2017-05-11_PERMIT FILE - C1981012 (18)

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In TRIM COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT, Water Quality Control Division Fact Sheet- Page 21, Permit No. C00000906 Outfall 001: the MEPC was greater than the MAPC and therefore limitations are required. The permittee may not be able to consistently meet the new limitation; therefore, a compliance schedule with interim limits based on monitoring data (the highest actual 30 -day average) is included in the permit. Outfalls 007, 008, and 010: a qualitative monitoring determination was made because the outfalls convey surface flow from the active mining area. The treatment provided by sedimentation ponds approved under the SMCRA authority are not expressly designed for all pollutants regulated under the WQCA, including metals removal, and for outfall 010, no treatment technology is implemented. A quarterly monitoring requirement has been added to the permit for these outfalls for the collection of data to support future RP determinations. Potentially Dissolved Nickel Outfalls 001: a quantitative RP analysis was conducted based on the WQBELs and ADBACs as calculated in the WQA. Less than 30% of the samples were above the detection limit; therefore, the MEPC could not be calculated. Monitoring data ranged from non -detect at PQL of 10 pg/l, to 10 pg/l compared to the WQBEL of 108. A quantitative determination of no RP has been made as sample results were significantly less than the potential limitation. Outfalls 007, 008, and 010: a qualitative determination of no RP was made as nickel is identified in the ELG development document as a parameter with no or limited detects (i.e., less than 20%). Potentially Dissolved Selenium A quantitative RP analysis was conducted for outfall 001 based on the WQBELs and ADBACs as calculated in the WQA. A qualitative RP analysis was conducted for outfalls 007, 008, and 010 as selenium is identified in the ELG Development Document as a parameter that can be found in alkaline coal -related discharges. Outfall 001: the MEPC was greater than the MAPC and therefore limitations are required. These are new limitations and previous monitoring indicates that the permittee may not be able to consistently meet the limitations for the 30 -day average; therefore, a compliance schedule with interim limits based on monitoring data (the highest actual 30 -day average) was added to the permit. Note that the daily maximum limitation is effective immediately. Outfalls 007, 008, and 010: a qualitative monitoring determination was made because the outfalls convey surface flow from the active mining area. The treatment provided by sedimentation ponds approved under the SMCRA authority are not expressly designed for all pollutants regulated under the WQCA, including metals removal, and for outfall 010, no treatment technology is implemented. A quarterly monitoring requirement has been added to the permit for these outfalls for the collection of data to support future RP determinations. Potentially Dissolved Silver Outfall 001: a quantitative RP analysis was conducted based on the WQBELs and ADBACs as calculated in the WQA. Less than 30% of the samples were above the detection limit; therefore, the MEPC could not be calculated. The samples ranged from non -detect at PQL of 0.5 pg/l, to 0.06 pgA compared to the WQBEL of 0.21 pg/l. A qualitative determination of no RP has been made as the samples were mostly non -detect and the samples at detection were less than half of the potential limitations. Outfalls 007, 008, and 010: a qualitative determination of no RP was made as silver is identified in the ELG development document as a parameter with no or limited detects (i.e., less than 20%). Potentially Dissolved Zinc A quantitative RP analysis was conducted for outfall 001 based on the WQBELs and ADBACs as calculated in the WQA. A qualitative RP analysis was conducted for outfalls 007, 008, and 010 as zinc is identified in the ELG Development Document as a parameter that can be found in alkaline coal -related discharges. Outfall 001: The MEPC was less than half of the MAPC therefore limitations are not necessary at this time. Because the parameter is identified in the ELG Development Document, a qualitative monitoring determination was made, and a semi-annual monitoring requirement is included in the permit.