ARCHIVED REPORTS_REMEDIAL INVESTIGATION REPORT 2000

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Mmadwemmio concentrations less than 300 mg/kg. Laboratory reports indicate that the significant 40 concentrations of petroleum hydrocarbons are in the motor oil to asphalt range. Prior to the recent investigation, Treadwell &Rollo had collected 10 soil samples for PAH analyses of which one 1 foot deep sample had a detection of one PAH, benzo(a)pyrene, at 110 ug/kg, which is below the 290 ug/kg PRG for industrial sites. At the request of DTSC 13 additional soil samples were collected for PAH analyses during the recent investigation. One 1 foot deep sample had a concentration of benzo(a)pyrene at 740 ug/kg, which exceeds the PRG for industrial sites. No TPH-g, TPHmo, PAHs, or VOCs have been detected in groundwater at this site. Low concentrations of one SVOC (less than 110 ug/1)have been detected in two samples. TPHd concentrations detected in groundwater have ranged from 0.12 to 0.48 mg/1. No significant concentrations of any metals have been detected in groundwater. 4.1.3 Area 20 • Elevated concentrations of arsenic have been detected in shallow soil, but at concentrations below California hazardous criteria or non-carcinogenic PRGs for industrial sites. Prior to the recent investigation Treadwell & Rollo collected 12 soil samples for arsenic analyses of which four 1 foot deep samples contained elevated concentrations of arsenic (32, 33, 43, and 110 mg/kg). These concentrations are below the California hazardous criteria of 500 mg/kg, or the non-carcinogenic PRG for industrial sites of 440 mg/kg. At the request of DTSC an additional 27 soil samples were collected for arsenic analyses during the recent investigation of which 1 sample contained an elevated concentration of arsenic (52 mg/kg). No petroleum hydrocarbons, SVOCs, or VOCs have been detected in groundwater at this site. No significant concentrations of metals have been detected in groundwater. 28 • 25970309.DGD 24 August 2000