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•• � raa INZON4UB968 ERMRST WC, i?, 003 <br /> Environmental <br /> Mr.Harlin Knoll i1 <br /> Resources <br /> 27 September 1994 Management <br /> Page 2 <br /> i <br /> i; <br /> • Total Petroleum Hydrocarbons (TPH;gasoline range)by US <br /> Environmental Protection Agency(USEPA) Method 8015 modified; <br /> • TPH(diesel range)by USEPA Method 8015 modified; aind <br /> • Volatile organic components of petroleum fuels-benzene, <br /> f ethylbenzene, toluene and xylenes(BTEX),fuel oxegenates(methyl <br /> tert-butyl ether [MTBE],tert-amyl methyl ether [TAME],2-Methyl-2- <br /> Propanol [TBA],diisopropyl ether [D1PE],and ethyl tert-butyl ether <br /> [ETRE]),and 1,2-dichloroethane(1,2-DCA)-by USEPA imethod 8260. <br /> i <br /> Monitoring Results <br /> Based on the sampling results presented in Tables 1 and 2,Catellus/ERM <br /> have concluded that site conditions do not appear to have changed <br /> significantly from those observed during previous monito .ring. ;;This <br /> conclusion is supported by the discussions provided belowfor the <br /> different compound classes. 3j, <br /> TPH/BTEX <br /> As in past sampling events,TPH as gasoline and BTEX compounds were <br /> detected in ground water samples. The magnitudes of the July 1999 TPH <br /> and BTEX detections are comparable to those of recent historical <br /> detections. As with previous sampling events, at both sites;the highest <br /> detections are associated with the wells located in the immediate vicinity <br /> of the former tanks(MW-5,MW-1A,and MW-2A), TPH acid BTEX <br /> detections decrease dramatically in nearby wells,indicating that the <br /> extent of affected ground water is limited. These results confirm the <br /> historical data indicating that the plumes are not migrating: Historical <br /> trend analysis indicates that TPH and BTEX concentrations,':have <br /> decreased significantly over time. <br /> Oxygenatesl%2-DCA <br /> i; <br /> q <br /> As summarized below,limited data exist regarding oxygenate arid 1,2- <br /> DCA occurrence patterns in ground water at the site. However,the <br /> available data support the conclusion that significant impacts to ground <br /> water quality are generally limited to the immediate vicinity of the <br /> former storage tanks. '` <br />