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'71 U { SITE BACKGROUND Raymond Investment Corporation—730 Channel Street, Stockton, California On April 29, 2003, Oil Equipment Services removed one underground storage tank(UST) and associated piping at the Site The UST was discovered as part of a Phase II Environmental Site Assessment performed in May, June, and September 2002, and completed for the City of Stockton Department of Housing and Redevelopment The San Joaquin County Environmental Health Department (SJCEHD) required removal of the UST Condor representatives were on Site to make field observations and collect soil samples following removal of the UST and the associated piping Dina Abate of the SJCEHD was on Site to observe the UST and piping removal activities and the collection of soil samples The UST was an approximately 1,000-gallon capacity single-wall steel tank twelve feet long and four feet in diameter The excavation associated with the UST was approximately six feet by fifteen feet by six feet deep Soil staining and petroleum odors were noted in the excavation and excavated soil Groundwater was not encountered in the excavation Approximately 85 feet of piping associated with the UST, a dispenser, and a diesel filter were also removed Following removal of the UST, piping, dispenser, and filter, soil samples were collected from locations directed by Ms Abate The tank excavation was backfilled with pea gravel Laboratory analytical results indicated that petroleum hydrocarbons were not detected at or above the laboratory reported detection limits in the soil samples collected from the north end of the UST excavation, from beneath the dispenser, and from two piping trenches Total petroleum hydrocarbons quantified as gasoline (TPH-G), total extractable petroleum hydrocarbons quantified as motor oil (TEPH- MO), and total extractable petroleum hydrocarbons quantified as diesel (TEPH-D) were detected at concentrations of 75 milligrams per kilogram (mg/kg), 18,000 mg/kg, and 2,400 mg/kg, respectively, in the soil sample collected from beneath the south end of the UST excavation at a depth of eight feet below ground surface (bgs) TPH-G and TEPH-D were also detected at concentrations of 2 0 and 200 mg/kg, respectively, in the soil sample collected from beneath the location of the diesel filter The UST removal activities and the results of the laboratory analyses were described by Condor in the Underground Storage Tank Removal Report dated May 14, 2003 In a letter dated November 4, 2003, to Beverly Garcia of the Raymond Investment Corporation, Victoria McCartney of the SJCEHD directed Raymond Investment Corporation to submit a work plan to investigate the lateral and vertical extent of contamination at the Site Condor prepared the Soil and Groundwater Investigation Work Plan, dated February 19, 2004, at the request of Ms Garcia in response to that letter Ms McCartney approved the work plan, with modifications, in a letter dated March 17, 2004 The modifications included the elimination of three proposed borings in the vicinity of the former UST location and the elimination of one proposed boring in the vicinity of the former location of the diesel filter and piping Ms McCartney also directed the soil and groundwater samples to be analyzed for 1,2-dibromoethane (EDB),methanol, and ethanol Condor conducted soil and groundwater investigation activities at the Site on May 5 and 6, 2004 The investigation included the installation of six direct push borings to collect soil and groundwater samples Laboratory analytical results of the soil and groundwater samples collected during the investigation indicated that the soil and groundwater at the Site were impacted by TPH-G and TEPH-D at those locations No petroleum hydrocarbons were detected at or above the laboratory reported detection limits in the three soil samples and the groundwater sample collected from boring SB-5, which was advanced adjacent to the former UST excavation This suggested that there was minimal impact to soil and ( groundwater to the vicinity of the former UST location Condor described the results of the investigation in the Soil and Groundwater Investigation Report, dated June 1, 2004 In the report, Condor