On May 14, 2018, the Town of Danville submitted to the Indiana Department of Environmental Management (IDEM) a site-specific Water-Effect Ratio (WER) study for copper under rules at 327 IAC 2-1-8.9(a)(1)(B)(i). 327 IAC 2-1-8.9 sets forth the procedures for the development of site-specific modifications to chronic or acute aquatic life criteria based on the local water quality characteristics, such as pH, hardness, temperature, or color, that alter the biological availability or toxicity of a pollutant. The applicable Indiana aquatic life criteria for copper contained in 327 IAC 2-1-6(a)(3), Table 6-2, are expressed as a function of the WER. A WER is a criteria adjustment factor that accounts for the effect of site-specific water characteristics on pollutant bioavailability and toxicity to aquatic life. The WER is expressed as the toxic effect concentration measured in site water divided by the toxic effect concentration measured simultaneously in laboratory dilution water. A value of one (1) is used for the WER, unless an alternate value is established as part of a site-specific study. The Town of Danville completed the WER study for copper for the receiving water (West Fork White Lick Creek) in order to reevaluate the final effluent limitations for copper in its National Pollutant Discharge Elimination System (NPDES) permit number IN0020079.

IDEM determined the WER study to be complete, and a public notice of the WER evaluation was published in the Hendricks County Flyer with a public comment period opened from August 18, 2018, through September 17, 2018. Information about Danville's WER study is available on the IDEM website at:

The site-specific WER was utilized by IDEM in a recalculation of the water quality-based effluent limits for copper based on Danville's May 14, 2018, request for permit modification of its NPDES permit. The draft NPDES permit, which utilized the site-specific WER, was public noticed in the Hendricks County Flyer with a public comment period opened from December 12, 2018, through January 11, 2019. The final NPDES permit that approved and utilized the site-specific WER for copper was issued to the Town of Danville on February 5, 2019. The amended provisions of the NPDES permit became effective on March 1, 2019.

According to 327 IAC 2-1-8.9(e)(1), approval of a site-specific modification that is determined using a WER must be noticed in the Indiana Register. This notice is in fulfillment of 327 IAC 2-1-8.9(e)(1).

DIN: 20190327-IR-327190171ONA

Composed: Apr 28,2024 6:24:40AM EDT

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