The U.S. Army Corps of Engineers appears likely to receive $44
million for more repairs to the Howard Hanson Dam, which officials hope
will prevent major flooding in the Green River Valley at least for a few
years.
U.S. Sen. Patty Murray persuaded her colleagues on the Senate
Appropriations Committee Thursday to put the money into a supplemental
spending bill the Senate is expected to vote on this month.
That money would be used to deepen and more than double the length of
an underground curtain of grout designed to temporarily prevent water
from seeping through an abutment and weakening the earthen dam.
“That would temporarily put us back to being where the dam was before
it was damaged,” said Corps spokeswoman Casondra Brewster.
Earlier this spring, the Corps told Congress that the existing grout
curtain — essentially a wall of cement and clay — only extends 475 feet
in length and allows the dam to be safely filled to about 54 percent of
its capacity. The Corps sought an immediate influx of cash to add
another 650 feet to this underground wall and to sink it to a depth of
200 feet.
“I’m ecstatic,” said Kent Mayor Suzette Cooke. “I know it was a tough
request to make at this point, but this is an issue about lives and
economic stability. We needed it.”
The dam was so weakened by heavy storms in January 2009 that the
Corps announced last summer that it was simply unable to hold back as
much water as it does most winters. As a result, Seattle District Col.
Anthony Wright said he might have to release water during winter rains
and intentionally cause a major flood that could wash over tens of
thousands of residents and businesses from Auburn to Tukwila.
In September Wright said the chance of flooding could be as high as 1
in 3, causing a panic among businesses and homeowners who sought
insurance and, in some cases, relocation plans. By late fall engineers
had made temporary fixes that increased the dam’s capacity, prompting
Wright to suggest odds of flooding had dropped to 1 in 25. And the rainy
season was dry enough that dam operators didn’t need to push their
luck.
“While we have been very fortunate with a mild winter, I don’t know
anyone who thinks we’re going to be that lucky again,” Cooke said. “This
gives us some breathing space, and certainly gives our business
community more promise for the future.”
The Corps has material and crews ready to start shortly after
Congress approves the emergency appropriation package with the money in
it. The additional fix could take six to 10 months to finish.
But even that would only last a few years, as heavy rains weaken and
erode grouting material.
“We’ll have geologists monitoring the grout curtain to see how it’s
holding up,” Brewster said. “The plan would be to get a permanent fix in
before it wears out.”
A permanent fix could cost up to $450 million and take three to five
years to complete, which is why Gov. Chris Gregoire, Cooke and other
mayors from the Green River Valley were in Washington, D.C., last week
lobbying White House officials.
– Seattle Times
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