A proposal requiring pipeline operators to report spills within an hour of their discovery will help mitigate damage, the U.S. transportation secretary said.

The Department of Transportation's Pipeline and Hazardous Materials Safety Administration is proposing a mandate that would require pipeline operators to issue spill notifications no later than one hour after a confirmed release.

"We constantly seek to raise the bar on safety," Transportation Secretary Anthony Foxx said in a statement. "This proposed rule will improve safety in a number of ways, including a notification time limit which eliminates any ambiguity about timeliness in reporting and is crucial to the ability to mitigate damage and protect people, property and the environment following an incident."

Existing federal regulations only advise operators to issue notifications at the earliest practicable opportunity, which the government estimates at between one and two hours after a confirmed release.

A pipeline operated by Plains All American leaked as much as 2,500 barrels of oil in Santa Barbara County in mid-May. The company said it notified federal authorities one hour and one minute after shutting down pumps controlling the pipeline May 19.

According to an account from the National Transportation Safety Board, Enbridge took 17 hours to recognize a leak on Line 6b in southern Michigan in 2010. The leak was among the largest ever inland spills in U.S. history.

Enbridge and the state of Michigan filed a settlement in a county court in May that requires the company to monitor the environmental impacts of the spill and spend as much as $75 million in restoration and remediation work in and around the Kalamazoo River.

The Department of Transportation submitted the proposal in the Federal Register. A public comment period expires in 60 days.