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An investigation into the cause of vibration experienced by residents living at No.18-20 Tai Wong Street East has confirmed that the vibration level recorded did not exceed the limit set out in the approved foundation plans for the Lee Tung Street redevelopment project, and that the safety of the buildings nearby the construction site is not affected. Residents can put their minds at ease, a spokesman for the Buildings Department said today (March 1).
The investigation was conducted upon receipt of complaints from residents of No.18-20 Tai Wong Street East concerning the vibration of their building on January 29 and 31, 2011.
The limit of the vibration level as set out in the approved foundation plans for the Lee Tung Street redevelopment project is 7.5 mm per second. Vibration tests were conducted to find out the level of vibration at 15 buildings near the site. During the investigation, the highest level of vibration recorded was 2.7 mm per second, even when vibration-generating construction activity was in full motion on the Lee Tung Street redevelopment site. The vibration level recorded is far below the limit as approved.
"Generally speaking, it is normal for construction activities to generate a certain degree of ground vibration which may or may not be perceptible," the spokesman said. "The investigation also revealed that the perceptible vibration, the measured level of which as recorded is far below the limit set out in the approved plans, occurred during the excavation of inter-bedded strata of rock and soil by the method of hydro-fraise for the construction of diaphragm wall at the Lee Tung Street re-development site."
The Building (Construction) Regulations stipulate that no building works shall be carried out which may affect adversely the stability of any adjoining building, structure, land, street or services. The Buildings Department also has issued Codes of Practice and Practice Notes on foundation works in order to set out guidelines and requirements on how to assess the effect of foundation works on adjacent buildings. Such assessments, as well as various precautionary and protective measures, have to be provided by the project's Registered Structural Engineer (RSE) to the satisfaction of the Buildings Department prior to the actual commencement of foundation works.
In order to address the concern of the residents of the buildings affected, the Registered Structural Engineer and the Registered Specialist Contractor for foundation works (RSC) for the Lee Tung Street re-development project has proposed, with the agreement of the Buildings Department, to adjust the construction method by minimising the use of hydro-fraise for excavation of inter-bedded strata of rock and soil with the aim of minimising the vibration that may be caused. The RSE and RSC will also implement the following measures for resumption of construction works on site for the diaphragm wall:
(i) to give advance notice to nearby residents about the specific dates and times during which the vibration-generating construction activities will be carried out;
(ii) to set up a telephone hotline to answer the residents' enquiries; and
(iii) to step up building monitoring.
In addition, the RSE and RSC will position staff at the vibration-affected buildings to continuously monitor the structural safety of the buildings during the vibration-generating construction activities.
The Buildings Department and the RSE briefed the District Council and the affected residents on the test results and the arrangements for the above measures last Tuesday and today respectively. The Buildings Department will continue to monitor the construction activities on site and the implementation of the above measures.
Ends/Tuesday, March 1, 2011
Issued at HKT 19:47
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