Crockett Diversion Rehabilitation Project
Team
- Phillip Duncan
- Zackary Pali
Existing Conditions
The Crockett Diversion is an irrigation diversion structure on the Logan River. This diversion serves the little Logan Canal and provides irrigation water to the valley. The diversion is operated using horizontal stop logs. Operators must manually install or remove these stop logs to maintain upstream water surface elevation as flow conditions change. The stop logs also cause a lot of build up of run off material such as logs, twigs, and other debris. The cleaning, maintenance, and manual operation of this current set up is tedious and requires a lot of extra work for the city. It can also be dangerous in spring run off and flood condition
Figure 1 – Crockett Diversion Structure – Front View
Crockett Diversion Structure – Back View
Design Options for Replacement of the Weir
Three options were weighed against one another. The first was to do nothing and leave the current system in place. The second option was to install a fixed crest (ogee) weir. The third option was an automated Obermeyer weir system.
Design Criteria Considerations and Analysis of Design Options
Design Criteria for the Crockett Diversion came down to five main points: cost, complexity, upstream flood control, water surface stability, and debris control. Cost was an important factor because a project like this would need to be funded by Logan City and its citizens. Complexity was a factor because people would be erecting and also running the weir system and would need to be able to do repairs as needed in the future. Upstream flood control and water surface stability were important to be able to regulate the flow and depth of water upstream of the weir. The Logan River Task Force wants to make the Logan River a place where citizens could enjoy activities in the future and have a source of recreation. Controlling the flow of water and making it stable would be necessary to accomplish this task. Finally, debris control was important, especially for flows in the early spring that bring debris down from the canyon. Having an option that could safely pass debris was very important. A Pugh matrix was created and each design option was scored based on their ability to fit the criteria. The cost to do nothing saved money immediately, while the fixed crest weir and Obermeyer weir had substantial up front costs. The do nothing option also came out as the best option in complexity as it is already built and simple in design. However, the Obermeyer weir won out as being the best option for upstream flood control, water surface stability, and debris control.
| Design Options | Cost | Complexity | Upstream Flood Control | Water Surface Stability | Debris Control | Totals |
|---|---|---|---|---|---|---|
| Do Nothing | 5 | 5 | 1 | 1 | 1 | 13 |
| 1 | 4 | 2 | 2 | 5 | 14 | |
| 3.5 | 2 | 5 | 5 | 5 | 20.5 |
The Obermeyer Weir: Best Design Option for Situation
An Obermeyer Weir is complex, but in its complexity is also simplicity. Transducers can be installed to monitor flow and depths in the river channel. These transducers will communicate with the pneumatically actuated bladders that control crest height. This system allows for a completely automatic operation. Operators can view current flow and stage data in real time from their cell phones. The supervisory control and data acquisition (SCADA) system controlling the weir will alert operators at any time if there is cause for concern at the site. The Obermeyers rounded shape allows debris to flow over the top allowing it to self clean as spring flows bring down debris from the canyon.
Function of the Obermeyer Weir
The Obermeyer weir inflates durable airbags to open and close the curved gates that either allow flow or block flow. These bags are extremely strong and are even bulletproof. The pneumatic actuators that inflate the bags can be controlled manually or automatically.
When the airbags are deflated, they fall under the gate panel and are protected by the gate panel. This allows flow over the top of the gate panel. The pneumatic bags can be inflated to varying sizes allowing for different flows or alternating depths behind the weir upstream. This simple and effective design makes the Obermeyer weir the best option for the Logan River.
Special Thanks
Special thanks to Lance Houser and Zac Sharp for their assistance and direction in the research of this project. Special thanks also to Logan City and the Logan River Task Force for allowing us to do research on the Logan River.