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recoverable selenium was measured as less than 0.5 µg/L. As previously described, a potentially <br /> dissolved metal concentration can not be greater than the total recoverable metal concentration as <br /> the potentially dissolved form is a subset of the selenium that is measured as a part of the total <br /> recoverable analysis. The potentially dissolved selenium was likely the result of matrix <br /> interference during the labs analysis. <br /> The post-mining land use of the reclaimed parcels in this Phase III bond release application are <br /> designated as livestock grazing and wildlife habitat. Therefore,the water quality data collected <br /> from the NPDES outfalls are compared to the Agricultural Use surface water standards as <br /> established in CWQCC Regulation 31. Permit CO-0000221 requires that the metals be collected <br /> in the potentially dissolved form whereas the Agricultural Use standards are based on the total <br /> form. For comparative purposes,when the total form is not available the potentially dissolved <br /> form is compared to the Agricultural Use standards. The selenium agricultural use standard(20 <br /> µg/L)was exceeded twice at Outfall 013. The exceedances occurred on April 27, 2015 and April <br /> 23, 2018. Outfall 013 only discharges in the spring after snow melt or precipitation events. <br /> Downstream monitoring point YSS2 was sampled for dissolved selenium during both discharge <br /> events. In both instances the dissolved selenium at YSS2 was < 1 µg/L indicating the streams <br /> water quality was not being influenced by the discharge. All remaining selenium samples at 013 <br /> were within the Agricultural Use standards. <br /> There were no other exceedances of the NPDES limits or water quality standards at the Yoast <br /> Mine Outfalls. See the Yoast Mine Annual Hydrology Reports for 2014 through 2018 for <br /> additional discussion about the frequency of discharge at the NPDES outfalls. <br /> D.) Clean Water Act Effluent Limitations(40CFR Part 434) <br /> Monitoring data from the past five years indicate the mine has not caused exceedances of the 40 <br /> CFR Part 434 settleable solids and pH limits that are applicable to reclamation areas on coal <br /> mines (settleable solids limit: 0.5 ml/l; pH limit: 6.0 - 9.0 S.U.). See the Yoast Mine Annual <br /> Hydrology Reports from 2014 through 2018 for additional discussion of the frequency of <br /> discharge and analytical data. Note that the results of the monthly settleable solids analysis for <br /> these outfalls are documented in the SCC field notebook and only values that are at or above the <br /> detection limit(0.4 ml/1) are entered in to the water quality database. The absence of those values <br /> SL-7 - 43 <br />