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CrtologualTeckxuslxc Page 2 ' 3`4 Quarter 2005 Groundwater Momtonng Report Project No 507 2 October 31,2005 1 Since there is uncertainty regarding the soil profile at the site, due to the 5-foot sampling ' interval, GTI proposed performing several continuous core bonngs GTI developed our March 7, 2005 "Site Characterization Work Plan" that includes three continuous core borings ' to determine the presence of sand/silt layers in the core contaminant area SJC PHS/EHD issued an April 15, 2005 correspondence that requested additional information and denied approval of the work plan We submitted a May 16, 2005 work plan addendum and SJC ' PHS/EHD approved the work plan in their June 21, 2005 letter However, in a letter dated June 27, 2005, SJC PHS/EHD stated that the Regional Water Quality Control Board-Central Valley Region (RWQCB) must approve any additional infection work so the site ' characterization and remediation work is on hold pending concurrence from the RWQCB GTI's Project Geologist Mr Joseph Angulo contacted Mr James Barton of the RWQCB ' regarding their requirements for ozone/peroxide infection Mr Barton confirmed that a bench scale (laboratory) pilot study would be acceptable to determine if the proposed infection would cause deleterious effects to groundwater He directed that a work plan for ' the bench scale pilot test be submitted for his review GTI submitted our August 8, 2003 "Ozone Sparging SECOR Benchscale Test" work plan for RWQCB consideration The RWQCB responded in a September 8, 2005 letter requesting additional information GTI submitted an October 25, 2005 work plan addendum addressing the RWQCB and we are currently awaiting a response 1.0 GROUNDWATER MONITORING ' 1.1 Hydrogeology of Site ' The geology of the site is predominately clays and sandy clays with lesser amounts of inter- bedded silts and sands The average groundwater elevation was —10 51 feet below msl on August 19, 2005, which corresponds to approximately 16 feet below grade surface (bgs) ' This average elevation represents a decrease of 159 feet since the May 27, 2005 monitoring event Groundwater gradient for this monitoring event was 0 003 ft/ft flowing N48'E The site consistently exhibits a flat groundwater gradient ' The gradient direction for the August 2005 monitoring event is shown in Figure 2, and the historical groundwater directions and gradients are shown in Figure 3, Groundwater Gradient ' Rose Diagram The groundwater elevation data are summarized in Table 1, Appendix A Table 5 provides a summary of monitoring well construction The groundwater gradient is relatively flat and the direction of groundwater flow has varied during the course of the investigation As evident in Figure 3, groundwater exhibited a strong bifurcated flow regime in 2000, trending predominantly to the southwest or north-northeast at approximately 180-degree direction reversal Since the installation of wells MW-7 and MW- 1