Standards for Utility Vegetation Management
2021 CT Utility Line Clearance Standards
Both Eversource and United Illuminating prefer to use Enhanced Tree Trimming ("ETT"), which applies fixed guidelines for pruning. Such pruning can lead to removal of healthy, structurally sound trees that would become hazardous.
Eversource Line Maintenance Plan for 2021 (in plan and in Appendix 3) and Vegetation Management Metrics for 2020
United Illuminating Line Maintenance Plan for 2021 (in plan and Attachment 2) and Vegetation Management Metrics for 2020
Alternatives to ETT:
In the past, United Illuminating's Line Clearance Standards, as revised in 2008, and used until its 11/01/13 Vegetation Management Plan adopted Enhanced Tree Trimming (ETT), called for use of directional pruning and for individual evaluation of each tree and consideration of its "growth rate, species, shape, condition and location of the tree." Eversource has long used ETT.
Directional Pruning for Line Clearance in Pennsylvania describes directional pruning and provides diagrams of proper pruning using this method.
Directional pruning appears to use branch reduction, an alternative to ETT that does not require removal of healthy tall trees. See "Assessing the Potential of Reduction Pruning in Mitigating the Risk of Branch Failure," by Biocompliance Consulting, October, 2012. Also, see Testimony of Goodfellow and Townsley to PURA, April, 2012, questioning ETT and discussing branch reduction.
The Arbor Day Foundation's TreeLine USA, promotes both dependable utility service and a healthy urban forest along the roadside. There are numerous TreeLine USA utilities throughout the United States that meet the requirements of the TreeLine USA program. Neither Eversource nor United Illuminating are on the list.