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t L1111 SECOR www secorcon, <br /> INTERNATIONAL <br /> INCORPORATED 3017 Kilgore Road Suite 100 <br /> Rancho Cordova,CA 95670 <br /> 916-86140400 TEL <br /> 916 861 0430 FAx <br /> OCT <br /> s << 2003 <br /> ENv <br /> October 10, 2003 <br /> �RW11TISERVICES 44 <br /> a <br /> Ms Lori Duncan <br /> San Joaquin County Environmental Health Division <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, California 95202-2708 <br /> Re Proposed Reductions in the Sampling Program and Response to SJCEHD Letter Dated <br /> September 11,2003 <br /> Chevron Service Station No 9-4275 and ARCO Service Station No 2133 Commingled Plume <br /> 2905 and 2908 Benjamin Holt Drive <br /> Stockton, California <br /> SECOR Project No 77BP 52133 03 0347 <br /> Dear Ms Duncan <br /> On behalf of BP and Chevron Environmental Management Company (Chevron), SECOR <br /> International Incorporated (SECOR) has prepared this letter in response to the San Joaquin County <br /> Environmental Health Division (SJCEHD) letter dated September 11, 2003 (Attachment 1), <br /> addressed In reference to the ARCO Service Station listed above This letter also includes a <br /> proposal to modify the current groundwater sampling program at the ARCO Service Station A <br /> summary of the current groundwater sampling program Implemented at the Chevron and ARCO <br /> Service Stations (Figures 1 and 2) is presented below, followed by SECOR's recommendations for <br /> future sampling at the ARCO Service Station, based on a review of historical groundwater analytical <br /> and hydraulic gradient data through the second quarter 2003 Historical data and maps from the <br /> second quarter 2003 monitoring and sampling event are included in Attachment 2 <br /> , <br /> CURRENT GROUNDWATER SAMPLING PROGRAM <br /> i <br /> The groundwater monitoring well network at the ARCO Service Station consists of 20 groundwater 1 <br /> monitoring wells (E-2 through E-12, PR-1, PR-2, BHD-1, BHD-2, and MW-1 through MW-5) The <br /> groundwater monitoring well network at the Chevron Service Station is comprised of 9 groundwater <br /> monitoring wells (MW-1 through MW-9) As part of the sampling program at the Chevron Service <br /> Station, groundwater samples are also collected from a nearby municipal well, City of Stockton <br /> Municipal Well#10, which is located east of the site (Figure 2) SECOR currently maintains oversight , <br /> of the groundwater monitoring and sampling programs implemented at both sites Monitoring and ] <br /> sampling activities at the ARCO Service Station are performed by SECOR personnel, and are jointly <br /> coordinated with those performed by Gettler-Ryan, Inc (GRI) at the Chevron Service Station <br /> Groundwater levels and dissolved oxygen (DO) are measured in all wells on a quarterly basis The <br /> current monitoring and sampling schedule for both sites is presented below <br /> y <br /> ARC01213311UIisc Letters\SHCEHD RspLtr&M&S Redx Req doc <br />