The following shall be deemed a single purpose:
(1) acquiring land for a site for a public building or for any other public use and constructing, erecting, or acquiring by purchase any building thereon and furnishing and equipping the same;
(2) acquiring of rights-of-way for street or other purposes, making improvements thereon, or constructing sewers or water pipelines;
(3) procuring of a water supply and constructing or acquiring of a water system and improving the same if necessary.