2016-08-25_REPORT - C2009087 - Laserfiche WebLink

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Peabody Sage Creek Mining, LLC Page 4 8/25/2016 discharges into Fish creek. The applicable stream segment is Segment 13g of the Yampa River basin (New segment as of December 31, 2014). This reach is classified as agriculture, aquatic life (Warm 1) and Recreation E. The following exceedances were noted: • SSC10 —Mercury, June 2015 • SSC10 —Total Rec. Selenium, May 2015. It is unclear if the Mercury standard was actually exceeded. The Method Detection Limit (MDL) for Mercury is .2 ug/1 and the stream standard is .01 ug/1. Given this, the MDL is higher than the standard. According to the AHR, there is a temporary modification (expired December 31, 2018) of the Selenium standard as "current conditions". Therefore, the excursion of the Selenium standard is not considered an exceedance. -Little Grassy Creek: Two PSCM surface water monitoring sites exist within the Little Grassy Creek drainage: The NPDES Pond 002 outfall and SSLG5. SSLG5 drains the upper portion of Little Grassy Creek which are undisturbed by mining. Both sites discharge into Grassy Creek which is on Segment 13i (Upper Grassy Creek) of the Yampa River basin. This stream standard came into effect as of December 31, 2014. The stream standards for Upper Grassy Creek are classified as agriculture, aquatic life (Warm 2) and Recreation N. The following exceedances were noted on Table 15 of the AHR: • SSLG5 — Total Rec. Iron, May and June 2015. • SSGL5, Total Mercury in April and June of 2015. According to the AHR, the Iron excursions is a result of high suspended solids and that a temporary modification (expires December 31, 2018) of the Iron standard as "current conditions". Given this the AHR indicates this excursion is not considered to be a standard exceedance. It is unclear if the Mercury standard was actually exceeded. The Method Detection Limit (MDL) for Mercury is .2 ug/1 and the stream standard is .01 ug/l. Given this, the MDL is higher than the standard.