1

7. NOISE IMPACT ASSESSMENT

7.1 Introduction

7.1.1 This chapter presents the potential noise impacts associated with the construction and operation of the Spur Line. Cumulative impacts with other concurrent projects are also addressed. Mitigation monitoring and audit requirements are described.

7.1.2 The railway operation noise assessment is based on the train speed profile and alignment information supplied by KCRC. Construction noise assessment is based on the equipment schedule and construction programme proposed by KCRC’s contractors.

7.1.3 The scope of this noise impact assessment follows the requirements under Section 3.8 of the EIA Brief issued on 15 October 2001.

7.2 Construction Noise Assessment

Introduction

7.2.1 This section presents the methodology, representative sensitive receivers, relevant assessment criteria, and up-to-date findings on the potential construction noise impact due to the development of the Spur Line.

7.2.2 Currently there are only three major public works projects scheduled near the Sheung Shui to Lok Ma Chau Spur Line. The projects are the Main Drainage Channel Realignment Works at River Beas, the San Tin Eastern Main Drainage Channel at Lok Ma Chau and the expansion works at Lok Ma Chau Boundary Crossing. The former is almost completed and the second will start in 2002. Based on the latest construction programme of Lok Ma Chau Boundary Crossing, the expansion works will be completed in 2003. It is expected that the main construction period for the viaduct section of the Spur Line will begin in 2003 and will coincide with the final stages of Lok Ma Chau Boundary Crossing construction. Consequently, the cumulative noise impact arising from Lok Ma Chau Boundary Crossing is expected to be very minor as far as the Spur Line Project is concerned. Concurrent noise impacts are possible with the San Tin Eastern Main Drainage Channel works, but these projects are both distant from the nearest sensitive receivers at this location.

7.2.3 The Sheung Shui to Lok Ma Chau Spur Line will be constructed between 2002 and 2007 and is unlikely to cause any cumulative construction noise impact with these projects.

Noise Assessment Criteria

7.2.4 Under Technical Memorandum (TM) on Environmental Impact Assessment Process, the day-time noise criterion for residential premises is 75 dB(A). The criterion for educational establishment is 70 dB(A) on normal days and 65 dB(A) during examination periods.

7.2.5 Should works be required during restricted hours, i.e. 1900 to 0700 hours or at any time on a general holiday, a Construction Noise Permit (CNP) must be obtained before works are allowed to take place. Percussive piling works are also subject to licensing under the Noise Control Ordinance (NCO).

7.2.6 A complete set of environmental legislation and standards related to construction noise is given in Appendix A.

Representative Noise Sensitive Receivers

7.2.7 A site survey and desk study of government survey maps were conducted to determine the locations of existing noise sensitive receivers, which include residential properties, hotels, schools, clinics, places of worship and other uses requiring verbal communication, concert halls or amphitheaters within 300m of either side of the proposed railway alignment. Representative Noise Sensitive Receivers (RNSRs) were selected to represent receivers of similar noise impacts, based on consideration of their respective distances from construction activities. Where there are a number of residences in the vicinity of the works areas, the most representative of these are chosen as the RNSRs.

7.2.8 The tunnel portals will be constructed using the cut and cover method while the tunnel will be constructed using an earth pressure balance boring machine. For assessment of construction noise, RNSRs are selected near the tunnel portals and ventilation shaft where Powered Mechanical Equipment (PME) will be used for construction. RNSRs are not selected along tunnel sections where PME is used underground. Ventilation fans and exhausts for supporting tunnel boring operation have been taken into account in the construction equipment schedule.

7.2.9 Figure 7.1 presents the locations of the selected RNSRs. Table 7.1 gives the details of each of these RNSRs and the type of noise sensitive land use they represent. The mPD levels of RNSRs which appeared in the previous EIA [1] are retained but all the RNSRs have been re-numbered in sequence from the Sheung Shui end through to the Lok Ma Chau end of the alignment for the current assessment.

Table 7.1

Details of Representative Noise Sensitive Receivers

RNSR	mPD at Ground Level	Description of Existing Use	No. of Storeys of Existing Use
1	+7.6	Low rise commercial / residential building at San Fung Avenue	3***
2	+9.2	Choi Pik House, Choi Po Court	36
3	+9.2	Choi Ying House, Choi Po Court	36
4	+5.9	Village House	3
5	+4.8	Village House	3
6	+9.8	Village House	2
7	+7.9	Village House	1
8	+10.1	Village House	1
9	+10.7	Kindergarten	1
10	+8.5	Village House	2
11	+12.6	School	2
12	+17.5	Old People’s Home	2
13	+19.1	Village House	3
14	+13.3	Village House	3
15	+15.7	Village House	2
16	+24.0	Village House	2
17	+9.0	Village House	2
18	+6.4	Village House	1
19	+6.4	Village House	2
20	+5.3	Village House	1
21	+3.5	Village House	3
22	+5.3	Village House	1
23	+4.5	Village House	1
24	+9.1	Village House	1
25	+7.2	Village House	1
26	+3.4	Village House	1
27	+3.2	Village House	2
28	+3.2	Village House	2
29	+2.9	Village House	1

*** 3 storeys dwelling on top of 3 commercial storeys

Construction Noise Assessment Scenarios

7.2.10 The construction work of the Sheung Shui to Lok Ma Chau Spur Line is divided into three contracts. Contract LDB201 includes all the works from Sheung Shui to the start of the viaduct at Chau Tau. Contract LCC202 includes all the viaduct works. Contract LCC300 includes all the works for the construction of the Lok Ma Chau Terminus and the widening of the Emergency Vehicle Access Road (EVA) at Lok Ma Chau.

7.2.11 The construction programme and preliminary construction equipment schedule was obtained from the KCRC East Rail Extensions (ERE) for Contract LDB 201. Construction programmes for Contracts LCC202 and LCC300 are being prepared by ERE and therefore unavailable. A preliminary construction equipment schedule for viaduct construction works and EVA widening works was suggested by the detailed design team and agreed with ERE. These are the current best estimates of the quantity of equipment to be used. The bored piling machine used for viaduct construction is assumed to have a sound power level of 115 dB (CNP 165, Technical Memorandum on Noise from Construction Works other than Percussive Piling). The construction works for the terminus and footbridge link to Huanggang are located well over 500 m from any noise sensitive receivers and are unlikely to cause any potential construction noise impact on their own or as part of any cumulative impact.

7.2.12 Appendix A7.1a presents the worst case construction noise assessment scenarios, with their respective duration, total sound power levels, affected RNSRs and their locations. The restricted hours work is outside the current scope of assessment and therefore not included in Appendix A 7.1a. (Refer to Sections 7.2.18 to 7.2.23 for further details).

7.2.13 For Contract LDB 201, the sound power levels of concurrent construction activities at various parts of the Spur Line alignment were calculated during different periods of the construction phase, based on the construction programme and preliminary construction equipment schedule. The various parts of the Spur Line thus considered are:

• East End - includes all works at the launching shaft, on the works area near the launching shaft, the eastern tunnel portal works, all the open cut and cut and cover works between the portal and Sheung Shui Station. East Emergency Access Point (EAP) - all works on the East EAP works area and East EAP shaft.

• Kwu Tung Station - Kwu Tung Station Box, works on the temporary works area.

• West EAP - all works on the West EAP works area and West EAP shaft.

• West End - includes all works at the exit shaft, on the works area near the west tunnel approach, the west tunnel portal works, all the open cut and cut and cover works between the western tunnel portal and the start of the viaduct at chainage 35+420.

The civil works for relocating the tracks of the existing East Rail to and back from their interim period position during construction phase will be carried out during restricted hours for intermittent evenings only. It will be under the control of CNP conditions and is outside the scope of the current assessment. The powered mechanical equipment (PME) required for moving the tracks is similar to those used in regular East Rail maintenance programme carried out during restricted hours, which are also under control of Construction Noise Permits (CNP) conditions. Requirements for CNP are therefore unlikely to pose insurmountable constraint to construction programme. Nevertheless, the Contractors are advised to note Sections 7.18 to 7.28 concerning CNP requirements. The relocation of existing East Rail tracks before and after the construction works of the Spur Line is an essential part of the construction sequence, which ensures the East Rail’s operational safety during and after Spur Line’s construction.

7.2.14 These areas of works are well separated by over 300m distance from one another and the potential construction noise from these areas are unlikely to constitute cumulative impacts. No construction works will be carried out in the immediate vicinity of the Sheung Shui Station.

7.2.15 Several cross passages will also be built between the twin tunnels but a review of their sound power levels of the construction equipment to be used show that these are too low to contribute to any cumulative impacts. The cross passage works are not included in the worst case scenarios. The worst case scenario concurrent activities, equipment schedule and the sound power levels of each relevant activity are presented in Appendix A7.1b.

7.2.16 The Engineering Design Team have confirmed that the equipment to be used for the construction of the TBM launching shaft will also be used to construct the cut and cover Phase 1 works. The conveyor shaft is no longer required when the launching shaft is located at the east end. At the west end, the equipment used for the construction of the west approach cut and cover works will also be used in the works for west ventilation building, with the exception of the superstructure works. These combinations of equipment usage have been reflected accordingly in Appendices A7.1b and A7.1 c.

7.2.17 The worst case scenario concurrent activities, equipment schedule and the sound power levels of each relevant activity selected for LCC202 and LCC300 are also presented in Appendix A7.1b. From discussions held with ERE and the detailed design consultants for LCC202 and LCC300, the numbers of equipment stated are those most likely to operate at the shortest distance from the relevant worst affected RNSRs at any given time during the construction phase. The relevant worst affected RNSRs are 27 for viaduct construction, and RNSRs 24 to 25 for EVA widening works.

7.2.18 The construction programme and preliminary equipment schedule for LDB 201 is presented in Appendix A7.1c for reference.

Construction Works During Restricted Hours

General

7.2.19 The following are the only construction activities which will be carried out during restricted hours:

- Use of PME above and below ground to support tunnel boring operation.

- East Rail diversion.

7.2.20 No movement of spoil off-site will be carried out during restricted hours. Spoil arising from the tunneling activities will be moved to settling tanks for overnight stock piling using conveyor system. Additional screening/covering of conveyor system can be provided if necessary.

7.2.21 Construction works within restricted hours will be under the control of the statutory conditions of the CNP. The assessment of these works is outside the current scope of the EIA Brief. The successful tenderers will shoulder the cost and responsibility of meeting the requirements from the Noise Control Ordinance as well as the scheduled programme for completing the Project on time. They will also be responsible for applying for the necessary CNPs and demonstrating the predicted noise impacts for their proposed construction activities during the restricted hours and the effectiveness of the proposed mitigation measures, if any.

7.2.22 Despite the description or assessment made in the subsequent sections, EPD will be guided by the relevant Technical Memorandum (Memoranda) in assessing an application once filed, for a CNP. All factors affecting the decision will be considered including contemporary situation / condition. Nothing in this report shall bind EPD in making its decision. If a permit is to be issued, EPD will include any conditions considered appropriate and such conditions are to be followed while the works covered by the permit are being carried out. Failure to comply with the conditions stipulated will lead to cancellation of the permit and prosecution action under the NCO.

Tunnelling Work at TBM Launching Shaft Site

7.2.23 Based on the construction programme, restricted hours civil works for moving tracks will be limited to intermittent evenings (20 evenings maximum for the entire construction phase) to minimize any disruption to existing East Rail services. For the operation of tunnel boring support PME, KCRC ERE have agreed that, if it is necessary to mitigate the construction noise impacts to achieve CNP conditions, the structures and facilities used or the mitigation equipment for the tunnel boring operation at West Rail DB320 Contract (Tsuen Wan) construction site, will be moved to the Spur Line Sheung Shui launching shaft and installed for the tunnel operation.

7.2.24 Comparing the Tsuen Wan site and Sheung Shui site, the former has a suggested Area Sensitivity Rating (ASR) of 'C' and the latter of 'A'. This implies the application of CNPs for Sheung Shui Site will have to meet a noise standard 10 dB below that at the Tsuen Wan site.

7.2.25 On the other hand, the sensitive receiver at Tsuen Wan is approximately 20 m from the construction site while at Sheung Shui the intervening distance between nearest receiver and works site is approximately 100m. By more than doubling the distance a minimum of 12 dB can be reduced.

7.2.26 From the supplementary information for the CNP application for West Rail Kwai Tsing Tunnel (Contract DB-320)[2], all the equipment which may be working in the shaft was screened by a movable cover on top of the shaft during the restricted hours, except from time to time a sliding door on this cover was opened to supply material to the TBM train. Equipment in the shaft include a ventilation fan with silencer, electric air compressor, water pump, passenger hoist, mortar car, diesel train and the tunnel boring machine (TBM). The last two operated far into the tunnel away from the shaft for much of the construction phase.

7.2.27 Other equipment which may be operated during the restricted hour, including the conveyor system, mortar plant and sedimentation plant and the gantry hoist, also have noise barriers attached to their motors and moving belts, or are acoustically enclosed. Quiet, insulated compressors are used. Similar site arrangement will be implemented if necessary for the application of CNPs at Sheung Shui.

7.2.28 While at Tsuen Wan the nearest receivers are high rise building which overlooks the opening on the shaft cover and any equipment which may be operating in the shaft, the nearest receivers from Sheung Shui are low rise buildings, which will be completely screened by the similar noise mitigation measures arranged over the shaft. From the low vantage point of the receivers at Sheung Shui, any proposed noise mitigation measures on Sheung Shui site will be more effective in achieving higher level of noise reduction than those arranged at the Tsuen Wan site.

7.2.29 As the requirements for the application of CNPs under the more constraining site layout at Tsuen Wan can be met, it would appear that the requirement for application of CNPs and installation of any construction noise mitigation measures are unlikely to be a constraint on the construction programme for the Spur Line or the service of existing East Rail.

Assessment Methodology

7.2.30 The construction noise assessment was undertaken based on acoustic principles, following the methodology given in the Section 2 of the Technical Memorandum on Noise from Construction Works other than Percussive Piling of the Noise Control Ordinance and the British Standards (BS) 5228: Part 1.

7.2.31 All PME are assumed to be stationary while performing the noisiest activity, such as loading / off-loading, lifting and ground breaking at the different Notional Noise Sources (NNS) attributed to various construction activities.

Assessment Results

7.2.32 Table 7.2 highlights the highest unmitigated worst case predicted noise levels at each RNSR and a comparison with noise assessment criteria for each part of the Spur Line alignment assessed. The predicted unmitigated noise levels due to the same relevant construction activities over a longer period that covers the whole duration when these activities are concurrent, are also presented in Table 1 of Appendix A7.1d for reference. The following paragraphs describes the duration of worst impact and the construction activities which cause them.

East End

7.2.33 The RNSRs representing the construction phase, east end of the Spur Line alignment are RNSRs 1 and 3. The east end includes all the construction works located between the Sheung Shui Station and the launching shaft. The works include site clearance, diaphragm wall construction, foundation and base slab, excavation of the east approach cut and cover tunnel and open ramp. The closest works from the worst affected RNSRs is the cut and cover Phase 2 works located at some distance north of RNSR3. RNSR 2 is therefore not a worst affected RNSR in terms of construction noise. Up to 5 dB of noise exceedance at RNSR 1 is expected for three months. Up to 3 dB of noise exceedance at RNSR 3 is expected for three months.

7.2.34 Based on the tender construction programme the exceedance is caused by the concurrent diaphragm wall and excavation works for the east approach cut as well as cut and cover tunnel phase 2 works. This is likely to be a worst case scenario, as diaphragm wall construction and excavation cannot usually be carried out concurrently.

7.2.35 The RNSR near the launching shaft is RNSR 4 which represents a number of low rise village houses at Hak Ka Wai and Tsung Pak Long which could be affected by potential construction noise impacts. The activities which are likely to cause potential noise impact include cut and cover tunnel phase 1 works, the construction of the launching shaft and conveyor shaft, as well as the operation of support equipment for the tunnel boring machine (TBM) excavation. Up to 6 dB of noise exceedance at RNSR 4 could be expected for approximately two months.

7.2.36 Based on the tender construction programme the exceedance is caused by the concurrent diaphragm wall and excavation works for the TBM launching shaft, conveyor shaft and the cut and cover tunnel phase 1 works.

East EAP

7.2.37 The RNSRs potentially affected by the construction noise impact from the east EAP works is RNSR 5. It is an isolated village house on Long Valley. Due to its close proximity from the EAP works, a noise exceedance of up to 3 dB could be experienced for four months at this RNSR.

Kwu Tung Station

7.2.38 There are two major components of construction works at the Kwu Tung area, the construction of the Kwu Tung Station box and the TBM inspection shaft. The TBM shaft is located at the southwest corner of the land reserved for the Kwu Tung Station. Due to the very close distance from many concurrent construction activities at the Kwu Tung station area, especially during the diaphragm wall, foundation, baseslab and excavation works for the Kwu Tung Station and TBM inspection shaft, the potential construction noise exceedance may reach 18 dB at RNSR 8 and RNSR 9 for up to two months.

7.2.39 Other affected RNSRs are RNSR 10 and 11, which may be affected by exceedance of 10 to 11 dB, and RNSR 7, 12, and 14 for up to 4, 1 and 2 dB for the same duration respectively.

7.2.40 These exceedances reflect, however, a worst case estimation since it is unlikely that the excavation works, foundation works, baseslab and excavation can occur concurrently at Kwu Tung Station. Further, as the works progresses a number of equipment will be operating at the bottom of the Station Box excavation and TBM inspection shaft remain out of site for low rise noise sensitive receivers located at a distance from the works. Receivers represented by RNSRs 10, 11, 12 are most likely to benefit from this.

7.2.41 Under the worst case scenario, when the TBM inspection shaft is being constructed, works for the Kwu Tung Station Box will start from a east to west direction. The TBM inspection shaft will be completed long before the Kwu Tung Station Box. It is, however, not certain the rate of progress of Kwu Tung Station works from east to west. It is noted that, under the worst case scenario, the NNS for the Kwu Tung Station construction activity will be closer to RNSR 12 than RNSR 13.

West EAP

7.2.42 As a worst case scenario, the close proximity of the RNSR 16 from the diaphragm wall works at the west EAP lead to an exceedance of 19 dB for up to six months.

West End

7.2.43 Construction activities at the west end include the construction of the TBM exit shaft, the west ventilation building, cut and cover tunnel works, and the west approach open cut works. Under the worst case scenario, an exceedance of up to 10 dB may be expected at RNSRs 18 and 20, and up to 4 dB at RNSR 19, all isolated low rise village houses for approximately four months. The exceedance is mainly due to the concurrent diaphragm wall construction activities for all the shafts and tunnels at the west approach in view of the tight schedule to support the TBM excavation works.

EVA Widening

7.2.44 Local road will be widened to form the EVA to the Lok Ma Chau Terminus. Noise sensitive receivers are located along the section of Lok Ma Chau Road from CH +875 to CH+2000 counting from the Terminus end. RNSRs 24 and 25 represent approximately six low rise houses along the section of the road to be widened that is expected to cause an exceedance of noise criteria of up to 15 dB, as the road works will be carried out at a very short distance of less than 10 m from the road side receivers. The likely exceedance with respect to each receiver is however expected to be intermittent as different part of the road works is carried out.

Viaduct Construction

7.2.45 The main activity which is likely to cause potential construction noise impact is the construction of piers and foundations. The potentially affected RNSR 27 is an isolated village house not representing any other receivers. Up to 1 dB of noise exceedance is expected at these receivers.

Table 7.2

The Highest Unmitigated Worst Case Predicted Noise Levels

at Each RNSR and Comparison with Noise Assessment Criteria

Construction Period	Concurrent Construction Activities	Scenario No. Listed in Appendix A7.1a	Potentially Worst Affected Representative Noise Sensitive Receivers	Predicted Unmitigated Noise Levels dB(A)	Level of Exceedance ¹Compared with Noise Assessment Criteria, dB(A)
Jul to Sep 2004	• East approach open cut - Site clearance and diaphragm wall. • East approach cut and cover phase 2 - Site clearance and diaphragm wall	6-1 6-2	1	80	5
Oct 2004	• East approach open cut - Site clearance and diaphragm wall • East approach open cut - excavation • East Approach Cut and Cover Phase 2 - Site clearance and diaphragm wall • East Approach Cut and Cover Phase 2 - Excavation	7-1 7-2 7-3 7-4	3	77	2
Jan to Dec 2002	• East Approach Cut and Cover Phase 1/TBM Launching shaft - Site clearance and diaphragm wall excavation	13-1 and 13-2	4	81	6
Jun to Sep 2003	• East EAP - Site clearance and diaphragm wall	14	5	78	3
Jun to Sep 2003	• East EAP - Site clearance and diaphragm wall	14	6	73	0
Oct 2003/Dec 2003	• Kwu Tung Station Box - Site clearance and diaphragm wall • Kwu Tung Station Box - Break out Treatment • Kwu Tung Station Box - Excavation • Kwu Tung Station Box - Construction • Shaft for TBM	22-1, 22-2, 22-3 and 22-4/ 24-1, 24-2, 24-3 and 24-4	7	79	4
			8	93	18
			9	88	18
			10	85	10
			11	76	11
			12	76	1
			13	75	0
			14	77	2
			15	73	0
Jan to Jun 2003	• West EAP - Site clearance and diaphragm wall • Shaft for TBM	26	16	94	19
Mar 2003/ Jun 2003	• Ventilation building west portal - Diaphragm wall • West approach cut and cover - Site clearance • Site clearance and diaphragm wall CH 34885>34800 • Site clearance and diaphragm wall • Exit Shaft - Diaphragm wall	29-1, 29-2 and 29-3/ 31-1, 31-2 and 31-3	20	85	10
			17	72	0
			18	83	8
			19	79	4
Viaduct Construction	• Foundation Works/Pier Works	38	21	63	0
			22	73	0
			23	73	0
			26	73	0
			27	76	1
			28	74	0
			29	68	0
EVA Widening	• Road Breaking/Sub base and base/Surface pavement	39	21	73	0
			24	90	15
			25	86	11

¹ The noise assessment criteria for all residential noise sensitive receivers is 75 dB(A).

The noise assessment criteria for schools is 70 dB(A) on typical schools days and 65 dB(A) during examinations.

NSR 9 is a kindergarten and does not hold examinations. The assessment criteria used for comparison is 70dB(A).

NSR11 is a secondary school and the criteria used for comparison is 65dB(A).

Haulage Equipment Noise on Purpose Built Haul Roads

7.2.46 Minor truck movements is expected for moving spoil from the Kwu Tung Station excavation for temporary stockpiling of spoil on the Kwu Tung works area over a maximum distance of about 240 m, but there are no fixed layouts for haul roads in this area at present. Truck movements within the Kwu Tung site will be very limited, where a maximum of one dump truck at any given instance will be sufficient for maneuvers between stockpiles and excavation.

7.2.47 The method of calculating mobile plant noise on fixed haul route from BS5225 Part 1 is used to estimate the potential noise impact from these minor movements with the following assumptions:

Sound Power Level of Truck : 117 dB

Speed of Truck on Site : 15 kph

Distance from Worst Affected RNSR (11) : 50 m

7.2.48 The estimated noise from these movements is estimated to be 58 dB(A). This will meet the noise assessment criteria for school during examination. Further, it is too low to contribute towards cumulative impact with the construction noise arising from works at Kwu Tung Station.

Construction Phase Road Traffic Noise

7.2.49 Kwu Tung is the only location within the scheme boundary of Spur Line where there is a possible haul route. At all the other works areas existing local roads will be utilized to transport stockpiled and excavated spoil from the various construction works areas. Trucks travelling on existing roads are assessed the same way in terms of normal traffic noise, not haulage equipment. Under the worst case scenario in 2003, the peak flow for the entire Spur Line construction is approximately 160 trips per hour. The flow on each road utilized will be much lower. Based on the CRTN method, the very low traffic volume implies traffic noise is not a constraint during construction phase.

Mitigation Measures

General

7.2.50 In general, potential construction noise impact can be minimized or avoided by imposing a combination of the following mitigation measures:

(a) Noisy equipment and activities should be sited by the Contractor as far from close-proximity sensitive receivers as practical. Prolonged operation of noisy equipment close to dwellings should be avoided.

(b) The Contractor should minimise construction noise exposure to the schools (especially during examination periods) as much as possible. The Contractor should liaise with the school and the Examination Authority to ascertain the exact dates and times of all examination periods during the course of the contract and to avoid noisy activities during these periods.

(c) Noisy plant or processes should be replaced by quieter alternatives where possible. Silenced diesel and gasoline generators and power units, as well as silenced and super-silenced air compressors, can be readily obtained.

(d) Noisy activities should be scheduled to minimise exposure of nearby sensitive receivers to high levels of construction noise. For example, noisy activities can be scheduled for midday, or at times coinciding with periods of high background noise (such as during peak traffic hours).

(e) Idle equipment should be turned off or throttled down. Noisy equipment should be properly maintained and used no more often than is necessary.

(f) The power units of non-electric stationary plant and earth-moving plant should be quietened by vibration isolation and partial or full acoustic enclosures for individual noise-generating components.

(g) Construction activities should be planned so that parallel operation of several sets of equipment close to a given receiver is avoided, thus reducing the cumulative impacts between operations. The numbers of operating items of powered mechanical equipment should be minimised. Noise can be reduced by increasing the distance between the operating equipment and the NSRs or by reducing the number of items of equipment and/or construction activity in the area at any one time.

(h) The use of quiet plant and working methods can further reduce noise level. Quiet plant is defined as Powered Mechanical Equipment (PME) whose actual sound power level is less than the value specified in the TMs for the same piece of equipment. To allow the Contractor some flexibility to select equipment to suit his needs, it is considered too restrictive to specify which specific items of silenced equipment to be used for the construction operations. It should be noted that various types of silenced equipment can be found in Hong Kong and are readily available on the market. BS 5228 also provides examples of quiet construction plant and their SWL.

(i) Construction plant should be properly maintained (well-greased, damage and worn parts promptly replaced) and operated. Construction equipment often has silencing measures built in or added on, e.g. bulldozer silencers, compressor panels, and mufflers. Silencing measures should be properly maintained and utilised. Where possible, rubber or damping materials should be introduced between metal panels to avoid rattle and reverberation of noise.

(j) Equipment known to emit sound strongly in one direction, should where possible, be oriented so that the noise is directed away from nearby NSRs.

(k) Material stockpiles and other structures (such as site offices) should be effectively utilised to shield construction noise. Noise can also be reduced by construction of temporary noise barriers which screen the lower floors from viewing the sites. Temporary noise barriers should be installed at active parts of construction areas where construction equipment is being operated in close proximity to NSRs.

(l) It is noted that under the WBTC No. 19/99, all construction sites are required to use metallic site hoarding to reduce the amount of timber. This metallic hoarding can be slightly modified (with the addition of steel backings) into temporary noise barriers. These barriers should be gap free and have a surface mass density of at least 7 kg/m2.

(m) All hand-held percussive breakers and air compressors should comply the Noise Control (Hand-held Percussive Breakers) Regulations and Noise Control (Air Compressors) Regulations respectively under the NCO (Ordinance No. 75/88, NCO Amendment 1992 No.6).

7.2.51 The Contractor shall devise, arrange methods of working and carry out the works in such manner as to minimise noise impacts on the surrounding environment, and shall provide experienced personnel with suitable training to ensure that these measures are implemented properly.

Site Specific Direct Technical Measures

7.2.52 The Contractor is required to either:

adopt Levels 1 and 2 site specific direct technical measures as specified below during construction phase;

submit alternative proposal for site specific direct technical measures, in which the Contractor shall demonstrate the compliance of noise assessment criteria of 75/70/65 dB(A) for residential properties /schools /schools during examination at all RNSRs, prior commencement of any construction works under his Contract. The Contractor is required to implement site specific direct technical measures in the approved alternative proposal during construction phase.

Level 1

7.2.53 Level 1 direct technical measures are proposed to mitigate potential construction noise impacts. Level 1 measures include limiting the concurrent use of construction equipment and using silenced and quiet equipment as far as practicable, without significant delay to the construction programme. Since receiving the construction programme and equipment schedule, discussion with the design team confirmed that site clearance, diaphragm wall construction and breaking of guide walls will be carried out in a non-concurrent sequence for any given location. The equipment schedule for site clearance and diaphragm wall construction should be modified accordingly. These have also been taken into account under the Level 1 mitigation measures. Table 2 of the Appendix A7.1d presents the PME schedule of the scenarios under which the non-concurrent construction sequences have been separated.

7.2.54 Appendix A7.1d Table 3 presents one of the possible combination of silenced and reduced quantity of PME. Discussion held with the Engineering Design Team reveal that while this combination is feasible, any further reduction to the number of equipment may result in unacceptable delay to the construction programme.

7.2.55 Table 7.3 presents the proposed limits of allowable sound power levels associated with the construction activities under worst case scenarios with respect to different RNSRs and locations along the Spur Line, from using of the equipment listed in Appendix A 7.1d Table 3. The reason for proposing sound power level limits is to retain flexibility on the choice of PME as long as an equivalent or lower sound power level can be reached for a given construction activity.

Table 7.3

Recommended Sound Power Levels Allowed

for Construction Activities at Various Locations of Spur Line

Geographical Location	Construction Activities	Recommended Allowable Sound Power Level, dB	Corresponding Sub-Scenario Nos. in Appendix A7.1d Table 4
East End	· Open cut · Cut and cover phase 2 works · Launching Shaft / Cut and cover phase 1 works	118 120 122	7-1 & 7-2 7-2 & 7-3 13-1-3 & 13-2
East EAP	All	118	14
Kwu Tung Area	· TBM Shaft works · Kwu Tung Station works	122 115	22/24
West EAP	All	116	26 Option B
West End	· Cut and cover works · Exit shaft works · Works on CH 34885 - 35200	118 119 118	31-4 31-1 + 31-2 31-3
EVA Widening Works	All	110	39

7.2.56 Appendix A7.1d Table 4 presents the predicted noise levels at the various affected RNSRs after implementation of Level 1 measures. It can be shown that noise exceedance is still expected at the RNSRs 8, 9, 10, 14, 16, 18, 20, 24, and 25. Further mitigation measures other than reduction of number of equipment are required to meet the noise assessment criteria without any unacceptable delay imposed on construction programme.

Level 2

7.2.57 Level 2 site specific mitigation measures comprising temporary noise barriers are proposed to mitigate the predicted exceedance following the application of Level 1 mitigation measures. Gap - free temporary noise barriers of material at least 10 kg/m² are to be installed at the following locations:

(1) A 2.5m tall gap free noise barrier around whole length of east end temporary works area except at site entrance.

(2) A 2.5m tall barrier around whole length of the east Emergency Access Portal (EAP) works area.

(3) 2.5m tall barriers around all the works area at Kwu Tung Station and TBM Shaft except for 20m long south of RNSR 8, and 100m long north of the RNSRs 9, 10 and 11. These sections will be 5m tall. (Note: The west sections of the 2.5m tall barrier is situated on the top of a cutting as the TBM shaft is being excavated. The top of the cutting is approximately 2.5m higher than the surrounding ground. As a result the effective height of the barrier around this part of the works area is 5m. Refer to Figure 7.1 for details).

(4) 5m tall barriers along whole length of west Emergency Access Portal (EAP) works area.

(5) 2.5m tall barriers around the works on the west approach, including ramp, cut and cover tunnel and west ventilation building, except: 40m long 5 m tall noise barrier south of RNSR 20.

(6) 5m tall barriers between CH+875 and CH+2000 of proposed EVA, on either sides of the works during construction at these chainages.

(7) 5m tall barriers on the section of the proposed EVA between CH36+350 to CH36+450, to screen viaduct construction works from RNSR 27 when construction works take place at these chainages.

These barriers are fixed in their respective locations described above throughout the construction phase in place of site hoarding. Notwithstanding the minimum height required, these barriers shall be constructed in a way such that no construction works and PME can be visible from the low rise noise sensitive receivers they protect.

7.2.58 The estimated noise reduction by means of fully screening the PME from line of sight from noise sensitive receivers is 10 dB for stationary PME and 5 dB for mobile PME.

7.2.59 Table 4 of the Appendix A7.1d presents the mitigated noise levels after the application of Level 1 and 2 mitigation measures.

7.2.60 Table 7.4 presents the highest predicted mitigated noise levels at the RNSRs following the implementation of proposed Level 1 and Level 2 mitigation measures under worst case scenarios respectively. From Table 7.4 it can be shown that there will not be any exceedance of noise assessment criteria by adopting the two levels of direct technical mitigation measures. With reference to Section 7.2.52, the Contractor is required to demonstrate compliance of noise assessment criteria of the proposed alternative proposals for site specific direct technical measures prior commencement of any construction works under this contract.

Residual Impacts

7.2.61 Residual construction noise impact is not expected after implementation of both Level 1 and Level 2 site specific measures as well as the general mitigation measures specified above.

Table 7.4

The Predicted Mitigated Noise Levels at Each RNSR during Worst Case Scenarios and Comparison with Noise Assessment Criteria

Construction Period	Concurrent Construction Activities	Corresponding Scenario/Sub-Scenario Nos. in Appendix A7.1d Table 4	Potentially Worst Affected Representative Noise Sensitive Receivers	Predicted Mitigated Noise Levels dB(A)	Level of Exceedance ¹Compared with Noise Assessment Criteria, dB(A)
Oct 2004	• East approach open cut - Site clearance and diaphragm wall • East approach open cut - excavation • East Approach Cut and Cover Phase 2 - Site clearance and diaphragm wall • East Approach Cut and Cover Phase 2 - Excavation	7-1, 7-2, 7-3 and 7-4	1 3	74 72	0
Jan to Dec 2002	• East Approach Cut and Cover Phase 1 - Site clearance and diaphragm wall • TBM Launching shaft - Site clearance and diaphragm wall • TBM Conveyor shaft - Site clearance and diaphragm wall	13-1-3 and 13-2	4	73	0
Jun to Sep 2003	• East EAP - Site clearance and diaphragm wall	14-1-3	5	71	0
Jun to Sep 2003	• East EAP - Site clearance and diaphragm wall	14-1-3	6	66	0
Oct 2003	• Kwu Tung Station Box - Site clearance and diaphragm wall • Kwu Tung Station Box - Break out Treatment • Kwu Tung Station Box - Excavation • Kwu Tung Station Box - Construction • Shaft for TBM	22-1, 22-2, 22-3 and 22-4	7	70	0
			8	75	0
			9	70	0
			10	72	0
			11	68	0
			12	68	0
			13	67	0
			14	69	0
			15	65	0
Jan to Jun 2003	• West EAP - Site clearance and diaphragm wall • Shaft for TBM	26 Option B	16	75	0
Jun 2003	• West approach cut and cover - Diaphragm wall/Excavation and bases lab • Site clearance and diaphragm wall CH 34885>34800 • Exit Shaft - Diaphragm wall	31-3, 31-2, 31-3 and 31-4	17	66	0
			18	67	0
			19	73	0
			20	70	0
Viaduct Construction CH36+350 to 36+450	• Foundation Works/Pier Works	38	21	60	0
			22	70	0
			23	70	0
			26	70	0
			27	73	0
			28	71	0
			29	65	0
EVA Widening CH+875 to CH+2000	• Road Breaking/Sub base and base/Surface pavement	39	21	68	0
			24	75	0
			25	71	0

¹ The noise assessment criteria for all residential noise sensitive receivers is 75 dB(A).

The noise assessment criteria for schools is 70 dB(A) on typical schools days and 65 dB(A) during examinations.

NSR 9 is a kindergarten and does not hold examinations. The assessment criteria used for comparison is 70dB(A).

NSR11 is a secondary school and the criteria used for comparison is 65dB(A).

[1] BBVHKL, Sheung Shui to Lok Ma Chau Spur Line – Environmental Impact Assessment, June 2000.

[2] Dragages-Zen Pacific Joint Venture for KCRC West Rail, KCRC West Rail DB320 Kwai Tsing Tunnels Noise Permit Application Phase 3 & 4 Tsuen Tsing Tunnels TBM Operations, August 1999.