SUPPLEMENTARY INFORMATION:

The USACE, Seattle District, will prepare an SEIS in accordance with 33 CFR 230.13(b) for proposed modifications to the recommended alternative for the downstream fish passage component of the previously authorized HAHD Additional Water Storage Project in King County, Washington. The scope of this SEIS will not extend to other elements of the project related to water supply or ecosystem restoration, as those components were not materially altered from the description evaluated in the 1998 EIS and have already been implemented. The purpose of the fish passage component of the larger ( printed page 52133) Additional Water Storage Project remains the same as the original EIS: To successfully pass migrating juvenile fish downstream.

The 1998 EIS evaluated a fish passage facility generally consisting of a floating fish collector. In their 2019 Biological Opinion (BiOp) for HAHD operations and maintenance, the National Marine Fisheries Service (NMFS) established survival criteria and transport pipe exit release location criteria that must be met by any fish passage facility for the project. In order to meet these criteria, the USACE has redesigned the downstream fish passage component of the project. In this SEIS, the USACE will evaluate implementation of downstream fish passage via a fixed multiport collection structure that would allow fish collection from a set of five intake ports at multiple elevations as the reservoir water level changes. Once collected through the multiport structure, fish would be transported downstream using one or more steep bypass pipes. The SEIS will evaluate and provide supplemental analysis, as applicable, on any impacts generated by the modification of the downstream fish passage component of the recommended alternative to the quality of the human environment not identified and evaluated in the August 1998 Final EIS. Evaluation may extend, for example, to potential changes in the study area to aquatic habitat, different species listed under the Endangered Species Act (ESA) in the study area, potential changes to the geological analysis associated with the construction of a fish passage facility, potential impacts to natural resources during construction, including elevated noise and disturbance to fish and wildlife at HAHD from rock blasting and operation of construction equipment, potential effects to cultural and historical resources, and temporary effects to water quality and aquatic habitat from construction.

As identified in the original EIS, USACE continues to propose monitoring to determine whether the facility provides safe downstream passage for fish. Once operational, the fish passage facility is expected to have significant benefits to ESA-listed salmonids thereby benefiting the ecosystem of the entire Green River watershed, as well as increasing a primary food source for the endangered Southern Resident killer whales. The anticipated authorizations required prior to construction are expected to include a BiOp from the U.S. Fish and Wildlife Service, a Clean Water Act Section 401 Water Quality Certification, concurrence from the Washington Department of Ecology on a Coastal Zone Management Act Consistency Determination, and consultation under Section 106 of the National Historic Preservation Act.

The SEIS will follow the same process and format as the original EIS ( i.e., draft, final, updated record of decision (ROD)), except that scoping is not required. The original EIS and other project documents are available online at https://www.nws.usace.army.mil/​Missions/​Environmental/​Environmental-Documents/​.

The draft SEIS will be made available for public and agency review and comment, which is expected to occur in October 2021. After public review of the draft SEIS and evaluation of the comments received, USACE will promulgate a final SEIS; this is expected to occur in 2022.

Comments or questions concerning this proposed action can be directed to the USACE contacts listed above.