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j SECTIONTWO aft Inkgrmal per liter (gg/L), nondetect to 8 µg/L, nondetect to 0 7 µg/L, and nondetect to 170 gg/L, respectively o A Problem Assessment Report (Woodward-Clyde, 1990) was prepared at the request of the CVRWQCB o A Supplemental Site Assessment (Alton Geoscience, 1992) was conducted to further delineate the extent, levels, and the type of petroleum hydrocarbons in soil and groundwater Three groundwater monitoring wells (MW-10 through MW-12) were installed and two soil borings were advanced (AB-1 and AB-2) Nineteen soil samples were collected and analyzed for TPH-g, TPH-d, and BTEX TPH-g were detected in two of the 19 soil samples, and TPH-d were detected in one soil sample TPH-g concentrations in soil ranged from nondetect to 270 mg/kg, and TPH-d concentrations ranged from nondetect to 12 mg/kg Benzene was detected above laboratory detection limits in four soil samples with soil concentrations ranging from nondetect to 4 4 mg/kg Toluene was detected above laboratory detection limits in two soil samples with soil concentrations ranging from nondetect to 17 mg/kg Ethylbenzene was detected above laboratory detection limits in two soil samples with soil concentrations ranging from nondetect to 5 5 mg/kg Xylenes were detected above laboratory detection limits in two soil samples with soil concentrations ranging from nondetect to 30 mg/kg Alton Geoscience sampled groundwater monitoring wells MW-7, MW-8, and MW-10 through MW-12 Groundwater monitoring wells MW-1 through MW-6, and MW-9 were dry TPH-g and BTEX concentrations decreased in groundwater monitoring wells MW-7 and MW-8 TPH-g concentrations in the new monitoring wells ranged from nondetect (MW-12) to 5,600 µg/L (MW-10) TPH-d concentrations ranged from nondetect (MW-11 and MW-12) to 1 8 gg/L (MW-10) 0 A limited vapor extraction pilot test was conducted by Alton Geoscience in September 1992 (Alton Geoscience, 1992)to evaluate the feasibility of using soil vapor extraction as a remedial alternative o An additional environmental site investigation was conducted by Environmental Assessors Inc in 1993 to evaluate the horizontal and vertical extent of petroleum hydrocarbons in soil and groundwater Six additional groundwater monitoring wells MW 13, MW-14,MW-16, MW-19, MW-20, and MW-24 and four soil borings SB-15, SB-17, SB-18, and SB-22 were installed One hundred and forty three soil samples were collected and analyzed to a depth of 75 feet bgs for TPH-g and BTEX Selected soil samples were analyzed for TPH d TPH-g concentrations in soul ranged from nondetect (116 soil samples) to 350 mg/kg, benzene concentrations ranged from nondetect (109 soil samples) to 4 7 mg/kg, toluene concentrations ranged from nondetect (109 soil samples) to 37 mg/kg, ethylbenzene concentrations ranged from nondetect (116 soil samples) to 7 2 mg(kg, and xylenes concentrations ranged from nondetect (104 soil samples) to 47 mg/kg TPH-d were not analyzed for during this investigation Groundwater concentrations for TPH g ranged from nondetect (MW-14, MW-16, MW-19, MW-20 and MW-24) to 1 gg/L (MW-13) Existing groundwater monitoring wells (MW-7, MW-10, MW 11, and MW 12) were sampled during this umvestigation Groundwater concentrations for TPH g and BTEX Q T%1807973008NAMOOCION rmPORT%SHOREP#1 Doce-FEu81873008NA15NA 2-5