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t%w° 08 September 2009 AGE -NC Project No. 03-1055 Page 8 of 19 2.4.2. Ground Water Flow Direction and Gradient Between December 2000 and June 2005, ground water flow direction and gradient were highly variable. Between September 2005 and July 2009, ground water flow direction was predominantly northeast to north, towards the former Tracy Diner site and away from the former Chevron site (Section 2.3.), under ground water gradients ranged between 0.001 foot/foot (ft/ft) and 0.006 ft/ft. Ground water monitoring data is summarized on Table 3; representative ground water elevations and ground water flow directions between 2000 and 2009 (including the July 2009 monitoring event) are presented in Appendix G. 2.4.3. Dissolved Petroleum Hydrocarbon Concentrations Based on the results of ground water samples collected during the 24 ground water monitoring events at the site, TPH-g has been established as the contaminant of concern. Ground water monitoring wells MW -2 and MW -3, destroyed in 2003 as part of over -excavation activities, contained the highest recorded concentrations of TPH-g and BTEX compounds at the site, �6.v with maximum concentrations of 110,000 µg/1 TPH-g, 640 gg/l benzene, 160 µg/1 toluene, 890 gg/l ethylbenzene, and 1,000 µg/l xylenes in well MW -2. Currently, wells MW -6 and MW -8 are the only site monitoring wells with consistent detections of TPH-g; between August 2005 and July 2009 TPH-g concentrations averaged approximately 400 µg/l in well MW -6 and 630 gg/l in well MW -8. BTEX compounds were reported only once in well MW -6 (December 2005) and have not been reported in well MW -8 for five consecutive quarters. During the July 2009 monitoring event, TPH-g were reported in well MW -6 at a concentration of 190 µg/1; TPH-g were not reported at or above detection limits in well MW -8 for the first quarter since the initiation of sampling in the well (August 2005). The lateral and vertical extents of the dissolved petroleum hydrocarbon plume is defined in all directions. TPH-g, BTEX, and fuel additive -impact exhibited in well MW -11, located on the western side of Adams Street immediately east of the former Chevron site UST area, depicts an up -gradient and off-site source of hydrocarbons, which has not declined over time since the closure of the Chevron site. Petroleum hydrocarbon -impact to ground water is further discussed in Section 4.0. Analytical results of ground water monitoring samples are summarized in Table 4. Graphs illustrating trends in analytical data are included in Appendix F. The July 2009 laboratory report (CTEL Lab Project. No. CT214-0907125), quality assurance/quality control report, and chain -of - custody form are included in Appendix H. Electronic deliverable format (EDF) files were uploaded to the State GeoTracker database under confirmation number 7153612434. Advanced GeoEnvironmental, Inc.