The Clean Air Act (CAA) includes measures to prevent significant deterioration of air quality (PSD) in areas where air quality is better than the national standards established by the Environmental Protection Agency (EPA) to protect public health and welfare. One of the express purposes of the PSD program is "to preserve, protect, and enhance the air quality in national parks, national wilderness areas, national monuments, national seashores, and other areas of special natural, recreational, scenic, or historic value." In general, "clean air areas" are protected through ceilings on the additional amounts of certain air pollutants over a baseline level. The PSD increment amounts vary based on the area’s classification.
Congress gave the greatest degree of air quality protection to certain national parks and wilderness areas. These “Class I” areas are national parks or national wilderness areas that were so designated as of August 7, 1977 , and that are greater than 6,000 acres (parks) or 5,000 acres (wilderness). There are 21 units of the National Wildlife Refuge System, 48 units of the National Park System, and 88 U.S. Forest Service Wilderness Areas designated as Class I areas . Only a small amount of new pollution is allowed in these Class I areas. All other clean air regions are designated Class II areas with moderate pollution increases allowed, unless an area is redesignated by a state or tribe.
In addition to the PSD increments, there are special provisions for protecting Class I area resources that may be affected by air pollution. These "air quality related values", or "AQRVs", include visibility, vegetation, lakes and streams, soils, fish, animals, and monuments. The CAA gave the Federal land managers (FLMs) an affirmative responsibility to protect AQRVs. Congress specifically established a national goal of preventing any future and remedying any existing human-caused visibility impairment in Class I areas.
One of the ways Congress chose to protect clean air was through preconstruction review of major sources of air pollution. Facilities wishing to build new, or significantly modify existing, facilities in clean air regions must obtain a prevention of significant deterioration (PSD) permit from the state, tribe or EPA and meet certain requirements generally designed to minimize air quality deterioration. In all cases, permit applicants must agree to install the best available control technology and demonstrate that the emissions will not cause a violation of the national ambient air quality standards (NAAQS) or a PSD increment. For more information on EPA PSD regulations, including which facilities are required to obtain a PSD permit, visit the EPA's New Source Review web site.
Where emissions from new or modified facilities might affect Class I areas, the Federal land managers (FLM) must be notified. The FLM for the Department of Interior administered Class I areas is the Assistant Secretary for Fish and Wildlife and Parks. Within the Department of Interior, the U.S. Fish and Wildlife Service Branch of Air Quality and the National Park Service Air Resources Division carry out the day-to-day technical work of this FLM.
The U.S. Forest Service has similar responsibilities under the Clean Air Act and Wilderness Act as the NPS and FWS. The U.S. Forest Service, which is part of the U.S. Department of Agriculture, is charged with managing national forest lands for the use of the public. The Forest Service manages 88 Class I areas, and the Federal Land Manager responsibilities under the Clean Air Act have been delegated to the Forest Supervisors.
The Clean Air Act (CAA) gives the FLMs an affirmative responsibility to protect air quality related values (AQRVs), and to consider, in consultation with the permitting authority, whether a proposed major emitting facility will have an adverse impact on these values. AQRVs include visibility, soil, water, odor, flora, fauna, and geological, archeological and historical resources.
The FLM's permit review process consists of three main analyses:
When a Class I area may be affected by emissions from a proposed source, there is a site-specific evaluation to determine whether emissions from the source will cause an adverse impact on the AQRVs. The adverse impact test works like this:
Often, the FWS's involvement in the permit process has resulted in changes to the proposed permit, such as the use of more efficient control technology or cleaner fuels, and have helped protect air quality at the affected Refuge Wilderness areas .
The Federal Land Managers' Air Quality Related Values Work Group (FLAG) was formed to develop a more consistent approach for Federal Land Managers to evaluate air pollution effects on their resources. Of particular importance is the New Source Review program, especially in the review of Prevention of Significant Deterioration (PSD) of air quality permit applications. The goals of FLAG have been to provide consistent policies and processes both for identifying air quality related values (AQRVs) and for evaluating the effects of air pollution on AQRVs, primarily in Federal Class I air quality areas, but in some instances, also in Class II areas.
The Air Resources Information System (ARIS) provides information on wilderness areas and parks managed by the U.S. Fish and Wildlife Service (FWS) and the National Park Service (NPS) as well as Inventory & Monitoring (I & M) networks. ARIS identifies air quality related values for Class I air quality areas and provides guidance on analysis for evaluating impacts to air quality related values. ARIS maintains information for 21 FWS Class I air quality areas and 48 NPS Class I areas.
There are several computer modeling tools that are used to analyze Class I area impacts. EPA's Support Center for Regulatory Atmospheric Modeling (SCRAM) contains documentation and guidance for these air quality models, including downloadable computer code, input data, and model processors. The specific application of the CALPUFF, VISCREEN, and PLUVUE models for Class I area analysis is outlined in the FLAG Report, discussed above.
FWS Class I Area maps and receptors are available from this webpage. Information for all Class I areas, including National Park Service and Forest Service units as well, is available through the NPS’ website.
Reference materials regarding emissions, control technology, and particulate matter speciation for various industrial source categories were developed by the National Park Service.
Desired Permit Review Process for Projects That May Impact Class I Areas - This document lists the steps the FWS and NPS recommend that applicants and permitting authorities follow regarding FLM involvement in the permit review process.
The National Park Service and Fish and Wildlife Service maintain an online archive of final correspondence , with links to electronic documents of both the FWS and NPS. These include comment letters and technical evaluations of PSD permit activities.
Educational Material on Visibility Science and Regulations - This site contains visibility information and various tools for looking at visibility data.