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 18, Permit No. C00000906 008, and 010; where a semi-annual monitoring requirement was applied to outfall 001, semi-annual monitoring was also required for outfalls 007, 008, and 010 pH - This parameter is limited by the water quality standards of 6.5-9.0 s.u. for discharges from outfalls 001, 007, 008 and 010 as this range is more stringent than other applicable standards. Total Arsenic 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 arsenic 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 typically required. However, the temporary modification "As(ch)=current condition" applies to discharge from outfall 001 through 12/31/2021; therefore, a report requirement is included in the permit for this permit term. Outfalls 007, 008, and 010: a qualitative monitoring determination was made because the outfalls transmit 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 monitoring requirement was added to the permit for the collection of data for future RP analysis. Dissolved Arsenic 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 arsenic is identified in the ELG Development Document as a parameter that can be found in alkaline coal -related discharges. Outfall 001: dissolved arsenic data was not available; therefore, total arsenic was used as a conservative estimate because dissolved arsenic is a subset of total arsenic. The MEPC was less than half of the MAPC and therefore limitations and monitoring are not necessary at this time. Outfalls 007, 008, and 010: a qualitative monitoring determination was made because the outfalls transmit surface flow from the active mining area. However, monitoring for total arsenic will provide sufficient data regarding the dissolved arsenic concentration in the discharge. Therefore, no monitoring for dissolved arsenic is required at these outfalls. Potentially Dissolved Cadmium A quantitative RP analysis was conducted for outfall 001 based upon 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 cadmium is identified in the ELG Development Document as a parameter that can be found in alkaline coal -related discharges. Outfall 001: Less than 30% of the sample results for dissolved cadmium were above the detection limit; therefore, the MEPC could not be calculated. Monitoring data indicate that dissolved cadmium ranged from non -detect to 0.1 pg/l with one sample result at 12 pg/l compared to the WQBEL of 0.86 pg/l. The 12 pg/1 sample may be an outlier; however, the reported result must be considered and a quantitative determination of RP was made. The 30 -day average, daily maximum and 2 -year average limitations are included in the permit. This is a new limit and it is unknown if the permittee can consistently meet the limit, therefore, a compliance schedule with interim limits based on monitoring data (the highest actual 30 -day average and daily maximum) was added to the permit to give the permittee time to meet this Limitation. Outfalls 007, 008, and 010: a qualitative monitoring determination was made because the outfalls transmit 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 monitoring requirement was added to the permit for the collection of data to support future RP determinations.