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GEOMATRIX <br /> QUARTERLY GROUNDWATER MONITORING REPORT <br /> tJANUARY — MARCH 2005 <br /> Former ContiGroup Grain Elevator Site <br /> Stockton, California <br /> 1 1.0 INTRODUCTION <br /> This report summarizes the results of the January-March 2005 (first quarter 2005) quarterly <br /> groundwater monitoring events conducted at the former Continental Grain Elevator property <br /> (the site) located at 1805 Harbor Street, Stockton, California (Figure 1) The report was pre- <br /> pared by Geomatnx Consultants, Inc (Geomatnx) on behalf of the ContiGroup Companies, <br /> Inc (Conn) and their consultant Huff& Huff, Inc (Huff& Huff) Monitoring activities were <br /> arranged by Huff& Huff with monitoring results provided to Geomatnx for interpretation and <br /> ' inclusion in this report The site is regulated by the San Joaquin County Public Health Ser- <br /> vices, Environmental Health Division (PHS/EHD) The purpose of the quarterly monitoring <br /> ' program is to assess groundwater conditions in the vicinity of a former release of petroleum <br /> hydrocarbon constituents to the subsurface as a result of operation of a former underground fuel <br /> storage tank (UST) <br /> The following sections provide information about the site background, field and analytical <br /> ' methods, results of the quarterly monitoring activities, and an annual summary <br /> ' 2.0 BACKGROUND <br /> The project site is located in Stockton, California south of the Port of Stockton's Deep Water <br /> Channel (Figure 2) The site is an active grain storage and transportation facility currently <br /> occupied by the Penny-Newman Grain Company The subsurface material underlying the site <br /> ' consists primarily of fine grained (e g , clay and silt) material with zones of sand The upper- <br /> most fine-grained clay and silt material exists from ground surface to a depth of approximately <br /> 15 feet below ground surface (bgs) under which lies a zone composed primarily of sand-sized <br /> material to a depth of approximately 41 feet bgs An approximately 5-foot thick clay zone is „ <br /> reported to exist from approximately 41 to 46 feet bgs followed again by sand-sized material to <br /> ' a depth of approximately 52 feet bgs which is the total depth explored at the site Measured <br /> depth to groundwater in the area of the former UST has ranged from 7 97 to 14 29 feet below <br /> ground surface (bgs) (off-site ground surface elevations near MW-5 and MW-6 are <br /> . approximately 4 to 5 feet lower than the site, and corresponding depth to water measurements <br /> I gw_Safe19000s19963 00111 st qtr 200512 Txt%txt doc 1 <br />