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, no construction vibration
monitoring was conducted for built
heritage when no 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) |
|
NIL |
NIL |
NIL |
NIL |
NIL |
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 |
|
NIL |
NIL |
NIL |
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, 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 is planned to be 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
No copies of calibration
certificates of the monitoring
equipment employed by the Contractor of the construction vibration monitoring are attached in Appendix C since no vibration monitoring was conducted in the
reporting period.
8.7
IIn the reporting
month, no construction vibration
monitoring was carried out by the Contractor for the built heritage features
when no 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.