Tree roots are generally located in the top 12–24 inches of soil and can extend to a distance exceeding the trees height and/or width. The roots located 3-5 feet from the trunk are often relatively inactive, and if cut, will cause a column of decay that can reach the top of the tree with time.  The feeder roots of the tree can sustain damage during construction from lack of water, soil compaction or physical damage resulting from cutting. The following guidelines are designed to minimize damage to the root system of protected trees.  These guidelines establish a “Root Protection Zone” to safeguard the health of protected trees.

1. Protective chain-link fencing with an access gate of minimal width should be installed at the Root Protection Zone of protected trees and approved in place by staff prior to the commencement of any construction, or demolition.
    

2. The protection zone should be irrigated sufficiently with clean potable water to keep the tree in good health and vigor before, during, and after construction. This may mean deeply soaking the ground periodically.
    

3. No construction staging or disposal of construction materials or byproducts including but not limited to paint, plaster, or chemical solutions is allowed in the Root Protection Zone.
    

4. The Root Protection Zone should not be subjected to flooding incidental to the construction work.
    

5. All work conducted in the ground within the Root Protection Zone of any protected tree should be accomplished with hand tools, unless an air spade is utilized. Trenches in the Root Protection Zone should be tunneled, or completed with an air spade to avoid damage to small feeder roots within the root protection zone. Information regarding air spades is available from staff.
    

6. Where structural footings are required and major roots (over 3” in diameter) will be impacted, the engineer of record should submit acceptable footing design alternatives and or location alternatives to staff before proceeding with further plan review.
    

7. Where more than 50% of the root zone is impacted or roots greater than 3 inches in diameter are to be removed within four feet of the trunk, the engineer of record should submit acceptable design alternatives to staff for review.
    

8. Any required trenching should be routed in such a manner as to minimize root damage. Radial trenching (radial to the tree trunk) is preferred as it is less harmful than tangential trenching. Construction activity should be diverted from the Root Protection Zone. Cutting of roots should be avoided (i.e. place pipes and cables below uncut roots). Wherever possible and in accordance with applicable code requirements, the same trench should be used for multiple utilities.
    

9. “Natural” or pre-construction grade should be maintained in the Root Protection Zone. At no time during or after construction should soil be in contact with the trunk of the tree above the basal flair.
    

10. In areas where the grade around the protected tree will be lowered, some root cutting may be unavoidable. Cuts should be clean and made at right angles to the roots. When practical, cut roots back to a branching lateral root.
     

11. When removing existing pavement in the Root Protection Zone, avoid the use of heavy equipment, which will compact and damage the root system.
     

12. If staff requires mulch in the Root Protection Zone the mulch materials and location should be shown on the plan. Larger projects will require construction staging plans to indicate where materials will be stored and how the equipment will move in and around the property to minimize damage to the Root Protection Zone and tree canopies. Root damage and soil compaction may be mitigated in some cases by using plywood or mulch in the Root Protection Zone.