Gross Dam ready to go up
The top of Gross Dam in Boulder County is bustling this spring as workers build the specialized structures needed to raise the dam.
Denver Water is raising the dam 131 feet as part of the Gross Reservoir Expansion Project. The project will nearly triple the storage capacity of the reservoir and add balance and resiliency to Denver Water’s collection system.
“Over the past two years we’ve excavated 260,000 cubic yards of rock and placed 27,000 cubic yards of concrete to get the existing dam and the rock around it ready for expansion,” said Doug Raitt, Denver Water’s construction project manager for the Gross Reservoir Expansion Project.
Learn more about dam good jobs at denverwater.org/Careers.
The next phase of the multiyear project begins in May, when crews will begin the process of building 118 new concrete “steps” that will create the higher dam. Construction on the expansion project began in April 2022 and is scheduled to wrap up in 2027.
The steps will be made of roller-compacted concrete and around 800,000 cubic yards of concrete will be needed to build them.
So, to prepare for raising the dam, a team from Kiewit Barnard is building a sophisticated concrete batch plant near the top of the dam. At the plant, cement, fly ash, sand and aggregates will be mixed together to make the specific type of concrete mixture used to build the steps.
“Producing the roller-compacted concrete on-site really makes for an efficient process so we don’t have to haul it in from off-site,” Raitt said. “We’re also crushing rock that we quarried on-site as well.”
Learn more about the Gross Reservoir Expansion Project at grossreservoir.org.
Crews are also building an elaborate conveyor system that will carry the concrete from the batch plant to the dam.
Once conveyed over the top of the dam, the concrete will slide to the bottom via a chute system, which also will be built this spring.
At the bottom of the dam, workers are creating a flat surface that will be the base for the new roller-compacted concrete steps.
“It’s an exciting time as we get ready for the actual dam raise phase of the project,” Raitt said. "Once the roller-compacted concrete process begins, it will take about three years to complete the expansion.”