8.1
In
accordance with the updated EM&A Manual, baseline condition survey and
baseline vibration impact assessment shall be conducted for identified built
heritage prior to the commencement of construction works. Baseline condition
survey and baseline vibration impact assessment shall be conducted by a
qualified building surveyor or qualified structural engineer to define the
vibration limit (a vibration limit at 7.5mm/s and 15mm/s could be adopted for
graded historical buildings and historical buildings respectively) and to
evaluate if construction vibration monitoring and structural strengthening
measures are required during construction phase to ensure the construction
performance meets the vibration standard stated in the EIA report.
8.2
According
to the condition survey report from cultural heritage condition survey for Castle
Peak Road Diversion under EP-466/2013/A, Kwu Tung
North New Development Area Road D1 to D5 under EP-468/2013/A, and Fanling
Bypass Eastern Section under EP-473/2013/A, a
vibration monitoring plan was proposed for the surveyed cultural heritage based
on the Buildings Department’s Practice Note (PNAP) APP-137. This section presents the
results of built heritage monitoring performed by the Contractor according to
the proposed monitoring plan in baseline condition survey report. Appendix B shows the Limit Levels for
the monitoring works.
8.3
In
the reporting month, construction vibration monitoring was conducted for built heritage features at FL02 when pile
driving operation was conducted within assessment area of the construction
works. The location of the construction vibration monitoring stations was summarised in Table
8.1 and shown in Appendix K.
Table 8.1 Location of Construction Vibration
Monitoring
|
EP. No |
Contract No. |
Monitoring Station (s) |
Nature of Cultural Heritage |
Location (s) |
|
EP-473/2013/A |
ND/2019/05 |
FL02 |
Grave |
Northwest side of Shung Him Tong Tsuen, at the
hillside behind On Lok Garden |
Monitoring Parameters and Frequency
8.4
Table 8.2 summarises
the vibration monitoring plan for surveyed cultural heritage under the Works
Contracts. Vibration monitoring was conducted for surveyed built heritage when
pile driving operation was conducted within the assessment
area of construction works.
Table
8.2 Vibration Monitoring Plan
|
EP. No |
Contract No. |
Monitoring Stations |
Distance with Construction Works |
Monitoring Plan |
|
EP-473/2013/A |
ND/2019/05 |
FL02 |
Within 50m |
Daily assessment is required |
|
Within 75m |
Bi-daily assessment is required |
|||
|
Within 100m |
Weekly assessment is required |
Remark:
[1] Baseline condition survey was conducted for built
heritage features at G202, G203, G303, G308, HKT03 and KT57 under
EP-468/2013/A, also HFL08, FL05, FL07, FL08, FL10, FL11, FL17, FL19, FL31 and
FL33 under ND/2019/04, and HFL05, FL02, FL04, FL24, FL27 and FL36 under
ND/2019/05 for EP-473/2013/A. As G202, G203, G303, G308, HKT03, KT57, HFL05, HFL08,
FL04, FL05, FL07, FL08, FL10, FL11, FL17, FL19, FL24, FL27, FL31, FL33 and FL36
were not within the assessment area of the related construction work, no
construction vibration monitoring was conducted for the built heritage in the
reporting month.
8.5
The
construction vibration monitoring was conducted throughout each event of the
pile driving operation on a daily basis. The effect of
ground-borne vibration from piling works on the surveyed built heritage was
assessed by the maximum peak particle velocity (ppv),
which was obtained from the maximum value of measurement of all pile driving
operation events.
8.6
Copies of calibration certificates
of the monitoring equipment employed by the Contractor of the construction vibration
monitoring are attached in Appendix C.
8.7
In
the reporting month, construction vibration monitoring was carried out by the
Contractor for the built heritage features at FL02 on a
daily basis when pile driving operation was conducted within 50m of the construction
work. No Limit Level exceedance for construction vibration monitoring was
recorded in the reporting month. The monitoring results are provided in Appendix K.
8.8
Table 8.3 summarises
the vibration limits for construction vibration monitoring for surveyed cultural
heritage.
Table 8.3 Vibration Limits for
Construction Vibration Monitoring
|
Type of Building |
Guide Values of Maximum ppv*
(mm/Sec) |
|
|
Transient Vibration |
Continuous Vibration |
|
|
Vibration-sensitive
/ dilapidated buildings# |
7.5 |
3.0 |
|
Declared monuments/ Historical structures |
3.0 |
|
Remarks:
* peak
particle velocity
# as cultural heritages are
sensitive receivers, vibration monitoring should be classified as
vibration-sensitive
8.9
If
any exceedance of limits is found or damage to either structural
or non-structural elements of the historic buildings is identified, the construction works
should be stopped
immediately and structural engineer’s advices should be sought for
any remedial work.