The Alaska Contractor - Summer 2008

Historic Moody Tunnel
he demolition this spring of the 262-foot-long historic
Moody Railroad Tunnel, an 88-year-old landmark along
the Alaska Railroad 600 feet north of the Nenana River
Bridge, marked the end of an era. Moody Tunnel was built in
the early 1920s during construction of the Alaska Railroad and
was the last of two remaining tunnels north of Anchorage.
The four-phase project included constructing the access
road to the job site from the top of the George Parks Highway,
blasting an equipment access road from the top of the tunnel
site down to track level, removing the bedrock over the top of
the tunnel, the tunnel demolition through schist bedrock, a
safety realignment scheduled for October that will move the
track off old timber cribbing, and the final clean up.
Advanced Blasting Services, one of only a few technical
explosives engineering contractors in Alaska and the company
responsible for the demolition that now makes the railroad
safer, says that technically the job was more challenging
than the typical rock excavation project because the rock had
to be excavated while preserving the tunnel’s structure so that
it could still be in use while undergoing demolition.
“That was the key,” said Mikel and Julia Saunders, owners
of Advanced Blasting Services, explaining how they worked
within scheduling windows between trains, maintaining
traffic with only one track. “We had to be able to shoot one
part while keeping the other part attached, safe and secure
so trains could continue to run until the project was done.”
Although the Alaska Railroad planned for a 36-hour shutdown,
the longest downtime was 12 hours.
demolished
BY HEIDI BOHI
The Moody Tunnel, which is eligible for listing on the
National Register of Historic Places, is a federally assisted
undertaking with funding through the Federal Transit Administration.
By the time the project is complete, the Alaska
Railroad will have spent between $3.5 million and $4 million
on the Moody Tunnel Demolition Project. The tunnel demolition
was divided into three shots or “blasts.” A total of 9,000
pounds of explosives, including 5,000 of dynamite and the
rest blasting agents, were used resulting in 260 feet of tunnel
collapsing into an estimated 4,000 cubic yards of rock, timber
and debris. For the entire project, to date, 45,000 pounds of
explosives have been used, including 10,000 pounds of dynamite,
resulting in a total of 35,000 cubic yards of debris.
Mikel Saunders said a lot of dynamite was required to
assure complete collapse because if the tunnel shook, but
did not completely come down, it would have been increasingly
dangerous to re-shoot the unstable tunnel.
The fourth and final phase of the demolition – safety realignment
that moves material further back from the rail – will
be completed this fall after passenger season ends in mid-September.
An “open cut” remains where the tunnel once stood.
Tunnels have always been a maintenance issue, said Regan
Brudie, Alaska Railroad Project Engineer for the Moody Tunnel
Demolition Project. But when the tunnel was first built in
1921 it was the only solution for getting around the corner
of Healy Canyon, which was a 10-degree curve through the
tunnel. As trains have gotten bigger, load sizes were limited to
what would fit through the Moody Tunnel. By removing the