The improvement of the parkway may be made by the owner or owners of the abutting lot. When made by such owner or owners, the parkway shall be brought to grade, which, on the street side, shall be at the line at the top of the curb, if the curb is constructed, otherwise to the line at the top of the curb as nearly as it can be determined at the time, considering the elevation of the sidewalk. The surface of the parkway shall be as nearly level as practicable.  The parkway so improved shall be maintained in good order thereafter.  (Ord. 86/T-5005).