ARCHIVED REPORTS XR0006666 - Laserfiche WebLink

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Flu S lEC ® R • the monthly groundwater sampling events are summarized in Table 2 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 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 None THIS QUARTER ACTIVITIES (Third Quarter 2005) 1 SECOR submitted the Quarterly Monitoring and Remedial Performance Summary Report— Second Quarter 2005 on August 23, 2005 2 Groundwater monitoring and sampling activities were performed by TRC on August 26, 2005 3 Continued operation, and performed monthly maintenance of the OS system 4 Prepared a work plan for additional off-site lateral delineation and on-site vertical delineation of dissolved impacts beneath and in the vicinity of the site NEXT QUARTER ACTIVITIES (Fourth Quarter 2005) 1 Groundwater monitoring and sampling event will be performed by TRC 2 Continue operation and perform monthly maintenance of the on-site OS system 3 Submit the work plan for additional delineation of dissolved impacts beneath and in the vicinity of the site Implement the work plan upon receipt of regulatory agency approval 4 Determine restoration actions needed for well MW-8 LIMITATIONS This report presents our understanding of existing conditions at the subject site The conclusions contained herein are based on the analytical results, and professional judgment in accordance with current standards of professional practice, no other