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9 November 1992 (GeoAudit CV 42E1-1. 8) Page 6 of 6 6. 3 Lateral and Vertical Extent of Contamination The data obtained during this investigation indicate that the area north of the UST's and the center dispenser island are contaminated. The boundaries of the zone of contaminated soil have not been defined, but the spacing of borings B1, B2 , and B4 indicates that the contaminated area is in excess of 30 feet x 60 feet. No contamination was detected in B3 , south of the tank cavity, in the southwestern corner of the site. The vertical extent of contamination is between 55 and 60 feet in the area between the dispensers and the store. The vertical extent was not determined in boring B2 and B4 , but exceeds 40 feet. The minimum volume of contaminated soil is therefore in excess of 2650 cubic yards. 7.0 CONCLUSIONS AND RECOMMENDATIONS Based on the information obtained to date, it is apparant that further investigation of contamination at this site is necessary. Due to the depth and lateral extent of contaminated soil, we believe that excavation and removal of the contaminated soil is not a viable alternative. Furthermore, contamination is undoubtedly present beneath the dispensers, and may extend beneath the building ' as well, making excavation unfeasible. It is evident that additional soil borings will be necessary to delineate the lateral extent of soil contamination. moreover, we believe that additional vapor extraction wells will be necessary because of the extent of contamination. Therefore, we recommend a ' second phase of drilling. As many as four borings may be necessary. Borings should be located north, east, and south of the present borings, and at least two of these should be completed as vapor wells for future monitoring and/or extraction. It may be advisable to slant drill a fourth boring beneath the store, so as to determine whether contamination extends that far to the west. I The present data regarding groundwater are equivocal. Soil data suggest that contamination does not extend to groundwater, but the single water sample suggests that contamination may be present. It is therefore advisable to complete one of the borings as a groundwater monitoring well, so that cross--contamination can be avoided and a reliable water sample can be obtained.