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Z, <br />{[ 's�w ,.s' L �' '-� '� e� y -� �'-.3f�! i - Y - f' 'f -•xie� y -� - � y ti,,. �r tix <br /> fY7 1. 3 Y <br /> f 19..May 1997 <br /> - <br /> AGE--NC_ Project No 95 0128x <br /> Page 3 of 4': <br /> _ _ x. x-!' k Y rp ;- .. ', r ��:J.,.. - k.r ��..-i .F ai.��.. :'�-� s 3t •�-y�; a�7 �: <br /> WE <br /> �. ,``.�f � _-r:c:.x .'.a•✓ � ..' -. . `�. _. _.,_ : s � '� a.Y {"-. y yfi- ,. � a - <br /> ' 4.0. ;CONCLUSIONS�AND RECOMMENDATIONS 'ter ' �}} <br /> N-'n _ <br /> 4.1 �CONCLUSIONS fes ♦ i1 <br /> - <br /> Fr The following conclusions were drawn m frothe results of this quarters investigation <br /> The:highest'concentration',of'disolved hydrocarbons quantified as TFH g'and TPH d <br /> - _ w <br /> - r <br /> - continues to be located iri the vicinity of well VW l located down"gradient_(northeast) of : <br /> �, „ a _, s <br /> , the former UST exca'vaGon However;con centratFons of MTBE and benzene decreased in <br /> vapor well VViW 1 between February acid Apri1;1997 <br /> Y "• 'Noteworthy,was the.increased concentration of drssolved;} ydrocairboris`in monitoring well r x <br /> ' _MW�6; 'located doert-gradrent (north�northwest) af vapor swell UW=1 The increased <br /> cozrcentratron§-of dissolved Hydrocarbons maybe ah indication that the dis5olveil petroleum; <br /> . hydrocarbon"plume is-not'.stable and. has,:began n to=:migrated:`northward towar FIs the <br /> Ts ycDonalds`site Also,'nsizig ground water may b'e-encountering more hydrocarbon rmpacted� <br /> -x n :JBI Tsoil; causing' increased dissolution of the fuel hydrocarbons into the:-grout water. The <br /> movement'of the-hydrocar-bon's=;off site;poses a greafer level of difficulty in Zrt <br /> y _mrtrgatin_ g th_e dissolved hydrocarbon plu_ ine:; <br /> • The concentration of dissolved hydrocarbons rn monitoring well iVIW increased over the J <br /> -' <br /> last quarter; again suggesting that the.petroleum hydrocarbon`'glume`is not'stable and js:. <br /> nirgrating northeastward off site under;the City,of.;Stockton right of way Because=of the. <br /> - <br /> „ ' <br /> movement' the-$ydrocarbons off site itis likely.that the.PHS EHD will require additional': ° =.*4 <br /> .4 down gradrerit.wells.;to.assess the-lateral extent of the dissolved by drocarbon pltu� edr <br /> {` = <br /> c � -TE <br /> .� y <br /> It is likely that well-MW-7 7 represents the westem";edge•of the dissolved TPH g ai d-'BTE&X. <br /> - <br /> plume and'that-well 1vIW 4 is closest`.to the easterTr edge of the dissolved'TPI-1 'g and BTE&X <br /> Y `r plume It-appears'tha dissolved lVITBE plume extends further'Soff site west and north <br /> Monitoring well MW 4 now a ears to--be the nearer to eastern ed e of the MTBE �.pme h .- <br /> _ .�, pp _ g p <br /> -4. O _ Y <br /> * a. NS <br /> 2 RECOMMENDATIes <br /> re - <br /> Based on the results of this investigation,_AGE.-recornmends�_thllowinge foQ *� d a <br /> -• If determining the,7ateral extent of the off site migration of_arssolved hydrocarbons,rs <br /> ' required;,the iristal_Iatron of-additional•ground water monitoring welIszwll be required sE ` <br /> �x ­• The collection.and;field screerurrg:ofgrab ground water,sarnples should be performed-prior` n <br /> to urstaliatron of any_riew niomtoring wells Addrtror ai well:Iocatrons should�be determined <br /> r ti ,q <br /> €: tl <br /> # .� <br /> � :' � i t-T}a -- �� - + '!a`' :, --�Y�•a. � -: --� � i,s T� - .fir <br /> T <br /> .:.....__,:a..-Y,t<r,t'..;' . r: 'r.9:"; .:.�. r* ..:.. }(,,,�,':�"�,.-,r�',.:.-.K"�-�,✓".1'•� «. .:.r't-:,'.S�F:"'�'`a ti,_...- tr".,'.�'.w. � �.:_.' Vie' ..3�4 . .5�.._._._ _ <br /> a <br />