The Army announced detailed plans yesterday to construct one of the world's most secure laboratories to conduct sophisticated experiments with deadly, highly infectious germ warfare agents.

In a lengthy report, the Army said the proposed $5.4 million laboratory at Dugway Proving Ground in the Utah desert will permit vital expansion of its germ warfare research and allow tests of deadly, genetically engineered biological organisms if it decides to do so in the future.

The service, responding to public criticism of the proposed facility, said the lab will be constructed according to the most stringent government safety standards and will "pose no threat" to employees, the public, or the environment.

"The most serious environmental consequence . . . would result from an accidentally infected laboratory worker exiting" the lab, the report said, but elaborate steps will be taken to prevent such an event, including immunizing workers against the diseases they will study.

The Army said organisms to be studied at the lab, to be built 70 miles southwest of Salt Lake City, may include those capable of causing anthrax, Q fever, tularemia, and encephalitis. No genetically engineered organisms will be used without further, public notification, the Army said.

The report grew out of a lawsuit to block the lab by the Foundation on Economic Trends, a private group led by Jeremy Rifkin, a critic of genetic engineering research. Rifkin yesterday criticized the Army for not building a less elaborate laboratory for testing simulated germ warfare agents.

Rifkin also questioned the Army's claim that the laboratory workers could be adequately immunized against germ warfare agents that may be studied in the future. "For most of the microorganisms they will be working with, there are no vaccines," Rifkin said.

Army officials said, however, that no work will be done with germ warfare agents that lack appropriate vaccines, even though the laboratory's safety features give it this capability.

Like workers at the handful of existing top-security government research labs, employees at the proposed Dugway facility would enter through special airlocks, wear protective gear with individual oxygen supplies, shower at shift's end and have their suits decontaminated. Filters and incinerators will eliminate deadly pathogens in waste material and laboratory air.

The Army said the facility is needed to test equipment being developed for defense against an enemy biological warfare attack. Some of this work is presently conducted at a Ft. Detrick, Md., Army laboratory, but the Army said it lacks equipment there needed for "critically controlled testing" with deadly pathogens in aerosol form.

The Army also said "the projected workload" at Fort Detrick is so great that it cannot "accommodate" any further work without interrupting Detrick's "medical research mission."

Independent scientists criticized the Army's plans when they were first announced in 1985, arguing that the laboratory was more elaborate than needed for defensive biological warfare research. A 1972 international treaty bars development, production, or storage of offensive biological weapons, but allows limited research aimed at defending against such weapons.

The Army acknowledged in the report that it has no present need for a laboratory designed with such elaborate safety specifications, but said it might in the future and would save money by incorporating the extra safety features now.

The Army also said that experimentation with less-dangerous, simulated biological agents is inadequate because they may not precisely mimic the effects of real agents. Moreover, good simulated agents cannot be developed without "as much . . . testing as would be done by direct testing" with real agents, the Army said.