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I�IYI�MI��IIIMfII-__ -- <br /> Working To Restore Nature <br /> The site is located in a relatively flat area at an elevation of approximately 25 feet above sea <br /> level (USES 7.5 Minute Lathrop Quadrangle Map). <br /> 1.2 Geolo /H <br /> y dro eolo <br /> r� <br /> The site is located in the Northern San Joaquin Valley, part of the Great Valley Province, <br /> California, a large north-westward trending asymmetric structural trough. The trough is filled <br /> with as much as six miles of sediment ranging from Jurassic to Holocene. The immediate <br /> U subsurface geology are Pleistocene and Recent alluvial deposits. These alluvial deposits <br /> consist of heterogeneous sequences of sands and gravels originating from active stream <br /> channels, and silts and clays originating from overbank and marsh depositional environments. <br /> The regional groundwater flow direction is expected to be north-northwest. First groundwater <br /> was present in the tank pit during excavation at approximately 16 feet below surface grade. <br /> The San Joaquin River lies approximately 3.6 miles west of the site and Walthal Slough lies <br /> 3.6 miles to the southwest. <br /> LAccording to the San Joaquin County Flood Control and Water Conservation District <br /> (FC&WCD), groundwater lies at approximately 16 feet below grade at an elevation of <br /> approximately 10 feet above sea level. <br /> 1_3 Site Background and Previous Work <br /> The subject property has been occupied by Manteca Unified School District since 1972. The <br /> site encompasses the District Office, Transportation Depot, Food Storage and Maintenance <br /> Buildings for Manteca Unified School District (Plate 2). <br /> According to WHF Consultants' August 31, 1993, Remedial Excavation Report, in June 1993, <br /> two underground storage tanks were removed from the site by SEMCO. The tanks, one <br /> 12,000-gallon gasoline (Tank #2) and one 12,000-gallon diesel (Tank #3), were removed on <br /> June 15, 1993. A 1,000-gallon tank (known as Tank #1) had been previously removed. <br /> Analytical results for soil samples collected during Tank #2 and Tank #3 removal recorded <br /> elevated concentrations of petroleum hydrocarbons. <br /> G <br /> G <br /> 2 <br />