The Army has destroyed more than 16 million pounds of chemical weapons during the past 20 years and is qualified to do so near Tooele without harming residents, a brigadier general said.

Gen. David A. Nydam said Utahns will continually be at risk unless the Army destroys its enormous arsenal of chemical weapons at the Tooele Army Depot.About 30 people attending a public hearing at the depot Thursday voiced no opposition to that assertion. None asked questions or made comments about the proposed destruction, mandated by Congress.

During the hearing, Nydam outlined the Army's plans for destroying the nation's chemical weapons, particularly the enormous amounts stored at TAD.

TAD houses 42 percent of the nation's stockpile, by far the largest such arsenal in the country. Pine Bluff Arsenal in Arkansas is second with only 12 percent of the total.

Some of the weapons at TAD are 40 years old, and the newest were built in the 1960s. An earthquake or other natural disaster could cause the weapons to leak, said Nydam, the Army's project manager for chemical demilitarization.

"That probability is very small, but if it did occur the damage would be very large," he said, acknowledging there also are risks involved with destroying the weapons.

"Whatever we do will put the community at a risk of one sort or another," he said.

The Army's plan calls for all chemical weapons stored at TAD to be destroyed at a facility that will be built for that purpose and immediately torn down when the destruction is complete. No chemical weapons will be transferred in or out of TAD.

Nydam said the Army's plan calls for a final environmental impact statement to be completed by next spring. Construction will begin in June 1989 and the first weapons will be destroyed in December 1992.

All the weapons will be destroyed by 1997, he said. The project will cost the Army $171.8 million in Utah and $2.7 billion nationwide.

Nydam pledged the Army would work closely with the state and with local communities, setting up intergovernmental boards to coordinate concerns. The state will have to issue a permit before the destruction begins.

"That is your state's check and balance," he said. "We realize we've got to work very closely with the state."

Nydam said the Army may eventually use a destruction method known as cryogenic incineration. Under that method, the weapons are frozen in liquid nitrogen, shattered and dumped into a furnace.

The liquid nitrogen will sap the strength of the chemicals, he said. The process is still in the experimental stages.

Chemical weapons will be destroyed at eight sites nationwide, including near the western cities of Umatilla, Wash., and Pueblo, Colo.