How do you dismantle a 330,000-pound intercontinental ballistic missile carrying 16,000 explosive gallons of toxic liquid fuel and the largest nuclear warhead in the Free World?

Very, very carefully, according to the Air Force deactivation crew at the Titan II missile silo here on the rolling green plains east of Wichita.

But you also have to do it very, very publicly.

For one thing, the Air Force takes pains to ensure that the farm families living near the 18 Titan II silos ringing McConnell Air Force Base are informed of every step as the huge ICBMs are taken apart and carted away.

But there's another interested audience: the Soviets.

The Air Force assumes that the Soviets are watching as the mighty rockets are gingerly removed from the nine-story-deep holes where they have stood at the ready for 22 years.

And after each of the missiles is pulled from its den, each empty silo is left alone -- uncovered, untouched -- for another six months so the Soviets can verify that weapon has been deactivated.

"We don't know exactly how they check," said Col. Jay W. Kelley, commander of the missile wing at McConnell. "It might be a guy driving by in a pickup. Maybe they fly over in a Piper Cub. It could be a satellite.

"All we know is that under the SALT treaty they have 180 days to verify the deactivation of this missile using 'national technical means,' whatever that is. And so we let the silo just sit there for six months before we bury it forever."

It is well-known that the United States is engaged in a trillion-plus-dollar military buildup. It is somewhat less well-known -- except to the farmers here and the unseen Soviet observers -- that the country is tearing down the oldest and most lethal single element of its nuclear arsenal: the Titan II missile force.

During the Kennedy administration the Air Force installed more than 50 of the missiles in underground silos in Arizona, Arkansas and Kansas. The 9-megaton nuclear warhead carried by each Titan reportedly was targeted for a Soviet city.

But keeping these giant weapons poised for action, their fuel tanks filled with poisonous liquid propellants, was dangerous and expensive. And the Titan's enormous single warhead did not mesh with emerging strategic doctrines that called for missiles bearing multiple, independently targeted warheads.

Before the Titan IIs were 10 years old, the Pentagon had decided to get rid of them. They were used as bargaining chips in the SALT I talks: It was agreed that weapons such as the Titan II would be removed and their silos would not be filled with new missiles.

Shortly after President Reagan took office in 1981, he ordered deactivation of the entire Titan II fleet.

The Air Force gave the mission a formal name -- "Project Rivet Cap" -- and set about the five-year task of dismantling the deadly missiles.

To date, all 18 Titan IIs in Arizona have been removed. Here in central Kansas, 11 missiles remain to be pulled out of the ground, and work began in earnest last week on the 17 Titan IIs stationed near Little Rock, Ark.

The delicate and potentially dangerous deactivation has been entrusted to a carefully trained corps of missile-maintenance experts.

The Kansas contingent includes Chief Master Sgt. Eugene Scoular, whose 33 years of service make him one of the few people who have been in the Air Force longer than the Titans have.

The casual, loquacious sergeant says removing the 11,000-pound warhead -- with a uranium payload equivalent to 9 million tons of TNT -- is the easy part.

"You haul her out of there with a crane and put her on a truck and say goodbye," he said.

Like all used nuclear weapons, the Titan warheads are turned over to the Department of Energy and shipped to the nuclear fuel plant in Amarillo, Tex., for reprocessing.

The tricky part of dismantling a missile is the removal of its liquid fuel. The dimethyl-hydrazine fuel and the nitrogen tetroxide oxidizer with which it mixes for blastoff are potent toxins; in 1978, two workers were killed by leaking fuel at one of the Titan sites near here.

A crew of "propellant transfer specialists" in bulky white spacesuits use a custom-built $280,000 vacuum cleaner to pump the dangerous liquids from the rocket to a fleet of tanker trucks.

If all goes well, it takes about eight hours to empty one Titan's fuel tanks.

But things sometimes turn sour: A rainstorm comes along. The wind blows too hard. The fuel lines leak, creating a scary phenomenon known to the crews as a "BFRC," which Master Sgt. Scoular translates delicately as "Big Flipping Red Cloud."

In such cases, fuel removal can take more than two weeks.

Once the fuel is safely out, the rocket's two stages are pulled from the long silo with a heavy-duty crane and loaded on rail cars for a slow trip to California, where they'll be used to launch satellites into orbit.

The silos, after sitting open long enough for the Soviets to make their verifications, will be dynamited, filled with rubble and covered over, waiting for a 22nd century archeologist to find them and ponder the purpose of these prodigious underground structures.