1969: Pipeline 6B installed.

1999: Enbridge begins carrying diluted bitumen from Alberta on Pipeline 6B, part of the company's Lakehead system.

2008: An internal Enbridge inspection identifies 140 corrosion defects on 6B.

2009: Another internal Enbridge inspection identifies 250 more corrosion defects on 6B.

2009: Enbridge tells PHMSA it will reduce pumping pressure along 6B while deciding whether to repair or replace the line.

July 2010: Enbridge in midst of dig-and-repair program on 6B in Marshall area and elsewhere.

July 15, 2010: Enbridge seeks permission from PHMSA to continue operating 6B at reduced pressure for another 2 ½ years.

July 15, 2010: Enbridge official tells a congressional subcommittee the company's response time to a leak can be "almost instantaneous."

About 34 miles of the Kalamazoo River in Southeastern Michigan were opened to the public Thursday, almost two years after the most expensive oil pipeline spill in U.S. history dumped more than 1 million gallons of heavy Canadian crude into an adjoining creek.

Crews have been cleaning the waterway since July 26, 2010, when a ruptured pipeline owned by Enbridge Energy Partners, the U.S. branch of Canada's largest transporter of crude oil, was discovered in wetlands in Marshall, Mich. The Canadian crude oil, known as diluted bitumen, contaminated more than two miles of Talmadge Creek and about 36 miles of the Kalamazoo, forcing people to flee their homes because of the overpowering smells.

The cost of the cleanup has now reached at least $765 million, making it the most expensive oil pipeline spill since the government began keeping records in 1968. Enbridge is responsible for all of the cost, with most of the cost being paid by its insurance company.

With Thursday's opening, all but a short stretch of the river known as the Morrow Lake delta is now available for recreation, according to the U.S. Environmental Protection Agency. That delta area, at the western edge of the contaminated section and near the city of Kalamazoo, remains closed to the public.

Although people can once again swim and boat on the Kalamazoo, that doesn't mean the river is oil-free. Cleanup of the remaining oil will continue in the Morrow Lake delta and other low spots along the river bottom. EPA officials in Marshall have told InsideClimate News that removing the rest of the oil could take months or years.

WASHINGTON—Those expecting a consistent climate change message from the White House are having trouble squaring two recent energy initiatives.

President Obama avoided any climate-related language when he stood in Cushing, Okla. on March 22 to encourage construction of the southern leg of the fiercely debated Keystone XL oil pipeline. Then, just five days later—when Obama was attending a nuclear security summit in South Korea—the Environmental Protection Agency modestly rolled out its first-ever carbon pollution standard for future power plants.

How, puzzled critics asked, could the Obama administration endorse a tar sands pipeline project that's been labeled the "fuse to the biggest carbon bomb on the planet" while simultaneously laying the groundwork for kicking coal to the curb as an electricity generator?

The short answer is that he has one eye on the polls and the other on his long-term energy goals.

WASHINGTON—A little-publicized Canadian court decision has thrown a monkey wrench into an on-again, off-again proposal to transport oil from tar sands mines in Alberta to a U.S. seaport in Maine for export.

Last month, judges with the Court of Quebec rejected a Montreal-based oil pipeline company's request to construct a pumping station near the Quebec-Vermont border. The court case pitted environmentalists and Quebec citizens against the owners of a South Portland, Maine-to-Montreal, Quebec oil pipeline.

Halting the pumping station is part of an overarching strategy by environmentalists to challenge Canada's expansion of tar sands oil extraction. They fear the station is the linchpin in opening an eastern gateway for the flow of a dirtier grade of oil from western Canada to Maine. From there, it would likely be shipped to refineries along the Gulf Coast.

Election-year politics, $4-a-gallon gasoline and an anti-regulatory fervor on Capitol Hill have aligned to thwart EPA's vow to issue final carbon emissions standards for oil refineries this year.

Changing course puts the Environmental Protection Agency woefully behind schedule on curbing planet-warming gases from a major polluter.

The pullback on refineries—combined with an earlier and separate delay on regulating greenhouse gases from fossil fuel power plants—means EPA has yet to control emissions from a pair of sizable industrial sources. Together, refineries and power plants account for nearly 40 percent of greenhouse-gas pollution nationwide.

As part of a 2010 legal settlement with environmental organizations, EPA was on track to release draft regulations for oil refineries in December 2011 and final rules by November 2012. That timetable began to crumble last November when the agency announced it wouldn't meet the December deadline.

EPA Administrator Lisa Jackson hinted that the slowdown would delay final oil refinery standards until beyond 2012 when she told members of the House Energy and Commerce Committee last week that "there are no current rules under development on that issue."

WASHINGTON—Industries in North Carolina, Pennsylvania and South Carolina will have the most catching up to do when—and if—EPA begins forcing factory owners to tackle toxic emissions from boilers powering their manufacturing plants.

That's what Earthjustice discovered recently by creating a map pinpointing the whereabouts of the 1,753 industrial boilers that would be forced to curb pollutants under new regulations crafted by the Environmental Protection Agency. The bulk of the "offending" boilers are operating in manufacturing-heavy states east of the Mississippi River.

"We've been scratching our heads figuring out how to make this conversation about industrial power plants more real," Jim Pew, a staff attorney with the nonprofit environmental law firm, told InsideClimate News. "The term boiler is misleading because people think it is what's in their own basement. But the scale of these on-site power sources is enormous.

People don't realize industrial power plants can be next door to their homes, Pew said. "Living near one of these plants, you are being exposed to a lot of pollution. People should know what these plants are emitting so they understand why they should be controlled."

WASHINGTON—Opponents intent on blocking EPA's "endangerment finding" and the agency's other efforts to regulate emissions of heat-trapping gases via the Clean Air Act will have their two days in court this week.

A three-judge panel with the U.S. Court of Appeals is slated to hear oral arguments on the legal challenges Tuesday and Wednesday in the nation's capital.

In addition to the endangerment finding, the court will be reviewing a trio of other regulations—abbreviated as the "tailpipe," "tailoring" and "timing" rules. Combined, they are the bedrock of the Environmental Protection Agency's attempts to regulate emissions of carbon dioxide and other greenhouse gases from vehicles and big industrial sources.

All four rules represent the agency's response to Massachusetts v. EPA. In that landmark 2007 decision, the Supreme Court gave EPA authority over carbon pollution. The high court justices also made it clear that agency officials could not shirk that authority unless they could provide a scientific basis for refusing to act.

The appeals court's rulings, expected to be issued this summer, are significant because they have the potential to halt, delay, modify or increase the scope of EPA's regulation of carbon under the Clean Air Act.

WASHINGTON—A remarkably balmy January—the fourth warmest on record—has prompted top Democrats on the House Energy and Commerce Committee to prod Republicans into scheduling a congressional hearing to explore why winters are warmer than average.

Reps. Henry Waxman of California and Bobby Rush of Illinois cited recent data released by the National Oceanic and Atmospheric Administration (NOAA) as the basis for their hearing request.

During January, the average temperature in the United States—excluding Alaska and Hawaii—was 5.5 degrees above normal, according to NOAA.

NOAA reports show that above-normal temperatures are part of a global trend. For example, they pointed to NOAA statistics listing 2001-2011 as ranking among the 13 warmest years worldwide since recordkeeping began in 1880.

In a Wednesday letter addressed to GOP committee leaders, Waxman and Rush wrote that a hearing to discuss these findings would "provide members with a more robust understanding of the scientific consensus around rising temperatures."

WASHINGTON—Congressional Republicans are floating a handful of measures to override President Obama's January rejection of a permit for the Keystone XL oil sands pipeline. But it's questionable whether any of these efforts, including a bill that could be debated in the House this week, would actually speed up approval of the Canada-to-Texas pipeline.

Legal experts agree that the Constitution allows Congress to bypass the president and legislate a permitting process for cross-border pipelines such as TransCanada's $7 billion project. But they also agree that it's a tricky endeavor likely to trigger a complex and drawn-out lawsuit.

For starters, a pro-pipeline measure focused solely on Keystone XL has only a tiny chance of passing muster in a Democrat-majority Senate. Plus, President Obama wouldn't sign such a bill into law.

If the GOP did somehow overcome those barriers, the law would almost certainly be challenged in federal court—probably by environmental organizations and/or landowners along the pipeline route. However, the nature of the lawsuit would depend upon the content of the law that passes.

WASHINGTON—A barrage of industry-led advertising and lobbying urging President Obama to "put jobs ahead of politics" has fueled the impression that labor unions universally champion the Keystone XL oil pipeline.

But that myth was blown apart just minutes after the president rejected the $7 billion project on Jan. 18.

That's when five labor unions that had kept low profiles on the pipeline—including the 2 million-member strong Service Employees International Union—issued a joint statement backing Obama's decision. Not only did they laud him for acting "wisely," but they also emphasized the need to address climate change and find sustainable and secure energy sources.

Since then, a more nuanced snapshot has emerged of where labor unions stand on Keystone XL. That newer picture weakens industry's argument that the pipeline has broad union support. The handful of unions that praised the president and questioned the project’s merits represent close to 5 million members. Membership in the five unions publicly promoting the project is near 3.3 million. (See chart.)