2017-08-24_REPORT - C2009087 - Laserfiche WebLink

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Page 4 Upper Grassy Creek: Four sites are monitored on Upper Grassy Creek that also fall within the Yampa Segment 13i; sites YSGF5, SSG1, SSG2 and NPDES Pond 003. The following exceedances were noted on Table 15 of the AHR:  SSG1, Total Rec. Iron in April through June of 2016  SSG1, Total Mercury in April through June of 2016  SSG1, Ammonia Nitrogen in April through June of 2015  SSG2, Total Rec. Iron in April through June of 2016  SSG2, Total Mercury in April through September 2016  YSGF5, Selenium in April through June of 2016  YSGF5, Total Mercury in April and September 2016  YSG5, Total Mercury in April and September 2016  YSG5, Total Rec. Iron in April through June of 2016 According to the AHR, the Iron excursions are 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 these excursions are 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/l and the stream standard is .01 ug/l. Given this, the MDL is higher than the standard. Lower Grassy Creek: Lower Grassy Creek is on Segment 13j of the Yampa River Basin. This segment is classified for Agriculture, Aquatic Life (Warm 2), and Recreation N. One monitoring site discharges into this segment, Site YSG5. The following exceedance was noted on Table 17 of the AHR:  YSG5, Total Mercury in April and September 2016  YSG5, Total Rec. Iron in April through June of 2016 It is unclear if the Mercury standard was actually exceeded. The Method Detection Limit (MDL) for Mercury is .2 ug/l and the stream standard is .01 ug/l. Given this, the MDL is higher than the standard. According to the AHR, there is a temporary