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Water Quality Monitoring Report <br /> Forward Landfill <br /> (Appendix F). The groundwater elevations were calculated for each well by subtracting <br /> the depth-to-water measurement from the top-of-casing reference elevation. The <br /> current groundwater elevation data for the Austin Unit are summarized in Table 3-6. <br /> The groundwater elevation data obtained during this quarterly monitoring period were <br /> used to generate the groundwater elevation contour map shown on Figure 3-1, which <br /> indicates that groundwater generally flows to the north with hydraulic gradients ranging <br /> from 0.001 to 0.002 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 0.002 sec— ft <br /> V = —_ R0.04—)* ]*2835 z 0.648 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 gt 0.002 at the site during the second quarter 2015. <br /> ® ne= Effective porosity (ne= 0.35); an estimated value. <br /> The maximum groundwater flow rate is calculated to be 0.648 feet/day (237 feet/year). <br /> 3.1.4 Detection Monitoring Program <br /> Field and laboratory results for the Austin Unit DMP wells for the second quarter 2015 <br /> are summarized in Table 3-1. <br /> Non-Statistical Data Analysis <br /> During the second quarter 2015 monitoring period, the CNSDAM was performed for <br /> VOCs detected in the DMP wells. As shown in Table 3-1, non-statistical indications of a <br /> release were identified at well AMW-6 as a result of a quantifiable concentrations of <br /> PCE, and trace-level concentrations of trichloroethene (TCE) and DCDFM. Forward had <br /> previously requested that well AMW-6 be reclassified as a CAP well, since similar <br /> concentrations have been historically measured in this well. There were no other VOCs <br /> detected in DMP wells for the Austin Unit. <br /> Concentration Limit Thresholds <br /> In accordance with RWQCB Order No. 115-2014-0006, the routine inorganic monitoring <br /> data obtained from the Austin Unit DMP wells during the second quarter 2015 <br /> M:\2015.0014\FA 2Q15.docx 10 <br /> 7/31/2015,Rev.0 <br />