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based on lower groundwater levels associated with observed pumping from adjacent <br /> agricultural wells, groundwater during the fourth quarter 2007 monitoring period appears <br /> to flow in a radial pattern from the center of the Forward Unit at a gradient ranging from <br /> 0.003 to 0.005 ft/ft. <br /> To calculate the approximate linear groundwater flow velocity for the site, conservative <br /> assumptions were used, including a hydraulic conductivity of 875 gallons per day per <br /> square foot(0.04 cm/sec) and an estimated effective porosity of 35 percent (CH2M Hill <br /> 2000). An estimated groundwater flow velocity was calculated using Darcy's Law: <br /> Ki cm 0.005 sec–ft <br /> V = _ [(0.04 —)* 1-2835 1.62 ft/day <br /> ne sec 0.35 cm –day <br /> where: V=Groundwater flow velocity. <br /> K=Hydraulic conductivity of the water-bearing unit(0.04 cm/sec). <br /> i=Hydraulic gradient: i�0.005 for the site during the fourth quarter 2007. <br /> ne=Effective porosity(ne=0.35);an estimated value. <br /> The groundwater flow rate is calculated to be 1.62 feet/day(591 feet/year). <br /> 2.1.4 Detection Monitoring Program <br /> Field and laboratory results for the groundwater monitoring wells for the fourth quarter <br /> 2007 are summarized in Table 2-2 and Appendix D presents time-series charts of select <br /> parameters. As shown on Table 2-2, estimated trace VOC constituent concentrations <br /> (between the method detection limit [MDL] and the practical quantitation limit[PQL])of <br /> 1,1-dichloroethane(1,1-DCA), dichlorodifluoromethane(DCDFM), and <br /> trichlorofluoromethane(TCFM) were measured in the sample from well MW-10; and <br /> 1,1-DCA and trichloroethene(TCE) were measured in the sample from well MW-14A. <br /> In addition, PCE was detected above the PQL in the sample collected from well MW-14. <br /> On behalf of Forward Inc., GLA prepared a letter report dated February 14, 2001 <br /> (RWQCB Case No. 2209), to assess the source and potential impacts of low-level VOCs <br /> in groundwater adjacent to the Forward Landfill. The letter report concluded that the <br /> sporadic detection of low-level VOCs in groundwater(and lysimeter samples) at the <br /> Forward Unit are most likely due to landfill gas from unlined unit WMU-B. Forward has <br /> continued to minimize gas related impacts to groundwater by limiting interim fill areas <br /> that promote ponding of water. Furthermore, in accordance with CCR Title 27, Section <br /> 20937, Forward continues to install additional landfill gas extraction wells, as needed. <br /> D:\2007_0043\Fo—a rd Au sdn_4Q07.doc <br /> 5 Geologic Associates <br />