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The Key to Commerce
The multi-year McAlpine Replacement Lock project will speed
up commercial traffic on the Ohio River through the port of
Louisville
By Sheila Bacon
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In March, a tug collided
with one of the circular cofferdam cells at the new lock,
closing the river to commerce for three days.
PHOTOS COURTESY OF U.S. Army Corps of Engineers, Louisville
District |
Keeping the Ohio River open for navigation
during construction of a new $358-million lock near Louisville,
Ky., is of utmost importance to the project team.
On March 30, crews found out just how important that really
is.
A tugboat and barges preparing to pass through the existing
McAlpine Lock immediately adjacent to the future lock's site
hit the cofferdam surrounding the construction and ripped
a 10-ft by 15-ft gash in the exterior steel sheets. The accident
not only shut down construction while emergency repairs were
made, it also closed down river traffic for three days. By
the time the lock was repaired and ready for use, 43 tugs
and their loads had backed up along the river.
"There was constant traffic through here for several
days," says Dave Klinstiver, a resident engineer with
the U.S. Army Corps of Engineers' Louisville District.
The incident was a sobering reminder to the construction
team of the historic lock's ongoing importance and the problems
that result when river traffic is blocked.
The original McAlpine Lock was built in the 1860s in a canal
dug parallel to the Ohio River, bypassing a 2.5-mile-long
series of rapids that made the river impossible to navigate
during the dry season. A larger 110-ft by 600-ft lock was
built next to the original lock in 1921, and the current 110-ft
by 1,200-ft lock, still in use today, was built in 1961. The
lock now under construction will mirror the larger one and
replaces the two smaller chambers.
Closing Doors
Before construction started on the replacement lock, boats
were able to use the 600-ft lock whenever the larger one was
closed. Although tugs with large loads would have to send
their cargo through the smaller lock in two trips, its availability
was a "safety net" of sorts. Now, with no back-up
lock, the 43 million tons of freight that pass through McAlpine
Locks annually will depend solely on the one operational chamber
until construction is completed in 2008.
Eighteen to 20 tows pass through the lock each day, with
each trip averaging nearly an hour. The new lock will alleviate
the demands placed on the main chamber, which currently is
operating at full capacity.
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Interstate
564 (at bottom) is all that separates the McAlpine Lock
Replacement construction site from a residential neighborhood.
PHOTOS COURTESY OF U.S. Army Corps of Engineers, Louisville
District |
Several years of preconstruction and demolition work (see
related story) has preceded the current contract, which involves
site excavation and construction of the lock itself. The work
is being done by the joint venture TGM Constructors, comprised
of Traylor Brothers Inc., Evansville, Ind.; Granite Construction,
Watsonville, Calif.; and Massman Construction, Kansas City,
Mo. TGM started blasting rock in 2003 after the cofferdam
was built and the water inside was drained. In some areas,
the excavation has reached 25 ft below the canal bed to make
way for the concrete monoliths that will form each side of
the lock. They are 46-ft to 55-ft wide and 67-ft to 100-ft
tall. There will be 23 on one side of the canal and 25 on
the other.
Construction of the lock's monoliths began in June 2004 and
involves the placement of more than 250,000 cu yd of conventional
concrete in 10-ft lifts. In some areas, roller-compacted concrete
is being used, something that has never before been attempted
in lock construction in the U.S., says Jim Whitworth, TGM's
project engineer.
RCC is a zero-slump, highly durable mix most often used in
large-scale industrial projects such as sorting yards and
warehouse facilities. In recent years its use has been expanded
to a variety of other uses, including dams. The concrete is
placed in a manner similar to that of asphalt, using high-density
paving equipment and compaction with steel-drum and pneumatic-tire
rollers.
Crews are placing approximately 133,000 cu yd of RCC, which
will save time and money. The nature of the mix allows crews
to place concrete in continuous 24 hour shifts without stopping
for it to cure. As a result, crews were able to place 7,000
yd of RCC in just two-and-a-half days, considerably faster
than conventional concrete, says Whitworth.
No Cookie Cutter
Though the monoliths are similar in size, their construction
is by no means "cookie cutter," says Klinstiver.
Each monolith has its own unique characteristics and lift
drawing. Some have tunnels through them to allow water flow
into the locks. Others have voids for the routing of conduit.
Some are taller, depending on foundation conditions. The monoliths
on either end of the lock are constructed to hold the miter
gates that let boats and barges in and out of the chamber.
The first set of gates, fabricated off site in three sections,
is scheduled to arrive on site in June, with the downstream
gates to be installed in the fall.
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| In some areas, excavation
has reached 25 ft below the canal bed to make way for
the monoliths that will line the new lock.
PHOTOS COURTESY OF U.S. Army Corps
of Engineers, Louisville District
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Once the concrete monoliths forming the sides of the lock
are completed, crews will construct three control buildings
that will house equipment to operate the locks. Next, the
lock's approach walls will be built atop sheet piling caissons
filled with tremie concrete.
Full construction of the approach walls will require the
removal of the cofferdam, which Klinstiver anticipates will
be in early 2008. Cofferdam deconstruction is a meticulous
process. First, water will be pumped back into the cofferdam
until its level matches that of the canal. Then the sand within
the cofferdam cells will be removed. Finally, an eye will
be cut into each sheet of the 16 cells to lift the sheets
out, one by one.
Recycle and Reuse
The McAlpine Lock Replacement has reused or redirected tons
of materials from other projects, including debris from demolition
of the old 600-ft lock. The concrete was transported to a
Corps' bank stabilization project along the river, saving
105,000 cu yd of debris from landfills, says Klinstiver. Sheet
piles used in earlier construction at the Olmstead Locks,
also along the river, were reused at McAlpine, saving $3 million.
Some of the sandstone blocks used in the construction of
the original 1860s lock were salvaged and passed on to the
Louisville parks department for road projects. Others will
be displayed at the visitors' center at the new lock's site
as a tribute to lock construction on the Ohio River through
the years.
A Multi-Phased Project
A Gateway for Commerce
What a Blast
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