Canadian pipeline giant Enbridge Inc. has been dealt another setback on its Line 5 replacement project in Michigan.

The company said Thursday it was "disappointed" by news that the timeline of a U.S. federal review of Enbridge's proposed $500-million Great Lakes tunnel project has been pushed back by more than a year.

The U.S. Army Corps of Engineers (USACE) said Thursday it now expects to complete its draft environmental impact statement for Enbridge's Line 5 tunnel permit application in spring 2025, rather than late 2023 as earlier indicated.

In an emailed statement, Enbridge spokesman Ryan Duffy said the USACE's decision to extend the permitting process further delays the replacement of the dual pipelines in Michigan's Straits of Mackinac, and will essentially push the start of construction until at least 2026. 

"While we are supportive of a thorough, comprehensive and carefully considered permitting process that ensures adequate opportunity for review and comment, we are disappointed with the extended timeline for a project of this scope," Duffy said.

He added Enbridge first submitted its application for the Great Lakes tunnel project in April 2020. 

"As such, the USACE is estimating it will need six years to review and issue a decision for the project," Duffy said.

Enbridge's Great Lakes tunnel project is intended to house a replacement segment of its existing Line 5 oil pipeline that crosses the bottom of the straits connecting Lake Huron and Lake Michigan.

The company said the tunnel will be bored through rock, as much as 100 feet below the lakebed, to "virtually eliminate" the chance of a pipeline spill affecting the Great Lakes.

It also said the project would cover only 6.4 km in length, require no construction within the waters of the straits, and is anticipated to impact less than one-quarter acre of wetlands. 

However, the USACE revised its timeframe for the environmental review after receiving more than 17,000 public comments during its initial "scoping period."

“We greatly appreciate the meaningful input received throughout scoping and will use this information to shape studies and continuing consultations throughout development of our draft environmental impact statement.” said USACE Detroit District Commander Lt. Col. Brett Boyle in a news release.

The development comes as yet another blow for Enbridge's embattled Line 5 pipeline in Michigan. The pipeline — which transports up to 540,000 barrels per day of light crude oil, synthetic crude and natural gas liquids to be refined into propane — was built in 1953 and supplies 55 per cent of the state's propane needs.

But in recent years, it has become a flashpoint for environmentalists and U.S. opponents of the fossil fuel sector. 

The state of Michigan itself has been in court for years with Enbridge in an effort to shut down Line 5, fearing a disaster in the Straits of Mackinac, the ecologically sensitive region where the pipeline crosses the Great Lakes.