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.
Table
4.2 Noise Monitoring Equipment
|
Equipment |
Model and Make |
|
Integrating Sound Level Meter |
SVAN977 |
|
Calibrator |
SV 30A |
Monitoring Parameters, Frequency and Duration
4.4
Table
4.3 summarizes the monitoring parameters, frequency and total duration of
monitoring.
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
As the Construction Phase EM&A Programme under
HY/2011/09 have been terminated since 24th October 2018, no
monitoring for construction noise was carried out in the reporting month.
4.9
Should non-compliance of the criteria occur, action
in accordance with the Action Plan in
Appendix C shall be carried out.