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�• — Page 1 of 2 <br /> Mike Infurna [EH] <br /> From: Mike Infuma [EH] <br /> Sent: Thursday, June 02, 2011 10:20 AM <br /> To: 'Ben Chevlen' <br /> Subject: RE: Circle K 1205- Lathrop: Review of Stantec's 4/29/11 Pilot Test Report <br /> thank you Ben, <br /> I am currently over-whelmed with concerns like this one. You/this site is about #8 on a list of <br /> 10... <br /> please bear with me as I prioritize these concerns. I plan to review the Stantec document and <br /> eventually meet with my PG to discuss the next plan/approval/recommendation. <br /> for now, ok to keep the OS system OFFline. SVE online is ok. <br /> I think monitoring manganese attenuation is a good idea. Do whatever it takes to support <br /> conclusions that maganese is not a problem on/offsite. <br /> a 3 month rebound sounds like a good plan. <br /> mike. <br /> From: Ben Chevlen [mailto:ben.chevlen@atcassociates.com] <br /> Sent: Thursday, June 02, 2011 10:10 AM <br /> To: Mike Infurna [EH] <br /> Subject: Circle K 1205 - Lathrop: Review of Stantec's 4/29/11 Pilot Test Report <br /> Mike—I downloaded a copy of Stantec's 4/29/11 report and reviewed the items you had concerns with. <br /> Your questions, along with my findings and observations are outlined below: <br /> • Is the system currently operating,and is that allowed? The ozone system is currently off-line. <br /> On the bottom of Page 5 and top of Page 6 of Stantec's Revised Work Plan for Remediation Pilot <br /> Test,dated 10/20/08,Stantec proposed that "OS/SVE will be performed on a continuous basis for <br /> a period of 6 months to evaluate the effectiveness of OS/SVE at the site. If the results of the <br /> OS/SVE operation appear favorable, the system will continue to run .." While Stantec <br /> determined that the OS operation had been effective, it appears that Stantec elected to cease OS <br /> operation, pending a response from SJCEHD. ATC has not restarted the OS equipment, but is <br /> operating the SVE system at the site. <br /> • Does the OS operation result in increased dissolved manganese concentrations? I do agree <br /> with Stantec's conclusion that there does not appear to be a clear correlation between OS <br /> operation and the periodic spikes(at concentrations>3,500 ug/L) in the dissolved manganese <br /> concentrations; however,there does seem to be a clear correspondence between operation of <br /> the OS system and an increase in dissolved manganese concentrations to levels exceeding both <br /> the secondary MCL of 50 ug/L and the drinking water notification level of 500 ug/L(there is no <br /> primary MCL for Manganese). While manganese concentrations have increased in off-site <br /> compliance-zone monitoring wells MW-6 and MW-9, it should be noted that the nearest <br /> identified irrigation or water supply well is located approximately 1,500 feet from the site(as <br /> stated in Stantec's Semi-Annual Status Report—First Quarter 2011). It maybe prudent to <br /> perform a 3-month rebound test to determine the rate at which dissolved manganese <br /> 6/2/2011 <br />