Go deep: LNG exporters eye subsea pipelines

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Those racing to carry natural gas to Canada's West Coast are contemplating an unusual detour onto the ocean floor near British Columbia as they seek ways to export energy across the Pacific.

Between the coast and the giant gas fields of northeastern British Columbia lies one of Canada's most difficult geographies. Mountains, landslide-prone slopes and powerful rivers all complicate the approach to the ocean for companies working to bring energy to terminals where it can be loaded onto ships destined for Asia.

The ocean-floor proposal, from Spectra Energy Corp., is the latest example of the unexpected decisions engineers are contemplating to conquer complicated terrain.

Spectra is planning a massive 4.2-billion-cubic-feet-per-day pipeline to a liquefied natural gas export terminal proposed by BG Group PLC near Prince Rupert. The companies have sketched a route across northern B.C. with three possible final legs: two on the sea bed, and another on land. The submarine options include 70 or 120 kilometres of underwater pipeline.

"We have looked at subsea pipeline options as a potential method to minimize disturbance to the land," Spectra said in a statement. The company is "working right now with independent marine and hydrographic experts to do detailed investigations of the characteristics of the sea bed."

Sub-sea pipelines are common in other countries. But they are rare in Canada, where energy moves primarily across land.

The west coast of British Columbia provides such formidable challenges that industry has devised widely different plans to reach the water. Three pipeline companies have contemplated a half-dozen routes to the coast. Enbridge Inc. has chosen a route for its Northern Gateway oil project to Kitimat, B.C., which it feels is better sheltered from tsunamis and allows for a pipeline "a few hundred kilometres" shorter than other alternatives, spokesman Todd Nogier said. Enbridge felt the ocean bottom was "less technically suitable for an oil/condensate pipeline system."

Spectra and TransCanada Corp., which has agreed to build a pipeline for Malaysia's Petronas, are examining ways to bring gas to the more westerly port at Prince Rupert.

The Spectra route travels through the Nass River valley, which boasts more open terrain than the Skeena River valley that is now the main transportation corridor to Prince Rupert. Bounded by steep cliffs, the Skeena is so constrained that to build a new pipeline that "you would literally have to lay through the river, which is one of the most sensitive salmon rivers in the world," said Betsy Spomer, senior vice-president of business development with BG.

The more northerly Nass route has the added advantage of travelling through territory controlled by the Nisga'a, which signed British Columbia's first modern-day land claim in 2000. The Nisga'a believe LNG exports are a "huge opportunity, which would be great for the country and the province," said president Mitchell Stevens.

The Nass route will likely require tunnels and aerial crossings, he said. And one of the submarine routes crosses a constitutionally protected Nisga'a mollusc-harvesting area. Still, the Nisga'a are not opposed to the ocean-floor idea. "With technology today the way things are, they say you can build anything – and I don't doubt that fact for a minute," Mr. Stevens said.

He added that TransCanada is also considering a route through the Nass; a company spokesman declined to provide details. Environmentalists argue that underwater crossings should be treated with caution. "The fact is leaks and ruptures happen, and there have been very few studies on the implications of a subsea gas rupture," said Tzeporah Berman, a long-time green campaigner in B.C.

Underwater maps show water on Spectra's proposed routes ranges in depth from 129 to 554 metres. Pipelines have been built in waters three times that deep in the Gulf of Mexico, where the U.S. has issued permits for more than 18,500 pipelines.

That network of oil and gas pipe routinely weathers hurricanes. Underwater pipelines are unaffected by freeze-up or spring melt, and use less invasive installation methods, said Terry Townend, a vice-president in charge of pipeline and sub-sea development for Houston-based Pinnacle Engineering Inc.

"You'd be much better off on the ocean floor than you are crossing environmentally sensitive areas and rivers," he said. "You have a floating vessel just laying pipe. Letting it rest on bottom makes a lot more sense to me."