10.
GROUNDBORNE NOISE IMPACT
10.1
Potential ground-borne noise impacts likely
arising from the construction and operation of the Project have been evaluated
and assessed in this section.
Environmental
Legislation, Standards and Guidelines
10.2
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.
10.3
Noise arising from the general construction
works of the Project during normal daytime hours (0700-1900 except general
holidays and Sunday) is governed by the EIAO-TM. With reference to the
Technical Memorandum for the Assessment of Noise from Places Other Than
Domestic Premises, Public Places or Construction Sites (IND-TM) under the NCO,
the criteria for noise transmitted primarily through the structural elements of
the building or buildings are expected to be 10dB(A) less than the relevant
acceptable noise level (ANL). These criteria apply to all residential buildings,
schools, clinics, hospitals, temples and churches.
10.4
In the restricted hours (i.e. between 1900
and 0700 on a normal working day or at any time on a general holiday and
Sunday), the construction noise is controlled by the Technical Memorandum on
Noise from Construction Work other than Percussive Piling (GW-TM). Similarly,
the ground-borne noise criteria is limited to 10dB(A)
below the respective ANL. A Construction Noise Permit (CNP) is required for
construction activities involving the use of PME carried out in restricted
hours.
10.5
The construction ground-borne noise criteria
for the identified ground-borne noise sensitive receivers (NSR) are tabulated
in Table 10.1
below.
Table 10.1 Construction
Ground-borne Noise Criteria
NSR/Assessment Description |
Ground-borne Noise Criteria, Leq
30 min dB(A) [a] |
||
|
Daytime (0700-1900 hrs) |
Daytime during general
holidays and Sundays and all days during Evening |
Night |
|
|
Domestic
premises, hotels and service apartments |
65 |
55 |
40 |
|
Schools [b] |
60/55 [c] |
55 |
[b] |
|
The |
60/55 [c] |
55 |
[b] |
Note:
[a] Ground-borne noise
is deemed not to be affected by external factors. Thus, an Area Sensitivity
Rating of B is used to determine the appropriate criteria during restricted
hours.
[b] No sensitive
use/activity during this period.
[c] A 5dB(A) reduction to
the ground-borne noise criteria is recommended for schools during the
examination period.
[d] HKAPA is currently used as performing arts centre
and provides professional education, training and research facilities in the
performing arts, theatre and entertainment arts, film and television. With a
similar nature of education, tutoring, communication and rehearsal in both performing arts centre and education institution, a
criterion for educational use is considered appropriate for HKAPA.
10.6
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) Regulations, Chapter 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 Superintendent of Mines will review the
application on a case-by-case basis before issuing the Mine Blasting
Certificate.
10.7
With reference to the IND-TM, the criteria
for noise transmitted primarily through the structural elements of the building
or buildings is 10dB(A) less than the relevant
acceptable ANL. The same criteria
are applied to all residential buildings, schools, clinics, hospitals, temples
and churches. The criteria applied
for assessment of ground-borne noise are summarised in Table
10.2 below.
Table 10.2 Operation
Ground-borne Noise Criteria
Type of NSR |
Ground-borne Noise Criteria, (Leq
30 min dB(A)) |
|
|
Day & Evening |
Night |
|
|
Domestic premises (including hotels and service
apartments) |
55 |
45 |
|
Churches, Schools and Clinics |
55 |
[a] |
|
HKAPA |
55 [b] |
[a] |
Note:
[a] No sensitive use/activity during this period.
[b] HKAPA is currently used as performing arts
centre and provides professional education, training and research facilities in
the performing arts, theatre and entertainment arts, film and television. With
a similar nature of education, tutoring, communication and rehearsal in both performing arts centre and education institution, a
criterion for educational use is considered appropriate for HKAPA.
Description of the Existing Environment
10.8
The Project runs from the south of the
proposed Hung Hom Station (HUH) across the Victoria Harbour to the Causeway Bay
Typhoon Shelter (CBTS), Exhibition Station (EXH) and then to Admiralty Station
(ADM).
10.9
The Project area in Hung Hom is located in
well developed urban areas. The
surrounding land uses mainly comprise a mixture of commercial,
Government/Institution/Community and residential uses. Dominant noise sources
identified were the traffic noise from
Identification of Ground-borne Noise Sensitive Receivers
10.10
The SCL (HUH – ADM) runs from the north of
the
10.11
Potential ground-borne noise impacts during
construction phase of the Project would arise mainly from the PME for rock breaking/drilling
works (such as hydraulic breaker, rock drill, pile rig, etc) and tunnel boring
machine (TBM).
10.12
Under the assumption of worst-case scenario,
representative NSRs were identified for the assessment of construction
ground-borne noise impact due to the TBM operation and the use of PME for rock
breaking/drilling works. The identified representative NSRs are presented in Table 10.3 and shown
in Figure Nos. NEX2213/C/331/ENS/M52/001 to NEX2213/C/331/ENS/M52/004.
Table 10.3 Representative
Noise Sensitive Receivers for Construction Ground-borne Noise Assessment
|
NSR ID |
Description |
Uses |
Horizontal Distance to the Work Site(s) (m) |
Nearest Site |
|
|
||||
|
HH9 |
Harbourfront Horizon |
Service Apartment |
220 |
Hung Hom Landfall |
|
Hong
Kong Side |
||||
|
CH2 |
|
Residential |
60 |
South Ventilation Shafts, Plant Rooms and
Emergency Access (SOV), TBM Launching Shaft |
|
48 |
Tunnel Construction by TBM |
|||
|
CH3 |
Elizabeth House, Block C |
Residential |
60 |
Tunnel Construction by TBM |
|
EX2 |
Renaissance Harbour View Hotel |
Hotel |
30 |
Tunnel Construction by Cut & Cover
Method |
|
EX3 |
Grand Hyatt Hotel |
Hotel |
30 |
Tunnel Construction by Cut & Cover
Method |
|
EX4 |
HKAPA |
Educational
|
40 |
Tunnel Construction by TBM |
|
AD4 |
Island Shangri-La Hotel |
Hotel |
Immediately above work site(s) |
Tunnel Construction by Drill and Blast |
10.13
Representative NSRs for the assessment of operational
ground-borne noise impact have been identified and are presented in Table 10.4 and their locations are illustrated in Figure Nos. NEX2213/C/331/ENS/M52/101
to NEX2213/C/331/ENS/M52/103.
Table
10.4 Representative
Noise Sensitive Receivers for Operational Ground-borne Noise Assessment
|
NSR ID |
Description |
Land Use |
No. of storey |
Area Sensitive Rating |
|
|
||||
|
HH9b |
Harbourfront
Horizon |
Service
Apartment |
22 |
B [a] |
|
Hong
Kong Side |
||||
|
CH2 |
|
Residential |
19 |
B [a] |
|
CH3 |
Elizabeth House, Block C |
Residential |
21 |
B [a] |
|
EX2 |
Renaissance Harbour View Hotel |
Hotel |
42 |
B [a] |
|
EX3 |
Grand Hyatt Hotel |
Hotel |
34 |
B [a] |
|
EX4 |
HKAPA |
Educational |
8 |
B [a] |
|
AD4 |
Island Shangri-La Hotel |
Hotel |
56 |
B [a] |
Note:
[a]
Ground-borne noise is deemed not to be affected by external factors. Thus, an Area
Sensitivity Rating of B is used to determine the appropriate criteria during
restricted hours.
10.14
Potential ground-borne noise impact during construction
phase would arise mainly from drill and blast, and TBM operation for tunnelling
works, as well as PME used for rock breaking/drilling including breakers, drill
rigs and pipe pile rigs. Drill-and-blast activities would only cause short term noise
impact and would not have significant contribution on the averaged noise level Leq 30min.
10.15 Since the Project would be constructed concurrently with SCL (MKK – HUH)
at Hung Hom, potential cumulative ground-borne noise impact from SCL (MKK-HUH)
would be assessed.
10.16
According to the
approved WDII and CWB EIA Report, the ground-borne noise impact on NSR
(including Hoi Kung Court i.e. CH2) due to rock breaking activity would be
minimal, taking into account the buffer distance of more than 150m. Hence, cumulative construction
ground-borne noise impact from the WDII/CWB project is not expected.
10.17
Based on the latest construction programme
for South Island Line (East) (SIL(E)), the construction of the ADM and the Hong
Kong Park Ventilation Building (HKB) (foundation
works and adits) under SIL (E) would not be undertaken concurrently with the
Project. Therefore, cumulative
construction ground-borne noise impact from SIL(E) is
not expected.
10.18
When trains operate in tunnels that are
located in close proximity to occupied structures, there is a possibility that
vibrations associated with train passbys can be transmitted through the ground
and structure and be radiated as noise in the occupied spaces within the
structure. The transmitted noise through structures may have potential impact
on the NSRs.
10.19
Cumulative
ground-borne noise impact from SIL(E) and the Project
at Admiralty would be expected and therefore was considered in the assessment.
10.20
The proposed SCL
alignment will come within 300m of the following existing rail lines in
·
Passing under the
Tsuen Wan Line in Admiralty; and
·
Passing under the
10.21
The cumulative
ground-borne noise impact from the operation of these existing rail lines and
the Project was also addressed.
Ground-borne Noise Prediction Methodology
10.22
The methodology used to determine
ground-borne noise levels in the Project 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 in the
approved Kowloon Southern Link (KSL) EIA Report[2].
10.23
The main components of the proposed
prediction model for ground-borne noise are:
·
Vibration source
level from operation of hydraulic breakers, drill rigs, piling rigs, hand-held
breakers and TBM;
·
Vibration
propagation through the ground to the structure foundation;
·
Vibration reduction
due to the soil/structure interface;
·
Vibration
propagation through the building and into occupied areas; and
·
Conversion from
floor and wall vibration to noise.
10.24
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
10.25
The predicted ground-borne noise level Lp
inside the noise sensitive rooms is given by the following equation.
Lp
= Lv,rms + Cdist + Cdamping
+ Cbuilding + Cfloor + Cnoise + Cmulti +
Ccum
Reference Vibration Source (Lv,rms)
10.26
For the assessment of ground-borne noise due
to hydraulic breaker, rock drill and pile rig, reference was made to the
assessment approach, source terms and transmission factors adopted in the
approved KSL EIA Report. The reference source levels adopted for the assessment
are given in Table 10.5.
Table 10.5 Reference Vibration Levels of
Powered Mechanical Equipment
|
Plant |
Vibration (rms) at reference
distance of 5.5m from source [a] |
Vibration (ppv) at distance 2m from
source |
|
Hydraulic Breaker |
0.298 mm/s |
- |
|
Handheld Breaker |
0.279 mm/s |
- |
|
Drill Rig |
0.536 mm/s |
- |
|
Pile Rig |
- |
19.3 mm/s |
Remark:
[a] Extracted from KSL GSA 5100 Environmental Impact Assessment &
Associated Services - Environmental Impact Assessment Report, Register No.:
EIA-098/2004.
10.27
The expected source vibration of the TBM is
extracted from the approved KSL EIA Report. The geology encountered during the KSL
EIA study consists predominately of granite, which is similar to the geology
expected to be encountered in the study area. The KSL source vibration measurements
are therefore considered the most appropriate available information for the
purpose of assessing TBM ground-borne noise. The reference vibration levels for the
TBM are illustrated in Appendix 10.1.
Soil Damping Factor
(Cdamping)
10.28
The assessment of ground
borne noise damping due to soil causing the vibration amplitude to decay
in inverse correlation to the propagation distance. The decay relationship is based on the
equation set out in the Transportation Noise Reference Book[3].
V(R) = V(Ro) ´ e-2pf h R/2c.
10.29
The velocity amplitude (V) is dependent on
the frequency (f) in Hz, the soil loss factor (h), the wave speed c in m/s and the distance (R) from the
source to the NSR. The properties
of the soil material expected to be encountered are shown in Table
10.6 below.
Table 10.6 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 |
10.30
No damping attenuation was applied for
propagation in rocks. All NSRs were assumed to have a piling foundation on
rockhead.
Coupling Loss into
Building Structures (Cbuilding)
10.31
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 10.7 below.
In addition, a coupling loss correction of -18 dB
from bedrock to pile should be adopted. However, the correction from bedrock to
pile depends on actual site condition and correction of zero dB is assumed for
conservative approach.
Table 10.7 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 (Cfloor)
10.32
The coupling loss per floor represents the floor-to-floor
vibration transmission attenuation.
For multi-storey buildings, a coupling
loss of 2 dB reduction per floor was assumed for a
conservative assessment to account for any possible amplification due to
resonance effects.
Conversion from
Floor Vibration to Noise Levels (Cnoise)
10.33
A -27dB correction was assumed for conversion
of vibration to noise (re. 20μPa). This is in line
with the previous approved EIA reports.
Multiply Source
Factor (Cmulti)
10.34
This represents the increase in noise level
due to multiple noise sources. The
ground-borne noise levels from construction plant were summed logarithmically
in accordance with standard acoustic principles to obtain the total
ground-borne noise level at the area of interest.
Cumulative Effect (Ccum)
10.35
The cumulative effect of construction
ground-borne noise from other nearby concurrent sources, if any, was also
included.
Conversion to
A-weighted Noise
10.36
For calculation of ground-borne noise impacts
from TBM, a 20dB(A) reduction was adopted for conversion
to A-weighted noise. This conversion factor was obtained from the “Transit
Noise and Vibration Impact Assessment”[4].
Operation Phase
10.37
The operational ground-borne noise impact
assessment was conducted in accordance with the procedures outlined in Federal
Transit Administration (FTA) Guidance Manual for detailed vibration
analysis. This methodology was
adopted in the approved West Island Line (WIL) EIA Report[5]. The ground-borne noise levels at the
representative NSRs have been calculated based on the following equation:
L
= FDL + TIL + TOC + TCF + LSR + BCF + BVR + CTN + SAF
where
|
L |
Train passby noise level, in dB |
|
FDL |
force density level, in dB re 1 lb/in1/2 |
|
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 1
(uin/s)/(lb/ft^0.5) |
|
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 |
Force Density Levels
(FDL)
10.38
The vibration source levels (force density
levels, FDL) for the existing SP1900 EMU were obtained from passby measurements
on the up track through Pat Heung Depot in previous rail projects. The deterioration in rail and rolling
stock condition has already been taken into account in FDL obtained by
measurements under rough rail condition.
In accordance with the approved KSL EIA Report, comparisions of FDL
obtained from the SP1900 EMU to other Hong Kong transit trains, including old
East Rail EMU, as well as several other heavy rail EMUs in operation in the
United States, indicated that the SP1900 FDL was 5 dB to 10 dB higher than the
maximum FDL for the other trains. The FDL adopted in the assessment was based
on previous approved EIA as shown in Appendix 10.2.
10.39
The maximum
operating train speed at the tunnel section across Victoria Harbour where there
are no NSRs in the vicinity will be up to 120kph while the speeds for the
tunnel section in the inland of Hong Kong Island are 60kph and 80kph at the
overrun and other sections respectively. Speed correction was
applied to the FDL using the following empirical relationship:
Trackform
Alternatives or Insertion Loss (TIL)
10.40
Trackform 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, larger trackform elements will take up more space
in tunnels and may cause spatial incompatibilities that are difficult to be
overcome in the design. The TIL for existing MTR trackforms in previous
approved EIA were adopted where appropriate.
10.41
The ground-borne noise levels at NSRs were
calculated initially with direct fixation
track without trackform insertion loss for the whole alignment, except a
section of alignment to the north ADM using Type 2 trackform (see below). If noise exceedances were predicted, low
noise trackforms including low stiffness fasteners, floating slab track, etc
would be considered. The attenuation provided by different low noise trackforms
was included in the calculation to determine the appropriate trackforms for
meeting the criteria. The type of vibration mitigating trackform is often
grouped into three categories listed below:
·
Type 1: 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 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;
·
Type 3: A floating mini slab trackform (FST)
with a loaded resonance frequency of approximately 16Hz.
Tunnel Coupling
Factor (TCF)
10.42
Generally heavier transit structures are
likely to lower the vibration levels.
With reference to FTA Manual, vibrations induced by trains in Cut and
Cover (CC) tunnels and Stations are 3dB and 5dB less than that in bored tunnels
constructed through soil. For bored
tunnels in soil, the TCF depends on the soil properties. Due to lack of comprehensive
data on different soil strata, TCF is conservatively assumed to be 0dB. Thus,
the TCF used is 0dB, -3dB and -5dB for bored tunnel, CC tunnel and stations
respectively. No TCF is applied to tunnel structures bored through rock.
Turnout and
Crossover Factor (TOC)
10.43
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. While it is not possible to machine
grind the rails through either the points or crossings, surface deterioration
is 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 is considered
appropriate. These corrections have been adopted in this study.
Line Source Response
(LSR)
10.44
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 (train) orientated
along the alignment. Therefore, the
basic quantity required for the determination of the LSR is the vibration
response caused by a unit point source impact, which is defined as the Point
Source Response (PSR). Given that
the PSR are located along the alignment, the LSR will follow directly by
incoherent integration of the PSR values over the train length. However, the determination of the LSR
from force point impacts in numerous boreholes along the alignment over the
length of the alignment is neither practical nor affordable. Thus, idealised assumptions of
transverse isotropy and layer-wise homogeneity are invoked, which allow PSR
obtained from a single borehole to be taken as representative along the
alignment near a building receiver and used in the calculation of LSR.
10.45
Soil mobility has already been measured in
Table 10.8 Typical
PSR Adopted for the Representative Noise Sensitive Receivers
|
Selected NSR |
Reference Borehole |
|||||
|
NSR No. |
Rock(R) / Soil-borne(S) |
Track Depth [m] |
Rockhead Depth [m] |
Borehole No. |
Borehole Depth [m] |
Rockhead Depth [m] |
|
HH9b
– Harbourfront Horizon |
S |
11 |
21 |
WIL D095 |
10.4 |
23 |
|
CH2
- |
R |
17 & 25 |
~12 |
WIL D012 |
41.4 |
30 |
|
CH3
- Elizabeth House |
South: S |
South: 15 |
~25-35 |
WIL D012 |
18 |
30 |
|
North: R |
North: 28 |
WIL D103 |
21 |
19 |
||
|
EX2 - Renaissance Harbour View Hotel |
S |
20 & 27 |
~35 |
WIL D012 |
18 |
30 |
|
EX3
- Grand Hyatt Hotel |
S |
27 & 34 |
~50 |
WIL D012 |
18 |
30 |
|
EX4 - HKAPA |
R |
33 & 35 |
20-34 |
WIL D012 |
41.4 |
30 |
|
AD4
– Island Shangri-La Hotel |
R |
48 & 49 |
25-30 |
WIL D012 |
41.4 |
30 |
10.46
The PSR is numerically interpolated between
setbacks to create a contoured surface in frequency and distance. The LSR is then determined by a
numerical incoherent integration of the PSR along the length of the train
centred on the receiver for each individual 1/3 octave bands.
where s =
perpendicular setback
d
= depth to top of rail
l
= train length
Building Coupling
Factor (BCF)
10.47
The recommended BCF established within FTA
Manual was adopted for this Project.
In general, larger and heavier structures have greater vibration
attenuation than smaller and lighter structures. Receivers in this study are divided into
5 types according to the structure type and assigned different BCF attenuation
ratings as below:
·
Type 0 – Large Masonry
with spread footings
·
Type 1 – 2-4 storeys medium sized structures
·
Type 2 – 1-2 storeys complexes
·
Type 3 – Single family detached residences
·
Type 4
– Large
10.48
The BCF for different structures takes into
account the greater vibration attenuation in larger and heavier structures than
smaller and lighter structure and they are presented in Appendix 10.4. 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. As both the
tunnel structure and building pilings are founded on rock and there is no impedance
contrast between the rock and the
foundation, the BCF for the Project is considered to be zero.
Building Vibration
Response (BVR)
10.49
The BVR is generally determined by two
factors as described below:
·
Resonance amplification due to floor, wall
and ceiling spans: With reference to the FTA Manual, a 6 dB
correction was adopted to account for structural resonances of typical reinforced concrete buildings. The spectral correction is
provided in
Appendix 10.5.
·
Floor-to-floor attenuation: A floor-to-floor
attenuation of 2 dB reduction per floor was assumed. Where there is a multi-floor occupancy,
only the structural borne noise impact on the lowest occupied floor was considered.
Conversion to Noise
(CTN)
10.50
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) was assumed in this study.
Safety Factor (SAF)
10.51
To tackle the problem of differences in
overall predicted and measured A-weighted noise levels, a safety factor was
applied in the model. As a conservative approach, a 10 dB safety factor was
adopted to account for uncertainty and variation in ground
characteristics.
Level of Uncertainty
10.52
The
predictions of ground-borne noise impacts were based on the methodologies
described in the FTA Guidance Manual.
The methodology which had previously been applied in other EIA studies
is generally accepted for use in assessing ground-borne noise impacts against
EIAO-TM and IND-TM noise criteria.
In carrying out the assessment, realistic worst case assumptions have
been made in order to provide a conservative assessment of noise impacts. The construction ground-borne noise
impact was assessed based on conservative estimates for the types of plant and
methods of working. For
operational ground-borne noise assessment, the soil mobility data was made
reference to previous measurements for other EIA studies having similar
rockhead level and borehole depth.
10.53
There
would be some limitations such as the accuracy of the predictive base data for
future conditions e.g. plant inventory for the proposed construction works and
uncertainty in the soil mobility for future operation. Uncertainties in the
assessment of impacts have been considered when drawing conclusions from the
assessment. For operational ground-borne noise assessment, 10dB overall safety
factor was incorporated to account for prediction uncertainty. Also the proposed
mitigation measures should be reviewed when more specific data are available at
later stage (e.g. after tunnel boring).
10.54
Ground-borne noise levels at the
representative NSRs associated with the construction of the Project using TBM
and PME for rock breaking/drilling works were predicted, and are summarized in Table 10.9 below.
For the worst case scenario, it was assumed in the calculation that all
the PME would be operated simultaneously.
Detailed calculations and assumptions for each representative NSR are
provided in Appendix 10.6.
Table 10.9 Predicted
Construction Ground-borne Noise Impact
|
NSR No. |
Description |
Predicted
Ground-borne Noise Levels Leq(30mins), dB(A) |
Overall
Predicted Ground-borne Noise Levels Leq(30mins), dB(A) |
Criteria, Leq(30mins) dB(A) |
Criteria Achieved? |
|
|
TBM |
PME |
|||||
|
HH9 |
Harbourfront
Horizon |
N/A |
41-49 |
41-49 |
65 |
Yes |
|
CH2 |
|
46 |
63 |
63 |
65 |
Yes |
|
CH3 |
Elizabeth
House, Block C |
32 |
N/A |
32 |
65 |
Yes |
|
EX2 |
Renaissance
Harbour View Hotel |
N/A |
52 |
52 |
65 |
Yes |
|
EX3 |
Grand
Hyatt Hotel |
N/A |
52 |
52 |
65 |
Yes |
|
EX4 |
HKAPA |
52 |
N/A |
52 |
60/55 |
Yes |
|
AD4 |
Island
Shangri-La Hotel |
N/A |
55 |
55 |
65 |
Yes |
Note:
N/A – Not applicable
10.55
As shown in Table 10.9, the predicted construction ground-borne
noise levels at all representative NSRs is expected to comply with the day time noise criteria. Adverse construction ground-borne noise
impact due to the use of TBM and PME during day time
period is
not envisaged.
10.56
In case of any construction activities being
conducted during restricted hours (i.e. between 1900 and 0700 on a normal
working day or at any time on a general holiday and Sunday), 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 a CNP application to the Noise Control Authority and abide
by any conditions stated in the CNP, should one be issued.
10.57
The Project would
be constructed concurrently with SCL (MKK – HUH) at Hung Hom Landfall.
Potential cumulative construction ground-borne noise impact from the Project
and SCL (MKK – HUH) was therefore assessed. Detailed
calculations are provided in Appendix
10.7 and the
results are summarized in Table 10.10 below. The
results indicate that the cumulative construction ground-borne noise levels at
the NSR would comply with the noise criteria.
Table 10.10 Cumulative
Construction Ground-borne Noise Impact from Concurrent Project
|
NSR No. |
Description |
Cumulative
Construction Ground-borne Noise Levels, dB(A) |
Criteria, dB(A)
(Leq(30mins) unless specified) Daytime (0700-1900 hrs) |
Criteria
Achieved? |
|
HH9 |
Harbourfront Horizon |
43-49 |
65 |
Yes |
10.58 The operational ground-borne noise levels from the Project at the
representative NSRs were assessed based on direct fixation track with a section
of alignment to the north ADM using Type 2 trackform for a length of about 170m.
With the provision of these trackform, the Lmax levels at HKAPA
were predicted to be below 25dB(A). Table 10.11 summarises the
predicted operational ground-borne noise levels. Detailed calculation and
assumptions and results in terms of Leq (30mins), Leq (24hr) and Lmax are
provided in Appendix 10.8. All input
parameters e.g. train speed and frequency had covered all scenario including
the normal and worst case. The lowest affected floor is considered as the worst
affected receivers for each NSR. As
indicated in Table 10.11, the predicted
operational ground-borne noise levels at all the representative NSRs would
comply with the noise criteria.
Table 10.11 Predicted
Operational Ground-borne Noise Impact
|
NSR No. |
Description |
Predicted
Ground-borne Noise Levels[a], Leq(30mins) dB(A) |
Ground-borne Noise Criteria, Leq(30mins) dB(A) |
Criteria Achieved? |
||
|
Day & Evening |
Night |
Day & Evening |
Night |
|||
|
HH9b |
Harbourfront
Horizon |
<20 |
<20 |
55 |
45 |
Yes |
|
CH2 |
|
38 |
37 |
55 |
45 |
Yes |
|
CH3 |
Elizabeth
House, Block C |
<20 |
<20 |
55 |
45 |
Yes |
|
EX2 |
Renaissance
Harbour View Hotel |
<20 |
<20 |
55 |
45 |
Yes |
|
EX3 |
Grand
Hyatt Hotel |
<20 |
<20 |
55 |
45 |
Yes |
|
EX4 |
HKAPA |
<20 |
<20 |
55 |
N/A |
Yes |
|
AD4 |
Island
Shangri-La Hotel |
20 |
<20 |
55 |
45 |
Yes |
Note:
[a] The
prediction is based on train frequency at peak hours as follow:
·
30 trains per hour
per direction during daytime/evening (0700-2300).
·
24 trains per hour
per direction at night (2300-0700).
N/A Not
applicable
10.59
Cumulative
ground-borne noise impact from the SIL(E) and the Project
at Admiralty would be expected. The cumulative ground-borne noise impact from SIL(E) was assessed by using the operational ground-borne
noise levels
predicted in the approved SIL(E) EIA Report[6].
Table
10.12
summarises the cumulative operational ground-borne noise levels at NSR AD4 that
is the worst-affected NSR in the vicinity of the interfacing area. As shown in Table
10.12,
the cumulative operational ground-borne noise levels at NSR AD4 would be well
below the night-time noise criterion by more than 20 dB(A).
No adverse cumulative operational ground-borne noise impact from SIL(E) is therefore anticipated.
Table 10.12 Cumulative
Operational Ground-borne Noise Impact from SIL(E)
|
NSR No. |
Description |
Predicted Ground-borne
Noise Levels, dB(A) |
Cumulative Ground-borne Noise Levels, dB(A) |
Criteria, dB(A) (Leq(30mins) unless
specified) |
Criteria Achieved? |
|
|
The Project |
SIL(E)[*] |
|||||
|
AD4 |
Island Shangri-La Hotel |
<20 |
16 |
20 |
45 (worst-case with
night-time operation) |
Yes |
Note:
[*] Operational
ground-borne noise levels at AD4 from SIL(E) is based
on the approved SIL(E) EIA Report (Register No. AEIAR-155/2010).
10.60 With regard to the cumulative impact with the existing rail lines, NSR
AD4 is also the nearest NSR to Island Line. As shown in the above table, the
predicted ground-borne noise levels at NSR AD4 would be at least 20 dB(A) below the night-time noise criterion. In addition,
Island Line trains will slow down and stop at the existing Admiralty Station
resulting in insignificant contributions to the cumulative impact. As such,
adverse cumulative ground-borne noise impact from the existing Island Line is
not expected.
10.61
The nearest
representative NSR to the existing Tsuen Wan Line is EX4. As shown in Table 10.11, the predicted
ground-borne noise levels from the Project during day and evening time is only
27 dB(A) that is 28dB(A) below
the noise criterion. Hence, cumulative ground-borne noise impact from the
existing Tsuen Wan Line would be unlikely to be a concern for the Project.
10.62
During abnormal or emergency operations of
the Project, the train service will be interrupted or stopped that will result
in the train frequency during that period being lower than the scheduled
timetable. Hence, adverse ground-borne noise impact arising from the abnormal
or emergency operations is not expected.
Recommended Mitigation Measure
10.63
As presented above, the predicted
construction ground-borne noise levels at all identified representative NSRs
would comply with the noise criteria and therefore no mitigation measure is
deemed necessary.
10.64 The predicted operational ground-borne noise at all identified
representative NSRs would comply with the noise criteria. Mitigation measure is
therefore deemed not necessary.
10.65 The prediction of ground-borne noise impact relied on a number of
conservative assumptions, however as a further conservative measure, provisions
have been made in the design of the tunnel for installation of contingency
mitigation measures should they be necessary to minimize the potential ground-borne noise impact on existing NSRs
and planned/committed noise sensitive developments that interface with the
Project. Implementation of the contingency mitigation measures should be
reviewed in connection with continuous liaisons with the relevant parties
during the design stage and prior to the installation of the railway tracks. In view of the lack of concrete details
and programme of those non-committed developments and extensions at this stage,
they will have to take into account this Project in their planning and
development stages.
10.66 Based on the size of the tunnel proposed under the Project, the
contingency mitigation measures may consist of:
·
Medium attenuation baseplates (Type 1) –– additional attenuation of about 5 to 10dB(A);
·
High attenuation baseplate or booted dual
sleepers (Type 2) additional attenuation of about 10 to 15dB(A); or
·
Floating mini slab trackform (Type 3) –– additional attenuation of about 20 to 30dB(A).
10.67 Nonetheless, these contingency mitigation measures would be reviewed
when more specific data are available at later stage (e.g. after tunnel boring
during the construction stage).
Evaluation of Residual Impacts
10.68
No adverse residual impact would be expected
during both construction and operation phases.
Environmental Monitoring and Audit Requirements
10.69
The predicted construction ground-borne noise
would comply with the noise criteria. Therefore, environmental monitoring is
considered not necessary during construction phase.
10.71
Construction ground-borne noise impacts
arising from rock breaking/drilling associated with the operation of TBM and
PME (such as hydraulic breaker, drill rig, pile rig, etc) were found to comply
with noise criteria. No adverse cumulative construction ground-borne noise
impacts were predicted. Therefore, in terms of ground-borne noise impacts, both
TBM and Cut & Cover tunnel construction methods are considered to be
feasible.
10.72 During operation phase, predictions of ground-borne noise levels at the
identified representative NSRs were performed using the methodology recommended
by the US Department of Transportation. With suitable trackform, the predicted
ground-borne noise criteria at all representative NSRs would comply with the
adopted noise criteria. Potential cumulative impact from existing/future rail
lines was considered. No adverse cumulative impact is anticipated.
10.73
Although adverse
impact of operational ground-borne noise from the Project is not anticipated,
provisions have been made in the design of the tunnel for installation of
necessary contingency mitigation measures should they be necessary. Such contingency mitigation measures would be reviewed when
more specific data are available at later stage (e.g. after tunnel boring).