TRAVERSE CITY, Mich. (AP) -- Michigan's attorney general and chief environmental regulator have asked the company that owns two oil pipelines stretched beneath an ecologically sensitive area of the Great Lakes for evidence that the 61-year-old lines are properly maintained and in good condition.
Attorney General Bill Schuette and Dan Wyant, director of the state Department of Environmental Quality, posed a lengthy series of questions and requested stacks of documentation in a letter sent Tuesday to Enbridge Inc. and made public Wednesday. They said the pipelines, which run beneath the Straits of Mackinac -- the waterway linking Lakes Huron and Michigan -- pose a unique safety risk.
"Because of where they are, any failure will have exceptional, indeed catastrophic effects," their letter said. "And because the magnitude of the resulting harm is so great, there is no margin for error. It is imperative we pursue a proactive, comprehensive approach to ensure this risk is minimized, and work together to prevent tragedy before it strikes."
Larry Springer, a spokesman for Enbridge, said Wednesday that officials with the Canadian company based in Calgary, Alberta, had met with Schuette in Lansing on April 10 and had "shared informally" much of the information sought in the letter. Enbridge will review the letter and "determine if there is any further information that we can provide concerning the safe operations" of the pipelines, which Springer said were "rigorously maintained beyond regulatory requirements."
The pipelines transport "petroleum products that are refined into propane, gasoline, and diesel fuels that are vital to all who live and work in Michigan communities," he said.
Schuette and Wyant joined a rising tide of criticism about the Straits of Mackinac pipelines that began after the rupture of another Enbridge line in 2010 that spilled more than 843,000 gallons of crude into the Kalamazoo River and a tributary creek in southwestern Michigan. The cleanup is mostly complete, although Enbridge is still working to remove oil from the river bottom.
The letter added bipartisan flavor to the official expressions of concern. Schuette is a Republican and Wyant is an appointee of Republican Gov. Rick Snyder. In December, three Democratic U.S. senators -- Carl Levin and Debbie Stabenow of Michigan and Richard Durbin of Illinois -- sent a letter to the U.S. Pipeline and Hazardous Materials Safety Administration about the Mackinac lines in northern Michigan.
"This demonstrates once more that the Great Lakes are not a partisan issue," said Andy Buchsbaum, director of the National Wildlife Federation's Great Lakes office. "It's gratifying to see the state of Michigan take the lead in seeking this information because they're the ones that are going to pay the most if there's an oil spill."
A community meeting in March hosted by Mackinac County's planning commissioner drew a standing-room-only crowd. Last summer, hundreds of activists attended a protest rally.
The two 20-inch pipes are part of Enbridge's 1,900-mile Lakehead network, which originates in North Dakota near the Canadian border. A segment known as Line 5 slices through northern Wisconsin and Michigan's Upper Peninsula before ducking beneath the Straits of Mackinac and winding up in Sarnia, Ontario. It carries nearly 23 million gallons of oil daily.
The single-walled underwater pipes extend more than 3½ miles beneath the straits. They were laid in 1953 and have never been replaced, Schuette and Wyant said. They added that in the event of a spill, the area's strong currents would quickly spread oil into Lakes Michigan and Huron, doing "grave environmental and economic harm."
Popular with tourists, the straits area features the Mackinac Bridge linking Michigan's lower and upper peninsulas and Mackinac Island, a resort destination famed for its horse-drawn carriages and fudge shops.
"Efforts to contain and clean up leaks in this area would be extraordinarily difficult, especially if they occurred in winter or other severe weather conditions that commonly occur at the straits," Schuette and Wyant said, noting that the waterway's surface was still solid after this year's deep freeze.
Schuette spokeswoman Joy Yearout said the officials were not requesting specific actions such as replacing the pipelines, as some environmentalists have demanded.
"We're not ready to make that determination until we see their response to our request for information," Yearout said.
Among the requested paperwork were documents about the lines' construction, modification, estimated "useful life" and potential replacement. The officials also asked about current and potential uses for the lines, including whether they will ever carry "diluted bitumen" oil from Canada's tar sands region, the heavy crude that spilled into the Kalamazoo River. Enbridge says only light crude presently moves through the straits lines.