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,...- <br /> Site Investigation Work Plan - April 1997 <br /> M & M DITCHING <br /> 775 West Second Street, Stockton, California <br /> I.O. INTRODUCTION <br /> In accordance with the request of Mr. Toni Maragliano of M & M Ditching. advanced <br /> GeoEnvironnnental, Inc. (AGE) has prepared this Site Investigation Work Plan for excavation of <br /> hydrocarbon-impacted soil from the former underground storage tank (UST) area at 775 West <br /> Second Street, Stockton, California (the site). The Iocation of the site is illustrated in Figure I - <br /> Location -Uap. A plan of the site is illustrated on Figure 2 - Site Plan. <br /> This work plan is prepared in accordance with San Joaquin County Public Health Services - <br /> Environmental Health Division (PHS-EHD) and Central Valley Regional Water Quality Control <br /> Board (CVRWQCB) guidelines for the investigation of UST sites. <br /> 2.0. BACKGROUND <br /> 2.1. UNDERGROUND STORAGE TANK REMOVAL <br /> Two 1,000-gallon diesel USTs (No. 3 and No. 4) were removed from the northeast portion of the <br /> property betv,7een 1985 and 1986 by M & M Ditching. No soil samples were collected at the time <br /> of removal. <br /> In August 1990, one 1.000-gallon gasoline UST (No. 1) and one 1,000-gallon diesel UST ('No. 2) <br /> were removed from the southwest portion of the site by SEMCO of Modesto, California. During the <br /> August UST removal, soil samples were collected from beneath UST Nos. I and 2. Furthermore, <br /> samples were collected from the former locations of UST Nos. 3 and 4. <br /> Total petroleum hydrocarbons quantified as diesel (TPH-d) was detected in sample Tank 1 West at <br /> 18 parts per million (ppm); toluene, ethylbenzene and xylenes were also detected in Tank I West <br /> at concentrations up to 0.28 ppm. TPH-d was detected in samples collected beneath Tank No. 3 at <br /> concentrations up to 1,800 ppm; toluene was also detected in sample Tank 3 West at 0.063 ppm. <br /> Analytical results of UST removal soil samples are summarized in Table 1. <br /> 2.2. GROUND WA'T'ER DEPTH AND FLOW DIRECTION <br /> Based Upon data obtained from monitoring wells in the area and the map entitled Lines of Equal <br /> Depth of Water- TVells, Fall 1993, prepared by the San Joaquin County Flood Control and Water <br /> Conservation District, ground water depth at the site is estimated at 20 to 30 feet below surface grade <br /> (bsg). Ground water flow direction for the region has historically been northeast. However, both <br />