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Permit Number C-1994-082 Page 13 of 17 <br />GWPOC were found to be lower than the Colorado Water Quality Control Commission (CWQCC) <br />Regulation 41 standards. For the past three water years (2014 to 2016), no standard was exceeded. <br /> <br />The Yoast Mine does not have a groundwater point of compliance for ground water in bedrock <br />stratigraphic units, based on the absence of the potential for the mine to negatively impact the quality <br />of bedrock ground water. The low hydraulic conductivities of the bedrock units and confining layers <br />isolate mine-impacted water-bearing units from the nearest usable aquifer, the Trout Creek <br />Sandstone, which lies approximately 300 to 400 feet below the Wadge Coal seam and approximately <br />60 to 100 feet below the Wolf Creek Coal seam. <br /> <br />Instream Numeric Standards (CWQCC 33) <br /> <br />The Yoast Mine Phase III bond release area discharges surface runoff and spoil leachate into <br />Segments 13e (Sage Creek and tributaries), Segment 13i (upper Grassy Creek), and Segment 13j <br />(lower Grassy Creek) of the Yampa River in CWQCC’s Region 12 of the Yampa River Basin. The <br />stream standards for Sage Creek and Grassy Creek are based on aquatic life standards. <br /> <br />Yoast Mine is required to monitor 14 of the parameters in Segment 13e, 13i, and 13j per CWQCC <br />and CDRMS. A review of the statistical summary of the water quality data provided in Yoast <br />Mine’s Annual Hydrology Reports and specifically for the past three years was conducted for the <br />mine’s NPDES Outfalls (NPDES10, NPDES11, NPDES12, NPDES13, NPDES14) and stream sites <br />YSSF3, YSS2, YSGF5, and YSG5. <br /> <br />The total recoverable iron standard, 1.0 mg/l, was exceeded a total of seven times at Sites YSS2, <br />YSGF5, and YSG5 from 2014 to 2016. On Segment 13e, no exceedances of the iron standard <br />occurred upstream at YSSF3, Ponds 12, 13, or 14; therefore, the exceedances are not likely caused by <br />runoff from the Yoast Mine. Exceedances at the upstream YSGF5 and downstream YSG5 indicate <br />that the exceedances are not likely caused by runoff from the site and are generally observed during <br />snowmelt runoff. <br /> <br />The Yoast Mine includes four monitored spoil springs (YSSPG1 through 4). Spoil Springs YSSPG3 <br />and 4 flow into Pond 012 (NPDES12), and Springs YSSPG1 and 2 flow into Annand Draw and Pond <br />011 (NPDES11) respectively. Due to the fact that the post-mining land uses for the Yoast Mine have <br />been approved as grazing and wildlife habitat, a review of the water quality data was compared to the <br />CWQCC surface water agricultural standards. Three of the surface water agricultural use standards <br />were exceeded for the past three years. The manganese standard was exceeded at YSSPG1, <br />YSSPG2, and YSSPG4. However, as indicated in CWQCC Regulation 31, the standard of 0.2 mg/l <br />applies to plants grown in acidic (<6.0 pH) soils. In alkaline soils, as found in the Yoast Mine Permit <br />area, a more appropriate standard is 10 mg/l. The 10 mg/l standard was not exceeded during the past <br />three water years (2014-2016). <br /> <br />Permit Requirements of the Colorado Discharge Permit System (CDPS) <br /> <br />The Yoast Mine maintains four outfalls which collect runoff from the SL-6, Phase III Bond Release <br />area, Pond 010 (NPDES10), Pond 011(NPDES11), Pond 012 (NPDES12), and Pond 014 <br />(NPDES14), which are monitored under the CPDS Permit No. CO-0000221. Ponds 10, 11, 12, and