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Ms. Kristi Shelton <br /> Page 3 of 6 <br /> • MW1 results indicated the presence of TPHg and TPHd at concentrations of 130 and 1,100 <br /> micrograms per liter (µg/L), respectively. Benzene was detected at a concentration of 1.1 µg/L <br /> and DCA was detected at 2.6 µg/L. No other analyzed constituent was detected above <br /> laboratory reporting limits. <br /> • MW2 results indicated the presence of MTBE at 1.3 pg/L and DCA at 34 gg/L. No other <br /> analyzed constituent was detected above laboratory detection limits. <br /> • No analyzed constituents were detected above laboratory detection limits in groundwater <br /> samples collected from MW3,MW4, and MW5. <br /> Assessment of Petroleum Hydrocarbons <br /> • TPHg/TPHd: There is strong evidence suggesting that TPHg and TPHd concentrations <br /> fluctuate seasonally with changes in groundwater elevation. Groundwater elevation has <br /> increased an average of 8.84 feet since November 6, 2009, petroleum hydrocarbon <br /> concentrations are below historic highs, and the plume appears to be stable. <br /> o TPHg concentrations in groundwater have never exceeded 480 µg/L and the results of <br /> this monitoring event show TPHg concentrations are currently 130 gg/L. Figure 5 <br /> depicts the seasonal fluctuations of TPHg concentrations in groundwater. <br /> o TPHd concentrations during the May 6, 2010 monitoring event were 1,400 pg/L and <br /> are currently at 1,100 µg/L. Historically, the concentrations have fluctuated from <br /> below 50 pg/L to 1,400 gg/L. Figure 6 depicts the seasonal fluctuations of TPHd <br /> concentrations in groundwater. <br /> • In general, most BTEX constituents are not detectable above laboratory detection limits. <br /> Benzene concentrations detected in MW 1 has ranged between 0.6 µg/L and 1.7 µg/L. <br /> Assessment of MTBE and 1,2-Dichloroethane <br /> • Trace levels of MTBE have been detected in MW2 although the concentrations have not <br /> exceeded 1.5 µg/L. <br /> • DCA has been detected in MW1 and MW2. Monitoring well MW2 has shown the highest <br /> historical concentrations. An isoconcentration map showing DCA concentrations in <br /> groundwater is included as Figure 7. <br /> • DCA concentrations have fluctuated with groundwater elevation and the relationship is <br /> depicted in Figure 8. <br /> G:\GROUNDZE\WCTOMATO\WCT-Investigation\Reports\QMR\2011\1 QM2011.doc <br />