The damage
A two-day rain event flooded two culverts (60m long and 3.5m
in diameter) on Rolla Road near Dawson Creek, B.C., making
the road impassable. The Peace Region is known for its silty,
porous soils thick with clay, which slip, slide and create geotechnical
challenges.
“It’s just slop, especially when it rains,” said Toma.
With time of the essence, the ministry reached out to
Formula to get started as soon as possible. The company has
done a significant amount of highway work, both directly and
as subcontractors, and their sterling reputation preceded them.
The solution
The fastest way to get it done efficiently was to build a temporary
detour structure off the road while Formula put in a double-lane,
36.5-metre long steel girder bridge on pile foundations.
“We assisted in designing a foundation solution for them
using six 762-mm diameter piles, three per end,” said Toma.
Designing and installing a permanent structure would
require significant government funding (upwards of $1.5 million)
and include a bidding, approval and design process,
which could take years before the bridge was complete. Due
to the urgent nature of the project, Formula was asked to
design and install a “long-term” temporary solution with a
budget of $1.5 million.
With temporary in mind, the bridge structure deck is
non-composite, comprised of pre-cast deck panels that are
fastened to the girders.
“We used a fabricated steel abutment cap on the pile foundation,”
said Toma. “When the time comes to disassemble
this structure, the pre-cast deck panels can be taken off, the
bridge girders unbolted and the piles can be either vibrated
back out or cut off at the ground line.”
Installing the bridge
The installation of the bridge is as straightforward as the
piling, but required a delicate touch given the soil local conditions.
The girders were cantilevered over the north abutment
cap, pushed out and grabbed by a 110-ton crane on the south
side and placed on the south abutment cap. The deck panels
were then placed on top of the girders and bolted in.
Project challenges
While the piling aspect of the project was straightforward,
it was challenging to achieve the end bearing required for
weight loading for the structure.
“We had to use a 10,000-pound drop hammer to get the
piles deep enough for the required engineered loading –
bearing and fixity,” said Toma.
A bigger challenge was transporting the 36.5-metre girders
from Chetwynd, B.C. to Dawson, about an hour’s drive.
Due to their length, the three bridge girders and associated
bracing had to be transported to the Rolla Road site through
Dawson Creek using a transport truck and rear steering
dolly configuration.
Dawson Creek has a roundabout, which made moving the
oversized load a challenge.
“This was not a cookie cutter part of the project,” said
Toma. “We needed to put a lot of engineering and logistics
into place to ensure it got there safely.”
Skilled labour could have presented a challenge on this
tricky project that required “the right guys with the right
mindset to make this job happen efficiently and safely,” said
Toma. “To launch a bridge is not an everyday thing.”
Fortunately, Formula was able to engage experienced
crane operators, bridgemen and perhaps most importantly,
a professional engineer who is able to create a proper design.
Their on-staff engineer just happens to have worked with the
ministry in the past, so brings a wealth of expertise to jobs
just like this.
In all, they had five workers on the job site, plus ministry
representatives, a project manager and an engineer.
“Overall, standing there on the job site when things are
smoking along busy, we probably had at least 15 people,” said
Toma.
Equipment
Two 110-ton Terex HC110 crawler cranes were used to get the
girders in place.
“For pile driving, we had a 32-inch set of leads with a
10,000-pound drop hammer,” said Toma.
Formula owns the equipment and supplied the 762-mm
diameter pipe piling out of Vancouver.
“We drove six locations, which went into the ground 32
metres each before they hit the refusal criteria in the design,”
he said.
The emergency bridge restored regular traffic flow
throughout the Peace Region, making life easier for people
and businesses alike.
Formula is working on a number of pre-planned projects
in the province, but Toma says they’re on alert for when
Mother Nature strikes again.
PROJECT SPOTLIGHT
“This was not a cookie cutter
part of the project. We needed
to put a lot of engineering and
logistics into place to ensure
girders got there safely.”
– Phil Toma, Formula Contractors
54 Q3 2016 www.pilingcanada.ca
/www.pilingcanada.ca
/www.pilingcanada.ca
