At its meeting today (August 17), the Expert Panel on Tree Management (EPTM) was briefed on the report on the emergency felling of four stonewall trees at Bonham Road by the Highways Department (HyD) on August 7.
Members noted that prompt removal of the trees was considered the most feasible option to ensure public safety in the absence of any other feasible mitigation measures and with the impending thunderstorm outlook. This proposal by the HyD was endorsed by the Tree Management Office (TMO) of the Development Bureau and the Geotechnical Engineering Office (GEO) of the Civil Engineering and Development Department.
The HyD's representatives reported that the department had been closely monitoring the trees together with the TMO subsequent to the collapse of one of the stonewall trees listed on the Register of Old and Valuable Trees and the removal of another tree in poor condition on July 22 at the said location.
Though the four trees concerned had already been pruned on July 22 to reduce the risk of collapse, at least 11 new cracks were noted on the parapet wall behind the group of large trees on August 5. In addition, a gap was noticed along the crest U-channel at the base of the parapet wall on August 7, together with another gap behind the coping of the stone wall adjoining the smaller tree at the bend of St Stephen's Lane. These cracks and gaps are additional to the five cracks already noticed on August 3, bringing the total number of cracks identified at the parapet wall to 16. These showed the anchorage of the trees might be weakening, leading to the risk of imminent collapse of the trees.
Representatives of the HyD and the GEO briefed the members that the HyD and the GEO held consistent views on the stability of the masonry retaining wall at the site. Both agreed that the cracks on the parapet wall and the gaps between the drainage channel and the parapet wall could suggest concern about possible tree instability due to root anchorage being compromised though they did not indicate overall instability of the masonry retaining wall.
Members also exchanged views with the TMO's representatives on enhancement of the existing notification mechanism for tree removal. They noted that tree management departments would seek the TMO's advice on proposed removal of old and valuable trees and stonewall trees under non-emergency circumstances. If removal is supported, the TMO would arrange to consult the EPTM in advance. In other words, the EPTM will be notified prior to the tree removal. Under emergency circumstances, the departments or the TMO would notify the EPTM of removal of trees under the categories named above as and when practicable, without compromising public safety. In any event, the departments would submit a report after tree removal to the EPTM for its information.
Ends/Monday, August 17, 2015
Issued at HKT 15:27
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