Gist of the Fourth Meeting held on 26 July 2012

1. Incident Report on Failure of OVT LCSD YTM/8 on Nathan Road (Paper No. 5/2012)
   • Members were presented with the above Incident Report. The subject Ficus microcarpa collapsed suddenly on 19 July 2012. It was diagnosed of Brown Root Rot (BRR) in 2010 and had been treated regularly to control the growth of the BRR fungus and was closely monitored by LCSD. Its general health conditions had been found improving since 2011. There was also no sign of heavy BRR infection above the root collar and trunk base of the subject tree.
   • The cause of failure was attributable to the decay of the central part of the trunk and main roots below soil level which could not be observed at the soil surface level of the raised planter.
2. Incident Report on Failure of OVT LCSD YTM/96
   • Members were presented with the above Incident Report. The subject Ficus microcarpa was found collapsed on 23 July 2012 at Kowloon Park while typhoon signal no.3 was in force.
   • It has been put under LCSD's close observation list as the tree was suspected to be infected by BRR through the nearby YTM/97 since May 2008. LCSD had enhanced the treatment regime since then and the obvious sign of decline in tree health was not observed in recent inspection.
   • The collapse was suspected to be attributable to the failure of root system and wood rot of tree trunk under the soil.
   • Members suggested that inspection of the major root system of other suspected BRR infected trees at Nathan Road near the trunk base with air spade (i.e. jets of high pressure air stream) in addition to resistography was worthwhile.
3. A Review of the 35 OVTs along Nathan Road
   • Members were briefed on the updated conditions of the above OVTs in particular those warranted special attention on their health or structural conditions (i.e. YTM/2, 11 and 12 ) after a recent visual tree assessment conducted by the TMO. The short and long term mitigation actions were also recommended for implementation by LCSD.
   • Members have the following views after deliberation:
     1. there was a serious concern about the structural integrity of YTM/11 and its health condition together with the effect of BRR.
     2. a more detailed investigation into the extent of the cavity and the condition of the roots of YTM/11 through the use of air-spade would be required.
     3. a support system might not be installed for YTM/11 if after detailed investigation where the data shown that the spread of BRR and cavity of the trunk had substantially jeopardized the structural stability.
     4. the same would apply to other infected trees and trees with grave structural weaknesses.
4. TMO Inspection Report on OVT LCSD Is/1
   • Members were briefed on the TMO's independent review of the updated health and structural conditions of OVT Is/1 and the recommendation. The subject tree Ficus microcarpa was growing on the landscape area outside the Tung Chung Sitting-out Area. The overall health and structural conditions was considered 'very poor'. Signs of BRR were also observed on the subject tree during recent inspection.
   • Roots were found splitting which indicated that the tree had high tendency to fail. In view of the little chance of recovery, removal was recommended to eliminate the hazard posing to the public and to reduce the chance of spread of BRR fungus.
   • Members in general agreed to the recommended removal of the tree.
5. TMO Inspection Report on OVT LCSD WCH/10
   • Members were briefed on the TMO's independent review of the updated health and structural conditions of OVT WCH/10 and the recommendation. The subject tree Ficus microcarpa was found nearly toppled but was stopped by the guy wires on 24 July 2012. It was reported to the TMO on the same day and tree removal was granted in view of public safety.
   • Members had no comments on the tree removal.
6. TMO Inspection Report on OVT LCSD E/2
   • Members were briefed on the TMO's independent review of the updated health and structural conditions of OVT E/2 and the recommendation. The subject tree was a mature Ficus microcarpa growing on a slope near to the main entrance of the Lei Yue Mun Park. It showed obvious signs of BRR. The overall health and structural condition of this tree was considered as 'poor'. The TMO recommended felling of the tree for the protection of public safety and reduction of the chance of spread of BRR fungus.
   • Members supported to remove the subject tree.
7. Site Visit to OVTs along Nathan Road, Tsim Sha Tsui
   • Upon detailed visual inspection of YTM/11 & 12, members opined that both the health and structural conditions of YTM/12 was in general satisfactory and no mitigation measures were required at the moment. As for YTM/11, more diagnostic works should be carried out before they could advise on the mitigation measures required.