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SECOW www.secor.cflm <br /> 4-41 INTERNATIONAL 3017 Kilgore Road,Suite 100 <br /> J E C O R INCORPORATED Rancho Cordova,CA 95670 <br /> 916-861-0400 TEL <br /> 916-861-0430 FAX <br /> December 8, 2006 <br /> NI6 DEC I I PM I: 09 <br /> Mr. Harlin Knoll 5AH JO;CUli4 COUHTY <br /> San Joaquin County Environmental Health Department EFi T1 H DF�F!EPdI':;E <br /> q ty P HEALT1 � Dl"PaRTrlErlr <br /> 3404 East Weber Avenue, Third Floor <br /> Stockton, California 95202 <br /> RE: Work Plan for Vertical Delineation of Groundwater Contamination <br /> 76 (Former BP) Service Station No. 11194 <br /> 2375 Tracy Boulevard <br /> Tracy, California 95376 <br /> SECOR Project No: 77CP.01750.01/77BP.11194.00 <br /> Dear Mr. Knoll: <br /> SECOR International Incorporated (SECOR) has prepared this letter on behalf of Atlantic Richfield <br /> Company(a BP affiliated company)and ConocoPhillips to present a work plan for the drilling of one <br /> additional groundwater monitoring well at the site referenced above(Figure 1). The purpose of the <br /> proposed work is to assess vertical extent and possible hydrocarbon impacts, if any, to deeper <br /> groundwater at the site prior to site closure. <br /> In a letter dated May 27, 2005, San Joaquin County Environmental Health Department (SJCEHD) <br /> directed ARCO to submit a work plan to conduct a vertical assessment of groundwater contamination <br /> beneath the site, and define the lateral extent of groundwater contamination downgradient of <br /> monitoring well MW-7(Attachment A). On July 12, 2005, a work plan was submitted to the SJCEHD <br /> by URS for the additional assessment of groundwater contamination (Attachment B). The <br /> installation of one deep monitoring well (MW-9) and one dual completion monitoring well (MW- <br /> 10S/MW-1 OD)was proposed, however the work was never conducted. This workplan addresses <br /> the installation of MW-9. The dual completion well (MW-10S/MW-10D) is no longer necessary <br /> because the lateral extent of contamination has been defined to the northwest. <br /> A brief discussion of site background, updated sensitive receptor survey, proposed scope of work, k <br /> and schedule are presented below. <br /> SITE BACKGROUND ` <br /> The site is located at the northwest comer of the intersection of N. Tracy Boulevard and Grant Line <br /> Road in Tracy, California (Figure 1). The site formerly operated as a Mobile retail gasoline station. <br /> Currently, the site is operating as a Seventy-Six (76) retail gasoline station. <br /> In August 1986, four gasoline underground storage tanks (UST)s were removed and replaced. Site <br /> investigations have been ongoing since 1986. A total of 14 groundwater monitoring wells (MW-1 <br /> through MW-8, and AMW-1 through AMW-6)have been installed at the site. Well locations are shown <br /> in Figure 1. Well locations include those drilled by former Chevron, former Scotty's, and Beyond <br /> Petroleum (BP). <br /> I:IBP-ARC0105 BP-COP Sites1111941Work Plan111194 Vertical Delineation WP.doc <br />