Gross Dam to be raised 131 feet after years of study

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BOULDER COUNTY, Colo. — Gross Dam in Boulder County soon will be raised after requests from Denver Water and 14 years of study by the Army Corps of Engineers.

Engineers will increase the dam’s height by 131 feet, to 471 feet. When completed, Gross Dam will be able to hold an additional 77,000 acre-feet of water — the equivalent of more than 25 billion gallons.

Experts believe the additional water stored in Gross Reservoir will help prevent shortfalls of water during droughts.

The approval of the $380 million project by the Army Corps of Engineers comes in the form of two documents: A record of decision and a 404 permit.

The additional height will make Gross Dam the tallest dam in the state.

Both are required by the federal government as part of the National Environmental Policy Act. The raising of the dam was determined to be a “net environmental benefit” for the area.

“Denver Water appreciates the Corps’ dedication and commitment to careful study of the anticipated impacts of this project,” Denver Water CEO Jim Lochhead said.

“We will complete this project responsibly, as evidenced by our actions during the public process and the resulting robust environmental protections we’ve agreed to along the way.”

As part of the project, Denver Water will provide millions of dollars to improve watershed health in the Colorado and South Platte river basins.

Pre-construction activities, including dam design and geo-technical work, are expected to begin in 2018. The project is expected to be completed in 2025.