Landscape Contractor / Design Build Maintain

SEP 2017

LC/DBM provides landscape contractors with Educational, Imaginative and Practical information about their business, their employees, their machines and their projects.

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by Robert Booty, Registered Consulting Arborist Above There are a number of methods used to excavate and identify roots in the soil for study. To some degree, root damage occurs during these procedures. Air- spades use compressed air to move soil from around roots. Hydro excavation or vacuum excavation is the use of pressurized water in con- junction with a vacuum that sucks the liquefied soil into a waiting tanker truck. The most widely used method is excava- tion by hand with a pick or shovel. Left This is a root inspection procedure diagram. This is how the radar looks for roots below ground. As the antenna is moved along the ground every 2/10ths of an inch, a radio signal is released into the soil at a predetermined depth set by the technician. I Its eight o'clock in the morning and your phone rings, the caller says he has a ninety year old red - wood tree (Sequoia sempervirens) in his backyard that is cracking the concrete slab of his patio and garage floor, and would like the roots cut. Not having the ability to see beyond the concrete slab makes things difficult, even for the experienced arborist. Traditionally, a reasonable conclusion is ob - tained after concrete removal and soil excavation is performed. In the end, you may find that the dam - age is just due to normal ground movement and set- tling. Hopefully your initial recommendation didn't involve root pruning or tree removal! So many trees could be preserved if we had a better way to deter - mine where their root systems are below ground. Ground Penetrating Radar Non-invasive ground penetrating radar has been successfully used for below-ground root mapping worldwide for over a decade. It has the ability to penetrate hard surfaces such as asphalt and concrete, and then into the soil to identify and map roots on a large scale. This technology has proven to be a very special tool for the arborist. How Does it Work? GPR is an established technique that has been used for many different applications worldwide for over 30 years. Radar is an object-detection system that uses electromagnetic waves— specifically, radio waves—to identify the range, altitude, direction or depth and speed of both moving and fixed objects. Its applications today seem endless. As this signal encounters a root, it is reflected primarily off the moisture within it, then back to a receiver inside the antenna with surprising accuracy. This is how radar distinguishes the difference between a root and a rock or piece of metal. How difficult is this technology to use? What are its limitations? Training and regular use are very essential for success with this equip - ment and software. TreeRadar Inc., 48 LC DBM PHOTOS: ARBORIST ONSITE GETTING TO THE ROOT OF THE PROJECT Scanning Over Bare Surface Scanning Over Covered Surface Scan Direction (Linear Feet) Depth (Feet) Cross-sectional View of Roots Reflected Radar Beam from Roots Radar Beam X X X X X X X X X X X X X X X X X X X = Detected Roots Courtesy of TreeRadar, Inc. 1.2 2.5 3.7 4.9 6.1 7.4 8.5 9.8 11 2.9 5.4 8.0 11 13

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