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Public Notice - 2 - 27 January 2021 Tracy Railyard — Offsite South Area Tracy, San Joaquin County evaluation was based on analytical results from soil samples and one soil vapor sample collected (from previous investigations) along the former TAOC and OVP Right of Way (ROW) near the Site. On 6 March 2020, Arcadis U.S., Inc., (Arcadis) (Chevron's current consultant) submitted a toxicologist review of the Report on behalf of Chevron. Leidos did not evaluate groundwater since it is not considered a residential exposure pathway and is not likely to be used as a source of drinking water Leidos evaluated analytical results for a residential scenario and determined that the combined TPH, BTEX, and PAHs cancer and non -cancer risks for soil and soil vapor were less than the thresholds of 1 E-06 and 1, respectively. Arcadis toxicologist determined that concentrations detected in soil samples were low and not considered a human health or environmental concern. However, the Arcadis toxicologist determined that the number of soil vapor samples collected for the evaluation was inadequate to characterize the Site. Staff determined that additional soil vapor samples were needed and requested that Chevron submit a work plan to further evaluate soil vapor impacts beneath the Site. Prior to preparation of the soil vapor work plan, Arcadis' determined that additional soil vapor data pertinent to the Site was available but had not been included in the human health risk evaluation prepared by Leidos. Arcadis presented the soil vapor data in a letter dated 9 July 2020. The additional soil vapor data was taken from the Chevron 6t" Street Railyard site which is adjacent to the Site. Five- and 10 -foot soil vapor samples were collected from five previously identified areas (borings SV -A through SV -E). Borings SV -A, SV -C, and SV -E were advanced adjacent to the residential developments located east, south, and west of the Site, respectively. Benzene and naphthalene concentrations for each of the ten samples were not detected that exceeded laboratory reporting limits. Non -detect, or very low level concentrations of ethylbenzene, toluene, and xylenes were reported for the soil vapor samples, which were found to be significantly less than both the 2010 California Human Health Screening Levels and the 2010 San Francisco Bay Area Regional Water Quality Control Board Environmental Screening Levels. Additionally, the analytical results for groundwater samples collected in the area were sufficiently low enough to support the conclusion that neither benzene nor naphthalene concentrations are considered a residential vapor intrusion health concern. Arcadis toxicologist determined that additional soil vapor assessment was not necessary and presented the data in the 9 July 2020 letter, in lieu of a work plan. Arcadis recommended a status of No Further Action (NFA) for the Site. Staff concurred with Arcadis recommendation in a letter dated 21 August 2020 and determined that prior to considering a status of NFA for the Site, Chevron needed to submit a list of water supply wells within 2,000 -foot radius from the Site, a list of interested parties within a 200 -foot radius of the affected area, and complete a 30 -day public participation period. On 9 October 2020, Arcadis submitted a list of interested parties and queried the State Water Resources Control Board's GAMA Groundwater Information System. No water supply wells were identified within 2,000 -foot radius of the Site.