(a) Where public walks are to be constructed or replaced in areas adjacent to existing walks, other than as specified in Section 903.03
(b), and where the grades at the extremities of the proposed construction are greater than six inches above or six inches below the existing adjacent walk grade, a permit shall be issued for the construction or replacement of the public walk as a temporary construction or replacement, and the owner or his agent shall sign an agreement to that effect. The agreement shall be attached to and shall become a part of the permit, and a record of agreement shall be maintained in the office of the City Engineer. The agreement signed by the owner and notarized shall not relieve him of future assessments for the construction of new walks required to meet the conditions resulting from a future street improvement program in the area involved. Nothing in this section shall prevent the owner or his agent from securing a permit for the construction of temporary or contour sidewalks, which shall not be construed as establishing the grade of any street.