ANCHORAGE - It was 20 years ago Tuesday, just after midnight in the calm waters of Prince William Sound, an oil tanker plowed over charted rocks known as Bligh Reef.
The impact did horrible damage, ripping open cargo tanks down nearly the entire length of the 987-foot ship.
No one died, the way hundreds or even thousands can die in an earthquake. Yet the wreck of the Exxon Valdez on March 24, 1989, is remembered as one of the world's worst disasters, an iconic environmental calamity that is still rippling through the lives of many Alaskans.
"We've fetched up hard aground," Joe Hazelwood would radio the U.S. Coast Guard. His career as a tanker captain was finished.
Nearly 11 million gallons of oil would drift as far as 470 miles, fouling beaches and fatally bathing scores of sea otters, birds and other wildlife.
A slow and ill-equipped cleanup was largely ineffective, though so epic it buoyed the entire Alaska economy. Even now, residual oil can be found in sediment along Prince William Sound beaches.
The biggest lingering concern from Exxon Valdez, however, is this:
Could it happen again?
"Wherever oil is shipped, it can spill," said Rick Steiner, a University of Alaska professor who has traveled widely to talk about shipping safety and the environment. "Even with the safety system in Prince William Sound, things can still go wrong."
The Exxon Valdez disaster was revolutionary.
It spawned sweeping safety upgrades in the Sound, including more tug escorts for tankers, improved radar monitoring of ship traffic, and a greatly expanded arsenal of spill containment and cleanup equipment.
The spill also produced a federal law that all large tankers by 2015 have a double hull, which experts believe could have greatly reduced the size of the Exxon spill. Today, much of the world's tanker fleet has moved to this standard, and all but one of the ships regularly loading oil at Valdez are double-hulled.
Oregon-based Alaska Tanker Co. operates four new double-hull ships - costing more than $1 billion total - to haul oil for BP.
Company president Anil Mathur said not only have the ships and spill prevention measures become far more robust since the Exxon disaster, the people transporting oil have become more environmentally aware.
"We spend our days and nights trying to make sure it doesn't happen again," he said. "It's such a changed mindset from the horrors of 20 years ago."
Bill Woody was the National Transportation Safety Board's lead investigator on the Exxon case. He continues to investigate shipwrecks for the agency at age 80.
Good equipment such as double-hull ships can work to prevent spills, he said. He's seen proof.
But shipping is a people business.
"As long as I've been here," Woody said, "the thing that always amazes me is mariners with good training on very well-maintained ships still somehow get into accidents - take chances where the gain is not very great but the consequences are great."
Investigators concluded Hazelwood was drinking and had left the bridge under the command of third mate Gregory Cousins when the Exxon Valdez was driven onto Bligh Reef.
A study of safety upgrades in the Sound - including the practice of escorting each loaded tanker with two powerful tugs - found the accident risk has been reduced by 92 percent.
Watchdogs and some state legislators now worry the industry might relax the tug escorts to save money. Federal law requires such escorts for single-hull tankers, but not for the new double hulls.
"We've said we don't plan to change the escort system, and we support a risk assessment being done before any changes do occur," said BP's Jeff Johnson, who chairs a spill-prevention committee of Alaska oil shippers.