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Mr. David Lieb 0 - 2 - • 19 July 2004 <br /> Marley Cooling Tower Facility, Stockton <br /> point indicate creation of a chemical reducing environment effectively reducing hexavalent chromium. <br /> As expected, there was a notable increasing trend in localized concentrations of calcium, sulfate, Total <br /> Dissolved Solids (TDS), arsenic, iron, and manganese in the test wells due to Phase I injection. <br /> However, over time, these concentrations have shown a declining trend or stabilized in most cases. In <br /> accordance with the WDRs, groundwater monitoring will be continued to evaluate the effects of calcium <br /> polysulfide and ethanol injection on aquifer chemistry. <br /> Phase II: The purpose of this phase of the study is to demonstrate the effectiveness of the direct <br /> multiple-injection approach and the persistence of reducing conditions in the shallow groundwater <br /> plume zone. The proposed pilot study consists of injecting calcium polysulfide (up to 5,000 gallons of <br /> three percent calcium polysulfide solution per injection point), and ethanol (up to 50 gallons per <br /> injection point) at up to 75 locations in shallow groundwater (60-80 feet below ground surface). The <br /> revised locations for the Phase II injection points and test wells and supporting information were <br /> provided in an email from Mr. Richard Thomasser (MWH Americas)received on 13 July 2004 (see <br /> attached Figure 1). Five test wells (TW-7 through TW-11) will be installed and sampled for baseline <br /> concentrations in accordance with the WDRs prior to calcium polysulfide and ethanol injection <br /> locations. Sampling and reporting will be conducted in accordance with the Monitoring and Reporting <br /> Program(MRP) included as part of the WDRs. <br /> Our comments on this report are provided below: <br /> 1. To evaluate the results of Phase II injection immediately down-gradient of the former retort pit <br /> area and to monitor potential effects in the groundwater flow, we request sampling of monitoring <br /> wells MW-6, MW-206, and MW-107 for the same parameters and frequencies similar to the <br /> other sampling locations identified in the MRP. <br /> 2. You may proceed with installation of the test wells and injection of calcium polysulfide and <br /> ethanol provided that the installation and injection are conducted in accordance with the San <br /> Joaquin County requirements and appropriate permits are obtained from the County. <br /> 3. Prior to start of fieldwork,please provide a clarification regarding the revised spacing for <br /> Phase II injection points. The MWH Americas email received on 13 July 2004 states that the <br /> spacing for Phase II injection points have been set at 20 ft based on the results of the Phase I test <br /> which demonstrated that a single point of injection can achieve approximately a 22-foot radius of <br /> treatment. However, Figure 1 appears to indicate a spacing assuming a 10-11 radius of treatment. <br /> 4. At least five days prior to start of fieldwork, please notify our office so that we may make field <br /> arrangements for a site visit. <br /> This letter serves as Regional Board concurrence for implementation of the Phase II pilot study <br /> contingent upon your acceptance of our comments. We look forward to reviewing the Phase II pilot <br /> study results, evaluation and recommendations. <br />