8.1.1.1 Construction ground-borne noise impact may occur along the majority of the KTE tunnel alignment. During construction, ground-borne noise could arise from hydraulic breakers, pipe pile rigs and drilling rigs during excavation. Other construction activities involving concreting, road paving and lorry movements are not anticipated to generate any significant ground-borne noise impacts.
8.1.1.2 Drill-and-blast activities are not considered as noise annoyance, as the duration of the blasting is very short and infrequent. As such, no assessment for blasting noise has been carried out for the identified sensitive receivers. In addition, if any blasting operations are required they would be carried out outside sensitive hours to avoid impacts to the nearby NSRs.
8.1.1.3 During the operation of railway systems, ground-borne noise arises from trains running on tracks which give rise to vibration propagating parallel to the ground surface as wave modes of layered ground. The vibration may enter the building structure causing vibration in building elements. At higher frequencies (30-200Hz), ground vibration may excite bending resonances in the floors and walls of buildings which then radiate a rumbling noise directly into rooms. This ground-borne noise is especially associated with tracks in tunnels where it occurs without masking from direct air-borne noise.
8.2.1
Construction Phase
8.2.1.1 The ground-borne construction noise during 0700-1900 except public holidays and Sundays is under the control of the EIAO. Under the IND-TM, 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 criteria applied for the KTE ground-borne noise assessment are summarised in Table 8.1.
Table 8.1: Construction
Ground-borne Noise Criteria
|
Noise Sensitive Receiver
(NSR) Description |
Ground-borne Construction Noise Criteria, dB(A) |
||||||
|
Daytime (0700-1900 hrs) |
Daytime
during general holidays and Sundays and all days during Evening |
Night-time |
|||||
|
A |
B |
C |
A |
B |
C |
||
|
Education
institutions |
60/55 [a] |
50 |
55 |
60 |
[b] |
||
|
Domestic
premises, hotels, hospitals and clinics |
65 |
50 |
55 |
60 |
35 |
40 |
45 |
|
Churches/temples,
libraries and courts |
60 |
50 |
55 |
60 |
[b] |
||
Note: [a] A
5dB(A) reduction to the ground-borne noise criteria is recommended for schools
during examination period.
[b] No sensitive use during this period.
8.2.1.2 In the evening (1900 – 2300hrs) and night-time (2300 – 0700hrs), the TM on Noise from Construction Work other than Percussive Piling (GW-TM) applies if no Specified Powered Mechanical Equipment (SPME) is used. Following the above principle, the ground-borne noise criteria are limited to 10dB(A) below the respective ANLs for the Area Sensitivity Rating category at the Noise Sensitive Receivers (NSRs). A summary of these criteria is also given in Table 8.1. A Construction Noise Permit (CNP) is required for construction works during restricted hours and detailed assessment will not be covered in this EIA.
8.2.1.3 For construction works involving the use of SPME during restricted hours, the DA-TM is in force and a CNP is required. Detailed assessment will not be covered in this EIA assessment.
8.2.2
Operational Phase
8.2.2.1 With reference to the Technical Memorandum on Noise from Places other than Domestic Premises (IND-TM) under the NCO, the noise transmitted primarily through the structural elements of buildings should be 10dB(A) less than the relevant criteria. The relevant criteria for ground-borne railway noise assessment are the limits given in Table 2 of the IND-TM based on appropriate Area Sensitivity Ratings (ASRs) at the assessment points and presented in Table 8.2.
Table 8.2 Ground-borne Operation Noise Criteria
|
GBNSR Description |
Ground-borne Noise Criteria, dB(A) |
|||||||
|
Daytime and Evening time (0700 to 2300 hrs) |
Night-time |
|||||||
|
A |
B |
C |
A |
B |
C |
|||
|
Schools –
classrooms, churches/temples, libraries and courts |
50 |
55 |
60 |
[a] |
||||
|
Domestic
premises, hotels, hospitals and clinics |
50 |
55 |
60 |
40 |
45 |
50 |
||
[a] No sensitive use during this period.
8.2.2.2 In setting the noise criteria for the NSRs, it has been assumed that there are no influencing factors (IF) affecting the NSRs. Since ground-borne noise affects internal areas, it is likely that there will be occupied spaces within the buildings which will not be affected by the IF, for example on the other side of the building or where not on a building façade. As such, in this assessment, an ASR of A or B has been assigned for the NSRs.
8.3.1.1 The KTE alignment is located within a densely populated urban area with residential buildings and schools, and there would be a number of NSRs within the vicinity of the alignment that could be affected by ground-borne noise as summarised in Table 8.3 below and Figures 8.1 to 8.7. Details of the NSRs included in this assessment, including the use of the building, number of floors and respective distance from nearest works site, are provided in Appendix 8.1.
Table 8.3: Representative Ground-borne NSRs
|
Ref |
NSR |
Construction |
Operation |
|
1 |
|
|
Y |
|
2 |
New King's Hotel |
|
Y |
|
3 |
|
|
Y |
|
4 |
Tang's Mansion |
|
Y |
|
5 |
|
Y |
Y |
|
6 |
|
Y |
Y |
|
7 |
Eaton Hotel |
Y |
Y |
|
8 |
Labour Tribunal |
|
Y |
|
9 |
Diocesan Girl's |
|
Y |
|
10 |
|
|
Y |
|
11 |
|
Y |
Y |
|
12 |
Primary School at |
Y |
Y |
|
13b |
Parc Palais Block 3 |
|
Y |
|
14 |
Shun Man House, Oi Man Estate |
|
Y |
|
15 |
|
|
Y |
|
18 |
Yee Fu Building |
|
Y |
|
20 |
Caritas Bianchi |
Y |
Y |
|
21 |
Lok Ka House |
|
Y |
|
24 |
Top |
|
Y |
|
25 |
|
|
Y |
|
26 |
Block R, Wing Fu Building, Whampoa Estate |
|
Y |
|
29 |
Block 9, Bauhinia Mansions,
Whampoa Garden Site 11 |
|
Y |
|
30 |
Block 1, |
|
Y |
|
34 |
|
|
Y |
|
35 |
|
|
Y |
|
36 |
Harbourfront Landmark |
|
Y |
|
40 |
Residential Building, Ho Man Tin Station Development
(Planned Future NSR) |
|
Y |
|
41 |
Residential Building, Dormitory for The |
|
Y |
|
44 |
|
Y |
Y |
|
45 |
|
|
Y |
|
62 |
|
Y |
Y |
8.4.1.1 Construction of the KTE project would be on-going between early 2011 and 2015 with its commissioning in 2015. In addition to the KTE project itself, there are various other projects that are planned to be constructed concurrently and these have been taken into account in the construction air-borne noise assessment. Details of the KTE project construction programme and the concurrent projects have been provided in Section 3 of this EIA Report and summarised below:
· The planned dormitory of the Hong Kong Polytechnic University (construction period: 2009-2012) – There is currently no detailed information on the construction works available for the assessment and, as such, this concurrent project has not been assessed for any cumulative impacts with the KTE project (Figure 3.19);
·
· Shatin to Central Link – Tai Wai to Hung Hom Section (tentative construction period: 2011-2015) – There are proposed to be the works sites for the cut-and-cover tunnel for the construction of SCL – Tai Wai to Hung Hom Section near Chatham Road North which are in the immediate neighbourhood of the southern end of the works sites for HOM Station of the KTE project as shown in Figures 3.21 and 3.22. The assessment of the cumulative impacts has been based on the best available information during the time of submission and any changes to the programmes of the concurrent projects will be reflected in the subsequent submissions for those projects;
· Shatin to Central Link – Mongkok East to Hung Hom Section (tentative construction period: 2011-2018) – There would be some works sites proposed for the cut-and-cover tunnel of the SCL – Mongkok East to Hung Hom Section near the existing East Rail Line (EAL) adjacent to Princess Margaret Road and Oi Man Estate which are close to the works sites of the KTE project for HOM Station as shown in Figure 3.23. The assessment of the cumulative impacts has been based on the best available information during the time of submission and any changes to the programmes of the concurrent projects will be reflected in the subsequent submissions for those projects. In addition, as SCL – Mongkok East to Hung Hom Section will also share the same barging point at Hung Hom Finger Pier cumulative construction air-borne noise impact at Harbourfront Horizon have also been assessed;
· Essential Public Infrastructure Works (EPIW) for the KTE project (tentative construction period: 2011-2015) – There would be some works sites allocated for the construction of the EPIW including subways and footbridges connecting HOM Station and Oi Man Estate and Ho Man Tin Estate, Public Transport Facilities along Chung Hau Street at the northwest of HOM Station and a covered footbridge stretching from HOM Station over Yan Fung Street, Chatham Road North and above the existing footbridge as shown in Figure 3.24. As these works will be concurrent to the KTE project. However, only construction ground-borne noise from the subway construction is anticipated. However, as there are no NSRs identified for ground-borne noise assessment in the close proximity of the subway works site, the EPIW have not been included in the assessment for cumulative construction ground-borne noise impacts.
8.4.1.2 The KTE will, also, run close to the other existing and planned rail lines, as follows:
· The existing TWL at YMT Station. Ground-borne noise from TWL operation would be insignificant and so cumulative impact from TWL is not anticipated;
· At HOM Station, there is an interchange with the future SCL – Tai Wai to Hung Hom Section. The cumulative impacts at this location will be assessed based on the results adopted from the SCL – Tai Wai to Hung Hom Section EIA study; and
· Between YMT Station and HOM Station, the existing EAL which is to be realigned as part of SCL – Mongkok East to Hung Hom Section will run at grade. Ground-borne noise is not relevant and, therefore, there will be no cumulative ground-borne noise impact associated with EAL and SCL – Mongkok East to Hung Hom Section during operation phase.
8.5.1
Construction Phase
Background
8.5.1.1 Details of the construction methodologies and programme have been given in Section 3 of this EIA report. Potential ground-borne noise impacts on NSRs during the construction phase will arise mainly from hydraulic breakers, pipe pile rigs and drilling rigs used in the excavation works. Other construction activities such as drilling and blasting in tunnel construction, lorry movement, concreting, road paving etc are unlikely to generate significant ground-borne noise. Air-borne construction noise of these activities has been addressed in Section 7 of this EIA Report.
8.5.1.2 It is anticipated that the rock breaking activities by large hydraulic breakers would represent the worst case for ground-borne noise impact. Pipe pile rigs are required for the construction of pipe-pile wall and drilling rigs are also proposed to be used in rock excavation. The method used to predict construction ground-borne noise is based on the U.S. Department of Transportation “High-Speed Ground Transportation Noise and Vibration Impact Assessment”, 1998. The vibration level Lv,rms at a distance R from the source is related to the vibration source level at a reference distance Ro. The conversion from vibration levels to ground-borne noise levels is determined by the following factors:
Cdist : Distance
attenuation
Cdamping : Soil
damping loss across the geological media
Cbuilding : Coupling
loss into building foundation
Cfloor : Coupling
loss per floor
Cnoise : Conversion
factor from floor vibration levels to noise levels
Cmulti : Noise
level increase due to multiple sources
Ccum : Cumulative effect due
to neighbouring sites
8.5.1.3 The predicted ground-borne noise level Lp inside the noise sensitive rooms is therefore given by the following equation.
Lp = Lv,rms + Cdist + Cdamping
+ Cbuilding + Cfloor + Cnoise + Cmulti
+ Ccum
Reference Vibration Sources
8.5.1.4 Reference vibration sources were adopted from Appendix 7-1 of the KSL EIA Report. The source vibration levels are shown in Table 8.4 below.
Table
8.4: PME Vibration Source
Levels
|
Plant |
Vibration (rms) at the
reference distance 5.5m from source |
Vibration (ppv) at distance
2m from source |
|
Drilling Rig |
0.536mm/s |
- |
|
Hydraulic Breaker |
0.298mm/s |
- |
|
Pipe-piling Rig |
- |
19.3mm/s |
Soil Damping
8.5.1.5 Internal losses of soil 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[[1]].
V(R) = V(Ro) ´ e-2p f h R/2c
8.5.1.6 The velocity amplitude V is dependent on the frequency f in Hz, the soil loss factor h, 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 8.5.
Table 8.5: Wave Propagation
Properties of Soil
|
Soil Type |
Longitudinal Wave Speed c, m/s |
Loss Factor, h |
Density, g/cm3 |
|
Soil |
1500 |
0.5 |
1.7 |
|
Rock |
3500 |
0.01 |
2.65 |
8.5.1.7 It is assumed that no damping attenuation would be applied for propagation in rocks. Therefore, soil damping for NSRs with piling foundation on rockhead would not be required.
Coupling Loss into Building
Structures
8.5.1.8 This parameter represents the change in the incident ground-surface vibration due to the presence of the piled building foundation. The empirical values have been based on the guidance set out in the Transportation Noise Reference Book are given in Table 7-3 as detailed in Table 8.6.
Table 8.6: Coupling Loss Factors
for Building Structures
|
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
8.5.1.9 This represents the floor-to-floor vibration transmission attenuation. In multi-storey buildings, a common value for the attenuation of vibration from floor-to-floor is approximately 1dB attenuation in the upper floor regions at low frequencies and greater than 3dB attenuation at lower floors at high frequencies. Coupling loss of 2dB reduction per floor is assumed for a conservative assessment.
Conversion to Noise (CTN)
8.5.1.10 A -27dB correction for conversion of vibration (re: 10-9m/s) in room walls, floors and ceiling to noise (re: 20mPa) has been assumed in this study. This adjustment is based on a typical residential building. There will be some buildings which will have larger spaces or more sound absorption, but which will be of the same building elements, and these may result in a slightly greater adjustment. However, to be conservative for these buildings, the -27dB adjustment has been adopted for all buildings.
Multiple PMEs and Other
Assumptions
8.5.1.11 It is understood that multiple PMEs will be used during the construction period. However, since the calculation refers to the vibration source of each stroke, the estimated noise level would refer to the Lmax instead of the Leq. Thus, on the basis that it is unlikely that multiple PMEs would strike and present a source of vibration which would reach the NSRs at the same moment, the multiple vibration sources have been assumed to not be cumulative.
8.5.1.12 However, the noise source distances have been taken at the closest point of excavation to represent the worst case scenario. In view of this assessment approach, it is expected that the estimations would reflect a realistic situation.
8.5.2
Operation Phase
Background
8.5.2.1 The methodology for the vibration and ground-borne railway noise impact assessment is in accordance with the procedures outlined in The Transit Noise and Vibration Impact Assessment[[2]] published by U.S. Department of Transportation Federal Transit Administration (FTA) (FTA Guidance Manual) for detailed vibration analysis. This is the methodology as used for the previously approved West Island Line (WIL) EIA Study[[3]],. The ground-borne noise level at NSRs was calculated as follows:
L = FDL + TIL + TOC + TCF + LSR + BCF + BVR + CTN + SAF
where:
L = ground-borne noise level, in dB re 20μPa
FDL = Force density level, in dB re 1N/m0.5
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 = line source transfer mobility, in dB re 10-9 (m/s)/(N/m0.5)
BCF = adjustment to account for building coupling loss, in dB
BVR = building vibration amplification within the structure, in dB
CTN = conversion from vibration to noise within the building, in dB
SAF = safety factor to account for wheel/rail condition and uncertainties in ground conditions, in dB
Rail Operation Assumptions
8.5.2.2 Information relating to the proposed operation which is relevant to the prediction of ground-borne noise is presented in Table 8.7 below.
Table 8.7: KTE Operational Information
|
Issue |
Details |
|
Train type |
M-stock or
K-stock |
|
Maximum
speed |
80km/h |
|
Minimum
radius |
300m |
|
Worst case
headway |
0600 to
0100, except peak periods 210s Peak
periods 105s |
|
Worst case
hourly movements each way |
0700 to
2300 34.3 2300 to
0700 17.1 24
hour 25.0 |
|
Turnout
locations |
Up – 8380
& 8497 Down –
8359 & 8476 |
8.5.2.3 All train movements would be from YMT Station to WHA Station during non-peak periods, but during the morning and afternoon peak periods, all train movements would be from YMT Station to HOM Station with only 50% of train movements continuing to WHA Station. Those trains stopping at HOM Station would turn around on the turn back.
8.5.2.4 The tunnel will be mostly through rock, with some in soil. The existing section of rail from YMT station, up to chainage 10000, is supported on relatively stiff baseplates of stiffness approximately 60kN/mm. The new track is proposed to be a direct fix system, with direct fixation baseplates (vertical stiffness approximately 25kN/mm) as the fixing method. This new fixation system will provide much higher vibration attenuation than the existing track. Upgraded trackforms will be considered if noise exceedances are predicted.
8.5.2.5 The trains to run on the extension will be the same as those currently running on the KTL, that is M-stock and K-stock trains of length 194m. As a worst case, the number of movements has been assumed to be the capacity of the system at daytime and evening and half this at night, with no train movements between 0100 and 0600 hours, as shown in Table 8.7.
8.5.2.6 The speed profiles for the operation are shown in Figure 8.8.
Ground-borne Noise Level within
Structure (L)
8.5.2.7 Train-induced ground-borne noise would have an impact with frequency, conservatively up to about 160Hz and 400Hz for tunnels situated in soil and rock respectively. 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, ground-borne noise levels are presented below in 1/3 octave bands over the frequency range of 12.5Hz to 400Hz for selected receivers.
Force Density Level (FDL)
8.5.2.8
The vibration source strength
level (FDL) for train operations on the KTE were taken as the upper envelope +2
standard deviations level derived from wayside vibration measurements taken
during operation of eight car M-stock Electric Multiple Units (EMU) pass-bys,
at grade, and in a tunnel structure (as reported in the WIL EIA Study). Ground vibration levels were recorded at
various setback distances from the track during train pass-bys at various
speeds between 20kph and 60kph and during impact hammer tests on the
trackform. The measurements were used to
determine the vibration source strength for the passing train. These FDL values are shown in Figure 8.9. As indicated in the WIL EIA Study,
Ground-borne Noise and Vibration Study, the adopted M-stock FDL is higher than
the values measured for other trains in
8.5.2.9 The FDL value is dependent on the speed of the train, and in accordance with the FTA Manual, the FDL has been adjusted for speed as 20 log S/Sref (where Sref is the reference speed at which FDL was measured, 80km/h).
8.5.2.10 The adopted FDL is based on operation on partly worn rails, consistent with MTR Corporation’s normal maintenance procedure. Since it is proposed that the system will continue to be maintained, this level represents the best assumption for analysis, and the ground-borne noise mitigation measures will be based on it. Deterioration beyond this is unlikely.
Turnout and Crossover Factor (TOC)
8.5.2.11 At turnouts, often associated with 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. While it is not possible to machine grind the rails through either the points or crossings, surface deterioration would often be evident. For standard level turnouts and crossings receiving average maintenance, the FTA Manual recommends a correction of 10dB. For modern inclined turnouts in good condition, where impact loads are lessened, a correction of 5dB would be appropriate. In the recent WIL EIA Study, 5dB(A) and 10dB(A) adjustments were added for inclined and vertical turnouts respectively. With all turnouts being inclined for this project, a 5dB factor has been adopted.
8.5.2.12 Each turnout is substantially shorter than a train, and a length of 20m has been adopted. Only the 20m section on turnout is increased by 5dB with the rest of the train remaining at non-turnout levels. Since the Lmax levels are a function of the full train length, this means that, even though an increase of 5dB has been adopted for each turnout, the increase in Lmax levels at the nearby NSRs is normally less than 5dB. The actual increase depends on the proximity of the turnout to the NSR. Since the Leq levels are calculated from the Lmax levels, the increase in Leq levels due to the turnout is also less than 5dB.
Trackform Alternatives or
Insertion Loss (TIL)
8.5.2.13 Attenuation provided by trackform has two components: the magnitude of the attenuation and the frequency above which attenuation occurs (resonance frequency of the trackform). Generally, more compliant trackform supports and more massive elements in the trackform will result in a greater magnitude of attenuation occurring at lower frequencies. Thus, floating slab track (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.
8.5.2.14 The type of vibration mitigating trackform is often grouped into four categories as listed below:
· Type 1: A medium attenuation baseplate based on a bonded or non-bonded compression style baseplate with a resilient elastomeric element having static stiffness of about 25kN/mm, to be fitted atop the invert;
· Type 2: A high attenuation baseplate including:
-
a
bonded “Egg” style baseplate with a resilient elastomeric element having static
stiffness of approximately 14kN/mm, to be fitted atop the invert; and
-
the
Pandrol Vanguard baseplate having static stiffness on the order of 3kN/mm to
5kN/mm;
· 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
· Type 4: A mini FST with loaded resonance frequency of about 16-20Hz.
8.5.2.15 In the KTE project, a medium attenuation type 1 trackform is proposed as the standard (baseline) for all new track. For the existing track near YMT station, up to chainage 10000, the existing baseplates are stiffer than type 1, 60kN/mm.
8.5.2.16 The ground-borne noise levels at NSRs were calculated initially with standard Direct Fixation Baseplate (type 1) for all new track and with stiffer baseplates (60kN/mm) for the existing track (up to chainage 10000). Where noise exceedances were predicted, low noise trackforms were considered. For the existing track, the first upgrade considered was type 1 and for the new track the first upgrade considered was type 2. However, as discussed below no upgrade has been necessary to meet the criteria.
8.5.2.17 The insertion loss values adopted for medium attenuation baseplates (25kN/mm) and the existing 60kN/mm baseplates are shown in Figure 8.10, relative to rigid system.
Tunnel Coupling Factor (TCF)
8.5.2.18 TCF is the vibration coupling between the tunnel and the ground for soil based tunnels. 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. The TCF to be adopted in this study was referenced from the previously approved EIA studies such as WIL EIA Study. In general, tunnels borne in rock generally do not exhibit any significant vibration attenuation across the tunnel rock interface, thus no TCF attenuation is applied for rock-founded tunnels. However, with reference to the FTA Manual, a 3dB(A) and 5dB(A) reduction in ground-borne noise level was assumed for cut-and-cover tunnels and station structures respectively in soil.
8.5.2.19
For bored tunnels in soil,
separate tests have been carried out in
Line Source Response (LSR)
8.5.2.20 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 a line source orientated along the alignment. 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 that the PSR would be along the alignment, the LSR would follow directly by incoherent integration of the PSR values. However, the determination of the PSR for force point impacts along the alignment over the length of the alignment is not practical. 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. 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:
· Ground is layer-wise homogeneous; and
· Ground is transversely isotropic along the alignment over the length of the train.
8.5.2.21 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 alignment.
8.5.2.22
LSR has already been measured
in
8.5.2.23 LSR values depend on the depth of the tunnel and the depth of the rock head, and to a lesser extent on the ground material types. They therefore vary along the length of any project. Whilst it is generally possible to measure LSR values at some sites on a project route alignment, it is not possible to measure at all NSRs. Further, it is uncommon to be able to measure at particular critical NSRs because of site constraints and difficulty of gaining testing and drill rig access, so the test results are generally not directly applicable to critical NSRs. For this reason, site measurements are mostly used to obtain generalised information pertinent to particular ground conditions so that the results can be used to establish the LSR values to apply to NSRs with the same or similar ground conditions.
8.5.2.24 When LSR testing was carried out for the WIL project, a number of tests were carried out to provide information for future MTR Corporation’s projects, as well as for WIL itself. Sixteen boreholes were tested in a range of ground conditions over the full length of the project. At each borehole, two depths were tested and, for each depth, seven measurement points (distances) were used. The extensive amount of information derived was more than was required for WIL analysis, but it lead to a database of LSR information. This database is a better source of LSR information for KTE than further measurements on the KTE alignment, especially when the similarities between KTE and WIL (operation and ground conditions) are taken into account. A significant section of the WIL project is in ground conditions similar to KTE. This means that there is sufficient information in the database to provide the LSR values for the KTE predictions.
Table
8.8: Adopted WIL LSR Values for KTE (Up Track)
|
KTE (Up Track) |
WIL LSR Selected |
|||||
|
Chainage |
Track Depth (m) |
Rockhead Depth (m) |
LSR Name |
Borehole Depth (m) |
Rockhead Depth (m) |
|
|
From |
To |
|||||
|
8055 |
8460 |
28 |
15 |
D018-39.8m |
40 |
28 |
|
8460 |
8520 |
30 |
10 |
D028-44.3m |
44 |
22 |
|
8520 |
8580 |
35 |
5 |
D028-44.3m |
44 |
22 |
|
8580 |
8650 |
60 |
15 |
D049-60.4m |
60 |
19 |
|
8650 |
8800 |
85 |
30 |
D049-87.8m |
88 |
19 |
|
8800 |
8960 |
75 |
15 |
D064-66.7m |
67 |
15 |
|
8960 |
9240 |
55 |
18 |
D064-54.6m |
55 |
15 |
|
9240 |
9340 |
45 |
30 |
D018-39.8m |
40 |
28 |
|
9340 |
9550 |
45 |
15 |
D028-44.3m |
44 |
22 |
|
9550 |
9760 |
35 |
10 |
D028-44.3m |
44 |
22 |
|
9760 |
10190 |
26 |
8 |
D018-39.8m |
40 |
28 |
|
10190 |
10230 |
23 |
15 |
D018-39.8m |
40 |
28 |
|
10230 |
10290 |
23 |
30 |
D002-19.6m |
20 |
24 |
|
10290 |
10400 |
23 |
15 |
D018-39.8m |
40 |
28 |
Table 8.9: Adopted WIL LSR Values
for KTE (Down Track)
|
KTE (Down Track) |
WIL LSR Selected |
|||||
|
Chainage |
Track Depth (m) |
Rockhead Depth (m) |
LSR Name |
Borehole Depth (m) |
Rockhead Depth (m) |
|
|
From |
To |
|||||
|
7394 |
7750 |
20 |
4 |
D018-39.8m |
40 |
28 |
|
7750 |
7810 |
20 |
6 |
D018-39.8m |
40 |
28 |
|
7810 |
7880 |
20 |
24 |
D002-19.6m |
20 |
24 |
|
7880 |
8100 |
25 |
12 |
D018-39.8m |
40 |
28 |
|
8100 |
8440 |
28 |
15 |
D018-39.8m |
40 |
28 |
|
8440 |
8500 |
30 |
10 |
D028-44.3m |
44 |
22 |
|
8500 |
8560 |
35 |
5 |
D028-44.3m |
44 |
22 |
|
8560 |
8630 |
60 |
15 |
D049-60.4m |
60 |
19 |
|
8630 |
8780 |
85 |
30 |
D049-87.8m |
88 |
19 |
|
8780 |
8930 |
75 |
15 |
D064-66.7m |
67 |
15 |
|
8930 |
9200 |
55 |
18 |
D064-54.6m |
55 |
15 |
|
9200 |
9300 |
45 |
30 |
D018-39.8m |
40 |
28 |
|
9300 |
9520 |
45 |
15 |
D028-44.3m |
44 |
22 |
|
9520 |
9750 |
35 |
10 |
D028-44.3m |
44 |
22 |
|
9750 |
10180 |
26 |
8 |
D018-39.8m |
40 |
28 |
|
10180 |
10220 |
24 |
15 |
D018-39.8m |
40 |
28 |
|
10220 |
10290 |
23 |
25 |
D002-19.6m |
20 |
24 |
|
10290 |
10400 |
23 |
15 |
D018-39.8m |
40 |
28 |
8.5.2.1 MTR Corporation will further review the LSR values during the construction stage after the tunnel boring.
Building Coupling Factor (BCF)
8.5.2.2 In general, larger and heavier structures have greater vibration attenuation than smaller and lighter structures. The recommended practice established within the FTA Manual was followed. Receivers in this study were divided into 4 types according to their structures and would have different BCF attenuation as below:
· Type 0 – Large structures with heavy foundations;
· Type 1 – 2-4 storeys medium sized structures;
· Type 2 – 1-2 storeys complexes; and
· Type 3 – Single family detached residences.
8.5.2.3
Figure 8.12
presents the BCF for different types of structure and indicates 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.
8.5.2.4
For structures founded on rock, there is no impedance contrast between
the soil and the foundation and therefore the BCF is considered to be zero.
Building Vibration Response (BVR)
8.5.2.5 The BVR is generally determined by three factors as described below:
· Resonance amplification due to floor, wall and ceiling spans. The FTA Guidance Manual indicates that the natural frequency for a lightweight framed building would be in the range 15-20Hz, and for a heavy concrete floored building would be in the range 20-30Hz. It recommends that an amplification of 6dB be added in the natural frequency range. The corrections in Figure 8.13 have been adopted for all buildings, as was the case for the WIL EIA Study, based on an assumed spread across the natural frequency range.
· Floor-to-floor attenuation: A floor-to-floor attenuation of 2dB reduction per floor was assumed. Where there is a multi-floor occupancy, only the structure-borne noise impact on the lowest occupied floor is considered.
· Attenuation across a structure, in the direction away from the alignment. When the noise sensitive area is situated in the back of the building away from the alignment, vibration attenuation across the structure would occur. Attenuation of 2dB reduction was considered conservatively in this study, because in those cases where there is more than one row of columns (equivalent to one floor) across the structure, more attenuation would occur.
Conversion to Noise (CTN)
8.5.2.6 As per Section 8.5.1.10, a -27dB correction for conversion of vibration (re: 10-9m/s) in room walls, floors and ceiling to noise (re: 20mPa) has been assumed in this study. This adjustment is based on a typical residential building. There will be some buildings which will have larger spaces or more sound absorption, but which will be of the same building elements, and these may result in a slightly greater adjustment. However, to be conservative for these buildings, the -27dB adjustment has been adopted for all buildings.
Safety Factor (SAF)
8.5.2.7 To tackle the problem of differences in overall predicted and measured A-weighted noise levels, a safety factor has been applied in the model. As a conservative approach, a 10dB safety factor was adopted to account for uncertainty and variation in ground characteristics.
Calculation of Leq
8.5.2.8 Sound Exposure Level (SEL) values have been determined by calculating the noise level from the train at numerous locations 10m apart for the full length of the project, then adding to obtain the total energy.
8.5.2.9 Leq values were then calculated by the method in the FTA guidance Manual:
Leq = 10
log [10(SEL + 10 log V)/10] – 35.6
Where:
V = number
of train movements in the relevant 30 minute or 24 hour period, expressed as
the average number of movements per hour:
For Leq(30min): V
= N(30min) x 2 (N = number of movements)
For
Leq(24hour): V = N(24hour) / 24 (N = number of movements)
8.6.1
Non-Mitigated Scenario
Construction Phase
8.6.1.1 The predicted construction ground-borne noise levels at the lowest occupied floor of NSRs are shown in Table 8.10. Detailed calculations are included in Appendix 8.3.
Table 8.10: Predicted Construction Ground-borne Noise
Levels
|
Calculated GBN Level for each PME, dB(A) |
Construction Noise Criteria |
|||
|
Excavator Mounted Breaker |
Drill Rig |
Pile Rig |
Daytime (Night time) |
|
|
5 |
38 |
43 |
-- |
65 (45) |
|
6 |
38 |
43 |
-- |
60/55[a]
(--[b]) |
|
7 |
36 |
41 |
43 |
65 (45) |
|
11 |
<20 |
<20 |
<20 |
65 (45) |
|
12 |
29 |
34 |
36 |
60/55[a]
(--[b]) |
|
20 |
21 |
26 |
28 |
60/55[a]
(--[b]) |
|
44 |
49 |
54 |
-- |
65 (45) |
|
62 |
29 |
34 |
36 |
65 (45) |
Note:
Underline
denotes exceedance during exam period.
[a] A 5dB(A) reduction to the ground-borne noise criteria is recommended
for school during examination period. In
addition, schools do not have sensitive use during night time and thus have no
respective ground-borne noise criteria.
[b] No sensitive use during this period.
8.6.1.2
Table 8.10 shows that ground-borne noise levels at all NSRs comply with the relevant
ground-borne noise criteria and no mitigation measures would be required.
Operation Phase
8.6.1.3
The predicted ground-borne noise levels as a result of KTE operation at
the lowest occupied floor of NSRs are shown in Table 8.11, and levels at higher floors will be lower. These predicted levels are based on medium
attenuation type 1 baseplates for all new track and the existing stiff
baseplates near YMT station.
Table 8.11: Predicted Ground-borne Noise Levels from KTE Alone
|
NSR |
Predicted Ground-borne
Noise Level, dB(A) |
Criteria |
||||
|
Leq (30min) |
Leq (24hr) |
Lmax |
Leq (30min) |
|||
|
Day |
Night |
Day |
Night |
|||
|
1 |
42 |
38 |
40 |
52 |
55 |
45 |
|
2 |
45 |
42 |
44 |
54 |
55 |
45 |
|
3 |
28 |
25 |
26 |
36 |
55 |
45 |
|
4 |
41 |
38 |
40 |
49 |
55 |
45 |
|
5 |
28 |
25 |
27 |
34 |
55 |
45 |
|
6 |
44 |
41 |
43 |
52 |
55 |
- |
|
7 |
30 |
27 |
29 |
39 |
55 |
45 |
|
8 |
28 |
25 |
27 |
37 |
55 |
- |
|
9 |
42 |
39 |
41 |
50 |
55 |
- |
|
10 |
<20 |
<20 |
<20 |
24 |
50 |
- |
|
11 |
<20 |
<20 |
<20 |
25 |
50 |
40 |
|
12 |
43 |
40 |
42 |
50 |
50 |
- |
|
13b |
<20 |
<20 |
<20 |
<20 |
50 |
40 |
|
14 |
31 |
28 |
30 |
38 |
55 |
|
|
15 |
<20 |
<20 |
<20 |
<20 |
55 |
- |
|
18 |
<20 |
<20 |
<20 |
22 |
55 |
45 |
|
20 |
27 |
24 |
25 |
33 |
55 |
- |
|
21 |
<20 |
<20 |
<20 |
<20 |
55 |
45 |
|
24 |
37 |
36 |
36 |
46 |
55 |
45 |
|
25 |
38 |
38 |
37 |
49 |
55 |
45 |
|
26 |
42 |
42 |
41 |
52 |
55 |
45 |
|
29 |
29 |
29 |
28 |
39 |
55 |
45 |
|
30 |
35 |
35 |
34 |
46 |
55 |
45 |
|
34 |
25 |
24 |
24 |
31 |
55 |
- |
|
35 |
24 |
24 |
23 |
30 |
55 |
- |
|
36 |
<20 |
<20 |
<20 |
<20 |
55 |
45 |
|
40 |
39 |
36 |
37 |
45 |
55 |
45 |
|
41 |
<20 |
<20 |
<20 |
<20 |
55 |
45 |
|
44 |
38 |
36 |
37 |
45 |
55 |
45 |
|
45 |
24 |
21 |
23 |
31 |
55 |
45 |
|
62 |
<20 |
<20 |
<20 |
<20 |
55 |
45 |
8.6.1.4 The predicted ground-borne noise levels shown in Table 8.11 show that levels will comply with the noise criteria at all NSRs and as such mitigation measures are not required to meet the criteria. Sample detailed calculations for the prediction of noise levels at NSRs 2, 12, 14, 15, 26, 30 and 44 are shown in Appendix 8.4.
Construction Phase
8.6.2.1 As no ground-borne noise exceedances are predicted, no mitigation measures would be required during the construction phase.
Operational Phase
8.6.2.2 No mitigation measures are required to meet the criteria, since the proposed medium attenuation baseplates proposed for new track are sufficient.
8.6.3
Cumulative Impacts
Construction Phase
8.6.3.1 During construction phase, no cumulative impacts were identified.
Operational Phase
8.6.3.2 All predicted ground-borne noise levels from KTE during daytime is 10dB(A) below the criterion so that cumulative impact contributed by the Project would be insignificant. The predicted ground-borne noise levels during night-time for KTE and SCL are presented in Table 8.12. For the estimations below 20dB(A), the cumulative levels has been calculated as 20dB(A) to present a conservative assessment. The levels in the table relating to SCL have been taken from the draft EIA for the project. No exceedance was observed.
Table 8.12: Cumulative Ground-borne
Noise Levels with SCL – Tai Wai to Hung Hom Section
|
NSR |
Predicted Ground-borne Noise Level Leq (30min),
dB(A) |
Criteria |
||
|
KTE |
SCL – Tai Wai to Hung Hom Section |
Cumulative Level |
||
|
Night-time |
Night-time |
Night-time |
Night-time |
|
|
18 |
<20 |
<20 |
<20 |
45 |
|
20 |
26 |
<20 |
26 |
- |
|
21 |
<20 |
<20 |
<20 |
45 |
|
40 |
36 |
42 |
43 |
45 |
|
45 |
23 |
<20 |
25 |
45 |
|
62 |
<20 |
24 |
24 |
45 |
8.6.4
Residual Impacts
8.6.4.1 No residual impacts are anticipated after the implementation of the proposed mitigation measures during the construction and operational phases of the KTE project.
8.7
Environmental Monitoring and Audit
Construction Phase
8.7.1.1 As the predicted ground-borne noise levels comply with the stipulated daytime noise criteria, ground-borne noise monitoring for the project is not recommended.
8.7.1.2 MTR will further review the proposed mitigation measures for operational ground-borne noise during the construction stage after the tunnel boring.
Operational Phase
8.7.1.3 Prior to the operation phase of the Project, a commissioning test should be conducted to ensure compliance of the operational ground-borne noise levels with the EIAO-TM noise criteria. Details of the test requirements are provided in a stand-alone EM&A Manual.
Construction Phase
8.8.1.1 Construction ground-borne noise assessment was conducted and the prediction results indicated that the PME induced ground-borne levels at NSRs comply with the EIAO noise limit.
Operational Phase
8.8.1.2 Ground-borne noise levels were predicted based on the worst case scenario of railway system and the prediction results at all NSRs comply with the stipulated EIAO-TM noise criteria without mitigation measures. It is anticipated that there would be no exceedance of the ground-borne noise criteria at the NSRs.
8.8.1.3 Although no trackform upgrade is required to mitigate ground-borne noise levels, it is noted that the tunnel is of sufficient diameter to accommodate a number of low noise trackforms, including the high performance isolated slab track (IST) which would reduce noise levels by approximately 13–15dB on those predicted.