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 19, Permit No. C00000906 Total Recoverable Trivalent Chromium A quantitative RP analysis was conducted for outfall 001 based on the WQBEL and ADBAC as calculated in the WQA. A qualitative RP analysis was conducted for outfalls 007, 008 and 010 as chromium is identified in the ELG Development Document as a parameter that can be found in alkaline coal -related discharges. Outfall 001: total chromium data was used for the RP analysis as total recoverable trivalent chromium data was not available. The MEPC was less than half of the MAPC and therefore limitations are not necessary at this time. However, because the parameter is identified in the ELG Development Document, a qualitative monitoring determination was made to ensure that sufficient data is available to support future RP determinations. Therefore, a semi-annual monitoring requirement 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 semi-annual monitoring requirement has been added to the permit for these outfalls for the collection of data to support future RP determinations. Potentially Dissolved Trivalent Chromium A quantitative RP analysis was conducted for outfall 001 based on the WQBEL and ADBAC as calculated in the WQA. A qualitative RP analysis was conducted for 007, 008, and 010 as chromium is identified in the ELG Development Document as a parameter that can be found in alkaline coal -related discharges. Outfall 001: total chromium data was used for the RP analysis as potentially dissolved trivalent chromium data was not available. The MEPC was less than half of the MAPC and therefore limitations are not necessary at this time. The monitoring data do not indicate a limitation is necessary, and total recoverable trivalent chromium monitoring data can be used to evaluate dissolved trivalent chromium concentrations. 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. Total recoverable trivalent chromium monitoring data can be used to evaluate dissolved trivalent chromium concentrations; therefore, no additional chromium monitoring requirements are necessary at these outfalls. Potentially Dissolved Hexavalent Chromium A qualitative RP analysis was conducted for outfalls 001, 007, 008 and 010 as chromium is identified in the ELG Development Document as a parameter that can be found in alkaline coal -related discharges. According to the Agency for Toxic Substances and Disease Registry, hexavalent chromium is produced by industrial processes. Activities at this facility would not generate hexavalent chromium. A qualitative determination of no RP has been made and the evaluation for chromium is limited to the trivalent form. Potentially Dissolved Copper A quantitative RP analysis was conducted for outfall 001 based on facility data and the WQBELs and ADBACs as calculated in the WQA. A qualitative RP analysis was conducted for outfalls 007, 008, and 010 as copper 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. This is a new limitation 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 for the 30 -day average limitation with interim limits based on monitoring data (the highest actual 30 -day average) has been 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. Therefore, a quarterly