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Crews one-third done with Kent's Briscoe levee first-phase repair

Crews install sheet piles to make a wall to help strengthen the Briscoe-Desimone levee along the Green River in Kent.  - COURTESY PHOTO, City of Kent
Crews install sheet piles to make a wall to help strengthen the Briscoe-Desimone levee along the Green River in Kent.
— image credit: COURTESY PHOTO, City of Kent

Crews are about one-third of the way done with the first phase of repairing the Briscoe-Desimone levee along the Green River in north Kent.

"Construction started about a month ago with removal of trees," said city engineer Chad Bieren during a June 17 update to the City Council. "We had to take out some trees in order to get our wall in place. People in the area will notice a lot of tree removal has been completed and it looks pretty stark right now but it will look better in the future."

The 2.7-mile project to strengthen the levee will cost about $18 million when it's all finishd by the end of 2015. Crews are installing sheet piles about 30 to 40 feet into the ground to build the flood wall to protect portions of Kent, Tukwila and Renton from flooding.

Sheet piles arrived in May from Belgium and are stockpiled at the site. Crews will place the wall along the levee between South 189th Street and South 194th Street that do not meet stability criteria.

"They (sheet piles) are about 30 to 50 feet in length with the majority underground to shore up the levee," Bieren said.

Crews use a large crane to drive the piles into the ground. A few minor issues popped up but the project remains on schedule.

"The ancient mudflows from Mount Rainier deposited logs throughout the valley and we hit those the logs that do not rot because they are below the waterline," Bieren said.

But workers used a chisel beam to break through the logs so the sheet piles could be installed.

"We're hopeful we've met all of the logs we are going to meet," Bieren said.

The King County Flood Control District is paying for the project. The flood district, formed in 2007, is funded by a property tax of 10 cents per $1,000 assessed valuation. That tax raises about $50 million per year. The state awarded the district a $7 million grant to help pay for the levee to protect the valley from flooding.

The project this summer will cost $6.7 million on two sections of the levee. Crews will reconstruct two more sections of the levee in 2015.

Once the flood wall is up, crews will plant the riverbank with trees to provide shade in the river and better habitat for fish.

Kent Mayor Suzette Cooke credited the city's Public Works Department for all of its hard work to get the project going and with the plan submitted by the city to the flood control district rather than a county proposal.

"I want to thank the public works team to even get to the point of agreement to even allow the sheet pile levees," Cooke said at the council meeting. "Because the piles are in the ground we are able to provide habitat along the river without having to set back those levees 600 feet which was at one point the recommendation and wipe out that whole section of business and jobs."

It took months of debate last year between city officials and county staff about the best way to repair the levee before the flood district board picked the Kent plan. The county had proposed setback levee options estimated at costs of more than $63 million and up to $416 million because of the need to buy property and move businesses to expand the levee.

The projects also include the city submitting applications to the Federal Emergency Management Agency (FEMA) to certify the levee so properties are removed from the Kent Valley floodplains and property owners are no longer required to buy flood insurance.

The popular Green River Trail along the levee remains closed until December between South 180th Street and South 200th Street because of levee construction. A detour has been set up.

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