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Grassy Valley hydrologic conditions 35 <br />Riparian areas are all approximately flat, so planar areas were used in this calculation. <br />ET from dry drainage areas was calculated using the sloped area of the ground surface. The <br />following calculation was performed: <br />ET rate x sloped segment <br />At some times, potential ET is greater than precipitation. During these periods, ET was <br />restricted to the amount of available water in that segment. <br />For the post-mining ECOSA area, evaporation was calculated as the lesser of: <br />• ET rate x ECOSA area; or <br />• ((rainfall + snowmelt] x ECOSAarea)-runoff from ECOSA area <br />Flow toward Grassy Creek: <br />For each segment of Grassy Valley, flow toward Grassy Creek was calculated as: <br />Water contributing to segment area - ET and evaporation from that area -deep <br />bedrock infiltration within that drainage area <br />This calculation was performed for all segments of the drainage, with the total flow to Grassy <br />Creek being calculated as the sum of the flow from all contributing segments. <br />Flow through to the shallow alluvium: <br />Flow through the shallow alluvial flow system in the vicinity of GV-03 was calculated using a <br />modified Darcy equation: <br />Q= K x i x A x effective flow area factor <br />Where: <br />Q =flow rate <br />K =hydraulic conductivity of alluvium <br />i =hydraulic gradient <br />A =cross-sectional area of flow <br />A hydraulic conductivity of 1 x 103 centimeters per second (cm/s) was conservatively <br />selected as typical for alluvial material. A hydraulic gradient of 0.04 was used based on the <br />average slope of the valley floor upgradient of GV-03.. The area of flow was conservatively <br />-estimated to be about 1000 feet wide and about 30 feet deep on the basis of boring data. <br />Boring data from the alluvium indicate that although some of the alluvium contains material at <br />the hydraulic conductivity with a hydraulic conductivity of about 1 x 103 (cm/s), most of it <br />contains at least some clay and it is likely that the higher conductivity materials are poorly <br />connected. The cross-sectional area of flow was modified to reflect the "effective flow area" <br />or the "transmissive alluvial area" by multiplying the cross-sectional area by a factor of 0.20. <br />2736 Cripple Creek & Victor Gold Mining Company <br />Water Management Consultants <br />