On September 7, 2016, the Division of Air Quality (DAQ) staff presented its proposed nonattainment designations for the 2015 Ozone NAAQS to the Air Quality Board. The proposal must be approved by the Governor before the official recommendation is sent by the Governor to EPA by October 1, 2016. The recommendation will include nonattainment designations of the Wasatch Front as well as portions of Uintah and Duchesne County that are under State jurisdiction. EPA will issue final nonattainment designations by October 2017.
The proposed designation of the Wasatch Front includes all of Salt Lake and Davis Counties, Weber and Utah Counties west of the Wasatch Front, and a part of Tooele County that includes Tooele. This designation essentially mirrors the existing PM2.5 nonattainment area. DAQ indicated that it expects this area will be in marginal nonattainment, which means that the State will not be required to develop a formal State Implementation Plan (SIP). Regardless, the state will have to demonstrate attainment in three years. While the State will not be required to impose reasonably available control technology (RACT) requirements on existing sources, other nonattainment area requirements, such as New Source Review permitting at a major source threshold of 100 tons per year of any ozone precursors, will be in effect upon designation.
The proposed designation of the Uinta Basin includes portions of Duchesne and Uintah Counties under State jurisdiction. DAQ staff is proposing that the designation boundary be below 6,000 feet in elevation. DAQ used elevation as a factor in drawing the nonattainment area boundary because ozone exceedances in the Uinta Basin result when temperature inversions trap ozone precursors emissions in the Basin. DAQ indicated that the Uinta Basin could be designated either as marginal or moderate nonattainment; if the area is designated as moderate nonattainment, the State must develop a SIP demonstrating attainment in six years. Existing source RACT requirements must be developed as part of the SIP, and the offset ratio increases to 1.15 to 1.