3.1
In
accordance with Updated EM&A Manual, construction noise monitoring was
conducted in terms of the A-weighted equivalent continuous sound pressure level
(Leq) to monitor the construction noise arising from the construction
activities. The regular monitoring frequency for each monitoring station shall
be on a weekly basis and conduct one set of measurements between 0700 and 1900
hours on normal weekdays. Appendix B
shows the established Action and Limit Levels for the environmental monitoring
works.
3.2
Impact
noise monitoring was conducted at the monitoring stations, as shown in Figure 2 according to Table 1.1 of
Updated EM&A Manual. Table 3.1 describes the locations of
the noise monitoring stations.
Table
3.1 Location
of Noise Monitoring Stations
|
Contract No. |
Monitoring Station |
Location |
|
ND/2019/01 |
CP-KTN-NMS5 |
N/A |
|
ND/2019/06 |
CP-FLN-NMS1 |
Belair Monte |
3.3
Integrating
Sound Level Meter was used for impact noise monitoring. The meters are Type 1
sound level meter capable of giving a continuous readout of the noise level
readings including equivalent continuous sound pressure level (Leq) and
percentile sound pressure level (Lx) that also complied with International
Electrotechnical Commission Publications 651:1979 (Type 1) and 804:1985 (Type
1) specifications. Table 3.2 summarizes
the noise monitoring equipment being used. Copies of calibration certificates
are attached in Appendix C.
Table 3.2 Noise
Monitoring Equipment
|
Equipment |
Model |
Quantity |
|
Sound & Vibration Analyser |
BSWA 801 |
2 |
|
Acoustical
Calibrator |
SV 30A |
1 |
3.4
Table 3.3 summarises the monitoring
parameters, frequency and total duration of monitoring. The noise monitoring schedule is shown
in Appendix D.
Table
3.3 Noise
Monitoring Parameters, Duration and Frequency
|
Contract No. |
Monitoring
Stations |
Parameter |
Duration |
Frequency |
Measurement |
|
ND/2019/01 |
CP-KTN NMS5 |
L10(30 min.) dB(A) L90(30 min.) dB(A) Leq(30 min.)dB(A) (as six consecutive Leq, 5min readings) |
0700-1900
hrs on normal weekdays |
Once per week |
Free-field[1] |
|
ND/2019/06 |
CP-FLN-NMS1 |
Façade |
Remarks:
[1]: Correction of +3dB (A) for Free-field Measurement.
[2]: A-weighted equivalent
continuous sound pressure level (Leq). It is the constant noise
level which, under a given situation and time period, contains the same
acoustic energy as the actual time-varying noise level.
L10 is the level
exceeded for 10% of the time. For 10% of the time, the sound or noise has a
sound pressure level above L10.
L90 is the level
exceeded for 90% of the time. For 90% of the time, the noise level is above
this level.
·
The
microphone head of the sound level meter was positioned at 1m from the exterior
of the noise sensitive facade and lowered sufficiently so that the building’s
external wall acted as a reflecting surface;
·
The battery condition was checked to
ensure the correct functioning of the meter;
·
Parameters such as frequency weighting,
the time weighting and the measurement time were set as follows:
—
frequency
weighting : A
—
time weighting : Fast
—
time measurement :
Leq(30 min.) dB(A)
(as six consecutive Leq, 5min readings) during non-restricted
hours (i.e. 0700-1900 hrs on normal weekdays)
·
Prior to and after each noise measurement,
the meter was calibrated using a Calibrator for 94.0 dB at 1000 Hz. If the difference in the calibration level
before and after measurement was more than 1.0 dB, the measurement would be
considered invalid and repeat of noise measurement would be required after re-
calibration or repair of the equipment;
·
During the monitoring period, the Leq, L90 and L10 were recorded. In
addition, site conditions and noise sources were recorded on a standard
record sheet;
·
Noise measurement was paused temporarily
during periods of high intrusive noise (e.g. dog barking, helicopter noise) if
possible and observation record during measurement period should be provided;
and
·
Noise monitoring was cancelled in the
presence of fog, rain, and wind with a steady speed exceeding 5 m/s, or wind
with gusts exceeding 10 m/s. The wind speed should be checked with a portable
wind speed meter capable of measuring the wind speed in m/s.
3.5
The
microphone head of the sound level meter and calibrator were cleaned with a
soft cloth at quarterly intervals.
3.6
The
sound level meter and calibrator were checked and calibrated at yearly
intervals.
3.7
Immediately
prior to and following each noise measurement, the accuracy of the sound level
meter should be checked using an acoustic calibrator generating a known sound
pressure level at a known frequency. Measurements would be accepted as valid
only if the calibration levels before and after the noise measurement agreed to
within 1.0 dB.
3.8
The
noise monitoring results are summarised in Table
3.4. Detailed monitoring results and graphical presentations of noise
monitoring are shown in Appendix E. The
weather information for the reporting month is summarized in Appendix F.
Table 3.4 Summary Table of Noise
Monitoring Results during the Reporting Month
|
Contract
No. |
Monitoring Station |
Construction Noise Level Leq (30 min), dB(A) |
Baseline
Level, dB(A) |
Limit
Level, dB(A) |
|
ND/2019/01 |
CP-KTN-NMS5 |
50.7-55.6 |
57.2 |
75 |
|
ND/2019/06 |
CP-FLN-NMS1 |
66.4-67.8 |
69.9 |
75
|
3.9
All
noise monitoring was conducted as scheduled in the reporting month. No complaint
was received during the reporting. No Action/Limit Level exceedance was
recorded. The summary of exceedance record in reporting month
is shown in Appendix H.
3.10
According
to our field observations, the major noise source identified at the designated
noise monitoring stations in the reporting month are as follows:
Table 3.5 Observation at Noise
Monitoring Stations
|
Contract No. |
Monitoring Station |
Location |
Major
Noise Source |
|
ND/2019/01 |
CP-KTN-NMS5 |
N/A |
Other
construction site not under ND/2019/01 |
|
ND/2019/06 |
CP-FLN-NMS1 |
Belair Monte |
Road Traffic at
Ma Sik Road |
3.11
Should
any project related non-compliance of the criteria occur, action in accordance
with the Action Plan in Appendix G
shall be carried out.