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12,000-gallon gasoline (Tank #2) and one 12,000-gallon diesel (Tank #3), were removed on <br /> ' June 15, 1993 A 1,000-gallon tank (known as Tank #1) had previously been removed <br /> Analytical results for soil samples collected during Tank #2 and Tank #3 removal recorded <br /> elevated concentrations of petroleum hydrocarbons <br /> On July 7 through 9, 1993, the former tank location was over-excavated to a depth of 18 feet <br /> below grade. Some soil and groundwater samples collected from the excavation on July 8 and <br /> 9, 1993, recorded concentrations of TPHg and BTEX above method detection limits <br /> On July 12, 1993, an area 20 feet by 35 feet at the south end of the excavation was deepened <br /> to a depth of approximately 23 feet In soil and groundwater samples collected on July 12, <br /> 1993, petroleum hydrocarbon analytes were present above method detection limits According <br /> to the results of confirmation soil samples (WHF, August 1993) residual hydrocarbon <br /> contaminated soil appeared mainly confined to the north end of the excavation The <br /> excavation was subsequently backfilled and paved with asphalt. <br /> RESNA was retained by Manteca, Unified School District to perform a second phase (Phase 2) <br /> subsurface investigation at the site This additional work was performed at the request of San <br /> Joaquin County Public Health Services Environmental Health Division (PHS/EHD). <br /> ' 2.0 METHOD AND PROCEDURES - PHASE 2 <br /> All work described herein was performed in accordance with RESNA's Quality <br /> ' Assurance/Quahty Control Plan and the Site Safety Plan, on file with PHS/EHD. <br /> 2.1 Drilling Activities <br /> On October 10 and 11, 1994, RESNA personnel supervised advancement of five soil bonngs <br /> (SB2, SB3, MWI, MW2, MW3) at the site to depths ranging from approximately 15 to 30 <br /> feet below grade at the project site to: 1) define the lateral and vertical extent of petroleum <br /> ' hydrocarbon soil contamination; 2) determine and define soil stratigraphy; and 3) install <br /> groundwater monitoring wells (MW I, MW2, MW3) within the uppermost aquifer The <br /> boring/well locations are shown on Plate 2. <br /> t <br /> 22.2 Sod ampling and Analysis <br /> Dnlling was conducted by Spectrum Exploration, Inc (C57# 512289) utilizing a hollow stem <br /> auger drill ng A field geologist continuously logged all drill cuttings and cored soil samples <br /> utilizing the Unified Soil Classification System (Appendix H) Descriptions of soil types <br /> 1501071SR-0295 2 CanonteEnvlronmental <br />