Gross Reservoir Expansion Project

The Gross Reservoir Expansion Project is a major component of Denver Water’s long-term, multi-pronged approach (including promoting water efficiency, recycling water and responsibly sourcing new storage) to ensure we are able to deliver safe, reliable water to the more than 1.5 million residents in our service area today and to many of the projected 8.1 million who will call Colorado home by 2050.


The project will raise the height of the existing dam by 131 feet, which will increase the capacity of the reservoir by 77,000 acre-feet. Construction is anticipated to begin in 2022 and continue through 2027.

Step One

First we will mobilize equipment and develop aggregate materials (sand and gravel) at an on-site quarry. This first phase will also include establishing the construction site, project offices and readying the existing dam and abutments.

Step Two

That will be followed by dam construction, which we expect will take approximately three years, during which most of the work will occur during spring, summer and fall months.

Step Three

Once the dam is complete, the final phase will begin, which involves removal of trees and brush from the new inundation footprint.

The additional water storage will help prevent future shortfalls during droughts and helps offset an imbalance in our North-South collection system. With this project, we will provide water to current and future customers while providing environmental benefits to Colorado’s rivers and streams.

Denver Water is working with communities we are likely to impact during all phases of the project. We continue to listen to concerns and have made significant commitments to adjust our practices to minimize inconvenience to the local community. We are sensitive to the concerns of stakeholders and are committed to being a good neighbor. Starting in fall 2017, we opened a community welcome and information center at Gross Reservoir. The public information yurt, is intended to provide a welcoming space where members of the local community and recreationists can stop and learn more about the project, express concerns and share experiences. We’re hopeful that this dedicated, more regular presence in the community will enable us to open lines of communication and increase understanding from all perspectives. During 2020, Denver Water began offering online office hours to continue to reach community members during the COVID-19 pandemic. These online office hours continue.

Securing our Future

Gross Dam was originally designed as a phased project; the first phase was completed in the 1950s and is the dam we currently use to supply water to the North end of the system. As our demand grew, Denver Water planned to raise the dam to provide water in a just in time approach.

With the metro area’s population projected to grow by 1 million people by 2040, the time has come to complete the original design intent by raising the dam to create a larger reservoir.

Expanding Gross Reservoir will help protect Denver Water customers from future drought and projected shortfalls in the overall water storage system. The project improves water dependability for many along Colorado’s Front Range by protecting against potential natural and human-caused disasters.

With demand projected to increase, expanding Gross Reservoir is one facet of Denver Water’s comprehensive strategy – including promoting water efficiency, recycled water and responsible sourcing new supply – to meet future customers’ needs.

This project goes beyond securing our customer’s water future; it helps secure the future of the natural environment for all Coloradans. In addition to the environmental commitments we’ve made to communities surrounding the project, agreements are in place that tie this project directly to protecting South Boulder Creek and the Fraser, Williams Fork, Blue and Colorado rivers. In short, because of this project, they are better protected now than they were yesterday.

Latest News / Blog

May 2022 Recreation Update

May 26, 2022 - As a reminder, some recreation areas have closed or been relocated to ensure safety during the Gross Reservoir Expansion Project. The overall recreation experience will also be different throughout the project. Below are some of the changes and things...

Former Gov. Endorses Gross Reservoir Expansion Project

Virtual Flyover

Sign up for Email Updates