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elevation. The current groundwater elevation data for the Forward Unit is summarized in Table 2-3. The groundwater elevation data obtained during the second quarter 2008 monitoring period were used to generate the groundwater elevation contour map shown on Figure 2-1, which indicates that groundwater generally flows to the north towards the Austin Unit, at an average hydraulic gradient of approximately 0.001 ft/ft. To calculate the approximate linear groundwater flow velocity for the site, conservative assumptions were used, including a hydraulic conductivity of 875 gallons per day per square foot (0.04 cm/sec) and an estimated effective porosity of 35 percent (CH2M Hill 2000). An estimated groundwater flow velocity was calculated using Darcy's Law: Ki cm 0.001 sec – ft V = — _ [(0.04 —) * ] * 2835 � 0.324 ft / day ne sec 0.35 cm – day where: V = Groundwater flow velocity. K = Hydraulic conductivity of the water -bearing unit (0.04 cm/sec). i = Hydraulic gradient: i ;z� 0.001 for the site during the second quarter 2008. ne= Effective porosity (ne = 0.35); an estimated value. The groundwater flow rate is calculated to be 0.324 feet/day (118 feet/year). 2.1.4 Detection Monitoring Program Field and laboratory results for the groundwater monitoring wells for the second quarter 2008 are summarized in Table 2-2 and Appendix D presents time -series charts of select parameters. As shown on Table 2-2, estimated trace VOC constituent concentrations (between the method detection limit [MDL] and the practical quantitation limit [PQL]) of 1, 1 -dichloroethane (1,1 -DCA), dichlorodifluoromethane (DCDFM), tetrachloroethene (PCE), trichloroethene (TCE), and trichlorofluoromethane (TCFM) were measured in the sample collected from wells MW -10 and diisopropyl ether was measured at a trace concentration in the sample collected from well W-21. On behalf of Forward Inc., GLA prepared a letter report dated February 14, 2001 (RWQCB Case No. 2209), to assess the source and potential impacts of low-level VOCs in groundwater adjacent to the Forward Landfill. The letter report concluded that the sporadic detection of low-level VOCs in groundwater (and lysimeter samples) at the Forward Unit are most likely due to landfill gas from unlined unit WMU-B. Forward has continued to minimize gas related impacts to groundwater by limiting interim fill areas that promote ponding of water. Furthermore, in accordance with CCR Title 27, Section 20937, Forward continues to install additional landfill gas extraction wells, as needed. DA2008_00101FA 2Q08.doc 5 Geologic Associates