City of Bunbury Library

Cimeco is a large project builder employed by the City of Bunbury to build a library in the city centre. Part of the project brief was that neighbouring and heritage trees were to be retained. An external Arborist report was commissioned in March 2007 that included an inspection of a number of identified trees. From a tree preservation viewpoint, the Arborist made the point that it was important to note that it is a tree's absorbing root zone that is primarily responsible for the health, vigour and the overall aesthetic appearance of the canopy of the tree. The Arborist also said that this absorbing root zone is generally found in the initial 300 mm to 500 mm of the soil profile, where soil oxygen, water and nutrient levels are at their highest. Any activity that results in a loss of a trees' absorbing root zone can have an effect on its future health and vigour. Severe root loss can also have an effect on the stability of the tree. The Arborist pointed out that it was essential that the retention of this area of the soil profile becomes the primary concern when designing and constructing an area of development adjacent existing trees if the trees are desired to be retained.

Two main specimen trees were noted as being located on the site boundary. One was identified as an Olive tree and the other as a Brazilian Pepper.

Arboreal Tree Care is the only qualified Arborist in the Bunbury region and were the logical choice by Cimeco to implement the recommendations of the report.

Excavation had already started and in some places up to 10 foot deep tapered to 2 foot. The olive tree was on the deeper excavated site and the pepper tree on the shallow site. Roots of both trees had already been exposed owing to excavation, an outcome not considered satisfactory if the health of the trees were to be maintained. The trees were selectively pruned to to bring the tree canopies back to the boundary line and to also proportion the root loss.

Management of the root zone was critical. Using an excavator, the root plate was undermined. Soil was then washed from the roots. Pruning was then carried out incrementally. Had excavation continued without Arborist intervention, the roots would have been damaged irreparably. Both trees were able to tolerate a certain amount of loss and damage to their absorbing root zone. Their preservation by Arboreal Tree Care was undertaken with sensitivity, ensuring the protection of their absorbing root zone during the remainder of the process to build the library for the City of Bunbury.

The following images show the finished project and how the trees have been preserved.