Preparing to monitor Line 3 horizontal directional drilling
Aerial view of site preparation for Line 3’s underground crossing of the Shell River.

Enbridge Line 3 would travel 337 miles across northern Minnesota, crossing 200+ waterbodies along the way. In most cases, Enbridge plans to trench through them. At 21 different crossings, Enbridge is going to tunnel underneath the waterbody, using a process called Horizontal Direction Drilling (HDD).

Enbridge will use HDD to tunnel under the Mississippi River at two separate locations.

Watch the Line monitors have seen the preparation work at several sites. Here’s what we’ll be looking for when the company is getting ready to drill.

Horizontal Directional Drilling graphic. Source: U.S. Army Corps of Engineers. Note: The waterbody isn’t called “river,” but “obstacle,” as if the river were the problem.

During HDD, the company will use a large auger to bore under the water body. It uses “drilling mud” as a lubricant and to keep the tunnel open. Once the tunnel is drilled, they will pull the pipeline through the tunnel.

A big area of concern is a “frac out,” where the drilling mud seeps through the cracks in the subsurface soils and eventually pushes its way to the surface and into the water body.

Source: U.S. Army Corps of Engineers

The industry refers to it as “an unintended” return of drilling fluids to the surface. Others simply call it pollution.

Enbridge has scaled back its work because of spring construction restrictions. We aren’t sure when the HDD will start, but we want to keep an eye on it.

One key thing to watch for is a stretch of pipeline welded together before it’s in the trench, such as this photo below from Hubbard County.

Pipeline welded together above ground.

We are still learning as we go. We aren’t 100 percent sure this is an HDD site, but the experts tell us that this is a tell-tale sign for HDD.