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ABI Mobilrams: The Right Choice For Winter Work In Alaska |
Before setting out to install 64 miles of power
transmission towers and lines throughout
central Alaska, Anchorage-based Global
Power & Communications determined that
the ABI Mobilram system would be the best choice
for the project. A winter of driving more than
1,200 piles through a variety of soil conditions
proved that to be a wise decision. "The Mobilram
was simply the right machine for the job," said
Mike Gearhart, general manager of Global Power.
The project – Golden Valley Electrical Association's
Northern Intertie Project – involved construction of
a 230-kilovolt transmission line between Healy and
Fairbanks. It was part of a project designed to meet
increasing power demands, and to enhance power
reliability, in that area. A total of 346 transmission
towers, spaced about 1,000 feet apart, were erected.
Crews used two Mobilram systems, the
TM14/17 and a TM16/20, both supplied by
Hammer & Steel. The
machines installed four piles at each
tower location. "We chose the
Mobilrams for their pre-augering
and driving capabilities,"
Gearhart explained. "Our crews
were driving into permafrost
and working in a multitude
of soil conditions,
from condensed soil to
very loose soils. About
50 percent of the piles
required soil release
drilling to allow for the
successful installation
of the piles."
Another reason for
selecting the ABI rigs
was their ability to
install the piling accurately.
Correct positioning
and verticality of the piles is crucial,
because prefabricated transmission tower frames
will be lowered over the piling tops by helicopter.
"The tolerances were very tight and the machines
handled them extremely well," Gearhart said.
The 40 to 70 foot piles ranged in diameter from 10
inches to 30 inches, with wall thicknesses of 3/8 and
1/2-inches. To ensure that the piles were driven
without deforming or damaging the casing, despite
the thin walls, ABI made special jaw pads and jaw
assemblies to fit inside the smaller casings. These
jaw assemblies matched the contour of the casings to
prevent deformation. The flexibility of ABI's
high frequency variable moment driver
allowed for the installation of the piling in
tough driving conditions without exceeding the
capacity of the piling, preventing the piles
from being damaged.
The transmission line ran through an environmentally
sensitive area, and construction
was carried out under 47 stipulations
designed to mitigate possible environmental
impacts. For example, trees 10 feet tall and
under remained standing in the right-of-way,
and the towers were
self-rusting so they would
blend into the landscape.
Both the Alaska
Department of Natural
Resources and the
U.S. Bureau of Land
Management frequently
reviewed the construction
operations.
The stipulations also prohibited construction of permanent
access roads. Motorized access was only
allowed when there is at least one foot of frost and
one foot of snow on the ground. Global Power began
work in early January 2002. Almost 90 percent of
the piling was installed before the company had to
stop in March, when it lost its ice road permits for
the season. The rest only took a couple
weeks to complete once the ice roads were available
the next winter.
The Hammer & Steel technical staff prepared the Mobilrams for
the harsh Alaska winter by modifying the hydraulic
systems to accommodate typical daytime temperatures
of minus 30 degrees Fahrenheit. At night, the
rigs were kept under army surplus parachutes and
warmed by large space heaters to maintain a toasty
10 degrees.
In addition, Hammer & Steel provided
training for the Mobilram operators at the start of
the project. Jim Fogarty from Hammer & Steel spent almost
two weeks on site. "We had outstanding
support on this project," Gearhart commented.
Gearhart was equally pleased with the ABI
Mobilrams, referring to them as "excellent
machines." He concluded, "They certainly proved
their value and durability here in Alaska."
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| Company Headquarters |
Branch Offices |
11916 Missouri Bottom Rd.
St. Louis, MO 63042
Ph: 800.325.PILE (7453)
Ph: 314.895.4600
Fx: 314.895.4070 |
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Ph: 877.224.3356
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Ph: 508-888-3314
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Ph: 952.469.6060
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