3.                  NOISE

 

3.1              Introduction

 

3.1.1        Noise impact is likely to arise from some of the activities during construction phase of the Project. The EIA recommended a number of mitigation measures that should be implemented to reduce potential impacts to acceptable limits. A monitoring programme is recommended for baseline conditions and during the construction phase to evaluate the performance of the proposed measures.

 

3.1.2        This section of the Manual lists all the recommended mitigative and preventive measures in the EIA for the control of construction noise, and the requirements for baseline and construction phase noise monitoring.

 

3.1.3        No adverse noise impact is expected during operation phase, hence noise monitoring during operation phase is considered not necessary.

 

3.2              Noise Parameters

 

3.2.1        The construction noise level shall be measured in terms of the A-weighted equivalent continuous sound pressure level (Leq). Leq(30 min) shall be used as the monitoring parameter for the time period between 0700-1900 hours on normal weekdays.

 

3.2.2        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.

 

3.3              Monitoring Equipment

 

3.3.1        As referred to in the Technical Memorandum (TM) issued under the Noise Control Ordinance (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.

 

3.3.2        Noise measurements shall 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 ms-1.

 

3.3.3        The ET Leader 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.

 

3.4              Monitoring Locations

 

3.4.1        The locations of noise monitoring stations are shown in Table 3.1 and Figure 3.1.  In case works is required for restricted hours, monitoring locations may also include those relevant to the application of Construction Noise Permit (CNPs) as advised by EPD.

 

3.4.2        The status and locations of Noise Sensitive Receivers (NSRs) may change after issuing this manual. In this case, the ET Leader shall propose updated monitoring stations and seek approval from ER and agreement from the ICE and EPD of the proposal.

 

Table 3.1

Noise Monitoring Stations for Baseline and Construction Monitoring

 

Noise Monitoring Stations

NSR ID

General Description

N1

NSR 1

Wing Jan Kindergarten

N2

NSR 2

Village house at No.84 Hang Hau Tsuen

N3

NSR 3

Village house at No. 88 Hang Hau Tsuen

 

Notes:

All monitoring stations shall be proposed by the Environmental Team Leader and verified by the Independent Environmental Checker before submitting to EPD prior to commencement of any monitoring.

 

3.4.3        When alternative monitoring stations are proposed, the monitoring locations should be chosen based on the following criteria:

 

(a)                at locations close to the major site activities which are likely to have noise impacts;

 

(b)               close to the noise sensitive receivers (N.B. For the purposes of this section, any domestic premises, hotel, hostel, temporary housing accommodation, hospital, medical clinic, educational institution, place of public worship, library, court of law, performing art centre should be considered as noise sensitive receiver); and

 

(c)                for monitoring locations located in the vicinity of the sensitive receivers, care should be taken to cause minimal disturbance to the occupants during monitoring.

 

3.4.4        The monitoring station shall normally be at a point 1m from the exterior of the sensitive receivers building facade and be at a position 1.2m 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 +3dB(A) shall be made to the free field measurements.

 

3.4.5        The ET Leader shall agree with the ER and 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.

 

3.5              Baseline Monitoring

 

3.5.1        The ET Leader shall carry out baseline noise monitoring prior to the commencement of the construction works. The baseline monitoring shall be carried out continuously for a period of at least two weeks (14 consecutive days) at interval of 5 minutes. The A-weighted noise level Leq, L10 and L90 shall be recorded. A schedule on the baseline monitoring shall be submitted to the ER and IEC for approval before the monitoring starts.

 

3.5.2        There shall not be any construction activities in the vicinity of the stations during the baseline monitoring. In exceptional cases, when insufficient baseline monitoring data or questionable results are obtained, the ET Leader shall liaise with IEC to agree on an appropriate set of data to be used as a baseline reference and submit to the EPD for approval.

 

3.6              Impact Monitoring

 

3.6.1        Noise monitoring shall be carried out at all the designated monitoring station in Table 3.1 during the construction phase of the Project. 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 per week basis when noise generating activities are underway:

 

•                     one set of Leq (30min) between 0700-1900 hours on normal weekdays.

 

3.6.2        The Action and Limit Levels for construction noise are given in Table 3.2 and the Event/Action Plan in Table 3.3.

 

3.7              Event and Action Plan for Construction Noise

 

3.7.1        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. The ET shall provide full documentation of his investigation on the cause of the non-compliance and whether it can be traced to activities other than those caused by the project, to the satisfaction of the ER and the IEC.

 

Table 3.2

Action and Limit Levels for Construction Noise

 

Time Period

Action

Limit

0700-1900 hrs on normal weekdays

When one documented complaint is received

75* dB(A)

 

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

 

 

Table 3.3   Event/Action Plan for Construction Noise Monitoring

EVENT

ACTION

ET Leader

IEC

ER

Contractor

Action Level

1.     Notify IEC, Contractor and ER

2.     Carry out investigation and identify source

3.     Report the results of investigation to the IEC, Contractor and ER

4.     Discuss with the Contractor and formulate remedial measures

5.     Increase monitoring frequency

6.     Check compliance to Action/Limit Levels after application of mitigation measures

1.     Review the analysed results submitted by the ET Leader

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

3.     Supervise the implementation of remedial measures

1.     Confirm receipt of notification of complaint in writing

2.     Notify Contractor

3.     Check monitoring data submitted by the ET

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

5.     Ensure remedial measures are properly implemented

1.    Submit noise mitigation proposals to ER and IEC within three working days of notification

2.     Liaise with the ER to ensure the effectiveness of the agreed mitigation

3.     Amend proposal if required

4.     Implement noise mitigation proposals

 

Limit Level

1.     Notify IEC, ER, EPD and Contractor

2.     Identify Source

3.     Repeat measurement 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 IEC, ER and EPD the causes & actions taken for the exceedances

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.     Check monitoring data submitted by ET

2.     Discuss amongst ER, ET Leader and Contractor on the potential remedial actions

3.     Review Contractor’s remedial actions whenever necessary to assure their effectiveness and advise the ER & ET accordingly

4.     Supervise the implementation of remedial measures

1.     Confirm receipt of notification of exceedance

2.     Notify Contractor

3.     Check monitoring data submitted by the ET

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

5.     Discuss with ET, IEC and Contractor on proposed remedial actions to be implemented

6.     Ensure remedial measures are properly implemented

7.     Assess the effectiveness of the remedial actions and keep the Contractor informed

8.     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 ER within 3 working days of notification

3.     Liaise with the ER to ensure the effectiveness of the agreed mitigation

4.     Amend proposal if required

5.     Implement the agreed proposals

6.     Resubmit proposals if problem still not under control

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

3.8              Mitigation Measures

 

Construction Phase

 

3.8.1        The predicted noise levels showed that construction works would give rise to daytime noise impacts to most of the Representative NSRs. The following types of mitigation measures are recommended.

 

Level 1 Mitigation - Use of Quiet Plant

 

3.8.2        The use of quiet plant (also referred as silenced equipment) can provide significant reduction in noise level. Quiet plant is defined as PME whose actual sound power level is less than the value specified in the TM-GW for the same piece of equipment. The common source of these information is from international standard / certification, e.g. BS 5228. To allow the Contractor some flexibility to select equipment to suit actual needs, it is considered too restrictive to specify which specified silenced equipment to be used for the construction works. Hence, it is preferable and practical to specify the noise performance specification of the plant on site in terms of the sound power level so that the Contractor is allowed some flexibility. It should be noted that various types of silenced equipment can be found in Hong Kong and are readily available on the market. The quiet plant used in the construction noise calculation is shown in Table 3.4 (and Appendix 4.1 of the EIA). The Contractor can propose other suitable alternative equipment with similar or lower sound power level.

 

3.8.3        The use of quiet plant is considered to be the most effective ways of alleviating construction noise impact. The Contractor should use quiet plant with sound power level lower than that stipulated in the TM-GW as the Level 1 mitigation for construction noise.

 

3.8.4        The use of mini or lower power rating equipment (e.g. mini excavator) should also be considered where practical. This technique would be feasible and practical at some locations given the limited space available for using large size construction equipment and the small scale works involved.

 

3.8.5        The Contractor should take note of ETWB TCW No. 19/2005 – “Environmental Management on Construction Sites” which sets out the policy and procedures requiring contractors to, among others, adopt Quality Powered Mechanical Equipment (QPME).

 

3.8.6        A list of quiet powered mechanical equipment (PME) recommended for use during construction phase is tabulated below in Table 3.4.

 

Table 3.4

Quiet Powered Mechanical Equipment Recommended for Use during Construction Phase

 

Powered Mechanical Equipment

Power Rating / Size, Weight

Reference

SWL, dB(A)

Excavator, loader

52 kW

BS5228 C.3-97

105

Dump truck

450 kW, 50 t

BS5228 C.9-39

103

Crane

62 kW

BS5228 C.7-114

101

Vibratory roller

9 kW

BS5228 C.3-115

102

Concrete lorry mixer

22 kW, 6 m3

BS5228 C.6-23

100

Vibratory poker

2 kW

BS5228 C.6-32

100

Asphalt paver / spreader

90 kW, 13 t

BS5228 C.8-24

101

Road roller

10 t

BS5228 C.8-25

96

 

3.8.7        With the use of quiet plant, most of the Representative NSRs still exceed the noise standard and will still require further mitigation measures.

 

Level 2 Mitigation - Use of Temporary Noise Barriers

 

3.8.8        Since most of the NSRs within the Project area are typically low-rise tin-sheeted village houses of not more than 2 storeys (all are less than 5 m tall), it would be effective to have noise screening structures or temporary noise barriers purposely-built along the site boundary to provide additional protection to NSRs close to the construction site boundary. This could be in the form of purposely-built site hoarding constructed from appropriate materials with a minimum superficial density of 7 kg/m2. Noise barrier should be provided for noisy construction activities that would be undertaken close (about 30 m or less) to NSRs. The noise barrier should have a vertical height of at least 3 m or (depending on the height of the NSRs to be protected) a height ensuring that the operating equipment can be shielded from the view of the NSRs. The temporary noise barrier should have no gaps or opening at joints. The Contractor should regularly inspect and maintain the noise barrier to ensure its effectiveness.

 

3.8.9        For the construction works which have the potential to exceed the noise standards on nearby NSR and whose line of sight cannot be effectively blocked by the temporary noise barrier, movable (mobile) barriers should be provided. This may also be applicable in situation where construction of a temporary noise barrier may not be possible due to site / space constraints, for example blocking village or emergency vehicle access. Movable barriers of at least 2.5 m height with a small cantilevered upper portion and skid footing can be located within a few meters of stationary plant (e.g. generator) and within about 5 m or more of a mobile equipment (e.g. excavator), such that the line of sight to the NSR is blocked by the barriers.

 

Good Site Practices

 

3.8.10    In general, potential construction noise impact can be minimised or avoided by imposing a combination of the following good site practices as mitigation measures:

 

(a)                      Only well-maintained plant should be operated on-site and plant should be serviced regularly during the construction period.

 

(b)                     Construction plant should be sited away from NSRs.

 

(c)                      Machines and plant that may be in intermittent use should be shut down between works periods or should be throttled down to a minimum.

 

(d)                     Equipment known to emit sound strongly in one direction should be orientated such that the noise is directed away from nearby NSRs.

 

(e)                      Material stockpiles and other structures (such as site offices) should be effectively utilised to shield on-site construction activities.

 

(f)                       Stationary equipment should be located within the channel when weather conditions permit (e.g. dry season).

 

(g)                      The Contractor shall devise, arrange methods of working and carrying out the works in such manner as to minimise noise impacts on the surrounding environment, and shall provide experienced personnel with suitable training to ensure that these measures are implemented properly.

 

(h)                      In the event that new schools are built near the works area, the Contractor should minimise construction noise exposure to the schools (especially during examination periods). The Contractor should liaise with the school and the Examination Authority to ascertain the exact dates and times of all examination periods during the course of the contract and to avoid noisy activities during these periods.

 

Public Relation Strategy

 

3.8.11    Having a good public relation with the local communities during the construction phase is indispensable for a smooth implementation of the Project. Prior to commencement of the construction, visits to the affected villages, local communities and property owners should be carried out. The purpose of the visits is to advise the public the following information in relation to the Project:

 

·                     the implementation programme of the works;

·                     the planned construction activities that will be involved;

·                     the possible impacts arising from the works;

·                     the measures to avoid or mitigate any adverse impacts;

·                     the monitoring programme to check the efficiency of the measures; and

·                     the communication channels between the local communities and the project office.

 

3.8.12    To maintain an effective communication channel with the public, a 24-hour hotline system should be established by the project office for the Contractor to receive any enquiry and complaint lodged by the public in respect of the Project. Upon receipt of enquiry / complaint, the Contractor (or its Environmental Team) should investigate the causes of the incident and take the appropriate action to rectify the situation. Periodic newsletters, information leaflets, notices or other means of communication should be provided to the affected villages, communities, and residents advising them the current progress, the schedule of works in future, the potential environmental impacts arising from the works and the corresponding mitigation measures. It is considered that such a close relation between the local communities and the project site office could ensure speedy resolution of any environmental non-compliance and maintain an environmental standard acceptable to the local communities during construction.

 

3.8.13    Further mitigation is recommended for NSRs 3, 4, 6 & 10 by restricting concurrent usage of several equipment at the same time during excavation and construction of the channel lining, crossings.

 

3.8.14    Table 3.5 summarises the mitigation measures proposed for the construction works. All these construction noise mitigation measures should be implemented by the Contractor during the construction stage of the works. The location of the temporary noise barriers and mobile noise barriers should be further reviewed by the Contractor during the construction stage based on the latest construction programme and contemporary conditions, including any changes with respect to NSRs. The Contractor should design, construct, operate and maintain the mitigation measures throughout the construction stage and as required by the Engineer. Before commencement of the works, the Contractor should submit to the Engineer for approval (as part of their method statement) details of the mitigation measures to be employed under the works. The Contractor’s proposed mitigation measures should also be certified by the ET Leader and verified by the IEC to ensure the intended noise reduction effectiveness can be achieved.

 

3.8.15    If the above measures are not sufficient to restore the impacts to acceptable levels upon the advice of ET Leader, the Contractor shall liaise with the ET Leader on some other mitigation measures, endorsed by IEC and propose to ER for approval, and implement the mitigation measures.

 

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

 

Table 3.5

Summary of Proposed Construction Noise Mitigation Measures

 

Proposed Mitigation Measures

Location

Timing / Duration

Implementation Agent

Specific Requirements

Use of quiet equipment including QPME

All construction works / sites

During the construction period

Contractor

Some examples of quiet plant and QPME are shown in Table 3.4. Contractor can propose other suitable alternative equipment with similar or lower sound power level.

Use of temporary noise barrier (purpose-built site hoarding) and/or movable (mobile) noise barrier

 

The temporary noise barrier shall be located as per Figure 4.2 (of the EIA) or wherever noisy construction works are being carried out close (30m or less) to NSRs

During the construction period

Contractor

Barriers should be of at least 3 m high or able to shield construction equipment from NSR’s view. These barriers should be constructed of appropriate material with a minimum superficial density of 7 kg/m2, with no gaps or openings. Also, regular inspection and maintenance should be carried out.

Where barriers cannot block line of sight, mobile barrier of 2.5 m high with a cantilevered upper portion should be provided.

Good site practices

All construction works / sites

During the construction period

Contractor

-----

Public relation strategy

All construction works / sites

During the construction period

Project office (Engineer) / Contractor

Maintain a 24-hour hotline for enquiry and complaint, periodic communication with affected parties.

Restrict concurrent usage of several construction equipment at the same time

For construction works in close proximity to NSRs 3, 4, 6 &10

During the construction period

Contractor

Contractor to propose details or other suitable alternatives to the Engineer and ET Leader for approval.