June 29, 2026

Shadow Mountain Dam Work to Begin

Repairs and maintenance will once again take place at Shadow Mountain Reservoir dam this summer.  

The work continues construction completed last summer and fall, when crews replaced half of the spillway floor with new concrete and reinforcement steel, installed new cables on the dam’s radial gates and completed other improvements. 

Construction is expected to occur from July 6 through September and will focus on replacing concrete and reinforcement steel on the remaining portions of the spillway floor.  

Similar to 2025, this year’s construction will require temporary closures of the East Shore Trail system access point that crosses over Shadow Mountain dam.  

Northern Water will collaborate with the U.S. Bureau of Reclamation, U.S. Forest Service, Rocky Mountain National Park and other partners to help minimize these impacts to recreation in the area and ensure the safety of pedestrians and bikers during construction. 

Men working on the concrete spillway below Shadow Mountain Reservoir.

Here are key points about the trail-access closures and recreation impacts:  

  • The Shadow Mountain dam access point to the East Shore Trail system will experience temporary closures during weekday working hours (typically between 8 a.m. to 5 p.m.). during construction. 
  • Throughout construction, the access point will be open in the evenings and on weekends, and will also be open Sept. 4 to7, while work pauses for an extended Labor Day weekend. 
  • Northern Water staff will be at the Shadow Mountain dam during weekday working hours to direct traffic and escort pedestrians and bikers over the dam when safe windows open. 
  • Barricades and signs will be posted onsite to help direct foot traffic around the dam as needed to an alternative East Shore Trail access point, located about a half-mile south of the dam.  
  • Bikers are not allowed on the alternative route, and instead must wait to be escorted across the dam by Northern Water staff when safe windows open, or otherwise access the trail at another location. 
  • Most of the dam, aside from the spillway area under construction, will remain open for fishing. Anglers can use the same nearby alternative route to go around the construction area to access the other side of the dam. 
Aerial image of Shadow Mountain Spillway work.
Aerial image showing where the work will be done on the Shadow Mountain Reservoir spillway.

Shadow Mountain Reservoir is a vital piece of the Colorado-Big Thompson Project, receiving water pumped from Lake Granby and delivering it to Grand Lake and then to the East Slope via the Alva B. Adams Tunnel. Inspections in recent years had determined work was required on the spillway concrete, which receives water each spring from the high inflows into both Grand Lake and Shadow Mountain Reservoir from the Colorado River and its tributaries.