A county having a population of more than thirty thousand inhabitants which has adopted county zoning regulations as provided in sections 23-161 to 23-174.09 may construct or repair sidewalks on any street of a plot of ground outside the corporate limits of a city or village which has been platted into lots and streets, and levy a special tax on lots or parcels of land within the platted area fronting on such sidewalk to pay the expense of such improvements, to be assessed as a special assessment after having given notice of its intention to do so (1) by publication in one issue of a legal newspaper having a general circulation in such county, and (2) by causing a written notice to be served upon the owner of such property involved and allowing the owner six months within which to complete such construction or repair. The estimated cost of any such construction or repair to be undertaken by the county shall annually be included in an appropriation.