In recent posts we’ve talked about some of the factors that go into deciding whether or not to save a tree on a construction project. We’ve talked about signs and symptoms of tree defects; we’ve talked about potential targets (things that could be hurt or broken if the tree fails); and we’ve talked about industry standards for tree risk assessment.
My friend Registered Consulting Arborist Ed Milhous reminded me that one thing we did not talk about was applicability. We would not go through this assessment process for every single tree on a parcel being developed. The trees the assessment will be performed on will be specified by your assignment, which will be based on specifications that may be written to comply with a local tree ordinance. They will usually specify something like: the assessment of all trees of a certain size (diameter); the assessment of all trees within a certain distance of the Limit of Disturbance; the assessment of all trees whose Critical Root Zones are bisected by the Limit of Disturbance; etc.
There is an industry standard for management of trees and shrubs during site planning, development, and construction – ANSI A300 (Part 5)-2012. The Secretariat for this standard is the Tree Care Industry Association. There is also Best Management Practices guide to the standard published by the International Society of Arboriculture.
The flow chart for management of trees during construction according to the standard can be found here. VERY IMPORTANT: the longer into the process you make a decision to try to save a tree, cost of intervention increases and probability of success decreases! Make your tree protection plans in the planning and design phases. Pre-construction and construction are for implementation.
Specific requirements will vary, but most will have a few elements common:
Install protective devices around trees, along the Limit of Disturbance, or both. These devices may look very different:
They should protect tree trunks and crowns from damage during construction and keep vehicles, materials, and equipment out of tree protection areas. Root pruning is normally performed along the Limit of Disturbance to separate the tree from the area of disturbance as grading can pull and tear roots and lead to subsequent tree damage and decline. All tree protection devices should be in place before construction begins.
If a tree declines because of construction activity (this normally takes a while, as in years, to happen), the owner may be left with removal of a large tree close to new improvements (translation: expensive tree removal). It is much more efficient to remove poor candidates during construction. Worse, structure rather than health may be impacted. Having a big tree fall on your new stuff is bad, and it is worse if people are on site when it happens.
Following industry standards will give you success with preserving trees on your project. Start early, plan well, honor tree protection zones and devices. Standards for tree management during construction are key tools for advancing compatibility of people + trees in cities. If you have a project, The Consulting Group @SavATree is happy to help with your construction-related tree management needs.