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Thwdwell&Rollo <br /> Prior to the recent investigation, Treadwell & Rollo had collected 45 soil samples for lead • <br /> analyses of which 2 samples exceeded 1,000 mg/kg (the PRG for industrial sites) and 3 other <br /> samples exceeded 400 mg/kg (the PRG for residential sites). At the request of DTSC, 52 <br /> additional soil samples were collected for lead analyses during the recent investigation of which <br /> 1 sample exceeded 1,000 mg/kg and 3 samples exceeded 400 mg/kg. Figures 8, 9, and 10 show <br /> the lead concentrations of all samples collected by T& R at 1, 3, and 6 to 7 feet deep <br /> respectively. The analytical results indicate total lead concentrations are generally elevated in <br /> the upper 3 feet of soil, but that significant concentrations of total lead (>1,000 mg/kg) have only <br /> been found in approximately 4 percent of the samples analyzed. <br /> Analytical results for soluble lead conducted during previous investigations has shown that some <br /> samples have exceeded hazardous criteria of 5 mg/l using STLC extraction process, and that one <br /> sample has exceeded the hazardous criteria of 5 mg/l using TCLP extraction process. Soluble <br /> lead concentrations performed during the recent investigation using the STLC DI method <br /> requested by DTSC, ranged from 0.011 to 0.081 mg/l, below the hazardous criteria. Table 4 • <br /> summarizes the results of soluble lead analysis at Area 10. <br /> Petroleum hydrocarbons have been detected in 49 of the 83 samples that T& R has collected at <br /> Area 10. Fifteen of these samples, approximately 18%, had concentrations greater than <br /> 1,000 mg/kg, and all but one of these samples were detected in the top 3 feet of soil. Laboratory <br /> reports indicate that the significant concentrations of petroleum hydrocarbons are in the motor oil <br /> to asphalt range. <br /> Prior to the recent investigation Treadwell & Rollo had collected 26 soil samples for PAH <br /> analyses of which 1 sample collected in 1996 (TR-13-3.0) had a detection of one PAH, benzo (b) <br /> flouranthene at 350 ug/kg, which is below the 2,900 ug/kg PRG for industrial sites. At the <br /> request of DTSC 34 additional soil samples were collected for PAH analyses during the recent <br /> investigation. One sample (1013-18-6.0) contained 330 µg/kg of benzo(a)pyrene, which exceeds <br /> the 290 µg/kg PRG for industrial sites. <br /> 26 • <br /> 25970309.DGD 24 August 2000 <br />