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Ms. Cynthia Parker <br />July 13, 2001 <br />Page 4 <br />external elements interfere with the groundwater level and the aquifer properties aze <br />homogeneous and uniform. A simplified form of the Theis equation (Freeze and Cherry, <br />1979) is as follows: <br />~h=264Q1o 0.3Tt2 <br />g <br />T r2S <br />Where: <br />~h =change in water table elevation (ft) <br />Q =pumping rate (gpm) <br />T = transmissivity (gpd/ft) <br />r =distance from pumping well (ft) <br />S = storativity <br />t =time (days) <br />Aquifer Properties <br />The following reports were reviewed in order to develop an understanding of <br />groundwater conditions at the tocation of concern: <br />• Hydrogeological Chazacteristics of the Valley Fill Aquifer in the Brighton Reach <br />of the South Platte River Valley, Colorado. 1972. R.T. Hurr and P.A. Schneider. <br />USGS Open File Report 73-124. <br />• Geohydrology of Shallow Aquifers in the Fort Lupton -Greeley Area, Colorado. <br />2000. S.G. Robson, J.S. Heiny, and L.R. Arnold. USGS Atlas HA 746c. <br />Based on information contained in these reports, aquifer properties were estimated as <br />follows: <br />Transmissivity (T) 50,000 - 200,000 gpd/ft <br />Storativity (S) 0.2 <br />Depth to Bedrock 20 - 60 feet below ground surface <br />Water Table Elevation less than 10 feet below ground surface <br />Saturated Thickness 10 - 400 feet <br />Results and Discussion <br />The Theis equation described above was used to estimate the effects of groundwater <br />pumping during mining operations on the Nix property. The predicted theoretical <br />drawdowns are based on the assumption that a single well is located 500 feet north of the <br />Hydrosphere Resource Consultants, 1002 Walnut Suite 200, Boulder, CO 80302 <br />