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21 <br />• <br />4.0 GRASSY VALLEY HYDROLOGIC CONDITIONS <br />This section presents the hydrologic assessment of the Grassy Valley drainage and the <br />potential effects of the proposed MLE on the hydrology of Grassy Valley. Surface water <br />and groundwater monitoring data collected by CC&V through 2007 are summarized and <br />presented in this section. Supplemental field investigations were conducted in the <br />Grassy Valley drainage in 2007, and a water balance was developed based on existing <br />and new field data to evaluate the current conditions and potential effects of the <br />proposed ECOSA and the WHEX portion of the East Cresson surface mine on the <br />Grassy Valley drainage hydrology and hydrogeology. Results of the water balance and <br />hydrogeologic assessment were used to evaluate the design of the proposed ECOSA. <br />Data and conclusions from previous reports prepared for the Grassy Valley area are <br />incorporated; this includes. reports by the CC&V Exploration Department, Adrian Brown <br />Consultants, Inc., Shepherd-Miller, Inc, and others. Each report is_referenced when data <br />or conclusions are used in the following discussions. <br />4.1 Grassy Valley description and background <br />The Grassy Valley drainage location and the MLE permit boundary are shown on Figure <br />3.1. A detailed topographic map of the Grassy Valley drainage and features is <br />presented in Figure 4.1. Grassy Valley drainage (above surface water station GV-03) is <br />a southeast-oriented, ephemeral drainage, located to the northeast of the main project <br />area. Grassy Creek flows through Grassy Valley across the diatreme granite boundary <br />and then into Beaver Creek approximately 1.5 miles downstream of the permit boundary <br />(Figure 4.1). <br />Historical mine structures and features which are located in Grassy Valley include a <br />group of ponds which historically contained mine process waters from activities <br />occurring unrelated to the Cresson Project. Historical tailings are present throughout <br />upper Grassy Valley, as well as the historical Cameron and other mine workings <br />including the Pinnacle mine and the School Section leach pad. <br />Surface mining was approved in the Grassy Valley drainage under the Amendment No. <br />8 permit, and is currently proceeding in the Wildhorse portion of the East Cresson Mine. <br />The proposed MLE includes expansion of the East Cresson surface mine (East Cresson <br />WHEX portion) further into the Grassy Valley drainage and placement of overburden <br />material in the ECOSA. The limits of these mine components are shown on Figure 1.2. <br />2736 Cripple Creek & Victor Gold Mining Company <br />Water Management Consultants <br />