KPLU Local News
(2009-11-06)
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Col. Anthony Wright of the U.S. Army Corps of Engineers explains repairs at the Howard Hanson Dam
KPLU
A devastating flood on the Green River is less likely than before. That's the update from the U.S. Army Corps of Engineers, which has been working on a temporary fix at the Howard Hanson Dam.
The chances of a flood that would go over the tops of levees in valley cities such as Auburn, Kent, Renton and Tukwila are now 1-in-25 instead of 1-in-4. That's because of repairs alongside the dam, where water was seeping through the soil. Col. Anthony Wright of the Army Corps warns people not to let the improved situation make them complacent.
"The message is to remain prepared. If you haven't bought flood insurance, you should still buy it," he says.
Anyone who lives or works in the flatlands of the Green River valley remains at risk, if we get a major winter storm. Still, some businesses or government agencies may re-think whether they need to entirely relocate their operations now, versus temporarily evacuating if flooding does happen.
The rain falling this week is barely a blip at the dam, which is just 1% full. For routine winter storms, there's not much threat. On the other hand, if anything like last January's record rainfall recurs, there would be serious flooding.
The army corps has pumped nearly 500,000 gallons of cement-like grout into the ground near the dam, to fill in porous areas. Pressure tests show it should handle the water from moderate storms. Sandbags and other material have also raised the levees higher. If you combine the effect of the higher levees and the new "grout curtain," the risk of flooding is about 1-in-33, according to Col. Wright.
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