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1 I <br /> I Mr. Nlichael Infurna <br /> January 12, 2000 <br /> i; Page 2 of 4 <br /> beneath the tanks contained no hydrocarbon constituents) above laboratory detection limits, <br /> except for the sample collected from beneath the west side of Tank 1 at 14 feet below ground <br /> surface (bgs), which contained 30 parts per million (ppm) total petroleum hydrocarbons as diesel <br /> (TPHd). However, a soil sample collected beneath the fuel dispenser (approximate depth of 6 <br /> i feet bgs) contained TPHd at 13,000 ppm and xylenes at 3.1 ppm. Tank pull analytical results are <br /> summarized in Table 1. The locations of the former USTs and dispenser are shown on Figure 2. <br /> 2.2 Investigations Undertaken <br /> f <br /> i9 <br /> In accordance with the approved workplan dated June 14, 1999, two soil borings were advanced at j <br /> the site to investigate the extent of residual soil contamination, as well as the potential threat to <br /> groundwater. Boring SB 1 was located south of the former 10,000 gallon 6ST, and boring SB2 was <br /> located at the former fuel dispenser. Soil boring locations are"depicted on Figure 3. <br /> ,a <br /> r <br /> 3.0 INVESTIGATIVE PROCEDURES <br /> Sean Garvey of Ground Zero supervised the subsurface investigation in the vicinity of the former <br /> USTs and dispenser on November 22, 1999. Mr. Michael 1F1 urna of San Joaquin County Public <br />' PHS/EHD conducted a site inspection and observed field activities. <br /> Fisch advanced the borings under the supervision of fields geologist Sean Garvey, and project <br /> manager John Lane, a California Registered Geologist. Boting SB 1 was advanced to a.depth of <br /> approximately 21 feet below ground surface (bgs), and boring S132 was advanced to approximately <br /> 26 feet bgs to explore the extent of contamination at the site. Fisch utilized a truck mounted <br /> Geoprobe 5400 direct push rig to advance the borings and collect soil samples. Soil samples were <br /> r` collected at 5-foot intervals using a 1 3/a-inch diameter by 24-inch long core sampler. The sampler <br /> was lined with clear acetate sleeves, affording soil identif)cation and subjective evaluation for j <br /> contamination. A flame ionization detector (FID) was used to monitor the presence of volatile <br />' organic compounds in the soil. Three soil samples from boring SBI (at depths of 10, 15 and 20 <br /> feet bgs) were sealed, labeled, and immediately placed in an iced cooler for transport to a state- <br /> certified analytical laboratory. Two soil samples from SB;2 (at depths of 10 and 25 feet bgs) <br /> were also submitted for analysis. Soil samples were selected based on observations and field <br /> screening results. Groundwater was not encountered during the investigation. <br /> !! I <br /> The completed borings were backfilled to the ground surface with neat cement grout and <br /> bentonite. No soil cuttings were generated. All down-hole drilling and sampling equipment was <br /> decontaminated by washing with a laboratory grade detergent and rinsing with water. Rinseate <br /> collected from decontamination procedures was disposed of via evaporation on the <br />{ asphalt/concrete surface within the confines of the investigation area. Soil samples were submitted <br /> under chain of custody protocol to Argon Laboratories for analysis. <br />� x <br /> I 4.0 RESULTS OF INVESTIGATION <br /> i 4.1 Subsurface Conditions ` <br /> i <br /> Pea gravel used to backfill the UST excavation overlies native bedding to a depth of <br /> '1 <br /> I taylorlrepoAslsummaryI.doc <br />