The chief purpose of the project was to increase navigational safety and efficiency and eliminate or greatly reduce delays for larger vessels by deepening the harbor's five principal tributaries from -35 ft to -40 ft. This involved removal and disposal of environmentally sensitive contaminated sediments not approved for off-shore disposal. Instead, large underwater disposal cells were excavated on the bottom of the harbor. Contaminated material was placed in these cells, then covered with a 3- to 5-ft thick capping layer of clean sand excavated from a simultaneous maintenance project in the Cape Cod Canal. Material removed from the cells was taken to the Massachusetts Bay Disposal Site. This was the first project of its kind to employ deep, in-channel disposal cells on such a scale. The company's resourceful management of the project earned a special quality award from the Federal Government.