The Keystone pipeline has now returned to service in North Dakota, following the approval of TC Energy's repair and restart plan by the US Pipeline and Hazardous Materials Safety Administration (PHMSA).

The pipeline was shut down on October 29, when a drop in pressure was detected by TC Energy's operations control center. The affected area was approximately 2,500 square yards, according to the company, which is less than half the size of a football field. In addition, the company provided an initial estimate that more than 9,000 barrels of oil was released, which is equivalent to half the size of an Olympic-sized swimming pool.

As part of the restart plan, TC Energy will operate the pipeline at a reduced pressure with a gradual increase in the volume of crude oil moving through the system. 

TC Energy says it will not speculate about the cause of the incident until we complete their internal investigation and the segment of the pipeline is thoroughly analyzed by the metallurgical lab. After the pipe is tested at the laboratory, an independent investigation into the root cause of the incident will be conducted by a third-party specialist acceptable to PHMSA.