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Sent by: CDAA/SJUA EPU 209 488 9704; 11116f99 1 :14PM;jeffim_#345;Page 11119 <br /> reason,would likely,i would anticipate it to result in the production of poor quality water that <br /> doesn't meet the State uh drinking water standards on the sea water intrusion issue alone,not to <br /> mention that there are also elevated nitrates background nitrates in the area,so the drinking water <br /> quality in the area is very poor. Viith regard to U'h the soil vapor extraction as an applicable <br /> remedy the high concentrations that were described at the 50 to 60 foot level are below the level <br /> of the groundwater. Soil vapor extraction relies on extracting constituents in the vapor phase, <br /> typically in what's called the unsaturated or wade-zone, uh you would not be able to do that in a <br /> scenario in which the constituents are trapped below the groundwater so soil vapor extraction <br /> alone would not work in this particular scenario l`or the zom that was described. Um this site <br /> because of the limited uh extent of the plume in the continuous monitoring record lbr 9 yearn,it's <br /> consistent with the Lawrence Livermore U.C.Lawrence Livermore report that was conducted on <br /> underground storage tanks on a statewide basis for the State Water Resources Control Board in <br /> 1995 in which I was an author of that report and we deternsined by statistical analysis and <br /> observation of the conditions that existed throughout the State that in over many a similar <br /> hydrogeolic conditions as what we see in the Stockton area that in 90%of the cases the benzene <br /> plume does not extend down v €turn the source for greater than 250 feet,this ease is <br /> consistent with that in which the plume uh benzene plume extends dawn gradient for <br /> approximmtely 140 feet. It's also consistent with other sites that we've worked on in the specific <br /> Stockton area in which we see the same kind of a pattern. That would be it. Oh one other one <br /> furl=point, the target wind in the case of a natural attenuadon approach to remediation the <br /> target level for remediation is not 9700 parts per billion benzene,it is to meet the graundwatcr <br /> basin plan. So the idea is that the natural Mechanisms that cause biodegradation will raft=the <br /> 10 <br />