SUMMARY OF
UTILITY CLEARANCE PRUNING GUIDELINES
The following guidelines are designed to maintain the required clearance of city trees, mature significant trees, and specimen (heritage) trees from high voltage transmission lines. Based upon known tree responses to various pruning techniques, these guidelines were developed to result in minimal re-sprouting and fewer pruning cycles.
· A tree’s growth under utility lines is most economically managed by lateral or directional pruning (thinning cuts). Directional pruning is the removal of a branch to the trunk or a significant lateral branch growing away from the conductor. Heading cuts (topping), on the other hand, encourages vigorous sprouting and increases the frequency of pruning cycles and the cost of maintenance.
· All trees should be examined for hazards before commencing with line clearance work. Hangers and dead wood should be removed.
· Where possible, the tree should be allowed to attain normal height, with crown development maturing away from high voltage conductors.
· Pruning should be restricted to removal of branches at crotches within the trees’ crown.
· As few cuts as are reasonable should e used to achieve the required clearances.
· When the pruning of a branch will result in the loss of more than one-half (1/2) of the foliage on the branch, it should be removed to the parent stem.
· Precautions shall be taken to pre-cut large limbs to avoid stripping or tearing the bark and minimize unnecessary wounding. Heavy limbs should e lowered on ropes to avoid damaging bark on limbs and trunks below.
· Placement of pruning cuts shall be determined by anatomy, structure and branching habit. Limbs should not be arbitrarily cut off based on a pre-established clearing limit.
· Final drop-crotch cuts should be made outside the branch bark ridge on the main stem or lateral branch. The remaining branch shall be no smaller than one third (1/3) the diameter of the portion being removed. The removed portion should be pruned out to direct the remaining growth away from the conductors.
·
The use of multiple, small-diameter shaping cuts
to create an artificially uniform crown form, commonly known as “roundover,” or
a hedge side-wall effect, is not cost effective nor consistent with proper
pruning practice. Both roundovers and the topping of trees for line clearance
shall be prohibited on historic sites in the City of