Contractor Faces Several Challenges in Months-Long Project to Install Water Main

Long, deep bore tests crews as they work to install new water main under Nebraska’s Niobrara River

Contractor Faces Several Challenges in Months-Long Project to Install Water Main

An aerial view of the job site from one side of the Niobrara River looking across to the other side. Crews had to drill a 4,320-foot bore under the river to replace a failed waterline.

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After the Spencer Dam in northern Nebraska collapsed in March 2019, public officials had numerous issues to contend with along with massive flooding, including a ruptured water main that left thousands of residents in Boyd County without water.

Even though the original 12-inch-diameter main ran about 10 feet under the riverbed, the dam’s failure — triggered by immense pressure from the rain- and ice-floe-choked Niobrara River — still wiped it out. That’s a testament to the raging power of the water and ice that flowed through the failed dam at 40,000 cubic feet per second, about 27 times faster than the normal flow rate at the dam, according to figures from the U.S. Geological Survey.

While officials used private wells to supply residents with limited amounts of nonpotable water that required sterilization, Horizontal Boring & Tunneling in Exeter was selected to install a new waterline.

The installation posed a daunting challenge: drilling a 4,320-foot bore, almost three-fourths of a mile long. Another complicating factor was the depth of the bore, which at its deepest point would run 80 feet below the riverbed.

But such jobs are nothing new to HBT, a company that’s developed a reputation over the years for successfully taking on complex and difficult projects, says Brent Moore, owner and president of the company, established in 1982.

“We specialize in crossings that other contractors can’t handle,” Moore says. “I know we weren’t the lowest bid, but they went with us because of our expertise, reputation and equipment. Unlike some of the other bidders, we had the equipment to do the job in one long crossing instead of two shorter shots.”

The company’s longest bore before this one was 2,600 feet. “It was a little daunting,” Moore says. On the other hand, the company had already compiled a resume filled with challenging jobs, including difficult bores for fiber optic lines in the front range of the Rocky Mountains in Colorado, a 2,200-foot-long bore for a fiber optic line roughly 35 feet under the Mississippi River in Minnesota and a 2,000-foot-long bore for a 32-inch-diameter waterline under the Platte River for the city of North Platte, Nebraska.

GOING DEEP

The goal was to install the new pipe 80 feet below the riverbed in a layer of shale that should better protect the 16-inch-diameter HDPE from future mishaps. “That’s about 40 to 60 feet deeper than usual, which made it a little more challenging,” Moore says.

The five-month-long project started during the first week of April and concluded in late August, just before Labor Day weekend. The company initially used an American Auger DD-440T horizontal directional drilling machine, which produces 440,000 pounds of pullback force and 100,000 pounds of rotary torque.

“We like American Auger equipment,” Moore says. “It’s built heavy and is very reliable. And the company provides great customer service.”

The company also used mud-cleaning systems made by Triflo International and Mud Technology International, as well as a TT-660 mud pump manufactured by Tulsa Rig Iron (up to 860 gpm at 975 psi).

The company started the pilot bore from the south side of river, with the drilling rig positioned about 105 feet above the river. But things got a little more challenging after drilling about 1,750 feet out, Moore says.

“We had a hard time maintaining mud circulation back to the rig,” he explains. “Keep in mind that with the rig 105 feet above the river, we were trying to move the fluids 185 feet in total elevation and it’s hard to get fluids to move uphill like that.

“In addition, shale is like a reactive clay,” he continues. “It’s hard to break it down and carry it with the fluids and suspend them enough to get them out of the hole.”

SHIFT TO PLAN B

To solve the problem, HBT officials decided on a bold strategy: Move to the north side of the river and continue the pilot bore from there — and try to intersect with the first pilot hole. The elevation there was only 45 feet above the river, for a total elevation above the pilot bore of about 125 feet — roughly 60 feet less than on the south side of the river, Moore points out.

“We still had some problems maintaining circulation,” he says. “We fracked out four or five times, but eventually we used different drilling fluids to seal up the frack-out and maintain circulation.”

To guide the drill on the remaining 2,570 feet of the intricate pilot bore, the company relied on wireline-steering technology provided by Prime Horizontal. The technology provides more accurate readings than conventional walk-over steering, he says.

“That technology enabled us to intersect that 16-inch pilot hole,” Moore says. “Trying to do an intersect like this wasn’t very common 10 to 15 years ago. In fact, we tried to avoid doing them as much as possible.

“Even with this technology, it’s not always successful,” he adds. “So hitting the intersect was a big win for us. It saved us a couple weeks of drilling time compared to trying to drill out to the south side.”

The pilot hole was created with a 6 5/8-inch-diameter drill pipe with a 12 1/4-inch bib. The crew then used a 24-inch HDX reamer manufactured by INROCK Drilling to make the bore big enough to accommodate bends and turns as the new pipe was inserted, as well as maintain circulation of drilling fluids, he says.

To get the water service restored as quickly as possible, HBT doubled the number of employees to 20 from 10 for the last five weeks of the project, essentially resulting in crews working 24-hour days. That move reflects the company’s can-do attitude, Moore notes.

“It takes hard work and dedicated employees to work the long hours and spend a long time away from their families,” he says. “We’re only as good as our employees.”



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