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Work Plan to Excavate Gasoline Tank Cavity December 10, 1990 <br /> ARCO Service Station No. 6020, Manteca, California AGS 30055-2W <br /> Excavat-on of Proyosed Tank Gam <br /> Excavation in the proposed tank cavity will continue uniil soil containing less than 10 ppm <br /> of T:'Hg and less than 1.0 ppm benzene are removed; however, excavation will be <br /> terminated if!U depth of the excavation reaches the safe operating limits of the equipment, <br /> if further excavation wouid endanger any existing structures or if ground water is <br /> encountered. We estimate that the final depth of the excavation will be approximately 12 <br /> I <br /> feet below grade. One soil sample will be collected ander each proposed tank location. <br /> Sidewall soil samples will be collected only if evidence of hydrocarbons remains in place. <br /> Estsrnate of Excavated Soil <br /> The approximate limits of the excavation are based on information gathered during our <br /> August 1990 investigation and,are shown on Plate P-2. The actual size of the excavation will <br /> depend on site conditions and the concentration of hydrocarbons encountered during <br /> excavation. We estimate 1,200 cubic yards of soil may be excavated. Excavated soil will be <br /> stockpiled offsite. The stockpiles will be covered with plastic sheeting to restrict vapor <br /> emissions and control Aust. <br /> 12 <br />