Arizona Department of Environmental Quality (AZDEQ)

EPA designated portions of Maricopa and Pinal Counties as moderate nonattainment for ozone.

For PM10, the counties of Maricopa and Pinal in Phoenix were designated as serious nonattainment for PM10. Moderate nonattainment for PM10 was assigned to the following counties: parts of Pima County in Ajo, parts of Gila and Pinal Counties in Hayden and Miami, parts of Santa Cruz County in Nogales, parts of Cochise County in Paul Spur/Douglas, parts of Pima County in Rillito, parts of Pinal County in West Pinal and parts of Yuma County in Yuma. Additionally, portions of Mohave County and Bullhead City in Mohave Co and Gila County in Payson were classified as moderate maintenance for PM10.

EPA also delegated parts of Gila and Pinal Counties in Hayden and parts of Gila County in Miami as nonattainment for SO2.

The ERC Program is jointly implemented by the Arizona Department of Environmental Quality (AZDEQ) and the Maricopa County Air Quality Department (MCAQD), but it is the AZDEQ that administers the banking of certified ERCs within Arizona. New major sources and major modifications of existing major sources of NOx, VOC, SOx, CO and PM are mandated to offset more than they emit to achieve an attainment status based on the 2015 NAAQS.

ERCs are available for five different pollutants:

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Pollutant Significant Emission Rates
Nitrogen oxides (NOx) >50 tons/year
Volatile organic compounds (VOC) >50 tons/year
Sulfur dioxide (SO2) >40 tons/year
Carbon monoxide (CO) >50 tons/year
Particulate matter (PM) >25 tons/year

New or modified major facilities in nonattainment areas must obtain ERCs to satisfy the offset ratio requirements for proposed emission increases. The offset ratio for moderate nonattainment area for ozone is 1.15. That means if 100 tpy of VOCs are emitted from a proposed new or modified major facility in Maricopa and Pinal counties, designated as marginal nonattainment area for ozone (2008 Standard), the facility must obtain 115 tpy of ERCs to offset the increase in VOC emissions.

Additionally, the offset ratio for moderate nonattainment area for PM10 is 1.15. That means if 100 tpy of for PM10 are emitted from a proposed new or modified major facility in a moderate nonattainment area for PM10, the facility must obtain 115 tpy of ERCs to offset the increase in PM10 emissions. For serious nonattainment areas, offset ratio is 1.2. Thus, the counties of Maricopa and Pinal in Phoenix being serious nonattainment for PM10 are required to obtain 120 tpy of ERCs to offset the increase in PM10 emissions.

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