3.1 In this section, the requirements, methodology, equipment, monitoring locations, criteria and protocols for the monitoring and audit of noise impacts during the construction phase of the Project are presented.
3.2 Construction noise impacts from this Project are predicted at the identified Noise Sensitive Receivers (NSRs). Noise mitigation measures would be required to reduce noise levels to the stipulated standard. A noise monitoring programme shall be undertaken to verify such mitigation measures would be implemented properly.
3.3 The EIA findings confirmed that proper designs of the PTWs, SCISTW and disinfection facilities would control the potential noise impacts at noise sensitive receivers within acceptable levels, thus operational phase noise monitoring would be considered not necessary.
3.4 The construction noise level shall be measured in terms of the A-weighted equivalent continuous sound pressure level (Leq). Leq (30 minutes) shall be used as the monitoring parameter for the time period between 0700 and 1900 hours on normal weekdays. For all other time periods, Leq (5 minutes) shall be employed for comparison with the Noise Control Ordinance (NCO) criteria.
3.5
Supplementary information for
data auditing, statistical results such as L10 and L90 shall also be obtained
for reference. A sample data record
sheet based on the one presented in the EM&A Guidelines for Development Projects
in
3.6 As referred to in the Technical Memorandum (TM) issued under the NCO, sound level meters in compliance with the International Electrotechnical Commission Publications 651: 1979 (Type 1) and 804: 1985 (Type 1) specifications shall be used for carrying out the noise monitoring. 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 level from before and after the noise measurement agree to within 1.0 dB.
3.7 Noise measurements shall not be made in fog, rain, 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.
3.8 The ET is responsible for the provision of the monitoring equipment. He shall ensure that sufficient noise measuring equipment and associated instrumentation are available for carrying out the baseline monitoring, regular impact monitoring and ad hoc monitoring. All the equipment and associated instrumentation shall be clearly labelled.
3.9 The locations of construction noise monitoring stations are summarized in Table 3.1 and shown in Figure 3.1 (a to h). These locations represent the worst affected sensitive receivers during construction.
Table 3.1 Construction Noise Monitoring Stations
|
Noise Monitoring Station |
NSR ID (Based on EIA Report) |
Noise Monitoring Location |
|
M1 (North Point PTW) |
N1 |
|
|
M2 (Wan Chai East PTW) |
N6 |
|
|
M3 ( |
N8 |
Block A, |
|
M4 ( |
N10 |
|
|
M5 ( |
N13 |
Chuk Lam Ming Tong |
|
M6 (Cyberport PTW) |
N17 |
Aegean Terrace |
|
M7 (Wah Fu PTW) |
N20 |
Wah Ming House, Wah Fu Estate |
|
M8 ( |
N21 |
Wah Lai House, Wah Kwai Estate |
|
M9 (Ap Lei
Chau PTW) |
N24 |
|
|
M10
(Disinfection Facilities) |
N26 |
Open
area near Naval Base Barrack * |
|
M11
(SCISTW) |
N27 |
Planned
FSD Diving Rescue and Diving Training Centre |
Note: * Due to the security reason, naval base
barrack would not be accessible. As such, noise monitoring should be carried
out at the open area near naval base barrack instead. The ET leader should
review the status and location of the monitoring station.
3.10 The status and locations of noise sensitive receivers may change after issuing this manual. If such case exists, the ET Leader shall propose updated monitoring locations and seek approval from EPD and agreement from the ER and the IEC before baseline monitoring commences.
3.11 When alternative monitoring locations are proposed, the monitoring locations shall be chosen based on the following criteria:
(i) Monitoring at sensitive receivers close to the major site activities which are likely to have noise impacts;
(ii) Monitoring at the noise sensitive receivers as defined in the Technical Memorandum; and
(iii) Assurance of minimal disturbance to the occupants during monitoring.
3.12 The monitoring station shall normally be at a point 1 m from the exterior of the sensitive receiver building facade and be at a position 1.2 m above the ground. If there is problem with access to the normal monitoring position, an alternative position may be chosen, and a correction to the measurements shall be made. For reference, a correction of +3 dB(A) shall be made to the free field measurements. The ET shall agree with the IEC on the monitoring position and the corrections adopted. Once the positions for the monitoring stations are chosen, the baseline monitoring and the impact monitoring shall be carried out at the same positions.
3.13 The ET shall carry out baseline noise monitoring prior to the commencement of the construction works. The baseline monitoring shall be carried out daily for a period of at least two weeks. Before commencing the baseline monitoring, the ET shall develop and submit to the IEC the baseline monitoring programme such that the IEC can conduct on-site audit to check accuracy of the baseline monitoring results.
3.14 There shall not be any construction activities in the vicinity of the stations during the baseline monitoring.
3.15 In exceptional cases, when insufficient baseline monitoring data or questionable results are obtained, the ET Leader shall liaise with the ER, EPD and IEC to agree on an appropriate set of data to be used as a baseline reference and submit to the ER and IEC for agreement and EPD for approval.
3.16 Noise monitoring shall be carried out at all the designated monitoring stations. The monitoring frequency shall depend on the scale of the construction activities. The following is an initial guide on the regular monitoring frequency for each station on a weekly basis when noise generating activities are underway:
(a)
one set of
measurements between 0700 and 1900 hours on normal weekdays.
3.17 If construction works are extended to include works during the hours of 1900 – 0700 as well as public holidays and Sundays, additional weekly impact monitoring shall be carried out during respective restricted hours periods. Applicable permits under NCO shall be obtained by the Contractor.
3.18 If a school exists near the construction activity, noise monitoring shall be carried out at the monitoring stations for the schools during the school examination periods. The ET Leader shall liaise with the school’s personnel and the Examination Authority to ascertain the exact dates and times of all examination periods during the course of the contract.
3.19 In case of non-compliance with the construction noise criteria, more frequent monitoring, as specified in the Action Plan in Table 3.3, shall be carried out. This additional monitoring shall be continued until the recorded noise levels are rectified or demonstrated to be unrelated to the construction activities.
3.20 The Action and Limit levels for construction noise are defined in Table 3.2. Should non-compliance of the criteria occur, action in accordance with the Event and Action Plan in Table 3.3 shall be implemented.
Table 3.2 Action and Limit Levels for Construction Noise
|
Time Period |
Action Level |
Limit Level |
|
0700 –
1900 hours on normal weekdays |
When one documented compliant is received |
75 dB(A) * |
Notes: If works
are to be carried out during restricted hours, the conditions stipulated in the
Construction Noise Permit (CNP) issued by the Noise Control Authority have to
be followed.
* 70 dB(A) and 65 dB(A) for schools
during normal teaching periods and school examination periods, respectively.
Construction Phase
3.21 For the following construction tasks of the Project, it is considered necessary to adopt quiet PME:
Drop/Riser Shaft
· Construction of upper shaft, Diaphragm wall at shaft
· Construction of upper shaft, Excavation at shaft
· Construction of lower shaft
· Drop/riser shaft finishing works
Production Shaft
· Construction of upper shaft, Diaphragm wall at shaft
· Construction of upper shaft, Excavation at shaft
· Construction of lower shaft
· Tunnel construction
PTW Upgrading Works
· Piling
· Excavation (shallow excavation with sheet piling)
· Concreting
· Demolition Works
· Roadwork
SCISTW Upgrading Works
· Site clearance and setup site office
· Shallow excavation
· Drill and blast excavation
· Deep excavation
· Civil works
· Pipeworks
· Demolition works
3.22
To alleviate the construction
noise impact on the affected NSRs, movable noise barriers and acoustic mats are
proposed to be provided for particular items of plant and construction works.
With a surface mass of not less than 2.5kg/m2, it is anticipated
that the acoustic mats can provide 5 dB(A) noise reduction. Besides, it is
anticipated that a movable noise barrier with a cantilevered upper portion
located within
3.23 For the following construction tasks of the Project, it is considered necessary to adopt movable noise barrier:
Drop/Riser Shaft
· Construction of upper shaft, Diaphragm wall at shaft
· Construction of upper shaft, Excavation at shaft
· Construction of lower shaft
· Drop shaft finishing works
Production Shaft
· Construction of upper shaft, Diaphragm wall at shaft
· Construction of upper shaft, Excavation at shaft
· Construction of lower shaft
· Tunnel construction
PTW Upgrading Works
· Piling
· Concreting
SCISTW Upgrading Works
· Site clearance and setup site office
· Shallow excavation
· Drill and blast excavation
· Deep excavation
· Civil works
· Pipeworks
· Demolition works
3.24 Besides, use of acoustic mats is recommended for the following construction tasks of the Project:
Drop/Riser Shaft
· Construction of upper shaft, Diaphragm wall at shaft
Production Shaft
· Construction of upper shaft, Diaphragm wall at shaft
· Construction of upper shaft, install pipe pile wall
PTW Upgrading Works
· Piling
· Excavation (shallow excavation with sheet piling)
SCISTW Upgrading Works
· Deep excavation with diaphragm wall
3.25
In addition, the good site practices listed below shall be
adopted by all the Contractors to further ameliorate the noise impacts.
· Only well-maintained plant shall be operated on-site and plant shall be serviced regularly during the construction program.
· Silencers or mufflers on construction equipment shall be utilised and shall be properly maintained during the construction program.
· Mobile plant, if any, shall be sited as far away from NSRs as possible.
· Machines and plant (such as trucks) that may be in intermittent use shall be shut down between works periods or shall be throttled down to a minimum.
· Plant known to emit noise strongly in one direction shall, wherever possible, be orientated so that the noise is directed away from the nearby NSRs.
· Material stockpiles and other structures shall be effectively utilised, wherever practicable, in screening noise from on-site construction activities.
3.26 If the above measures are not sufficient to restore the construction noise quality to acceptable levels upon the advice of ET Leader, the contractor shall liaise with the ET Leader to identify further mitigation measures. They shall be proposed to ER for approval, and the contractor shall then implement these additional mitigation measures.
3.27 The implementation schedule for the recommended mitigation measures is presented in Appendix A.
Operation Phase
3.28 Based on the design information, most of the newly proposed equipment would be housed/enclosed in a concrete structure. In addition, acoustic louvers have been proposed for air supply fans/extraction fans of transfer pumping stations and ventilation fans of deodourization unit at Sandy Bay PTW, Cyberport PTW and Wah Fu PTW. It is recommended that the maximum allowable sound power level (SWL) of each new transformer at Sandy Bay PTW shall be limited to 89 dB(A) during the detailed design stage.
3.29 The implementation schedule for the recommended mitigation measures is presented in Appendix A.
Table 3.3 Event/Action Plan for Construction Noise
|
Event |
Action |
|||
|
ET |
IEC |
ER |
Contractor |
|
|
Action
Level being exceeded |
1.
Notify ER, IEC and Contractor; 2.
Carry out investigation; 3.
Report the results of investigation to the IEC, ER and
Contractor; 4.
Discuss with the IEC and Contractor on remedial measures
required; 5. Increase monitoring
frequency to check mitigation effectiveness. |
1.
Review the investigation results submitted by the ET; 2.
Review the proposed remedial measures by the Contractor and
advise the ER accordingly; 3.
Advise the ER on the effectiveness of the proposed
remedial measures. |
1.
Confirm receipt of notification of failure in writing; 2.
Notify Contractor; 3.
In consolidation with the IEC, agree with the Contractor
on the remedial measures to be implemented; 4.
Supervise the implementation of remedial measures. |
1. Submit
noise mitigation proposals to IEC and ER; 2. Implement
noise mitigation proposals. |
|
Limit
Level being exceeded |
1.
Inform IEC, ER, Contractor and EPD; 2.
Repeat measurements to confirm findings; 3.
Increase monitoring frequency; 4.
Identify source and investigate the cause of exceedance; 5.
Carry out analysis of Contractor’s working procedures; 6.
Discuss with the IEC, Contractor and ER on remedial
measures required; 7.
Assess effectiveness of Contractor’s remedial actions and
keep IEC, EPD and ER informed of the results; 8.
If exceedance stops, cease additional monitoring. |
1.
Discuss amongst ER, ET, and Contractor on the potential
remedial actions; 2.
Review Contractor’s remedial actions whenever necessary to
assure their effectiveness and advise the ER accordingly. |
1.
Confirm receipt of notification of failure in writing; 2.
Notify Contractor; 3.
In consolidation with the IEC, agree with the Contractor
on the remedial measures to be implemented; 4.
Supervise the implementation of remedial measures; 5.
If exceedance continues, consider stopping the Contractor
to continue working on that portion of work which causes the exceedance until
the exceedance is abated. |
1. Take immediate action to
avoid further exceedance; 2. Submit proposals for
remedial actions to IEC and ER within 3 working days of notification; 3. Implement the agreed
proposals; 4. Submit further proposal
if problem still not under control; 5. Stop the relevant
portion of works as instructed by the ER until the exceedance is abated. |