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• 5. 0 RECOMMENDATIONS <br /> The findings presented in Section 4 confirm the suspicion that <br /> aircraft washpad contaminants have been released into the <br /> environment. In this section recommendations for investigating the <br /> extent of contamination and for site remediation are presented. <br /> 5 . 1 Washpad <br /> Washpad contamination appears to be minor in concentration, shallow <br /> and localized. The California Military Department has scheduled <br /> the existing Washpad for replacement in the near future. It is <br /> recommended that soil contamination be excavated after washpad <br /> demolition. The total amount of soil requiring excavation is <br /> estimated to be 200-500 cubic yards . Average excavation depth will <br /> probably be about 4 feet. <br /> Following contaminated soil excavation based on field measurements <br /> ( ie hand held photoionization detector) closure soil samples <br /> should be taken. one discreet soil sample per 250 square feet of <br /> surface area within the excavated zone is recommended. Using this <br /> ratio approximately 15 samples are pro3ected. Analysis for TPH <br /> only will be a reliable indicator of remediation effectiveness . <br /> if soil conditions under the Washpad have been accurately <br /> characterized by the soils boring/analysis investigation, described <br /> in this report remediation as specified in the preceding paragraph <br /> should be adequate. If deeper or more widespread contamination is <br /> discovered, the remediation may have to be suspended pending <br /> further site investigation. <br /> A deep ( 10-11 feet) soil sample from the boring 3 vicinity should <br /> be collected for TPH analysis during the soil excavation project. <br /> Analysis will verify the results obtained from sample 2-3 . If <br /> verified, some deeper excavation may be required in this area. <br /> 5 .2 Clarifier <br /> No reliable estimate of soil contaminant migration extent, either <br /> laterally or vertically, can be made based on the site <br /> investigation performed to date. A more thorough investigation is <br /> recommended to determine both the lateral and vertical extent of <br /> soil contamination as well as the potential impact to groundwater. <br /> The recommended site investigation program would consist of <br /> powered, hollow stem auger, borings with associated soil sampling <br /> every five feet. At least four boring locations will be required <br /> • 19 <br />