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Cw&gical7-eckoda I" Page 2 <br />' Groundwater Momtormg Report <br /> Project No 723 2 <br /> March 21,2005 <br />' stretched out on the ground in the sun to warm and relax the coils The result of this twist in <br /> the tubing is that depth to water measurements could not be made because the instrument <br /> probe becomes lodged in the small chambers of the tubing Subsequently, Del-Tech <br /> Geotechnical Support has procured a micro-water level meter that can be used in the CMTTM <br /> wells The first quarter of 2005 was the first time that the well chambers could be sounded <br />' G adient calculations show that shallow groundwater flow is N58°E at 0 0051 <br /> Groundwater gr <br />' ft/ft This is consistent with the site's historical directions that have been predorninantly to <br /> the northeast The intermediate and deep aquifer zones' gradients were calculated to be <br /> N55°E at 0 006 ft/ft and N68°E at 0 0076 ft/ft, respectively The deepest aquifer zone <br />' gradient monitored by wells MW-101, MW-307, MW-308 and MW-309 was calculated to be <br /> S7511E at 0 0057 ft/ft This direction is anomalous to the other three calculated gradients but <br /> additional monitoring is needed to determine trends with the inclusion of the CMT rm wells <br />' Field evidence recorded during borehole installation indicates that petroleum hydrocarbon <br /> contamination is present on the adjacent property across N El Dorado Street—an active Shell <br />' service station The Valentine (Castle Motors) site plume extends off site toward the Shell <br /> Station and evidence suggests that a co-mingled plume may be present The lateral extent of <br /> the groundwater plume is undefined down gradient of CMTTM well set MW-8/108/208/308 <br /> A limited site investigation should take place to define the down gradient extent of the <br /> plume This should consist of direct push probe drilling methods such as CPTTM to collect <br /> discrete groundwater samples rather than installing additional monitoring wells A work plan <br /> to accomplish this task has been sent to SJC/EHD for approval <br /> We recommend that interim remediation be considered before this plume migrates any <br />' further and the cost for cleanup continues to increase Interim remedial action can be <br /> initiated by installing a high vacuum dual phase extraction unit to address the on site <br /> contamination Extraction should be performed on the existing wells EW-1, VEW-1 & <br />' VEW-2 and a new extraction well set at a deeper depth The treatment system should include <br /> air stripping and carbon filtration of extracted groundwater to be discharged to City of <br /> Stockton public treatment works A work plan to accomplish this task has been sent to <br /> SJC/EHD for approval Our goal is to have an interim remedial action plan installed and <br /> operational by the end of 2005 <br /> 1.0 GROUNDWATER MONITORING <br />' In November, 2003, three new continuous multi-chambered tubing (CMTrM) wells were <br /> installed to further define the vertical and lateral extent of the soil and groundwater plumes <br />' (see Figure 13 for well locations and Table 8 for well construction details) The boreholes for <br /> the new wells' were installed to the north, east, and southwest of the site across E Castle, N <br /> El Dorado Street and W Adams Street, respectively <br /> 1 <br />