Construction of branch or lateral sewer lines in territory annexed to first-class city

class city. Where adequate sanitary sewers, combined sewers, drains, appurtenances, or property service connections have not been constructed in any territory annexed to a city of the first class since July 1, 1946, the city legislative body may, by ordinance, on recommendation of the board of the metropolitan sewer district, which includes such city, construct sanitary sewers, combined sewers, drains, appurtenances or property service connections within such territory, to connect with the city sewerage or drainage system, at the cost of the area benefited.