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S E C 0 R In addition to the collection of monthly groundwater samples, SECOR also records oxidation reduction potential (ORP) and dissolved oxygen (DO) measurements in wells MW-3 and MW-4 on a monthly basis In December 2005, ORP and DO reading were not taken due to a equipment scheduling miscommunication The ORP and DO data are also included in Table 2 Remediation System Effectiveness The area of well MW-3 and nearby well MW-7, immediately north of the former UST complex, has reportedly contained the highest concentrations of petroleum hydrocarbons, MtBE, and TBA impacts beneath the site Review of quarterly groundwater monitoring results and historical monthly groundwater analytical results for well MW-3, and quarterly monitoring results for well MW-7 since the start-up of the OS system by GRI in December 2002, indicate significant decreases in MtBE concentrations to low to non-detectable concentrations above laboratory MRLs Decreasing TBA concentration trends have also been observed in the wells, however, both of these wells continue to contain elevated concentrations of TBA Decreasing TBA and/or MtBE concentration trends have been observed in other wells located in the vicinity of the OS wells (MW-1, MW-4 through MW-6, MW-12, and MW-13) Concentration versus time graphs for wells MW-3 and MW-4 are provided as Figures 2 and 3, respectively Remediation system certified laboratory analytical reports and chain-of-custody documentation are provided in Attachment 3 RECENT SUBMITTALS 1 CORRESPONDENCE . SECOR submitted the October 18, 2005 Work Plan for Additional Site Assessment, which was approved by the SJCEHD in correspondence dated November 9, 2005 The work plan called for the installation of three off-site shallow zone groundwater monitoring wells (MW-14, MW-15, and MW-16), two off-site intermediate zone groundwater monitoring wells (MW-17 and MW-18), and one on-site deep zone groundwater monitoring well (MW-19) The purpose of the work is to further define the vertical and lateral extent of dissolved fuel oxygenate impacts beneath and in the vicinity of the site THIS QUARTER ACTIVITIES (Fourth Quarter 2005) 1 SECOR submitted the Quarterly Monitoring and Remedial Performance Summary Report— Third Quarter 2005 on October 25, 2005 2 Groundwater monitoring and sampling activities were performed by TRC on November 11, 2005 3 Continued operation, and performed monthly maintenance of the OS system 4 SECOR submitted a Work Plan for Additional Site Assessment dated October 18, 2005, which was approved by the SJCEHD in correspondence dated November 9, 2005 SECOR is in the process of obtaining permits for the installation of the wells lE3P-ARC01111921Reportsl01VIR-QRPS120051402005 QSSR and QRPS doc