Chimney Hollow Reservoir poised for construction — @Northern_Water #ColoradoRiver #COriver #SouthPlatteRiver #aridification

Members of the Northern Water Municipal Subdistrict Board of Directors turn ground at the site of Chimney Hollow Reservoir on Friday, Aug. 6. From left are directors Don Magnuson, Sue Ellen Harrison, David Nettles, Todd Williams, Vice President Bill Emslie, President Dennis Yanchunas, Mike Applegate and Dale Trowbridge. Photo credit: Northern Water

Here’s the release from Northern Water (Jeff Stahla):

Northern Water’s Municipal Subdistrict celebrated the groundbreaking for Chimney Hollow Reservoir on Friday, culminating a 20-year permitting process to add resilience to the water supply for more than 500,000 northeastern Colorado residents.

The groundbreaking also triggers a host of environmental efforts that will occur in the headwaters of the Colorado River on the West Slope. Those include construction of the Colorado River Connectivity Channel to reconnect portions of the river located above and below Windy Gap Reservoir, wastewater treatment plant upgrades in the Fraser River Valley, environmental improvement projects through the Learning By Doing coalition, and other work providing water and storage that can be used for environmental purposes.

“Today marks a long-awaited milestone that required years of hard work and cooperation among many groups with diverse interests to achieve a project that has benefits for everyone in Colorado,” said Northern Water General Manager Brad Wind.

The addition of water storage is a key component of the Colorado Water Plan. Our population continues to grow as climate change brings higher temperatures and greater precipitation variability to the Colorado River headwaters. Construction of Chimney Hollow Reservoir gives the regional Windy Gap Firming Project participants a reliable water supply during dry years.

Since the Windy Gap Project was envisioned, water managers have recognized the need for additional storage specifically dedicated to storing Windy Gap water. Currently the Windy Gap Project depends on Lake Granby to store water when the project’s water rights are in priority. However, Lake Granby’s first priority is to store Colorado-Big Thompson Project water.

Chimney Hollow Reservoir is a key component for these Windy Gap Firming participants: Broomfield, Platte River Power Authority, Loveland, Greeley, Longmont, Erie, Little Thompson Water District, Superior, Louisville, Fort Lupton, Lafayette and Central Weld County Water District. Each of the reservoir project participants that provide residential water service has committed to reduce per capita water supply through water conservation.

Northern Water’s Municipal Subdistrict and Larimer County cooperated to purchase the Chimney Hollow property in 2004 from Hewlett-Packard. Chimney Hollow Reservoir will provide a much-needed outdoor recreational opportunity that can be enjoyed by everyone in Northern Colorado.

In recent weeks crews have been preparing the site for construction by bringing water and power to temporary administrative offices. In addition, the Western Area Power Administration relocated a high voltage power line from the footprint of the reservoir to a location up the hillside to the west.

Full dam construction activities are planned to begin Aug. 16. Barnard Construction Co. Inc. of Bozeman, Montana, is the general contractor for the four-year project. The cost of dam construction is estimated at $500 million, with the complete project including West Slope improvements at $650 million. The 12 project participants are paying its cost.

This graphic, provided by Northern Water, depicts Chimney Hollow Reservoir, located southwest of Loveland, after it is built.

When the dam is built, it will rise about 350 feet off the dry valley floor. The dam incorporates a technology common in Europe but less so in the United States. Its water-sealing core will consist of a ribbon of hydraulic asphalt instead of the clay that serves that purpose at the Carter Lake and Horsetooth Reservoir dams. Geologists discovered there wasn’t enough high-quality clay material within the footprint of Chimney Hollow Reservoir, and instead of bringing it in from elsewhere, the hydraulic asphalt core option was chosen. The dam’s rock-fill shoulders will use material mined from the reservoir footprint, which will reduce costs, pollution and increase storage capacity.

This new storage project allows us to supply clean water reliably, even in times of drought, to the people of northeastern Colorado from the existing Windy Gap Diversion. Starting construction on Chimney Hollow Reservoir is a major step to address water supply shortages for our growing population, much like our visionary predecessors did for us, while demonstrating that modern storage projects can also improve the environment.

For more information, go to http://www.chimneyhollow.org.

Site of Chimney Hollow Reservoir via Northern Water.

From The Greeley Tribune

More than 500,000 Coloradans across the Front Range can look forward to a more resilient water supply in the near future, after a groundbreaking Friday set in motion a $650 million project that will give water providers more reliable access to a vital resource that’s become increasingly scarce due to growing populations and climate change.

A crowd of about 200 gathered Friday morning for the groundbreaking of the Chimney Hollow Reservoir, a 90,000 acre-foot reservoir at least 20 years in the making. The reservoir will be located west of the Flatiron Reservoir in Larimer County.

A dozen municipalities, water providers and a power authority are participating in the Northern Water project, which boasts a price tag of $650 million, $500 million of which is for the dam construction. Other costs are going to environmental and water quality improvements in collaboration with affected communities. Adding in things like permitting costs, project manager Joe Donnelly said the total program costs were about $690 million.

Greeley is one of the participants, making up about 10% of the project. Other participants include Longmont, Fort Lupton, Central Weld County Water District, Broomfield and more. Greeley Water and Sewer director Sean Chambers said the city is putting about $57 million toward the construction…

The project had relied on Lake Granby to store water when the project’s water rights were in priority, but the lake’s first priority is to store Colorado-Big Thompson water. Over time, it became clear Front Range water providers would need a way to store Windy Gap water because the water wasn’t available when Front Range communities needed it the most…

Northern Water cooperated with Larimer County to purchase the Chimney Hollow property from Hewlett-Packard in 2004…

Drager and other speakers detailed numerous setbacks, including years of federal litigation after environmental groups filed a 2017 lawsuit. A judge in December dismissed the lawsuit, according to BizWest. The biggest setback, according to Drager, was needing to get a 1041 permit from Grand County. State officials also took issue when project officials hadn’t developed a mitigation plan with the state.

“We kind of argued a little bit, but we came to the conclusion that to really make this thing work, we would have to give something,” Drager said.

Restoring a river channel in the Upper Colorado Basin. Graphic credit: Northern Water

In a meeting with a Division of Wildlife official, they eventually settled on stream restoration for the Colorado River — one of many environmental considerations and concessions that helped pave the way for the partnerships that made the project possible…

Though some environmental work is being done at the site, most is at the headwaters of the Colorado River, according to Northern Water spokesman Jeff Stahla. The environmental mitigation and improvements will cost more than $90 million, including about $45 million to provide water for the river when it’s running low. Other improvements include helping the town of Fraser upgrade its wastewater treatment plant and stream restoration projects.

“These are things that wouldn’t have happened if this project doesn’t get built,” Stahla said. “By doing these things, it’s … mitigation and enhancement, because we’re not just mitigating for the effects of this project, but we’re enhancing what’s already there.”

The site will also serve as an outdoor recreational opportunity managed by Larimer County.

Map of the Colorado-Big Thompson Project via Northern Water

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