Dam Safety – classroom presentations

Presentations are:

Kerr Dam Spillway Risk Reduction – An Owner’s Perspective, presented by Steve Jacoby, Grand River Dam Authority (GRDA), and John Osterle, Rizzo International

Leveraging Plant Automation Systems for Dam Safety and Penstock Rupture Monitoring, presented by Matt Roberts, Emerson

Replacing 5000-lb Trunnion Pins on a Large Radial Spillway Gate, presented by Tony Vader, Grant County PUD

Details about each presentation and the speakers are below:

Kerr Dam Spillway Risk Reduction – An Owner’s Perspective
Presented by Steve Jacoby, Grand River Dam Authority (GRDA), and John Osterle, Rizzo International

The Markham Ferry Hydroelectric Project consists of Kerr Dam and an integral 114 MW Powerhouse is owned and operated by the Grand River Dam Authority (GRDA). The facility is purposed for hydropower electricity generation, water supply, and flood control management under the jurisdiction of the Tulsa District, U. S. Army Corps of Engineers (USACE) with directed releases performed by GRDA operational staff.

Continued high flow events along the Neosho River from 2015 to 2020 resulted in significant stilling basin deterioration at the toe of the dam. The most recent flooding event occurred in January 2020. This event was initially managed with limiting gate operations, but a mid‐March storm resulted in high flow for the last half of the month peaking at near 100,000 cubic feet per second through the spillway. Sonar data indicated that the scour depth downstream from the spillway toe ranged from three to fifteen feet in some areas and extends from 20 to 100 feet downstream. In collaboration with the FERC, GRDA initiated the following risk reduction measures for protecting, monitoring and expediting foundation scour improvements:

• Conducting a focused potential failure mode analysis for the Spillway section of the dam;
• Limiting gate operations to distributed flow methods to reduce further scour;
• Limiting the maximum reservoir elevation to minimize hydraulic load and future discharges;
• Initiating Computational Flow Dynamics (CFD) and physical model studies to determine operational and physical modifications to limit the potential for scour during future high discharge events; and
• Reevaluating the sliding stability of the spillway to account for the observed toe scour and uncertainties in rock shear strength.
Lowering the maximum elevation of the reservoir has significantly impacted the operation of the hydroelectric project which has resulted in a significant loss in revenue from hydroelectric generation and has also limited the USACE’s ability to manage floods within the river basin.

48 high-capacity (i.e., up to 2,000 kips) anchors were installed in the spillway section of the dam in September 2023 to April 2024 as an interim risk reduction measure. The enhanced sliding stability of the spillway section has resulted in returning the maximum allowable reservoir elevation to the original level.

Additional risk reduction measures currently under consideration by GRDA based on the results of physical modeling studies and CFD analyses include modifying the existing spillway structure to include USBR slotted flip buckets and adjusting spillway gate operation protocols based on tailwater elevations.

Leveraging Plant Automation Systems for Dam Safety and Penstock Rupture Monitoring
Presented by Matt Roberts, Emerson

Dam safety and penstock rupture monitoring are increasingly becoming an integral part of plant automation systems.

The main objective of this presentation is to provide operational information to protect human life and prevent damage to hydroelectric units and flooding of hydroelectric power plants, while ensuring compliance with local national standards.

Online information and rapid response are essential when the development of power generation and transmission technologies is rapidly progressing and breaking away from the current state of civil structures.

This paper will discuss dam monitoring and penstock rupture, challenges to overcome, and lessons learned. Particular attention will be paid to the status, problems, tasks and ways of developing the system of operational monitoring of the dam and pressure pipelines, protection of hydroelectric units and the station from flooding.

The algorithms used for evaluation, construction of the protection system, issues of visualization and presentation of information, collection of information, application of modern wireless technologies, display of safety factors, communication with the GA operation mode, data collection in manual and automatic modes will be discussed in detail. Several examples of implementation will be considered within the framework of this work.

Highlights:
1. Distributed control system architecture for dam safety and penstock rupture monitoring as part of plant control systems
2. Flow and level monitoring systems plus flow measurement and leak detection in penstocks
3. Wireless solutions for filtration monitoring: challenges and benefits
4. Geodesic monitoring; data collections in manual and automatic modes; data presentation best practices; safety coefficient calculations
5. Penstock rupture approaches: algorithms; data processing; connections with unit(s) modes of operation

Replacing 5000-lb Trunnion Pins on a Large Radial Spillway Gate
Presented by Tony Vader, Grant County PUD

Tainter Gate 12 at Wanapum Dam had been out of service for 4 years, limiting the crucial ability to pass flows on one of the nation’s largest rivers. Like many on the Columbia River, this is a truly massive spillway gate, standing 65-ft tall and 50-ft wide. In early 2020, workers observed improper rotation of the pin indicating high trunnion friction. The gate was immediately placed in emergency-use-only status until repairs could be made. Like many things in 2020, this work was postponed for the global pandemic. Add in questions about the capacity of the dam’s resident cranes, competing priorities, and a host of other issues, and years slipped by without progress. With that time, our institutional knowledge of how to perform repairs began to degrade.

The project was jump-started in 2023 with a new commitment to the FERC to complete repairs by the end of 2024. Our first task was research. We combed through old records, interviewed contractors and manufacturers, and employed the only in-house inspector remaining who’d worked on the project to upgrade our trunnions. Our goal was a fool-proof plan involving personnel access, gate stabilization, pin swapping, and thorough testing. We endeavored to leave very little to chance once work began.

Grant PUD, dam owner, ultimately elected to hire a contractor to perform the work using nearly all District materials, equipment, and tools. The contractor provided the crane, the crew, and years of experience on similar projects. The District spent nearly 18 months planning, building tools, milling precise replacement pins, and negotiating a contract. All these efforts culminated in a successful 4-week project for our contractor. Intent on leaving a better record of how we accomplished this project, a post-project effort was undertaken to document the procedure. The contractor submitted lessons-learned and provided a fantastic library of project photos. District personnel compiled daily reports and our own photos and focused especially on parts of the project where information had been missing before. We were able to close this project knowing that we’ve left the District in a better position to handle this particular problem in the future.

As an introduction to our project presentation, a brief history is provided of Grant PUD’s efforts to minimize trunnion friction, to measure it, and to understand its sources and the risk it poses to our project, both for dam safety and asset management.

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