COMMENTS: Exceptional Events Proposal and Draft Guidance

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February 3, 2016

U.S. Environmental Protection Agency
EPA Docket Center
Docket No. EPA-HQ-OAR-2013-0572 and
Docket No. EPA-HQ-OAR-2015-0229
Mail Code 2821T
1200 Pennsylvania Avenue, NW
Washington, D.C. 20460

Dear Ms. Palma:

The Western Governors’ Association (WGA) appreciates the opportunity to comment on the Environmental Protection Agency’s (EPA) proposed rule, Treatment of Data Influenced by Exceptional Events (the Exceptional Events Proposal), promulgated under section 319(b) of the Clean Air Act (CAA), and the related Draft Guidance on the Preparation of Exceptional Events Demonstrations for Wildfire Events that May Influence Ozone Concentrations (the Draft Guidance), both published November 20, 2015 (80 FR 72839).


WGA represents the Governors of 19 western states and 3 U.S.-flag islands. The association is an instrument of the Governors for bipartisan policy development, information exchange and collective action on issues of critical importance to the western United States.

Western Governors recognize the critical importance of maintaining air quality in our states and the western region and appreciate the opportunity to work with EPA to achieve this. As stated in WGA Policy Resolution 2014-13: State Clean Air Act Authority and Air Quality Regulation, Western Governors believe EPA should engage states as co-regulators and should ensure state agencies and representatives have a robust voice and play a meaningful role in any EPA rule promulgated under the CAA.

Western Governors previously expressed concern that the 2007 iteration of the Treatment of Data Influenced by Exceptional Events rule (the 2007 Exceptional Events Rule) did not adequately address factors impacting air quality over which states have little or no control. Western Governors also requested that substantive consultation, as described in WGA Policy Resolution: 2014-09: Respecting State Authority and Expertise occur prior to publication of the Exceptional Events Proposal. (1)

Background of Western Governors’ Position

Under section 319 of the CAA, (2) the term “exceptional event” refers to either a natural event or an event caused by human activity that is unlikely to recur at a particular location. Exceptional events can affect air quality but are not reasonably controllable or preventable by states. Section 319 of the CAA further states, “EPA may exclude air monitoring data influenced by exceptional events from use in making designations” provided states establish certain criteria.

The exceptional events rule is intended to ensure a state is not required to submit a State Implementation Plan (SIP) to address monitored air quality data from sources over which states have little or no control. The current exceptional events submission process is lengthy, inconsistent and ambiguous. As a result states, out of practical necessity, address exceptional events in a SIP. Given time and resources needed to create or modify a SIP, an efficient, consistent exceptional event submission process is vital.

Western Governors support EPA’s effort to improve the exceptional events rule and submission process. A review of EPA’s proposal shows that, while the agency has taken state concerns into account in certain circumstances, there are several additional steps the agency should take to ensure states’ obligations are commensurate with regulatory authority delegated to states in the CAA.

EPA Change to “Clear Causal Relationship” Standard

The 2007 Exceptional Events Rule requires exceptional event submissions to establish that, “there would have been no exceedance or violation but for the event” (i.e., the “but for” standard). (3) It is extremely difficult to quantitatively establish that a particular exceptional event was the sole cause of a monitored National Ambient Air Quality Standard (NAAQS) exceedance.

Western Governors appreciate EPA’s proposed shift to a “clear causal relationship” standard and removal of the “but for” test. This change will bring directives of the exceptional events rule within the statutory requirements of CAA section 319(b). It will enable states to establish a clear causal relationship between a monitored NAAQS exceedance and an exceptional event. This standard will allow for reliable and consistent reviews.

EPA Effort to Streamline State Submission Processes

Western Governors support EPA’s effort to streamline the exceptional event submission process when circumstances surrounding an event are clear. EPA plans to codify certain fire-related definitions and exceptional event demonstration factors. While we raise some concerns in these comments, we hope EPA’s effort will help with a common understanding of relevant terms.

Western Governors agree with EPA’s proposed rebuttable presumption that every wildfire on wildland satisfies the “not reasonably controllable or preventable” criterion unless the record shows otherwise. (4) EPA’s inclusion of this proposed directive in section 5 of the Draft Guidance will help address longstanding concerns about the extraordinary commitment of resources required in an exceptional event submission.

Role of Past Occurrences in Exceptional Event Submission

The Western States Air Resources Council (WESTAR) has previously expressed concern to EPA (5) about the agency’s interpretation of the “not reasonably controllable or preventable” aspect of an exceptional event submission within the meaning of the 2007 Exceptional Events rule. It is WESTAR’s position – and that of Western Governors – that EPA’s past interpretation required a state to implement an undefined set of emission control or prevention measures in anticipation of uncontrollable events that may occur in the future. (6)

Section 319(b)(1)(A)(ii) of the CAA states an exceptional event, whether caused by natural phenomena or human activity, is one that is, “not reasonably controllable or preventable.” EPA’s past approach to the criterion, as described in section V(E)(2) of the proposal, has been:

  • An exceptional event must be ‘‘not reasonably controllable.” Under EPA’s interpretation, this means if a set of measures to reduce the magnitude and impact of event-related emissions should reasonably have been in place for emission sources that contribute to emissions, then those controls must have been in place; and
  • An exceptional event must also be “not reasonably preventable.” Under EPA’s interpretation, this means if a set of measures to stop or avert the event should reasonably have been in place (for human activity-caused sources), then those measures must have been in place for the event.

The Exceptional Events Proposal retains this interpretation and section 5 of the Draft Guidance incorporates this approach. This interpretation, as a pre-condition for approval of an exceptional event request, requires states to demonstrate to EPA’s satisfaction any state emission control or prevention measures that “reasonably” could have been in place at the time of the events were in place. This would require control measures in all areas that might experience dust events, wildfire events, or volcanic events. (7)

Natural emission sources in western states are often on federal land. Under EPA’s interpretation states would be required to take undefined emission reduction steps to account for future events that are both uncontrollable and unpredictable, but that also may occur under federal managers.

This approach creates a potential disadvantage for western areas in attainment with current NAAQS that are home to expanses of federal land. It could require state implementation of proactive emission control or prevention measures prior to event occurrence and prior to a finding of NAAQS non-attainment.

States should not be held accountable for determining on a prospective basis:

  • What control or prevention measures EPA or federal land managers (FLMs) would find “reasonable” under the exceptional events rule; or
  • What unforeseen and uncontrollable NAAQS pollutant emitting events may occur in the future.

EPA should consider relevant control measures included in recent non-attainment or maintenance SIPs as sufficient to meet the “not reasonably controllable or preventable” criterion. This concept should apply in attainment areas as well. (8)

Prescribed Fires, Wildfires and Deference to Fire Managers

State and local agencies are responsible for achieving or maintaining NAAQS attainment status. Consequently, Western Governors have concerns about substantive changes EPA proposes to address NAAQS impacts from wildfires. The changes could detrimentally affect state and local agencies by necessitating an exceptional event submission under the exceptional events rule. In particular, Western Governors are concerned about EPA’s proposed deference to a land management agency representative conducting prescribed fires to declare a prescribed fire a wildfire because a unilateral FLM decision to prescribe a fire, and later declare it a wildfire, would necessitate action – or additional action – by a state.

The proposed rule’s language regarding exceptional event submissions by FLMs exacerbates Western Governors’ concern. The proposed rule requires the FLM’s “discuss[ing] such submittal with the state” before submitting it to EPA. However, it does not require the FLM to integrate a state’s concerns into its submittal to EPA. Therefore, a FLM’s submittal to EPA could conflict with a state’s position. We also recommend that western states with existing, comprehensive state air quality regulatory programs should have the option of being the lead entity, instead of the EPA, for the receipt of exceptional event submissions from FLMs or from state land or fire managers.

Finally, Western Governors seek to clarify in the proposed rule on the application of definitions of wildfire (9) and wildland (10) to areas of the wildland urban interface (WUI). Wildfire can begin in a wildland area and progress through the WUI into suburban areas. Also, air pollution emissions originating in a wildland area can have subregional effects beyond the wildland area or WUI. The proposed rule should clearly state that in those cases, the entire fire progression is a natural event for the purposes of an exceptional event submission.


Western Governors appreciate those state concerns addressed in the Exceptional Events Proposal and Draft Guidance, including the “clear causal relationship” standard and EPA’s effort to better streamline the state exceptional event submission process. WGA continues to be concerned by the retention of “not reasonably controllable or preventable” criterion (and its interpretation) and the deference accorded by EPA to FLMs and federal fire managers. While it is Western Governors’ position that there is a vital need for a more active federal role in forest management, that role must respect state authority and not create unnecessary burdens on state or local regulators. Western Governors ask EPA to address these concerns before finalizing the Exceptional Events Proposal and Draft Guidance and to engage western states as partners to identify workable solutions for all parties involved.


Matthew H. Mead
Governor of Wyoming
Chairman, WGA

Steve Bullock
Governor of Montana
Vice Chair, WGA

(1) Prior related WGA communications are: March 17, 2015, comments to EPA on the proposed rule, National Ambient Air Quality (NAAQS) Standards for Ozone (79 FR 75233, December 17, 2014), and August 27, 2015, letter to EPA Administrator Gina McCarthy requesting substantive consultation with states on the then-expected revisions to the Treatment of Data Influenced by Exceptional Events rule.
(2) 42 U.S.C. § 7619 – Air Quality Monitoring.
(3) 40 C.F.R. 50.14(c)(3)(iv)(D).
(4) Section V(F)(2)(c)(ii) of the Exceptional Events Proposal.
(5) Public Hearing Testimony of Dan Johnson, Executive Director of WESTAR: Proposed Exceptional Events Revisions. Testimony given before the Environmental Protection Agency. December 8, 2015.
(6) Id.
(7) Section V(B)(1) of the Exceptional Events Proposal notes volcanoes are known to vent plumes of sulfur dioxide (SO2) as well as particulate matter (both PM2.5 and PM10) precursors.
(8) Id.
(9) EPA’s proposal would also revise the definition of a “natural event” so that an event with a mix of non-anthropogenic emissions and reasonably controlled human-affected emission sources may be considered a natural event. Section V(D)(2) of the Exceptional Events Proposal.
(10) Id. Section 1 of the Draft Guidance also incorporates relevant definitions, including the definition of “wildland” EPA plans to adopt.

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