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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 beneath the Austin Unit generally flows to the north-northwest <br />at an average hydraulic gradient of approximately 0.0025 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 0.0025 sec - ft <br />V =-=[(0.04-)* ]*2835 � 0.81 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 � 0.0025 for the site during the current the fourth quarter 2006. <br />ne= Effective porosity (ne = 0.35); an estimated value. <br />The groundwater flow rate is calculated to be 0.81 feet/day (296 feet/year). <br />3.1.4 Detection Monitoring Program <br />Field and laboratory results for the DMP wells for the fourth quarter 2006 are <br />summarized in Table 3-1 and time -series plots are presented in Appendix D. As shown <br />in Table 3-1, excluding suspected laboratory contaminants, two VOCs were measured in <br />DMP well AMW-13 with PCE measured above the PQL; and four VOCs were measured <br />in DMP well AMW-14, all measured above the PQL. For the DMP wells at the Austin <br />Unit, CLs are used for the water quality protection standards (WOPS). The CLs shown <br />in Table 3-1 were calculated by Herst & Associates using Sanitas , a state -approved <br />statistical software program. Based on a comparison of the data obtained during the <br />fourth quarter 2006 monitoring period, the following analytes were found to equal or <br />exceed a CL. The results of the statistical analyses performed by Herst & Associates are <br />presented in Appendix D. <br />CONSTITUENT <br />Concentration <br />Limit <br />DMP MONITORING WELL <br />AMW-2a I AMW-6 I AMW-7 AMW-12 I AMW-13 <br />I AMW-14 <br />ONITORING PARAMETERS (m <br />H 8.372 <br />1 8.44 <br />arium 0.2465 <br />1 1 10.260 <br />hromium, Hexavalent 0.005126 <br />0.0061 0.015 <br />VOLATILE ORGANIC COMPOUNDS <br />1,2-Dichloropropane 0.5 <br />0.54 <br />romoform 0.5 0.78* <br />1.2* 1.8* <br />ibromochloromethane 0.5 0.56* <br />1.2* <br />chlorodifluoromethane 0.5 <br />0.56 <br />etrachloroethene 0.5 <br />1.5 <br />8.8 <br />richloroethene 0.5 <br />1 <br />1.1 <br />NOTES: (B) - Background Well. <br />(j) - Trace Value (between MDL and PQL). <br />(*) - Suspected Laboratory Contaminant <br />n <br />D:\2003_021\ForwardAusdn_f%.doc\ <br />10 Geologic Associates <br />