3. NOISE

3.1 Introduction

3.1.1 Noise impacts would be emanated during the construction and operation phase of the project. The following sections detailed the approaches, criteria and guidelines on monitoring and managing noise impacts.

3.1.2 Noise would be the key environmental issue during construction. It is necessary to monitor noise emanating from the construction activities after timely implementation of the mitigation measures listed in Section 3.8 in this Manual. The purpose of monitoring is to ascertain that the noise levels would comply with the noise criteria at the sensitive receivers, and that the recommended mitigation measures are effective in suppressing noise levels.

3.1.3 The objectives of the monitoring are:

(a) To identify the magnitude of construction noise impacts on nearby sensitive receivers;
(b) To determine the effectiveness of the recommended noise mitigation measures to control noise from construction activities;
(c) To recommend further mitigation measures where necessary; and
(d) To ascertain that the noise levels would comply with the noise criteria at nearby sensitive receivers as defined in this EM&A Manual.

3.2 Construction Noise Monitoring

Noise Parameters

3.2.1 Monitoring and audit of noise levels should be carried out by the ET to ensure that any unacceptable noise impacts could be readily detected and timely and appropriate action be undertaken to rectify the situation.

3.2.2 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. For all other time periods, Leq(5 min) shall be employed for comparison with the NCO criteria.

3.2.3 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-2A for reference.

Monitoring Equipment

3.2.4 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.

3.2.5 Noise measurements should be made in accordance with standard acoustical principles and practices in relation to weather conditions.

3.2.6 The ET Leader should be responsible for the provision of the monitoring equipment. He/she should 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 should be clearly labelled. The equipment installation location should be proposed by the ET Leader and agreed with the ER and EPD in consultation with the IEC.

Monitoring Locations

3.2.7 Two noise monitoring stations are proposed to set up at SWC-AN1(AP 8009) and SWC-AN2(AP8025) which are the village houses at Ngau Hom Shek during construction phase. Figure EM2.1 and Table 3.1 show the locations of the proposed noise monitoring stations. Impact monitoring of noise should be carried out whenever there is ongoing construction work of SWC.

3.2.8 The status and locations of noise sensitive receivers (NSRs) may change after issuing this Manual. If such cases exist, the ET Leader should propose updated monitoring locations and seek approval from ER and agreement from the IEC and EPD of the proposal.

3.2.9 When alternative noise monitoring locations 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, with proper position/siting and orientation of the monitoring equipment ensured;
(b) close to the noise sensitive receivers (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.

3.2.10 The monitoring station should 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 should be made. For reference, a correction of +3dB(A) should be made to the free field measurements. The ET Leader should agree with the 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 should be carried out at the same positions.

Baseline Monitoring

3.2.11 The ET Leader should carry out baseline noise monitoring prior to the commencement of the construction works. The baseline monitoring should be carried out daily for a period of at least two weeks. A schedule on the baseline monitoring should be submitted to the ER for approval before the monitoring starts.

3.2.12 During the baseline monitoring, there should not be any construction activities in the vicinity of the monitoring stations.

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

Impact Monitoring

3.2.14 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 per week basis when noise generating activities are underway:

(a) one set of measurements between 0700-1900 hours on normal weekdays;
(b) measurement(s) between 1900-2300 hours (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);
(c) measurement(s) 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) measurement(s) 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).

3.2.15 For the measurements (b), (c) & (d) above, as an indication one set of measurements shall at least include three consecutive Leq(5 min) results and shall only be carried out when there are construction activities scheduled during those periods. This will be subject to the CNP and the approval by the Noise Control Authority.

3.2.16 In case of non-compliance with the construction noise criteria, more frequent monitoring as specified in the Action Plan as shown in Table 3.3 should be carried out. This additional noise monitoring should be continued until the recorded noise levels are rectified or provide to be irrelevant to the construction activities.

3.2.17 Construction work carrying out during restricted hours is controlled by CNP system under the NCO. The Contractor shall obtain a CNP prior to any construction work during restricted hours.

3.3 Operation Noise Monitoring

3.3.1 As the noise sensitive receivers close to the SWC will be exposed to traffic noise during the operational phase, a noise monitoring programme is developed to include noise measurements at noise sensitive receivers 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 mitigation measures recommended.

Noise parameters

3.3.2 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-2B for reference.

Monitoring Equipment

3.3.3 Sound level meters to be used shall be in compliance with the International Electrotechnical Commission Publications 651: 1979 (Type 1) and 804: 1985 (Type 1) specifications 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(A).

3.3.4 Noise measurements should be made in accordance with standard acoustical principles and practices in relation to weather conditions.

3.3.5 The ET Leader is responsible for the provision and maintenance of the monitoring equipment. He/she 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 should be clearly labelled.

Monitoring Locations

3.3.6 The monitoring locations shall be selected according to the following criteria:
(a) the monitoring locations should be so chosen that noise from SWC 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 operation of the proposed road.

3.3.7 Two operational noise monitoring stations are proposed to set up at SWC-AN1(AP8009) and SWC-AN2(AP8025) which are village houses at Ngau Hom Shek. The two stations allow a large angle of view over SWC to be selected rather than over DBL and are chosen to review the traffic noise predictions for SWC. Figure EM2.1 and Table 3.1 show the locations of the proposed operational noise monitoring stations.

3.3.8 The status and locations of noise sensitive receivers 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 IEC and EPD of the proposal. The purpose of the monitoring is to review the different situations predicted in the EIA. Monitoring point/facade should be chosen such that it is dominated by the traffic noise from the proposed road.

3.3.9 When alternative monitoring locations are proposed, the monitoring locations shall be chosen based on the following criteria:
(a) alternative location shall be similarly exposed to potential noise impacts;
(b) it shall be close to the noise sensitive receivers; and
(c) shall be located so as to cause minimal disturbance to the occupants.

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

3.3.11 No baseline operational noise monitoring is generally required.

Impact monitoring

3.3.12 Noise monitoring shall 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:
(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.

3.3.13 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.

3.3.14 A sample data record sheet for operational noise monitoring is shown in Appendix B-2B for reference.

3.4 Summary of Noise Monitoring Requirements

3.4.1 Table 3.1 summarises the monitoring requirements for noise.

Remark: The monitoring locations for the purpose of DBL project are also indicated in Figure EM2.1, the monitoring data will also be used for SWC project analysis where appropriate and necessary.

3.5 Event and Action Plan for Noise

Construction phase

3.5.1 The Action and Limit levels for noise are defined in Table 3.2. Should non-compliance of the criteria occur, action in accordance with the Action Plan in Table 3.3 should be carried out.

Operational Phase

3.5.2 The measured/monitor noise levels 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.

3.6 Noise Mitigation Measures

3.6.1 The EIA Report has recommended construction noise control and mitigation measures. The Contractor should be responsible for the design and implementation of these measures under the supervision of the Engineer and the Environmental Team.

3.6.2 Noise emissions from construction sites during construction phase could be minimised by adopting good site practice, selecting quiet plant, using quiet working methods and installing temporary barriers. Recommended noise mitigation measures are detailed below. If the noise mitigation measures detailed below are not sufficient to restore the construction noise quality to an acceptable level upon the advise of ET, the Contractor should liaise with ET on some other mitigation measures, propose to the ER for approval, and implement the mitigation measures.

Construction Phase

Use of Quiet Plant and Working Methods

3.6.3 The use of quiet plant was identified to be a feasible solution to tackle the adverse impacts associated with construction works. The Contractor should obtain particular models of plant that are quieter than standard types given in the GW-TM. The benefits achievable in this way would depend on the details of the Contractor's chosen methods of working, and it would be too restrictive to specify that a Contractor has to use specific items of plant for the construction operations. It is therefore both preferable and practical to specify an overall plant noise performance specification to apply to the total SWL of all plants on the site so that the Contractor is allowed some flexibility to select plant items to suit his needs. It should be noted that various types of silenced equipment could be found in Hong Kong. However, the Authority, when processing a CNP application, will apply the noise levels contained in the relevant statutory TMs unless the noise emission of a particular piece of equipment can be validated by a certificate or through a demonstration.

3.6.4 Quiet PME is defined as PME whose actual SWL is less than the value specified in the GW-TM for the same item of plant. Reference can be made to the British Standard BS5228: Part 1:1997 Control on Construction and Open Sites.

Using Temporary and Movable Noise Barriers

3.6.5 Movable barriers that can be located close to noisy plant can be very effective at screening NSRs from particular items of plant or noisy operations. Movable barriers of 3 to 5m height with a small cantilevered upper portion and skid footing can be located within a few metres of stationary plant and within about 5m or more of mobile equipment such as an excavator and mobile crane etc., such that the line of slight to the NSR is blocked by the barriers. It would be possible for the Contractor to provide purpose-built noise barriers or screens constructed of appropriate material (minimum superficial density of 15 kg/m2) located close to operating PME, in order to reduce the noise impact to the surrounding sensitive uses. Certain types of PME, such as generators and compressors, can be completely screened by portable barriers giving a total noise reduction of 10 dB(A) or more.

Reducing the Numbers of Plants Operating in Critical Areas Close to NSRs

3.6.6 In general the number of plant should be left to the choice of the Contractor so that in combination with the selection of quiet plant, any further reduction in the total plant noise level, or the site specific maximum sound power levels, as described above, can be achieved. It would be appropriate to restrict the number of operating PME within certain parts of the site that are very close to the NSRs in order to reduce the level of noise impacts. This method could be more effective for activities associated with foundation work, pile construction and excavation activities in which a large number of PME are anticipated, but not all of them would be utilised at the same time. A noise reduction of up to 6 dB(A) could be achieved if the number of PME used on site is reduced to one, as estimated from the predicted values.

Using Noise Screening Structures or Purpose-built Noise Barriers along the Site Boundary

3.6.7 Considering the low-lying nature of surrounding NSRs (typically village houses or temporary houses), it would be effective to have noise screening structures along the site boundary to protect NSRs close to the construction site boundary. The following measures could be applied to reduce the construction noise:
· Site buildings such as office and stores could be grouped together to form a substantial barrier separating site operations and nearby noise sensitive premises. This may be applicable for road alignment sites.
· Stacks of certain materials such as bricks, aggregate, timber or top soil can be strategically placed to form a barrier. This may be applicable for construction of road alignment.
· Earth bunds can be built to provide screening for major earthmoving operations. This may be applicable for road alignment sites.
· For adverse cases, purpose-built noise barriers or screens could be placed along the site boundary. This may be applicable for road alignment sites.

Good Site Practice

3.6.8 The following good site practice should be adopted during the construction phase:
· The contractor should site noisy equipment and activities as far from sensitive receivers as practical. Also, temporary site offices (and other similar structures) should be located, as far as is possible, such that sensitive receivers are screened by these structures from the line of sight of the construction areas.
· Intermittent noisy activities should be scheduled to minimize exposure of nearby NSRs to high levels of construction noise. For example, noisy activities could be scheduled at times coinciding with periods when the schools are likely to be unoccupied. Prolonged operation of noisy equipment close to the schools should be avoided.
· Idle equipment should be turned off or throttled down. Noisy equipment should be properly maintained and used no more often than is necessary.
· Construction activities should be planned so that parallel operation of several sets of equipment close to a given receiver is avoided.
· Where possible, the numbers of concurrently operating items of plant should be reduced through sensitive programming.
· Construction plant should be properly maintained and operated. Construction equipment often has silencing measures built in or added on, e.g. compressor panels, and mufflers. Silencing measures should be properly maintained and utilized.

Proposed Construction Noise Mitigation Measures

3.6.9 The proposed mitigation measures for construction noise are arranged in an increasing level of efforts. Since the actual activities in the construction sites may vary at local site level, the level of mitigation measures adopted should also be determined with reference to the findings of the EM&A programme. The following mitigation levels are recommended.
Mitigation Level 1 - Use of quiet plant and working methods
Mitigation Level 2 - Use of quiet plant and working methods, and- Use of noise screening structures or purpose-built noise barriers along the site boundary

3.6.10 The number of PME used on site should be reviewed from time to time to avoid excessive or dummy PME located too close to NSRs. Good site practice should be followed through the construction phase.

3.6.11 Specific measures are also recommended to be adopted for SWC in order to minimise the potential of adverse impact:
(1) a construction site boundary wall or hoarding is constructed in such a way to act as an acoustic screen/noise barrier for active carriageway construction work proximity to NSRs. The screening effect is expected for ground level equipment. The boundary wall or hoarding should:
· have a mass per unit of surface area in excess of 7 kg/m2 to prevent sound transmitted through the screen;
· have no gaps or openings at joints in the screen material; and
· have a vertical height of 3m.
(2) Quiet plant/power mechanical equipment of sound power level lowered than those listed in Table 3 of the GW-TM shall be used for all construction sites.

Operational Phase

Road Traffic Noise

3.6.12 Low noise surfacing for the alignment would be adequate to mitigate the noise impact into acceptable levels. It is a standard provision for the roads with vehicle speed limit greater than 70km/hr under the current policy. All low noise surfacing should be designed according to the design guidelines/practice notes issued by HyD Guidance Note No. RD/GN/011B Guidance Notes on Noise Reducing Road Surfacing. No adverse operational impact from the Project is expected on the nearest sensitive receivers.