A long-delayed Enbridge Inc. pipeline extending from Canada’s oil sands to the U.S. Midwest will enter service Friday after years of opposition from environmentalists and indigenous groups.  

The company said its Line 3 replacement project, which will nearly double the capacity of the older line, is substantially completed. Enbridge will begin filling the line with crude Friday. Once that that’s done, oil should begin to move to U.S. refineries. The pipeline is expected to be fully operational in mid-October, Jesse Semko, Enbridge spokesperson, said by email.

Canada’s oil-sands producers have struggled with a shortage of export pipelines as fossil-fuel proposals face increasing scrutiny. U.S. President Joe Biden, on his first day in office, rescinded a permit for TC Energy Corp.’s Keystone XL project, which would have helped increase shipments of Canadian crude to the U.S. Gulf Coast. 

The start of Line 3, which can carry 760,000 barrels a day of crude from Alberta to Wisconsin, is happening after Enbridge fought court and regulatory battles for years, delaying construction multiple times. The pipeline was fiercely opposed by many environmentalists and indigenous groups, who argued the pipeline would sully waterways and contribute to climate change. 

The pipeline continues to face legal challenges, including a case filed in tribal court over a Minnesota water permit issued to Enbridge and a U.S. federal court challenge to the U.S. Army Corps of Engineers water permit. 

“A victory for pipeline opponents in this case could send the Corps back to the drawing board on its environmental review and shut down operation of the pipeline in the meantime,” Gabby Brown, Sierra Club spokeswoman, said in a release. Enbridge doesn’t expect such an outcome as the project has “passed every test so far,” Enbridge’s Semko said. 

Protesters had urged Biden to stop Line 3. In June, groups of anti-Line 3 protesters clashed with law enforcement along the construction route, resulting in hundreds of arrests.

The start of the first new cross-border Canadian oil export pipeline built in years is poised to help alleviate a shortage of export conduits that depressed prices for Canadian crude oil and prompted some producers to ship oil to U.S. refineries on rail cars.