An aging pipeline that passes through a critical stretch of the Great Lakes region has had at least 29 leaks in its 64-year history—spilling more than 1 million gallons of oil and gas liquids, according to information released this week based on federal data.

The spills along Line 5, which range from 285,600 gallons to 8 gallons and span the years 1968 to 2015, illustrate a steady drumbeat of incidents. Environmentalists and a tribe that lives along the line say this checkered past lends credibility to the fear that accidents do happen—and that should an oil spill happen in the wrong place, it could result in catastrophe.

Line 5 carries as much as 540,000 barrels of fossil fuels each day from Superior, Wisconsin, through Michigan to Sarnia, Ontario, and is owned by Canadian pipeline giant Enbridge. It passes under the Straits of Mackinac, where Lake Michigan and Lake Huron meet, which has provoked concerns that if the pipeline were to leak, it could contaminate the Great Lakes. Just last month, Enbridge acknowledged that the outer casing of underwater pipeline in that area had fallen off in 18 places.

“There’s mounting evidence for serious concern for the Great Lakes,” said Mike Shriberg, the executive director of the Great Lakes Region of the National Wildlife Federation, which released the data on Line 5. “The Great Lakes provide water for 40 million people. They are critical to the economy…This is a potentially high-consequence situation here, and what we’re finding—and this is just the newest piece of it—is that there’s increasing cause for concern.”

The data about the pipeline’s spills was pulled from the federal Pipeline and Hazardous Materials Safety Administration, which regulates pipelines.

Enbridge spokesman Michael Barnes took issue with the National Wildlife Federation’s assessment of Line 5’s leak history, stating that the line has had just three leaks in the last 15 years, which spilled 21 barrels of oil (or 882 gallons), all of which was recovered. However, he acknowledged that during that same period, Line 5 had 11 incidents of product released at Enbridge facilities, like metering and pump stations. He said the majority of what was spilled was recovered, though did not specify how much.

The National Wildlife Federation appears to count all 14 incidents as spills, resulting in a total of 654 barrels (or 27,468 gallons).

Enbridge has been facing political pressure over Line 5. In January, the Bad River Band of the Lake Superior Tribe of Chippewa Indians voted not to renew easements that allowed the pipeline to pass through tribal lands in northern Wisconsin. The easements expired in 2013 and are typically needed for pipelines on native land.

Robert Blanchard, chairman of the Bad River Band, said that he hadn’t known there were so many spills along Line 5, but that he wasn’t surprised. “A line that’s 64 years old, you’re going to have some questions about that. Is it really as good as they say it is? I don’t think so.”

Blanchard said they have no intention of renewing the easement, and that they may end up in court defending their right to do so.

At the same time, state and national officials are pushing legislation to either shut the line down or review whether it is safe enough to continue operating.

On Jan. 12, U.S. Reps. Dave Trott (R-Mich.) and Debbie Dingell (D-Mich.) introduced legislation calling for a shutdown of the pipeline if a federal study determines it poses significant threat to the Great Lakes.

“This new data raises significant concerns about the integrity of Line 5 and the safety of the Great Lakes water supply, our economy and way of life,” Dingell said in an emailed statement to ICN. “A spill in this area would pose a serious threat to the entire Great Lakes region.”

The legislation has been referred to the Energy and Commerce Committee, which Dingell is a member of, and the Transportation and Infrastructure Committee.

At the state level, Republican Sen. Rick Jones introduced legislation in late March to shut down the line.

While politicians from both sides of the aisle raise questions about the pipeline’s safety and its potential threat to the Great Lakes, the Trump administration has moved in a different direction. In an executive order issued on Jan. 24, President Trump ordered an expedited approval process for high priority infrastructure projects—including pipelines. And the administration’s proposed budget would eliminate funding for the Great Lakes Restoration Initiative, a program that directs funds to various state and local environmental projects to protect and restore the lakes.

At a Michigan Pipeline Safety Advisory Board meeting on March 13, Enbridge acknowledged that where the pipeline crosses under the Straits of Mackinac, there are 18 points that have “delaminated,” meaning an outer casing has fallen off. The company said the pipeline is still functioning safely, and there are no locations where bare pipeline is exposed.

“Right now we are focused on several large safety projects scheduled for this summer,” said Barnes, the Enbridge spokesman. “We will be conducting a hydrotest on Line 5 in the Straits, installing additional anchor supports, and completing a study of the Line 5 coating.”

Under a settlement between the Environmental Protection Agency and Enbridge over its pipeline spill in Michigan in 2010, Enbridge must spend $110 million on

safety upgrades across its North American pipeline network, including on Line 5. The Grand Traverse Band of Ottawa and Chippewa Indians in Michigan is challenging that deal.

Carl Weimer, the executive director of the Pipeline Safety Trust, said that the map released by the National Wildlife Federation shows that concerns about pipeline safety and Line 5 should extend beyond the most obviously sensitive areas. “It’s not only where it crosses the Straits,” he said. “There are other concerns.” The spills on the map are found along the entire path of the pipeline.

He also noted that the majority of the spills had been identified by local workers or the public, not by a detection system.

Weimer took heart in one aspect of the data, though. “It appears the size of the spills has decreased dramatically since the late ‘60s, early ‘70s,” he said. “That is what we would hope to see as basic regulations, more inspection requirements, and better materials and technology are employed.”