ARCHIVED REPORTS XR0006787 - Laserfiche WebLink

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Determining the Extent of Contamination A number of soil and groundwater samples were acquired from the tank pits and pipeline trenches on April 11-12 , 1991 . Seven samples , designated A-G were obtained from the tank pits at depths of 7-9 feet below ground surface (bgs ) Samples H-K were acquired from product lines at depths of 3 feet bgs These locations are illustrated on the transparency overlaying the site map enclosed The only soil sample containing significant concentrations of Total Petroleum Hydrocarbons as Diesel (TPH-D) was that acquired from the waste oil tank pat (Sample G) This sample contained 220 parts per million (ppm) TPH-D The next highest concentration of TPH-D was 37 ppm in a product line sample taken near the west end of the northern pump island . In contrast , the groundwater sample acquired from Location L (i e the east central floor of the fuel tank pit , apparently beneath the unleaded gasoline tank) contained 60 , 000 parts per billion (ppb) TPH-D Soil Samples C-F, acquired from the west and east boundaries of the fuel tank pit excavation , contained 140-1 , 300 ppm Total Petroleum Hydrocarbons as Gasoline (TPH-G) In addition to containing 60 , 000 ppb TPH-D, the groundwater sample from Location L also contained 120 , 000 ppb TPH-G and 14 , 000 ppb benzene On March 17 , 1994 , EPM and Del Tech Geotechnical Support Services hand augered four soil borings along the sidewalk located 3ust north of the northern boundary of the site Each of these borings was advanced to a depth of 9 feet bgs Soil samples were obtained at 5 feet and from the soil -groundwater interface at 6 5 to 8 feet Grab water samples were also acquired The soil samples taken at 5 feet were either free of detectable concentrations of TPH-G, TPH-D, and BTEX (benzene, toluene , ethylbenzene , and total xylenes ) , or contained only low levels of these analytes In contrast , the soil samples from the soil -groundwater interface , particularly those from EP-2 and EP-4 , contained high lvels of TPH-G and BTEX ( levels of TPH-D were not significant ) Groundwater samples were also free of TPH-D, but contained moderate to 1 5 to 720 ppm TPH-G and 3 to 1 , 500 ppb benzene (as well as toluene, ethylbenzene, and xylenes) The lowest levels of contamination in water were at EP-3 ( 1 5 ppm TPH-G and 3 1 ppb benzene) The Installation and Sampling of Groundwater Monitoring Wells The three site groundwater monitoring wells were installed Page 9