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California conal Water Quality Coo Board
<br /> Central Valley Region is
<br /> Katherine Hart, Chair Nom'`
<br /> Linda S.Adams Arnold
<br /> 11020 Sun Center Drive#200, Rancho Cordova,California 95670-6114
<br /> Secretary Phone(916)464-3291 •FAX(916)464-4645 Schwarzenegger
<br /> Environmental
<br /> l
<br /> Governor
<br /> Protection Rmgovlcentralvalley
<br /> 21 July 2010
<br /> JUL Z 7 cu IU
<br /> Ms. Stephanie McKenna ENVIRONMENT HEALTH Mr. Jay Allen
<br /> Chevron Environmental ManagepEq{ gES Stone Brothers Management Company
<br /> 6001 Bollinger Canyon Road 5757 Pacific Avenue, Suite 220
<br /> San Ramon, CA 94583 Stockton, CA 95207
<br /> DOCUMENT REVIEW, MONTGOMERY WARDS AND UNOCAL STATION#5098, 5400-5606
<br /> PACIFIC AVENUE, STOCKTON, SAN JOAQUIN COUNTY, CASE NOS. 390258 AND 390014
<br /> I reviewed the Report of Soil Vapor Well Installation and Soil Vapor Sampling Activities (Report)
<br /> received 16 July 2010 from Chevron Environmental Management's consultant AECOM. The Report
<br /> documents the 13 May 2010 installation of three shallow soil vapor wells (SV-1 through SV-3)
<br /> completed with six inch welt screens placed at 5.5 feet below ground surface. The wells were sampled
<br /> using Summa Canisters TM on 20 May 2010 after the landscape sprinklers had saturated soil around
<br /> SV-1. Maximum soil vapor concentrations, detected at SV-1, were total petroleum hydrocarbons as
<br /> gasoline (TPHg), 470,000 micrograms per cubic meter(ug/m); benzene, 49 ug/m3; and toluene,
<br /> 38 ug/m3. Toluene (16 ug/m3) and total xylenes (5 ug/m3) were detected in the field blank, a possibly
<br /> indication of compromised sample tubing. The San Francisco Bay Environmental Screening Levels
<br /> (ESLs) for commercial or industrial sites and the California Office of Environmental Health Hazard
<br /> Assessment's California Human Health Screening Levels (CHHSLs) were exceeded for TPHg
<br /> (ESLs, 29,000 ug/m3 and CHHSLs, 73,000 ug/m) at SV-1 (a former Unocal site, now a bank). A
<br /> Johnson and Ettinger model used the data to show cancer risk did not exceed 10,6; however, the
<br /> Hazard Index (HI for non-carcinogenic risk), at 1.9, exceeded the US Environmental Protection Agency
<br /> target HI of 1.0. The Report recommends conducting a second round of soil vapor sampling, to
<br /> evaluate potential seasonal variations in soil vapor concentrations, and to validate the results of the
<br /> reported event. If soil gas concentrations do not indicate a risk, then a closure report will be submitted.
<br /> The recommendation to resample SV-through SV-3 is acceptable and approved. Please provide an
<br /> email with a schedule for the field work by 30 July 2010, with a report due by 30 September 2010.
<br /> You may contact me regarding questions by phone at (916) 464-4615; or by e-mail at
<br /> Larton Ca�waterboards.ca.aov.
<br /> James L.L. Barton, P.G:
<br /> Engineering Geologist
<br /> cc: Judy Reid, SWRCB, UST Cleanup Fund (Commingled Plume Program), Sacramento
<br /> Mike Infurna, San Joaquin County Environmental Health Division, Stockton
<br /> Nichole Gleason, Downey Brand, 621 Capitol Mall, 18th Floor, Sacramento 95814
<br /> Jennifer Johnston, AECOM, 10461 Old Placerville Rd, Ste 170, Sacramento 95827
<br /> Jim Brake, Geocon Inc., 3160 Gold Valley Dr.; Ste. 800, Rancho Cordova 95742
<br /> California Environmental Protection Agency
<br /> a Recycled Paper
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