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CJeofo icaf?echnirs inc. L�.I �,�j Page 3 Soil Investigation Report Arctic Ice(D St.) Project No.691.2 December 10, 1998 a.. 3.0 RESULTS & CONCLUSIONS Results Subsurface soils are dominated by sand with a high content of fine-grained silt and clay matrix. Thus the permeability of these soils is low and the movement of water and other fluids are reduced as compared to well-sorted sandy soils. At a depth of approximately 23 and 40 feet, a well-sorted sand unit was encountered Soil test results show that no diesel compounds were detected in the soil samples tested. The laboratory analytical data reports are attached in Appendix A. i"w During tank removal, sample analysis showed that diesel was present in the soil under the north end of the tank at a depth of approximately 10 feet at a concentration of 3,300 mg/kg (ppm). However, the sample tested at I1 feet (SB-1 at 9.5-11 ft) did not contain diesel. 'r There was field evidence of contamination: In the depth interval of 9 to 15 feet, horizons of gray soil was encountered with a distinct hydrocarbon odor. • Below the dept of 15 feet, the soil staining decreased significantly and the hydrocarbon odor disappeared. • By 20 feet bgs, no evidence of diesel was observed. In borehole SB-2 & 3, no evidence of diesel contamination was observed. Conclusions The test results and field observations suggest the following conclusions: • The former UST did release some diesel fuel during the period of operation. • The volume of fuel was small and did not migrate to a depth greater then 15 to 20 feet. • The lateral spreading of the diesel was less then 15 feet from the tank. • The diesel has undergone extensive biodegradation and the only diesel is at the 8 to 10 foot depth interval. • The residual diesel in these soils does not pose a threat to public health or the `' environment. • This site should be closed. t. 4.0 LIMITATIONS ,+ This report was prepared in accordance with the accepted standards and practices of the field of environmental geology, groundwater hydrology and good business practices. It should be recognized that definition and evaluation of environmental conditions is a difficult and inexact science. Judgments leading to conclusions and recommendations are generally made '-" with an incomplete knowledge of the site-specific conditions present. The tasks proposed and completed during this project were reviewed and approved by the �. local regulatory agency for complianc6 with the law. No warranty, expressed or implied, is made. V V V