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F E-1.IMiNARY ROPORT AND TAM C1.OSIJRf REPORT Tracy Boulevard Sheli 3775 Trary Boulevard,Tracy,California Delta Project No.40494112 Page 14 d.A lnstnllntfan a Sotl Remecliutinrt 5 stem Com stoats In the event that remediation of soil containing petroleum hydrocarbons at the water tabie (Figure 10) becomes necessary,a ground water gradient control pipe and soil vent pipe were installed an June 7,19)0, before the site was paved. Perforated pipe was placed in a trench at 13 feet below the surface and connected to a sump which may later be used to lower the water table. This would allow remediation of the soil near the water table that contains petroleum constituents by vapor extr2ctioa through the slotted pipe placed in the trench at 9 feet. Figures 10, 11,and 12 display the pipe locations and configurations. 4.9 Dis sal of stack lied SoBs Approximately 400 cubic ya•ds of soil containing petroleum hydrocarbons have been excavated at the subject site and transported to disposai facilities. The soil has been removed from the former and new product storage tank Iocations and from the former pump island locations. Approximately 150 cubic yards a€soil containing TPH concentrations greater than the analytical method detection limit but less than 10 ppm rt`as transported to the Sacramento City Landfill for disposal. Approximately 250 cubic yards of soil containing TPH concentrations greater than 10 ppm but less than 250 ppm was transported to Liquid Waste m Management,Inc.(a Class I'disposal facility),in McKittrick,California,for disposal. Soil containing TPH concentrations in access of 250 ppm was not encountered. Appro)dmately 1,300 cubic yards of soil containing no detectable concentrations of BTEX or TPH was used on-site as fill. 4.11Dewnterin of Ground%voter )urine New'l'nnk Installations During the installation of the new storage tanks,ground water was encountered approximately 10 feet below the ground surface. The bottoms of the tanks were; placed at approldmately 12 feet below the surface. Therefore, it%vas necessary to dLwater the underground storage tank excavation during tank installation. A Wastewater Discharge Permit for discharge of the dewatering system water to the:unitary sewer had been issued by the City of Tracy on December 18, 1989(Appendix K). -------- --- — --- ---- —A hole 15 feet deep and several feet wide was excavated near the upgradient comer of the excavation. An --- 18-inchAjameter slotted pipe was placed in the hole and a gravel pack placed around the pipe A sump pump was lowered to the bottom of the pipe. The pump was used to dewater the excavation while the new tanks were being installed.