Enbridge - Northern Gateway Pipelines

Water Course Crossing Methods

For Northern Gateway, the following construction methods may be used for water course crossings:

Isolation Method

• The work area is isolated from the flow of the stream and the pipeline is installed in dry conditions

Trenchless Method

• Includes horizontal directional drill, “bore” microtunnel and aerial options
• Construction of the crossing and installation of the pipeline has little impact on the stream itself
• Streams that have high flows during construction and/or high fisheries sensitivity may be crossed this way

Open Trench Method

• Occurs without any isolation or diversion of flow away from the work area
• Streams that cannot be crossed using the other methods may be crossed this way
• Any stream that is dry or frozen to the bottom will be crossed with this method