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page 2, 1612 Hammer Lane <br /> not readily understand how a response from the AS system will be detected under the <br /> proposed SVE and AS test designs. Considering likely diffusion rates and groundwater <br /> seepage velocities, SJC/EHD is not certain how the ROI of the AS wells will be <br /> differentiated from soil fracturing and breakthrough of injected air into observation wells. <br /> SJCIEHD cannot approve the proposed SVE/AS tests as currently proposed, but will <br /> reconsider if provided a technical basis for the proposed designs and a reasonable <br /> explanation of how each tests result will be evaluated. <br /> As expressed in the SJCIEHD letter of June 12, 2006, SJC/EHD's main concern is <br /> recovery of the sparged air and any hydrocarbon contaminants stripped by the sparging <br /> process, and minimizing the poteriiial for spreading the plume of impacted groundwater <br /> laterally. This concern arises as the sparging will be in fine-grained soil as shown in <br /> previously submitted cross sections. SJCIEHD had thought a test design would entail <br /> SVE operation until recovered vapor concentrations had demonstratively stabilized, at <br /> which time the AS would be put into operation and a concentration increase in the SVE <br /> vapor noted. However, SJCIEHD recognizes that several test designs are possible to <br /> provide the demonstration. <br /> Please submit the technical justification and discussion for the proposed SVE/AS test <br /> designs, or a revised feasibility test proposal to SJCIEHD by November 15, 2006. <br /> If you have any questions please call Lori Duncan at (209) 468-0337 or Nuel Henderson <br /> at (209) 468-3436. <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> Lori Duncan, Senior REHS Nuel C. Henderson, Jr., PG <br /> LOP/Site Mitigation Unit 1V LOP/Site Mitigation Unit IV <br /> cc: James Barton, PG, CVRWQCB <br /> Rusty Benkosky, PE, SECOR <br />