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| February
3, 2004 |
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The monotonous metronomic clonking is more than
halfway done.
On February 3 2004, KFM-JV crews drove in the last of the roughly
300 foot long steel piles that will support the eastbound lanes. The
bonk-bonk-bonk won’t stop, however. Now, pile driving crews,
(or pile bucks), are giving the westbound lanes their full attention.
As of early April, 2004, 88 of the 160 piles were in place.
Finishing the pile driving even for the eastbound lanes is a significant
milestone. The ten-person pile buck crews have been working ten hours
a day, five days a week.
Driving a single pile takes between 7,500 and 10,000 hits from a pile-driving
hammer to slam one into place.
It’s lot of steel. If placed end-to-end, the piles already placed
would extend over 4.5 miles. It’s a distance equivalent to the
length of both east and west spans combined.
All told, the new bridge will have 28 piers, or support columns. Four
of the piers will be stand on four piles; the other 24 piers get six
piles each. Each pile is knocked in at an angle, not directly down.
This makes them more stable, just as a person standing with their
legs apart enjoys better balance than a person standing with their
feet together.
The piles themselves are so long that they are made and shipped in
two separate segments. The parts are welded together once most of
the first piece is pounded into place.
Though largely unseen, these daunting steel tubes are among the biggest
distinctions between the new bridge’s design and the original.
While the eight-foot diameter pipe smashed through the bay mud and
anchored into more secure geological strata below. The existing bridge,
which has served the Bay Area since the 1930s by contrast is supported
by groups of 80-foot long Douglas fir logs, lashed together.
The new bridge, with its steel supports is intended to be far more
solid. Construction is projected to be completed in 2008.
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