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Limited Phase ll Environmental Site Assessment United Storage 2115 West Washington Street Stockton, California Delta Project No. A002-124-1 Page 3 3.3 Soil Borehole Advancement and Soil Characterization On September 30 and October 2, 2002, Mr. John Smith of Delta supervised a subsurface soil investigation to evaluate the potential presence of subsurface impacts on the subject property. A permit authorizing the drilling and sampling program was obtained from the San Joaquin County Environmental Health Department (Permit No. 0031322). Fisch Environmental Exploration Services, Inc. of Valley Springs, California, advanced 10 direct-push soil borings using a Geoprobe® Model 540B mounted on a New Holland Skid Steer. The borings were advanced until saturated conditions were encountered and were completed to depths ranging from 10 to 16 feet below ground surface (bgs). Soil boring locations are identified on Figure 2. Soil samples were obtained continuously at 4-foot intervals using a direct-push sampler to obtain a 1-inch diameter soil core sheathed in a clear polyethylene core liner. As the liners were split open to expose the soil cores, a portion of the soil sample was immediately containerized in the appropriate manner for field headspace screening (Section 3.4) or laboratory analysis (Section 3.5). To minimize the possibility of cross-contamination, latex gloves were used and replaced between each sampling event. In addition, sampling tools were adequately cleaned between samples. Soil samples were described in general accordance with ASTM standards. Soil boring logs (Appendix B) were constructed from information collected during the borehole advancement, including sample depth, lithology, stratigraphy change, sediment color, moisture content, indication of contamination, and water level. 3.4 Field Screening Procedure Soil samples collected for field screening by headspace method were placed in a one-quart polyethylene bag and filled so that the soil sample occupied between 1/3 and 3/4 of the container's volume. Headspace vapor readings were measured using a Photovac photoionization detector (PID) equipped with a 10.6 eV UV lamp. Vapor readings were obtained by pushing the probe of the PID into the equilibrated headspace of the bag samples, gently breaking and manipulating the soil in the bag, and recording the highest meter reading. PID readings are indicated on the soil boring logs (Appendix B). The Photovac was calibrated in accordance with the manufacturer's directions (at least weekly when used infrequently or daily during heavy use) with a standard calibration gas of 100 parts per million by volume (ppmv) isobutylene. In addition to weekly or daily calibration, the 10.6 eV probe is also frequently disassembled, cleaned, and inspected. e:twestwayterminalcota002124 \1-stockton, ca\docststockton phase ii report.doc