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SJCDEH (continued) Rationale for Excavation Background The primary historic source of petroleum fuel contaminants appears to be the Regular Unleaded underground storage tank near to and slightly east of a packing warehouse building on site. The area to be excavated is open and access is at its best now. To date no data has been discovered that supports the possibility of additional sources. On the basis of the previous grab samples, the interpreted area of potentially contaminated soil is projected at 1 to less than 10 Tons. This cleanup would be to primarily address contaminant source removal. The extent of excavation is interpreted from the data, but the data itself is limited to the sample locations. Conclusions and Recommendations Historic excavation during fueling system repairs revealed discolored soil that contains at least some contaminants in the soil beneath and near the Regular Unleaded Dispenser and Fill Bucket. Previous experience with soil excavations of similar types of contaminant problems indicates that limited soil removal in the immediate area may remove the contaminants in their entirety. LO-nka M'611 ,,a The estimate of subsurface soilnextent is variable and relies primarily upon sampling location and the quantitative chemical analysis data collected. The estimatedllg) 'enY" i interpreted using assumptions of extent based upon visual observations and the attached laboratory data and cannot be guaranteed given the actual limited data available. The currently available chemical analysis data from soil samples in the excavated area, and surface observations of discolored soil removed indicate that some additional contaminated soil is still present. It is Wright's opinion that since, (1) our equipment is still present on site, (2) the contamination may not be present in great quantity, (3) the soil is also located in a readily accessible area, that (4) it is prudent to remove this contaminated soil as a part of the source removal at this time. Wright feels that limited hand excavation of the soils 2' to 3' beneath the Regular Unleaded Dispenser and Fill Bucket resting areas, and removal of 2' to 3' of soil from all four (4) sidewalls surrounding these two (2) defined areas would remove soil contaminated with detectable levels of MTBE and tert-Butanol. Additional soil samples would be taken at the limits of these hand excavations and analytically tested at a state certified laboratory for gasoline by EPA Method 5030/LUFT and Fuel Oxygenates by EPA Method 8260 to confirm the successful removal of contaminants. Page 2