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The groundwater elevation data obtained during the second quarter 2011 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-northeast towards the Austin Unit, at an average hydraulic gradient of approximately 0.002 ft/ft. However, a south-southwest gradient of 0.009 ft/ft was calculated in the northwest comer of the Forward 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). An estimated groundwater flow velocity was calculated using Darcy's Law: Ki cell 0.002 Sec - li - = 1(0,04 ----)* - 2835 0.648 ft , daY lie sec 0.35 cin - daY where: V=Groundwater flow velocity. K=Hydraulic conductivity of the water-bearing unit(0.04 cm/sec). i=Hydraulic gradient: i�0.002 for the site during the second quarter 2011. n,=Effective porosity(n,=0.35);an estimated value. The groundwater flow rate is calculated to be 0.648 feet/day (237 feet/year). 2.1.4 Detection Monitoring Program Field and laboratory results for the groundwater monitoring wells for the second quarter 2011 are summarized in Table 2-2. The organic results for the Forward Unit indicate that the following VOCs were measured at estimated trace concentrations (between the method detection limit [MDL] and the PQL), dichlorodifluoromethane (DDFM) and Trichlorofluoromethane (TCFM) in the sample collected from well MW-10; and 1,1- dichloroethane (1,1-DCA), cis-1,2-dichloroethene (cis-1,2-DCE),tetrachloroethene (PCE),trichloroethene (TCE), and TCFM in the sample collected from well MW-14. In addition, diisopropyl ether(DIPE) was measured above the PQL in the sample collected from well MW-2A. 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. The particular VOCs detected in samples during the current monitoring period appear to support this conclusion. 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, and make adjustments to the LFG wells. W201 1_0050\FA_2Q I Ldocx 5 Geologic Associates