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California R_ jional Water Quality Con )I Board <br /> �\ Central Valley Region V� <br /> o <br /> Katherine Hart, Chair <br /> Linda S. Adams 1685 E Street, Fresno, California 93706 Arnold <br /> Secretary for (559)445-5116• FAX (559)445-5910 Schwarzenegger <br /> Environmental http://www.w@terboards.ca.gov/centraIvaIley Governor <br /> Protection p <br /> U <br /> TO: Douglas K. Patteson FROM: C. Dean Hubbard <br /> Supervising WRCE Engineering Geologist <br /> P. G. No. 6357 <br /> SIGNATURE: <br /> Shelton R. Gray <br /> DATE: 8 June 2010 Senio _Engineering Geologist <br /> SIGNATURE <br /> SUBJECT: CONSIDERATION OF REQUEST FOR NO FURTHER ACTION REQUIRED <br /> DETERMINATION, VERNALIS OFFSITE, VERNALIS, SAN JOAQUIN AND <br /> STANISLAUS COUNTIES <br /> Rationale: The area of groundwater affected by crude oil has been delineated on the <br /> Chevron Environmental Management Company (Chevron) Vernalis Offsite property (Site). <br /> Affected groundwater has migrated downgradient (to the east) from the historical Old <br /> Valley Pipelines (OVP, Chevron predecessor) and/or the former Vernalis Pump Station <br /> facility, adjacent to the west. <br /> Affected groundwater is of limited extent, in close proximity to the Site groundwater <br /> monitoring wells and two nearby offset borings. The analytical results of groundwater <br /> samples from lateral offset borings were non-detect (ND) for total petroleum hydrocarbons <br /> as diesel (TPHd), which defines the downgradient extent of affected groundwater. Low <br /> concentrations of two polynuclear aromatic hydrocarbons (PAHs) compounds were <br /> detected at or below respective screening levels. Subsequent investigations determined <br /> groundwater had been adequately defined and additional work was not required. At the <br /> request of the property owner, the two monitoring wells were properly destroyed. <br /> Chevron's consultant, Science Applications International Corporation (SAIC), indicated that <br /> residual petroleum hydrocarbons as crude oil detected at the Site is limited in extent, will <br /> naturally degrade with time, and is not anticipated to pose a health risk. SAIC's report <br /> indicated that based on the laboratory analysis, the water quality values do not meet <br /> minimum State and Federal drinking water quality standards as well as for agricultural use. <br /> Petroleum hydrocarbon/crude oil affected soil was not observed in 2008 Site borings drilled <br /> to depths of 40 to 44 feet below ground surface (bgs) to collect groundwater samples. <br /> Total petroleum hydrocarbon as crude oil (TPHc) at a concentration of 380 milligrams per <br /> kilogram (mg/kg), which was detected in a soil sample at a depth of one foot bgs from a <br /> boring more than 300 feet east of the former OVP pipeline and former pump station facility, <br /> was likely from a surface spill unrelated to the historical pipelines. For the other fourteen <br /> soil samples submitted for analysis, TPHc compounds; benzene, toluene, ethylbenzene, <br /> California Environmental Protection Agency <br /> � Recycled Paper <br />