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A 4-by-8-mile pit deep in the wilderness of northwest Canada is taking center stage in America’s energy debate.

The Athabasca tar sands in Alberta Province is the largest mine in what is the second largest oil reserve in the world, behind only Saudi Arabia.

The United States gets 20 percent of its imported oil from Canada, about half of it coming from the vast Athabasca tar sands. And now there are plans to more than double the oil sands production and pipe nearly all of the oil through a new pipeline that would take it to refineries in Texas.

Recovering the estimated 175 billion barrels of oil is costly and controversial. The Athabasca tar sands produce a low-grade asphalt-like petroleum product, called bitumen, that must be melted out of the ground, a process that environmental groups say produces three times more carbon dioxide than traditional oil drilling. But the pipeline needs U.S. approval all the way up to the State Department, a decision that is expected to made later this year.

The Sierra Club has dubbed tar sands as “the most toxic form of oil on earth,” and the organization will join a coalition of environmental groups planning to protest the importation of this oil at the White House starting Aug. 20.

Among the concerns by green groups are leaks and the environmental impact from the proposed pipeline, which would cross several major watersheds and aquifers.

The American Petroleum Institute has a very different take and says the environmental concerns are far overblown.

“It’s our No. 1 trading relationship,” the energy industry trade group's Cindy Schild said. “You have the ability to increase our domestic energy security throughout North America so it’s a win-win situation.”

Last week American Petroleum Institute invited journalists to take a tour of two oil sands production sites in Alberta.

The Millennium mine is run by Canadian energy giant Suncor. The mine is a massive operation with 200 huge trucks carrying up to 400 tons of oil sands at a time. Each day 1.5 million barrels of oil comes out of the Canadian tar sands, with 900,000 barrels sent to the American Midwest by pipeline.

While the Suncor mine is the biggest oil sands operation, it is far from the only one, and eventually its surface extraction method will be replaced. That’s because only 20 percent of the tar sands oil is recoverable through mining. The remaining 80 percent is too deep.

Ten years ago, Conoco Phillips started using a system it calls SAGD – steam-assisted gravity drainage.

Two pipes are drilled horizontally, a few feet apart, hundreds of feet underground. The pipes release steam into the tar sands deposit causing the bitumen to loosen. It’s then sucked into the lower pipe and brought to the surface, where it goes through several more treatment steps, turning it into the heavy oil fit for the pipeline to the U.S.

Patty Glick of the National Wildlife Federation says in addition to the massive environmental impact to produce the oil, increasing U.S. imports from Canada would not lead to a decrease in imports from the Middle East.

“It takes a tremendous amount of energy just to extract it,” Glick says. “That energy is contributing to greenhouse gases, making our global environment and global economy worse in the process.”

Canadian officials appear confident that if the U.S. doesn’t want all the additional oil from the tar sands that will be produced in the coming years, there will be plenty of buyers lining up.

“Oil is a globally-traded commodity,” Alberta Energy Minister Ron Liepert said. “In the last year and a half, we’ve had some $15 billion of investment, primarily from China but certainly from other parts of Asia.”

Others see it as a jobs issue. A pipeline would create, at a minimum, thousands of temporary construction jobs. Additionally, the mining operation creates a direct benefit to U.S. companies.

“Those (truck) tires come from South Carolina,” says ravis Davies of the Canadian Association of Petroleum Producers said. “The casing comes from Indiana, the engine from Illinois. You look at the pipes, you look at all kinds of infrastructure that comes from the U.S.”

For now, oil companies forge full-steam ahead ramping up tar sands production.