How do you place pipelines under a river?

In the case of large rivers or certain sensitive crossings, Enbridge uses horizontal directional drilling (HDD) technology whenever possible to install underground pipelines. HDD projects can be completed in a way that minimizes environmental and stakeholder impact, even in sensitive areas.

The HDD construction technique, employed when geological conditions and other factors are favorable, involves drilling an underground arched tunnel, and pulling the pre-assembled pipe section back through the tunnel. Crews drill a tunnel 12 inches wider than the diameter of the pipe, using a mixture of water and natural, non-toxic bentonite clay to keep the tunnel open and lubricated.

When not spread on farm soil as a nutrient enriching strategy, the clay and mud removed from the drill tunnel are transported to an approved disposal facility.