Legislation being considered by a Senate subcommittee would exempt a 5.5-acre tract of land east of Union Station from District of Columbia land-use laws and regulations, clearing the way for construction of a federal judicial office building exceeding the 80-foot height limit for the area.

Several Washington preservationists told the subcommittee this week that the removal of the height limit would set a "damaging precedent."

The federal government wants to build a 94-foot structure on the federally owned land to house nearly 800 employees of the Supreme Court and other federal courts. These workers are scattered in seven buildings in the Washington area, according to L. Ralph Mecham, director of the U.S. Courts Administrative Office. The building also would house the Federal Judicial Center, a research and training agency, and would provide conference space for judges and other judicial branch employees.

Construction costs are estimated at between $75 million and $115 million, depending on which of the five architectural designs being considered is chosen. The proposals were among 19 submitted by architects and developers, according to a report sent to Congress last spring.

Former Supreme Court Chief Justice Warren E. Burger told the water resources, transportation and infrastructures subcommittee of the Senate Environment and Public Works Committee that if an office building had been constructed 17 years ago when he began lobbying for it, the money that would have been saved in rent would have paid for the construction.

But D.C. planning and preservation advocates said they have no quarrel with construction of a judicial building on the site, but oppose plans to exceed the 80-foot height limit.

"How can we be sure that in the future a telling argument won't be made" for exceeding legal height limits at other sites using the judicial center as a precedent? Elizabeth Rowe, a trustee for the Committee of 100 on the Federal City, asked the subcommittee. The committee is a private planning group established in 1923.

The Building Height Act of 1910 set limits intended to prevent construction of buildings that would overshadow the U.S. Capitol and other monuments. Efforts to overturn the law have been defeated in the past, but the District government has permitted construction of some buildings that exceed the limits set nearly 80 years ago.

Although one section of the 1910 act specifies that buildings facing Columbia Plaza, in front of Union Station, should not be taller than 80 feet, Architect of the Capitol George M. White set a 94-foot limit when he issued guidelines for developers, saying the project would not be economically viable without the added height. White also argued that amendments to the 1910 law allow construction of penthouses recessed from the edges of a building. He said the increased height on the new judicial building would have little visual impact because the portion of the building exceeding 80 feet would be recessed from the front of the structure.

The new judicial building will occupy land on the opposite side of Union Station from the old city post office, which has been at the center of controversy because of the U.S. Postal Service's planned $100 million renovation of the structure. The National Capital Planning Commission, the central planning agency for the federal government in the Washington area, recently rejected a Postal Service proposal for the renovation, largely because the plan would add 1 1/2 stories to the building. Legislation has also been introduced that would give Congress the right to buy the post office building for office and storage uses.

The legislation to provide for development of the judicial center, introduced in December, provides that a building constructed on the site would be considered within the boundaries of the Capitol grounds and thus not subject to any D.C. laws and regulations. Opponents argued that this was simply a means to exempt the building from the 1910 act's height limits.

Sen. Daniel Patrick Moynihan (D-N.Y.), the subcommittee chairman and a sponsor of the bill, said in an interview that a building on the site would frame Union Station and "put a building where there should have been one since 1910."

The bill, also sponsored by Sen. Robert T. Stafford (R-Vt.) and Sen. Quentin N. Burdick (D-N.D.), would authorize White to hire a private developer for design and construction of the office building and establishes terms of the agreement.

The government would retain ownership of the land while the developer builds and owns the structure. The building would be leased to the government for not more than 30 years, and at the end of that period, title to the structure would be given to the government. Funds for the lease payments are provided in the budgets of agencies that would occupy the building, a subcommittee staff aide said.

Design and development of the building will be carried out with little cost to the government, Moynihan said. The Office of Management and Budget has approved the financing and design plans, he added.

The developer-architect teams whose proposals are being considered include Quadrangle Development Corp. of Washington with architects I.M. Pei and Partners; The Oliver Carr Co. of Washington and Kohn, Pedersen, Fox; Boston Properties and the architectural firm of Edward Larrabee Barnes; Gerald D. Hines Interests and Kevin Roche, and Trammel Crow Co. and Skidmore, Owings, and Merrill.