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Q++' SECOR wwwsecorcom <br /> INTERNATIONAL 3017 Kilgore Road,Suite 100 <br /> S E C ® R INCORPORATED Rancho Cordova CA 95670 <br /> 916 861 0400 TEL <br /> 916 861 0430 FAX <br /> I <br /> September 30, 2003 <br /> Mr Michael Infurna <br /> o C T - 3 2003 <br /> San Joaquin County Public Health Services ENVIRONMENT HEALTH <br /> Environmental Health Division PERMIT/SERVICES <br /> 304 East Webber Avenue,Third Floor <br /> Stockton, CA 95202 z <br /> f <br /> Re Results of Offsite Assessment and Site Conceptual Model <br /> ConocoPhlllips <br /> Former 76 Service Station No 4409 <br /> 1502 N EI Dorado Street <br /> Stockton, California <br /> Site Code 508431 <br /> Dear Mr Infurna 1 <br /> SECOR International Incorporated (SECOR) has prepared this report on behalf of ConocoPhillips to <br /> document the findings of an offsite assessment and submit a Site Conceptual Model for the site <br /> referenced above (Figure 1) The objective of this work was to delineate the lateral and vertical <br /> extent of petroleum hydrocarbons in groundwater at the site The scope of work consisted of the <br /> installation of four offsite groundwater monitoring wells (MW-11, MW-12, MW-13, MW-14) completed <br /> at depths of approximately 78 to 83 feet below ground surface (bgs) This work was performed as <br /> described in SECOR's Work Plan for Additional Off-Site Assessment, dated June 27, 2002, and in <br /> accordance with conditions stated In a San Joaquin County Environmental Health Department <br /> (SJCEHD) approval letter dated July 8,2002 (Attachment 1) <br /> r� <br /> BACKGROUND <br /> The site is located on the northeast corner of Harding Way and EI Dorado Street In Stockton, <br /> California (Figures 1 and 2) The site Is a Former 76 Unocal service station that dispensed gasoline y <br /> and diesel fuel x <br /> SITE HISTORY <br /> Previous Investigations <br /> On April 7, 1999, three 10,000-gallon capacity underground storage tanks (USTs), which contained <br /> gasoline and diesel fuel, were removed from the site Excavation dimensions were approximately 35 , <br /> feet by 40 feet by 15 feet deep Initial remedial activities included source removal of obviously <br /> impacted soil to a depth of approximately 18 feet below ground surface (bgs) beneath the center of <br /> the western fuel tank Additional remedial activities Included source removal of obviously impacted <br /> soil in the area beneath the former dispenser and product lines A concrete pad restricted the lateral <br /> extent of excavation During excavation of impacted soil, unidentified fiberglass piping was found <br /> Additional excavation and sampling was completed on April 8, 1999 to remove the unidentified piping <br /> Samples were collected from the bottom and sidewalls of the excavated area Following removal of <br />