UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

Washington, D.C. 20460 

JUN 13 1989 

MEMORANDUM 

SUBJECT: Guidance on Limiting Potential to Emit in New Source Permitting 

FROM: Terrell E. Hunt 

Associate Enforcement Counsel 

Air Enforcement Division 

Office of Enforcement and Compliance Monitoring 

John S. Seitz, Director

Stationary Source Compliance Division

Office of Air Quality Planning and Standards

TO: Addressees 

This memorandum transmits the final guidance on conditions in construction permits 

which can legally limit a source's potential to emit to minor or de minimis levels. We received 

many helpful comments on the January 24, 1989 draft of this guidance, and have incorporated the 

comments into the final document wherever possible. A summary of the major changes which 

have been made to the guidance in response to these comments is provided below. 

Several commenters noted that the draft guidance used the term "federally enforceable" to 

mean both federally enforceable as defined in the new source regulations (40 C.F.R. Sections 

52.21(b) (17), 51.165(a) (1) (xiv), 51.166(b) (17)), and enforceable as a practical matter. We 

have tried to distinguish the places where each term should be used, explained the relationship 

between the two terms, and indicated that in order to properly restrict potential to emit, 

limitations must be both federally enforceable as defined in the regulations and practically 

enforceable. 
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Some commenters requested that the section on averaging times for production limits be 

more specific as to when it is appropriate to use limitations which exceed a one month time basis. 

We have tried to explain why it is not possible to develop generic criteria for making this 

distinction, and to indicate situations where exceptions to the policy that production and operation 

limitations not exceed one month may be warranted. 

There were some requests for a section on enforcement. We have included a new Section 

VI which addresses this topic. We also received many good suggestions on the example permit 

limitations. The section on examples has been substantially reworked to reflect your comments. 

Finally, we learned through the comments that in two specific circumstances, short term 

emission limits are the most useful and reasonable way to restrict and verify limits on potential to 

emit. These circumstances are: 1) when control equipment is installed but control equipment 

operating parameters are difficult to measure during enforcement inspections; and 2) in surface 

coating operations with numerous and unpredictable use of coatings containing varying VOC 

content, where add-on control equipment is not employed. Therefore, we have made a narrow 

exception to the flat prohibition on use of emission limits to restrict potential to emit for these 

specific circumstances, and only when certain additional conditions have been met. 

Again, we appreciate the thoughtful comments we have received on this guidance. Please 

insert this document into your Clean Air Act Compliance/Enforcement Policy Compendium as 

Item Number H.3. If you have any questions, please contact Judith Katz in the Air Enforcement 

Division at FTS 382-2843, or Sally Farrell in the Stationary Source Compliance Division at FTS 

382-2875. 

Addressees: 

Regional Counsels 

Regions I-X 

Regional Counsel Air Branch Chiefs 

Regions I-X 

Air Management Division Directors 

Regions I, III, and IX 

Air and Waste Management Division Director 

Region II 
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Air, Pesticides, and Toxics Management Division Directors 

Regions IV and VI

Air and Radiation Division Director 

Region V

Air and Toxics Division Directors 

Regions VII, VIII and X

Air Compliance Branch Chiefs 

Regions I-X

New Source Review Contacts 

Regions I-X

Alan Eckert

Associate General Counsel

Greg Foote, OGC

Gary McCutchen, NSRS, AQMD

David Solomon, NSRS, AQMD

Sally Farrell, SSCD

Judy Katz, AED

David Buente, Chief 

Environmental Enforcement Section

DOJ
LIMITING POTENTIAL TO EMIT IN NEW SOURCE PERMITTING 

JUNE 13, 1989 

AIR ENFORCEMENT DIVISION

OFFICE OF ENFORCEMENT AND COMPLIANCE MONITORING

STATIONARY SOURCE COMPLIANCE DIVISION

OFFICE OF AIR QUALITY PLANNING AND STANDARDS
Limiting Potential to Emit in New Source Permitting 

I. Introduction

II. The Louisiana-Pacific Case

III. Types of Limitations that will Limit Potential to Emit

IV. Time Periods for Limiting Production and Operation

V. Sham Operational Limits

A. Permits with conditions that do not reflect a source's planned mode of operation 

are void ab initio and cannot act to shield the source from the requirement to 

undergo preconstruction review.

1. Sham permits are not allowed by 40 CFR 52.21(r) (4)

2. Sham permits are not allowed by the definition of potential to emit:

40 CFR 52.21(b) (4), 51.165(a) (1) (iii), 51.166(b) (4)

3. Sham permits are not allowed by the Clean Air Act

B. Guidelines for determining when minor source construction permits are

shams.

1. Filing a PSD or nonattainment NSR application

2. Applications for funding

3. Reports on consumer demand and projected productions levels

4. Statements of authorized representatives of the source regarding plans

for operation

VI. Enforcement Procedures

VII. Examples

VIII. Conclusion
Limiting Potential to Emit in New Source Permitting 

I. Introduction 

Whether a new source or modification is major and subject to new source review under 

Parts C and D of the Clean Air Act is dependent on whether that source or modification has or 

will have the potential to emit major or significant amounts of a regulated pollutant. Therefore, 

the definition of "potential to emit" under the new source regulations is extremely important 

in determining the applicability of new source review to a particular source. The federal 

regulations define "potential to emit" as: 

the maximum capacity of a stationary source to emit a pollutant under its physical and 

operational design. Any physical or operational limitation on the capacity of the source to 

emit a pollutant, including air pollution control equipment and restrictions on hours of 

operation or on the type or amount of fuel combusted, stored or processed, shall be 

treated as part of its design if the limitation or the effect it would have on emissions is 

federally enforceable. 

40 C.F.R Sections 52.21(b) (4), 51.165(a) (1) (iii), 51.166(b) (4). 

Permit limitations are very significant in determining whether a source is subject 

to major new source review. This is because they are the easiest and most common way 

for a source to obtain restrictions on its potential to emit. A permit does not 
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have to be a major source permit to legally restrict potential emissions. A minor source 

construction permit issued pursuant to a state program approved by EPA as meeting the 

requirements of 40 C.F.R. Section 51.160 is federally enforceable. In fact, any permit limitation 

can legally restrict potential to emit if it meets two criteria: 1) it is federally enforceable as defined 

by 40 C.F.R. Sections 52.21(b) (17), 51.165(a) (1) (xiv), 51.166(b) (17), i.e., contained in a 

permit issued pursuant to an EPA-approved permitting program or a permit directly issued by 

EPA, or has been submitted to EPA as a revision to a State Implementation Plan and 

approved as such by EPA; and 2) it is enforceable as a practical matter. The second criterion is an 

implied requirement of the first criterion. A permit requirement may purport to be federally 

enforceable, but, in reality cannot be federally enforceable if it cannot be enforced as a practical 

matter. 

Non-permit limitations can also legally restrict potential to emit. These limitations include 

New Source Performance Standards codified at 40 C.F.R. Part 60 and National Emission 

Standards for Hazardous Air Pollutants codified at 40 C.F.R. Part 61. 

The appropriate means of restricting potential to emit through permit conditions has 

been an issue in recent enforcement cases. Through these cases and through guidance 

issued by EPA, the Agency has addressed three questions: what types of permit 
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limitations can legally limit potential to emit; whether long averaging times for production 

limitations are enforceable as a practical matter; and whether sources may limit potential to emit 

to minor source levels as a means of circumventing the preconstruction review requirements of 

major source review. 

II. The Louisiana-Pacific Case 

In United States v. Louisiana-Pacific Corporation, 682 F. Supp. 1122 (D. Colo. Oct. 30, 

1987) and 682 F. Supp. 1141 (D. Colo. March 22, 1988), Judge Alfred Arraj discussed the type 

of permit restrictions which can be used to limit a source's potential to emit. The Judge concluded 

that: 

... not all federally enforceable restrictions are properly considered in the calculation of a 

source's potential to emit. While restrictions on hours of operation and on the amount of 

materials combusted or produced are properly included, blanket restrictions on actual 

emissions are not. 

682 F. Supp. at 1133.

The Court held that Louisiana-Pacific's permit conditions which limited carbon monoxide

emissions to 78 tons per year and volatile organic compounds to 101.5 tons per year should not

be considered in determining "potential to emit" because these blanket emission limits did not

reflect the type of permit conditions which restricted operations or production such as limits on

hours of operation, fuel consumption, or final product.
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The Louisiana-Pacific court was guided in its reasoning by the D.C. Circuit's holding in 

Alabama Power v. Costle, 636 F. 2d 323 (D.C. Circuit 1979). Before Alabama Power, EPA 

regulations required potential to emit to be calculated according to a source's maximum 

uncontrolled emissions. In Alabama Power, the D. C. Circuit remanded those regulations to EPA 

with instructions that the Agency include the effect of in-place control equipment in defining 

potential to emit. EPA went beyond the minimum dictates of the D.C. Circuit in promulgating 

revised regulations in 1980 to include, in addition to control equipment, any federally enforceable 

physical or operational limitation. The Louisiana-Pacific court found that blanket limits on 

emissions did not fit within the concept of proper restrictions on potential to emit as set forth by 

Alabama Power. 

Moreover, Judge Arraj found that: 

...a fundamental distinction can be drawn between the federally enforceable limitations 

which are expressly included in the definition of potential to emit and (emission) 

limitations.... Restrictions on hours of operation or on the amount of material which may 

be combusted or produced ... are, relatively speaking, much easier to "federally enforce." 

Compliance with such conditions could be easily verified through the testimony of officers, 

all manner of internal correspondence and accounting, purchasing and production records. 

In contrast, compliance with blanket restrictions on actual emissions would be virtually 

impossible to verify or enforce. 

Id. Thus, Judge Arraj found that blanket emission limits were not enforceable as a practical 

matter. 
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Finally, the Court reasoned that allowing blanket emission limitation to restrict potential to 

emit would violate the intent of Congress in establishing the Prevention of Significant 

Deterioration (PSD) program. 

III. Types of Limitations that will Restrict Potential to Emit 

As an initial matter in this discussion, a few important terms should be defined. Emission 

limits are restrictions over a given period of time on the amount of a pollutant which may be 

emitted from a source into the outside air. Production limits are restrictions on the amount of final 

product which can be manufactured or otherwise produced at a source. Operational limits are all 

other restrictions on the manner in which a source is run, including hours of operation, amount of 

raw material consumed, fuel combusted, or conditions which specify that the source must 

install and maintain add-on controls that operate at a specified emission rate or efficiency. All 

production and operational limits except for hours of operation are limits on a source's capacity 

utilization. Potential emissions are defined as the product of a source's emission rate at maximum 

operating capacity, capacity utilization, and hours of operation. 

To appropriately limit potential to emit consistent with the opinion in Louisiana-Pacific, all 

permits issued pursuant to 40 C.F.R. Sections 51.160, 51.166, 52.21 and 51.165 must contain a 
6

production or operational limitation in addition to the emission limitation in cases where the 

emission limitation does not reflect the maximum emissions of the source operating at full design 

capacity without pollution control equipment. Restrictions on production or operation that will 

limit potential to emit include limitations on quantities of raw materials consumed, fuel 

combusted, hours of operation, or conditions which specify that the source must install and 

maintain controls that reduce emissions to a specified emission rate or to a specified efficiency 

level. Production and operational limits must be stated as conditions that can be enforced 

independently of one another. For example, restrictions on fuel which relates to both type and 

amount of fuel combusted should state each as an independent condition in the permit. This is 

necessary for purposes of practical enforcement so that, if one of the conditions is found to be 

difficult to monitor for any reason, the other may still be enforced. 

When permits contain production or operational limits, they should also have 

recordkeeping requirements that allow a permitting agency to verify a source's compliance with its 

limits. For example, permits with limits on hours of operation or amount of final product should 

require an operating log to be kept in which the hours of operation and the amount of final 

product produced are recorded. These logs should be available 
7

for inspection should staff of a permitting agency wish to check a source's compliance with the 

terms of its permit. 

When permits require add-on controls operated at a specified efficiency level, permit 

writers should include, so that the operating efficiency condition is enforceable as a practical 

matter, those operating parameters and assumptions which the permitting agency depended upon 

to determine that the control equipment would have a given efficiency. 

An emission limitation alone would limit potential to emit only when it reflects the 

absolute maximum that the source could emit without controls or other operational restrictions. 

When a permit contains no limits on capacity utilization or hours of operation, the potential to 

emit calculation should assume operation at maximum design or achievable capacity (whichever is 

higher) and continuous operation (8760 hours per year). 

The particular circumstances of some individual sources make it difficult to state operating 

parameters for control equipment limits in a manner that is easily enforceable as a practical matter. 

Therefore, there are two exceptions to the absolute prohibition on using blanket emission limits to 

restrict potential to emit. If the permitting agency determines that setting operating parameters for 

control equipment is infeasible in a particular situation, a federally enforceable permit 
8

containing short term emission limits (e.g. lbs per hour) would be sufficient to limit potential to 

emit, provided that such limits reflect the operation of the control equipment, and the permit 

includes requirements to install, maintain, and operate a continuous emission monitoring (CEM) 

system and to retain CEM data, and specifies that CEM data may be used to determine 

compliance with the emission limit. 

Likewise, for volatile organic compound (VOC) surface coating operations where no 

add-on control is employed but emissions are restricted through limiting VOC contents and 

quantities of coatings used, emission limits may be used to restrict potential to emit under the 

following limited circumstances. If the permitting agency determines for a particular surface 

coating operation that operating and production parameters (e.g. gallons of coating, quantities 

produced) are not readily limited due to the wide variety of coatings and products and due to the 

unpredictable nature of the operation, emission limits coupled with a requirement to calculate 

daily emissions may be used to restrict potential to emit. The source must be required to keep the 

records necessary for this calculation, including daily quantities and the VOC content of each 

coating used. Emission limits may be used in this limited circumstance to restrict potential to emit 

since, in this case, emission limits are more easily enforceable than operating or production limits. 
9

IV. Time Periods For Limiting Production and Operation 

As discussed above, a limitation specifically recognized by the regulations as reducing 

potential to emit is a limitation on production or operation. However, for these limitations to be 

enforceable as a practical matter, the time over which they extend should be as short term as 

possible and should generally not exceed one month. This policy was explained in a March 13, 

1987 memorandum from John Seitz to Bruce Miller, Region IV. The requirement for a monthly 

limit prevents the enforcing agency from having to wait for long periods of time to establish a 

continuing violation before initiating an enforcement action. 

EPA recognizes that in some rare situations, it is not reasonable to hold a source to a one 

month limit. In these cases, a limit spanning a longer time is appropriate if it is a rolling limit. 

However, the limit should not exceed an annual limit rolled on a monthly basis. EPA cannot now set 

out all inclusive categories of sources where a production limit longer than a month will be 

acceptable because every situation that may arise in the future cannot now be anticipated. However, 

permits where longer rolling limits are used to restrict production should be issued only to sources 

with substantial and unpredictable annual variation in production, such as emergency 
10

boilers. Rolling limits could be used as well for sources which shut down or curtail operation 

during part of a year on a regular seasonal cycle, but the permitting authority should first explore 

the possibility of imposing a month-by-month limit. For example, if a pulp drier is periodically 

shut down from December to April, the permit could contain a zero hours of operation limit for 

each of those months, and then the appropriate hourly operation limit for each of the remaining 

months. Under no circumstances would a production or operation limit expressed on a calendar 

year annual basis be considered capable of legally restricting potential to emit. 

V. Sham Operational Limits 

In the past year, several sources have obtained purportedly federally enforceable permits 

with operating restrictions limiting their potential to emit to minor or de minimis levels for the 

purpose of allowing them to commence construction prior to receipt of a major source permit. In 

such cases where EPA can demonstrate an intent to operate the source at major source levels, EPA 

considers the minor source construction permit void ab initio and will take appropriate enforcement 

action to prevent the source from constructing or operating without a major source permit. 
11

The following example illustrates the kind of situation addressed in this section: An 

existing major stationary source proposes to add a 12.5 megawatt electric utility steam generating 

unit, and applies for a federally enforceable minor source permit which restricts operation at the 

unit to 240 hours per year. Because the project is designed as a baseload facility, EPA does not 

believe that the source intends to operate the facility for only 240 hours a year. Further 

investigation would probably uncover documentation of the source's intent to operate at higher 

levels than those for which it is permitted. 

This situation raises the question of whether a source can lawfully bypass the 

preconstruction or premodification review requirements of Prevention of Significant Deterioration 

(PSD) and nonattainment New Source Review by committing to permit conditions which restrict 

production to a level at which the source does not intend to operate for any extensive time. If, 

after constructing and commencing operation, the source obtains a relaxation of its original permit 

conditions prior to exceeding them, does this constitute a violation of the preconstruction review 

requirements? This section discusses why it is improper to construct a source with a minor 

source permit when there is intent to operate as a major source, and provides guidelines for 

identifying these "sham" permits. 
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A. Permits with conditions that do not reflect a source's planned mode of operation are 

void ab initio and cannot act to shield the source from the requirement to undergo preconstruction 

review. 

1. Sham permits are not allowed by 40 CFR Section 52.21(r) (4) Section 

52.21(r) (4) states: 

At such time that a particular source or modification becomes a major stationary source or 

major modification solely by virtue of a relaxation in any enforceable limitation which was 

established after August 7, 1980 on the capacity of the source or modification otherwise 

to emit a pollutant, such as a restriction on hours of operation, then (PSD) shall apply to 

the source or modification as though construction had not yet commenced on the source 

or modification. 

When a source that is minor because of operating restrictions in a construction permit later 

applies for a relaxation of that construction permit which would make the source major, Section 

52.21(r) (4) prescribes the methodology for determining best available control technology 

(BACT). However, it does not foreclose EPA's ability, in addition to the retroactive application of 

BACT and other requirements of the PSD program, to pursue enforcement where the Agency 

believes that the initial minor source permit was a sham. EPA will limit its activity to requiring 

application of 40 CFR 52.21(r) (4) only for the cases where a source legitimately changes a 

project after finding that the operating restrictions which were taken in good faith cannot be 

complied with. Whether a source has acted in good faith is a factual question which is answered 

by available evidence in the particular case. 
13

2. Sham permits are not allowed by the definition of potential to emit: 

40 C.F.R. Sections 52.21(b) (4), 51.165(a) (1) (iii), 51.166(b) (4). 

The definition of potential to emit enables sources to obtain federally enforceable permits 

with operational restrictions as a means of limiting emissions to minor source levels. However, 

implicit in the application of these limitations is the understanding that they comport with the true 

design and intended operation of the project. 

3. Sham permits are not allowed by the Clean Air Act 

Parts C and D of the Clean Air Act exhibit Congress's clear intent that new major sources 

of air pollution be subject to preconstruction review. The purposes for these programs cannot be 

served without this essential element. Therefore, attempts to expedite construction by securing 

minor source status through the receipt of operational restrictions from which the source intends 

to free itself shortly after operation are to be treated as circumvention of the preconstruction 

review requirements. 
14

B. Guidelines for determining when minor source construction permits are shams. 

EPA's determination that a purportedly federally enforceable construction permit is a sham 

is made based on an evaluation of specific facts and evidence in each individual case. The 

following are criteria which should be scrutinized when making such a determination: 

1. Filing a PSD or nonattainment NSR permit application 

If a major source or major modification permit application is filed simultaneously with or 

at approximately the same time as the minor source construction permit, this is strong evidence of 

an intent to circumvent the requirements of preconstruction review. Even a major source 

application filed after the minor source application, but either before operation has commenced or 

after less than a year of operation should be looked at closely. 

2. Applications for funding 

Applications for commercial loans or, for public utilities, bond issues, should be 

scrutinized to see if the source has guaranteed a c ertain level of operation which is 

higher than that in its construction permit. If the project would not be funded or if it 

would not be economically viable if operated on an extended basis 
15

(at least a year) at the permitted level of production, this should be considered as evidence of 

circumvention. 

3. Reports on consumer demand and projected production levels. 

Stockholder reports, reports to the Securities and Exchange Commission, utility board 

reports, or business permit applications should be reviewed for projected operation or production 

levels. Ifreported levels are necessary to meet projected consumer demand but are higher than 

permitted levels, this is additional evidence of circumvention. 

4. Statements of authorized representatives of the source regarding plans 

for operation. 

Statements by representatives of the source to EPA or to state or local permitting agencies 

about the source's plans for operation can be evidence to show intent to circumvent 

preconstruction review requirements. 

Note that if a determination is made that a permit is a "sham" for one pollutant and, 

therefore, the source is a major source or major modification, the permit may possibly still contain 

valid limits on potential to emit for other pollutants. 
16

In such cases, the entire source must still go through new source review, during which, for 

PSD review, all pollutants for which there is a net significant increase must be analyzed for 

BACT. In nonattainment new source review, new sources must have LAER determinations only 

for pollutants for which they are major. Major modifications, however, must have LAER 

determinations for all nonattainment pollutants emitted in significant amounts. If the valid 

limits in a partially void minor source construction permit keep certain pollutants below 

significance levels, then those pollutants would not have to be analyzed for BACT or LAER. 

However, if a source or modification is determined to be major for PSD or NSR because part 

of its minor permit is deemed void, it would have to undergo BACT or LAER analysis for all 

significant pollutants. 

VI. Enforcement Procedures 

This guidance has discussed permit conditions which will legally restrict potential to emit, 

shielding a source from the requirement to comply with major new source permitting regulation. 

Failure by a permitting agency to adhere to these guidelines may result in a permit that does 

not legally restrict potential to emit, thereby subjecting a source to major new source 

review. If that source has not gone through preconstruction review, it is a significant 

violator of the Clean Air Act and is subject to enforcement for constructing or 
17

modifying without a major new source permit. 

The enforcement options available to EPA in these situations include administrative action 

under Sections 167 or 113 (a) (5) of the Act or federal judicial action under Sections 113 (b) (2), 

113 (b) (5), 113(c), or 167. Which enforcement option is selected depends on the facts of the 

particular situation. (See July 15, 1988 guidance on EPA Procedures for Addressing Deficient 

New Source Permits.) 

VII. Examples 

The following examples are provided to illustrate the type of permit restrictions which 

would and would not legally limit potential to emit to less than major source thresholds. These 

examples are provided for purposes of clarifying the potential to emit and averaging time 

guidance only. They are not intended to reflect all the permit conditions necessary for a valid 

permit. Specific test methods, compliance monitoring and recordkeeping and reporting 

requirements are necessary to make permit limitations enforceable as a practical matter. The use 

of examples where averaging times are the longest times allowed under EPA policies is not 

intended to necessarily condone the selection of the longest averaging times; averaging times 

should in practice be as short as possible. 
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1. The minor source construction permit for a boiler contains the following restrictions: 

250,000 gal fuel/month; 0.8% S fuel; 8000 hours/year. 

These conditions are federally enforceable production and operation limits, but do not 

limit potential to emit because one of them does not meet EPA policies on enforceability as a 

practical matter. The averaging time for hours of operation, one of the operational limits 

necessary to restrict emissions to less than 250 tpy, exceeds a monthly or rolling yearly limit. If, 

instead of 8000 hours/year, the hourly restriction were stated as 666 hours/month, the permit 

would serve to keep the source a minor source, assuming the permit contains appropriate 

recordkeeping provisions. 

2. A waferboard plant which has the physical capacity to emit over 300 tpy of carbon 

monoxide in the absence of using specific combustion techniques has the following permit 

restriction as the sole emission limitation: 249 tpy. 

This does not limit potential to emit since an operational or production restriction is 

necessary for the source to be restricted to 249 tpy. The permit must contain a restriction on 

hours of operation or capacity utilization which, when multiplied by the maximum emission rate 

for the CO sources at the plant, results in emissions of 249 tpy. Additionally, while the 
19

emission limit alone cannot restrict potential to emit, the emission limit is unenforceable as a 

practical matter since it is limited on an annual basis. The permit should contain a short term 

emission limit (in addition to the annual emission limit), consistent with the compliance period or 

parameter in the applicable test method for determining compliance. 

3. A small scale rock crushing plant that cannot emit more than 240 tpy under maximum 

operation without controls (including plant-wide particulate emissions from transfer and storage 

operations) has the following permit restriction as the sole emission limitation: 240 tpy 

particulate matter. 

Since no operational limitations are necessary for the source to emit below 250 tpy, no 

operational restrictions need be in the permit to limit potential to emit. However, although this is 

not a major source, the state agency should express the emission limit in this permit as a lb/hour 

measure or gr/dscf so that it will be enforceable as a practical matter. 

4. A plant consisting solely of a small rock crusher has the following permit restrictions: 

0.05 lb gr PM/dscf; fabric filter must be employed and maintained at 99% efficiency. 

Assuming that maintaining the fabric filter at 99% efficiency will result in 

emissions of less than 250 tpy, this permit would limit 
20

potential to emit if it also contained either 1) parameters that allowed the permitting agency to 

verify the fabric filter's operating efficiency or 2) a requirement to install and operate continuous 

opacity monitors (COMs) and a specification that COM data may be used to verify compliance 

with emission limits. Note that if this second alternative were adopted, it would not be necessary 

to require that the fabric filter be maintained at 99% efficiency. 

To determine potential to emit, the efficiency rate of the fabric filter would be multiplied 

by the maximum uncontrolled emission rate, the maximum number of operating hours and 

maximum throughput capacity since there are no other operating or production limits. However, 

the efficiency rate of the fabric filter would not be enforceable as a practical matter unless there 

were an enforceable means to monitor ESP performance on a short term basis. The two 

alternatives mentioned above would satisfy this requirement. 

5. A surface coating operation has the capability of utilizing 15,000 gal coating/month, 

with the following permit restrictions: 3.0 lb VOC/gal coating minus water; 20.5 tons 

VOC/month; monthly VOC emissions to be determined from records of the daily volumes of 

coatings used times the manufacturers specified VOC content. 
21

This does not limit potential to emit since the source has the physical capacity to exceed 

250 tpy of VOC, and the permit does not contain a production or an operational limitation. A 

monthly limit on gallons of coating used which when multiplied by 3.0 lb/gal equates to less than 

the 250 tpy threshold 13,500 gallons/month), with appropriate recordkeeping, would generally be 

necessary to limit potential to emit. If, however, the permitting agency determines, due to the 

wide variety of coatings employed and products produced, that restrictions on operation or 

production are not practically enforceable, then the above emission limits could restrict potential 

to emit if there are requirements that the source calculate emissions daily, and keep the 

appropriate records. 

If the source was alternatively to meet the 20.5 ton/month limit by employing add-on 

controls, the permit would need to contain an operational limit, such as the requirement to install 

and operate an incinerator at 99% efficiency. A requirement to monitor incinerator efficiency 

(either directly or indirectly via temperature monitoring for example), and appropriate 

recordkeeping retirements to verify compliance with each of the permit conditions would also be 

necessary to make the permit conditions enforceable as a practical matter. Note, however, that in 

the case where add-on controls are employed, the source may be able to meet a shorter term 

emission limit than the ton per month figure. 
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VIII. Conclusion 

We hope this guidance will help EPA Regions identify sources which have the potential to 

emit major amounts of an air pollutant which will subject those sources to the requirements of 

preconstruction new source review. Every source which is subject to these requirements but has 

not obtained a major new source permit should be seriously considered for enforcement 

action.