4.1
In
accordance with EM&A Manual, two noise monitoring stations, namely NMS1 and
NMS4 were selected for impact monitoring for the Contract. Impact noise
monitoring was conducted for at least once per week during the construction
phase of the Contract. Appendix B
shows the established Action and Limit Levels for the noise monitoring works.
4.2
Impact noise
monitoring was conducted at the 2 monitoring stations under the Contract, as
shown in Figure 3. Table 4.1 describes the locations of
the air quality monitoring stations.
Table
4.1 Location
for Air Quality Monitoring Locations
Monitoring Stations |
Location |
NMS1 |
Sha Lo Wan |
NMS4 |
San Tau |
4.3
Table 4.2 summarizes the noise monitoring equipment. Copies of calibration certificates are
provided in Appendix C.
Table
4.2 Noise
Monitoring Equipment
Equipment |
Model and Make |
Qty. |
Integrating
Sound Level Meter |
SVAN 957 |
2 |
Calibrator |
SV
30A |
2 |
Monitoring
Parameters, Frequency and Duration
4.4
Table 4.3 summarizes the monitoring parameters, frequency and total duration of
monitoring. The noise monitoring
schedule is shown in Appendix D.
Table
4.3 Noise
Monitoring Parameters, Frequency and Duration
Monitoring Stations |
Parameter |
Period |
Frequency |
NMS1 NMS4 |
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 |
Monitoring
Methodology and QA/QC Procedures
·
The
microphone head of the sound
level meter was positioned 1m exterior of the noise sensitive facade and lowered sufficiently so that the
building’s external wall acts 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 was recorded when
intrusive noise was not avoided.
·
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 shall
be checked with a portable wind speed meter capable of measuring the wind speed
in m/s.
4.5
The
microphone head of the sound level meter and calibrator were cleaned with a
soft cloth at quarterly intervals.
4.6
The
sound level meter and calibrator were checked and calibrated at yearly
intervals.
4.7
Immediately
prior to and following each noise measurement the accuracy of the sound level
meter shall be checked using an acoustic calibrator generating a known sound
pressure level at a known frequency. Measurements may be accepted as valid only
if the calibration levels from before and after the noise measurement agree to
within 1.0 dB.
4.8
The
noise monitoring results are summarized in
Table 4.4. Detailed monitoring results and graphical presentations of noise monitoring are shown in
Appendices G.
Table 4.4 Summary
Table of Noise
Monitoring Results during the Reporting Month
Monitoring Station |
Noise Level, Leq (30min)
dB(A) |
Limit
Level |
|
Average |
Range |
||
NMS1 |
68 |
57 – 72 |
75 dB(A) |
NMS4 |
60 |
53 – 63 |
Remark:
+3dB(A) Façade correction included
4.9
All
noise monitoring was conducted as scheduled in the reporting month. No Action/Limit Level exceedance was recorded.
4.10
According
to our field observations, the major noise source identified at the designated noise
monitoring stations in the reporting month are as follows:
Table 4.5 Observation
at Noise
Monitoring Stations
Monitoring Station |
Major
Noise Source |
NMS1 |
Air
traffic & marine traffic noise |
NMS4 |
Air
traffic & marine traffic noise |
4.11
Should
non-compliance of the criteria occur, action in accordance with the Action Plan
in Appendix K shall be carried out.