2024-01410. Notice of Intent To Prepare an Environmental Impact Statement for the Scoggins Dam Safety Modifications Project

AGENCY:

Bureau of Reclamation, Interior.

ACTION:

Notice of intent; request for comments.

SUMMARY:

The Bureau of Reclamation (Reclamation) intends to prepare an environmental impact statement (EIS) for the Scoggins Dam Safety Modifications Project in the Tualatin Basin, Oregon. The purpose of the project is to improve public safety by reducing risk associated with severe seismic loadings while continuing to meet authorized project purposes. Reclamation is seeking public comments to identify significant issues or other alternatives to be addressed in the EIS.

DATES:

Submit written comments on the scope of the EIS on or before February 26, 2024.

Reclamation will hold two in-person and two web-based virtual public scoping meetings on the following dates:

1. February 8, 2024, 5 p.m. to 6:30 p.m. (PST), Forest Grove, OR.

2. February 8, 2024, 6:30 p.m. to 8 p.m. (PST), Forest Grove, OR.

3. February 13, 2024, 11 a.m. to 1 p.m. (PST), Virtual (Zoom webinar).

4. February 13, 2024, 4 p.m. to 6 p.m. (PST), Virtual (Zoom webinar).

ADDRESSES:

Send written scoping comments, requests to be added to the project mailing list, or requests for other special assistance needs via email to [e-mail].

The in-person meetings will be held at the Community Auditorium, 1915 Main Street, Forest Grove, OR 97116.

The web-based virtual meetings will be accessible at: https://www.virtualpublicmeeting.com/​scoggins-sod-eis.

To view more information regarding this project, go to: https://www.usbr.gov/​pn/​programs/​sod/​scoggins/​index.html.

FOR FURTHER INFORMATION CONTACT:

Rebecca Thompson, Bureau of Reclamation, Columbia-Pacific Northwest Regional Office, 1150 Curtis Road, Suite 100, Boise, Idaho 83706–1234; telephone [phone]; email [e-mail].

Individuals who are deaf, deafblind, hard of hearing, or have a speech disability may dial 711 (TTY, TDD, or TeleBraille) to access telecommunications relay services to contact the above individual during normal business hours or to leave a message or question after hours. You will receive a reply during normal business hours.

SUPPLEMENTARY INFORMATION:

This Federal Register notice provides the public with information regarding Reclamation's intent to prepare an EIS pursuant to the National Environmental Policy Act (NEPA) of 1969, as amended. Reclamation will hold public scoping meetings to solicit comments on the scope of the EIS and the issues and alternatives that should be analyzed. Additionally, this notice serves to provide notice and request public input on potential effects on historic properties from this project in accordance with the Section 106 process as defined in the National Historic Preservation Act (36 CFR 800.2(d)(3)).

Background

Scoggins Dam is an earthfill embankment dam located on Scoggins Creek, a tributary of the Tualatin River, about 25 miles west of Portland, Oregon. Construction of this 151-foot-high, 2,700-foot-long dam was completed in 1975. The dam's reservoir, Henry Hagg Lake, is the primary source of water for the Tualatin Basin, storing nearly 60,000 acre-feet (active 53,600 acre-feet), providing water for municipal and industrial uses, irrigation, water quality, fish and wildlife habitat, recreation, and flood control. The facility is operated and maintained by the Tualatin Valley Irrigation District. There are roughly 11 miles of shoreline around the lake at full pool; recreation facilities and trails in this area are managed by Washington County as Scoggins Valley Park.

The area of Scoggins Dam and its reservoir have high potential for severe loading initiated by an extreme seismic event from identified active faults, primarily the Cascadia Subduction Zone (CSZ), a 600-mile fault stretching from northern California to northern Vancouver Island in Canada. At its closest, the CSZ is 118 miles to the west of the dam. The principal concerns for Scoggins Dam are uncontrolled releases or dam breaches (dam failure) caused by severe loading from a CSZ seismic event. The dam could also experience less severe loading from local crustal fault earthquakes, the closest being the Gales Creek fault zone.

Around 2007, after completing general investigations of potential seismic hazards at the dam, Reclamation recognized the potential impacts of a CSZ seismic event to Scoggins Dam. Reclamation continued field data collection and evaluation and risk analyses updates through 2011 to improve the understanding of seismic risk to the dam. Since 2011, Reclamation has looked at various structural and non-structural options to reduce seismic risk, including options that would increase reservoir storage. In 2022, following completion of a Dam Safety Advisory Team review, Reclamation began furthering design of a dam-safety only structural option that would reduce risk in accordance with Reclamation's public protection guidelines. This alternative will be evaluated in the EIS.

Proposed Action

Reclamation proposes to reduce the risk to Scoggins Dam in the occurrence of a CSZ seismic event by improving the loadings response performance of the facility. This would be accomplished by raising the dam crest, constructing a downstream shear key, creating a new spillway, and placing additional berm material over the existing dam. This project would not create additional reservoir storage in Henry Hagg Lake.

Proposed dam structure modifications include:

• Excavate and backfill portions of the crest and existing embankment.
• Construct a downstream shear key.
• Install a downstream rock filter and drain.
• Install a stability berm over the shear key and downstream slope of dam.
• Raise the dam crest by ~7 feet.
• Demolish the existing spillway, bridge, and ancillary features.
• Construct a new spillway, bridge, and ancillary features and extend outlet works.
• Construct a new two-lane road across the dam.

The existing road across the dam would be closed during construction. An alternative road would be constructed to provide safe public transport. The project may also require permanently rerouting a portion of the Stimson Mainline Road to accommodate the expanded stability berm.

In addition to work on the dam, the project would include modification to structures around the reservoir such as culverts and recreation trails. Materials for construction would be excavated at one or more borrow sites on the east side of the reservoir, requiring the removal of large trees. Alternatives for accessing and transporting materials from the borrow sites will be investigated in the EIS and may include a combination of constructing a temporary haul route and using the existing Scoggins Valley Road.

Previous Water Supply Studies

In 2001, the Tualatin Basin Water Supply Feasibility Study was initiated to evaluate a range of water supply options in the basin, including raising Scoggins Dam (publication in the Federal Register on December 13, 2001, 66 FR 64454). A draft EIS was prepared in 2007, but never published, due to the need to further evaluate the seismic risk of the CSZ to the dam. During 2013, some of the partners in the feasibility study began separately pursuing other water supply options that did not include Scoggins Dam or Reclamation participation. In 2017, following receipt of a Joint Project Authority secured in amendments to the Safety of Dams Act in 2015, Reclamation began working jointly with Clean Water Services, analyzing the feasibility of three options (dam safety only modification, dam raise, and new downstream dam); all options would have reduced seismic risk at the dam, and two would have increased water supply in the basin. In 2021, a determination was made to forego further development of increasing reservoir storage and to support development of a dam safety only modification.

Statutory Authority and Anticipated Permits

NEPA [42 U.S.C. 4321 et seq.] requires Federal agencies to conduct an environmental analysis of their proposed actions to determine whether the actions may significantly affect the human environment. The EIS will analyze the environmental effects of implementing the proposed action and alternatives, and a no action alternative. The U.S. Army Corps of Engineers, Tualatin Valley Irrigation District, Washington County, Joint Water Commission, Clean Water Services, and Confederated Tribes of the Grand Ronde Community of Oregon have accepted invitations to participate as cooperating agencies for the EIS. Other entities will be considered, as necessary, during the EIS process. In addition to NEPA, various other Federal, state, and local authorizations may be required for the proposed action. Applicable Federal laws include, but are not limited to, the Endangered Species Act, National Historic Preservation Act, and Clean Water Act.

Public Disclosure

Before including your address, phone number, email address, or other personal, identifying information in your comment submission, please be advised that the entire submission, including your personal identifying information, may be made publicly available at any time. While a commenter may request that Reclamation withhold personal identifying information from public review, Reclamation cannot guarantee that it will be able to do so.

How To Request Reasonable Accommodation

For special assistance at one of the scoping meetings, please contact Rebecca Thompson or the TDD line (see FOR FURTHER INFORMATION CONTACT section of this notice) at least 5 working days before the meetings. All meeting facilities are physically accessible to people with disabilities. Information regarding this project is available in alternate formats upon request.

Jennifer Carrington,

Regional Director, Columbia-Pacific Northwest Region, Bureau of Reclamation.