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detects (carbonate alkalinity, oil and grease, volatile petroleum hydrocarbons, and
<br />VOCs), trend evaluations were performed on data from the earliest detection through the
<br />present. The observed groundwater quality constituent trends were evaluated using
<br />Mann -Kendall / Sen's Slope trend analyses to determine if statistically significant
<br />increasing or decreasing trends were evident in the data. Trend analyses, performed by
<br />Herst & Associates, are presented in Appendix D and summarized below. Wells and
<br />analytes not discussed below either do not show significant trends (rising or falling) or
<br />have too few data points to establish meaningful trends.
<br />Well
<br />Increasing Trends
<br />Decreasing Trends
<br />Number
<br />AMW-2
<br />Bicarbonate, Nitrate -N, Specific
<br />None Apparent
<br />Conductance
<br />AMW-6
<br />Barium, Chloride, Magnesium, Nitrate -N,
<br />None Apparent
<br />pH, Specific Conductance, Strontium, TDS
<br />AMW-7
<br />Bicarbonate, Calcium, Chloride,
<br />Hexavalent Chromium, Potassium
<br />Magnesium, Nitrate -N, Specific
<br />Conductance, Sulfate, TDS
<br />AMW-12
<br />None Apparent
<br />Calcium, Chloride, Strontium
<br />AMW-13
<br />Bicarbonate, Sulfate
<br />Chloride, Nitrate -N, 1,1 -DCA
<br />AMW-14
<br />Barium, Calcium, Chloride, Hexavalent
<br />DCDFM, PCE, TCE
<br />Chromium, Magnesium, Nitrate -N,
<br />Potassium, Sodium, Strontium, Sulfate
<br />Notes: l,1 -DCA —1,1-dichlorethane cis-1,2-DCE—cis-1,2-dichloroethene DCDFM— Dichlorodifluoromethane
<br />With the exception of barium and chloride concentrations measured in well AMW-14, no
<br />constituent that exhibited a statistically significant increasing trend during the third
<br />quarter 2012 monitoring event also exceeded their concentration limits. It should be
<br />noted, however, that the barium and chloride concentrations measured in the sample
<br />collected from well AMW-14 (0.280 mg/L and 100 mg/L, respectively) are within the
<br />historical range of values observed at this well. No increasing trends were noted for
<br />VOC constituents in the DMP wells. However, one or more decreasing trends were
<br />noted for VOCs in wells AMW-13 and AMW-14.
<br />Corrective Action Program
<br />Field and laboratory results for CAP wells for the third quarter 2012 monitoring period
<br />are summarized in Table 3-2. As shown in Table 3-2, 14 VOCs were detected in CAP
<br />wells during the current monitoring period. Well AMW-1 had the greatest number of
<br />VOCs with seven measured above their PQLs.
<br />Trend Analyses
<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. For constituents
<br />whose historical data consists primarily of non -detects (carbonate alkalinity, oil and
<br />grease, volatile petroleum hydrocarbons, and VOCs), trend evaluations were performed
<br />on data from the earliest detection through the present. The observed groundwater
<br />CA2012-0025TA3Q12.doc 10 Geo -Logic Associates
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