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Ripona Market October 28,2004 <br /> Corrective Action Plan <br />' table Cost would include initial equipment leasing and ongoing operations, <br /> maintamance, and waste disposal costs <br />' 5.0 CONCLUSIONS AND RECOMMENDATIONS <br />' The SWRCB low risk closure criteria appears to fit the Ripona Market site due to <br /> the low concentrations of MTBE in the source area, the limited extent of the <br />' plume and the absence of nearby potential receptors in the down gradient <br /> direction Based on the preliminary modeling, closure by Monitored Natural <br /> Attenuation appears to be viable option Groundwater monitoring has not detected <br />' the plume migration beyond a distance of 35 feet from the source area <br /> Dual phase air / water extraction would probably be an effective method in <br />' reducing the contamination in the source area However, the high cost of <br /> preliminary testing, continuing operation, maintenance, and contamination <br /> treatment and disposal costs do not make dual phase extraction a viable clean up <br />' option <br /> The use of Oxygen Release Compound (ORC) to create an aerobic environment <br /> I which will accelerate the biodegradation of the contamination in the source area <br /> will provide a cost effective passive remediation of the release The installation of <br /> the material in a grid in the source area will have minimal impact on the facility <br /> operation and does not have the continuing operation, maintenance, and <br /> contamination treatment and disposal costs associated with active clean up <br /> systems A work plan for the installation of ORC slurry in shallow soil borings in <br />' the source area should be submitted for review and approval by the San Joaquin <br /> County Environmental Health Department and the UST Cleanup Fund for <br /> approval <br /> IThe existing monitoring wells should be sampled for contamination, natural <br /> attenuation parameters, total and hexavalent chrome, and arsenic prior to <br /> installing the system Quarterly groundwater monitoring of the monitoring wells <br /> for contamination concentrations and dissolved oxygen content should continue <br /> Natural attenuation parameters should be collected annually as pert of the <br /> I groundwater monitoring If the contamination reduction is stable and continuing <br /> after three years of monitoring, the site should be proposed for closure <br /> I <br /> I <br /> 11 <br />