4 AIRBORNE NOISE

Introduction

4.1 This Section presents an assessment of the potential airborne noise impacts associated with the construction and operation of the Project. The noise impact assessment was conducted in accordance with the requirements of Annex 5 and Annex 13 of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM) as well as the requirements set out under Clause 3.4.2 of the EIA Study Brief. Ground-borne noise impact associated with the operation of powered mechanical equipment, in particular, tunnel boring machine, was also assessed, and the findings are presented in Section 5 of this EIA Report.

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.

4.5 With regard to the assessments of the construction noise impact during restricted hours and operational noise impact, 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 (see Table 4.1). 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.

Table 4.1 Area Sensitivity Ratings (ASRs)

Type of Area Containing NSR	Degree to which NSR is affected by Influencing Factor
Type of Area Containing NSR	Not Affected	Indirectly Affected	Directly Affected
Rural Area	A	B	B
Urban Area	B	C	C
Low density residential area consisting of low-rise or isolated high-rise developments	A	B	C
Area other than those above	B	B	C

Construction Noise

4.6 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 1B of Annex 5 in the EIAO-TM. The noise limit is L_eq (30 minutes) 75 dB(A) at the façades of dwellings and L_eq(30 minutes)70 dB(A) at the façade of schools (L_eq (30 minutes)65 dB(A) during examinations).

4.7 Between 1900 and 0700 hours and all day on Sundays and public holidays, activities involving the use of PME for the purpose of carrying out construction work is prohibited unless a construction noise permit (CNP) has been obtained. A CNP may be granted provided that the Acceptable Noise Level (ANL) for the NSRs can be complied with. ANLs are assigned depending upon the area sensitive rating (ASR). The corresponding basic noise levels (BNLs) for evening and night time periods are given in Table 4.2.

Table 4.2 Construction Noise Criteria for Activity other than Percussive Piling

Time Period	Basic Noise Level (BNLs)
Time Period	ASR A	ASR B	ASR C
Evening (1900 to 2300 hours) ⁽¹⁾	60	65	70
Night (2300 to 0700 hours)	45	50	55

Note: (1) Includes Sundays and Public Holidays during daytime and evening

4.8 For the purpose of assessing the feasibility of carrying out construction works during restricted hours, if any, the ASRs for noise sensitive receivers in the Study Area are assumed (see Table 4.3) depending on the type of area within which the NSR is located and the degree of the effect on the NSR of influencing factors.

Table 4.3 Area Sensitivity Rating (ASR) for NSRs in the Close Vicinity of Project Sites

Area	ASR	Rationales for Assigned ASR
North Point PTW	B	Urban area. Not affected by Influencing Factors (IFs).
Wan Chai East PTW	C	Urban area. Directly affected by the major road (i.e. Gloucester Road).
Central PTW	C	Urban area. Directly affected by the major road (i.e. Connaught Road West).
Fung Mat Road Site in Sai Ying Pun	C	Urban area. Directly affected by the major road (i.e. Connaught Road West).
Sandy Bay PTW	A	Low density residential area consisting of low-rise or isolated high-rise developments. Not affected by IFs.
Cyberport PTW	B	Area other than rural area, low density residential area and urban area. Not affected by IFs.
Wah Fu PTW	B	Area other than rural area, low density residential area and urban area. Not affected by IFs.
Aberdeen PTW	B	Area other than rural area, low density residential area and urban area. Not affected by IFs.
Ap Lei Chau PTW	B	Area other than rural area, low density residential area and urban area. Not affected by IFs.
Stage 2A Disinfection Facilities	C	Area other than rural area, low density residential area and urban area. Directly affected by the major road (i.e. Container Port Road South).
Stonecutters Island Sewage Treatment Works (SCISTW)	C	Area other than rural area, low density residential area and urban area. Directly affected by industrial operations (e.g. shipyards, dockyard, refuse transfer station, bus depot, etc.).

Note: PTW = Preliminary Treatment Works

4.9 The Area Sensitivity Ratings assumed in this EIA Report are for indicative assessment only. Despite any description or assessment made in this EIA Report on construction noise aspects, there is no guarantee that a Construction Noise Permit (CNP) will be issued for the project construction. The Noise Control Authority will consider a well-justified CNP application, once filed, for construction works within restricted hours as guided by the relevant Technical Memoranda issued under the Noise Control Ordinance. The Noise Control Authority will take into account contemporary conditions/ situations of adjoining land uses and any previous complaints against construction activities at the site before making his decision in granting a CNP. Nothing in this EIA Report shall bind the Noise Control Authority in making his decision. If a CNP is to be issued, the Noise Control Authority shall include in it any Condition he thinks fit. Failure to comply with any such conditions will lead to cancellation of the CNP and prosecution action under the NCO.

4.10 Percussive piling is prohibited between 1900 and 0700 hours on any weekday not being a general holiday and at any time on Sunday or general holiday. A CNP is required for the carrying out of percussive piling between 0700 and 1900 hours on any day not being a general holiday. PP-TM sets out the requirements for working and determination of the permitted hours of operations. ANLs for percussive piling for different types of NSRs are shown in Table 4.4.

Table 4.4 Acceptable Noise Levels for Percussive Piling

NSR Window Type or Means of Ventilation	ANL, dB(A)
NSR (or part of NSR) with no windows or other opening	100
NSR with central air conditioning system	90
NSR with windows or other openings but without central air conditioning system	85

Note: 10 dB(A) shall be subtracted from the ANLs shown above for NSRs which are hospitals, medical clinics, educational institutes, courts of law or other NSRs which are considered by the Authority to be particularly sensitive to noise.

4.11 Under the TM on Noise from Construction Work in Designated Areas, the use of five types of Specified Powered Mechanical Equipment (SPME) and three types of Prescribed Construction Work (PCW) within a designated area during restricted hours would require a valid CNP. The SPME includes hand-held breaker, bulldozer, concrete lorry mixer, dump truck and hand-held vibratory poker. The PCW are:

Ÿ erecting or dismantling of formwork or scaffolding;

Ÿ loading, unloading or handling of rubble, wooden boards, steel bars, wood or scaffolding material;

Ÿ hammering.

4.12 In general, it should not be presumed that a CNP would be granted for carrying out PCW within a designated area during the restricted hours. The CNP may be granted for the execution of construction works during restricted hours involving the use of PME and / or SPME if the relevant Acceptable Noise Levels and criteria stipulated in the GW-TM and DA-TM can be met.

Operation Noise

4.13 Fixed noise sources associated with the Project would be controlled by the NCO and IND-TM. The Acceptable Noise Levels (ANL) is a function of the type of area within which the NSRs are located, and the degree of the effect on the NSRs of influencing factors such as major roads and industrial areas. According to the IND-TM, the ANLs for different Area Sensitivity Ratings (ASRs) are given in Table 4.5.

Table 4.5 Acceptable Noise Levels for Fixed Noise Sources

Time Period	Acceptable Noise Level (ANLs)
Time Period	ASR A	ASR B	ASR C
Daytime and Evening (0700 to 2300 hours)	60	65	70
Night (2300 to 0700 hours)	50	55	60

4.14 In any event, the Area Sensitivity Rating assumed in the EIA Report is for indicative assessment only. It should be noted that the 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/situations of adjoining land uses. Nothing in the EIA Report shall bind the Noise Control Authority in the context of law enforcement against all the fixed noise sources being assessed.

4.15 While the noise impact arising from newly proposed fixed plant would be assessed against the planning criterion stipulated in EIAO-TM, the cumulative noise impact arising from both new and existing fixed plant would be assessed against ANL under NCO. This approach was adopted in an EIA Study for Tai Po Sewage Treatment Works Stage V which was approved by EPD under EIAO in October 2004.

Noise Criteria for Newly Proposed Equipment

4.16 Taking into account the type of area within which the NSR is located and the degree of the effect on the NSR of influencing factors, the ASRs for the NSRs in the vicinity of the proposed Project sites have been assumed as shown in Table 4.3 above. The EIAO-TM recommends that the level of the intruding noise at the façade of the nearest sensitive use should be at least 5 dB(A) below the appropriate ANL or, in the case of background noise being 5 dB(A) lower than the ANL, the predicted noise level arising from the operation of the proposed Project at the façade of the nearest sensitive use should not exceed the background noise level. In this regard, on-site background noise measurements have been carried out to determine the recommended noise criteria for each Project site.

Noise Criteria for Cumulative Noise Impact

4.17 Cumulative noise impacts arising from all items of equipment including new equipment and existing equipment would be calculated and compared against relevant ANL criteria as shown in Table 4.5.

4.18 Appendix 4.1 has summarized the prevailing noise levels at representative measurement locations. The assessment criteria for newly proposed fixed noise sources and cumulative impact, as adopted in this EIA Study, have also been presented.

Description of the Environment

Prevailing Background Noise

4.19 A noise survey was undertaken in October and November 2006 to determine the background noise levels. Prevailing background noise levels were obtained through on-site noise measurements at thirteen representative noise measurement locations near the PTWs/SCISTW/Stage 2A Disinfection Facilities. All the noise measurements were conducted in accordance with IND-TM. A summary of prevailing noise levels at representative measurement locations is shown in Appendix 4.1. A Background Noise Survey Report is presented in Appendix 4.2.

Noise Sensitive Receivers

4.20 The Study Area for noise impact assessment is defined by a distance of 300m from the boundary of the Project site. In accordance with Annex 13 of the EIAO-TM, the representative NSRs within the Study Area, including residential premises, schools, home for the aged and institutional uses, have been identified and summarized in Table 4.6 for construction noise and fixed plant noise assessments. Only the first layer of NSRs has been identified for assessment because it would provide acoustic shielding to those receivers at further distance behind. Locations of these NSRs are depicted in Figures 4.1 to 4.9. The noise assessment points have been agreed with Environmental Protection Department.

4.21 A number of relevant Outline Zoning Plans (OZPs) have been studied. These OZPs include: S/H5/24, S/H25/1, S/H3/21, S/H10/15, S/H15/24, S/H8/19 and S/SC/8. Except the planned FSD Diving Rescue and Diving Training Centre at Stonecutters Island, no other planned/committed noise sensitive developments were identified based on the relevant OZPs. Noise sensitive uses in the close vicinity of the Project sites, as shown in the relevant OZPs, have been duly represented by the existing representative NSRs.

4.22 With reference to an EIA Study for the Provision of Disinfection Facilities at Stonecutters Island Sewage Treatment Works (ADF EIA), the construction contract of the diving training centre had been commenced in December 2006 and is scheduled to be completed in August 2008. The diving training centre will be provided with VRV air-conditioning system, and it might rely on opened windows for ventilation. As such, the dormitories and a classroom of the diving training centre have been identified as representative NSR for the noise impact assessment. Figures 4.10 and 4.11 shows the layout of the dormitories and the classroom within the diving training centre, respectively.

Assessment Methodology

Construction Noise

4.23 The Project is tentatively scheduled to be commenced in February 2009 and to be completed in December 2013. According to the construction programme, there are three major construction tasks. Some individual tasks have different stages. Table 4.7 summarises the different tasks and phasing. General above-ground construction tasks are planned to be carried out during unrestricted hours.

Table 4.6 Noise Sensitive Receivers

Area	NSR ID	Description	Use	NSR for Assessment
Area	NSR ID	Description	Use	Construction	Fixed Noise
North Point PTW	N1	Madam Chan Wai Chow Memorial School	Educational	Ö	Ö
	N2	Block C, Healthy Gardens	Residential	Ö	Ö
	N3	Block A, Elegance House	Residential	Ö	Ö
	N4	Hong Cheung Court, Healthy Village	Residential	Ö	Ö
	N5	Kar Fu Building	Residential	Ö	Ö
Wan Chai East PTW	N6	Kei Wa Building	Residential	Ö	Ö
Wan Chai East PTW	N7	Elizabeth House	Residential	Ö	Ö
Fung Mat Road Site	N8	Block A, Kwan Yick Building Phase III	Residential	Ö	Ö
Fung Mat Road Site	N9	Block 1, Connaught Garden	Residential	Ö	Ö
Central PTW	N10	Chi Cheung Building	Residential	Ö	Ö
Central PTW	N11	Talon Tower	Residential	Ö	Ö
Sandy Bay PTW	N12	53 Mount Davis Road	Residential	Ö	Ö
	N13	Chuk Lam Ming Tong	Homes for the Aged	Ö	Ö
	N14	Block C-D, Scenic Villa	Residential	Ö	Ö
	N15	Block 2, La Mer	Residential	Ö	Ö
	N15a	SAGE Madam Ho Sin Hang Home for the Elderly	Home for the Aged	Ö	Ö
	N15b	Block B, The Duchess of Kent Children’s Hospital at Sandy Bay	Hospital	Ö	Ö
Cyberport PTW	N16	Point Breeze	Residential	Ö	Ö
	N17	Aegean Terrace	Residential	Ö	Ö
	N18	Block 18, Baguio Villa	Residential	Ö	Ö
Wa Fu PTW	N19	TWGH Tsui Tsin Tong School	Educational	Ö	Ö
Wa Fu PTW	N20	Wah Ming House, Wah Fu Estate	Residential	Ö	Ö
Aberdeen PTW	N21	Wah Lai House, Wah Kwai Estate	Residential	Ö	Ö
	N22	Waterfront South	Residential	Ö
	N23	Po Leung Kuk Wai Yin College	Educational	Ö
Ap Lei Chau PTW	N24	Mei Chun Court, South Horizons	Residential	Ö	Ö
Stage 2A Disinfection Facilities SCISTW	N25	Naval Base Barrack	Residential	Ö	Ö
	N26	Naval Base Barrack	Residential	Ö	Ö
	N27	Planned FSD Diving Rescue and Diving Training Centre	Institutional	Ö	Ö

Table 4.7 Summary of Construction Tasks and Stages

Item	Tasks and Stages	Construction Period	Main Construction Elements
1. North Point PTW
Barging Facilities	n/a	February 2009 – July 2009	Construction of ramp and tipping hall
Barging Facilities	n/a	August 2009 – September 2013	Barging activities
Drop Shaft	Phase I, II, III ^#	February 2009 – December 2013	Construction of upper and lower shaft; PTW upgrading; Drop shaft finishing works
Production Shaft	n/a	February 2009 – September 2013	Construction of upper / lower shaft; Tunnel construction
2. Wan Chai East PTW
Drop/Riser Shaft	n/a	February 2009 – September 2013	Construction of upper and lower shaft; Drop/riser shaft finishing works
Production Shaft	n/a	February 2009 – September 2013	Construction of upper and lower shaft; Tunnel construction
PTW Upgrading	n/a	January 2011 – December 2013	PTW upgrading works
3. Fung Mat Road Site
Barging Facilities	n/a	February 2009 – July 2009 June 2009 – November 2009	Construction of ramps and tipping halls for two sets of barging facilities
Barging Facilities	n/a	August 2009 – February 2013 December 2009 – February 2013	Barging activities at two barging facilities
Production Shaft / Drop Shaft	n/a	February 2009 – September 2013	Construction of upper and lower shaft; Tunnel construction; Conversion to drop shaft
Production Shaft / Riser Shaft	n/a	June 2009 – September 2013	Construction of upper and lower shaft; Tunnel construction; Conversion to riser shaft
4. Central PTW
Drop Shaft	Phase I, II, III ^#	February 2009 – December 2013	Construction of upper and lower shaft; PTW upgrading; Drop shaft finishing works
5. Sandy Bay PTW
Production Shaft / Drop/Riser Shaft	n/a	June 2009 – September 2013	Construction of upper and lower shaft; Tunnel construction; Conversion to drop/riser shaft
Production Shaft	n/a	June 2009 – September 2013	Construction of upper / lower shaft; Tunnel construction
PTW Upgrading	n/a	September 2010 – December 2013	PTW upgrading works
6. Cyberport PTW
Production Shaft / Drop/Riser Shaft	n/a	June 2009 – September 2013	Construction of upper and lower shaft; Tunnel construction; Conversion to drop/riser shaft
PTW Upgrading	n/a	March 2011 – December 2013	PTW upgrading works
7. Wan Fu PTW
Drop Shaft	Phase I, II, III ^#	June 2009 – December 2013	Construction of upper and lower shaft; PTW upgrading; Drop shaft finishing works
8. Aberdeen PTW
Drop Shaft	Phase I, II, III ^#	June 2009 – December 2013	Construction of upper and lower shaft; PTW upgrading; Drop shaft finishing works
Production Shaft	n/a	June 2009 – September 2013	Construction of upper / lower shaft; Tunnel construction
Tunnel Q	n/a	June 2009 – September 2013	Tunnel construction (Horizontal Directional Drilling)
9. Ap Lei Chau PTW
Drop Shaft	n/a	June 2009 – September 2013	Construction of upper and lower shaft; Drop shaft finishing works
PTW Upgrading	n/a	September 2010 – December 2013	PTW upgrading works
10. Stage 2A Disinfection Facilities
New Chlorine Contact Tank	n/a	February 2011 – March 2013	Excavation / Foundation / Civil / E&M Works
New Effluent Culvert	n/a	November 2011 – January 2013	Excavation / Civil Works
Modification of Flow Distribution Chamber, Chamber 15 and Construction of Chamber 15A	n/a	November 2011 – April 2013	Excavation / Civil Works
11. SCISTW
Riser Shaft	n/a	February 2009 – September 2013	Construction of upper and lower shaft; Remaining civil works
Production Shaft	n/a	February 2009 – September 2013	Construction of upper / lower shaft; Tunnel construction
SCISTW Upgrading	n/a	September 2010 – February 2014	Construction of main pumping station, CEPT tanks, sludge treatment facilities, effluent tunnel, odour control facility and miscellaneous works

Note: ^#Phase I – Construction of upper shaft and lower shaft

Phase II – PTW upgrading

Phase III – both PTW upgrading and drop shaft finishing works

4.24 The construction noise assessment has been carried out on a monthly basis from the commencement of the Project. The construction tasks of the Project taking place concurrently within 300m of a given NSR are considered to contribute to the cumulative impact at that NSR. Noise sources from the areas greater than this distance have been excluded from the assessment.

4.25 In accordance with the EIAO-TM, the methodology outlined in the GW-TM has been 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.

4.26 Sound Power Levels (SWLs) of the equipment were taken from Table 3 of the GW-TM. Where no SWL was supplied in the GW-TM, reference was made to BS 5228, previous similar studies or from measurements taken at other sites in Hong Kong. Schedule of powered mechanical equipment (PME) for the different construction tasks during normal daytime working hours is presented in Appendix 4.3. Appropriate on-time percentage for all items of PME was reasonably assumed as presented in Appendix 4.3. The items of PME to be operated underground were not considered in noise assessment. The Engineer has confirmed that it is practicable and feasible in the context of the construction programme.

4.27 It was assumed that all PME items required for a particular construction activity would be located at the notional or probable source position where such activities are to be performed for PTWs & SCISTW upgrading works. For shaft construction activities including drop/riser shaft, production shaft and junction shaft, the exact locations would be considered instead of the notional source point since some of the shafts are located at the edge of the site boundary. The assessment was based on the cumulative SWLs of PME likely to be used at each location.

4.28 To predict the noise level, PME was divided into groups required for each discrete construction task in Phase I works. The objective was to identify the worst case scenario representing those items of PME that would be in use concurrently at any given time.

4.29 Taking into account the works sequence, PME grouping would be implemented for excavation works in PTW upgrading works and drop shaft finishing works. Either Group 1 or Group 2 PME for excavation works and drop shaft finishing works would be operated at any one time under the construction schedule. Being the worst case scenario, the construction activities with highest SWL for PTW upgrading works and drop shaft finishing works were adopted for assessment throughout the whole corresponding construction periods.

4.30 In addition to drop shaft finishing work, the following construction tasks of PTW upgrading works at North Point, Central, Aberdeen and Wah Fu PTWs, being the worst case scenario with the highest SWL, have been adopted for cumulative noise assessment in Phase III works.

North Point PTW – excavation work for seawater pumping station

Central PTW – landscape work and roadwork

Aberdeen PTW – excavation work for seawater pumping station

Wah Fu PTW – landscape work and roadwork

4.31 In view of the limited site area of Wah Fu PTW, it is anticipated that less numbers of PMEs would be employed for Phase II construction work.

4.32 Upon commissioning of HATS Stage 2A, demolition of the existing CEPT complex at Cyberport PTW has been tentatively scheduled to be commenced in May 2014 for 6 months. The noise impact arising from such demolition work has also been included in the assessment.

4.33 Based on the latest design information, barging facilities would not be required for the Project. The barging activities near North Point and Fung Mat Road sites were assumed in this EIA for worst-case assessment only. Figure 2.9 shows the assumed locations of the barging facilities near North Point PTW and Fung Mat Road site. It is assumed in the assessment that the tipping halls for these two barging facilities would be enclosed to control the noise impact and dust nuisance, and the separation distance between the barging point and the nearest representative NSR would be approximately 160m for North Point and 240m for Fung Mat Road. The noise assessment would consider the construction noise impact of the ramps and tipping halls for barging facilities near North Point PTW and Fung Mat Road site as well as the noise impact of barging activities.

4.34 The noise levels at NSRs were then predicted by adding up the SWLs of all concurrent construction tasks, taking into account the distance attenuation. A positive 3 dB(A) façade correction was added to the predicted noise levels in order to account for the facade effect at each NSR. A 10 dB(A) reduction was applied to the noise levels at NSR N27 (i.e. planned FSD Diving Rescue and Diving Training Centre) due to the screening of line of sight by the structure of FSD Diving Training Centre itself.

4.35 The Project is scheduled to be commenced in February 2009 and to be completed in December 2013. All concurrent projects, which may have cumulative environmental impacts during its construction period, have been identified. Table 4.8 summarises the concurrent projects that would have cumulative noise impacts during the construction phase of the Project.

Table 4.8 Concurrent Projects for Construction Noise Assessment

Area	Projects	Remarks
North Point PTW	N/A	N/A
Wan Chai East PTW	- Wan Chai Development Phase II (WDII) and Central Wanchai Bypass & Island Eastern Corridor Link (CWB & IECL) - Shatin to Central Link - MTRC South Island Line Extension (East)	- The construction progamme for WDII and CWB & IECL is from 2009 to 2016. It would interface with the Project. The predicted noise impacts arising from WDII and CWB & IECL are extracted from WDII draft EIA report. - No available information - Alignment selection still under consideration (Information is not available)
Central PTW	- MTRC West Island Line Extension - Reprovisioning of Central District Headquarters and Central Divisional Police Station at Chung Kong Road, Sheung Wan	- No interface with Central PTW (the alignment and worksite are outside our study area). - The construction activities would be internal fitting-out works during the overlap period. Therefore, cumulative construction noise impact would be insignificant.
Fung Mat Road Site	- MTRC West Island Line Extension - Laying of Western Cross Harbour Main and Associated Land Mains from West Kowloon to Sai Ying Pun - Sun Yat Sen Memorial Park, Phase 2 at Waterfront of Sheung Wan	- No interface with Fung Mat Road Site (the alignment and worksite are outside our study area). - Trench dredging, pipe laying, backfilling and seawall reinstatement would interface with the Project. The predicted noise impacts arising from these works are extracted from approved EIA Report (Register No.: AEIAR-109/2007). - Construction work is scheduled to be commenced in March 2008 and completed in April 2011. It would interface with the Project. Typical SWL of the construction activities would be adopted to predict cumulative noise impact.
Sandy Bay PTW	N/A	N/A
Cyberport PTW	- MTRC South Island Line Extension (East) - Drainage Improvement in Northern Hong Kong Island - Hong Kong West Drainage Tunnel	- Alignment selection still under consideration (Information is not available). - TBM supporting activities and finalized stage works for western portal of drainage tunnel would interface with the Project. The predicted noise impacts arising from these works are extracted from approved EIA Report (Register No.: AEIAR-099/2006)
Wah Fu PTW	- MTRC South Island Line Extension (East)	- Alignment selection still under consideration (Information is not available).
Aberdeen PTW	- MTRC South Island Line Extension (East) - Route 4 (formerly known as Route 7)	- Alignment selection still under consideration (Information is not available). - No programme (Information is not available).
Ap Lei Chau PTW	N/A	N/A
SCISTW and Disinfection Facilities	- Route 8 Ngong Shuen Chau Viaduct	- Based on the latest information available (updated as at 31 August 2007) on the contract web site of Highways Department, Route 8 Ngong Shuen Chau Viaduct has bee scheduled to be completed in early 2008. There would be no interface with the Project.

4.36 Based on the currently available information, the noise impact arising from dredging works at temporary public cargo working area under WDII, CWB & IECL project was considered in cumulative noise assessment for NSRs N6 and N7 near Wan Chai East PTW throughout the overlapping period.

4.37 For Sun Yat Sen Memorial Park (Phase II) project, construction works include site clearance, excavation, reinstatement, slurry pipe wall, rock socketted H-pile, building work and landscape work. The highest SWL of 122 dB(A) associated with rock socketted H-pile would be adopted to predict the cumulative noise impact at NSRs N10 and N11 near Central PTW throughout the overlapping period.

4.38 Besides, with reference to an approved EIA Reports for Hong Kong West Drainage Tunnel and Laying of Western Cross Harbour Main and Associated Land Mains from West Kowloon to Sai Ying Pun, the following construction activities would be carried out concurrently with the construction work at Cyberport PTW and Fung Mat Road site. Construction noise impacts of these concurrent projects were considered in cumulative noise assessment for NSRs N16 to N18 and N8 to N9, respectively.

Hong Kong West Drainage Tunnel (Western Portal)

TBM Supporting Activities (June 2008 – June 2011)

Finalized Stage - General Works, Concreting, Marine Transport (April 2011 – November 2011)

Laying of Western Cross Harbour Main (Sai Ying Pun site)

Trench Dredging (February 2009 – August 2009)

Pipe laying (September 2009 – November 2009)

Backfilling (December 2009 – February 2010)

Seawall Reinstatement (February 2010 – March 2010)

4.39 The predicted noise impacts arising from the above-mentioned concurrent projects are extracted from the relevant EIA Reports. Construction tasks for the Project and other concurrent projects, within 300m of a given NSR at the same period, are considered to contribute to the cumulative impact at that NSR. Noise sources from the areas greater than this distance will be excluded from the assessment.

Operation Noise

4.40 For the assessment of noise from fixed plant, the noise level at NSR was predicted using the standard acoustic principle:

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)

4.41 Specifications and noise data for the existing noise sources within the PTWs is not available at the time of carrying out this EIA. Based on information provided by the Designer, no existing equipment at Wah Fu PTW and Ap Lei Chau PTW will be retained after PTW upgrading works. In order to assess the cumulative fixed noise impact (i.e. existing equipment + new equipment) on the nearby representative NSRs, on-site noise measurements were carried out at other six PTWs for those equipment to be retained after PTW upgrading works. As advised by DSD, the period with most of the pumps in operation would be 21:00 – 00:00 hours in general. Thus, on-site noise measurements were conducted within this time period. The sound power level (SWL) of the existing equipment was then be backward calculated with reference to the on-site measured noise levels of the existing plant operation using the following standard acoustic principle. Findings of on-site noise measurement and the corresponding SWL of the existing equipment have been presented in Appendix 4.4.

SWL = SPL + Distance Attenuation – Façade Correction (if façade measurement was undertaken)

4.42 With reference to the EIA Study for the Provision of Disinfection Facilities at Stonecutters Island Sewage Treatment Works (ADF EIA), the predicted noise level at FSD Diving Rescue and Diving Centre would be adopted to calculate the cumulative noise level at the same sensitive receiver in this EIA. A total of 2 design arrangements of deodorizing system are proposed at SCISTW, namely, Option 1 - Centralized design with foul air discharged at 4 locations and Option 2 - Decentralized design with foul air discharged at 9 locations. Option 2, in terms of the number of exhaust fans, has been adopted for the worst case noise impact assessment in this EIA.

4.43 The tentative plant inventories and the corresponding SWLs have been presented in Appendix 4.5. As confirmed by the Designer, the plant inventory used for prediction of operation noise impact is practical and realistic.

4.44 Noise impact was assessed on the basis of the following three conservative assumptions:

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

· A +3 dB(A) façade correction was added to the predicted noise levels to account for the façade effect at each NSR.

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

Identification of Environmental Impacts

Potential Noise Impacts

4.45 Major potential noise impacts arising from the Project would be:

· Construction noise

· Operation noise

Construction Noise

4.46 The potential source of noise impact during the construction phase of the Project would be the use of PME for various construction activities. The construction noise impact arising from the proposed Project is discussed in Section 4.52. The major scopes of this Project include construction of drop/riser shaft, production shaft, tunnel construction and upgrading works of PTWs/SCISTW.

4.47 The construction works of Sun Yat Sen Memorial Park (Phase II) project, Western Cross Harbour Mains project, WDII, CWB & IECL project and Hong Kong West Drainage Tunnel would contribute to the cumulative construction noise impacts at the NSRs in the close vicinity of Central PTW, Fung Mat Road site, Wan Chai East PTW and Cyberport PTW.

4.48 A sewage conveyance system (or tunnels) would be constructed by either Drill and Blast (D&B) or Tunnel Boring Machine (TBM). These options would be determined by the Engineer and specified in the tender document at the later stage. Should D&B method be adopted, all the detonation will be conducted underground within the tunnel. As blasting is under the control of the Dangerous Goods Ordinance, the contractor shall obtain a valid blasting permit from the Mines Division of CEDD before carrying out the blasting. The contractor shall enclose a method statement including manner of working and protective measures to protect adjacent land and property when blasting is carried out. It is noted that each blast would last for a few seconds. Considering the duration of blasting is very short and infrequent, TBM would be assumed as the construction method all along the tunnel alignment for the worst case noise assessment.

4.49 Airborne noise impacts arising from operation of PME during the construction of drop/riser shafts, production shafts, tunnels construction and PTW/SCISTW upgrading works would be assessed in the following sections, while groundborne noise induced by the tunneling and shafting activities would be assessed in Section 5 of this EIA Report.

Operation Noise

4.50 The potential source of noise impact during the operation phase of the PTWs, SCISTW and disinfection facilities would be the use of ventilation fans and various pumpsets. The operation noise impacts arising from the proposed Project are discussed in Sections 4.53 to 4.55.

4.51 As part of Stage 2A disinfection facilities, a new chamber no. 15A will be located adjacent to the existing drop shaft and chamber no. 15 on the Stonecutters Island. Based on information provided by the Designer, equipment likely to be installed in the chambers would be percolated pipe, sensors and CCTV which are not considered as noisy equipment. Noise impact from the drop shaft and the chambers would be negligible and therefore cumulative noise impact from the shaft and chambers was not further assessed.

Prediction and Evaluation of Environmental Impacts

Construction Noise

4.52 For normal daytime working hours, exceedences of the construction noise criteria (L_{eq
(30 minutes)} 75 dB(A) for residential uses and 70 dB(A) for educational institutions (65 dB(A) during examinations)) would be predicted at representative NSRs in the absence of mitigation measures. Details of construction noise calculations and results are presented in Appendix 4.6. Results show that the predicted noise levels related to the Project and other concurrent projects are in the range of 56 to 89 dB(A). A summary of the unmitigated construction noise levels of the representative NSRs during normal daytime working hours within the construction period of the Project is shown in Table 4.9. Noise mitigation measures would therefore be required to reduce noise levels to the stipulated noise standards.

Table 4.9 Summary of Unmitigated Construction Noise Levels at Representative NSRs During Normal Daytime Working Hours

Representative NSRs	Predicted Unmitigated Construction Noise Levels during Normal Daytime Working Hour (L_eq (30-min) dB(A))
N1#	68 - 78
N2	67 - 85
N3	65 - 80
N4	63 - 77
N5	71 - 78
N6	71 - 76
N7	72 - 77
N8	71 - 76
N9	70 - 75
N10	67 - 77
N11	67 - 76
N12	64 - 75
N13	67 - 87
N14	62 - 78
N15	59 - 73
N15a	69 - 87
N15b	72 - 85
N16	66 - 74
N17	69 - 78
N18	61 - 73
N19#	71 - 77
N20	81 - 89
N21	61 - 74
N22	58 - 69
N23#	57 - 68
N24	62 - 74
N25	60 - 85
N26	63 - 84
N27	56 - 71

Note: # For normal daytime working hours, the noise criteria are 70 dB(A) and 65 dB(A) for normal teaching periods and examination periods, respectively.

Operation Noise

4.53 The tentative plant inventory and the corresponding SWL are summarised in Appendix 4.5. 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. For conservative assessment, the noise impact has been assessed against a more stringent night-time noise criteria.

4.54 Based on the information provided by the Designer, most of the newly proposed equipment would be housed/enclosed in a concrete structure. With reference to “Good Practices on Pumping System Noise Control” and “Good Practices on Ventilation System Noise Control” published by Environmental Protection Department, facilities that would be enclosed in a concrete structure were assumed to have a 20 dB(A) reduction of noise emitted from the source due to transmission loss of the wall. Besides, the grit trap’s equipment would be partially enclosed to avoid line of sight between the noise source and the receiver, and a noise reduction of 20 dB(A) was assumed in accordance with the aforesaid booklets. For the proposed Stage 2A SCISTW, items of equipment would be screened from the line-of-sight of NSR by the structure of planned FSD diving training centre itself. This allowed a 10 dB(A) reduction in accordance with the relevant Technical Memorandum. Due to the facade effect, a positive 3 dB(A) has been added to predict noise levels at the NSRs. For determining the distance correction factors, the distances between the probable source positions and the NSRs were considered.

4.55 According to the plant inventory for the proposed Project, the predicted noise levels at representative NSRs in the close vicinity of PTWs, SCISTW and disinfection facilities are presented in Table 4.10. For newly proposed equipment, the predicted noise levels at all representative NSRs except N12, N13, N14, N15a, N15b, N16, N17 and N20 would comply with the night-time planning noise criteria. The noise levels at these affected NSRs would exceed the planning noise criterion by 1 to 13 dB(A). For cumulative noise impact, the predicted noise levels at all representative NSRs except N13, N15a and N15b would comply with the night-time ANL. The cumulative noise level at N13, N15a and N15b would exceed the night-time ANL of 50 dB(A) by up to 8 dB(A). As a result, further specific noise mitigation measures would be required for Sandy Bay PTW, Cyberport PTW and Wah Fu PTW. Details of the fixed plant noise calculations under unmitigated scenario are presented in Appendix 4.7

Table 4.10 Predicted Fixed Plant Noise Levels at Representative Noise Sensitive Receivers (Unmitigated Scenario)

Area	NSR ID	Newly Proposed Equipment		Cumulative Impact (Existing Equipment + New Equipment)
Area	NSR ID	Noise Criterion ^*	Predicted Noise Level	Noise Criterion ^*	Predicted Noise Level
North Point PTW	N1	50	45	55	47
	N2	50	48	55	52
	N3	50	45	55	49
	N4	50	41	55	44
	N5	50	42	55	44
Wan Chai East PTW	N6	55	45	60	56
Wan Chai East PTW	N7	55	46	60	56
Fung Mat Road Site	N8	55	37	60	37
Fung Mat Road Site	N9	55	36	60	36
Central PTW	N10	55	43	60	53
Central PTW	N11	55	43	60	54
Sandy Bay PTW	N12	45	47	50	47
	N13	45	54	50	55
	N14	45	47	50	48
	N15	45	43	50	44
	N15a	45	57	50	57
	N15b	45	58	50	58
Cyberport PTW	N16	43	44	55	51
	N17	43	48	55	54
	N18	43	43	55	47
Wa Fu PTW	N19	50	43	55	43
Wa Fu PTW	N20	50	53	55	53
Aberdeen PTW	N21	50	40	55	49
Ap Lei Chau PTW	N24	50	45	55	45
Stage 2A Disinfection Facilities	N25	55	32	60	32
Stage 2A Disinfection Facilities	N26	55	35	60	35
SCISTW	N27	55	30	60	48

Note: * A more stringent night-time noise criterion has been adopted for conservative assessment.

Mitigation of Environmental Impacts

Construction Noise

4.56 In order to reduce the excessive noise impacts at the affected NSRs during normal daytime working hours, mitigation measures such as adopting quiet powered mechanical equipment, movable noise barriers and acoustic mats are recommended (see Appendix 4.8). The above mitigation measures have been confirmed by the Engineer as being practicable in completing the works within scheduled timeframe. The Contractor may be able to obtain particular models of plant that are quieter than the PMEs given in GW-TM. It is considered too restrictive to specify that a Contractor has to use specific items of plant for the construction operations. It is practical to specify the total SWL of all plant to be used on site so that the Contractor is allowed some flexibility to select plant to suit his needs.

4.57 In this assessment, the recommended quiet PME are taken from the BS 5228: Part 1: 1997, and the PME are known to be available in Hong Kong. The noise mitigation measures adopted for the two concurrent projects are in accordance with draft EIA Report for WDII, CWB & IECL and approved EIA Report for Hong Kong West Drainage Tunnel.

4.58 For the following construction tasks of the Project, it is considered necessary to adopt quiet PME:

Drop/Riser Shaft

· Construction of upper shaft, Diaphragm wall at shaft

· Construction of upper shaft, Excavation at shaft

· Construction of lower shaft

· Drop shaft finishing works

Production Shaft

· Construction of upper shaft, Diaphragm wall at shaft

· Construction of upper shaft, Excavation at shaft

· Construction of lower shaft

· Tunnel construction

PTW Upgrading Works

· Piling (socket H-piles)

· Excavation (shallow excavation with sheet piling)

· Concreting

· Demolition Works

· Roadwork

SCISTW Upgrading Works

· Site clearance and setup site office

· Shallow excavation

· Drill and blast excavation

· Deep excavation

· Civil works

· Pipeworks

· Demolition works

4.59 To alleviate the construction noise impact on the affected NSRs, movable noise barriers and acoustic mats are proposed to be provided for particular items of plant and construction works. With a surface mass of not less than 2.5 kg/m², it is anticipated that the acoustic mats can provide 5 dB(A) noise reduction. Besides, it is anticipated that a movable noise barrier with a cantilevered upper portion located within 5m from any static or mobile plant can provide 5 dB(A) noise reduction for mobile plant and 10 dB(A) noise reduction for static plant. The barrier material shall have a surface mass of not less than 14 kg/m² on skid footing with 25mm thick internal sound absorptive lining to achieve the maximum screening effect. Figure 4.12 shows a typical section of movable noise barrier.

4.60 For the following construction tasks of the Project, it is considered necessary to adopt movable noise barrier:

Drop/Riser Shaft

· Construction of upper shaft, Diaphragm wall at shaft

· Construction of upper shaft, Excavation at shaft

· Construction of lower shaft

· Drop shaft finishing works

Production Shaft

· Construction of upper shaft, Diaphragm wall at shaft

· Construction of upper shaft, Excavation at shaft

· Construction of lower shaft

· Tunnel construction

PTW Upgrading Works

· Piling (socket H-piles)

· Concreting

SCISTW Upgrading Works

· Site clearance and setup site office

· Shallow excavation

· Drill and blast excavation

· Deep excavation

· Civil works

· Pipeworks

· Demolition works

4.61 Besides, use of acoustic mats is recommended for the following construction tasks of the Project. Figure 4.13 illustrates the practical way of using acoustic mat for bored piling chisel during the construction of upper shaft.

Drop/Riser Shaft

· Construction of upper shaft, Diaphragm wall at shaft

Production Shaft

· Construction of upper shaft, Diaphragm wall at shaft

· Construction of upper shaft, install pipe pile wall

PTW Upgrading Works

· Piling (socket H-piles)

· Excavation (shallow excavation with sheet piling)

SCISTW Upgrading Works

· Deep excavation with diaphragm wall

4.62 As shown in Appendix 4.9, with the use of quiet equipment, movable noise barriers and acoustic mats, the overall noise levels at NSRs would be reduced by up to 14 dB(A), depending on the type of construction activities. The predicted mitigated construction noise levels at representative NSRs would range from 47 to 75 dB(A). With the exception of NSRs N1 during examination periods, the predicted construction noise levels arising from the Project at all representative NSRs would comply with the EIAO-TM construction noise criteria. Assessing against the noise standard of 65 dB(A) during examination periods, the predicted noise level at NSR N1 (i.e. Madam Chan Wai Chow Memorial School) would exceed the noise standard by up to 5 dB(A). A summary of mitigated noise levels during normal daytime working hours at representative NSRs is presented in Table 4.11.

Table 4.11 Summary of Mitigated Construction Noise Levels at Representative NSRs during Normal Daytime Working Hours

Representative NSRs	Predicted Mitigated Construction Noise Levels during Normal Daytime Working Hour (L_eq (30-min) dB(A))
N1#	65 - 70
N2	66 - 74
N3	64 - 70
N4	63 - 68
N5	63 - 73
N6	67 - 68
N7	61 - 68
N8	62 - 73
N9	61 - 73
N10	58 - 73
N11	60 - 70
N12	59 - 67
N13	63 - 74
N14	57 - 65
N15	54 - 62
N15a	64 - 74
N15b	67 - 75
N16	58 - 68
N17	62 - 71
N18	57 - 63
N19#	62 - 65
N20	73 - 75
N21	56 - 64
N22	53 - 61
N23#	52 - 61
N24	57 - 61
N25	48 - 71
N26	51 - 71
N27	47 - 62

Note: # For normal daytime working hours, the noise criteria are 70 dB(A) and 65 dB(A) for normal teaching periods and examination periods, respectively.

Operation Noise

4.63 As mentioned in Section 4.55, the predicted noise levels at NSRs N12, N13, N14, N15a, N15b, N16, N17 and 20 would exceed the night-time planning noise criteria by 1 to 13 dB(A) due to the newly proposed equipment at Sandy Bay PTW, Cyberport PTW and Wah Fu PTW, while the cumulative noise level at N13, N15a and N15b would exceed the night-time ANL of 50 dB(A) by up to 8 dB(A). Air supply fans/extraction fans of transfer pumping stations and ventilation fans for deodourization unit would be the dominant noise sources causing noise exceedance at these affected NSRs. In this regard, acoustic louvers have been proposed for these fans to mitigate the noise impact. With reference to EIA Report for Siu Ho Wan Water Treatment Works Extension, a noise reduction of 20 dB(A) would be achieved with acoustic louvers. As shown in Table 4.12, Except N15a due to the newly proposed equipment at Sandy Bay PTW, the predicted noise levels at these affected NSRs would comply with both the night-time ANL and night-time planning noise criteria with acoustic louvers in place. Details of noise calculations under mitigated scenario are presented in Appendix 4.10

Table 4.12 Predicted Fixed Plant Noise Levels at Representative Noise Sensitive Receivers (Mitigated Scenario)

Area	NSR ID	Newly Proposed Equipment		Cumulative Impact (Existing Equipment + New Equipment)
Area	NSR ID	Noise Criterion ^*	Predicted Noise Level	Noise Criterion ^*	Predicted Noise Level
Sandy Bay PTW	N12	45	35	50	39
	N13	45	42	50	49
	N14	45	35	50	42
	N15	45	31	50	37
	N15a	45	46	50	50
	N15b	45	45	50	49
Cyberport PTW	N16	43	33	55	49
	N17	43	37	55	53
	N18	43	31	55	45
Wa Fu PTW	N19	50	34	55	34
Wa Fu PTW	N20	50	44	55	44

Note: * A more stringent night-time noise criterion has been adopted for conservative assessment

4.64 To further mitigate the noise impact at N15a due to the newly proposed equipment at Sandy Bay PTW, it is recommended that the maximum allowable sound power level (SWL) of each new transformer at Sandy Bay PTW shall be limited to 89 dB(A) during the detailed design stage. With the control of SWL of the transformer, the predicted noise level at N15a would be 45 dB(A) which comply with the relevant night-time planning noise criterion.

Evaluation of Residual Impacts

Construction Noise

4.65 With the implementation of the above-mentioned mitigation measures, the construction noise levels at all representative NSRs except N1 are predicted to comply with the noise standards stipulated in the EIAO-TM. Residual impacts at NSR N1 are summarised in Table 4.13.

4.66 The on-site survey has revealed that NSR N1 (i.e. Madam Chan Wai Chow Memorial School) has already been noise insulated with air-conditioners, therefore no adverse noise impact would be expected at the indoor environment. Notwithstanding this, it is recommended that the particularly noisy construction activities should be scheduled to be undertaken during the summer vacation period as far as practicable.

Table 4.13 Construction Noise Residual Impacts

NSR	Exceedance of the EIAO-TM Noise Criterion ^*	Construction Activity Causing Exceedance	Approximate duration of Exceedance ^#
N1	5 dB(A) 5 dB(A) 4 - 5 dB(A) 4 dB(A) 4 dB(A) 4 dB(A) 4 dB(A) 5 dB(A) 5 dB(A)	Diaphragm wall (drop shaft and production shaft), lower shaft, Phase III works and baraging activities	4 months(March – June 2009) 1 month (December 2009) 4 months (March - June 2010) 1 month (December 2010) 4 months (March - June 2011) 1 month (December 2011) 4 months (March - June 2012) 1 month (December 2012) 4 months (March – June 2013)

NSR

Exceedance of the EIAO-TM Noise Criterion ^*

Construction Activity Causing Exceedance

Approximate duration of Exceedance ^#

5 dB(A)

4 - 5 dB(A)

4 dB(A)

5 dB(A)

Diaphragm wall (drop shaft and production shaft), lower shaft, Phase III works and baraging activities

4 months(March – June 2009)

1 month (December 2009)

4 months (March - June 2010)

1 month (December 2010)

4 months (March - June 2011)

1 month (December 2011)

4 months (March - June 2012)

1 month (December 2012)

4 months (March – June 2013)

Notes:

* Against the noise EIAO-TM noise criterion of 65 dB(A) for examination periods.

# Public examination is assumed to be held in March, April and May, while school examination is assumed to be held in December and June of each year.

4.67 In addition to the above-mentioned mitigation measures, the good site practices listed below shall be adopted by all the Contractors to further ameliorate the noise impacts. Although the noise mitigating effects are not easily quantifiable and the benefits may vary with the site conditions and operating conditions, good site practices are easy to implement and do not impact upon the works schedule.

· 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 utilised 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 works periods or shall be 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.

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

Operation Noise

4.68 Based on the information provided by the Designer, most of the newly proposed equipment would be housed/enclosed in a concrete structure. In addition, acoustic louvers have been proposed for air supply fans/extraction fans of transfer pumping stations and ventilation fans of deodourization unit at Sandy Bay PTW, Cyberport PTW and Wah Fu PTW. It is recommended that the maximum allowable sound power level (SWL) of each new transformer at Sandy Bay PTW shall be limited to 89 dB(A) during the detailed design stage. With such proper designs, no adverse residual operation noise impact arising from the Project is expected.

Construction Activities during Restricted Hours

4.69 The construction programme for the Project takes into account the likelihood that the contractor will, if permitted, undertake the construction works within the tunnel and bottom of shaft over a 24-hour working day. The tunnels would be constructed by either D&B or TBM. For TBM method, no noisy PME except ventilation fans would be operated above ground during restricted hours (1900 to 0700 hours) according to information provided by the Engineer. The tunnel spoil would be conveyed to the ground surface for collection and disposal of during non-restricted hours (0700 – 1900 hours).

4.70 For D&B method, there would be two times of blasting per day (i.e. one in daytime and one in night-time) for the tunnel construction. During restricted hours, in addition to the ventilation fans, only a gantry crane will be operated on ground to lift up the spoil to the shaft top and dump at the stockpile area adjacent to the production shaft. The spoil will then be disposed of off site during non-restricted hours.

4.71 For the purpose of this indicative assessment, D&B method would be adopted for the worst case noise assessment taking into account the items of PME to be involved. At each production shaft, the items of PME to be operated on ground for tunnel construction using D&B method during restricted hours are presented in Table 4.14. Appropriate on-time percentage for the items of PME was reasonably assumed. According to information provided by the Engineer, four ventilation fans with volume flow rate of 10,800 m³/hour each would be required for each production shaft at North Point, Wan Chai East, Fung Mat Road, Sandy Bay, Cyberport, Aberdeen and SCISTW. According to “Good Practices on Ventilation System Noise Control” published by EPD, the SWL of 85 dB(A) for each ventilation fan would be adopted for noise assessment during restricted hours. Besides, with reference to EIA Report for KCRC Kowloon Southern Link, the SWL of 95 dB(A) for gantry crane has been adopted.

Table 4.14 Powered Mechanical Equipment (PME) for Tunnel Construction During Restricted Hours (Without Mitigation Measures)

Powered Mechanical Equipment	No. of Items	SWL/Item dB(A)	Total SWL dB(A)
Gantry crane	1	95	95
Ventilation fan	4	85	91

Powered Mechanical Equipment

No. of Items

SWL/Item

dB(A)

Total SWL

dB(A)

Gantry crane

Ventilation fan

4.72 The noise impact has been assessed against a more stringent night-time noise criteria. The assessment results are presented in Appendix 4.11. A summary of unmitigated noise levels at these representative NSRs is presented in Table 4.15.

Table 4.15 Summary of Unmitigated Construction Noise Levels at Representative NSRs During Restricted Hours

Representative NSRs	Noise Criterion ^*	Predicted Unmitigated Construction Noise Levels (L_eq (30-min) dB(A))
N1	50	47
N2	50	44
N3	50	42
N4	50	40
N5	50	50
N6	55	44
N7	55	43
N8	55	46 - 49
N9	55	45 - 48
N12	45	46 - 49
N13	45	49 - 53
N14	45	44 - 48
N15	45	41 - 44
N16	50	43
N17	50	48
N18	50	42
N21	50	41
N22	50	40
N23	50	40
N27	55	41

Note: * A more stringent night-time noise criterion has been adopted for conservative assessment

4.73 As shown in Table 4.15, with the exception of representative NSRs near Sandy Bay PTW (i.e. N12 to N14), the predicted construction noise levels at other representative NSRs during restricted hours would comply with the corresponding noise limits.

4.74 To mitigate the noise impact at NSRs N12 to N14, ventilation fans and motors of gantry at the production shafts of Sandy Bay PTW shall be properly housed. Silencers shall also been installed at outlet and inlet of the enclosure for ventilation fans. A 10 dB(A) noise screening reduction for both the motors of gantry and ventilation fans was assumed in the assessment. Predicted noise levels after mitigation at representative NSRs are shown in Appendix 4.12. A summary of mitigated noise levels at representative NSRs is presented in Table 4.16.

Table 4.16 Summary of Mitigated Construction Noise Levels at Representative NSRs During Restricted Hours

Representative NSRs	Noise Criterion ^*	Predicted Unmitigated Construction Noise Levels (L_eq (30-min) dB(A))
N12	45	36 - 39
N13	45	39 - 43
N14	45	34 - 38

Note: * A more stringent night-time noise criterion has been adopted for conservative assessment

4.75 With the adoption of the recommended mitigation measures, the predicted noise levels at NSRs N12 to N14 would comply with the construction noise criterion of 45 dB(A) during restricted hours. In applying for a Construction Noise Permit, the Applicant (that is, the Contractor) shall be required to demonstrate to the satisfaction of the Noise Control Authority the noise reduction effect of mitigation measures to be adopted. Otherwise, values in the GW-TM will be used in assessing the application.

4.76 The above assessment only demonstrates that the construction works in restricted hours would be feasible in the context of programming construction work. If the Contractor considers that there is a need to carry out construction works during restricted hours, a Construction Noise Permit shall be obtained from the Noise Control Authority prior to commencement of such works. There are some factors affecting the assessment results of a CNP application, such as the assigning of Area Sensitivity Rating, Acceptable Noise Levels etc. The Noise Control Authority would decide these at the time of assessment of such application based on the contemporary situations / conditions. It should be noted that the situations / conditions around the sites may change from time to time. The Authority may make correction for multiple permit situations if in the opinion of the Authority the NSR will be materially affected by noise from construction work associated with more than one CNP, and the Authority may make such correction to the relevant noise level as it considers appropriate having regard to standard acoustical principles and practices. The Area Sensitivity Ratings assumed in this EIA Report are for indicative assessment only.

Environmental Monitoring and Audit

4.77 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.

4.78 The EIA findings confirmed that proper designs of PTWs, SCISTW and disinfection facilities would control the potential noise impact at noise sensitive receivers within acceptable levels, operational noise monitoring is not considered necessary.

Conclusions

Construction Noise

4.79 This assessment has predicted the construction noise impacts of the Project during normal daytime working hours, taking into account other concurrent projects including Sun Yat Sen Memorial Park (Phase II) project, Western Cross Harbour Main project, the WDII, CWB & IECL project and Hong Kong West Drainage Tunnel. The predicted unmitigated noise levels would range from 56 to 89 dB(A) at the representative NSRs. With the use of quiet PME, movable barriers and acoustic mats for construction tasks under the Project, the noise levels at all representative NSRs except N1 during the examination periods would comply with the construction noise standards.

4.80 Assessing against the noise standard of 65 dB(A) during examination periods, the predicted noise level at NSR N1 (i.e. Madam Chan Wai Chow Memorial School) would exceed the noise standard by up to 5 dB(A). The on-site survey has revealed that NSR N1 has already been noise insulated with air-conditioners, therefore no adverse noise impact would be expected at the indoor environment. Notwithstanding this, it is recommended that the particularly noisy construction activities should be scheduled to be undertaken during the summer vacation period as far as practicable.

4.81 An indicative assessment has been undertaken for possible construction activities within the tunnel and bottom of shaft during restricted hours. Based on information provided by the Engineer, no major items of PME except ventilation fans and gantry crane would be operated above ground during restricted hours (1900 to 0700 hours). The assessment results show that the predicted construction noise levels at representative NSRs during restricted hours would comply with the corresponding noise limits, provided that the ventilation fans and motors of gantry at the production shafts of Sandy Bay PTW would be properly housed and the silencers would be installed at outlet and inlet of the enclosure for ventilation fans. It should be noted that the results of the construction noise impact assessment for restricted hours are for indicative purposes, the Noise Control Authority will process any CNP application based on the NCO and the relevant technical memoranda in addition to considering the contemporary situations / conditions.

4.82 A construction noise EM&A programme is recommended to check the compliance of the noise criteria during normal daytime working hours.

Operation Noise

4.83 The noise impact associated with the operation of the Project was assessed. For newly proposed equipment, the predicted noise levels at all representative NSRs except N12, N13, N14, N15a, N15b, N16, N17 and N20 would comply with the night-time planning noise criteria. The noise levels at these affected NSRs would exceed the planning noise criterion by 1 to 13 dB(A). For cumulative noise impact, the predicted noise levels at all representative NSRs except N13, N15a and N15b would comply with the night-time ANL. The cumulative noise level at N13, N15a and N15b would exceed the night-time ANL of 50 dB(A) by up to 8 dB(A).

4.84 To mitigate the noise impact at the affected NSRs, acoustic louvers have been proposed for air supply fans/extraction fans of transfer pumping stations and ventilation fans of deodourization unit at Sandy Bay PTW, Cyberport PTW and Wah Fu PTW. Besides, it is recommended that the maximum allowable sound power level (SWL) of each new transformer at Sandy Bay PTW shall be limited to 89 dB(A) during the detailed design stage. With such proper designs, the predicted noise levels at all representative NSRs would comply with both the night-time ANL and night-time planning noise criteria. No residual operation noise impact arising from the Project is anticipated.

4.85 Proper designs of PTWs, SCISTW and disinfection facilities would control the potential noise impact at noise sensitive receivers within acceptable levels, operational noise monitoring is not considered necessary.