Deep Drill Solves City’s Water Main Crisis

Under The Boise River
December 2012, Vol. 67 No. 12

“Jeff Sorenson is a very capable bore operator. He’s shot a lot of tough bores all over the country, including under rivers in Alaska -- which gave us the confidence that it could be done,” Mace pointed out.

After reviewing the city’s project plan and consulting with the team, Sorensen and Mace decided to take a little longer approach with the bore. “Even though it was a rush project,” says Mace, “it’s not something that we wanted to rush into -- skipping a bunch of steps just to get it done fast. For example, we didn’t know what would happen if we pulled back a 10-inch backreamer and then went straight to a 30-inch reamer. We agreed that it would be better to take it in progressive steps and allow a little more time to get the project done right the first time.”

Mace explains that the city dictated that the project’s completion deadline was four weeks. To meet their deadline, Mace says the crew had a week of setup and a week to bore across the river with the wire line. Sorensen and the drilling crew used a single roller cone pilot bit and bentonite quick gel to make the initial bore. “We had some pretty good-sized boulders we had to get through,” adds Mace. “And it’s extremely important on a bore like this one to keep the hole open and get the cuttings back out of the hole, so we didn’t have any hang-up when we pulled the final pipe through.”

Once they shot through, the crew had to backream seven to eight times, starting with a 10-inch backreamer, then going to a 14-inch and progressively getting larger, finally ending with a 30-inch backreamer to make sure they could get the product across and not lose their hole. Mace says that the backreaming process took about two weeks. “We actually trailed steel through the hole behind the backreamer to make sure that the opening stayed steady and made a nice hole through the riverbed for the new 20-inch water line.”

As Track Utilities prepared for this project, Mace points out some specific elements of the company’s processes that were critical to their success. “The biggest thing we do to prepare for our projects is to know what ground and site conditions we are going into,” says Mace. “It is important to know the soil conditions, how the locating will be done and what tools were needed to complete the project. Being prepared up front made sure we had what we needed to complete the project, on time, on budget and to the client’s satisfaction.”