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'�t'�4 -� <br /> - <br /> e� <br /> [hl Pont MoSN'5tems <br /> Page 36 <br /> August 10, 1989 <br /> Job No.211-:71-6 <br /> _ 2. Biodegradation <br /> 3. Soil venting/vacuum extraction <br /> Excavation of the contaminated soil is not economically practical due to the lateral extent and the <br /> depth of contaminated soil (at least 45 feet). Even if the soil is excavated to a TPHg concentration <br /> of 100 ppm, this method of remediation would require some method of foundation support (e.g. <br /> underpinning) for the existing garage and office building or its demolition and subsequent <br /> reconstruction, Costs for this remedial approach could easily be over$1 million. We understand <br /> that the tcnks are planned for removal during 1989 as part of a general renovation and remodeling <br /> plan for the gas station. The shallow (< I5-20 feet) contaminated soils could be removed and <br /> - treated at that time. <br /> In-situ biodegradation would require additional studies in order to ascertain the presence or <br /> absence and abundance of the appropriate microbes, to determine the nutrient and oxygen <br /> requirements necessary to achieve successful treatment, and to determine the proper well depths <br /> and spacing. Because of the fine-grained nature of the unsaturated soils, biodegradation will <br /> probably only be applicable to the cleanun of the water-bearing zone. <br /> { Recent studies have shown that soil venting and vacuum extraction may be quite successful in fine- <br /> grained soils. This alternative would require a pilot program in order to determine the effectiveness <br /> and the proper well spacing. Rough costs for this remediation method are provided below: <br /> _ i <br /> Pilot Program (Install Two Test Wells, <br /> De-elop Flow Curves, and System Design) $25,000 <br /> �- Install 4-Inch Diameter Recovery Wells $ 3,000 ea. <br /> Install Piping, Vacuum Pump, etc. $25,000 <br /> Maintenance and Montioring $10,000 <br /> Ground Water <br /> A ground-water remediation system at this site could include: <br /> 1. Physical containment (i.e.,slurry wall) <br /> 2. In-situ biod:gfudation <br /> J, 3. Ground-water extraction and treatment (e.g.,air stripping) <br />