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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 />l i CM OMI I sec – ft <br />1' = 1(0.04 —) —I * 2835 q 0 324 .ft ' do <br />lie sec 0.35 arra – clear <br />where: V = Groundwater flow velocity. <br />K = Hydraulic conductivity of the water -bearing unit (0.04 cm/sec). <br />i = Hydraulic gradient: i t� 0.001 for the site during the current the third quarter 2011. <br />n, = Effective porosity (n, = 0.35); an estimated value. <br />The groundwater flow rate is calculated to be 0.324 feet/day (118 feet/year). <br />3.1.4 Detection Monitoring Program <br />Field and laboratory results for the DMP wells for the third quarter 2011 are summarized <br />in Table 3-1. As shown in Table 3-1, the following VOCs were measured at trace <br />concentrations: DCDFM and TCE in the sample collected from well AMW-6; and <br />1,1 -DCA, cis-1,2-DCE, DCDFM, and TCFM in the sample collected from well <br />AMW-13. In addition, the following concentrations were measured above the their PQL, <br />PCE in the samples collected from wells AMW-6, AMW-13, and AMW-14; and TCE in <br />the sample collected from well AMW-13. <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 Sanitase, a state -approved statistical software program. Based on a comparison of <br />the data obtained during the third quarter 2011 monitoring period, the following analytes <br />were found to exceed a CL. The results of the statistical analyses performed by Herst & <br />Associates are presented in Appendix D. <br />CONSTITUENT <br />Concentration <br />Limit <br />DMP MONITORING WELL <br />AMW-6 I AMW-12 AMW-13 I AMW-14 <br />MONITORING PARAMETERS m <br />Barium <br />1 0.2252 1 0.270 <br />1 0.270 1 0.270 <br />hioride <br />74.71 89 <br />92 <br />OLATILE ORGANIC COMPOUNDS ) <br />etrachloroethene <br />0.5 <br />1.1 <br />1 <br />7.2 <br />1.1 <br />richloroethene <br />1 0.5 <br />1 <br />2.0 <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 />C:\zo1a-oo50TA_3Qu.doex 9 Geo -Logic Associates <br />