Gross Dam sits 340 feet above the streambed of South Boulder Creek.
Building Lasting Relationships to Raise a Dam Denver Water’s Jeff Martin on the Gross Reservoir Expansion
John Crotty: Please provide some background on the expansion project and the needs the project will meet. Jeff Martin: The dam’s original designers planned to raise the dam to keep up with water demands in two phases: the first adding an additional 40 feet, and the second, 80 feet.
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With that in mind, we are really just building off that original vision. As we look at our system now, we need to pursue this expansion for a couple of reasons. One is increased demand due to Colorado’s growing population. The other is the need to improve system resilience. This is especially true for Gross because of the two watersheds that provide water to Denver. Denver Water’s South System, which has been in operation for over 100 years, accounts for about 90 percent of the water we manage. With 90 percent of our water flowing through one corridor and the remaining 10 percent through our North System corridor, we began assessing what we would do if an event were to occur in the future that would exploit this imbalance. For example, Colorado’s largest wildfire, the 2002 Hayman Fire, caused a lot of destruction to the South System watershed. We look at events like this and try to make sure our systems are balanced so that we have the right resiliency to move forward. We started the expansion right after the Hayman Fire. That year, a drought, in addition to the fire, caused us to almost run out of water on the North System, stressing its MUNICIPAL WATER LEADER
PHOTO COURTESY OF DENVER WATER.
Gross Reservoir is a critical component in Denver Water’s North System. Completed in 1955, the original designers had envisioned the reservoir’s expansion as a way to keep up with demand. The current reservoir holds 42,000 acre-feet of water, impounded by a 340-foot concrete dam. Denver Water is in the process of raising Gross Dam by an additional 131 feet, making it 471 feet tall and increasing its storage capacity to 119,000 acre-feet. Municipal Water Leader’s senior writer, John Crotty, spoke with Gross Reservoir Expansion Project Manager Jeff Martin about the logistics of storage expansion, the need for collaboration among stakeholders on the west and east slopes of the Rockies, and how process is as important as results when tackling big water projects.
