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 with the vibration standard stated in
the EIA report.
8.2
According
to the condition survey report from cultural heritage condition survey for
Fanling Bypass Eastern Section under EP-473/2013/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 feature at FL02 and FL27 when
pile driving operation was conducted within assessment area of 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 |
|
FL27 |
Monument |
At the opposite of Shung Him Tong Public Toilet, at the bottom of slope feature |
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 were 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 and FL27 |
Within 50m |
Daily assessment is required |
|
Within 75m |
Bi-daily assessment is required |
|||
|
Within 100m |
Weekly assessment is required |
Remarks:
[1] Baseline condition survey was
conducted for built heritage features at HFL05, FL02, FL04, FL24, FL27 and FL36
under ND/2019/05 for EP-473/2013/A. As HFL05, FL04, FL24, FL27 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
The
copies of calibration certificate of the monitoring equipment employed by the
Contractor for 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 feature at FL02 and FL27 on a daily basis
when pile driving operation was conducted within 50m of 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 limit for
construction vibration monitoring for surveyed cultural heritage.
Table 8.3 Vibration Limit 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 limit have been found or damage to either structural or
non-structural elements of the historic buildings have been identified, the
construction works should stop immediately and seek structural engineer’s
advices for any remedial work.