One important activity in Seattle right now is
complaining. It’s one of many sites
across the nation where people wander around complaining. It’s like a national sport without trophies.
Digging tunnels is another activity in Seattle. We have new sewage tunnels, light rail
tunnels, and tunnels where they store wine until its ready.
The State DOT (WashDOT) is replacing a part of Highway 99 in
Seattle called the Alaska Way Viaduct.
The replacement will be a tunnel.
The old viaduct sustained damage in an earthquake and WashDOT realized
it might collapse when we have the next big one. Tunnels don’t have so far to fall.
The other big reason to replace the viaduct is that it annoys
some of the nearby property owners. Regular
people want to live close to the city where the busses are free and so are some
of the street people. That means a good
use for many of the old buildings is conversion to condos. It’s hard to sell a condo if the view is just
a noisy six lane highway. That’s low
rent stuff and not very attractive.
Condos also get much higher property tax for the state.
Hundreds of thousands of cars use that corridor every month
so we can’t just tear it down and pass out good luck charms. If those cars went over to I-5 it would be
horrible. We experience that from time
to time because they shut down the viaduct for inspections and damage repair.
I-5 runs under the convention center in downtown Seattle and
nobody can figure out how to make the highway wider and still have conventions. I have an idea but nobody listens to me. It involves dynamite.
Back to Alaska Way.
Many years before I was born, more than 10,000 years ago, Seattle was
covered in ice. I read someplace they think
it was 3,000 feet thick here. That ice
carried huge boulders, sand and gravel, dirt, and maple leaves from Canada and
left much of it in Seattle. The debris
included chunks of ice caught beneath the other stuff. When the surface ice melted this stuff was
left behind. The buried chunks of ice
also eventually melted and left voids.
Some of those voids are still there.
Most of the lakes around the area were formed by ice gouging
out depressions. The Seattle area
terrain was largely formed when the glaciers melted away. This is important when you want to dig a
tunnel. It’s also a nuisance when you
want to plant a flower.
Seattle has about 40 miles of tunnels. They first ones were dug over 120 years
ago. We like to dig tunnels. To dig an adequate tunnel years ago you needed
a good sturdy shovel. They use powerful Tunnel
Boring Machines now. These are custom
built to the diameter of the expected tunnel.
They have carbide tipped teeth that are supposed to chew through
anything.
The conglomerate left
by the glaciers makes it a particular challenge. What if you crunch through a granite boulder
right into one of those voids? What if
it’s still full of water? There are other
risks as well. What if you punch into
one of the existing tunnels or an old abandoned well? What if the Governor shows up with her giant
bulldozer? These are all questions the
planning team has to answer. Certainly
not me, I can hardly plan cereal for breakfast.
Tunnels in Seattle carry trains, cars and busses, water, gas,
electricity, beer, and sewage. If the
boring machine hits any of those it could delay the project for decades. Thus planning and testing are important. Already around town we’ve seen rigs poking
holes in the proposed path of the new tunnel to verify what might be down
there.
During the actual tunnel operation that Verizon guy will be
yelling “Can you hear me now?” If anyone
in the bus tunnel hears him then they have to back up and try again. Maybe they could get an iPhone and just ask
it. We at the Lake Boren Rapid Transit
Report have many suggestions (actually Glen, the Lake Boren Carp) for how to
avoid hitting existing tunnels. I
imagine WashDOT has its own suggestions.
Theirs is probably “Don’t punch a hole in another tunnel.”
Another key to
successful tunneling is to make sure the TBM doesn’t get stuck. That’s what happened in the Brightwater
discharge tunnel. The plant sits over in
Woodinville and they want to run clean former sewage through the tunnel to
Puget Sound. The plant has plenty of
cleaning processes so the waste water should be OK for the fish. Anyway, during the digging a machine got
stuck. They couldn’t move it any
direction now matter how hard they cussed.
Finally a world class tunnel rat worked it out. Whew!
Lucky for us that fiasco was hidden underground or we might have had
Occupy Brightwater.
One of the other characteristics of boring a big tunnel is
they need a huge staging area. They need
to dig a big hole and assemble the boring machine down there. They need a place to pile up the tunnel
lining modules before hauling them into the tunnel. They need room for the muck they pull out
behind the TBM. That muck has to be
trucked to Maple Valley. That means they
also need room for big trucks to turn around, load up, and head out. There will be several construction trailers,
big orange machines, and hundreds of feet of rented fence. That fence is to keep me out because
otherwise I’d be right there watching.
The plan is to open the new tunnel in about 2006. We don’t think they’ll make it. But if we keep our fingers crossed they might
get started before summer. They’ve
already torn down about a mile of the viaduct to make room for the huge staging
area. The rented fence is everywhere. Everyone grab a shovel and come on out to
Seattle and help out. It’s better than just
pitching a tent and complaining about everything.
Al
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