A D.C. Superior Court jury ordered the city yesterday to pay $475,000 in damages to a Gaithersburg woman whose leg was severely injured in 1981 when a portion of the sidewalk gave way and she fell into the city's sewer system, according to her attorney, Patrick Christmas.

Virginia Ali-Brown, 39, who was then a secretary at the Department of Energy, was walking on Pennsylvania Avenue at 14th Street NW on March 27, 1981, when a catch basin that surrounds a manhole cover gave way and she fell chest-high into a hole, Christmas said.

Christmas charged that District officials were negligent because they knew of the "dangerous condition" for at least nine days and did nothing about it until after the accident. City work crews, he said, arrived on the scene as the ambulance came to take her to the hospital.

According to Christmas, Thomas J. Regan Jr., then executive director of the Pennsylvania Avenue Development Corp., testified that on March 18 he noticed the defective catch basin and told an employe to call the city to report it. The employe testified that he had noted the problem and had called the city to report it even before asked to.

Martin Grossman, head of the civil division of the D.C. corporation counsel's office, said the city denied any negligence on its part and will ask for a new trial.