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Page 1 of 1 1 ti./ v Harlin Knoll [EH] From: Nuel Henderson [EH] Sent: Monday, December 13, 2010 3:57 PM To: Harlin Knoll [EH] Subject: FW: Shell Station at 2320 N. EI Dorado Street Sorry Harlin, I though Mike had inherited this one. Nuel From: Nuel Henderson [EH] Sent: Monday, December 13, 2010 2:52 PM To: 'Jim Barton' Cc: Mike Infurna [EH]; Adrienne Ellsaesser [EH] Subject: Shell Station at 2320 N. EI Dorado Street Jim, I'm thinking of closing the site at 2320 N. EI Dorado Street, Stockton, a Shell site. TPHg, BTEX and fuel oxys are generally delineated and at moderate to low concentrations. TPHg is highest in MW-1, and CRA estimates its return to"ESLs"in 12 years. Only benzene and xylenes in soil exceed ESLs for leaching, but CRA notes that GW impact demonstrates little active leaching. Impact in MWA and MW-2 is not inconsistent with being a part of the 2315 N. EI Dorado St site's plume, but CRA did not note this. CRA estimates dissolved mass at 1.35 pounds TPHg and 0.0044 pounds benzene; soil mass at 1.2 pounds TPHg and 0.004 pounds benzene. Problem with site for some time has been PCE and TCE in groundwater, mostly mW-1 and MW-2. Site had a waste oil tank pulled circa 1984, no record of its former location available. CRA noted that a cleaners on the site in 1960-1965 and state that this was the probable source of the PCE/TCE and it isn't Shell's problem. I checked out the Polk Directories at the library and found the business—Service Cleaners -listed under clothes cleaners at 2326 N/ EI Dorado Street from 1928 to 1960. For much of the 32 years the business was there I'd speculate they used Stoddard solvent or some such, but there is some time where PCE would be the likely chemical of choice, assuming cleaning on site was performed. CRA hints that the station was built circa 1975, taking up the entire east side of the 2300 block. PCE and TCE were present in MWA and MW-2 at concentrations of 44 ppb PCE and 210 ppb TCE in MWA and at 140 ppb PCE and 48 ppb TCE in MW-2 in January 2010. Both have been in the low to middle 100's of ppbs in the past. The down-gradient well MW-2 is generally the more impacted, so lateral extent is not demonstrated. The PCE and TCE in MW-2 is accompanied only by minor TPHg and occasional low 1,2-DCA. With the relatively short time period a waste oil tank was on the site compared to how long the cleaners was there, and the lack of significantly impacted soil encountered that could indicate a waste oil LIST release, and with the site ready for closure in all other respects, I am reluctant to try to get more down-gradient investigation. I can't prove it, but I think CRA has it right this time. I think we should close this site Jim. Let me know what you think. Nuel 12/20/2010