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Enbridge Line 5

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Enbridge Line 5
Line 5 passes underneath the Straits of Mackinac
Line 5 passes underneath the Straits of Mackinac
CountryUnited States, Canada
StateWisconsin, Michigan
FromSuperior, Wisconsin
ToSarnia, Ontario
General information
Commissioned1953; 71 years ago (1953)
Technical information
Length645 mi (1,038 km)
Diameter30 in (762 mm)

Enbridge Line 5 is a 645-mile oil pipeline owned by the Canadian multinational corporation Enbridge. Constructed in 1953, the pipeline conveys crude oil from western Canada to eastern Canada via the Great Lakes states. Line 5 is part of the Enbridge Lakehead System and passes under the environmentally sensitive Straits of Mackinac, which connect Lake Michigan to Lake Huron. The 30-inch pipeline carries 540,000 barrels (86,000 m3) of synthetic crude, natural gas liquids, sweet crude, and light sour crude per day[1] as of 2013.[2]

In December 2018 the Michigan Department of Natural Resources announced that the Mackinac Straits Corridor Authority (MSCA), with outgoing Governor Rick Snyder, had approved Enbridge's plan to replace the underwater segment of Line 5 and with a new pipeline segment housed in a tunnel.


The Line 5 pipeline runs between Superior, Wisconsin, and Sarnia, Ontario, two major nodes of the Enbridge Pipeline System. The Enbridge terminal at Superior conveys western Canadian crude oil from various incoming pipelines (including lines 1–4) to Line 5 and Line 6, which go around the northern and southern shores of Lake Michigan respectively. From Superior, Line 5 travels east to the Upper Peninsula of Michigan, then runs southeast to Rapid River, near Escanaba.[3] At Rapid River, natural gas liquids (NGL) are side stream delivered for stripping, and the stripped NGLs are reinjected.[4]

From Rapid River, the pipeline runs near the northern shore of Lake Michigan until it reaches the Straits of Mackinac. There the pipeline divides into two separate 20-inch (51 cm) lines, which reunite when they reach McGulpin Point on the southern side of the straits.[4] The lines are buried until they reach a depth of 65 feet (20 m).[5] The lines descend to a depth of approximately 270 feet (82 m) under the straits.[6]

Once on land again in the Lower Peninsula, Line 5 runs near Interstate 75 to Bay City.[7] At the Lewiston pumping station, US sweet crude may be injected.[4] From Lewiston, Line 5 loops around Saginaw Bay, then runs southeast to the St. Clair River.[3]

Just before the St. Clair River, Line 5 reaches the Marysville pumping station. Volumes destined for Michigan and Ohio refineries such as BP Husky and Marathon Detroit are offloaded there,[4] and transferred to a Sunoco pipeline that runs from Marysville to Toledo.[8][9]

The line then proceeds east across the St. Clair River to Ontario, where it rejoins Enbridge Line 6 and terminates at Sarnia.[1] Any volumes not destined for Sarnia-area refineries are then pumped into tanks for transfer to Enbridge Line 7.[4]


Enbridge headquarters in Edmonton, Alberta

The construction of Line 5 was completed in 1953.[6] The pipelines from western Canada to Superior had been completed in 1950. Prior to the construction of Line 5, the crude oil was conveyed from Superior to southern Ontario by oil tankers.[10]

In 2013, the line's capacity was increased by 50,000 barrels (7,900 m3) per day, from 490,000 to 540,000 barrels (78,000 to 86,000 m3).[11] The upgrade involved US$100 million in improvements to pumping stations, but with no upgrades to the actual pipes.[7]

As of 2017, Line 5 had spilled at least 1.1 million gallons since 1967.[12] In 2018, a tugboat anchor hit the pipeline and caused minor damage to the pipe.[13]

Also in 2018, Enbridge and the State of Michigan agreed to build a tunnel beneath the Straits of Mackinac that will contain the pipeline.[14] Line 5 in the Straits consists of two 20-inch pipelines, an east leg and a west leg, running parallel to each other for the 4.5 miles across the lakebed.

On June 18, 2020, a screw anchor support on the east leg was found to have shifted from its original position. The shift was caused by Enbridge's seasonal maintenance work, which affected the anchor support and not the pipeline itself. On June 20, 2020, Enbridge reported that a June 19 remote-operated vehicle inspection of the west leg of Line 5 in the Straits had detected no issues or damage to the anchor structures or pipeline.[15] Operations resumed on that line on the same day. The east leg was to remain shut down. The federal regulator, Pipeline and Hazardous Materials Safety Administration raised no objections to the plan. Enbridge CEO Al Monaco responded to Michigan Governor Gretchen Whitmer to confirm that Enbridge was committed to sharing what is learned about the incident with the screw anchor assembly on the east leg with PHMSA and the State of Michigan.[citation needed]

Mackinac Straits Corridor Authority (MSCA) agreement about tunnel[edit]

On December 19, 2018, the Michigan Department of Natural Resources announced that the Mackinac Straits Corridor Authority (MSCA), in correspondence with outgoing Governor Rick Snyder, had approved a plan to build a multi-purpose tunnel that would house multiple utility lines, to remove the old Enbridge Line 5 and to construct a new line. The MSCA approved the transfer of a property right, allowing Enbridge to construct the new tunnel in the bedrock beneath the Straits of Mackinac.[16] The project has faced fierce opposition from environmentalists and several Tribal Authorities.[17]

Lawsuits (2019–2021)[edit]

In late June 2019, the state of Michigan filed a lawsuit asking the Ingham County Court to compel the decommissioning of the segment of Line 5 that runs under the Straits of Mackinac. The dual pipes, in use since 1953,[18] were then shipping 540,000 barrels of oil and propane per day. A Reuters news report defined Line 5 as "a critical part of Enbridge's Mainline network, which delivers the bulk of Canadian crude exports to the United States". The basis of the suit is the claim that the pipeline is a public nuisance and violates the Michigan Environmental Protection Act since it may become a major source of pollution. The news report added that "it is unclear if Line 5 could operate without the Straits segment".[19] Attorney General Dana Nessel commented: "We cannot prevent accidental or emergency anchor deployments in one of the busiest shipping channels in the Great Lakes. And it only takes one such incident to cause an environmental and economic catastrophe. That is a risk no one should be willing to take". Michigan Senate Republicans expressed concern about the potential shutdown of the pipeline, which they said could create other problems: "the loss of thousands of construction jobs expected from the tunnel construction, an increase in costs at Detroit and Toledo refineries and the loss of a significant mode of propane transportation in Michigan. It is estimated that replacing the propane lost by closing the line would require an additional 30,000 truckloads and 9,600 rail cars annually".[20]

In June 2020, the U.S. Sixth Circuit Court of Appeals ruled the emergency response for the pipeline was adequate to protect wildlife in the Straits of Mackinac and the Michigan Court of Appeals sided with its ruling. Enbridge has stated that the pipeline is in good condition even though the outer coating has worn away in some places and steel braces are placed at places hit by erosion. It plans the construction of a utility tunnel in the bedrock under the Straits of Mackinac-the connector of Lake Michigan and Lake Huron, to house the Line 5 pipeline and to replace its six-kilometer underwater segment. Enbridge intends to begin work on the tunnel once it received all the necessary permits and expected to complete construction by 2024.[17]

In May 2021, citing a 1977 treaty with the United States on the uninterrupted flow of oil and gas across the border, the Canadian government asked a U.S. court to stop Michigan from shutting down the pipeline, thus triggering a bilateral negotiation with Washington.[21][22] The pipeline supplies fuel to much of Ontario and Quebec.[21]

In June 2022, the Environmental Permit Review Commission inside the Michigan Department of Environment, Great Lakes and Energy re-instated a petition from the Bay Mills Indian Community, who challenged a permit Enbridge needs to build its tunnel.[23]


The 2013 expansion, coupled with the anticipated expansion of the Alberta Clipper pipeline, led to concerns from the National Wildlife Federation and other groups over the possible shipment of diluted bitumen from the Alberta oil sands through Line 5.[24] However, Enbridge has denied any plans to pump such materials. Line 5 ships nearly 23 million gallons of crude oil and petroleum products every day.[25] A 2011 toll agreement describes the materials as "condensate, light synthetic, sweet, light sour and NGL,"[4] as does a 2013 summary of the Mainline System.[1] Due to national security concerns, however, the Pipeline and Hazardous Materials Safety Administration does not divulge the materials actually carried on major US pipelines, including Line 5.[24]

Technicians preparing to remove a section of Enbridge pipeline

Public concerns have particularly focused on the risk of a spill under the Straits of Mackinac, and the difficulty of controlling any spill that might occur.[6][11] According to Enbridge, the pipes under the straits have never leaked, are continuously monitored, and are regularly inspected by underwater autonomous vehicles.[5][6] However, there have been numerous spills elsewhere in Michigan from Enbridge pipelines, including a major Line 5 spill at Crystal Falls in 1999, as well as the 2010 Kalamazoo River oil spill on Line 6.[6][24]

In 2014, it was found that Enbridge had failed to comply with the spacing requirement for supporting anchors for the pipeline; anchors should be placed at least every 75 feet.[26] In a statement, Michigan Attorney General Bill Schuette requested that Enbridge to comply with the safety regulations, "We will insist that Enbridge fully comply with the conditions of the Straits Pipeline Easement to protect our precious environmental and economic resources and limit the risk of disaster threatening our waters."[26]

By the end of 2015, eight Michigan counties or municipalities were calling for the retirement of Line 5 including Cheboygan, Cheboygan County, Emmet County, Genesee County, Mackinaw City, Mentor Township, Munising Township, and Wayne County.[27]

According to a 2016 study published by the University of Michigan, in partnership with the National Oceanic and Atmospheric Administration, a leak in Enbridge 5 near the Straits of Mackinac could affect roughly 700 miles of shoreline.[28] Key areas recognized for the highest potential risk include Mackinac Island, Bois Blanc Island, Mackinaw City, and areas on the northern shore and southern shore of the Straits with 3,528 square miles (15%) of Lake Michigan's open water and roughly 13,611 square miles (60%) of Lake Huron's open water possibly impacted by visible oil.[28][29] In addition, highly turbulent flowing currents found within the Straits of Mackinac, combined with the degrading enzymes secreted by zebra mussels, and aging pipe welds and coal tar enamel, increases the risk for corrosion and potential fissures to occur in the pipes.[30][31][28] Due to these issues, expert reports concluded that Line 5 should be shut down in the Straits pending a full review under state public trust law.[32] Although the U of M study showcased worst case scenarios, experts recommend completing a risk analysis that includes, "1) analysis of environmental impacts, 2) cleanup costs, 3) restoration and remediation measures, 4) a natural resource damage assessment, and 5) Economic damage to public and private sector interests."[28]

On April 15, 2022, the Wisconsin Department of Natural Resources (WDNR) closed the public comment period for its draft Environmental Impact Statement (EIS) after multiple extensions prompted by overwhelming numbers of public comments received.[33] The current working draft of the EIS was released by the WDNR on December 16, 2021.[34] The 369-page first volume of the document almost immediately drew sharp criticism from environmental advocates and tribal leadership of the Bad River Band of the Lake Superior Tribe of Chippewa Indians[35] whose land is intersected by the pipeline. The WDNR hosted a public hearing on February 2, 2022, that lasted nearly 10 hours and was host to a number of arguments over the environmental, economic, and public health ramifications of the project. Congressman Tom Tiffany spoke in favor of the pipeline expansion and former Bad River Band chairman Mike Wiggins Jr. was one of many speaking against it.[36]

In the course of the comment period, the DNR reportedly received over 32,000 comments.[34] Parallels have been drawn between this controversy and the similar controversy surrounding Enbridge's Line 3 pipeline in Minnesota.[36]

Bad River Band opposes Line 5 because of leak risks and expired easements.[37] Its Mashkiiziibii Natural Resources Department has responded to numerous threats posed by the pipeline and summarized key concerns (anomaly digs, two helicopter crashes on their land, pipeline exposure within the Denomie Creek subwatershed and odor investigations).[38]

In August 2022, the Canadian government again invoked a 1977 treaty with the United States in order to prevent the shutdown of the pipeline in Wisconsin, citing concerns about jobs, energy security, and the economy. Canada, which backs Enbridge, invoked the treaty for the first time in 2021 when the state of Michigan attempted to shut down Line 5 under the Straits of Mackinac due to environmental concerns.[37][22]

See also[edit]


  1. ^ a b c "Pipeline System Configuration: Quarter 1, 2013". Enbridge. 2013. p. 1. Archived from the original on March 31, 2014.
  2. ^ "2013 ENB Investment Community Booklet" (PDF). Enbridge. 2013. p. 25.
  3. ^ a b Enbridge Liquid Pipeline Map (PDF) (Map). Enbridge. 2012. Archived from the original (PDF) on November 11, 2014.
  4. ^ a b c d e f Enbridge Pipelines Inc. (July 1, 2011). "Competitive Toll Settlement" (PDF). p. 89. Archived from the original on September 24, 2015. Retrieved March 30, 2014.
  5. ^ a b "Line 5 Underwater Images". Enbridge. Archived from the original on March 31, 2014. Retrieved March 31, 2014.
  6. ^ a b c d e Flesher, John (March 3, 2014). "Submerged Enbridge Pipeline Under Michigan's Straits of Mackinac Raises Spill Fears". The Huffington Post. Associated Press. Archived from the original on April 7, 2014. Retrieved April 1, 2014.
  7. ^ a b Sherburne, Morgan (July 12, 2013). "Enbridge to Increase Oil Flow under Straits, Rally Planned". Petoskey News. Archived from the original on April 7, 2014. Retrieved March 31, 2014.
  8. ^ "Crude Oil Pipeline System". Sunoco. Archived from the original on January 6, 2014. Retrieved April 1, 2014.
  9. ^ Proposed Line 79 Pipeline Project (PDF) (Map). Enbridge. Archived (PDF) from the original on February 26, 2014. Retrieved April 1, 2014.
  10. ^ Simonson, Mike (January 25, 2013). "Bakken Boom Has Calumet Considering Building Oil Loading Dock in Superior". BusinessNorth. Archived from the original on April 7, 2014.
  11. ^ a b "Senators Stabenow and Levin Urge Transportation Department to Verify Safety of Enbridge Pipeline in Great Lakes" (Press release). Office of Debbie Stabenow. December 11, 2013. Archived from the original on March 28, 2014. Retrieved March 31, 2014.
  12. ^ Ellison, Garret (April 26, 2017). "Enbridge Line 5 has spilled at least 1.1M gallons in past 50 years". michiganlive. Retrieved August 3, 2022.
  13. ^ "Enbridge: Damaged oil pipeline was dented less than 1 inch". Associated Press. May 14, 2018. Archived from the original on May 21, 2018. Retrieved May 20, 2018.
  14. ^ Kransz, Michael (October 3, 2018). "Enbridge will pay for Line 5 tunnel in Straits of Mackinac, state says". MLive. Archived from the original on October 4, 2018. Retrieved October 5, 2018.
  15. ^ "Enbridge reports Straits crossing support issue on Line 5 to State of Michigan". www.enbridge.com. June 20, 2020. Retrieved August 3, 2022.
  16. ^ Golder, Ed (December 19, 2018). "Mackinac Straits Corridor Authority approves multi-use tunnel agreement". Michigan Department of Natural Resources. Archived from the original on December 21, 2018. Retrieved December 20, 2018.
  17. ^ a b "Enbridge's Line 5 Tunnel Receives Another Favorable Ruling". finance.yahoo.com. June 15, 2020. Retrieved August 3, 2022.
  18. ^ "Michigan sues to shut down Enbridge Line 5 pipeline in Great Lakes". Global News. June 27, 2019. Archived from the original on June 30, 2019. Retrieved June 30, 2019. Michigan's attorney general sued Thursday to shut down twin 66-year-old oil pipelines in the Great Lakes, saying they pose an "unacceptable risk" and the state cannot wait five to 10 years for Enbridge Inc. to build a tunnel to house replacement pipes running through the Straits of Mackinac.
  19. ^ "Michigan sues Enbridge to shut down Line 5 oil pipeline through Great Lakes". Financial Post. June 27, 2019. Archived from the original on June 30, 2019. Retrieved June 30, 2019. The location of the pipelines…combines great ecological sensitivity with exceptional vulnerability to anchor strikes," said Nessel in a statement. "This situation with Line 5 differs from other bodies of water where pipelines exist because the currents in the Straits of Mackinac are complex, variable, and remarkably fast and strong.
  20. ^ LeBlanc, Beth (June 27, 2019). "Nessel to court: Shut down Line 5 as environmental risk". The Detroit News. Archived from the original on February 28, 2021. Retrieved May 15, 2021.
  21. ^ a b "Canada asks U.S. court to prevent Michigan from shutting down Line 5 pipeline". CBC News. May 11, 2021. Archived from the original on May 14, 2021. Retrieved May 15, 2021.
  22. ^ a b "White House: U.S. is not considering shutting down Enbridge's Line 5 pipeline". Reuters. November 9, 2021. Retrieved October 7, 2022.
  23. ^ McWhirter, Sheri (July 15, 2022). "Tribal challenge to Line 5 tunnel permit reinstated by oversight panel". michigan live. Retrieved August 3, 2022.
  24. ^ a b c Leahy, Derek (March 6, 2014). "Concerns Mount About 61-Year Old Enbridge Pipeline in the Great Lakes". The Narwhal. Archived from the original on August 10, 2018. Retrieved October 30, 2018.
  25. ^ Ellison, Garret (October 22, 2014). "Environmental concerns trip up Enbridge oil pipeline project in Ontario". MLive. Archived from the original on August 10, 2018. Retrieved August 10, 2018.
  26. ^ a b Klug, Fritz (July 24, 2014). "Enbridge pipeline in Straits of Mackinac needs more supports, Attorney General says". MLive. Archived from the original on November 10, 2017. Retrieved November 8, 2017.
  27. ^ Oil & Water Don't Mix (2015) "Local governments are issuing resolutions calling for the shutdown of the flow of oil in Line 5 at the Straits of Mackinac Archived January 8, 2016, at the Wayback Machine"
  28. ^ a b c d Schwab, David (March 2016). "Statistical Analysis of Straits of Mackinac Line 5 Worst Case Spill Scenarios" (PDF). Graham Sustainability Institute at University of Michigan. Archived (PDF) from the original on June 22, 2016. Retrieved November 8, 2017.
  29. ^ Erickson, Jim (March 31, 2016). "More than 700 miles of Great Lakes shoreline potentially vulnerable to Straits of Mackinac oil spills". University of Michigan News. Archived from the original on September 19, 2017. Retrieved November 8, 2017.
  30. ^ "Status and Strategy for Zebra and Quagga Mussel Management". Michigan.gov. Archived from the original on November 9, 2017. Retrieved November 8, 2017.
  31. ^ Lachman, Samantha (May 22, 2016). "This Aging Oil Pipeline Is In Great Lakes' 'Worst Possible Place' For A Spill". Huffpost. Archived from the original on September 20, 2017. Retrieved November 8, 2017.
  32. ^ "Experts Recommend Shutting Down Mackinac Straits Oil Lines". Graham Sustainability Institute News (published December 4, 2015). January 6, 2016. Archived from the original on July 3, 2017. Retrieved November 8, 2017.
  33. ^ "DNR Extends Public Comment Period For Draft Environmental Impact Statement On Proposed Enbridge Pipeline Relocation". Wisconsin Citizens Media Cooperative. March 16, 2022. Retrieved September 13, 2022.
  34. ^ a b "Enbridge Pipeline Projects in Wisconsin". dnr.wisconsin.gov. Retrieved September 13, 2022.
  35. ^ Kaeding, Danielle (December 20, 2021). "Intertribal agency raises concerns with state's draft review of a proposed oil pipeline reroute". Wisconsin Public Radio. Retrieved September 13, 2022.
  36. ^ a b Holmes, Isiah (February 4, 2022). "Enbridge Line 5 spurs 10 hour hearing, over 140 people speak against pipeline". Wisconsin Examiner. Retrieved September 13, 2022.
  37. ^ a b Shakil, Ismail (August 30, 2022). "Canada invokes pipeline treaty with U.S. over Wisconsin Line 5 dispute". Reuters. Retrieved October 7, 2022.
  38. ^ "Enbridge Line 5 Issues Within the Bad River Reservation" (PDF). Mashkiiziibii Natural Resources Department. February 2020. p. 6.

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