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SECOR <br /> . International Incorporated <br /> February 15, 2002 <br /> Project 77 BP 50595 00 0150 RECENED <br /> Ms Lon Duncan <br /> San Joaquin County Public Health Services FEB 1 9 2002 <br /> 304 East Weber Avenue <br /> Stockton, California 95202 �N1lE F�ER _ � It 1 <br /> M1 1'T1`'J�� � � w• <br /> Re Work Plan for Additional Site Assessment <br /> ARCO Station#595 <br /> 6100 North Highway 99 <br /> Stockton, California <br /> Dear Ms Duncan <br /> This letter, prepared by SECOR International Incorporated (SECOR) on behalf of <br /> Atlantic Richfield Company, presents a work plan for additional site assessment activities <br /> involving the installation of 3 deep groundwater monitoring wells and 2 shallow <br /> groundwater monitoring wells at the subject site (Figures 1 and 2) This work plan has <br /> been prepared in response to the San Joaquin County Environmental Health Department <br /> (SJCEHD) letter, dated December 31, 2001 (Attachment A) The purpose of the <br /> proposed work is to define the lateral and vertical extent of hydrocarbons in the <br /> groundwater beneath the site This work plan includes a brief discussion of site <br /> background, proposed scope of work, and schedule <br /> SITE DESCRIPTION AND BACKGROUND <br /> The site is located at 6100 N Highway 99 in Stockton, California, and is an operating <br /> AM/PM mini-mart and ARCO service station The site is bordered by orchards to the <br /> north, east, and south, and by Highway 99 to the west (Figure 1) The site currently <br /> contains three 12,000-gallon gasoline underground storage tanks (USTs), associated <br /> product lines, and dispensers (Figure 2) Additionally, a domestic water supply well <br /> (WSW) is located on the southwest corner of the property <br /> During September 1999, product lines and dispensers at the site were upgraded and <br /> replaced within the same trench locations Twenty-one soil samples were collected from <br /> beneath the product lines, vapor lines, dispensers, and previously abandoned-in-place <br /> product lines Total petroleum hydrocarbons as gasoline (TPHg) were reported in <br /> eighteen of the twenty-one samples, with concentrations ranging from 1 94 mg/kg to <br /> 11,300 mg/kg Benzene was reported in fifteen of the twenty-one samples at <br /> concentrations ranging from 0 0316 mg/kg to 48 3 mg/kg Methyl tert-butyl ether <br /> (MtBE) was reported in fourteen of the twenty-one samples ranging in concentration from <br /> ti <br /> 3017 Kilgore Road, Suite 100, Rancho Cordova, CA 95670 916 861 0400 916 861 0430 Fax www secor com <br />