Protecting Public Health and the Environment.

Air Quality Planning in Idaho

Under the authority of the federal Clean Air Act (CAA), EPA has developed and promulgated health-based air quality standards that limit the maximum levels of certain pollutants in outdoor air. Idaho has adopted most of these standards into the state Rules for the Control of Air Pollution in Idaho (IDAPA 58.01.01) and has been delegated authority to issue air quality permits and enforce air quality regulations in the state. States that have been delegated this authority are authorized to develop plans demonstrating how they will achieve, maintain, and enforce the standards. Jointly, the state rules and these plans are known as state implementation plans (SIPs).

What is a SIP?

A SIP is the framework for each state's program to protect the air. It is not a single plan, but the accumulated record of a number of air pollution documents showing what the state has done, is doing, or plans to do to ensure compliance with federal National Ambient Air Quality Standards (NAAQS) for criteria pollutants. Criteria pollutants are certain pollutants—carbon monoxide, sulfur dioxide, ozone, nitrogen oxides, lead, and particulate matter—that are known to be hazardous to human health.

States must involve the public, through hearings and opportunities to comment, in developing SIPs. The plans are subject to approval by EPA, which provides for some consistency among different state programs and ensures that each state program complies with the requirements of the CAA and EPA rules.

What's in a SIP?

The contents of a SIP can be considered in two broad categories:

  1. State air quality rules and programs to attain and maintain the NAAQS, including the new source review program, a program to prevent state emergency episodes, and visibility protection.
  2. Site- or area-specific plans and documents. The CAA requires that state SIPs delineate areas in the state where the air does not meet the standards set by EPA. These are known as nonattainment areas and the SIP must outline what the state is doing to address these problems and include compliance schedules to attain the NAAQS.

What's in Idaho's SIP?

Idaho's original SIP was submitted in 1980 and, because it is a living document, has undergone multiple revisions over the years, including the following:

Interstate Transport

Section 110(a)(2)(D)(i) of the federal CAA, known as the good neighbor provision, requires states to demonstrate to EPA that emissions from one state do not adversely affect another state. Specifically, the CAA prohibits any source or other type of emissions activity within the state from emitting any air pollutant in amounts which will:

(I) contribute significantly to nonattainment in, or interfere with
maintenance by, any other state with respect to any ... national
primary or secondary air quality standard, or

(II) iterfere with measures required to be included in the applicable implementation plan for any other state ... to prevent significant deterioration of air quality or to protect visibility.

DEQ has evaluated its SIP and has determined that it meets the requirements of the CAA.

Transportation Planning

Emissions from motor vehicles are among several major sources of air pollution, particularly in urban areas. As a consequence, the impact of transportation on air quality must be considered in planning to protect public health from the impacts of air pollution and to meet long-term transportation needs. Control strategies may include such items as emission limits on permitted facilities, open burning bans, and in the case of vehicle emissions, a motor vehicle emissions budget that place a cap on future allowable vehicle emissions within the nonattainment area.

Metropolitan planning organizations are responsible for preparing long-range transportation plans that project road projects needed to meet transportation needs over a 20-year period. Those projects that are scheduled to be built within 3 to 5 years are included in a Transportation Improvement Program (TIP), which includes a process for approving and funding the projects.

The conformity process is the important link between air quality improvement and transportation planning. To conform, an area's long-range transportation plan and TIP must ensure that the estimated emissions from the projects will not exceed the emissions limits prescribed in the SIP's motor vehicle emissions budget. Failure to limit emissions within the SIP budget means federally funded highway and transit projects cannot move forward to the construction phase.

Federally funded transportation projects also must show that they will not cause or contribute to new or additional violations at the individual project level.