California's sunny, mediterranean climate and the mountain ranges that form distinctive backdrops to the cities have made California an attractive place to live, resulting in growth that has made it most populated state in the nation. Unfortunately these three factors -- climate, geography and population-growth are also the major reasons for the state's worst air pollution. The mountain ranges that encircle the cities combine with layers of warm air in the upper atmosphere( a process known as temperature inversion) to create stagnant air masses. Population growth adds many sources of pollution. Sunlight triggers chemical reaction that turn invisible emissions into the familiar haze (impaired visibility) commonly known as "smog" and which results in many different air quality problems.

There are four major processes that effect air pollution (SPAM 1998):

1. Radiative Transfer
2. Atmospheric Transport and Dispersion
3. Chemical reactions
4. Hydrodynamics.

These fine particulates impair the visibilty of Class I areas. Visibility impairment results from both the scattering and absorption of light by particles and gases in the air. Fine particles (less than 2.5 micron in diameter-- PM_2.5) are especially efficient at scattering light. Fine elemental carbon particles (soot) and nitrogen dioxide gas are the typical absorbers of light . Scattering by "air" molecules (primarily oxygen and nitrogen with diameter less thn 0.0001 microns) causes the sky to appear blue and, in the absence of natural particlulates, sets the limit on the best possible visibility for a specific geographic region.

Polluted air coming from outside a forest can impact the forest flora or fauna or watershed. On the other hand forest activities can generate pollutants that can affect the forest or the area and communities outside the forest boundaries. To fully understand the affected environment it is important to know the regulatory framework. For this reason, the laws and regulations concerning air quality are described below first followed by existing air quality descriptions of the area.

Regulatory Framework and Meteorological Factors Related to Air Quality

Air quality is managed through a complex series of federal, state, and local laws and regulations. The Environmental Protection Agency (EPA) has the primary federal role of ensuring compliance with the requirements of the Clean Air Act. The EPA issues national air quality regulations, approves and oversees State Implementation Plans (SIPs), and conducts major enforcement actions. States and local Air Pollution Control Districts (APCDs) and Air Quality Management Districts (AQMDs)have the primary responsibility of carrying out the development and execution of State Implementation Plans (SIPs), which must provide for the attainment and maintenance of air quality standards.

The original Air Quality Act was passed in 1963. This act was followed by the Clean Air Act Amendments in 1970, 1977, and 1990. The Clean Air Act Amendments of 1970, Section 109, required the EPA to develop primary National Ambient Air Quality Standards to protect human health and secondary standards to protect welfare.

National Ambient Air Quality Standards (NAAQS)

To protect human health, the EPA established National Ambient Air Qualiy Standards (NAAQS) for the following six criteria pollutants:

Particulate Matter less than 10 microns in diameter (PM ₁₀),

Sulfur dioxide (SO₂),
Nitrogen dioxide (NO₂),
Ozone (O₃),
Carbon monoxide (CO), and
Lead (Pb).

The standards for these pollutants are shown in Table 1. If the standards are violated in an area, that area is designated as "nonattainment" for that pollutant, and the State must develop a plan for bringing that area back into "attainment."

1 Annual standards are never to be exceeded. Other standards are not to be exceeded more than once a year.
2 Arithmetic mean.
3 Geometric mean.

New Revised Standards

In July 1997, the EPA revised the existing national air quality standards for Ozone and particulate matter, and adopted a new standard for fine particles. The scientific review process determined that the ``old'' standards did not adequately protect public health. For ozone, longer- term exposures can cause significant health effects, including asthma attacks, breathing and respiratory problems, loss of lung function, and possible long-term lung damage and lowered disease immunity. For particulate matter, exposures to smaller sized particles (PM _2.5) can cause premature deaths, increased respiratory symptoms and disease ( especially for children and individuals with asthma), decreased lung function, and other serious respiratory problems. The new standards for particulate matter and Ozone are as follows:

Particulate Matter (PM_2.5 )

The standard for PM₁₀ remains essentially unchanged, while a new standard for PM_2.5 is set at an annual limit of 15 micrograms per cubic meter, with a 24-hour limit of 65 micrograms per cubic meter.

Ozone

For ozone, the final standard is updated from 0.12 parts per million of ozone measured over one hour to a standard of 0.08 parts per million measured over eight hours, with the average fourth highest concentration over a three-year period determining whether an area is out of compliance.

The EPA's new ozone standards provide significant health benefits, especially for children. The new standard will prevent approximately 1 million incidences per year of significant decreases in children's lung function that can limit a healthy child's activity or increase medical treatment for children.

Prevention of Significant Deterioration Program (PSD)

The Prevention of Significant Deterioration (PSD) program was established in 1978 as a result of a lawsuit alleging that the Clean Air Act Amendments of 1977 required that a program be established to prevent degradation of air quality of regions in attainment. The program requires permits for new air pollution sources above a certain size. The emission from these sources cannot cause deterioration of ambient air quality beyond certain increments (referred to as PSD increments ) . The PSD increments for NO₂, SO₂, and PM₁₀ were established for three classes of attainment areas: Class I and Class II as shown in table 2).

Class I areas include international parks, national parks larger than 6,000 acres, National Wildernesses greater than 5,000 acres, and National Wildlife Refuges in existence on August 7, 1977, when the amendments were signed into law. The Class I areas located in the affected area are:

1. Thousand Lakes Wilderness
2. Caribou Wilderness and
3. Lassen national park

(1) not violate national or state ambient air quality standards,
(2) use the best available control technology to limit emissions,
(3) not violate either Class I or Class II PSD increments for SO₂, NO₂, and PM₁₀ , and
(4) not cause or contribute to adverse impacts on Air Quality Related Values in any Class I area.

Class II and Class III areas are allowed respectively larger increments of deterioration. The Clean Air Act did not mandate Class III designations but allowed states the authority to petition for redesignation to Class III. No area of California has requested redesignation to Class III; therefore, all the remaining attainment areas in the affected forests are designated as Class II. States also have the authority to redesignate areas to Class I if they fit the established criteria.

Air Quality Related Values

The 1977 Clean Air Act amendments gave federal land managers an "afirmative responsibility" to protect the Air Quality Related Values (AQRVs) of Class I areas from adverse air pollution impacts. AQRVs, as defined by Congress, include "the fundamental purposes for which Class I areas have been established and preserved by the Congress and the responsible federal agency" (Senate Report 95-127, p. 36). AQRVs are also those features or properties of a Class I area that can be changed by air pollution. A detailed discussion of AQRVs and sensitive indicators of pollution established on National Forests in the Pacific Southwest Region can be found in Peterson et al. (1992).

In April 1997 FLAG ( Federal Land Managers' Air Quality Related Values Work Group) was formed to develop a national document. The main objective was "to achieve greater consistency in the procedures each agency uses in identifying and evaluating AQRVs". The main items are:

· Define sensitive AQRVs
· Identify the critical loads or levels and the criteria that defines adverse impacts
· Standardize the methods and procedures for conducting AQRV analysis.

1. Terrestrial effects of Ozone
2. Aquatic and terrestrial effects of wet and dry pollutant deposition
3. Visibility
4. Process and Policy issues

Table 3 gives examples of AQRVs, sensitive receptors of pollution, and factors potentially changed by air pollutants. Among the sensitive receptors of air pollution, lichens and ponderosa pine are moderately studied. One of the ozone injury studies to ponderosa pine (Project Forest) plots is located in Lassen National Park.

Visibility as an AQRV

Visibility is an AQRV that is protected for all Class I areas. Congress established as a National goal "the prevention of any future and remedying of any existing impairment of visibility in mandatory Class I Federal areas where impairment results from man made air pollution."

Visibility conditions are affected by scattering and absorption of light by particles and gases. The fine particles most responsible for visibility impairment are sulfates, nitrates, organic compounds, soot, and soil dust. Fine particles are more efficient per unit mass than coarse particles at scattering light. Light scattering efficiencies also go up as humidity rises, due to water absorption on fine particles, which allows the particles to grow to sizes comparable to the wavelength of light. There are distinct regional variations in visibility between eastern and western states, due to generally higher relative humidities in the East. Naturally occurring visual ranges in the East may be between 105 to 190 kilometers, while natural visual ranges in the West are between 190 to 270 kilometers.

Visibility is an important public welfare consideration because of its significance to enjoyment of daily activities in all parts of the country. Visibility may be thought of as the atmosphere's tran11sparency to visible light (National Researcch Council 1993) and may be expressed in terms of :

· Visual Range - or the greatest distance at which a large black object can be distinguished against the horizon.
· Light Extinction -or the fraction of light attenuated by scattering or absorption over a given unit of the atmosphere (Visibility decreases as light extinction increases)
· Haziness Index - which is expressed in deciview (dv). The dv index increases from zero (representing pristine conditions) as visibility degrades.

IMPROVE Network

Because most visibility degradation is from fine particulate matter, the EPA initiated continuous size-selective monitoring and elemental analysis of particles in 1977. This was replaced by the Interagency Monitoring of Protected Visual Environmental (IMPROVE) program. The National Park Service started the IMPROVE program as a coopertative effort with three other federal land management agencies (U.S. Forest Service, U.S. Fish and Wildlife Service, and Bureau of Land Management) and the EPA to monitor visibility at selected Class I areas. Data analysis in these areas is conducted by the University of California, Davis. Figure 2 shows IMPROVE sites within the Affected area.

The sampling and analytical protocols of IMPROVE are designed to meet the needs of the visibility studies. They must thus perform two functions that are quite independent: (1) determine fine particulate mass and all its major constituents, which, together, degrade visibility, and (2) determine element tracers to aid in establishihng the sources of the particles, natural and human-made, that degrade visibility. Hence, the purpose of the IMPROVE program is to provide a baseline of aerosol data to help identify possible sources of pollution. The standard protocol is to collect 24-hour samples, twice a week (Wednesday and Saturday). All major fine aerosol components and PM10 mass are measured, including several redundant measurements for quality assurance.

Existing requirements to consider effects on visibility which are reasonably attributable to a single nearby source or small number of sources are contained in the regulations published by EPA in 1980 at 40 CFR 51.300 (Protection of Visibility). Additional regulations (Regional Haze) are currently being finalized to address impairment of visibility that is more regional in its character and origins.

Regional Haze Program

The Preliminary Haze Program was released by the EPA on July 18, 1997 for public review. The final rules were released on April 22, 1999. Regional Haze is a revision to 1980 visibility regulations protecting class I areas.

Regional Haze rules sets the framework for each state. It sets criteria for measuring reasonable progress and provides flexibility for implementation. At present visibility impairment rules apply to the states with class I areas. The new rules apply to the states which `` may reasonably be anticipated to cause or contribute to any impairment of visibility'' in any class I area. Therefore interstate pollutants transport is fully addressed. Regional Progress Targets are established under the rules. Targets seek to improve the worst visibility days and maintain the best visibility days by implementing the following:

1. For the worst 20% of days, states will show one deciview improvement only 10 to 15 years
2. For the best 20% of days, states will not allow any degradation

The present IMPROVE network will be expanded to accomodate the new haze rules. The rule requires states, in consultation with federal land managers, to determine additional sites needed such that the monitoring network is ``representative'' of all Class I areas. If targets are not being achieved, each state contributing to impairment at the Class I area must check emission reductions achieved through its SIP. The state may coordinate with other pollutant contributing states for development of new measures.

Under the new rules the states are supposed to issue a visibility SIP. Each Class I area or its representative will be monitored from 2000 to 2004. The IMPROVE site at Lassen National park will represent Caribou and Thousand Lakes Class I areas. This will provide the baseline data for visibility. By the year 2060 the state will be required to achieve the visibility level to its natural background (which the state must presently identify).

INTERIM AIR QUALITY POLICY ON WILDLAND AND PRESCRIBED FIRES

The EPA on April 23, 1998 issued an Interim Air Quality Policy on Wildland and Prescribed Fires. The policy stresses collaboration of owners/managers of public, private and Indian wildlands with state/tribal air quality managers/air regulators to achieve their goals of :

1. allowing fire to function in its natural role in the wildlands
2. protecting public health and welfare

This is an interim policy for two reasons:

1. The EPA is expecting recommendations on how to treat air quality impacts from agricultural burning from the USDA's Air Quality Air Task Force.
2. The EPA will soon formulate the Regional Haze Rule. The impact of wildland and prescribed fires on regional haze can only be finalized then.

1. to miligate the nuisance and public safety hazard (e.g. on roadways and airports, posed by smoke intrusions into populated areas)
2. to prevent deterioration of air quality and NAAQS violations
3. to address visibility impacts in mandatory class I federal areas

A. Authorization to burn
B. Minimizing Air Pollutant Emissions
C. Smoke Management Components of Burn Plans
D. Public Education and Awareness
E. Surveillance and Enforcement
F. Program Evaluation

Section 190 of the Clean Air Act required the EPA to issue technical guidance on Reasonably Available Control Measures (RACMs) and Best Available Control Measures ( BACMs) for prescribed silvicultural and agricultural burning. RACMs or BACMs can be used as mitigation measures. Some examples of mitigation measures are:

1. annual burn plans,
2. emissions inventory systems,
3. daily burn planning/authorization and administration programs,
4.smoke dispersion evaluation processes etc,

The 1990 amendments to the Clean Air Act include a list of 189 pollutants identfied as hazardous to human health. These pollutants are known to, or have the potential to, cause cancer, mutations, be toxic to nervous tissue, or cause reproductive dysfunction. Some of these air pollutants are emitted during forest fires, but they are not emitted in significant amounts and are not considered at this level of planning. Atmospheric transport of pesticides from California's Central Valley to the Sierra Nevada forests has been verified. The impacts of these pesticides to water quality and aquatic or terrestrial systems is not fully understood.

State Implementation Plans

Section 110 of the Clean Air Act requires states to develop State Implementation Plans (SIPs) that identify how the state will attain and maintain National Ambient Air Quality Standards and other federal air quality regulations. For all nonattainment areas, the state must demonstrate when and how these areas will be able to maintain National Ambient Air Quality Standards. How these areas will attain the standards is often based on the state's controls on new or existing air pollution sources. Controls can include more stringent pollution control requirements for industry, tighter requirements on wood-burning stoves or prescribed burning, or more stringent controls on mobile sources of emissions. States also have the authority to include air quality standards and regulations more stringent than federal standards and regulations. The Forest Service is required to comply with all of the requirements of a SIP.

California Clean Air Act

The California Clean Air Act of 1988 is administered by the California Air Resources Board. It added several requirements concerning plans and control measures to attain and maintain the State ambient air quality standards. One such requirement is for the board to establish designation criteria and to designate areas of the state as attainment, nonattainment, or unclassified for any state standards. Table 1 shows the state and national standards for six criteria pollutants. California has also established ambient air quality standards for sulfate, hydrogen sulfide, vinyl chloride, and visibility-reducing particles.

States have direct responsibility for meeting requirements of the Federal Clean Air Act and corresponding Federal regulations. As authorized by Division 26 of the California Health and Safety Code, California (i.e., the California Air Resources Board) is directly responsible for regulating emissions from mobile sources. However, authority to regulate stationary sources has been delegated to Air Pollution Control and Air Quality Management Districts (APCD or AQMD) at the county and regional levels. The state still has oversight authority to monitor the performance of district programs and can even assume authority to monitor the performance of district programs. It can even assume authority to conduct district functions if the district fails to meet certain responsibilities.

Many air pollution control and air quality management districts have not received delegation from the federal government for the Prevention of Significant Deterioration (PSD) Program. In California, districts that have received delegation and, therefore, have regulatory control are the Bay Area Air Quality Management District, Mendocino County Air Pollution Control District, Monterey Bay Unified Air Pollution Control District, North Coast Unified Air Quality Management District, Northern Sonoma County Air Pollution Control District, Sacramento County Air Pollution Control District, San Diego County Air Pollution Control District, Santa Barbara County Air Pollution Control District, and Shasta County Air Pollution Control District. Where districts have not been delegated, the PSD program is administered by the U.S. Environmental Protection Agency.

Title 17 Revision

The CARB issued Title 17 draft guidelines for updating California's prescribed burning regulations on August 10, 1998 with the following two objectives:

1. To accomodate large increases in prescribed burning without unacceptable increases in air quality.
2. To define a workable management plan for California's smoke management by working with all affected parties- local air districts, land management agencies, private industry and the public.

1. Annual Registration for Prescribed Burns
2. Burn Plans to contain pertinent information
3. Burn Requests and Authorization
4. Smoke Dispersion Evaluation
5. Burn Accomplishment - Record Keeping
6. Wildland Fires Plans; Authorization; Monitoring and Interagency Consultation
7. Emission Reduction Techniques e.g. BMPs
8. Monitoring
9. Burner Qualification
10. Public Awareness Program
11. Surveillance and Enforcement
12. Oversight
13. Forms; Electronic copies; Information Transfers

Nevada Smoke Management Plan

The state of Nevada issued on August 21,1998 a similar draft to Title 17 in California. The comments are being solicited. The purpose of this plan is to coordinate and facilitate the statewide regulation of prescribed outdoor burning on lands in the state of Nevada. This plan is designed to meet the requirements of NRS445B.100 through 445B.845, inclusive which deals with air pollution, and the requirements of the EPA Interim Air Quality Policy on Wildland and Prescribed Fires.

· The major goals identified in the plan are:
· Protect human health and safety from the effects of outdoor burning
· Facilitate the enjoyment of the natural attractions of the state
· Keep the resident of the state informed
· Provide the opportunity for essential forest and range land burning while minimizing emissions
· Foster and encourage the development of reasonable alternative methods for disposing of or reducing the amount of organic refuse on lands in Nevada
· Acknowledge the role of fire in Nevada and allow the use of fire under controlled conditions to maintain healthy ecosystems while meeting the requirements of the Clean Air Act

North East Air and Smoke Alliance

The agencies (USFS, NPS, BLM, CDF ) and the private timber companies involved in the use of prescribed fire, in the counties of Lassen, Plumas, Sierra, Modoc, Tehama and Yuba and the respective APCDs have formed an alliance. The purpose is to achieve the prescribed fire objectives and maintain levels of air quality which will protect human health and welfare. The group meets quarterly and share the pertinent information about the burns and develop strategies to resolve air and smoke issues.

PRESCRIBED FIRE INCIDENT REPORTING SYSTEMS (PFIRS)

The Interagency Air and Smoke Council (IASC) has cooperatively developed a Prescribed Fire Incident Reporting System that will track prescribed fires in the state. The burn agency will enter all the pertinent information about the burn project. The local regulatory agency will be able to access the burn information and issue ``go'' ``no go'' authorization. The server is located at Mather, Aviation Office of US Forest Service. The system will be operational by the end of 1999.

The Sierra Nevada Conservation Framework EIS will discuss other air issue like ozone injury, nitrogen deposition, acid deposition, pesticide transport and deposition. Only the particulate emission originating from wildland fires and their impacts are discussed here. The new revised PM_2.5 standards, updated Title 17 and Nevada Smoke Plan would put additional pressure on mountain counties and urban communities to control winter wood burning smoke. Continued monitoring , data tracking will provide opportunity for reduction of emission through other alternative application like biomass, mechanical and chemical treatment.

Meteorological Factors Related to Air Quality

Weather patterns strongly influence air quality and smoke management by controlling the dispersion of emissions from fires. The primary weather conditions that affect dispersion are atmospheric stability, mixing height, and transport wind speed. Atmospheric stability refers to the tendency for air to mix vertically through the atmosphere. Mixing height is the vertical distance through which air is able to mix. The transport wind speed is a measure of the ability to carry emissions away from a source horizontally. These three factors determine the ability of the atmosphere to disperse and dilute emissions that are released from prescribed fires and wildfires.

The physical shape of landscapes interacts with and controls some weather patterns that influence emission dispersion. On a local or regional basis, the air flow in California is channeled by mountain ranges. The predominant wind direction in a valley is parallel to the valley's longitudinal axis in one direction, and the second most prevalent wind direction is in the opposite direction.

The coastal mountain ranges limit the accessible routes for marine air to move to the interior of California, and accessible routes are limited to breaks or low points in the coastal range. The principal break occurs in the San Francisco Bay Area (Carquinez Straits), and the greatest part of the marine air reaching the Central alley of California traverses this area (California Air Resources Board, Aerometric Data Division, February 1994).

During the winter, wind occasionally originates from the south and flows in a north-northwesterly direction. The valleys experience light, variable winds of less than 10 miles per hour. Low wind speeds, combined with low inversion layers in the winter, create a climate conductive to high PM10 concentrations.

During the summer, winds usually originate in the north and flow in a south-southeasterly direction.

It is not uncommon for wind speeds and directions to change throughout the day. During the day, north-northwesterly winds prevail. However, in the late evening through early morning hours, wind flow is affected by cooler drainage winds from the surrounding mountains, and wind direction changes to a south-southwesterly flow.

The major large scale meterological feature occuring in spring is movement of the Pacific High to the north, which shifts the tracks of storms; precipitation therefore declines. However spring weather is rarely warm and dry. Significant precipitation continues and temperatures remain cool throughout the spring. A common occurrence during the spring months is the incursion of cold unstable air from the North Pacific causing brief periods of intense rain and often accompanied by thunderstorms. During summer climate becomes dry and temperature increases. The fall is typically a transition period between dry summer and wet winter conditions. Generally weather conditions are dominated by clear cool days with temperature at night falling to almost below freezing.

Weather systems are generally accompanied by good dispersion conditions (i.e. strong winds and unstable air mass). During fair weather periods the atmosphere stabilizes and wind speeds are reduced. The terrain induced features (i.e. valleys, canyons) could produce local stagnation and trapping of pollutants.

Prescribed burning is conducted when transport winds are not expected to carry emissions to designated areas in quantities that affect prevention of Significant Deterioration increments and visibility. State law requires the regulation of prescribed burns. Prescribed burning activities are coordinated with the states and local air quality agencies to ensure that atmospheric stability and mixing heights are advantageous for dispersion of emissions. The state board declares a Permissive Burn Day when expected weather conditions will provide enough ventilation to disperse the smoke pollutants. Daily agricultural burning control decisions are issued for fourteen air basins.

Table 4 shows the air basins and air pollution control districts associated with each Affected Forest and each affected county. The three air basins in the analysis area are the Northest Plateau, Sacramento Valley and Mountain Counties. All local air pollution control districts are responsible for controlling acreages and placement of prescribed burns in their districts.

Air quality in the analysis area

State and federal agencies have established ambient air quality standards for various pollutants. If the permissible levels of a particular pollutant are not exceeded in an area, the area is said to be in "attainment" for that pollutant; if the standards are violated, the area is designated as "non-attainment.". Table 5 shows the designation for the area counties.

Table below gives existing emissionsof Total Organic Gases (TOG), Reactive Organic Gases ( ROG), Carbon Monoxide (CO), Nitrogen Oxides (NO), Sulfur Oxides (SO) and Particulates smaller than ten microns (PM₁₀)

Emissions from Fires in the Affected Forests

Forest activities that generate air pollutants include timber sales, road construction, site preparation, mining, and prescribed burns. Although activities other than prescribed burns and wildfires can contribute significant amounts of air pollutants at a local level, at the scale of analysis in this EIS, the contribution of these other activities to air pollution is insignificant.

Prescribed burning is a diverse, dynamic source of air pollution, representing hundreds of individual fires annually in California. Individual fires vary in size from a few acres to several thousand acres. The affected forests vary greatly in the number of acres burned, the type of material or vegetation burned, and when that burning occurs. No two situations are exactly alike in terms of the factors that control the mass of pollutants emitted during prescribed burning.

Prescribed fires followed pretreated acres. The fuel loading amounted to 10 tons per acre (personal communication with the forest). Percent combustion was assumed to be sixty. For wildfire acres, it was assumed that fire went through untreated acres. Fuel loading was assumed to be 35 tons per acre and eighty percent of the fuel was consumed.

Prescribed burning on the affected forests was analyzed for 1993 through 1998. Trends in the use of prescribed fire for this period were representative of recent forest management practices, and data quality was reasonably good during this period. Information regarding fuel consumed (in tons) by burning was more difficult to obtain, therefore estimates were made based on average fuel consumption data from the literature and expert opinion. The emission tables given in the R-5 Conformity Handbook (approved by EPA Region IX) were utilized to calculate PM _10.

Prescribed burning during the 1980s was generally used to dispose of debris left over from timber harvests (usually called ``slash burning'') and to reduce moisture stress and growing-space competition on trees from other vegetation. Slash burning was used to reduce wildfire hazard and to prepare harvested sites for planting. After the 1990s the acres requiring prescribed fire for slash burning and site preparation decreased due to decreased timber harvest.

The impact of prescribed burning on air quality from 1993 to 1998 is difficult to quantify. The burning of logging debris can create large quantities of particulate matter and other pollutants. This burning usually takes place, however, in relatively remote areas with intensities that vent smoke high into the atmosphere, where it is widely dispersed.

PM₁₀ emissions from wildfire on the Primary Forests from 1993-1998 are shown in table 8 by each county. The wildfires emit high amount of emissions per acre as compared to prescribed fires.

Visibility in Class I Areas

Visibility conditions in the Sierra Nevadas improve from south to north and also from low elevation to high elevations. Visibility conditions at Lassen Volcanic national park, the most northerly and highest Class I area in the Sierra Nevadas are among the cleanest measured nation wide, while Sequioa National Park , one of the southernmost and lowest , experiences some of the worst visibility conditions for a western U.S. Class I area.

Lassen National park is the site for the IMPROVE network and will represent Caribou and Thousand Lake Class I areas. The major aerosols contributing to visibility impairment are sulfate, nitrate, organic, elemntal carbon and particulates. Table 9 shows the aerosol concentration.

The data analyzed in the IMPROVE report is an average of data from Crater lake and Lassen Park. Both sites are very similar. The report names this region as "Humboldt Mountain Ranges". . For this region, total reconstructed light extinction averaged 31.6 Mm ^-1 with maximum extinction in summer (37.6 Mm ^-1 ) and minimum extinction in winter (23.2 Mm ^-1). The seasonality is primarily variations from sulfate and organic extinctions and absorption. Organic carbon, sulfate, and elemental carbon contribute almost equally to annual extinction at 29.4%, 27.3% and 23.2%, respectively.

The best visibility in the West occurs during the winter with a minimum deciview (dv) of 7 being reported at Bridger Wilderness followed by 8 dv at Jarbridge and Lassen. The region of 10 or less dv's encompasses a broad expanse that covers the Sierra-Humboldt, Sierra Nevada, Great Basin, Central Rockies, and the northwestern half of the Colorado Plateau.

Fine aerosols are the most effective in scattered light and are the major contributors to light extinction. In most cases, the sulfate component of fine aerosol is the largest single contributor to light extinction. This is because sulfate, being hygroscopic, generally has a higher light extinction efficiency than other species due to associated liquid water. This is especially true in the eastern United States. Organics are the major source for the Class I areas.

Environmental Consequences

Estimates of the expected annual acreage of prescribed fire, wildfire, and mechanical removal of fuels were calculated for the Affected Counties for each of the alternatives. Assumptions regarding the ecological need for prescribed burning, the hazard reduction that might be necessary for site preparation were made at a programmatic level. These estimates are very generalized because many assumptions for each alternative within each county can be validated only with watershed and landscape-level analysis.

A description of the dominant forest vegetation type was assumed based on field experience of forest personnel for each of the prescribed and wildfires from 1993 to 1998. Forest area descriptions were used to assign preburn fuel loadings based on standardized values available from the natural photo series. Fuel loadings were estimated for areas where natural fuels dominated and where activity-generated fuels dominated. Activity generated fuels may originate from timber harvest or thinning activities, and they may be left in place or concentrated into piles before burning. Fuel loading was estimated in two categories, woody fuels and litter/duff, and then totaled. Finally one average value was assumed for calculations based on the field experience. Separate tables were developed for prescribed fire and wildfire displaying fuel loading, percent combustion, and emission factor by vegetation type during write up of California Spotted Owl EIS. These tables, also given in the Air Quality Conformity Handbook, 1995 ( Tables 7 and 8 and approved by the EPA), were utilized to calculate PM ₁₀ emissions. Emission levels for PM₁₀ were calculated for wildfire and prescribed fires separately and are displayed in the affected environment section..

The amount and type of prescribed burning projected under each alternative represent a shift in emphasis compared to historical uses of prescribed fire. In the eighties, the majority of prescribed burning has consisted of broadcast burning of logging slash for site preparation and management of competing vegetation. Now, a pretreatment thinning or biomass removal or a mechanical treatment will be done. Much of this burning would be underburning, in which a low- to moderate-intensity fire burns under a stand of residual trees. Burning for hazard reduction and site preparation may frequently take place in stands with many more trees retained than previously left after harvest, necessitaing changes in prescribed fire techniques. Burning piles of slash after harvest, or for hazard reduction, will be done during the most favorable emission dispersion conditions.

For emissions, the shift in emphasis to underburning has some inherent risks along with its advantages. Large areas may burn in mosaics with varying fire intensity and severity. Although this mimics natural underburning, there are risks associated with retaining coarse woody debris. The likelihood for reburning is increased, as is the possibility for a prescribed burn to escape the planned burn area. Consequently the potential for additional, unanticipated emissions is also increased. Furthermore, costs associated with the need for rapid extinguishment of smoldering fuels may also become higher. Thus, fire management planning and risk assessment would need to become more fully integrated into land management planning decisions as part of ecosystem management.

Where extensive fuel hazard reduction by prescribed burning is considered, a tradeoff analysis is necessary to compare emission levels from both wildfire and prescribed fire. It is expected that prescribed burning under advantageous weather conditions may reduce subsequent wildfire emissions by decreasing the amount of available fuel and lowering the risk of large-scale wildfire. A tradeoff analysis would document this reduction and the possible associated changes in air quality impacts.

The forests are also looking at opportunities to reduce fuel loading through biomass and mechanical removal or treatment, which would result in a net reduction in emissions to the atmosphere. There are some problems associated with these opportunities, however. Biomass removal requires proximity to cogeneration facilities, and mechanical removal depends upon factors such as terrain, soil type, and surface rockiness.

Fugitive dust will be produced during road construction. Mitigations measures such as watering roads to control dust would make cumulative impacts insignificant.

Emissions by alternative

Emissions of PM₁₀ were calculated based on projections of the number of acres to be burned under each alternative. Tables 1 - 3 shows PM₁₀ and PM_2.5 emitted under each alternative by county and type of prescribed burning.

Table 4 shows the emissions saved through biomass and sawlog removal, and mechanical removal of fuels. The latter may be termed savings (equivalent of offsets).

Levels of PM₁₀ between 1981 and 1990 provide a useful comparative baseline for assessing projected emissions under the various alternatives for the Primary Forests . This data was calculated during the California Spotted EIS write up and is shown in Table 5.

Altenatives 2 and 3 would generate the greatest PM₁₀/PM _2.5 emissions in the first five years (Tables 1 - 3).Alternative 1 and 4 would generate the least PM_10/ ^PM2.5 emissions. Maximum emissions are generated in Plumas county in all alternatives except alternative 1 where maximum emissions are in Lassen county.

Under Alternative 2, 3 and 5 emissions are projected to increase above historic levels in Lassen and Plumas Counties. These increases are largely due to increases in prescribed burning under the Alternatives.

In the forests for which historic data are available ( Lassen, Plumas, Tahoe, ) emissions are projected to increase under all alternatives relative to the historic level. Emissions would be highest in these forests under Alternative 2, 3 and 5. Alternative 1 would generate the lowest projected emission of 6267 tons per year.

The projected overall increase in estimated emissions makes it reasonable to conclude, at this scale, that the proposed actions may degrade air quality. Nonetheless, aggregated emissions could mask regional or basin-level conditions that may result in localized adverse impacts.

The characterisitcs and quantification of emissions (e.g., plume direction and pollutant concentration) from prescribed fire are critical when evaluating impacts on human health and the environment. The analyses need to include the application of available air dispersion models in order to understand and estimate the downwind impacts on air quality from prescribed fire. Models currently available, such as NFSPUFF, SASEM, and CALPUFF, vary in scope and function, and none has been extensively field tested to verify accuracy in predicting downwind pollution concentrations. NFSPUFF has been modified to be applicable to Region 5 of the USFS. NFSPUFF includes an emission production module (EPM) with National Weather Service predictions for upper level winds, and an alogrithm to correct these winds fo terrain effects at lower levels. It

combines these pieces to produce a graphic display of predicted smoke trajectories and concentrations. NFSPUFF can handle many fires on the same day, each with separate emission characteristics and ignition times. Wind predictions are downloaded through a modem from the National Weather Service nested grid model; the resulting local data file is parsed automatically by NFSPUFF. Terrain effects are computed with a user's option of 1,2,4,and 8 kilometer resolution in the western US between 30 and 50 degrees north latitude and 100 to 125 degrees west longitude.

We used NFSPUFF model to predict the downward smoke dispersion and PM₁₀ concentrations by simulating a worst case scenario. We assumed four test burns from alternative 2 with maximum acreage for burning, within twenty miles of Susanville, being ignited the same day. The burn date was assumed to be May 5, 1999. The weather conditions were assumed to be what existed on May 5, 1997 and model was run assuming May 5, 1997 as May 5, 1999. The test site locations were selected based on historical burns around those vacinities. The following tables lists the assumed burn unit characteristics:

The following table gives the fuel loading characteristics. It is assumed that all the prescribed burn sites had a preburn treatment. Two types of vegetation was assumed --Ponderosa pine and Mixed conifers. Ten tons of fuel loadings with the following characteristics were assumed. The fuel loading is low because the projected burns will follow the pretreated acres.

The assumed understory burn scenario is given in the following table :

The burn was assumed to have taken place on May 5, 1999 but metrological conditions were assumed as that what existed on May 5, 1997. It is also assumed that it is a state declared burn day. This means that the background level is average or below the standards for the area for those days. The modeling analysis shows that under similar conditions the concentations of PM₁₀ and PM_2.5 will stay below standards. Figures that display smoke dispersion and PM₁₀ average (24 hour) concentrations are available for public review in the project file.

At this programmatic, broad scale of analysis, the alternatives would not create conditions that are likely to violate state or federal standards. However, additional air quality analysis would need to be done at the project level with exact metrological and field conditions.

Emissions of smoke during prescribed burning may reduce visibility in some locations, but implementation of smoke dispersion practices, mitigation measures, and best available control measures can minimize the visibility impairment. Smoke emissions may also cause adverse health effects on sensitive individuals, including asthmatics, children and the elderly, especially in the vicinity of the fire.

Unpleasant odors and reduced visibility may be detected by wilderness visitors and could effect the recreational experience for those trying to seek solitude and escape signs of human activity.

The PM₁₀ emissions from prescribed burning would contribute to PM₁₀ loading locally, regionally, and globally. The local effects include cumulative prescribed burn emissions from within federal, state, and private lands in the area. Currently, PM₁₀ atmospheric concentrations do not exceed national standards. However, the Affected Forests generally exceed the more restrictive California State Standards. Additional PM₁₀ emissions from prescribed burning could increase the existing problem. PM₁₀ or PM _2.5 emissions from household wood burning and fugitive dust from soil-disturbing activities within or outside the area could aggravate the problem. These impacts should be analyzed at the project level.

Regulatory authorities are primarily concerned with public exposure to PM₁₀/PM_2.5 concentrations measured in 24-hour increments. Emissions from prescribed burning projects will be managed for dispersion and separation over time and space to minimize the potential for violation of standards.

Carbon dioxide emitted by burning of wood can contribute to the global ``green house effect.'' The effect of pescribed burning on the greenhouse effect is probably negligible but its cumulative impact is unknown.

Emission Savings

The projected emissions are low due to disposition of fuels through alternative methods - that is , biomass or mechanical removal or treatment to reduce fuel loading (see Table 4). Cogeneration plants can burn this wood with substantially lower emissions than would result from wildfire or prescribed burning. Various types of mechanical treatment can be used to clear away brush and trees to prepare land for planting, and to break up slach into finer material. Mechanical mowers and shredders can be used to clear away brush and trees for tree planting in open areas. Bulldozers or tractors used to clear land could be used to reduce fuel loading. However, this kind of clearing has the potential for soil compaction.

Improved utilization of timber is an attractive alternative to prescribed burning that the forests are employing. This encompasses the use of material, which is normally burned, as well as improved harvesting techniques that generate less slash material. Examples of improved harvesting methods that are being used include the following:

· Directional felling to reduce log breakage
· Prelogging or postlogging activities to recover small-diameter timber
· Better techniques for handling material normally discarded as slash.
· Design of contractual agreements to encourage recovery of small-diameter material.

No burn treatment is another method of preventing emissions on a short term basis. The elimination of any form of prscribed burning causes no immediate adverse side effects on the environment, but it does not accomplish any of the benefits for which prescribed fires are used. Moreover, no treatment for extended periods of time can increase the risk of losses due to wildfire or insect infestation and can diminish species diversity and site productivity. A no-burn strategy cannot be considered a viable option for saving emissions.

The ability to reduce emissions by altering the firing technique is limited because firing techniques are dictated by the type of fuel and the objectives of the prescribed burning. Field and laboratory tests have indicated that various firing techniques are asssociated with various levels of emissions. For example, back fires emit relatively little particulate matter.

Fugitive dust is expected under each alternatives that require road construction. The dust will be kept to minimum through dust abatement procedures (e.g. watering). The cumulative impact to particulate concentrations will be insignificant but will be analysed at the project level.

MITIGATION, MONITORING, AND THE NEED FOR ADDITIONAL ANALYSIS

Mitigation

Various techniques can be used to reduce the amount of smoke produced from a prescribed burn. The techniques used would depend upon whether there is an overstory of trees and whether there are activity-generated fuels or natural fuels. The techniques can be categorized according to factors that determine the amount of emissions generated, such as the number of acres burned, preburn fuel loadings, fuel consumption, and weather.

Number of acres burned --- Perhaps the most obvious method to reduce emissions is to consider each project area and determine whether prescribed burning is the most effective option for treatment. In some cases, alternative silvicultural stand management methods, mechanical removal, or other methods may be viable alternatives for meeting management objectives, eliminating the need to burn.

Density management through thinning and understory removal would improve stand conditions in some cases and may alleviate the need for burning. Silvicultural activities could concentrate on the development of late-successional forest characteristics and increasing resiliency to large-scale disturbances by fire, wind, insects, and disease.

Manual treatment consists of hand piling and may not include burning fuels. This method is generally used for specific silvicultural and hazard reduction objectives. Manual treatment is labor intensive and is thus associated with high costs. It is not usually cost effective in areas of heavy fuel loadings or large areas.

Mechanical treatments rearrange and change size and shape of the slash (fuels) components. Mastication (mowing or shredding) crushes and shreds small-diameter concentrations of slash into a scattered layer of residue on the ground. This level of treament is generally sufficient for silvivultural objectives but may not significantly reduce wildfire hazard. Equipment is limited to slopes less than 30 percent. Application in areas with heavy fuel loadings may not be feasible, and mechanical treatments in natural stands may conflict with other resource management objectives.

Chipping on-site may be used to treat slash. Chipping can range from labor-intensive to highly mechanized operations. Residue can be spread on site or hauled away depending on local chip market conditions. Residue can be piled with various types of machinery. Piling could be used for all levels of fuel concentrations depending on the type of equipment. Terrain and soil conditions are the limiting factors. Although some grappler machines are made for slopes in excess of 20 percent, cost may become a critical issue.

Preburn fuels loading --- If prescribed fire is determined to be the optimal treatment for an area, reducing the preburn fuel loading will reduce the subsequent emissions. Methods to reduce fuel loading include whole-tree removal, firewood sales, and increased utilization . Because of new technology, there are more opportunities for increased utilization of residue. For example, some lumber mills are able to use hole wood down to a 4-inch diameter. However, this may conflict with guidelines for retention of coarse woody debris.

Fuels consumption -- Burning under conditions that reduce the portion of biomass that is consumed would lower the emissions produced. The objective should be to burn only the biomass that needs to be burned. This could be accomplished by burning woody fuel when duff moisture contents are high, increasing the rate of mop-up, isolating large fuels and stumps from burning, burning only fuel concentrations, burning when moisture is high in large fuels, or using high-intensity firing techniques.

Favorable weather conditions --- Managing smoke emissions may include transporting smoke away from sensitive areas and diluting emissions by projecting the smoke plume into transport winds. Burning during the spring affords the greatest opportunity to mitigate to prescribed fire smoke impacts because atmospheric instability and persistent transport winds are common. Fuel moisture is optimal for emission reduction during early spring. Fall and winter temperature inversions often restrict pollutants to ground level when burning takes place under the inversion layer. Winter burning of piles, if conducted at high elevations, may not affect smoke-sensitive areas because burning is done above the inversion layer.

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