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GROUNDWATER MONITORING WELL INSTALLATION RESULTS REPORT <br /> 707 East Yosemite Avenue Manteca Caldomia <br /> . 2.0 BACKGROUND <br /> 2.1 Site Description <br /> The 707 East Yosemite Avenue site is an active mini-mart/service station and carwash <br /> in Manteca Three steel underground storage tanks (UST) are located adjacent to the <br /> carwash building and two fuel dispensing islands west of the UST (Figure 2) <br /> 2.2 Site History <br /> In January 1987, Canonie Environmental, of Stockton California, trenched and collected <br /> two soil samples from beneath the product piping adjacent to the western fuel dispensing <br /> island, after a Petrotite test Soil analysis indicated total petroleum hydrocarbon (TPH) <br /> concentrations ranged from below detection limits (BDL) to 1,500 parts-per-million (ppm) <br /> Subsequent to the soil sampling, approximately 3 to 5 cubic yards of petroleum-bearing <br /> soil were excavated adjacent to the western dispenser island, under the supervision of <br /> the San Joaquin County Environmental Health Department (SJCEHD) The excavation <br /> was backfilled with clean fill material The UST are approximately 30 years old, however <br /> Armor-Seal of Cincinnati, Ohio, fiberglassed the UST in November 1987 The product <br /> and vapor lines were replaced after the UST fiberglass work <br /> In July 1993, Aegis conducted a subsurface investigation that included drilling three soil <br /> borings to 15 feet below grade in the vicinity of the pump islands and UST basin (Figure <br /> 2) Soil sample analytical results indicated no petroleum hydrocarbons were detected, <br /> except 0 008 ppm of xylenes at 15 feet bg adjacent to the western dispenser island (SB- <br /> 1) <br /> 2.3 Adiacent„Land Uses <br /> The site is located in a commercial/residential area of Manteca (Figure 1) The site is <br /> surrounded by small retail stores and private residences <br /> 2.4 General Geology and Hydro-geology <br /> As indicated on the geologic Map of California (1977), the site consists of Quaternary <br /> Aged alluvium, unconsolidated to semi-consolidated of nonmanne origin Within the <br /> vicinity of the site, the subsurface includes mostly sands with interlayered silty and clayey <br /> sand lenses, becoming semi-consolidated at approximately 25 to 30 bg <br /> Based on depth-to-groundwater measurements collected on August 17, 1993, <br /> groundwater varies from approximately 25 to 26 feet below existing grade The <br /> groundwater flow direction is estimated to be to the northeast <br /> 93-010A PER 2 <br />