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11.0 Water Quality Monitoring Plan <br />Water quality monitoring requirements at the Sunday Mines Group currently include <br />the monitoring requirements set forth in the existing CDPS General Stormwater <br />Permit. In addition, Denison is collecting quarterly samples from the underground <br />well nest in the West Sunday Mine to define ambient groundwater conditions. This <br />quarterly sampling is expected to be completed in the first quarter, 2010. Denison <br />proposes to increase the existing water quality monitoring program to include <br />installation and future monitoring of groundwater at two wells located south and <br />west of the Sunday Mines Group. Denison proposes that the two new monitoring <br />wells would be groundwater quality compliance points for the DRMS permits, and <br />thus the compliance limit be based on the ambient groundwater condition. The <br />proposed location for these two wells is shown in Figure 11-1. The revised Sunday <br />Mines Group water quality monitoring plan would include the following <br />components: <br />¦ Surface water monitoring as set forth in the existing CDPS general stormwater <br />permit; <br />¦ Groundwater monitoring at the two downgradient monitoring wells. <br />The existing surface water monitoring program is adequate and appropriate for the <br />Sunday Mines Group, because perennial or intermittent surface water bodies are not <br />present in the affected areas of the mines, because existing stormwater BMPs are in <br />place, and because an existing permit is in place that addresses surface water. Denison <br />proposes to continue maintaining compliance with the existing CDPS General <br />Storm.water Permit, and to report the performance monitoring data to CDPHE as <br />specified in the existing permit. <br />A groundwater quality monitoring program has not previously been in place at the <br />Sunday Mines Group. Therefore, Denison proposes to establish a groundwater <br />monitoring program at the Sunday Mines Group through the DRMS mine permits in <br />accordance with this EPP. The monitoring program would include the following <br />components: <br />¦ Continued quarterly monitoring of the subsurface monitoring well nest until a <br />period of at least five quarters of data are available to determine ambient <br />groundwater conditions; <br />¦ "Monitoring of the two compliance wells on a quarterly basis for the first five <br />quarters of sampling will be completed. At which time, the Division will <br />determine the adequacy of the data and work with Denison to determine if <br />conditions arise necessitating a different sampling frequency or duration." <br />It is proposed that groundwater compliance points be established at the two <br />compliance wells based on the ambient groundwater quality determined from the <br />subsurface monitoring well nest. The compliance limit at the groundwater compliance <br />points is proposed to be the 95th confidence interval of the mean, as defined by the <br />11-1 <br />CADocuments and Settings\c od,w rd.DMC\Desktop\Current TO DO\Sundays\FINAL ORMS Report RTCv2 - EPP Sunday Mines.doc