"The 5,000 feet of water between the Gulf of Mexico's surface and the Deepwater Horizon blowout has kept the oil and natural gas flowing.
Each time BP has tried to cap its runaway well, the company has warned that no one has ever tried it at such a depth.
But off the coast of Texas, companies have been drilling in far deeper water, sometimes twice as deep -- and making the same environmental and safety promises that BP made for its Deepwater Horizon operation.
The BP blowout is calling attention to unique engineering challenges and environmental risks associated with seeking oil and gas at unprecedented depths in the gulf.
Equipment designed to withstand harsh conditions at extreme depth failed, perhaps because of those conditions, making some engineers discount assurances that unexpected problems could be stopped at far greater depths.
At the same time, the depth at which the blowout occurred has triggered much more harm to the gulf ecosystem than a shallower leak would have caused, leading to concerns about even worse effects from a possible deeper spill."