Blog: Putting pipelines safely under rivers

Included in the protests and blockades of the Coastal GasLink pipeline is the proposition that drilling a tunnel for the pipe beneath the Morice River and its side-channels will endanger salmon runs.

The Morice River (Wedzin Kwa to the Wet’suwet’en people) is indeed a salmon river. It supports chinook, pink, coho and sockeye salmon, and steelhead and trout.

“There are fish of one species or another that are in that waterway at all times of the year,” says Michael Price, a fisheries biologist and researcher with Simon Fraser University.

Concern expressed — and understood.

But the advanced “micro-tunneling” technique proposed by Coastal GasLink under Wedzin Kwa is a proven method of using a remote-controlled tunnel-boring machine, and then hydraulic jacks to push concrete casing segments through the tunnel deep under water bodies.

The pipeline is then safely pulled through the tunnel created by the concrete casing.

In this case, the pipeline will be a full 11 metres beneath the riverbed.

As Coastal GasLink notes: “After completing environmental and technical assessments such as water flow, bank stability, wildlife, vegetation and the quantity and quality of fish habitats, it was determined that a trenchless micro-tunneling crossing would be the safest method for construction to cross the Morice River.

“Trenchless crossings are proven to allow pipe to be installed under the water body without ever affecting the flow of the river or stream. Currently there are thousands of trenchless crossings throughout BC, operating safely under rivers and streams of all sizes.

“This won’t be the first time that micro-tunneling is used. In fact, it’s regularly used in our communities for public works and infrastructure projects, such as hydro lines, sewer systems and other utilities in BC, and we have support from local and Indigenous communities to use this method at the Morice.

“Recently, TC Energy utilized micro-tunneling in our Sur-de-Texas project in Mexico. This project holds the world record for the longest micro-tunnel for an offshore-onshore pipeline, and like our other water crossings across the TC Energy footprint, we have had no incidents in construction.”

That Sur-de-Texas project, moving natural gas from Texas to Pedro Escobedo, Mexico, includes an underground micro-tunnel of 2.2 km in length and 3.2 meters in diameter. “A milestone in engineering and the longest of its type in the world.”

The Morice River crossing is only one of many “trenchless” crossings of water and other items on the Coastal GasLink line. They include the use of Direct Pipe Installation® (DPI) under the Kitimat River (with a 270-metre tunnel) and horizontal directional drilling (HDD) under the Murray River in northeast BC in 2021 (with a drilled pipe-tunnel 1.3km long.)

That HDD technique has been safely used for more than 30 years to place pipelines under highways, railroads, rivers and streams, populated urban areas, and environmentally sensitive areas. Like micro-tunneling, it has also been used to install power cables, water lines, sewer lines, and fibre-optic telecom cables.

Following geotechnical and geophysical studies, feasibility studies, and engineering design, the drilling for a trenchless project starts at a staging site on one side of the river.

A small drilled tunnel is angled and directed to a spot well under the river bed, then angles upward to a staging site on the other side of the river. At no point does the tunnel impact the riverbed or the water.

This first tunnel is a small “pilot” tunnel, which is electronically checked to ensure it’s in the right place and is not in any way going to impact the river. The tunnel is then enlarged by “reaming”, in repeated passes, to the diameter needed for the pipeline itself to go through.

Or, in micro-tunneling, until it is the right size for the segments of concrete pipe to be  pushed through by jacks to form a strong tunnel through which the pipeline will run.

For Coastal GasLink, the pipe will be 48 inches (just under 122 cm) in diameter, the same size as has been used in many trenchless crossings for major pipelines.

When the final tunnel is tested and checked and ready, a section of the main pipe is literally pulled through the tunnel from the starting point to the finishing point. The process is monitored throughout.

The pipe then is tested, and then can be connected to the main pipeline. The flow of natural gas through it can begin.

After the pipe is pulled through the its tunnel, the staging sites on both sides of the river are restored.

And, throughout, the process for Coastal GasLink is monitored by First Nations people.

And here are three videos that show how the tunneling techniques work:

  • From Coastal GasLink, this video shows “Direct Pipe Installation®” (DPI) under the Kitimat River (a 270-metre tunnel) and HDD under the Peace River:
  • From Trans Mountain, this video shows the technique and technology used to direct its TMX expansion pipeline under the Fraser River in Coquitlam:

(The TMX project from Alberta to tidewater at Burnaby includes some 40 trenchless crossings, of up to 1,600 metres in length.)

Here’s a graphic illustration from Coastal GasLink:

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