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03 April 2002 <br /> AGE-NC Project No. 97-0333 <br /> ' Page 5 of 12 <br /> ' 2.5. GROUND WATER DEPTH AND GRADIENT <br /> The estimated depth to ground water at the site is between 15 and 20 feet below surface grade(bsg) <br /> based on information from Lines of Equal Depth of Water Wells Spring 1998, published by the San <br /> Joaquin CountyFlood Control District and Water Conservation District(SJCFCD).Based on review <br /> of a regional ground water elevation map published by the SJCFCD,the prevailing ground water <br /> flow direction in Manteca is generallytoward the north,although flow directions maybe both locally <br /> and seasonably variable. <br /> ' Depth to ground water was measured at approximately 18 feet bsg during a 04 December 2001 <br /> ground water monitoring event at the site; ground water flow direction was inferred towards the <br /> north-northwest at a gradient of 0.001 ft/ft. <br /> 3.0. SCOPE OF WORK <br /> ' Based on the results of previous subsurface investigation at the site, ground water at depths of 150 <br /> ' <br /> feetbsg or greater may have been impacted by chlorinated solvents and petroleum hydrocarbons.The <br /> full extent ofpetroleum hydrocarbon-impacted groundwater must be assessed prior to implementing <br /> a remediation plan. Therefore, AGE proposes to advance seven (7) multi-level ground water <br /> monitoring wells to depths of approximately 175 feet bsg to characterize and delineate the vertical <br /> extent of petroleum hydrocarbon-impacted ground water. The ground water multi-level monitoring <br /> well installation project will require completion of the following tasks: <br /> • Permitting and pre-field work activities; <br /> • Soil bore-hole drilling and soil sample collection; <br /> ' • Multi-level monitoring well installation and development; <br /> • Ground water sample collection; <br /> • Preparation of a report of findings. <br /> 3.1. PERMITTING AND PRE-FIELD WORK ACTIVITIES <br /> ' Applicable site assessment permits will be obtained from the PHS-EHD;encroachment permits will <br /> be obtained from the City of Manteca Public Works Department.In addition,an update to the health <br /> ' <br /> and safetyplan presently on-file will be prepared in accordance with Occupational Safety andHealth <br /> Guidance Manual for Hazardous Waste Site Activities (National Institute for Occupational Safety <br /> and Health Administration,U.S. Coast Guard and U.S. Environmental Protection Agency, 1985). <br /> 1 Advanced GeoEavironmental,Inc. <br /> i <br />