WEDNESDAY, NOVEMBER 22, 2017
The final version of an independent analysis of Enbridge’s controversial Line 5 pipeline was released to the public Monday (Nov. 20), largely echoing the conclusions drawn in an earlier draft but admitting that a 2016 study of the line’s cathodic protection current missed the coating gaps that have since been revealed by the energy company.
The alternatives analysis, authored by Dynamic Risk Assessment Systems Inc., was first published as a draft over the summer, detailing the relative risks and benefits of several alternative approaches to the future of Line 5. The liquid pipeline, which delivers crude oil and natural gas liquids from Alberta to Sarnia, Ontario, crosses under the Straits of Mackinac, between Michigan’s Upper and Lower Peninsula.
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The new alternatives assessment explores several possibilities for the future of Enbridge's Line 5 liquids pipeline, which runs under the Straits of Mackinac, in Michigan. |
The pipeline, constructed in 1953, has been under fire in recent years from citizens and environmentalists concerned about the environmental effects of a potential leak. The state of Michigan hired Dynamic Risk, of Calgary, to assess all of the possible courses of action moving forward.
The Alternatives
The alternatives entertained included shutting down Line 5 in favor of a new pipeline that doesn’t cross the Straits; shutting down Line 5 in favor of using existing infrastructure to move the liquids, using non-pipeline transport like railcars, replacing Line 5 with a new pipeline under the Straits, maintaining Line 5 as it exists, or simply cutting Line 5 off before the Straits.
The five possible courses of action that received a semi-quantitative discussion in the report are:
A new trench crossing would likely cost $27 million, the firm says, while a new tunnel crossing would cost $153 million, according to the report.
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| Dynamic Risk |
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Line 5 was constructed in 1953, and Dynamic Risk says it was coated with coal tar enamel. |
If a new pipeline were to be built under the Straits, it would likely be coated with a three-layer polyethylene coating as well as a two-inch, welded-cage reinforced concrete coating, the report notes.
An all-new pipeline circumventing the Straits would come with a price tag upward of $2 billion, the report says, while switching to rail transport would take three years and cost just over $1 billion.
Corrosion Notes
The report concludes that the threat of corrosion “does not currently contribute to the overall probability of failure at a magnitude that is significant.” Dynamic Risk says that the pipeline is coated with coal tar enamel, and the firm’s draft report in July said that cathodic protection current mapping performed in 2016 indicated no anomalies in current. “The fact that the tool reported no current density anomalies supports the contention of an intact coating,” the draft said.
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Since the final report was finished, Enbridge has admitted that there are more than 40 areas on the underwater pipeline where coatings are missing, leaving bare metal exposed. |
The final report takes into account more recent revelations that there are a number of gaps in the protective coating, and is based on Enbridge’s admission in September that there were three spots on the underwater pipeline that exhibited loss of coating down to bare metal.
Last week, the company revealed that there are in fact more than 40 areas on the pipeline that have lost coatings. That fact was not taken into account in the final report from Dynamic Risk, which was finished in October.
Coating Questions
While Dynamic Risk and Enbridge both report that the line is coated with coal tar enamel, which was common at the time of the pipeline’s construction, a report authored by former Dow engineer Edward Timm, released earlier this year by the National Wildlife Federation, contends that this may not be the case.
Timm says in his report that, while the order for the pipeline called for coal tar enamel, other documentation is less clear about what the actual coating used was. Timm concludes it’s more likely it was “a solvent-based asphalt primer, two layers of asphalt-saturated glass fiber fabric and a white protective overlayer of white craft paper bonded with asphalt enamel.”
State-Commissioned Study
The state of Michigan commissioned the study in August 2016; a risk analysis meant to accompany the alternatives analysis was abandoned earlier this year when it was found that one of the contractors working on it had also contracted with Enbridge. The state is currently working on a new contract for a risk analysis.
The studies are meant to guide any future decisionmaking on the pipeline. There is a public comment period taking place now through Dec. 20.
Tagged categories: Coal tar epoxy; Government; Infrastructure; Oil and Gas; Pipelines; Program/Project Management; Three-layer polyethylene (3LPE)
