ARCHIVED REPORTS_REMEDIAL INVESTIGATION REPORT 2000

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7hN3dweII&RoIIo Harza performed a soil and groundwater investigation in 1995, consisting of ten soil borings • spread over the east and west portions of the site for soil sampling, collecting groundwater samples from MW-1 through MW-9, and collecting a surface water sample from the Stockton Ship Channel adjacent to the site. Soil analyses indicated total lead was present at up to 4,600 mg/kg, although the average value was less than 110 mg/kg when the 4,600 mg/kg sample was excluded from the sample population. The groundwater analyses detected only arsenic and selenium, at levels at or slightly above method reporting limits of 0.01 mg/1. TPH-d was detected in groundwater from well MW-9 at 0.63 mg/l. No dissolved metals or petroleum hydrocarbons were detected in the Channel sample. Treadwell & Rollo performed soil and groundwater sampling in October 1996. Fifteen soil borings were advanced across the site to an average depth of approximately 10 feet bgs. Soil samples were collected at approximately 3 and 7 feet bgs, and analyzed for Total Recoverable Petroleum Hydrocarbons (TRPH), TPH-g and TPH-mo,polycyclic aromatic hydrocarbons (PAHs), total arsenic, chromium, lead, and mercury, and soluble lead. Groundwater samples • were collected from wells MW-2 through MW-9, and analyzed for the same parameters as the soil. Well MW-1 could not be located. TRPH was detected in all but six of the thirty soil samples at 10 to 3,300 mg/kg. TPH-mo was detected in eight of nine samples at 26 to 2,500 mg/kg. TPH-d was detected in one of nine samples analyzed at 65 mg/kg. A single PAH, Benzo (b) flouranthene was detected in one of fifteen soil samples analyzed at 350 µg/kg. Total lead was detected in all soil samples at 8 to 3,600 mg/kg, and soluble lead in nineteen of twenty samples at 0.2 to 39 mg/kg. Soluble lead was analyzed using the Cal-WET STLC method. Only TPH-d was detected in groundwater at wells MW-3 through 9, with lesser amounts of petroleum contaminants detected in wells MW-3 and MW-6. No PAHs were detected in groundwater, and lead was detected only in well MW-2, at 0.06 mg/l. Arsenic was detected in all groundwater samples, ranging from 0.011 to 0.11 mg/l. Treadwell & Rollo conducted additional shallow soil sampling in December 1996. Surface soil samples were collected at each of the fifteen sampling locations from the October 1996 work, • 6 25970309.DGD 24 August 2000