Indiana Department of Environmental Management (IDEM)

EPA designated parts of Lake County in Chicago and the counties of Clark and Floyd in Louisville as marginal nonattainment for ozone based on the 2015 8-Hour Ozone Standard. The counties of Lake and Porter were classified as moderate nonattainment for ozone based on the 2008 8-Hour Ozone Standard. Parts of Delaware County in Muncie were classified as nonattainment for lead.

Several counties and townships in Indiana were nonattainment for SO2 including parts of Huntington County and Huntington Township in Huntington, parts of Marion County and the townships of Wayne, Center and Perry in Indianapolis, parts of Daviess and Pike Counties and Veale and Washington Townships in Southwest Indiana, parts of Morgan County and the townships of Clay and Washington in Morgan County, and parts of Vigo County and the townships of Fayette and Harrison in Terre Haute.

For PM10, parts of Lake County and the cities of East Chicago, Hammond, Whiting and Gary located in East Chicago were classified as moderate maintenance. Additionally, portions of Vermillion County were also designated as moderate maintenance for PM10.

New major sources and major modifications of existing major sources of NOx, VOC, SOx, CO and PM are mandated by IDEM to offset more than they emit to achieve an attainment status based on the 2015 NAAQS.

ERCs are available for seven different pollutants:

Pollutant Significant Emission Rates
Nitrogen oxides (NOx) >25 tons/year
Volatile organic compounds (VOC) >25 tons/year
Sulfur dioxide (SO2) >>25 tons/year
Carbon monoxide (CO) >100 tons/year
PM10 >25 tons/year
PM >25 tons/year
Pb (Lead) >5 tons/year

To satisfy offset requirements, new or modified major facilities in nonattainment areas must obtain ERCs for proposed emission increases. The offset ratio for marginal nonattainment area for ozone is 1.1 to 1. That means if 100 tpy of VOCs are emitted from a proposed new or modified major facility in the counties of Lake in Chicago, Clark and Floyd in Louisville, the facility must obtain 110 tpy of ERCs to offset the increase in VOC emissions.

On the other hand, offset ratios for moderate nonattainment area for ozone is 1.15. Thus, 115 tpy of VOC ERCs must be obtained by the proposed new or modified major facility in the Lake and Porter Counties to offset the increase in VOC emissions.

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