SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

1 NO FURTHER ACTION REQUIRED REQUEST REPORT MOUNTAIN HOUSE DEVELOPMENT SITE #6 I. INTRODUCTION ! SAIC Energy, Environment& Infrastructure, LLC (SAIC) prepared this No Further Action Required (NFAR) Request Report for Mountain House Development Site #6 (the Site) located in Mountain House, California(Figure 1) on behalf of Chevron Environmental Management ! Company (CEMC). Site investigations performed by SAIC identified the presence, and delineated the extent, of total petroleum hydrocarbons (TPH) in soil and groundwater at the Site. The Site is defined by the area investigated, and is delineated by borings GP 150, SB-36, SB-25, SB-38, SB-37, SB-30, SB-27, SB-24, and SB-44 advanced during site investigations (Figure 2). The Site measures approximately 1,330 feet by 490 feet, or an area of approximately 12 acres; and contains sections of the Old Valley Pipeline (OVP)right of way (ROW) and the former Tidewater Associated Oil Company (TAOC)pipeline ROW, as well as portions of adjacent parcels. The former pipeline systems are part of the CEMC Historical Pipeline Portfolio— Bakersfield to Richmond(HPP-BTR). At least 40 years have elapsed since the former OVP and ' TAOC pipelines were decommissioned, and the plume size has stabilized and may now be shrinking as natural attenuation continues to degrade TPH in soil and groundwater. Use of the shallow affected groundwater is not anticipated, and no sensitive receptors exist in the area. ' SAIC prepared a risk evaluation in 2011, which demonstrated that constituents of potential concern(COPCs) do not pose a threat to human health (SAIC, 2011), and that the Site is therefore suitable for NFAR status. ' Consistent with State Water Resources Control Board (SWRCB) Resolution No. 92-49, in particular Section IIIA through C (SWRCB, 1992), SAIC evaluated available cleanup technologies and found that all options would be highly ineffective, infeasible, and costly(SAIC, 2005a). TPH and PAHs in groundwater will naturally attenuate over time to levels below the Water Quality Objective (WQO; Central Valley Regional Water Quality Control Board [RWQCB], 2008a). CEMC requests that the Central Valley RWQCB issue an NFAR letter for this low-risk site for these reasons. This report contains the technical data and rationale necessary to support a decision by the Central Valley RWQCB to issue an NFAR letter for the Site. SAIC prepared this report taking ' into consideration the documentation outlined in Appendix A of the Tri-Regional Recommendations (Central Valley RWQCB, 2004). In support of the NFAR request, this report provides summaries of previous site investigations and removal actions in Section 2; the documentation outlined in the Tri-Regional Recommendations in Section 3; conclusions and recommendations in Section 4; and a list of previous technical reports in Section 5. ' 2. PREVIOUS INVESTIGATIONS Condor Earth Technologies, Inc. (Condor) conducted one investigation in the area of the Site in 2001; SAIC conducted two additional site investigations in 2008 and 2010 to assess the extent of soil and groundwater affected by crude oil. Copies of reports describing these activities are provided as Appendix A, and the results of these investigations are summarized in sections 2.1 and 2.2. Regulatory correspondence is included as Appendix B. For investigations performed by SAIC at the Site, soil analytical results were compared to the lowest, most conservative United States Environmental Protection Agency(EPA) Preliminary Remediation Goals (PRGs, ' l SAIC