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 |
SVAN977 |
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
¡P
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.
¡P
The battery condition was checked to ensure the correct functioning of
the meter.
¡P
Parameters such as frequency weighting, the time weighting and the
measurement time were set as follows:
¡X
frequency weighting :
A
¡X
time weighting :
Fast
¡X
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)
¡P
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.
¡P
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.
¡P
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.
¡P
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 |
66 |
54 ¡V 70 |
75 dB(A) |
NMS4 |
57 |
51 ¡V 59 |
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.