Twomile Ecological Restoration Project Air Quality Report Anna Payne, Mi-Wok District Fuels Specialists August 2011

Transcription

1 Twomile Ecological Restoration Project Air Quality Report Anna Payne, Mi-Wok District Fuels Specialists August 2011 The National Environmental Policy Act (NEPA), the Federal Clean Air Act, and California State Clean Air Act establish the regulatory framework for assessing air quality impacts from prescribed burning in California s national forests. The General Conformity Rule (established under the Clean Air Act (section 176(c)(4)), plays an important role in helping states improve air quality in those areas that do not meet the National Ambient Air Quality Standards (NAAQS). Forest Service managers consider two key elements of the Clean Air Act as they plan prescribed burning projects: conformity with National Ambient Air Quality Standards (table 4.1.1) and protecting air quality values in Class I Areas. The General Conformity rule established specific criteria and procedures for determining the conformity of planned federal projects and activities. In so doing, Environmental Protection Agency (EPA) chose to apply general conformity directly to nonattainment and maintenance areas only. A conformity determination is required for each pollutant where the total of direct and indirect emissions caused by an agency s actions would equal or exceed conformity de minimis levels (table 4.3.1), or are regionally significant. Regionally significant is defined as emissions representing 10 percent or more of the total emissions for the area.

2 Affected Environment The Twomile analysis area is located within Tuolumne County, California, which is contained within the Mountain County Air Basin (MCAB) and is classified as a Class 2 airshed, as described in the Clean Air Act. The Emigrant Wilderness is located approximately five miles east of the analysis area and is a Class 1 airshed that receives the most stringent protection from air quality degradation. Monitoring of visibility is currently being conducted in the Emigrant Wilderness with the use of cameras. Photos are then analyzed to produce a measure of visibility called Standard Visual Range (SVR). The last SVR in the Emigrant Wilderness was taken in 2004 and measured 86 miles (139 kilometers); essentially meaning that one can see objects such as mountaintops up to 86 miles away. Smoke from fires and pollution from the valley can reduce these SVR values temporarily. The current quality of the air over both the analysis area and the Wilderness areas is very good. Forest activities in the area do not contribute negatively to the air quality, except during periodic prescribed burning that occurs during the spring and fall months on the Summit and Mi-Wok Ranger Districts. Pollution from the San Joaquin Valley is known to obscure views during the summer months due to emissions from vehicles, industry, and farming related sources. The pollution works its way up to the Sierra Nevada Mountains by way of wind patterns. Wind patterns in the analysis area fluctuate on a diurnal and seasonal basis. The prevalent wind direction is generally from the southwest that would affect smoke dispersal within the analysis area. Based on monitoring data and comparisons to national ambient air quality standards, the Environmental Protection Agency (EPA) has categorized all counties within the state into either attainment/unclassified or non-attainment classifications. Tuolumne County is currently classified non-attainment moderate for ozone, unclassified for PM 10, and attainment for NOx and CO. Ozone is not emitted directly into the air but is formed through complex chemical reactions between precursor pollutants: volatile organic compounds (VOC) and nitrogen oxides (NOx). Carbon monoxide (CO) is a colorless, odorless gas, produced as a product of incomplete combustion. It is produced in the largest amounts during the smoldering stages of fire. Particulate matter (PM) means any airborne finely divided material, except uncombined water, which exists as a solid or liquid at standard conditions (e.g., dust, smoke, mist, fumes or smog). PM 10 means particles with an aerodynamic diameter less than or equal to a nominal 10 micrometers (including PM2.5).

3 Design elements for Alternatives 1 and 3 All prescribed burning will be in accordance with Title 17, Smoke Management Guidelines for Agricultural and Prescribed Burning, as required by the California Air Resources Board. Guidelines for reducing adverse effects of prescribed burns are termed Best Available Control Measures (BACMs) and are based on EPA s guidelines entitled Prescribed Burning Background Document and Technical Information Document for Prescribed Burning Best Available Control Measures. BACMs will be applied to ensure emission reductions. These include: 1. Attain lowest achievable emission rates by diluting or dispersing emissions. Obtain a site specific meteorological smoke forecast prior to and during prescribed burning through the Tuolumne Counties Air Pollution Control Districts (APCD). Burn when conditions are favorable for transport and dispersion. 2. Reduce the amount of pollutants per unit area. Reduce the amount of fuel to be consumed while burning by utilizing other fuel reduction methods such as biomass removal. Burn under conditions that will retain a portion of the ground fuels. 3. Spread the concentration of smoke emissions over time: Implement prescribed burning over multiple seasons (spring, fall, winter). Coordinate acres burned with Yosemite National Park, and other local fire agencies. Burning will be conducted under optimum meteorological conditions as required by the APCD. 4. Protect visibility in Federal Class I Airshed, Emigrant Wilderness. Burn under meteorological conditions that will transport and disperse emissions adequately reducing effects on visibility. In the appropriate fuel types, you can aim to burn only the fuels necessary to meet management objectives, which can be one of the most effective methods of reducing emissions. The removal of fine and intermediate diameter fuels may be sufficient and reduce emissions by limiting the consumption of larger fuels and the organic layer. The effects of prescribed burning on air quality would be minimized by monitoring, mitigation, and contingency measures identified in the Smoke Management Plan. Under air quality regulations, prescribed burning is usually considered a temporary, intermittent source of air pollution and therefore is not subject to the same visibility requirements as a major Prevention of Significant Deterioration (PSD) source. The Prescribed Fire Burn Plan will include a Smoke Management Plan that provides information on the estimated smoke emissions (particulate matter) projected for the prescribed burn and/or pile burn units. Desirable meteorological conditions such as favorable mixing layer and transport winds would be part of the Smoke Management Plan, to facilitate venting and dispersion of smoke. In discussing prescribed burning, the combustion process is divided into preheating, flaming, glowing, and smoldering phases. The different phases of combustion greatly affect the amount of emissions produced. The preheating phase seldom releases significant quantities of material to the atmosphere. Glowing combustion is usually associated with burning of large concentrations of woody fuels such as logging residue piles.

4 The smoldering combustion phase is a very inefficient and incomplete combustion process that emits pollutants at a much higher ratio to the quantity of fuel consumed than does the flaming combustion of similar materials. The amount of fuel consumed depends on the moisture content of the fuel. For most fuel types, consumption during the smoldering phase is greatest when the fuel is driest. When lower layers of the fuel are moist, the fire usually is extinguished rapidly. The major pollutants from wildland burning are particulate, carbon monoxide, and volatile organics. Particulate emissions depend on the mix of combustion phase, the rate of energy release, and the type of fuel consumed. Dependent on where and how prescribed fire treatments are being utilized, the fuel loading can range from 8 to 47 tons per acre and be in the form of machine or hand created piles and/or in concentrations across a broad area such as the case in understory burning. On average, the fuel loading for an area requiring prescribed fire as a primary treatment and/or post activity treatment would be tons/acre. The focus of prescribed fire implementation is to reduce surface fuel loadings that contribute to fire behavior rates of spread and flame length the greatest. These are the 1, 10 and 100 hour time lag categories (mainly needles, twigs and branches less than 3 inches in diameter). Prescribed fire burn plans set objectives for what percent consumption of these fuels are to be accomplished by the implementation of the prescribed fire. For pile burning, burn plan objectives typically set the objective at 80 to 90 percent consumption. Pile burning is conducted when the fuels have had a period to dry and are no longer green. For understory burning, burn plan objectives typically set the objectives at 60 to 70 percent consumption (or reduction) of these fuels. A typical understory burn is implemented to create a mosaic burn pattern, leaving patches of unburned areas amongst burned areas. A detailed emission calculation from AP-42 is located in appendix. Summary of criteria pollutants by alternative listed below (table 1). Alternative 1: Prescribed burn: acres, Pile burn: acres, for a total of 7,670 acres Alternative 2: Wildland fire: 1,857 acres Table 1: Criteria Pollutants Criteria Pollutant* (tons) Alternative 1 & 3 (tons) Alternative 2 (tons) Wildfire PM 10 Prescribed fire: Pile burn: CO Prescribed fire: Pile burn: NOx Prescribed fire: Pile burn: VOC Prescribed fire: Pile burn: * EPA, AP-42. January

5 Alternative 1 and 3 Direct Effects The treatments proposed in the Twomile project could affect air quality both locally and in the Class 1 airshed in the form of prescribed and pile burning emissions and from fugitive dust from roads and treatment activities during implementation. The proposed project would generate short-term smoke emissions suspended in the atmosphere from prescribed burning and fugitive dust (primarily from timber hauling activities and vehicular traffic). One of the goals of the district is to achieve and maintain all state and federal ambient air quality standards related to particulate matter through implementation of emission reducing measures. Based on the smoke management plan submitted by the Forest Service, that details the BACMs to be employed and the estimated tons of PM 10 that would be generated from the proposed burning, the APCDs determine how much burning can be conducted on any given day. This is expected to result in meeting the ambient air standards. Thinning and Biomass: Removal of approximately 40,000 green tons of biomass within the project area would remove fuel available to burn if a wildfire and/or prescribed fire occurs, reducing emissions. Fugitive dust caused by reconstruction and use of unpaved roads can produce PM 10 in quantities great enough to impair the visual quality of the air. These effects are localized and can be mitigated by effective dust abatement methods. Dust created by logging and hauling operations contributes to fugitive dust; however, the level contributed by these activities is minimal. Dust abatement measures for road construction and hauling would be used to mitigate fugitive dust effects during implementation of the proposed action. Indirect Effects Short-term adverse effects on public health related to air quality from broadcast burning and pile burning are a slight possibility and management requirements have been developed to mitigate these effects. These potential short-term effects are of limited scope and duration and have been minimized to the extent possible through timing of pile burning and use of mechanized fuel reduction methods. Treatment of fuels would reduce potential fuels available for consumption and resulting particulate emissions during future wildfire. Temporary and short-term visibility impacts can be expected in the immediate project area during actual ignition and would be affected by wind speed and direction. Drainage inversions will affect nighttime dispersal of smoke, with possible smoke effects 5 to 10 miles down canyon. Visibility is not expected to be negatively impacted in the wilderness areas due to distance and duration of proposed projects. Smoke from burning forest fuels can affect human health, particularly for the ground crews at the site. The localized effects of burning in the project area would be short-term degradation of air quality, primarily during the burnout stage and during nighttime canyon inversions.

6 If a wildfire event does occur after project implementation of the proposed action, concentrations of all smoke related emissions would be expected to be less than in the No Action alternative due to the reduced levels of fuel available. All burning activities are coordinated with the state and local air quality agencies to ensure that atmospheric stability and mixing heights are advantageous for dispersion of emissions. Therefore, although burning would contribute to cumulative effects, the effects are not expected to exceed state and local air quality standards. Cumulative Effects Additional emissions from operations on privately owned land and state lands are unknown but are assumed to comply with the state and federal rules and regulations pertaining to air quality, since the county air pollution control boards approve burn plans on both public and private lands. Staging of the burning over a five to ten-year period will ensure compliance with federally mandated annual threshold levels. Efforts to reduce PM 10 will be implemented due to the health threat and possible deterioration of visibility to Class I airshed. The effects of prescribed fire can be manipulated to reduce adverse effects to air quality. Following BACMs and identifying them in burn plans should prevent adverse air quality effects. There would be a cumulative increase in emissions from prescribed fire associated with this project and others on the Stanislaus National Forest, Yosemite National Park, and private lands within the area. Alternative 2 (No Action) The No Action alternative will not provide any opportunities to reduce existing fuel loads. There would be a decrease in cumulative emissions associated with prescribed fire on the Stanislaus National Forest, Yosemite, and adjacent private lands by not burning the proposed acres. There is a potential for degradation of air quality within the air basin from smoke produced by unplanned wildfire with pollutants from other sources. Direct Effects There would be no prescribed burning. Expected PM 10 resulting from wildfires would occur all at once, which could affect air quality. A 1,857-acre wildfire occurring at the 90 th percentile weather, with no treatment in the area could produce tons of emissions. These emissions would likely be occurring when smoke dispersion is not favorable, and could cause human health impacts. Indirect Effects Emissions of PM 10 would not be reduced in the advent of unwanted wildfires. There would be negative effects due to uncontrolled emissions in the advent of a wildfire. Cumulative Effects There would be a decrease in cumulative emissions associated with prescribed fire and an increased potential for degradation of air quality within the air basin from smoke produced by unwanted wildfire in combination with pollutants from other sources.

7 Summary Modeling a hypothetical fire using the average fire size for the project area of 1,857 acres and burning at the height of fire season has a potential to produce tons of PM 10 emissions. These particles pose the greatest health concern because they can pass through the nose and throat and get into the lungs) in a very short period, resulting in potential human health issues. With the reduction in fuel by burning under prescribed conditions proposed, the affect to air quality would be a reduction in potential PM 10 emissions spread over approximately 5-10 years and at a time when meteorological conditions are favorable for smoke dispersal. Future potential wildfire smoke emissions would be reduced. In terms of actual implementation, all treated units would be evaluated after treatment to determine if surface fuels were meeting desired conditions. The units meeting desired conditions may not be burned, thereby decreasing total burned acres and emissions. Wildfires typically burn at a time of year when smoke dispersion is not favorable. Short-term adverse effects on public health related to air quality from broadcast burning and pile burning are a small possibility and management requirements have been developed to reduce these effects. These potential short-term effects are of limited scope and duration and have been minimized to the extent possible through timing of pile burning and use of mechanized fuels reduction methods (shredding and/or biomass removal) in some cases. Treatment of fuels would reduce potential fuels available for consumption and resulting particulate emissions during future wildfire. PM10 Calculations are on the next three pages wildfire, Prescribed fire and pile burning. References EPA. AP-42, Compilation of Air Pollutant Emission Factors Volume I: Stationary Point and Area Sources. January 1995.

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