SITE INFORMATION AND CORRESPONDENCE

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C. Scott Mansholt - Chevroe - 3 - 19 June 2008 Mountain House #4 per day. However, the TDS values reported are greater than the U.S. EPA Secondary Maximum Contaminant Level (MCL) of 500 mg/L for drinking water, which is based on taste and odor, and staining and corrosion characteristics. Department of Water Resources (DWR) records report two private wells approximately 3,000 and 4,900 feet crossgradient of the site. Screen intervals range from a depth of 65 to 160 feet and the wells are completed with a seal from the surface to 35 feet. The extent of the impacted groundwater plume at Site #4 is defined and appears to be stable. Considering the distance from the site and depths of the well seals and screen intervals, the limited extent of affected soil and groundwater coupled with the distance from the project, it is unlikely that petroleum constituents would affect these wells. Soils at the Mountain House Development sites are fine-grained, unconsolidated sediments consisting of silt and clay with minor amounts of fine sand and some gravel, considered to have low permeability. Since the site is limited to within the public roadway ROW easement and beneath the highway, it is unlikely that water supply wells would be constructed within the project area. SAIC's investigative report concluded that: • Affected soil and groundwater is limited in extent and occurs within the ROW along the southwest side of Byron Road, beneath the highway and the former OVP alignment. • TPHc, TPHg, xylenes, benzo(a)anthracene, benzo(a)pyrene, and naphthalene in soil exceeded the lowest, most conservative (residential) ESLs and/or U.S. EPA Region IX Preliminary Remediation Goals (PRGs). • Boring MH4-1 is likely located near a leak from the former OVP and the lateral extent of affected groundwater attributed to the OVP was defined in the vicinity of this boring. The vertical extent of impacts to soil and groundwater was defined at 44 and 46 feet, respectively at this boring location. • The area of affected soil is limited, with approximate circular dimensions of less than 100 feet across; affected groundwater is slightly larger at approximately 75 by 125 feet, generally centered around borings MW4-1 and GP-180. • DWR records indicate that two domestic wells are approximately one-half mile cross- gradient of the site and of sufficient distance that they will not likely be affected by leaks from the pipelines. • Fuel fingerprint evaluation determined that refined petroleum products in soil and groundwater in MH4-6 likely originated from an adjacent active refined petroleum product pipeline. • No further site characterization is needed.