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, C SM,TH • CONCLUSIONS Field observations and analytical data indicate that vertical migration of hydrocarbons through the soil has exceeded 15 feet below surface grade and that lateral migration appears to be extensive in the northern direction Analytical results of excavation confirmation samples indicate that the majority of impacted soil has been removed from the southern, southwestern, and eastern portions of the excavation Field observations indicate contarrunation along eastern portion of the northern sidewall (in the vicinity of sample GP-NW-11 0') appeared to be limited to only the saturated zone The northwest portion of the excavation was obviously discolored and impacted above and below the water table, however due to the close proximity of an adjacent structure and underground utilities, in addition to the instability of the excavation sidewalls, the excavation was limited in the northern and western directions Subsequent to pumping approximately 10,000 gallons of water from the open excavation the excavation was backfilled with clean, imported, self compacting material The excavated soil stockpile remains on-site covered and underlain with plastic sheeting Laboratory analyses of water samples collected from site monitoring wells indicate the lateral extent of the dissolved contaminant plume associated with the former underground fuel storage tanks has been essentially defined, except in the vicinity of well MW4, north of the former tank It is unclear whether contamination at MW4 can be attributed to the former tank or from a potential off-site contributing source RECOMMENDATIONS Based on field observations and analytical data from site excavation activities discussed herein, Smith Environmental proposes an additional phase of the subsurface investigation be performed to further delineate petroleum hydrocarbon contamination in the areas north and west of the excavation boundaries The investigation should include an adequate number of soil borings to determine the lateral and vertical extent of soil impaction Subsequent to the additional investigation site remedial alternatives should be re-evaluated based upon the newly acquired data Based on the analytical results of samples collected from the stockpiled soil, Smith Environmental proposes remediation of the soil by on-site aeration and/or as an alternative, impacted soil should be disposed of at an appropriate landfill 1500WSXR-0995 DOC Jr