Attainment versus Nonattainment
Based upon levels of air pollutants, geographic areas are classified by EPA as attainment or nonattainment areas.
- A geographic area that meets or has pollutant levels below the NAAQS is called an attainment area.
- An area with persistent air quality problems is designated a nonattainment area. This means that the area has violated federal health-based standards for outdoor air pollution.
Each nonattainment area is declared for a specific pollutant. Nonattainment areas for different pollutants may overlap each other or share common boundaries.
States strive to achieve attainment with state and federal air quality standards for a number of reasons. First and foremost, remaining in compliance helps protect public health, a key element of DEQ's mission. In addition, compliance contributes to economic growth. Nonattainment status can potentially limit production capabilities of existing industries and preclude siting of new industries that provide job opportunities. Attainment of air quality standards also helps avoid a potential loss of federal highway funding that can result from nonattainment status. Lastly, it is costly and time-consuming to develop and implement plans to reattain attainment status.
In addition to areas classified as attainment and nonattainment, some areas are described as maintenance areas. Maintenance areas are those geographic areas that were classified as nonattainment but are now consistently meeting the NAAQS. Maintenance areas have been redesignated by the EPA from nonattainment to attainment with a maintenance plan; commonly called maintenance areas. These areas have demonstrated through monitoring and modeling they have sufficient controls in place to meet and main the NAAQS. They also have contingency measures in place that would be implemented should the areas start showing exceedances.
Nonattainment and Maintenance Areas in Idaho
At present, the four geographical areas described below are classified as nonattainment or maintenance areas in Idaho.
- Idaho Air Quality Planning Areas Map: Shows nonattainment areas, areas of concern, and Class I areas (Class I areas include all national parks greater than 6,000 acres, wilderness areas and national memorial parks greater than 5,000 acres, and certain international parks.)
Cache Valley - PM2.5
The Cache Valley (Logan, UT-ID) was designated as a PM2.5 nonattainment area in 2009. Straddling the border between Utah and Idaho, this nonattainment area presents unique challenges with respect to topographical features and jurisdictional authority issues (two states and two EPA regions). The Cache Valley encompasses a bowl-shaped, topographically isolated valley that experiences air stagnation events in the wintertime. During wintertime cold-air pool episodes, dispersion is poor due to the very stable air mass, and concentrations of primary and secondary PM2.5 elevate because the pollutants are trapped in the cold-air pool. Episodes may last from a few days to tens of days until meteorological conditions change to once again allow for good mixing. The emission inventory identified road sanding (70%) and residential wood combustion (14%) as the top two contributors to directly emit PM2.5 on the Idaho side of the valley. During air stagnation events, the area is dominated by the formation of ammonium nitrate a secondary aerosol.
The Cache Valley PM2.5 Nonattainment Area State Implementation Plan (SIP) was submitted to EPA in December 2012. The document contains the necessary evidence, analysis, and Idaho control strategies (in conjunction with a separate SIP for the Utah side of the Cache Valley) to demonstrate that the area will attain the national standard by January 1, 2015.
- Cache Valley Idaho PM2.5 Nonattainment Area State Implementation Plan | Appendices
- Cache Valley Nonattainment Area Map
Sandpoint - PM10
Located in Bonner County, the Sandpoint area rests on the northwest corner of Lake Pend Oreille within the Panhandle National Forest. The topography influences much of the PM buildup in the area. In 1997, the area was designated moderate PM10 nonattainment, and an emissions inventory identified the primary PM10 source as residential wood burning. Fugitive road dust and some industrial sources were also considered significant contributors.
Since 1997, significant improvements in air quality have been realized thanks to the efforts of the community. In December 2011, DEQ submitted a PM10 Limited Maintenance Plan and Redesignation Request to EPA to redesignate the area to attainment status. The plan focuses on a comprehensive residential wood combustion program, controls on fugitive road dust, and emission limitations on industrial sources. In April 2013, EPA approved in part and disapproved in part the Sandpoint PM10 Limited Maintenance Plan and redesignated the Sandpoint area to attainment for PM10.
- Sandpoint PM10 Maintenance Plan
- Limited Maintenance Plan and Request for Redesignation of the Sandpoint, Idaho PM10 Nonattainment Area
Pinehurst - PM10
The Pinehurst area is located in Shoshone County and rests in the Silver Valley surrounded by the Coeur d'Alene and St. Joe National Forests. The area's topography is a significant factor in the buildup of pollutants that result in poor air quality. The emission inventory identified residential wood burning as the primary PM10 source and fugitive road dust as a secondary source.
Pinehurst was designated nonattainment for PM10 upon enactment of the Clean Air Act Amendments of 1990. Idaho submitted a PM10 attainment plan for Pinehurst in April 1992, and EPA approved the plan in August 1994. In April 1992, Idaho also submitted a PM10 attainment plan revision for the portion of the Shoshone County nonattainment area just outside the city of Pinehurst. This area was designated nonattainment in January 1994. EPA approved the plan revision in May 1995. The plan relies on control strategies needed to ensure attainment of the PM10 NAAQS. The strategy focuses on control of residential wood combustion.
On August 23, 2001, EPA published a finding that the two areas had attained the PM10 standard by their respective attainment dates (66 FR 4403). However, the designation status in 40 CFR part 81 remains moderate nonattainment for both areas until such time as Idaho meets the Clean Air Act requirements for redesignations to attainment.
Portneuf Valley (Maintenance Area) - PM10
This area consists of 96.6 square miles of Pocatello, Chubbuck, and surrounding areas. It was formerly the Power/Bannock County PM10 area, which was split into the Portneuf Valley and federal Fort Hall PM10 areas. It includes federal land managed by the Bureau of Land Management and the Caribou National Forest, as well as privately owned land in the cities of Pocatello and Chubbuck.
- Portneuf Valley PM10 Nonattainment Area State Implementation Plan, Maintenance Plan, and Redesignation Request
Northern Ada County (Maintenance Area) - Carbon Monoxide and PM10
At present, Northern Ada County is a limited maintenance area for carbon monoxide. Northern Ada County is Idaho's only designated carbon monoxide maintenance area. Mobile and area source emissions are the two major sources of carbon monoxide. Northern Ada County is also a maintenance area for PM10. The main sources of PM10 are fugitive road dust and agriculture.
- Limited Maintenance Plan and Request for Redesignation to Attainment for the Northern Ada County Carbon Monoxide Not-Classified Nonattainment Area | Appendices
- Northern Ada County PM10 SIP Maintenance Plan and Resdesignation Request
Redesignating Nonattainment Areas
Several nonattainment areas in Idaho now appear to be meeting NAAQS. This apparent compliance with the federal standards does not automatically bring an area's nonattainment status to an end, however. The Clean Air Act requires states to follow an extensive process to prove that the nonattainment designation should be removed.
DEQ and local governments are working to gain redesignation in all areas that are meeting outdoor air quality standards. Redesignation is a complicated and lengthy process that can take up to 2 years for each area. To attain reclassification, the nonattainment area must meet national ambient air quality health standards as follows:
- Coarse particulate matter (PM10) and ground-level ozone: No more than an average of one violation of the standard per year for three consecutive years.
- Carbon Monoxide: No more than one violation of the standard each year for two consecutive years (averaging prohibited; cannot have two violations one year and none the next).
Data must be acquired through actual monitoring with equipment located in places likely to have the highest concentrations of the pollutant. A computer modeling analysis also must be completed to show that monitoring occurred in high concentration areas and to support the case that the standard has been met. These steps must be followed:
Develop a Nonattainment Area Plan
DEQ must complete and obtain EPA approval of a state implementation plan (SIP) for bringing each area into attainment. The federal planning process must be completed before completing other redesignation requirements.
Demonstrate Proof of Real Pollution Reduction
DEQ must prove to EPA that the air quality improvements are permanent and enforceable. Improvements cannot be attributed to unusually favorable weather conditions or factors such as economic downturns that resulted in less traffic and industrial activity.
Develop a Maintenance Plan
DEQ must develop and obtain EPA approval of a maintenance plan designed to keep the area's air healthful. This plan must outline the pollution prevention steps that the state will implement to maintain air quality standards for 10 years after redesignation is attained. Circumstances will dictate whether fewer, the same, or additional pollution prevention strategies will be required. The plan also must describe measures that will be taken to correct violations if they occur. DEQ may submit the maintenance plan at the same time it applies for redesignation.
- Inventory: DEQ must prepare an inventory showing all sources of air pollution and how much they generate. Sources are things such as vehicles, wood stoves, and commercial or industrial facilities that generate air pollution. DEQ must identify the maximum amount of emissions that can be allowed without violating air quality standards.
- Maintenance Demonstration: Using a computer model, DEQ must demonstrate to EPA's satisfaction that the maintenance plan will keep air quality within the federal standards for 10 years, even if the number of pollution sources increases (e.g., increased traffic or more industrial areas in the area).
- Monitoring: DEQ must submit a monitoring plan that will show whether the federal standards are being maintained. The plan must allow for special studies in case traffic patterns or other pollution producing patterns change. These studies could lead to new permanent monitoring sites if high pollution persists.