Contaminated soil removed from spill site on Enbridge’s Line 5 in northern Wisconsin

Enbridge crews have been removing contaminated soil at the site of a gas leak on the company’s Line 5 oil and gas pipeline in northern Wisconsin. The Aug. 25 leak occurred as the company has been building a new 41-mile segment of Line 5 around the Bad River Band of Lake Superior Chippewa’s reservation in Ashland and Iron counties. A subcontractor’s unoccupied flatbed truck rolled into an open construction trench in the town of Saxon, striking the pipeline. More than 1.3 million gallons of natural gas liquids were released into the air, and federal data shows it’s state’s largest oil and gas pipeline spill in over 50 years. The company has been sampling and excavating soil to remove contaminated material, said Christine Sieger, remediation and redevelopment director with the Wisconsin Department of Natural Resources. “If those samples come back with exceedances, then they’re continuing to scrape and excavate to move more of that contaminated material off-site,” Sieger said. “They have assured us that they will excavate and remove anything that exceeds a state standard.” Enbridge spokesperson Juli Kellner said work is still underway. “Environmental monitoring remains ongoing. No ground water impacts have been detected in samples,” Kellner wrote. GEI Consultants, an engineering and environmental consulting firm, submitted a report on behalf of Enbridge stating that initial sampling shows no impacts to surface water, private wells or groundwater outside the site’s safety perimeter. About 4,275 tons of contaminated soil and debris were removed from the site last month. The material was disposed of at Waste Management’s Timberline Trail Landfill in Weyerhaeuser. About 4,500 gallons of water mixed with firefighting foam that does not include PFAS has also been disposed of at the Reworld Fox Valley/Oshkosh Material Processing Facility in Winneconne. Soil sampling has detected volatile organic compounds, or VOCs, and polycyclic aromatic hydrocarbons, or PAHs, that are related to petroleum products at the site. Initial testing also found benzene above the state’s residual contaminant levels that aim to protect groundwater from contaminants that may move through soil. A temporary monitoring well also exceeded groundwater standards for benzene. Sieger said Enbridge would be taking action with respect to elevated levels. She stressed the company’s work is only just beginning. “When they’re done with this excavation, they will still be required to complete a full site investigation, and that site investigation will look at groundwater, surface water, potentially sediment,” Sieger said. “It’ll look at how the contamination was transported from the spill site.” Sieger said the company has submitted plans to backfill the site with crushed rock that will be topped with soil. The DNR is seeking input on Enbridge’s plans from 11 federally recognized tribes in Wisconsin in addition to the Brothertown Indian Nation and Great Lakes Indian Fish and Wildlife Commission. While Enbridge is continuing to excavate, Sieger said the agency’s goal is that the company would backfill affected areas by the end of the year. Enbridge says it’s addressing concerns on the Line 5 project Last month, the DNR issued a notice of violation against Enbridge for alleged violations of the state’s environmental laws tied to the spill and work on the Line 5 reroute, including construction of a temporary bypass in September without state approvals. The agency had set an enforcement conference with Enbridge for Oct. 26. A DNR spokesperson said the agency is still considering options for enforcement. Kellner said it takes the agency’s concerns seriously and added all of them have either been mitigated or are in the process of being addressed. She said work is also ongoing to meet terms of a corrective action order issued by the federal Pipeline and Hazardous Materials Safety Administration. Understanding Wisconsin, Together. WPR’s “Wisconsin Today” newsletter keeps you connected to the state you love without feeling overwhelmed. No paywall. No agenda. No corporate filter. LinkedIn This field is for validation purposes and should be left unchanged. Email Subscribe Work continues to address groundwater release Work is also ongoing to address groundwater released as part of installing pipe directly underneath the Marengo River. “Groundwater flow at the Marengo River work site has decreased significantly to a very low level as the bore hole continues to seal naturally. There have been no measurable environmental impacts to the Marengo River,” Kellner said. A DNR spokesperson confirmed groundwater flows have decreased to roughly half a gallon per minute. The agency has said it’s unknown whether an aquifer breach occurred. “Three monitoring wells have been installed along the length of the pipe in an attempt to help understand the source of the release,” an agency spokesperson said. Line 5 carries up to 23 million gallons of oil daily from Superior to Sarnia, Ontario. Work on Enbridge’s project to reroute the pipeline is now more 90 percent complete, employing over 600 workers. Kellner said the project is set to wrap up in the first few months of next year. Wisconsin Public Radio, © Copyright 2026, Board of Regents of the University of Wisconsin System and Wisconsin Educational Communications Board. Related Stories Enbridge says another fire destroys drill rig on Line 5 project in northern Wisconsin Wisconsin DNR says it’s still evaluating whether aquifer breach occurred on Line 5 Enbridge estimates gas leak on Line 5 in northern Wisconsin will cost $15M FBI leads probe into fire at Enbridge drill site on Line 5 reroute in northern Wisconsin Federal data shows Enbridge leak is the largest reported oil and gas spill in Wisconsin