The end of an era
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Narrator Says:
It’s not exactly the Golden Gate, but the
Mt. Si
Bridge has its own story to tell.
The story starts where the bridge was born, not in North Bend where it
is now, but about 36 miles southwest of its current location in Buckley.
The Mt. Si Bridge was once half of a two-part span called the Buckley
Bridge and provided transportation access over the White River.
Interestingly, what happened to the other half of the Buckley Bridge
remains unknown.
The Buckley Bridge was a boon to the logging industry, which peaked in
the Snoqualmie Valley in the early 1900’s; around the time the bridge
was built.
Its design is rare nowadays, but was very popular in 1914, which is when
county records indicate work finished on the structure.
A pound of bacon cost a little over a quarter, and a loaf of bread was
about a nickel.
Mt. Si’s structure is called a Pratt Truss, named after the two men that
patented the bridge’s design. It’s also held together with 36 of these
steel pins.
Though the bridge has held up just fine over the years, the pins are
actually a bit of an Achilles Heal for the bridge.
King County Engineer Julia Turney Says:
The pin connections while unique in the development of bridge
construction in the United States, also represent a weakness in the
bridge, in that in one pin failing, the entire bridge can fail, so that
the piers themselves that the bridge rests on, are original to a 1930’s
bridge in this location.
And the bridge itself is scour critical from
flooding from the bridge, all things will be corrected by the new
construction of the new structure.
Narrator Says:
The new structure, seen in a computer rendering here, will replace the
Mt. Si Bridge, which would hit the century mark in 2014.
The bridge is showing its age, and its dated design.
Mt. Si offers no pedestrian access, the new structure will. The existing
bridge is only 19 feet wide from curb to curb, a width that doesn’t
allow today’s bigger vehicles the safest access over the river.
A new structure will be an opportunity to improve the sole access those
living on the north side of the river have to their homes, and replace a
bridge that’s given travelers in King County more than their money’s
worth.
King County Senior Engineer Gwen Lewis Says:
The condition of this bridge right now is there are several areas that
show signs of rust, the deck has corrosion, the bridge is 92 years old,
right now the timber supports are deteriorating.
And portions of the
bridge under the asphalt pavement, is a metal deck, and that metal deck
is relatively soft in nature, and what happens right now, is when heavy
trucks do come across the bridge, it results in cracking the asphalt
pavement and that cracking requires a great deal of maintenance from the
Roads Services Division.
Narrator Says:
This passage over the middle fork Snoqualmie will
step into the 21st century, marking the end of the Mt. Si Bridge’s
useful life.
During construction, transportation over the existing bridge will only
be minimally impacted if at all.
It’s a structure that’s seen this region of the northwest come to life
and change much over its near century of service.
Even though we can no longer head to the story with 30 cents today and
walk out with a pound of bacon and a loaf of bread.
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