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 New Video Provides Overview of Project’s Extensive West Slope Environmental Commitments
Beneficiaries of the Chimney Hollow Reservoir Project go beyond the 12 communities and water providers who will use its additional water supplies and recreationists who will enjoy the new amenities. Add to that list the aquatic life and environment along stretches of the Colorado River in Grand County, as well as residents and visitors to that area.
Since Chimney Hollow Reservoir will be filled using Colorado River water rights associated with the existing Windy Gap Project, Chimney Hollow participants and Northern Water’s Municipal Subdistrict have agreed to numerous environmental commitments in the watershed above and below Windy Gap. The objective of these mitigation and enhancement measures is to vastly improve the overall health of this stretch of river. This effort has brought together a variety of diverse partners with the same goal, including Grand County, Trout Unlimited, Colorado Parks and Wildlife, the Colorado River District and the Colorado Water Conservation Board, among many others.
Altogether, there are $90 million in West Slope environmental measures associated with construction of Chimney Hollow Reservoir, the focal point being the Colorado River Connectivity Channel (CRCC). The CRCC calls for reconnecting two segments of the Colorado River around what will be a much smaller Windy Gap Reservoir, in order to make that segment of the river function more as a natural system for fish and supporting aquatic life. The connecting channel will also be open to the public for recreation once construction is completed.
In addition to the CRCC, there are several other important components to the West Slope environmental commitments made by the project participants and Northern Water’s Municipal Subdistrict, including:
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Collaborative efforts to improve stream channel, riparian and wetland areas above and below Windy Gap Reservoir
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Upgrades to the Fraser Wastewater Treatment Plant to reduce downstream levels of phosphorous, metals and nitrogen
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Additional water supplies for Grand County and the Middle Park Water Conservancy District
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Water releases into the Colorado River to support beneficial flushing flows during spring runoff
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Operational changes when needed to improve river temperatures for fish and other aquatic life
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Public access amenities at some of the restored sites along the river and connectivity channel
This new video provides an overview of the West Slope environmental measures associated with construction of Chimney Hollow Reservoir. A full list of these commitments can also be found on the Chimney Hollow Reservoir website.
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Where Ancient Seas and New Mountains Meet
Almost every reservoir in Colorado has been formed by placing a dam at one or more ends of a valley and using the hillsides to store water. Most of these valleys have been carved by geologic activity, flowing water and weathering, meaning the exposed rocks on each side will be similar to each other along the length of the reservoir.
Chimney Hollow is much different, and that brings both benefits and challenges for construction of the new reservoir.
If you were able to see current-day Colorado as it appeared in the Mesozoic Era 66 million years ago and longer, you would have seen an area of shallow seas, where sediment deposits formed sandstones, shales, limestone and more into horizontal layers. About 66 million years ago, however, an abrupt change occurred. A mountain building era known as the Laramide Orogeny thrust peaks of granite into the sky in central Colorado, creating the Rocky Mountains and the Front Range.
As those new mountains rose over millions of years, they forced the existing rocks to be tilted upward. Erosion and other weathering effects created a series of north-south valleys along the Front Range where the ancient sedimentary rocks formed the two sides. These are visible in places such as Red Rocks, Horsetooth Reservoir and Carter Lake.
What makes Chimney Hollow a special place is that it sits at the boundary between those ancient sedimentary rocks and the newer Rocky Mountains. That means the rocks that constitute the strength and mass of the dam can be quarried from the harder and stronger crystalline rocks on the west side of the valley, while the tunneling to create the inlet/outlet works is through less-brittle sedimentary rocks on the valley’s east side.
The geology does pose some challenges, however, as the dam crosses many layers of rock that have different properties. Through our dam design partners at Stantec, builders have been able to meet those challenges.
When the reservoir is complete, visitors will be looking at an open book that tells the story of billions of years of Colorado geology – right in one single valley.
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 How Did the Chimney Hollow Valley Get Its Name?
In the foothills of southern Larimer County sits Chimney Hollow, the valley tucked behind Carter Lake just west of the City of Loveland. Prior to becoming the location for Colorado’s newest water storage project – Chimney Hollow Reservoir – the area was scouted for other purposes, including a potential mountain retreat for computer hardware company Hewlett-Packard and as a site for transmission lines for the Western Area Power Administration, one of four power marketing administrations within the U.S. Department of Energy. However, the valley’s history stretches even further back, begging the question: Why was the valley named Chimney Hollow?
Mark French, president of the Berthoud Historical Society and writer for the Berthoud Weekly Surveyor, admits that there is no evidence citing exactly when or how the valley was named. “It was named so early on that it is not well documented. It’s really an oral tradition,” remarks French. “The first time it appears anywhere is in 1908 on a United States Geological Survey (USGS) map.” French also noted that unfortunately, several maps of the area were destroyed in a fire at a Larimer County building in the 1920s.
What we do know from other intact historical records is the Cherokee Trail once ran along the Front Range from the late 1840s through the early 1890s. In 1849, the trail was established by a group of Cherokee and other members of the expedition with a wagon train heading west to California in search of gold. It is reported that in the first few decades after 1849, the trail became very active with hundreds of wagons passing by the Chimney Hollow valley each day. During their long journeys, some travelers built cabins in the foothills along the route in order to survive the winter.
According to narratives passed down from locals in the area, a cabin constructed by one of these travelers once stood in the valley. Remnants of the structure remained there for years, predominantly the cabin’s chimney which became the most conspicuous feature of the valley during that period. Another noteworthy aspect of the valley is Chimney Hollow Creek, the feature that alludes to why the area is called a hollow, not just a valley. Hollows are small valleys surrounded by mountains, hills or ridges that often have a stream running through them. With all of this information, French and other historians conclude that this is likely how this valley became known as Chimney Hollow.
As the valley’s name caught on and began appearing on USGS maps, Northern Water’s project management staff kept the designation for Chimney Hollow Reservoir. Construction on the 90,000-acre-foot project is estimated to be complete by 2025 and full by 2028, when it will appear on maps as a new reservoir.
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 Virtual Tour Summer 2023
In this summer 2023 edition of the Chimney Hollow Reservoir Project Virtual Tour, Project Engineer Jeremy Deuto takes us through the valley to get an inside look at key components of project construction, including the conduit, tunnel, main dam and saddle dam.
Equipment Spotlight: Tunnel Concrete Liner
Crews have finished excavating the downstream portion of Chimney Hollow Reservoir’s inlet/outlet tunnel and are now installing the concrete liner. In mid-June, crews began installing the first reinforced concrete section with an Everest Carrier Form, which is 67 feet long and weighs approximately 183,000 pounds.
This equipment changes its profile three times in the 715-foot tunnel. The entrance to the downstream portal is a 26-foot-diameter horseshoe formation that gradually transitions into a smaller, circular structure before opening up to the 30-foot-diameter valve chamber.
“This machine has ports inside the form that shoot out, connect into a fitting, and place concrete along the tunnel’s structure,” said Kyle Knaeble, a project engineer with Barnard Construction.
For the placement, crews use a self-consolidated concrete to avoid using built-in vibrators, which makes it much easier to place the concrete and maintain quality.
The downstream liner is expected to be complete in March 2024 while crews continue excavating the upstream portion. Within a year, the 2,000-foot-long tunnel’s excavation and ground support will be complete.
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 Employee Spotlight: Zach Remus
Zach Remus plays an integral role in the construction of Chimney Hollow Reservoir as one of Barnard Construction’s Concrete Superintendents. He spends his days overseeing the concrete batch plant, which will generate more than 35,000 cubic yards of concrete throughout construction at areas including the main dam, saddle dam and tunnel. As the first in and last out, Remus spends the majority of his time coordinating with crews.
Before beginning on the Chimney Hollow project in July 2021, Remus worked on several other dam projects for Barnard. His past experiences working on complex dams has readied him for the work that he is now doing at Chimney Hollow, which is the only dam project of its size currently under construction in the United States.
“All scopes of work are involved in the success of Chimney Hollow, which requires me and other superintendents to always think ahead,” he said. “This project is complex, which keeps me on my toes, but it is unlike any other opportunity.”
Outside of work, Remus enjoys spending time with his wife and son, hunting, playing softball and visiting his hometown of Glasgow, Montana.
Grand County Organizations Awarded Grants from Municipal Subdistrict Contributions
Three Grand County organizations were awarded grant funding made available from the first round of funds contributed by the Northern Water Municipal Subdistrict as part of the settlement to end the federal lawsuit over Chimney Hollow Reservoir. Grant funds made available totaled nearly $1 million.
Construction of the reservoir began in August 2021 after an April settlement that resolved a federal lawsuit challenging the permit issued by the Bureau of Reclamation and Army Corps of Engineers. The settlement required the Subdistrict to contribute $15 million throughout the four-year construction timeline that will be administered by the Grand Foundation to pay for projects that enhance the Colorado River and its many tributaries in Grand County.
The largest of the grants awarded was $660,000 to the Kawuneeche Valley Ecosystem Restoration Collaborative. This multi-agency initiative is helping to restore the valley ecosystem, which depends on functioning wetlands along the headwaters of the Colorado River that flows from Rocky Mountain National Park into Shadow Mountain Reservoir. The goal of the collaborative is to restore and protect the characteristics of the region by bringing back ecological and hydrologic functions lost due to an imbalance between local wildlife and changes to the Earth’s surface. This grant is for the first phase of the project on the North Fork of the Colorado River watershed.
Another recipient of $250,000 in grant funding is the Three Lakes Water and Sanitation District, which is conducting an investigation of septic systems in the Three Lakes area. The investigation will determine what the benefits and feasibility are of connecting residences to the sewer system in order to eliminate nutrient loading to the watersheds from their current septic systems.
The third grant recipient is the Town of Grand Lake. It was awarded $80,000 for development of a stormwater management plan to improve the quality of stormwater runoff that enters Shadow Mountain Reservoir from Columbine Creek.
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Stay Connected
Visit the Chimney Hollow Reservoir Project website for the latest news and project highlights.
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About Chimney Hollow Reservoir
The Chimney Hollow Reservoir Project is a collaboration between 12 Northeastern Colorado water providers to improve the reliability of, or make firm, water supplies from the Windy Gap Project. Chimney Hollow Reservoir will be located just west of Carter Lake in Larimer County to provide dedicated storage to supply a reliable 30,000 acre-feet of water each year for future generations.
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