4.                   CONSTRUCTION noise

Introduction

4.1               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.

Methodology and Criteria

4.2               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 (15 minutes) shall be employed for comparison with the Noise Control Ordinance (NCO) criteria.

4.3               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 C for reference.

4.4               Whilst the Noise Control Ordinance (NCO) does not provide for the statutory control of construction activities occurring on weekdays during normal working hours (i.e. Monday to Saturday inclusive 0700-1900 hours), a daytime standard of Leq(30 minute) 75dB stipulated in Annex 5 of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM) shall be used as the appropriate criterion for all residential dwellings; while a daytime standard of Leq(30 minute) 70dB will be adopted for all educational institutions during normal school days and Leq (30 minute) 65dB during examination periods.

4.5               The NCO provides statutory controls on general construction works during restricted hours (i.e. 1900-0700 hours Monday to Saturday and at any time on Sundays and public holidays). The ANLs for evenings and holidays and for night-time are dependent on the Area Sensitivity Rating at the NSR. The relevant ANLs are provided in Table 4.1.

Table 4.1          Acceptable Noise Levels (ANLs)

Time Period

Area Sensitivity Rating

A

B

C

All days during the evening (1900-2300 hours) and general holidays (including Sundays) during the day and evening (0700-2300 hours)

60

65

70

All days during the night-time (2300-0700)

45

50

55

 

4.6               The locations of noise sensitive receivers (NSRs) adjacent to the project area are shown in Figure 4.1. The Area Sensitivity Rating of the NSRs in the vicinity of the Project Area is considered as ‘A’. However, construction works during the restricted hours for this Project is not expected.

Monitoring Equipment

4.7               As referred to 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 levels from before and after the noise measurement agree to within 1.0 dB.

4.8               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.

4.9               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

4.10            Based on the EIA Report, locations designated for construction noise monitoring are listed in Table 4.2 and illustrated in Figure 4.2.

Table 4.2          Noise Monitoring Stations during Construction Phase

Identification No.

NSR ID in EIA Report

Noise Monitoring Location

CN1

N1

Block A, Po Shan Mansions

CN2

N2

Block A, Po Shan Mansions

4.11            Noise impacts during the operation phase included project-induced road traffic noise, fixed plant and entertainment noises. The EIA revealed that adverse project-induced traffic and fixed plant noise impacts on the NSRs would not occur.

4.12            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 the ER and agreement from the IEC and deposit the proposal with EPD. 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

4.13            The monitoring station shall normally be at a point 1m from the exterior of the noise sensitive facade and be at a position 1.2m 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 +3dB(A) shall be made to the free field measurements. The ET shall agree with the IEC and deposit with 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 Noise Environment

4.14            Regular noise monitoring is carried out at the designated monitoring stations under the adjacent on going CEDD project which was controlled under Environmental Permit EP-235/2005/A. These noise monitoring results could be referenced as the baseline noise levels for this Project.

Impact Monitoring

4.15            Noise monitoring shall be carried out at all the designated monitoring stations. The monitoring frequency shall depend on the scale of the construction activities. An initial guide on the monitoring is to obtain one set of 30-minute measurement at each station between 0700 and 1900 hours on normal weekdays at a frequency of once a week when construction activities are underway.

4.16            If construction works are extended to include works during the hours of 1900 – 0700, or general holidays and Sundays, impact monitoring in terms of 3 consecutive Leq (5 minutes) shall be carried out at a minimum frequency of once a week during evening, general holiday or night-time works. Applicable construction noise permits (CNP) under NCO shall be obtained by the Contractor.

4.17            In case of non-compliance with the construction noise criteria, more frequent monitoring, as specified in Event / Action Plan in Table 4.5 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.

4.18            The ER or ET shall maintain communication with the local residents through the liaison office established by the adjacent CEDD concurrent project which was controlled under Environmental Permit EP-235/2005/A.

Event and Action Plan

4.19            The action and limit levels for construction noise are defined in Table 4.4. Should non-compliance of the criteria occur, action in accordance with the Event / Action Plan in Table 4.5 shall be carried out. If exceedances are resulted from cumulative impacts, all steps stipulated in the Event / Action Plan shall be carried out.

 

Table 4.4          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 from any one of the sensitive receivers

75 dB(A)*

1900-2300 on all days and 0700-2300 on general holidays (including Sundays)

60/65/70 dB(A)**

2300-0700 on all days

45/50/55 dB(A)**

*      Reduced to 70dB(A) for schools or institution and 65dB(A) during school examination periods

**     To be selected based on the Area Sensitivity Rating of A/B/C, and the conditions of the            applicable CNP(s) must be followed.

 

Table 4.5          Event / Action Plan for Construction Noise

Event

Action

 

ET

Contractor

ER

IEC

Action Level

1.    Identify source.

2.    Notify IEC, ER and Contractor.

3.    Conduct additional noise monitoring to investigate the causes.

4.    Report the investigation results to the IEC, ER and Contractor.

5.    Discuss with Contractor for their formulation of remedial measures if the exceedance is related to construction works.

6.    Conduct additional monitoring to check mitigation effectiveness.

1.    Take immediate action to avoid further exceedance.

2.    Submit noise mitigation proposals to ET, ER and IEC.

3.    Implement noise mitigation proposals.

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.    Review the analysed results submitted by the ET.

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

3.    Supervise and confirm in writing the implementation of remedial measures

Limit Level

1.    Identify source.

2.    Notify EPD, IEC, ER and Contractor.

3.    Conduct additional noise monitoring and analyse Contractor’s working procedures to determine possible cause of exceedance.

4.    Provide interim report to EPD, IEC and ER on the causes and proposed actions to be taken for the exceedances if exceedance is related to construction works

5.    Assess effectiveness by additional monitoring and report to EPD, IEC, ER and Contractor the results.

6.    If exceedance stops, cease additional monitoring.

1.    Take immediate action to avoid further exceedance.

2.    Submit proposals for remedial actions to ET, ER and IEC 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.

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.

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.    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.

3.    Supervise and confirm in writing the implementation of remedial measures.

 

 

Mitigation Measures

Good Site Practice

4.20            Although the noise mitigation effects are easily quantifiable and the benefits may vary with site conditions and operating conditions, good site practices are easy to implement and do not impact upon the works schedule. The site practices listed below should be followed during each phase of construction:

·         Only well-maintained plant should be operated on-site and plant should be serviced regularly during the construction program

·         Mobile plant, if any, should be sited as far 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 utilized, wherever practicable, in screening noise from on-site construction activities

Adoption of Quieter Plant

4.21            In order to reduce the excessive noise impacts at the affected NSRs during normal daytime working hours, quieter plants are recommended. The Contractors do not have to use specific items of quiet plant adopted in this assessment. The Contractors may use other type of quiet plant, which have the same total SWL, to meet their needs.

Use of Movable Noise Barrier

4.22            The use of movable barrier for certain PME could further alleviate the construction noise impacts. In general, 5dB(A) reduction for movable PME and 10dB(A) for stationary PME can be achieved depending on the actual design of movable noise barrier.

4.23            The Contractor should be responsible for design of the movable noise barrier with due consideration given to the size of the PME and the requirement of intercepting the line of sight between the NSRs and PME. Barrier material of surface mass in excess of 7kg/m2 is recommended to achieve the predicted screening effect.

Use of Noise Insulating Fabric

4.24            As Works Area E is close to the NSRs, noise insulating fabric has to be adopted when drill rig is operating in this area. The maximum number of drill rig to be operated in Works Area E is two.