A few miles north of Coal Creek Canyon, through the pines and gambel oak, and past yards, fences and hillsides dotted with “No Trespassing” signs, the Gross Dam horseshoes against two mountainsides to collect Colorado’s most precious resource: water.
The Denver metro couldn’t go a day without it, Denver Water Engineering Manager Doug Raitt said as he looked across the frozen Gross Reservoir. Other amenities, sure, but not water.
Demand for water in Denver is expected to increase by a third within the next decade, according to the utility’s 2014 study. That could lead to an annual shortfall of more than 34,000 acre-feet of water, enough to last 225,000 people an entire year.
Wildfires, drought and climate change constantly endanger the state’s snowpack, which feeds into the utility’s reservoirs and supply streams and rivers. Long-standing conservation efforts — perhaps you’ve seen the billboards — can no longer keep pace with Denver’s growth, said Greg Fisher, Denver Water’s demand planning manager.
The utility’s solution to keep the taps running for 1.5 million customers is expanding Gross Reservoir, which is southwest of Boulder. But it’s a complicated proposal. Not only is the project costly and lengthy –$464 million and five years — it’s also not yet a done deal, nor is everyone in support.
The proposal, in the works since 2002, already has sparked one lawsuit. And Denver Water will need approval this year from commissioners in Boulder County, an area that would receive none of the increased water security and all of the construction traffic and ecosystem damage.
Those “no trespassing” signs even have company in the canyon: “Stop Gross Reservoir Expansion.”
Gross Dam is 340 feet tall, 1,000 feet long and made from about 800,000 cubic yards of concrete, Raitt said. It was built in 1954, and for the most part, he added, the glory days of building reservoirs are decades in the past.
If Gross Reservoir is expanded, it would use another 850,000 cubic yards of concrete to raise it 131 feet (making it the tallest in the state by a foot) and widening it by 800 feet. Water capacity would increase to nearly 120,000 acre-feet — enough for about 800,000 people for an entire year and turning Gross Reservoir into Denver’s second-largest reservoir.
By the time water levels peak in early July, Denver Water’s reservoirs will “recover” about 180,000 acre-feet of water, Water Resource Engineer Nathan Elder said. About 80% of that will come from snowmelt and the remaining 20% from rainfall.
At its fullest, Gross Reservoir can currently hold enough water for nearly 300,000 people for a year, about 6% of the capacity of Denver Water’s 11 main reservoirs, Elder said.
But it won’t be that full for years, Project Manager Jeff Martin said. If the project gets the green light, the utility must keep the water level low during construction. Crews will aim to keep the reservoir open to the public during that time, though, he added, calling the area a “recreation gem.”
With the lower water level, workers will dig a new, on-site quarry to mine the rock and sand needed for the extra concrete, Martin said. Tripling the size of the reservoir is no easy feat, and much of that concrete must be poured at night to keep temperatures cool enough to harden effectively, Raitt said.
Then there’s needing to cut about 100 feet into the mountains to the east and west of the reservoir in order to build it out, Raitt said, calling it “like building a 40-story building from the side.”
Denver Water officials acknowledge they can no longer plan for a constant supply of water year to year to meet a relatively constant demand.
Ninety percent of the utility’s water comes through the South Platte and Roberts Tunnel collection systems, Elder said, both of which depend heavily on the Colorado River. The remaining 10% comes from the Moffat collection system, which feeds into the Gross Reservoir and the Ralston Reservoir northwest of Golden.
It’s a lopsided ratio that can be problematic when a drought, wildfire or any other force of nature cuts into that southern water supply, Elder said. Plus, wildfires can contaminate water and interfere with collection systems because they burn up underbrush that would otherwise absorb rain and snowmelt.
Denver Water’s annual reports show its water collection has remained fairly stable over the past decade, but Raitt noted humans only have a short glimpse into the state’s climatological history. The area has suffered severe, multi-year droughts in the past.
Colorado State University climatologist Becky Bolinger said even without an obvious local pattern of drought and climate change, the risk is real. Not to mention, she added, the Colorado River is already overtaxed by communities in and out of state that rely on it.
Expanding the Gross Reservoir would double Denver Water’s reserve capacity in the northern system to 20%, Martin said, a more preferable ratio than the current 90-10 to better safeguard against natural disasters.
During construction, Martin acknowledged that the system will be more exposed to droughts and fires. The utility’s planning department will likely store more water at the other reservoirs to compensate for that added risk.
The last disaster, a multi-year drought, started in 2002, Martin said. Utility officials launched into a conservation campaign with the tagline of “use only what you need.” It worked.
By 2016, Denver Water customers had reduced their per-person water consumption by 22%, Fisher said, effectively offsetting demand increases from the new arrivals to the city. In that time, the utility added 17,035 active taps to its service area and tens of thousands more people moved to the area, annual reports and U.S. Census Bureau data show.
Conservation just isn’t enough to make up for that still-increasing demand. And by 2026, there’ll be 70,000 more people in Denver Water’s service area, spokesman Todd Hartman estimated.
“The early 2000s rut was our early indication. It really woke the entire state up to growing water scarcity,” Fisher said. “Without (the) Gross (expansion), we are taking on, and our customers are taking on, too much risk. We don’t have the water security to meet our customers’ needs.”
Utility officials began looking into expanding the Gross Reservoir during the multiyear drought, knowing it was built to be expanded. And the pushback began almost as immediately.
Arguments against the expansion largely fit into two categories, local complaints and big-picture concerns. Bev Kurtz, president of The Environmental Group, fits into both camps.
Her home rests near the existing reservoir’s north shore, and she and her neighbors would undoubtedly suffer annoyances and more for years from the constant construction. There’ll be construction lights all night, year round, and noise pollution from trucks and helicopters ferrying materials to and from the site.
Kurtz said she fears air pollution and more, too, considering crews must dig the quarry, pour concrete and cut down tens of thousands of trees.
She is one part of a coalition — including Wild Earth Guardians and the Sierra Club — that sued the U.S. Army Corps of Engineers in 2018 in U.S. District Court in Denver to block the project. A federal judge dismissed that lawsuit in late March, though Kurtz said she wants to appeal.
Raitt acknowledges her concerns and others’ are real, but reiterates the project is necessary for the Denver metro’s long-term survival.
Bob Bartusiak, who moved a few miles south of the reservoir in November, said most of the opposition he’s heard about focuses on the traffic along Gross Dam Road. Many people walk the road during the day, and the quiet nights would be interrupted by hundreds if not thousands of trucks.
That’s an argument Jeff Fisher said he’s heard repeatedly since moving to his home on Crescent Park Drive near Gross Dam Road in 2011, but thinks it’s selfish to outright oppose the project.
“You’ve got to look at the greater good,” he said, “and from a high level, it seems like a good thing.”
Boulder County would bear the brunt of all of the construction and environmental damage, and receive none of additional water security from the expanded reservoir. And Kurtz is also unconvinced the project will succeed once it’s finished anyway.
“We’re in a 20-year drought,” she said. “Even if they do build this, they’ll never fill it. There simply isn’t enough water.”
Reservoirs are dated, Kurtz added, questioning whether Denver Water could instead look into other storage options, like pouring water back into the large underground aquifer that stretches from Greeley to Colorado Springs and as far east as Limon.
Hartman countered that aquifer storage and recovery isn’t a suitable standalone solution to increasing demand and water insecurity, though the utility is open to the idea in the long run.
After more than 13 years of work, Denver Water already has the necessary permits for the Gross Reservoir expansion from federal agencies like the U.S. Army Corps of Engineers, the Federal Energy Regulatory Commission and the Office of the State Engineer, Greg Fisher said.
What’s left is the permitting process with the Boulder County Commission, Kurtz’s last hope to stay Denver Water’s hand.
Denver Water needs from Boulder County a 1041 permit — something that in recent years generated a headache for Colorado Springs Utilities, which negotiated a similar permit with Pueblo County for the $829 million Southern Delivery System water project.
Denver Water CEO Jim Lochhead said the utility applied for its 1041 permit earlier this year and anticipates approval by fall.
Dale Case, Boulder County’s director of Community Planning and Permitting, said the county and the utility are communicating on outstanding issues in the proposal, a number of which still haven’t been addressed by Denver Water, he said, but didn’t give specifics.
“This project has tremendous impacts both environmentally and on the folks that live up in that area,” Case said. “There are a lot of issues like transportation impacts, hauling routes, road improvements that would have to be made. Lots of concerns about the environmental impacts, impacts to neighborhoods, the tree removal plan.”
The negotiation process must be completed before the permit application goes in front of the three-person Boulder County Commission for consideration and a public hearing, Case said.
Kurtz said she hopes local opposition can sway the commission to vote against the project, though she acknowledges a no-vote from the group would more than likely spark a lengthy and costly lawsuit between the utility and Boulder County.
If the commission does approve the project, however, Project Manager Jeff Martin said construction could begin by July 2022 and end in the summer of 2027.
Denver’s population is already about 30% larger than when the utility started talking about the expansion and two things are certain: the population is only getting bigger and the state’s water supply isn’t.
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