Longmont to use concrete barriers to protect homes from spring runoff

Makeshift dam to be placed on Airport Road

LONGMONT, Colo. - Residents of two Longmont subdivisions hard hit by the September floods are starting to worry about spring runoff.

Public Works officials have come up with a novel way to address those concerns.

They plan to install concrete “Jersey” barriers in the middle of Airport Road.  But instead of controlling traffic, those barriers will act as a dam to control floodwaters.

Dale Rademacher, the director of Longmont’s Public Works and Natural Resources Department says they don’t anticipate a high runoff, but want to plan for it just in case.

“I’m very concerned about runoff,” said Longmont resident Dick Spangler. “We still haven’t recovered from the flood.”

Spangler said the September floodwaters entered his basement through a drain in the floor.

“I had just remodeled it,” he said. “We lost carpet, padding and everything down there.”

“It was a big mess,” said his granddaughter, Haley Juarez. “We nearly lost one of our pets.”

“We know that runoff is the next challenge we’re up against,” Rademacher said.

He told 7NEWS that normal spring runoff in Longmont is about 800 to 1000 cubic feet per second. “To be on the safe side,” he said, “we want to be able to handle two-and-a-half to three times that.”

He said the city is working on a protocol to protect homes and to keep the stream flowing in its main channel.

The protocol involves four main efforts

  • Designing a repair of the breach in the St. Vrain (with the County and U.S. Army Corp of Engineers) north of 75th and Hygiene.
  • Planning to intentionally breach Hygiene Rd if necessary.
  • Creating an emergency stream channel east of North 75th.
  • Placing Jersey barriers along a half mile stretch of Airport Rd for use as an emergency dam.

The jersey barriers would protect the Greens and Champion Greens subdivisions immediately east of Airport Rd.

“The reason we think this will work,” Rademacher said, “is that during the peak of the catastrophic flood the raised concrete medians were above the water line.”

He said they’ll connect the raised medians with a string of Jersey barriers.

“I think that’s a step in the right direction,” Spangler said.

When asked if that’s something the city will have to do every spring, Rademacher said, “I don’t think this is an annual or permanent solution.”

He said, “I believe some of the work that we need to do upstream, and maybe even in the channel itself is the answer, but we won’t have that done by spring runoff.”

Rademacher said they’re looking to rebuild the St. Vrain to handle a 100 year flood.

“That’s an $80 to $90 million proposition,” he said.

The temporary barriers will cost much less.  Rademacher estimated that they would cost around $50,000 to $100,000.

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