SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

• Lee Higgins � -2 - � 2b January 2U�1 Chevron • Mountain House Site#3 by SAIC, the wells are for agricultural and not for domestic use. The Fish family well was re- sampled and an evaluation of the results by the analytical laboratory staff determined the TPH detected was not consistent with crude oil which was transported in the historical OVPITAOC pipelines. Based on the investigative findings of 2001 to 2008 investigation reports conducted by SAIC and other consultants, I concurred in an April 2008 response letter to Chevron, that soil and groundwater had been adequately defined and a human health screening evaluation (Screening Evaluation) could be prepared. SAIC determined the total potential cancer risk determined for the Site was estimated to be 5E-07, which is below the threshold lifetime de minimus cancer risk of 1 E-06 (i. e., one in one million). The non-cancer hazard index was determined to be 2E-03, which is below the de minimus value of 1 . Area groundwater beneath the Site exceeds numerous California and Federal standards for total dissolved solids for drinking water and agricultural purposes. Given that the Site is within a highwaylpipeline/UPRR easement and in an agricultural field, it is unlikely installation of drinking water wells would be considered. The California Natural Diversity Database, 2009, maintained by California Department of Fish and Game, was reviewed by SAIC to search for threatened, endangered, or sensitive species in the vicinity of the Site; none have been observed within one mile. According to the Screening Evaluation, the residual crude oil remaining at the Site occurs primarily beneath/within the highway ROW, under the existing pipelines, UPRR tracks, and in the adjacent alfalfa field. Previously, SAIC assessed available cleanup technologies and various remedial alternatives for residual crude oil in soil and groundwater at OVPITAOC projects. The assessment summarized that residual weathered crude oil is highly viscous, relatively immobile, and primarily occurs within low permeability soil found at the Site. SAIC concluded that affected soil/groundwater has been delineated and in-place management of residual crude oil by natural attenuation is cost effective, feasible, and easily implemented. Concentrations of petroleum hydrocarbons will diminish with time. Based on the alternative cleanup technological assessment and consistent with State Water Resources Control Board Resolution No. 92-049, SAIC concluded there is no known feasible cost effective means, or easily implemented process to effectively remove the petroleum hydrocarbons identified on the Site. Future use of Site groundwater is not anticipated due to low yield, poor quality, and access to the utility easements and alfalfa field is very restrictive. Summary I concur that based on SAIC's findings, exposure to petroleum hydrocarbons present at the Site should not result in an unacceptable health risk for an onsite resident or ecological receptors. No remedial action is necessary, and the Site is a candidate for closure. Consistent with other OVPITAOC sites, Chevron needs to submit a site-specific Soil and Groundwater Management Plan (SGMP) that designates Chevron as the responsible party. The SGMP serves as a guideline for Chevron to implement for the handling, reuse, and