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 |
65 |
61 ¡V 68 |
75 dB(A) |
NMS4 |
59 |
57 ¡V 61 |
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.