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1. Page 1 of 1 <br /> Mike Infurna [EH] <br /> From: Ben Chevlen [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. Your <br /> 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. On the <br /> bottom of Page 5 and top of Page 6 of Stantec's Revised Work Plan for Remediation Pilot Test,dated <br /> 10/20/08, Stantec proposed that "OS/SVE will be performed on a continuous basis for a period of 6 <br /> months to evaluate the effectiveness of OS/SVE at the site. If the results of the OS/SVE operation <br /> appear favorable,the system will continue to run ..." While Stantec determined that the OS operation <br /> had been effective, it appears that Stantec elected to cease OS operation, pending a response from <br /> SJCEHD. ATC has not restarted the OS equipment, but is operating the SVE system at the site. <br /> • Does the OS operation result in increased dissolved manganese concentrations? I do agree with <br /> Stantec's conclusion that there does not appear to be a clear correlation between OS operation and the <br /> periodic spikes (at concentrations>3,500 ug/L) in the dissolved manganese concentrations; however, <br /> there does seem to be a clear correspondence between operation of the OS system and an increase in <br /> dissolved manganese concentrations to levels exceeding both the secondary MCL of 50 ug/L and the <br /> drinking water notification level of 500 ug/L(there is no primary MCL for Manganese). While <br /> manganese concentrations have increased in off-site compliance-zone monitoring wells MW-6 and MW- <br /> 9, it should be noted that the nearest identified irrigation or water supply well is located approximately <br /> 1,500 feet from the site (as stated in Stantec's Semi-Annual Status Report—First Quarter 2011). It may <br /> be prudent to perform a 3-month rebound test to determine the rate at which dissolved manganese <br /> attenuates. <br /> Additionally, based on the results of the results of the SVE influent data (both lab and field-collected), I question <br /> the effectiveness of the SVE system at the site. The data suggests the SVE system is not removing significant <br /> quantities of hydrocarbons from the vadose zone, and does not appear to warrant continued operation. <br /> At your convenience, please let me know if you would like ATC to re-start the OS system, and if you agree that <br /> the SVE system warrants being shut-down (possibly for a rebound test prior to being shut-down indefinitely). <br /> Ben Chevlen,PG I Senior Project Manager I ATC Associates Inc. I Los Angeles <br /> 805-496-1217 direct ( 916-425-4849 mobile <br /> 25 Cupania Circle I Monterey Park, California 91755 <br /> 323-517-9780 tel 1323-517-9781 fax I www.ptcas$Qcidt2S•comn <br /> ATC is a leader in developing innovative Environmental, Geotechnical/CMT/Special Inspections and Health&Safety solutions. View <br /> our yleo Link to learn more. PLEASE NOTE: This message, including any attachments, may include privileged, confidential <br /> and/or inside information. Any distribution or use of this communication by anyone other than the intended recipient is <br /> strictly prohibited and may be unlawful, if you are not the intended recipient, please notify the sender by replying to this <br /> message and then delete it from your computer, <br /> 6/2/2011 <br />