EPA Example EE Categories

From Earth Science Information Partners (ESIP)

< Back to Exceptional Event Workspace

The content of this EE Categories page was partially copied form the EPA Exceptional Event Rule


Please use the Discussion page to comment on any aspects of this topic
Definitions according to EE Rule

(j) Exceptional event means an event that affects air quality, is not reasonably controllable or preventable, is an event caused by human activity that is unlikely to recur at a particular location or a natural event, and is determined by the Administrator in accordance with 40CFR 50.14 to be an exceptional event. It does not include stagnation of air masses or meteorological inversions, a meteorological event involving high temperatures or lack of precipitation, or air pollution relating to source noncompliance.

(k) Natural event means an event in which human activity plays little or no direct causal role.

(l) Exceedance with respect to a national ambient air quality standard means one occurrence of a measured or modeled concentration that exceeds the specified concentration level of such standard for the averaging period specified by the standard.

Exceedances Due to Transported Pollution

Transported pollution, whether national or international in origin, and whether from natural or anthropogenic sources, may cause exceedances eligible for exclusion under this rule, as long as all of the criteria and requirements related to exceptional events are met as defined in this rule.

Smoke from Fires outside the US

For example, States may flag, and EPA may exclude, data associated with fires occurring outside of the borders of the United States, such as forest fires in Mexico, Central America, and Canada;

Transported African, Asian Dust

Transport events such as African dust and Asian dust which contribute significantly to ambient concentrations of a pollutant in an area, leading to exceedances or violations of a NAAQS. An example of interstate transported emissions which may be flagged as due to an exceptional event would be emissions due to smoke from wildfires or wildland fire use fires which cause exceedances or violations of the NAAQS at monitoring sites in other States.

Transported Mining, Agricultural Emissions

Other examples could include data affected by emissions from mining and agricultural activities when such emissions are subjected to longrange transport, and the criteria and event are met as defined in this rule. In general, events due to transported pollution may be considered on a caseby-case basis.

Natural Events

The natural events addressed by this final rule are: (1) Natural disasters and associated cleanup activities; (2) volcanic and seismic activities; (3) high wind events; (4) wildfires and wildland fire use fires; and (5) stratospheric ozone intrusions. The EPA will consider other types of natural events on a case-by-case basis.

Natural Disasters and Associated Clean-Up Activities

For the purpose of flagging, major natural disasters such as hurricanes and tornadoes for which State, local, or Federal relief has been granted, and clean-up activities associated with these events, may be considered exceptional events. The EPA believes that for a major natural disaster, a timeframe up to 12 months is a reasonable time period to allow for clean-up activities associated with these types of activities. In cases where the damage caused by the event is so substantial that a 12- month period is inadequate to address the clean up that is necessary, a State may submit a request to EPA for an extension of the 12-month time period. The EPA will grant requests for extensions of the time period related to such events on a case-by-case basis if the States submit adequate supporting information concerning the reason for the extension as well as the length of time being requested for the extension.

Volcanic and Seismic Activities

Ambient concentrations of particulate matter for which volcanic or seismic activity caused or significantly contributed to high levels of particulate matter in an affected area will be treated as natural events. While generally not occurring frequently, volcanic and seismic activity can affect air quality data related to the particulate matter NAAQS for an extended period of time after an event. Volcanic activities can contribute to ambient concentrations in several ways: it may influence concentrations of particulate matter due to primary emissions (e.g., ash), and emissions of precursor pollutants (e.g., sulfur dioxide) that contribute to the secondary formation of particulate matter. Seismic activity (e.g., earthquakes) can also contribute to ambient particulate matter concentrations by shaking the ground, causing structures to collapse, and otherwise raising dust which may lead to exceedances or violations of the NAAQS.

High Wind Events

High wind events are events that affect ambient particulate matter concentrations through the raising of dust or through the re-entrainment of material that has been deposited. In some locations, concentrations of coarse particles like PM10 are most likely affected by these types of events, although PM2.5 standards may be exceeded under such circumstances as well. Section VII.B. also includes a discussion of this issue.‘‘high winds’’ with the term ‘‘windgenerated dust’’ because (1) it places the emphasis on the natural mechanism, (2) dust may become entrained at relatively low wind velocities, and (3) the change will eliminate confusion between the wind speeds associated with a natural event and wind speeds needed to qualify for a ‘‘high wind’’ exceptional event under EPA’s 1986 guidance. Response: The EPA is retaining the term ‘‘high wind’’ event because it accurately connotes the type of natural event that should be excluded under this rule, as well as the action which caused the exceedance or violation of the standard. The term also serves as an indicator concerning the level of wind which caused the exceedance or violation of the standard and indicates that it was unusually high for the affected area during the time period that the event occurred. Therefore, States must provide appropriate documentation to substantiate why the level of wind speed associated with the event in question should be considered unusual for the affected area during the time of year that the event occurred. The EPA will evaluate such instances on a case-by-case basis, including factors such as historically typical windspeed levels for the season of the year that the event is claimed.11

Wildland Fires

Federal land managers have afforded recognition to several different types of wildland fires (i.e., wildfire, wildland fire use fire and prescribed fire), depending on their causal circumstances and the role that such fires play in the affected ecosystems. Prescribed fire is addressed more fully in the following section. The question of what is a natural versus an anthropogenic fire has particular significance when considering the impacts of wildland fires (wildfire, wildland fire use fire and prescribed fire) on air quality and how these impacts should be regarded under this rule. A ‘‘wildfire’’ is defined as an unplanned, unwanted wildland fire (such as a fire caused by lightning), and include unauthorized human-caused fires (such as arson or acts of carelessness by campers), escaped prescribed fire projects (escaped control due to unforeseen circumstances), where the appropriate management response includes the objective to suppress the fire. In contrast, a ‘‘wildland fire use’’ fire is the application of the appropriate management response to a naturallyignited (e.g., as the result of lightning) wildland fire to accomplish specific resource management objectives in predefined and designated areas where fire is necessary and outlined in fire management or land management plans. Using these definitions, we believe that both wildfires and wildland fire use fires fall within the meaning of ‘‘natural events’’ as that term is used in section 319. Therefore, ambient particulate matter and ozone concentrations due to smoke from a wildland fire will be considered for treatment as an exceptional event if the fire is determined to be either a wildfire or wildland fire use fire.

Stratospheric Ozone Intrusions

Stratospheric ozone intrusion is considered to be a natural event. A stratospheric ozone intrusion occurs when a parcel of air originating in the stratosphere, which is at an average height of 20 km or 12.4 miles, is transported directly to the surface of the earth. Stratospheric ozone intrusions are very infrequent, localized events of short duration. They are typically associated with strong frontal passages and, thus, may occur primarily during the spring season.

Prescribed Fire

A ‘‘prescribed fire’’ is defined as any fire ignited by management actions to meet specific resource management objectives. According to existing Federal policy, prior to ignition a prescribed fire must have an approved prescribed fire plan and must meet the National Environmental Policy Act (NEPA) requirements (where applicable)(see National Wildland Fire Coordination Group Glossary of Wildland Fire Terminology, 2003). For purposes of section 319, a prescribed fire cannot be classified as ‘‘natural,’’ given the extent of the direct human causal connection, however, a prescribed fire may meet the statutory criteria defined in section 319 of ‘‘affect[ing] air quality,’’ being ‘‘unlikely to recur at a particular location’’ and is ‘‘not reasonably controllable or preventable.’’ The determination of whether a prescribed fire can be considered an exceptional event should be made on a case-by-case basis taking into account the factors described below. A prescribed fire carried out for resource management objectives is frequently designed to restore essential ecological processes of fire and mimic fire under natural conditions. As such, a prescribed fire’s expected frequency can vary widely, depending on the natural fire return interval of a particular landscape or wildland ecosystem. The natural fire return interval can range from once every year to less frequently than once in more than 200 years. Thus, in many, though not all cases, it may be possible to demonstrate that the likelihood of recurrence is sufficiently small enough to show that a prescribed fire under these conditions meets the ‘‘unlikely to recur at a particular location’’ requirement of the statutory language. A prescribed fire may also meet the condition of ‘‘not reasonably controllable or preventable’’ by examining whether there are reasonable alternatives to the use of fire in light of the needs and objectives to be served by it. For instance, there may be a significant build-up of forest fuels in a particular area that if left unaddressed would pose an unacceptable risk of catastrophic wildfire, which could result in adverse impacts of much greater magnitude, duration, and severity than would result from careful use of prescribed fire. A particular ecosystem may also be highly dependent on a natural fire return interval to maintain a sustainable natural species composition. Alternatively, pest or disease outbreaks in an area may be such that there are no reasonable alternatives to prescribed fire. In some cases, other legal requirements may preclude the use of mechanical fuel reduction methods such as in designated wilderness or National Parks. Where such ecological conditions exist, or where mechanical or other treatments are not reasonably feasible for reasons that include, but are not limited to, a lack of access, or severe topography, we believe that prescribed fire qualifies as being ‘‘not reasonably controllable or preventable.’’ Thus, we believe that a prescribed fire, conducted by Federal, State, Tribal or private wildland managers or owners, under the conditions described above may qualify as an exceptional event. In addition, one of the principles contained in SAFE–TEA–LU, section 6013(b)(3)(A), includes the principle that States must take necessary measures to safeguard public health regardless of the source of air pollution. We believe it reasonable to tie the qualifying criteria for an anthropogenically generated prescribed fire to State accountability for public health protection. Consistent with historical practice governed by the guidance contained in the ‘‘Interim Air Quality Policy on Wildland and Prescribed Fires,’’ issued on May 15, 1998, EPA approval of exceedances linked to a prescribed fire used for resource management purposes is contingent on the State certifying that it has adopted and is implementing a Smoke Management Program (SMP) as described in that policy. A State SMP establishes a basic framework of procedures and requirements for managing smoke from a prescribed fire managed for resource benefits. A SMP is typically developed by a State or Tribe with cooperation and participation by wildland managers, both public and private, and the general public. As reflected in the Interim Air Quality Policy on Wildland and Prescribed Fires, States are provided flexibility on the structure of a SMP. Thus, a SMP can be extensive and detailed, or simply identify the basic smoke management practices for minimizing emissions, and controlling impacts from a prescribed fire.12 In the proposal to this rule, EPA proposed to continue the use of that approach. We also proposed to expand the criteria for contingent approval to a prescribed fire where, in lieu of a SMP, basic smoke management practices, that minimize emissions and control impacts, are being employed by burners. In order to protect public health in areas where a SMP has not been adopted, in the final rule, the Agency has elected to expand, on a case-by-case basis, the qualifying criteria by which a prescribed fire may qualify as an exceptional event. In those cases, the Agency will judge on a case-by-case basis whether the State has ensured that appropriate basic smoke management practices have been employed in determining whether the prescribed fire qualifies as an exceptional event. If an exceptional event occurs using the basic smoke management practices approach, the State must undertake a review of their approach to ensure public health is being protected and must include consideration of development of a SMP.

Chemical Spills and Industrial Accidents

Structural Fires

Exceedances Due to a Terrorist Attack