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® The groundwater elevation data obtained during this quarterly monitoring period were used to generate the groundwater elevation contour map shown on Figure 3-1, which indicates that groundwater beneath the Austin Unit generally flows to the northwest and northeast at a hydraulic gradient ranging from 0.002 to 0.004 ft/ft. To calculate the approximate linear groundwater flow velocity for the site, conservative assumptions were used, including a hydraulic conductivity of 875 gallons per day per square foot (0.04 cm/sec) and an estimated effective porosity of 35 percent (CH2M Hill 2000). An estimated groundwater flow velocity was calculated using Darcy's Law: V = Kt = [(0.04 cm )* 0.004 1* 2835 sec— ft z 1.30 ft /day ne sec 0.35 cm — day where: V=Groundwater flow velocity. K=Hydraulic conductivity of the water-bearing unit(0.04 cm/sec). i=Hydraulic gradient: i=�0.004 maximum for the site during the second quarter 2013. ne=Effective porosity(ne=0.35);an estimated value. The maximum groundwater flow rate is calculated to be 1.30 feet/day(473 feet/year). Detection Monitoring Program Field and laboratory results for the Austin Unit DMP wells for the second quarter 2013 are summarized in Table 3-1. Non-Statistical Data Analysis The non-statistical VOC water analyses performed on the DMP well data indicates that there were three non-statistical exceedances for VOCs. The non-statistical exceedances were identified at well AMW-6 as a result of the detection of tetrachloroethene (PCE) above the PQL and dichlorodifluoromethane (DCDFM) and trichloroethene (TCE) at estimated trace concentrations; at well AMW-13 as a result of the detection of DCDFM, PCE, and TCE at concentrations above the PQL and cis-l,2-dichloroethene (cis-1,2- DCE) and trichlorofluoromethane (TCFM) at estimated trace concentrations; and for well AMW-14 as a result of the detection of PCE above the PQL. Trend analyses indicate that statistically significant increasing temporal trends were calculated for PCE and TCE in well AMW-13 and a statistically significant decreasing temporal trend was calculated for PCE in well AMW-14. Trend analyses are included in Appendix D. These results are similar to previous results and it is recommended that wells AMW-6, AMW-13, and AMW-14 be re-designated as CAP wells since they have historically contained VOCs. Concentration Limit Thresholds As specified in RWQCB Order No. R5-2003-0049 the routine monitoring parameters ® obtained during the second quarter 2013 monitoring period were compared to interwell CLs established for the Austin Unit DMP wells. The CLs shown in Table 3-1 were C:U013-0021\FA_2Q13.doc 9 Geo-Logic Associates