV; Director, Air and Waste Management Division, 

Region II; Director, Air, Radiation, and Taxies 

Division, Region III; Director, Air and Radiation 

Division, Region V; Director, Air, Pesticides and 

Taxies Division, Region VI; Director, Air and Taxies 

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-establi~hed 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 Taxies Division Region IV and VI; 

Director, Air and Radiation Division Region V; and 

Director Air and Taxies 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. 1 

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 

~~rrect 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 1. 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 Register, 

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 Taxies 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 Taxies 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 Dorin 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 llO(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 

'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-1 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. 

2. 

"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, JohnS., 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. 

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 NAPQS, or to otherwise comply with 

any additional requirements of the Act. Relevant exceptions 

to these requirements for plan revisions are set forth in 

section llO(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 

llO(k) (5) finding must correct the plan deficiency and meet 

all other applicable plan requirements under sections 

llO(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 S02 

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 802 

NAAQ8 would, by definition, fail to be S02 RACT. 

The EPA intends to continue defining RACT for 802 as 

that control technology which will achieve the NAAQ8 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 NAAQ8 are inventory-wide. The 

definition is generally less pertinent to pollutants such as 

802 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 802 , 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 overlyoptimistic 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 S02 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 S02 

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 ~FP 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 NAAQ8 or P8D 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 802 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 802 sources have the potential to emit at least 100 

tons of 802 per year; major modifications occur if the net 

increase in 802 emissions at a major 802 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 qemonstrated to be technically 

infeasible, site-specific cost cousiderations 

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 NAAQ8 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 8, section 

(IV)(D). 

7.2.2.4 Net Air Quality Benefit. In order to satisfy the 

location requirements for 802 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 802 is defined as an increase in 

ambient S02 concentrations that exceeds: 25 ~g/m3 for a 

• 

• 

3-hour average; 5 ~g/m3 for a 24-hour average; and, 1 ~g/m3 • 

7-4 February 1994 
• 

• 

• 

for an annual average (see Table 7-1). 

7.2.2.5 Other Reguirements. 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 

approve_d 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 

NAAQS 

PSD Increments Class I 

II 

III 

PSD significant ambient 

impact concentrations. 

PSD significant monitoring 

concentration 

Averaging Time 

(micrograms per cubic meter) 

3-Hour 24-Hour Annual 

1,300 365 80 

25 5 2 

512 91 20 

700 182 40 

25 5 1 

13 

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 regula~ions 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 prog~ams 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 th~ requirements of 

appendix S to 40 CPR 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 P?Sition 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 compfete 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 802 include 

section 173 offset requirements. 18 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 regulat~on 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 802 in an area 

designated attainment or unclassifiable for 802 must undergo 

PSD review with respect to those 802 emissions. Similarly, 

any existing major stationary source that proposes a 

physical or operational charge that would increase emissions 

of 802 by 40 tpy or more is also subject to P8D for 802 • 

7.2.4.2 Control Technology Requirements. Major sources 

subject to P8D review for 802 are required to control their 

potential so2 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 NAAQ8 and increments for 802 are 

expressed for annual, 24-hour; and 3-hour·periods. '• 

Guidance for preparing a demonstration of compliance 

with the NAAQS and the 802 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 

determi~ing 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) . n29 

The air quality analysis should also be used as a basis 

for establishing 802 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 802 

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 802 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 (1) a stringent Class I PSD 

increment and (2) air quality-related valves (AQRV's) that 

the Federal Land Manager (FLM) has an afi~rmative du~y 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 ~AAQS 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 802 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 

51.16S(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 

0 

notificationi and 

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-1; 1200-2400 

bps, (919) 541-5742; 9600 bps, (919) 541-1447. SYSOP 

(919)541-5384. 

2. U.S. Environmental Protection Agency. New Source 

Re.view 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 Fede~al 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 

9 . 

173(a) (5). Washington, D.C. U.S. Government Printing 

Office. 

"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, JohnS., 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. 

12. 

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." 

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 provisio~s 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 ~ 
• 

• 

• 

13. 

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." 

Reference 9, p. 18076-7. "Pursuant to section 

llO(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. 11 

14. Reference 9, p. 18077. 11 The NSR permitting program in 

an existing FIP remains in effect until a SIP is 

approved or a revised FIP is adopted. 11 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. 11 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. 11 

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 provi:sions 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. 11 Memorandum from 

Seitz, JohnS., 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. 11 Where States do not submit the part D 

18. 

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 ameRded 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. 11 

Reference 16. 11 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 

• 

• 
• 

• 

• 

19. 

20. 

21. 

22 . 

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 0 3 nonattainment areas and the NOTR." 

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." 

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.) 

Reference 2. 

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 Cle~m Air Act, as 

amended by section 301 of Public Law:lo1-549, 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 

Regulations. 

51.166 (j) (2). 

Register. 

Protection Agency. Code of Federal 

Title 40, chapter I, subchapter C, part 

Washington, D.C. Office of the Federal 

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, ~nd 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 ban~ing 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 S02 -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 S02 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 include 5 : 

(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 hei~ht as dete;mined. 

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 sign~ficant 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 Feder~l 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, 11 The 

Clean Air Act Compliance/Enforcement Policy Compendium. 11 

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 ; 

0 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 state 6 ; 

o recordkeeping and reporting requirements; 

o requirement of continuous compliance; and 

o methods to be used to determine compliance 7 

(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.: 1 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. 802 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 

certain percentage reduction from sources. 

should be clear as to how the baseline from 

reduction is to be accomplished is set." 

require a 

The regulation 

which such a 

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: 

0 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. All 

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 enforce~ent 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 shutdown 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 

llO(f). Under section llO(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 llO(f) ~ 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 llO(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 

specificallyprovide 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 • 

pdrevent 11loMss of l~fe, pedrsotntalhinjutryf, orBsevertet prKopMerty . amage . emoranaum an a ac men rom enne , . 1. , 

OANR, to Regional Administrators, Regiaps I - X. February 

15, 1983. Policy on Excess Emissions o'uring Startup I 

Shutdown, Maintenance, and Malfunctions. · 

( PN 113 - 8 3 - 0 2 - 15 - 0 1 7 ) . 

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. Reference 2. "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 

Durning, 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 Durning, 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)]. 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 802 emissions, continuous emission monitoring systems 

(CEMS) provide the best means for directly determining source 

compliance with emission regulations. In some 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 mor.itor 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 CPR 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 witr 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." 

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 5l.260(a)). 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 pract~cable .. 

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·lll 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 802 • 

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 

111(b) {1) (A). Washington, D.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 

11l(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 

111{d) (1). 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 Generators 1 • 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, S02 emissions are limited to 

0.80 pounds (lb) of pollutant per MM Btu heat input for 

liquid fuel and 1.2 lb/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 Generatina Units 2 • 

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 lb/MM Btu heat input and 90 percent S02 reduction 

from the potential combustion concentration or (2) to 

9-4 February 1994 

• 

• 

• 
• 

• 

• 

0.20 lb/MM Btu heat input (without any percent S02 reduction 

required) . 

For those units combusting solid fuels, S02 emissions 

are limited to either: (1) 1.2 lb/MM Btu heat input and 

90 percent reduction or (2) 0.6 lbs/MM Btu and 70 percent 

S02 reduction. 

Compliance with this regulation is determined by 

continu~usly monitoring the S02 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 

Stearn Generators 3 • 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 S02 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 lb/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 lb/MM Btu heat input (for coal-fired units) and 

0.5 lb/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 De--Small Industrial-Commercial-Institutional 

Steam Generating Units 5 • 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 De requires an S02 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 percP.nt amlUal capacity factor, limit: S02 emissions to 

1.2 lb/MM Btu for all coal-fired units, and limit S02 

emissions from oil-fired units to 0.5 lb/MM Btu heat input. 

• 

• 

Compliance with subpart De 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 co~~usts 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 S02 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 Turbine~ • 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 Plants 8 • 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 lb 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 Refineries 9 • This NSPS applies 

to petroleum refineries with fuel combustion devices that 

commenced construction after June 11, 1973, and with Claus 

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 Subparts P, Q, and R--Smelters 10 •

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 502 in smelter exhaust gases to 

0.065 percent (by volu~e). 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 De does not apply to process dryers or 

kilns." Memorandum from Jordan, B. , OAQPS, to 

Addressees. Applicability of NSPS subparts Db/De 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 De. 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.e. 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, D.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 Combustors 1 • 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 

classif~ed 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 S02 

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, D.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.l 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 sue~ 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 SOz REGULATIONS IN 40 CFR 60.40 

Subpart 0--Standards of Performance for 

fossil-fuel-fired Steam Generators • 

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

Affected facility 

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). 

Applicable time frame 

After 8/17/71 

9-16 

Emission limits 

340 ng/J (0.80 lb!MMBtu) heat input 

derived from liquid fossil fuel and 

wood residue. 

520 ng/J (1.2 lb/MMBtu) heat input 

(1.2 lb/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(SOz) = [y(340) + z(520)]/(y + Z) 

(See Section 60.43.) 

• 

• 

February 1994 
• 

• 

• 

TABLE 9·1. 

Initial performance testing 

Performance test in accordance with 

Section 60.8. Performance 

Specification 2 (Appendix 8) used in 

evaluating acceptability of CEMS 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) = (1,000y + 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 

pp11. 

SUMMARY OF SOz REGULATIONS IN 40 CFR 60.40 (CONCLUDED) 

Subpart D··Standards of Performance for. 

Fossil-Fuel-Fired Steam Generators 

Monitoring 

Continuous monitoring system (to measure so2 and either co or Oz> 

required except for: (1) a steam 

generating 111it that bums only 

gaseous fossil fuel and (2) a unit 

without an FGD system if the 

owner/operator monitors so2 by fuel 

sampling and analysis. 

If no continuous monitoring system 

used for so2, then none required for 

Oz or COz. 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 so2. Method 6A may 

be used whenever Methods 6 or 6C and 

3 or 3A data are used to determine 

the SOz 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, 

ZO min.; and min. sample vol. = 0.02 

dscm (0.71 dscf) for each sample. 

Arithmetic average of Z samples = 1 run. Samples taken -30 min. For 

Methods 6 and 6C, the o2 sample shall 

be obtained simultaneously at the same point in the duct . 

9-17 

·. 

Definition of 

Nonc0111Jl i ance 

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 so2 as 111easured by 

a continuous monitoring system exceed 

the standards. 

February 1994 
TABLE 9-2. SUMMARY OF so2 REGULATIONS IN 40 CFR 60.40a 

Subpart Da--Standards of Performance for 

-------------------------------------E-l_e_c-tr_i_c __ u_t,_.l_i_t_y_s_t_e_a_m_G_e_n_e_ra_t_o_r_s------------------------------------~ 

Affected facility 

Electric utility steam generating 

U"lit capable of conb.lsting >73 MW 

heat input (250 MMBtu/hour) of fossil 

fuel (either alone or in combination 

with any other fuel) 

Applicable time frame 

After 91'8178 

9-18 

Emission limits 

When conb.lsting solid or solid-derived fuel: 

(1) 520 ng/J (1.20 lb/MMBtu) heat 

input and 10X of the potential 

combustion cone. C90X> or 

(2) 30X of the potential conb.lstion 

cone. (70X reduction) When emissions are ~260 ng/J (0.60 lb/MMBtu> heat 

inp.Jt. 

When combusting liquid or gaseous 

fuels (except those derived from 

solid fuels): 

(1) 340 ng/J (0.80 lb/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 lb/MMBtu) heat 

input. 

When combusting solid solvent refined 

coal ( SCR- I ) : -

520 ng/J (1.20 lb/MMBtu) heat input...., 

and 15% of the potential combustion 

,~one. (85%) 

~ 

February 1994 
• 

• 

• 

TABLE 9-2. 

Initial performance testing 

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. esti .. ted hourly 

potential emissions of the fuel fired 

(at the inlet) and SOX Cat 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. 

SUMMARY OF so2 REGULATIONS IN 40 CFR 60.40a (CONCLUDED) 

Subpart De--Standards of Performance for 

Electric Utility Steam Generators 

Monitoring 

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 co2• 1 

hour averages must contain at least 2 

data points. 

Methods 3 or 3A, 6 or 6C. Method 6A or 68 may be used whenever Methods 6 

and 3 data are required to determine 

the so2 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 68 operated for 24 hours per 

samp1e. Min. sample vol. = 0.02 

dscm5 (0.71 dscf) for each sample. 

Each Method 68 sample = 24 1-hour 

averages . 

9-19 

Definition of Nonc~liance 

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. 

February 1994 
TABLE 9-3. SUMMARY OF so2 REGULATIONS IN 40 CFR 60.40b 

Subpart Db--Standards of Performance for 

Industrial-Commercial-Institutional Steam Generators • 

Affected facility 

Steam generating unit with input 

capacity from fuels conb.lsted of 

>29 MW ( 100 MMBtu/hour) heat input 

Steam generating unit with input 

capacity from fuels combusted of 

Applicable time frame 

After 6/19/84 

Emission limits 

When combusting coal or oil: 

10X of the potential combustion cone. C90X reduction) and an emission limit 

determined by the following foMILila: 

where: 

E, = so2 emission limit, 

(ng/J [lb/MM Btu]) 

K, = 520 ng/J (1.2 lb/MMBtu) 

K, = 340 ng/J (0.80 lb/MMBtu) 

H, = heat input from contlusting 

coal, J (MMBtu) 

H0 = heat input from combusting 

oil, J CMMBtu) 

When combusting coal refuse alone in an FBC: 

20% of the potential combustion cone. (80% reduction) with S02 emissions ~520 ng/J (1.2 lb/MMBtu) heat input .• 

When combusting coal or oil (alone o in combination) and using an emerging 

·technology: 

50% of the potential combustion cone. (50% reduction) and.emission (imit 

calculated using the following 

formula: 

where: 

E, = S02 emission limit, 

Cng/J [lb/MM Btul) 

K, 260 ng/J (0.60 lb/MMBtu) 

Ka 170 ng/J (0.40 lb/MMBtu) 

H, = heat input from combusting 

roal, J (MMBtu) 

Ha = heat input from combusting 

oil, J (MMBtu) 

When combusting coal: 

520 ng/J (1.2 lb/MMBtu) heat input 

When combusting oil: 

215 ng/J (0.50 lb/MMBtu) heat input 

No % reduction here. 

>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 rombination with a~other fuel, in a duct burner as part of a combined 

cycle system where 30% 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. • 

--------------------------------~ 

9-20 February 1994 
• 

• 

• 

TABLE 9·3. SUMMARY OF so2 REGULATIONS IN 40 CFR 60.40b (CONCLUDED) 

Subpart Db--Standards of Performance for 

Industrial-Commercial-Institutional Steam Generators 

Initial performance testing 

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). 

Monitoring 

Continuous monitoring system for so2, 

and o2 or co2 (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 corixlsted; 

and (3) no other fuel is cOIID.Isted. 

Alternative methods: 

(1) Collect coal or oil samples at 

inlet and analyze for sand 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) • 

9-21 

Definition of 

Noncoq:,l i ance 

Any 30-day period during which the 

average (rolling) emissions of S02 as ~~teasured by a continuous monitoring 

system (i.e., CEMS) exceed the 

standards. 

February 1994 
TABLE 9-4. SUMMARY OF so2 REGULATIONS IN 40 CFR 60.40c 

Subpart De--Standards of Performance for Small 

Industrial-Commercial-Institutional Steam Generating Units • 

Affected facility 

Industrial-commercial-institutional 

steam generating unit <29 MW (100 MM 

Btu/hr> and > 2.9 MW (10 MM Btu/hr) 

heat input capacity. 

Applicable time frame 

After 6/9/89 

9-22 

Emission limits 

When combusting coal: 

520 ng/J (1.2 lb/MM Btu) heat input. 

When conubsting 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 lb/MM Btu) heat input 

and 10% of the potential combustion cone. (90%). 

When combusting oil: 

215 ng/J (0.50 lb/MM Btu) heat input; or firing oil with a sulfur content 

of 0.5 wt. X or less. 

• 

• 

February 1994 
• 

• 

• 

TABLE 9-4. SUMMARY OF SOz REGULATIONS IN 40 CFR 60.40c (CONCLUDED) 

Subpart De--Standards of Performance for Small 

Industrial-Commercial-Institutional Steam Generating Units 

Initial performance testing 

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?· 

Perform,nce specifications 1, 2, and 

3 (Appendix 8) 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). 

Monitoring 

Coal-fired units subject to 

percent-reduction may use continuous 

monitoring system, as-fired fuel 

sampling, or emission measurements 

using Method 68, at inlet and outlet 

30-day rolling average basis. 

Units subject to emission limits may 

use CEMS, Method 68 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 . 

9-23 

Definition of 

Noncoq:>l i ance 

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. 

· . 

February 1994 
TABLE 9-5. SUMMARY OF SOz REGULATIONS IN 40 CFR 60.50a 

__________ 

Subpart Ea--Standards of Performance for Municipal Waste Combustors _. • 

Affected facility 

Municipal waste combustor combusting 

>225 Mgtday (250 tpd) of municipal 

solid waste (residential, commercial 

and/or institutional discards). 

Applicable time frame 

After 12/20!89 

9-24 

Emission limits 

When combusting acid gases:· 

BOX reduction in so2 emissions or a 30 ppm so2 emission limit on a daily 

(block average) 24-hour geometric mean basis measured continuously • 

• 

• 

February 1994 
• 

• 

• 

TABLE 9-5. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.50a (CONCLUDED) 

Subpart_Ea--Standards of Performance for Municipal Waste Combustors 

Initial compliance testing 

Compliance test in accordance with 

Section 60.8. Procedures U"'der 

Section 60.13 for installation, 

evaluation, and operation. 

Performance specifications 1, 2, and 

3 (Appendix B> provide applicable 

procedures for operation of CEMS. 

Ouarterly accuracy detenminations 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 M~C unit combusted (at the 

inlet>; ~0% (at the outlet) • 

Monitoring 

Continuous monitoring system for so2, or 02 or co2 from acid gases on a 

daily (block) 24-hour geometric mean 

basis. 

9-25 

Definition of 

Noncompliance 

Any 24-hour period during which the 

average (rolling) emissions of so2 as 

measured by a continuous monitoring 

system (i.e, CEMS) exceed the 

standards. 

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 

• 

Stationary gas turbine with a heat 

input at peak load >10.7 GJ!hour, 

based on the lower heating value of 

the fuel fired. 

Applicable time frame 

After 10/3/n 

9-26 

Emission limits 

One of the following conditions must 

be met: 

(1) ~ 0.015X by vol. of so2 from 

gases discharged to the atmosphere at 

15X 02 (dry basis); 

(2) ~0.8X by weight S content of fuel 

burned. 

• 

• 

February 1994 
TABLE 9-6. SUMMARY OF SOz REGULATIONS IN 40 CFR 60.330 (CONCLUDED) 

• 

Subpart GG--Standards of Performance for Stationary Gas Turbines 

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

• 

• 

Initial performance testing 

Perfonmence test in accordance with 

Section 60.8. 

Monitoring 

Reference Method 20 for the 

concentration of SOz. 

S02 content of fuel fired nust 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 c.ndergo 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, 0-4084-82, or D-3246-81 for gaseous fuels . 

9-27 

Definition of Nonc~l iance 

Any daily period during which the S 

content of the fuel fired exceeds 

0.8X. 

February 1994 
TABLE 9-7. SUMMARY OF SOz REGULATIONS IN 40 CFR 60.80 

Subpart H··Standards of Performance for Sulfuric Acid Plants • 

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

Affected facility 

Sulfuric acid production unit (any 

facility producing sulfuric acid by 

the contact process burning 

elemental s, alkylation acid, HzS, 

organic sulfides and mercaptans, or acid sludge). 

A source that processes elemental S or an ore that contains elemental S 

and uses air to supply oxygen. 

Applicable time frame 

After 8/17/71 

9-28 

Emission limits 

!2 kg SOz/metric ton of acid produced 

(4 lb/ton), production being 

expressed as 100X Hzso4• 

·. • 

• 

February 1994 
TABLE 9-7. SUMMARY OF so2 REGULATIONS IN 40 CFR 60.80 (CONCLUDED) 

Subpart H--Standards of Performance for Sulfuric Acid Plants 

·-----------------------

• 

• 

Initial performance testing 

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 •ixtures). 

Performance Specifications 2 and 3 

used to evaluate the acceptability of 

CEMS at time of installation (i.e., 

used in preparing calibration gas 

mixtures). 

Monitoring 

Continuous monitoring system. 

Determine conversion factor 3 times 

daily by measuring the cone. of so2 entering the converter. 

Span = 1,000 ppm of so2• 

Reference Method 8 (only the S02 

portion). 

An alternative method (not required) 

would be to continuously monitor so2, CO, and C02 (if required). 

Span for C02 (if required) = 10%. 

Span for 02 = 20.9%. 

No so2 conversion factor needed. 

Method in reg. to calculate so2 emission rate. Reference Method 8 

for so2 and acid mist; reference 

Method 3 for 02 and C02. No 

production rate or total gas flow 

rate needed . 

9-29 

Definition of 

Noncompliance 

All 3-hour periods (or the arithmetic 

average of 3 consecutive 1•hour 

periods) during which the integrated 

average SOz emissions exceed the 

applicable emission limits. 

February 1994 
!ABLE 9·8. SUMMARY OF so2 REGULATIONS IN 40 CFR 60.100 

Subpart J··Standards of Performance for Petroleum Refineries • 

--------------------------------~ 

Affected facility 

Fuel gas combustion device 

All Claus sulfur recovery plants 

>20 long tons/day 

Applicable time frame 

After 6/11/73 

After 10/4/76 

9-30 

Emission limits 

~230 mQ/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 so2 

emissions). 

~0.025% vol. so2 at 0% o2 (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 Hzs calculated as so2 

.at 0% o2 Cdry basls). 

• 

February 1994 
TABLE 9·8. SUMMARY OF S02 REGULATIONS IN 40 CFR 60.100 (CONCLUDED) 

• 

SubpSrt J·-Standards of Performance for Petroleum Refineries 

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

Initial performance testing 

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 •ixtures). 

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 HzS. 

Span = 600 ppm for monitoring reduced 

S compounds. 

Reference Method 15 (or Reference 

Method 1Sa for reduced S compounds). 

Monitoring 

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 so2, Method 1 for velocity traverse and 

Method 2 for determining velocity and 

volumetric flow rate. Reference 

Method 11 for H~S (for both methods, 

min. sampling t1me = 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 . 

9-31 

Definition of Nonc~l iance 

All 3-hour period when the average 

H2S cone. exceeds 230 mg/dscm 

(0.10 gr/dscf), if HzS is removed 

from the fuel gas before it is 

burned; or any 3-hour period when the 

average cone. SOz level exceeds the 

specified limits 1f compliance is 

achieved by removing so2 from the 

combusted fuel gases. 

Any 12-hour period when the average cone. so2 in the discharged gases 

exceeds 250 ppm at 0% o2 (dry basis). 

Any 6-hour period during which the 

average emission (arithmetic average 

of 6 contiguous 1-hour periods) of 

SOz as measured by a continuous 

monitoring system exceed the 

specified emission limits. 

Any 12-hour period when the average 

cone. of HzS, or reduced sulfur 

compounds 1n the discharged gases, 

·~xceeds 10 ppm or 300 ppm, 

"respectively, at 0% Oz (dry basis). 

Any 6-hour period dur1ng 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. 

February 1994 
TABLE 9-9. SUMMARY OF SOz REGULATIONS IN 40 CFR 60.160 

Subpart P-·Standards of Performance for Primary Copper Smelters 

--------------------------------~· Affected facility 

Primary cooper smelter (dr•,er, 

roaster, smelting furnace, and copper 

converter) 

Applicable time frame 

After 10/16/74 

9-32 

Emission limits 

~0.065X by vol. of so2 from gases 

discharged to the atmosphere. 

(Reverbertory smelting furnaces are ex~ted 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.) 

• 

• 

February 1994 
• 

• 

• 

TABLE 9·9. SUMMARY OF SOz REGULATIONS IN 40 CFR 60.160 (CONCLUDED) 

Subpart P··Standards of Performance for Primary Copper Smelters 

Initial performance testing 

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 SOz by vol. if necessary 

to maintain system output between 20X 

and 90X of full scale. 

Reference Method 6. 

Monitoring 

Maintain a monthly record of the 

total smelter charge and weight X 

(dry basis) as As, Sb, Pb, and Zn in 

this charge. Approved methods nust 

be accurate to !10X. Continuous 

monitoring system. 

Span = 0.20X so2 by vol. 

One 6-hour average shalt constitute 

1 run. 

Monitoring drift not to exceed ZX of 

span . 

9-33 

Definition of 

Noncompliance 

All 6-hour periods during which the 

average emissions of so2, 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. 

February 1994 
TABLE 9-10. SUMMARY OF so2 REGULATIONS IN 40 CFR 60.170 

Subpart Q--Standards of Performance for Primary Zinc Smelters • 

-----------: 

Affected facility 

Primary zinc smelter (roaster and 

sintering machine) 

Applicable time frame 

After 10/16/74 

9-34 

Emission limits 

~0.065% by vol. of so2 from gases 

discharged to the atmosphere. (Any 

sintering machine which eliminates more than 10X of the S initially 

contained in the zinc sulfide ore will be considered as a roaster.) 

February 1994 

• 

• 
TABLE 9·10. SUMMARY OF so2 REGULATIONS IN 40 CFR 60.170 (CONCLUDED) 

• 

Subpart O··Standards of Performance for Primary Zinc Smelters 

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

• 

• 

Initial performance testing 

Performance test in accordance with 

Section 60.8. Performance 

Specification 2 (Appendix 8) 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 so2 by vol. if necessary 

to maintain system. 

Monitoring 

Continuous monitoring system. 

Span = 0.20X so2 by vol. 

One 2-hour average shall constitute 

run. 

The 2-hour average so2 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 so2 cones. 

provided by the CEMS). 

Monitoring drift not to exceed 2% of 

span • 

9-35 

Definition of 

Noncoq:>liance 

Any 2-hour period during which 

average S02 emissions exceed the 

standard. 

February 1994 
~ABLE 9-11. SUMMARY OF SOz REGULATIONS IN 40 CFR 60.180 

__________ Subpa~t R--Standards of Performance for Primary Lead Smelters • ______;;; 

Affected facility 

Primary lead smelter (sintering 

machine, electric smelting furnace, 

and converter) 

Applicable time frame 

After 10/16/74 

9-36 

Emission limits 

!0.065X by vol. of so2 from gases 

discharged to the atmosphere. 

February 1994 

• 

• 
TABLE 9-11. SUMMARY OF SOz REGULATIONS IN 40 CFR 60.180 (CONCLUDED) 

Subpart R-·Standards of Performance for Primary Lead 5melters 

tt---------------------------------- Definition of 

• 

• 

Initial performance testing 

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 end for 

calibration checks). Span of 

continuous monitoring system 

may= 0.15X so2 by vol. if necessary 

to maintain system. 

Monitoring 

Cont_inuous monitoring system. 

Span= 0.20X so2 by vol. 

One 2-hour average shall constitute 

1 run. 

The 2-hour average so2 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 so2 

cones. provided by the CEMS). 

Monitoring drift not to exceed 2~ of 

span . 

9-37 

NoncOIJllliance 

Any 2-hour period during which 

average S02 emissions exceed the 

standard. 

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 

Municipal waste combustor 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). 

Applicable time frame 

Before 12/20/89 

9-38 

Emission limits 

70X reduction in so2 emissions or a 30 ppm S02 emission limit on a daily 

(block average) 24-hour geometric mean basis measured continuously. 

SOX reduction in so2 emissions or a 30 ppm S02 emission limit on a daily 

(block average) 24-hour geometric mean basis measured continuously. 

• 

• 

February 1994 
• 

• 

• 

TABLE 9-12. SUMMARY OF so2 REGULATIONS IN 40 CFR 60.30a (CONCLUDED) 

Subpart Ca--Emissions Guidelines and Compliance Times 

for Municipal Waste Combustors 

Initial compliance testing 

C~liance test in accordance with 

Section 60.8. Procedures under 

Section 60.13 for installation, 

evaluation, and operation. 

Performance specifications 1, 2, and 

3 (Appendix B). Provide epplicable 

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) . 

Monitoring 

Continuous monitoring system for S02, 

or o2 or co2 from acid gases on a 

daily (block) 24-hour geometric mean 

basis. 

9-39 

Definition of Nonc~liance 

Any 24-hour period during which the 

average (rolling) emissions of so2 as 

111easured by a continuous monitoring 

system exceed the standards. 

February 1994 
TECHNICAL REPORT DATA 

(Pk4se rud Instructions on the re11me before ~D,Inlel'inttl 

MING ORGANIZATION N ADDRESS 

U.S. Environmental Protection Agency 

Office of Air Quality Planning and Standards (MD-15) 

Research Triangle Park, NC 27711 

12. SPONSORING AGENCY NAME AND ADDRESS 

Same as 9 

15. SUPPLEMENTARY NOTES 

Supersedes S0 2 Guideline EPA-450/2-89-019 

The S0 2 (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 

S0 2 policy and guidance in effect at the time of the document 1 s preparation and does 

not present any new policy or guidance. Each chapter summarizes relevant policy and 

guidance and provides detailed refereQces 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. 

Sulfur dioxide, S0 2 , 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 

TRIBUTION STATEM NT 

Release unlimited 

PREVIOUS EDITION IS OBSOLETE