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. vapor monitoring and on-site analyses to evaluate the limits of excavation ' When on-site evaluations indicate that all soil above regulatory limits has been removed, confirmation samples should be taken and analyzed in a State of California certified laboratory If laboratory analyses confirm the field observations, the excavations should be backfilled The full extent of hydrocarbon impacts to groundwater has yet to be evaluated The observation of hydrocarbons in the groundwater samples taken directly from the borings during the recent sampling indicate that petroleum hydrocarbons are present However, this may be the result of groundwater coming in contact with hyrocarbon impacted soils during the boring operations As a result, prior to instituting groundwater remediation, further investigations should be conducted This should I include installation of three new monitoring wells which are completed in the true water bearing zone, but which are double cased down through the zones of already observed hydrocarbon impacts to the soil In this way, the in-situ condition of the groundwater can be assessed more accurately It is possible that with an upward vertical gradient, the groundwater below 30 feet may not be impacted, thus limiting or even eliminating the need for groundwater remediation 2 3 Alternatives for Soil RemediationlDisposal lieIn selecting an approach to remediating and/or disposing petroleum impacted soil, it is important to evaluate more than first cost In addition ' to cost, MARK recommends that a client consider ■ Effectiveness in achieving cleanup goals, s Eliminating or limiting long term liability for materials disposed off-site, ■ Regulatory agency and community acceptance, and n Time to achieve cleanup goals Soil analysis data provided by Mark Zygutis of Norcal Waste Systems indicated that currently stockpile soil contains up to 1,000 mg/kg of gasoline and up to 3,000 mg/kg of diesel constituents Soil with hydrocarbons in this range (above 100 mg/kg) typically require disposal at a Class I landfill In addition, soil with hydrocarbon concentrations above ' 1,000 mg/kg must be treated as a hazardous waste, requiring rigorous analysis and manifest preparation prior to transportation ' To provide a comparison of remedial approaches, we have evaluated three alternatives ' ■ Transportation and off-site treatment and disposal, ■ On-site bioremediation treatment and off-site disposal, 2-3 COMPANY CONFIDENTIAL TRADE SECRET AND PROPRIETARY INFORMATION OF TFiE MARK GROUP "Ira