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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 3)5 percent (CH2M Hill <br /> 2000). An estimated groundwater flow velocity was calculated using Darcy's Law: <br /> Ki flit 0.002 SLC 1't <br /> V — - ­ = 1(004 ----)* ...............Iti-2835 ­---­­11___ 1 20.0fi!d"1v <br /> ne sec 0.35 <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 second quarter 2011. <br /> n,=Effective porosity(n,=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 second quarter 2011 are <br /> summarized in Table 3-1. As shown in Table 3-1, the following VOCs were measured at <br /> trace concentrations: DCDFM and TCE in the sample collected from well AMW-6; 1,1- <br /> DCA, cis-1,2-DCE, and TCFM in the sample collected from well AMW-0; and TCE in <br /> the sample collected from well AMW-14. In addition, the following concentrations were <br /> measured above the their PQL, PCE in the sample collected from well AMW-6; <br /> DCDFM, PCE, and TCE in the sample collected from well AMW-I'); and PCE in the <br /> sample collected from well 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 second quarter 2011 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 /> I Limit AMW-7 I A -121 AMW-13 I AMW-14 <br /> MONITORING PARAMETERS(m /1) — <br /> Barium 1 0.225 0.260 1 0.260 1 0.260 <br /> Chloride 1 77.39 1 85 <br /> Hexavalent Chromium 1 0.004837 0.0050 0.0057 1 <br /> VOLATILE ORGANIC COMPOUNDS(itg/1) <br /> Dichlorodifluoromethane 1 0.5 1 0.68 <br /> Tetrachloroethene 1 0.5 1 0.90 1 1 8.6 1.3 <br /> Trichloroethene 1 0.5 1 1 1 2.2 <br /> D:12011_0050\FA_2Q11.docx <br /> 9 Geologic Associates <br />