No person shall place or maintain upon the ground in any public place any stone, concrete, brick or other impervious material or substance in such a manner as to obstruct the free access of air and water to the roots of any tree upon any public place in the city without first obtaining written permission therefor. Unless otherwise provided, there shall be maintained about the base of the trunk of each tree at least nine square feet of open ground for each three inches in diameter of the tree, and for every additional two inches of such diameter there shall be an increase of at least one square foot of open ground.
(Ord. 13-87, passed 3-16-1987)