After years of tests and hundreds of millions of dollars, disposal began Wednesday at a remote site near the Columbia River of one of the U.S. military's last stockpiles of deadly chemical weapons left over from the Cold War (search).

Carrying gas masks and syringes of antidote, workers at the Umatilla Chemical Depot (search) used remote-controlled equipment to begin destroying nearly 4,000 tons of nerve gas rockets and other chemical weapons stockpiled since 1962.

"It's an incredibly historic day. This is a Cold War-era mission that is today starting to end," said Mary Binder, an Army spokeswoman at the depot.

With the first rocket disposal on Wednesday, the Army now has three working chemical weapons incinerators in the United States — Hermiston; Tooele, Utah; and Anniston, Ala. A fourth is expected to open next spring in Pine Bluff, Ark.

Four other four sites — at Newport, Ind., Blue Grass Ky., Edgewood, Del., and Pueblo, Colo. — use chemical neutralization rather than incinerators.

An M-55 rocket loaded with sarin nerve agent was the first of more than 220,000 weapons scheduled to be destroyed, officials said. Workers had removed a pallet of 15 M-55 rockets from an earth-covered and concrete-reinforced storage igloo Tuesday.

The disposal process starts with robotic machinery removing the explosive charge, then punching open the warhead to drain about a gallon of deadly sarin into a storage tank.

The metal rocket would then be chopped into eight parts and run through a decontaminating furnace, one of four high-temperature incinerators at the sprawling facility in the northeastern corner of the state.

Exhaust from the incinerators would be sent through an afterburner and filters before being released into the atmosphere.

Liquid chemical agent drained from the warheads would be collected for about a month until a sufficient amount accumulates to begin destroying it in a separate high-temperature incinerator.

The first incineration comes after years of delays in construction and testing, and in spite of a pending lawsuit seeking to block the process.

A Multnomah County judge denied a request by the opposition group GASP for a preliminary injunction in August. Oregon Court of Appeals Judge Walt Edmonds gave the group 10 days to seek an injunction in higher court, but the group had not filed by Tuesday.

Hermiston-based GASP says burning the weapons risks an accidental release of chemical agents. The group favors the newer chemical neutralization process.

Burning was to have begun Aug. 16, but was postponed at the last minute after a trial run because ventilation system monitors showed larger amounts than expected of a test chemical.

The Umatilla Chemical Depot holds about 12 percent of the nation's remaining chemical weapons. The military began stockpiling rockets, artillery shells, bombs, land mines and sprayers containing nerve and mustard agents there beginning in 1962.

The 7.3 million pounds of weapons are scheduled to be destroyed by 2010 at a cost of $2.4 billion.