Largest dam expansion in US history underway
Located in the heart of Colorado, USA, Gross Reservoir is a vital structure for managing water flow across the North American Continental Divide.
To secure the future water supply for the region, Denver Water is undertaking the largest dam expansion in US history. The project involves raising the 70-year-old Gross Reservoir dam by 40m (131ft) to nearly triple its capacity. This substantial increase requires about 554,000 cubic metres (725,000 cubic yards) of roller-compacted concrete (RCC) and over 69,000 cubic metres (90,000 cubic yards) of conventional concrete.
The expansion also includes the construction of 118 concrete steps on the downstream side, extending from the base of the existing dam to the new crest.
Challenges
The project presented several challenges for Doka's formwork engineers:
- The formwork system needed to align with the dam face for both aesthetic reasons and to effectively support the walls against the pressure of newly placed concrete.
- The system had to be quick and efficient to move, but with minimal ties to allow for greater flexibility.
- The dam face steps back with each lift, becoming progressively wider, which increased the complexity of the concrete pour.
Solution
To address these challenges, Doka’s Infrastructure Group worked closely with the project team to design a custom formwork system. The system, which included Doka’s Xclimb 60, a guided climbing formwork system, and Framax S Xlife, a framed formwork system designed for high loads and reuse across multiple pours, allowed for horizontal adjustments to maintain consistent tie spacing as it rises up the dam face.
The solution combines both custom and standard girder forms, creating a flexible and easily movable system that supports continuous 24/7 concrete pouring.
Doka also provided DokaXact, a digital sensor system used for precise real-time monitoring of formwork loads and concrete pressures. For the Gross Reservoir expansion, DokaXact ensures the concrete pours were within safe load limits and that the formwork systems were not being overstressed.
By providing accurate data on the pressure being exerted on the formwork, DokaXact enabled the project team to make informed adjustments during the pour, optimising the workflow and maintaining the integrity of the structure. This level of control was essential for managing the complexities of the dam’s stepped face and varying widths, allowing for consistent quality throughout the construction process.
Project Information:
- Completion Year: 2027
- Project Duration: 2024-2027
- Location: Golden, Colorado, USA
- Contractor: Kiewit Infrastructure and Barnard Construction
- Structure Type: RCC Dam
- Height of Expansion: 143m (469ft)
- Number of Sections: 118
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