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2.3.1 Excavation of Impacted Soil <br /> The proposed excavation limits will extend approximately 20 feet from the former UST in all <br /> directions, to a depth of between 15 and 20 feet bgs (Figure 3). The actual excavation limits will be <br /> based on field observation and screening, and confirmatory soil sample analyses. <br /> Soil in the vicinity of the former UST will be excavated to the first evidence of groundwater. <br /> During excavation, soil samples from the excavation side walls and floor will be collected for field J <br /> observation and screening with a PID. Based on field evidence, the excavation will be extended 1 <br /> until additional excavation becomes unnecessary or impractical. All excavated soil will be <br /> stockpiled on and covered with plastic sheeting pending analytical characterization and disposal <br /> profiling. Temporary fencing will be used to secure the excavation when personnel are not at the <br /> site. <br /> 2.3.2 Excavation De-Watering <br /> Groundwater beneath the site tends to be influenced by some confining conditions. During prior <br /> investigations, the potentiometric groundwater surface rose approximately two to three feet from the <br /> depth at which it was first encountered. As such, some groundwater recharge-into the open <br /> excavation should be expected. Groundwater will be pumped from the excavation into a rented <br /> water storage tank and stored on-site. <br /> To allow for maximum groundwater recharge and discharge, groundwater will be pumped <br /> periodically, during the excavation operation. Excavation de-watering will be concluded when <br /> recharge significantly decreases and/or when the concentrations of petroleum hydrocarbons in j <br /> groundwater apparently diminish. <br /> Upon completion of the de-watering operation, the contained groundwater will be treated with <br /> granular activated carbon and discharged to the local sewer system. Prior to discharge, water <br /> samples will be collected for analysis to confirm that treatment was effective. The rented water <br /> storage tank will be cleaned at the site and the waste activated carbon will be transported off site <br /> for regeneration. { <br /> 1 <br /> 7 <br /> i <br />