On March 10, 2022, Denver Water issued a news release stating that Denver Water is closing all recreation on the south side of Gross Reservoir on Monday, March 14, as contractors begin mobilizing and preparing for expansion-related construction. The closure will shift recreation access to the north side of the reservoir for the duration of the project.

A full closure to recreation is likely for two to three weeks in the April to May time frame to make access improvements on the north side for the upcoming boating season. Those dates are still being finalized.

Recreation closures include access on the south side of the dam, including South Side and Windy Point picnic areas, Miramonte picnic area, Osprey Point boat launch, and Osprey Point trailhead, which closed in mid-March 2022. No access to hiking trails and picnic areas from the south side will be available, and the scenic overlook will also be closed. The south side access will not reopen until construction is complete.

The North Shore and South Boulder Creek Trail (below the dam) will remain open to the public throughout the project. All access to on-water recreation will be relocated to the North Shore. Denver Water also plans to evaluate a pilot shuttle program that would aid recreators in getting from the North Shore parking lot to the water’s edge, as the existing access route is longer and steeper than the previous access point on the south side at Osprey Point.

A brief closure in the April to May period of a few weeks will allow for improvements ahead of boating season. Access to Winiger Ridge, another popular location, will remain largely unchanged until tree removal activities begin in 2025. Additional closure information will be shared closer to the beginning of that work.

As the project moves forward, there will also be periodic on water recreation closures to ensure recreationist safety. Such closures will be temporary, and every effort will be made to alert the public to closure periods ahead of time.

Doug Raitt, construction manager of the project for Denver Water, told The Mountain-Ear that they have plenty of manpower. They are planning on kicking things off on April 1.

The project will raise the dam 131 feet to a final height of 471 feet. The Dam was first started in 1954, and it was planned to be raised back then. “Now is the time,” he said.

Regarding extension of the water line to the northwest, after expansion the waterline of the reservoir when full will extend an additional 700 feet to the northwest. An interactive map on the grossreservoir.org site can help visualize this: https://grossreservoir.org/about-the-project/ gis-map/. If you look at the layers on the left side of the map, you can click on boxes that show current and future waterline.

Denver Water is making provisions for visitors to come visit the project because it is a popular project and has an international profile for those in water resources, Raitt said. This year, they will be concentrating on infrastructure development. It will take them a while to get things ready, and they are installing some cameras.

Regarding traffic, residents will see increases on Highway 72, the Gross Dam Road, and Highway 93. They will be consolidating travel for the work force in vans from the industrial park on Highway 93.

Most of the traffic will come from the east. No materials need to go west of the Gross Dam Road. Later in the project, tree clearing activity will take place on the west side of the reservoir, but that won’t start until quite a bit of work has been done.

The project will have some tree removal products such as logs and chipping that will need to go out to the west. The intersection at Magnolia and 119, which is controlled by CDOT, will have to be regulated. Raitt said CDOT will know what the plans are and which days of the week will be impacted. This plan will be developed over the next few years.

Excavation will create quite a bit of noise. There is a quarry in the area, which will be crushing materials onsite. The project also includes considerable rock excavation around the dam and blasting once or twice a day.

“It will be noticeable,” Raitt said. Most of the work will be done during the day, but several years into the project they might be doing night work. Now that they have a settlement agreement with Boulder County, funds will be available to help with mitigating the impacts. That was created to address concerns of near neighbors.

Neighbors have been concerned, along with a coalition of six environmental advocacy groups, which filed a lawsuit at U.S. District Court in Denver challenging the decision of the U.S. Army Corps of Engineers to issue a permit for the expansion of Gross Reservoir in 2018. The lawsuit pointed out that the project would raise Gross Dam and increase the capacity of the reservoir by 77,000 acre feet. It has been estimated that construction would require the removal of as many as 650,000 trees from about 12.5 miles of shoreline, although some estimates have put that at a lower number.

According to the suit, Denver Water’s Gross Reservoir plans call for diversion of additional water from the headwaters of the Colorado River, transport in the existing Moffat Tunnel through the Continental Divide, and release into South Boulder Creek for storage.

Denver Water’s proposal to build the largest dam in Colorado history will hurt the 40 million people in six states and two counties who depend on the Colorado River, the suit claims. “The progress of the project has been monitored closely by those living close to Gross Reservoir, who fear a range of adverse effects, both short term and long term, should it go forward.

“Many of them live in Coal Creek Canyon and will lose everything they moved here for: wild pristine beautiful scenery, clean air, clean water, boating, fishing, peace and quiet. The construction associated with the expansion of the reservoir will bring explosives, big trucks and machinery, pollution, toxic coal fly ash, and will destroy more than 200,000 trees which provide critical wildlife habitat and ecosystem services like erosion prevention.”

Raitt said now Denver Water has obtained all the approvals to move ahead with the project, which was issued a permit by the U.S. Army Corps of Engineers on July 7, 2017. Boulder County is now on board through a settlement, and 60 permits are in place with agencies including the Colorado Department of Health and Environment, the Colorado Department of Transportation (for Highway 72) and the U.S. Forest Service, so they can start work on April 1.

Denver Water will have plenty of oversight. The Colorado Department of Natural Resources is active, including site visits and weekly conversations. They will have a continued exchange throughout the construction process.

For outreach, there is an active website and mailers to nearby residents.

“Our goal is to keep this recreational amenity open in the safest way possible throughout the duration of the project, and we’re pushing hard to have it all ready for boating season this year,” said Brandon Ransom, manager of recreation for Denver Water.

“Denver Water recognizes Gross Reservoir is a popular recreation site, and we plan to proactively communicate with recreationists via signage, traditional media, websites, email newsletters, and social media, among other means – and we strongly encourage visitors to check these channels before heading to a facility to ensure they are aware of any closings or changes.”

A consistent place to get up-to-date information on the expansion project will be through the project website grossreservoir.org as well as via Google My Map. The public also can contact Denver Water through email, a phone line, and virtual office hours, as well as by signing up for email updates and following the utility’s social media channels. Contact and other details are available at the Denver Water website as well as on the project website.

Ways for the public to stay informed

Email: grossreservoir@denverwater.org

Phone: 303-628-6348

Schedule a one-on-one office hour appointment: grossreservoir.org/contact

Receive the email newsletter, sign up here: eepurl.com/gU6oLM

Find project information: grossreservoir.org

Find information on access closures and roadwork (My Map): bit.ly/368pNSz

Denver Water posts project updates on the Next Door neighborhood app.