Aided by a private mediator paid for by the District government, George Washington University officials and residents of a Northwest Washington community announced yesterday that they had agreed on how to protect the neighborhood during renovation of the school's Mount Vernon women's campus.

The hiring of a professional mediator--for about $15,000--to patch up differences between the two sides was a novel approach that could be used in redevelopment disputes elsewhere in the city, Mayor Anthony A. Williams (D) said during a campus ceremony at which he signed the agreement.

Turning to the mediator, Robert C. Fisher, the mayor joked, "You've got about 15 other assignments after this one."

But the hiring of Fisher, of Washington, also was an admission of a broken planning process, in which some developers and residents don't trust each other enough to settle their differences over project proposals.

The D.C. government is supposed to referee such disputes but has a poor track record. Residents of the Foxhall and Palisades, near the Mount Vernon campus, gave up on the city to protect them from traffic, noise, tree loss and other concerns posed by GWU's 10-year renovation at Mount Vernon. They hired an attorney to sue the university. City Planning Director Andrew Altman then recommended the mediator.

"Mediation doesn't supplant good planning. My goal is to strengthen the planning process so we don't have mediation," said Altman, who announced an initiative last month to rebuild the city's planning process so developers address community objections from the start.

The agreement virtually guarantees city approval of GWU's plan to renovate buildings and expand its 23-acre Mount Vernon campus, which has been in the middle of a residential neighborhood since 1946.

With Fisher refereeing, university officials agreed to set a limit on the number of students assigned to the campus, to fine students who park along nearby residential streets, to restrict the height of buildings to 40 feet, to increase the number of trees saved and to maintain a landscaped buffer along the three residential sides of the campus.

"It took someone with no stake in the process to come in and objectively put all the issues on the table and find common ground," said resident Gary Groat.

GWU President Stephen Joel Trachtenberg said, "The mayor's intervention and use of mediation gave us a forum to work through our differences."