Base of the Gross Reservoir Dam to increase another 180 feet this year

Workers on the historically controversial Gross Reservoir Dam Expansion Project plan to expand the base of the dam approximately 180 feet more this year. To achieve this, they're adding a new layer of concrete on the old dam.

Concrete for the dam is being made on site next to the dam.

"It's massive, one of the biggest batch plants you'll ever see," a representative from Denver Water told Denver7. "And much of the machinery that you see on the batch plant is there to cool the aggregates, cool the water. We throw in ice with our giant snow cone maker, and we make very cold concrete, which helps us control the heat gain that normally happens in large concrete structures."

Next year, workers will use the new wider dam as the base to raise the dam another 131 feet in order to nearly triple the storage capacity of Gross Reservoir.

The additional space is needed to spread out capacity outside of Denver for the water utility used by 1.4 million people in the city and its surrounding suburbs, Denver Water said .

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Gross Reservoir dam expansion to give more water to Denver

The construction project is not without opposition from neighbors and environmentalists who said they will endure years of construction on a water project that will never provide water to their taps.

Denver water has 90% of its storage lakes west and south of the metro area, but only has 10% up north. This new dam project will add significantly more water storage north of the city.

Neighbors living near the lake worried about the construction noise and damage to wildlife. They tried putting a stop to the project by going to informational meetings and voicing their displeasure. They also posted signs opposing the project in their driveways and along the county road near the dam.

In July of 2021 , Denver Water filed a federal lawsuit, alleging that Boulder County leaders were stalling on getting the utility the permit needed to begin on the reservoir expansion. The legal battle temporarily put the Gross Reservoir Expansion Project on hold.

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On May 3 of this year, Denver Water and its contractor Kiewit Barnard began placing concrete to raise Gross Reservoir Dam.

The most recent update was workers on the expansion project told Denver7, they had hit 160 vertical feet.

Denver Water | Kiewit Barnard

The current dam is 340 feet tall. After the expansion project, it will stand 471 feet high.

"While the old dam had a flat surface, the front of the expanded one will look more like the ancient pyramids of Egypt," Denver Water said .

Denver Water | Kiewit Barnard

Once workers add enough concrete to the front of the old dam this year to reach its current height, they'll add another 131 feet next year to get to the final goal.

This year's work in Boulder County is expected to go through November, depending on the weather, then restart next May.