MEMORANDUM 

From: The Office of Air Quality Planning and Standards 

 U.S. Environmental Protection Agency 

To: Combustion Turbine NSPS Docket (EPA-HQ-OAR-2004-0490) 

Date: June, 2012 

Subject: Malfunction Affirmative Defense 

Malfunction Affirmative Defense 

Consistent with Sierra Club v, EPA, the EPA has proposed standards in this rule that apply at all times. 

In proposing the standards in this rule, the EPA has taken into account startup and shutdown periods 

and, for the reasons explained in this preamble, has proposed different standards for those periods. 

Periods of startup, normal operations and shutdown are all predictable and routine aspects of a source’s 

operations. However, by contrast, malfunction is defined as a “sudden, infrequent, and not reasonably 

preventable failure of air pollution control equipment, process equipment or a process to operate in a 

normal or usual manner * * *’’(40 CFR 60.2). The EPA has determined that Clean Air Act (CAA) 

section 111 does not require that emissions that occur during periods of malfunction be factored into 

development of CAA section 111 standards. 

Further, accounting for malfunctions would be difficult, if not impossible, given the myriad different 

types of malfunctions that can occur across all sources in the category and given the difficulties 

associated with predicting or accounting for the frequency, degree and duration of various malfunctions 

that might occur. As such, the performance of units that are malfunctioning is not “reasonably” 

foreseeable. See, e.g., Sierra Club v EPA, 167 F. 3d 658, 662 (D.C.Cir. 1999) (“[T]he EPA typically has 

wide latitude in determining the extent of data-gathering necessary to solve a problem. We generally 

defer to an agency's decision to proceed on the basis of imperfect scientific information, rather than to 

"invest the resources to conduct the perfect study."). See also, Weyerhaeuser v Costle, 590 F.2d 1011, 

1058 (D.C. Cir. 1978) (“ In the nature of things, no general standard, individual permit or even any upset 

provision can anticipate all upset situations. After a certain point, the transgression of regulatory limits 

caused by ‘uncontrollable acts of third parties,’ such as strikes, sabotage, operator intoxication or 

insanity and a variety of other eventualities, must be a matter for the administrative exercise of case-bycase enforcement discretion, not for specification in advance by regulation.”). In addition, accounting 

for malfunctions when setting standards of performance under section 111 which reflect the degree of 

emission limitation achievable through “the application of Best System of Emission Reduction” that the 

EPA determines is adequately demonstrated could lead to standards that are significantly less stringent 

than levels that are achieved by a well-performing non-malfunctioning source. The EPA’s approach to 

malfunctions is consistent with section 111 and is a reasonable interpretation of the statute. 

In the event that a source fails to comply with the applicable CAA section 111 standard as a result of a 

malfunction event, the EPA would determine an appropriate response based on, among other things, the 

good faith efforts of the source to minimize emissions during malfunction periods, including 

preventative and corrective actions, as well as root cause analyses to ascertain and rectify excess 

emissions. The EPA would also consider whether the source's failure to comply with the CAA section 

111 standard was, in fact, “sudden, infrequent, not reasonably preventable” and was not instead “caused 

in part by poor maintenance or careless operation.” 40 CFR §60.2 (definition of malfunction). 

Finally, the EPA recognizes that even equipment that is properly designed and maintained can 

sometimes fail and that such failure can sometimes cause a violation of the relevant emission standard. 
(See, e.g., State Implementation Plans: Policy Regarding Excessive Emissions During Malfunctions, 

Startup, and Shutdown (Sept. 20, 1999); Policy on Excess Emissions During Startup, Shutdown, 

Maintenance, and Malfunctions (Feb. 15, 1983)). The EPA is, therefore, proposing to add an affirmative 

defense to civil penalties for violations of emission standards that are caused by malfunctions. See 40 

CFR 60.4334 (defining “affirmative defense” to mean, 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.). We also have added other regulatory provisions to specify the elements that are necessary 

to establish this affirmative defense; the source must prove by a preponderance of the evidence that it 

has met all of the elements set forth in 60.4334. (See 40 CFR 22.24). The criteria ensure that the 

affirmative defense is available only where the event that causes a violation of the emission standard 

meets the narrow definition of malfunction in 40 CFR 60.2 (sudden, infrequent, not reasonable 

preventable and not caused by poor maintenance and or careless operation). For example, to successfully 

assert the affirmative defense, the source must prove by a preponderance of the evidence that the 

violation “[w]as caused by a sudden, infrequent, and unavoidable failure of air pollution control, process 

equipment or a process to operate in a normal or usual manner....” The criteria also are designed to 

ensure that steps are taken to correct the malfunction, to minimize emissions in accordance with section 

60.11 and to prevent future malfunctions. For example, the source must prove by a preponderance of the 

evidence that “[r]epairs were made as expeditiously as possible when a violation occurred...” and that 

“[a]ll possible steps were taken to minimize the impact of the violation on ambient air quality, the 

environment and human health....” In any judicial or administrative proceeding, the Administrator may 

challenge the assertion of the affirmative defense and, if the respondent has not met its burden of 

proving all of the requirements in the affirmative defense, appropriate penalties may be assessed in 

accordance with section 113 of the Clean Air Act (see also 40 CFR part 22.27). 

The EPA is proposing an affirmative defense in this rule in an attempt to balance a tension, inherent in 

many types of air regulation, to ensure adequate compliance while simultaneously recognizing that 

despite the most diligent of efforts, emission standards may be violated under circumstances beyond the 

control of the source. The EPA must establish emission standards that “limit the quantity, rate or 

concentration of emissions of air pollutants on a continuous basis.” 42 U.S.C. §7602(k) (defining 

“emission limitation and emission standard”). See generally Sierra Club v. EPA, 551 F.3d 1019, 1021 

(D.C. Cir. 2008) Thus, the EPA is required to ensure that section 111 emissions standards are 

continuous. The affirmative defense for malfunction events meets this requirement by ensuring that even 

where there is a malfunction, the emission standard is still enforceable through injunctive relief. While 

“continuous” standards, on the one hand, are required, there is also case law indicating that in many 

situations it is appropriate for the EPA to account for the practical realities of technology. For example, 

in Essex Chemical v. Ruckelshaus, 486 F.2d 427, 433 (D.C. Cir. 1973), the D.C. Circuit acknowledged 

that in setting standards under CAA section 111 “variant provisions” such as provisions allowing for 

upsets during startup, shutdown and equipment malfunction “appear necessary to preserve the 

reasonableness of the standards as a whole and that the record does not support the ‘never to be 

exceeded’ standard currently in force.” See also, Portland Cement Association v. Ruckelshaus, 486 F.2d 

375 (D.C.Cir. 1973). Though intervening case law such as Sierra Club v. EPA and the CAA 1977 

amendments call into question the relevance of these cases today, they support the EPA’s view that a 

system that incorporates some level of flexibility is reasonable. The affirmative defense simply provides 

for a defense to civil penalties for violations that are proven to be beyond the control of the source. By 

incorporating an affirmative defense, the EPA has formalized its approach to upset events. In a Clean 

Water Act setting, the Ninth Circuit required this type of formalized approach when regulating “upsets 

beyond the control of the permit holder.” Marathon Oil Co. v. EPA, 564 F.2d 1253, 1272-73 (9th Cir. 

1977). See also, Mont. Sulphur & Chem. Co. v. United States EPA, 2012 U.S. App. LEXIS 1056 (Jan 

19, 2012)(rejecting industry argument that reliance on the affirmative defense was not adequate). But 
see, Weyerhaeuser Co. v. Costle, 590 F.2d 1011, 1057-58 (D.C. Cir. 1978) (holding that an informal 

approach is adequate). The affirmative defense provisions give the EPA the flexibility to both ensure 

that its emission standards are “continuous” as required by 42 U.S.C. §7602(k), and account for 

unplanned upsets and thus support the reasonableness of the standard as a whole.