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1 <br /> Artesian Environmental Consultants <br /> 1 <br />' SITE HISTORY <br />' A Phase I Preliminary Hazardous Materials Site Assessment(PSA) was prepared by <br /> Kleinfelder of Sacramento, California, and dated November 16, 1988 The PSA was <br /> prepared for Nomellim Construction Company, a construction and tool rental <br /> operator <br /> Three underground storage tanks (USTs) located at the subject site were removed in <br /> August, 1988 The tank numbers, sizes, contents and histories were as follows two <br />' 1,000 gallon fuel tanks (containing regular and unleaded gasoline) were excavated <br /> southeast of the warehouse building One 550 gallon waste oil tank was excavated <br /> from a separate site The subsurface investigations that followed relate to the two <br /> 1,000 gallon fuel tanks The tanks, which reportedly stored unleaded gasoline, may <br />' also have held kerosene at one time Analytical results of soil samples collected <br /> beneath the tanks indicated that petroleum hydrocarbons and gasoline related <br /> constituents were present in the soil beneath the two 1,000 gallon tanks The sample <br />' collected beneath the waste oil tank did not contain these constituents at regulatory <br /> action levels Results of this investigation were presented in a Kleinfelder report <br /> dated September 22, 1988 <br />' According to the Kleinfelder Report dated June 14, 1989, additional soil was <br /> removed from the fuel tanks'excavations on November 9, 1988 to further assess the <br /> extent of petroleum hydrocarbon contamination One section of the former tank pit <br /> was excavated an additional 8 feet to a total depth of 19 feet below ground surface <br /> (BGS) Soil samples were screened for organic vapors using a photoioruzation <br /> detector(PID) Organic vapor readings were detected at 408 parts per million (ppm) <br />' from a sample collected at a depth of 19 feet BGS within the former tank pit, and 740 <br /> ppm from a sample collected 10 feet away from the excavation at a depth of 16 feet <br /> BGS Based on the positive organic vapor screening results, Nomellini Construction <br />' decided to backfill the excavation with clean fill and further assess the extent of the <br /> contamination with a soil boring program <br /> In May, 1989, Kleinfelder supervised the drilling of nine soil borings (B-1 through <br />' B-9) in the vicinity of the former tank pit Samples were analyzed from depths of <br /> 10 5 to 26 feet BGS Ten of the 15 soil samples contained total petroleum <br /> hydrocarbons as gasoline (TPH-g) at levels ranging from non-detect to 450 ppm <br />' High concentrations of TPH-g, benzene, toluene,ethylbenzene, and xylenes (BTEX) <br /> were detected just above and below the groundwater surface in boring B-1, located <br /> adjacent to the south edge of the excavation Similarly, high TPH-g concentrations <br /> I were detected lust above the groundwater surface in B-2, approximately 20 feet north <br /> of the former tank excavation The remaining samples had relatively low detectable <br /> concentrations of petroleum hydrocarbons , but these compounds were consistently <br />' detected just above the groundwater surface Groundwater was encountered at a <br /> depth of about 25 feet below ground surface <br /> In February, 1991, Kleinfelder drilled three borings B-10 through B-12 These <br /> borings were subsequently converted into monitor wells MW-1 through MW-3 <br /> TPH-g was detected in the groundwater on February, 1991 in MW-1 through MW-3 <br /> at concentrations of 1,700 ppm, 10,000 ppm and 1,500 ppm, respectively In June, <br /> I <br /> 3I75 Kerner Blvd, Suite E•San Rafael,CA 94901 • (415) 257-4801 -FAX (415) 257-4805 <br /> I <br />