How much oil lies under U.S. coastal waters?
Quite a bit. Geologists generally agree that the waters off America’s east and west coasts, on what is known as the outer continental shelf, hold about 18 billion barrels of oil—enough to satisfy U.S. energy needs for two and a half years. That oil is currently off-limits, though, because of a longstanding federal ban on offshore drilling. Oil drilling is allowed in the western half of the Gulf of Mexico, which holds an estimated 70 billion barrels and where about 4,000 drilling rigs are currently in operation. Oil from the outer continental shelf would provide a small boost in available supplies. But even if the drilling ban were lifted tomorrow, production wouldn’t begin until 2017.

Why was offshore drilling banned?
Largely because of a single, catastrophic spill. On Jan. 28, 1969, at a Unocal drilling platform about six miles off the coast of Santa Barbara, Calif., muddy, highly pressurized oil exploded from the well as workers were removing drilling pipe. Over the next 10 days, more than 3 million gallons of oil poured from the ocean floor and floated to the surface, eventually coating more than 30 miles of coastline with foul-smelling crude. Some 10,000 seabirds died, along with untold numbers of fish, sea mammals, and marine plants. “There is nothing more gut-wrenching to watch on television than dying animals,” says California environmentalist Richard Charter. In 1970, Congress declared a moratorium on offshore drilling, though some rigs that were in service before the ban were allowed to continue operating, and many still do.

Has drilling gotten safer?
Even the most zealous environmentalists concede that it has. Today’s deep-water wells have safety valves far below the ocean floor that prevent blowouts such as the Santa Barbara spill. During heavy storms, the pipelines that transport oil to shore shut down automatically, limiting the amount of oil released if a pipe ruptures. As a result of such technical improvements, the drilling rigs off the California coast have produced more than 1 billion barrels of oil since 1969, while spilling only 852 barrels. Republican presidential candidate John McCain, who now favors offshore drilling, says that “not even Hurricanes Katrina and Rita could cause significant spillage.”

Is that really what happened?
No. It’s true that the storms didn’t cause a spill of 100,000 gallons or more from any single rig—the official threshold for a “significant” spill. But the damage was nevertheless widespread. The two hurricanes destroyed 113 drilling platforms in the Gulf of Mexico, damaged 457 pipelines, and caused more than 740,000 gallons of crude oil and petroleum distillates to wash into the gulf, according to the federal Minerals Management Service. These petroleum products didn’t get much attention because they didn’t reach the shore. What did foul the Gulf coastline were oil and distillates from onshore facilities that handle offshore oil, such as refineries and storage tanks. A 2005 report by the Houston Chronicle counted 595 separate spills caused by the storms, including one releasing more than 3.7 million gallons. “It was not a single spill from one single source,” says Coast Guard Cmdr. Ron Cantin. “It was literally hundreds of spills across the region.”

Are spills the only environmental issue?
No. In drilling down under the ocean floor, oil exploration and pumping release tons of toxins such as benzene and arsenic, which can poison fish, coral, and marine plants. Drilling also leaves behind heavy metals such as mercury and lead. A study of one U.S. offshore site found that the marine-animal population around the rig plunged from 8,000 animals per square meter to 1,700 after drilling started. Chemical releases from drilling, the U.S. Energy Department concluded in 1999, can have “long-term, severe impacts” on undersea organisms. Exploration firms also use specialized air guns to map the regions under the ocean floor; the concussion from the guns can kill dolphins, whales, and other marine mammals.

So is offshore drilling worth the risk?
As the old saying goes, where you stand depends on where you sit. People in coastal states that cater to tourists have long been opposed to drilling and mostly remain so. Erich Torngren, a 20-year-old shopkeeper in Panama City Beach, Fla., says people visit his town on the Gulf Coast “for only one reason, and that’s the beach. Mess up that white sand and we’re in a lot of trouble.” But with gasoline at $4 a gallon, polls show that 69 percent of Americans now favor additional drilling, up from 42 percent in January 2007, when a gallon of regular gas averaged $2.22. And recently, even some coastal dwellers—including longtime residents of Santa Barbara, where the 1969 spill has not been forgotten—are reconsidering their opposition to new drilling. “Everybody’s got a price,” says Santa Barbara Mayor Marty Blum, “and at a certain price per gallon, we’re all going to want more drilling.”

The Norwegian model
When opponents raise environmental concerns about offshore drilling, advocates like to cite the safety record of Norway, the world’s 10th-largest oil producer. Indeed, Norwegian rigs in the North Sea have operated largely accident-free since they first started pumping, in the 1970s. The government-owned oil company StatoilHydro, which has won awards for its environmental record, pioneered the technique of carbon sequestration—in which carbon produced by drilling and refining is captured and buried far below the sea. But even Norway’s record has blemishes. In December 2007, 25,000 gallons of oil spilled into the North Sea and drifted toward the Arctic, after a pipe ruptured while oil was being transferred from a drilling platform to a tanker. And in 2005, 1.6 tons of hydraulic oil, a highly toxic pollutant, leaked into the sea, forcing Statoil to suspend a prospecting mission. Occasional spills, though, have done little to lessen Norway’s enthusiasm for its oil operations, since they produce more than $40 billion in revenue every year, and have given the country one of the world’s highest standards of living. The wealth almost makes politics irrelevant in Norway, says economic consultant Knud Norve. “We’re able to fulfill all the parties’ dreams,” he says, “and still have billions left over.”