2022-09-06_REPORT - C1982056 (3)

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Foidel Creek Mine C-82-056 2021 Annual Hydrology Report 3.6 CDPS Discharge Sites Under State of Colorado Department of Public Health and Environment (CDPHE), Colorado Discharge Permit System (CDPS) permit No.'s CO-0027154, CO-0036684, CO-0042161, COG- 850051 and COG-850054 eleven discharge points are monitored throughout the year. Note that CDPS has also been referred to as the National Pollutant Discharge Elimination System (NPDES) in previous AHRs. Monitoring results (CDPHE Colorado Discharge Monitoring Reports, or DMRs) are copied to DRMS in accordance with CDPS requirements. The monitoring frequencies and analytes required to be analyzed vary by outfall and permit number. Attachment 6 shows the CDPS water quality data for the report period. During the 2021 water year there were 5 exceedances at the outfalls associated with Permit CO- 0027154. Outfall 003 exceeded the daily max and monthly average TSS limit in February. The sample collected on February 10th had a TSS of 81 mg/L, however the TSS in the sample collected the following week was only 13 mg/L indicating the TSS had returned to compliance levels. The outfall did not discharge during the first or last week of February resulting in a monthly average exceedance. Poor sampling conditions requiring removal of snow and ice from the monitoring location prior to sampling may have disturbed sediment on the channel bottom resulting in the exceedance. Outfall 006 (Site 85) exceeded the pH limit of 9.0 twice in June and Outfall 005 (Site 84) exceeded the pH limit of 9.0 once in September. The pH of the three exceedances ranged from 9.1 to 9.3. All three exceedances were associated with pH measurements made at the laboratory. The pH measured in the field for these three samples ranged from 8.7 to 8.9. Review of the lab reports indicate that the lab did not measure the pH on the day the samples were collected but were measured five to 13 days after sample collection. These results should have been considered invalid due to the potential for additional and biological reactions to occur during this time period. No exceedances occurred at the outfalls associated with permit CO-0036684, CO-0042161, COG-850051 or COG-850054 in 2020. 3.7 Mine Water Discharge Sites There are three mine water discharge monitoring sites associated with the TC operation. Attachment 6 shows the water quality results during the report period. Site 109 (Foidel Creek Mine surface facilities) requires quarterly monitoring for flows, field parameters, and water quality samples (when flowing). Site 109 has not discharged in about 20 years and will not be discharging in the conceivable future. Site 115 (Fish Creek Borehole) is monitored as a CDPS 26