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PRIMEX TECHNOLOGIES • <br /> Corrective Measures Study Workplan, EPA ID No. CAD 000 626 762 <br /> May 2000 <br /> Task Wk 1 -3 Wk 4 Wk 5 Wk 6 Wk 7 Wk 8 to 12 <br /> Site Mobilization <br /> Sampling at SWMU #21 —� <br /> Analysis of SWMU#21 Samples <br /> Evaluation of SWMU#21 Results <br /> Excavation at AOC#4 <br /> Collection of Verification Samples at AOC#4 —i <br /> Analysis of AOC#4 Verification Sample <br /> Add'I Excavation at AOC#4 if necessary) —' <br /> Collection of Verification Samples AOC#4 if neces. <br /> (Analysis of Verification Sam les AOC#4 if neces. —' <br /> Excavation at SWMU#21 <br /> Collection of Verification Samples at SWMU#21 <br /> Analysis of SWMU#21 Verification Samples <br /> Soil Profiling, Disposal, Site Demobilization <br /> Preparation of Report for Submittal <br /> 4.0 AOC #4— CORRECTIVE MEASURES <br /> Based on the results of the RFI Field Investigation, only one boring (location AOC 4-4) <br /> sample results indicated concentrations of hydrocarbons exceeding 100 mg/kg, and <br /> samples 2 to 4 feet away were below 100 mg/kg, it is surmised that the hydrocarbons <br /> are likely localized. Further soil characterization is not recommended. <br /> 4.1 Corrective Measure Alternatives for AOC #4 <br /> Corrective measures for AOC #4 considered the following: 1) the estimated volume of <br /> hydrocarbon impacred soil is likely less than 5 to 10 cubic yards, 2) hydrocarbon <br /> impacted did not penetrate deeply, and 3) saturated conditions are not likely to be <br /> encountered since depth to groundwater is generally considered to be approximately <br /> 50 feet bgs. Three remedial options were considered for AOC #4, 1) no action, 2) in- <br /> situ treatment methods, and 3) excavation. The 'No action' alternative is not <br /> recommended since the vertical extent of soil impacted with concentrations of <br /> hydrocarbons exceeding 100 mg/Kg is not known and the area may be readily <br /> remediated. In-situ remedial methods such as bioremediation or electrolysis treatment <br /> would not be economically feasible given the low volume of hydrocarbon impacted soil. <br /> Excavation is technically feasible and the most economic alternative given the low <br /> volume of material that is easily accessible from the surface. Excavation and off-site <br /> management, at an appropriate landfill or recycling facility, is therefore the <br /> recommended remedial method. <br /> CHOW ENGINEERING, INC. 4 <br />