What can home builders and land developers do to safeguard valuable existing trees? The proper mindset is essential. As project leader, the builder should make a commitment to conservation, and take the lead in making sure his team understands his goals and shares his values. By creating formal training programs and manuals on tree care during construction, developers and builders can get this critical point across. And requiring contractors and subs to take the course as a prerequisite for getting the work emphasizes this.
The Right Equipment Protects Trees
Specialized equipment, such as wide-track dozers, utility tunneling devices, or smaller equipment with rubber wheels, allows contractors to work with exacting care in tight spots. This ensures minimum disturbance in designated tree-save areas.
Using a substantial tree protection fence made of heavy posts and large-gauge wire is a good practice. Installing barbed wire as part of the tree fence is even better. Place the tree fence outside the tree's critical root zone (extending at least out to the canopy's drip line). Hang colorful flagging from the fence, and repair any damage promptly.
Saving Mature Trees Using Appropriate Construction Techniques
Lowering grades around mature trees require retaining walls (or, if on a slope, a combination retaining wall and tree well). Build the wall just outside the root zone, and just far enough away so that installing the wall's back fill won't impact roots. Keep in mind that with a mature shade tree the viable root zone may extend farther than the tree's canopy.
Trees don't like too much earth fill placed over their roots. If construction calls for raising grades, builders can use walls or tree wells to avoid root suffocation. The absolute minimum distance from a tree's trunk is three feet (3'). Tree survival improves dramatically when construction is kept out of the drip line. If filling around a specimen tree is unavoidable, use a tree well, and install perforated pipe or vertical shafts to get air to the roots.
There's a trade-off here - working further within the root zone may stress the tree, but extending retaining walls or earthwork farther out takes up more valuable real estate. The question a developer must ask: is the value of the impacted tree more important to the project than the value of the impacted land?
Protecting Trees from Utility Construction
Developers should avoid laying utilities in the critical root zones, if possible. If utility paths must go through root zones, tunneling under is better than trenching through, although more expensive. Use tunneling with significant trees, or where stands of large, established trees are to be saved within building areas. If several utilities can share a trench, it may reduce impact on root systems.
Significant trees add real value to a project. Where saving mature trees is the goal, builders must plan before they dig. A little attention to detail before construction can head off problems before they occur, and eliminate the need for removing dying trees at a later date - and ensure developers wind up with the tree conservation benefits they envisioned.
References:
American Forests/National Association of Home Builders. Building Greener Neighborhoods: Trees as Part of the Plan. Published Jointly by American Forests and Home Builders Press, 1998.
Richard Freeland - Hi! Glad to meet you. I'm a registered landscape architect in Georgia, specializing in sustainable land planning, garden design, and ...
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