Michigan regulators agreed last week to allow Canadian pipeline operator Enbridge Inc. to replace a 160-mile segment of an aging line that in 2010 spilled more than a million gallons of crude oil.

The decision by the Michigan Public Service Commission disappointed local landowners who had hoped for more scrutiny and oversight of the project.

"I am concerned with the haste with which this project has proceeded," said Jeff Insko, an English professor at Michigan's Oakland University who started the Line 6B Citizens' Blog for concerned landowners. "It's been fast-tracked both by Enbridge and the regulatory body here in Michigan. And given Enbridge's history in our state, it seems to me prudence and caution ought to guide us, and they haven't."

The 2010 spill from Line 6B contaminated 36 miles of the Kalamazoo River and has been difficult to clean up. The U.S. Environmental Protection Agency recently asked Enbridge to remove submerged oil from several miles of the riverbed, a task that Enbridge is resisting. The price tag for the cleanup has already reached $810 million, making it the most expensive oil pipeline spill in U.S. history.

2/5/13: This story has been updated to include information from PHMSA received after publication.

Oil and gas pipelines could be made safer if pipeline operators had clear guidelines for how quickly they must respond to accidents—but federal regulators don't have the data they need to establish those rules, according to a report by the Government Accountability Office (GAO), an independent arm of Congress.

The first few minutes and hours after a pipeline accident are considered crucial for effective cleanup and damage prevention. But the Pipeline and Hazardous Materials Safety Administration (PHMSA), which regulates the nation's 400,000-mile network of large volume transmission pipelines, requires only that operators respond in a "prompt and effective" manner.

The GAO urged the agency to replace this open-ended regulation with performance-based standards—specific, measurable goals that would make it easier to determine when operators have been negligent. To do that, PHMSA would have to set different rules for different types of pipelines depending on their contents, location, operating pressure, pipeline diameter and other factors.

Matthew Cook, a GAO senior analyst and a co-author of the report, said that to create those rules, PHMSA must first determine how fast operators are currently responding to accidents. But the GAO report warned that PHMSA's existing database, where pipeline accident information is filed, is incomplete and often inaccurate.

President Obama hasn't publicly drawn a connection between climate change and the Keystone XL pipeline, but new pressure is building on him and other officials to connect those dots.

Protests are springing up from Maine to Washington, D.C. to Oklahoma urging leaders to stop the Keystone XL and other oil sands import projects on climate change grounds. The Texas-bound Keystone XL is the biggest of many projects being proposed to connect Canada's oil sands to U.S. refineries and export ports. Protesters claim the pipelines would commit the United States and other countries to a form of heavy oil that would worsen global warming.

On Jan. 26, some 1,400 people marched through Portland, Maine, against possible plans to move oil from Canada's tar sands mines to local ports. Days earlier, hundreds of people joined solidarity rallies across New England and in Canada, where they picketed outside gas stations, locked arms along bridges and hoisted signs that read "Tar Sands = Game Over for Climate." On Monday, indigenous rights activists In Texas and Oklahoma filled public squares to show support for efforts by Canada's First Nations to block oil sands growth.

"We're trying to build the social movement" against expansion of tar sands oil extraction,  said Sophie Robinson, who organized events last week through the Massachusetts chapter of 350.org, a grassroots organization that focuses on climate change.

Two and a half years after the costliest oil pipeline spill in U.S. history, the company responsible for the disaster is balking at digging up oil that still remains in Michigan's Kalamazoo River.

The cleanup has been long and difficult because the ruptured pipeline was carrying bitumen, a heavy oil from Canada's tar sands region. Bitumen is so thick that it can't flow through pipelines until it's mixed with liquid chemicals to form diluted bitumen, or dilbit. When more than one million gallons of dilbit poured out of the broken pipeline in July 2010, the chemicals evaporated and the bitumen began sinking to the riverbed.

Today, regulators and oil spill experts are still struggling to deal with the accident, which was the first major spill of dilbit into a U.S. waterway. The cleanup tools and techniques developed for conventional oil spills—which mostly float on water—are ineffective for submerged bitumen, so experts have had to come up with new methods.

In October, the U.S. Environmental Protection Agency asked Enbridge Inc., the pipeline's Canadian owner, to clean up several miles of the river where submerged oil is still accumulating. The proposed order told Enbridge to dredge 80 to 100 acres of the riverbed. The request was based on the results of a yearlong study the EPA conducted with oil cleanup experts, Michigan state regulators and a committee of about 15 scientists.

The dredging is needed, the agency said, because the oil could spread into uncontaminated areas of the river if it isn't removed.