March 9 (UPI) — An expansion to a Minnesota oil pipeline poses a direct threat to water supplies in the region, conservationists and tribal groups told the State Department.

Hundreds of activists turned out for the only public vetting of the State Department’s draft environmental report on plans to expand the Alberta Clipper oil pipeline through the state. Canadian pipeline company Enbridge aims to double the pipeline’s capacity to around 800,000 barrels per day of heavier tar sands through the route.

Opponents of the pipeline said the expansion would undermine federal treaty obligations and pose a threat to the regional Great Lakes. Irene Folstrom, the regional coordinator for the Minnesota Environment Partnership, said communities in the north of the state, where the pipeline runs, have the most to lose.

“Pipelines leak, and when this pipeline leaks it will go directly into our water supply and impact our health and way of life,” she said in an emailed statement.

Line 6b of a larger Enbridge network leaked in southern Michigan in 2010 in what was one of the worst inland oil spills in U.S. history. The heavier nature of the oil running through Enbridge pipelines in the area makes remediation difficult.

Enbridge has faced continued scrutiny over its safety record in the region. A “pinhole” leak was discovered in late 2014 on an Enbridge pipeline in Michigan’s Upper Peninsula, though no spill was associated with the incident.

The row over the Enbridge pipeline expansion through Minnesota follows steady losses for opponents of the Dakota Access oil pipeline. A federal judge ruled Tuesday against the Cheyenne River Sioux and Standing Rock Sioux, who were challenging the permit process for a pipeline at the center of the U.S. energy debate for more than a year.

Winona LaDuke, executive director of advocacy group Honor the Earth, said U.S. Secretary of State Rex Tillerson, whose department is charged with vetting cross-border pipelines, has yet to hear the full voice of opposition.

“What he may not realize is that Standing Rock has sparked a historic resurgence of Indigenous Nations, and that we, as water protectors, are bringing that energy to the Great Lakes,” she said.