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Because no detected hydrocarbon impacts remain in soils above 10 feet bgs, it is unlikely <br /> that workers or the general public would come into direct contact with impacted soils or <br /> constituents of concern <br /> 5 3 3 Limited Action Groundwater Monitoring and Cap Maintenance - Option 3 <br /> This Limited Action option includes both long-term groundwater monitoring and periodic <br /> inspection and maintenance of the existing asphaltic concrete pavement to improve its long-term <br /> performance as a runoff and infiltration control system This program is assumed to continue <br /> for a period of five years <br /> Option 3 is similar to Option 2, but includes active cap maintenance The existing <br /> asphaltic concrete pavement would act as a cap to enhance surface runoff in the area of impacted <br /> soils The pavement would limit percolation through impacted soils, thereby reducing potential <br /> for migration of diesel constituents to the groundwater table <br /> The existing asphaltic concrete would be regularly inspected and repaired as needed to <br /> maintain it as a barrier to infiltration The entire pavement would be carefully inspected by an <br /> engineer or qualified paving contractor once per year prior to the start of the rainy season <br /> Cracks and otherwise damaged areas would be repaired using cold patch or slurry seal-type <br /> application, as appropriate In addition, naturally occumng soil microbes would continue to <br /> degrade the hydrocarbons <br /> Because no detected hydrocarbon impacts remain in soils above 10 feet bgs, it is unlikely <br /> Y p <br /> that workers or the general public would come into direct contact with impacted soils or <br /> constituents of concern <br /> 5 3 4 Bioventing Option 4 <br /> Option 4 consists of in-situ bioventing to reduce the concentration of hydrocarbons in <br /> soil A groundwater monitoring program identical to that developed for Option 2 would also <br /> be undertaken until the biological treatment is completed <br /> The bioventing system would consist of a series of air venting and extraction wells <br /> intended to enhance natural microbial activity by introducing oxygen into the impacted soil zone <br /> SAC127 10 14 <br /> DAMES & MOORE <br />