Work Concludes for 2026 at Shadow Mountain Spillway

Northern Water once again partnered with the Bureau of Reclamation this summer to continue repairs and upgrades at the Shadow Mountain Reservoir spillway, with that work completed by Dietzler Construction and Northern Water staff. 

This year's work began in early July, wrapping up in August. Similar to last summer, the spillway efforts focused on concrete replacement along the spillway floor, among other upgrades. The work required coordination with U.S. Forest Service and other partners to ensure safe recreation could continue in the area during construction. 

The first two phases of work on the 80-year-old structure have cost a combined $1.35 million, with additional project phases planned for future years. 

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 maintenance work was required on the spillway, which receives water each spring from the high inflows into both Shadow Mountain Reservoir and Grand Lake from the Colorado River and its tributaries, and conveys that water to Lake Granby. 

With this summer’s work completed at the Shadow Mountain spillway, Northern Water and Reclamation are working on similar upgrades at the Green Mountain Reservoir spillway, with that work expected to be completed by October.