Laney Directional Drilling, which last year used Direct Pipe technology to make an underground pipeline crossing through wetlands in the Northeast feasible, explained the process to attendees at a symposium on Oct. 14 in Houston.
Direct Pipe is a single-pass process that uses a steerable tunnel-boring “pipe thruster” to push pipe into place, while at the same time filling the void as it progresses. The process, according to Laney, is highly advantageous when crossing levees and environmentally sensitive areas.
“One of the great things is there are no people on the exit side,” said Robert Hutz, manager of engineering at Laney. “When you punch out, that’s when you’re done.”
In the case of the Northeast project, a 250-dth/d supply link for Williams, special protocols were in place because the Aquashicola Creek area in Monroe County, PA is home to the endangered bog turtle. The tunnel covered 1,350 linear feet and was wide enough for 42-inch pipe.
Developed by Herrenknecht, a German manufacturer of tunnel-boring machines, Direct Pipe made traversing the complex subsurface conditions, including rock, shale, gravel and two steep hills possible. Because of the low annular pressure exerted during the installation, the risk of hydraulic fractures is also greatly reduced.
“Look how much shorter we were able to make this crossing, even if HDD crossing had been possible here,” Alan Snider, vice president of engineering at Laney, told the 120 attendees.
Laney’s portion of the contract took 81 days to complete, according to Hutz, involving 390 tunneling hours at a cost of $7.1 million.
While HDD is usually less expensive, Snider said, it is not necessarily as reliable or safe as Direct Pipe technology in certain situations, as Direct Pipe requires a smaller footprint, one-step installation and no rotation of equipment.
“This is extremely safe,” he said. “Probably the safest process out there, and there are very few people doing it.”
Alan Snider addresses attendees at a symposium on Direct Pipe technology.