4                                  NOISE

4.1                            Introduction

The requirements, methodology, equipment, monitoring locations, criteria and protocols for the monitoring and audit of noise impacts during construction of the Project are presented in this section.

4.2                            Methodology and Criteria

Noise measurements should be carried out in accordance with the guidelines given in Annex – General Calibration and Measurement Procedures of Technical Memorandum on Noise from Construction Work other than Percussive Piling (GW-TM).

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

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

Supplementary information for data auditing, two statistical sound levels L10 and L90; the levels exceeded for 10 and 90 percent of the time respectively, should also be recorded during the monitoring for reference.  A sample data record sheet is shown in Annex C for reference.

Noise measurements should generally 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 should be checked with a portable wind speed meter capable of measuring the wind speed in ms-1.

4.3                            Monitoring Equipment

As referred to the GW-TM, sound level meters in compliance with the International Electrotechnical Commission Publications 651:1979 (Type 1) and 804:1985 (Type 1) Specifications should be used for carrying out the noise monitoring.  Immediately prior to and following each noise measurement the accuracy of the sound level meter should 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.

The ET should ensure that the equipment is maintained in a good working order in accordance with the manufacturer's recommendations with sufficient spare equipment available in the event of breakdown to maintain the planned monitoring programme.

The ET is responsible for the provision of the monitoring equipment and will ensure that sufficient noise measuring equipment and associated instrumentation are available for carrying out the baseline monitoring and impact monitoring.  All the equipment and associated instrumentation will be clearly labelled.

4.4                            Monitoring Locations

Representative locations were selected to monitor the noise levels from the construction of the Project.  The noise monitoring stations are listed in Table 4.1 and presented in Figure 4.1.

Table 4.1        Noise Monitoring Stations for Construction Noise

Monitoring Station

Description

KMYLS1

Kwong Ming Ying Loi School

JCCAH1

Jockey Club Care & Attention Home

The status and locations of noise sensitive receivers (NSRs) may change after issuing this Manual and the location of the noise monitoring station may need to be adjusted accordingly.  If such changes occur, the ET should propose an updated monitoring location for the agreement from the ER, IEC and EPD.

When alternative monitoring location is proposed, the following criteria, as far as practicable, should be followed:

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

·           Close to the NSRs; and

·           For monitoring locations located in the vicinity of the NSRs, care should be taken to minimise disturbance to the occupants during monitoring.

The monitoring station will normally be at a point 1 m from the exterior of the NSR building façade and at a height of approximately 1.2 m above ground or at the height that has the least obstructed view of the construction activities in relation to the NSR.  If access to the normal monitoring position cannot be obtained, an alternative position will be chosen, and a correction to the measurements should be made, if appropriate.  For instance, a correction of +3 dB(A) should be made to free-field measurements.  The ET should agree with the ER, IEC, EPD and the owners/occupants of the premises on the monitoring position.  Once the positions for the monitoring stations are chosen, the baseline monitoring and the impact monitoring should be carried out at the same positions.

4.5                            Baseline Monitoring

The ET should carry out baseline noise monitoring prior to the commencement of any construction works.  The baseline monitoring should be measured for a continuous period of at least 14 consecutive days at a minimum logging interval of 30 minutes for daytime and 15 minutes (as three consecutive Leq(5min) readings) for evening, holidays and night-time.

Before commencing the baseline monitoring, ET should inform the Contractor, IEC, ER and the EPD of the baseline monitoring schedule programme such that relevant parties could conduct on-site audit to ensure accuracy of the baseline monitoring results.

During the baseline monitoring, there should not be any construction activities in the vicinity of the monitoring stations.  Any non-Project related construction activities in the vicinity of the stations during the baseline monitoring should be noted and the source(s) and location(s) be recorded.

In case the baseline monitoring could not be carried out at any of the designated monitoring locations during the baseline monitoring period, the ET should carry out the monitoring at alternative location which could effectively represent the baseline conditions at the impact monitoring locations.  The alternative baseline monitoring locations should be agreed with the ER and IEC and approved by EPD.

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

4.6                            Impact Monitoring

Noise monitoring should be carried out at all the designated monitoring stations.  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.

If construction works are extended to include works during the hours between 1900 and 0700 hours, or on general holidays and Sundays, applicable Construction Noise Permits (CNPs) will be obtained by the Contractor under the NCO requirements, and the frequency and scope of monitoring will be determined by EPD in the capacity of the Noise Control Authority (NCA).

4.7                            Environmental Quality Performance Limits

Action and Limit (A/L) Levels provide an appropriate framework for the interpretation of monitoring results.  Interpretation of monitoring results is undertaken through checking them against the Action and Limit (A/L) Levels defined in Table 4.2.

Table 4.2        Action and Limit Level for Construction Noise Monitoring

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)(Note) 

Note:

(1)       Acceptable Noise Levels for Area Sensitivity Rating of A/B/C. Limit Level is reduced to 70dB(A) for schools and 65dB(A) during school examination periods.

(2)       If works are to be carried out during restricted hours, the conditions stipulated in the construction noise permit issued by the NCA have to be followed.

 

To account for cases where ambient noise levels, as identified by baseline monitoring, approach or exceed the stipulated Limit Level prior to commencement of construction, a Maximum Acceptable Impact Level, which incorporates the baseline noise level and the identified construction noise Limit Level, might be defined upon agreement with the EPD.  This amended level will, therefore, be greater than 75 dB(A) and will represent the maximum acceptable noise level at a specific monitoring station.

For compliance checking, after taking into account any adjustments agreed with EPD, comparison with either the Limit or the Maximum Acceptable Impact Level will represent the governing criteria for noise impact assessment during impact monitoring.

4.8                            Event and Action Plan

The ET should compare the impact monitoring results with the noise criteria as defined in Table 4.2.  In cases where exceedance of these criteria occurs, actions should be carried out in accordance with the Action Plan shown in Table 4.3.

Table 4.3        Event and Action Plan for Construction Noise

Event

Action

 

ET

IEC

ER

Contractor

Action Level

1. Notify IEC and Contractor;

2. Carry out investigation;

3. Report the results of investigation to the IEC, 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 IEC;

2. Implement noise mitigation proposals.

 

Limit Level

1. Identify source;

2. Inform IEC and ER:

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 IEC, ER and 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 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 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.

4.9                            Audit Requirements

It is necessary to undertake regular environmental audits and site inspections to ensure those recommended mitigation measures were properly implemented.  The requirements of the environmental audit programme were set out in Section 8 of the Manual.

The audit programme will verify the implementation status and evaluate the effectiveness and stability of the mitigation measures.

4.10                        Mitigation Measures

4.10.1                  Construction Phase

In order to reduce the noise impact of construction site activities on nearby NSRs, the following mitigation measures have been considered:

·           Good Site Practice;

·           Use of quiet PME;

·           Use of acoustic enclosure;

·           Adoption of movable noise barriers, and

·           Scheduling of PME/construction activities.

Good Site Practices

Good site practices and noise management can considerably reduce the impact of construction site activities on nearby Noise Sensitive Receivers (NSRs).  The noise benefits of these practices can vary according to specific site conditions and operations.  The following site practices should be followed during the construction of the Project:

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

·           Silencers or mufflers on construction equipment should be utilized and should be properly maintained 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 utilised, wherever practicable, in screening noise from on-site construction activities; and

·           The contractor should liaise with the school regarding the examination periods.  Noisy construction activities, including piling, excavation and earth-breaking works, will be carried out outside the examination periods.

Use of Quiet Powered Mechanical Equipment (PME)

The use of quiet PME was considered to be a practicable means to mitigate the construction noise impact.  Quiet plant is defined as a PME having actual SWL lower than the value specified in the GW-TM.

Use of Acoustic Enclosure

Temporary acoustic enclosure is a common and effective means to mitigate the noise impact arising from operation of certain small size PMEs.  A frame covered with noise insulation materials (sound insulation materials with a superficial surface density of at least 7 kg/m2 or sound absorbing materials of at least 50mm and average absorption coefficient between 125 Hz and 4000 Hz of 0.4) could at least 5 dB(A) reduction for plant items such as hand-held breaker and circular wood saw.  The locations of the temporary acoustic enclosure should be adjusted wherever and whenever necessary to protect the noise sensitive receivers, the enclosures should have no openings or gaps.

Adoption of Movable Noise Barriers

The use of noise barriers will be an effective means to mitigate the noise impact arising from the construction works, particularly for low-rise NSRs.  For the low-rise nature of the NSRs, movable noise barriers of 3 to 5 m high (depending on the size of the plant that requires to be screened) with skid footing should be used and located within a few metres of stationary plant and mobile plant such that the line of sight to the NSR is blocked by the barriers.  The length of the barriers should be at least five times greater than its height.  These movable noise barriers could produce at least 5 dB(A) noise reduction for mobile plant such as backhoe and roller as well as large scale plant such as crane.  With reference to A Practical Guide for the Reduction of Noise from Construction Works, the noise barrier material should have a superficial surface density of at least 7 kg/m2 and have no openings or gaps.

Scheduling of Construction Works

To further alleviate the construction noise impacts, only one group of PME (Group A or B) will be operated during road drainage, utilities and water mains works at work site of slip road A and also during site works like road resurfacing and remarking A and B.  All noisy construction activities should be suspended at work site of slip road A and flyover A during examination period of the Kwong Ming Ying Loi School.  

4.10.2                  Operational Phase

Notwithstanding the prediction that the NSRs will not be subject to adverse noise impact during the operational phase of the Project, noise monitoring should be carried out during the first year after opening to ensure noise compliance. 

The ET should prepare and deposit to EPD, at least 6 months before the operation of the works under the Project, a monitoring plan for the purpose of assessing the accuracy of traffic noise predictions by comparing the project noise impact predictions with the actual impacts.  The monitoring plan should contain information on the monitoring locations, monitoring schedules, methodology of noise monitoring including noise measurement procedures, traffic counts and speed checks, and methodology of comparison with the predicted levels.   The ET should implement the monitoring plan in accordance with the deposited monitoring plan unless with prior justification.  Monitoring details and results including the comparison between the measured noise levels and the predicted levels should be recorded in a report to be deposited with EPD within one month of the completion of the monitoring.  The report should be certified by the ET Leader and the Project Proponent before deposit with EPD.

The traffic noise levels should be measured twice at 6-month intervals within the first year upon completion of the Project.  Measurements should be made in terms of the A-weighted L10 over 3 half hour periods during the peak traffic hour, other parameters including Leq should also be taken for reference.

As shown in Table 4.4 and Figure 4.1, two designated monitoring stations are selected for the operational noise monitoring.  The status and locations of noise sensitive receivers may change after this Manual is issued.  If such cases exist, the ET Leader should propose updated monitoring locations and seek approval from the ER and IEC and agreement from EPD of the proposal.

Table 4.4        Noise Monitoring Stations for Operational Traffic Noise

Monitoring Station

Description

KMYLS1

Kwong Ming Ying Loi School

JCCAH1

Jockey Club Care & Attention Home

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

·           they should be at NSRs in the vicinity of recommended direct technical remedies; preferably, there should be one representative monitoring locations near each types of noise screening element (ie vertical barrier, cantilever barrier and enclosure);

·           one high floor and one medium floor monitoring points should be chosen at each location as far as practicable; and

·           selected monitoring locations should allow monitoring to be done twice within one year after implementation of the mitigation measures during operation of the Project.

The status and location of NSRs may change after issuing this manual. If such case exists, the ET Leader should propose updated monitoring locations and seek approval from EPD and agreement from the ER and the IEC before baseline monitoring commences.

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

·           alternative location should be similarly exposed to potential noise impacts;

·           it should be close to the NSRs; and

·           should be located so as to minimise disturbance to the occupants.

The operational noise monitoring should be carried out at a distance of 1 m from the openable window and 1.2 m above the floor level of the noise sensitive receivers identified.  The ET Leader should agree with the IEC on any necessary corrections adopted.

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

·           one set of measurements during the morning traffic peak hour on a normal weekday;

·           one set of measurements during the evening traffic peak hour on a normal weekday;

·           a concurrent census of traffic flow and percentage heavy vehicles should be conducted for the far-side and near-side of the road and the existing road network in the vicinity of each measurement points;

·           average vehicle speed estimated for far-side and near-side of the road and the existing road network in the vicinity of each measuring points; and

·           the two sets of monitoring data should be obtained within the first your of operation.

Measured noise levels should be compared with the 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 traffic noise monitoring during operational phase is shown in Annex C for reference.

The measured/ monitored noise levels should 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.