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• • <br />Project: Cripple Creek Geohydrology <br />Task: Summary <br />EVALUATION OF CRIPPLE CREEK DISTRICT GEOHYDROLOGY <br />OBJECTIVE <br />This workbood evaluates the hydrology of the Cripple Creek Mining District. <br />METHOD <br />The method used is the performance of a water balance. <br />The water balance in the district is made up of the following: <br />1 Precipitation (approximately 19.58 inches per year) <br />2 Infiltration (moderate, estimated at 25% pre-mining) <br />3 Surface runoff (close to zero) <br />4 Evapotranspiration (large; comprises approximately 75% of the precipitation) <br />5 Groundwater discharge (the balance: averages about 1662 gpm for the period 1992-2007) <br />PRECIPITATION <br />Precipitation has been measured at a variety of locations in the operational period 1992-2007. <br />The data has been assembled, and the monthly total precipitation is presented in "Precipitation DB" and "Precipitation Table". <br />To complete the table, the precipitation for December 2007 has been set equal to the average precipitation for that month. <br />CARLTON FLOW <br />The flow from the Carlton Tunnel was measured at different locations before and after 1996. <br />In addition, the flow was interrupted as the flow was diverted to clean the existing ponds and construct a new pond at that time. <br />The flow has been corrected so that the data provides a consistent estimate of the actual flow from the diatreme over the period of record. <br />This correction is presented in "Carlton Outflow", and the measured, correction, and corrected flows are shown in "Carlton Outflow-Pic". <br />is <br />Date: 4/8/2008 <br />Page 1-1 <br />FLOW EVALUATION <br />The impact that mining has had on flow can be evaluated by comparing the precipitation with the outflow from the Carlton Tunnel. <br />This is presented in a double-mass chart, which is presented as "Double Mass". <br />The cumulative outflow is proportional to the cu mul_ati_v_e precipitation, which-indicates-that-there-are_mining-related-changes-in-infltration:- - -- <br />YIELD <br />The impact of mining can be evaluated by considering the yield of the basin as a function of precipitation. <br />The yield of the basin is a strong function of the precipitaiton; the higher the precipitation the lower the apparent yield. <br />This is contrary to expectation; standard yield evaluations show yield increasing with precipitation, as shown in "Yield-Pic" <br />The reason is the large constant-flow component to the yield; when precipitation is low, apparent yield is dominated by this constant flow. <br />Accordingly, the apparent yield is very high in low precipitation periods, and correspondingly very low in high precipitation periods. <br />This large constant flow component is a key part of the infiltration model developed in this workbook. <br />Adrian Brown Consultants, Inc.