As building manager for the General Services Administration's State Department area, Robert M. Beacham is responsible for ordering maintenance work on government buildings in his area and verifying that the work is done properly.

So when Levcon Construction Co. of Washington was hired by GSA in 1975 to paint a Commerce Department building at 2400 M St. NW, it was Beacham who determined how many square feet of surface area Levcon should paint and how many square feet had been done well enough to be accepted by the government.

Signing for the "United States of America," Beacham certified on GSA documents that Levcon had been ordered to apply two coats of paint to 320,000 square feet of surface in the six-story building and had painted all 320,000 square feet properly.

On the basis of Beacham's signature, GSA paid Levcon $28,572, and Levcon subsequently certified it had received the money.

Everything seemed in order - except that the Commerce building has 76,552 square feet, or less than a quarter of the surface area listed by Beacham as having been painted by Levcon, according to Robert G. Scharf & Associates, a construction estimating firm hired by The Washington Post to determine the building's area.

Asked about his figures. Beacham said he would comment only if given permission by GSA.

After Richard Q. Vawter, GSA's public information director, said the agency had no objection and had informed Beacham of that, Beacham did not return telephone calls made by a reporter to his office in the State Department.

Michael O'Connor, the principal owner of Levcon, said when asked about the figure. "It beats me."

O'Connor said prosecutors recently subpoenaed his company's books, canceled checks, and contracts. In addition, he said FBI agents had come to interview him last week, but he was not in at the time.

The U.S. attorney's office in Washington and the FBI are conducting an extensive investigation into GSA maintenance contracts. The FBI currently has 12 agents working on the case, according to knowledgeable sources.

A Washington Post story previously reported that O'Connor's firm was hired by GSA to paint about half the offices in the GSA headquarters building at 18th and F streets NW, in 1975. Levcon received payment from GSA for applying two coats of paint ot 2.4 million square feet of surface area. However, the entire building has only 1.9 million square feet, according to the Scharf firm.

At about the time Levcon painted the Commerce building, Beacham ordered Levcon to apply two coats of paint to 831,630 square feet of surface in a complex of seven buildings known as Potomac Annex at 2300 E St. NW. The buildings, located on a grassy hill overlooking the State Department, house the Navy's Bureau of Medicine and Surgery.

Based on Beacham's certification, GSA paid Levcon $108,102 for painting the buildings.

But the Scharf firm determined that the buildings have a surface area of 469,474 square feet, or slightly more than half of the square footage Levcon was paid for painting.

After Levcon completed its work in August 1975 Beacham again ordered Levcon to perform painting work in the Potomac Annex, along with the State Department and a building known as State Department Annex 2. Levcon received $40,242 for this work.

Three months later, Beacham ordered another $23,824 worth of painting by Levcon in Potomac Annex and the State Department.

Because Beacham did not segregate the amount of work to be done in Potomac Annex from that to be performed in the State Department, it could not be determined how much of the additional painting was done in that complex.