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CLEARWATER <br /> G R O U P <br /> Environmental Services <br /> 1 <br /> in soil samples collected from an underground storage tank (UST) excavation According to an <br />' April 30, 1996 SJC/SJC/EHD letter, two USTs were removed from the site on June 15, 1992 <br /> Both USTs were 10,000-gallon capacity tanks that had been used to store diesel fuel Four soil <br />' samples were collected from the bottom of the excavation at a depth of approximately 16 feet <br /> below ground surface (bgs) Soil samples were analyzed for total petroleum hydrocarbons as <br />' gasoline (TPHg), as diesel fuel (TPHd), as kerosene (TPHk), and as motor oil (TPHmo) <br /> Samples were also analyzed for benzene, toluene, ethylbenzene, and total xylenes (BTEX) The <br />' highest concentrations of TPHg, TPHd, and BTEX were detected at 5,700 milligrams per <br /> kilogram (mg/kg) TPHg, 50 mg/kg TPHd, and 48 mg/kg benzene TPHk and TPHmo were not <br /> detected in any of the four samples <br />' 1997 <br /> On September 25, 1997, Clearwater supervised the drilling of six soil borings to depths from 32 <br /> to 38 feet bgs Three of the borings were converted to groundwater monitoring wells (MW-1 <br /> through MW-3) Soil samples collected from four of the six borings contained detectable <br /> concentrations of petroleum hydrocarbons The highest concentrations of TPHg (570 mg/kg) <br /> and benzene (4 0 mg/kg) were detected in the sample from SB-2 at a depth of 25 feet bgs <br />` Groundwater samples collected September 29, 1997 from all three monitoring wells contained <br /> detectable concentrations of dissolved petroleum hydrocarbons The highest concentrations of <br /> TPHg (32,000 micrograms per liter fµg/L]) and benzene (2,200 pg/L) were detected in the <br /> sample from monitoring well MW-1 Low concentrations of TPHd were detected in soil samples <br /> rfrom SB-5 (11 mg/kg) and SB-6 (2 mg/kg), and in the groundwater sample from MW-1 (300 <br /> µg/L) Subsequent groundwater sample results have been non-detect for all three wells and with <br /> approval from the SJC/EHD, analysis for TPHd has been discontinued Results of these efforts <br /> were presented in Clearwater's Subsurface Investigation Report, dated November 20, 1997 <br /> 1998 <br /> Based on these initial investigation results, the SJC/EHD requested additional monitoring wells <br /> Ibe installed to better define the aerial extent of soil and groundwater contamination After <br /> 4Q/04 Groundwater Monitoring Report 2 <br /> I <br />