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No Further Action Required Determination - 3 - 6 August 2009 <br /> Mountain House Development Site <br /> • A site-specific Soil Management Plan (SMP) submitted in November 2008, describes <br /> procedures to follow and contains the contact names and phone numbers for <br /> representatives of Chevron and the San Joaquin County Environmental Health <br /> Department if future activities encounter crude oil-affected soil. The SMP serves as a <br /> guideline for Chevron to implement for the handling, reuse, and disposal of any crude <br /> oil-affected soil and/or groundwater that may be encountered or excavated at the Site in <br /> the future. The SMP provides procedures for Site property owners, developers, and/or <br /> maintenance firms to follow that addresses such topics as trench excavations, <br /> dewatering, and health and safety guidelines. <br /> • On 10 June 2009, Central Valley Regional Water Quality Control Board (Central Valley <br /> Water Board) staff provided notification to property owners and adjacent property <br /> owners that the Central Valley Wafer Board was considering a no further action <br /> determination for Mountain House Development Site #5. No responses were received <br /> during the 30 day comment period. <br /> Extent defined: Yes. <br /> Estimated Residual Petroleum Mass: Unknown. Petroleum occurs primarily as degraded <br /> TPHc (immobile petroleum hydrocarbon fractions) at depths of approximately 1 to 32 feet <br /> bgs. The highest TPHc concentration was detected at a depth of 16 feet bgs. <br /> Threat to Groundwater: The historical pipeline leaks, the source of the crude oil, were <br /> removed from service approximately 35 or more years ago. The lateral and vertical extent <br /> of affected groundwater is limited having slightly larger dimensions than the area of <br /> affected soil. Affected groundwater beneath the highway and existing active pipelines has <br /> been defined to be within the highway ROW easement. Review of Department of Water <br /> Resources records, indicated no existing water wells within a one-half mile radius of the <br /> area of affected groundwater. Considering the site is located within the highway ROW <br /> easement and utility corridor, the installation of new water wells is not anticipated. <br /> Threat to Human Health: <br /> • Vapor intrusion hazard: there is no vapor intrusion pathway. <br /> • Dermal contact hazard: future maintenance excavation within the ROW is possible. <br /> Consequently, the applicable ESLs are for a construction/trench worker scenario. The <br /> concentrations of residual crude oil are below health protection ESLs for <br /> construction/trench workers. The site is located within the West Byron Road ROW <br /> easement and usage of this feature is not expected to change, thus <br /> reducing/minimizing potential human contact with TPH compounds remaining at the <br /> site. <br /> Summary: <br /> The TPH detected in soil and groundwater is degraded, highly immobile and limited in extent, <br /> defined in close proximity to the former pipelines, and will continue to attenuate naturally. <br /> There are no monitoring wells to be destroyed. Based on results of the site <br />