Tesoro Logistics Restarts Mountrail County, North Dakota Pipeline

Tesoro Logistics, L.P. (“TLLP”) is restarting its Mountrail County, North Dakota pipeline following shutdown on Sept. 29 due to a crude oil spill. Permission to return the line to service was granted by the Pipeline and Hazardous Materials Safety Administration (PHMSA) following:

  • Acceptance by TLLP of a Safety Order from PHMSA;
  • Review by PHMSA and TLLP of the preliminary mechanical analysis of the failed segment;
  • PHMSA approval of a detailed restart plan submitted by TLLP.

The damaged portion of the pipeline was removed and sent to an independent laboratory for analysis. While final results are pending, the preliminary report indicates that the likely cause of the small diameter hole in the pipeline was from electrical discharge. The source of the electrical current remains under investigation. According to the initial lab report, there were no signs of corrosion or other defects at the failure location.

To ensure integrity before restarting the line, TLLP took the following steps:

  • Performed a hydrotest on the replaced segment.
  • Executed a tightness test holding pressure on the 35-mile section of the line from Tioga to Black Slough to verify soundness of the system.
  • Conducted investigations at six different locations on the pipeline to address findings from the Sept. 10-11 smart pig inspection of the 35 mile section of the line from Tioga to Black Slough and found no areas of concern.
  • Installed additional integrity monitoring equipment and online analysis along the entire 35-mile section designed to detect indications of a potential leak.

As of October 31, more than 4,500 of the estimated 20,000 barrels released have been recovered from the site. There have been no injuries or known impacts to water or wildlife as a result of this incident. Remediation is underway. Since becoming aware of the spill, TLLP has worked closely with the landowner; PHMSA; the North Dakota Department of Health; and public safety and regulatory authorities.

Tesoro Logistics LP, headquartered in San Antonio, Texas, is a fee-based, growth-oriented Delaware limited partnership formed by Tesoro Corporation to own, operate, develop and acquire crude oil and refined products logistics assets.