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CONESTOGA:ROVERS <br /> &ASSOCIATES <br /> April 9,2009 Reference No.241511 <br /> -3- <br /> Cost of Operation <br /> During our system performance evaluation we looked at the cost to remove 1,2-DCA and <br /> prepared a graph(Figure 4) which depicts the cumulative costs to operate the GWE system <br /> versus the mass of 1,2-DCA removed. The graph shows that to remove 0.07 pound of 1,2-DCA <br /> we have spent approximately$76,000. Further evaluation of the cost indicates that the median <br /> cost to remove 1 pound of 1,2-DCA at this site would t e approximately$1,338,000. As <br /> mentioned above, as the mass removal rate declines (d e to declining 1,2-DCA concentrations <br /> at the site) the cost per pound to remove 1,2-DCA will increase. This cost per pound indicates <br /> that this is not a cost effective remedial approach for t11 is site. <br /> Summary <br /> We request that GWE system at this site be shutdown for the following reasons: <br /> • Operation of the GWE system has reduced the concentration of 1,2-DCA in groundwater <br /> beneath the site. <br /> • The mass removal rate for this GWE system is very low. <br /> • The GWE system is not cost effective to operat . <br /> CASE CLOSURE REQUEST <br /> Along with reviewing the GWE system performance d recommending shutdown of the <br /> system,we also looked at the need to evaluate alterna ve remedial approaches for this site. We <br /> concluded that additional remediation at this site is no warranted and that case closure may be <br /> appropriate for this site. The reasons for this are press ited below. <br /> • Site investigation activities have been complete at this site and the extent of petroleum <br /> hydrocarbons in soil beneath the site is defined j <br /> I <br /> • Quarterly groundwater monitoring has been performed at this site since January 2003 <br /> and the extent of petroleum hydrocarbons in gi oundwater beneath the site is primarily <br /> limited to the vicinity of well MW-1. All other site wells do not contain,or contain only <br /> low levels of petroleum hydrocarbons. <br /> • 1,2-DCA is the primary contaminant of concern at this site. The horizontal and vertical <br /> extent of 1,2-DCA has been delineated by quarterly groundwater monitoring data and <br /> I <br /> Wa rides de Engineering,Environmentat,Construction,and IT Services <br />