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® 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 />discussed below either do not show significant trends (rising or falling) or have too few <br />data points to establish meaningful trends. As shown in the following table, of the <br />detected VOCs, increasing trends were noted for PCE in DMP well AMW-13, while <br />decreasing VOC trends were noted for PCE and TCE in well AMW-14. <br />Well Number <br />Increasing Trends <br />Decreasing Trends <br />AMW-2 <br />Nitrate -N, Specific Conductance <br />Arsenic <br />AMW-6 <br />Barium, Bicarbonate, Chloride, Nitrate -N <br />Sulfate <br />AMW-7 <br />Bicarbonate, Chloride, Nitrate -N, <br />Specific Conductance, TDS <br />Arsenic <br />AMW-12 <br />Bicarbonate, Hexavalent Chromium <br />Calcium, Chloride, Magnesium <br />AMW-13 <br />Bicarbonate, PCE <br />Nitrate -N, Potassium <br />AMW-14 <br />Calcium, Magnesium, Potassium, <br />Sodium, Strontium <br />Chloride, Specific Conductance, <br />Sulfate, TDS, PCE, TCE <br />0 3.1.5 Corrective Action Program <br />Field and laboratory results for CAP wells for the fourth quarter 2006 monitoring period <br />are summarized in Table 3-2. Data were graphed on time -series concentration plots by <br />Herst & Associates from data collected through the fourth quarter 2006, and are <br />presented in Appendix D. As shown in Table 3-2, excluding suspected laboratory <br />contaminants, 13 VOCs were measured in CAP wells during the current monitoring <br />period, with the greatest number of VOCs measured above the PQL (seven) in the sample <br />from well AMW-1. <br />In order to evaluate the effectiveness of corrective action measures, particularly with the <br />groundwater treatment facility (GTF), trend analyses were performed for CAP wells at <br />the Austin Unit, beginning in 1994 when the GTF began operation. The observed <br />groundwater quality constituent trends were evaluated using Sen's Slope trend analyses <br />to determine if significant increasing or decreasing trends were evident in the data. Trend <br />analyses, performed by Herst & Associates, are presented in Appendix D and are <br />summarized below. Wells and analytes not discussed below either do not show <br />significant trends (rising or falling) or have too few data points to establish meaningful <br />trends. As shown in the following table significant increasing trends were calculated for <br />VOC constituents in CAP wells AMW-1 and AMW-10, while decreasing trends were <br />calculated for VOCs in CAP wells AMW-1, AMW-4, and AMW-11. <br />D:\2003_021\ForwardAustin i06.doc\ <br />11 Geologic Associates <br />