Jan. 11, 2024

Chimney Hollow Rises Above 150 Feet Tall in 2023

With more than two years of construction in the rearview mirror, Chimney Hollow Reservoir is rising quickly to meet the challenges of providing resilient water supplies for 11 Northern Colorado water providers and one electric utility. 

In April 2023, crews started full production on site, using double shifts to ramp up production at the quarry and the main dam. The on-site quarry is producing about 62,000 tons of material daily, and that rockfill material is used to build the embankments that contain the 90,000-acre-foot reservoir. By the end of December, the main dam hit 157 feet tall on the way to its final height of about 350 feet.  

About two-and-a-half miles south, the foundation work for the saddle dam is complete. The foundation has been winterized, and the embankment work will begin next summer. The smaller 40-foot saddle dam allows the reservoir's overall capacity to increase by about 30 percent.  

Other components of the project are also showing progress. Last fall, construction crews placed the final section of the Chimney Hollow Conduit to bring water from the Colorado-Big Thompson’s Project Bald Mountain Interconnect to the new reservoir’s valve house at the base of the dam. In 2024, the valve house will have its 43 valves installed to provide safe and accurate delivery of water. 

More features of work are underway and will help crews get a running start on the final full year of construction in 2024. The project is anticipated to be completed in late summer 2025.