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S E C 0 R Mr Jim Barton February 23, 2006 Page 3 total depth of site monitoring wells are presented in Table 1 Depths to water during 4Q2005 are included in Table 2 During the 4Q2005 monitoring event groundwater elevations ranged from -26 25 feet to -28 79 feet below mean sea level (msl) Groundwater elevations across the site decreased an average of 0 39 feet from the previous sampling event Groundwater flow direction at the time of sampling was to the east-southeast (Figure 2) Historical groundwater flow direction was tabulated and plotted on a rose diagram to gain a better understanding of the historical groundwater gradient beneath the site (Figure 3) Where necessary the potentiometric surface was assessed using RockWorksTm This data was then used to determine the groundwater flow direction for each historical sampling event Based on the data from fifty-eight quarterly monitoring events conducted from September 1990 to present, the groundwater flow direction trend is predominately to the east-southeast ANALYTICAL METHODS Groundwater samples from MW-2, MW-3, MW-4, MW-5, MW-6, MW-7, MW-11D, GEW- 005A, GEW-006A, GEW-007A, GEW-008A, GEW-022B, and GEW-023B were analyzed for . the following parameters, • BTEX, MtBE, PCE, and TCE by EPA Method 8260B, • TPH by EPA Method SW-846 80156 Modified gas chromatography with a flame ionization detector (GC-FID) for the following petroleum hydrocarbons TPHg, diesel #2 fuel, kerosene, mineral spirits, fuel oil, and coal tar oil The GC-FID analytical method was chosen because it is capable of identifying specific petroleum- hydrocarbon compounds such as TPHg or diesel fuel by their retention time and characteristic chromatographic patterns, rather than by a non-specific set of peaks eluting within a range of retention times on the gas chromatograph RESULTS Laboratory analytical results are summarized in Tables 1 through 5 These tables represent a summary of data tables presented in the G-R report included as Attachment A No petroleum hydrocarbon constituents were reported in the certified laboratory analytical reports for groundwater samples collected from monitoring wells MW-2, MW-3, MW-4, MW- 5, MW-6, MW-7, MW-11D, and extraction wells GEW-005A, GEW-006A, GEW-008A, GEW-0226, and GEW-023B A single detection of MtBE occurred in the extraction well GEW-007A at a concentration of 220 micrograms per liter (pg/L) Well GEW-007A is screened from 28 feet to 83 feet bgs On site monitoring wells MW-7 and MW-11 D, located . crossgradient and upgradient, respectively of well GEW-007A, are screened through the same approximate interval, and yielded no detections of MtBE Based on this observation it N AleslProjecfslCtrevron4RefaiA#9-617i1Penodre Monrt0nng1200514QMRY4Q2005QMR doc