Fairchild Industries Inc., with headquarters in Montgomery County, was indicted today on 86 counts of hazardous waste disposal and water pollution violations at its sprawling aircraft plant in Hagerstown.

A Washington County [Hagerstown] grand jury returned the indictment against the aerospace and telecommunications company following a six-month investigation led by the state attorney general's Hazardous Waste Strike Force. If convicted, Fairchild could be fined a total of $2.15 million, the largest amount in the history of Maryland's antipollution laws.

The indictment said that between October 1980 and December 1981 more than 200,000 gallons of waste water containing hexavalent chromium, chromic acid and nitric acid were dumped or leaked into the ground near the Fairchild Republic plant on Showalter Road in Hagerstown. The discharges have since been stopped by Fairchild, state officials said today.

All three chemical substances were described by state health authorities as "corrosive," causing irritation and burns if ingested in large enough doses. Officials said there are no known victims of the discharges and no large public water supplies affected.

Two of 45 drinking wells monitored since 1979 within a one-mile radius of the plant, however, showed hexavalent chromium levels above state drinking water standards, according to a spokeswoman for the Maryland State Health Department's Office of Environmental Programs. Both ground water wells and drinking wells are still being monitored around the plant, officials said.

Attorney General Stephen H. Sachs announced the indictment at a press conference in his office here, saying the state "can prove that responsible officials at [Fairchild] were aware" of leaks and discharges of hazardous wastes but did nothing until state health authorities intervened.

In a statement issued by its corporate headquarters in Germantown, Fairchild said it was "shocked and incensed" that the state had decided to charge the company with criminal violations. Fairchild said that when it first learned of the state investigation last March it proposed a "joint action" with the state to resolve the concerns through the common practice of negotiation and administrative action.

"The state appears much more interested in making a criminal case in this matter," Fairchild said, "than it is in guaranteeing a prompt and efficient method of safeguarding the local environment."

Richard R. Molleur, Fairchild's vice president and general counsel, said "the company intends to vigorously defend itself against all charges."

Fairchild said it has spent more than $1 million since 1964 in upgrading the hazardous waste system at Hagerstown.

The 175-acre Hagerstown plant, which employs almost 2,000 workers, makes the A10 close air-support military aircraft, a low-flying, single-seat plane for the Air Force. It also makes parts for the Boeing 747 passenger plane and other aircraft.

Sachs said at least 200,000 gallons of waste water containing hexavalent chromium had been discharged from a tank in one of the company's buildings, "flowing into an open drain from which it flowed to groundwater."

At a second building, he said, an undetermined amount of waste water containing hexavalent chromium, nitric acid and chromic acid "leaked to groundwater due to a leak in a concrete pit."

"We're dealing not only with pollutants," Sachs said, "but with hazardous and toxic substances."

The waste water, state officials said, was the residual liquid left in large tanks after airplane parts were rinsed by workers in a special manufacturing process. Fairchild officials declined to discuss details of the waste water.

The Hazardous Waste Strike Force, headed by Assistant Attorneys General James J. Lyko and Charles R. Taylor, was formed last year and has successfully prosecuted nine criminal cases, Sachs said, with courts levying more than $100,000 in fines and jailing one defendant.

No individuals were charged in the Fairchild case. "This was a corporate responsibility," Sachs said.