Laserfiche WebLink
SE www.secor.com <br /> INTERNATIONAL 3017 Kilgore Road,Suite 100 <br /> S INCORPORATED Rancho Cordova,CA 95670 <br /> E C O R <br /> 916-861-0400 TEL <br /> 916-861-0430 FAX <br /> June 18, 2004 <br /> Mr. Harlin Knoll <br /> San Joaquin County Environmental Health Department <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, CA 95202 <br /> RE: Offsite Assessment Work Plan <br /> 7-Eleven Store#20632 <br /> 4627 Da Vinci Drive <br /> Stockton, CA <br /> SECOR Project No.: 77EL.20632.04.0104 <br /> Dear Mr. Knoll: <br /> This work plan, prepared by SECOR International Incorporated (SECOR) on behalf of 7-Eleven Inc., <br /> proposes advancing eight soil borings south and southwest of 7-Eleven store #20632, located at <br /> 4627 Da Vinci Drive in Stockton, California (Figures 1 and 2). The purpose of the borings is to <br /> collect grab groundwater samples to define the lateral extent of petroleum hydrocarbons dissolved in <br /> groundwater south and southwest of the site. This work plan was prepared at the request of the San <br /> Joaquin County Environmental Health Department (SJCEHD) in a-letter dated April 14, 2004 <br /> (Attachment A). <br /> BACKGROUND <br /> I <br /> Initial site assessment activities were executed in accordance with directives from SJCEHD (Fluor <br /> Daniel GTI 1997). The assessment concluded that soil impacted with gasoline appeared restricted <br /> to a limited area surrounding the underground storage tank (UST) pit and underlying the fuel <br /> dispensers. The USTs were replaced as part of 1998 upgrading requirements. Concurrent with <br /> limited overexcavation, several.days of high-volume dewatering occurred as part of construction <br /> activities, which also served as a short-term remediation event. <br /> Additional lateral and vertical assessment of dissolved methyl-tert-butyl ether (MtBE) and <br /> hydrocarbons was conducted through 2002. There are.currently seven onsite monitoring wells. In <br /> April 2002, three onsite monitoring wells (MW-4R, MW-6, and MW-7), two dual-nested sparge/vent <br /> wells (SPV-1 and SPV-2)and a vertical delineation soil boring (SB-1)were installed at the site. <br /> On April 22, 2002, a soil vapor extraction (SVE)test was conducted at the site. Vapor was extracted <br /> from MW-4R, MW-7, SPV-1, and SPV-2. Low influent vapor concentrations and poor vacuum <br /> response in observation wells were documented during the test. An air sparge test in SPV-1 <br /> increased the groundwater dissolved oxygen concentration from 0.5 to 2.4 milligrams per liter(mg/L) <br /> in SPV-1. <br /> In April 2003, 7-Eleven, Inc. upgraded the product lines at the site. Benzene, total petroleum <br /> hydrocarbons as gasoline (TPHg), and MtBE were reported at maximum concentrations of 0.019 <br /> milligrams per kilogram (mg/kg), 4.7 mg/kg, and 0.60 mg/kg, respectively, in soil samples collected <br /> beneath the product lines and fuel dispensers. <br /> I:\7-Eleven\7-11 Stores\20632\Workplans\20632 Offsite Assessment.doc ENPERMIT�SERVICES <br />