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PROBLEM ASSESSMENT REPORT <br /> 1SO,South E3 Dorado Street Stockton Wq}ornse <br /> Vapor extraction wells were installed because previous site information indicated this <br /> is likely the most effective soil remedial action alternative A general discussion of <br /> vapor extraction is included in Appendix G. Important elements for effective vapor <br /> extraction include high hydrocarbon removal rates, relatively homogeneous soils, and <br /> a good radius-of-influence The borings and vapor extraction testing performed at the <br /> site confirmed these factors In addition, soil vapor extraction has been shown to <br /> have a remedial effect on volatile organics in groundwater <br /> Vapor extraction testis indicates VEW-1 and VEW-2 should be sufficient to remediate <br /> p g <br /> the former UST backfill and impacted native soil, respectively <br /> 5 2 Groundwater <br /> Like sods, groundwater remediation generally falls into ex-situ and in-situ alternatives. <br /> An option also considered is "no action" and/or monitoring only Ex-situ groundwater <br /> I remediation alternatives involve the design, installation, operation, and maintenance <br /> of a suitable groundwater extraction and water treatment system In-situ options <br /> include passive approaches to groundwater remediation or injection of various media <br /> into the subsurface to enhance volatilization and/or biodegradation <br /> The following groundwater remediation alternatives are discussed in Appendix G <br /> • No action <br /> • Ex-situ (groundwater extraction) remediation options <br /> Air stripping <br /> - Bioremediation <br /> Ultraviolet degradation <br /> Adsorption <br /> - Separation/filtration <br /> I - Direct discharge to sanitary or storm sewer <br /> • In-situ remediation options <br /> - Bioremediation <br /> Air sparging <br /> Physical containment <br /> I Because of relatives low hydrocarbon concentrations �n the roundwater, and <br /> Y Y g , <br /> potential offsite sources, no active groundwater remediation is recommended at this <br /> time Soil vapor extraction, if implemented, should have a remedial effect on volatile <br /> organics in the groundwater, as well as remove the presumed on site hydrocarbon <br /> source Continued groundwater monitoring should indicate whether active <br /> groundwater remediation is necessary <br /> 91 044A PAR 11 <br />