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Treadwell&Rollo <br /> • <br /> hazard-based concentrations were determined in the Risk Assessment, and can be used to set <br /> alternative target concentrations. For example,the target cancer risk-based benzene <br /> concentration is groundwater for landscape maintenance workers at Area 15 is 294 ug/1, as <br /> opposed to the benzene MCL of 1 ug/1. Use of alternative cleanup values will be determined by <br /> the SJCEHD. <br /> 4.3.1 Monitoring Only <br /> Monitoring Only is potentially applicable for sites where groundwater contamination has been <br /> found at relatively low levels, and for sites with treatment operations that are near completion. It <br /> does not require a specific technology, and is generally a low-cost alternative. This option would <br /> require defining acceptable closure levels that may exceed MCLs, particularly for sites with <br /> active groundwater treatment systems. This alternative has been retained for consideration. <br /> • 4.3.2 Collection <br /> Groundwater collection and treatment is a viable remedial alternative at sites with known <br /> contamination. The technology of extracting groundwater from unconsolidated sediments is well <br /> defined, as are the various treatment alternatives. To a lesser extent, this response action has <br /> been used at Areas 15, 16, and 21, when groundwater in UST excavations was removed and <br /> disposed of off site. Capital and operations and maintenance costs for groundwater collection <br /> are medium, relative to other alternatives. The collection alternative has been retained for <br /> consideration. <br /> 4.3.3 Treatment <br /> Two variations of physical treatment and two of chemical treatment were screened. Physical <br /> treatment options include air sparging and vacuum extraction, and chemical treatment includes <br /> ozone sparging and hydrogen peroxide injection. Air sparging may be applicable for <br /> remediation of light-end petroleum hydrocarbons and chlorinated compounds by enhancing <br /> • bioremediation. Vacuum extraction has limited application for groundwater remediation,but <br /> 33 <br /> 25970318.PGS 15 November 2000 <br />