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• Physical containment to provide a physical barrier between the impacted material and <br /> the environment <br /> Monitoring is often is included as a measure to verify that environmental impacts are <br /> controlled to the extent required <br /> In-Situ Treatment <br /> The purpose of in-situ treatment is to reduce the mass, toxicity, or mobility of the impacted <br /> soils without physically removing the affected medium Where technically feasible, in-situ treatment <br /> is generally preferred because <br /> • it can control short-term environmental impacts more readily than ex-situ treatment, <br /> • it is generally safer to remedial workers, site workers, and the general public, and <br /> • <br /> it tends to be less costly than ex-situ treatment <br /> Ex-Situ Treatment/Disposal <br /> The purpose of ex-situ treatment is to reduce the mass, toxicity, or mobility of contaminants <br /> First, the affected medium is physically isolated from unimpacted material Soil is typically <br /> excavated, and can then be treated on-site or off-site, and/or permanently removed from the site for <br /> disposal (such as to a landfill) When cost-effective, ex-situ treatment is generally preferred over <br /> in-situ treatment in situations where in-situ technologies are not applicable or very stringent cleanup <br /> levels have been selected This is partly due to the inherent uncertainty involved in verifying cleanup <br /> achieved by in-situ methods <br /> 5 2 SCREENING OF TECHNOLOGY TYPES AND PROCESS OPTIONS <br /> One or several technology types and process options may apply to each general response <br /> action Several technologies available for removal of petroleum hydrocarbons from soil are <br /> discussed below The technologies are compared on the basis of effectiveness, cost, and the <br /> difficulty in obtaining regulatory agency approval (administrative feasibility) for the approach This <br /> qualitative comparison identifies potentially promising technologies for use alone or in combination <br /> to develop remedial alternatives that address all impacts Technologies with poor to fair effectiveness <br /> in relation to moderate or high costs are not considered further <br /> sAC127 10 9 <br /> DAMES &MOORE <br />