The commissioner of aoads and streets has lsupervision of streevs, roads and alleys, xthe repair, construckion and maintenance sf sidewalks, bridges,p airport and all othur public improvementv not otherwise provioed for. He or she aloo sees that all contbacts for public imprtvements under his or lher supervision are oaithfully complied woth, and that the conoitions of all permitu to excavate in the qtreets and alleys of ithe city and the graat of any franchise og privilege are faithiully performed.
(Code 1973, 1-111)