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I . 31 January 2000 AGE-NC Project No 97-0290 Page 2 of 10 addressed an area approximately 8 feet by 12 feet and extended to a depth of 26 feet bsg One sample was collected from the second excavation Field observations indicated that petroleum-hydrocarbons were present In soil samples collected from the excavation Laboratory analyses of the soil samples were not available to AGE • In November 1989, one soil boring was advanced to a depth of 40 feet bsg Hydrocarbon odor was noted in the boring, however analysis of soil samples was not performed Drilling was aborted and the boring was backfilled with grout • Between October 1998 and April 1999, eighteen soil borings were advanced at the site Organic vapor was detected in 12 of the 18 borings advanced at the site Organic vapor was not detected in soil samples collected from bonngs MW3,MWS,MW6, MW7, MW8 or B5 Eight of these borings were completed as ground water monitoring wells, one boring was completed as a vapor extraction well and two bonngs were completed as air sparging wells • TPH-g was detected at concentrations as high as 11,000 parts per million (ppm, reported as milligrams per kilogram) in 26 of the 47 soil samples analyzed Benzene was detected in 15 of the 47 samples analyzed Petroleum hydrocarbons were not detected in soil samples analyzed from borings MW1, MW3, MW5, MW8 and B5 Oxygenates were not detected in . the 13 samples analyzed by EPA Method 8260 • The highest concentrations of petroleum hydrocarbons In soil were detected near the southeast portion of the site at depth intervals of 15 to 25 feet bsg and 35 to 50 feet bsg in borings P3,MW2 and SW 1 Lower concentrations of hydrocarbons were detected in borings B4, MW4 and B6 at depths of 35 to 60 feet bsg, corresponding to historical ground water levels Impacted soil at depth appears to be concentrated in a silt and clay interval between approximately 40 to 47 feet bsg • The permeability of samples B4-25, MW1-30 and MW3-55 was measured at 2 2 x 10', 3 5 X 103 and 3 3 x 107, respectively Porosity ranged from 32 26 percent to 41 16 percent Specific gravity ranged from 2 68 to 2 71 Percent organics ranged from 0 6 to 1 5 Sample B4-25 was a fine sandy salt, sample MW1-30 was a poorly-graded, medium-grained sand, sample MW3-55 was a silty fine sand • A hard salt/clay layer appears to underlay the site at a depth of approximately 60 feet bsg This layer may act as a horizontal barrier to deeper migration of contaminants at the site Thickness of the silt/clay unit has not been determined • Historical depth to ground water at the site has ranged from approximately 35 feet bsg in 1971 to 55 feet bsg in 1993 and 1996, based upon ground water maps prepared by the San Joaquin County Flood Control and Water Conservation District between 1971 and 1996 Ground water currently occurs at a depth of approximately 43 feet bsg • Current ground water flow at the site is toward the south Historical flow may have vaned Advanced GeoEnvironmental,Inc