The operator of a Canadian oil pipeline closed since an April spill said it was confident it was ready to resume safe operations.Operators closed the Rainbow oil pipeline in April after a spill was discovered in northern Alberta. Canada\'s Energy Resources Conservation Board said about 28,000 barrels of oil spilled from the pipeline, making it one of the largest spills since the 1970s.Plains All American Pipeline, the parent company of Rainbow operator Plains Midstream Canada, was scrutinized in 2006 for a 7,500-barrel leak at a section of the same pipeline in Edmonton. Investigators blamed stress and corrosion for the 2006 leak. The pipeline was built in 1966.Plains in an e-mail statement to United Press International said it submitted a request to the ERCB to restart the pipeline.\"We remain confident the pipeline is ready and safe to operate and can resume operation independent of the cleanup efforts,\" the statement read.The company added that it\'s met all restart requirements outlined by the ERCB. A return to normal service of the Rainbow pipeline, which typically carries about 200,000 barrels of crude oil per day, was dependent on regulatory approval.\"We do not have a firm timeline for restart of the pipeline,\" the company added.