Federal Data Expose Enbridge Leak as Wisconsin’s Largest Reported Oil and Gas Spill

An Enbridge pipeline leak in northern Wisconsin has emerged as the largest reported oil and gas spill in the state in more than half a century, according to a Wisconsin Public Radio review of federal records. The incident has intensified scrutiny of Line 5 and the company’s billion dollar reroute project.

The Aug. 25 leak in Iron County released about 31,000 barrels, equal to roughly 1.3 million gallons, of natural gas liquids. Line 5 remains shut down as investigators examine the damaged section and Enbridge works toward restoring service.

Wisconsin Public Radio analyzed hazardous liquid accident reports submitted to the federal Pipeline and Hazardous Materials Safety Administration. The review also included records filed since 1970 by Enbridge and its predecessor, Lakehead Pipe Line Company.

Federal data indicate that the Iron County incident is the largest release Enbridge has reported to federal pipeline regulators in Wisconsin. The records cover pipeline facilities that transport hazardous liquids, including crude oil and natural gas liquids.

Enbridge said the leak occurred after an unoccupied flatbed truck belonging to a subcontractor rolled into an open excavation for a Line 5 valve project. The truck struck the pipeline, releasing material composed mainly of propane and butane into the atmosphere.

“The vast majority of the remaining two thousand barrels of liquid initially contained within the excavation site, have now also vaporized and dispersed. Today crews continue working on removing the remaining liquid from the trench,” Enbridge spokesperson Juli Kellner said in a statement.

Environmental organizations are pressing the Wisconsin Department of Natural Resources to take a stronger role in the response. Their demands include an independent investigation, broader environmental monitoring and the revocation of permits for the Line 5 reroute.

“The number of issues have now started to add up to a point where it’s problematic and concerning about what are other issues that are going to happen as they continue construction, both at the valve site where they had the leak and the other areas as well as on the reroute itself,” Clean Wisconsin senior staff attorney Evan Feinauer told Wisconsin Public Radio.

Nine groups, including the National Wildlife Federation, sent a letter to Gov. Tony Evers, the DNR and other state agencies seeking permit revocation. “We call on Governor Evers to use the authority he already has,” the letter states.

The governor’s office referred questions to the DNR, which did not immediately respond. Advocates also want the National Transportation Safety Board involved instead of leaving the investigation solely to Enbridge and the federal pipeline safety regulator.

The federal regulator has issued a corrective action order requiring Enbridge to send the failed pipe section to an independent laboratory for mechanical and metallurgical testing. The company must also provide an independent analysis of the failure and determine whether similar conditions exist elsewhere along Line 5.

A National Transportation Safety Board spokesperson said the agency does not appear to be investigating the incident, noting that it does not examine every pipeline leak or explosion. That absence has sharpened calls for Wisconsin agencies to participate directly in air, surface water and groundwater monitoring.

Enbridge said monitoring and soil management plans are in place, including procedures for testing and proper disposal. The company reported no detected impacts in nearby surface water or a residential well, while monitoring wells have been installed and air quality outside the evacuation zone has remained within safe levels.

DNR Secretary Karen Hyun told Wisconsin Public Radio and PBS Wisconsin that the agency had not received permission from the federal regulator to enter the site because of safety concerns. National Wildlife Federation official Beth Wallace called that situation “unheard of” and warned against sidelining state oversight.

“We have major concerns that there may be an effort to preempt state oversight in this moment, and spill response absolutely requires state authorities to be part of the unified command,” Wallace told Wisconsin Public Radio. She also questioned what emergency approvals were granted for Enbridge’s planned 1,500 foot temporary bypass.

The company aims to use the bypass to restore Line 5 service by Sept. 12, but advocates argue the pipeline should remain shut until the investigation is complete. Their concerns have grown after at least five drilling fluid releases occurred during construction of the reroute.

A Sept. 2 drilling incident released about 100 gallons while crews worked beneath the Potato River, according to the Milwaukee Journal Sentinel. Similar drilling activity spilled as much as 1,900 gallons in late June.

Line 5 normally transports up to 23 million gallons of crude oil and natural gas liquids each day between Superior and Sarnia, Ontario. Enbridge is constructing a new 41 mile segment around the Bad River Band of Lake Superior Chippewa reservation.

The reroute follows years of legal conflict over pipeline easements on tribal land. A federal appeals panel ruled in August that Enbridge was trespassing and must remove Line 5 from the reservation, while granting additional time to finish the reroute.

Enbridge has completed about two thirds of the project, which employs roughly 700 workers. The record setting leak now places the company’s construction practices, emergency response and regulatory permissions under even harsher examination.