Battery Park City, contains nearly 92 acres of permanently protected open space, including beautifully designed and maintained parks and public gardens, playing fields and playgrounds, plazas, and walkways. It was built on a landfill on the Hudson River using 1.2 million cubic yards of dirt and rocks excavated during the construction of the World Trade Center and other construction projects, plus sand dredged from New York Harbor. Named for adjacent Battery Park in 1968, Battery Park City is owned and managed by the Battery Park City Authority, a public-benefit corporation created in 1968 under the authority of the Urban Development Corporation. Gateway City is the only complex predating the 1979 master plan by Cooper Eckstut. Parcels of land are leased to developers, who build in accordance with the Authority's guidelines. These incorporate green provisions mandating state-of-the-art environmentally-friendly building methods to maximize energy efficiency and minimize water usage. Sustainability is a key part in maintaining Battery Park City with an organically managed landscape and the continual implementation of composting and recycling initiatives.