2.                   AIRBORNE NoISE

 

Introduction

 

2.1               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.

 

2.2               The EIA study provided the maximum permissible sound power levels (Max SWLs) of the identified fixed noise sources of the Project.  The Max SWLs should be implemented and refined by the Contractor.  In order to ensure the operational airborne noise levels would comply with the noise standards as stipulated in the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM), the Contractor should carry out a noise commissioning test for all major fixed noise sources before operation of the Project.  A summary of noise criteria for fixed plant noise sources is provided in Appendix B.

 

Methodology and Criteria

 

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

 

2.4               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.

 

2.5               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 assessment criterion 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 assessment criterion for all residential dwellings; while a daytime assessment 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.

 

2.6               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 2.1.

 

Table 2.1          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

 

Monitoring Equipment

 

2.7               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.

 

2.8               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.

 

 

2.9               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.

 

Monitoring Locations

 

2.10            Based on the EIA study, twenty potentially worst affected locations are designated for construction noise monitoring as listed in Table 2.2 and illustrated in Figure 2.1 to 2.7.

Table 2.2          Noise Monitoring Stations during Construction Phase

Identification No.

NSR ID in EIA Report

Noise Monitoring Stations

CN1

KET 15

Sisters of the Immaculate Heart of Mary (Kongmoon) – Kit Sam Convent

CN 2

KET 9

Hong Kong Institute of Vocation Education (Tsing Yi) Kennedy Town Centre

CN 3

KET 10

Lui Ming Cho Primary School

CN 4

KET 3

Luen Tak Apartments

CN 5

UNI 1

Western Court (Block 1)

CN 6

UNI 15

Yick Fung Garden (Block A)

CN 7

UNI 7

The Bauhinia

CN 8

UNI 10

St. Paul's College Primary School

CN 9

UNI 12

Hill Court

CN 10

UNI 13

Graceful Court

CN 11

UNI 6

Sun Shing Building

CN 12

UNI 18

Wah Po Building

CN 13

SYP 1

No. 18-20 Eastern Street

CN 14

SYP 6

Bon-Point

CN 15

SYP 8

Ivy Tower

CN 16

SYP 12

No. 9-11 Ki Ling Lane

CN 17

SYP 14

No. 1 Third Street

CN 18

GT 2

Princeton Tower

CN 19

GT 4

Yu Hing Mansion

CN 20

GT 5

Ka On Building

CN 21

KET 13

The Merton (Block 2)

 

 

2.11            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 EPD on the proposal.  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 close to the noise sensitive receivers as defined in the Technical Memorandum

§          Assurance of minimal disturbance to the occupants during monitoring in the vicinity of sensitive receivers

 

2.12            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 Leader shall agree with the IEC 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

 

2.13            The ET shall carry out baseline noise monitoring prior to the commencement of the construction works.  The baseline monitoring shall be measured for a continuous period of at least 14 consecutive days at a minimum logging interval of 30 minutes for daytime (between 0700 and 1900 hours of normal weekdays) and 15 minutes (as three consecutive Leq, (5 minutes) readings) for evening time (between 1900 and 2300 hours of normal weekdays), general holidays including Sundays (between 0700 and 2300 hours) and night-time (between 2300 and 0700 of all days). The Leq, L10 and L90 shall be recorded at the specified interval.  A schedule on the baseline monitoring shall be submitted to the IEC for approval before the monitoring starts.  The baseline noise monitoring period shall cover the proposed operation hours of the Project.

 

2.14            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.

 

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

      

Impact Monitoring

 

Construction Noise

 

2.16            Noise monitoring shall be carried out at all the designated monitoring stations.  The monitoring frequency shall depend on the scale of the construction activities.  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.

 

2.17            Any General construction work carried out during restricted hours is controlled by Construction Noise Permit (CNP) under the NCO.

 

2.18            For school exists near the construction activity, noise monitoring shall be carried out at the monitoring stations for the schools during 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.

 

2.19            In case of non-compliance with the construction noise criteria, more frequent monitoring, as specified in Event / Action Plan in Table 2.4 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

 

2.20            The Action and Limit levels for construction noise are defined in Table 2.3. Should non-compliance of the noise quality criteria occur, actions in accordance with the Event and Action Plan in Table 2.4 shall be taken.

 

Table 2.3 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)

0700-2300 hrs on holidays; and 1900-2300 hrs on all other days

65/70 dB(A) #

2300-0700 hrs of next day

50/55 dB(A)#

* Limit for school is reduce to 70 dB(A) and 65 dB(A) during school examination periods.

# Limit depends on Area Sensitivity Rating (ASR). The ASR for monitoring locations is “B”,  the limit should be 65dB(A) and 50dB(A) for the period during 0700-2300 and 2300-0700 respectively. The ASR for monitoring locations is “C”, the limit should be 70dB(A) and 55dB(A) for the period 0700-2300 and 2300-0700 respectively.

 

2.21            To account for cases where ambient noise levels as identified by baseline monitoring approach or exceed the stipulated Limit Levels prior to commencement of construction, a Maximum Acceptable Impact Level may be defined and agreed with EPD, which incorporates the baseline noise levels and the identified construction noise Limit Level. The amended level will therefore be greater than 75 dB(A) and will represent the maximum acceptable noise level at a specific monitoring station. Correction factors for the effects of acoustic screening and/or architectural features of NSRs may also be applied for as specified in the TM.


EVENT

ACTION

ET

IEC

ER

CONTRACTOR

Action Level

1.     Notify IEC and ER

2.     Carry out investigation

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

4.     Discuss jointly with the ER and 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 ER with copy to IEC

2.    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, EPD the causes and 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.    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 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

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 ER with copy to IEC

3.Implement the agreed proposals

4.Revise and 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

Table 2.4      Event and Action Plan for Construction Noise Monitoring

 

Mitigation Measures

 

2.22            The EIA report indicated that construction activities would cause noise exceedance at NSRs. Therefore, appropriate mitigation measures and good site practices are recommended to be properly implemented. The Contractor shall be responsible for the design and implementation for these measures.

 

2.23            The mitigation measures recommended in the EIA report are summarized below:

 

§          Implementation of the following good site practices:

-          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 utilized 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 work periods or 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; and

-          material stockpiles and other structures shall be effectively utilized, wherever practicable, in screening noise from on-site construction activities.

§          Adoption of silenced types of PME, which should be in accordance with BS 5228: Part 1, 1997, as proposed in the EIA report

§          Use of movable noise barrier

§          Use of noise enclosure or acoustic shed

§          Use of acoustic enclosure to cover the rock drill

§          Use of noise insulating cover

§          Use of silencer

§          Use of noise insulating fabric

§          Use of “Noise Control Curtain” for the demolition works at Ex-Police Quarter site

§          Use of temporary noise barrier

§          Decking over the excavation area or lift shaft

§          Full enclosure of works areas

§          Use of alternative quieter construction method such as concrete crusher

 

2.24            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 on some other mitigation measures, propose them to ER for approval, and carry out the mitigation measures.

 

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