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Mr. Maurice Benson <br /> January 13, 2010 <br /> Page 4 <br /> DTSC recommends that DESJC consider resizing the blower for added 25-30% <br /> reserve capacity, or as an alternative, include a VFD controller in combination <br /> with a variable diameter pulley on the compressor to allow added flexibility for <br /> system optimization/expansion efforts. Moreover, the above recommended <br /> combination would also support reduced flow conditions when the system is <br /> being optimized to target remaining mass or when the system is reaching levels <br /> of diminishing returns, enabling DESJC substantial savings in electrical costs <br /> over the operational life of the system. <br /> Conclusion <br /> DTSC recommends either resizing the blower for additional reserve capacity in case of <br /> system expansion or orientation changes are required, or as an alternative, include a <br /> VFD and variable diameter pulley to enhance optimization efforts and to help reduce <br /> electrical costs over life of the system. DTSC recommends adding sampling ports to <br /> each of the effluent lines for the granular activated carbon vessels to eliminate the <br /> proposed composite sampling of effluent stream. Sampling ports on each vessel's <br /> effluent line would provide useful information on the individual performance of each <br /> vessel, including breakthrough. DTSC recommends DESJC provide rationale in the <br /> report why no SVE wells are proposed in the location of CP1127 where TCE vapor <br /> concentrations were recorded as high as 1200 ppbv, exceeding the cleanup goal of 350 <br /> ppbv. VLEACH modeling should be used to demonstrate that chlorinated vapors at <br /> CP1127 do not pose a threat to groundwater quality by exceeding the maximum <br /> contaminant level of 5 pg/L. If the evaluation does show that TCE mass in the vadose <br /> zone in the location of CP1127 is a continuing source of groundwater contamination <br /> then the SVE system should be amended to include an additional VEW or the <br /> re-orientation of the proposed SVE circuit to remediate the localized contaminant mass. <br /> If you have any questions or concerns with the comment letter, please contact me at: <br /> (916) 255-3713 or e-mail at: pmacnich(a)dtsc.ca.gov <br /> Sincerely, <br /> Peter MacNicholl, P.E. <br /> Remedial Project Manager <br /> Sacramento Office <br /> Brownsfield and San Joaquin Cleanup Program <br />