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groundwater quality data, evaluates groundwater quality trends, and once permit <br />limits are established, compares the compliance well data to the permit limits. <br />11.2.4 Evaluation of Groundwater Monitoring Data <br />Groundwater monitoring data collected in accordance with this EPP will be used for <br />two primary purposes: <br />• With respect to the two compliance wells, evaluation of compliance with <br />permit limits; and <br />• With respect to the other wells, general monitoring of any effects of the <br />underground mine on groundwater quality. <br />Groundwater Quality Permit Limits <br />Groundwater quality permit limits for the Sunday Mines Group are under the <br />jurisdiction of DRMS as set forth by the BSGW and the stipulations of the <br />Memorandum of Agreement for the Implementation of SB181 Amendments to the Colorado <br />Water Quality Control Act Pertaining to the Regulation of Metal Mines (CDPHE 2010). <br />Permit limits established in accordance with this EPP are defined in two phases: <br />• Interim permit limits; and <br />• Final permit limits. <br />The interim permit limits will be established after collection of five quarterly <br />groundwater samples, and will be used until ambient groundwater quality is <br />adequately characterized through collection of 8 to 10 quarterly samples. Once <br />ambient groundwater quality is adequately characterized, the final permit limits will <br />be established. <br />Regulatory Considerations <br />Groundwater at the Sunday Mines Group is unclassified, and therefore, the narrative <br />standard is applicable as set forth by BSGW §41.5(C)(6)(a). This standard requires <br />groundwater to meet either the "existing ambient quality as of January 31, 1994, or <br />that quality which meets the most stringent criteria set forth in Tables 1 through 4 of <br />the Basic Standards for Groundwater, whichever is less stringent." Although similar, <br />the definitions of background water quality and ambient groundwater quality are <br />distinct within the regulatory framework established by the BSGW and the HRMMR. <br />• Background water quality is the quality of groundwater unaffected by the <br />activity (BSGW §41.3(3)); and <br />• Ambient water quality is the quality of groundwater on January 31, 1994 for <br />mines permitted prior to January 31, 1994; and the water quality at the time of <br />submittal of the permit application for mines permitted after January 31, 1994 <br />(HRMMR §1.1(5)). <br />C \ Users\ cwoodward\ Desktop \Sundays\FINAL - Environmental Protection Plan Sunday Mines Revised January 2012 docx <br />11 -5 <br />