Patrick Springer, Published August 22 2010
The cattails are not a good sign, he said.
They mark the insidious flow of water from the lake, now a bay of massive Devils Lake, seeping to the edge of Tolna Coulee, the lake’s natural outlet.
If Devils Lake rises another 6 feet – it surged 3½ feet last year – it will begin spilling into the Sheyenne River, threatening downstream communities including Valley City and Lisbon.
In other words, Tolna Coulee, a highly erodible channel filled with sediment deposited by melting glaciers and blowing winds, is all there is to prevent a downstream disaster.
“This would be the restriction, so to speak,” Grafsgaard said, now pointing to a nearby slope forming the high ground in the coulee. “Once it leaves this area, it’s all downhill at this point.”
And if Tolna Coulee is left unreinforced, a huge volume of water could leave in a big hurry if the lake rises enough and a big deluge hits.
If that happens, the result would be a downstream disaster.
Engineers calculate that a worst-case spill would unleash a torrent into the Sheyenne River more than twice the flows during the devastating floods of 1997 and 2009 – for almost three weeks after, 8 feet of soils, 900,000 cubic feet, washed away from Tolna Coulee.
And the Sheyenne would stay at a higher-than-normal level for half a year as Devils Lake continued to drop, according to the preliminary analysis by the U.S. Army Corps of Engineers.
A worst-case spill assumes Devils Lake would reach its overflow level – now 1,458 feet, the high ground in Tolna Coulee – and then get inundated with 550,000 acre-feet of water, the equivalent of the 1997 flood.
With Devils Lake now about 6 feet short of its spill level, concerns about the critical importance of preventing a Tolna Coulee blowout are mounting.
And, as the new owner of Tolna Coulee, the city of Devils Lake holds a strategic piece of real estate in determining what happens downstream.
As the engineer for the city of Devils Lake, Grafsgaard is the coulee’s landlord.
His suggestion is to build a dam on the coulee’s high ground that would serve as a control structure to regulate flows.
The control structure would hold back water at times of flooding downstream, he said, and serve as the emergency spillway for the dam protecting much of the city of Devils Lake from being submerged.
With downstream worries and frustrations building, people are eagerly anticipating the recommendations of a federal task force report expected next month.
With no sign the 17-year wet period will abate, people around Devils Lake, and now downstream, are increasingly anxious for a permanent solution.
“The time we all have is based on whatever Mother Nature gives us,” Grafsgaard said, adding that he regards an overflow as likely. “I’ll bet that it will happen, but I don’t know when.”
Sitting at his desk more than 80 miles downstream on the Sheyenne River, Valley City Mayor Bob Werkhoven has his own ideas about what should be done with Tolna Coulee.
He wants it reinforced at the natural spill level of 1,458 feet to prevent a catastrophic, uncontrolled release of water from Devils Lake.
“We’ve been told that there’s some weak soils in the Tolna Coulee adjacent to Stump Lake,” Werkhoven said. “That thing could possibly break out at any level, not necessarily 1,458 feet.”
Downstream communities are entitled to be protected against the Devils Lake flood, Werkhoven said, noting that many millions of dollars have been spent protecting the city of Devils Lake.
Others have pointed out that when Devils Lake overflowed naturally with the melting of Glacial Lake Minnewaukan 10,000 years ago, most recently about 1,250 years ago, no significant washout occurred in the coulee.
A study by the North Dakota Geological Survey concluded that the elevation of Tolna Coulee once was 1,453 feet, but 6 feet of sediment filled in after the glacier melted.
An uncontrolled release of water down the Sheyenne would raise the river to a level more than 5 feet above the crest in the record 2009 flood, Werkhoven said.
“Which would overtop the levee we built by 2 or 3 feet,” he added, meaning a third to half of the city’s south side would be under water.
“We’d be in a world of hurt,” Werkhoven said. “There wouldn’t be much left of the business section of the city.”
Potential flood destruction isn’t the only problem flowing from Devils Lake. Degraded water quality is also a major concern.
Valley City is upgrading its water treatment plant to allow it to treat sulfate in the Sheyenne River being pumped into the river from an outlet on the west end of Devils Lake.
Officials hope the outlet, recently enhanced to pump more water, together with evaporation, will remove 8 to 12 inches of water from the lake.
Because Devils Lake is closed until it reaches a very high level, dissolved solids, including sulfates, become highly concentrated – especially in Stump Lake, which could drain into Tolna Coulee.
Therefore, any outlet built on the east side of Devils Lake should be located farther west, where the water is fresher, not at Tolna Coulee, Werkhoven said.
Drawing water from Stump Lake would send water with sulfate concentrations of about 2,500 parts per million. Concentrations are less than half that level as close as the Jerusalem Coulee, which connects east Devils Lake to Stump Lake.
Drawing water from Jerusalem Coulee and perhaps blending it with water from the west end outlet would result in sulfate concentrations of 700 to 750 parts per million, levels that are easier and less costly to treat, Werkhoven said.
Under emergency rules, state health officials are allowing the sulfate standard on the upper Sheyenne River to go up to 750 parts per million. The city of Devils Lake is asking for that higher standard, triple the limit on the Red River, to extend to the lower Sheyenne.
The city of Fargo, which relies heavily on the Sheyenne River as a backup water source, drawing from it 40 percent of the time in the past three years, also has concerns about the much higher level of sulfates.
West Fargo, which doesn’t use Sheyenne water but expects to do so as the city continues to grow, also has asked for state and federal support to cope with elevated sulfate concentrations flowing from Devils Lake.
Fargo estimates it would cost $50 million to $70 million to upgrade its water treatment plant and projects annual operating costs would rise $3.7 million to $5.5 million to treat sulfates, which cause odor and taste problems at relatively modest levels and can cause diarrhea at high concentrations.
Despite looming steep water treatment cost increases, downstream officials agree it’s better to increase flows from Devils Lake in order to prevent an uncontrolled flood pouring out of Stump Lake with the worst water quality.
Joe Belford’s old gas station in the city of Devils Lake would be almost 12 feet under water without the miles of dikes protecting the city.
So would the Walmart store across the way and roughly a third of the city, including everything built in the past 50 years, he said.
Trucks rumbling on the edge of town attest that the dikes are being raised, yet again, to 1,466 feet, higher in places exposed to tall waves.
Already the earthen dikes tower over nearby homes, and massive pumps remove rainwater trapped inside the protected area and send it into the lake. Streets and parking lots crumble from the high water table, and basement sump pumps run frequently.
At least two homes in the Lakewood subdivision near Devils Lake were flooded this spring, joining more than 15 neighboring homes submerged earlier by creeping floodwaters. So far, almost 400 homes around the lake have been destroyed or relocated.
“It’s just like cancer,” said Belford, a Ramsey County commissioner. “It takes a bite at a time.”
Across the lake on the western shore, the town of Minnewaukan expects to lose 13 more homes this year. Residents are waiting to hear if federal officials will approve relocating part of the town of 300, the Benson County seat, to higher ground.
Devils Lake has swallowed an estimated 125,000 acres of farmland as it quadrupled in size, wiping out millions of dollars of property and income throughout the basin, literally eroding the tax base, Belford said.
People around the spreading lake clearly are weary of the prolonged disaster and are eager to see more water coming off the lake.
But Tolna Coulee is something of a political divide as well as a topographical divide.
People living downstream from Devils Lake on the Sheyenne and Red rivers – 40 percent of North Dakota’s population – have their own chronic flooding problems.
Fearful of an outbreak of extremely poor quality water, Valley City and Barnes County last week passed resolutions urging the Army Corps of Engineers to armor Tolna Coulee to prevent an overflow.
In the case of Barnes County, the recommendation was to reinforce the coulee a foot higher than its current elevation, restoring a foot of topsoil the city of Devils Lake removed earlier this year, soil that sediment experts concluded had drifted in since statehood.
But the corps can’t touch Tolna Coulee without approval from the landowner, the city of Devils Lake.
Belford and Grafsgaard believe a consensus will emerge, striking a balance of upstream and downstream interests, to devise a permanent flood solution for Devils Lake incorporating the three-pronged approach settled upon years ago: protecting infrastructure, removing water and identifying upstream storage.
A broad plan consisting of a series of lake levels that would trigger certain actions seems likely to Grafsgaard.
“Based on the art of compromise, I would suspect it won’t be perfect for the people around Devils Lake,” he said, “and it won’t be perfect for the people downstream.”
Readers can reach Forum reporter Patrick Springer at (701) 241-5522
- 1940: The level of Devils Lake falls below 1,401 feet, its lowest recorded level since the area was settled.
- 1993: A prolonged wet period begins, starting the lake’s rise.
- 1997: After heavy rains and snowfall, Devils Lake climbs to almost 1,443 feet.
- 1999: Devils Lake reaches 1,446 feet and begins flowing into Stump Lake through the Jerusalem Coulee.
- 2009: The lake rises 3½ feet that spring and reaches a new record peak in June at 1,450.73 feet.
- 2010: The city of Devils Lake buys Tolna Coulee and in January removes a foot of sediment in two areas, restoring it to the estimated level at statehood. This lowers the level of the natural outlet of Devils Lake from 1,459 feet to 1,458 feet.
- 2010: Devils Lake reaches another record, 1,452.1 feet, though recently has fluctuated in a narrow band just below 1,452 feet.
Devils Lake was carved out by Glacial Lake Minnewaukan, which melted about 10,000 years ago.
The lake has merged with Stump Lake via Jerusalem Coulee.
If Devils Lake-Stump Lake rises another 6 feet, it will start flowing into the Sheyenne River via Tolna Coulee.
Geologists have determined that Devils Lake has overflowed several times since the glacier melted, most recently, according to one estimate, 1,250 years ago.