Once raised, the Gross Dam will become the tallest dam in Colorado and the tallest roller-compacted concrete (RCC) dam in the United States.

Barnard teamed with Kiewit in a joint venture to complete the Gross Reservoir Expansion, which will triple the reservoir’s size. By placing RCC on the downstream face of the dam from the bottom up, our team will add 131 feet to the Gross Dam resulting in the largest RCC dam raise in the world. During preconstruction, the team collaborated on design, identified risks, and implemented mitigation strategies. Work is occurring in high-altitude with extreme weather conditions and limited access. The additional water storage gained from this expansion will help protect Denver Water’s customers from future drought and offset imbalances in the water supply.


Location: Boulder County, CO

Owner: Denver Water

Construction Manager: Black & Veatch

Contract Type: CM/GC; Design-Assist

Status: Currently under construction


  • Largest concrete dam raise in the world using RCC

  • Tallest RCC dam in the United States

  • Tallest dam in Colorado

  • 2,000,000 tons of aggregate processing

  • 230,000 SF of hydro-demolition

  • 1,000,000 CY of site excavation

  • 90,000+ CY of conventional concrete

  • 23,000 SF of wire saw demolition

  • Onsite crushing and batching operations

131-ft RCC dam raise

258,000 CY of steep foundation excavation

725,000 CY of roller compacted concrete