UNIT Working the Five-Step EDUCATION Felling Plan

By Ralph (Rip) Tompkins

LEARNING OBJECTIVES tree. A hazard is defined in ISA’s Glossary of Arboricultural Terms as CONTINUING The arborist will be able to “a situation or condition that may result in personal injury, property h explain the five-step planning process for felling a tree damage, or disruption of human activities.” Hazards can include site 5hazards, such as power lines. They can also include tree hazards, such h 5 discuss techniques for estimating the height of a tree for felling as deadwood, hangers, decayed wood, vines, or animals in trees. h explain the reactive forces that can result when using a chain saw Obstacles are considered to be anything you can hurt or damage in the process of felling a tree. Obstacles may include other trees, h plan the notch, hinge, and back cut technique for felling a tree with lean people, houses, vehicles, or other personal property. It may be nec- essary to determine the height of a tree before felling it to make sure CEUs for this article apply to Certified Arborist, Utility Specialist, no obstacles will be damaged. Municipal Specialist, Tree/Worker Climber, and the BCMA practice category. Determining a tree’s height helps to answer several important ques- tions when creating a plan: Is it possible to fell the tree at all? Is there enough room for it to fit? Would it fit if part of the top were removed? A good definition of an accident is “an unplanned event.” Most There are several techniques that can be used to determine tree height. people don’t wake up in the morning and say, “I’m going to go out Most techniques for height estimation are based upon a geometric prin- today and get into an accident,” or “I think I’ll drop a tree across ciple of similar right triangles. There are devices available to assist workers some power lines.” But these things happen every day. Why? with height estimation, such as the hypsometer and the rangefinder. Because people sometimes fail to properly plan their tasks. Another technique for estimating tree height employs nothing It is especially important to use proper planning and procedures more than a straight stick. Hold the stick so that the distance from when felling trees. In its most basic sense, a tree felling plan is your eye to your hand equals the distance nothing more than taking information from your hand to the top of the stick. about the tree, the site, and any surround- Hold your arm horizontally and the ing hazards and obstacles, and then apply- stick vertically. Walk forward or back- ing cutting skills and other tools (e.g., ward until the distance from your hand pull lines, wedges, pulleys) to bring the to the top of the stick is proportional tree safely to the ground. However, many (visually equal) to the distance from the people fail to take the time to look closely felling cut to the top of the tree. You can at the information available, which results then estimate the height based on the in far too many “unplanned events.” distance you are standing from the tree. Felling a tree as a whole may be the There are some limitations to this quickest and most profitable way to get last method. The estimation technique the job done, but it may not always be the assumes that the tree is vertical, the best way to get the job done. Before any ground is level, and the top of the tree cutting begins, it is important to develop can be seen. Also, it may be necessary a thorough plan and decide whether the to adjust for the difference between your tree can be safely felled at all. This article height and the height of the felling cut. discusses a five-step plan for tree felling. Another good reason to determine the height of the tree is to establish a Step #1: Checking danger zone around the tree. Don’t assume the tree will go exactly where you want for Hazards Any tree can pose a variety of hazards for a tree crew, The five-step plan begins with an assess- including power lines, deadwood, hangers, decayed wood, it. One good rule of thumb is to establish ment of hazards in, on, and around the vines, and animals. a circular danger zone around the tree

12 www.isa-arbor.com ARBORIST • NEWS

with a radius (distance from the tree base to the perimeter of the If you stand away from the tree at some distance in the intended UNIT circle) that is at least 1.5 times the tree’s height. Everyone present, direction of fall, you can’t accurately tell whether the tree leans toward except the sawyer, should be outside of this zone when a tree is you or away from you, but you can see whether the tree has lean being felled. to one side or the other. This is important, because it tells you what All hazards present should be considered before continuing with the good and bad sides of the tree are. The bad side is the side where a felling plan. For example, the tree may be surrounded by houses the lean is. If possible, you should finish your cutting from the and may not have solid wood where the hinge needs to be. Identifying good side of the tree. That way, if something goes wrong, the tree such issues may be reason to abandon the plan at the start and seek is more likely to fall away from you rather than toward you. It may another means of tree removal. Once you have determined that all also be necessary to adjust your felling aim to account for side lean. EDUCATION identified hazards can be managed, you may move on to the next To determine forward or backward lean, stand to one side of the step of the plan. tree at 90 degrees to the fall. If the tree is straight up or has back- Devices for ward lean, you will need something, such as a pull line or wedges, determining to lift the tree over center and let gravity do the rest. If there is a lot tree height of back weight, you may want to add some mechanical advantage generally use the principles to help pull the tree over. Generally, a forward-leaning tree does not of geometric need a pull line because it’s already obvious which way the tree triangulation. wants to fall. If one is installed, as many company policies dictate,

Using a straight there is no need to pull with excessive force. It is important that CONTINUING stick can also pull lines are used properly. Excessive pre-tensioning of pull lines achieve an esti- mate of tree can create a more dangerous cutting situation for the sawyer. height using a Side lean is often one of the greatest challenges in precision tree geometric prin- felling. The hinge wood is strongest from front to back and weakest ciple of similar right triangles. from end to end. As a tree falls, the hinge begins weakening, with the tension fibers at the back of the hinge pulling apart, and the fibers Find the position at which the at the front of the hinge compressing. Depending on the strength of distance from the wood fibers of a particular species of tree and the amount of side your hand to lean, it may be hard for the hinge to work all the way to the ground. the top of the stick visually equals the height of the tree from the cut.

Step #2: Determining the Lean of the Tree The lean or weight of the tree is key for several reasons. Looking for the way a tree leans depends on the direction from which you are looking at the tree. It is important to put yourself in the correct position to get the correct information. There are two types of potential leans in relation to the direc- tion of fall. The tree may have forward or backward lean, or it may have side lean. It is important when determining lean to take into account the entire crown of the tree, not just the trunk. Frame the tree with your hands on both sides of the crown, find a center spot, and drop a plumb line down. Where the plumb line hits the ground A tree with side lean can be challenging to fell, because tree species with in relationship to the base of the tree will tell you where the lean is. weak wood fiber may not hold the hinge all the way to the ground. D

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