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The GWPOC well in the Grassy Creek alluvium is Well SCAL70, located 0.6 miles downstream of <br />the PSCM permit boundary. NPDES2 discharges into Grassy Creek by way of Little Grassy Creek. <br />No exceedances of applicable groundwater standards were observed in SCAL70 in the past 5 years. <br />The Peabody Sage Creek Mine does not have a groundwater point of compliance for ground water in <br />bedrock stratigraphic units, based on the absence of the potential for the mine to negatively impact <br />the quality of bedrock ground water. The low hydraulic conductivities of the bedrock units and <br />confining layers isolate mine - impacted water bearing units from the nearest usable aquifer, the <br />Trout Creek Sandstone, which lies approximately 300 to 400 feet below the Wadge Coal seam and <br />approximately 60 to 100 feet below the Wolf Creek Coal seam. <br />Instream Numeric Standards (CWQCC 33) <br />PSCM discharges surface runoff and spoil leachate into Segment 13g (all tributaries to Fish <br />Creek from the confluence with Cow Camp Creek to the confluence with Trout Creek) of the <br />Yampa River based on Colorado Water Quality Control Commission (CWQCC) Regulation 33. <br />Regulation 33 was recently revised in August 2014 as part of the Upper Colorado River Basin <br />Rulemaking Hearings. PSCM is required to monitor 17 parameters (as shown in Table 5 of the bond <br />release application) in that segment per its CDPS and CDRMS permits. <br />Data (shown in Table 7 of the SL -4 application) indicate the total recoverable (TR) iron standard, 1. 0 <br />mg/1, was exceeded a total of nine times (out of sixteen samples) at Fish Creek Sites SSF11 and <br />SSF13. High TR iron values are normally associated with high total suspended solids. No excursions <br />of this standard occurred upstream at SSC 10 (Cow Camp Creek, NPDES4 basin), SSB12 (Bond <br />Creek, NPDES8 basin). In addition, no NPDES discharges (NPDES8 at Seneca and NPDES 4 at the <br />PSCM) exhibited an excursion of the iron standard from 2011 through 2015, except one occurrence <br />during January 2014 at NPDES4 with a concentration of 1. 55 mg/ 1. Sixty samples were collected <br />and analyzed for iron (TREC) at NPDES4 between January 2011 and December <br />2015, and 59 out of 60 were below the iron standard. <br />As a result of the 2014 Upper Colorado River Basin Rulemaking Hearings, the CWQCC assigned a <br />temporary modification for the chronic aquatic life selenium standard of 4.6 ug/1 in Segment 13g, <br />which removed the numeric limit and set it to a narrative standard of "current conditions". The <br />temporary modification was established due in part to significant uncertainty regarding the numeric <br />standard necessary to protect uses, and because there is substantial uncertainty about the extent to <br />which existing quality is the result of natural or irreversible human -induced conditions. The <br />temporary modification is set to expire on December 31, 2018. Because the current chronic aquatic <br />life standard is set at "current conditions", only the acute aquatic life selenium standard of 18. 6 ug/1 <br />was compared to data collected from 2011 and 2015. No exceedances of the acute aquatic life <br />selenium standard (18.4 ug/1) occurred from 2011 through 2015 at NPDES4 or any surface water <br />sites downstream, including lower Fish Creek Site SSF13. <br />PSCM discharges surface runoff and spoil leachate into Segment 13i (Grassy Creek and tributaries <br />from the source to immediately above the confluence with Scotchman's Gulch) of the Yampa River <br />based on Colorado Water Quality Control Commission (CWQCC) Regulation 33. The pH standard of <br />6.5 to 9 was exceeded once at Site SSG2 with a value of 6.44 on 6/ 3/ 13. The pH values upstream at <br />C-2009-087 Page 10 of 14 <br />