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.