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groundwater in the northwest corner of the site generally flows northwest towards the Austin Unit. 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). The estimated maximum groundwater flow velocity was calculated using Darcy's Law: Kicm 0.01 sec– ft V = —_ [(0.04—)* ]*2835 ;ze 3.24 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--0.01 for the site during the first quarter 2006. ne=Effective porosity(n,=0.35);an estimated value. The groundwater flow rate is calculated to be 3.24 feet/day(1183 feet/year). 2.1.4 Detection Monitoring Program Field and laboratory results for the groundwater monitoring wells for the first quarter 2006 are summarized in Table 2-2 and Appendix D presents time-series charts of select inorganic parameters. As shown on Table 2-2,dichlorodifluoromethane(DCDFM), tetrachloroethene(PCE), and trichlorofluoromethane(TCFM),were measured at estimated trace levels(between the method detection limit[MDL] and the practical quantitation limit [PQL])in the sample collected from well MW-10;trace levels of 1,1- dichloroethane(1,1-DCA), cis-l,2-dichloroethene(cis-1,2-DCE),trichloroethene(TCE), and a low level of PCE were measured in the sample collected from well MW-14; acetone was measured in the sample collected from well MW-19; and a trace-level of carbon disulfide was measured in the sample collected from well MW-23R. 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 Landfill are most likely due to landfill gas from unlined unit WMU-B. Forward has continued to minimize gas related impacts to groundwater by minimizing 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. New Historical Intrawell Maximum Values The results of the first quarter 2006 monitoring period indicate that 13 new historical intrawell maximum values were measured, including one first-time VOC detection, in samples collected from groundwater monitoring wells. D:\2003_021\ForwardAustin_w06.doc\4/20/2006 6 Geologic Associates