SITE INFORMATION AND CORRESPONDENCE FILE 2

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Page 1 of 2 Mike Infurna [EH] From: Mike Infurna [EH] Sent: Tuesday, December 21, 2010 8:36 AM To: 'Barclay, Diane' Subject: RE: 76 (Former BP) Service Station No. 11192, 1403 West Country Club Blvd, Stockton welcome aboard.... as or before you start your work at this site, I recommend you look at the EHD letter dated May 28, 2010. Nuel and I spent some time on this back then. then look at the work plans submitted SINCE this letter and you'll see why I'm not too happy with the site. in addition, you may want to look at Geotracker data for the Shell station wells installed downgradient (and the latest gw data) along Elmwood (monitoring wells "S-5", "S-6", "S-15", and "S-17"). Justification will be needed by COP if you continue to propose MW-14 and MW- 15 where the latest figure shows them (further east/northeast of these Shell wells). GT ID# for the Shell site is T0607700721 the following are concerns the EHD still has with the latest workplan revision/addendum. -MW-11 is incorrectly labelled as a "D" well on Brad's last figures. It's a "C" well. -Proposed MW-17 appears to be in an acceptable place but not completely. With a NE plume direction, MW-17 is more laterally WEST of the plume? it's a good start tho'. the EHD has concerns about the gw plume east of this point. We have thought about a C zone well EAST across Pershing,just north of Elmwood in the right of way; sort of a 'mirror image' of MW-17, but on the other side of Pershing. A well here would close/monitor the gap between proposed MW-17 and the next C zone well (—S-17?). We think Shell well S-17 is also laterally cross gradient and leaves too large of a gap for MW-11 plume investigation. -We like the idea of proposed MW-16, but cannot understand how the proposed screened interval of 92'-102'bgs was determined. No litho data deeper than 57' bgs is available from CPT-1 in the immediate area of MW-16 and CPT-3 the next closest deep data point (-50' ?) does not support this depth as the most permeable zone for the MW-16 (D zone) screened interval. CPT-3 gw grab data presents more questions than it answers with the TBA data ND at 74' and 1 00' only to report TBA at 125"...Back in 2002 MtBE in CPT-3 was the concern with the highest gw hits at the deepest depths..(also not vertically defined). we suspect cross contamination but without repeatable data, neither of us can support/deny this. -progress to date and the way we see this site: MW-11 is the deepest well and the one with the most contamination. It's not vertically defined. It's not downgradient laterally defined. and think about it....where would you draw the 'zero-line' for the TBA plume at this site. Do you even have 68'-78' bgs gw data anywhere ONSITE besides MW-11? The concept of'site characterization', plume definition, residual mass of COC, stability all seem unaddressed. after close 20 years, why are we still addressing this? am I missing something here? mike. 12/21/2010