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Class 1 Area Impact Analysis

Class 1 Areas

  Class I areas are areas of special national or regional natural, scenic, recreational, or historic value for which the PSD regulations provide special protection.
  Under the CAA, three kinds of Class I areas either have been, or may be, designated. These are
  • Mandatory Federal Class I areas
  • Federal Class I areas
  • Non-Federal Class I areas
  For each proposed major new source or major modification that may affect a Class I area, the applicant is responsible for:
  • identifying all Class I areas within 100 km of the proposed source and any other Class I areas potentially affected
  • performing all necessary Class I increment analyses (including any necessary cumulative impact analyses)
  • performing for each Class I area any preliminary analysis required by a reviewing agency to find whether the source may increase the ambient concentration of any pollutant by 1 µg/m 3 (24-hour average) or more
  • performing for each Class I area an AQRV impact analysis for visibility
  • providing all information necessary to conduct the AQRV impact analyses (including any necessary cumulative impact analyses)
  • performing any monitoring within the Class I area required by the reviewing agency
  • providing the reviewing agency with any additional relevant information the agency requests to "complete" the Class I area impacts analysis

Mandatory Federal Class 1 Areas

  Mandatory Federal Class I areas are those specified as Class I by the CAA on August 7, 1977, and include the following areas in existence on that date
  • International parks
  • National wilderness areas
    • (including certain national wildlife refuges, national monuments and national seashores) which exceed 5,000 acres in size
  • National memorial parks which exceed 5,000 acres in size
  • National parks which exceed 6,000 acres in size

Mandatory Federal Class I areas, which may not be reclassified, are managed either by the Forest Service (FS), National Park Service (NPS), or Fish and Wildlife Service (FWS).

Federal Class 1 Areas

  The States and Indian governing bodies have the authority to designate additional Class I areas. These Class I areas are not "mandatory" and may be reclassified if the State or Indian governing body chooses. States may reclassify either State or Federal lands as Class I, while Indian governing bodies may reclassify only lands within the exterior boundaries of their respective reservations.
  Any Federal lands a State so reclassifies are considered Federal Class I areas. In so far as these areas are not mandatory Federal Class II areas, these areas may be again reclassified at some later date. (there are as of the date of this manual, no State-designated Federal Class I areas.) However, in accordance with the CAA the following areas may be redesignated only as Class I or II:

an area which as of August 7, 1977, exceeded 10,000 acres in size and was a national monument, a national primitive area, a national preserve, a national recreation area, a national wild and scenic river, a national wildlife refuge, a national lakeshore or seashore

a national park or national wilderness area established after August 7, 1977, which exceeds 10,000 acres in size

  Federal Class I areas are managed by the Forest Service (FS), the National Park Service (NPS), or the Fish and Wildlife Service (FWS).

Non-Federal Class 1 Areas

  State or Indian lands reclassified as Class I are considered non-Federal Class I areas. Four Indian Reservations which are non-Federal Class I areas are the Northern Cheyenne, Fort Peck, and Flathead Indian Reservations in Montana, and the Spokane Indian Reservation in Washington.

Class 1 Increments

  One way in which air quality degradation is limited in all Class I areas is by stringent limits defined by the Class I increments for sulfur dioxides, particulate matter measured as total suspended particulate (TSP), and nitrogen dioxide.

  PSD Class 1 Increments are the maximum increases in ambient pollutant concentrations allowed over the baseline concentrations established for a given Class 1 area.  Thus, these increments should limit increases in ambient pollutant concentrations caused by new major sources or major modifications near Class I areas.

  Increment consumption analyses for Class I areas should include not only emissions from the proposed source, but also include increment-consuming emissions from other sources.

Class 1 Area Air Quality Related Values (AQRV)

  Federal Land Managers (FLM) of each Class I area is charged with the affirmative responsibility to protect that area’s unique attributes, expressed generically as air quality related values (AQRV’s).

  The FLM, including the State or Indian governing body, where applicable, is responsible for defining specific AQRV’s for an area and for establishing the criteria to determine an adverse impact on the AQRV’s.  The AQRV's are those attributes of a Class I area that deterioration of air quality may adversely affect. For example, the Forest Service defines AQRV's as "features or properties of a Class I area that made it worthy of designation as a wilderness and that could be adversely affected by air pollution."

  Adverse impacts on AQRV's in Class I areas may occur even if pollutant concentrations do not exceed the Class I increments.

  Air quality-related values generally are expressed in broad terms. The impacts of increased pollutant levels on some AQRV's are assessed by measuring specific parameters that reflect the AQRV's status. For instance, the projected impact on the presence and vitality of certain species of animals or plants may indicate the impact of pollutants on AQRV's associated with species diversity or with the preservation of certain endangered species. Similarly, an AQRV associated with water quality may be measured by the pH of a water body or by the level of certain nutrients in the water. The AQRV's of various Class I areas differ, depending on the purpose and characteristics of a particular area and on assessments by the area's FLM. Also, the concentration at which a pollutant adversely impacts an AQRV can vary between Class I areas because the sensitivity of the same AQRV often varies between areas.