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SECTIONTWO 2.4 LAN® USE Land use in the vicinity includes county fairgrounds, maintenance facilities, office buildings, light industnal, and agriculture The malonty of the site is currently paved with 6 to 8 inches of asphalt and concrete Future land use development plans indicate that the asphalt and concrete paving will remain at the site for use as a Imaintenance facility 2.5 PREVIOUS SITE INVESTIGATIONS Environmental investigations have been performed at the Shop 10 site since 1987 A summary of the previous environmental investigations is discussed below o The initial soul and groundwater assessment was conducted by Woodward-Clyde in 1987 Four groundwater monitoring wells (MW-1 through MW-4) were installed in the vicinity of the four 5,000-gallon USTs Groundwater sample results indicated that total petroleum hydrocarbons gasoline range (TPH-g) concentrations in groundwater ranged from 154 to 231 mg/1 and benzene concentrations ranged from 14 7 to 25 7 mg/1 Twenty soil samples were collected and analyzed for TPH-g and benzene, toluene, ethylbenzene, and xylenes (BTEX) TPH-g concentrations soil samples were below detection limits in samples collected from MW-1 through MW-3 and ranged from nondetect to 1,100 milligrams per kilogram (mg/kg) in soil samples collected from MW-4 Benzene concentrations ranged from nondetect to 7 7 mg/kg Toluene concentrations ranged from nondetect to 29 5 mg/kg, ethylbenzene concentrations ranged from nondetect to 12 1 mg/kg, and xylenes concentrations ranged from nondetect to 55 2 mg/kg The highest BTEX concentrations were detected in MW-4 between 20 and 30 feet bgs A soil and groundwater evaluation report was prepared summarizing the assessment (Woodward-Clyde, 1987) o In 1989, the four USTs and a waste-oil UST were removed by Placer Tractor Service Soil samples were collected beneath the USTs TPH-g concentrations in soil from beneath the gasoline and diesel fuel USTs ranged from 2 2 to 3,700 mg/kg and TPH diesel range (TPH-d) concentrations in soil from beneath the diesel and waste oil USTs ranged from 100 to 1,700 mg/kg, and 11 to 12 mg/kg, respectively o An additional site assessment was conducted by Woodward-Clyde between 1989 and 1990 Five additional groundwater monitoring wells (MW-5 through NW-9) were installed Twenty-four soil samples were collected and analyzed for TPH-g and BTEX BTEX were detected above laboratory detection limits in one soil sample collected from MW-7 at a depth of 30 feet bgs at the following concentrations 0 4 mg/kg, 0 2 mg/kg, 0 1 mg/kg and 0 2 mg/kg, respectively TPH-g concentrations in the soil samples from the five borings were not detected above the laboratory detection limit TPH-g concentrations in groundwater ranged from nondetect to 3 4 mg/1 BTEX concentrations in groundwater ranged from nondetect to 200 micrograms woodw=d4luf TklWNJOOONAMTOCKTON%REPORTGHOREM NA%mA 2-4