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PRIMEX TECHNOLOGIES • • Corrective Measures Study Workplan, EPA ID No. CAD 000 626 762 May 2000 Protection Agency (EPA), Region IX, Preliminary Remedial Goals (PRG) for chromium and lead, and no further sampling or analysis for these metals was deemed necessary. Samples from 10 of the 11 locations at AOC #4, indicated Total Petroleum Hydrocarbons as diesel (TPHd) and Oil and Grease (0&G) concentrations that were less than 100 mg/Kg. At sample location AOC #4-4, TPHd concentrations of 100 and 860 mg/kg were detected in the surface and in the 6 to 12 inch bgs samples, respectively. Based on this finding, this CMS WP presents the remedial methodology for the hydrocarbon imp[acted soils at AOC #4-4. At SWMU #21, 15 soil samples were collected at seven (7) locations as shown on Figure 4. The surface sample results for chromium and lead were significantly below the PRGs. Therefore, further sampling and analysis for these metals was not deemed necessary. Additionally, polychlorinated biphenyls (PCBs) analytical results, identified the detected PCBs as Aroclor 1254, indicated the detected concentrations for Aroclor 1254 were below the PRG, and further sampling and analysis was not warranted for PCBs. Hydrocarbon levels exceeding 100 mg/kg (either TPHd or O&G) were detected at each of the seven sampling locations of SWMU #21, with concentrations at the 6 to 12 inch bgs sample locations ranging from 110 to 7,100 mg/kg. Based on this finding, this CMS WP also describes additional sampling and analysis proposed to determine the horizontal and vertical extent of hydrocarbon in the soil as well as the proposed remedial activities for addressing the hydrocarbon soil impact at SWMU #21. 2.0 OBJECTIVES The objectives of the CMS Workplan are 1) assess the extent of petroleum hydrocarbon impact in the soil at sites AOC #4 and SWMU #21 and 2) remediate the two sites to levels below specified criteria. In establishing the specified cleanup criteria, the site-specific conditions were evaluated, which included the following: 1. The sites are part of an isolated, industrial property, adjacent to Lawrence Livermore National Laboratory Site 300. The site is likely to remain in industrial use. 2. Groundwater is approximately 50-feet bgs. 3. Annual precipitation is approximately 10-inches (LLNL Site 300 meteorological data). 4. The petroleum hydrocarbons are heavyweight oil that are biodegradable and largely immobile. Based on these factors, the potential for significant negative impact on health of potential receptors or the environment is considered to be very low. The proposed CHOW ENGINEERING, INC. 2