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(209)468-2807 desk (209)468-0341 fax Email: amarin@sicehd.com From: Scott [mailto:SBittingerClustratusinc.net] Sent: Thursday, September 18, 2014 11:10 AM To: Nuel Henderson [EH] Cc: cori.condonOwaterboards.ca.aov; Angelica Sandoval Marin [EH] Subject: RE: 1140 W. Hammer Lane, Stockton The 3rd quarter sampling event will be performed next week. It is really hard to evaluate ozone injection on the basis of'remedial efficiency', unlike vapor extraction or DPE. With ex- situ techniques,if you drop from 60 lbs/day to 6 lbs/day recovery,the decline is apparent. In this case,we are using data from only a few wells sampled once every three months to evaluate performance in-situ. Harlin Knoll verbally told me,when we designed the cleanup plan 2+years ago,that he thought that the case was a good closure candidate even before remediation started, because the plume was stable and relatively small. But the high level of benzene in MW-11 at the time prevented low threat closure. Thus the groundwater data from one well was used as the basis for starting remediation, and now data from this well and new well MW-12(which was added to provide an additional data point)are really the only data points being used to evaluate remedial performance. I don't need a letter from you to continue remediation, but hopefully if the third and fourth quarter well sampling events show positive results,we can begin to think about moving the site to closure. Scott From: Nuel Henderson [EH] [mailto:nhenderson(&sjcehd.coml Sent: Thursday, September 18, 2014 10:50 AM To: Scott Cc: cori.condon(&waterboards.ca.gov; Angelica Sandoval Marin [EH] Subject: RE: 1140 W. Hammer Lane, Stockton Scott, I have reviewed the analytical data for MW-11 and MW-12 and notice that the benzene in MW-12 dropped from 11,000ppb at injection startup, declined to 3,000ppb on 11/28/12, rose steadily to 4,400ppb on 8/7/13 before declining again to 3,300ppb on 3/20/14, the event just prior to the 2,100ppb in May 2014. 1 think we should see consistent concentrations below 2,000ppb for several events, not just two, or better yet one or two orders of magnitude decline of concentrations, such as is exhibited by MW-11, before turning off the system. I know it is tempting to use the LTCP criteria as cleanup goals, which may be what we effectively will do, but I think we should be running remediation systems until they decline in remedial efficiency and then evaluating the results in regard to the LTCP. So at this point, the EHD cannot approve turning off the ozone injection system until the above circumstances are met. If you need a letter to this effect, we will generate one. Regards, Nuel From: Scott [mailto:SBittinoerCalstratusinc.net] Sent: Wednesday, August 27, 2014 7:58 AM To: Nuel Henderson [EH]; Angelica Sandoval Marin [EH] Cc: cori.condonCa)waterboards.ca.gov Subject: 1140 W. Hammer Lane, Stockton 2