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02 September 2003 1Y AGE-NC Project No. 98-0468 Page 10 of 11 not detected the grab ground water samples. The laboratory report (CTEL Lab I.D. 214-0307068) I ' Quality Assurance and Quality Control (QA/QC)report and chain-of-custody form are included in' Appendix C. Analytical results of the CPT grab ground water sample are summarized in Table 2. 6.0. SUMMARY/CONCLUSIONS ' The following conclusions were drawn from the results of this investigation: • Silt and clay.were generally encountered to a depth of 60 feet bsg with significant.sand ' encountered at approximately 60 feet, 70 feet to 90 feet bsg. Ground water was encountered at 10 feet bsg in the CPT soundings. ' Pore pressure dissipation tests suggest that hydraulic conductivities were typical for.sand ' where sample were generally collected. ' TPH-g, BTEX, and fuel additives have not impacted ground water a depth of 80 feet bsg in the area of monitoring wells MW-4/6. Impacted ground water was not encountered in the down-gradient samples at 55 feet'or 80 feet bsg"at monitoring wells MW-9/10. ' The limits of the dissolved plume has been determine on the site. • The low mass of dissolved MTBE (Appendix D; ,0.65 kilograms or 1.4 lbs of MTBE), the i ' lack of whole petroleum hydrocarbons in monitoring well network(natural attenuation)and the lack of receptors (golf course) should justifies site closure. • The low concentrations, relatively low mass and vertical distribution of MTBE would not allow for cost effective MTBE-remediation,based on a reasonable time line for clean up.The excessive remediation cost for ground water extraction or in-situ chemical oxidation are not justified. '. 7.0. RECOMMENDATIONS Based on the results of this and previous investigations, AGE recommends: ' Site closure based on low concentration of one fuel additive: • Decommissioning of groundwater monitoring wells in accordance with the EHD well code. 1 Advanced GeoEnvironmental,Inc.