ARCHIVED REPORTS_REMEDIAL INVESTIGATION REPORT 2000

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7kadwell&Rollo • RESNA performed additional groundwater monitoring in August 1992, collecting groundwater samples from wells MW-1 through MW-9, and measuring water levels at wells MW-1 through MW-3 at Area 20. All groundwater samples were analyzed for Title 22 Metals, and groundwater from wells MW-1 and MW-4 for volatile organics (EPA Method 8240). Barium, selenium, and zinc were detected at some of the wells at levels exceeding MCLs. No volatile organics were detected. RESNA concluded that the groundwater contaminants found at Area 10 were representative of conditions found at other sites in the immediate vicinity, and that groundwater is generally of poor quality due to infiltration of tidally-influenced water from the deep water channel and influx of water through dredge spoils adjacent to the channel. RESNA further stated that the level of Title 22 Metals in shallow soil and groundwater"...are.substantially the same as those present beneath a large area of Stockton, and are consistent with regional non-point sources of contamination." No further investigation was recommended. Luhdorff and Scalmanini performed a soil gas survey in April 1993 that identified petroleum • hydrocarbons at two general areas (the former ship building yard and an area southwest of the former ship building and steel fabrication shop). Four soil borings were completed to confirm the results of the soil gas survey. Soil samples were collected at 1.5, 3, and 5 feet bgs, with groundwater collected at each boring. Soil samples were analyzed for benzene,toluene, ethyl benzene, and total xylenes (BTEX), and total petroleum hydrocarbon as gasoline (TPH-g), diesel (TPH-d), and motor oil (TPH-mo). Soil samples were also analyzed for total copper, lead, mercury, and zinc. Groundwater samples were analyzed for BTEX, TPH-g,TPH-d, and TPH-mo. Results of the soil analyses indicated that TPH-mo was present in shallow soil at up to 860 milligrams per kilogram (mg/kg), with TPH-g found in two samples at up to 5.1 mg/kg. Trace BTEX was detected in one sample. Total lead at up to 1,100 mg/kg was found in soil, with zinc concentrations ranging from 66 to 570 mg/kg. Copper ranged from 36 to 310 mg/kg, and mercury was detected in one sample at 1.2 mg/kg. Only groundwater from Boring B4 contained fuel hydrocarbons, at less than a combined 0.25 milligrams per liter. The report concluded that additional characterization was warranted. 5 25970309.DGD 24 August 2000