A “rooster tail” is formed by the water descending the Granby Dam spillway on July 19. Photo credit: Northern Water
Wolford Mountain Reservoir
FromThe Grand Junction Daily Sentinel (Dennis Webb):
Some rejiggering of reservoir operations in the upper Colorado River watershed is taking the heat off trout in Grand County through the early release of water that had been set aside for endangered fish in Mesa County.
The approach is being made possible by storing water elsewhere so it can be released for the endangered fish when they need it later.
Under the agreement involving the U.S. Fish and Wildlife Service, the U.S. Bureau of Reclamation and Colorado River District, an additional 35 cubic feet per second of water started being released last week from Lake Granby, also known as Granby Reservoir, in the Colorado River headwaters. That nearly doubled Colorado River flows immediately downstream.
The increased flows help reduce daytime temperatures in the river, which had begun topping 60 degrees and threatening the health of trout. The releases involve water normally stored in Granby for use in boosting flows in the river near Grand Junction for endangered fish such as the humpback chub and razorback sucker.
The endangered fish still will get water under the deal, however. In exchange for the additional water coming out of Granby, the river district is withholding 35 cfs of water from Wolford Mountain Reservoir, which sits above Kremmling on Muddy Creek, a Colorado River tributary. That’s below the problem stretch of the Colorado River, thanks to inflows to the river coming from Muddy Creek and other tributaries, so the Wolford water that’s being withheld doesn’t hold the importance to the trout that the released Granby water does.
“There’s plenty of water in the river except for in that stretch below Granby,” said Jim Pokrandt, a river district spokesman.
Pokrandt said the Colorado River is currently a “free river” right now in Colorado. There are no calls on it to meet the needs of senior water rights holders when flows are more limited. But the upper stretch in Grand County in the Hot Sulphur Springs area is depleted due to transmountain diversions to the Front Range.
Withholding the Wolford water means it will be available for the endangered fish during lower-flow periods on the Colorado River in Mesa County, in lieu of the water that is being released from Granby.
Officials from the Colorado River District, which owns and operates Wolford Mountain Reservoir, announced in spring 2016 that they were scrapping plans to conduct a multimillion dollar rehabilitation project on Ritschard Dam, which when full holds back Wolford’s 66,000 acre-feet of water. At that time the district announced it would initiate an earthwork project to restore the dam to its original height after several years of settling dropped the dam’s crest by roughly one-and-a-half feet.
District officials, however, announced plans this week to postpone the dam heightening project until 2018.
Jim Pokrandt, spokesperson for the river district, explained the decision was based on several factors including that the project is still working through the permitting process and officials were concerned about a late start for construction and the potential for bumping up against colder weather.
Pokrandt further noted that 2017 has been a very busy construction season and bids on the project would have been high.
“This is still a good project and it needs to be done. It will just take another year,” Pokrandt said.
The River District had previously planned to draw down Wolford to accommodate the earthwork but the recent announcement means accelerated drawdowns will not occur.
According to Ray Tenney, Deputy Chief Engineer for the District, for the remainder of summer and fall, the usual and expected water deliveries for contract and endangered fish habitat purposes will occur, resulting in a typical seasonal drawdown of about 10 feet in water elevation in coming months.
Wolford’s recreational amenities, including camping, boating, fishing, and day-use, will still remain open to he public.
Upper Colorado River Endangered Fish Recovery Program
Wolford Mountain Reservoir
Ruedi Reservoir. Photo credit Greg Hobbs
Green Mountain Dam via USBR.
Grays and Torreys, Dillon Reservoir May 2017. Photo credit Greg Hobbs.
Williams Fork spill.
Willow Creek Reservoir.
From the U.S. Fish and Wildlife Service via The Los Alamos Daily Post:
Coordinated releases from a series of Upper Colorado River Basin reservoirs began Saturday, June 3, and are anticipated to continue through this week as part of the Coordinated Reservoirs Operations Program.
The US Bureau of Reclamation, the Colorado River District, Denver Water and Northern Colorado Water Conservancy District as owners and operators of upper Colorado River reservoirs have mutually agreed to modify their operations to benefit the endangered fish of the Upper Colorado River Basin.
The Coordinated Reservoir Operations (CROS) program was established in 1995 as part of the Upper Colorado River Endangered Fish Recovery Program. The purpose of the Coordinated Operations is to enhance spring peak flows in a section of the Colorado River upstream of Grand Junction, Colo. Determined to be critical to the survival of four endangered fish species: the Humpback Chub, Razorback Sucker, Bonytail and the Colorado Pikeminnow. The higher peak flows remove more fine sediment from cobble bars that serve as spawning habitat for the endangered fish. In years with sufficient snowpack, surplus inflows to the reservoirs can be passed downstream to benefit these fish without impacting reservoir yields or future beneficial water uses.
Coordinated Reservoir Operations were most recently conducted in 2016, 2015 and 2010. In 2011 and 2014, wet conditions caused streamflows in certain areas of the basin to approach or exceed levels associated with minor flooding, so CROS was not performed. In 2012 and 2013, reservoirs did not have surplus inflow to contribute due to extremely dry conditions.
Managers of the reservoirs completed a conference call June 2, agreeing to voluntarily run the program this year. Planned reservoir operations as of June 2 are described below. Release and flow amounts are approximate. Most reservoirs will step up releases over the next several days, hold at a constant rate for 3-7 days, and then wind down releases.
Green Mountain Reservoir, operated by the Bureau of Reclamation, will increase releases from 418 cubic feet per second (cfs) to powerplant capacity of around 1400 cfs. Releases from Green Mountain include inflows bypassed by Dillon Reservoir, operated by Denver Water, that will be increased by approximately 100 cfs during CROS.
Denver Water also operates Williams Fork Reservoir, which is releasing 200 cfs. Releases will likely increase to approximately 600 cfs over the coming week to bypass increasing inflows.
Willow Creek Reservoir, operated by the Bureau of Reclamation and Northern Colorado Water Conservancy District, is releasing 90 cfs. Releases will increase this week to roughly 600 cfs by curtailing pumping operations to Granby Reservoir and bypassing those inflows instead.
Wolford Mountain Reservoir, operated by the Colorado River District, is passing inflows of 350 cfs. Outflows will be increased to around 600 cfs for approximately five days.
Ruedi Reservoir, operated by the Bureau of Reclamation, is releasing 182 cfs and will increase releases to approximately 600 cfs over the next few days.
The Colorado Basin River Forecast Center (CBRFC) will incorporate these planned reservoir operations into their streamflow forecasts. Based on weather forecasts and planned reservoir operations, flows in the Colorado River near Cameo (upriver of Palisade, Colo.) are anticipated to be approximately 14,000 – 17,500 cfs, June 7 through June 12, with the highest flows Thursday or Friday June 8 or 9. Flows in the forecasted range are still below defined “bankfull” and flood stages for the area.
More detailed information about forecasted streamflows in the Colorado River basin are available from the CBRFC website at http://www.cbrfc.noaa.gov. A map-based interface allows viewing of hydrographs detailing recent, current and anticipated flows.
For more information, contact Don Anderson, U.S. Fish & Wildlife Service, at 303.236.9883, firstname.lastname@example.org, Michelle Garrison, Colorado Water Conservation Board, at 303.866.3441, ext. 3213, email@example.com or James Bishop, Bureau of Reclamation, at 970.962.4326, firstname.lastname@example.org.
The Upper Colorado River Endangered Fish Recovery Program is a cooperative partnership of local, state and federal agencies, water developers, power customers and environmental groups established in 1988 to recover the endangered fishes while water development proceeds in accordance with federal and state laws and interstate compacts.
Through both natural and man-made activities, the area’s waterbodies will ramp back up to seasonal heights this week. The National Oceanic and Atmospheric Administration anticipates the Colorado River and its primary Summit County tributaries will reach their highest 2017 levels this Wednesday, June 7.
The volume-based flow rates, measured as cubic feet per second, on North Tenmile Creek, for example, will rise from about 600 to 900 cfs and the Blue River north of Dillon should grow in the next two days by another couple hundred cfs from its present 600. To offset forthcoming supply, Denver Water, which owns and oversees Dillon Reservoir, stated that it plans to up flows from Dillon Dam into the Lower Blue River from its Monday total of 380 cfs to 600 no later than Tuesday morning, and between 1,400 and 1,800 cfs by the end of the week.
“The snowpack up on the mountain, it’s now warmed up and is starting to come off,” said Jim Pokrandt, spokesman for the Colorado River District, a public policy agency that closely monitors the region’s major waterway. “It’s fast water, but shouldn’t flood anybody out. All streams will be quicker-paced than people are used to, but the flooding is not the danger.”
North of Silverthorne, additional releases at Green Mountain Reservoir also allow the Bureau of Reclamation to increase power plant capacity and generate more electricity. Those levels could reach approaching 1,400 cfs from the current 418.
Estimating that 40 percent of the winter’s snowpack still remains above Dillon, Denver Water is comfortable increasing the flows from Dillon Reservoir into the Lower Blue River that ultimately head to northern Arizona’s Lake Powell. That result is threefold, preventing wasteful overflow of the reservoir, maintaining ideal recreational heights on the lake, as well as fulfilling the demands of Lower Basin states based on senior water rights.
“Our experts are monitoring conditions carefully with the goal of ending runoff season with a full reservoir,” Matt Wittern, Denver Water Summit County liaison, wrote by email. “That way, we’re able to meet our customers’ needs while providing locals and tourists alike with valued summer recreation activities that have a positive impact on the local economy.”
Where spring runoff has been something like average—and where it hasn’t
Spring runoff of the Yampa River likely peaked on May 14 this year as it flowed through northwestern Colorado. That makes it an anomaly in the precipitation-dripping mountains of the West.
In most other locations, the peak runoff—the time when the largest volume of water in rivers occurs as winter’s snow melts—more normally occurs in early June after temperatures finally warmed. This year looks to be more or less normal, despite a trend to earlier runoff in many locations during the last several decades.
“The Yampa did have an early runoff, and that was the result of the warm temperatures and below-average snowpack,” said Ashley Nielson, senior hydrologist with the Colorado Basin River Forecast Center in Salt Lake City, when interviewed last week by Mountain Town News. The Yampa, she noted, will probably rise again in the next week or so, if not to the same high mark.
But elsewhere, the show is now, not a month ago. Peak runoff of the Green River was expected this week or next. It originates in the Wind River Range of west-central Wyoming. Unlike the Yampa, that basin still has a significant snowpack. That was also reported to be the case in Jackson Hole, at the headwaters of the Snake River. The snowpack there was 181 percent of average in late May, not a record but “up there,” in the words of one water official cited by the Jackson Hole News&Guide.
Peak runoff in the upper Colorado River at its headwaters along the Continental Divide in Colorado was also expected to occur in early June.
Winter had wild swings: barren until late fall, then torrents of snow in December and January. Temperatures were unseasonably warm in February and almost hot in March. It looked like an early runoff everywhere. Then May turned cold and snowy.
What explains the Yampa’s aberrant behavior? Karl Wetlaufer, a hydrologist with the Natural Resources Conservation Service in Denver, said the peak snowpack in northwestern Colorado arrived about a month earlier than usual. That snowpack around Steamboat Springs occurred on March 12, compared a more typical April 10.
Instead of mid-May for the Yampa, he says that rafters floating through Dinosaur National Monument more often experience the highest water flows of the year in early June.
Flows in the Animas River through Silverton and Durango have had some “pretty wild swings,” Wetlaufer says. The Arkansas River has been slow to get started with runoff.
The Snake River of Wyoming and Idaho has a very different story than the Yampa, with around 200 percent of snowpack this year. The Snake originates in Jackson Hole and picks up water from the Big Wood River, which originates in the Sawtooth Mountains above Ketchum and Sun Valley, before joining the Columbia at the Idaho-Washington border.
“My takeaway is that this year is pretty normal” in terms of timing, says Bruce Anderson, the senior hydrologist at the Northwest River Forecast Center, in Portland, Ore. It was cooler and wetter in spring, but the big story was the amount of precipitation that fell during winter. “We are hugely above normal for precipitation.”
In the Tahoe-Truckee area of California’s Sierra Nevada, the snowpack was among the deeper ones on record after three bad drought years and then a so-so winter in 2015-16. Snowfall this winter was not a record, but it was a record for total precipitation. Being somewhat lower and closer to the coast than Colorado, the Sierra Nevada gets more rain during winter. This year it got a lot of rain.
Colorado, too, had rain on snow, which is not unprecedented. But it happened frequently this winter. The result was telling for travelers on I-70 who crossing Vail Pass.
“In general, there was less snow than you would expect,” says Klaus Wolter, a research scientist at the National Oceanic and Atmospheric Administration in Boulder.
Were those rain on snow storms of this past winter a result of accumulating greenhouse gas emissions? Wolter told Mountain Town News that thinks this is “probably partially climate change.”
Wolter, whose focus is empirical climate research, using statistical methods to solve climate problems, is reluctant to pin climate change on much of what we have seen this year. True, he says, one storm during May left 42 inches of fresh snow in the foothills above Boulder, a storm unprecedented since the 1920s. As extreme as that storm was, proving causality is difficult, he says.
A scientist in Oregon also shared the difficulty of proving causality. John Stevenson of Oregon State University told the Idaho Mountain Express in Ketchum that it’s “really difficult to judge any one year” to be a result of rising global temperatures.
“That’s one of the challenges we run into in the science world where people say, ‘Oh, it’s climate change.’ We’re not at the point where we can take any one random event and say it’s climate change.”
That said, his 2015 study concluded that the point each spring when half of the water year’s streamflow had run off was occurring an average 1.9 days earlier per decade.
But more extreme events are happening with greater frequency, said Mark Davidson, director of conservation initiatives with The Nature Conservancy. He pointed out that the Big Wood River has had two 100-year floods in the last 15 years.
Warm temperatures in the Ketchum and Sun Valley area were 6 to 13 degrees warmer than normal for early May, producing a flood in the Big Wood River that peaked on May 8. It was regarded as the largest in 101 years of recorded history, reports the Idaho Mountain Express.
But more warm weather was producing another surge in early June that threatened to surpass that peak of a month before, the newspaper reported last week.
Jim Lochhead, the CEO and manager of Denver Water, said Tuesday that building new dams in the Colorado River basin is not at the top of his to-do list. Nor, for that matter, is drying up farms to provide water for Colorado’s growing cities.
But he says Colorado still needs to have hard conversations about how to flexibly manage its water. In particular, he wants farmers to be able to share water with Denver and other cities without worrying that they may lose their water rights.
Speaking at the annual Western Water Symposium at Colorado State University, Lochhead credited the 2015 Colorado Water Plan as being a useful “compendium of the issues” but said it highlighted relatively easy solutions without fully addressing the harder challenges.
“I don’t think the solution is $20 billion of new water projects for Colorado, but that’s an easy thing to go look for,” said Lochhead, head of the state’s largest water utility that supplies 1.4 million people, and stores nearly 40 percent of its water in Summit County’s Dillon Reservoir.
A coordinated plan is needed, Lochhead said.
“We’re not there yet with the state water plan to develop any kind of coordinated principle vision for the future, much less how to get there,” he said.
Lochhead, who took the helm of Denver Water in 2010, described Colorado’s historical approach to water as a zero-sum game where there had to be a winner and a loser.
That zero-sum game lost its moorings in the second half of 20th century as a result of new federal and state laws, court decisions and political fights, Lochhead said.
He said that two decades have brought more collaboration between diverse interests, including those on both sides of the Continental Divide, and it is reflected in such projects as Wolford Mountain Reservoir near Kremmling.
Both Denver Water and the Colorado River Water Conservation District have an interest in Wolford Reservoir, with Denver Water on track to soon own 40 percent of the water in the reservoir. The water has many benefits, among them providing late-summer water to meet needs of four endangered fish species in the Colorado River near Grand Junction.
Another collaborative effort has been launched in the Winter Park area. There, Denver plans to increase diversions from the Fraser and Williams Fork rivers, but is doing so with the blessing of local authorities, thanks to a collaborative “learning by doing” effort in Grand County that seeks to reduce streamflow impacts from both new and existing diversions.
But Lochhead believes Colorado must still dramatically change its water allocation methods as it faces population growth. Demographers project that Colorado’s 5.4 million population will double within a few decades. If we seek to provide the water for the additional residents the way we provided for the first 5 million, he said, “we won’t like the outcome very well.”
The river itself
A second challenge is the Colorado River itself, the fountain that supplies at least part of the water for 40 million people, from corn farms in northeastern Colorado to San Diego. And despite some good snow years, the two big reservoirs on the lower Colorado River, Lake Powell and Lake Mead, are both low enough to keep a ballroom full of water experts up at night.
It could get worse. And, according to projections of climate models, it likely will.
Laurna Kaatz, an in-house climate expert at Denver Water, recently told the Metro basin roundtable it’s still not clear if it will be hotter and drier, or hotter and wetter in Colorado in the future, but there is little doubt it will be hotter.
More major dams on the Colorado River are not the solution, Lochhead said. Evaporative losses would result in more loss than gain, he said, although he did allow for the possibility of relatively small dams.
Denver Water is, however, studying the potential for putting water into aquifers beneath the city, creating underground storage — storage that could, in theory, hold water from the Western Slope.
And Denver Water is looking to store up to an additional 15,000 acre-feet of Western Slope water in an expanded Gross Reservoir, southwest of Boulder. The $360 million project seeks to raise the elevation of the dam by 131 feet, which would increase the capacity of the reservoir by 77,000 acre-feet, bringing it up to 119,000 acre-feet.
Lochhead said that Colorado needs more flexible water management options that allow for greater sharing of the resource.
About 85 percent of water in Colorado is used by agriculture and ranchers and farmers tend to have the oldest and most senior water rights.
Water rights are private, said Lochhead, “but you can’t really do anything with that property right except what you are currently doing with it unless you go to water court. And by going to water court you put that entire water right at risk.”
In Colorado’s water courts, objections to changes in uses of water rights are often filed. The process can be lengthy and expensive for those seeking to make changes.
“You need a safe process where you don’t have to put your water right at risk, and you understand that you don’t have to spend years negotiating,” he said.
And Lochhead thinks Colorado also needs another conversation about conservation, where the emphasis is not about sacrifice but about innovation.
Denver Water intends to demonstrate what is possible as it redevelops its 35-acre headquarters campus along Interstate 25 near downtown Denver. There, planners think they can reduce demand for potable water by more than 50 percent.
In water reuse, said Lochhead, Colorado is “way behind the curve” as compared to some world cities, including Amsterdam and Sydney.
Editor’s note: Aspen Journalism and the Aspen Daily News are collaborating on the coverage of water and rivers. The Daily News published this story on Friday, July 29, 2016.
KREMMLING – Denver Water has taken steps to distance itself from a recent risk assessment of Ritschard Dam, which forms Wolford Reservoir five miles north of Kremmling.
The 21-year-old dam has found to be moving slightly and settling more than normal and a risk analysis workshop was held in February by a group of experts assembled by the Colorado River District, which owns the dam and reservoir.
After the risk workshop John Currier, the chief engineer for the River District, wrote a memo to the district’s board saying “a key conclusion” of a consultant review board is that “the dam is safe” and “there is no need for immediate action.”
Currier also wrote in his April 7 memo that the “key parties and participants” in the February risk workshop “included 1) the State Dam Safety Branch, 2) Denver Water, 3) our consultant review board, 4) our engineer, AECOM and 5) River District staff.”
But on May 2, Robert Mahoney, the director of engineering for Denver Water, sent Currier a letter critical of his April memo.
“In the memorandum, you characterize Denver Water as a ‘risk estimator’ and an active participant during the workshop,” Mahoney wrote. “Denver Water takes exception to these characterizations. At no time did Denver Water participate in the workshop as a risk estimator, nor was it ever invited to participate as a risk estimator on the panel.”
Mahoney also said that Denver Water “disagrees with characterizations in the memorandum implying that Denver Water was an active participant and that we concluded and agreed with the findings of the risk estimators. Denver Water’s role in attending the workshop was that of a concerned observer.”
Currier included the letter from Denver Water in a July 7 memo to the River District board. The memo and the letter were made public this week when the public agenda was released for the district’s July 20 board meeting in Glenwood Springs.
Mahoney raised other concerns in his letter as well.
“Based on our observations, the workshop and your memorandum only addressed the probability of a dam failure consequence,” Mahoney wrote. “While the probability of a dam failure appears low, dam failure is not the only potential adverse impact of concern to Denver Water. The probability of cracking in the core of the dam, which could reduce storage capacity, has a much greater range of uncertainty.”
Denver Water currently leases 40 percent of the water in Wolford Reservoir from the River District.
The reservoir can store 66,000 acre-feet of water and on July 14 the dam was holding back 65,240 acre-feet.
When its lease expires at the end of 2020, Denver Water is slated to become a part owner of the water in the reservoir.
“The River District will convey ownership, use and control of 40 percent of storage space and water right in Wolford Reservoir to Denver Water,” according to Jimmy Luthye, a communications specialist with Denver Water who checked Friday on the status of Denver Water’s stake in the facility.
As Jim Pokrandt, director of community affairs at the Colorado River District put it on Friday, “Denver Water currently holds a 40 percent lease. After 2019, it will be a 40 percent owner.”
Dam has issues
In his letter, Mahoney also suggested that developing a plan to fix the dam would be “beneficial.”
“According to Mr. Dick Davidson (of AECOM), cracking of the core has a 50 percent annual probability of occurrence starting in 20 years (the time criteria set for the workshop and probability estimation),” Mahoney wrote. “Given this uncertainty, it would be beneficial to develop plans now to remediate Ritschard Dam in the event of a crack.
“Further, based on the information presented at the workshop, Denver Water does not agree that Ritschard Dam is functioning as designed because no dam is designed to function with the degree of movement observed at Ritschard Dam to date.
“As addressed in the April 27, 2016 letter from Bill McCormick, chief of the Dam Safety Branch of the state engineer’s office, Ritschard Dam is in the category ‘of dams with significant issues’ and is on ‘an abnormal trend,'” Mahoney wrote.
Ritschard Dam is 122 feet tall, 1,910 feet wide, and sits across Muddy Creek, which flows into the Colorado River east of Gore Canyon. It was built for the River District in 1995 at a cost of $42 million by D.H. Blattner and Sons of Minnesota.
The dam has an impermeable clay core that is covered on both the upstream and downstream sides with rock fill, including shale rock excavated on site during construction.
In 2008, engineers working for the river district noticed the dam had settled downward by a foot-and-a-half, instead of the expected normal settling of one foot.
They decided to install monitoring equipment, including inclinometers, which measure slope angles.
Engineers for the river district have since installed an increasingly sophisticated array of monitoring devices. And they’ve verified that the dam has settled over 2 feet downward.
The dam has also moved horizontally, by 8 inches, at a location about 40 to 50 feet from the top of the dam.
Mike May, an engineer with AECOM, told the river district board in January 2015 that because of “poorly compacted rock fill,” the dam’s rocky outer shells are still moving, especially the downstream shell, and that the clay core of the dam, which is somewhat elastic, is also moving.
While the dam does not have “a global stability problem,” May said the concern is that if enough movement occurs, it could cause cracks in the clay core.
Water could then find its way into those cracks, start transporting material and widening the cracks, and the dam could eventually be at risk of failing.
McCormick, in his April 27 letter referenced by Mahoney, also included Denver Water as part of the risk assessment group.
“At the conclusion of the meeting it was the opinion of the participants, CRD, AECOM, risk analysis consultants John Smart and Larry Von Thun, Colorado Dam Safety and Denver Water that the risk of sudden failure of the dam by any of the failure modes analyzed was remote,” McCormick wrote. “It was also agreed that given that determination the need to continue to actively pursue physical modifications to the dam was not warranted at this time.”
McCormick also said that the results of the risk analysis session “now allow the Colorado River District and Colorado Dam Safety Branch to return to more normal reservoir operations with confidence that public safety is not being compromised.”
However, McCormick also noted that “due to the remaining uncertainty of the deformation behavior we agreed that Ritschard can only be classified as ‘conditionally satisfactory’ and that continuing action with respect to monitoring and observations is required by Colorado River District to operate the reservoir as planned.”
In his letter, McCormick cited a presentation at the risk workshop by Dr. Gavin Hunter, a professor at the University of New South Wales who has researched deformation behavior in 130 embankment dams.
Gavin compared the magnitude of the settlement observed at Ritschard dam with other dams in his data set.
“The displacement observed at Ritschard exceeds the majority of the dams studied, with only half the available data,” McCormick wrote. “Dr. Hunter describes this as ‘an abnormal trend.'”
McCormick also noted that Gavin’s research on the amount of settlement at Ritschard put it in the “region of dams with significant issues” category.
As such, McCormick said the River District should develop a plan for remediation work on the dam.
“We would encourage the Colorado River District to fully appreciate the abnormal and as yet not fully understood behavior of Ritschard dam and put an appropriate timeline on the ‘foreseeable future,’ McCormick wrote. “Based on the analyses done to date one could reasonably anticipate that remediation work will be necessary at some point in the future. We strongly encourage the Colorado River District to continue to plan for such remediation to avoid undue pressure on the operation of that facility as might be caused by a sudden change in the dam’s performance.”
McCormick said Friday that a workshop to develop an “action plan” has been set for the third week of August.
In his April 4 memo, Currier of the River District had written that the district’s analysis indicated that risk of failure of the dam from deformation was 1 in 100 million, while the risk of the dam failing by a “probable maximum flood” causing overtopping – a standard measure of risk – was one in a million.
He also explained why monitoring the dam’s movement was a better approach than trying to stop the dam from moving.
“With the dam failure risk so low, even with twice the current deformation, the estimators concluded that there is really no compelling technical or health, safety and welfare reason to embark on a remediation plan,” Currier wrote. “In fact, from a ‘do no harm’ perspective continued monitoring is equally if not more preferable to active remediation.
“While remediation might put to rest some nagging uneasiness about on-going deformation and when it might end, there is no absolute certainty that it would or should allay that uneasiness.
“In essence, remediation might replace one known uncertainty with a new, unknown, uncertainty. All dam owners are faced with some level of future uncertainty, we just happen to be keenly aware of it by virtue of extensive monitoring and investigation,” Currier wrote.
And in his July 7 memo sent to the River District board, Currier said an additional inclinometer has recently been installed at the toe of the dam to track movement, and that he would be sending Mahoney of Denver Water “a short response clarifying a few matters and inviting Denver’s continued involvement and expertise in the deformation issues.”
Click here to read the latest board meeting summary from the Colorado River Water Conservation District. Here’s an excerpt:
The Colorado River District has found that there is no compelling safety reason to proceed with remediation of Ritschard Dam at Wolford Mountain Reservoir in Grand County, now or in the foreseeable future.
This conclusion comes after exhaustve study of the settlement and a failure-risk assessment of the rock-fill, clay-core dam put into service in 1995. The River District’s consulting engineers and a separate Consultant Review Board it commissioned, together with the State of Colorado Dam Safety Branch, have concluded that the dam remains safe.
FromThe Grand Junction Daily Sentinel (Dennis Webb):
A review has led to the determination that there’s no need for the Colorado River District to make potentially expensive repairs to its Wolford Mountain Reservoir dam in the foreseeable future and it can resume full filling of the reservoir.
The review found that the risk of the Ritschard Dam in Grand County failing is extremely low despite the deformation problems it has been experiencing.
“We’re a public agency and we’re pretty gratified that we’re not looking at a 30-plus-million-dollar fix right now,” River District spokesman Jim Pokrandt said.
The rock-fill, clay-core dam was completed in 1995. It has settled near its center by about 2 feet, a foot more than expected of it as an earthen dam.
Its crest also has moved about 8 inches downstream.
The district already has spent about $1.5 million to install instruments to measure the dam’s movement.
It has considered possible repairs ranging from injecting concrete into the dam to shore it up to rebuilding it. The latter is something the district several years ago estimated could cost $30 million.
The district is taxpayer-funded and includes Mesa County. Any repairs might have come at least partly out of a separate enterprise fund the district derives from revenues such as water sales.
The district has called the dam problem the most important issue it faces. The reservoir is on Muddy Creek, and the town of Kremmling is just downstream, where the Muddy meets the Colorado River.
The reservoir can hold about 66,000 acre-feet of water.
The district began to rethink how it should deal with the dam movement after a three-person outside team of dam experts said no immediate action was required.
In February, it then held a workshop on the matter with participants including, among others, the outside team of experts, the state Dam Safety branch of the Colorado Division of Water Resources and Denver Water, which has a leasehold interest in the reservoir.
Participants concluded that the risk of the dam failing from the movement in a given year is one in 100 million, compared to the normally acceptable one-in-a-million risk of the dam failing from a flood overtopping the dam.
“Thus, the deformation- related public risk is much lower than other, normally acceptable dam-related risks,” the river district’s chief engineer, John Currier, said in a memo to the district board.
He wrote that the workshop participants concluded the chance of a dam failure from the problem is “very remote,” and that from a risk perspective “there is no compelling reason to proceed with remediation of the dam now or in the foreseeable future.”
“The dam is functioning properly, and has a very high probability of continuing to function properly even if deformation continues at the historical rate for many more years,” he wrote.
The district has been voluntarily keeping the water 10 feet below full as a precaution.
But those involved in the review agreed “that normal reservoir operation along with continued reasonable monitoring is appropriate,” Currier wrote, and that keeping water lower, while slowing down the dam’s deformation, merely prolongs how long it will take for that deformation to be complete.