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cl Site Delineation and RAP Addendum Proposal April 16,2006 Former Canteen Fac il4y—1500 Shaw Rd Page 2 Nov 2006: Operations of the AS-SVE System with GAC vessel treatment was initiated on November 8, 2006. Each GAC vessel holds a total of 400 lbs of GAC and will be changed-out as necessary. Jan-Dec 2007: Full AS-SVE operations continued,with vapor abatement via the GAC vessels.The system uptime for this year was 94.1%. Overall system uptime was at approximately 82%. Feb 2008: Several PID readings and laboratory results in a row have indicated that influent concentrations may be below standards set by SJVAPCD (2 lbs/day). A request was made to SJVAPCD to temporarily remove the GAC vessels from the equipment train. SJVAPCD granted the request, though the vessels will remain on-site should hydrocarbon recovery monitoring indicate an increase in concentrations requiring the vessels to be placed back in use. ASSESSMENT A total of 17 monitor wells currently exist at and around the Former Canteen Facility. There are 12 on-site wells and five(5) off-site wells. The monitor wells were designated wells MW-1 through MW-13; including two three-well dusters described in the next section. MW-3 and MW-13 Series Wells Of special note are the MW-3 and MW-13 well series. The areas around the MW-3 and MW-13 series have been the primary focus for assessment and remediation at the site.At each of these locations are three wells installed to varying depths.The details of each series and their screened intervals are summarized in the table below: Well Screen Well Screen IDs Interval BTEX MTBE TPH IDs Interval BTEX MTBE TPH MW-3A 47'-67' 1 M.Low 1 48124 4.61<1350 MW-13 39'-59' M.Low 2312.5 3.1 K1770 MW-3 i 65'-85' i Mod ] 17111 j 5.6K/290 MW-13A I 71'-76' 7.1/ND I 1.11ND i 320145 MW-3D 76'-81' High 11/ND 20K112K MW-136 116'-121' BDL I BDL BDL Note: The values"y denotes recent ranges of reported concentrations in 11g/L. Other Impacted Wells Other site wells have had groundwater impacts during the course of time.A summary of these other wells is presented below: • Wells MW-1, MW-2, MW-4, and MW-10 have had detectable concentrations of petroleum hydrocarbons, but the reported concentrations have declined over time. • Wells MW-5, MW-6, MW 7, MW-8, and MW 9 are similar to the last group with the exception of the acute appearance of detectable benzene concentrations at the time of the site's highest historical water table in 1999. • Off-site well MW-11, located down-gradient of the MW-3 series, has had detectable concentrations of MTBE, 1,2-DCA, and TPH since initially reported in 2000. This well has also been marked by occasional detectable concentrations of benzene. • Off-site well MW-12, located somewhat down-gradient of MW 11, has had two events of detectable benzene concentrations since its installation in 1997.