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w� <br /> i <br /> . Subsurface Investigation Results <br /> 6131 Pacific Ave., Stockton, CA. <br /> Aegis Project No. 90-020 <br /> r" Page 2$ <br /> E <br /> "A <br /> §,5 GROUNA_WATF�R 1 <br /> A saturated horizon was encountered at approximately 53 feet <br /> below grade. Soil sample 83/10 collected from 50 below grade <br /> contained 9700 ppm TPH. The presence of petroleum hydrocarbons in <br /> ground water has not been documented. However, the presence of <br /> petroleum hydrocarbons within the capillary fringe zone indicates <br /> the need to document ground water quality conditions. Aegis has <br /> submitted a work plan and has received approval to install three <br /> ground water monitoring wells at the site. Locations of the <br /> proposed monitoring wells are shown on Figure 5. <br /> 6.0 CONCLUSIONS <br /> Aegis offers the following conclusions regarding petroleum <br /> hydrocarbons in soils beneath the site: <br /> 1) Petroleum hydrocarbons exist in fill material within the <br /> original tank basin, in native soils adjacent to and below <br /> .. the original tank basin, and beneath the location of the <br /> product lines. <br /> �N 2) The primary source of petroleum hydrocarbons in soil the <br /> appears to have been a hole (cause unknown) in the bottom of <br /> the regular unleaded (tank #3) . <br /> i <br /> 4 <br /> 3) Ground water exists beneath the site at approximately 53 <br /> feet below grade. <br /> 4) Petroleum hydrocarbons in soil have been detected within the <br /> capillary fringe zone indicating the need to document <br /> F r.A hydrogeologic conditions and ground water quality beneath <br /> the site. <br /> j <br /> 5) Excavation of the soils from beneath the pump islands and j <br /> z ± canopy footings is not feasible due to the danger of <br /> ` collapse of the structure. <br /> f'? 6) Native soils are probably suitable for in-situ treatment k <br /> technologies, such as vapor extraction. <br /> 6. <br /> 7) An interim soil remediation plan is included herein and will <br /> be further designed after all backfill is in place and air <br /> flow testing can be completed. This system will address the <br /> petroleum hydrocarbons in soils. <br /> i <br /> i <br /> ! J <br /> - <br />