Any tree on city property in the immediate vicinity of any excavation, demolition or construction site of any building, structure or street work, which in the city forester's discretion has any potential for injury or damage shall be guarded with a substantial fence, frame or box. Such a protective structure shall be not less than four feet (4') high and eight feet (8') square, or at a distance in feet from the tree equal to two (2) times the diameter of the tree trunk in inches measured four and one-half feet (41/2') above ground, whichever is the greater distance from the tree. All building materials, vehicles, extra dirt or other debris shall be kept outside the barrier. (Ord. 88-7 § 1, 1988: prior code § 15-4-15)