By Edward McAllister and Ratul Ray Chaudhuri
June 25 (Reuters) - Enbridge Inc has returned a large section of its 540-km (335-mile) Athabasca oil pipeline in Alberta to service after severe flooding in the western Canadian province last week, and it said on Tuesday other lines are expected back soon.
A leak was detected on Saturday on a smaller line linking to the 345,000 barrel per day Athabasca line after some suspected earth movement during the floods, forcing Athabasca and other main crude arteries in the region to shut as a precaution.
The southern portion of the Athabasca pipeline, which carries blended crude to the Hardisty terminal in Alberta, much of it bound for the United States, was restarted late on Sunday, but the northern segment remains shut after the floods, Enbridge said.
Meanwhile, the 380-km (235-mile) Waupisoo line, another main line in the province which can carry up to 600,000 bpd of crude to Edmonton, is being assessed and is expected back "today or very soon" an Enbridge spokesman said.
Athabasca and Waupisoo carry crude from the production centers around Fort McMurray in northern Alberta to the storage and pipeline hub in Hardisty, connecting to Enbridge's main export pipeline that runs into the United States.
The floods and leak have hindered efforts to transport heavy crude in the region since the weekend. Suncor Energy Inc , one of Canada's biggest oil producers, said it has reduced output at its oil sands operations in northern Alberta temporarily as a result of the pipeline shutdowns.
Enbridge ordered the shutdowns after it discovered a 750-barrel spill from its 17-km (11-mile) Line 37, a smaller pipe which serves CNOOC Ltd's Long Lake oil sands project in northern Alberta. The leak was detected in a remote area about 70 km (43 miles) southeast of the oil sands hub of Fort McMurray.
Pipelines which move about 1 million bpd of Alberta oil sands crude were shut following the leak.
"While the cause of the spill is yet to be confirmed, unusually heavy rainfall in the region is believed to have resulted in ground movement on the right-of-way that may have impacted the pipeline," Enbridge said in a statement on Monday.
The company said it would take an extended period to return the Line 37 to service, given the heavy rains in the area. The leak was contained within Line 37's right-of-way and there had been no reports of harm to wildlife, Enbridge said.
Enbridge said around 75 workers were at the site of the leak, which is only accessible by helicopter and all-terrain vehicles.
TransCanada Corp said on Tuesday that its Keystone crude oil pipeline system is operating normally, despite the flooding.
Earlier on Tuesday, pipeline and refinery monitor Genscape said flows on Keystone 1 had slowed to around 357,000 bpd from 580,000 bpd.
"The Keystone operational system remains available to transport full capacity as determined by customers," TransCanada spokesman Shawn Howard said in an email.