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.� ri 3 : psi 11Ckw <br /> Area 3 - Vicinity of Former Aboveground Diesel Tank <br /> Three quarterly rounds of ground-water sampling in the <br /> vicinity of the former aboveground diesel tank have shown <br /> low and decreasing concentrations of diesel fuel and trace <br /> or non-detectable concentrations of BTEX compounds. Toluene <br /> was detected at a concentration of 0. 001 mg/l during the <br /> April 1990 sampling event. The concentration of diesel fuel <br /> found in well LF-2 decreased from 1. 2 mg/l in October 1989 <br /> to 0. 7 mg/l in April 1990. Concentrations of diesel fuel in <br /> wells LF-1, LF-3, and LF-4 were below the detection limit of <br /> 0. 3 mg/l in the January and April 1990 quarterly samples. <br /> These data indicate that residual diesel-affected soils are <br /> not significantly impacting ground water in the vicinity of <br /> the former aboveground diesel fuel tank. Therefore, further <br /> excavation of soils in this area and continued ground-water <br /> monitoring do not appear to be warranted. <br /> Area 1 - Two rounds of sampling have been completed at six <br /> ground-water monitoring wells in the vicinity of the two <br /> former underground gasoline storage tanks in Area 1. Wells <br /> LF-6, LF-7, LF-8, and LF-9 were sampled in January and in <br /> April 1990. Wells LF-11 and LF-12 were sampled in August <br /> and November 1990. Petroleum hydrocarbons and benzene, <br /> ethylbenzene, and xylenes were not detected in the two <br /> rounds of sampling of any of the six monitoring wells. <br /> Toluene was only detected at a trace concentration (0. 001 <br /> mg/1) in one sample collected in January 1990 from well <br /> LF-9, and was not detected in April 1990. Based on these <br /> results, and the results from soil sampling following <br /> excavation of fuel-affected soil from the vicinity of the <br /> tanks, additional sampling of these wells does not appear to <br /> be warranted. <br /> We recommend at this time that you request authorization from the <br /> RWQCB to discontinue further monitoring of these areas, and <br /> properly abandon the monitoring wells. If you have any <br /> questions, please contact me or Chuck Pardini. <br /> Sincerely, <br /> Beth GurneyA. <br /> . <br /> Senior Scientist <br /> 1875/NAS 2 <br />