4                     NOISE




4.1               This section presents an assessment of potential noise impact pertinent to the construction and operation phase of the Project. Appropriate mitigation measures have been recommended, where necessary, to alleviate the potential noise impacts to acceptable levels.


Environmental Legislation, Policies, Plans, Standards and Criteria


4.2               Noise impacts were assessed in accordance with the criteria and methodology given in the Technical Memoranda made under the Noise Control Ordinance (NCO), and EIAO-TM.


4.3               The NCO provides the statutory framework for noise control. This defines statutory limits applicable to equipment used during the construction and operation phases of the proposed works in the study area.  The NCO invokes four Technical Memoranda, which define the technical means for noise assessment:


         Technical Memorandum on Noise from Places other than Domestic Premises, Public Places or Construction Sites (IND-TM);

         Technical Memorandum on Noise from Construction Work in Designated Areas (DA-TM);

         Technical Memorandum on Noise from Construction Work other than Percussive Piling (GW-TM); and

         Technical Memorandum on Noise from Percussive Piling (PP-TM).


4.4               The NCO and the accompanying Technical Memoranda provide a mechanism for assessing noise levels and provide the statutory power to control noise.


Construction Activities


4.5               The NCO provides the statutory framework for noise control of construction work, other than percussive piling, using powered mechanical equipment (PME) between the hours of 1900 and 0700 hours or at any time on Sundays and general holiday (that is, restricted hours).  Noise control on construction activities taking place at other times is subject to the Criteria for Evaluating Noise Impact stated in Table 1A of Annex 5 in the EIAO-TM.  The noise limit is Leq (30 minutes) 75 dB(A) at the façades of dwellings and 70 dB(A) at the façade of schools (65 dB(A) during examinations).


4.6               The construction works would not be carried out during restricted hours, therefore, the EIAO-TM standard was used as the assessment criteria in the construction noise assessment.


Operational Activities


4.7               Operational noise emitted from the proposed Project is controlled under the IND-TM. With regard to the assessment of the operational noise impacts, the NCO designates acceptable noise levels for Noise Sensitive Receivers (NSRs) on the basis of an Area Sensitivity Rating (ASR), based on the characteristics of the area within which they are located such as rural, village, low-density residential, or urban. Within these areas, the presence of "influencing factors" (such as the presence of industrial activities or major roads) can further affect the ASR and hence the acceptable noise level (see Table 4.1).




Table 4.1      Area Sensitivity Ratings (ASRs)


Type of Area Containing NSR

Degree to which NSR is affected by Influencing Factor

Not Affected

Indirectly Affected

Directly Affected

Rural Area




Urban Area




Low density residential area consisting of low-rise or isolated high-rise developments




Area other than those above





4.8               The Acceptable Noise Level (ANL) is a function of the type of area within which the NSR is located, and the degree of the effect on the NSR of influencing factors such as major roads and industrial areas.  According to the TM, the ANLs for different Area Sensitivity Ratings (ASRs) are given in Table 4.2.


4.9               The Study Area for noise impact is defined by a distance of 300m from the boundary of the Project site.  The study area is a rural area with low-density residential development.  There is no industrial operation or major roads are noted within the study area, therefore, the Area Sensitivity Rating (ASR) of “A” is determined.


Table 4.2      Acceptable Noise Levels (ANLs) (dB(A))


Time Period




Day (0700 to 1900 hours)




Evening (1900 to 2300 hours)

Night (2300 to 0700 hours)





4.10            When assessed in accordance with the IND-TM, the level of the intruding noise at the facade of the nearest sensitive use should be at least 5 dB(A) below the appropriate ANL shown in Table 2 of the IND-TM or, in the case of the background being 5 dB(A) lower than the ANL, the predicted noise level should not exceed the background.


4.11            As stated in Section 4.9, the Area Sensitivity Rating (ASR) of “A” is determined for the study area, i.e. its planning criteria for NSRs would be 55 dB(A) for daytime operations and 45 dB(A) for night-time operations.


4.12            A noise survey in the proximity of TM54SPS was undertaken on 13 November 2007 to determine the background noise levels.  Four sets of noise data at each measurement period were collected,  The measured minimum daytime (measurement during 16:00 – 18:00), evening time (measurement during 21:00 – 23:00) and nighttime (measurement during 00:00 – 01:00) noise levels at Kei Lun Wei were 51.5dB(A) (Leq (30 min)), 50.3 dB(A) (Leq (30 min)) and 51.7 dB(A) (Leq (5 min)) respectively.  The recommended daytime, evening time and nighttime noise criteria in the assessment are therefore 51.5dB(A), 50.3 dB(A) and 45 dB(A) respectively.


4.13            In any event, the Area Sensitivity Rating assumed in this EIA Report is for indicative assessment only. It should be noted that fixed noise sources are controlled under section 13 of the NCO. At the time of investigation, the Noise Control Authority shall determine noise impact from concerned fixed noise sources on the basis of prevailing legislation and practices being in force, and taking account of contemporary conditions/ situation of adjoining land uses. Nothing in this EIA Report shall bind the Noise Control Authority in the Context of law enforcement against all the fixed noise sources being assessed.


Description of the Environment


4.14            TM54SPS will be constructed in the central part of Site 4A of Tuen Mun Area 54, north of Kei Lun Wai, south of Tsz Tin Tsuen and west of Site 2 of Tuen Mun Area 54.  Site 4A is zoned “Government, Institution or Community” (G/IC) on the Tuen Mun Outline Zoning Plan (OZP) No. S/TM/24 and is reserved for school development.  Site 2 is zoned “Residential (Group A)” and Site 3&4(East) is zoned “Residential (Group A)” on the Tuen Mun OZP No. S/TM/24.  Public housing will be developed at Site 2 and Site 3&4(East).


Noise Sensitive Receivers


4.15            In order to evaluate the construction and operational noise impacts likely to arise from the Project, representative existing noise sensitive receivers (NSRs) and planned NSRs (in accordance with the Tuen Mun OZP No. S/TM24) within 300m of the Project boundary were selected according to the criteria set out in the Annex 13 of the EIAO-TM.  Details of the NSRs are summarized in Table 4.3.  Figure 4.1 shows the locations of representative NSRs.


Table 4.3      Details of Noise Sensitive Receivers





Distance between NSR and nearest Project Boundary (m)


Unicorn Garden




Kei Lun Wei



Siu Hang Tsuen



Planned Secondary School

Educational Institution



Planned Secondary School



Planned Primary School



4.16            The construction work for TM54SPS would be completed in early 2014.  The operation year of the planned schools (NSR N4 – N6) would be beyond 2016.  Therefore, the construction noise impact assessment would be focused on the representative NSRs N1 – N3.  For the operation phase impact assessment, the planned primary and secondary schools would not be operated during nighttime, the fixed plant noise impact on the planned schools during daytime and evening time would be assessed only.


Identification of Environmental Impacts


Construction Phase


4.17            The potential source of noise impact during the construction phase of the Project would be the use of PME for various construction activities. As shown in Figure 2.3, the construction of the Project (including testing & commissioning) has been scheduled to commence in early 2011 and to be completed in early 2014. The Project would involve the following major construction activities.


·        Site Clearance

·        Bulk Excavation for Sub-Structure and Site Formation

·        Steel Fixing Concreting of Sub-Structure

·        Steel Fixing and Concreting of Roof and Columns

·        Brick Work and Finishing

·        M&E Installation and Pipeworks

·        Landscape Works and Roadworks


4.18            Referring to the construction programme, the following construction activities would be undertaken concurrently.  Cumulative noise impacts on the representative NSRs were also assessed.


·        Brick Work & Finishing and M&E Installation & Pipeworks

·         Brick Works & Finishing, M&E Installation & Pipeworks, Landscape Works & Roadworks


4.19            Generally, the construction activities of the Project would be carried out in non-restricted hours (0700-1900 hours) during normal working days. In case of any construction activities during restricted hours, it is the Contractor’s responsibility to ensure compliance with the NCO and the relevant TMs. The Contractor will be required to submit CNP application to the Noise Control Authority and abide by any conditions stated in the CNP, should one be issued.


4.20            There would have two other projects to be undertaken concurrently within 300m of the study area.  The concurrent activities includes (i) site formation and infrastructural works for Site 2 under the project “Formation, Roads and Drains in Tuen Mun Area 54 – Phases 1 and 2, Private and Public Rental Housing Development in Tuen Mun Area 54” (be commenced in September 2010 and completed in September 2013); and (ii) Village sewerage works under the project “Sewerage Upgrading Works in Tune Mun under Agreement No. CE 38/2006 (DS)” (be commenced in mid 2009 for completion in end 2015).  The project proponent of the village sewerage’s works agreed that the construction of the proposed village sewerage works at Kei Lun Wai and Unicorn Garden within 300m of the study area would be scheduled with the consideration of the construction of TM54SPS (i.e. no overlap with the construction of TM54SPS) so as to minimize the cumulative noise impact to the sensitive receivers. Therefore, only cumulative construction noise impacts from site formation and infrastructural works for Site 2 were assessed in the study.


Operation Phase


4.21            The potential sources of noise impact during the operation phase of TM54SPS would be the operation of pumps, mechanically racked screens, transformer and ventilation fan of deodourization unit.  Four main pump sets (3 operations and 1 standby), two mechanically racked screens and one transformer would be installed in TM54SPS.  A ventilation fan of the deodourization unit would also be installed.


4.22            The transformer would be located in an enclosed reinforced concrete structure while the pump sets and mechanically racked screens would be located in the underground level and housed in a reinforced concrete structure with acoustic louvers .  The structure material of TM54SPS would be 200mm reinforced concrete.  Silencer would also be installed at the ventilation fan of the deodourization unit.


Assessment Methodology


Construction Phase


4.23            In accordance with the EIAO-TM, the methodology outlined in the GW-TM was used for the construction noise assessment. The general approach is summarized below:


·        Locate the NSRs which would most likely be affected by noise from the construction work

·        Determine the items of Powered Mechanical Equipment (PME) for each discrete construction activity, based on available information or agreed plant inventories

·        Assign sound power levels (SWLs) to the proposed PME according to the GW-TM or other sources

·        Calculate distance attenuation and screening effects to NSRs from notional noise source

·        Predict construction noise levels at NSRs in the absence of any mitigation measures

·        Include a 3 dB(A) façade correction to the predicted noise levels in order to account for the façade effect at each NSR.


4.24            Sound power levels (SWLs) of the equipment were taken from Table 3 of GW-TM.  Groups of PME were assigned for various construction activities of the proposed Project. The proposed plant inventory for the construction of the Project is presented in Appendix 4.1a. The Project Proponent has confirmed the proposed plant inventory as being practical and adequate for completing the works within the scheduled timeframe.


4.25            For assessing cumulative construction noise impacts, the plant inventories in the approved EIA Report “Planning and Development Study of Potential Housing Site in Area 54, Tuen Mun (Agreement No. CE 21/97)” were used for calculation.  The plant inventories of this project are presented in Appendix 4.1e.


Operational Phase


4.26            For the assessment of noise from equipment, the noise level at NSR was predicted using the standard acoustic principles:


Predicted Noise Level = Sound Power Level of Equipment - Distance Attenuation - Enclosure Reduction (if any) - Screening Reduction (if any) + Facade Correction 


where Distance Attenuation     = 20 log D + 8 [where D is the distance in meters]

Façade Correction     = 3 dB(A)


4.27            The SWL of the pumps and motors were taken with reference to the Central and Wan Chai East Pumping Stations and Screening Plants – Operation and Maintenance Manual Volume 1 (Contract No. DE/95/12) published by DSD.  The SWL of the ventilation fan was in accordance with Good Practices on Ventilation System Noise Control published by EPD. 


4.28            Noise impact was assessed on the basis of the following assumptions:


·        All items of operational plant required for operation of the proposed facilities would be located at the actual source position. 

·        A +3 dB(A) façade correction and a +6dB(A) for tonal correction were added to the predicted noise levels to account for the facade effect at each NSR.

·        Noise impacts at the nearest facades of the NSRs to the source positions were assessed.


Prediction and Evaluation of Environmental Impacts


Construction Phase


4.29            Noise impacts arising from different construction activities have been predicted and are shown in Appendix 4.1a – 4.1b. 


4.30            The predicted noise levels at the three existing representative NSRs were in the range of 63 to 80 dB(A).  The predicted noise levels at NSR N1 and N2 would exceed the daytime noise criteria of 75 dB(A) during the following construction activities.   Noise mitigation measures are required to alleviate the adverse impact arising from the Project.


·         Bulk excavation for sub-structure and site formation

·         Landscape works & roadworks

·         Brick Works & Finishing + M&E Installation & Pipeworks + Landscape Works & Roadworks


Operation Phase


4.31            The plant inventory and the corresponding SWL are summarised in Appendix 4.2.  As confirmed by the Project Proponent, the plant inventory used for prediction of operation noise impact is practical and realistic. To represent the worst case scenario, all items of equipment were assumed to operate concurrently 24 hours a day and the directivity was not included in the calculation.


4.32            The transformer would be housed in an enclosed 200mm reinforced concrete structure with the soundproof door.  The noise attenuation of 20 dB(A) due to transmission loss of wall was therefore assumed for the noise emitted from the transformer in the assessment.  The pump sets and mechanically raked screens would be located at the basement and housed in a 200mm thick reinforced concrete structure with the soundproof door.  The silencers would be provided at the louvers of the pump house to reduce the operation noise emitting to the NSRs via the opening.  The overall noise reduction under such arrangement would have 20 dB(A) for the pump sets and mechanically raked screens.  Acoustic silencer with noise attenuation of 10 dB(A) would be provided for the exhaust fan of the deodorization unit.  The location of the exhaust fan of the deodorization unit will be located facing proposed road L54B, as such the NSR has no direct line of sight to the ventilation fan of deodourization unit and 10 dB(A) of noise attenuation was assumed in the assessment. 


4.33            According to the plant inventory for TM54SPS as shown in Appendix 4.2, the predicted noise levels at the residential NSR N1 and N2 would be 36 dB(A) and 40 dB(A) respectively.  The predicted noise levels at the educational institutes including NSR N4, N5 and N6 would be in the range of 39 dB(A) and 44 dB(A).  The predicted noise levels at all representative NSRs would comply with daytime and evening time noise criteria of 51.5 dB(A) and 50.3 dB(A) respectively.  The predicted noise levels at the existing residential NSRs would also comply with the night time criteria of 45 dB(A).  Thus, mitigation measures would not be required for TM54SPS. Details of the calculation are presented in Appendix 4.2.


4.34            Referring to Figure 4.1, the distance of NSR N3 to TM54SPS is much farther than that of NSRs N1 and N2.  Since the predicted noise level is distance dependent and the predicted noise levels of NSRs N1 and N2 did not exceed the noise criteria even for their shorter distances than NSR N3.  Hence, NSR N3 was not assessed as noise exceedance at NSR N3 would not be expected.


Mitigation of Adverse Environmental Impacts


Construction Phase


Use of Quiet PME


4.35            In order to reduce construction noise impacts on the NSRs, silenced types of PME, which are in accordance with BS 5228: Part 1, 1997, are recommended. The total Sound Power Level (SWL) of PME for each construction activity was calculated and is summarized in Appendix 4.1c.


4.36            With the use of quiet PME for these construction activities, a noise reduction of up to 13 dB(A) at the NSRs could be achieved. A detailed calculation of construction noise impact for the mitigated scenario is presented in Appendix 4.1c – 4.1d. The results indicate that the mitigated maximum noise levels predicted at NSR N1, N2 and N3 due to this Project would be ranged from 59 to 69 dB(A),  complying with the daytime noise standard of 75 dB(A).


Good Site Practice


4.37            In addition to adoption of quiet PME, good site practices listed below should be adopted to further abate any residual impacts during the construction phase of the Project and should be included in the contract document:


·        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; and

·        Material stockpiles and other structures should be effectively utilised, wherever practicable, in screening noise from on-site construction activities.


Cumulative Construction Noise Impact


4.38            As mentioned in Section 4.20, the site formation and infrastructural works for Site 2 under the project “Formation, Roads and Drains in Tuen Mun Area 54 – Phase 1 and 2, Private and Public Rental Housing Development in Tuen Mun Area 54” would be undertaken concurrently within 300m of the study area.  The detail calculation for cumulative construction noise impacts is presented in Appendix 4.1e.  The predicted cumulative noise levels at NSR N1, N2 and N3 would be 70 dB(A), 70 dB(A) and 67 dB(A), which would comply with the EIAO TM construction noise criterion of 75 dB(A).  Therefore, no further mitigation measures would be proposed for this Project.


Operation Phase


4.39            As the predicted noise levels at representative NSRs would comply with the daytime, evening time and nighttime noise criteria, no mitigation measures are proposed. 


Evaluation of Residual Impacts


Construction Phase


4.40            No adverse residual construction noise impact from the Project is expected with the use of silenced PME and implementation of good site practices.  The mitigated cumulative construction noise impact at NSRs N1 and N2 would also complied with the construction noise criteria.


Operation Phase


4.41            No adverse residual operation noise impact from TM54SPS is expected. 


Environmental Monitoring and Audit


Construction Phase


4.42            It is recommended to establish an Environmental Monitoring and Audit (EM&A) programme for control of construction noise. The recommended mitigation measures should be incorporated into the EM&A programme for implementation during the construction period. Details of the programme are provided in a stand-alone EM&A Manual.


Operation Phase


4.43            The EIA findings confirmed that proper designs of TM54SPS (i.e. the pump sets and mechanically racked screens to be located at underground and housed in 200mm reinforced concrete structure with soundproof door, the transformer to be housed in enclosed reinforced concrete structure with soundproof door, provision of acoustic silencer for louvers of pump house and exhaust fan of deodourizing unit, and specify the maximum allowable sound power levels of noisy equipment) would control the potential noise impact at noise sensitive receivers within acceptable levels, no operational noise monitoring would be conducted after commissioning of the TM54SPS.




Construction Phase


4.44            The potential noise impact arising from construction of TM54SPS on the nearest representative NSRs was assessed. Results indicated that noise exceedance was predicted at the NSRs N1 and N2 during some construction activities of the Project.  With the adoption of quiet PME during these construction activities, the predicted construction noise levels at representative NSRs would all comply with the relevant noise criteria.  Good site practices were also proposed to further abate the impacts on the NSRs.  Taking into account of concurrent construction activities undertaken by other projects within 300m of the study area, the predicted noise levels at NSRs N1, N2 and N3 would still comply with the construction noise criterion.  The mitigated impact at NSRs N1, N2 and N3 are therefore considered acceptable.


Operation Phase


4.45            The noise impacts associated with the operation of the Project were assessed. In view of proper design of TM54SPS as mentioned in S4.43, the operation noise levels at representative NSRs would comply with the daytime, evening time and night time noise criteria.  No mitigation measures were proposed.