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In February 2002, Avalon installed four additional permanent groundwater monitoring wells to further evaluate the downgradient lateral and vertical distribution of MTBE in groundwater. Three of these wells (MWO-1 through MWO-3) were installed across the water table within Sand A on the adjacent property to the north and northeast of the site. One well (MWO-1 X) was installed on-site adjacent to existing Sand A monitoring well MW-2, but was screened within Sand B. Analytical results of the initial samples collected from these new wells indicated no detectable MTBE concentrations in wells MWO-1, MWO-2, or MWO-3, but elevated concentrations of MTBE (570 gg/L) in deeper well MWO-I x. Results of this investigation were summarized in Avalon's Phase II Environmental Assessment of Soil and Groundwater Report, dated May 15, 2002. In September 2003, Stratus compiled all historic geologic, hydrogeologie, and chemical data at the site and prepared a Site Conceptual Model (SCM) for submittal to SJCEHD. In the SCM, Stratus concluded that additional lateral and vertical soil and groundwater assessment was warranted to adequately characterize contamination beneath the site and site vicinity. In May 2004 with SJCEHD's approval, Stratus oversaw the advancement and soil/grab water sampling of eight on- and off-site cone penetration test borings (CPT-1 through CPT-8). Based on analytical results of soil/groundwater samples collected from the CPTs, Stratus concluded that the vertical and lateral extent of groundwater impact appeared to be adequately characterized. Also in May 2004, Stratus oversaw, the drilling and installation of one additional on-site groundwater monitoring well (MW-7) which was installed to facilitate the completion of dual ,( phase extraction (DPE) feasibility testing. Results of this investigation were summarized in 4✓ Stratus' Subsurface Assessment Report, dated August 11, 2004. In June 2004, Stratus conducted feasibility testing for DPE at the site using welt MW-7 as the extraction point for soil vapor and groundwater. During the test, well MW-7 sustained a groundwater extraction rate of approximately 7.2 gallons per minute (gpm); however, influent soil vapor concentrations were low. Dissolved-phase average MTBE concentrations in the influent water stream from well MW-7 were only 93 µg/L. Based on this data, Stratus concluded that DPE was a technically viable remedial option, but that it did not appear to be a cost effective remedial option. In February 2005, Stratus prepared and submitted an Interim Remedial Action Plan (IRAP) proposing groundwater extraction (GWE) from wells MW-2, MW-3, and MWO-lx as interim remediation and the pursuit of sewer permit to discharge treated water from the system. In March 2005, SJCEHD reviewed the IRAP but requested extended pump testing on the three wells proposed for GWE (to obtain actual rather than estimated extraction rates). In May 2005, SECOR International, Inc. (SECOR) submitted a work plan to SJCEHD proposing the SJCEHD-requested pump tests and the installation of three additional Sand A wells and one additional Sand B well. In September 2005, SECOR oversaw the drilling and installation of four additional groundwater monitoring wells (MW-8, MW-9, MW-10, and MW-11), In December 2005, SECOR conducted the pump testing on wells MW-2, MW-3 and MWO-1 x. Results of the test indicated that wells MW-3 and MW-2 (each pumped for 6 hours) sustained flowrates of 5.0 �1 Page 8 STRATUS