The controversial project is complete, Enbridge says.
The pipeline company breached a groundwater aquifer, causing water to flow uncontrolled into a trench.
The senator was quickly ushered away from the scene.
Walz left the Alexandria fundraising event early.
This coincided with a demonstration at the state capitol.
A group of demonstrators remained on the grounds after the event permit expired.
The security fence is back up.
He gave them back "as an act of desperation, and because I saw no other way to help bring the necessary urgency and attention to this matter."
The MPCA previously reported nine drilling fluid releases.
That includes at least one fluid release into wetlands, which is a violation.
The dispute is over a local property used by protesters.
The ongoing drought has led to worryingly low stream flow levels in some areas.
The spill happened July 6 during a drilling procedure.
Officials used rotor downwash in an attempt to clear Line 3 protesters.
People from Minnesota and out of state were among those arrested last week.
The protests were the latest in a series of demonstrations against the pipeline.
Construction on the Minnesota portion of the pipeline began in December.
It happened Friday afternoon in Carlton County.
It happened in Hubbard County, northwestern Minnesota.
The protests in Carlton County are just the latest in demonstrations against the project.
The project has attracted criticism from environmental and tribal groups.
"We cannot continue to legitimize and provide cover for the MPCA's war on black and brown people," their resignation letter states.
Honor the Earth filed the petition with the Minnesota Public Utilities Commission Tuesday.