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' - 04 August 2000 - _ - �, AGE-NC Pioject No 98-0521 Page_2 of 11 _ The UST I emovals were witnessed by a reps esentative of the PHS-EHD Ti ackmg records for waste '_ -- removed fiom the UST should have been supplied to the PHS-EHD in the UST removal report -`= History of the UST use, tank tests, product Inventory and repairs are not known to AGE y After being removed, the tanks were visually inspected and appeared to be intact, with no holes or extensive tori osion noted Pea gi avel was used to backfill the base portion of the UST excavation ' -- equal the volume of the removed USTs Plastic sheeting was then placed into the excavation and the stockpiled soil was replaced and compacted back into the UST excavation The UST excavation was _ then capped with i oad base and leveled _ Following i emoval of the tanks, an excavator was used to collect six soil samples fiom 2 feet below - the ends of the former USTs Giound water was encountered in the bottom of the excavation In ' - accoi dance with PHS-EHD requii ements,three separate ground water samples were also collected In addition, the PHS-EHD requested that ten soil samples be collected fi om two soil stockpiles ' s TPH-g, BTEX, fuel additives (MTBE/ET-BE)and lead were detected in each of the soil and water samples analyzed ' ! Total petioleum hydrocaibons-as gasoline (TPH-g) was detected in the UST floor soil samples at concentiations up to 350 milligram pef kilogram (mg/kg) Purgeable aromatic hydrocarbons (benzene;toluene,ethylbenzene and xylenes,BTE&X)were detected at concentrations up to 8 mg/kg ' (benzene) MTBE was also detected at concentrations up to 13 mg/kg in the forinei UST excavation - _ - Total lead was detected-in the same samples at concentrations as high as 8 02 mg/kg ' Stockpile soil samples contained TPH-g at concenti ations up to 19 mg/kg while BTE&X compounds _ Wei e detected at concentrations as high as 0 14 mg/kg MTBE was also detected in the stockpiled soil at concenti ations up to 0 08 mg/kg Total lead was detected in the same samples at concentrations up to 8 46 mg/kg TPH-g was detected m the UST `gi ab'water samples at concenti ations up to 950 milligram per liter r (mg/1) while BTE&X cdmpounds were detected at concentrations up to 62,900 microgram per liter (}tg/1) MTBE was also detecfed at concenti ations up to 32,650 µg/1 in the water samples Total lead ' was detected in the same samples at concenti ations up to 0 86 mg/l 2 3 REGIONAL GEOLOGIC/HYDROGEOLOGIC SETTING The site is located within the northern San Joaquin Valley which comprises part of the Great Valley ' geomorphic piovince of California The San Joaquin Valley is formed by the Great Valley geosynchne, which is a large, elongate, northwest-trending asymmetrical structural trough (basin) - _ _It is bordered by the Coast Ranges-to the west, the Klamath Mountains and Cascade Range to the - - - Advanced GeoEnvironmental,Inc - - 4 --i• r T--