Upon a determination, by resolution, of the governing body of the city in which such land is located, that the acquisition and development of undeveloped vacant land, not within a substandard and blighted area, is essential to the proper clearance or redevelopment of substandard and blighted areas or a necessary part of the general community redevelopment program of the city, or that the acquisition and development of land outside the city, but within a radius of three miles thereof, is necessary or convenient to the proper clearance or redevelopment of one or more substandard and blighted areas within the city or is a necessary adjunct to the general community redevelopment program of the city, the acquisition, planning, and preparation for development or disposal of such land shall constitute a redevelopment project which may be undertaken by the authority in the manner provided in the Community Development Law.