Completion of the dam-raising phase of the Gross Reservoir Expansion Project in Boulder County marks a significant engineering feat for Denver Water, one that highlights the utility’s ongoing work to ensure water security for 1.5 million people in Denver and surrounding suburbs.
As Denver Water marks the construction milestone, Jeff Martin, the program manager for the Gross Reservoir Expansion Project, gave an update on the work and discussed the benefits of the project designed to nearly triple the storage capacity of Gross Reservoir.
What milestone for the Gross Reservoir Expansion Project occurred in June?
Raising Gross Dam is an incredible engineering and construction feat that Denver Water has been pursuing for over 20 years. On June 3, 2026, Denver Water marked a major milestone by topping out the roller-compacted concrete portion of the expansion project, raising the dam 470 vertical feet from the valley floor to the top, 130 feet higher than the old dam.
What work is still left to do?
Denver Water has about a year and a half worth of work to complete the dam-construction phase of the expansion project. The remaining work includes adding 1 foot of protective, conventional concrete to the top of the roller-compacted concrete, installing a water gate, completing the spillway crest, building a bridge over the spillway itself, and finishing the stilling basin at the bottom.
What is the benefit of a larger reservoir for Denver Water?
The new reservoir is designed to boost Denver Water’s overall water storage capacity by 11%. The expanded reservoir is capable of holding an additional 25 billion gallons of water…