The project involves soil excavation and off-site disposal of impacted soil at permitted disposal facilities, and institutional controls such as land use covenants or deed restrictions. The former Vallejo Manufactured Gas Plant (MGP) is comprised of Operable Unit-1 (OU-1) and Operable Unit-2 (OU-2). On September 12, 2019, the Department of Toxic Substances Control (DTSC) adopted a Negative Declaration in connection with the approval of two Remedial Action Plans (RAPs). The RAPs addressed the remediation of contamination associated with the Former Vallejo Manufactured Gas Plant (MGP) in the City of Vallejo. The site has two Operable Units, OU-1 (26 acres) and OU-2 (0.67 acres), on the south and north sides of Curtola Parkway, respectively.
On September 12, 2019, DTSC approved the Initial Study and Negative Declaration (IS/ND) for the RAP and filed a Notice of Determination with the Governor’s Office of Planning & Research, State Clearinghouse. Project activities included remediation plans for OU-1 and OU-2 consisting of excavation and off-site disposal of contaminated soils, and in-place treatment of deeper contaminated soils. The filing documented that the project’s approval would not have a significant effect on the environment and that mitigation measures were not made a condition of project approval.
The approved OU-1 RAP called for a combination of excavation and off-site disposal of soils, along with stabilization of soils beneath the groundwater table to achieve cleanup goals. The remedial design and implementation plan for this project indicated that there may be a need to replace the existing storm drain line with new stormwater conveyance routes, however at the time no consideration was made to performing work in the Mare Island Strait. Therefore, this Addendum to the Final IS/ND for the Site is necessary to address the modification to the Project. The updated project activities are consistent with the original activities described in the OU-1 RAP and all work will occur in accordance with both the 2019 RAP and Negative Declaration. No other revisions to the OU-1 RAP are planned.