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Stantec . <br /> September 15, 2008 <br /> Page 8 of 9 <br /> Reference: Response to RWQCB July 30, 2008 Letter <br /> Comment Number 4 of the RWQCB's July 30, 2008 letter warrants clarification. It states in part the <br /> following: <br /> • "During the 5 June meeting, the STTC stated that a firm has been hired to upgrade the OS <br /> system to solve the wintertime shutdown problems that are caused by high groundwater." <br /> STTC is in the planning process for upgrading the first generation ozone production equipment for <br /> the east and west systems. However, the wintertime shutdown problems will not be "solved" by the <br /> new equipment. These issues are inherent with the extremely shallow groundwater, which is often <br /> manifested as standing surface water during the winter. The system is shut down during these high <br /> water stages to avoid channeling by ozone along the annular seal/boring surface interface. These <br /> physical processes and the attendant corrosion of the annular seal by ozone will create preferential <br /> pathways. If this is left unchecked, it would destroy the ability of the sparge wells to deliver the <br /> ozone to the surrounding saturated zone by reducing the effective radius to essentially zero. <br /> Because the ozone generation equipment is first generation technology, its upgrade will increase <br /> runtime by eliminating breakdowns of the complex, maintenance-intensive systems. STTC will <br /> continue to provide updates on this process in future quarterly reports as requested by the <br /> RWQCB. <br /> CONCLUSIONS <br /> Based on the above information, STTC does not agree the addition of TBA to the list of compliance <br /> analytes is warranted. STTC will continue quarterly evaluation of the compliance analytes as part <br /> of the EMP, which is more than adequate for monitoring the effectiveness of the barrier arrays. <br /> STTC is committed to expending all reasonable efforts to monitor plume stability and continues to <br /> commit considerable resources to mitigate onsite impacts. Installation of pilot test well TS/MW-3D <br /> and associated vertical delineation efforts on Tesoro terminal property this quarter and subsequent <br /> evaluation of various technologies to abate relatively high concentrations in the D-zone will facilitate <br /> mitigation of groundwater impacts at the Port of Stockton. <br /> lASTTC-Stockton\Reports\Resp to RWQCB July 30,2008\Response to RWQCB July 30, 2008 Letter final.doc <br />