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' FEC S 1462 01 UnIF]rst Stockton _ SentembU 24.2004 3.2.3 Subsurface Investigation On November 10, 2003 and November 11, 2003, nine borings (131-139) were advanced in the ' northwest corner of the construction area using a truck-mounted hydraulic-powered direct push drill rig(Geoprobe) The locations of the borings are shown on Figure 3 Drilling was conducted by Jet Drilling, Inc (Jet) of Signal Hill, California under the supervision of EEC The nine ' borings were drilled to evaluate the lateral and vertical extent of TPH and VOC impacted soil encountered during site redevelopment activities Soils encountered during the Geoprobe investigation consisted of brown to dark brown, dense silt, sand and clay Soil samples were collected at five-foot intervals to depths ranging from 10 to 25 feet bgs Earth materials encountered during drilling were logged by an EEC field geologist using the Unified Soil Classification System (USCS) Field work was performed under the direction of a California Registered Geologist Soil samples were collected by advancing the Geoprobe boring to a point immediately above the sample depth With the use of a percussion hammer, a 1 75-inch diameter sampler outfitted with a 1-inch diameter clear acetate sleeve was driven approximately 12-inches into undisturbed soil Following sample retrieval, the lowermost intact portion of the sleeve was cut, covered with a Teflon sheet and sealed with a plastic end cap Samples were labeled, sealed in a Zip-loch bag and placed into a chilled cooler The collected soil samples were transferred to CLS laboratory under proper Chain-of-Custody protocol for analyses A total of 26 soil samples were selected for laboratory analysis Each sample was analyzed for TPH full range scan by EPA Method 8015 and for VOCs by EPA Method 8260 3.14 Geoprobe Sampling Results TPH and/or VOC constituents were detected in the majority of the samples analyzed Laboratory ' results are summarized in Table 2 and described below A complete copy of the laboratory data is included in Appendix B Results of the geoprobe sampling indicate the following + TPH in the motor oil range was detected at relatively low concentrations ranging from ' non detect(<1 0 ppm)to 14 ppm, No TPH was detected in the gasoline or diesel range, 1 . Ethylbenzene was detected at concentrations ranging from non detect (<5 0 ppb) to 9 8 ppb, ' • PCE was found at concentrations ranging from non detect(<5 0 ppb)to 73 ppb, • Total xylenes were found at concentration ranging from non detect (<5 0 ppb)to 77 ppb, I • No other VOC constituents were detected 5