Building A Pipeline

If approved, Williams will design, construct, operate and maintain the proposed Island Gas Connector Project (IGC Project). As an international pipeline, the proposed IGC Project will be subject to the approval of the National Energy Board in Canada and the Federal Energy Regulatory Commission in the United States.

Survey Process

Constructing an underground and subsea natural gas pipeline begins after many steps including:

  • Extensive research
  • Environmental, engineering and design studies
  • Route planning, including securing easements from landowners
  • Regulatory approvals

Land Construction

The land portion of the IGC Project is proposed to run approximately 34 miles (54 kilometres) from Williams’ Northwest Pipeline’s Canadian gas interconnect at Sumas, Washington to the shoreline in the Birch Bay/Custer, Washington area.

Early in the routing process, landowners along the proposed route are contacted to request permission to survey and stake the area for environmental, engineering and construction evaluations. Our goal is for every landowner to understand all of the proposed design and safety features of the proposed pipeline before construction, including the underground depth, pipe size, temporary and permanent width of the easement and above-ground equipment.

From digging trenches to laying pipe to final testing, pipeline construction is a complex process that involves many steps. Many people are surprised by the number of people and amount of equipment required to build a pipeline. Pipeline construction looks much like a moving assembly line. As one crew completes its work, the next crew will move into position to complete its piece of the construction process. It includes many components.


Subsea construction



A portion of the IGC Project would travel approximately 47 miles (75 kilometres) across the Salish Sea. Underwater pipelines are a safe and well-established way to transport natural gas across large bodies of water.

Williams owns and operates more than 2,000 miles (3,200 kilometres) of subsea pipeline, including a 745-mile (1,200-kilometre) pipeline in the Gulf of Mexico.

Williams owns and operates more than 3,200 kilometres (2,000 miles) of subsea pipeline, including a 1,200-kilometre (745-mile) pipeline in the Gulf of Mexico.

Underwater Factors

When determining the best underwater route in the Salish Sea for the IGC Project, a number of factors will be considered:

  • Consulting with potentially affected Canadian Aboriginal groups, Native American Tribes, landowners, local stakeholders and communities
  • Avoiding underwater obstacles, unsuitable substrate and natural and man-made obstructions
  • Avoiding sensitive marine habitats
  • Considering ship traffic, anchoring areas and fishing activities
  • Using existing underwater corridors wherever possible
  • Ensuring pipeline construction is feasible along the land approaches to the marine crossing
  • Pipelines installed on the seafloor are flexible enough to withstand substantial movement

Marine Vessel

A special marine vessel – a complete assembly plant on the water – is used to build an underwater pipeline. An inclined ramp is used to lower the pipeline sections from the vessel through the water to the seabed. High-density concrete may be used to coat the pipeline, allowing it to be sunk into place on the seabed. The underground pipeline will have a cathodic protection system, in addition to corrosion resistant coating to help prevent corrosion.

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