SITE INFORMATION AND CORRESPONDENCE

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Mi.thael Oliphant -2 - 18 October 2012 w NFAR- Former Vernalis Pump Stat Environmental Protection Agency, Department of Toxic Substances Control, Preliminary Endangerment Assessment (PEA) Guidance Manual, 1999. Given that the Site is beneath/within the various right=of- way easements, it is not likely shallow groundwater would be considered for use as a source of drinking water, etc. A sample from an existing onsite water supply well did not contain site-related TPHc compounds at or above laboratory reporting limits. SAIC estimated the cancer risk and non-cancer hazard from exposure to onsite soil (upper 10 feet) using a residential exposure scenario (the most conservative approach), following equations and assumptions provided in the PEA Guidance Manual. SAIC's report estimated the exposure routes for incidental soil ingestion and dermal contact with soil, inhalation of windblown dust for non-volatile constituents from onsite soil. The aggregate cancer risk for oral, dermal, and inhalation from exposure to onsite soil and soil vapor was 1 E-06. This level of risk is equivalent to the de minimus level of 1 E-06, which does not present an unacceptable health risk. Additionally, the aggregate non-cancer hazard was 3E-03, well below an acceptable health hazard of 1. Thus, the Report estimated that both the cancer risk and non-cancer hazard indicate the Site does not pose a health risk to potential residents. SAIC's review-of the California Department of Fish and Game 2010 California Natural Diversity Database for wildlife indicates that a threat to sensitive ecological receptors do not appear to exist within a one mile radius of the Site. Consistent with State Water Resources Control Board (SWRCB) Resolution No. 92-049, Section III, A through C, SAIC evaluated alternative cleanup technologies and determined that any process other than natural attenuation would be ineffective, infeasible, and disproportionally costly. Residual crude oil concentrations naturally degrade with time, likely over a period of several years. Issues: In the late 1990's, a release of non-hazardous crude oil to soil and groundwater from the historical pipelines'andlor pump station was discovered. Soil and groundwater impacts consist of TPHc constituents. Setting: The Site includes/underlies portions of the highway, railroad tracks and rights-of-way for active pipelines. Adjacent land use to the east consists of agriculture and includes rural residences. Source: Historical leaks from crude oil pipeline(s) and/or the former pump station facility installed in the 1900's. Both features were removed from service during the late 1960's to early 1970's. Actions: Field investigations were conducted between 1995 and 2009. • From 1995 to 1998, soil and groundwater samples were collected for TPH analysis from borings drilled in the vicinity of the historical pipelines and the southeast corner of the former pump station facility. Concentrations of TPH compounds were detected in soil at sample depths of 21 to 31 feet bgs. Four monitoring wells were installed, with one well having separate phase hydrocarbon present which was not sampled. Results for the other three wells reported TPHd detected at a maximum concentration of 230 micrograms per liter(pg/L). Subsequent sampling of the wells in latter 1998 for TPH compounds reported results of ND for groundwater samples. Additional characterization was needed. • in 2002 and 2003, follow-up investigations were conducted to further evaluate the extent of crude oil affected soil/groundwater. Twenty-six borings were drilled on- and offsite to depths of about 90 feet bgs for sample collection. Concentrations of TPHc in samples were mostly ND to depths of about 40 feet bgs, to highs of 17,000 to 39,000 mg/kg at depths up to 57 feet bgs. TPHd groundwater results ranged from ND, to a high of 3,400 pg/L; benzene, toluene, ethylbenzene, and xylenes (BTEX) were ND. Fuel fingerprint evaluation confirmed TPH present was consistent with SJV crude oil. The extent of crude oil affected soil and groundwater was not defined and additional characterization was needed.