The existing grade and contours of any parcel, plot or lot shall not be altered or modified by excavating, grading, terracing, filling or any other means whatsoever except to provide necessary ingress thereto and egress therefrom or in conjunction with the sinking of foundations, footings, utility lines, cesspools and similar subterranean or partially subterranean structures constructed as an accessory or appurtenance to a use permitted in the building zone. After the installation of such structures, the terrain shall, except where it has been lawfully built over, be restored to its original contours.

Where necessary to provide adequate ingress to and egress from premises, the grade may be lowered or raised not to exceed five feet measured to the finished surfaces of actual walkways or driveways used for ingress and egress.

Where all or any portion of any open excavation now or hereafter made, whether or not it shall contain a structure of any sort, shall be more than 29 inches in depth from its bottom to the top of its lip or edge, such excavation or any such portion of any excavation shall be provided with a surrounding enclosure not less than four feet in height, which shall be so constructed as to prevent access to such excavation or portion thereof through or beneath such enclosure and to hinder, impede and obstruct access thereto by climbing or scaling such enclosure.

Where any construction, excavation or fill shall, or may according to recognized engineering standards and principles, act to divert or increase the course or amount of run-off water to public land, streets or land of another, or where liquid industrial or commercial waste of any sort shall be created, adequate provision shall be made for the containment of all such waters and wastes or their diversion to other than sanitary sewers, streets, public land or land of another.

Where any construction or excavation shall, or may according to recognized engineering standards and principles, cause public land, streets and land of another to be eroded or to subside, adequate retaining structures shall be provided to prevent such erosion or subsidence.