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Page 2, 2360 Grant Line Road <br /> Two remedial methods were tested for feasibility for interim remediation at this site, oxygen <br /> injection and groundwater extraction. One sparge point and one extraction well were installed to <br /> conduct these tests. The oxygen injection test was conducted on June 21, 2004. SECOR <br /> injected 150 cubic feet of oxygen over a period of 30 minutes. Dissolved oxygen concentrations <br /> in observation wells located approximately 5 and 10 feet from the injection point were measured <br /> immediately before and after the-injection. Concentrations of dissolved oxygen increased an <br /> average of only 0.1 milligrams per liter in the measurement taken after the injection. Based on <br /> this result, SECOR recommends that oxygen injection is not a feasible remedial alternative for <br /> this site. However, in the "Work Plan for Additional Site Assessment and Interim Remediation, <br /> SECOR had proposed to inject 150-300 cubic feet of oxygen over a period of up to two hours, <br /> and to take dissolved oxygen measurement readings in the observation wells 24 hours after the <br /> injection. Before SECOR dismisses oxygen injection as a remedial option at this site, SJC/EHD <br /> considers that the test should be conducted as proposed and approved, or a justification and <br /> validation for the test method employed should be presented to SJC/EHD for further evaluation. <br /> Please demonstrate the test design as conducted provided adequate response time for dissolved <br /> oxygen to migrate through fine grained soil to the observation wells. <br /> The groundwater extraction tests were conducted August 11-12, 2004. A step drawdown test <br /> was followed by a 24-hour constant rate pumping test. SECOR reported that during the constant <br /> rate test, the maximum drawdown in the observation wells was 0.09 feet in well S-1 and 0.07 feet <br /> in well MW-5. SECOR stated that they considered this observed drawdown to be due to earth <br /> tides, and the values were therefore not used in the data analysis. Please provide a <br /> demonstration to SJC/EHD that the observed drawdown was an effect of"earth tides". Maximum <br /> drawdown in the extraction well, EX-1, was 6.17 feet. This data was used in the analysis using <br /> the AQTESOLV and FLOWPATH modeling software. From the models SECOR predicted a <br /> capture zone of"280 feet in the 'a' direction and 440 feet in the 'b' direction". <br /> SECOR proposes to conduct an extended groundwater pump test"to confirm the ROI and <br /> drawdown calculations determined during the 48-hour pump test..."Although a 24-hour pump <br /> test has been performed at the site, and SECOR has not yet stated what the target ROI has been <br /> determined to be, SJC/EHD approves conducting an extended groundwater pumping test. <br /> Please submit a work plan addendum by April 1, 2005 describing the pumping test design. <br /> SJC/EHD recommends designing the test so that earth tidal effects can be demonstrated and <br /> compensated for in the test evaluation. If necessary, piezometers should be installed to obtain <br /> drawdown measurements closer to the pumping well to help compensate for pumping well <br /> inefficiency and its effect on the evaluated hydraulic conductivity. In addition, please submit a <br /> work plan to continue the investigation of the vertical and lateral extent of the documented <br /> contamination by the same date. <br /> If you have any questions please call Lori Duncan at(209)468-0337. <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> Lori Duncan, Senior REHS Nuel C. Henderson, Jr., RG <br /> LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit IV <br /> cc: James Barton, CVRWQCB <br /> Jaff Auchterlonie, SECOR <br />