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670-04lcal rechfdaI a Page 7 <br /> Groundwater Monitoring Report <br /> Project No 723 2 <br /> June 20, 2005 <br /> ' o Downradient well MW-8 contained 6 4 u <br /> g g/1 benzene <br /> ' • The intermediate wells contained benzene concentrations ranging <0 5 — 13,000 <br /> ug/l <br /> o The highest level of benzene was detected in well MW-3 that is located in the <br /> ' core of the gasoline plume <br /> o Well MW-109 defines the up gradient extent of the plume <br /> o Down gradient well MW-108 contained 21 ug/1 benzene <br /> ' • The deep wells contained benzene concentrations ranging c0 5 — 11 ug/l <br /> o The highest level of benzene was detected in well MW-208 that is located <br /> down gradient of the former dispenser island <br /> ' o Well MW-209 is clean and defines the up gradient extent of the plume <br /> 4 Other gasoline constituents detected <br /> • Well MW-8 contained 9 2 ug/1 1,2 DCA <br /> • Well MW-108 contained 6 3 ug/1 DIPE, 36 ug/l 1,2 DCA <br /> ' The distribution of groundwater contaminants is summarized as follows <br /> (Note The Isoconcentrataon contours are generated utilizing the SURFER® computer <br /> modeling program We recognize that computer generated contour maps do not provide the <br /> most accurate representation of what is taking place in the field However, even hand- <br /> contoured map at best provide a shadow of reality Both need to be looked at as <br /> interpretation, not reality) <br /> ' 1 TPH-G <br /> • The Valentine (Castle Motors) shallow well TPH-G data for the 2nd quarter 2005 <br /> groundwater monitoring event for site are included in Figure 4 A localized high is <br /> ' centered in well MW-5 that attenuates to the east in the location of MW-8 <br /> s Figure 5 illustrates the distribution of TPH-G in the intermediate wells A localized <br /> high is centered in well MW-3 that attenuates to non-detectable levels in up gradient <br /> ' well MW-109 The plume also attenuates to the north and east locations of wells <br /> MW-107 &MW-108,respectively <br /> • Figure 6 illustrates the distribution of TPH-G in the deep wells A localized high is <br /> ' present in cross gradient well MW-207 that attenuates to non-detectable levels in up <br /> gradient well MW-209 The plume also attenuates to the east location of well MW- <br /> 208 <br /> ' 2 MTBE <br /> • Only well MW-7 (one data point) contained MTBE at 0 5 ug/1 and therefore contour <br /> diagrams were not produced EPA Method 8260B was utilized for this event <br /> ' • MTBE appears not to be an issue at this site <br /> 1 <br />