Pitting Corrosion and the Impact of Zebra and Quagga Mussels on Bare Steel Pipelines

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FOR IMMEDIATE RELEASE TO MEDIA: November 3, 2017


Liz Kirkwood, Executive Director                                                                  Cell: 570-872-4956
FLOW (For Love of Water)                                                                             Email: liz@flowforwater.org

Gary Street, Technical Advisor                                                                       Phone: 231-944-1568
FLOW (For Love of Water)                                                               


Portions of the steel oil pipelines in the Mackinac Straits may have lost half their wall thickness since installation in 1953 and become dangerously weakened due to hard-to-detect pitting corrosion, an engineering expert said today.

The independent analysis further strengthens the case for an immediate shutdown of Line 5 to prevent a catastrophic oil spill in the Great Lakes, according to FLOW, a Great Lakes law and policy center based in Traverse City. The full analysis can be found at www.FLOWforWater.org.

The possible damage stems from invasive zebra and quagga mussels that have covered portions of the dual underwater pipelines for years, inhibiting external inspection of Line 5 while possibly weakening the steel.

“The cause of their corrosiveness is the excrement from the mussels, which is acidic. An acidic deposit on bare steel leads to corrosion,” said Gary Street, MS, PE, the former director of engineering at Dow Environmental who conducted the analysis. Street notes that pipeline inspection tools called “smart pigs,” which Enbridge uses to detect corrosion, are not very accurate in detecting pitting corrosion.

The disturbing possibility of a significantly weakened Line 5 in the Mackinac Straits comes after recent acknowledgement by the pipeline owner and operator, Enbridge, that there are several large areas of the pipeline where the protective coating is missing. According to Enbridge, the bare steel on Line 5 in the Mackinac Straits was detected by Canadian oil transport giant Enbridge in 2014 when the company installed more supports, but not revealed to regulators until this summer.

“What else is Enbridge hiding from the public and state regulators?” asked Liz Kirkwood, executive director of FLOW and an environmental lawyer. “Attorney General Bill Schuette must immediately enforce the laws protecting the Great Lakes and revoke the state easement that has allowed a private Canadian company conditional use of our public waters and bottomlands.”

Not all types of corrosion are equally harmful. Some forms are far worse than others. Pitting corrosion is a localized form of corrosion by which tiny cavities or “holes” are produced in the material. The National Association of Corrosion Engineers has stated, “While corrosion of bare steel can take many forms, the most insidious, is pitting corrosion.”

“The prudent scenario is to assume that damage originally occurred in 2003 when the first of the new supports was installed,” said Street, whose 35+ year career in industry and consulting has covered an extensive range of experience in environmental engineering, chemical process design, ethanol production processes, minimization of waste materials, project management, and engineering management. “That being the case, it is very possible that the Line 5 pipe wall has suffered serious pitting corrosion beginning at that time. Making the matter worse, pitting corrosion is very difficult to detect.”

Enbridge acknowledged the areas of external anti-corrosion coating loss in September. Several of the areas are larger than the “Band-Aid“-sized areas Enbridge initially described when the gaps were revealed. The largest patch of exposed pipeline metal is 16 inches long and 10 inches wide. Others are narrower but also exceed a foot in length.

Also detailed in the Enbridge reports is a “disturbed” coating area that’s more than 3 feet long, a “dislodged” coating area that’s 13 feet long and a mysterious 8-inch “white deposit” of unknown origin that Enbridge says “remains under investigation.”

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