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9 <br /> -_ Student Login Date <br /> Staff Review.Date <br /> GROUND ZERO ANALYSIS, ction <br /> fiaken <br /> 1714 Main Street <br /> Escalon, California 95320-1927 - /� <br /> Telephone:.(209) 838-9888 <br /> Facsimile: (209) 838-9883 <br /> November 1, 2001 <br /> Mr. Marty Hartzell <br /> CA Regional Water Quality Control Board, <br /> Central Valley Region <br /> 3443 Routier Rd.,.Ste. A <br /> Sacramento, CA 95827-3098 <br /> Subject: North Stockton Auto Service <br /> 8709 N. Davis Rd., Stockton, CA (Site Code 0786) <br /> Additional Infonnation on Domestic Water Supply Well <br /> Dear Mr. Hartzell: <br /> We are writing to provide you with the additional information you verbally requested concerning <br /> the domestic water supply well located north of the subject fuel leak site. The well is located <br /> at the residence at 8723 N. Davis Rd. ` <br /> • Well Construction: We were unable to find any documentation of well construction <br /> details. The property owner had no information either. <br /> • Well Use: According to the property owner, the well is the only water supply for the <br /> residence and the residence is not connected to public water. <br /> • Location: The well islocated approximately 80 feet, N23°E of the former tankpit at <br /> 8709 N. Davis Rd. A Site Plan showing the domestic well location is attached. <br /> You also asked that we prepare an opinion concerning the potential for dissolved contaminants <br /> to migrate from beneath the former underground storage tank location to the domestic well. We <br /> evaluated the worst-case scenario by modeling the transport of 1,1-DCA, cis-1,2-DCE and <br /> F MTBE from the tankpit area to the domestic well. These compounds were previously detected <br /> in a grab groundwater sample at concentrations slightly above their respective MCLs. <br /> For the transport modeling it was assumed that the hydraulic_conductivity of the aquifer_.is_10-2 <br /> r cm/sec, hydraulic gradient is 0.0015 ft/ft, the plume width at the source area is 15 feet, the <br /> vertical mixing zone is 6 feet, the distance from the source to receptor is 75 feet, effective <br /> porosity of the aquifer material is 35%, organic carbon content of the aquifer material is 0.1 %, <br />