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Table 15 Dissolved Zinc 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 0.029 0.025 0.110 2.0 Agricultural 0.052 0.39 0% 5% 0%Good Spring POC-8 7 mg/L 0.029 0.025 0.050 2.0 Agricultural 0.052 0.39 0% 0% 0%Good Spring POC-9 2 mg/L 0.108 0.025 0.190 2.0 Agricultural 0.052 0.39 0% 50% 0%Good SpringPOC-10 7mg/L0.025 0.025 0.0252.0 Agricultural 0.052 0.39 0% 0% 0%Good SpringPOC-11 7mg/L0.025 0.025 0.025 2.0Agricultural0.052 0.390% 0%0%Good SpringPOC-12 7mg/L0.025 0.025 0.0252.0 Agricultural 0.052 0.39 0% 0% 0%Good SpringPOC-13 7mg/L 0.025 0.025 0.025 2.0 Agricultural 0.052 0.39 0% 0% 0%Good SpringPOC-14 7mg/L0.025 0.025 0.0252.0 Agricultural 0.052 0.39 0% 0% 0%TaylorMT-95-02 21mg/L0.025 0.025 0.0252.0 Agricultural 0.052 0.39 0% 0% 0%Taylor POC-3 7 mg/L 0.025 0.025 0.025 2.0 Agricultural 0.052 0.39 0% 0% 0%Wilson GOSSARD WELL 21 mg/L 0.025 0.025 0.025 2.0 Agricultural 0.052 0.39 0% 0% 0%WilsonPOC-1 7mg/L0.025 0.025 0.0252.0 Agricultural 0.052 0.39 0% 0% 0%Wilson POC-2 7 mg/L 0.025 0.025 0.025 2.0 Agricultural 0.052 0.39 0% 0% 0%Wilson POC-5 7 mg/L 0.025 0.025 0.025 2.0 Agricultural 0.052 0.39 0% 0% 0%Wilson POC-16 7 mg/L 0.025 0.025 0.025 2.0 Agricultural 0.052 0.39 0% 0% 0%Wilson POC-6 7 mg/L 0.025 0.025 0.025 2.0 Agricultural 0.052 0.39 0% 0% 0%WilsonPOC-15 7 mg/L 0.025 0.025 0.025 2.0Agricultural0.052 0.390% 0%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 dissolved zinc reported at upgradient wells A-6 and A-8.(4) Site Background Value represents the 95 percent Upper Tolerance Limit for dissolved zinc reported at NGSW and Gossard Well using Pre-1994 data.(5) Non-detect sample results were assigned one-half of the reporting limit.Dissolved Zinc ConcentrationPage 1 of 1