Amending an Ordinance approved December 15, 1969, as amended, which approved the redevelopment proposal, the urban renewal plan and the relocation plan of the Redevelopment Authority of the City of Philadelphia for the redevelopment of the Model Cities Urban Renewal Area, by approving the twenty-ninth amendment of the redevelopment proposal, the twenty-first amendment to the urban renewal plan and the twentieth amendment to the relocation plan, which provide, inter alia, for changes in the eastern boundary of the urban renewal area and excluding therefrom the boundaries of the American Street — Open Common Ground