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' could be stockpiled on plastic sheeting during the treatment period. However, space at this lot is sufficient to treat less than 300 cubic yards at a time (50 feet x 50 feet x 3 feet). Several treatment periods would therefore be required, and the excavation would remain open for several months. Though treatment with a portable thermal destruction unit could be performed in a week or less, these units are typically quite large, and require more space than is available on site. This method also requires space for temporary storage of treated and untreated soil. ' The space problem could be avoided by disposing of the excavated soil at a licensed facility. Off-site disposal would require transport of some of the soil to a Class II landfill, because ' contamination levels exceed the limits of Class III facilities. Landfills also require characterization of the contaminants, with one sample per 25 cubic yards and analysis for metals in addition to TPH and BTE&X. Disposal costs generally range between $20 per ' yard at Class III facilities to $90 per yard at Class II facilities. All of these methods require excavation of the contaminated soil, which is generally the ' fastest and most effective method for soil remediation. However, most of the contaminated soil underlies the Art & Artists building, and contamination extends to depths inaccessible to excavation equipment. Therefore, excavation is not practical at this site. In addition, on- site space limitations, aeration limits set by the San Joaquin Valley Air Quality Management District, sampling and analysis requirements set by landfills, and the cost of replacing the disposed soil make ex-situ treatment impractical. 6.1.2 In-Situ Treatment Alternatives ' 6.1.2.1 Bioremediation Acceptance of this treatment technology by the regulatory community has grown somewhat in recent years, as success has been achieved at several sites in California and elsewhere. Geological Audit is currently conducting three in-situ bioremediation projects in Southern California and is preparing to initiate in-situ bioremediation at another site in Lodi. 6.1.2.1.1 Principles ' In this method, hydrocarbon-consuming bacteria are grown in a liquid medium, which is then poured into inoculation wells that are screened through the zone of contamination. Once in the contaminant plume, the bacteria degrade the hydrocarbons and spread laterally ' and vertically by migrating and reproducing, creating an advancing remediation front. ' Hydrocarbon-degrading bacteria are able to metabolize hydrocarbons and assimilate the resulting organic chemicals into biomass for reproduction and growth. The light-end hydrocarbons are consumed first, followed by heavier compounds. GeobD"l Audit S,wic .1 A A&A PAM-28.941.47 26