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Work Plan—PEA Page 2 Former Haley Flying Service GPE Project 474.2 Hydrogeology As shown on the USGS topographic map, the area is in nearly flat-lying, with little topographic variation. The north lot line is bounded by an irrigation ditch, which flows inside a raised levee or berm. According to a report entitled Bring 1999 Groundwater Report by the San Joaquin County Flood Control District, it appears that first groundwater lies approximately 6 to 10 feet below ground surface and flows in a north to northeasterly direction. Soils&Geology The geologic features of this portion of San Joaquin County are typical of California's Central Valley, a large northwest/southeast trending asymmetric trough bounded by mostly pre- Tertiary metamorphic, sedimentary and granitic rocks. Depth to basement rock in the Valley ranges from up to at least 6 vertical miles in the southern portions of the Central Valley (the "San Joaquin" Valley) to up to 10 miles in sediment thickness in the northern expanse of the valley (the "Sacramento" Valley). In most of San Joaquin County, with the exception of its eastern and western margins which are dominated by the foothills of the Sierra Nevada and Coast Ranges, respectively, recently (Cenozoic) deposited terrestrial, lacustrine, and marine sediments overlie older (pre-Tertiary in age) consolidated marine sediments. These older sedimentary units in turn overlie pre-Tertiary crystalline basement rocks. (source: R.W.page, U.S. Geological Survey Professional Paper 1401-C, Geology of the Fresh Ground-Water Basin of the Central Valley, California, 1986). The formation of soils in San Joaquin County is a function of the sedimentary transport path from the primary sediment sources. These sediment sources are the Coastal Range to the west and the Sierra Nevada to the east of the County. Generally, the longer the transport path the greater the working of the sediments prior to deposition as soils. Soils in much of the County to the east of the San Joaquin River are deposited as alluvial fans of the three major rivers of the east County, i.e., the Stanislaus, the Calaveras and the Mokelumne rivers. These soils can grossly be characterized as mixtures of well to poorly sorted sands and silt with little clay and organic material. Along the San Joaquin River and in the delta regions west of Stockton, the low energy river and flood plain environments deposit layers of silt and clays during seasonal floods. These fine-grained sediments flocculate out of slack water as floodwaters recede. Portions of far western San Joaquin County soils are formed by the erosion of the Coast Range and transport of these sediments is facilitated through seasonal run-off of the minor streams of the Coast Range. These soils are formed in environments similar to those of eastern San Joaquin county, i.e., alluvial fans, but tend to be less well worked in comparison to their Sierran derived counterparts due to the shorter transport path relative to Sierran derived sediments. According the Mugger Map Book of California Oil and gas Fields, and to the California Division of Oil and Gas Resources publication, California Oil and Gas, the Property lies within a natural gas producing field called the Tracy Gas Field. The field is productive from sands of the Tracy Formation at a depth of about 4,000 feet. Based on the available 2937 Veneman Avenue, Suite B240 Geo-Phase Environmental Inc. Phone: (209) 569-0293 Modesto, Ca 95356 Fax: (209) 569-0295