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Page 2 of 2 <br /> by the SJCEHD;ATC requests guidance regarding whether the SJCEHD would like the work implemented <br /> as proposed by Stantec, as modified by ATC in this email, or based on a response to this email from <br /> the SJCEHD. <br /> • Potential obstacles towards closure— MTBE and TBA appear to have migrated off-site to the northeast <br /> along Elmwood Avenue; better delineation and risk characterization of this plume are warranted. The <br /> proposed on-site CPT borings are expected to achieve vertical delineation at the site. On-site shallow <br /> soil vapor sampling has yet to be performed. <br /> Former Thrifty Oil Station No. 172—7647 Pacific Ave., Stockton <br /> • Current status—Site currently being redeveloped as a 7-11 store (no USTs). Several site monitoring <br /> wells and remedial wells were destroyed or protected in preparation for redevelopment. <br /> Redevelopment was delayed several months but now underway. Site being sampled semi-annually <br /> during 2Q/4Q <br /> • Proposed and pending work—ATC to perform well repair and well installation activities as proposed in <br /> 4/13/11 work plan addendum. ATC will use results of pending well installation activities to determine <br /> the remedial path forward. Additionally, all proposed monitoring wells will be sampled quarterly for a <br /> minimum of one year following installation. <br /> • ATC's recommended changes to proposed work—None; ATC expects that an HHRA and/or new CAP <br /> will be prepared for the site upon completion of pending well installation activities and subsequent <br /> review of site conditions. <br /> • Potential obstacles towards closure—Elevated dissolved-phase benzene concentrations on-site. The <br /> previous remedial system at the site was no longer effective and results of June 2010 5-day SVE pilot <br /> test suggest SVE no longer warranted. Shallow soil vapor sampling should be performed to evaluate <br /> potential risks associated with benzene volatilization. <br /> Former 76(Former BP)Service Station No. 11195—16500 South 1-5, Lathrop <br /> • Current status— Remedial systems currently offline and post-remediation rebound testing is underway. <br /> • Proposed and pending work—Stantec performed shallow soil gas sampling during 1Q11 and will <br /> prepare a report documenting results of that work. Stantec also to prepare 1Q11 groundwater <br /> sampling report. <br /> • ATC's recommended changes to proposed work— None; ATC feels the work currently under way is <br /> appropriate. <br /> • Potential obstacles towards closure —None currently seen; site closure dependent on results of <br /> shallow soil gas sampling. <br /> Please feel free to contact me at your convenience to discuss any of these sites further. Thank you. <br /> Ben Chevlen, PG i Senior Project Manager I ATC Associates Inc. I Los Angeles <br /> 805-496-1217 direct 1 916-425-4849 mobile <br /> 25 Cupania Circle I Monterey Park, California 91755 <br /> 323-517-9780 tel 1 323-517-9781 fax I www.atcass9ciates.co_m <br /> ATC is a leader in developing innovative Environmental, GeotechnicaVCMT/Special Inspections and Health& safety solutions, view <br /> our video 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 /> 4/22/2011 <br />