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i <br /> Emcon <br /> 1433 North Market Boulevard • Sacramento California 95834-1943 • (916)928-3300 * Fax(916)928-3341 <br /> i <br /> January 28, 1998 <br /> Project 0805-140 006 <br /> Mr Paul Supple <br /> ARCO Products Company �O <br /> P O Box 6549 <br /> Moraga, California 94570 <br /> R<:Workpl Conduct an Off-site Subsurface Investigation at ARCO Service Station <br /> o 48, Located at 1612 Hammer Lane, Stockton, California <br /> Dear Mr Supple <br /> At the request of ARCO Products Company (ARCO), EMCON has prepared this <br /> workplan to conduct an off-site subsurface investigation adjacent to the subject site at <br /> 1704 Hammer Lane (see Figure 1) The purpose of this investigation is to delineate <br /> dissolved hydrocarbons crossgradtent and downgradient from the underground storage <br /> tanks (USTs) Work will include the drilling and sampling of up to three soil bonngs and <br /> installing up to three groundwater monitoring wells This work will be performed in <br /> conjunction with on-site tasks associated with UST removal, well abandonment, and well <br /> installation as presented in the workplan dated July 23, 1996 <br /> BACKGROUND <br /> From December 1990 through November 1993, RESNA Industries, Inc (RESNA <br /> [formerly Applied GeoSystems]), of Rancho Cordova, California, observed the drilling of <br /> 21 bonngs (B-1 through B-21), and the installation of five on-site groundwater monitoring <br /> wells (MW-1 through MW-5), one off-site groundwater monitoring well (MW-6), and <br /> four vapor extraction wells (VW-1 through VW-4) (RESNA, June 26, 1992, Report <br /> No 30004-4, RESNA, June 21, 1993, Report No 30004-8, and RESNA, May 11, 1994, <br /> Report No 30004-8) The locations of soil borings, wells, and other site features are <br /> presented on Figure 2 Residual hydrocarbons were analytically identified in soil samples <br /> collected from the bonngs near the tank cavity Low concentrations of hydrocarbons were <br /> detected to soil samples collected from the bonngs near the dispenser islands <br /> During drilling of soil boring B-18, a product line was accidentally fractured and product <br /> leaked into the adjacent soil RESNA collected a soil sample from 6 feet below the <br /> product lute (S-6-PLI), gasoline hydrocarbons were detected in this sample RESNA <br /> installed one vapor extraction well (VW-4) near the product release Total petroleum <br /> hydrocarbons as gasoline (TPHG), and benzene, toluene, ethylbenzene, and total xylenes <br /> (BTEX) were below laboratory detection huts in soil collected at 11 feet, 26 feet, and <br /> l0 46 feet below ground surface (bgs) <br /> SAC1N\PJM80"8051400 6AS-Wcbefl 2 <br />