Gross Reservoir Expansion Project update

Gross Dam enlargement concept graphic via Denver Water

From TheDenverChannel.com (Jace Larson):

The project will require significant construction over seven years to increase the reservoir’s holding capacity to 119,000 acre-feet of water.

When built, the dam will be the tallest in Colorado.

Denver Water says the additional space is needed to spread out capacity outside of Denver for the water utility used by 1.4 million people in the city and its surrounding suburbs.

The proposed construction project is not without opposition from neighbors and environmentalists who say they will endure years of construction on a water project that will never provide water to their taps.

“Boulder County is going to host this reservoir but gets no water from it. We derive no benefit from it. We only pay the price of having this thing in our county,” said Tim Guenthner, who lives just above the dam in a subdivision of about 1,000 people.

Denver7 decided to take a 360 look at this issue and gathered perspectives from five people connected to the proposed construction project…

Boulder County Commissioners have also taken a stance that Denver Water must get local permits before it can start the project.

Denver Water spokesman Travis Thompson said Denver Water doesn’t believe the law requires that and points out it has undergone numerous environmental studies and worked through the state permit process. This issue will likely be decided by another judge…

Denver Water’s Gross Dam project manager, Jeff Martin, acknowledges the project will cause noise for neighbors.

“Well we don’t hide from the fact there’s going to be some disruption from the noise, but we are looking at ways of minimizing that noise,” Martin said.

As an example, Denver Water decided to move the quarry needed to make cement to a portion of the lake that will be covered by water once more capacity is added. The original plan had the quarry on a portion of land jetting out into the lake.

Have an on-site quarry will also mean less truck traffic.

Martin said even with conservation efforts, Denver Water needs more capacity. He said experts have provided the water utility with data showing there will be 5 million more people in Colorado by 2050.

Denver water has 90% of its storage lakes west and south of the metro area, but only has 10% up north. This new dam project will add significantly more water storage north of the city.

“That’s important because if we have a catastrophic event or a drought in one of the systems, it leaves us depending on the other system,” he said. “What we want to do is create a little bit more balance and put more water in Gross Reservoir. This project is going to triple the size of the reservoir.”

[…]

Kirk Klanke is a member of Trout Unlimited, an environmental group seeking to protect and restore rivers across the country.

His perspective is one many wouldn’t expect from a member of the environmental group. He’s a supporter of the new dam.

“I think it’s extremely selfish to think we shouldn’t grow,” he said.

He says Denver Water has the legal right to build more capacity someplace. Gross Reservoir is the best option.

“Raising an existing dam has far less environmental damage than building a new one somewhere else,” Klanke said.

He says Denver Water has agreed to put significant effort into protecting the Colorado River. When it is hot out, river temperatures rise if there’s only a little water flowing.

Denver Water has agreed to keep water in the river during those periods and fill the lake during spring runoff. It will also draw water at different places in the river to minimize the impact to one area.

Gross Reservoir. Photo: Brent Gardner-Smith/Aspen Journalism

@DenverWater hires contractor for Gross Reservoir Expansion Project

The Gross Reservoir Expansion Project will add 77,000 total acre feet — 72,000 for Denver Water use and 5,000 for an environmental pool that provides additional water for South Boulder Creek during low-flow periods — nearly tripling reservoir capacity.

From Denver Water:

Denver Water’s five-member Board of Water Commissioners on Wednesday approved a two-year, $4.5 million contract with Kiewit Barnard, a Joint Venture, for planning and pre-construction work during the final design phase of the $464 million Gross Reservoir Expansion Project.

If the team’s performance during the planning and pre-construction phase meets Denver Water’s expectations, a separate contract to build the dam may be signed between Denver Water and Kiewit Barnard.

“This is a major milestone in our 16-year effort to expand Gross Reservoir, as its original designers intended decades ago, to ensure a more reliable water supply in a future marked by greater uncertainty in weather patterns,” said Denver Water CEO/Manager Jim Lochhead.

Denver Water, the state’s largest water utility, serves 1.4 million people in Denver and surrounding suburbs.

Gross Dam enlargement concept graphic via Denver Water

The Gross Reservoir Expansion Project will raise the height of the existing dam, completed in 1954, by 131 feet, allowing the reservoir to nearly triple in size. When complete, the reservoir will be capable of holding about 119,000 acre-feet of water to provide greater system balance and resiliency.

The selection process for a construction manager/general contractor for the project began in August 2018 with information meetings, followed by a formal Request for Qualifications in October 2018. Three teams responded to the request and underwent extensive evaluations and interviews by a selection team that included experts from Denver Water, the project’s design engineer and subject matter experts.

The selection team focused on a value-based competitive process that examined each team’s qualifications, project approach, technical approach and cost.

“Kiewit Barnard met Denver Water’s high bar for doing a project that’s important not only to the 1.4 million people who rely on us for their drinking water, but also to the people who live around the reservoir,” said Jeff Martin, Denver Water’s program manager for the expansion project.

“We were impressed by the team’s experience with roller-compacted concrete dam construction, innovative approach and commitment to safe and responsible building practices,” Martin said.

The project calls for adding 900,000 cubic feet of concrete to the existing structure and building the first roller-compacted, concrete, arch dam in the United States. When complete, the Gross Dam will be the tallest in Colorado and the tallest roller-compacted concrete dam in the U.S.

“Kiewit Barnard, a Joint Venture, is very pleased to have been selected to work on this important project to support water demand for the greater Denver area,” said Jamie Wisenbaker, senior vice president of Kiewit Infrastructure Co., and an executive sponsor of the project. “We believe the team’s collective infrastructure experience in dam and reservoir construction and engineering will be a huge asset and look forward to safely delivering a high-quality project on time for Denver Water and the region.”

Kiewit is one of North America’s largest construction and engineering organizations with extensive heavy-civil experience in water/wastewater construction, including serving as lead contractor on the Oroville Spillways Emergency Recovery project in California. Kiewit is the No. 1 contractor for dams and reservoirs in the United States according to Engineering News-Record. The company also has strong roots and experience in Denver and across Colorado, including having constructed the Interstate 25 T-REX Expansion project, the U.S. 34 Big Thompson Canyon emergency repair project and the I-225 Light Rail Line project. The company also is building Denver Water’s new Northwater Treatment Plant.

Barnard Construction Co. Inc. brings a long track record of safety and quality on infrastructure projects in the U.S., including construction on more than 80 dams, reservoirs and dikes over the last four decades. The company’s work in this area includes new construction, raising dams and conducting emergency repairs. In 2019, Barnard was honored as a “Global Best Project” award winner by Engineering News-Record in the dam/environment category for the Muskrat Falls North and South Dams project located in Muskrat Falls, Newfoundland and Labrador, Canada.

The Gross Reservoir Expansion Project is awaiting a final federal government approval from the Federal Energy Regulatory Commission. Provided the remaining federal approvals come by the end of this year, the project is slated to be complete in 2025.

When finished, the expanded reservoir and associated mitigation projects will create what the Colorado Department of Public Health and Environment has described as a net environmental benefit to state water quality by generating a wide range of environmental improvements to streams, river flows and aquatic habitats.

Moffat Collection System Project update: “Our problem is rooted in demand and resiliency” — Jeff Martin

Gross Reservoir , in Boulder County, holds water diverted from the headwaters of the Colorado River on the West Slope. The reservoir is part of Denver Water’s storage system. Photo: Brent Gardner-Smith/Aspen Journalism

From The Colorado Sun (Amanda K. Clark):

Raising the 55-year-old dam near Boulder is essential to keep a stable water supply in a changing climate, utility says. Residents insist conservation could be just as effective.

Denver Water — Colorado’s largest and oldest utility company — in July 2017 received one of the final permits needed to raise Gross Reservoir Dam by 131 feet to increase water storage capacity by 77,000 acre-feet, or an additional 25 billion gallons of Western Slope water…

The expansion, in the works for more than a decade, is part of the company’s long-term plan to help meet increasing water demands along the Front Range and buffer customers from future water-supply variability due to climate change…

Denver Water has been met with sustained opposition from Boulder County residents and a handful of environmental groups who say the utility can address its water needs through expanded water conservation efforts on the Front Range.

But with Colorado’s population growth showing no signs of slowing, water conservation may be inadequate to address projected shortages in the coming decades.

Other concerns raised by opponents include sustained disruption to surrounding residents, increased traffic, health concerns and environmental impacts to fish and wildlife.

Gross Reservoir is filled primarily from snowmelt that flows from the Fraser River, a tributary of the Colorado River. The water is transported underground from west of the Continental Divide to the east by a pipeline called the Moffat Water Tunnel.

The controversy over the Gross Reservoir expansion, estimated to cost $464 million, echoes an all-too-familiar story: a highly contentious discussion of tradeoffs that has rippled across the Western United States for decades.

As cities and states across the West grapple with swelling population alongside diminishing water supplies as a result of climate change, water-resource agencies such as Denver Water are faced with the delicate task of balancing the health of ecosystems with municipal, agricultural and recreational needs…

Jeff Martin, Denver Water’s project manager for the expansion project, doesn’t skirt around the controversy. He recognizes that the project is going to cause disruption and says that Denver Water has worked with the residents to find ways to minimize the project’s impact.

“This has been a process,” Martin said. “We started in 2004, it took 13 years to move through the environmental assessment and permitting process. And we’ve made a lot of changes and adjustments to our plans since the beginning.”

“No single solution is out there,” he said. “Our problem is rooted in demand and resiliency, and what I mean by resilience is that we have to make sure we have the water when we need it, and where.”

[…]

For Patty Limerick, director of the CU Boulder’s Center for the American West and former Colorado Historian, you can’t talk about water issues on the Front Range without first looking back in time.

When early white explorers arrived here, they deemed the Front Range unfit for settlement due to lack of water. Today, 1.4 million Denver residents have access to clean drinking water due in large part to Denver Water’s enormous infrastructure web that diverts water from the South Platte, Blue, Williams Fork and Fraser river watersheds to be stored in a network of reservoirs spread over eight counties, including Dillon, Strontia Springs and Cheesman.

“One thing that I find fascinating, and is important to talk about, is the incredible amount of engineering that had to occur to make any of this possible in the first place,” Limerick said.

“We, as a society, have to recognize the improbable comfort that was made possible by a taken-for-granted, but truly astonishing, water infrastructure that was put in place a hundred years ago.”

[…]

“The year 2018 was very similar to what we would expect to see under a climate change regime. And that was a very intense but short-term drought,” said Taryn Finnessey, senior climate change specialist with the Colorado Water Conservation Board.

“We saw some reservoirs in the state declined by 50 percent in a three- to four-month period. So that obviously could not be sustained multiple years in a row,” she said. “Water providers are increasingly integrating climate change models into their water supply projections. They know that what we’ve seen in the past might not fully represent what we might see in the future. Denver Water is one of the more advanced utilities when it comes to this.”

Finnessey says it’s not just about how much precipitation falls from year to year. It also has a lot to do with increasing temperatures, contributing to the long-term drying out of the West, a phenomenon scientists are referring to as aridification. As temperatures rise, more moisture is sucked up by the atmosphere through evapotranspiration, leaving less viable water for humans-use in the system.

“We are planning for infrastructure that will be built in the next 20 years, that is supposed to last for the following 100 years,” said Reagan Waskom, director of Colorado State University’s Colorado Water Institute. “Our world is changing significantly faster than that. And not in a linear way. How do we adapt to that?

“Water managers have to plan for extremes,” he added. “A year like this year is an argument for reservoirs. Even with climate change, you’re still gonna have some good years. And we need to be able to capture it and save it for the bad years, whether that’s in underground aquifers or in reservoirs.”

Denver Water’s collection system via the USACE EIS

Gross Reservoir expansion makes sense — Boulder Daily Camera

The dam that forms Gross Reservoir. Photo: Brent Gardner-Smith/Aspen Journalism

From the editorial board (Quentin Young) of the Boulder Daily Camera:

Denver Water serves 1.4 million people in Denver and surrounding communities, and that figure will rise substantially in the coming decades. As more residents demand service, climate change increasingly will exert its own strain on the water supply. One of the primary ways the utility plans to meet this imminent challenge is by expanding one of its northern storage facilities, Gross Reservoir, in the foothills southwest of the city of Boulder.

The project has met with intractable opposition. It’s the subject of lawsuits and uncertain government reviews. Neighbors are scandalized by the prospect of years of disruptive construction, and some environmentalists contend the project won’t even be able to perform its intended purpose.

But a dispassionate consideration of the project leads to the conclusion that Denver Water’s plan to expand Gross Reservoir is a reasonable and responsible measure, provided the utility proceeds with the utmost sensitivity to the residents who would be impacted by construction and with the expectation that increased storage is no substitute for continued conservation efforts.

The roots of the project go back to the proposed Two Forks Dam. Denver Water had proposed storing water from the Colorado and Platte rivers by building a 615-foot dam southwest of Denver near Deckers. But a coalition of environmental groups successfully opposed the project, which the Environmental Protection Agency spiked in 1990. Environmentalists argued at the time that a better option would be for Denver Water to expand a storage facility it already operated: Gross Reservoir.

Gross Dam enlargement concept graphic via Denver Water

Now that the utility is following opponents’ former advice, environmentalists have changed their mind about Gross. The project would raise Gross Dam by 131 feet to 471 feet, roughly tripling the reservoir’s current capacity of 41,811 acre-feet (for comparison, Denver Water’s largest reservoir, Dillon, has a capacity of more than 257,000 acre-feet). Critics say the expansion would result in the state’s tallest dam, and much of the opposition focuses on the project’s substantial environmental impact. It would require years’ worth of noisy construction, traffic and the removal of about 650,000 trees. The reservoir pulls water from the headwaters of the Colorado River, and critics argue that the utility should refrain from further depleting that waterway, which runs all the way to the Gulf of California and is subject to the Colorado River Compact, an agreement that governs water allocation in seven states that rely on the river as an invaluable resource. Population growth in the Southwest has stressed the river, and climate change is expected to further compromise the river’s capacity to deliver water to users. Some Gross expansion opponents even assert that there won’t be enough water available from the Colorado River Basin to fill a bigger reservoir. And anyway, the opponents say, water needs can be met through conservation rather than dam-building.

Construction to expand Gross Reservoir would indeed bring acute hardship to nearby residents, and concern for local environmental damage should not be dismissed. But construction is temporary, and the environmental impact seems less intolerable than merely regrettable when weighed against the project’s purpose of ensuring for decades the delivery of a vital resource to thousands of people.

Utilities should be judicious in exercising their rights to Colorado River Basin water, but the volume associated with the proposed Gross expansion is relatively small. The entire Denver Water utility accounts for less than 2% of the state’s total water use, while it serves about 25% of the population. As part of planning for the expansion, Denver Water worked with West Slope communities in the Colorado River Basin to earn support for the project, efforts that in 2012 resulted in the Colorado River Cooperative Agreement. The CRCA, which depends on final approval of the Gross Reservoir expansion, calls for Denver Water to help restore habitats and maintain flows in the Fraser River, a Colorado River tributary in Grand County. Some West Slope officials so favor implementation of the CRCA that a Grand County commissioner in March warned of “a ton of litigation” were Boulder to block the Gross expansion.

Colorado River flows will almost certainly decrease due to climate change in future decades. A widely cited 2017 study suggests the river increasingly will be subject to droughts, and flows could drop more than 35% by the end of the century because of higher temperatures. But this doesn’t necessarily constitute an argument against expanding Gross. No one can claim with certainty that flows would drop such to render useless an expanded reservoir, but Denver Water would certainly be justified in viewing the threat of persistent droughts and lower flows as a reason to increase storage capacity, since there’s more incentive to collect water during the fewer occasions it’s available. The utility would be seen to have failed customers were it to find itself with nowhere to store precious water to which it had rights.

That Denver Water should do more to promote conservation gets no argument here. The utility’s customers have already demonstrated that they can get by splendidly with reduced volume — they’re using about 20 percent less water today than 15 years ago, according to Denver Water CEO Jim Lochhead — and there’s much room for further conservation. But conservation has limits, and Denver Water says it won’t be able to meet future demand solely by this method. In Denver alone, the current population of 729,000 is expected to swell by more than 20% in just 20 years. Besides, the project is meant not just to add yield to the utility’s system but also stability. The vast majority of Denver Water’s storage is in the south part of its system, and forest fires near those facilities, such as the Buffalo Creek Wildfire in 1996, have exposed a vulnerability that an expanded Gross would address.

The proposed expansion of Gross Reservoir has provoked waves of protest from Boulder County residents, and the county has asserted what it claims is its right to review the project. Known as a 1041 process, the move is contested by Denver Water. But though Denver Water doesn’t serve Boulder-area residents, water users throughout Boulder County every day enjoy the use of water pulled from the Colorado River, and water customers in such Boulder County communities as Longmont, Louisville, Lafayette, Erie and Superior are participants in the proposed Windy Gap Firming Project, which involves the construction of a whole new reservoir, not just an expansion, west of Carter Lake to store water from the Colorado River Basin. (That project similarly is tied up in litigation.)

Denver Water has already secured the bulk of required regulatory approvals for the expansion of Gross Reservoir. A final decision from the Federal Energy Regulatory Commission, whose staff has already recommended approval, is pending. Denver Water needs the FERC approval, because Gross also serves as a hydroelectric facility. Roadblocks include a lawsuit brought by a coalition of environmental groups that is led by Save the Colorado and Boulder County’s 1041 review.

Boulder County officials have a legitimate interest in reviewing what would be the largest construction project in county history, and they are encouraged to take an exhaustive look at Denver Water’s plans. Any objections to the expansion of Gross Reservoir, however, should be based on factors intrinsic to the proposal, not on a mere preference for Gross to be left alone.

Quentin Young, for the editorial board, quentin@dailycamera.com, @qpyoungnews

Denver Water’s collection system via the USACE EIS

Save the Colorado is allowed to intervene in @DenverWater lawsuit v. @BoulderCounty

Workers build the Moffat Tunnel in the 1920s.

From The Loveland Reporter-Herald (Sam Lounsberry) via The Denver Post:

An environmental group’s motion to intervene in a dispute between Denver Water and Boulder County over the proposed expansion of Gross Reservoir was granted by a judge on Tuesday.

Court documents show Boulder District Judge Andrew Ross Macdonald will allow the group, Save the Colorado, to enter the case as a party on behalf of Boulder County, the defendant in the suit.

Denver Water filed the complaint against the county after it decided the utility would have to subject its controversial proposed dam expansion — which would be the largest construction project in the county’s history — through the county development approval process.

The case is still moving through court, with Denver Water trying to avoid subjecting its project to county [1041 regulations].

On Stressed #ColoradoRiver, States Test How Many More Diversions Watershed Can Bear — KUNC #COriver #aridification

Gross Reservoir — The Gross Reservoir Expansion Project will raise the height of the existing dam by 131 feet, which will allow the capacity of the reservoir, pictured, to increase by 77,000 acre-feet. The additional water storage will help prevent future shortfalls during droughts and helps offset an imbalance in Denver Water’s collection system. With this project, Denver Water will provide water to current and future customers while providing environmental benefits to Colorado’s rivers and streams. Photo credit: Denver Water

From KUNC (Luke Runyon):

The Colorado River is short on water. But you wouldn’t know it by looking at a slate of proposed water projects in the river’s Upper Basin states of Colorado, Utah and Wyoming.

The river and its tributaries provide water for 40 million people in the Southwest. For about the last 20 years, demand for water has outstripped the supply, causing its largest reservoirs to decline.

In the Bureau of Reclamation’s 2012 Colorado River Basin Water Supply and Demand Study, you can pinpoint when the lines crossed somewhere around the year 2002. It’s a well-documented and widely accepted imbalance.

That harsh reality — of the river’s water promised to too many people — has prompted all sorts of activity and agreements within the seven Western states that rely on it. That activity includes controversial efforts in some states in the Colorado River’s Upper Basin to tap every available drop before things get worse.

The utility that owns [Gross Reservoir], Denver Water, wants to increase the size of the dam by 131 feet, and fill the human-made lake with more water from the headwaters of the Colorado River via a tunnel that traverses the Continental Divide.

Imagine a tractor trailer hauling dam-building materials making this turn, Long says.

“If they truck all of this material up our canyon, people in our community are gonna get killed by those trucks. Period,” Long said. “There’s a lot of other issues here but the safety thing should really be a serious priority.”

Long and his wife, April Lewandowski, live near the reservoir in a community called Coal Creek Canyon. Like many of her neighbors, Lewandowski commutes from the sparsely populated canyon to her job on the state’s dense Front Range. Her daily commute on the canyon’s two-lane highway is the same as a haul route for trucks needed to build the dam addition.

Long pulls up to a small parking area that overlooks the dam. It’s a deep wall of concrete, stretched between the tree-lined canyon walls of South Boulder Creek.

“I mean you look at how the land splays out, you can see why they want to (build it),” Long said. “It’s so much wider all the way around.”

If the expansion goes through, the place where we’re standing will be submerged in water. The addition to Gross Dam will raise it to 471 feet in height, making it the tallest dam in Colorado…

Denver Water first started taking an expansion of Gross Reservoir seriously after the dry winter of 2002. Exceptional drought conditions took hold across the Mountain West. The utility’s CEO, Jim Lochhead, said in the midst of those historic dry conditions, a portion of its service area nearly ran out of water.

“This is a project that’s needed today to deal with that imbalance and that vulnerability and to give us more drought resiliency,” Lochhead said.

Since then, Denver Water has filed federal permits to start construction, and negotiated an agreement with local governments and environmental groups on the state’s Western Slope to mitigate some effects of the additional water being taken from the headwaters.

Before leaving office, former Colorado Democratic governor and current presidential hopeful John Hickenlooper threw his weight behind the project, giving it an endorsement and suggesting other water agencies in the West take notice how Denver Water approached the process.

But despite the political heft behind the project, it faces considerable headwinds.

Environmentalists are suing, arguing the expansion will harm endangered fish. A group of local activists say the additional water will spur unsustainable population growth along the state’s Front Range. In recent months, the utility began sparring with Boulder County officials over whether they were exempt from a certain land use permit.

Building a 131-foot dam addition does come with baggage, Lochhead said. But he argued his agency has done its part to address some of the concerns, like reducing the number of daily tractor trailer trips up Coal Creek Canyon and planning upgrades to the intersection where trucks will turn onto Gross Dam Road.

“It is a major construction project. I don’t want to gloss over that. It will have impacts to the local community,” Lochhead said.

Denver Water staff are doing more outreach in the canyon as well, Lochhead said.

“We are committed to the project and seeing it through. We’re also committed despite the opposition to working with the local community in doing this the right way,” he said…

The Gross Reservoir Expansion Project will add 77,000 total acre feet — 72,000 for Denver Water use and 5,000 for an environmental pool that provides additional water for South Boulder Creek during low-flow periods — nearly tripling reservoir capacity.

The latest scuffle with Boulder County has brought the Gross Dam expansion squarely back into public view. At a county commissioner’s meeting in March, residents criticized Denver Water on all fronts, from specific concerns about the construction itself, to broader concerns about water scarcity in the Colorado River basin…

“This project represents an effort by Denver Water … to actually grab water while they can, before federal legislation and management of the Colorado River Basin is imposed,” McDermott said.

What McDermott is referring to is a stark disconnect in the Colorado River watershed. States downstream on the river — Arizona, Nevada and California — signed a new agreement in May called the Drought Contingency Plan that keeps them from becoming more reliant on the Colorado River. It requires cutbacks to water deliveries should levels in Lake Mead, the river’s largest reservoir, continue to drop.

Meanwhile, upstream in Colorado, Wyoming, Utah and New Mexico, no such agreement was made. Those states wound up agreeing to study the feasibility of a program that would compensate farmers to stop irrigating their cropland if reservoirs dropped, with no solid way to pay for it. They agreed too to better coordinate releases from their biggest reservoirs to aid an ailing Lake Powell. While they figure out how to develop those two concepts, the Upper Basin states keep inching along on their development projects to divert more from the river.

The 1922 Colorado River Compact, the river’s foundational governing document, gives Upper Basin states the legal cover to continue developing projects like the Gross Reservoir expansion. In the compact, each basin is allocated 7.5 million acre-feet of the river’s water. Over the decades the rapidly growing and intensely farmed Lower Basin has used much more than that. The less populated Upper Basin has never reached its full allotment. Those state have been using roughly 4.5 million acre-feet for the last 13 years, with the rest flowing downstream for the Lower Basin to use as it sees fit…

Conservation programs tend to be less expensive than massive new projects, [Doug] Kenney said. But additional water supplies stored in reservoirs give more security and reliability. It’s why water leaders push for them, even when the economics don’t make sense.

Denver Water’s collection system via the USACE EIS

New Reservoirs, Dams Planned for Colorado Front Range — Engineering News Record

From the Engineering News Record (Thomas F. Armistead):

“In the water-scarce West, there is little to no new water,” says Laura Belanger, water resources and environmental engineer with Western Resource Advocates. “What we’re seeing is a shift to a suite of solutions that make the most of our region’s water resources. So the first line is and always should be conservation, because that’s the most cost-effective thing utilities can do, and it’s also fast.”

[…]

In Colorado’s Front Range, the Northern Colorado Water Conservancy District is accepting qualification statements for construction of Colorado’s tallest new dam in a half-century, with selection of a contractor and notice to proceed by December, says Joe Donnelly, spokesman. The main dam will be a rockfill structure with a hydraulic asphalt core, 360 ft tall and 3,500 ft long at the crest. The dam will impound the 90,000 acre-ft Chimney Hollow Reservoir for the Windy Gap Firming Project. A contract for design was awarded to Stantec in 2016.

The reservoir would store water for 12 municipalities and other water suppliers. The project has support from both public authorities and some environmental advocates. But six environmental groups are contesting the project in federal court because it will divert 30,000 acre-ft annually from the Colorado River, taxing the already challenged flow of that body.

Denver Water is proceeding with the expansion of Gross Reservoir, built in the 1950s with a 1,050-ft-long, 340-ft-tall concrete gravity arch dam impounding 42,000 acre-ft of water. Following 14 years of planning, the U.S. Army Corps of Engineers issued a 404 permit in July 2017, allowing Denver Water to raise the reservoir’s dam 131 ft and expand the reservoir’s capacity to 77,000 acre-ft.

The utility is expanding the reservoir to address a known imbalance in the city’s water system, said Jeff Martin, program manager for the project, in a video on the project’s website. The North System, where Gross Reservoir is located, stores about 30% of the water, and the South System the rest. The imbalance results from differential snowpack runoff on the system’s north and south sides. “This will provide extra insurance and extra reservoir capacity to make sure that we can weather those times when we do have issues in our system,” Martin said…

Some existing storage facilities are being expanded or are having their water reallocated, and regional water sharing also is beginning to grow, Belanger says. She cites the Chatfield Reservoir, built in 1965 on the South Platte River south of Denver for flood control, as an example. The U.S. Army Corps of Engineers determined that up to 20,600 acre-ft of the water can be reallocated to drinking water and industrial supply, agriculture, environmental restoration and other purposes without compromising its flood-control function. Environmental mitigation and modifications are expected to cost about $134 million.