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� EC ® R <br /> Mr Mike Infurna <br /> October 29, 2004 <br /> Page 4 <br /> MONITORING AND SAMPLING <br /> TRC's Groundwater Monitoring Report dated August 10, 2004 is included as Attachment B, including <br /> Tables 1- 3, field data sheets, and groundwater analytical reports The site has been monitored and <br /> sampled since 1st quarter, 2000 Currently, 14 wells are monitored and sampled quarterly Samples <br /> are analyzed for TPHg, BTEX, and fuel oxygenates Well construction details are included as <br /> SECOR's Table 1 <br /> Each of the 14 groundwater monitoring wells at the site was gauged and sampled on July 13, 2004 <br /> Groundwater flow direction within the shallow zone is radially inward toward well MW-1 <br /> Groundwater flow direction within the deep zone was to the northeast at a gradient of 0 004 ftlft <br /> Shallow and deep groundwater contour maps are included as Figures 1 and 2 <br /> Based on the third quarter 2004 monitoring and sampling event (July 13, 2004) (Attachment B) the <br /> maximum TPHg, MtBE, and 1,2-DCA concentrations were 2,100 ppb (MW-10), 1,100 ppb (MW-10), <br /> and 27 ppb (MW-11), respectively <br /> TPHg and MtBE concentrations in shallow groundwater have exhibited an increasing trend in wells <br /> . MWA and MW-4, likely due to upgradient gasoline service stations such as the ARCO site <br /> TPHg, benzene, MtBE, and 1,2-DCA generally show a decreasing trend in deep wells with the ti <br /> exception of MtBE in well MW-10 which reported a concentration of 1,100 ppb <br /> Based upon data collected during ongoing quarterly groundwater monitoring and sampling, TPHg, <br /> benzene, and MtBE are effectively delineated both laterally and vertically in the vicinity of the site <br /> 1,2-DCA is not currently delineated <br /> Review of shallow isoconcentration maps indicates that ConocoPhillips has performed adequate <br /> delineation within the shallow zone Deep isoconcentration maps indicate the following TPHg is <br /> delineated to 100 ppb or below, MtBE and benzene are delineated in all directions to below their <br /> respective maximum contaminant levels (MCL's), and 1,2-DCA is not currently delineated, however <br /> concentration are higher offsite than onsite Shallow and deep lsoconcentratlon maps are included <br /> as Figures 4 through 10 <br /> F <br /> RECENT QUARTER ACTIVITIES (Third Quarter 2004) <br /> Quarterly groundwater monitoring and sampling performed by TRC on July 13, 2004 <br /> + Prepared and submitted the quarterly summary report <br /> Conducted additional vertical assessment of soil and groundwater " <br /> Submitted work plan for the installation of deep monitoring wells <br /> iM <br /> NEXT QUARTER ACTIVITIES (Fourth Quarter 2004) <br /> Perform quarterly groundwater monitoring and sampling (TRC) <br /> Prepare and submit a quarterly summary report <br /> a Install deep monitoring wells <br /> 1ConocoPhillipsWosco Marketing144091Qssrs120041302004_QSR doc SECOR International Incorporated <br />