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v 07 May 2004 AGE-NC Project No 98-0534 ' Page 10 of 14 , 2 5 GROUND WATER DEPTH AND FLOW DIRECTION Based on the San Joaquin County Flood Control District and Water Conservation District Lines of Equal Depth-of Water Wells Fall 1996 map, the estimated depth to ground water in the vicinity of ' the site is 10 and 20 feet below surface grade (bsg) Historical ground water depths have been as great as 20 feet bsg Based upon information obtained from the UST removal, ground water was at a depth of approximately 15 feet bsg Based on ground water information obtained from wells on the site the average depth to ground water was 10 to 12 feet bsg ' Based upon data obtained from nearby sites, the prevailing ground water flow direction in the vicinity of the site is estimated to be north However, flow direction may be both locally and seasonably variable The Stockton Deep Water Channel is the nearest surface water feature to the ' property, located approximately 1,750 feet north of the site Water from the channel drains into the San Joaquin River and is primarily used for commercial and recreational boating,with agricultural as a secondary use The channel contains water continually and has a potential tidal effect upon ' ground water depth or flow direction in the area The Stockton Deep Water Channel is a water body which is impacted by semi-volatile organic compounds (PCP/Dioxin) and not suitable for recreational use, human consumption nor agricultural use gr Depth to ground water was measured atapproximately 9 33 feet bsg during a 06 February 2004 p ground water monitoring event at the site, ground water flow direction was inferred towards the northwest at a gradient of 0 02 ft/ft 3.0. GROUND WATER MONITORING EVENTS: JUNE 2000 TO MARCH 2001 Ground water monitoring was performed at the site on nine occasions 02 August 2000, ' 18 December 2000, 29 May001, 08 January 2002, 14 June 2002, 02 October 2002, 23 January 2003, 31 October 2003 and ONFebruary 2004 Dunn'g4his time, depths to ground water from wells MW-1 through MW-8 were measured between 7 and' 13 46 feet below the tops of the well ' casings Generally,ground water elevation at the site decreased approximately 0 31 feet between the '- August and-December 2000 monitoring events, ground water-elevation-increased approximately ' 2 87 feet between December 2000 and January 2002 ground water monitoring events, ground water elevation decreased approximately 4 82 feet between January 2002 and October 2002 ground water monitoring events,ground water elevation increased approximately 3 84 feet between October 2002 ' and January 2003 ground water monitoring events,ground water elevation decreased approximately 3 84 feet between January 2003 and October 2003 ground water monitoring events, and ground water elevation increased approximately 3 32 feet between October 2003 and February 2004 ground ' water monitoring events Ground water monitoring data in the area of MW-1 through MW-8 indicated a ground water flow direction generally toward the northwest at gradient of approximately M0 02 ft/ft (Figure 4) Due to the Slow gradient at the site, slight variations in ground water 1 Advanced GeoEnvi ron mental,Inc ` 1 y r