9 In relation to the arborists' reports, it is worth making the following comments as the quality and substance of these reports was debated by both legal representatives.
1. Nigel Smith Tree Services prepared a report in March 2007 for the respondents for a previous application and re-assessed the tree in May 2008 for this application. He found no need to change his original findings. He notes a minor bark inclusion at the base of the two leaders. He was the only arborist to provide and internal assessment of the fork by carrying out a Resistograph test and included the original graphs in his report. The tree was drilled through the fork and through the more northern of the two leaders. The graphs showed no signs of significant internal defects. He concludes that the tree appeared sound and healthy and is retainable for the next 15-40 years with an acceptable degree of risk, assuming reasonable maintenance. He makes some recommendations for pruning and other maintenance. References from the literature, although not correctly cited, are including in his report.
2. Ross Leaver of Harbour Arbour assessed the tree for the respondents in May 2008. The findings of this report are somewhat contradictory. Mr Leaver found that the tree had good vigour, a normal amount of deadwood and sound branch unions but that the major problem was a bark inclusion at the base of the co-dominant stem. He states that, at this stage, however, there is no evidence of this union failing. He goes on to state that this is not a species that is prone to failure from included bark. He expressed concerns over its stability under easterly winds. He concludes that the included basal union poses a moderate risk to the neighbouring property but is unlikely to fail in the near future under normal conditions. He then goes on to talk about the risk posed under storm conditions and offers a range of management options from removal, to pruning to cabling. He does not make any specific recommendation. One reference to the published literature is included.
3. Andrew Izard of Northern Beaches Treecare Services was engaged by the applicants to assess the tree and to make comments on Nigel Smith's report. Mr Izard discusses likely changes to the soil and site, especially the possible compaction of the soil. He discusses work practices in the region and tree removals in the vicinity of the tree in question. He also discusses the possible impact of proposed works (by the applicants) within the root zone of the tree. He does not discuss the bark inclusion but concentrates on falling debris. He ultimately concludes that the tree should be removed. Mr Izard provides no substantiation of any of his assumptions either by providing evidence of testing or by the use of the published literature.
4. In conclusion, the quality of the reports was variable with all lacking elements of technical knowledge, adequate use of the published literature and logical conclusions and recommendations based on fact and validated assumptions. However, the inclusion of internal test results by Nigel Smith was appropriate and useful in this matter.
5. No arborist acknowledged the short summary of the Practice Directions for Expert Witnesses obligations for expert witnesses which are contained in Direction 14 of the Standard Tree Directions (and made in these proceedings).
10 Under s.12 of the Act, a number of matters must be considered. The relevant clauses in this case are: