Protect Trees from Construction Damage
Tips on protecting trees from construction damage
Round Rock Leader, Saturday, November 13, 2004
By Emsud Horozovic, City of Round Rock Forestry Manager
In the past I wrote articles about tree planting, tree care, and various diseases and pests. In this article, we will explore how to save trees that mother nature has invested years in growing. Saving trees during construction often requires courage and wisdom by an individual, particularly if one lives in a community which traditionally bulldozes almost everything before construction begins.
The processes involved with construction can be deadly to the nearby trees. Unless the damage is extreme, the trees may not die immediately but could decline over several years. Years later you may not associate the loss of the tree with previous construction. Consider the following steps when construction is being done on your property.
1. Show the location of trees you want to save on a plat of your property. Enlist the help of an arborist to help decide which trees to remove and which to save. Your arborist can determine which trees are healthy and structurally sound and can withstand construction, and suggest measures to preserve and protect them.
2. Harmonize your project with the natural terrain and the trees you want to save. Consider this natural arrangement when you plan the location of buildings, sidewalks and driveways.
3. Protect “save” trees from soil compaction and severed roots with barrier fencing of the critical root zone. Vehicles driving or parking over roots or construction materials stored over roots result in compaction of the soil which cuts off the air and water passages in the soil. Some cutting of roots near construction is inevitable but much is avoidable. For example, the routing of underground utilities does not have to follow a straight line from street to house. When this is not possible, tunneling can be used to significantly reduce root damage.
4 .Choose a builder who shares your commitment to saving trees and has tree preservation experience.
5. Communicate your tree-preservation goals to everyone working on the project. Work with planners and architects, engineers and utility managers to place improvements where the impact on trees will be at a minimum. Meet with all foremen, contractors and sub-contractors who will work on the site. You might consider posting signage on the tree indicating the value of the tree. Attach such signage with tied wire—avoid nailing into your tree. Such signage may prevent individuals working on your site from damaging your tree and the area under it. Visit the site at least once a day if possible. Take photos at every stage of construction. If any infraction of the specifications does occur, it will be important to prove liability.
6. Provide aftercare to help trees recover from the stress of construction. Water periodically, especially in times of drought, and mulch the trees.
How trees are damaged during construction
Construction equipment can injure the above-ground portion of a tree by breaking branches, tearing the bark, and wounding the trunk. These injuries are permanent and can be fatal.
Cutting of roots
Digging and trenching necessary to construct a house and install underground utilities will likely sever a portion of the roots of many trees in the area. Roots typically will be found growing a distance of one to three times the height of the tree. Severing one major root can cause the loss of 5 to 20 percent of the root system.
The roots will be found mostly in the upper 6 to 10 inches of the soil.
Another problem due to digging and trenching is that the potential for the trees to fall over is increased. If the major support roots are cut on one side of a tree, the tree may fall or blow over. Less damage is done to tree roots if utilities are tunneled under a tree rather than across the roots.
An ideal soil for root growth and development is about 50 percent pore space. These pores, the spaces between soil particles, are filled with water and air. The heavy equipment used in construction compacts the soil and can dramatically reduce the amount of pore space. This not only inhibits root growth and penetration but also decreases oxygen in the soil that is essential to the growth and function of the roots.
Smothering roots by adding soil
Ninety percent of the fine roots that absorb water and minerals are in the upper 6 to 12 inches of soil. Roots require space, air, and water. Piling soil over the root system or increasing the grade will smother the roots. It only takes a few inches of added soil to kill a sensitive mature tree.
Protecting your trees
Installing Tree Protection Fences
Because our ability to repair construction damage to trees is limited, it is vital that the trees be protected from injury. The single most important action you can take is to set up construction fences around all of the trees that are to remain. Allow one foot of space from the trunk for each inch of trunk diameter, or simply install them at the dripline at least. The intent is to protect the above-ground portions of the trees and the root systems.
Instruct the construction personnel to keep the fenced area clear of building materials, waste, and excess soil. No digging, trenching, or other soil disturbance should be allowed in the fenced area.
If at all possible, it is best to allow only one access route on and off the property. All contractors must be instructed where they are permitted to drive and park their vehicles.
Specify storage areas for equipment, soil, and construction materials. Limit areas for burning (if permitted), cement wash-out pits, and construction work zones. These areas should be away from protected trees.
All of the measures intended to protect your trees must be written into the construction specifications. The written specifications should detail exactly what can and cannot be done to and around the trees. Fines and penalties for violations should be built into the specifications. The severity of the fines should be proportional to the potential damage to the trees, and should increase for multiple infractions.
Installing irrigation systems and rototilling planting beds are two ways root systems of trees can be damaged. Small increases in grade, as little as 2 to 6 inches can be devastating to your trees.
Your trees will require several years to adjust to the injury and environmental changes that occur during construction. Continue to monitor your trees and have them periodically evaluated for declining health or safety hazards.