4.1
In accordance with approved
EM&A Manuals for Stage 1 works in Year 2015, no noise impact monitoring is
required for Stage 1 works of the Project.
4.2
According to approved EM&A
Manual for Stage 2 works (Year 2015), construction noise monitoring was
conducted to monitor the construction noise arising from the construction
activities under the Stage 2 works of the Project. The regular monitoring
frequency for each monitoring station shall be on a weekly basis and conduct
one set of measurements between 0700 and 1900 hours on normal weekdays.
Appendix B shows the established Action and Limit Levels for the environmental
monitoring works.
4.3
Noise monitoring was conducted
at 6 designated monitoring stations (N1, N2, N3, N5, N6 and N7) in the
reporting month. Figures 2a – 2c show the locations of these stations.
Table 4.1 Noise Monitoring Stations
|
Monitoring Stations |
Locations |
Location of Measurement |
|
N1 |
HKMLC Wong Chan Sook Ying
Memorial School |
Rooftop (about 5/F) area |
|
N2 |
Bethel High
School |
Rooftop (about 4/F) area |
|
N3 |
No. 159 Mai Po San Tsuen |
G/F area |
|
N5 |
Block 2, Dills Corner
Garden |
G/F area |
|
N6 |
Home of Loving
Faithfulness |
Rooftop (about 3/F) area |
|
N7 |
Village House
in Shek Wu Wai |
G/F area |
4.4
Integrating Sound Level Meter
was used for impact noise monitoring. The meters are Type 1 sound level meter
capable of giving a continuous readout of the noise level readings including
equivalent continuous sound pressure level (Leq)
and percentile sound pressure level (Lx) that also complied with
International Electrotechnical Commission
Publications 651:1979 (Type 1) and 804:1985 (Type 1) specifications.
4.5
Acoustic Calibrator was used to
check the accuracy of the sound level meter. The calibrators generate a
continuous and highly stable sound pressure level at known frequency of 1 kHz
that also complied with IEC 942: 1988 Class 1 specifications. Table 4.2 summarizes the noise
monitoring equipment in reporting period. Copies of calibration certificates
are provided in Appendix C.
Table 4.2 Noise Monitoring Equipment
|
Equipment |
Model No. |
Qty. |
|
Integrating Sound Level
Meter/ Sound & Vibration Analyser |
BSWA
308 / SVAN 957 |
2 |
|
Acoustic Calibrator |
ST-120 / SV30A |
2 |
4.6
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
Frequency and Parameters of Noise Monitoring
|
Monitoring Stations |
Parameter |
Period |
Frequency |
Measurement |
|
N1 |
Leq(30 min.) dB(A) L10(30
min.) dB(A) L90(30
min.) dB(A) |
0700-1900 hrs on
normal weekdays |
Once per week |
Façade |
|
N2 |
Façade |
|||
|
N3 |
Free Field |
|||
|
N5 |
Free Field |
|||
|
N6 |
Façade |
|||
|
N7 |
Free Field |
Monitoring
Methodology and QA/QC Procedures
4.7
The monitoring procedures are
as follows:
·
The monitoring station were
normally be at a point 1m from the exterior of the sensitive receivers building
façade and be at a position 1.2m above the ground.
·
For free field measurement, the
meter was positioned away from any nearby reflective surfaces. All records for
free field noise levels were adjusted with a correction of +3 dB (A).
·
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
- Measurement time : 30 minutes
·
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 is more than 1.0 dB, the measurement was
considered invalid and repeat of noise measurement was required after
re-calibration or repair of the equipment.
·
At the end of the monitoring
period, the Leq, L90 and L10
were recorded. In addition, noise
sources were recorded on a standard record sheet.
·
Noise measurement would be
paused temporarily during periods of high intrusive noise if possible and
observation would be recorded when intrusive noise was not avoided.
·
Noise monitoring would be
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. supplementary monitoring would be
provided to ensure sufficient data would be obtained.
4.8
The microphone head of the
sound level meter and calibrator were cleaned with a soft cloth at quarterly
intervals.
4.9
The sound level meter and
calibrator were checked and calibrated at yearly intervals.
4.10
Immediately prior to and
following each noise measurement, the accuracy of the sound level meter was
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.
4.11
All construction noise monitoring
were conducted as scheduled in the reporting month except 29th
January 2020 since all works were cancelled. No Action/Limit Level exceedance
was recorded. The summary of exceedance record in the reporting month is shown
in Appendix F.
4.12
The baseline noise level and
the Noise Limit Level at each designated noise monitoring stations are presented
in Table 4.5.
4.13
Noise monitoring results and
graphical presentations are shown in Appendix
E.
4.14
The other noise sources
identified which might affect the noise monitoring results at the designated
noise monitoring stations are as follows:
Table
4.4 Other Noise Sources Identified Which Might
Affect the Noise Monitoring Results
|
Monitoring Stations |
Locations |
Other Noise Source(s) |
|
N1 |
HKMLC Wong Chan Sook Ying Memorial School |
Road
traffic noise Noise
from daily school activities |
|
N2 |
Bethel High School |
Road
traffic noise Noise
from daily school activities |
|
N3 |
No. 159 Mai Po San Tsuen |
Road
traffic noise |
|
N5 |
Block
2, Dills Corner Garden |
Road traffic noise |
|
N6 |
Home
of Loving Faithfulness |
Road traffic noise Noise from activities at the premise and
workshops near the premise |
|
N7 |
Village House in Shek Wu Wai |
Road traffic noise Noise
from activities at workshops near the village house |
Table
4.5 Baseline Noise Level and Noise
Limit Level for Monitoring Stations
|
Station |
Baseline Noise Level, dB
(A) |
Noise Limit Level, dB
(A) |
|
N1 |
62.2 (at 0700
– 1900 hrs on normal weekdays) |
70* (at 0700 –
1900 hrs on normal weekdays) |
|
N2 |
55.2 (at 0700
– 1900 hrs on normal weekdays) |
|
|
N3 |
68.8 (at 0700
– 1900 hrs on normal weekdays) |
75 (at 0700 –
1900 hrs on normal weekdays) |
|
N5 |
70.7 (at 0700 – 1900 hrs on normal
weekdays) |
75 (at 0700 – 1900 hrs on normal
weekdays) |
|
N6 |
72.0 (at 0700 – 1900 hrs on normal
weekdays) |
75 (at 0700 – 1900 hrs on normal
weekdays) |
|
N7 |
70.7 (at 0700 – 1900 hrs on normal
weekdays) |
75 (at 0700 – 1900 hrs on normal
weekdays) |
(*) Noise Limit Level is 65 dB (A) during
school examination periods.