mobilized one of its Manitowoc 2250 cranes and performed several
test extractions at non-production steel pile locations. Penetration of
the mudline required the clamp to function in the jaw open position.
As the hammer was lowered over the pile, the vibratory hammer was
turned on with the jaw open. This allowed the clamp and extension
to penetrate the mud while still slipping over top the pile and ultimately
allowed the jaw to clamp the pile below the mudline. The test
also indicated that approximately 85,000 lbs. of extraction force was
required to remove the 90- to 100-foot-long yellow pine timber pile
with the vibratory hammer in operation. Those results indicated that
the 2250 was the crane needed for the job.
While the design of the clamp was successful, the challenge of
finding the piles was still one that Trevcon’s crew had to figure out.
At most tides, the piles were completely submerged. During spring
tides and on days with winds out of the west, the low tide was low
enough that the tops of the piles sufficiently protruded and a map of
the piles could be recorded. By a combination of overhead photography,
installation of future falsework and survey, and other methods
of marking the new pile locations, the crew was successfully able to
navigate the clamp over the specific piles to be extracted. The skilled
operators of the crane were key in setting the hammer precisely over
the pile, vibrating the clamp down over the pile, and extracting the
pile intact. Along with dock builders on float stages and the skillful
operation of the equipment, the crew was able to guide the clamp
over the piles and extract the piles.
The final challenge to be addressed was crew efficiency and
productivity. Because the piles were completely submerged at times
of high tide, the task of removing the piles had to be meticulously
planned and orchestrated between low-water work and high-water
work to stay productive. Essentially, all extraction was performed
between the falling and rising tide surrounding the low tide. The
focus during the low-water cycle was to pull the timber piles up high
enough that the mud friction was no longer a constraint on removal,
but keep enough in the ground that the piles could maintain an
upright position in the mud. During cycles of “high water,” the focus
was extracting the timber piles and lying them down in a debris scow
for disposal off site and setting up the next set of falsework. This
system allowed Trevcon crews to stay productive at all hours of the
workday while progressing the project effectively.
However, due to the sheer volume of timber piles that had to
be extracted, Trevcon had to mobilize a second crane and crew to
maintain the schedule, despite the effectiveness of the work plans.
With the operation bumped up to two crane crews working simultaneously,
Trevcon issued a purchase order to American Piledriving
Equipment (APE) to fabricate a second timber extension, based on
the Trevcon design and concept. APE substituted a pipe pile structure
for the extension, in lieu of the box structure fabrication on the
other extension. The functions of the clamp and protective requirements
of the mechanical and hydraulic systems remained. The extension
was operated by another ICE® power pack and hammer owned
by Trevcon. Both extensions performed as expected and were able to
complete the job.
Timber pile extraction operations are not new to Trevcon, but
this project had unique challenges and requirements on a very largescale
operation. The collaboration of the management team down to
the field crew and vendors was key in the success at Pier 9. With the
development of the extractor and the proven effectiveness of its function,
especially on heavily deteriorated piles, Trevcon is working on
obtaining a patent. With many of the old piers in the New York harbor
built upon timber piles deteriorated at mudline, this equipment
has great potential on future work requiring a similar approach. t
PROJECT SPOTLIGHT
Trevcon extracting timber piles from Pier 9 North during select demo in August 2017
Timber pile extraction operations
are not new to Trevcon, but this
project had unique challenges
and requirements on a very
large-scale operation.
96 | EDITION 2 2019 www.piledrivers.org
/www.piledrivers.org
