ARCHIVED REPORTS XR0002747 - Laserfiche WebLink

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V 1.0 Scope of Work The purpose of this project is to ♦ Perform additional site assessment by installing three shallow and three deep wells This HASP was prepared for the use of SECOR personnel while performing the following tasks Task 1 Drill and install monitoring wells Task 2 Develop and sample monitoring wells The above stated task will be conducted in a manner consistent with standard methods and practices 2.0 Background Information on the Project Site The site is located at the intersection of Center Street and Harding Way in Stockton, California, and is an operating AM/PM mini-mart and ARCO service station The site is located in a mixed residential and commercial area of Stockton Facilities at the site currently include one 20,000-gallon gasoline underground storage tank (UST), and one 22,000 gasoline UST, and associated product lines and dispensers Excavation and removal of three gasoline USTs, and associated dispensers and product lines were performed by Gettler Ryan Construction of Dublin, California between May 25 and June 9, 1999 The excavated USTs consisted of three 10,000-gallon capacity USTs of double- walled fiberglass construction Over-excavation was performed in the UST complex to accommodate the larger new USTs Approximately 631 tons of soil was over-excavated from the UST complex Over-excavation of the UST complex was completed and samples were collected on June 9, 1999 Six samples were collected from the bottom of the UST complex at approximately 19 feet below ground surface (bgs) Total petroleum hydrocarbons as gasoline (TPHg) and methyl tert-butyl ether(MtBE) were reported in one sample each at concentrations of 102 milligrams per kilogram (mg/kg) and 0 579 mg/kg, respectively Benzene and fuel oxygenates were reported as nondetect in all samples from the UST after over-excavation Approximately 150 tons of soil was over-excavated from the product line and dispenser areas TPHg was reported in three of the six samples at a maximum concentration of 5,430 mg/kg Benzene was reported in two samples at a maximum concentration 10 6 mg/kg MtBE was reported in two samples at a maximum concentration of 55 5 mg/kg In August 2000, four groundwater monitoring wells (MW-1, MW-2, MW-3, and MW-4) and one vapor extraction well (SVE-1) were installed at the site TPHg, benzene, and MtBE were reported in initial groundwater samples collected from the groundwater monitoring wells at maximum concentrations of 166,000 ppb, 10,500 ppb, and 708,000 ppb, respectively(MW-4) Fuel oxygenates tert-amyl methyl ether(TAME) and 1,2- dichloroethane (1,2-DCA) were reported in all wells, except MW-3, at maximum concentrations of 427 ppb (MW-4) SECOR International Incorporated 1 Genenc HASP i