The department says the alleged violations, which occurred between March 30 and Sept. 21, include breaches of permit conditions and state laws governing water quality, wetlands, navigable waterways, air quality, stormwater and endangered resources. The notice also alleges the company constructed an unpermitted bypass around the spill site following the August accident.

The agency, which has scheduled an enforcement conference with Enbridge to discuss the allegations, says it could issue citations or refer the case to the Wisconsin Dept. of Justice that could seek financial penalties and other court-ordered remedies.

The department says it continues to review alleged incidents that occurred after Sept. 21 and could pursue added enforcement action. Spokesperson Molly Meister said in an email that the agency is monitoring a surface groundwater release that emerged in late September under the Marengo River during installation of a section of new pipeline through a recently completed borehole.

It is not yet known if the groundwater release, also in Ashland County, was caused by an aquifer breach by Enbridge. She said pipeline installation operations at the release site are complete and measures are in place to contain the flow of groundwater. 

In the Aug. 25 accident that caused the natural gas spill, an unoccupied parked third-party-owned semi-truck delivering equipment rolled into an excavation site on the east side of the pipeline, striking a bypass valve that Enbridge was adding to connect the existing pipeline to a line under construction.

Enbridge spokesperson Juli Kellner said the company has received the notice and is reviewing it. She added the company “has worked closely with the [state natural resources department] through the [Line 5 reroute project] permitting process and construction ... as well as with the response to the line strike incident.”

Enbridge is constructing a 41-mile pipeline to avoid tribal lands while continuing to operate a disputed 12-mile pipeline segment on reservation land owned by the Bad River Band of Lake Superior Chippewa. That segment is the subject of legal proceedings seeking its removal. Line 5 is part of a pipeline network that transports oil and gas from Canada to the U.S.

The existing pipeline was shut down for about 10 days in August and early September as Enbridge built a bypass around the damaged section.

A fire was reported at about 5:20 a.m. Oct. 13 at the pipeline construction site in White River, Wis., also in Ashland County. It involved an equipment trailer and two boring machines. No one was injured, and the cause and origin are under investigation, according to the Ashland County Sheriff's Office. 

The fire is the third involving Enbridge facilities in recent weeks. The Federal Bureau of Investigation is leading an investigation into two allegedly suspicious fires that occurred in mid-September—one involving an equipment trailer and two boring machines at a different drilling site in Ashland County and another at a company office in Superior, Wis.

Kellner said graffiti was found on the site of the third fire but did not identify what it said or depicted, condemning the fires as “neither legal nor peaceful.”

She said: “Illegal and unsafe acts by criminal saboteurs endanger themselves, the local community, first responders and our workers. We take these incidents very seriously and will seek prosecution of those individuals involved to the fullest extent of the law." 

The Ashland County Sheriff's Office has submitted bills totaling $234,726 for law enforcement coverage related to calls at Enbridge Line 5 pipeline reroute locations, according to a local news report.