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6.0 CONCLUSIONS AND RECOIVT,IMENDATIONS Field observations and laboratory data indicate that an unauthorized release of unleaded gasoline, probably from tank #2, has contaminated the soil in the main UST cavity to a depth in excess of 15 feet. Elevated concentrations of TPH-g remain in the central portion of the excavation. We recommend that further excavation be performed to remove this contaminated soil. Field observation did not reveal any evidence of a release from the waste -oil tank. Laboratory analysis, however, indicates that soil excavated from this tank cavity contains heavy metals, gasoline, diesel, motor oil, and minor halogenated hydrocarbons. Only xylene was detected beneath the tank, suggesting that very little contamination remains in the waste -oil tank excavation. Hydrocarbon concentrations in the stockpiles presently preclude replacement of this soil in the excavations. Several methods are available for remediation of this soil on site Alternatively, it could be transported to an appropriate landfill facility for disposal. Due to the elevated total threshold concentration (TTLC) of lead in the waste -oil stockpile sample, this sample should be ` re -analyzed using the California wet -lead (STLC) procedure to determine lead leachability potential before removal or remediation of this stockpile. r. 7.0 RFMA.RICSAND SIGAT�1NRF. L The recommendations contained in this report represent a professional opinion, and are based in part on information supplied by the client. The opinions are based on currently available infomation and are arrived at in accordance with currently accepted hydrogeologic and engineering practices at this time and location. Other than this, no warranty is implied cr intended. L 6. b. Respectfully Submitted, Upgradieut Environmental Consultants e Victor B. Cherven Registered Geologist #3475 2