Corps Now Forecasts Coralville Lake To Overtop Spillway June 7

By Hayley Bruce & Gregg Hennigan, Reporters

The spillway at the Coralville Lake Tuesday, May 28, 2013 in Iowa City. Outflow at the Coralville Lake Dam is expected to increase to 10,000 cfs Wednesday morning which should cause some minor flooding in City Park but with more rain in the forecast later this week preparations are underway for a more severe situation. (Brian Ray/KCRG-TV9)

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By Richard Pratt

IOWA CITY, Iowa -- If weather requires, Johnson County officials are prepared to close more roads over the next few days in order to take a pre-emptive strike against flooding throughout the area.

The Army Corps of Engineers said Wednesday that current forecasts call for Coralville Lake to top the dam's spillway on June 7. The Corp's forecast shows the lake level will rise 712 feet above sea level — the level at which water would flow over the spillway -- around 3 a.m. next Friday.

The National Weather Service also shows rises in the Iowa River overnight, though it remains a foot below a minor flood stage at 21 feet.

During a meeting Wednesday morning, Johnson County Supervisor Janelle Rettig said the county currently has 24 pallets of 50 sandbags available to the public from 6 a.m. to 8 p.m. until they run out, as well as 2 pallets of empty sandbags.

The county has also currently closed four roads, two of which are expected to re-open by the end of the day, including:

• 140th Street east of Ely Road (at the ATV Park)

• Sandy Beach Road (at the beach)

• Cosgrove Road between Black Diamond and 480th (expected to re-open today)

• Blackhawk Avenue south of Black Diamond Road (expected to re-open today)

She also said more roads are expected to close later today near Y avenue, adding the county's IT department will update it's website everyday at 8 a.m. and 3 p.m. with road closures.

As of Wednesday morning, county officials said the biggest concern throughout the rest of the week will be the possibility of 1-2 inches of rain on Thursday and Friday, creating the possibility for 2-5 inches of rain before Saturday.

"It's just a combination of are we going to have a perfect storm like we did in '08, or is this more like '93?" said Supervisor Terry Neuzil. "But the inflows in the basin are concerning, and it's going to come down to what happens on Thursday and Friday."

Rettig said the county's current plan for water outflow at the Coralville dam is to release 10,000 cubic feet per second today, 12,000 cubic feet per second on Thursday — which will likely cause flooding on Dubuque Street in Iowa City — and 14,000 cubic feet per second on Saturday, which could start to cause flooding along Normandy Drive in Iowa City. She said there has been talk about increasing inflows sooner, but no decision has been made on that yet.

The corps increased the amount of water coming out of the lake to 10,000 cubic feet per second Wednesday morning. Just Tuesday afternoon, officials were hopeful that could hold for two weeks.

Instead, outflow is expected to jump to 12,000 cfs on Thursday and possibly 14,000 cfs as soon as Friday, said Rick Fosse, Iowa City’s public works director.

Dubuque Street starts to flood near City Park at 12,000 to 13,000 cfs. Fosse said he’s pretty sure the northbound lanes will flood. The southbound lanes depends on the amount of water coming from Rapid and Clear creeks, he said.

The city is likely to either close that section of Dubuque Street completely on Thursday afternoon or close the northbound lanes and switch the southbound lanes to two-way traffic, he said. Dubuque Street is a major road in Iowa City, connecting Interstate 80 to the University of Iowa campus and downtown.

Fosse expects the community to deal with the threat of flooding for “a number of weeks.”

“Unless we settle into a dry period, this is not going away quickly,” he said.

"The key to all of this is we have history on our side a bit and being more proactive than reactive is something we have on our side this time," said Supervisor Terry Neuzil. "The coordinated effort is as strong as I've ever seen it and what is unique as well is almost all the players of the '08 flood are still employed and part of this process for '13."

The Board of Supervisors will discuss further flood updates at their informal meeting and work session tomorrow at 9 a.m.

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