Monday , November 27, 2017 - 5:15 AM
A flood control dam at Sullivan Hollow Park is shown here Friday, Nov. 24, 2017, in Ogden. The spot is one of several areas the Utah Division of Water Rights mapped out to show the likely floodplain if the dam were to ever fail. On a day with heavy rain, UDWR estimated the floodplain reaching as far west as Union Station, and then banking north to the Ogden River above 20th Street.
In November 2006, a farmer operating a feedlot on the southeast side of Willard Reservoir noticed the ground bubbling and boiling. He notified his local water district two days later.
That evening, a Monday, the U.S. Bureau of Reclamation visited the site and realized the Arthur V. Watkins dam was seeping at a rate of around 100 to 200 gallons per minute. It was on the verge of catastrophic failure.
Thanks to quick actions taken by Weber Basin Water Conservancy District and the bureau, the dam didn’t fail. But a decade later, it’s a stark reminder about how many dams saturate the West, how close those dams are to major population areas and that, sometimes, dams can fail.
Dams along and near the Wasatch Front supply drinking and irrigation water. They create reservoirs for boating and swimming. Some provide protection during heavy rainstorms and floods. But when dams fail in urban areas, they can cause serious damage.
“Northern Utah has a greater concentration of reclamation projects than really anywhere in the rest of the West. What that means is we have a lot of dams that are fairly old,” said Wayne Pullan, area manager for the U.S. Bureau of Reclamation.
There are two types of dams in Utah. First, there are the big ones part of early reclamation projects meant to green the West — dams like Pineview, Causey and Echo, built by the federal government and turned over to local water providers to manage. The U.S. Bureau of Reclamation still oversees their safety.
All other dams are state-managed. They range from diversion dams built by farmers to flood control dams built to protect cities. Those structures usually aren’t as noticeable, but they’re everywhere, in neighborhoods, in urban parks, at the mouths of canyons on the Wasatch Front.
There are 5,664 state-managed dams in Utah versus 25 U.S. Bureau of Reclamation dams.
State-managed dams in Weber, Davis, Morgan and Box Elder counties
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The Utah Division of Water Rights mapped the locations of state-managed dams. They’ve also modeled the likely floodplains should the structures fail during days with sunny weather and days with heavy rain.
Those footprints give Utah residents and property owners an idea of whether they’re in the path of potential damage and danger.
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Dam floodplains during rainy conditions
Dam floodplain during sunny conditions
The federal Bureau of Reclamation doesn’t map floodplains for its dams, citing security concerns.
“A lot of them need to be well-monitored to remain secure,” Pullan said. “They could be targets for terrorist threats.”
Safety engineers have three risk classifications for dams — low, moderate and high. They don’t indicate whether a dam’s in danger of failing. Instead, they’re categorized based on the amount of damage and loss of life they’d cause if they did fail.
Dams classified as “high” risk are close to towns or urban areas. Failure would result in possible loss of life and major loss of property. There are 255 state-managed dams in Utah labeled high-risk.
Dam managers often have to re-evaluate and re-classify dams as cities grow and suburbs spread.
“St. George is a great example of that. There are flood control dams, mainly, that when they were built, we weren’t really worried about them,” said Everett Taylor, a dam safety engineer with the Utah Division of Water Rights. “Now all of a sudden, there have been explosions of development. People live right below them.”
There are five high-hazard dams in Weber County. Four are used for flood control. Only one, Ten Acre Lake dam at Wolf Creek, is used to store water.
Davis County, by contrast, has 26 high-hazard dams. Around half are used for water storage.
Both state-managed and federal high-hazard dams are inspected annually. The state inspects moderate-hazard dams every two years and low-hazard dams every five years.
Lots of things can cause a dam to fail — earthquakes, water surges that overflow the structures or even burrowing rodents.
Slow leaks like the one discovered at Willard Bay in 2006 are what concern local dam engineers most.
“Earthen dams tend to perform well under earthquake loading and the majority of dams in Utah are earthen dams. Earthquakes don’t keep me up at night,” Taylor said. “Seepage, that keeps me up ... a dam can seep for years, 50 years, then all of a sudden it fails.”
Seepage happens when water makes it through the materials designed to hold it back. David Marble, dam safety engineer with the Division of Water Rights, compares those materials to a box full of baseballs.
“There are voids, openings, between the baseballs,” he said. “Soil is the same way … you may not see it, but any soil is made up of individual small particles. As you stack them together, there are voids.”
Many dams in Northern Utah are old, part of a larger aging water infrastructure problem in the region.
“Owning and operating these facilties is like owning an operating an old car,” Pullan said. “It was the best technology when you bought it, but over a period of decades new technology comes along.”
The U.S. Bureau of Reclamation upgraded Pineview dam three times in the 1990s. It also upgraded Echo and Lost Creek dams. It finished repairs and upgrades at Willard Bay’s Arthur V. Watkins dam in 2008.
The Division of Water Rights is working to upgrade old state-managed dams to meet current seismic and engineering standards, at a rate of around one or two projects per year. For privately owned dams, the state offers a grant covering 80 percent of the cost. There are around 80 upgrade projects left to go, Taylor said.
Federal dams are inspected annually, with a more rigorous evaluation every four to five years. Most of those larger dams also have people on-site every day.
“The dam tenders who actually operate facitlies, the ones who work for our partners … they actually perform, in some cases, daily reviews of the facilities,” said Dale Hamilton, technical advisor for the Bureau of Reclamation. “We are in regular comm with them to monitor the facility throughout the year.”
Almost all high-hazard dams in the state have emergency action plans in case of failure. The dam safety engineers on both the federal and state levels, however, only deal with the dams themselves. Alerts and evacuation responses fall to local city or county emergency crews.
“Generally for a dam to wash out it’s going to take some time. It’s not immediate,” Marble said.
Those concerned about living near a state-managed dam can check the most recent inspection reports online on the Division of Water Rights Dam Safety Database or request records from the division by calling 801-538-7240.
“I spend a lot of time ... being concnered about our facilities, making sure we’re ready to respond to any eventuality,” Pullan said. “But if I lived at the base of one of our dams, I wouldn’t spend any time worrying about whether I were in some kind of danger. I’d be wiling to build my house and raise my failmy there. We’re dedicated to keeping things safe.”