ARCHIVED REPORTS_XR0006394 - Laserfiche WebLink

Home Browse Search

S E C 0 R Conceptual Site Model . Chevron Service Station ##9-6171 March 25,2005 IPage 18 borings Sod samples collected from the boring drilled in the former UST location (GE02) contained TPHg concentrations up to 7,000 ppm (at 16 feet bgs) and benzene concentrations up to 10 ppm (at 49 feet bgs) TPHg and benzene were not detected in soil from the other borings 6.2.2 Groundwater Sampling and Analyses Groundwater monitoring wells (MW-1 to MW-3) and vapor extraction wells (VEW-1 and VEW-2) were Installed In the northwest, northeast, and southern edges of the property, respectively The purpose of these wells was to characterize the extent of vertical and horizontal migration of hydrocarbons in soil and determine if the hydrocarbons had entered the groundwater I Groundwater samples were collected from the monitoring wells on July 23, 1990 All three groundwater samples contained detectable petroleum hydrocarbon concentrations The concentrations of unspecified "petroleum hydrocarbons volatile" were reported at concentrations ranging from 350 ppb (MW-1) to 63,000 ppb (MW-3) The concentrations reported for benzene ranged from 1 9 ppb (MW-1) to 10,000 ppb (MW-3), toluene ranged from 1 5 ppb (MW-1) to 18,000 ppb (MW-3), ethylbenzene ranged from 0 6 ppb (MW-1) to 1,800 ppb (MW-3), and total xylenes ranged from 2 0 ppb (MW-1) to 11,000 ppb (MW-3) The highest concentrations of hydrocarbons were detected in groundwater samples collected from MW-3 The relatively high concentrations were probably due to the wells being located downgradient from the original UST basin In September 1995, four groundwater grab samples were collected from during the completion of four borings (GE01 to GE04) The groundwater samples contained TPHg ranging from 14 ppm (GE03) to 75 ppm (GE04), benzene ranging from 4 1 ppm (GE03) to 9 8 ppm (GE02), toluene ranging from 0 66 ppm (GE03) to 15 ppm (GE04), ethylbenzene ranging from 0 22 ppm (GE03) to 1 0 ppm (GE04), and total xylenes ranging from 0 410 ppm (GE03) to 5 6 ppm (GE04) In 1996, two vapor extraction wells (VEW-1 and VEW-2) were installed Concentrations of TPHg, BTEX, and MtBE were reported at 3,500 µg/L, 55 µg/L, 6 µg/L, 410 l.cg/L, 380 µg/L, I and 91µg/L, respectively, in VEW-1 Concentrations at or above the method detection limits for TPHg, BTEX, and MtBE were not reported in VEW-2 In September 1997, Cambria Environmental Technology, Inc , (CET) Installed groundwater monitoring wells MW-4 through MW-7 Only the soil samples collected at 55 ft bgs contained detectable concentrations of petroleum hydrocarbons The concentrations of ` TPHg and benzene reported In soils samples ranged from 3 3 ppm to 92 ppm and 0 37 l ppm to 2 9 ppm, respectively Groundwater samples collected from monitoring wells MW-4 through MW-7 contained concentrations of TPHg ranging from 1,300 ttg/L to 31,000 µg/L, lN IFdes\Projects\Chevron\Retail\#9-61711Site Conceptual Model\FINAL_CSM doc 1 i