Fortis scrambles to keep the gas flowing
In wake of pipeline fire, utility diverts flow on other lines and converts LNG for emergency use
FortisBC is scrounging far and wide to keep natural gas flowing to its customers after a massive fire at an Enbridge pipeline near Prince George on Tuesday cut off about 60 per cent of its normal gas supply.
With one large pipeline still shut down by the incident, the province’s gas distributor is pulling new supply from an existing east-west pipeline, revaporizing liquid natural gas (LNG) stored on Vancouver Island, and is drawing gas back that would otherwise be headed to the United States.
“When a major artery like this is cut, we have some options to serve customers — we have flexibility to take gas from several points into our system,” said Dennis Swanson, FortisBC’s vice-president of energy supply and resource development.
The company was able to pull additional gas from Alberta through the Southern Crossing Pipeline, which runs close to the U.S. border.
“We also have an interconnection to the south with neighbouring utilities and they really leaned in to help us out,” said Swanson.
Northwest Natural, Puget Sound Energy and Northwest Pipe — which normally receive gas from the Enbridge pipeline — were able to reverse the flow back north.
“By operating with stored LNG, they were able to push gas back up into B.C. to help us survive this crisis,” he said.
Fortis also pushed gas from its own Mt. Hayes LNG plant on southern Vancouver Island by revaporizing the gas stored there for export and backfeeding it to from the Island to the Lower Mainland.
At the Fortis LNG plant, natural gas is cooled until it condenses into a liquid at about 1/600th of its usual volume. It can be stored in its liquid form, loaded for transport from the facilities, or converted back to gas and returned to the Fortis distribution system.
Gas at the company’s second LNG plant in Delta is being held in reserve.
“If the pressure in the system drops, we can quickly shoot that one in and keep the pressure to keep as much service going as possible,” said Swanson. “Because it’s smaller, we are using it as our tool of last resort.”
The 47-year-old Tilbury LNG plant in Delta is used to buffer supply during peak demand and to supply industrial customers.
The storage tank there holds 17 million cubic metres of natural gas, “enough to keep a community of 12,000 warm for about 45 very cold days.”
Mt. Hayes holds 42 million cubic metres of natural gas.
Fortis is in the process of expanding the Tilbury facility, which also supplies LNG for export by ship and by truck. The new storage tanks will hold 40 million cubic metres, providing a substantial buffer in the event of a future service interruption.
There was also a considerable amount of gas stored within the pipelines themselves, under pressure, but not in liquid form, said Swanson.
“Because it’s a gas, we can compress it under pressure, which is called line pack,” he said. “You can survive for a while with the extra gas that is in those lines.”
Early Thursday morning gas flow was restored to the undamaged gas lines at the site of the rupture.
“Now that the 30-inch line has been deemed fit for service, our restart plan is to gradually bring the line’s pressure up to approximately 80 per cent of normal operating capacity,” Enbridge said in a statement.
Gas flow will be restored when the line has been tested and pressurized.