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r4e4100-91 Tech&&$!iu Page 2 Groundwater Monitonng Report Project No 723 2 June 21,2006 ' consecutive event This condition is reflective of the greater than normal precipitation this winter/spring Groundwater gradient calculations indicate that shallow groundwater flow is N43'E at 0 007 ft/ft This is consistent with the site's historical directions that have been predominantly to ' the northeast The intermediate and deep aquifer zones' gradients were calculated to be N45°E at 0 007 ft/ft and N53°E at 0 003 ft/ft, respectively The deepest aquifer zone gradient monitored by wells MW-101, MW-307, MW-308 and MW-309 had a variable gradient due to a localized high near MW-101 Field evidence recorded during borehole installation indicates that petroleum hydrocarbon contamination is present on the adjacent property across N El Dorado Street— an active Shell service station The Valentine (Castle Motors) site plume extends off site toward the Shell Station and evidence suggests that a co-mingled plume may be present The lateral extent of the groundwater plume was undefined down gradient of CMTTM well set MW- 8/108/208/308 A limited site investigation consisting of three CPTTM borings was ' completed on February 21 — 23, 2006 The results of that effort showed that the plume appears to extend approximately 300 feet or less down gradient to the northeast of the site) We have recommended that interim remediation be considered before this plume migrates any further and the cost for cleanup continues to increase A work plan for interim remedial action utilizing high vacuum dual phase extraction, air stripping and carbon filtration of ' extracted groundwater technologies has been sent to SJC/EHD for approval SJC/EHD approved the work plan and the permitting for the extraction and treatment system procurement, installation, and operation is underway We have received building and sewer ' discharge permits from the City of Stockton PG&E has identified high pressure gas service at the adjacent residential property and we received permission from this property owner to extend a line to the Castle Motors site on March 31, 2006 We have re-applied to the City of ' Stockton Building Department for an amended permit for the new gas service on the east side of the building GTI will continue to follow up on this issue ' 1.0 GROUNDWATER MONITORING In November, 2003, three new continuous multi-chambered tubing (CMTTM) wells were installed to further define the vertical and lateral extent of the soil and groundwater plumes (see Figure 13 for well locations and Table 8 for well construction details) The boreholes for the new wells' were installed to the north, east, and southwest of the site across E Castle, N El Dorado Street and W Adams Street, respectively rAs previously reported by GTI, the CMTTM wells were so tightly coiled for shipping that it was difficult to install the wells without the tubing corkscrewing in the borehole, even when the casing was stretched out on the ground in the sun to warm and relax the coils The result