SITE INFORMATION AND CORRESPONDENCE

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California R ional Water Quality Con4 )I Board `' w Central Valley Region ' Katherine Hart, Chair `��6��• Linda S. Adams Arnold 1685 E Street, Fresno,California 93706 Secretary for ;� � aeneger (559)445-5116 • Fax(559)445-5910 ��I� }�EF—MwGo`vemrg Environmental http://www.waterboards.ca.gov/centraIvaIley u (j I!tf `f Protection FACT SHEET E.':' 0 4 `°i0 ENVIRONMENT HEALTH PERMTSERVIGES PROPOSED NO FURTHER ACTION REQUIRED, VERNALIS OFFSITE PROPERTY, VERNALIS, SAN JOAQUIN AND STANISLAUS COUNTIES This Fact Sheet is to inform interested parties of the Central Valley Regional Water Quality Control Board's (Central Valley Water Board) consideration of No Further Action Required for the Vernalis Offsite project and to request any comments on the proposed action. The project location is noted on the enclosed Figure. From the early 1900s to the late 1960s historical pipelines, located on properties west of the referenced project, transported crude oil from Kern County oil fields to San Francisco Bay area refineries. During 2005, a release of non-hazardous crude oil was discovered from the historical Old Valley Pipeline (OVP), Tidewater Associated Oil Company pipelines, and/or associated pump station facilities located west of the project. Consequently, crude oil affected groundwater has migrated downgradient to the east onto the Vernalis Offsite from the former pump stations and/or related historical pipeline facilities. Soil and groundwater characterization activities continue at the nearby projects with regulatory oversight provided by Central Valley Water Board staff. Between 2005 and 2008, 12 borings were drilled and samples collected for analysis by a California certified analytical laboratory. Two soil borings were converted to monitoring wells. Visually affected soil was not observed in borings drilled to depths of 40 to 44 feet below ground surface (bgs). With one exception, total petroleum hydrocarbon as crude oil (TPHc) was non-detect (ND) for TPH compounds. TPHc at a concentration of 380 milligrams per kilogram (mg/kg) was reported in a soil sample collected at a depth of one foot bgs in a boring located more than 200 feet east of the former pipelines. The result exceeded the environmental screening level (370 mg/kg) for direct human exposure contact. However, considering the sample depth and distance, it is likely the TPHc detected is attributable to current site activities and not associated with the nearby historical crude oil facilities. Analysis of groundwater constituents reported TPH as diesel (TPHd) at concentrations of 160 micrograms per liter (pg/L) and 240 pg/L in samples from two lateral downgradient borings drilled in 2008. The remaining samples were ND at the detection limit for TPHd as well as other petroleum hydrocarbons constituents of potential concern which were at or slightly above respective method detection limits. Based on the findings, the lateral downgradient extent of affected groundwater and soil was defined and additional investigation is not needed. The property owner asked that the site access agreement be terminated and in August 2008 the two monitoring wells were destroyed. In an August 2009 report, Chevron Environmental Management Company's consultant indicated that the crude oil related compounds detected in soil and groundwater are limited in extent and/or do not exceed environmental screening levels. Residual concentrations of crude oil constituents will naturally degrade and are not present at concentrations that would pose an unacceptable health risk for a residential scenario setting or to any ecological receptor. California Environmental Protection Agency ZaRecycled Paper