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' Site Background Information CONTINENTAL GRAIN COMPANY 1805 Harbor Street, Stockton, California ' INTRODUCTION This document includes the site background information forthe Continental Grain Company,located at 1805 Harbor Street,Stockton,California,as it was presented by Huff&Huff,Inc ,Environmental Consultants (Huff& Huff) in their report entitled Quarterly Ground Water Monitoring Report ' January-March 2005, dated 29 April 2005 BACKGROUND The project site is located in Stockton, California south of the Port of Stockton's Deep Water ' Channel(Figure 1) The site is an active grain storage and transportation facility currently occupied by the Penny-Newman Grain Company The subsurface material underlying the site consists primarily of fine-grained (e g, clay and silt) material with zones of sand The upper-most fine- gained clay and silt material exists from ground surface to a depth of approximately 15 feet below ground surface(bgs)under which lies a zone composed primarily of sand-sized material to a depth of approximately 41 feet bgs An approximately 5-foot thick clay zone is reported to exist from ' 0 approximately 41 feet to 46 feet bgs followed again by sand-sized material to a depth of approximately 52 feet bgs, which is the total depth of the explored site Measured depth to ground water in the area of the former underground storage tank (UST) has ranged from 7 97 feet to 14 29 feet below bgs. (off-site ground surface elevations near MW-5 and MW-6 are approximately 4 feet to 5 feet lower than the site, and corresponding depth to water measurements vary accordingly) The direction of the horizontal hydraulic gradient ranges from approximately southeast ' to southwest One 10,000-gallon UST used for the storage of petroleum fuel was removed from the site on January 22, 1998 under the supervision of the San Joaquin County Environmental Health Department(EHD) Soil and ground water assessment activities,including the dnlling and logging of soil borings and the installation of ground water monitoring wells, were performed beginning in October 1997 by ATC Associates, Inc and by Haley and Aldrich, Inc on behalf of Conti ' Seven(7)ground water monitoring wells(MW-1 through MW-7)have been installed at the site and quarterly ground water monitoring activities have been performed since 1998 Monitoring wells MW-1 through MW-6 have 20-foot well screens and are screened between depths of approximately ' 5 feet and 28 feet bgs Monitoring well MW-7 is screened across an approximately 30-foot to 35-foot depth interval ' Groundwater samples collected from monitoring wells installed within the affected soil area(MW-2 through MW-4) have consistently been reported by analytical laboratories to be impacted by petroleum-fuel related analytes Including total petroleum hydrocarbons quantified as diesel(TPH-d) Advanced GeoEnvironmental,Inc