Mitigating Flood Risk: Replacing the Crockett Diversion Structure and Restoring the Logan River

Introduction

The sediment buildup upstream of Crockett Diversion currently poses a flood risk to residents living near SumacPark in Logan, Utah. The location is shown in Figure 1.
The Crockett Irrigation Company currently manages the structure with manually placed wooden blocks. The diversion structure’s purpose is to redirect water into the Little Logan River Canal; this canalsupplies 100 cfsof water into Cache Valleys canal network. Working with Cache Water District, the Bear River Engineering team designed a solution with the following goals:

  • Public Safety
  • System Efficiency
  • Flood Mitigation
  • Recreational Opportunities
Top arrow shows the location of Old Main. Bottom arrow points to where the Crockett Diversion Structure sits between River Hollow and Sumac Park.

Top arrow shows the location of Old Main. Bottom arrow points to where the Crockett Diversion Structure sits between River Hollow and Sumac Park.

Figure 1 –Local Location

Alternatives and Criteria

Five alternatives were proposed and then evaluated using criteria based on the client’s needs and the goals mentioned above.

The five alternatives evaluated:

  1. Pump Station & Closed Conduit
  2. Relocate Diversion to First Dam
  3. Structure Redesign
  4. Retrofit Design
  5. Do Nothing

The Criteria:

  1. Flood Mitigation
  2. Safety around site
  3. Public/Private Stakeholder Opinion
  4. Cost
  5. Environmental Impact
  6. Efficiency
  7. Recreation
  8. Construction Speed

The Pump Station alternative met the most criteria, the percentage of criteria met can be seen in Figure 2.

chart on the percentage of different criteria met

Figure 2–Pump Station Percent of Criteria Met

Selected Alternative

The selected alternative was building a pump station and closed conduit system. The selected alternative will affect the area in the following ways

Diversion Structure

  • The current structure will be demolished and replaced with a V-Shape Rock Weir and Rock Stairs (Figure 4).

Sediment

  • Sediment buildup will be removed prior to construction to prevent unsafe conditions, and to align with proposed regrading

Recreation

  • The structure will become passible via watercraft when river flow permits.

Irrigation

  • Water rights for the Little Logan River will be pumped
old design

The current weir creates a largedrop that makes it impassible by watercraft. The current design is also dangerous for operation and maintenance

Figure 3–Old Design

new design

The current structure will be replaced with a V-Shaped weir to divert water to the pump station and create small drops in elevation

Figure 4–New Design

new pump design

The new pump stationwill provide the required flow for irrigation. The regraded river will allow for increased safety when recreating.

Final Design

The Bear River Engineering team, seen in Figure 6, designed the foundation, walls, and roof slab of the pumphouse with reinforced concrete.
A concrete stilling basin was designed to hold the required volume of water rights for the irrigation canal.
A rock weir system will divert water into the stilling basin and a sluice gate will control how much water can enter the basin.
The estimated cost of this project is $1,745,000

Bear River Engineering

Figure 6–Bear River Engineering

From left to right: Matthew Penrod, Jake Douglas, Trevor Wilson, Bailey Nielson, Jennifer Farfan, and Jill Woodhouse.

Acknowledgements

Pump Station Elevation and Plan View

Figure 7–Pump Station Elevation and Plan View

Thank you to everyone that provided professional guidance to assist our team:

  • Weston Bellon (PE), J-U-B Engineers
  • Nathan Daugs (Client), Cache Water District
  • Dr. Brian Crookston (Faculty Advisor)
  • Dr. Beth Neilson (Faculty Advisor)
  • Austin Ball (Professor)