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7kN3dweII8RWIo <br /> a product used by machine shops for degreasing metal, suggesting that operations at the Carando <br /> Machine Works may have contributed to the identified soil and groundwater contamination <br /> Two sumps that may have been used for degreasing operations are located approximately 60 to <br /> ' 80 feet south and upgradient of boring CSB-2 (Figure 2) These sumps will be excavated and <br /> samples collected from below them, following the subsurface demolition at the Site in April <br /> 2004, to determine if releases have occurred from the sumps <br /> Figure 2 also shows a potential 10-foot deep excavation area that is proposed for most of the Site <br /> to address soil that must be recompacted for geotechnical reasons During this work, soil will be <br /> ' screened for potential contamination as described in a soil management plan that has been <br /> approved by the DTSC (Treadwell &Rollo 2004) <br /> 5.3 Proposed Remedial Method <br /> We propose to excavate the contaminated soil in the cross-hatched area as shown on Figure 3 <br /> The proposed excavation is 43' long by 14' wide by 23' deep The proposed excavation would <br /> be extended to approximately 4-feet below the groundwater table (18 5 feet bgs) in order to <br /> remove contaminated groundwater, and contaminated saturated soil During excavation <br /> 1 backfilling, oxygen release compound (ORC) would be mixed into the backfill below the <br /> groundwater table to assist with enhanced bioremediation of groundwater downgradient of the <br /> excavation <br /> ,t <br /> The excavation dimensions were determined after considering the previous and current soil and <br /> groundwater analytical data and the geologic and hydrogeologic data gathered during our recent <br /> investigations The southern portion of the excavation is bounded by Boring CSB-5, located <br /> approximately 10-feet from the property line, and 16 feet south southeast of boring B-3 This <br /> indicates that the identified contamination in the sidewalk along Fremont Street likely extends <br /> less than 10 feet onto Site The excavation depth and it's northern edge is limited by Fremont <br /> Street and the associated utilities present dust past the sidewalk curb Shoring will be required <br /> 8 <br /> 25971013 DGD 12 April 2004 <br />