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Table 13 Sulfate Concentration Statistics in Temporary Site Monitoring WellsColowyo Mine, Meeker, ColoradoDrainage Well NameNo. of Samples(1)Unit Average Minimum MaximumGroundwater Standard(2)Standard TypeUpgradient Well Site Background Value(3)Downgradient Well Site Background Value(4)% Exceeding Groundwater Standard% Exceeding Upgradient Well Background% Exceeding Downgradient Well BackgroundGood Spring NGSW 21 mg/L 884 674 997 250 Drinking Water 626 997 100% 100% 0%Good Spring POC-8 7 mg/L 293 115 603 250 Drinking Water 626 997 57% 0% 0%Good Spring POC-9 2 mg/L 422 220 623 250 Drinking Water 626 997 50% 0% 0%Good SpringPOC-10 7mg/L610 592 654250 Drinking Water 626 997 100% 14% 0%Good SpringPOC-11 7mg/L647 334 731 250Drinking Water626 997100% 86%0%Good SpringPOC-12 7mg/L1594 1360 1720250 Drinking Water 626 997 100% 100% 100%Good SpringPOC-13 7mg/L 1149 815 1330 250 Drinking Water 626 997 100% 100% 71%Good SpringPOC-14 7mg/L1696 1340 3030250 Drinking Water 626 997 100% 100% 100%TaylorMT-95-02 21mg/L949 842 1170250 Drinking Water 626 997 100% 100% 14%Taylor POC-3 7 mg/L 1084 1020 1180 250 Drinking Water 626 997 100% 100% 100%Wilson GOSSARD WELL 21 mg/L 801 629 1030 250 Drinking Water 626 997 100% 100% 5%WilsonPOC-1 7mg/L578 277 661250 Drinking Water 626 997 100% 29% 0%Wilson POC-2 7 mg/L 597 483 645 250 Drinking Water 626 997 100% 14% 0%Wilson POC-5 7 mg/L 886 414 1100 250 Drinking Water 626 997 100% 86% 29%Wilson POC-16 7 mg/L 1933 1760 2160 250 Drinking Water 626 997 100% 100% 100%Wilson POC-6 7 mg/L 1330 267 2610 250 Drinking Water 626 997 100% 86% 86%WilsonPOC-15 7 mg/L 648 602 715 250Drinking Water626 997100% 57%0%Notes:mg/L = milligrams per liter(1) The period of record used to calculate statistics was January 2015 through March 2020 for the existing permanent monitoring wells, and October 2019 through November 2020 for the temporary wells.(2) Groundwater standard obtained from Colorado Department of Public Health and the Environment (CDPHE) Regulation No. 41, The Basic Standards for Ground Water (BSGW), adopted May 11, 2020, and effective June 30, 2020. (3) Site Background Value represents the 95 percent Upper Tolerance Limit for sulfate reported at upgradient wells A-6 and A-8.(4) Site Background Value represents the 95 percent Upper Tolerance Limit for sulfate reported at NGSW and Gossard Well using Pre-1994 data.(5) Non-detect sample results were assigned one-half of the reporting limit.Sulfate ConcentrationPage 1 of 1