The District contracted Panorama in May 2020 to prepare an Environmental Impact Report, Biological Assessment, Section 404 permit application including Section 106 consultation, 401 Water Quality Certification application, California Department of Fish and Wildlife Section 1600 Agreement application, and USACE Environmental Assessment for the Section 408 authorization. Panorama was also responsible for leading public outreach meetings, presentations to the County Board of Supervisors, and all agency consultation meetings. The EIR was prepared on an expedited schedule and certified by the Board of Supervisors in September 2021. All permit applications and the BA were filed in June 2021 and the EA was completed in November 2021.

The key issues technical issues that were addressed in the EIR and technical studies conducted by Panorama included: hydrology/hydraulics and change in downstream flooding and sediment dynamics under an existing condition baseline, climate change scenario (future condition), and cumulative baseline considering other flood control projects proposed upstream; impacts on aesthetic resources and recreation due to new floodwalls and modifications to Frederick Allen Park; impacts on fish passage and special-status fish species due to construction and the proposed channel modifications; climate change resiliency; air quality and health risk impacts from construction; and noise impacts on surrounding residential areas.

Panorama used technical studies prepared by the USACE as part of the 2018 Draft EIS/EIR to the extent feasible. However, additional surveys and analyses were needed to address air quality impacts from construction including a health risk assessment; updated hydraulic modeling and modeling of climate change scenarios; visual simulations to assess the proposed project change on visual quality; wetland delineation; and noise data collection and historic resource evaluation to address data gaps.