Keeping a Pipeline Safe

The risk associated with the 62-year-old pipelines under the Straits of Mackinac in northern Michigan was the subject of an article by Steve Friess in The Washington Post on Sunday.

After a different Enbridge pipeline in Michigan failed in 2010 and released about 20,000 barrels of oil, the state appointed a task force to study the oil pipelines throughout Michigan, include those under the Straits of Mackinac.  The task force report made four recommendations about the Straits pipelines and nine others for the whole state.  The task force recommended that the Straits pipelines should not transport heavy crude oil.  Enbridge has stated that the pipelines carry only light crude oil and light synthetic crude and natural gas liquids, including propane.  See, for instance, its Operational Reliability Plan.  The Enbridge website has more information about the pipelines and their plans to keep it safe; see http://www.enbridgeus.com/Line-5.aspx

Everyone agrees that a failure of the Straits pipelines could cause severe environmental damage. 
Enbridge, of course, also has a financial risk; they would lose revenue if the pipeline fails and has to be shutdown.  An Enbridge spokesperson stated, “Every day we’re out repairing pipelines and shutting down due to release, we’re not moving product. It’s in our interest as a pipeline company to keep it in the pipe.”

The Michigan Petroleum Pipeline Task Force website also has some interesting documents about the pipeline construction, including the 1953 engineering analysis (http://michigan.gov/documents/deq/Appendix_A.2_493980_7.pdf), which describes the selection of the location, the construction of the pipeline, and the analysis of the stresses involved.  In general, it is a good example of risk assessment and mitigation.  It acknowledges both the environmental and financial risks.  The pipeline elsewhere in Michigan has only one pipe, but two pipelines were used at the Straits, "for purposes of extra flexibility, extra strength, and a greater factor of safety against possible damage," according to this report.  If there are two pipes, then a leak in one pipe should release less oil, and the other pipe can continue to operate, which minimizes the financial and operational disruptions.  The report mentions the hazard from a ship's anchor and describes why this is unlikely in general and how the pipeline design will reduce this risk.  It also mentions that "any possible contamination of the waters caused by oil spillage from the pipeline crossing is considered remote in comparison to the amount and possibility of spillage from oil tankers."

This last point remains extremely relevant: given that people in Michigan use oil from Canada, all of the transportation options have risks, which the task force report acknowledged. 
For example, trains transporting oil had accidents in Quebec and Virginia.