Gross Reservoir Dam Expansion


Boulder, CO

General Contractor:
Kiewit-Barnard JV



Denver Water

Project Manager:
Black & Veatch

Denver Water’s Gross Reservoir Dam Expansion Project will nearly triple the reservoir’s water-storage capacity. Low-carbon roller-compacted concrete (RCC) will be used to increase the dam’s height by 131 ft., its length by 890 ft., and its thickness by up to 90 ft. Upon its completion in 2027, the project will provide one-quarter of Colorado’s population (1.5 million people) with greater water security during droughts and deliver essential resiliency in the face of increasing climate-change impacts


  • Reducing carbon footprint of construction, a high priority for project stakeholders.
  • Constructing the foundation initially called for an estimated  15,000 tons of Type I/II Ordinary Portland Cement (OPC) for producing 68,000 CY of high-performance concrete.
  • Building 118 steps to raise the dam’s height from 340 ft. to 471 ft. initially called for approximately 60,000 tons of Type I/II OPC for producing 740,000 CY of RCC in batch plant on jobsite.
  • The remote mountainous work area—150 miles from the cement plant and with limited onsite storage capacity—created logistical challenges for continuous supply of large product volumes. 




  • Switching from Type I/II OPC to Type IL Portland Limestone Cement (PLC) will reduce the concrete dam’s embodied carbon by 6% while achieving the project’s stringent performance requirements.
  • Estimated 75,000 tons of low-carbon OneCem® PLC used in 800,000+ CY of concrete for the project will provide CO2 savings of 4,050 tons when compared to OPC.
  • Extensive production forecasting, logistics planning and coordination with project partners will ensure reliable, on-demand product deliveries to keep construction schedules on track 24/7.


Gross Reservoir Expansion Project March 2024 Update

Denver Water is preparing to raise the height of Gross Dam in Boulder Colorado. This is an update on the progress from spring 2024. 

Testing roller-compacted concrete at Gross Reservoir

Denver Water is testing the roller-compacted concrete process in preparation of raising the height of Gross Dam for the Gross Reservoir Expansion Project.

Raising dams to provide water security

The Gross Reservoir Expansion Project will provide water security to the Colorado Front Range from multiple sources and reduce vulnerability in the face of extreme weather events. 

Photos and videos courtesy of Denver Water.

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