PUBLIC NOTICE
Draft Environmental Assessment for Big Cliff Dam Structural Enhancement for
Total Dissolved Gas Abatement Project, Marion and Linn Counties, OR
Comment Period Opening Date: September 4, 2024
Comment Period Closing Date: October 3, 2024
Interested parties are hereby notified that the U.S. Army Corps of Engineers, Portland District (Corps) is seeking public comments on the Draft Environmental Assessment (EA) for Big Cliff Dam Structural Enhancement for Total Dissolved Gas (TDG) Abatement Project, Marion and Linn Counties, OR. The Preferred Alternative includes the installation of up to two prototype rock weirs in the North Santiam River, downstream of the Big Cliff Dam, to force hydraulic jumps, generate bubbles, and to ultimately reduce levels of TDG in the water.
The prototype rock weir(s) would be monitored for one year following completion of construction. Monitoring would focus on the effectiveness of the design at abating TDG downstream of Big Cliff Dam. Following completion of the one-year monitoring, the results of the monitoring would be used to update design of the prototype weir(s) over the course of a one-year period, resulting in a design for permanent weir(s).
The prototype rock weir(s) would span the river and would tie into the shoreline. The weir(s) would be comprised of varying sized riprap ranging from approximately 6 inches up to 4 feet in diameter. Each prototype rock weir would be approximately 135 feet long, 100 feet wide, and 4 feet high at the crest.
Existing onshore infrastructure would be utilized for staging and access. A crane operated from the north riverbank would be used to install the prototype rock weir(s). Up to two temporary cofferdams would be used during installation of the prototype rock weir(s); these are necessary to isolate work areas from high velocity flow in the North Santiam River.
The Proposed Action also includes post-construction removal and site restoration for each of the temporary construction/staging features. The Proposed Action would be implemented after USACE has received all required environmental clearances and assuming that Corps determines a Finding of No Significant Impact (FONSI) for the Proposed Action.
Specific project actions include the following:
• Installation of up to two prototype rock weirs in the North Santiam River, downstream of the Big Cliff Dam, to reduce levels of TDG in the water.
• All disturbed areas (laydown areas, crane pads, etc.) will be restored with plantings to pre-disturbance conditions.
Environmental Document: The draft document for the proposed activity is available for public review.
Agency Coordination: The USACE is the lead Federal agency preparing this EA. No agencies were invited to formally participate as Cooperating Agencies in the development of this EA.
Assessment of the Need for an Environmental Impact Statement: The Corps has preliminarily determined the proposed action is not likely to result in significant effects on the human environment; therefore, an environmental impact statement was not prepared.
Cultural Resources Consideration and Tribal Consultation: Nation-to-Nation consultation was conducted with the following Federally recognized Tribe(s): Confederated Tribes of the Warm Springs Reservation of Oregon, Confederated Tribes of the Grand Ronde Community of Oregon, and Confederated Tribes of Siletz Indians. The letters notified the Tribes of the TDG Project and of the Draft EA for comment. Any responses received from the Tribes will be summarized for inclusion in the Final EA.
Water Quality Certifications: The Preferred Alternative would involve construction site activities resulting in point source discharges of construction stormwater runoff regulated under Section 402 of the Act that require a construction stormwater permit from Oregon Department of Water Quality. All construction stormwater permits would be obtained by the contractor prior to Project implementation as required by the contract specifications.
The Preferred Alternative would involve in water construction site activities regulated under Section 401 of the Act that require a Water Quality Certification from Oregon Department of Water Quality. On 17 July 2024, ODEQ approved the 401 Certification under US Army Corps of Engineers (USACE) Nationwide Permit (NWP) category #27. All ODEQ 401 Certification stipulations will be followed by the contractor and included in the contract specifications.
Endangered Species Act Consultations: The Preferred Alternative is expected to result in a beneficial effect to fish species due to a decrease in TDG, thus improving fish survivability to barotrauma. Based upon review of the ESA species lists, designated critical habitat, action area, previous Section 7 consultations and submittal of a 2024 Biological Assessment (BA) for the TDG project; the National Marine Fisheries Service (NMFS), on 16 May 2024, determined the project is consistent with the purpose of the Standard Local Operating Procedures for Endangered Species (SLOPES) SLOPES V Restoration Programmatic Opinion, which is intended to provide ESA Section 7 coverage for "...actions for which short-term environmental effects are likely to be low intensity, repetitive, and predictable, and for which long-term effects are likely to contribute to the recovery of listed species". The boulder placement will have predictable short-term construction effects followed by long-term benefits to fish by ameliorating harmful TDG levels.
Project Area Maps:
Public Hearing: Any person who has an interest, which may be affected by the proposed project may request a public hearing. The request must be submitted in writing to the district engineer within the comment period of this notice and must clearly set forth the interest, which may be affected, and the manner in which the interest may be affected by this activity.
Additional Information and Comments: Questions or comments regarding the draft document should be directed to Mr. Barry Moncrief, (503) 808-5101, james.b.moncrief@usace.army.mil at the address below. Mailed comments must be postmarked by the above closing date and sent to:
District Engineer
U.S. Army Corps of Engineer District, Portland
Attn: CENWP-PM-E/Barry Moncrief
P.O. Box 2946, Portland, Oregon 97208-2946
In your response, please include: "Big Cliff Dam Structural Enhancement for Total Dissolved Gas Abatement Project" in the subject line of your email/title of your mailed comment along with the submission date. A “no comment” response will be assumed if no response is received prior to or postmarked by the above expiration date.