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I ' 19 December 2005 AGE-NC Project No 99-0645 ' Page 2 of 8 ' The closest surface water feature to the site is the Calaveras River(Diverting Canal)which is located approximately 10,500 feet southwest of the site Water from the Calaveras River drains into the San Joaquin River Deep Water Channel and is primarily used for commercial, agricultural, and ' recreational boating Ground water at the site is currently encountered at a depth of approximately 90 feet below surface grade(bsg),flow direction typically fluctuates from the northeast to southwest Layers of sandy material occur at depths of 15 feet to 30 feet bsg and 75 feet to 80 feet or 80 feet to ' 85 feet bsg Ground water over the majority of the site occurs in a stratigraphic layer generally consisting of clayey silt, sandy silt, and silt Ground water elevation data from November 2001 to July 2005 is presented in Table 1 2 2 UST REMOVAL AND OVER-EXCAVATION On 07 May 1999,three underground storage tanks(USTs),associated piping,and a dispenser island were removed from the site by Semco of Modesto Six soil samples were collected beneath the ' USTs, two soil samples were collected beneath the dispenser area, and four laboratory composlted soil samples were collected from the excavated soil ' Approximately 150 cubic yards of soil were excavated during the removal of the USTs, subsequent to the soil sampling activities, the soil was placed back into the excavation ' Laboratory analysis of the soil samples detected total petroleum hydrocarbons quantified as gasoline (TPH-g) at concentrations as high as 17,000 milligrams per kilogram(mg/kg)beneath the northern UST(Tank#1),benzene,toluene,ethylbenzene,and xylenes(BTEX)were detected at concentrations ' as high as 3,000 mg/kg Methyl tertiary-butyl ether(MTBE)and/or tertiary-butyl alcohol(TBA)were detected In soil samples collected from the former UST excavation and stockpiled soil at the site at concentrations as high as 160 mg/kg MTBE The presence of high concentrations of MTBE in the ' soil samples indicated that an unassessed mass of MTBE remained at the site Analytical results of soil samples are summarized in Table 2 23 INTERIM SOIL REMEDIATION ' On 21 March 2000,AGE personnel excavated 195 metric tons of impacted soil from the former tank pit utilizing an excavator outfitted with a 2 45 cubic yard bucket Following the removal of the ' original soil backfill material, the excavation was enlarged and deepened to an approximate depth of 22 feet bsg, and soil samples were collected from the floor(F- 1)and walls (WW, EW,NW, and SW)of the excavation,as well as the soil stockpiles, for laboratory analysis On 22 March 2000,the impacted soil was transported from the site and disposed of at Forward Landfill • Advanced GcoEnvironmental,Inc