A. Protection Or Removal: In the circumstances where construction and utility operations underground will affect the health of a tree, a determination will be made considering the overall value of the tree. The criteria for determining a value for a tree will be based on species, age, condition, cost of preserving the tree, and urgency of work to be completed. A decision based on this value will be made concerning the protection or removal of the tree in question. This decision shall be made jointly by the public works department and the city engineer or the appropriate city official.
B. Cutting Roots: Large roots shall be cut with the proper pruning equipment. Clean, flush, smooth cuts shall be made on tree roots.
C. Open Work Pits: Work pits that need to be open for an extended time require special protection methods for trees. The roots shall be cut closer to the tree in relation to the construction zone. A temporary wall shall be put up between the tree and construction zone. The area between the root zone and the construction zone should then be backfilled and kept moist. Work pits should not stay open any longer than necessary.
D. Construction Zones:
1. Trees to be protected in construction zones and the dimensions of those zones shall be determined by the public works department and the city engineer or appropriate city official.
2. Clearly mark the "root protection zone" before construction begins. Snow fencing is often used for this purpose. Absolutely no activity or traffic can be tolerated within the "root protection zones" during construction.
3. Mulch the "root protection zones" with wood chips generated from tree removals. Mulch helps insulate the rooting environment from changes imposed by opening the forest canopy.
4. Prune the crown to compensate for stress. Reducing the number of leaves and branches will counterbalance the changes imposed on the root environment. All trees must be pruned by a qualified arborist who can remove the dead wood and selectively thin the live branches without disfiguring the tree. Regular pruning may be required every three (3) to five (5) years.
5. Watering during dry periods is important, both during and after construction. Shallow tree roots are very subject to drought stress. Mulch will help reduce evaporation, but watering will be required during periods of scarce rainfall. Water the entire root zone slowly so that the top eight (8) to twelve inches (12") is thoroughly wet.
6. Fertilization of mature trees is not usually recommended as long as growth is adequate and nutrient deficiencies are not evident. Mulch recycles nutrients naturally. Heavy fertilization may stimulate excessive growth in the top and could counteract pruning intended to reduce the crown size.
E. Utility Operations:
1. Any underground utility installations or operations that come in conflict with city street tree roots are subject to the review and approval of the public works department.
2. If the determination to tunnel under a tree for underground utility installations or operations is made, the depth and distance shall be provided by the public works department. Under no circumstances is the tunnel to be less than two feet (2') in depth.
a. Recommendations for trenching and tunneling for utility operations:
Tree Diameter
| Distance Of Tunnel From Center Of Tree
| Minimum Depth Of Tunnel Or Trench
| ||
5–9 inches | 6 feet | 21/2 feet | ||
10–14 inches | 10 feet | 3 feet | ||
15–19 inches | 12 feet | 31/2 feet | ||
20 + inches | 15 feet | 4 feet |
(Ord. 08-11, 8-4-2008)