ARCHIVED REPORTS_2023-NOV 17 WASTE UNIT 1 VERIFCATION RPT

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17 November 2023 Project No. 14-3154 Page 2 of 3 On 15 April 2019, verification samples were collected from thirteen (13) locations within the excavation area (VS-1 through VS-13) under the oversight of Central Valley Regional Water Quality Control Board (CVRWQCB) and EHD staff. The results of the verification samples analyses indicated that all contaminants of concern (COC) were below the appropriate screening levels. Except for arsenic, all COC concentrations were below the January 2019 California RWQCB Environmental Screening Levels (ESLs) for commercial/industrial and residential shallow soil exposure. Arsenic was detected below the Environmental Protection Agency (EPA) Region 9 Regional Screening Level (RSL) for industrial soil and below the established site-specific background concentration of 8.6 mg/kg (Tables 1 through 3). The WU1 capped landfill area that extended onto Parcel A was removed. Minimal residual surface glass remained extending to the north from the excavated area to the railroad tracks. The remaining surface glass was mixed in with the topsoil and located in the upper 12 inches of the surface and was not part of WU1. However, considerable effort was made to remove as much of the surface glass as possible without compromising the structural support for the active railroad tracks, and a significant quantity of it was removed during excavation activities. It is AGI’s opinion that all waste has been excavated and removed from and beyond the boundaries of the known landfill area/capped waste area identified as WU1. The residual surface glass remaining is not part of the capped land fill area. The property owners have removed the WU1 area that extended onto Parcel A, and then exceeded the scope of work by removing as much of the surficial glass as possible. Additionally, trenching performed in the excavation confirmed that WU1 has been removed and verification sample results indicated that COC concentrations are below the appropriate screening levels. The work agreed to during meetings with the EHD in December 2018 to attain clean closure for WU1 on the subject property has been performed. The WU1 area has been removed and the trenching and verification sample results support this conclusion. Furthermore, excavated soil has been removed from the subject property and properly disposed. The property owners and AGI believe the EHD should fulfill the agreement and commitment communicated in December 2018 and approve clean closure of this area on the subject property. AGI reported and summarized all of the above information in the Verification Sampling Results and Clean Closure Clarification letter dated 10 June 2019. The letter was submitted to the EHD and CVRWQCB on 10 June 2019. AGI followed up several times with the EHD through the end of 2019 and into early 2020 requesting comment on the letter. As of the date of this letter, EHD and CVRWQCB have not commented on or replied to the Verification Sampling Results and Clean Closure Clarification. In 2020-2021, having had no response from the EHD and CVRWCB, the property owners had the soil stockpiles characterized and properly disposed. On 29 January 2021, a total of 52 discrete soil samples were collected from stockpiles SP-1 through SP-3 to characterize the waste for disposal. Soil samples were collected by hand-packing the