Tunnel Excavation for Water Purification Project Comes in Ahead of Schedule
Project team sets one-day excavation record, boring through 219 ft of hard rock in a single shift
Customers of the Ute Water Conservancy District in Grand Junction, Colo., will be enjoying better tasting drinking water ahead of schedule, thanks to an early completion of a tunnel that houses part of the district’s new raw water transmission pipeline.
Affholder, Inc. of Chesterfield, Mo., completed excavation
for the second and final
tunnel for the district’s Raw Water Flow Line more
than a month ahead of schedule, setting a one-day tunneling record in the
process according to Brent Duncan, project engineer for Affholder.
A work crew began boring the 9,916-foot Lower Canyon Tunnel
on September 7, 2000, just days after completing the 3,300-foot Lower Mesa
Tunnel farther up the mountainside. They emerged on the other side on March 16,
2001, having excavated through an average of 79 feet of sandstone and siltstone
rock a day.
That is a good pace, said Duncan, considering the rock they
were boring through is more than five times stronger than the concrete
typically used in highway construction.
The crew also was aided by an very strong start. On
September 14, 2000, workers excavated through 219 feet of rock in a single
shift — a record for a 10-foot diameter tunnel of this kind, according to
the manufacturer of the Robbins tunnel boring machine they were using.
day, we were still near the beginning of the tunnel,” recalled Duncan.
“So the turnaround time for the trains carrying debris from the tunnel
was very fast. Everything was working in our favor.”
Good fortune, in fact, appeared to stay with the project
from its very beginning, said Duncan. “In no way was this a
straightforward job,” he said.
One of the portals where the project team entered the
mountain, for example, was more than 275 feet above ground level, with no
passageway leading up to it. Workers, as a result, had to build a road and
launching area so they could access the work site, and run power generators day
and night for electricity.
Because the tunnels run adjacent to Plateau Creek, an
ecologically sensitive area rich in fish and wildlife, the crew needed to take
special precautions while performing drill and blast activities required to
position the tunnel boring machine on the mountainside. They also had to be
sensitive to the handful of people whose homes are near the tunnel portals.
When both tunnels were completed, the Ute Water Conservancy
District entered the final phase of its program to construct its new 13.5-mile
water transmission pipeline.
Affholder installed 13,543 feet of new 48-inch-diameter
steel pipeline in the tunnels. These pipelines were connected with the nearly
11 miles of underground pipe Barnard Construction, Affholder’s joint
venture partner, installed using open cut construction.
The pipeline is used to transport water from a mountain
reservoir east of Grand Junction to a treatment plant near Palisade, Colo. style="mso-spacerun: yes"> After the water is purified there, it
provides drinking water for the district’s 65,000 customers. The pipeline
replaced a deteriorated 24-inch-diameter concrete pipeline that could no longer
meet the district’s demands, according to Ralph Ohm, project manager for
the Ute Water Conservancy District.
“In the summer months, we often exceeded demand for
the old line and had to pump water from the Colorado River,” said Ohm.
It’s cheaper to treat the water from off the top of the mountain and
really is better tasting water.”
The new main
became operational two months ahead of the original schedule. Affholder and
Barnard Construction completed their joint venture contract $1.6 million under
Affholder, Inc., a subsidiary of Insituform Technologies,
uses tunneling methods to perform trenchless installations of new pipelines
throughout North America. Additional information about the company can be
obtained at www.insituform.com.
For additional information, contact Insituform at
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