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
shows 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 |
4.2 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.
4.3
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 |
SVAN 957, BSWA 801 |
2 |
|
Acoustic Calibrator |
SV30A, B&K 4231 |
2 |
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
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
4.5 The monitoring procedures are as follows:
Ÿ 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.
Ÿ 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).
Ÿ The battery condition was checked to ensure the correct functioning of the meter.
Ÿ 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
Ÿ 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.
Ÿ 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.
Ÿ 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.
Ÿ 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.
4.6 The microphone head of the sound level meter and calibrator were cleaned with a soft cloth at quarterly intervals.
4.7 The sound level meter and calibrator were checked and calibrated at yearly intervals.
4.8 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.
4.9 All construction noise monitoring was conducted as scheduled in the reporting month. No Action/Limit Level exceedance was recorded. The summary of exceedance record in the reporting month is shown in Appendix F.
4.10 The baseline noise level and the Noise Limit Level at each designated noise monitoring stations are presented in Table 4.5.
4.11 Noise monitoring results and graphical presentations are shown in Appendix E.
4.12 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.