1. How were the design modifications for Phase 2 determined?
Engineers worked through a variety of scenarios using advanced hydraulic modeling and analysis in order to assess the Phase 2 adjustable wave setup and understand the complex elements resulting in the unstable wave feature created by the initial design. They used the best available technology, hydraulic modeling, engineering analysis, hands on operating experience of City of Boise operations staff and more to determine the best path forward to create a more reliable feature that is functional in a variety of conditions and river flow levels. Modifications to the existing spillway gates will also be completed to provide more flexible flow control and offer a pass-through option for stray boaters.
2. What changes will be made to the Phase 2 at the Boise Whitewater Park?
- Modification of the spillway structure to split current 20-foot-wide Gate 5 and Gate 6 to create four, 10-foot-wide gates. This will provide increased flexibility for operations of the main spillway as well as providing a pass-through option for stray boaters
- Modification of the waveshaper to allow for downstream tailwater control making the waveshaper less sensitive to overall changes in flow rate. A fully submerged downstream gate will allow our wave technicians the ability to increase tailwater depth and stabilize the wave feature
- Running additional air lines and wiring for the replacement spillway gate and submersible wave structure gate
- Waterproof vault components for flood resiliency and reduced maintenance needs
- Add a plunge pool downstream of the spillway gates to increase safety for stray boaters
- Mitigate leakage associated with the fish ladder structure on the left riverbank
3. Why are these design modifications necessary?
The original Phase 2 adjustable wave design does not create a predictable and consistent wave feature suitable for a variety of users. Due to its intensity and unpredictability, modifications are needed to create a more user-friendly experience. This will reduce the amount of staff time dedicated to the maintenance and monitoring of the wave feature, while creating a more reliable experience similar to what users have come to expect at the Phase 1 wave upstream from Phase 2.
4. What can users and park visitors expect to see happening at Phase 2 this winter (2023/2024)?
Construction crews will be working in the riverbed and visitors will see an area where water is diverted around the construction site. Construction equipment will be staged at Esther Simplot Park adjacent to the Phase 2 adjustable wave. Crews will follow all necessary safety and environmental protocols while completing these park modifications. A Greenbelt closure is anticipated throughout construction and will be signed appropriately.
5. What’s the timeline for completion?
Construction mobilization is scheduled to begin November 2023 with maintenance modifications expected to wrap up in the spring of 2024.
6. Once the design modifications are completed (expected in 2024) what will the user experience be like at Phase 2?
The Boise Parks and Recreation Department will determine this once the proposed modifications are completed. The goal of this project is to provide a more predictable wave for users to practice in without the need for monitored sessions with wave operators on site whenever river flows allow the wave to be operable. Just like the implementation of Phase 1 of the Boise Whitewater Park, it is expected to take several years for city wave techs to learn how to manipulate the new Phase 2 waveshaper gate, read river flows, and adjust on site to create various recreational experiences based on a variety of external factors.
7. Are modifications planned for any of the downriver features from the Phase 2 adjustable wave?
No adjustments are planned at other Phase 2 in-river structures at this time. The Boise River is a wild and scenic river that experiences streambed fluctuations and more each season. The project team will be closely monitoring for any impacts to downstream features to see if future modifications are necessary.
8. Will any of the planned modifications at Phase 2 affect the Phase 1 adjustable wave feature?
No, engineers do not anticipate changes to the Phase 2 adjustable wave feature to affect the Phase 1 wave feature located upstream at the park.
A community open house is planned from 5:45 to 7:15 p.m. in the William F. Hayes Memorial Auditorium at the Boise Public Library (715 S Capitol Blvd) on Monday, November 20th for the project team to update recreationists on the status of the project, outline the planned maintenance modifications at Phase 2 and answer any questions.