3.                  NOISE MONITORING


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.  These requirements are applicable to the non-designated project elements only as no noise sensitive receivers were identified within the vicinity of the proposed Siu Ho Wan WTW Extension site.  As the construction noise is the prime concern, noise levels shall be monitored to evaluate the construction noise impact during the construction phase.  No operational noise monitoring was recommended in accordance with the EIA Report for the Project.

Noise Parameters

3.2       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.

3.3       Supplementary information for data auditing, statistical results such as L10 and L90 shall also be obtained for reference.  A sample data record sheet is shown in Appendix B for reference.

Monitoring Equipment

3.4       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 should be accepted as valid only if the calibration level from before and after the noise measurement agrees to within 1.0 dB. 

3.5       Noise measurements should not be made in fog, rain, wind with a steady speed exceeding 5 m s-1 or wind with gusts exceeding 10 m s-1.  The wind speed shall be checked with a portable wind speed meter capable of measuring the wind speed in m s-1.

3.6       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 labeled.

Monitoring Locations

3.7       Based on the EIA Report, three worst affected locations are designated for construction noise monitoring as listed in Table 3.1 and illustrated in Figure 3.1.  The status and location of noise sensitive receivers may change after issuing this manual.  If such cases exist, the ET Leader shall propose updated monitoring locations and seek approval from ER and agreement from the IC(E) and EPD on the proposal.


Table 3.1         Noise Monitoring Stations during Construction Phase

Project Classification

Identification No.

Noise Monitoring Location

Non-designated Project


Bui O Public School

Non-designated Project


Pui O Lo Wai Tsuen facing South Lantau Road

Non-designated Project


Pui O Lo Wai Tsuen facing the Pumping Station

3.8       When alternative monitoring locations are proposed, the monitoring locations shall be chosen based on the following criteria:

·        Monitoring at sensitive receivers close to the major site activities which are likely to have noise impacts;

·        Monitoring at the noise sensitive receivers as defined in the Technical Memorandum;

·        Assurance of minimal disturbance to the occupants during monitoring.

3.9       The monitoring station shall normally be at a point 1 m from the exterior of the noise sensitive facade and be at a position 1.2 m above ground.  If there is a problem with access to the normal monitoring position, an alternative position should 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 IC(E) 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.

Baseline Monitoring

3.10     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.  A schedule on the baseline monitoring shall be submitted to the IC(E) for approval before the monitoring starts.

3.11     There shall not be any construction activities in the vicinity of the stations during the baseline monitoring.  Any non-project related construction activities in the vicinity of the stations during the baseline monitoring shall be noted and the source and location recorded.

3.12     In exceptional cases, when insufficient baseline monitoring data or questionable results are obtained, the ET shall liaise with the EPD to agree on an appropriate set of data to be used as a baseline reference and submit to the ER for approval.

Impact Monitoring for Construction Noise

3.13     Noise monitoring shall be carried out at all the designated monitoring station.  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:

·        one set of measurements between 0700 and 1900 hours on normal weekdays.

3.14     If construction works are extended to include works during the hours of 1900 - 0700, additional weekly impact monitoring shall be carried out during evening and night-time works.  Applicable permits under NCO shall be obtained by the Contractor.

3.15     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 proved to be irrelevant to the construction activities.

Event and Action Plan for Construction Noise

3.16     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 Action Plan in Table 3.3 shall be carried out.

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 complaint is received

75 dB(A) for residential dwellings

  70 dB(A) for educational institutes (65dB(A) during examination period)


Table   3.3       Event / Action Plan for Construction Noise








Action Level

1.        Notify IC(E) and Contractor;

2.        Carry out investigation;

3.        Report the results of investigation to the IC(E), ER and Contractor;

4.        Discuss with the Contractor and formulate remedial measures;

5.        Increase monitoring frequency to check mitigation effectiveness.

1.     Review the analysed results submitted by the ET;

2.        Review the proposed remedial measures by the Contractor and advise the ER accordingly;

3.        Supervise the implementation of remedial measures.

1.        Confirm receipt of notification of failure in writing;

2.        Notify Contractor;

3.        Require Contractor to propose remedial measures for the analysed noise problem;

4.        Ensure remedial measures are properly implemented.


1.   Submit noise mitigation proposals to IC(E);

2.   Implement noise mitigation proposals.

Limit Level

1.        Identify source;

2.        Inform IC(E), ER, EPD and Contractor;

3.        Repeat measurements to confirm findings;

4.        Increase monitoring frequency;

5.        Carry out analysis of Contractor’s working procedures to determine possible mitigation to be implemented;

6.        Inform IC(E), ER and EPD the causes and actions taken for the exceedances;

7.        Assess effectiveness of Contractor’s remedial actions and keep IC(E), 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 Contractors remedial actions whenever necessary to assure their effectiveness and advise the ER accordingly;

3.        Supervise the implementation of remedial measures.

1.        Confirm receipt of notification of failure in writing;

2.        Notify Contractor;

3.        Require Contractor to propose remedial measures for the analysed noise problem;

4.        Ensure remedial measures properly implemented;

5.        If exceedance continues, consider what portion of the work is responsible and instruct the Contractor to stop that portion of work until the exceedance is abated.

1.        Take immediate action to avoid further exceedance;

2.        Submit proposals for remedial actions to IC(E)  within 3 working days of notification;

3.        Implement the agreed proposals;

4.        Resubmit proposals if problem still not under control;

5.        Stop the relevant portion of works as determined by the ER until the exceedance is abated.

Mitigation Measures


Construction Phase


3.17     As detailed in the EIA Report for the Project, raw water mains construction at Pui O, and demolition and reprovisioning of Pui O Raw Water Pumping Station would cause adverse noise impacts on the noise sensitive receivers.  Appropriate mitigation measures were therefore recommended.  The mitigation measures recommended in the EIA Rreport for these non-designated elements of the Project are summarised below:

·        Use of quiet equipment during raw water mains construction at Pui O, and demolition and reprovisioning of Pui O Raw Water Pumping Station;

·        Use of movable noise barriers during laying raw water mains at Pui O for Bui O Public School and the NSRs located less than 25m from the raw water mains construction site.; 

3.18  Regarding the educational NSR BOS, the following mitigation measures were proposed for carrying out raw water mains construction in vicinity of this NSR such that it would comply with noise criterion of 65 dB(A) during examination period.

·Excavation of Trench / Breaking up Pavement – wheeled excavator/loader fitted with hydraulic breaker would not be operated during examination period;

·Reinstating Road Surface during raw water mains construction – Reduction of 50% operated On-time percentage of lorry;

Installation of Pipes and Bedding – Reduction of number of operated mobile crane.  (Use one mobile crane only) 

3.19     In addition, implementation of the following good site practices is recommended:

-     Only well-maintained plant should be operated on-site and plant should be serviced regularly during the construction programme;.

                  -    Silencers or mufflers on construction equipment should be utilised and should be properly maintained during the construction programme;.

                  -    Mobile plant, if any, should be sited as far away from NSRs as possible;.

                  -    Machines and plant (such as trucks) that may be in intermittent use should be shut down between work periods or should be throttled down to a minimum;.

                  -    Plant known to emit noise strongly in one direction should, wherever possible, be orientated so that the noise is directed away from the nearby NSRs;.

                  -    Material stockpiles and other structures should be effectively utilised, wherever practicable, in screening noise from on-site construction activities.


Operation Phase


3.20     Since the predicted operation noise levels at all closest representative NSRs would not comply with the night -time criteria, mitigation measures would be required.  It was recommended to provide silencersacoustic louvres for the ventilation fans and acoustic louvres for ventilation openings of pump hall at reprovisioned Pui O Raw Water Pumping Station, which would provide a minimum insertion loss of 120 dB(A).    

The implementation schedule for the recommended mitigation measures is presented in Appendix A.