A record-breaking achievement in horizontal directional drilling

The Bakken Missouri River Crossing project in North Dakota was proposed by a major pipeline operator to connect a compressor station in Williams County with a natural gas gathering system in McKenzie County. The project required installing a pipeline beneath the Lake Sakakawea Reservoir.

According to the pipeline operator, the project would capture approximately 180 million to 240 million cubic feet (5.1 million to 7 million cubic m) per day of natural gas that would otherwise be flared into the atmosphere.

Engineering design and innovation

Mott MacDonald was retained to perform engineering design, support the environmental permitting process with the US Army Corps of Engineers, review construction contractor work plans, and perform construction inspection.

We developed several risk mitigation measures to lower the potential for environmental impacts at the crossing location. The horizontal directional drilling (HDD) alignment was designed at a depth of 525 feet (160 m) below the northern portal and 320 feet (100 m) below the southern portal. The depth of cover beneath Lake Sakakawea was 270 feet (80 m). A drill and intersect approach was used to lower the drilling fluid pressures beneath the lake.

Award-winning design

On October 30, 2019, Michels Directional Crossings finished work on the crossing of Lake Sakakawea. At 20 inches (50 cm) in diameter, with a length of 13,247 feet (4,038 m), this was the longest HDD installation of its size completed in North America. Construction was completed ahead of schedule.

Trenchless Technology magazine later named the Bakken Missouri River Crossing its 2020 Project of the Year for New Installation.

The pipeline operator’s project manager wrote, “Because of the way this project was executed, Lake Sakakawea remained untouched, winter construction was prevented, and the pipeline was installed ahead of schedule.”

The project manager pointed out that the pipeline would move up to 240 million standard cubic feet (7 million cubic m) of gas per day, reducing flaring and helping the local economy. It would support the North Dakota economy, where the pipeline operator employs over 350 people and pays more than $5.5 million in taxes. It would avoid impacting Lake Sakakawea, a world-class recreational resource that is critical to flood management, water supply, and power generation. And it would help act as a bridge between coal and renewable power.

“If those facts don’t impress,” the project manager concluded, “the horizontal directional drill under Lake Sakakawea is the longest to-date. As far as the project team can identify, the 13,158-foot straight line distance (13,247-foot true length) is a new world record length for any diameter pipeline. You are a world record holder!”