WORK PLANS - Laserfiche WebLink

Home Browse Search

S E C O R RECO ED July 31, 2007 Alf^ 0 1 2007 ENVIRONk-1-NT HEAC(H PERMIT/SERVICES Mr. Mike Infurna San Joaquin County Environmental Health Department 600 E. Main Street ,l� 1-01 Stockton, California 95202 p 5' RE: Work Plan for Monitoring Well Installation ARCO Service Station No. 4932 16 East Harding Way Stockton, California SECOR Project No.: 77BP.04932.09.0336 Dear Mr. Infurna: This work plan has been prepared by SECOR International Incorporated (SECOR) on behalf of Atlantic Richfield Company (ARC), a BP Affiliated Company. The purpose of this work plan is to propose the installation of additional monitoring wells at ARCO Service Station No. 4932 located at 16 East Harding Way, Stockton, California (the "site"). The site location is shown on Figure 1. The work plan, prepared at the request of the San Joaquin County Environmental Health Department (SJCEHD) letter dated June 25, 2007, presents a brief site description, reviews the current environmental data, and provides a detailed site assessment scope of work. The purpose of the additional lateral groundwater assessment is to provide additional wells screened across the water table to the east and northeast (generally downgradient) of the site, and to assist in the definition of dissolved-phase fuel-related hydrocarbon plumes, especially the methyl tert butyl ether (MTBE) plume. The purpose of the vertical groundwater assessment is to delineate the soil zones further, provide monitoring wells screened shallower than the B zone (B' zone) north, east, and northeast of the site from which to collect data to evaluate the vertical distribution of contaminants, if any, and to provide a groundwater flow direction in the B' zone. SITE DESCRIPTION The site is located at the southeast corner of Center Street and Harding Way in Stockton, California. The site is an operating AM/PM mini-mart and ARCO service station. Facilities at the site include one 20,000-gallon gasoline underground storage tank (UST), and one 22,000 gasoline UST, and associated product lines and dispensers. The surrounding land is a mix of commercial and residential properties in the City of Stockton. Groundwater monitoring and sampling was coordinated with activities performed at former 76 Service Station No. 4409, located approximately 300 feet northeast of the site. CHARACTERIZATION HISTORY Between May 25 and June 9, 1999, Gettler Ryan Construction of Dublin, California removed three 10,000-gallon double-walled fiberglass under groundwater storage tanks (UST's) and enlarged the excavation to accommodate the larger new UST's. Approximately 631 tons of soil was over-excavated from the UST complex. Over-excavation of the UST complex was completed and six soil samples were collected from the excavation at approximately 19 feet below ground surface (bgs) on June 9, 1999. . One sample contained gasoline range organics (GRO) and MTBE at concentrations of 1.02 milligrams per kilogram (mg/kg) and 0.579 mg/kg, 4932 WP for MW Installation 2007.doc SECOR International Incorporated