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12 October 2000 <br /> • AGE-NC Project No 99-0637 <br />' Page 3 of 7 <br />' 2 4 GROUND WATER DEPTH AND FLOW DIRECTION <br /> Based on the San Joaquin County Flood Control District and Water Conservation District Lines of <br />' Equal Depth of Water Wells Fall 1998 map and monitoring wells located approximately 0 5 miles <br /> to the northwest,the estimated depth to ground water in the vicinity of the site is 15 to 20 feet below <br /> surface grade(bsg)with a northwesterly flow direction However, flow direction may be both locally <br />' <br /> and seasonably variable Based on the San Joaquin County Flood Control District and Water <br /> Conservation District Lanes of Equal Depth of Water Wells Fall 1971, 1980, 1985, 1990, 1993 and <br /> 1998 maps the historical estimated depth to ground water in the vicinity of the site has ranged <br />' between 10 and 20 feet bsg <br />' 3.0. PROCEDURES <br />' On 20 March 2000, three soil probe borings (BI through B3) were advanced at the site as part of <br /> assessment activities related to the former USTs The field work was conducted as outlined in the <br /> PHS-EHD-approved Site Investigation Work Plan, dated 21 January 2000 and approved by letter <br />' dated 11 February 2000 <br />' 3 1 DRILLING ACTIVITIES <br /> Soil probe borings B1 through B3 were advanced utilizing a van-mounted Geoprobe 5400 equipped <br />' with 1 125-inch diameter probe rods with an attached 2 15-inch diameter soil sampler, using"direct <br /> push"technology Soil probe borings B 1, B2 and B3 were advanced vertically to a depth of 25 feet <br /> bsg <br /> 1 <br /> 3 1 1 Soil Sample Collection <br />' Discrete soil samples were collected at 5-foot intervals,beginning at 5 feet bsg,to total depth of each <br /> boring Soil samples were collected using a Geoprobe soil sampling assembly loaded with four pre- <br /> cleaned 1 125-inch by 6-inch brass sleeves Soil samples were preserved by covering both ends of <br /> the brass sleeve with Teflon sheets, capping, and sealing with tape Each sample sleeve was labeled <br /> with soil probe boring location, depth, time, date and sampler's initials <br /> 1 <br /> Each preserved sample was logged on a chain-of-custody form, placed in a chilled container and <br />' transported to a California Department of Health Services (DHS)-certified laboratory under chain <br /> of custody, selected samples were analyzed for <br /> TPH-g and TPH-d by EPA Method GCFID 5030AJ8015Modified, and <br /> Advanced GeoEnviron mental,Inc <br />