Key to watershed management, dam system includes weak links
Ed Stremick understands just how close the city of Cavalier came to a disaster in May, when floodwaters threatened Renwick Dam on the Tongue River west of town.
“We were lucky,” he said.
Stremick, a member of the Pembina County Water Resource Board, was construction superintendent of the project to build Renwick Dam, as well as the Larimore and Fordville dams and 14 others in North Dakota some 40 to 50 years ago.
Renwick Dam and Lake Renwick are located at Icelandic State Park, a popular recreation area with camping, boating and a beach with public swimming, about five miles west of Cavalier.
Renwick also is the last of 10 dams in the Tongue River Watershed — the last line of defense for people living in the city of Cavalier — on the river that flows into the Pembina River just before it empties into the Red River at Pembina.
In May, as heavy rains mixed with runoff from a snowy late winter, floodwaters overtopped the earthen — sand and soil, with vegetation — emergency spillways on seven of the 10 dams — five each in Cavalier and Pembina counties.
“That’s never happened before,” Stremick said.
The U.S. Army Corps of Engineers built a 6-foot-high, 300-foot-long emergency levee to prevent floodwaters from washing out the Renwick spillway.
As a precaution, the 1,300 residents of Cavalier were evacuated for about 60 hours.
“It was really a tense time there, especially for two or three days,” said Keith Weston, Red River Basin coordinator with the Natural Resource Conservation Service. “If we would have picked up some additional rain a day or two after that, it would have been devastating.”
Renwick Dam is part of the NRCS Small Watershed Program, which began in the 1950s. While a chief purpose is watershed protection and flood prevention, projects also include erosion and sediment control, water supply, fish and wildlife habitat enhancement, wetlands creation and restoration.
Some, including Renwick, as well as the Larimore and Fordville dams west of Grand Forks, also provide public recreation, including camping, fishing and swimming.
“In the early stages of planning, we talk with locals, township boards, planning commissions, North Dakota Game and Fish, county water boards,” Weston said. “If there’s a lot of interest in multipurpose areas, we will build those structures.”
County water resource districts operate and maintain the recreation areas.
Larimore Dam Recreation Area is a fully developed multipurpose project on the Turtle River, northeast of Larimore. Completed in 1979, it includes a campground and swimming beach. It has a boat ramp and a handicapped-accessible dock for fishing.
It also features the Myra Arboretum, a 26-acre garden that includes about 500 varieties of trees and shrubs and serves as a resource for ecological, horticultural and historical education.
Turtle River flood
Rich Axvig followed this spring’s Renwick Dam emergency with more than a passing interest.
The retired NRCS district conservationist, who now serves as chairman of the Grand Forks County Water Resource District, was in the thick of a flood fight in Grand Forks County in June 2000, when a 19-inch overnight rain unleashed a torrent of floodwater through western Grand Forks County.
“It was a hot, humid day,” Axvig said. “It started to build some thunderstorms in the south. Then, it started to rain and it didn’t quit.”
While the storm hit a wide area of northeast North Dakota and northwest Minnesota, it produced a deluge in the Upper Turtle River Basin. The storm produced hail and tornadoes, too.
The land couldn’t hold it all, and waves of water funneled across paved and gravel roads, washed out railroad track, turned fields to lakes and overflowed drainage ditches.
Worst hit was western Grand Forks County, where Larimore and Kolding dams strained to hold more water than ever before.
In Gilby, about 15 homes were inundated. Mekinock was evacuated when floodwater washed through town. Manvel spent the last half of the week worrying and preparing as the Turtle overflowed, but residents were spared in the end. In Northwood, the golf course flooded, and rural homes along the Goose River were in trouble.
Two men died and two boys were seriously injured as vehicles succumbed to washed-out roads.
About 270,000 acres of crops suffered $31 million in damage from the storm.
The flooding resulted in major damage to spillways at four dams along the Turtle River.
“We didn’t lose any dams, but we lost spillways,” Axvig said. “It totally wiped out the spillway at Larimore Dam.”
NRCS repaired the damage. While they remain earthen spillways, they are much more secure than the original, he said.
Stremick was Pembina County Water Board chairman back in 1973, when Renwick Dam was ranked as the most hazardous dam in North Dakota and one of the top 10 high-hazard dams in the nation. Larimore Dam also made the state’s hazardous list.
At that time, he asked the board’s attorney if the board and the county could be held liable if someone were seriously injured or killed in an accident at or near the dam.
Then, the board started a campaign to get funding for a dam rehabilitation project.
The pleas fell on deaf ears until the early 2000s, he said, when then-Sens. Kent Conrad and Byron Dorgan, both North Dakota Democrats, included funding through the Watershed Rehabilitation Act of 2000.
Construction finally began in 2010 on a $9.6 million renovation project to replace the earthen, vegetative spillway with a 500-foot-long concrete structure that is more than 5 feet higher than the original spillway.
Similar flooding incidents have prompted reconstruction projects in other watershed dams in the Red River Valley, according to Weston, the NRCS Red River Basin coordinator.
In 2009, for example, the Absaraka Dam, 35 miles west of Fargo, was compromised by spring flooding, which included saturated ground and an unusually large amount of water being held back by the dam and emergency spillway. It was damaged again in 2010.
Since then, the dam in the Swan-Buffalo Creek watershed has been fortified with a concrete structure, according to Weston.
The Renwick Dam project is scheduled for completion in 2014.
“The last time Cavalier flooded to any degree was in 1950,” Weston said. “They had 50-plus years of non-events. They dodged a bullet this year.”
For Stremick, the project cannot be completed too soon.
“We’ll rest easier when it’s done,” he said.