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Table 2Comparison of the Regulation No. 41 Basic Standards for Ground Water to Site Background ConcentrationsColowyo Mine, Meeker, ColoradoConstituentUnitsRegulation 41 Human Health Standard(1)Regulation 41 Drinking Water Standard(1)Regulation 41 Agricultural Standard(1)Most Stringent Regulation 41 StandardUpgradient Background (A-6 + A-8) 95/95 UTLPre-1994 Data(Gossard + NGSW)95/95 UTLArsenic mg/L 0.01 --- 0.1 0.01 0.005 0.007Chloride mg/L --- 250 --- 250 (2) (2)Field pH s.u. --- 6.5 - 8.5 6.5 - 8.5 6.5 - 8.5 8.50 8.40Iron mg/L --- 0.3 5 0.3 1.48 No DataManganese mg/L --- 0.05 0.2 0.05 0.09 0.75Mercury mg/L 0.002 --- 0.01 0.002 0.001 0.001Nitrate (as N) mg/L 10.0 --- --- 10.0 12.2 1.62Nitrate+Nitrite (as N) mg/L 10.0 --- 100 10.0 12.2 2.9Nitrite (as N) mg/L 1.0 --- 10 1.0 0.1 0.14Selenium mg/L 0.05 --- 0.02 0.02 0.022 0.006Sulfate mg/L --- 250 --- 250 626 997Total Dissolved Solids(3)mg/L---1,700---1,7001,3601,840Zincmg/L---5220.0520.39Notes:mg/L = milligrams per liters.u. = standard unitsUTL = upper tolerance limit(1) 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.(2) No background data were available because chloride is not a monitored constituent in Colowyo's Mine Permit.(3) Per Regulation 41, the standard for total dissolved solids (TDS) was calculated as 1.25 times the Upgradient Background UTL.Page 1 of 1