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ttt3-dtl-ly`S! 11;Id 4bWKt_tVt U_zHN WHItK VKL;dr-7 <br /> � Forster TexACO,Z..odi a� <br /> Fast 3 <br /> Dissolved benzene concentrations measured onsite and dow.ugradient have been <br /> consistently low to"nem- "' The maximum ever measured Many monitoring <br /> well was 120 Ppb,which in and of.tself indicates "low risk" given the 2,0100 ft <br /> upgradient distance to the nearest well. Recurring "no -detect"levels in all <br /> monitoring wells indicate law residual risk. <br /> fteparted historic trends ofzmarginal to"non-detect"B,TEX concentrations furEher <br /> indicate that residual pet [eum deposits in subsurface;:soil are not leaching <br /> sigmficatlt Of eve detectable}ctmcentrations into underlying groundwater.. <br /> Reliance by iZejgivn l i o8rO.sfff on a theoretical leaching model to suggest <br /> dete+Ctabte leachate gener86011 from residual fuel hydrocarbon onstituents rn soils <br /> tori mace.infiltration and percolation (the site his beef paved for nearly tv�'o <br /> codes)is inccrosts°tom#mj6verified,empirical data+established aver Overal.years <br /> of exgsen ve m[ tering and analysis": <br /> j <br /> There is no substanttial. vidence in the record to indicate that.formrter relies at the <br /> r <br /> Tog site contn'b�ted or would be expected to coot butt,to dere ole <br /> concwmtrations of dichlotoed ane in groundwater rap ,down-,artd cross-gmdient of <br /> the-site(which thr+ t h ng.fault of is own lies`vvithin a more a. vasive 4hlarinated <br /> �.. <br /> solventsplume). I. to its fate and transport properties ht8herr mobility in <br /> oundwater thaun benzene and less tendency to adsorb to soil particles than <br /> r <br /> benzene)it is likely that over the decades dichloroethane(if any Diad originated <br />:. <br /> nnsrte)would havetlspersed in groundwater longasci Given thefact that <br /> didhloroetI is mare mobile and is much less likely to adsorb to soil and that at <br /> least 2.0 yearsi: elapsed since any leakage might leve occurred,it is unlikely <br /> than deteetab a concentrat.ons-of dichloroethane would continue to exist in the <br /> i subsurface even ifs some may have originated at the site.: <br /> r <br /> Thus,a further sea ch for detectable concentrations of dichloroethanc in soil(or <br /> groundwater)beneath the Togo's site offers little water quality benefit- Further <br /> investigation may reduce "uncertainty"over whether(1) dichloroethane was <br /> present at sufTic ient proportion in the particular fuels;which may have leaked at <br /> this site during its 5 0 year operational history through 1977 ,(2)detectable residual <br /> concentrations-have remained far at least 20-plus years despite high mobility,and <br /> (3)that a sufficient adsorbed mass of"immobile" dichloroethane has nevertheless <br /> continued for two decades to add measurably to the)i idespread chlorinated <br /> solvents plume endanating from upgradent sources. ` <br />� i <br /> In my opinion,the evidence accepted by the County that dichloroethane is-a <br /> predicted and widespread component of the solvents,1111plume overwhelms any <br /> t <br /> g raj OW mission is to pmnerve;gnd cnhtt we the gustily of C(d0rrutt s water resources.and <br /> ptstrsa l iz prp �allocation slut efficient ase for the beet-fit of prescnt;ttnd future genereatiam <br /> r <br /> x <br /> i <br /> 4.. 1 <br />