Enbridge - Northern Gateway Pipelines

Pipeline Construction

Construction of Northern Gateway will be divided into segments, or spreads, to break the work into manageable sizes for the winter and summer construction periods.

• It is expected that 12 construction spreads will be required
• Construction spreads will range in length between 70 km and 190 km
• The number of construction spreads may change as more engineering and environmental details become known

Pipeline construction typically has five major phases:

1. Preparing the right-of-way
2. Grading the right-of-way
3. Pipeline installation
4. Cleaning and testing
5. Clean-up and restoration

1. Preparing the right-of-way

   This work involves clearing vegetation from the right-of-way

   • Certain vegetation, such as market-quality timber, is salvaged
   • Other vegetation, such as woody debris, is either cleared or used to create controlled access points
   • Temporary access to and along the right-of-way is established, including the installation of bridges at stream crossings to accommodate construction vehicles
2. Grading the right-of-way

   This work generally involves removing and stockpiling the topsoil, and blasting and removing large rocks from the route.

   • Emphasis is on environmental conservation and salvaging topsoil
   • Grading on Northern Gateway’s right-of-way will be limited, but is required along portions of the route to safely accommodate pipe installation and equipment travel
3. Pipeline installation

   This work involves stringing, pipe welding, installing, trenching and backfilling activities.

   • Stringing is when individual pipe sections are laid end-to-end – individual pipe joints are bent to fit the terrain and then welded together to form long “strings”
   • Welds are inspected using X-ray or ultrasonic methods
   • Pipeline joints are coated and re-inspected
   • Trenching is completed and the pipe is gently lifted and laid, generally to a depth of a metre or more beneath the surface, and then the trench is backfilled
4. Cleaning and testing

   Once the pipeline is installed, it is cleaned thoroughly and pressure-tested using water and air.

   • Water is pumped through the pipeline at a higher level of pressure than when operational to ensure the integrity of the pipe
   • The same testing is also conducted with air
5. Clean-up and restoration

   The final phase includes closing off all temporary construction access, replacing topsoil, and installing cross-beams and surface water control.

   • Land and water crossings are restored
   • Because the land is rebuilt to exacting standards, right-of-ways can usually be used as they were prior to the construction