A Minnesota Indigenous environmental group told state utility regulators Tuesday that Enbridge has been adding considerable capacity to its existing oil pipelines in recent years, making the company’s controversial new $2.6 billion pipeline unnecessary.

Honor the Earth, in a filing, asked the Minnesota Public Utilities Commission to investigate Enbridge’s capacity additions, saying the company made no mention of such moves during extensive hearings for the pipeline, a replacement for its deteriorating Line 3.

“It is difficult to see how (the new Line 3) is in the public interest in light of the apparent fact that Enbridge has already achieved (the pipeline’s) capacity addition goals through other less impactful means,” Honor the Earth said in a PUC filing.

Calgary-based Enbridge has been adding capacity to its “mainline” across Minnesota through various efficiency improvements.

“There have been several initiatives that Enbridge has implemented in recent years to optimize its pipeline network to better meet customer demands,” the company said in a statement. “We’ve talked about these optimizations and efficiency-led capacity increases in a variety of public forums.”

Tuesday’s PUC filing is the latest missive in the six-year battle over the new pipeline. The existing Line 3 is corroding and operating at only 51% of capacity.

The PUC reapproved the $2.6 billion new Line 3 earlier this year, though Enbridge is still waiting on several other state and federal permits. A new Line 3 would add 375,000 barrels per day to Enbridge’s Minnesota oil flow.

Before economic effects of the coronavirus pandemic shrunk oil demand earlier this year, the mainline was pumping 2.8 million barrels per day.

The mainline’s volume is now down to just over 2.4 million barrels per day, about what was considered capacity during PUC hearings a few years ago over the new pipeline.

Honor the Earth claims in its filing that Enbridge did not disclose to the PUC the roughly 400,000 barrels per day in capacity additions to the PUC.

Enbridge said in its statement that the company has been “transparent” throughout the Line 3 review process.

Honor the Earth in its filing also lodged a complaint about capacity expansion proposals on two of the six pipelines that currently run across northern Minnesota to the company’s terminal in Superior, Wis.

Those proposals, for Line 4 and Line 67, are currently under review by Wisconsin natural resource regulators.

Enbridge filings in Wisconsin indicate the company plans on boosting the two pipelines’ throughput to “maximum design capacity,” adding another 178,400 barrels per day in oil flowing across Minnesota to Superior.

Honor the Earth in its complaint says Line 4 and Line 67 should be recertified in Minnesota if they are expanded.

Enbridge says the new Line 3 project would be a major safety improvement. Environmental and Ojibwe groups, including Honor the Earth, say new Line 3 — which would run partly on a new corridor — would open up more Minnesota waters to oil spill damage.