Trans Mountain Pipeline has secured approval to partially start construction of its growth enabling export capacity expansion for Canada’s top natural gas user, Alberta thermal oilsands production.

The National Energy Board (NEB) gave permission to resume work that an appellate court verdict suspended last August on additions to the line’s British Columbia outlet terminal in Vancouver Harbor.

Regulatory review continues on an application for a simultaneous construction start on Trans Mountain’s Alberta inlet at Edmonton, with the NEB raising questions about spill control and fire safety.

No work schedule has been established yet. An added regulatory procedure is holding back the majority of the C$9 billion ($6.8 billion) job of tripling capacity to 890,000 b/d by adding pipe to the 1,147-kilometer (688-mile) conduit.

The pause resulted from an NEB order to repeat a detailed route approval process that presents construction plans to landowners, gives them 30 days to file statements of opposition and resolves disputes with negotiations or hearings.

“This decision has introduced uncertainty into the construction schedule,” Trans Mountain said in a filing with the NEB. “Activities are dynamic and subject to change in response to regulatory and permitting developments.”

The detailed route process was 20 months old and 73% complete when the Canadian Federal Court of Appeal stopped the exercise a year ago by overturning the first project approval. The Trans Mountain expansion affects about 3,200 tracts of land held by private, business, local government and native tribal owners.