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'# Ms. Lori Duncan February 22, 2000 Page 4 of 5 Analytical results of soil samples are summarized in Table 2. Laboratory reports and chain of custody documentation are included in Attachment B. 5.0 SUMMARY AND CONCLUSIONS 5.1 Summary • Soil beneath the site consists primarily of silts and sandy clay to approximately 12-15 feet bgs, poorly graded sand from approximately 12-15 to 26-28 feet bgs, and gravel and clay from 26-28 feet to 30 feet bgs, which was the practical depth limitations of the Geoprobe 5400 drilling rig. Groundwater was not encountered during the investigation. • Petroleum hydrocarbon constituents, primarily TPHg and TOG, were detected at moderate levels in boring SB3. TPHg ranged from 3,000 ppm at 10 feet bgs to 92 ppm at 25 feet bgs. • No contaminants were detected at appreciable levels from borings SB 1, SB2, SB4, or SB5. • No gasoline oxygenate additives were found at or above the respective detection limits. 5.2 Conclusions • No significant impact to the soil in the vicinity of the former waste oil tank appears to exist. • The lateral extent of soil contamination associated with the former gasoline USTs has been defined. • The vertical extent of residual soil contamination in the vicinity of the former gasoline USTs has not been completely defined due to refusal of the drilling rods. However, the documented soil contamination attenuated rapidly with depth, approaching non-detect levels at a depth of 25 feet bgs(Figure 4). • Groundwater beneath the site does not appear to be threatened by shallow soil contamination associated with the former USTs, based on the rapid attenuation with depth and the 100-foot "buffer" of uncontaminated soil between the groundwater and the estimated depth of contamination. 6.0 RECOMMENDATIONS Based upon the rapid attenuation of soil contamination with depth and the apparent lack of threat to groundwater beneath the site, Ground Zero recommends the site be considered for case closure, with no further action, as a low-risk, soil contamination only site. 7.0 CERTIFICATION Signature of this report certifies that Ground Zero's professional services have been performed, our findings obtained, and our conclusions prepared in accordance with customary principles and practices in the fields of environmental science and engineering. No hazardous wastes were generated as a result of these investigations. No waste from this investigation will remain on site. The analytical laboratory will ultimately dispose of collected soil samples. This investigation was performed under the direct supervision of John Lane, who has reviewed and data\groundze\franks tire\subsurfsum.doc