2.                  NOISE MONITORING

 

Introduction

2.1              Representative noise sensitive receivers (NSRs) along the proposed alignment were identified and assessed in the EIA Report.  The locations of the representative NSRs are shown in Figure 2.1.  It was anticipated that some NSRs would be subjected to construction noise and traffic noise impacts from the Project. 

2.2              This section presents the requirements, methodology, equipment, monitoring locations, criteria and protocols for the monitoring and audit of noise impacts during the construction and operation phases of the Project.  

 

Construction Noise Monitoring

 

Noise Parameters

2.3              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.

2.4              As 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

2.5              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.

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

2.7              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.

 

Monitoring Locations

2.8              Based on the EIA Report, three worst affected locations were designated for construction noise monitoring as listed in Table 2.1 and illustrated in Figure 2.2. 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.

 

Table 2.1         Noise Monitoring Stations during Construction Phase

Identification No.

Noise Monitoring Location

CM1

Village house near San Tin Highway

CM2

Village house near San Tin Highway

CM3

Village house near Kwu Tung Road

2.9              If, for example, there are difficulties obtaining access to the proposed noise monitoring locations, alternative monitoring locations may be proposed. The selection of these alternative monitoring locations shall be based on the following criteria:

·        At locations close to the major site activities which are likely to have noise impacts;

·        Close to the NSRs (any domestic premises, hotel, hostel, temporary housing accommodation, hospital, medical clinic, educational institution, place of public worship, library, court of law, performing arts center shall be considered as a NSR); and

·        For monitoring locations located in the vicinity of the NSRs, care shall be taken to cause minimal disturbance to the occupants during monitoring.

2.10          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 or at the height that has the least obstructed view of the construction activity in relation to the receiver.  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 IC(E) and EPD 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

2.11          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.

2.12          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.

2.13          In exceptional cases, when insufficient baseline monitoring data or questionable results are obtained, the ET shall liaise with the IC(E) and 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

2.14          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;

(b)         one set of measurements between 1900-2300 hours (if there is construction work during the restricted hours, the frequency and scope of monitoring shall be determined by the Construction Noise Permit (CNP)  application and the Noise Control Authority);

(c)          one set of measurements between 2300-0700 hours of next day (if there is construction work during the restricted hours, the frequency and scope of monitoring shall be determined by the CNP application and the Noise Control Authority); and

(d)         one set of measurements between 0700-1900 hours on holidays (if there is construction work during the restricted hours, the frequency and scope of monitoring shall be determined by the CNP application and the Noise Control Authority).

2.15          For the measurements (b), (c) and (d) above, at least one set of measurements shall include 3 consecutive Leq (5 min) results and shall only be carried out when there are construction activities scheduled during those periods. 

2.16          General construction work carried out during restricted hours is controlled by CNP system under the Noise Control Ordinance (NCO).  The Contractor shall obtain a CNP prior to any construction work during restricted hours.

2.17          In case of non-compliance with the construction noise criteria, more frequent monitoring, as specified in the Action Plan in Table 2.3, 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

2.18          The Action and Limit levels for construction noise are defined in Table 2.2. Should non-compliance of the criteria occur, action in accordance with the Action Plan in Table 2.3 shall be carried out.

 

Table 2.2         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)

Note :     If works are to be carried out during restricted hours, the conditions stipulated in the construction noise permit issued by the Noise Control Authority have to be followed.

 

Table 2.3         Event / Action Plan for Construction Noise

 

EVENT

 

ACTION

 

 

ET

 

IC(E)

 

ER

 

CONTRACTOR

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.

Operational Phase Noise Monitoring

2.19          Since the NSRs near the proposed slip roads would experience traffic noise impact during the operation of the Project, a noise monitoring programme was developed to include noise measurements at NSRs during the peak traffic hour.  The programme shall be carried out by the ET to ensure that the traffic noise levels are comparable to those predicted in the EIA under the full provision of the recommended mitigation measures.  The Highways Department will be responsible for the operational phase monitoring.

 

Noise Parameters

2.20          The traffic noise level should be measured twice within the first year of the road opening.  Measurements should be made in terms of the A-weighted L10 over 3 half hour periods during the peak traffic hour, other metrics like Leq may be added as seen fit.  A sample data record sheet is shown in Appendix B for reference.

 

Monitoring Equipment

2.21          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.

2.22          Noise measurements should not be made in accordance with standard acoustical principles and practices in relation to weather conditions.

2.23          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.

 

Monitoring Locations

2.24          The monitoring locations should be selected according to the following criteria:

 

(a)          The monitoring locations should be so chosen that noise from the slip roads would dominate;

(b)         One high floor and one medium floor monitoring points should be chosen at each locations as far as possible; and

(c)          Selected monitoring locations should enable monitoring to be done twice within one year after implementation of the mitigation measures during the operation of the proposed slip roads.

2.25          Two stations were selected for the operational noise monitoring as described in Table 2.4.  Figure 2.3 shows the locations of the proposed operational noise monitoring stations.

 

Table 2.4         Noise Monitoring Stations during Operational Phase

Identification No.

Noise Monitoring Location

OM1

Village house near Slip Road A

OM2

Village house near Slip Road A

 

2.26          The status and locations of NSRs may change after issuing the EM&A Manual.  In such cases, the ET Leader shall propose updated monitoring locations and seek approval from the ER, and agreement from the IC(E) and EPD of the proposal.  The purpose of the monitoring is to review the different situations predicted in the EIA.  Monitoring point/façade should be chosen such that it is dominated by the traffic noise from the proposed slip roads.

2.27          If alternative monitoring locations are proposed, the chosen monitoring locations shall be based on the following criteria:

·        they shall be similarly exposed to potential noise impacts;

·        they shall be close to the NSRs; and

·        they shall be located so as to cause minimal disturbance to the occupants during monitoring.

2.28          The operational noise monitoring station shall normally be at a point 1 m from the openable window and be at a position 1.2 m above the ground or at the height that has the least obstructed view of the proposed roads in relation to the receiver.  The ET shall agree with the IC(E) and EPD on the monitoring position and the corrections adopted. 

 

Baseline Monitoring

2.29          No baseline operational noise monitoring is required.

 

Impact Monitoring

2.30          Noise monitoring shall be carried out at all the designated monitoring stations.  The following is an initial guide on the traffic noise monitoring requirements during the operational phase:

(a)    one set of measurements at the morning traffic peak hour on normal weekdays;

(b)   one set of measurements at the evening traffic peak hour on normal weekdays;

(c)    a concurrent census of traffic flow and percentage heavy vehicle shall be obtained for far-side and near-side of the road and the existing road network in the vicinity of each measuring point;

(d)   average vehicle speed estimated for far-side and near-side of the road and the existing road network in the vicinity of each measuring point; and

(e)    the two sets of monitoring data should be obtained within the first year of operation.

2.31          Measured noise levels should be compared with predicted noise levels by applying appropriate conversion corrections to allow for the traffic conditions at the time of measurement.  A sample data record sheet for operational noise monitoring is provided in Appendix B for reference.

 

Event and Action Plan

2.32          The measured/monitored noise level shall be compared with the predicted results and the predicted traffic flow conditions (calculated noise levels based on concurrent traffic census obtained).  In case discrepancies are observed, explanation should be given to justify the discrepancies.

 

Mitigation Measures

 

Construction Phase

2.33          The mitigation measures recommended in the EIA report include:

·        Use of quiet powered mechanical equipment (PME)

·        Adoption of movable noise barriers

·        Implementation of the following good site practices:

-         All plant operated on-site should be well maintained and plant should be serviced regularly during the construction works;

-         Machines and plant 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, where possible, be orientated to direct noise away from the NSRs;

-         Mobile plant should be sited as far away from NSRs as possible; and

-         Material stockpiles and other structures should be effectively utilised, where practicable, to screen noise from on-site construction activities.

 

Operational Phase

2.34          According to the EIA report, the following noise mitigation measures are proposed.

For existing NSRs

 

·        A 1.5m high reflective plain barrier of about 121m long erected along the western edge of Slip Road A.

 

For Future/Planned NSRs

 

·        A 2m high reflective plain barrier of about 303m be erected along Slip Road F.

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