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' 45 E Harding Way, Stockton, California September 1, 1993 <br /> Chevron USA Products Company Page 1 <br /> 1.0 INTRODUCTION <br /> I <br /> This report is presented by Groundwater Technology, Inc on behalf of Chevron USA Products <br /> Company (Chevron) as a summary of additional environmental assessment work conducted at the <br /> ' former Chevron service station #9-1918 located at 45 East Harding Way, Stockton, California (Figure 1) <br /> The work included drilling two soil borings, installation of a monitoring well In each boring, soil and <br /> groundwater sampling, laboratory analyses of samples, and preparation of this report The purpose for <br /> ' this additional work was to replace lost data points as a result of some of the on-site wells being dry, <br /> and to further define the extent of down-gradient dissolved petroleum hydrocarbons at the site The <br /> ' work was conducted following the steps outlined in Groundwater Technology's work plan addendum of <br /> February 1, 1993, which was accepted by the San Joaquin County Public Health Services, <br /> ' Environmental Health Division (SJCPHS-EHD) <br /> 2.0 BACKGROUND <br /> The site, currently an empty lot, was formerly a Chevron service station which dispensed gasoline from <br /> ' three underground storage tanks All underground tanks, piping and pumps have been removed and <br /> the structures demolished <br /> Eight separate subsurface investigations have been conducted at the site since November 1987 The <br /> first six investigations were conducted by EA Engineering, Science, and Technology The seventh and <br /> eighth subsurface Investigations were conducted by Groundwater Technology in July 1991 and <br /> ' June 1993 <br /> ' On November 18, 1987, a soil-vapor contaminant assessment was conducted in which samples were <br /> collected samples at various depths down to 15 feet below grade, using a 5/8-inch diameter steel probe <br /> ' that was driven into the vadose zone The sample area included the tank pit and pump islands No <br /> concentrations of petroleum hydrocarbons greater than 1 part per million (ppm) were detected in the <br /> ' sampled soil vapors <br /> ju GROUNDWATER <br /> ' 3399EAR.RRr ��n� TECHNOLOGY <br />