Sand Bags Delivered To Flood-Prone Areas Levees Need To Be Upgraded

Disasters and AccidentsFloods and FloodingSeattleMetal and MineralBuilding MaterialPoliticsLocal Government

Sand bags are being distributed Monday in an effort to stop water flowing into flood-prone areas.

'Super Sacks' are being moved into Kent. Super Sacks are the heavy sand bags that takes a fork lift to move.

The sand bags are being distributed to Auburn, Tukwila and Renton. About 650,000 regular sized bags will be given to the community.

So far, $3.2 million dollars will be spent on the bags themselves.

Work to strengthen a reservoir wall and to raiselevees means there is a slightly lower chance of flooding thiswinter in the Green River Valley south of Seattle, the districtcommander for the Army Corps of Engineers said Monday.

However, Col. Anthony Wright told the King County Council thateven with interim repairs to the hillside next to Howard HansonDam, he still can't risk filling the dam's reservoir to capacity.The dam in the Cascade foothills southeast of Seattle controlsflooding from the river in the heavily developed Green RiverValley.

A record 15 inches of rain fell in 12 hours on the Green River'supper watershed in January, sending torrents into the 235-foot-highdam's reservoir. The reservoir rapidly filled 6 feet higher thanever before.

The dam held the water back and remained sound. But engineersfound excess seepage and signs of weakness within the dam's rightabutment, a 450-foot-wide pile of rock deposited by a hugelandslide 10,000 years ago.

Since then, crews have been injecting grout into the abutment toform a shield that will help strengthen the hillside. Wright toldthe council that those interim repairs are on track to be completedby Nov. 1, and that work is under way to raise the height of thelevees in the Green River Valley.

He said those efforts have lowered the possibility ofcatastrophic flooding from the 1-in-3 chance he gave earlier thisyear to 1-in-4.

Still, Wright cautioned the council that the grout shield willonly reduce but not eliminate the seepage, and he can't riskfilling the reservoir to capacity. Corps officials hope toconstruct a concrete wall in the abutment as a permanent fix, buthave said that work will take at least three years.

A news release from the County Council said Wright praisedefforts by the county and cities in the valley to prepare forpossible flooding. He said 750,000 sandbags were being deliveredfor distribution, including 750 "supersacks" - large plastic andfiber bags filled with rock and gravel.

While the sandbags will help prevent levees from beingovertopped, Wright warned that communities should not get into whathe called "levee wars" - building levees higher than thoseelsewhere on the river system.

"This creates the risk of damaging the levees under their ownweight" and causing them to collapse, Wright said. "Building thesystem up to capacity is an appropriate balance to preventovertopping while still not placing too high of an overburden."

About 25,000 people live on the valley floor, which includesparts of the cities of Kent, Auburn, Renton and Tukwila, buthundreds of thousands work, shop or travel there daily. Stateofficials say 22,000 people might have to be evacuated in a flood.

Officials have urged residents to buy flood insurance, stowvaluables in safe places and be ready to flee if a heavy rainstormhits.

Copyright © 2014, Los Angeles Times
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