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' 26 July 1999 <br /> AGE-NC Project No 97-0301 <br /> Page 3 of 9 <br /> 2 4 GROUND WATER DEPTH AND GRADIENT <br /> Based on review of the Lines of Equal Depth to Groundwater Fall 1997 map published by the San <br /> Joaquin County Flood Control District and Water Conservation District(FCD&WCD),the estimated <br /> depth to ground water at the site is between 35 and 40 feet below surface grade(bsg) Review of the <br /> map Lines of Equal Elevation of Groundwater Fall 1997(FCD&WCD)depicts the regional ground <br /> water flow direction towards the northeast <br /> 3.0. PROCEDURES <br /> On 03 June 1999, four soil probe borings (P-1 through P-4) were advanced on-site as part of site <br /> assessment activities related to the three former USTs The field work was conducted as outlined in <br /> the PHS-EHD approved work plan dated 19 January 1999 <br /> 3 1 DRILLING ACTIVITIES <br /> Soil probe borings P-1 through P-4 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 SoiI probe boring P-I was advanced vertically to a depth of 50 feet bsg, P-2, P-3 <br /> and P-4 were advanced to 40 feet bsg (See Figure 2) <br /> ' 3 1 1 Soil Sample Collection <br /> Discrete soil samples were collected at 5-foot intervals,beginning at 5 foot bsg,to total depth of each <br /> boring Soil samples were collected rising 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 /> 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 /> t <br /> TPH-g and TPH-d by EPA Method 5030/8015M, <br /> ' - BTEX and MTBE by EPA Method 8020, and <br /> - Tertiary butanol (TBA), di-isopropyl ether (DIPE), ethyl tert butyl ether (ETBE) and tert <br /> ' Adranced GeoEmironmental,Inc <br />