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Mr Mike Infurna May 26, 2005 S E C ® R Page 2 to evaluate the extent of intermediate zone groundwater impacts In June and July 2003, four offsite intermediate zone groundwater monitoring wells (MW-11 through MW-14, Attachment A) were installed to further delineate the lateral extent of dissolved petroleum a hydrocarbon plume within the intermediate water bearing zone Vr= 1WA In November of 2004, SECOR installed one onsite deep zone groundwater monitoring well, w� MW-15 This well was incorporated into the quarterly monitoring and sampling program immediately following its installation even though the remaining two wells that were proposed under the work plan for the project were not completed during the fourth quarter 2004 A report documenting the installation of MW-15 will be submitted under separate cover MONITORING AND SAMPLING Monitoring and analytical data are included in Tables prepared by TRC in Attachment B j t{ Current fluid levels and selected analytical results are included as Table 1 of this , attachment Historic fluid levels and selected analytical results are included as Table 2, and additional analytical results are included as Table 3 TRC's Data Transmittal, Groundwater Monitonng Field Notes and Laboratory Report dated February 23, 2005, is included in Attachment B The report includes TRC's field and laboratory procedures, field data sheets, and certified laboratory analytical reports The site has been monitored and sampled since the first quarter 2000 Currently, a total of 15 wells r S are monitored and sampled quarterly Samples are analyzed for total petroleum ' hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, total xylenes (BTEX), and fuel oxygenates by EPA Method 8260B Selected samples were also analyzed for lead by EPA Method 6010B The 15 groundwater monitoring wells at the site were gauged and sampled by TRC on January 12 and 13, 2005 Water levels within groundwater monitoring wells that are part of the monitoring and sampling program at the ARCO Service Station (16 East Harding Way) were cooperatively measured by SECOR on January 12, 2005, and sampled on January 12 and 13, 2005 Regional groundwater flow direction within the shallow zone was to the northeast at approximately 0 005 ft/ft, with local variation near batch extraction wells EW-2, EW-4 and EW-5 Regional groundwater flow direction within the intermediate zone was to the northeast at an approximate gradient of 0 004 ft/ft Shallow and intermidiate groundwater contour maps are included as Figures 1 and 2 Based on the first quarter 2005 monitoring and sampling event (January 12 and 13, 2005, Attachment B) the maximum TPHg, methyl tertiary butyl ether (MtBE), and 1,2- dichloroethane (1,2-DCA) concentrations were 9,500 parts per billion (ppb) (MW-5), 3,200 ppb (MW-10), and 29 ppb (MW-11), respectively TPHg and MtBE concentrations in shallow groundwater have exhibited an increasing trend in wells MW-1, MW-3 and MW-4, likely due to the upgradient ARCO gasoline service station site 1,2-DCA is increasing slightly in MW-4 as well