Demolition crews on Sunday destroyed the 499-foot cooling tower at a defunct commercial nuclear power plant.

With a rumble, the tower leaned to the side and collapsed upon itself — leaving a cloud of dust and multi-ton pile of rubble. It took less than 10 seconds and roughly 2,000 pounds of explosives to complete.

Portland General Electric ordered the implosion at the Trojan Nuclear Power Plant, located about 40 miles north of Portland along the Columbia River, as part of its decommissioning. Trojan closed in 1993 for financial and safety reasons and the facility been decommissioned in stages since then.

The hourglass-shaped cooling tower has been a landmark for travelers on Interstate 5, just across the Columbia on the Washington state side of the river.

The tower is the largest in the nation to be destroyed, according to Controlled Demolition Inc., the Maryland-based contractor handling the implosion.

The company placed explosives in about 3,000 holes drilled on the bottom half of the tower to help control the implosion. The debris landed largely within the footprint of the tower.

"It looks this morning like things went perfectly," said Mark Loizeaux, president of Controlled Demolition.

PGE estimates the full decommissioning will not be complete until 2024. Remaining buildings will be destroyed gradually through 2008. And the spent radioactive fuel rods that sit above ground need to be moved to a federal repository that hasn't been developed yet.