FARGO, N.D. — The near-failure of a small and aging dam in northwestern North Dakota this spring has put the focus on similar structures elsewhere, with state officials saying that many will likely need repair after a third straight soggy spring.
Burlington Dam No. 1 ultimately held its ground last week against the worst floodwaters from the bloated Des Lacs River, but not before about 200 people were advised to evacuate a threatened part of town as a precaution. Officials don't have a clear picture of how many dams like Burlington's need attention.
"It's difficult to put a number on it until we get out there," said Todd Sando, North Dakota's state engineer. "I would say more than 10."
Sando and state dam safety engineer Karen Goff downplayed the danger from such dams, saying that most are low-risk, a definition that means they are in rural or agricultural areas with little possibility of future development.
North Dakota has about 3,000 dams, according to state Water Commission records. Some are as small as a couple of feet tall. The commission classifies each dam according to risk, with more stringent construction and maintenance standards applied to the higher-hazard structures.
Those defined as medium-risk are located in mostly rural areas where failure could damage isolated homes and highways, but with limited potential for loss of life. High-risk dams are located upstream of urban areas where failure could cause serious damage to homes and buildings, and there is the potential for the loss of more than a few lives.
Officials say the high-risk dams, many of which are maintained by the federal government, are in good shape and the chance of failure is low. The U.S. Army Corps of Engineers performs routine checks every year and conducts an intensive inspection every five years, a corps spokesman said.
Dams that are weak or near populated areas get inspected by the state each spring. Otherwise, because it's impossible to inspect 3,000 dams a year, officials rely on a rotating inspection schedule and depend on area residents to help monitor the structures, Sando said. His office has received several calls this spring from rural residents reporting problems.
"Their eyes and ears are very important out there, the locals," Sando said. "We can't be at these dams all around the state, and they are owned by local entities."
The integrity of Burlington's Dam No. 1, built by the federal government in the 1930s, has been suspect for many years, but locals say there's usually more silt than water in the pond.
"I don't know that it's hardly even deep enough to fish in the summertime," said Gary Neshem, a Berthold farmer and member of the Ward County Water Resource Board, which manages the dam.
Neshem said many people in the county don't know about the dam — and that they own it.
"We've ended up with a lot of stuff that was built by the federal government that we didn't even know we owned," Neshem said. "Every water board in the state is facing this problem. Where's the money going to come from to fix these dams?"
The state Water Commission has a general water management budget of $26 million to deal with projects like Burlington Dam No. 1. All projects are placed on a priority list that's based on recommendations from the state Water Coalition, a group of representatives from about 30 groups.
Harley Swenson, a member of the state Water Commission, believes fixing Burlington Dam No. 1 will be near the top of the list if the county applies for financial help from commission, which funds up to 50 percent of projects. It wasn't clear how much a Burlington fix would cost.
"We're going to have to look to partnering with the people who want to maintain that dam to make sure we protect the people downstream," Swenson said. "To me, that's the most important part."
Many water districts have only recently started to set up assessments or other methods of funding for maintaining dams and other water projects, said Mark Brodshaug, spokesman for the Southeast Cass Water Resource District.
"A lot of these districts weren't involved in the construction of these dams, but they were left to deal with them," Brodshaug said. "You need to build up that pool of money for when there are repairs needed, and these dams didn't have that process in place."
The 2009 flood that threatened the Clausen Springs Dam, above the town of Kathryn, and dams near Absaraka and LaMoure alerted local governments about the need to maintain those structures, said Chad Engels, a senior project manager with Moore Engineering in West Fargo.
"I do think 2009 was an eye opener to many of these water resource districts that, OK, we need to be looking a little closer at these dams," Engels said.
Clausen Springs has been waiting on repairs since a 2009 scare that saw 55 residents evacuated. Renovation is scheduled to resume when the weather allows.
"There are a number of dams that don't have enough volume behind them to be an issue if they washed out," said Engels, who has worked on dam projects with several water resource districts. "If they breached, you might slowly see the creek down by the pasture rise a foot and then go back down again."
Burlington Dam No. 1 is classified as a low-risk structure. A 1999 study showed that the increase in water level caused by a dam failure would be less than other conditions that would cause the river to spill its banks, such as ice or debris jams, or backwater flooding, said Goff, the state's dam safety engineer.
"In other words, the effects of a dam failure during a flood are so small, they really can't be differentiated from the flood itself," Goff said.
Burlington Dam No. 1 was last checked in May 2010, Goff said. The review showed some risky conditions, including trees and inadequate grass cover on the embankment, rock missing from the spillway, and erosion below the spillway.
The inspections might not always show how a dam will hold in unusually high water, Goff said. Burlington's dam hadn't shown a history of significant seepage before this spring.
"When water levels exceed what the dam normally experiences, there are a lot of unknowns," she said. "High water creates additional stress on the dam that can cause new problems or cause previously undetected problems to become apparent."