Potential New Dam Concept Identified#
Preliminary design efforts revealed that two viable dam concepts exist for enlarging Halligan Reservoir:
- Existing Dam Concept: The existing dam would need to be significantly modified to meet current regulations and hold up to the increased scrutiny given to dam design following the 2017 Oroville Dam spillway failure. Modifying the more than 110-year-old dam will present unique challenges during design and construction.
- Adjacent Dam Concept: An additional dam concept was identified, which would entail building a replacement dam immediately downstream of and adjacent to the current dam.
We have started preliminary design activities and alternatives evaluation for the proposed dam enlargement, with our second round of subsurface data collection starting this summer.
This phase of work will be very similar to last fall’s fieldwork.
Site preparations will begin July 19 with drilling and survey activities beginning July 26. This work will last through Sept. 1, weather permitting. Site restoration will occur the following week. Connell Resources and Dragados-Pulice JV will provide site preparation services and Authentic Drilling will provide the subsurface drilling services.
We will be investigating the existing rock and foundation for rock type, soil properties, density, fractures, shape, depth and hardness by extracting cores and performing seismic surveys. This will determine the properties, strength, and composition of the existing rock.
By doing these studies, we will learn more about the geotechnical and geologic properties of the rock. This information will continue to inform our preliminary design efforts, including learning more about any design modifications that need to be considered for the spillway size, stilling basin, and dam type based on the data.
You've spoken, and we've heard you.
We received approximately 60 public comment letters or statements on the draft Environmental Impact Statement (EIS) and Conceptual Mitigation Plan. Together, with the U.S. Army Corps of Engineers, we’re evaluating each comment to determine next steps for the final EIS and final Conceptual Mitigation and Enhancement Plan.
State Fish and Wildlife Mitigation and Enhancement Planning Kicks Off#
We kicked off the process for the state Fish and Wildlife Mitigation and Enhancement Plan with Colorado Parks and Wildlife (CPW) in May 2020. Through this process the City will continue to develop and refine mitigation and enhancement measures for fish and wildlife affected by the Project.
Under Colorado law, fish and wildlife resources impacted by water development projects such as the Halligan Water Supply Project must be mitigated (37-60-122.2 C.R.S.). To do so, the City must develop a Fish and Wildlife Mitigation and Enhancement Plan. Once complete, the City of Fort Collins will seek approval of the Plan from the CPW Commission and the Colorado Water Conservation Board. Once approved, the Fish & Wildlife Mitigation and Enhancement Plan becomes the official state position on fish and wildlife resource mitigation.
Draft Environmental Impact Statement Released#
The draft EIS for the Halligan Water Supply Project was released Friday, Nov. 22, 2019. This is a critical milestone in the federal permitting process. The EIS describes the project, other water supply alternatives considered and the potential impacts of each.
The draft EIS is available online and physical copies are available at the following locations:
- CSU Morgan Library, 1201 Center Ave., Fort Collins, CO 80523
- Poudre River Public Library District-Old Town Library, 201 Peterson St., Fort Collins, CO 80524
- Poudre River Public Library-Harmony Library, 4616 S. Shields St., Fort Collins, CO 80526
- UNC, James A. Michener Library, 14th Ave. and 20th St., Greeley, CO 80639
- U.S. Army Corps of Engineers, Denver Regulatory Office, 9307 S. Wadsworth Blvd., Littleton, CO 80128
A public hearing was held Jan. 13, 2020, and the comment period closed Feb. 26, 2020, which included a 30-day extension from the Corps.