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.
FromThe Grand Junction Daily Sentinel (Dennis Webb):
The Colorado River District has been given some breathing room for dealing with a problem dam at its Wolford Mountain Reservoir five miles from Kremmling.
A three-person outside team of dam experts has advised the district that the Ritschard Dam is safe despite the settling that has occurred there, no immediate action is required, and the district should be deliberate in determining how to address the problem.
“The Consultant Review Board has emphatically emphasized that time is on our side,” the district’s chief engineer, John Currier, said in a memo to the district board in advance of its meeting next week.
The recommendation comes as good news to the district, which has identified the dam as the most important issue it currently faces. It already has spent about $1.5 million to install sophisticated instruments to measure the dam’s settlement. Since its completion in 1995, the rock-fill, clay-core dam has settled near its center by about two feet. While earthen dams settle, in this case the drop was a foot more than expected. The dam crest also has shifted about eight inches downstream.
The three-person team, district staff and consulting engineers are now proposing that the district hold a workshop with the Dam Safety branch of the Colorado Division of Water Resources and Denver Water, which has a leasehold interest in the reservoir, to consider next steps.
“We were thinking that some kind of work would begin in 2016 or (20)17, to begin some kind of remediation program, but now we’re saying OK, let’s dig deeper into the issue based on this third-party finding,” district spokesman Jim Pokrandt said.
He said the finding means the district has more time to make sure it takes the right next steps regarding the dam. The most expensive repair would involve rebuilding the dam, which several years ago the taxpayer-funded district estimated could cost $30 million. Another approach could involve injecting concrete into the dam to reinforce it.
The original dam and reservoir project cost $42 million, including land acquisition, permitting, construction and other expenses…
The dam sits on Muddy Creek, a tributary of the Colorado River. The river district has consulted with the town council of Kremmling, which is downstream of the reservoir on the Colorado River, and Grand County commissioners. It also has held public meetings and kept emergency managers informed of the situation.
Bill McCormick, the state’s chief of dam safety, agrees that there is no reason for immediate concern regarding the dam.
“It is displaying some unusual behavior but (the findings of) all the analysis that’s been done to date is that it’s not creating unsafe conditions,” he said.
Still, he said he thinks everyone involved agrees there’s a long-term issue pertaining to continued settling, which requires a long-term solution.
“The long-term solution isn’t clear or obvious just yet but we’re continuing to work on it,” McCormick said.
It could cost $15 million to dig up and recompact the rocks on the downstream side of the dam that creates Wolford Reservoir, north of Kremmling, in order to stop the dam from moving slightly, but steadily.
“It is a pretty significant surgery of the dam,” John Currier, chief engineer at the Colorado River District, told the district board July 22 during a presentation.
Ritschard Dam was built for the river district in 1995 by D.H. Blattner and Sons of Minnesota for $42 million. The dam is 122 feet tall and 1,910 feet wide.
The $15 million estimate to rehabilitate the dam includes a 35 percent contingency factor and is still preliminary, Currier stressed.
The project would include removing the top 25 feet of the dam and then stepping down the downstream face of the dam in layers to get to three “bad acting” zones of poorly compacted rock, some of which are 90 feet inside the dam.
“At some point that movement will compromise the ability of the core of the dam to hold back the water,” Currier said.
Currier said there are “no near-term safety concerns” regarding the dam’s current ability to hold back 66,000 acre-feet of water from Muddy Creek, which flows into the upper Colorado River east of Gore Canyon.
“We’re not in any crisis,” Currier said. “We’re just ready to move this forward.”
Engineers with the district noticed in 2008 that the dam had settled vertically by a foot-and-half instead of just 1 foot, as expected.
The dam has now settled 2 feet, at the rate of about an inch a year. And it has also moved horizontally, by about 8 inches, at a spot 40 to 50 feet below the crest of the dam.
The dam’s impermeable clay core is held in place by rock shells on both the upstream and downstream sides of the dam.
Trouble at some point
The upstream rock shell appears to have settled appropriately in place, perhaps because of varying degrees of water pressure on its face as reservoir levels have fluctuated.
But the downstream shell is still moving.
“At some point that movement will compromise the ability of the core of the dam to hold back the water,” Currier said.
Currier said construction-sequence photos indicate the movement appears to be related to how fill material above and below haul roads was compacted during construction.
The plan is to dig into sections of the shell, remove the poorly compacted rock, and then recompact those zones, mainly using the same rocks.
“The bad-acting layers may be more a function of how the material was placed, not the material itself,” Currier said.
Currier said a consulting engineer at the firm of AECOM had observed that the construction work is essentially “just a big dirt job,” albeit one that will require complicated sequencing and careful on-site supervision by experienced engineers.
Over the last six years staff and consulting engineers have taken a variety of steps to investigate the situation at Ritschard Dam.
$1.5 million spent
They’ve installed inclinometers, established an expert review panel, developed modeling and conducted lab tests on the core material to establish that the dam did not present an immediate safety problem.
The river district has now spent close to $1.5 million on instrumentation and analysis, Currier said, and recent work on a range of alternatives has given engineers enough information to move from the “what” stage to the “how” stage.
“We have a very good understanding of what solutions might, or might not work, and thus we can we have a great deal more confidence in our solution,” Currier said. “We’re confident that structural rehab is required.”
Currier said that simply storing less water in order to take pressure off the dam won’t solve the long-term problem.
In a memo to the board, Currier wrote “operating at reduced levels slows the deformation rate but does not stop the deformation.”
The river district has been operating the reservoir at 10 feet below normal levels since 2014 as a standard precautionary measure.
Another option looked at was installing a series of concrete columns down through the downstream shell of the dam in order to stiffen it, but Currier said it was ruled out due to higher costs and doubts about its effectiveness.
There is also the opportunity to increase the amount of water the reservoir can hold by increasing the height of the existing spillway, but Currier advised it was better to first just fix the dam to avoid a “permitting quagmire” by trying to also expand the reservoir’s capacity.
Water in the dam would likely have to be lowered or completely drained during the project in order to take enough pressure off the dam. Those lower water levels could cause ripples in regional water-supply operations, especially in a dry year.
But Dan Birch, the district’s assistant general manager, said water-supply concerns would not be the tail that wags the dog of the rehabilitation project and related safety concerns.
However, it was also noted that the project would take 220 days over two construction seasons and would likely have an affect on four years of water operations in all.
“It could have some impact on water operations for one year pre- and one year post-construction,” Currier said.
Currier and other engineers plan on continuing their analysis of the proposed solution, including meeting with the state dam safety engineer in August and continuing to ask a panel of experts to peer review the plans.
A refined proposal will be presented to the River District board in September as part of the district’s annual budget meetings.
Editor’s note: Aspen Journalism is collaborating with the Glenwood Springs Post Independent and The Aspen Times on coverage of rivers and water. The Post Independent published this story on July 27, 2015.
Wolford Mountain Reservoir
Muddy Creek outfall Wolford Mountain Reservoir
Ritschard Dam movement graphic Colorado River District
Colorado River Basin in Colorado via the Colorado Geological Survey
The Ritschard Dam on Wolford Mountain Reservoir near the town of Kremmling has some residents in the area concerned.
There have already been a few public meetings regarding the dam in Grand County. The Ritschard Dam has a clay core and is filled in around that with rocks, but the dam hasn’t held its shape. Something has happened with the settling of all the material over the past two decades.
“In 2009 it was discovered that pieces of the dam have settled faster than was expected by designers,” Jim Pokrandt with the Colorado River District said.
Sophisticated monitors have been placed inside the dam. The crest of the dam has settled down 2 feet, twice as much as expected — and also shifted downstream 8 inches.
“We’ve been studying that since 2009, spent $1.5 million or more on this, and we really can’t say why exactly, other than there could be some compaction issues that date back to construction time,” Pokrandt said.
Engineers have said it’s the river district’s top priority, and not fixing the dam could send a devastating flood down the Colorado River.
“Public safety is not at risk and it won’t be at risk because we’re going to take this quick action,” Pokrandt said.
Exactly how the dam will be secured and fixed won’t be decided until later in the year. One idea is making the dam and reservoir bigger.
“You can imagine that if you’re going to fix a settlement issue you might be scraping off part of the dam and rebuilding it. How much, we don’t know.”
Forty percent of the water in the dam is owned by Denver Water. The rest is to ensure water in the river for endangered fish and water for municipalities on the Western Slope. But making the reservoir hold more water brings in a whole new set of issues.
“It’s premature to talk about what the exact repair scenario could be,” Pokrandt said. “There’s no quick fix.”
The Colorado River District board will likely make a decision on how the dam will be fixed by the end of the year.
Ritschard Dam impounds Wolford Mountain Reservoir, located on Muddy Creek just north of Kremmling. Construction on the Dam was completed in 1995 and falls under the auspices of the dam’s owners the Colorado River Water Conservation District.
Ritschard Dam is an earth-filled dam. As [Jim] Pokrandt explained, “With anything involving earth, settlement is expected.”
Unfortunately, as Pokrandt went on to explain, a portion of the dam has settled faster than the dam designers expected.
“The variations are small, but there is an abundance of caution,” he said…
“We are monitoring the conditions at the dam. The dam is not considered unsafe,” said Bill McCormick, chief of the Dam Safety Branch of the Division of Water Resources.
McCormick explained, “approximately four to five years ago there were anomalous instrumentation readings showing the dam had settled unexpectedly in ways that were not predicted in the design.”
“We have not identified a safety concern that has required us to put a restriction on the reservoir,” he pointed out.
According to Pokrandt, construction equipment visible on the dam is part of ongoing work to install measuring devices to gauge both water levels and movements within the dam.
Data collection and analysis regarding settlement of the earth-fill structure has been under way for several years now and the process will continue.
Pokrandt explained that any construction on the dam undertaken by the District, “will be very expensive” and the District wanted more information and data before any decisions were made regarding new construction.
Here’s the release from Denver Water (Stacy Chesney/Travis Thompson):
Two back-to-back, drought-plagued winters in Western Colorado have triggered an agreement to “relax” a senior water rights call on the Colorado River at the Shoshone Hydro Plant to allow water providers to store more water this spring, a move that benefits Denver Water and the West Slope.
The Shoshone Hydro Plant is owned by Xcel Energy and is located in Glenwood Canyon. Its senior 1902 water right of 1,250 cubic feet a second (cfs), when called, is administered by the Colorado Division of Water Resources against junior water storage rights upstream that include Denver Water’s Dillon and Williams Fork Reservoirs, the Colorado River District’s Wolford Mountain Reservoir and the Bureau of Reclamation’s Green Mountain Reservoir.
The agreement “relaxes” the call to 704 cfs when river flows are low, or takes a Shoshone call totally off the river when flows are rising, which is the current situation. This practice gives the upstream juniors water rights holders the ability to store water once the spring runoff begins in earnest. Currently, the Colorado River is flowing through Glenwood Canyon at about 825 cfs. (The long-term historical average for this date is about 1,150 cfs.)
Two tripping points activate the agreement: when Denver Water forecasts its July 1 reservoir storage to be 80 percent of full or less, and when the Colorado River Basin Forecast Center predicts spring runoff flows at Kremmling in Grand County will be less than or equal to 85 percent of average. Currently, the reservoir forecast is 74 percent full on July 1 and the Kremmling forecast is 60 percent of average.
Denver Water has already enacted its Stage 2 Drought Restrictions to limit outdoor water use and enact other conservation measures.
The winter of 2012 was the fourth worst on record in the Colorado River Basin and 2013 has been tracking just as poorly. The only improvement between the two winters occurred in March 2013 as storms continued to build snowpack. By this time in 2012, runoff was already under way.
The relaxation period is between March 14 and May 20, in deference to boating season on the river and irrigation needs in the basin.
As for the water that Denver Water gains by the relaxation, 15 percent of the net gain is saved for Xcel Energy power plant uses in the Denver Metro Area and 10 percent is delivered to West Slope entities yet to be determined by agreement between Denver Water and the Colorado River District.
“This is a statewide drought, and we all need to work together to manage water resources for the health and safety of our residents, our economic vitality and the environment,” said Jim Lochhead, CEO/manager of Denver Water. “The Colorado River Cooperative Agreement and the Shoshone Outage Protocol are great examples of the partnership between Denver Water and the West Slope to do just that. Last year, even though the CRCA was not yet in effect, Denver Water released water to the river even though the Shoshone Power Plant was not operating and the call was not on. This year, under the Denver Water-Xcel Energy agreement, the Shoshone call will be relaxed.”
“Relaxing the Shoshone water right in this limited way benefits the West Slope as well,” said Colorado River District General Manager Eric Kuhn. “It might make the difference between having a full supply at Green Mountain Reservoir and not having a full supply. In a year like this every extra drop of water we can store now will help us later.”