Heavy weights used to hold Line 3 pipeline down in wetlands

Line 3 construction site in Aitkin County, east of Highway 65.

Enbridge Line 3 construction is damaging wetlands. The proposed route is crossing 78 miles of wetlands, or one fifth of its entire route. Workers often install temporary plank roads in and around wetlands to support heavy equipment.

Line 3 is crossing different types of wetlands: emergent, unconsolidated bottom, scrub-shrub, and forested wetland, Enbridge says. One challenge in trenching a pipeline through a wetland is that pipelines can float. Workers have to put weights on them to get them to sink and stay down.

When you are monitoring Line 3 construction, you might see some large black bags near construction sites. These are bags filled with local aggregate to sink the pipeline in place. The industry term is “buoyancy control.”

In water saturated wetlands, one crossing method is called the “push-pull.” Workers excavate a trench working from the plank road, float the assembled pipeline, put weights on it, then push and pull it to get it to sink.

Horizontal Directional Drilling also is used to cross wetlands. Click here for Enbridge’s summary of wetland crossing methods.

Enbridge diagram of a wetland crossing.