ARCHIVED REPORTS XR0001113 - Laserfiche WebLink

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1 SITE HISTORY ' A Phase I Preltrrunary Hazardous Materials Site Assessment(PSA) was prepared by Kleinfelder of Sacramento, California, and dated November 16, 1988 The PSA was prepared for Nomellini Construction Company, a construction and tool rental ' operator Three underground storage tanks (USTs) located at the subject site were removed in August, 1988 The tank numbers, sizes, contents and histories were as follows two ' - 1,000 gallon fuel tanks (containing regular and unleaded gasoline) were excavated from southeast of the warehouse building One 550 gallon waste oil tank was excavated from a separate site. The subsurface investigations that followed relate to the two 1,000 gallon fuel tanks. The tanks reported to store unleaded gasoline may also have held kerosene at one time Analytical results of soil samples collected beneath the tanks indicated that petroleum hydrocarbons and gasoline related constituents were present in the soil beneath the two 1,000 gallon tanks Constituents ' were detected below levels of concern in the sample collected beneath the waste oil tank Results of this investigation were presented in a Kleunfelder report dated September 22, 1988 ' According to the Klennfelder Report dated June 14, 1989, additional soil was removed from the fuel tanks' excavation on November 9, 1988 to further assess the extent of petroleum hydrocarbon contamination. One section of the former tank pit was excavated to a depth of 19 feet from about 11 feet below ground surface Soil samples were screened for organic vapors using a photoionizatlon detector(PID) Organic vapor readings were detected at 408 parts per million (ppm) from a sample collected at a depth of 19 feet within the former tank pit and 740 ppm from a sample collected 10 feet away from the excavation at a depth of 16 feet. Based on the positive organic vapor screening results, Nomellunt Construction decided to backfill the excavation with clean fill and further assess the extent of the contamination with a soil boring program. In May, 1989, Kletnfelder supervised the drilling of nine soil bonngs (B-1 through B-9) in the vicinity of the former tank pit Samples were analyzed from depths of 10.5 to 26 feet Ten of 15 soil samples contained total petroleum hydrocarbons as gasoline at levels ranging from non-detect to 450 ppm. ' High concentrations of TPH as gasoline (TPH-g), benzene, toluene, ethylbenzene, and xylenes (BTEX) were detected just above and below the groundwater surface in boring B-1, located adjacent to the south edge of the excavation Snrrilarly, high ' TPH-g concentrations were detected just above the groundwater surface in B-2, approximately 20 feet north of the former tank excavation The remaining samples had relatively low concentrations detected, but TPH,s were consistently detected just ' above the groundwater surface Groundwater was encountered at a depth of about 25 feet below ground surface ' In February, 1991, Kleinfelder dnlled three borings B-10 through B-12 These borings were subsequently converted into monitor wells MW-1 through MW-3 TPH-g was detected in the groundwater on February, 1991 in MW-1 through MW-3 at concentrations of 1,700 ppm, 10,000 ppm and 1,500 ppm, respectively In June, 1991, 15 feet of free product was measured in MW-1 Artesian Environmental Consultants measured hydrocarbon thickness in MW-1 on March 16, 1992 to be 182 feet Groundwater flow direction on March 16, 1992 was