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Ryan Johnson, Published June 25 2012

After Duluth flood, Fargoans ask: Could it happen here?

FARGO – As the Duluth area reels from last week’s flash flooding, the director of Fargo’s engineering department said the city has taken major steps to limit the damage that kind of heavy rainfall can bring.

But it also has a natural advantage in avoiding the damage that struck Duluth.

Mark Bittner said that since 2000 Fargo has spent about $150 million upgrading its storm system, expanding the capacity of retention ponds that hold back water when the system is overwhelmed and improving the more than 350 miles of pipes that carry rain underground until it eventually reaches the Red River.

Those upgrades were prompted by the tough lessons the city learned from its own brush with a storm like the one that pummeled Duluth. On June 19-20, 2000, more than 7 inches of rain fell in eight hours, flooding 50 percent of Fargo roads, swamping the Fargodome and causing more than $100 million of damage to the community.

“It was the flood of the greatest damage that we ever had, and it was all internal flooding,” Bittner said.

Bittner said such a heavy rain eventually overwhelms the capacity of the storm system and ponds in the street because of the region’s flat terrain.

Once the puddles and ponds get deep enough, it can inundate the sanitary sewer system or flow into buildings.

Duluth is a different case, he said, because the hilly terrain meant the water from last week’s storm rushed down streets, tearing up pavement and washing out roads entirely.

“It will just sit and pond until the storm sewer can take it away here,” he said.

WDAY-TV meteorologist John Wheeler said that difference is noticeable in how long it took for the water to go down in the two cities. In Duluth, the floodwaters were mostly gone 24 hours after the rain stopped.

“Whereas when we get a heavy rain like that in Fargo, there will be big puddles and ponds for days,” he said.

Boosting defenses

Over the course of five years following the 2000 flash flood, Fargo beefed up its defenses against Mother Nature to better withstand these damaging storms.

Bittner said that included adding new “relief” storm systems in some low-lying areas, with crews installing a second pipe to move the storm water to the river faster. The city also expanded the capacity of its storm water retention ponds, including the Rabanus Park Basin that can now hold back 50 acre-feet of water that otherwise would flood out into streets and low spots.

Another major effort was upgrading drains in problem areas, including tripling the capacity of the drainage ditch that runs along 45th Street. It can how handle about 270,000 gallons of water per minute.

Bittner said the upgrades mean there should be less damage if another storm on the scale of the 2000 thunderstorm hits Fargo.

“I think the biggest thing is to protect the sanitary sewer system, and we’ve done a lot to do that,” he said. “The biggest problem in 2000 was the flooded sanitary sewer system.”

But Bittner said there is only so much that can be done to protect against such severe storms.

“There’s no way you can handle that kind of water, but you can at least try to keep it out of people’s basements as much as you can,” he said.

Wheeler said storms that dump heavy rain on isolated areas are “not unusual,” and a storm of the scope that hit Duluth seems to happen every summer somewhere in the Great Plains.

“But the thing is, they don’t hit a metropolitan area,” he said. “They happen in a rural spot.”

Wheeler said it is not uncommon for thunderstorms to produce 2 to 3 inches of rain each hour, but the storms typically are fast-moving and the heaviest rain will only last for a few minutes.

The “significant” storms that caused heavy damage in Fargo and Duluth were different, stalling over the cities for several hours and bringing the rainfall totals well above 6 inches, he said.

Wheeler said another storm like this is “bound to happen” somewhere in the Midwest, and chances are one will eventually douse Fargo again.

“If we got 10 inches of rain in downtown Fargo, we’re going to have a mess,” he said. “The sewer system would probably be better able to take care of it than it was in 2000, but it’s still going to be a mess just because the drainage in the Red River Valley is so slow that the water just ponds.”

Readers can reach Forum reporter Ryan Johnson at (701) 241-5587