SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

No Further Action Required Determi )n - 2 - 8 June 2010 Vernalis Offsite Vernalis, San Joaquin and Stanislaus Counties and total xylenes (BTEX); or polynuclear aromatic hydrocarbons (PAHs) constituents were ND or did not exceed applicable environmental screening levels. SAIC conducted an evaluation of risk to human health based on conservative residential setting and ecological screening levels. Results of the screening evaluation determined that residual TPH concentrations present at the Site, attributable to the former crude oil pipelines, do not pose a human health risk and/or ecological receptors. Consistent with State Water Resources Control Board (State Water Board) Resolution No. 92-049, Section III, A through C, SAIC evaluated alternative cleanup technologies and found that processes other than natural attenuation would be ineffective, infeasible, and disproportionally costly. Residual crude oil concentrations naturally degrade with time. Issues: In the early 1990's a release of non-hazardous crude oil to soil and groundwater was discovered at the nearby historical OVP pipelines and the former Vernalis pump station project, adjacent to the west. The pipelines and pump station facilities were utilized by Chevron predecessors to transport crude oil from Kern County to San Francisco Bay area refineries from the 1900's to the 1970's. Subsequent investigations determined visually affected soil was not present in borings drilled at the Site. Groundwater impacts identified at the Site in 2005 consisted primarily of crude oil (analyzed as TPHd). Analysis for PAH and BTEX constituents results were reported ND and/or below screening levels. Groundwater affected by petroleum hydrocarbons/crude oil has been delineated. Setting: Primarily agricultural, consisting of alfalfa and tree crop orchards with some rural residences and light commercial/industrial facilities surrounding the Site. California State Highway 33 and the Union Pacific Railroad easements are adjacent to the west-southwest. There are no known plans for further development or land use changes. Source: Historical OVP crude oil pipeline leaks and/or from the former pump station facility located on adjacent properties to the west-southwest of the Site. The historical features operated from the early 1900's to the 1970's. The pipelines and former pump station facilities were removed from service during the late 1960's to early 1970's. Chevron is presently investigating the historical OVP/Vernalis pump station project with regulatory oversight provided by Central Valley Regional Water Quality Control Board (Central Valley Water Board) staff. Actions: Preliminary soil/groundwater investigations conducted between 2005 and 2008. • In July 2005, three exploratory soil borings and two groundwater monitoring wells were drilled and samples collected and analyzed for petroleum hydrocarbon compounds. Depth to groundwater was approximately 32 to 39 feet bgs. The results of soil samples submitted reported TPHc from ND to a maximum concentration of 380 mg/kg in a sample from a depth of one foot bgs (determined to be unrelated to the historical facilities). The analytical results for BTEX and PAH compounds were ND at their respective method detection limits (MDLs) for the remaining soil samples to maximum depths up to 44 feet bgs.