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 |
62 ¡V 68 |
75 dB(A) |
NMS4 |
55 |
50 ¡V 58 |
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.