Green River disaster that never happened

The warnings were dramatic: A one-in-three chance of
catastrophic failure, loss of life, billions of dollars in
damage, businesses ruined. The Howard Hanson Dam on the
upper Green River was at risk of failure from a heavy
rainstorm, according to the U.S. Army Corps of Engineers.

The worst case scenario suggested six cities would flood
and downtown Auburn could be under 20 feet of water.

So, starting in 2009, King County and cities along the
Green River took extensive precautions to protect the
valley until repairs to the dam could be finished. Giant
sandbags, each about three feet tall and weighing 1-1/2
tons were placed along 26 miles of the river.

Homeowners and businesses placed their own sandbags while
the cities and counties developed evacuation routes and
spent millions of dollars to beef up levees. The county
even moved animal control and election offices in the
valley.

Of course, there was no flood disaster and the dam has
been repaired.

County councilmember Reagan Dunn, chair of King County’s
Flood District Executive Committee says the precautions
were appropriate.

“We had a high probability that the dam would breach, a 33
percent chance,” said Dunn. The loss, if it did breach,
was catastrophic, billions of dollars in industry, lives,
property and so, the 20-or-so million dollars that we put
in to sandbags, construction and implementation to protect
against that during a time of great vulnerability was the
right thing to do.”

Dunn admitted the devastation that resulted from Hurricane
Katrina a few years previous was on the minds of leaders
as they considered what might happen if the dam failed.

Today, we’re left with a strengthened dam, a beefed up
system of levees and an extensive flood warning network
that raised the cost of flood prevention to more than $30
million.

Contractors are busy removing the giant sandbags, with the
county picking up about 75 percent of the almost $6
million cost and the cities covering the rest. The sand
inside is low grade and considered not suitable for such
re-use as sanding streets, building sidewalks or patios or
even filling sandboxes. The sand will be sent to Cedar
Grove Composting for evaluation.

Dunn said it appears the bags are in good shape. The hope
is that the sandbags have not damaged the trail system
that runs along the river. The sandbag removal should be
finished by the fall.