Pressing for new ways to speed the sales of unneeded federal property as part of the Reagan administration's "assets management" program, the General Services Administration has asked, for the first time, for an open listing with local real estate agents of a seven-acre parcel of land.

The property, in the southeast part of the District, is known as the Wilburn tract.

Earl E. Jones, assistant GSA commissioner of real property, said the "creative proposal for an open listing" was being used because the "sale of this particular parcel is difficult . . . and complex."

Since the administration took office in January 1981, GSA has tried five times to sell the Wilburn tract--each time receiving high bids that were less than what the agency regards as the fair market value.

That value, which is kept confidential, is prepared in advance of each bid. The high bids in each of the first two offerings were above $200,000, but by June 1982, the bidding wars had waned and the high bid had sunk to just $11,000.

Declining real estate values in the southeast part of Washington helped to make the sales difficult, Jones said. Under the new system, the Washington Board of Realtors and the Society of Industrial Realtors will circulate fliers about the property.

Jennie Shamey, a realty specialist who has been assigned to manage the test program, said a pre-bid conference is scheduled at GSA's auditorium on 18th and F St. NW on July 12 at 10 a.m. Two hundred sales packages will be prepared, she said. Agents will have until Sept. 7 to submit sealed bids.

"Since we're under the presidential initiative to accelerate the sale of properties, it is natural that we would turn to the professionals in the field who could help us," Shamey said. "If this works out, then we'll do it in other places."

Part of St. Elizabeth's Farm in the early 1800s, the triangular Wilburn parcel came into federal hands by unknown means during the Civil War. Eventually it was given to the War Department for use for housing, but the military instead erected a communications center. It was used until the mid-1970s.

At one time in the late 1970s, the District wanted the property for a park and recreation area, but then withdrew its interest. If the property is purchased, GSA officials said, documents show the District likely would zone it R-5A residential.

GSA has only used real estate agents infrequently. The policy is to pay Realtors a 1 percent finders fee (on sales up to $1 million) if an agent's client wins a high-bid sale.

The depressed economic climate may be helping GSA save more than $30 million in construction costs on federal office buildings going up across the country. Through Friday, low bids totalling $192.2 million had been received on eight construction projects--18.4 percent below the $235.5 million estimated cost.

GSA Public Buildings Commissioner Richard O. Haase said that 5 percent should be added to the low-bid figure to allow for "contingencies" for "change orders to the scope of work."

"If we hit the 5 percent mark for change orders, we're delighted," he said.

Haase, however, may be overly optimistic.

A spot check of the five companies that did the most dollars' worth of GSA construction business in the National Capital Region over the past dozen years turned up 12 projects. Bid awards on those projects totalled $359.36 million, but GSA has paid out $436.16 million--or 21 percent more--due to changes in the scope of the project.

J. W. Bateson Co., for example, received four contracts worth $123.16 million at the time of award. By the time the contracts were settled, Bateson had collected $132.5 million. Blake Construction Co., on the other hand, received only two contracts during the same period, worth $118.6 million. By the time of final settlement, contract amendments and change orders upped the total to $133.1 million.

Terminal Construction, of Wood-Ridge, N.J., had the low bid on the construction contract this week for the proposed Jamaica, N.Y., federal office building.

Terminal outbid six competitors, including the George Hyman Construction Co. of Bethesda, with an offer of $60,695,000. Hyman bid $63,249,000. The building, the most expensive to be constructed by GSA this year, will house the northeastern regional Social Security Administration offices, the Treasury Department and GSA.

The next construction bid opening is Tuesday for the proposed El Paso, Tex., federal building. The estimated value is $16.9 million. The only other project scheduled to be put up for bid this year is the expansion of the U.S. Mint facility in Denver, which will be offered in September.