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PUBLIC HtALTH SERVICtS <br /> SAN JOAQUIN COUNTY •r :;tl Z< <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 <br /> 209/468-3420 FILE <br /> US RENTALS OCT 0 7 1999 <br /> 2081 E CHARTER WY <br /> STOCKTON,CA 95205 <br /> Re: US Rentals Site Code:2223 <br /> 1444 Mariposa Rd. <br /> Stockton,CA 95205 <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD)has reviewed the <br /> Report of Findings dated August 26, 1999 prepared by Wallace-Khul & Associates for the above <br /> referenced site. Further evaluation of the groundwater at this site is necessary. <br /> The receptor survey in the above referenced report did not include a map showing wells located within a <br /> 2,000 foot radius. Please provide PHS/EHD with a map depicting wells located in a 2,000 foot radius of <br /> this site. Identify the wells on the map as they correspond to address locations reported in the above <br /> survey. <br /> Continue quarterly monitoring of all Monitoring Wells(MWs)and the on-site water well until otherwise <br /> directed by PHS/EHD. If analytical results for water samples collected from on-site MWs continue to <br /> reflect a decline in concentration, an attenuating contaminant balance may be demonstrated. Upon <br /> confirmation that the contaminant plume size is decreasing,a Closure Report for this site will be requested. <br /> This report should include all data supporting the conclusions stated in the above referenced Report of <br /> Findings, including calculations for the mass of contaminants remaining at this site. <br /> The potential for contaminant plume migration should be evaluated based on sound hydrogeological data. <br /> Any soil data regarding permeability,bulk density,moisture,porosity,and organic carbon content should <br /> be used for evaluation of the site. Provide construction details for the on-site water well. Groundwater <br /> hydraulic velocity should be determined and contaminant migration potential should be evaluted with <br /> respect to the contaminant mass. It may be necessary to conduct well drawdown tests and calculate the <br /> radius of influence of on site wells. A site conceptual model should be provided to PHS/EHD which <br /> depicts data supporting site closure. <br /> Pending further evaluation of the groundwater and the findings in regards to the migration potential of the <br /> contamination,mitigation measures may be necessary. Please contact Carol Oz at(209)468-3440 if you <br /> have questions regarding this letter. <br /> Donna Heran,REHS,Director <br /> Environmental Health Division <br /> Carol Oz, Senior REHS Margaret agorio,REHS <br /> Site Mitigation Unit Supervisor <br /> cc: Matthew Taylor, Sen.Engineer, Wallace-Kuhl&Assc., <br /> RWQCB,Central Valley Region-Mark List <br /> A Division of San Joaquin County Health Care Services <br />