1. How were the design modifications for Phase 2 determined?
Engineers worked through a variety of scenarios 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 technicians, user feedback, and the professional whitewater features design experience of project engineers to determine the best path forward.
Modifications to the existing spillway gates will also be completed to provide more flexible flow control and operation on Drop Structure 1.
2. What changes will be made to the Phase 2 adjustable wave feature?
Design modifications planned by the engineering team include updates to a variety of aspects of the Phase 2 adjustable wave feature and Drop Structure 1 at the Boise Whitewater Park. Planned modifications, which will be implemented over the winter will include:
- Modification of the spillway gates to provide smaller gate sections providing more flexibility for operation and flow control
- Replacement of the wave gate to improve performance
- Adding a downstream weir below the waveshaper gate to increase wave stability and operational flexibility.
- Modification of the flow control gate (bypass) to improve hydraulics and make the wave and all associated features more user friendly
- Adding a plunge pool below the main spillway to increase river safety.
- Modification of electrical components to increase resiliency during flood events.
- Installation of new public information, safety, and user guidance signage at Phase 2
3. Why are these design modifications necessary?
The original Phase 2 adjustable wave design does not create a reliable and consistent wave feature suitable for a variety of users. Due to its unpredictability, modifications are needed to create a better experience. This work seeks to make the wave feature more available for users, easier to maintain, and more predictable. A similar experience to what users have come to expect at the Phase 1 wave upstream from Phase 2. For example, spillway gates modifications will allow more flexibility for flow control and operation at various river flow levels.
4. What can users and park visitors expect to see happening at Phase 2 this winter (2024/2025)?
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, and there will be some temporary area and pathway closures due to staging. Crews will follow all necessary safety and environmental protocols while completing these park modifications.
5. What’s the timeline for completion?
Construction mobilization is scheduled to begin in November 2024 with construction and modifications work continuing in-river until March of 2025 to complete the project.
6. Once the design modifications are completed (expected in spring 2025) what will the user experience be like at Phase 2?
While the feature may not be as intense and challenging as it has been, the goal of this project is to provide a more predictable wave for users to practice and play in, with the goal of reducing the need for restricted hours and monitored sessions if possible.
7. Will the new wave gate allow for real-time adjustability?
The modifications planned for installation this winter will provide more flexibility for gate operators and technicians to respond to changing river conditions while improving wave stability and performance.
8. Are modifications planned for any of the downriver features from the Phase 2 adjustable wave?
Drop Structure 2, the in-river boulder feature below the Phase 2 adjustable wave, is being evaluated to address potential exposed boulder conditions under varying flow conditions that could affect user experience. Removal of high points on the existing drop structure’s boulders will be completed as part of the 2024/2025 winter work period.
9. Will any of the planned modifications at Phase 2 affect the Phase 1 adjustable wave feature?
Our team does not anticipate changes to the Phase 2 adjustable wave feature to affect the Phase 1 wave feature located upstream at the park. However, construction at Phase 2 over the course of the fall and winter in 2024/2025 is anticipated to affect the experience at Phase 1. For this reason, the Phase 1 wave at the Boise Whitewater Park is expected to be closed during construction (approximately November 2024 through March 2025). We appreciate your understanding and cooperation during this off-season closure.
If you’d like additional information about this project, please contact Boise Parks and Recreation to be connected with project managers.