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SECOR www.secor.com <br /> INTERNATIONAL 3017 Kilgore Road,Suite 100 <br /> Rancho Cordova,CA 95670 <br /> S E C O R INCORPORATED 916-861-0400 TEL <br /> 916-861-0430 FAX <br /> November 24, 2004 <br /> n r� <br /> SM <br /> Ms. Victoria McCartney 204 <br /> San Joaquin County Environmental Health Division NQV 2 9 <br /> 304 East Weber Avenue, Third Floor ENT HEALTH <br /> Stockton, California 95202 ENVIRONM V1GES <br /> PERMITISER <br /> RE: Work Plan for Additional Assessment <br /> Chevron Service Station 9-1452 <br /> 334 East Main Street <br /> Ripon, California <br /> SECOR Project No.: 77CH.91452.06.0120 <br /> Dear Ms. McCartney: <br /> SECOR International Incorporated (SECOR), on behalf of Chevron Environmental <br /> Management Company (Chevron), presents this assessment work plan (Work Plan) for the <br /> above-referenced site. The purpose of this Work Plan is to further evaluate the lateral <br /> extent of petroleum hydrocarbon impacts to soil and groundwater and to investigate the <br /> integrity of the underground storage tank (UST) system. <br /> In addition, the County has requested that Chevron investigate the vertical extent of <br /> impacts to soil and groundwater at the site. Impacts to groundwater were reported in <br /> SECOR's CPT and Monitoring Well Installation Assessment Report, dated February 28, <br /> 2004. Methyl tertiary butyl ether (MtBE) was reported in cone penetrometer (CPT) test <br /> boring CPT-1 at concentrations of 4, 5, and 13 micrograms per liter (ug/L) at 66 feet, 91 <br /> feet, and 116 feet below ground surface (bgs), respectively. MtBE was reported in CPT test <br /> boring CPT-2 at concentrations of 2 ug/L, 22 ug/L, and 12 ug/L at 75 feet, 96 feet, and 111 <br /> �< feet bgs, respectively. Impacts to groundwater are primarily at or below maximum <br /> 41),,,contaminant levels (MCLs). Therefore, it is SECOR's opinion that the County should <br /> m consider vertical impacts to soil and groundwater in the apparent source area defined. No <br /> 3 <br /> M eo N M'r*E i n e r",f r n:5 Lv;+' de piA <br /> 1n CPT-1, <br /> This Work Plan has been prepared as requested by the San Joaquin County Environmental <br /> Health Department (County) as indicated in the letter, dated September 14, 2004 <br /> (Attachment 1). The submittal of this Work Plan was extended from November 1 to <br /> December 1, 2004, as indicated in the letter from the County, dated October 26, 2004. <br /> This Work Plan includes a brief site description, scope of work, and schedule. <br /> SITE DESCRIPTION <br /> The site is an active service station located at 334 East Main Street in Ripon, California <br /> (Figure 1). Current site facilities include three 12,000-gallon gasoline USTs, two dispenser <br /> I:\Chevron\91452\REPORTS\2004\monitoring well work plan 2004 rev_a.doc <br />