Almost
one hundred years after the
original construction, the
rehabilitation taking place
in PATH Tunnels 'E" and
'F' under the Hudson River
does not look much different
than it did in 1908 when the
tunnels were first being
built. After completely
removing all of the water
damaged equipment from the
tunnels so that only the
16'-wide cast iron tunnel
ring liners remained (still
intact after nearly a
century of
use), workers set about
restoring all of the
previous systems. This work
included replacement of the
tunnel trackwork, duct
banks, cables, lighting,
drainage, fire protection,
communications and railroad
signals. While the materials
were upgraded to bring the
specifications up to current
codes and industry standards
(for example, fiber
reinforced epoxy conduit
replaced the old clay ducts
and steel reinforced
concrete duct banks replaced
the original, severely
deteriorated duct banks),
the configuration of the new
systems is strikingly
similar to the original
design. Much of the labor is
even being done manually,
because the confined space
and limited access in the
tunnels precludes the use of
large modern machinery.
One
element that has changed
significantly however is the
replacement of the original
wooden tie and ballast track
bed system. In the original
design, the running rail was
fastened to evenly spaced
wooden crossties that were
embedded in a layer of
ballast (stone gravel) for
stability.
In the current
reconstruction, a series of
direct fixation fasteners
will be used instead to
secure the rail to the track
bed. These direct fixation
fasteners are composed of a
steel baseplate with rail
seat and baseplate pads,
side insulators, rail clips,
and threaded anchor bolts.
They are attached at even
intervals to the rail and
then bolted to the concrete
track bed, eliminating the
need for wooden crossties or
a ballast layer. The
innovative design of the
direct fixation fasteners
allows for some thermal
expansion and contraction of
the continuously welded
rails, while keeping them
securely in place. This is
the first such application
of the direct fixation
method used by PATH.
There
are many clear advantages to
the use of the direct
fixation fastener system.
Because of the elimination
of the wooden cross ties and
ballast layer, there are
significant savings in track
maintenance, electrical
insulation, load
distribution and longevity.
In addition, trains running
on tracks using the direct
fixation system will sway
less and work more
efficiently in the narrow,
century-old tunnels.
For
passengers, the benefits of
a change to a direct
fixation fastener system
will include a smoother and
quieter ride when service is
restored between the
Exchange Place and World
Trade Center PATH stations
in 2003.