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California Reyiional Water Quality Cont. Board .,. <br /> Central Valley Region ���` � -NIP'" <br /> Katherine Hart, Chair <br /> yl <br /> ws. <br /> 1685 E Street, Fresno, California 93706 <br /> Linda S.Adams (559)445-5116 • FAX (559)445-5910 Edmund G.Brown Jr. <br /> Acting Secretary for httpi//www.waterboards.ca.govicentralvalley Governor <br /> Environmental Protection <br /> To: Shelton R. Gray FROM: C. Dean u.bbard <br /> Senior Engineering Geologist Engin�eii;"g eologist <br /> DATE: 1 June 2011 SIGNATURE: <br /> SUBJECT: REVIEW— NO FURTHER ACTION REQUIRED REQUEST, FORMER VERNALIS <br /> PUMP STATION, VERNALIS, SAN JOAQUIN AND STANISLAUS COUNTIES, <br /> CA <br /> Chevron Environmental Management Company (Chevron) submitted a report dated <br /> 30 March 2011 entitled No Further Action Required Request (NFAR, Report), Former Vernalis <br /> Pump Station Property (Site), at 35500 Welty Road in Vernalis. The Report was prepared for <br /> Chevron by Science Applications International Corporation — Benham Companies, LLC <br /> (SAIC). The Site is one-half mile south of Grant Road, southeast of the intersection of Welty <br /> Road and California State Highway 33. 1 have reviewed the Report and related project file <br /> reports prepared for Chevron and my comments are provided below. <br /> Investigations for crude oil affected soil and groundwater were completed by SAIC and others <br /> between the late 1990's and 2010 with regulatory oversight by Central Valley Regional Water <br /> Quality Control Board (Central Valley Water Board) staff. The investigations determined the <br /> origin of crude oil to be from the former Vernalis Pump Station facility and the historical Old <br /> Valley Pipeline (OVP) system. The former OVP pipelines, located east of the Site, are within a <br /> right-of-way easement which also contains Union Pacific Railroad (UPRR) tracks and active <br /> refined petroleum product pipelines. Additionally, the historical Tidewater Associated Oil <br /> Company (TAOC) pipelines are present within the UPRR easement. California State Highway <br /> 33 is adjacent to the east side of the historical pipelines and the UPRR tracks. <br /> In September 2010 SAIC submitted a Human Health Screening Evaluation (HHSE) for <br /> estimating the potential human health cancer risks and non-cancer health hazards associated <br /> with exposure to residual crude oil in soil and groundwater. The HHSE utilized a conservative <br /> approach incorporating a conservative residential risk exposure scenario, but the most likely <br /> future use of the Site will be for commercial/industrial purposes. <br /> According to the Report, the HHSE was developed in accordance with the Preliminary <br /> Endangerment Assessment Guidance Manual (California Environmental Protection Agency <br /> [Cal EPA] Department of Toxic Substances Control [DISC], 1999, and the Vapor Intrusion <br /> Guidance (DISC and Cal/EPA, 2004). An incremental lifetime cancer risk of 1 E-06 (i.e., 1 in 1 <br /> million), in accordance with the National Contingency Plan, was used as a point of departure <br /> for the HHSE. <br /> SAIC's HHSE estimated that the aggregate oral, dermal, and inhalation cancer risk from <br /> exposure to onsite soil and subsurface vapor intrusion was 1 E-06 which is equivalent to the <br /> California Environmental Protection Agency <br /> '�Recycied Paper <br />