About 2:12 a.m., central daylight time, on July 4, 2002, a 34-inch-diameter steel pipeline owned and operated by Enbridge Pipelines, LLC ruptured in a marsh west of Cohasset, Minnesota. Approximately 6,000 barrels (252,000 gallons) of crude oil were released from the pipeline as a result of the rupture. The cost of the accident was reported to the Research and Special Programs Administration Office of Pipeline Safety to be approximately $5.6 million. No deaths or injuries resulted from the release.
We determined that the probable cause of the July 4, 2002, pipeline rupture near Cohasset, Minnesota, was inadequate loading of the pipe for transportation that allowed a fatigue crack to initiate along the seam of the longitudinal weld during transit. After the pipe was installed, the fatigue crack grew with pressure cycle stresses until the crack reached a critical size and the pipe ruptured.
The following safety issues were identified during this investigation:
- The effectiveness and application of line pipe transportation standards.
- The adequacy of Federal requirements for pipeline integrity management programs.
As a result of this investigation, we made the following new safety recommendations.
To the Research and Special Programs Administration:
- Remove the exemption in 49 Code of Federal Regulations 192.65 (b) that permits pipe to be placed in natural gas service after pressure testing when the pipe cannot be verified to have been transported in accordance with the American Petroleum Institute recommended practice 5L1. (P-04-01)
- Amend 49 Code of Federal Regulations to require that natural gas pipeline operators (Part 192) and hazardous liquid pipeline operators (Part 195) follow the American Petroleum Institute recommended practice 5LW for transportation of pipe on marine vessels. (P-04-02)
- Evaluate the need for a truck transportation standard to prevent damage to pipe, and, if needed, develop the standard and incorporate it in 49 Code of Federal Regulations Parts 192 and 195 for both natural gas and hazardous liquid line pipe. (P-04-03)
To the American Society of Mechanical Engineers:
- Amend American Society of Mechanical Engineers B31.8, Gas Transmission and Distribution Piping Systems, section 816, to remove the provision that pressure testing may be used to verify the integrity of pipe that may not have been transported in accordance with the American Petroleum Institute recommended practices for transportation of pipe by railroad or marine vessels. (P-04-04)
- Amend American Society of Mechanical Engineers B31.4, Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids, section 434.4, to require the use of the American Petroleum Institute recommended practice 5LW for marine transport of pipe. (P-04-05)
To the American Petroleum Institute: Review the equations in American Petroleum Institute recommended practice 5L1, Recommended Practice for Railroad Transportation of Line Pipe, and American Petroleum Institute recommended practice 5LW, Recommended Practice for Transportation of Line Pipe on Barges and Marine Vessels, for calculating the static load stresses at the bearing or separator strips and revise the recommended practices based on that review. (P-04-06)
