SITE INFORMATION AND CORRESPONDENCE

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Tracy Rail Yard Offsite-West - 2 - 10 March 2014 No Further Action Required Human Health and Ecological Screening Evaluation A human health and ecological screening evaluation (HHESE), dated July 2012, used a hypothetical adult and child land use risk exposure scenario (considered the most conservative approach) for evaluation of exposure to TPH chemicals of potential concern (COPCs). The HHESE used a methodology and approach described in the California Environmental Protection Agency, Department of Toxic Substances Control, Preliminary Endangerment Assessment (PEA) Guidance Manual, 1999. The HHESE estimated the cancer risk for COPCs and non-cancer hazard from exposure to on-site soil (upper ten feet) using a residential exposure scenario following equations and assumptions provided in the PEA Guidance Manual. The report indicated that the single reported COPC detected in soil, benzo(g,h,i)perylene has not been identified as a carcinogen, and as such, it was not appropriate to calculate potential cancer risk associated with this COPC. The non-cancer hazard index (HI) calculated for the one reported COPC - benzo(g,h,i)perylene of the combined direct and non-direct soil exposure at 1.6 X 105, is less than the acceptable HI of 1. This HI indicates that potential exposure to on-site soils would not result in a public health risk. The consultant noted that analysis for the upper groundwater samples collected at a nearby Chevron site exceeded California and federal total dissolved solids for drinking water. A City of Tracy municipal code prohibits use of shallow groundwater. Groundwater may be impaired for reasons unrelated to the historical TAOC pipelines. The HHESE stated because it was not likely on-site groundwater would be used for domestic needs this potential exposure pathway was thus not considered for the risk evaluation. Since the potential exposure pathway for shallow groundwater is incomplete, the risks and non-cancer hazards from this incomplete pathway were not considered for the HHESE. In conjunction with the risk assessment, Chevron's consultant reviewed the 2012 California Department of Fish and Game - California Natural Diversity Database for threatened and endangered wildlife. A threat to sensitive ecological receptors does not appear to exist. No Further Action Request Required Chevron submitted a No Further Action Required Request Report (NFAR), dated 28 June 2013, which summarizes the various investigations and the human health and ecological screening evaluation in support of the no further action request. In addition, Chevron also submitted a Soil and Groundwater Management Plan, which provides contact information for Chevron or interested parties if future construction activities encounter crude oil impacted soil or groundwater. Staff prepared a Fact Sheet that summarized the assessment activities which have occurred at the Site. The Fact Sheet and a 21 January 2014 notification letter sent to property owners surrounding the former pump station provided documentation of the Central Valley Water Board's intention to issue a no further action required (closure) status for the Site. The public was provided a 30-day review period to submit comments to the proposed no further action determination. Comments were received from two owners of one property, who requested a discussion with Staff to provide an explanation for the NFAR process. Staff discussed the investigation findings summarized in the 21 January 2014 Fact Sheet and transmittal letter. No other comments were received during the 30-day public review period. Conclusion Based on documentation provided by Chevron, the Site qualifies for a no further action required determination.