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Union Pacific Railroad Company - 4 - 14 July 2023 Former Bunker C Vaults Central Valley Water Board staff does not concur with this evaluation. An analysis of soil and groundwater impacts beneath the northern structure was not conducted during the initial investigation and is still needed to evaluate whether this structure has had a release. The petroleum concentrations detected in the soil samples outside of the southern structure show that a historical release from this tank has occurred. Potential impacts to groundwater from this release need to be evaluated for petroleum and metals in accordance with the LUFT Manual. An analysis of soil samples beneath the structures is still needed to complete the risk assessment for this site. If further investigation shows that the structures are contributing to an ongoing release on site, then the tanks will need to be removed in accordance with county guidelines. Dunsmuir Site (GeoTracker ID: T10000005772) Antea Group did not perform an initial investigation for the Dunsmuir site because the property already has an ongoing Site Cleanup case for another release. Since there is currently an active investigation of petroleum impacts on Site associated with a different case, Antea Group determined that additional site investigation on this property is not necessary. Central Valley Water Board staff does not concur with this assessment. Investigation of potential historical fuel storage infrastructure on this property is still needed to determine if there is a risk to human health and to the environment from past or future releases. Central Valley Water Board staff requests that this investigation be conducted as part of the assessment for case #T10000005772 and will inform the case manager. Gold Run Site (GeoTracker ID: T10000021203) During the initial investigation, Antea Group identified the presence of one underground UST structure at the Gold Run site. Antea Group collected a composite soil sample from three borings located outside of (not beneath) the UST at 4.5 feet bgs and from one boring located within the tank. Antea Group also collected a liquid sample from the interior of the tank. The analytical results for the liquid sample were not included in the Report. The analysis of the composite soil sample detected 2,400 mg/kg of diesel range organics, which exceeds the ESLs for leaching to groundwater and direct contact in commercial settings. The composite soil sample also contained 400 fag/kg of benzo[a]pyrene (BaPE). Though the BaPe concentration was reported as a laboratory estimate, this value is above ESL associated with a human cancer risk. The sum of PAHs represented as BaPe equivalents also exceeded regulatory levels in the Low- Threat Closure Policy. While Antea Group identified the liquid in the UST as petroleum fuel, they did not state whether the contents of the tank were removed during the investigation. Antea group did not remove the UST structure during the investigation. In the Report, Antea Group concluded that no further action is necessary for the site based on its current use and location. Central Valley Water Board staff does not concur with this evaluation. Petroleum impacts to soil were not delineated during the initial investigation. An analysis of soil samples from beneath the base of the tank is needed to evaluate soil impacts. This analysis should also include BTEX compounds, as listed in LUFT Manual. An analysis of groundwater near the UST is also needed to evaluate