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Beacon Station No 419 August 13, 1997 <br /> Stockton California Aquifer Testing Report <br /> . Graphs of time vs drawdown, as measured with the water level indicators are included in <br /> Attachment B Using the time-drawdown method for the long-term water level indicator <br /> data collected in May and early June 1997, and an average pumping rate of 3 0 gpm, the <br /> calculated transmissivities (T) were 1,015 gpd/ft for MW-1, 966 gpd/ft for MW-2, and 1,182 <br /> gpd/ft for MW-6 The calculated storativities (S) were 0 040 for the MW-1 data, 0 014 for <br /> the MW-2 data, and 0 031 for the MW-6 data Using an aquifer thickness of 19 feet in well <br /> MW-1, results in an estimated value of hydraulic conductivity (K) of approximately 7 1 feet <br /> per day Using an aquifer thickness of 22 5 feet in well MW-2, results in an estimated value <br /> of hydraulic conductivity (K) of approximately 5 7 feet per day Assuming an aquifer <br /> thickness of 22 5 feet in well MW-6, results in an estimated value of hydraulic conductivity <br /> (K) of approximately 7 0 feet per day <br /> Graphs of distance vs drawdown, as measured with the water level indicators in wells MW- <br /> 1, MW-2, and MW-6 are included in Attachment B Using the distance-drawdown method <br /> for the long-term water level indicator data collected in June 1997, and an average pumping <br /> rate of 3 0 gpm, the calculated transmissivity (T) was 3,168 gpd/ft, and the calculated <br /> storativity (S) was 0 125 Using an aquifer thickness of 20 feet from the boring log for <br /> pumping well MW-3, results in an estimated value of hydraulic conductivity (K) of <br /> approximately 21 feet per day <br /> Based upon the above calculations, the range of hydraulic conductivity (K) values between <br />• 5 7 and 46 feet per day (or between 43 and 347 gpd per square foot) are reasonable, as the <br /> aquifer materials encountered beneath the site consist predominantly of silty sand (SM) with <br /> interbeds of sandy to clayey silt (ML) and sandy to silty clay (CL) <br /> Conclusions <br /> Based upon the above field test data and using time-drawdown calculations, an average <br /> value of hydraulic conductivity (K) of 19 5 feet per day was used to calculate a theoretical <br /> steady state capture zone that would be created by pumping from morutormg well MW-3 at <br /> a rate of 3 0 gpm The downgradient stagnation point was estimated to be approximately <br /> 110 feet and the maximum width of the capture zone was estimated to be approximately 700 <br /> feet At a rate of 2 5 gpm, the downgradient stagnation point was estimated to be <br /> approximately 92 feet and the maximum width of the capture zone was estimated to be <br /> approximately 580 feet Sustained, continuous pumping may result in a larger capture zone <br /> Based upon the above field test water level indicator data and using distance-drawdown <br /> calculations, a value of hydraulic conductivity (K) of 28 feet per day for well MW-3 was <br /> used to calculate a theoretical steady state capture zone that would be created by pumping <br /> from monitoring well MW-3 at a rate of 3 0 gpm The downgradient stagnation point was <br /> estimated to be approximately 82 feet and the maximum width of the capture zone was <br /> estimated to be approximately 550 feet At a rate of 2 5 gpm, the downgradient stagnation <br />. point was estimated to be approximately 68 feet and the maximum width of the capture zone <br /> was estimated to be approximately 430 feet Graphical representations of the average <br /> theoretical capture zones for 3 0 gpm and 2 5 gpm are shown in Figures 4 and 5 <br /> 1419 11-rpt HORIZON ENVIRONMENTAL INC <br />