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FORMER AMERICAN FOREST PRODUCTS 3.0 Groundwater <br /> Closure Summary Report July 2009 <br /> URS Project 17322736 Page 3-5 <br /> F <br /> DMW f 1!and non-detect to low concentrations for'DDW -2._Downgradient definition to the north is <br /> provided by consistent near-to-non-detect results for DMW=11, together with the non-detect result of June <br /> 2008 for DMW=10. Lateral plume definition to the northeast is provided by the near-to-non-detect result <br /> ranging from 1 A µg/L to 2.4 pg/L for DMW_12. <br /> 3.3.4 Trends in 1,2-DCA Concentrations <br /> Plots of 1,2-DCA concentrations versus time are presented on Figures 9 through 13. Trend lines based on <br /> a linear regression analysis are shown on these plots together with their equation in the form of y=MX+b <br /> where m is the slope of the line. A negative slope to the trendline is statistically indicative of declining <br /> " <br /> concentrations. The regression analysis shows a declining trend for the'6o �wells in whic�h2'-DCA w�as <br /> consistently r_ orted_(DMW=2;1DMW±5,iDNiW=6 rand.DMW-9).,wTrends shown on Figures 9 and 10 <br /> appear reasonably predictive and indicate that water quality goals would be reached by approximately <br /> X2012. ' <br /> Plots are also included for the five wells installed during the second quarter 2008 (DMW-10 through <br /> DMW-14). These wells were placed to provide lateral and vertical plume delineation. 1,2-DCA was <br /> below detection in the sample collected from DMW-10 in June 2008; however insufficient water was <br /> recovered from that well during the subsequent four quarters of monitoring because of declining water <br /> levels. After five quarters of monitoring that included the remaining four of the five new wells, 1,2-DCA <br /> was detected only for downgradient well DMW-11, and sidegradient well DMW-12.Results have <br /> remained relatively consistent for the four quarters, with 1,2-DCA concentrations for DMW-1 I remaining ' <br /> less than 1 µg/L, and less than 2.5 gg/L for DMW-12. <br /> - 3.3.5 Mass of 1,2-DCA in Groundwater <br /> No active groundwater remediation has been conducted at this site. Steady declines in the concentration <br /> of 1,2-DCA resulted from natural attenuation alone.Inasmuch as the concentration trends for I,2-DCA <br /> are reasonably predictive ofreaching'water qualitygoaWwithin five ye ais or..lee s:aind no.activA <br /> oundwater.remediation was coiiductedit is URS'o inion that no useful <br /> F �__.__. .,.. .�. ;, ,,�...: . p purpose would be served by the <br /> calculations, which would necessarily be approximations. <br /> r. <br /> e <br /> K:1WpraceQs1227361Amcrican ForestlClosure-Summary-RcporS-Rev0l.doc • <br />