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0 0 <br /> TENTATIVE WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2003-OOXX 2 <br /> LINCOLN CENTER ENVIRONMENTAL REMEDIATION TRUST <br /> SAN JOAQUIN COUNTY <br /> I <br /> 5. The Discharger has estimated that remediation of the site using SVE and groundwater extraction <br /> would require approximately 5 years of continued operation of the SVE system and more than 30 <br /> years of continued operation of the groundwater extraction system. <br /> 6. The Discharger estimates that implementation of in-situ contaminant reduction in the low <br /> permeability sediments underlying the source area would shorten the duration of the time <br /> required to remediate the site to less than 30 years. The discharger therefore proposes to perform <br /> pilot testing of an in-situ remediation technology described below. <br /> i <br /> Pilot Study Layout and Operation <br /> I <br /> 7. The objective of the pilot study is to: (a) evaluate the efficacy of in-situ PCE reduction in low <br /> permeability sediments by injection of nitrogen under pressure to pneumatically fracture the low <br /> permeability sediments, followed by the injection of granular zero-valent iron (GZVI)powder to <br /> create a reductive environment, (b) assess the secondary impacts of in-situ chemical reduction on <br /> groundwater quality, (c) identify design and operational factors that influence the successful <br /> performance of the in-situ chemical reduction approach, and (d) generate performance, design <br /> and cost data that can be used for design of a full-scale in-situ treatment system. <br /> 8. GZVI is a strong reducing agent. Electrons released during GZVI oxidation reduce the <br /> chlorinated solvent compound whereby the chlorine atoms are replaced by hydrogen. During the <br /> reductive dechlorination, PCE and subsequent daughter products act as electron acceptors. The <br /> reaction series from PCE to ethene is as follows: <br /> PCE >TCE> cis-dichloroethene >vinyl chloride > ethene <br /> The hydronuim ion (affecting pH) and chlorine is also produced in this reaction. <br /> 9. This technology has been successfully demonstrated to reduce concentrations of volatile organic <br /> chemicals at several sites including the Hunter's Point Naval Shipyard in San Francisco, <br /> California. <br /> 10. The Discharger proposes to install two injection points to be drilled using hollow-stem auger <br /> techniques to a target depth of approximately 50 feet below ground surface (bgs). One injection <br /> point will be installed 30 feet in the upgradient direction from existing monitoring well MW- <br /> 006A and the second injection point will be installed 60 feet in the upgradient direction from <br /> existing monitoring well MW-006A. Using these injection wells, compressed nitrogen, at a flow <br /> rate of 1,000 to 1,500 standard cubic feet per minute (SCFM) and under approximately 100 to <br /> 200 pounds per square inch(psi), will be injected into the low permeability sediments at 3-foot <br /> intervals between 30 and 50 feet bgs. A dense, fracture network is expected to be created around <br /> the injection points. Once fractures have been propagated, GZVI particles (dry or suspended in a <br /> water slung) will be injected through the injection nozzle. Compressed nitrogen will be used to <br /> carry GZVI slurry into the subsurface. A total of approximately 10,000 pounds of GZVI will be <br /> used. After injection is completed, the injection points will be abandoned by pressure grouting. <br />