Where the grade of any street or part of a street has not been established or where a street has not been worked or filled to the established grade or where the street has been graded but does not conform to the established grade the owner of any lots or lands abutting on such street shall only be required to construct or repair such temporary sidewalk along such street with such material as the city may direct.
Neb. Rev. Stat. §§ 14-3,104