Customers of the Ute Water Conservancy District in Grand Junction, CO, 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, a subsidiary of Insituform Technologies (www.insituform.com) that uses tunneling methods to perform trenchless installations of new pipelines throughout North America, 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-ft. Lower Canyon Tunnel on September 7, 2000, just days after completing the 3,300-ft. Lower Mesa Tunnel farther up the mountainside. It emerged on the other side on March 16, 2001, having excavated through an average of 79 ft. of sandstone and siltstone rock a day.

That's a good pace, remarks Duncan, considering that the rock they were boring through is more than five times stronger than the concrete typically used in highway construction.

The crew was also aided by an exceptionally strong start. On September 14, 2000, workers excavated through 219 ft. of rock in a single shift–a record for a 10-ft.-diameter tunnel of this kind, according to the manufacturer of The Robbins Company tunnel boring machine they were using.

"On that day we were still near the beginning of the tunnel," recalls 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, notes Duncan. "In no way was this a straightforward job," he adds. One of the portals where the project team entered the mountain, for example, was more than 275 ft. above ground level, with no passageway leading up to it. Workers, as a result, had to build a road and a launching area so they could access the work site and had to run power generators day and night for electricity.

Because the tunnels run adjacent 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-mi. water transmission pipeline.

Affholder installed 13,543 ft. of new 48-in.-diameter steel pipeline in the tunnels. These pipelines were connected with the nearly 11 mi. of underground pipe that 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, CO. After the water is purified there, it provides drinking water for the district's 65,000 customers. The pipeline replaced a deteriorated 24-in.-diameter concrete pipeline that could no longer meet the district's demands, explains 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," relates Ohm. "It's cheaper to treat the water from off the top of the mountain, and it 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 budget.