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Report: Tunnel, trench offer options for replacing pipeline

Nuts, bolts and fittings are ready to be added earlier this month to the east leg of a pipeline near St. Ignace, Mich., as Enbridge prepares to test the east and west sides of the Line 5 pipeline running under the Straits of Mackinac. A report released on Friday concluded the 65-year-old pipeline could be replaced with pipes buried in a tunnel or partially enclosed in trenches. (Dale G Young/Detroit News via AP)

Nuts, bolts and fittings are ready to be added earlier this month to the east leg of a pipeline near St. Ignace, Mich., as Enbridge prepares to test the east and west sides of the Line 5 pipeline running under the Straits of Mackinac. A report released on Friday concluded the 65-year-old pipeline could be replaced with pipes buried in a tunnel or partially enclosed in trenches. (Dale G Young/Detroit News via AP)

By JOHN FLESHER
AP Environmental Writer

TRAVERSE CITY, Mich. (AP) — A 65-year-old pipeline carrying crude oil beneath a delicate waterway connecting two of the Great Lakes could be replaced with pipes buried in a tunnel or partially enclosed in trenches that would pose virtually no leak risks but would require years and hundreds of millions of dollars to build, according to a report released on Friday.

Enbridge Inc., the Canadian company whose Line 5 runs 645 miles between Superior, Wisconsin, and Sarnia, Ontario, recently produced an analysis looking at different options for replacing the 4.5-mile-long segment, which runs along the bottom of the Straits of Mackinac between Lakes Huron and Michigan.

The study was required by an agreement the company and Michigan Gov. Rick Snyder reached in response to concerns about the safety of Line 5, which was recently slightly damaged, most likely after being struck by a ship anchor, and has been the target of a campaign by environmentalists demanding that it be shut down.

“Line 5 cannot remain in the straits indefinitely. We need a concrete strategy and timeline to expedite its replacement,” Snyder said. “This report will help us define a comprehensive solution for all utility crossings.”

Enbridge insists the underwater segment — which is divided into two 20-inch lines — has never leaked and remains in good condition.

But a spokesman said the Calgary, Alberta-based company is “committed to exploring the eventual replacement of the section in the straits.”

The report is the first of four Enbridge has agreed to provide this month. Others will deal with possible improvements to Line 5, ways to prevent more anchor strikes and an assessment of risks to other waterways that are crossed by Line 5.

A final decision on Line 5’s future is expected this fall.

The company has hired engineering firms with expertise in tunneling, offshore pipelines and horizontal drilling to analyze the feasibility of three replacement alternatives. Other outside experts have tried to estimate the likely environmental effects of the proposed projects.

The report concludes that there are two ways the current pipe might be replaced.

The first would route a new pipeline segment inside an underground tunnel up to 100 feet beneath the lakebed. The segment would be 12 feet in diameter and contain one 30-inch pipeline. The concrete tunnel would have reinforced lining to provide extra protection in case of pipeline failure.

The likelihood that oil would find its way into open water from the tunnel would be “virtually zero,” the report said.

It estimated the tunnel option would take up to six years to complete and cost from $350 million to $500 million.

The second alternative, known as the “open cut method,” would place a new, double-layered pipeline along the lake bottom. Sections in shallow areas, with water depths of up to 30 feet, which extend roughly a half-mile offshore on both sides of the straits, would be buried in a trench. Sections in deeper areas would rest directly on the lake bottom, covered with a layer of cobble and gravel six to eight feet thick.

That option would take up to five years to complete and cost $250 million to $300 million and have an “extremely low” risk of leaks, the report said.

The analysis dismissed a third alternative as unfeasible: running a pipe through an opening that would be drilled horizontally from the shore.

“Both feasible alternatives would help ensure the continued safety and protection of the Great Lakes for future generations, and we look forward to our continued collaboration with the State to further explore the viability of these options,” Enbridge said in a statement.

Environmental groups complained the analysis ignored their preferred action: shutting down line 5 and finding routes other than the Straits of Mackinac for transporting the 23 million gallons of oil and natural gas liquids the line carries daily.

“In a time of water shortages and changing climate in this century, it doesn’t make sense to even contemplate constructing Canadian oil pipelines in a tunnel under the world’s largest supply of fresh surface water,” said Liz Kirkwood of the Oil & Water Don’t Mix coalition.

Copyright 2019 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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