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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 = — _ [(0.04 —)* ]* 2835 � 0.65 ft /day <br /> ne sec 0.35 cm – dnv <br /> where: V=Groundwater flow velocity. <br /> K=Hydraulic conductivity of the water-bearing unit(0.04 cm/sec). <br /> i=Hydraulic gradient:i-&0.002 for the site during the current the fourth quarter 2008. <br /> ne=Effective porosity(ne=0.35);an estimated value. <br /> The groundwater flow rate is calculated to be 0.65 feet/day(237 feet/year). <br /> 3.1.4 Detection Monitoring Program <br /> Field and laboratory results for the DMP wells for the fourth quarter 2008 are <br /> summarized in Table 3-1 and time-series plots are presented in Appendix D. As shown <br /> in Table 3-1, a trace concentration of 1,1-DCA was measured in the sample collected <br /> from well AMW-13 and trace concentrations of carbon disulfide were measured in the <br /> samples collected from wells AMW-13 and AMW-14. In addition, PCE and TCE were <br /> measured above the PQL in the samples collected from wells AMW-13 and AMW-14. <br /> For the DMP wells at the Austin Unit, CLs are calculated for the water quality protection <br /> standards(WQPS). The CLs shown in Table 3-1 were calculated by Herst&Associates <br /> using Sanitas®, a state-approved statistical software program. Based on a comparison of <br /> the data obtained during the fourth quarter 2008 monitoring period, the following <br /> analytes were found to exceed a CL. The results of the statistical analyses performed by <br /> Herst &Associates are presented in Appendix D. <br /> CONSTITUENT Concentration DMP MONITORING WELL <br /> Limit AMW-20 AMW-6 AMW-7 I AMW-13 AMW-14 <br /> MONITORING PARAMETERS(m 1) <br /> Barium 1 0.242 1 0.26 <br /> hromium,Hexavalent 1 0.005 0.0055 0.0055 <br /> OLATILE ORGANIC COMPOUNDS(It ) <br /> etrachloroethene 0.5 3.8 17 <br /> richloroethene 0.5 1.1 1 1.2 <br /> NOTES: (B)-Background Well. <br /> DMP- Trend Analyses <br /> In order to evaluate changes in water quality in DMP wells at the Austin Unit,historical <br /> trends in groundwater were evaluated beginning in 1994 when the groundwater treatment <br /> facility began operation. The observed groundwater quality constituent trends were <br /> evaluated using Sen's Slope trend analyses to determine if significant increasing or <br /> decreasing trends were evident in the data. Trend analyses,performed by Herst& <br /> Associates, are presented in Appendix D and summarized below. Wells and analytes not <br /> D:\2008_0o10\FA_4Q08.doc <br /> 10 Geologic Associates <br />