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Ms. Lori Duncan August 25, 2008 Page 2 of 4 HYDROGEOLOGIC SETTING The site is situated in central Escalon in T2S, R9E, Section 4, San Joaquin County, California. The property is located in the San Joaquin Valley physiographic province. The valley is a topographic and structural basin bounded on the east by the Sierra Nevada and on the west by the Coast Ranges. The local topography slopes gently toward the west at approximately 8 ft/mi. The Site is likely underlain by heterogeneous, alluvial sediments ranging from clay to sand as seen in soil borings collected in nearby sites. The existing and potential uses of groundwater in the area include irrigation, private and municipal water supply, stock watering, process water, and service supply (California Regional Water Quality Control Board's Water Quality Control Plan, 1994). The 'older alluvium" is the most extensively developed geologic unit in the area and includes both unconfined and confined zones. The unconsolidated, mostly coarse grained nature of the aquifer material results in high well yields. Regional groundwater flow in the site area is generally in a northwesterly direction, toward the San Joaquin River Delta and a regional groundwater depression centered about 4 miles east of Stockton (San Joaquin County Flood Control and Water Conservation District, Fall 1998). City of Escalon personnel also indicated that groundwater flows northwest. Groundwater has been encountered at 60 feet below grade at nearby locations. According to City of Escalon personnel, the nearest active water supply well (City Well 41) is located approximately 1,600 feet southeast (generally upgradient) of the Site. The nearest schools are Escalon High School located more than 1,100 feet to the north-northeast and El Portal Junior High School located approximately 1,800 feet to the west-southwest. SCOPE OF WORK Ground Zero proposes advancing five soil borings to approximately 25 feet below grade surface (bgs) near the locations of the former USTs and between the Kleinfelder boring with elevated hydrocarbons and the former fuel dispenser island. Soil samples will be collected and submitted to a Certified California Laboratory for analysis. The results will be used to determine if soil beneath the former USTs has been impacted by petroleum hydrocarbons. Soil Confirmation Drilling and Sampling Ground Zero proposes to advance five soil borings near the former USTs and between the former dispenser island and Kleinfelder boring B-24 to a total depth to approximately 25-feet bgs. An experienced Ground Zero geologist, under the supervision of a California Professional Geologist, will supervise the advancement and logging of the five soil borings. The soil borings will be GAGROUNDZEWATDRepom Work PlansUnitial Site Investigation.doc 40