4. GROUND-BORNE NOISE impact

Introduction

4.1 Potential ground-borne noise impacts likely to arise from the proposed Project during both the construction phase and operation phase have been evaluated and the results are presented in this section.

4.2 Potential ground-borne noise impacts on Noise Sensitive Receivers (NSRs) during the construction phase would arise mainly from hydraulic breakers, hand-held breakers, pipe pile rigs, drill & blast and tunnel boring machine (TBM). Potential ground-borne noise arising from the TBM and Powered Mechanical Equipment (PME) was assessed, and the predicted noise levels and necessary noise mitigation measures are presented in this section.

4.3 The drill and blast alternative is not considered with respect to noise annoyance, as the duration of blasting is very short and infrequent. As mentioned in section 3.14, no assessment has been carried out regarding noise annoyance impacts within any of the identified sensitive receivers. However, it is recommended that if there is a blasting operation, it should be carried out outside sensitive hours to avoid nuisance to nearby sensitive receivers.

4.4 When trains operate in tunnels that are located in close proximity to occupied structures, there is a possibility that vibrations associated with train passbys will be transmitted through the ground and structure, and be radiated as noise in the occupied spaces within the structure. The assessment of the ground-borne noise impacts within the structure is presented below.

Environmental Legislation, Standards and Guidelines

Construction Phase

4.5 Construction ground-borne noise is under the control of the Noise Control Ordinance (NCO), the Environmental Impact Assessment Ordinance (EIAO), and their subsidiary Technical Memorandum. With reference to the Technical Memorandum for the Assessment of Noise from Places Other Than Domestic Premises, Public Places or Construction Sites (TM-Places) under the NCO, the criteria for noise transmitted primarily through the structural elements of the building or buildings should be 10dB(A) less than the relevant acceptable noise level (ANL). These criteria apply to all residential buildings, schools, clinics, hospitals, temples and churches.

4.6 The construction ground-borne noise criteria for the representative ground-borne noise sensitive receivers (GBNSR) along WIL alignment are tabulated in Table 4.1 below.

Table 4.1 Construction Ground-borne Noise Criteria

	Ground-borne Noise Criteria, dB(A)
GBNSR Description	Daytime (0700-1900 hrs) (except General Holidays & Sunday)	Daytime during general holidays and Sundays and all days during Evening (1900 to 2300 hrs)	Night (2300 to 0700 hrs)
Churches, School – Classrooms and Temples	60/55 ^[a]	55	^[b]
Domestic premises, clinics^[c] and hospitals along WIL alignment	65	55	40

[a] A 5dB(A) reduction to the ground-borne noise criteria is recommended for school during examination period.

[b] No sensitive use during this period.

[c] Clinics are considered to be noise sensitive during daytime and evening time only.

4.7 For construction activities involving the use of TBM and PME in restricted hours (1900-0700), it is necessary to apply for a CNP. However, there is no guarantee that a CNP will be issued for the project construction.

Operation Phase

4.8 In the projection and measurement of ground-borne noise from transit trains operating at grade, or in tunnels, to receivers adjacent to the alignment, it is customary to calculate or measure the impact of a single train passby, where the noise level from it is rms (root mean square) averaged over the duration of the passby (Appendix 4.1: Ref. 1). This is, by definition, the equivalent noise level of the passby, where duration is defined as the period between the passage of the front and rear ends of the train pass the closest point on the alignment to the building foundation. This measure is assumed in this study and is known as the rms level of the passby. Given train lengths and passby frequencies along the WIL, the 30 minutes overall equivalent A-weighted noise level shall be determined at each GBNSR from the maximum rms level of a single train passby.

4.9 With reference to the TM-Places under the NCO, the criteria for noise transmitted primarily through the structural elements of the building or buildings should be 10dB(A) less than the relevant acceptable noise level (ANL). The same criteria are applied to all residential buildings, schools, clinics, hospitals, temples and churches.

4.10 The operational ground-borne noise criteria for the representative GBNSRs along WIL alignment are tabulated in Table 4.2 below.

Table 4.2 Operational Ground-borne Noise Criteria

	Ground-borne Noise Criteria, dB(A)
GBNSR Description	Day & Evening (0700 to 2300 hrs)	Night (2300 to 0700 hrs)
Churches, School – Classrooms and Temples	55 (Leq 30 min)	[a]
Domestic premises, Clinics^[b] and Hospitals along WIL alignment	55 (Leq 30 min)	45 (Leq 30 min)

Note: [a] No sensitive use during this period.

[b] Clinics are considered to be noise sensitive during daytime and evening time only.

Identification of Ground-borne Noise Sensitive Receivers

Construction Phase

4.11 Under the assumption of worst-case scenario, two sets of representative GBNSRs were identified for the assessment of noise impact induced by (1) TBM operation for tunnelling and (2) PME (e.g. hydraulic breakers, drill rigs and pile rigs) operation at open works areas and during the construction of adits and vent shaft. Twenty-six GBNSRs identified along the WIL alignment were designated for the assessment of TBM-induced ground-borne noise impact. As for the assessment of noise impact due to the use of PME for rock breaking / drilling, including hydraulic breakers, drill rigs and pile rigs, at open works areas, adits and vent shaft, twenty-five representative GBNSRs located in the closest proximity to the concerned open works areas were identified. These identified GBNSRs are presented in Tables 4.3a, b and c and shown in Figures 4.1 to 4.5.

Table 4.3a Identified NSRs for Assessment of Ground-borne Construction Noise Impacts due to TBM operation

Construction GBNSR No.	Location	Uses	Horizontal Distance from NSR to Tunnel (m)	Vertical Distance from NSR to Tunnel (m)
1	No.153 Queen's Road West, West Point	Residential	96	29
2	Sai Ying Pun Jockey Club Polyclinic at 32 Hospital Road	Clinic	75	40
3	No.36 Eastern Street, West Point	Residential	0	43
4	Sai Ying Pun Community Complex	Kindergarten, hostel & community centre	100	61
5	Eastern Street Methadone Clinic	Clinic	69	65
6	Nos. 18-24 Third Street, West Point	Residential	18	61
7	Prewar Buildings Under the Development Project of Yu Lok Lane and Central Street of the Urban Renewal Authority	Residential	15	64
8	No.35 Bonham Road, Mid Level	Residential	0	43
9	King's College at No.63A Bonham Road	Educational Institution	12	67
10	Chinese Rhenish Church (Lai Yin Church) at Bonham Road	Church	0	68
11	Tang Chi Ngong Building of the University of Hong Kong	Educational institution	15	76
12	Fung Ping Shan building , the University of Hong Kong at Pok Fu Lam Road	Educational institution	0	66
13	St. Stephen's Church at 71 Bonham Road	Church	75	84
14	Hung Hing Ying Building of the University of Hong Kong	Educational institution	33	84
15	Main Building of the University of Hong Kong	Educational institution	0	84
16	St. Anthony's Catholic Church at Pok Fu Lam Road	Church	45	57
17	Senior Staff Quarters, Workmen's Quarters and Treatment Works Building, Elliot Pumping Station and Filters at Pok Fu Lam Road	Residential	0	90
18	Lo Pan Temple, No. 15 Ching Lin Terrace, Kennedy Town	Temple	0	55
19	Hon Wah Middle School at Ching Lin Terrace	Education Institution	0	51
20	Fok Hing Tong, Hong Kong Society for the Promotion of Virtue at 8-9 Tai Pak Terrace	Temple	69	48
21	Bonham Road Government Primary School, 9A Bonham Road	Educational Institution	129	61
22	Po Leung Kuk Chan Au Big Yan Home For The Elderly, 12 Belcher's Street	Hostel	150	15
23	St. Louis School, 179 Third Street	Educational Institution	120	45
24	Kau Yan Church	Church	120	64
25	Western District Community Centre	Community Centre	150	58
26	Hongway Garden	Residential	0	24

Table 4.3b Identified NSRs for Assessment of Ground-borne Construction Noise Impacts due to Construction Works at Open Works Areas

Construction GBNSR No.	Description	Uses	Horizontal Distance to the Site Boundary (m)	Nearest Site
KET
27	Hong Kong Institute of Vocation Education (Kennedy Centre)	Educational Institution	21	Ex-Police Quarters Kennedy Town
28	Luen Tak Apartment	Residential	22 (2 Sites)	KET Station site
29	Kam Po Mansion	Residential	13	Entrance B
30	Pokfield Garden	Residential	6	KET Station site
UNI
31	The Belcher’s Tower 3	Residential	8	Entrance C2
32	39 Hill Road	Residential	6	Vent shaft (VS-Y)
33	Western Court Block 1-4	Residential	4	Entrance B1
33a	The Kadoorie Biological Sciences Building	School	11	Entrance A
SYP
34	Kiu Shing Building	Residential	6	Entrance of B3
35	Bon-Point	Residential	6	Vent shaft (VS-Z) and Entrance C
36	Queen’s Hotel	Hotel	6	Entrance A1 and Vent Shaft (VS-Y)
37	College View Mansion	Residential	6	High Street Site

Table 4.3c Identified NSRs for Assessment of Ground-borne Construction Noise Impacts due to the Construction of Adits

Construction GBNSR No	Description	Uses	Adits / Vent Adits	Vertical Distance to Adit (m)	Rock Head ditance to Adits (m)
UNI
38	Bowie Court	Residential	Adit to Entrance A	50	35
39	Intelligent Court	Residential	Adit to Entrance B1	30	10
40	Sik On Building	Residential	Adit to Entrance B2	20	20
31	The Belcher’s Tower 3	Residential	Adit to Entrance C2	65	45
41	Yick Fung Garden	Residential	Construction Adit	40	20
42	Wing Fu Lau	Residential	Vent adit (YS-Y)	30	20
SYP
34	Kiu Shing Building	Residential	Adit to Entrance B3	22	~20
36a	6-28 Eastern Street	Residential	Vent adit (YS-Z)	45	20
43	Tat Hing Building	Residential	Adit to Entrance A1	25	5
44	Yee Shun Building	Residential	Adit to Entrance B1/B2	35	0
45	Jade Court	Residential	Adit to Entrance C	42	32
46	21-23 High Street	Residential	Vent adit (YS-Z)	49	25
47	Sun Luen Building	Residential	Vent adit (YS-Z)	55	40

Operation Phase

4.12 Sensitive receivers along the WIL alignment generally include educational institution and domestic premises. Domestic premises and hospital are taken into account during both the daytime and night time periods. School classrooms, churches, clinics and temples are considered to be noise sensitive during daytime and evening only.

4.13 A total of ten operational phase GBNSRs were identified, and are listed in Table 4.4. Their locations are shown in Figures 4.6 to 4.9. Information necessary for noise prediction is also provided in the table below, including the geometry of the closest point on a GBNSR relative to the alignment, and the structure characterisation. The train speed at each operational phase GBNSR is shown in Appendix 4.11. The maximum allowable acceleration for existing Island Line trains is 1m/s². The train speeds at NSRs close to stations were assumed to be 50 or 60kph for conservatism.

Table 4.4 Operational Ground-borne Noise Sensitive Receivers

GBNSR No (a).	Location	Chainage	Turn- out	Lowest Sensitive Floor	Building Type (b)	Building Height, storey	Foundat’n Depth, m	EB Track Dist to G/F Building Edge, m				WB Track Dist to G/F Building Edge, m
								Hori	Rail Depth	Rock- head Depth	slant dist to foundat’n	Hori	Rail Depth	Rock- head Depth	slant dist to foundat’n
1	Luen Yee Building	SYP-SHW E0+940	Y	1	0	5	2	7	28	28	27	13	28	31	29
2	Hongway Garden	SYP-SHW E0+820	Y	2	0	35	5	0	28	28	23	0	28	31	23
3	Kian Nan Mansion, 81-85 Bonham Strand West	SYP-SHW E0+620	N	1	0	19	2	0	30	32	28	0	30	32	28
4	No. 36 Eastern Street, West Point	SYP-SHW E0+150	N	1	1	5	2	0	42	29	40	2	42	29	40
5	Po Shu Lau, Tse, 35-43 Sands Street	KET-UNI E0+270	N	1	0	13	2	0	42	10	40	0	42	10	40
6	Tower 1, University Heights	KET-UNI E0+180	N	3	0	37	2	0	57	20	55	0	57	20	55
7	Block D, Kwun Lung Lau	OVR-KET E0+700	N	>1	0	20	2	26	44	8	49	22	44	16	47
8	Kwun Lung Lau New Development Site	OVR-KET E0+620	N	5	0	24	0	36	34	8	50	40	34	16	52
9	East Terrace, Sai Wan Estate	OVR-KET E0+560	Y	1	0	12	0	17	46	23	49	17	46	23	49
10	Tower 3, Academic Terrace	KET-UNI E0+310	N	1	0	26	2	20	72.9	Above track	74	0	72.9	Above track	71

Note: (a) All GBNSR are residential buildings.

(b) Building Type: 0 – Heavy Tall Structures, 1 – 2-4 Storeys Medium Height

Ground-borne Noise Sources

Construction Phase

4.14 Potential ground-borne noise impacts on GBNSRs during the construction phase will arise mainly from drill & blast and TBM, as well as PME for rock breaking/drilling including breakers, drill rigs and pile rigs.

4.15 There are no statutory procedures and criteria under the NCO and EIAO for assessing blasting noise impacts. Blasting in this Project, if required, would be carried out underground. Any such blasting noise, which is transient and short in duration, is not assessed in this EIA. However, the administrative and procedural control of all blasting operations in Hong Kong is vested in the Mines Division of the Civil Engineering and Development Department (CEDD). The Dangerous Goods (General) Regulation (Cap 295) also stipulates that no person shall carry out blasting unless he possesses a valid mine blasting certificate to be issued by the Mines Division of CEDD. The Superintend of Mines will review the application on a case-by-case basis before issuing the Mine Blasting Certificate. Blasting, if unavoidable, should be carried out outside sensitive hours as far as practicable, and the blasting schedule should be submitted to the concerned authority for approval prior for its implementation.

Operation Phase

4.16 When trains operate in tunnels that are located in close proximity to occupied structures, there is a possibility that vibrations associated with train passbys will be transmitted through the ground and structure, and be radiated as noise in the occupied spaces within the structure. The noise levels within the structure may be high enough to cause annoyance to the GBNSRs.

Ground-borne Noise Prediction Methodology

Construction Phase

4.17 As described above, projections of Peak Particle Velocity (PPV) assumed worst case assumptions along the WIL alignment. The projection methodology is empirically based on, and is the same as that used to determine noise impacts on sensitive receivers from operational trains, as described in the operation ground-borne noise section. The projection methodology is recommended by the U.S. Department of Transportation and Federal Transit Administration[1] . This projection methodology has been previously used for Ground-Borne Noise & Vibration Assessment for approved Kowloon Southern Link (KSL) EIA[2] (EIA Register No. AEIAR-083/2005).

4.18 The main components of the proposed prediction model for ground-borne noise are:

l Vibration source level from operation of TBM;

l Vibration propagation through the ground to the structure foundation;

l Vibration reduction due to the soil/structure interface;

l Vibration propagation through the building and into occupied areas; and

l Conversion from floor and wall vibration to noise.

4.19 The empirical based prediction model used to project noise level within occupied areas of the structures adjacent to the WIL is described below. The basic equation describing the model, in decibels, is

L = FDL + LSR + BCF + BVR + CTN + SAF

where the prediction components are:

L	ground-borne noise level within the structure, re: 20 μ-Pascal,
FDL	force density level for the TBM in rock, mixed face or soil, re: 1 lb/in0.5 in English unit and re: 1 N/m0.5 in SI unit,
LSR	unit force incoherent line source response for the ground, re: 1 μ -in/sec/(1 lb/in0.5) in English unit and 10-8 m/s/(1 N/m0.5) in SI unit,
BCF	vibration coupling loss factor between the soil and the foundation, relative level,
BVR	building vibration reduction or amplification within a structure from the foundation to the occupied areas, relative level,
CTN	Conversion from floor and wall vibration to noise, 10^-8 m/s or 10^-6 in/s to 20 μ Pascal, and
SAF	Safety margin to account for wheel/rail condition and projection uncertainties.

4.20 The measurement and analysis equipment used in obtaining these empirical results is given in operation ground-borne noise section. Predictions are based on assuming the closest distance along the alignment to the building foundation of the receiver.

Adaptation to TBM

4.21 The above methodology has been altered for TBM in the following ways:

1. The source vibration level, or force density level (FDL), is obtained from vibration measurements taken during the passby of a tunnel boring machine operating in soil and rock along the KCRC Lok Ma Chau extension. A summary of measurement data is provided in Appendix 4.2: Figure 1. Measurements were performed underground in an access shaft adjacent to the alignment at 7m setback from tunnel centreline. The associated line source response (LSR) was obtained from surface and borehole impact tests were performed on similar soil and rock geology, as shown in Appendix 4.2: Figure 2. The length of the LSR along the TBM is assumed to be 10m. The resulting FDLs are given in Appendix 4.2: Figure 3 and compared to a typical FDL for a heavy rail transit train. It can be seen that the FDL for the TBM in rock is considerably higher than that in soil, especially at low frequencies. The FDL for the TBM in soil is roughly comparable to the graph of a typical heavy rail transit train. In mixed face geology, the FDL for rock is assumed, for conservatism.

2. The LSR along the WIL alignment was taken from borehole impact tests performed along the WIL, as described in operation ground-borne noise section, except the line source length is assumed to be 10m.

3. RMS vibration measurements are used for the ground-borne noise assessment.

4.22 In all other respects, the components of the projections are the same as that used for the assessment of operational trains.

Ground-Borne Noise Level within the Structure (L)

4.23 At setback distances characteristic of this study, ground-borne noise from TBM would have an impact, conservatively, up to about 160 Hz for tunnels situated in soil and up to 500 Hz for tunnels situated in rock. Above these frequencies, the material attenuation of the ground would reduce the amplitude of the propagating waves below which there would be adverse impact. Thus, structure borne noise levels will be presented in octave bands over the frequency range of 31.5 Hz to 500 Hz.

Line Source Response (LSR)

4.24 The LSR determines the vibration levels or attenuation in the ground as a function of distance caused by an incoherent line source of unit force point impacts, with line source orientated along the alignment and the length of the line source equalling 10m measured from the front of the TBM. Thus, the basic quantity required for the determination of the LSR would be the vibration response caused by a unit point source impact, which is defined as the Point Source Response (PSR). Given the PSR would be along the alignment over the length of the train, the LSR would follow directly by incoherent integration of the PSR over the length of the train.

4.25 However, the determination of the PSR for force point impacts along the alignment over the length of the train is neither practical nor affordable. For example, at underground sections, force impacting would have to be performed in numerous boreholes drilled to the depth of the alignment and closely spaced along the alignment over the length of the train just for the determination of the LSR at one location. Thus, certain assumptions are invoked, which allow one PSR to be taken as representative along the alignment near a building receiver and to be used in the determination of the LSR. These assumptions include:

l The ground is layer-wise homogeneous,

l The ground is transversely isotropic along the alignment over the length of the train

l The ground is between the alignment segment and the vibration receivers at which the LSR is to be determined.

4.26 If the ground satisfies these assumptions rigorously, it would be acceptable to use one PSR in the determination of the LSR. In normal circumstances, deviation from the idealised assumptions of transverse isotropy and layer-wise homogeneity is not significant enough to warrant the time, expense and impracticality of impacting along the entire length of the train. Also, the flanking effect of vibration from remote cars towards the front and rear of the train is not very significant: it is the vibration from the train section opposite to the shortest distance from the track to the receiver that, in most circumstances, determines the vibration level at the receiver.

4.27 A detailed description of the PSR testing along the WIL and the LSR model can be found in operation ground-borne noise section, where the PSR testing is referred to as borehole impact testing.

Building Coupling Factor (BCF)

4.28 The recommended practice established within the USFTA handbook is followed. Structures are divided into 4 types, with BCF attenuation given in the follow:

Type 0 – Large structures with heavy foundations

Type 1 – 2-4 storeys medium sized structures

Type 2 – 1-2 storeys complexes

Type 3 – Single family detached residences

4.29 It can be seen from Appendix 4.2: Figure 4 that, larger and heavier structures have greater vibration attenuation than smaller and lighter structures. In fact, the extent of the attenuation is governed by the difference in mechanical impedance between the soil and the foundation, with impedance being determined by differences in mass and stiffness within the soil and foundation. For structures founded on rock, there is no impedance contrast between the soil and the foundation; thus, in this case, the BCF is zero.

Building Vibration Response (BVR)

4.30 The building vibration response is generally determined by three factors:

l Resonance amplification due to floor, wall and ceiling spans;

l Floor-to-floor attenuation; and

l Attenuation across a structure, in the direction away from the alignment.

4.31 Resonance amplification due to wall, floor and ceiling spans is usually an issue for small, lightweight housing, generally single-family homes constructed of wood. The frequencies at which resonances occur can vary widely, and the magnitude of the resonance amplification would depend on the structure. In large, heavy framed structures, generally multi-floor concrete construction, structural resonances usually occur at sub-audible frequencies, with small resonance amplification due to massive structural elements having low mobility.

4.32 The FTA Handbook recommends that the BVR includes no correction for heavy framed structures, a 3 dB correction for moderate weight structures and a 6 dB correction for lightweight structures to account for structural resonances that may be present in smaller and less massive structures located along the alignment. Lightweight structure refers to hollow block, lightweight concrete, brick, timber or composite structures of only several stories high. A moderate weight structure is generally light weight concrete construction up to 6 or 7 storeys. As the frequency at which such resonances may occur is not known, these corrections add either 3 or 6 dB to all frequency bands considered.

4.33 The BVR shown in Appendix 4.2: Figure 5 is applied to all structures conservatively, which is a modified version of the 6 dB rule across all frequencies, as recommended for light weight structures.

4.34 Usually, occupied spaces within a structure are assumed to be located at or above the nearest setback distance from the alignment to the receiver. However, vibration attenuation across a structure may be relevant where the noise sensitive area is situated in the back of the building away from the alignment. Although vibration attenuation has been measured across a number of structures in Hong Kong, this attenuation is considered conservatively in this study.

4.35 A floor-to-floor attenuation of 2 dB reduction per floor is assumed. Where there is a multi-floor occupancy, only the structure borne noise impact on the lowest occupied floor is considered.

Conversion to Noise (CTN)

4.36 A -2 dB correction for conversion of vibration (re: 10-6 in/s) in room walls, floors and ceiling to noise (re: 20 micro Pa) is assumed;

Safety Factor (SAF)

4.37 In the determination of the components of the prediction model, data undergoes extensive averaging, thus making the overall prediction of ground-borne noise a sum of averages. In many of our comparisons of predicted and measured levels, it has been generally found that differences in overall predicted and measured A-weighted noise levels fall within about ±5dB. Thus if noise criteria are regarded as simple design guidelines, no safety factor would be appropriate. If all but a few exceptional passbys are expected to produce noise and vibration levels below criteria, then a safety factor of 5 dB would be appropriate. If strict adherence of every passby to noise and vibration criteria is expected, then a safety factor of 10dB or more would likely be appropriate. In this study, a conservative 10dB safety factor has been adopted.

4.38 A large safety factor results in higher projected noise and vibration levels, thus exceeding the criteria in a larger extent. Therefore, greater requirements for trackform vibration attenuation, both in type and extent, would be needed.

Adaptation to Hydraulic Breaker, Rock Drill and Pile Rig

4.39 The source terms and transmission factors for the ground-borne noise assessment of hydraulic breaker, rock drill and pile rig would be different from the TBM calculation above. Reference was made to the assessment approach, source terms and transmission factors adopted in the approved EIA study for the Kowloon Southern Link project. The assumptions adopted in the present assessment are provided in Appendix 4.3.

Soil Damping

4.40 Internal losses of soil would cause the vibration amplitude to decay against the propagation distance and the decay relationship is based on the equation set out in the Transportation Noise Reference Book[3].

V(R) = V(R_o) ´ e^{-2pf h R/2c}.

The velocity amplitude V is dependent on the frequency f in Hz, the soil loss factorh, the wave speed c in m/s, the distance R from the source to the NSR. The properties of soil materials are shown in Table 4.5.

Table 4.5 Wave Propagation Properties of Soil

Soil Type	Longitudinal Wave Speed c, m/s	Loss Factor, h	Density, g/cm^3
Soil	1500	0.5	1.7
Rock	3500	0.01	2.65

4.41 No damping attenuation was applied for propagation in rocks. All GBNSRs were assumed to have a piling foundation on rockhead except Kiu Shing Building and Yee Shun Building where shear piles were found. Soil damping was applied in the prediction of noise levels at Kiu Shing Building and Yee Shun Building, and the damping distances would be 22m and 7m respectively. Relevant geological profiles and the alignment of the adits are presented in Figure 4.18-4.28.

Coupling Loss into Building Structures

4.42 The coupling loss into building structures represents the change in the incident ground-surface vibration due to the presence of the piled building foundation. The empirical values with reference to the “Transportation Noise Reference Book”, 1987 are given in Table 4.6.

Table 4.6 Loss factor for Coupling into Building Foundation

Frequency	Octave Band Frequencies, Hz
	16	31.5	63	125	250	500
Loss factor for coupling into building foundation, dB	-7	-7	-10	-13	-14	-14

Coupling Loss Per Floor

4.43 The coupling loss per floor represents the floor-to-floor vibration transmission attenuation. For multi-storey buildings, a common value for the attenuation of vibration from floor-to-floor is approximately 1 dB attenuation in the upper floor regions and greater than 3 dB attenuation at lower floors. Coupling loss of 1 dB reduction per floor was assumed in this report for a conservative assessment to account for any possible amplification due to resonance effects.

Conversion from Floor Vibration to Noise Levels

4.44 Conversion from floor vibration levels to indoor reverberant noise levels is based on standard acoustic principles. The conversion factor is dependent on the surface area S of the room in m², the radiation efficiencys, the volume of the room V in m³ and the room reverberation time RT in seconds. Conversion factors from floor vibration levels to indoor reverberant noise levels are 27 and 23 dB(A) for residential units and educational institution respectively.

Operation Phase

4.45 The most current and evolved projection methodology recommended by the FTA Manual is used in this EIA study. This manual is issued by the US Department of Transportation in 1995 and is intended to provide guidance in preparing and reviewing the noise and vibrations sections of environmental submittals to the US Government for grant applications. The methodology has been applied on a number of transit systems over the years, including West Rail, East Rail Tsim Sha Tsui Extension, Kowloon Southern Link and MTR Tseung Kwan O Line.

4.46 The main components of the proposed prediction model for ground and structure borne noise are:

l Vibration source level from operation of MTRC Trains;

l Trackform vibration attenuation or amplification;

l Soil-based tunnel vibration reduction;

l Vibration propagation through the ground to the structure foundation;

l Vibration reduction due to the soil/structure interface;

l Vibration propagation through the building and into occupied areas; and

l Conversion from floor and wall vibration to noise.

4.47 The empirical based prediction model used to project noise and vibration level within occupied areas of the structures adjacent to the SDTE is described in detail in Appendix 4.1: Refs 2 and 3. A summary is given below. The basic equation describing the model, in decibels, is

L = FDL + TIL + TOC + TCF + LSR + BCF + BVR + CTN + SAF

where the prediction components are:

L	ground-borne noise level within the structure, re: 20 -Pascal,
FDL	force density level for the KRTC EMU, re: 1 lb/in0.5 in English unit and re: 1 N/m0.5 in SI unit,
TIL	trackform attenuation or insertion loss, relative level,
TOC	turnout and crossover factor,
TCF	vibration coupling between the tunnel and the ground for soil based tunnels, relative level,
LSR	unit force incoherent line source response for the ground, re: 1 -in/sec/(1 lb/in0.5) in English unit and 10^-8 m/s/(1 N/m0.5) in SI unit,
BCF	vibration coupling loss factor between the soil and the foundation, relative level,
BVR	building vibration reduction or amplification within a structure from the foundation to the occupied areas, relative level,
CTN	Conversion from floor and wall vibration to noise, 10^-8 m/s or 10^-6 in/s to 20 Pascal,
SAF	Safety margin to account for wheel/rail condition and projection uncertainties.

4.48 The measurement and analysis equipment used in obtaining these empirical results is given in Appendix 4.4. Predictions are based on assuming the closest distance along the alignment to the building foundation of the receiver.

Description of the Components and Data Sources

Ground-Borne Noise Level within the Structure (L)

4.49 At setback distances characteristic of this study, ground-borne noise from transit trains can have an impact, conservatively, up to about 160 Hz for tunnels situated in soil, and up to 500 Hz for tunnels situated in rock. Above these frequencies, the material attenuation of the ground would reduce the amplitude of the propagating waves below which there would be adverse impact. Thus, structure borne noise levels will be presented in octave bands over the frequency range of 31.5 Hz to 500 Hz. “Feelable” vibration levels will be presented in 1/3 octave bands over the frequency range of 3.15 Hz to 500 Hz.

4.50 In the projection and measurement of ground-borne vibration or noise from transit trains operating at grade, or in tunnels, to receivers adjacent to the alignment, it is customary to calculate or measure the impact of a single train passby, where the vibration or noise level from it is rms (root mean square) averaged over the duration of the passby (Appendix 4.1: Ref. 3). This is, by definition, the equivalent noise or vibration level of the passby, where duration is defined as the period between the passage of the front and rear ends of the train past the closest point on the alignment to the building foundation. This measure is assumed in this study.

Force Density Level (FDL)

4.51 The vibration source strength level (Force Density Level FDL) for train operations on the WIL extension was derived from wayside vibration measurements taken during operation of eight car MTRC M-stock EMU passbys, at grade, and in a tunnel structure. Ground vibration levels were recorded at various setback distances from the track during train passbys at various speeds between 20 kph and 60 kph and during impact hammer tests on the trackform. These measurements are used to determine the vibration source strength for the passing train. A description of the measurements and development of the FDL is given in Appendix 4.5.

4.52 In Appendix 4.5, it is shown that the vibration source level, or the FDL determined for the Metro-Cammell EMU (M-stock) was obtained from train passby and impact hammer test on the at grade Up track through Heng Fa Chuen Depot and Down track tunnel near Po Lam station. The FDL taken for the WIL EMU is the maximum envelope of FDLs obtained at Heng Fa Chuen Depot (Island Line) and Po Lam (Tseung Kwan O Line). Maximum envelope is defined as the maximum levels occurring at all 1/3 octave band frequencies for all passbys considered; it is independent of any one specific passby. The two FDLs and the maximum envelope are given in Appendix 4.5: Figure 8.

Trackform Alternatives and Attenuation (TIL)

4.53 It is a well-known fact that the greater the trackform attenuation, the greater the cost and the engineering complexity. Attenuation has two components: the magnitude of the attenuation and the frequency above which attenuation occurs (resonance frequency of the trackform). Generally, more compliant trackform support and more massive elements in the trackform will result in a greater magnitude of attenuation occurring at lower frequencies. Thus floating slab trackform (FST) will produce significantly more attenuation at lower frequencies than a resilient baseplate. However, greater compliance in the trackform support results in greater mobility of the rail, which requires careful examination of changes in rail geometry under loading, and consideration of associated fatigue and component life expectancy. In addition, more massive trackform elements would take up more space in tunnels and may cause spatial incompatibilities that are difficult to be overcome in the design.

4.54 The approach taken in this study is to try and reduce the number of different trackform types to a minimum, whilst providing the necessary vibration attenuation for satisfaction of the noise and vibration criteria along the alignment. The type of vibration mitigating trackform is often grouped into four categories listed below:

1. Type 1a: A medium attenuation baseplate or booted dual sleepers based on a bonded or non-bonded compression style baseplate with a resilient elastomeric element having static stiffness of about 25 kN/mm, to be fitted atop the concrete sleepers or atop the invert,

Type 1b: Resiliently supported sleepers whose resilient support pad is manufactured from natural rubber and has a static stiffness in the order of 15kN/mm to 20 kN/mm;

2. Type 2: A high attenuation baseplate or booted dual sleepers including

i. a bonded “Egg” style baseplate with a resilient elastomeric element having static stiffness in the range of 7 kN/mm to 14 kN/mm, to be fitted atop concrete sleepers or on the invert;

ii. the Pandrol Vanguard baseplate having static stiffness on the order of 3kN/mm to 5kN/mm; or

iii. resiliently supported sleepers whose resilient support pad is manufactured from natural rubber and has a static stiffness in the order of 8kN/mm to 12 kN/mm - an alternative for tangent, or near-tangent track only.

3. Type 3: An isolated slab trackform (IST), which is a ballast mat with bedding modulus in the order of 20N/mm³ placed beneath an in situ poured concrete slab, with loaded resonance frequency in the order of 20Hz to 25Hz; and

4. Type 4: A floating mini slab trackform (FST) with loaded resonance frequency of about 16Hz.

5. Type 0: Trackform is assumed to be one where no vibration mitigation is required.

4.55 The details of insertion loss of Type 1a and 1b trackform are given in Appendix 4.6.

Tunnel Coupling Factor (TCF)

4.56 Vibration attenuation occurs at the interface between a transit tunnel and the surrounding soil on account of a mismatch in the soil and tunnel wall impedances. Given the same soil, the heavier and stiffer the tunnel, the greater the attenuation. Tunnels borne in rock generally do not exhibit any significant vibration attenuation across the tunnel rock interface. The TCF was examined in detail in a measurement study described in Appendix 4.1: Ref. 5. The approach taken was to measure vibration levels on the ground surface with a linear array of vibration transducers (Appendix 4.7: Photos 1-6) in response to impacting within a tunnel. With the linear array in place, additional measurements were performed during impacting on the ground surface above the tunnel centreline. By obtaining the LSR for both the tunnel and surface impact measurements, and correcting for setback and surface vs. below surface impacting, TCF factors were developed.

4.57 A detailed description of the TCF test utilised in this study can be found in Appendix 4.7. Interestingly, the TCF curve is similar to the BCF curve for type 2 (1-2 storeys residential complexes). The TCF taken for the WIL projection is the maximum envelope of TCF obtained and the type 2 BCF curve (Appendix 4.7: Figure 1).

4.58 No TCF attenuation is applied for rock-founded tunnels. However, with reference to the FTA Manual, a 3dB(A) and 5dB(A) reduction in groundborne noise level was assumed for cut-and-cover tunnels and station structures respectively.

Line Source Response (LSR)

4.59 The LSR determines the vibration levels or attenuation in the ground as a function of distance caused by an incoherent line source of unit force point impacts, with line source orientated along the alignment and the length of the line source equalling that of the train. Thus, the basic quantity required for the determination of the LSR would be the vibration response caused by a unit point source impact, which is defined as the Point Source Response (PSR). Given the PSR along the alignment over the length of the train, the LSR would follow directly by incoherent integration of the PSR over the length of the train.

4.60 However, the determination of the PSR for force point impacts along the alignment over the length of the train is neither practical nor affordable. For example, at underground sections, force impacting would have to be performed in numerous boreholes drilled to the depth of the alignment and closely spaced along the alignment over the length of the train just for the determination of the LSR at one location. Thus, certain assumptions are invoked, which allow one PSR to be taken as representative along the alignment near a building receiver and to be used in the determination of the LSR. These assumptions include:

l The ground is layer-wise homogeneous,

l The ground is transversely isotropic along the alignment over the length of the train,

l The ground is between the alignment segment and the vibration receivers at which the LSR is to be determined.

4.61 If the ground satisfies these assumptions rigorously, it would be acceptable to use one PSR in the determination of the LSR. In normal circumstances, deviation from the idealised assumptions of transverse isotropy and layer-wise homogeneity is not significant enough to warrant the time, expense and impracticality of impacting along the entire length of the train. Also, the flanking effect of vibration from remote cars towards the front and rear of the train is not very significant: it is the vibration from the train section opposite the shortest distance from the track to the receiver that, in most circumstances, determines the vibration level at the receiver.

4.62 A detailed description of the PSR testing along the WIL and the LSR model can be found in Appendix 4.8, where the PSR testing is referred to as borehole impact testing.

Building Coupling Factor (BCF)

4.63 The recommended practice established within the USFTA handbook (Appendix 4.1: Ref 3) was followed. Structures are divided into 4 types, with BCF attenuation given in (Appendix 4.9: Figure 1):

Type 0 – Large structures with heavy foundations

Type 1 – 2-4 storey medium sized structures

Type 2 – 1-2 storey complexes

Type 3 – Single family detached residences

4.64 As shown in Appendix 4.9: Figure 1, larger and heavier structures would have greater vibration attenuation than smaller and lighter structures. In fact, the extent of the attenuation is governed by the difference in mechanical impedance between the soil and the foundation, with the impedance being determined by differences in mass and stiffness within the soil and foundation. For structures founded on rock, there is no impedance contrast between the soil and the foundation; thus, in this case, the BCF is zero.

Building Vibration Response (BVR)

4.65 The building vibration response is generally determined by three factors:

1. Resonance amplification due to floor, wall and ceiling spans;

2. Floor-to-floor attenuation; and

3. Attenuation across a structure, in the direction away from the alignment.

4.66 Resonance amplification due to wall, floor and ceiling spans is usually an issue for small, lightweight housing, generally single-family homes constructed of wood. The frequencies at which resonances occur can vary widely, and the magnitude of the resonance amplification would depend on the structure (Appendix 4.1: Ref. 6). In large and heavy framed structures, generally multi-floor concrete construction, structural resonances usually occur at sub-audible frequencies, with small resonance amplification due to massive structural elements having low mobility.

4.67 The FTA Handbook (Appendix 4.1: Ref. 3) recommends that the BVR includes no correction for heavy framed structures, a 3 dB correction for moderate weight structures and a 6 dB correction for lightweight structures to account for structural resonances that may be present in smaller and less massive structures located along the alignment. Lightweight structure refers to hollow block, lightweight concrete, brick, timber or composite structures of only several storeys high. A moderate weight structure is generally lightweight concrete construction up to 6 or 7 storeys. As the frequency at which such resonances may occur is not known, these corrections add either 3 or 6 dB to all relevant frequency bands in which building resonance may occur.

4.68 From past experience, structural resonance in the order of 3 to 6 dB occurring in moderate and heavyweight structures, which characterise most of the buildings along the WIL alignment. Structural resonance has been observed to be significantly higher than 6 dB in some types of lightweight structures, especially single-family residences constructed of wood, which are not the types of buildings found along the WIL alignment. Thus, the BVR given in Appendix 4.10: Figure 1 is applied to all structures, which is an extended version of the 6 dB rule across the frequencies of 20Hz to 40Hz, as recommended by Appendix 4.1: Ref. 3 for light weight structures.

4.69 Usually, occupied spaces within a structure are assumed to be located at or above the nearest setback distance from the alignment to the receiver. However, vibration attenuation across a structure may be relevant where the noise sensitive area is situated in the back of the building away from the alignment. Although vibration attenuation has been measured across a number of structures in Hong Kong, this attenuation is considered conservatively in this study.

4.70 A floor-to-floor attenuation of 2 dB reduction per floor is assumed (Appendix 4.1: Ref. 3). Where there is multi-floor occupancy, only the structure borne noise impact on the lowest occupied floor is considered.

Turnout and Crossover Factor (TOC)

4.71 At points and crossings, where the wheel transitions from one rail to another, the sudden loading/unloading of the leading and trailing rails results in increased broad band vibration levels over that of plain line continuous rail. In addition, it is not possible to machine grind the rails through either the points or crossings, so surface deterioration, compared with that of the place track, is often evident.

4.72 The increase in vibration level at turnouts and crossings is not easily characterized. For standard level turnouts and crossings receiving average maintenance, the USFTA handbook (Appendix 4.1: Ref 3) recommends a correction of 10dB. For modern inclined turnouts in good condition, where impact loads are lessened, it was found through measurement that a correction of 5dB is often more appropriate. In this study, 5dB(A) and 10dB(A) adjustment were added for inclined and vertical turnouts respectively. The adjustment factor for inclined turnout was determined based on measurement results (refer to Appendix 4.12),

Conversion to Noise (CTN)

4.73 A +2 dB correction for conversion of vibration (re: 10^-6 in/s) in room walls, floors and ceiling to noise (re: 20 micro Pa) is assumed (Appendix 4.1: Ref 3 and 7).

Safety Factor (SAF)

4.74 In the determination of the components of the prediction model, data undergoes extensive averaging, thus making the overall prediction of ground-borne noise and vibration a sum of averages. In many of our comparisons of predicted and measured levels, it has been generally found that differences in predicted and measured noise levels often fall within about ±5dB, not taking into account variability introduced by the condition of rail and wheel running surfaces, which in large part determines the FDL. Occasionally, predictions vary by as much as ±10dB. Thus if noise criteria are regarded as simple design guidelines, no safety factor would be appropriate. If most passbys were expected to produce noise levels below criteria, then a safety factor of 5 dB would be appropriate. If strict adherence of every passby to noise criteria is expected, then a safety factor of 10dB or more would likely be appropriate. In this study, a conservative 10dB safety factor is used that has been adopted for ground-borne assessment for approved Kowloon Southern Link EIA and strict adherence to Criteria is expected under the NCO.

Calculation of the NCO Criterion Noise Level (L_{eq 30min})

4.75 Predicted Noise Level L_Aeq(30min) = SEL for a passby + Tailing Effect + 10*log(number of passby in 30min) – 10*log(1800s)

4.76 SEL (Sound Exposure Level) for a passby is determined by adding the 10*log(passby duration in seconds) to the L_Aeq(passby). The passby duration in seconds is obtained by Train Length (194m) / Speed of train (m/s). Additional 3dB is added for head-tail effect. 30-minute SEL is obtained by adding the 10log(number of passby in 30 minutes) to the L_Aeq(passby). The prediction is based on eight-car train consists operating at a minimum headway of 3 minutes (assumed night time headway). The final predicted noise level L_Aeq(30min) is obtained by subtracting the projected 30-minute SEL by 10log(1800s).

4.77 In this study, maximum nighttime train frequency was assumed to be 3 minute in each direction and the train types is assumed to be similar to trains being used in urban line with 8-cars, i.e. total length 200m.

Prediction of Results

Construction Phase

4.78 Ground-borne noise projections associated with TBM operation have been predicted under the assumption of worst-case scenario along eight segments of the WIL alignment, and the results are summarised in Table 4.7 and the detailed sample calculations for selected receivers are given in Appendix 4.11.

Table 4.7 Predicted Overall A-weighted Noise Level for Tunnel Boring

Construction GBNSR No.	Tunnel Founding	Tunnel Depth^(1) (m)	Predicted Overall Noise Levels (dB(A))	Criteria^(2)Achieved?
1	Mixed face	24	52.9	Yes
2 & 3	Rock	31	54.3	Yes
4*, 5, 6, 7, 8, 21*, 24 & 25	Rock	47	45.6	Yes
9*, 10 & 11*	Rock	71	34.7	Yes
12*, 13, 14*, 15*, 16 & 23*	Rock	47	41.0	Yes
17, 22	Rock	80	27.2	Yes
18, 19* & 20	Rock	40	49.1	Yes
26	Mixed face	18	60.6	Yes

* GBNSR is an educational institution.

⁽¹⁾ Tunnel Depth is the depth from ground surface to the top of tunnel.

⁽²⁾ Ground-borne noise criteria for educational institution is 60dB(A) during day time (0700-1900) weekday and 55dB(A) during examination period. For other GBNSR, the criteria is 65 dB(A) during daytime weekday.

4.79 From Table 4.7, ground-borne construction noise levels at construction GBNSR No.1-26 would comply with the day time (0700-1900) noise criteria of 60/65 dB(A). Adverse ground-borne construction noise impact due to the use of TBM would not be envisaged.

4.80 Ground-borne noise impacts from hydraulic breakers, drill rig and pile rig to the nearby sensitive receivers were predicted, and the prediction results are summarized in Table 4.8a & b. It was assumed in the calculation that the hydraulic breaker, drill rig and pile rig would not operate simultaneously. Detail calculation and assumptions for each GBNSR are provided in Appendix 4.3.

Table 4.8a Predicted Construction Ground-borne Noise Impact Associated with the PME Use at Open Works Areas

Construction GBNSR No.	Description	Predicted Ground-borne Noise Levels Leq(30mins), dB(A)			NCO Criteria for daytime (0700-1900)	Criteria Achieved?
		Breaker	Drill Rig	Pile Rig
27	Hong Kong Institute of Vocation Education (Kennedy Centre)	48	53	55	60	Yes
28	Luen Tak Apartment	44	49	50	65	Yes
29	Kam Po Mansion	48	54	55	65	Yes
30	Pokfield Garden	55	60	62	65	Yes
31	The Belcher’s Tower 3	53	58	59	65	Yes
32	39 Hill Road	55	60	62	65	Yes
33	Western Court Block 1-4	59	64	65	65	Yes
33a	The Kadoorie Biological Sciences Building	50	55	56	60	Yes
34	Kiu Shing Building	55	60	62	65	Yes
35	Bon-Point	55	60	62	65	Yes
36	Queen’s Hotel	55	60	62	65	Yes
37	College View Mansion	55	60	62	65	Yes

Table 4.8b Predicted Construction Ground-borne Noise Impact Associated with the PME Use for Construction of Adits

Construction GBNSR No.	Description	Predicted Ground-borne Noise Levels Leq(30mins), dB(A)		NCO Criteria for daytime (0700-1900)	Criteria Achieved?
		Breaker	Rock Drill
UNI
38	Bowie Court	41	46	65	Yes
39	Intelligent Court	52	57	65	Yes
40	Sik On Building	46	51	65	Yes
31	The Belcher’s Tower 3	39	44	65	Yes
41	Yick Fung Garden	46	51	65	Yes
42	Wing Fu Lau	46	51	65	Yes
SYP
34	Kiu Shing Building	29	34	65	Yes
36a	6-28 Eastern Street	46	51	65	Yes
43	Tat Hing Building	58	63	65	Yes
44	Yee Shun Building	37	42	65	Yes
45	Jade Court	42	47	65	Yes
46	21-23 High Street	44	49	65	Yes
47	Sun Luen Building	40	45	65	Yes

4.81 As shown in Table 4.8a & b, construction ground-borne noise levels at construction GBNSR No. 27-47 would comply with the day time (0700-1900) noise criteria of 60/65 dB(A). Adverse ground-borne construction noise impact due to the use of PME at open works areas would not be envisaged.

4.82 In case of any construction activities during restricted hours (1900-0700), it is the Contractor’s responsibility to ensure compliance with the Noise Control Ordinance (NCO) and the relevant technical memoranda. The Contractor will be required to submit construction noise permit (CNP) application to the Noise Control Authority and abide by any conditions stated in the CNP, should one be issued.

Operation Phase

4.83 The predicted operational ground-borne noise results are summarised in Table 4.9 and detailed sample calculations demonstrating the predicted ground-borne noise for selected receivers are shown in Appendix 4.11.

4.84 Exceedance of night-time criterion of 45dB(A) was predicted at Operational GBNSR No. 1, 2, 3, 5 and 9. For Operational GBNSR No. 1, 2 and 9, exceedance would mainly be due to the turn-out located underneath which would increase the vibration level.

Table 4.9 Summary of Operational Ground-Borne Noise Impact Assessment (without mitigation measure)

GBNSR No.	Location	dB(A) Leq,30mins		Criteria Achieved?
		NCO Nighttime Criteria	Unmitigated
1	Luen Yee Building	45	58	No
2	Hongway Garden	45	59	No
3	Kian Nan Mansion, 81-85 Bonham Strand West	45	49	No
4	No. 36 Eastern Street, West Point	45	40	Yes
5	Po Shu Lau, Tse, 35-43 Sands Street	45	55	No
6	Tower 1, University Heights	45	42	Yes
7	Block D, Kwun Lung Lau	45	43	Yes
8	Kwun Lung Lau New Development Site	45	39	Yes
9	East Terrace, Sai Wan Estate	45	58	No
10	Tower 3, Academic Terrace	45	38	Yes

Cumulative Impacts to Reflect Worst Case Scenarios

4.85 No cumulative impacts would be expected during the construction phase and the existing MTR Island line during the operation phase.

Mitigation of Adverse Environmental Impacts

4.86 During construction phase, the TBM tunnel construction method would be feasible and designed to achieve the NCO criteria, with possible operational prohibition during night time hours near SHW and UNI stations.

4.87 During the operation of WIL, the groundborne noise levels predicted at operational GBNSRs No. 1, 2, 3, 5 & 9 would exceed night-time criterion of 45dB(A) and mitigation measures would be required.

4.88 It is recommended Type 1a Trackform – Resilient Baseplate with stiffness of about 25 KN/mm to be installed at both the west and east bounds starting from Luen Yee Building (GBNSR1) to the alignment before West Point (GBNSR4) and also the alignment starting from Tower 3 of Academic Terrace (GBNSR10) to Sai Wan Estate (GBNSR9). Mitigated operational ground-borne noise levels are presented in Table 4.10 and the proposed trackform are shown in Figure 4.7 & 4.8. Sample calculation is provided in Appendix 4.11.

Table 4.10 Summary of Operational Ground-Borne Noise Impact Assessment (with mitigation measure)

GBNSR No.	Location	dB(A) Leq,30mins		Mitigation	Criteria Achieved?
		Criteria	mitigated
1	Luen Yee Building	45	43	Inclined Turnout, type 1a resillient baseplate	Yes
2	Hongway Garden	45	44	Inclined Turnout, type 1a resillient baseplate	Yes
3	Kian Nan Mansion, 81-85 Bonham Strand West	45	39	Type 1a resillient baseplate	Yes
5	Po Shu Lau, Tse, 35-43 Sands Street	45	44	Type 1a resillient baseplate	Yes
9	East Terrace, Sai Wan Estate	45	42	Inclined Turnout, type 1a resillient baseplate	Yes

4.89 The assessment results indicated that the ground-borne noise levels at operational GBNSR No.1, 2, 3, 5 & 9 would comply with the NCO Criteria after mitigation.

4.90 The currently proposed Type 1a resilient baseplates can be replaced by Type 1b or Type 2 where practicable and necessary to accomplish a further 3-6dB(A) noise reduction as a contingency measure (Type 1b and Type 2 baseplates would not be suitable at turnouts due to maintenance and safety concerns). Changing of the tunnel dimensions would not be required if these contingency measures have to be in place. Further measurements would be conducted to check the accuracy of the noise prediction after the tunnel construction where necessary.

Environmental Monitoring and Audit

Construction Phase

4.91 An Environmental Monitoring and Audit (EM&A) programme is recommended to be established according the predicted ground-borne noise generating construction activities. The measurement locations shall be above the cutting face of the TBM, and shall be located as close to the cutting face as practicable. Details of the EM&A requirements are provided in a stand-alone EM&A Manual.

Operation Phase

4.92 Prior to the operation phase of the Project, a commissioning test should be conducted to ensure compliance of the operational airborne noise levels with the EIAO-TM noise criteria. Details of the test requirements are provided in a stand-alone EM&A Manual.

Conclusion

4.93 For the construction phase, the drill and blast construction option is not considered with respect to noise annoyance, as the duration of blasting is very short and infrequent. No assessment has been carried out regarding noise annoyance impacts within any of the identified sensitive receivers.

4.94 The TBM tunnel construction method would be feasible and designed to achieve the NCO noise criteria, with possible operational prohibition during night time hours near SHW and UNI stations. Ground-borne construction noise impacts pertinent to the use of breaker, drill rig and pile rig at open works areas, adits and vent shaft were also found to comply with relevant criteria of NCO. Overall, no adverse ground-borne construction noise impacts were predicted.

4.95 During operation phase, projections of ground-borne noise at identified GBNSR have been performed, based on a methodology recommended by the US Department of Transportation and assuming an additional 10 dB safety factor, using vibration measurements taken during operation of eight-car MTRC M-stock EMU passbys, at grade, and in a tunnel structure. The entire WIL railway design is predicted to meet the NCO criteria with installation of resilient baseplate from Luen Yee Building (GBNSR1) to the alignment near West Point (GBNSR4) and also the alignment starting from Tower 3 of Academic Terrace (GBNSR10) to Sai Wan Estate (GBNSR9).

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[1] Transit Noise and Vibration Impact Assessment. Report No. FTA-VA-90-1003-06

[2] KCRC, KSL GSA 5100 Environmental Impact Assessment & Associated Services Environmental Impact Assessment Report. 2005. (EIA Register No. AEIAR-083/2005)

[3] P. M. Nelson. Transportation Noise Reference Book. 1987.