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""logical Tecluucs lxc Page 2 <br /> Feasibility Study&Investigation Work Plan <br /> Cardoza(Main St} <br /> Project No 662 2 <br /> Apn1 19, 2004 <br /> In accordance with SJC/EHD directives, a continuously cored, single boring was installed <br /> on May 30, 2002 A discretely screened deep monitoring well, MW-104, was installed in <br /> t the boring This well has been sampled six times since its installation and it has contained <br /> MTBE on all occasions <br /> Since well MW-104 was installed, SJC/EHD staffing had changed In their November 18, <br /> ' 2002 letter correspondence, SJC/EHD rescinded previously submitted work plans and called <br /> for phased approach to continue the site investigation The phased approached consisted of <br /> cone penetrometer testing (CPT), followed by monitoring well installation, and groundwater <br /> ' extraction well installation and aquifer testing GTI submitted our January 17, 2003 work <br /> plan to meet the SJC/EHD directives and they approved the CPT and groundwater <br /> extraction well portion of the work plan in their February 14, 2003 letter Eight CPT <br /> borings, CPT-1 through CPT-8, and an extraction well, EW-1, were installed in December <br /> ' 2003 <br /> Groundwater samples obtained from the CPT boreholes reveal that the residual <br /> ' contamination is sourcing a submerged plume that has migrated to the location of CPT-7 A <br /> sand layer is present at a depth of 38 — 48 feet across the site and it appears to act as a <br /> preferential pathway for contaminant migration <br /> In accordance with our January 17, 2003 work plan and SJC/EHD directives GTI has <br /> prepared the following work plan for additional groundwater plume definition and an <br /> aquifer pumping test <br /> 2.0 ADDITIONAL SITE CHARACTERIZATION <br /> ' The CPT boreholes advanced in December 2003 revealed that most of the residual soil <br /> contamination is located under the former USTs This soil contamination continues to <br /> source a submerged plume that is migrating off site to the location of CPT-7 at a depth of 45 <br /> ' feet below grade surface (bgs) and is located within an area within a 100-foot radius around <br /> the former USTs (see Figures 3 & 4) As reported in our February 9, 2004, "Additional Site <br /> Characterization - Soil and Groundwater Investigation"report, sand layers at a depth of 38 — <br /> ' 48 feet beneath the former excavation act as a preferential pathway for the MTBE plume to <br /> migrate eastward In order to further define the extent of the MTBE plume GTI proposes to <br /> install two additional groundwater monitoring wells (MW-5 & MW-6) The wells will be <br /> constructed with screened intervals that intercept the depth of the submerged plume <br /> 2.1 Soil Borings <br /> Figure 5 includes the proposed well boring locations Well MW-5 is proposed for <br /> installation adjacent to the CPT-7 location Well MW-6 will be placed approximately 75 <br /> feet east of MW-5 These locations are selected because the north side of North Street has <br /> overhead utilities, numerous driveways, and doctor offices making borehole installation <br /> problematic <br /> Prior to commencing work, encroachment permits and soil boring/monitoring well permits <br /> will be secured and the SJC/EHD will be notified 48 hours in advance The subsurface will <br /> be cleared of underground utilities by notifying Underground Service Alert <br />