UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

SEP 2 0 1999 

MEMORANDUM 

SUBJECT: State Implementation Plans: Policy Regarding Excess 

Emissions During Malfunctions, Startup, and Shutdown 

FROM : 

Assistant Adminis 

TO : Regional Administrators, Regions I - X 

EPA's policy for state implementation plans (SIPs) regarding 

excess emissions during malfunctions, startup, shutdown, and 

maintenance is contained in memoranda from Kathleen Bennett, 

formerly Assistant Administrator for Air, Noise and Radiation 

dated September 28, 1982 and February 15, 1983. A recent review 

of SIPs suggests that several contain provisions that appear to 

be inconsistent with this policy, either because they were 

inadvertently approved after EPA issued the 1982-1983 guidance or 

because they were part of the SIP at that time and have never 

been removed. In order to address these provisions in a 

consistent manner, today we are reaffirming and supplementing the 

1982-83 policy. In so doing, we are taking this opportunity to 

clarify several issues of interpretation that have arisen since 

that time. The attached updated policy will clarify the types of 

excess emissions provisions states may incorporate into SIPs so 

that they can in turn provide greater certainty to the regulated 

community. 

As EPA stated in its 1982 memorandum, because excess 

emissions might aggravate air quality so as to prevent attainment 

or interfere with maintenance of the ambient air quality 

standards, EPA views all excess emissions as violations of the 

applicable emission limitation. Nevertheless, EPA recognizes 
that imposition of a penalty for sudden and unavoidable 

malfunctions caused by circumstances entirely beyond the control 

of the owner or operator may not be appropriate. Accordingly, a 

state or EPA can exercise its "enforcement discretion" to refrain 

from taking an enforcement action in these circumstances. 

The main question of interpretation that has arisen 

regarding the old policy is whether a state may go beyond this 

"enforcement discretion" approach and include in its SIP a 

provision that would, in the context of an enforcement action for 

excess emissions,. excuse a source from penalties if the source 

can demonstrate that it meets certain objective criteria (an 

"affirmative defense"). This policy clarifies that states have 

the discretion to provide such a defense to actions for penalties 

brought for excess emissions that arise during certain 

malfunction, startup, and shutdown episodes. 

In the context of malfunctions, EPA recognizes that even 

equipment that is properly designed and maintained can sometimes 

fail. At the same time, EPA has a fundamental responsibility 

under the Clean Air Act to ensure that SIPS provide for 

attainment and maintenance of the national ambient air quality 

standards ("NAAQSU)and protection of PSD increments. Thus, EPA 

cannot approve an affirmative defense provision that would 

undermine the fundamental requirement of attainment and 

maintenance of the NAAQS, or any other requirement of the Clean 

Air Act. See sections 110(a) and (1) of the Clean Air Act, 42 

U.S.C. § 7410 (a) and (1) .l Accordingly, an acceptable 

affirmative defense provision may only apply to actions for 

penalties, but not to actions for injunctive relief. This 

restriction insures that both state and federal authorities 

remain able to protect air quality standards and PSD increments. 

Furthermore, this approach is appropriate only when the 

respective contributions of individual sources to pollutant 

concentrations in ambient air are such that no single source or 

small group of sources has the potential to cause an exceedance 

of the NAAQS or PSD increments.' Where a single source or small 

'pursuant to Section 110(1), EPA may not approve a SIP 

revision if "the revision would interfere with any applicable 

requirement concerning attainment and reasonable further 

progress, or any other applicable requirement of this chapter." 

See also CAA 5 193, 42 U.S.C. 5 7515, and the definitions of 

"emission limitation" and "emission standard" contained in CAA 

5 302 (k), 42 U.S.C. 5 7602 (k) . 

' In the case of lead and sulfur dioxide, attainment 

problems usually are caused by one or a few sources and an 
group of sources has the potential to cause an exceedance of the 

NAAQS or PSD increments, EPA believes an affirmative defense 

approach will not be adequate to protect public health and the 

environment, and the only appropriate means of dealing with 

excess emissions during malfunction, startup, and shutdown 

episodes is through an enforcement discretion appr~ach.~ 

EPA is also taking this opportunity to clarify that it does 

not intend to approve SIP revisions that would recognize a state 

director's decision to bar EPAfs or citizens' ability to enforce 

applicable requirements. Such an approach would be inconsistent 

with the regulatory scheme established in Title I of the Clean 

Air Act. EPA is also adding contemporaneous record keeping and 

notification criteria to make its policy regarding these types of 

events consistent with its enforcement approach. 

Finally, EPA is clarifying how excess emissions that occur 

during periods of startup and shutdown should be addressed. In 

general, because excess emissions that occur during these periods 

are reasonably foreseeable, they should not be excused. However, 

EPA recognizes that, for some source categories, even the best 

available emissions control systems might not be consistently 

effective during startup or shutdown periods. In areas where the 

respective contributions of individual sources to pollutant 

concentrations in ambient air are such that no single source or 

small group of sources has the potential to cause an exceedance 

of the NAAQS or PSD increments, these technological limitations 

may be addressed in the underlying standards themselves through 

narrowly-tailored SIP revisions that take into account the 

potential impacts on ambient air quality caused by the inclusion 

of these allowances. In these instances, as part of its 

justification of the SIP revision, the state should analyze the 

affirmative defense is not appropriate. This situation can be 

particularly aggravated where a short-term standard (e.g., where 

exceedances or violations are based on a few hour period) is also 

in place. Although this policy is generally applicable for other 

NAAQS, enforcement discretion is the only appropriate approach 

for dealing with excess emissions during startup, shutdown, and 

malfunction in a specific area where a single source or a small 

group of sources has the potential to cause nonattainment of a 

short-term NAAQS. 

3 In American Trucking Association v. EPA, 175 F. 3d 1027 

(D.C. Circ., 1999), the court remanded the PM2.5 NAAQS to the 

EPA. The Agency has not determined whether this policy is 

appropriate for PM2.5 NAAQS. 
impact of the potential worst-case emissions that could occur 

during startup and sh~tdown.~ 

In addition to this approach, states may address this problem 

through the use of enforcement discretion or they may include a 

general affirmative defense provision in their SIPs for short and 

infrequent startup and shutdown periods along the lines outlined 

in the attachment. As mentioned above, however, in those areas 

where a single source or small group of sources has the potential 

to cause an exceedance of the NAAQS or PSD increments, issues 

relating to excess emissions arising during startup and shutdown 

may only be addressed thqough an enforcement discretion approach. 

All Regions should review the SIPs for their states in light 

of this clarification and take steps to insure that excess 

emissions provisions in these SIPs are consistent with the 

attached guidance. 

Attachment 

4~tates may account for such emissions by including them in 

their routine rule effectiveness estimates. Rule effectiveness 

estimates may be prepared in accordance with an EPA policy 

document entitled "Guidelines for Estimating and Applying Rule 

Effectiveness for Ozone/Carbon Monoxide State Implementation Plan 

Base Year ~nventories." (EPA-452/R-92-010) November 1992. . . . . . . 
Attachment 

POLICY ON EXCESS EMISSIONS DURING MALFUNCTIONS, STARTUP, AND 

SHUTDOWN 

Introduction 

This policy specifies when and in what manner state 

implementation plans (SIPS) may provide' for defenses to 

violations caused by periods of excess emissions due to 

 malfunction^,^ startup, or shutdown, Generally, since SIPS must 

provide for attainment and maintenance of the national ambient 

air quality standards and the achievement of PSD increments, all 

periods of excess emissions must be considered violations. 

Accordingly, any provision that allows for an automatic 

exemption' for excess emissions is prohibited. 

However, the imposition of a penalty for excess emissions 

during malfunctions caused by circumstances entirely beyond the 

control of the owner or operator may not be appropriate. States 

may, therefore, as an exercise of their inherent enforcement 

discretion, choose not to penalize a source that has produced 

excess emissions under such circumstances. 

This policy provides an alternative approach to enforcement 

discretion for areas and pollutants where the respective 

contributions of individual sources to pollutant concentrations 

in ambient air are such that no single source or small group of 

sources has the potential to cause an exceedance of the NAAQS or 

PSD increments. Where a single source or small group of sources 

has the potential to cause an exceedance of the NAAQS or PSD 

increments, as is often the case for sulfur dioxide and lead,3 

EPA believes approaches other than enforcement discretion are not 

appropriate. In such cases, any excess emissions may have a 

significant chance of causing an exceedance or violation of the 

applicable standard or PSD increment. 

1 The term excess emission means an air emission level which 

exceeds any applicable emission limitation. Malfunction means a 

sudden and unavoidable' breakdown of process or control equipment. 

 he term automatic exemwtion means a generally applicable 

provision in a SIP that would provide that if certain conditions 

existed during a period of excess emissions, then those 

exceedances would not be considered violations. 

3 This policy also does not apply for purposes of PM2.5 

NAAQS. In American Trucking Association v. EPA, 175 F. 3d 1027 

(D.C. Circ., 1999), the court remanded the PM2.5 NAAQS to the 

EPA. The Agency has not determined whether this policy is 

appropriate for PM2.5 NAAQS. 
Except where 'a single source or small group of sources has 

the potential to cause an exceedance of the NAAQS or PSD 

increments, states may include in their SIPS affirmative 

defenses4 for excess emissions, as long as the SIP establishes 

limitations consistent with those set out below. If approved 

into a SIP, an affirmative defense would be available to sources 

in an enforcement action seeking penalties brought by the state, 

EPA, or citizens. However, a determination by the state not to 

take an enforcement action would not bar EPA or citizen acti~n.~ 

In addition, in certain limited circumstances, it may be 

appropriate for the state to build into a source-specific or 

source-category-specific emission standard a provision stating 

that the otherwise applicable emission limitations do not apply 

during narrowly defined star'tup and shutdown periods. 

I. AUTOMATIC EXEMPTIONS AND ENFORCEMENT DISCRETION 

If a SIP contains a provision addressing excess emissions, 

it cannot be the type that provides for automatic exemptions. 

Automatic exemptions might aggravate ambient air quality by 

excusing excess emissions that cause or contribute to a violation 

of an ambient air quality standard. Additional grounds for 

disapproving a SIP that includes the automatic exemption approach 

are discussed in more detail at 42 Fed. Reg. 58171 (November 8, 

1977) and 42 Fed. Reg. 21372 (April 27, 1977). As a result, EPA 

will not approve any SIP revisions that provide automatic 

exemptions for periods of excess emissions. 

The best assurance that excess emissions will not interfere 

with NAAQS attainment, maintenance, or increments is to address 

excess emissions through enforcement discretion. This policy 

provides alternative means for addressing excess emissions of 

criteria pollutants. However, this policy does not apply where a 

single source or small group of sources has the potential to 

cause an exceedance of the NAAQS or PSD increments. Moreover, 

4 The term affirmative defense means, in the context of an 

enforcement proceeding, a response or defense put forward by a 

defendant, regarding which the defendant has the burden of proof, 

and the merits of which are independently and objectively 

evaluated in a judicial or administrative proceeding. 

'~ecause all periods of excess emissions are violations and 

because affirmative defense provisions may not apply in actions 

for injunctive relief, under no circumstances would EPA consider 

periods of excess emissions, even if covered by an affirmative 

defense, to be "federally permitted releases" under EPCRA or 

CERCLA. 
nothing in this guidance should be construed as requiring states 

to include affirmative defense provisions in their SIPS. 

11. AFFIRMATIVE DEFENSES FOR MALFUNCTIONS 

EPA can approve a SIP revision that creates an affirmative 

defense to claims for penalties in enforcement actions regarding 

excess emissions caused by malfunctions as long as the defense 

does not apply to SIP provisions that derive from federally 

promulgated performance standards or emission limits, such as new 

source performance standards (NSPS) and national emissions 

standards for hazardous air pollutants (NESHAPS).6 In addition, 

affirmative defenses are not appropriate for areas and pollutants 

where a single source or small group of sources has the potential 

to cause an exceedance of the NAAQS or PSD increments. 

Furthermore, affirmative defenses to claims for injunctive relief 

are not allowed. To be approved, an affirmative defense 

provision must provide that the defendant has the burden of proof 

of demonstrating that: 

1. The excess emissions were caused by a sudden, 

unavoidable breakdown of techno10$~, beyond the control of the 

owner or operator; 

2. The excess emissions (a) did not stem from any activity 

or event that could have been foreseen and avoided, or planned 

for, and (b) could not have been avoided by better operation and 

maintenance practices; 

3. To the maximum extent practicable the air pollution 

control equipment or processes were maintained and operated in a 

manner consistent with good practice for minimizing emissions; 

4. Repairs were made in an expeditious fashion when the 

operator knew or should have known that applicable emission 

limitations were being exceeded. Off-shift labor and overtime 

must have been utilized, to the extent practicable, to ensure 

that such repairs were made as expeditiously as practicable; 

5. The amount and duration of the.excess emissions 

(including any bypass) were minimized to the maximum extent 

practicable during periods of such emissions; 

90 the extent a state includes NSPS or NESHAPS in its SIP, 

the standards should not deviate from those that were federally 

promulgated. Because EPA set these standards taking into account 

technological limitations, additional exemptions would be 

inappropriate. 
6. All possible steps were taken to minimize the impact of 

the excess emissions on ambient air quality; 

7. All emission monitoring systems were kept in operation 

if at all possible; 

8. The owner or operator's actions in response to the 

excess emissions were documented by properly signed, 

contemporaneous operating logs, or other relevant evidence; 

9. The excess emissions were not part of a recurring 

pattern indicative of inadequate design, operation, or 

maintenance; and 

10. The owner or operator properly and promptly notified 

the appropriate regulatory authority. 

EPA interpreFs these criteria narrowly. Only those 

malfunctions that are sudden, unavoidable, and unpredictable in 

nature qualify for the defense. For example, a single instance 

of a burst pipe that meets the above criteria may qualify under 

an affirmative defense. The defense would not be available, 

however, if the facility had a history of similar failures 

because of improper design, improper maintenance, or poor 

operating practices. Furthermore, a source must have taken all 

available measures to compensate for and resolve the malfunction. 

If a facility has a baghouse fire that leads to excess emissions, 

the affirmative defense would be appropriate only for the period 

of time necessary to modify or curtail operations to come into 

compliance. The fire should not be used to excuse excess 

emissions generated during an extended period of time while the 

operator orders and installs new bags, and relevant SIP language 

must limit applicability of the affirmative defense accordingly. 

111. EXCESS EMISSIONS DURING STARTUP AND SHUTDOWN 

In general, startup and shutdown of proc-ess equipment are 

part of the normal operation of a source and should be accounted 

for in the planning, design, and implementation of operating 

procedures for the process and control equipment. Accordingly, 

it is reasonable to expect that careful and prudent planning and 

design will eliminate violations of emission limitations during 

such periods. 

A. SOURCE CATEGORY SPECIFIC RULES FOR STARTUP AND SHUTDOWN 

For some source categories, given the types of control 

technologies available, there may exist short periods of 

emissions during startup and shutdown when, despite best efforts 

regarding planning, design, and operating procedures, the 
otherwise applicable emission limitation cannot be met. 

Accordingly, except in the case where a single source or small 

group of sources has the potential to cause an exceedance of the 

NAAQS or PSD increments, it may be appropriate, in consultation 

with EPA, to create narrowly-tailored SIP revisions that take 

these technological limitations into account and state that the 

otherwise applicable emissions limitations do not apply during 

narrowly defined startup and shutdown periods. To be approved, 

these revisions should meet the following requirements: 

1. The revision must be limited to specific, narrowlydefined source categories using specific control strategies 

(e-g., cogeneration facilities burning natural gas .and using 

selective catalytic reduction); 

2. Use of the control strategy for this source category 

must be technically infeasible during startup or shutdown 

periods; 

3. The frequency and duration of operation in startup or 

shutdown mode must be minimized to the maximum extent 

practicable; 

4. As part of its justification of the SIP revision, the 

state should analyze the potential worst-case emissions that 

could occur during startup and shutdown; 

5. All possible steps must be taken to minimize the impact 

of emissions during startup and shutdown on ambient air quality; 

6. At all times, the facility must be operated in a manner 

consistent with good practice for minimizing emissions, and the 

source must have used best efforts regarding planning, design, 

and operating procedures to meet the otherwise applicable 

emission limitation; and 

7. The owner or operator's actions during startup and 

shutdown periods must be documented by properly signed, 

contemporaneous operating logs, or other relevant evidence. 

B. GENERAL AFFIRMATIVE DEFENSE PROVISIONS RELATING TO 

STARTUP AND SHUTDOWN 

In addition to the approach outlined in Section II(A) above, 

states may address the problem of excess emissions occurring 

during startup and shutdown periods through an enforcement 

discretion approach. Further, except in the case where a single 

source or small group of sources has the potential to cause an 

exceedance of the NAAQS or PSD increments, states may also adopt 

for their SIPS an affirmative defense approach. Using this 
approach, all periods of excess emissions arising during startup 

and shutdown must be treated as violations, and the affirmative 

defense provision must not be available for claims for injunctive 

relief. Furthermore, to be approved, such a provision must 

provide that the defendant has the burden of proof of 

demonstrating that: 

1. The periods of excess emissions that occurred during 

startup and shutdown were short and infrequent and could not have 

been prevented through careful planning and design; 

2. The excess emissions were not part of a recurring 

pattern indicative of inadequate design, operation, or 

maintenance; 

3. If the excess emissions were caused by a bypass (an 

intentional diversion of control equipment), then the bypass was 

unavoidable to prevent loss of life, personal injury, or severe 

property damage; 

4. At all times, the facility was operated in a manner 

consistent with good practice for minimizing emissions; 

5. The frequency and duration of operation in startup or 

shutdown mode was minimized to the maximum extent practicable; 

6. All possible steps were taken to minimize the impact of 

the excess emissions on ambient air quality; 

7. All emission monitoring systems were kept in operation 

if at all possible; 

8. The owner or operator's actions during the period of 

excess emissions were documented by properly signed, 

contemporanecus operating logs, or other relevant evidence; and 

9. The owner or operator properly and promptly notified the 

appropriate regulatory authority. 

If excess emissions occur during routine startup or shutdown 

periods due to a malfunction, then those instances should be 

treated as other malfunctions that are subject to the malfunction 

provisions of this policy. (Reference Part I above).