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EDMAID G.BROWN JR. <br /> CD. AID <br /> C A L I P O R N E A 9ETION <br /> Ron IOUEZ <br /> CRE <br /> WaterBoards ENVIRONMENTAL PROTECTION <br /> Central Valley Regional Water Quality Control Board <br /> 15 June 2015 <br /> Chevron Environmental Management Company <br /> and Phillips 66 (L&M Group) <br /> c/o Dan Schreiner <br /> Stantec Consulting Services Inc. <br /> 3017 Kilgore Road, Suite 100 <br /> Rancho Cordova, CA 95670 <br /> SOIL VAPOR ASSESSMENT REPORT, L&M OPERABLE UNIT, 666 WEST WEBER AVENUE, <br /> STOCKTON, SAN JOAQUIN COUNTY <br /> Central Valley Water Board staff has reviewed the 15 May 2015 Soil Vapor Assessment Report <br /> prepared by Stantec Consulting Services Inc. on behalf of Chevron Environmental Management <br /> Company and Phillips 66 (L&M Group)for the L&M Operable Unit site in San Joaquin County. The <br /> report presents the results of a soil vapor survey and was submitted pursuant to our 3 November <br /> 2014 letter that concurred with a 30 May 2014 work plan. <br /> As proposed in the approved work plan, nine additional soil vapor probes were installed at 5 to 6 feet <br /> below ground surface to address data gaps in the existing soil vapor probe network or to replace <br /> existing probes that have been compromised. The new locations include seven offsite locations <br /> around the Delta View Apartment Buildings (APSV-11, 12, and 14 through 18), and two onsite <br /> locations (UPSV-7 and 8). Soil vapor samples were collected from the new probes and the remaining <br /> existing probes and analyzed for total petroleum hydrocarbons as gasoline (TPH-g), BTEX <br /> constituents (benzene, toluene, ethylbenzene, and xylenes), fuel oxygenates, naphthalene, and <br /> methane. Additionally, the report includes a revised table with proposed screening levels for BTEX <br /> constituents and naphthalene that are based on either California Department of Toxic Substances <br /> Control (DTSC) modified screening values for indoor air or USEPA Regional Screening Levels for <br /> indoor air that are adjusted for shallow soil gas by dividing them by an attenuation factor of 0.002 for <br /> existing buildings. The report proposes to eliminate the previously proposed screening level for TPH-g <br /> of 295,000 micrograms per cubic meter(ug/rn ) because of the limited toxicity data for inhalation of <br /> TPH-g. <br /> Based on the soil vapor survey, the report notes that two locations (UPSV-6 and APSV-15) exceed <br /> the proposed screening levels for benzene and/or naphthalene. We also note that these locations <br /> exceed the previously proposed screening level for TPH-g, as do probes APSV-9 and APSV-10 that <br /> the report recommends be eliminated because it says they are not representative of current vapor <br /> intrusion protection measures. The reports states that this is because they are in a low spot of the <br /> parking driveway, which was the former Edison Street, that acts as a collection area for surface water <br /> and there may be unidentified preferential pathways resulting from its former use. The report <br /> KARL E. LONGLEY SCD, P.E.,CHAIR I PAMELA C. CREEOON P.E., 8CEE,EXECUTIVE OFFICER <br /> 11020 Sun Center Drive#200,Rancho Cordova,CA 95670 1 www.waterboards.ca.gov/centralvalley <br /> 0 RECYCLED PAPER <br />