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New look for stretch of forest critical to Denver’s water supply

Forest thinning project treats 1,500 acres in Denver Water’s watershed.

The rolling hills southwest of Denver offer spectacular views of the Pike National Forest, and the land is as rugged as it is beautiful. 

Tucked in among the ponderosa pines, hills and rock formations is Miller Gulch, a popular recreation area for bikers and hikers near Bailey, Colorado. To the casual observer, seeing a forest dense with trees looks healthy, but it’s actually cause for concern.

That’s why in 2022, the U.S. Department of Agriculture’s Forest Service and Denver Water launched a forest health project to thin 1,500 acres of ponderosa pine and Douglas fir trees in the area. 

The goal was to help return the forest to its natural structure and composition. The project wrapped up in the spring of 2024. 

A look at the Miller Gulch area of the Pike National Forest after thinning work was completed. The spacing between the trees leads to a healthier forest that is less prone to large, catastrophic wildfires. Photo credit: Denver Water.

“While small fires are beneficial to the forest, large wildfires can be devastating,” said Ryan Kolling, a Forest Service Supervisory Forester. “Thinning the forest helps reduce the risk of large wildfires and helps the trees become more resilient to disease and insect infestation.”

Improving the health of the forest protects nearby homes and recreation trails from large fires. A healthier forest also offers better protection for an area that supplies water to Denver and several surrounding suburbs.

The Miller Gulch area before tree thinning shows the overly dense forest that is susceptible to large wildfires. Photo credit: Denver Water.

“Denver’s source water begins as the snow and rain that travels across the forests west of Denver,” said Madelene McDonald, a watershed scientist at Denver Water.

“As the water flows downhill into rivers and streams, the forest acts as a natural filter for what will eventually become our drinking water. That’s why forest health is critical to Denver Water and our customers.” 

Forest treatments

Improving the health of the forest is done through “treatments” that reduce the amount of vegetation, or “fuels,” that could catch fire. Treatments range from using machines to remove trees and thin the forest to using prescribed fires to burn away debris on the forest floor.

Before any treatments began in the Miller Gulch area, the Forest Service conducted an analysis of the area and created a “prescription” that outlined which trees should be removed and which ones would stay. The agency partnered with the nonprofit Stewardship West to streamline the process and complete the work.

The treatment work involved a multistep process to thin the forest. 

Learn how Denver Water is “Building a better forest.” 

The first step involved removing selected trees with a large feller-buncher cutting machine equipped with two saws and a large “claw.” 

After the trees were cut down, a machine called a “skidder” dragged them to a collection area, where another machine called a “dangle-head processor” removed the branches. 

The last step involved a bulldozer-like machine called a “masticator” that works like a lawnmower, chopping up any remaining debris and spreading it across the ground. 

A cutting machine, known as a feller-buncher, saws the bottom of a tree, lifts it and sets it aside on the ground for removal. Photo credit: Denver Water.

A “skidder” grabs the downed trees and drags them to a collection area. Photo credit: Denver Water.

A dangle-head processor removes branches from the downed trees and stacks the trees in piles. Photo credit: Denver Water.

A mastication machine drives around the area where trees have been removed like a lawnmower. The machine’s blades chop up debris and spread it across the forest floor. Photo credit: Denver Water.

After the treatment is complete, the forest will have openings and meadows between groups of trees, so if one tree is hit by lightning and catches fire, it will be harder for flames to jump to other trees and spread.

The area in the foreground shows the treated areas of Miller Gulch. There is more space between the trees and the forest is less dense compared to the untreated areas in the background. Photo credit: Stewardship West.

“The forest land recovers quickly after treatments. As an example, in areas around here where we’ve done treatments in the past, there are now grasses, new trees and wildflowers already coming back,” Kolling said. 

“Thinning also helps stimulate new growth and gives the forest more diversity in terms of the age of trees as older ones are removed and new ones take root.”

Putting debris to good use

A key part of forest management is to make sure the removed trees are put to beneficial use. 

In the Miller Gulch area, the cut trees were separated into large and small piles. The larger trees are taken to sawmills in Colorado where they’re turned into materials such as two-by-four boards and wood pallets. 

Some tree piles are left on-site for the public to cut into smaller pieces for use as their own firewood. (A permit is required.) 

Large trees on the left are taken to sawmills and turned into various wood products. The smaller branches and trees on the right are turned into firewood and mulch to be sold in the community. Photo credit: Denver Water.

The smaller trees and branches are used for firewood or turned into mulch and sold in the community. Other debris is scattered across the forest in areas where work was done to help the land recover. 

“We’ve worked hard over the years to make sure we’re getting added benefit from our forest treatments, so these projects help the community in many ways,” Kolling said.

From Forests to Faucets

The first phase of the Miller Gulch project was funded through From Forests to Faucets, a partnership between Denver Water, the U.S. Forest Service, the Colorado State Forest Service, the National Resources Conservation Service and the Colorado Forest Restoration Institute. The partnership started in 2010 to reduce the risk of catastrophic wildfires in Denver Water’s collection area for water.

“The Buffalo Creek, Hayman and Hi Meadow fires were all high-intensity fires that burned on the Pike National Forest, which is in our South Platte watershed,” McDonald said. 

“When these types of wildfires occur, the exposed landscape can experience significant erosion that degrades our water quality and fills up our reservoirs with sediment.”

Downed trees and debris from the 1996 Buffalo Creek fire ended up in Strontia Springs Reservoir after a flood hit the burn scar. Denver Water is trying to prevent future disasters from happening by investing in forest health to prevent major wildfires. Photo credit: Denver Water.

Denver Water has prioritized treatment in the Miller Gulch area because of its proximity to the North Fork of the South Platte River, which flows into Strontia Springs Reservoir. The reservoir is where 80% of the utility’s water passes through before heading to water treatment facilities.

“It’s very important to reduce the wildfire risk above Strontia Springs,” McDonald said. 

“We’ve seen several big fires here in the past three decades that have caused significant problems to our water treatment operations and water delivery infrastructure.”

Federal help

The Pike National Forest is located in the Colorado Front Range Landscape, an area of 3.6 million acres recently identified in the Forest Service’s Wildfire Crisis Strategy as one of 21 landscapes at high risk for large wildfires. This is due to the area’s fire history, current vegetation conditions, number of homes and importance to the water supply for people across metro Denver.

The Wildfire Crisis Strategy is a 10-year plan developed by the Forest Service to dramatically increase the pace, scale and scope of forest health treatments across the Western U.S. The plan addresses wildfire risks to critical infrastructure, protecting communities and making forests more resilient.

The original From Forests to Faucets plan for Miller Gulch called for treating 419 acres. However, since the project was already in progress, it was selected for additional federal funding in 2022 and received $3.3 million from the Bipartisan Infrastructure Law and the Inflation Reduction Act. This additional funding allowed for the treatment of an additional 1,102 acres.

A section of Miller Gulch in 2023 shows how quickly the land recovers after treatment as grasses and wildflowers grow back. Photo credit: Denver Water.

“For years, Denver Water and the Forest Service have leveraged resources through the From Forests to Faucets partnership. And with support from the Wildfire Crisis Strategy, we are able to continue this proven approach and essentially triple the number of acres treated in Miller Gulch,” McDonald said.

“All of the work expands our efforts to reduce the wildfire risk in the area and helps protect our water supplies.” 

Connecting landscapes

The Miller Gulch project is one of many forest health efforts that in recent years have been done in the Upper South Platte River Basin on the Pike National Forest. May of those projects are in the area of Bailey, Buffalo Creek and the Colorado Trail.

A prescribed fire along the Colorado Trail near Buffalo Creek in June 2023 is an example of other fuel reduction treatments in the Pike National Forest. Photo credit: Andrew Slack, Colorado Forest Restoration Institute.

“The goal is to connect the dots of forest treatments across the landscape,” Kolling said. 

“We try to combine our treatment efforts with our partners and work with natural features like roads and rivers. This creates fuel breaks which will help us bring large-scale fires down to fighting size if one breaks out.” 

Stewardship Agreements and partnerships

The Miller Gulch project is a prime example of what partnerships can accomplish by using Stewardship Agreements

In 1999, Congress created the Stewardship Agreement tool, which gave the Forest Service the authority to work with partners collaboratively across shared landscapes. The goal is to accomplish impactful work and achieve mutually beneficial goals for the national forests. 

For Miller Gulch, the Forest Service partnered with Stewardship West to speed up the treatment process and achieve shared forest health goals. Stewardship West is a nonprofit organization that is dedicated to improving forest health across the Western U.S. 

“We are a boots-on-the-ground, action-focused organization with a mission of engineering heathy and resilient forests,” said Kevin Zeman, president and CEO of Stewardship West. 

“The Forest Service gives us the treatment plan and we do the coordination and implementation to make the project happen. This has allowed us to treat 1,500 acres in just 2.5 years, which is really unheard of in terms of land management." 

Ryan Kolling (right), a Forest Service supervisory forester, meets with Stewardship West’s Jennifer Baker (left) and Kevin Zeman to discuss the forest treatments in Miller Gulch. Photo credit: Denver Water.

As a neighboring water provider with shared wildfire risks, Aurora Water joined forces with Denver Water and the Forest Service in 2022 to help fund the Miller Gulch project. Aurora Water works with Denver Water and also uses Strontia Springs Reservoir to deliver water to its customers. 

The Miller Gulch project also received funding from the Colorado Department of Natural Resources’ Strategic Wildfire Action Program, also known as COSWAP, because the Miller Gulch area is considered a high-risk landscape within the state. 

Denver Water’s collection system spans more than 4,000 square miles of forest land, so working with other agencies is critical, according to McDonald.

“We rely on our regional, state and federal partners to help protect our watersheds,” McDonald said. 

“It really is a team effort, and the Miller Gulch project is a great example of how we can ensure a reliable water supply and improve the forest health at the same time.”