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Limited Site Investigation � Terracon <br /> Vacant Property I Tracy, California <br /> May 26, 2023 1 Terracon Project No. NA197074B <br /> Groundwater investigations were performed by Kleinfelder in 2005 and by Terracon in <br /> 2021. The groundwater data collected to date indicates relatively low concentrations of <br /> petroleum hydrocarbons and limited area of impact. Based on the age of the release <br /> (approximately 20 years) and the fuel type (crude oil) it is unlikely the dissolved crude <br /> oil plume has migrating beyond its extent. Furthermore, it is likely that natural <br /> attenuation processes will continue to degrade the petroleum hydrocarbons over time. <br /> 2.2.1 Groundwater-Specific Criteria <br /> The site appears to fall into Low-Threat Policy Class 2 criteria for groundwater: <br /> (2) <br /> a. The contaminant plume that exceeds water quality objectives is less than <br /> 250 feet in length. Appears to be true, based on the site data. <br /> b. There is no free product. Free product was removed after the release. Soil <br /> and groundwater samples from the site investigations performed to date do not <br /> indicate free product remains in place. <br /> c. The nearest existing water supply well or surface water body is greater <br /> than 1,000 feet from the defined plume boundary. Appears to be true, based <br /> on the site and surrounding data. <br /> d. The dissolved concentration of benzene is less than 3,000 micrograms <br /> per liter (Ng/1), and the dissolved concentration of MTBE is less than <br /> 1,000 Ng/1. Historical reports present site data that document the dissolved <br /> concentrations of benzene and MTBE that are less than the LTCP criteria above. <br /> 2.2.2 Petroleum Vapor Intrusion to Indoor Air <br /> To date, soil vapor data has not been collected from the site; however, due to the <br /> limited concentrations of volatile compounds reported in soil and groundwater samples <br /> from SB7. SB17, and SB18, and the close proximity to the utility easement and the <br /> restrictions of building on or near the easement, the site appears suitable to unrestricted <br /> land use. <br /> 2.2.3 Direct Contact and Outdoor Air Exposure <br /> The LTCP criteria denotes that a site is considered low threat for direct contact and <br /> outdoor air exposure if soil concentrations of benzene, ethylbenzene and naphthalene <br /> are lower than those listed in Table 1 of the LTCP for soil 5 feet bgs or less. Volatilization <br /> to outdoor soil concentrations are also represented in LTCP Table 1. Based on the site <br /> investigations performed by Terracon in November 2019 and June 2021 concentrations <br /> do not exceed the LTCP values in Table 1; therefore, the site meets the direct contact <br /> and outdoor air exposure criteria. <br /> Facilities I Environmental I Geotechnical I Materials 6 <br />