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walls, compartmentalization, and wound -wood formation), no one can know <br /> for certain how long a living, growing tree will continue intact. <br /> These tests reveal only a sampling of the trees' potential survivability. At <br /> best we can only provide you with an educated guess, since there could be a <br /> major failure mere inches away from a testing location where no <br /> abnormality is apparent. <br /> We offer our recommendations based on these data and our experience, but <br /> it is up you where to draw the line. This will depend on your priorities, and <br /> how much risk you are willing to accept and live with. <br /> • <br /> Our data shows a third of the trees having hazard ratings of ten, eleven, and <br /> twelve, (twelve being the highest hazard rating assigned by International <br /> Society of Arboriculture). All trees with 10, 11 and 12 ratings should be <br /> replaced as soon as possible. Nature is unpredictable, and a tree in this range <br /> could, against all odds and reason, live for over a decade. Rationally, the <br /> highest hazard trees must be dealt with right away. <br /> On the other hand, we may select a tree to be pruned and treated, and due to <br /> the unknown nature of the wood fiber formation and scarring history of its <br /> limbs, it could potentially have a major failure. In spite of our testing and <br /> analysis, no one can predict the future outcome for these trees for sure. We <br /> can only make recommendations based upon our best professional <br /> judgement using the data collected. <br /> Another third of the study trees had ratings of nine, which may be <br /> considered a balance point for deciding whether to keep or replace a tree. <br /> All trees with this rating are to be replaced over time, sometime within the <br /> next 10 years, unless future changes require immediate action for safety <br /> reasons. <br /> Bear in mind that these ISA rating numbers are not absolutes. It is up to you <br /> to determine the length of the treatment and replacement process, by <br /> skewing the curve of this "sliding scale" according to your priorities. You <br /> must decide whether to replace the mid -range risk trees within the next few <br /> years, or to replace them over a longer period. This decision will depend <br /> upon your priorities, the budget allocated for thin project, and the agreed <br /> upon level of appropriate risk management. <br /> 6 <br />