Hermosa Creek Aquatic Organism Passage

Acknowledgements

Project Advisor: Marcus Florida

Technical Advisors: Prof. Jeff Holley, Dr. Kristoph Kinzli, and Dr. Andreas Guerra   

Donations Made by: Trout Unlimited 

Video

Elevator Pitch

Colorado River Cutthroat Trout (CRCT) occupy the colder waters of the Colorado’s tributary streams above the Grand Canyon and west of the Continental Divide. CRCT now occupy 16% of their historical habitat, and 8% of that population lives in what are considered as “conservation populations” [1]. In the San Juan National Forest, located in the southwestern portion of Colorado (CO), there has been a push for sustainable reintroduction and conservation of the CRCT population. Re-design of an aquatic organism passage (AOP) was proposed in two streams in Durango, CO within the San Juan National Forest. Team AOP, from Colorado School of Mines, has been tasked with this project. The purpose of the project is to reconnect two fragmented fish supporting tributary streams by replacing road culverts with spans that allow for heavy traffic on the road surface and free migration of fish both upstream and downstream under all flow conditions.

The proposed solution for the project is to replace the two existing steel pipe culverts with bottomless corrugated steel culverts. This solution comes from the recommendation of the client with the intent to maintain a natural stream bed, reduce costs, and the feasibility of transportation and construction of materials. With the bottomless steel culvert, the challenges faced from the existing soil conditions, including bedrock, are minimized due to the reduced excavation required. Corrugated steel can also be transported in sections making the transportation down the forest service road much more feasible than a large concrete structure driving down costs.  

The intent of this project was to cut costs of the necessary redesign of the two culverts by having the design work completed by a Senior Design team. In turn, the Forest Service will be able to use this information provided to them to publish a public contract with construction starting ideally by the summer of 2022.  

Design Approach

Design Solution

HY-8 hydraulic analysis concluded that Relay Creek with have an 11 ft span and 3.5 ft rise to accommodate all flow conditions calculated above while not overtopping with water. 12 ft span and 4 ft rise were chosen for Sig Creek. The low–profile arch allows the design to meet the existing bank fill width of the channel to minimize unnatural channel constriction and provide a culvert height that will minimize the road regrade. 

According to USFS streambed simulation guide, this streambed system is categorized as a step pool channel due to its relatively high slope (3-9%) and large colluvium and wood forming natural steps as the channel descends in elevation. This is clearly seen through the photos captured in the initial site visit and confirmed by the Civil 3D surface. For this channel type, it is necessary to match these steps underneath the culvert. 

Cast-in-place reinforced concrete footing foundations were designed for each side of the corrugated metal arches. The dimensions of each footing were found by calculating the minimum dimensions to prevent over burden stress, sliding, overturning, and settlement. The determining factor of the four active forces was used for dimensions in the final design. One of the footings for Sig Creek can be seen below. The shape of the foundation is a typical shape for small footings used on bottomless arch roadway culverts. Colorado Division of Transportation (CDOT) specifications were used to check that the minimum dimension ratios were up to code. The compressive strength, unit weight, and rebar enforcement of the concrete was determined with the latest ACI code.  Assumptions for geotechnical soil prosperities were based on a silty sand with gravel. This type of soil is typically found in creek beds in mountainous areas.  

Next Steps

The intent of this project was to cut costs of the necessary redesign of the two culverts by having the design work completed by a Senior Design team. In turn, the Forest Service will be able to use this information provided to them to publish a public contract with construction starting ideally by the summer of 2022.  

Final steps for this project to be completed by the Forest Service include: 

• Review of SD design proposal by Forest Service engineers 
• Public bid proposal by local contractors 
• Review and selection of bids by Forest Service 
• Construction plan for completion of project by the contractor 
• Construction estimated to start by summer 2022  

Meet the Team