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The groundwater elevation data obtained during the third quarter 2012 monitoring period <br />were used to generate the groundwater elevation contour map shown on Figure <br />2-1, which indicates that groundwater generally flows to the northeast towards the Austin <br />Unit, at an average hydraulic gradient of approximately 0.003 ft/ft, although a localized <br />southwest gradient of 0.010 to 0.013 was noted along the northeast perimeter of the <br />Forward Unit. <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 0.003 sec – ft <br />V [(0.04 —) * —] * 2835 — � 0.972 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� 0.003 for the site during the third quarter 2012. <br />n, = Effective porosity (n, = 0.35); an estimated value. <br />The groundwater flow rate is calculated to be 0.972 feet/day (355 feet/year). <br />is Detection Monitoring Program <br />11 <br />Field and laboratory results for the Forward Unit groundwater monitoring wells for the <br />third quarter 2012 monitoring period are summarized in Table 2-2. <br />Volatile Organic Compounds <br />As shown in Table 2-2, tetrachloroethene (PCE) was measured at estimated trace <br />concentrations (between the method detection limit [MDL] and the PQQ in the sample <br />collected from well MW -14 during the third quarter 2012 monitoring period, though PCE <br />was not detected in the duplicate sample <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 />CU012-0025TA 3Q12.doc 5 Geo -Logic Associates <br />