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.� , SE -I' www_secorcom <br /> INTERNATIONAL 3017 Kilgore Road,Suite 100 <br /> S E C O R INCORPORATED Rancho Cordova,CA 95670 <br /> 916-861-0400 TEL <br /> 916-861-0430 FAX <br /> April 25, 2005 <br /> Ms. Lori Duncan fCD)[E 0l% [ED <br /> San Joaquin County Environmental Health Division <br /> 304 East Weber Avenue, Third Floor APR 2 <br /> Stockton, CA 95202 <br /> ENVIRONMENT HE <br /> hLTH <br /> RE: Work Plan Addendum for Well Destruction and UST Removal PERM T/SERV;CES <br /> Chevron Service Station 9-4275 <br /> 2905 Benjamin Holt Drive <br /> Stockton, CA <br /> SECOR Project No.: 77CH.94275.08.0370 <br /> Commingled Plume#35 <br /> Dear Ms. Duncan: <br /> SECOR International Incorporated (SECOR), on behalf of ChevronTexaco Environmental <br /> Management Company (EMC), presents this addendum to the Work Plan for Well Destruction and <br /> UST Removal, dated February 18, 2005, for the above referenced site. San Joaquin County <br /> Environmental Health Department (SJCEHD) approved the work plan, with comments, in a letter <br /> dated March 3, 2005 (Attachment 1), The purpose of this addendum is to further discuss the limits of <br /> the existing underground storage tank (UST) proposed excavation. In addition, SECOR proposes <br /> three additional soil borings at the location of the proposed new UST pit in the southeast corner of <br /> the site. <br /> SOIL BORINGS <br /> In addition to the well destructions proposed in SECOR's original work plan, three soil borings are <br /> proposed to be advanced at the location of the proposed new UST pit in the southeast corner of the <br /> site (Figure 1). Laboratory data obtained from soilsamples collected during boring advancement willv\w �J <br /> be used for pre-profiling the soil expected to be generated during soil removal at the new proposed <br /> UST pit. Once pre-profiled for an approved landfill, the soil can be hauled directly to the landfill <br /> during soil removal and not stockpiled onsite. Each boring will be advanced using hollow stem auger <br /> to a depth of approximately 20 feet below ground surface (bgs). Soil samples will be collected at 5- <br /> foot intervals and will be sent under chain-of-custody procedures to a California State-certified <br /> laboratory for analysis. The soil samples will be analyzed for the presence of total petroleum <br /> hydrocarbons calculated as gasoline (TPHg), benzene, toluene, ethylbenzene, xylenes (BTEX <br /> compounds), and methyl tertiary butyl ether (MtBE) by EPA Methods 8015 and 8020, and total lead <br /> by EPA Method 6010. <br /> I <br /> EXISTING UST REMOVAL AND OVEREXCAVATION <br /> After the removal of the existing UST's, SECOR proposes limited over-excavation if soils <br /> contaminated with hydrocarbons ate encountered. Over-excavation will be limited to approximately <br /> 100 to 500 cubic yards of soil. The area of possible over-excavation is shown as a dotted line on <br /> Figure 1. The maximum vertical extent of the over-excavation will be based on the limits of the <br /> excavation equipment, or approximately 20 feet. <br /> I:\Chevron\94275\REPORTS\2005\WorkPlan Addendum.doc <br />