Allseas to install subsea link of Canadian gas pipeline
Allseas has secured a contract with Western LNG to install the subsea section of the Prince Rupert Gas Transmission pipeline in the remote waters of north-western British Columbia, near the Alaska border. The subsea section forms the final link in a 700 km system carrying Canadian natural gas to the planned Ksi Lisims LNG export facility on the Pacific coast. The scope covers approximately 50 km of 36-inch and 48-inch concrete-weight-coated pipeline connecting the onshore transmission system to a floating LNG facility on Pearse Island.
Offshore installation is scheduled for 2029 and will be carried out by the pipelay vessels Solitaire and Sandpiper in water depths ranging from the shoreline to approximately 450 m. That range is the defining difficulty. Deepwater pipelay is a well-established discipline, but the shallow end of this route requires an entirely different set of techniques, and a single campaign has to accommodate both without the vessels being able to work in their most efficient mode throughout.
The work includes multiple shore crossings, shore pull-ins, above-water tie-ins, trenching, route stabilisation and span rectification before and after laying. Shore crossings and pull-ins are labour-intensive operations conducted in the surf zone, where weather windows are short and equipment is exposed. Span rectification, correcting sections of pipe left unsupported by an uneven seabed, has to be assessed after the pipe is on the bottom, which means the scope is not fully known until the lay is complete. The contractor describes the combination, together with the remote location, as a technically demanding campaign.
Ksi Lisims LNG is a proposed 12 mtpa floating export facility being developed by the Nisga'a Nation, Rockies LNG and Western LNG, situated on Nisga'a Nation-owned land. The site offers direct routes to growing Asian markets, and the choice of a floating facility avoids much of the onshore construction that has slowed comparable projects on the same coast. Indigenous ownership of the land and a stake in the development also change the consent landscape that has held up other British Columbian energy infrastructure.
Both the export facility and its feed pipeline have received key environmental approvals and have been identified as projects of national interest by the Canadian government. A final investment decision by the co-developers remains outstanding, with construction potentially beginning by early 2027. Awarding the offshore installation contract well ahead of that decision reflects how far in advance specialised pipelay capacity has to be reserved, and how few vessels are capable of the work.
