3.1
According
to the EM&A Documents for HKLR listed in Table 1.1, baseline noise monitoring shall be carried out for a period of fourteen days at all
the monitoring locations.
3.2
The
noise levels shall be measured in terms of the A-weighted equivalent continuous
sound pressure level (Leq).
3.3
Logger
function check and calibration was carried out according to manufacturer’s
recommendations. The equipment was
checked and inspected not less than once every two days after the set up at
each monitoring station.
3.4
Baseline
noise monitoring was conducted at the two monitoring stations
under the Contract, as shown in Figure 2. Table
3.1 describes the locations of the noise monitoring stations.
Table 3.1 Location
for Noise Monitoring Stations
|
Monitoring Stations |
Location |
|
NMS 1 |
Sha Lo Wan |
|
NMS 4 |
San Tau |
3.5
Integrating
Sound Level Meter was used for noise monitoring. The meter is a 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) and also complied with International Electrotechnical Commission Publications 651:1979 (Type 1)
and 804:1985 (Type 1) specifications.
The noise monitoring equipment being used and copies of the calibration
certificates for the sound level meter and calibrator can be referred to the Baseline
Environmental Monitoring Report for HKBCF..
3.6
In
accordance with the EM&A Documents, baseline noise for the A-weighted
levels Leq, L10 and L90
was recorded. Data obtained from
the baseline noise monitoring was processed and presented according to the
following periods:
Ÿ Daytime: 0700-1900 hrs on
Ÿ Evening-time: 1900-2300 hrs
Ÿ Holiday-time: 0700-1900 hrs on holidays
Ÿ Night-time: 2300-0700 hrs of next day
3.7
The frequency and parameters of noise
measurement are presented in Table 3.2.
Table 3.2 Frequency
and Parameters of Noise Monitoring
|
Monitoring Stations |
Location
for Measurement |
Time Period |
Duration, min |
Parameter |
|
|
NMS 1 |
Area in front of No. 12 Sha Lo Wan |
Daytime on normal
weekdays (0700-1900 hrs) |
30 min |
Leq, L10 & L90 |
|
|
Evening time on
all days (1900-2300 hrs) and Holidays (including Sundays) during daytime and
evening (0700-1900 hrs) All days during
the night-time (2300-0700 hrs) |
5 min |
||||
|
NMS 4 |
San Tau (Rooftop of Village Office) |
3.8
Table 3.3
summarizes the types of measurement undertaken in the two monitoring
stations.
|
Monitoring Station |
Measurement |
|
NMS 1 |
Free
Field
measurement |
|
NMS 4 |
Free
Field
measurement |
3.9
Weather data was recorded during the baseline
period and is presented in Appendix B. The air temperature, precipitation and the relative
humidity data was obtained from Hong
Kong Observatory where the wind speed and wind direction were recorded by the
installed Wind Anemometer. The general
weather conditions (i.e. sunny, cloudy or rainy) were recorded by the
field staff’s observation on the monitoring days.
3.10
The monitoring procedures are as follows:
· The microphone head of the head level
meter was normally positioned
·
For
free field measurement, the meter was positioned away from any nearby
reflective surfaces. All records for free field noise levels will be adjusted
with a correction of +3 dB(A).
· The
battery condition was checked to ensure good 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 : 5 minutes (Leq
(30-min) would be determined for daytime noise by calculating the
logarithmic average of six Leq (5min)
data.)
· Prior
to and after noise measurement, the meter was calibrated using the 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.
· Noise
monitoring was carried out continuously for 24 hours during the 14 days
baseline monitoring period. Monitoring data was recorded and
stored automatically within the sound level meter system. At the end of the monitoring period, noise levels in term of Leq, L90 and L10 were recorded. In
addition, site conditions and noise sources were recorded when the equipment
were checked and inspected every two days.
· All
the monitoring data within the sound level meter system was downloaded through
the computer software, and all these data was checked and reviewed within the
computer.
3.11
Maintenance and Calibration procedures were as
follows:
· The
microphone head of the sound level meter and calibrator were cleaned with a
soft cloth at quarterly intervals.
· The
sound level meter and
calibrator were checked and
calibrated at yearly intervals.
· 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.
3.12
Baseline noise monitoring was conducted at the six monitoring station in the period
between 18th October 2011
and 1st November 2011.
The monitoring schedule is shown in Appendix
A.
3.13
The baseline noise monitoring results are
summarized in Table 3.4
to 3.6. All baseline noise monitoring results and graphical presentations of the data can be referred to Appendix G
and the Baseline Environmental
Monitoring Report for HKBCF respectively. Weather conditions recorded during the
baseline monitoring period are shown in
Appendix B.
Table 3.4 Summary
of Daytime Noise Monitoring Results (Normal Weekdays)
|
Daytime 0700-1900 hrs on normal weekdays |
|
||||||||
|
Leq (30 min) |
L10 (5 min) |
L90 (5 min) |
|||||||
|
Mean |
Max |
Min |
Mean |
Max |
Min |
Mean |
Max |
Min |
|
|
NMS 1 |
66.9 |
77.2 |
48.9 |
69.6 |
85.0 |
46.6 |
52.7 |
77.2 |
38.3 |
|
NMS 4 |
56.0 |
70.9 |
49.1 |
57.7 |
82.1 |
47.1 |
52.1 |
57.1 |
42.9 |
Table 3.5 Summary of Evening-Time
& Daytime (Holidays) Noise Monitoring Results
|
Evening-time 1900-2300 hrs on all days
& Daytime 0700-1900 hrs on holidays |
|
||||||||
|
Leq (5 min) |
L10 (5 min) |
L90 (5 min) |
|||||||
|
Mean |
Max |
Min |
Mean |
Max |
Min |
Mean |
Max |
Min |
|
|
NMS 1 |
67.1 |
79.2 |
42.0 |
70.6 |
84.0 |
44.8 |
52.9 |
76.2 |
35.5 |
|
NMS 4 |
56.2 |
66.5 |
48.0 |
58.2 |
70.4 |
50.3 |
52.9 |
56.4 |
44.3 |
Table 3.6 Summary
of Night-Time Noise Monitoring Results
|
Night-time 2300-0700 hrs of the next day |
|
||||||||
|
Leq (5 min) |
L10 (5 min) |
L90 (5 min) |
|||||||
|
Mean |
Max |
Min |
Mean |
Max |
Min |
Mean |
Max |
Min |
|
|
NMS 1 |
59.3 |
82.7 |
40.5 |
62.2 |
89.4 |
42.4 |
49.3 |
71.7 |
37.0 |
|
NMS 4 |
54.6 |
66.8 |
42.7 |
56.0 |
65.3 |
44.3 |
52.4 |
56.8 |
41.0 |
3.14
The weather was generally sunny and
fine during the baseline monitoring periods.
3.15
During the baseline noise monitoring period, the
influencing factors which may affect
the results are summarized in Table 3.7:
Table 3.7 Influencing Factors at
Noise Monitoring Stations
|
Monitoring Station |
Influencing Factors |
|
NMS
1 |
Air traffic noise |
|
NMS
4 |
Insect and bird calling |
3.16
The Action and Limit Levels were established in
accordance with the EM&A Documents
for HKLR. The baseline noise
level shall be referenced during the compliance check in the impact noise
monitoring period. Table 3.8
presents the Action and Limit Levels for construction noise.
Table 3.8 Action
Limit Levels for Noise during Construction Period
|
Time Period |
Action Level |
Limit Level |
|
0700-1900 hrs on normal weekdays |
When one documented
complaint is received |
75 dB(A) * |
Noted: If works are to be
carried during restricted hours, the conditions stipulated in the construction
noise permit issued by the Noise Control Authority have to be followed.
(*) reduce
to 70 dB(A) for schools and 65 dB(A) during school
examination periods.