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41 I In❑c i,Iluid�.IE', fnt�tI II-OU K 71117
<br /> 1IITIT uI EI I 1 \1innI
<br /> I ,I X161 iAl(,
<br /> I IatLrall\ Ind \Lr1IL,lli\ LxtL1is1%L Lla\ horrion In HIL tilts subsurtaLL (that would ',enc, to halt \Lrt)LJl
<br /> mil,rat ion tit thL Lont uTil7lant',) IhLretorL \\,:s 110t oh,Lr\ed nor undiLat(,d
<br /> 1lthou h Lcini2nln� unit flatLlall\ Ind \Lr11L 111\ L\1Lri,I\L \\1th higli Llay LtintLnt} I, not hrL,Lnt at thL
<br /> 111I1 ill\ i€I cel thL 1uh',urfaLL I', Lc11111)0SL�d (il ,I rLlali\LI\ tight 1111L-Lrdim-d matrix that ',11011ld SLr\L
<br /> to 11111:111 thL \Lrt1L it imuratlon 01 Lnntamui,Int, I hL lahoratorN allal\tiLal result,, of thL ,oil and
<br /> I_li\unrl\\JILI M(fiLatL th it 0111\ 11 ILL LonLL?ItI,Itrorzs of \11131 Iirk, prLscnt r!n ground\\atLr from
<br /> lh1 dLLpLI ',till ,ti,Ita It thL IOLatlon', In\L,rteatLd
<br /> HIL IL,Itlts 0t 1111 a it anti around\\a1Lr III\L',tlt~at101I IndiL,ttc shat thL Yl 1131 lunnc "WiLiall\ L\1Lnds 111
<br /> �- p � _
<br /> I ILI,It1\ely IoM LonLLntratlons 111 ,hallow IIrotindwatLr beyond the drainage claul and Into 111L agriLultural
<br /> FILld to the La',t nt thL ,11L l,o-ulnLLntratsori LOntours for M f BE in ,hallow groundwatLr arL ,hown in
<br /> FlgurL S '\ppendlx A R(Jativi-N high M 1'131 LonLentrations arc. present in shallow groundwatLr to thL
<br /> wLst of tic drainage drtLh southeast of sttc monitor well MW-2 the concentration of MTB: present at
<br /> thL localion of DP-5 is approximately three orders of magnitude greatLr than tileF'
<br /> concentration of M FB
<br /> at the loLatron of DP-9 Mrs rclatively rapid attenuation of MTBE conLentrations suggests that the
<br /> MT131 pltirnL IS bLing truncated by the hydraulic 111f7uence Lxerted by the island drainage Lhanncl
<br /> Ipumping that uLLurs at the south portion oIt the site
<br /> 6 RE( i)NI'V SNDA flON5
<br /> Based 011 thL IL,UIt', of thL IM11 and groundwatLr InvL,tlgatlon ( ondor doLs not rLLOInrnLnd that an
<br /> Lngr11eeied appioaLh to remediation of the 1Vl l B1 PILMIL hL Initiated AlternatsvLly ( ondor
<br /> rlconimLnds IHt-thlr in\e',tigation and monitoring of the apparent leading LdgL of the M 1131 pIu11IL I he
<br /> following ohstr\ations support this approach
<br /> • the. Island diamage channel pumping as discussed above, appears to be largely contiolling the
<br /> M I ill plume at thL site.
<br /> • a hr1-1h petLLntage of MI 131 emanating from the site should be entering the island drainage
<br /> Lhannel and thL pump Intake up to thi- I ittle ( onneLtlon Slough
<br /> • 111011110ring thL impact of thL M 1131- on thL Island drainage Lhannel the drainagL ditLh and the
<br />' potential Impact on the I 1 t1L ( onnection Slough is conducted on a quarterly basis
<br /> • surfaCL watei monitoring results have Indicated that MTBE- is present in water samples
<br />' LOIIeLtLd bLtOrC the island drainage channel pump intake at concentrations that are generally
<br /> I epi ewntative of background water quality often reported for delta waterways,
<br /> • \ertrc al ni Igi ation of'MTBE. at the site appears to be minimal, and
<br /> • no irnrnediatL SLnsitive reLeptors have been Identified to the east of the site
<br />' Foi the reasons Indicated ( ondor beheVLS that turther investigation and monitoring of the down-gradient
<br /> Lxtent ut the M 113F LOntamination is more appropriate than conducting remedial operations beyond what
<br /> Is prc',eptly ocLuirmg at the site Additional extraction and treatment of MTBE at the site would be a
<br /> n
<br /> L«j CONDOi(
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