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 noise monitoring stations.
Table
4.1 Location for Noise Monitoring Stations
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 |
BSWA 801 |
1 |
Calibrator |
SV 30A |
1 |
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 |
67 |
57 – 71 |
75 dB(A) |
NMS4 |
58 |
55 – 62 |
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.