Laserfiche WebLink
December 16, 1992 Working To Restore Nature <br /> Unocal Service Station No 6981, Stockton, California <br /> t <br /> REMEDIATION OPTIONS <br /> Based on the size of the site, the size of the hydrocarbon plumes in soil and ground water, <br /> hydrocarbon concentrations, and the type of soils present at the site, in-situ bioremediation, <br /> chemical oxidation, air sparging, and slurry wall containment are not viable or economically <br /> feasible options The following feasible options are presented <br /> 1 <br /> Excavation <br /> Soil with residual gasoline hydrocarbons occurs beneath the tanks and the dispenser islands <br /> at depths to approximately 55 feet or the top of ground water Because of these depths, <br /> proximity to existing structures, and the proximity of two major roads, these conditions are <br /> not conducive for removal of all hydrocarbon containing soil by excavation Furthermore, <br /> this alternative would require the removal of the fuel UST's, the cashiers booth, and both <br /> dispenser islands RESNA estimates that if the soil could be excavated without structurally <br /> compromising the two roads and the adjacent parking lot, over 6,500 cubic yards of soil will <br /> require treatment onsite by either uncontrolled aeration or vapor extraction of soil <br /> stockpiles, direct disposal without pre-treatment is also an alternative <br /> If the tanks and dispensers are removed from the site, some soil may be excavated at that <br /> time The vertical extent of soil containing hydrocarbons beneath the tanks is not well <br /> defined because soil containing 1,900 ppm TPHg was left in place at 22 feet below grade <br /> and no data are available underneath the tanks below 22 feet Similarly, soil containing <br /> hydrocarbons is present near the dispenser islands Upon removal of the islands, excavation <br /> of soil will minimize the volume requiring in-situ remediation The proximity and possibility <br /> of damaging existing monitoring and vapor-extraction wells will need to be assessed with the <br /> benefits of excavating hydrocarbon-containing soil at that time <br /> 1 <br /> 38032-10 14 <br />