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Corrective Action Remedy Selection,General Dynamics OTS(California Inc.) <br /> _ -- Statement of Basis,March 2001 <br /> Page 4 of 5 <br /> recommended excavation of all impacted soils followed by confirmation sampling to <br /> ensure removal of all soils above the approved cleanup level. The facility requested <br /> that soils with contaminants above the cleanup levels under the existing tank pad at <br /> SWMU #21 be allowed to remain in place. This request was denied by DTSC. <br /> Environmental Setting <br /> Land Use: The facility is located in an area zoned for general agricultural use on <br /> the eastern slopes of the Altamont Hills. Elevation of the property ranges from <br /> 400 feet to about 1,280 feet above sea level. Slopes range from 9 percent to <br /> about 48 percent at the steepest. <br /> Surface Water: Corral Hollow Creek is a seasonal waterway which runs through <br /> the eastern portion of the property. Areas of contamination to be remediated are <br /> over 500 yards from the creek. <br /> Groundwater: Based upon results of hydrogeologic investigations at Lawrence <br /> Livermore Site 300, located immediately west of the facility, the depth to <br /> groundwater is expected to be greater than 100 feet. No drinking water wells, or <br /> wells of any type, at located on the property. <br /> Plant and Animal Life: This is an isolated area which is undoubtedly habitat for <br /> environmental sensitive species of animals and possible plants. <br /> Site-Specific Cleanup Levels <br /> EPA's Preliminary Remedial Goals (PRGs), residential levels, were used to screen <br /> hazardous constituents. This decision was made based on the absence of unusual <br /> exposure scenarios or highly sensitive receptors. Also, the depth to groundwater(100 <br /> feet) and dryness of the area makes the probability of impacts to groundwater or <br /> surface water remote. <br /> The cleanup level for petroleum hydrocarbons and oil and grease was set at 1000 ppm <br /> based on historical DTSC and Bay Area Regional Water Quality Control Board practice <br /> for remediating petroleum hydrocarbon and oil and grease impacted soils which test <br /> negative for hazardous constituents (benzene, toluene, and xylene) and which are not <br /> in close proximity to surface waters or groundwater. <br /> Remedy <br /> DTSC guidelines require that the proposed remedy consider the future use of the <br /> property. The facility is in an agricultural/light industry zoned area and no plans have <br />