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whether or not it lies upon the current, smaller school site boundary. Further sampling of this possible fill to confirm or deny contamination is warranted. 5.0 ENVIRNOMENTAL SETTING 5.1 General Geologic Conditions and Topography The subject property is relatively flat. The EDR Radius Map with GeoChece (2006) shows the property and surrounding areas to slope five feet to the south over a two mile span. From west to east the area surrounding the site gently rolls with a total elevation gain/loss of 20 feet over two miles. The Site itself lies on an approximately 1/2 mile wide plateau rising above the adjacent areas by five to ten feet. The subject property lies within the Great Valley geomorphic province. The Great Valley is an alluvial plain measuring 400 miles in length and up to 50 miles in width. It receives the drainage from most of the Sierra Nevada and a sizable portion of the Coast Ranges. As the ranges on both sides of the valley rise, the deposits washed down into the valley over millions of years have caused the valley to warp downward, tilting the older strata along its margins. The continental alluvial gravels, sands, silts, and clay deposits in the valley are up to 9,000 feet thick and overlie ancient marine deposits that are as thick as 25,000 feet. 5.2 General Soil Conditions The soils of the Site are described by the database from the United States Department of Agriculture (USDA) Soil Conservation Service (SCCS) as Jacktone clay. This type of soil has very slow infiltration rates, is typically shallow and drains poorly. 5.3 General Hydrogeological Conditions The San Joaquin County Flood Control and Water Conservation Districts Lines of Equal Elevation of Groundwater, Spring 2003 map shows the water level to be approximately 40 feet below ground surface (bgs) and flowing east southeast in the area. Boring logs at the Site from the Geologic Hazard and Geotechnical Engineering Report dated June 29, 2006 report by Wallace Kuhl &Associates titled found groundwater at 37 feet bgs. Groundwater is not expected to be used for either potable water or irrigation at the Site. 6.0 PROPOSED PEA SCOPE OF WORK The sampling plan defined below was created in conjunction with the PEA Guidance Manual, the Ag. Guidance, and in past consultations with DTSC Project Managers. The proposed sampling plan may be constrained or modified due to a variety of factors at the Site. If significant modifications to the sampling plan are required, DTSC will be notified prior to the commencement of sampling. Preliminary Environmental Assessment Workplan Proposed Podesta Ranch Elementary School December 4,2006 Page 6 of 27