Construction kicks off at Gross Reservoir: Denver Water’s critical project to raise the dam by 131 feet gets underway — News On Tap #BoulderCreek #FraserRiver #ColoradoRiver #COriver #aridification

Click the link to read the article on the Denver Water website (Jay Adams):

Construction began April 1 on Denver Water’s five-year project to expand Gross Reservoir by raising the height of the dam.

The reservoir and dam, located in the foothills west of Boulder, were named after former Denver Water Chief Engineer Dwight Gross. The dam was completed in 1954 to store water from the West Slope for Denver’s growing population.

The dam was originally designed to be raised in the future when needed.

Now, Denver Water is raising the height of the dam by 131 feet to help ease a storage imbalance in the utilities’ water collection system. Once completed, Gross will be the tallest dam in Colorado.

The dam was originally designed to be raised in the future when needed.
Now, Denver Water is raising the height of the dam by 131 feet to help ease a storage imbalance in the utilities’ water collection system. Once completed, Gross will be the tallest dam in Colorado.

“We’ve been busy bringing trucks, cranes and other heavy equipment to the site to prepare for construction,” said Doug Raitt, construction manager of the Gross Reservoir Expansion Project for Denver Water. “A lot has to be done just to prepare the site for all the work that has to happen.”

Crews navigate a winding road near the dam to bring a large crane to the construction site. Photo credit: Denver Water.

Early work involves blasting rock on the sides of the canyon to make way for the additional concrete that will be placed over the downstream face and above the existing dam.

A machine drills holes into the rock above the dam to place explosives for blasting operations. Photo credit: Denver Water.

Crews also are building a walkway on the upstream side, or reservoir side, of the dam to provide access for workers to walk from one side of the dam to the other.

Upcoming work includes hydroblasting 2 to 3 inches of concrete from the face of the dam so the new concrete will adhere to it. Part of the dam’s spillway will also be removed to prepare for the addition.

Early work involves installing walkways on the upstream side, or reservoir side, of the dam. The walkways are needed because the top of the dam will be removed to make way for the addition. Photo credit: Denver Water.

To raise the dam, crews will start at the bottom and extend the base of the dam out. Then they will build a series of steps up to the dam’s new height — similar to what you see on the sides of an Egyptian pyramid.

The Gross Reservoir Expansion Project involves raising the height of the existing dam by 131 feet. The dam will be built out and will have “steps” made of roller-compacted concrete to reach the new height. Image credit: Denver Water

“When it’s done, it will be the largest dam in Colorado and nearly triple the storage capacity of the existing reservoir,” said Jeff Martin, manager of the Gross Reservoir Expansion Project for Denver Water. “We’re really excited to begin construction on this important project.”

Doug Raitt, construction project manager for Denver Water, stands next to a 60-ton dump truck at the construction site on April 20, 2022. Photo credit: Denver Water.

Martin said that work conducted during 2022 and 2023 will be mostly site preparation for the on-site concrete production and foundation work on the rock on the sides of the dam and around the bottom.

At the height of construction there may be as many as 400 workers on site at a time, Raitt said.

“Raising a dam is often trickier than simply building a new one,” Raitt said. “We have to continue sending water through the dam during construction while transforming the dam into a new structure.”

Crews remove rock that has been blasted away on the north side of the dam. The area near the red machine at the top of the picture will be the new crest of the dam. Photo credit: Denver Water.

Throughout the project, safety will be the No. 1 priority at the site.

“Denver Water and our construction partners have an emphasis on safety for the public and our workers every day,” Raitt said. “We all go through safety training and will continue to evaluate our operations throughout the project.”

Workers take part in safety training with Kiewit-Barnard, the general contractor for the expansion project in April. At the peak of construction, up to 400 workers will be on-site at the dam during the day. Photo credit: Denver Water.

Protecting the environment and wildlife is another important part of the project. Denver Water worked with biologists to make sure there were no bird nests in the area before the start of construction and will continue to do so throughout the project.

Additional environmental mitigation efforts were put in place to protect South Boulder Creek and the reservoir from sediment and erosion washing in during the work. These efforts will continue throughout the project.

Erosion control measures are put up around construction areas to protect dirt and rocks from falling or washing into South Boulder Creek and Gross Reservoir. Photo credit: Denver Water.

Denver Water also is spending time updating community members around the reservoir.

“It’s important that we let them know what’s happening with the project,” Raitt said.

“For months, we’ve been doing outreach to the community with public meetings, newsletters and emails. We’ve received a lot of feedback from our neighbors letting us know what’s important to them and we’ll continue to work with them and update them throughout the project.”

Denver Water is hosting community meetings with residents who live around Gross Reservoir to update them on the project and answer questions. Photo credit: Denver Water.

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