Construction

The Gross Reservoir Expansion Project will undergo approximately three years of design followed by four years of construction.

Primary dam construction is anticipated to last two construction seasons, a total of 18 months. During this time, work at the construction site will often be 24 hours a day, 7 days a week. The project involves the raising of the existing 340 foot tall Gross Dam by an additional 131 feet to create the new larger reservoir and additional storage. Based on the concept design, once complete, Gross Reservoir will be the tallest dam in Colorado and will contain about 1.5 million cubic yards of concrete, about half the volume of Hoover Dam.

The U.S. Army Corps of Engineers, Omaha District Regulatory Branch, prepared an Environmental Impact Statement beginning in 2003 to analyze environmental effects of enlarging the existing Gross Reservoir (near Boulder, Colorado) to supply 18,000 acre-feet per year new firm yield of water to its Moffat Collection System. On July 6th 2017, the U.S. Army Corps of Engineers approved Denver Water’s request to raise Gross Dam in Boulder County.

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