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Excluding confirmed laboratory contaminants, 12 VOCs were measured in CAP wells
<br /> during the current monitoring period,with the greatest number of VOCs (four)measured
<br /> above the PQL in the sample from well AMW-19B.
<br /> In order to evaluate the effectiveness of corrective action measures,particularly with the
<br /> GTF, trend analyses were performed for CAP wells at the Austin Unit,beginning in 1994
<br /> when the GTF began operation. The observed groundwater quality constituent trends
<br /> were 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 are summarized below. Wells and analytes
<br /> not discussed below either do not show significant trends(rising or falling) or have too
<br /> few data points to establish meaningful trends. As shown in the following table
<br /> statistically significant increasing trends were noted for VOC constituents in CAP wells
<br /> AMW- and -10,while decreasing trends were noted for several VOCs in CAP
<br /> well -11.
<br /> Well Increasing Trends Decreasing Trends
<br /> Number
<br /> AMW-1 Barium,Bicarbonate,Specific Conductance, Chloride,Nitrate-N,pH,Sulfate,
<br /> cis-1,2-DCE,Vinyl Chloride Dichlorodifluoromethane(DCDFM)
<br /> AMW-3 Chloride,Nitrate-N,Specific Conductance gH,Arsenic,Barium
<br /> AMW-4 None Apparent Barium,Chloride,Strontium,
<br /> Calcium,Magnesium,Potassium
<br /> AMW-5 Chloride,Nitrate-N,pH,Specific Conductance, None Apparent .
<br /> Sulfate,TDS
<br /> AMW-10 Specific Conductance,Sulfate,cis-1,2-DCE,TCE Trichlorofluoromethane TC
<br /> AMW- None Apparent Calcium,Chloride,Magnesium,
<br /> TDS,cis-1,2-DCE,DCDFM,PCE
<br /> AMW-19 Strontium,TDS Arsenic
<br /> The presence of cis-1,2-DCE suggests natural dechlorination is occurring in the vicinity
<br /> of wells AMW-1 and AMW-10. As summarized in the Annual Corrective Action
<br /> Evaluation prepared by Herst&Associates (2006), the overall groundwater quality at the
<br /> site is improving.
<br /> 3.1.6 Domestic Well Monitoring
<br /> Two domestic wells(7898-A and 8106-A)were sampled on August 29, 2006. Table
<br /> 3-3 summarizes the current analytical results for the domestic well samples collected.
<br /> Excluding confirmed laboratory contaminants, three VOCs (DCDFM,PCE, and TCE)
<br /> were measured above the PQL in the samples from domestic wells 7898-A and 8106-A.
<br /> In addition, two VOCs(1,1-DCA and cis-1,2-DCE)were measured at estimated trace
<br /> levels in the samples from domestic well 8106-A.
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<br /> D:N2003 021\FwwardAusNn sam06.doc
<br /> 12 Geologic Associates
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