New South Dakota Flood-Control Project to Protect Properties

September 8, 2010

A flood-control project in the works for more than 20 years should be completed next year, removing 1,500 properties from Sioux Falls, S.D.’s’ flood plain, a city official said.

Once the flood-control measures are in place, probably by the end of next year, the Federal Emergency Management Agency will redo its flood-plain maps. In turn, fewer properties will be in the flood plain — saving money for property owners.

“Walmart, Sam’s Club, The Empire Mall, Target are some of the businesses” that will be taken out of the flood plain, said project manager Tom Berkland.

Businesses and residents learned three years ago that FEMA was “modernizing” its flood-plain map, which required updates in the levee system and resulted in an expansion that included a number of properties in western Sioux Falls.

“The reason we’re making improvements is, when they built them, there was only about 10 years of data on flooding on Skunk Creek and the Big Sioux River,” Berkland sad. “As statistics go, that isn’t much. They did not make an accurate projection out to a 100-year event.”

The U.S. Army Corps of Engineers determined that the city’s flood-control system was inadequate to protect the city during a 100-year flood, which is estimated to have a 1 percent chance of occurring in a given year. After a number of area floods, controls were re-examined by the corps beginning in the 1980s, Berkland said.

When it was found that the levees did not provide protection to the newly calculated 1 percent chance of major floods each year, the levees could not be certified. The corps determined they needed to be raised another five feet.

Property owners who moved into the newly identified flood plain with federally regulated mortgages were required to buy flood insurance, costing hundreds of dollars a year — at least.

The corps, which constructed the levees in the late 1950s, notified the city in the 1980s that it would need to strengthen and raise its levees. But insufficient money restrained the work. Congress authorized the project in 1996 but initially put only $2 million a year into it. That made quick progress difficult, Berkland said.

“We were getting little pieces done at a time, but it’s not very efficient, not getting very far very fast,” he said. “That’s when the city passed the bond issue to pay for the 41st Street bridge and all of the work on the levee system to get it done, with the idea we’ll get it done as quickly as possible.”

Levee improvements will cost a total of $55 million, not including rebuilding the 41st Street bridge.

Sioux Falls has 27 miles of levees and three major structures, including a spillway and a dam. Another dam is being built near the confluence of the Big Sioux River and Skunk Creek. It should be completed this year at a cost of $4 million.

“With that now, we’re raising all the levees in the southwest part of town by about five feet,” Berkland said. “The spillway has already been completed.”

Earlier this year, the city agreed to pay more than $1.3 million to Minnehaha County Club for land needed to raise the levee along the course. As part of that agreement, the city decided it needed less of the golf course’s property by building a concrete wall atop the existing levee.

The number of properties in the flood plain was not immediately available from FEMA. A new flood-plain map takes about a year to become completed, and flood insurance rates aren’t affected until the map becomes final, said Derek Jensen, a FEMA spokesperson.

During construction of the flood-control projects, some stretches of the Sioux Falls bike trails have been cut off or led to detours. The 41st Street bridge trail will open temporarily from 49th Street to Sherman Park, but will close again in October for levee construction. The trail section is closed from Falls Park to North Drive, and the downtown bike trail will be closed into next year because of another phase of the sewer replacement project, according to city information.

“The trail will be improved, but the width of the trail will remain pretty constant,” said Kelby Mieras, park operations manager for the city Parks and Recreation Department.

Avid cyclist Phil Tau said that while he does more street riding than trail riding, the bike trails should be widened with a thicker surface and a better base.

“The bike trail is the most dangerous place to ride for accidents,” Tau said, adding that he thinks the city is fighting a losing battle by repairing only small sections of the trail at a time.

While there will be continual maintenance and monitoring on flood-control projects, Berkland said the city shouldn’t have to raise the levees again, barring major changes in weather patterns.

“It could happen, but we would not anticipate that in the near future,” he said. “We will be very pleased to have this project completed. It will be a good day for the citizens of Sioux Falls and for the city when this project gets completed and we can get the high flood insurance rates off a lot of people’s expenses.”

Information from: Argus Leader

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