One month after a North Dakota (ND) farmer discovered a ruptured pipeline leaking crude oil into his wheat field, the company that owns the line received permission from the Pipeline and Hazardous Materials Safety Administration (PHMSA) to resume pumping operations.  The 700-mile pipeline containing the failed section is owned by Tesoro Logistics LP, which is based in San Antonio, Texas.  According to the PHMSA, the approved restart followed the company’s agreement to undertake corrective measures listed in a safety order.

PHMSA reported that the leak in Williams County near Tioga was discovered September 29, 2013.  The line was shut down the same day; it was estimated that 20,000 barrels of oil had been released.  Subsequently, PHMSA began to monitor Tesoro’s response to the action; this included overseeing extraction of the failed section, reviewing Tesoro’s control room procedures and records, and coordinating with state regulatory and environmental officials. 

Restart

After removing the failed section, Tesoro placed and tested new pipe and installed pressure- and flow-detection systems.  Before authorizing restart, PHMSA required that Tesoro agree to carry out corrective actions specified in the safety order.  These included conducting frequent aerial and ground inspections and installing additional leak detection equipment.  Tesoro must also update maps of the entire 700-mile-long High Plains Pipeline System and evaluate the pipeline to identify further preventive measures to protect important water bodies.  The system is employed in the development of resources in the Bakken Shale/Williston Basin area of Montana and North Dakota.

In addition to implementing the corrective measures included in the safety order, PHMSA required that Tesoro submit a restart plan for the entire pipeline for the Agency’s approval, conduct mechanical and metallurgical testing and failure analysis of the failed pipe, and evaluate previous inspection results.  In an announcement, Tesoro said PHMSA had approved the restart plan. 

Electrical discharge possible cause

The company also reported that the failed section was sent to an independent laboratory for analysis, as required by PHMSA.  “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,” said Tesoro in a statement.  “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.
Tesoro also reports that it took the following steps before restarting the line:

• Performed a hydrotest on the replaced segment.
• Executed a tightness test holding pressure on the 35-mile section of the line to verify soundness of the system.
• Conducted investigations at six different locations on the pipeline to address findings from a September 10–11, 2013, smart pig inspection of the 35-mile section. No areas of concern were found.
• Installed additional integrity monitoring equipment and online analysis along the entire 35-mile section. These actions are designed to detect indications of a potential leak.

Tesoro says it is currently recovering oil from the site.  The company also states that there have been no injuries or known impacts to water or wildlife as a result of the incident and that remediation is under way.

PHMSA says its investigation will determine if the failure resulted from noncompliance and if enforcement is warranted.