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19 March 2001 <br /> • AGE-NC Project No 98-0492 <br /> ' Page 3 of 7 <br /> ' deposited in lacustrine, fluvial, and alluvial environments with sediment sources being the mountain <br /> ranges surrounding the valley (Olmsted and Davis, 1961) The site is located on unconsolidated and <br /> semi-consolidated alluvium, lake, playa and terrace deposits of Quaternary age (California Division <br /> of Mines and Geology, 1977) <br /> The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the <br /> ' pnneipal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground <br /> Water Basin(Basin 5-22) <br /> ' 2 5 GROUND WATER DEPTH AND FLOW DIRECTION <br /> ' Based on information obtained from this investigation, ground water depth in the vicinity of the site <br /> is approximately 20 feet bsg The prevailing ground water flow direction in the vicinity of the site <br /> is inferred to be toward the northwest to north-northeast However, flow direction may be locally and <br /> ' seasonably variable <br /> • 3 0. PROCEDURES <br /> ' On 24 January 2001, five soil probe borings (P-7 through P-11) were advanced at the site as part of <br /> assessment activities related to the three former USTs The field work was conducted as outlined in <br /> the AGE work plan titled Preliminary Site Assessment Work Plan, dated 14 August 2000 <br /> 3 1 DRILLING ACTIVITIES <br /> ' Soil probe borings P-7 through P-11 were advanced utilizing a van-mounted Geoprobe 5400 <br /> equipped with 1 125-inch diameter probe rods with an attached 2 15-inch diameter soil sampler, <br /> using"direct push"technology The probe borings were advanced vertically to depths of 25 feet bsg <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 /> ' Advanced GeoEnvironmental,Inc <br /> 1 <br />