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11 March 2002 AGE-NC Project No 95-0130 IPage 5 of 13 Jackson-Hallenbeck-Stockton (JHS) association The JHS soils are located within basins, and generally consist of moderate to poorly drained fine textured soils The soils are generally derived from both marine and non-manne sediment, and are generally formed in alluvium derived from mixed rock sources The Modesto,Riverbank, Turlock Lake Formations and overlying recent alluvium are the principal ' source of domestic ground water in the 13,500 square-mile San Joaquin Valley Ground Water Basin (Basin 5-22) This basin is drained primarily by the San Joaquin River The nearest surface water feature in the vicinity of the property is the Stockton Deep Water Channel, located approximately ' 3,000 feet west of the property ' 2 5 GROUND WATER DEPTH AND FLOW DIRECTION The estimated depth to ground water at the site is approximately 40 feet below surface grade (bsg) ' based on information from Lanes of Equal Depth of Water Wells Spring 1999, published by the San Joaquin County Flood Control District and Water Conservation District(SJCFCD) Based on review • of a regional ground water elevation map published by the SJCFCD, the prevailing ground water flow direction in central Stockton is generally toward the northeast, although flow directions may be both locally and seasonably variable Based on data collected during the December 2001 ground water monitoring event, first observed ground water was approximately 42 feet bsg, the ground water flow direction was inferred to be towards the northeast at a calculated gradient of 0 002 Ground water flow direction at the site was inferred towards the northeast from sixteen consecutive quarterly ground water monitoring events between September 1997 and December 2001 3.0. SCOPE OF WORK ' AGE proposes to drill and install nine wells screened through Vadose Zone (located between surface grade and 40 feet bsg)and Hydrologic Unit 1 (located between 40 and 57 feet bsg) one 6-inch diameter ground water extraction well(EW-1)will be screened between 35 feet and 55 feet bsg, one 4-inch diameter SVE well(VW-4)will be screened between 10 and 40 feet bsg, one 2-inch diameter IAS well(AW-1)will be screened between 50 and 55 feet bsg,two 2-inch ' diameter ground water monitoring wells(MW-8 and MW-9)will be screened between 35 and 55 feet bsg (Figure 2) AGE proposes to advance four additional multi-level ground water monitoring wells to depths of 145 feet bsg to characterize and delineate the off-site vertical extent of petroleum hydrocarbon-impacted ground water MW IO- 1 tw 13 " • Following installation of the above referenced wells, a series of pilot tests will be performed Advanced GeoEnviron mental,Inc