Denver Water began efforts to expand Gross Reservoir more than a decade ago. Since that time, Denver Water has completed many of the permitting milestones necessary to move the Gross Reservoir Expansion (GRE) project forward and is preparing for the delivery phase of the project. The U.S. Army Corps of Engineers granted Denver Water its 404 permit and Record of Decision in July 2017 and Denver Water expects the Federal Energy Regulatory Commission (FERC) to issue a License Amendment for the project in 2018.
The existing Gross Dam is an on-stream facility located on South Boulder Creek in Boulder County, Colorado, and in the Arapahoe-Roosevelt National Forest. The dam and reservoir, owned and operated by Denver Water, provides raw water storage for municipal use and hydroelectric power to Colorado’s electric grid. The dam structure is a 340-foot-tall curved concrete gravity dam with a crest length of 1,050 feet (including spillway section) and is formed to a radius of 1,740 feet. The dam impounds Gross Reservoir and is capable of storing 41,811 acre-feet of water with the reservoir at the spillway crest, elevation 7,282 feet.
Denver Water proposes to raise Gross Dam by 131 feet to a final height of 471 feet, increasing storage volume from 41,811-acre feet to about 119,000 acre-feet. A downstream roller compacted concrete (RCC) buttress raise matching the existing curvature of the dam is planned and will require approximately 800,000 cubic yards of RCC. The raise will involve the following major work: aggregate development from an on-site borrow area, foundation preparation, and RCC and conventional concrete construction of the dam and spillway. Minor modifications to the outlet works and mechanical/electrical/operations enhancements are also planned.
The entire program costs (including permitting, mitigation, engineering, management and construction) are currently estimated at $464 million. The new raised dam is scheduled for completion in 2025 with the first filling occurring in 2026.
Communication is encouraged throughout the RFQ process. All communication from respondents shall be directed to theOwner’s Representative, Greg Zamensky, at Greg.Zamensky@denverwater.org. Respondent communication regarding the qualification process or proposal with other Denver Water personnel is prohibited and shall be grounds for disqualification.
