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| Tuesday, September 25, 2007 -- Article
at Highline Times |
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| Copter aids repairs to Miller Creek in
Normandy Park |
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Repairs to Southwest Suburban Sewer District's main trunk
line along Miller Creek near Sixth Avenue Southwest got a lot of public attention last
week with a giant Sikorsky helicopter hovering overhead.
 The
Sikorsky helicopter transported machinery and materials to otherwise inaccessible repair
sites for several days, prompting complaints from a number of Normandy Park residents.
Sewer district engineers determined that repairs were needed after an annual inspection of
the 30-inch main sewer line in the Miller Creek basin found exposed parts of the line.
In addition, the upper five feet of one manhole were fully exposed to high stream flows.
The stream was running over the top of the line in some locations, which could have caused
a catastrophic failure by drying up Miller Creek during low flows in summer.
 This
problem also could have overwhelmed the plant, resulting in the discharge of millions of
gallons a day of raw sewage into the stream and ultimately Puget Sound during winter high
flows.
The original trunk line was constructed in the mid-1960s, four to
six feet below the stream, crossing back and forth underneath the stream bed.
Miller Creek channel erosion, which eventually exposed sections of the sewer line, is
generally caused by higher peak storm flows from adjacent urban development.
Over time, the flows have been gradually increasing due to this development.
Local agency storm water regulations have attempted to reduce the
severity of the problem. Flows may also be impacted by increased runoff associated with
the construction of the Port of Seattle's third runway.
New detention ponds built by the Port and recent major changes by the city of Burien are
expected to ease the flashiness of the stream.
Preventing impending winter storms from damaging the sewer line by raising and stabilizing
the stream channel provides the needed protection and also replaces washed out fish
habitat.
The biggest concern in proceeding with the Miller Creek project was how to gain access to
the environmentally sensitive project area to do the work, according to Ken Neilsen, an
engineer with Pace, the engineering company in charge of the project.
They determined that using a helicopter and a Sypder Hoe would minimize the area of
disturbance, Neilsen said.
That would enable the project be completed in the shortest possible
time since they would be working directly on repair and restoration instead of road
building.
A 72-foot long Sikorsky helicopter with a 10,000-pound lift capacity
airlifted all the materials-pumps, hoses, boulders, large woody debris, rootwads,
streambed gravel and anchoring components to the multiple project sites.
To keep the disturbance to the environment at a minimum a Spyder Hoe was brought in to
place all the materials.
The Spyder Hoe is similar to a backhoe, but with legs and wheels that can cross streams
with minimum impact and climb steep hills, and it appears to walk to minimize damage to
plants.
Rock and gravel was placed in a way that protects the sewer line and creates a
fish-friendly stream channel. Adult salmon are expected to return this fall. These repairs
should ensure their unimpeded access upstream to their native spawning grounds.
"Consider the alternatives", said Brett Fish, chairman of Citizens Against Sea-Tac
Expansion. "This project helps restore Miller Creek, protects it from raw sewage and
keeps Miller Creek a historically fish-friendly stream we can continue to enjoy for
generations to come." |
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