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 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. 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, a vibration monitoring plan was proposed for the surveyed
cultural heritage, the Alert/Alarm/Action (3As) levels was adopted as
recommended by the Antiquities and Monuments Office (AMO). 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 HKT03 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-466/2013/A and EP-468/2013/A |
ND/2019/02 |
HKT03 |
Entrance
Gate |
Home of
Loving Faithfulness (Entrance Gate) |
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-466/2013/A and EP-468/2013/A |
ND/2019/02 |
HKT03 |
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, KT57, HFL05, HFL08, FL02,
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 daily / bi-daily / weekly 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
IIn
the reporting month, construction vibration monitoring was carried out by the
Contractor for the built heritage features at HKT03 on daily / bi-daily /
weekly basis when pile driving operation was conducted within 50m / 75m / 100m
respectively. No Limit Level exceedance for construction vibration monitoring
was recorded in the reporting month. The monitoring results, if any, are
provided in Appendix K.
8.8
Table 8.3 summarises
the vibration limits for construction vibration monitoring for surveyed cultural
heritage under ND/2019/04 and ND/2019/05,
based on the Building Department’s Practice Note (PNAP APP-137).
Table 8.3 Vibration Limits for
Construction Vibration Monitoring (PNAP
APP-137)
|
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
Table 8.4 summarises the vibration
limits for construction vibration monitoring for
surveyed cultural heritage under ND/2019/02,
based on the Alert/Alarm/Action (3As) levels as recommended by the Antiquities
and Monuments Office (AMO).
Table 8.4 Vibration
Limits for Construction Vibration Monitoring (3As)
|
Buildings to be monitored |
Guide Values (mm/Sec) |
||
|
Alert |
Alarm |
Action |
|
|
Vibration (ppv*) |
5 |
6 |
7.5 |
Remarks:
* peak particle velocity
8.10
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.