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Point of Compliance Well Investigation <br /> <br /> <br /> <br />AECOM <br />11 <br /> <br />meets the standard values. According to the Interim Narrative Standard described in Section <br />41.5.C.6. of Regulation 41: <br />“…ground-water quality shall be maintained for each parameter at whichever of the <br />following levels is less restrictive [emphasis added]: <br />(A) existing ambient quality as of January 31, 1994, or <br />(B) that quality which meets the most stringent criteria set forth in Tables 1 through 4 of <br />“The Basic Standards for Ground Water.” <br />It has been shown for Colowyo Mine that existing ambient water quality as of January 31, 1994 <br />was in many cases higher (and therefore less restrictive) than the most stringent criteria set <br />forth in Tables 1 through 4 of the BSGW. As such, AECOM believes that a hybrid approach for <br />establishing groundwater compliance standards is appropriate for the Mine. The applicable <br />standard for each regulated groundwater constituent included in the Mine Permit should be the <br />higher of the most stringent groundwater quality criteria or the pre-1994 background UTL. <br />Following this approach, proposed groundwater compliance standards for the monitored <br />constituents are shown in Table 16. The table also indicates whether each proposed standard <br />is derived from Regulation 41 or from the pre-1994 background UTL. Using the pre-1994 <br />background value as the standard is proposed for manganese, sulfate, and TDS. Compliance <br />criteria for the remaining constituents would be evaluated using the most stringent groundwater <br />standard from Regulation 41.