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_ r ' f • • UNDERGROUND STORAGE TANK.REMOVAL 4 The OST system was removed in 1988:Ground water was encountered in the'tank excavation during "removal. Subsequently,one soil and one grab water sample were collected from the tank excavation in,August 198$. - Both sampleswere analyzed for total petroleum hydrocarbons,quantified as gasoline (TPH-g), Stoddard;solvents.,paint thinner,diesel;kerosene,•motor oil(TPH-ss; TPH-thinner, TPH-d,TPH-k and TPH-mo) and.-volatile 'aromatics (benzene, toluene and total xylene). TPH-g, toluene' and xylenes were detected in the soil sample at concentrations of 560 milligrams per kilogram(mg/kg), 21-mg/kg•and 79 mg/kg, respectively. TPH-g, benzene, toluene and xylenes were detected in the ' water sample at concentrations of 117,000 micrograms.per liter(gg/l), 10,100 µg/1, 11,300 gg/1•and, 9,330 REA respectively. EXCAVATION OF UNDERGROUND STORAGE TANK AREA I. The former UST area was excavated on 24 August .1995 to remove impacted soil. Excavation procedures were supervised by a representative of AGE. Soil was excavated,to a depth of 12 feet I below surface grade(bsg). Approximately 100 cubic yards of impacted sail were removed from.the former UST area. lie TPH-g was'•detected in the soil sarnpild collected at a'depth of 8 feet bsg from the sidewall of the excavation at concentrations as high as 5,800 mg/kg and benzene was detected in the samples at.a maximum concentrations of54 mg/kg. Petroleum hydrocarbons were not detected in soil samples ' collected from the floor of the excavation at a depth of 12 feet bsg.TPH-g was.detected in stockpile soil sample-.at a concentration of 440 mg/kg.and volatile aromatic compounds;benzine, toluene, , ethylbenzehe and total xylenes(BTEX)were detected at concentrations of 1.1 mg/kg; 12 mg/kg, 8.1 Img/kg and 40 mg/kg, respectively.. The'excavated soil was stockpiled'adjacent to the excavation on plastic. sheeting. On 09 October 1996,approximately 100.cubic yards of stockpiled soil were transported to Forward Inco p orated'' a Class•It •landfill located in Manteca,,California: Soil was loaded into transport vehicles by Stokley Construction'of Tracy, California and hauled to .Forward by Bob Evans Trucking of Manteca, California.Tlie disposal of the soils was Summarized.in,the Quarterly geport' prepared by.AGE"'dated 21 November:1996. SITE ASSESSMENT ACTIVITIES I' '..-'Six soil probe borings were advanced at the site on 20 December 1996. Soil and water samples were collected at,discrete depth intervals from the majority.of,th,e probe borings. Figure 2 depicts the Ilocations of the probe borings: • TPH-g was detected in three of the soil samples analyzed at concentrations as high as 2,800 mg/kg I (P3-6).BTEX compounds 'were detected'-in the same three sarriples at concentrations as.high as Advanced GeoEnvironmental,Inc.