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Canepa's Car Wash <br /> 6230 Pacific Avenue, Stockton, California January 31, 1995 <br /> Groundwater Pump Test Page 6 <br /> where <br /> P=permeability, in gpd/sq ft <br /> Q=pumping rate, in gpm <br /> ri =distance to nearest observation well, in feet <br /> trz =distance to farthest observation well, in feet <br /> saturated thickness, in feet, at the site of the farthest observation well <br /> =saturated thickness, in feet, at the site of the nearest observation well <br /> 45 Well Efficiency <br /> Well efficiency was detern-uned from the distance-drawdown plot (Appendix D) The <br /> intersection of the straight line plot with the radius of the pumped well (the gravel <br />' pack outer radius is 0 5 ft for MW-1) shows the theoretical drawdown for a 100% <br /> efficient well to be 4 05 feet The actual drawdown in MW-1 was 7 74 feet The <br /> efficiency is calculated as 4 05n74 x 100 = 52% This is caused mainly by partial <br />' penetration of the aquifer by the well screen Vertical permeability is almost always <br /> less than horizontal permeability and this results in considerable head losses from the <br /> vertical flow involved <br /> 5.0 Conclusions <br />' Theoundwater test performed on December 22- 23, 1994, resulted in the calculation <br /> �" pump <br /> of several aquifer hydraulic properties <br /> Transmissibility(averaged) ------------------- 15,400 gpd/ft <br />' Storage Coefficient (averaged) ----------------- 00028 <br /> Permeability ------------------------ ------------- 126 gpd/sq ft <br /> Effective radius ---------=`-=---=»===--N--==---- 140 feet <br /> Optimum pumping rate 5 gpm <br /> The pump test has demonstrated that there is a source of recharge affecting observation. wells <br /> MW-4, 6& 8 Aquifer boundaries are apparent on the plots of MW-4, 6 &7 <br /> The above represents our best professional opinion as to environmental conditions at this site <br /> These opinions were derived using data at hand, and using standards of care common to the <br /> environmental consulting community in Northern California Additional work or sampling at <br /> this site may generate data that could lead to a change of opinion regarding site conditions or <br /> appropriate site remediation procedures, or both <br />