Laserfiche WebLink
09/02 '00 WED 15 47 FAX 19289469968 ERIWEST WC I1020 <br /> P AGE 3 <br /> (1,24DCA), 0,5-trimethylbenzene (1,3,5-TMS),and 1,2,4- <br /> tnmethylbenaene (1,2,4-TMB)2 <br /> All of these constituents are commonly associated with weathered <br /> gasoline, and all of these constituents were considered constituents of <br /> potential concern for the purposes of the HRA <br /> Soil and ground water data for the subject properties included analysis of <br /> total petroleum hydrocarbons(MPH). However, both ASTM (1996) and <br /> USEPA, (1989) recommend Oat evaluation of chemical nuxtures should <br /> focus on specific chenucal constituents(e g, benzene)that may be present, <br /> rather than on an evaluation of the chernncal mixture_ Thts <br /> recommendation is based on the following <br /> a The toxiaty of mixtures may be highly variable,particularly in the case <br /> of weathered materials such as those present at these saes <br /> a Little informakaon is available to characterize the toxicity of nuxtuzes <br /> o The toxicity of mixtures is largely related to the presence of specific <br /> constituents. <br /> For these reasons, ittis HRA focused on an evaluation of the specific <br /> constituents present(e g,benzene) However,with regard to the TPH <br /> detections, it is worth noting that weathering appears to have resulted in <br /> the loss of the more volatile(and typically more toxic)fractions,as <br /> reflected in the most recent sampling event Furthermore,its will be <br /> discussed w the following section, the opportunity for any exposure to <br /> constituents of potential concem is limited both by land use and by the <br /> infrequent occurrence of residual compounds <br /> IIDENTIFICA7 ON OF REALISTIC EXPOSURE PATHWAYS <br /> The following subsections describe land use information for the subject <br /> properties, discuss potential exposure pathways for soil and ground <br /> water, and summary ze the realistic exposure pathways for the subject <br /> properties. <br /> ' Edentifuabon of these compounds was based on mformation provided alt the <br /> Closure Report(ERM,-1999)regarding the results of ground water samptmg <br /> conducted after oxygen regenerat ng compounds were introduced into the <br /> moruto nng system to enhance natural degradatson processes <br />