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® during the second quarter 2006 monitoring period, only the bicarbonate concentration in
<br /> well AMW-13 exceeded a concentrations limit.
<br /> Well Number Increasing Trends Decreasing Trends
<br /> AMW-2 Nitrate-N,Magnesium,Specific Conductance Arsenic
<br /> AMW-6 Bicarbonate,Chloride,Nitrate-N Sulfate
<br /> AMW-7 Barium,Chloride,Nitrate-N,Specific Arsenic
<br /> Conductance,TDS
<br /> AMW-12 Barium,Bicarbonate,Hexavalent Chromium Arsenic,Chloride
<br /> AMW-13 Bicarbonate,cis-1,2-DCE,PCE,TCE Potassium,Nitrate-N
<br /> AMW-14 Calcium,Magnesium,Potassium,Sodium, Chloride,Specific Conductance,
<br /> Strontium Sulfate,TDS,PCE,TCE
<br /> 3.1.5 Corrective Action Program
<br /> Field and laboratory results for CAP wells for the second quarter 2006 are summarized in
<br /> Table 3-2. Data were graphed on time-series concentration plots by Herst&Associates
<br /> from data collected through the second quarter 2006, and are presented in Appendix D.
<br /> As shown in Table 3-2, 17 VOCs were measured in CAP wells during the current
<br /> monitoring period,with the greatest number of VOCs(four)measured above the PQL in
<br /> the samples from wells AMW-10 and AMW-11.
<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-1 and AMW-10,while decreasing trends were noted for several VOCs in CAP
<br /> well AMW-11.
<br /> Well Number Increasing Trends Decreasing Trends
<br /> AMW-1 Bicarbonate,Specific Conductance,cis-1,2-DCE; Chloride,Nitrate-N,pH,
<br /> Vinyl Chloride Sulfate,DCDFM
<br /> AMW-3 Chloride,Nitrate-N,Specific Conductance pH,Arsenic,Barium
<br /> AMW-4 None Apparent Chloride,Strontium,Calcium,
<br /> 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 TCFM
<br /> AMW-11 None Apparent Chloride,Magnesium,TDS,
<br /> cis-1,2-DCE,DCDFM,PCE,
<br /> TCFM
<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 /> D:12003_021\ForwardAusBn_sp06.doc
<br /> 12 GeoLogic Associates
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