Designing and engineering a pipeline and associated facilities is a lengthy and detailed process.

Pipeline construction consists of a number of distinct activities that each contribute to the long-term integrity of the pipeline, as well as minimize the impact to the environment and to the landowner.

Pipeline integrity starts with sourcing the materials – oil pipelines are generally constructed from steel with a diameter typically ranging from 100 mm to 1,200 mm (4 inch to 48 inch). The highest quality steel is used. It is manufactured to stringent Canadian Standard Association (CSA) specifications, which include chemistry and material properties. Through production, transportation to the job site and installation, quality management processes ensure the pipe fully meets the requirements.

We are using three distinct construction methodologies in the Trans Mountain Expansion Project to place the pipe in the ground: conventional construction (often referred to as baselay), trenchless construction and water crossing construction.

Conventional Construction

For the majority of the pipeline route, conventional construction will be used. This is the style of construction most people think of when they imagine pipeline installation. Skilled tradespeople use specialized machinery in the 12 important steps to build a pipeline.


This method is called open-cut construction and will be used in both urban and rural areas along the Expansion Project route.

Water Crossing Construction

River and watercourse crossing construction techniques will be used where the pipeline crosses a body of water. There are two techniques to draw on: stream isolation (dam and pump technique) or horizontal directional drill. In some circumstances, where flows are too high for stream isolation and geotechnical conditions preclude trenchless techniques, we will use an open cut crossing of the watercourse with conventional construction methodologies.

With the stream isolation technique, the stream is temporarily dammed and rerouted through temporary pumps or using piping often referred to as a flume. The pipe is then installed using conventional construction techniques before the dam is removed and the stream returned to its normal flow path. Great care is taken to preserve the environmental features around the stream such as the wildlife and aquatic habitat provided within the riparian zone.

Water Crossing Construction (Isolated Trench)

Stream Isolation

Horizontal directional drill (HDD) technique is used for larger water crossings depending on geotechnical conditions at the stream crossing. This methodology is described within trenchless construction techniques.

Conventional pipeline construction will take place on either side of the water crossing.

Trenchless Construction