"Unprecedented" river flows are being blamed for a pipeline leak that sent as much as 32,000 litres of oil into the Red Deer River and Gleniffer Lake north of Calgary.
The pipeline, owned by Pembina Pipelines, was undermined by "unprecedented river flows and channel movement" in June 2008, causing a segment of pipe to be suspended in the water. External stress then caused the leak, said a report released Tuesday by Alberta's energy regulator.
The Energy Resource Conservation Board, which completed an investigation into the incident, said it accepts the Calgary-based company's technical explanation of what happened and is satisfied with subsequent repairs and activity to prevent similar problems.
According to Pembina, between 75 and 125 barrels, or about 20,000 litres, of sweet crude oil was released from the pipeline near Sundre. But Alberta Environment estimated the leak to be as much as 200 barrels of oil, or about 32,000 litres.
An oily sheen covered parts of Gleniffer Lake, a popular recreational lake about 130 kilometres north of Calgary. Officials issued restrictions on drinking water in the area and told people to stay off the lake for about 10 days during the cleanup.
No enforcement action imposed on company
The pipeline was repaired, buried more than four metres under the riverbed and returned to service on Aug. 25, the conservation board said.
"Pipeline failures in or near water crossings are typically a result of the rapid deviation of the existing river channel or a rapid erosion of the riverbed due to significant rainfall combined with spring melt," the board said.
The board said pipeline failures in Alberta are rare, with 2.1 failures per 1,000 kilometres of pipeline in 2007.
In August 2000, a pipeline owned by Pembina Pipelines ruptured in B.C., spilling about 6,200 barrels of light crude oil into the Pine River, about 110 kilometres upstream of the community of Chetwynd. The Pine River flows into Alberta's Peace River.
The company was charged by Environment Canada and was eventually fined $5,000 and ordered to pay $198,000 to repair damaged fish habitat.
No action was taken against Pembina in the June 2008 leak.