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. e Since the 'in-situ" approach would add time to the cleanup timeline, Wright <br /> had several telephone conferences with the EHD representative, Mr Mike <br /> Infurna regarding the soil excavation approach and EHD desire to move <br /> the cleanup along Consequently the decision was made to excavate <br /> limited areas assessable within the site surface and subsurface <br /> constraints Excavation in the areas of MW-9 and MW-3 were proposed <br /> to EHD (Exhibit-4) The excavation and pit dewatering proposed were to <br /> remove these sources assumed to be the cause of the elevated dissolved <br /> highs within the otherwise "static" dissolved plume <br /> ® All work was performed in conference with the EHD representatives <br /> Once excavation was started, the residuals were observed present and <br /> removed as close to the sensitive utilities as possible At that time a <br /> review of possible action was made with EHD regarding next steps The <br /> dual phase option was revisited A letter from EHD (Exhibit-6) <br /> summarized this discussion and the EHD indicated that previous <br /> experience with dual phase systems in the immediate site region showed <br /> only mediocre performance While Wright had estimated a potential lower <br /> cost, that preliminary cost estimate was made on the basis of site data <br /> and duration of use with an assumed relatively high performance Since <br /> EHD experience indicated otherwise, a field decision was made to <br /> continue soil excavation to remove obviously contaminated residual soil, <br /> especially in the vadose zone (and adjacent to pathways along large <br /> pipelines) Excavation dewatering removed limited areas of sheen to <br /> carbon treatment Once the excavation was completed, replacement <br /> monitoring wells MW-3R and MW-9R were installed for monitoring at the <br /> areas of previously elevated concentrations <br /> Recent quarterly monitoring events (Exhibit-7) has shown a marked decrease in <br /> dissolved contaminants and a trend is forming that indicates the otherwise <br /> immobile, stable plume is now declining in contaminant concentractions This <br /> documented reduction is attributed in Wright's opinion to removal of the residual <br /> vadose and upper aquifer contaminated sediment Ergo, the clean up work has <br /> been effective and may ultimately be determined to have been effective enough <br /> to support EHD providing a letter of "No Further Action required" and the closure <br /> of this site with the concurrence of RWQCB <br /> Page 5 of 7 <br />