5.1
As
part of the HATS Stage
5.2 No groundborne noise would be expected during operation of the Project and hence no operational impact assessment was carried out under this Section.
5.3
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 Noise Control Ordinance (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 levels (ANL). These criteria
apply to all residential buildings, schools, hospital, temple and church in
accordance to the Area Sensitivity Rating (ASR). These groundborne noise
criteria have been adopted in the “Project Profile for Development of the
Former Marine Police Headquarter (FMPHQ) for direct application of
Environmental Permit” and “Kowloon Southern Link” (KSL) by Kowloon-Canton Railway Corporation (KCRC) with the EIA report (Application No. EIA-098/2004) approved by Environmental
Protection Department (EPD) in March 2005.
5.4
For
any construction work with the restricted hours period (1900-0700) a
construction noise permit must be applied in accordance to the Technical
Memorandum of NCO.
5.5
The construction groundborne
noise criteria for the representative noise sensitive receiver(s) (NSR) for ASR
along HATS
Table 5.1 Construction Groundborne Noise Criteria for Schools, Hospital, Hotel Guestrooms and Domestic Premises
|
|
Groundborne Noise
Criteria, dB(A) |
||||
NSR Description |
Daytime |
Daytime during General Holidays and Sundays and All Days during
Evening |
Night-time |
||
|
|
All ASR |
ASR “A” |
ASR “B” |
ASR “A” |
ASR “B” |
|
School
(Classrooms) |
60/55* |
50 |
55 |
- |
- |
|
Hotel
guestrooms and Domestic premises |
65 |
50 |
55 |
35 |
40 |
*For schools during examination
period
5.6
The
proposed deep tunnel alignments will run from North Point to Sai Ying Pun, Ap
Lei Chau to Sai Ying Pun and then from Sai Ying Pun to Stonecutters Island. It
is a 3.5 -
Table 5.2 Tunnel Depth with respect to District
|
Tunnel ID |
District |
Depth (mPD) |
Construction Method |
|
J |
North Point to Wanchai |
-160 |
TBM or D&B |
|
K |
Wanchai to Sai Ying Pun |
-150 |
TBM or D&B |
|
L |
Sai Ying Pun to |
-140 |
TBM or D&B |
|
M |
Sai Ying Pun to |
-120 |
TBM or D&B |
|
N |
|
-70 |
TBM or D&B |
|
P |
Cyberport via Wah Fu to |
-80 |
TBM or D&B |
|
Q |
Ap Lei Chau to |
-60 |
HDD |
|
Effluent Tunnel |
Flow Distribution Chamber at SCISTW to Outfall |
-50 |
TBM or D&B |
Notes: Locations of the tunnel sections can be referred to the figures in Section 2.
5.7 Representative noise sensitive receivers (NSRs) located closest to each tunnel section, which are supposed to receive the highest vibration impacts imposed by construction works, are presented in Table 5.3.
Table 5.3 Summary of Identified Noise Sensitive Receivers
|
Tunnel Section |
NSRs |
Noise Criteria (ASR) |
Rock head depth (mPD) |
Tunnel Depth (mPD) |
Horizontal Distance
from Tunnel to NSR (m) |
NSR Height (mPD) |
Slant Distance from
Tunnel to Piles/ Foundation of NSR (m) |
|
J |
|
B |
-40 |
-160 |
38 |
+4.0 |
126 |
|
|
B |
-40 |
-160 |
32 |
+4.0 |
124 |
|
|
K |
|
C |
-40 |
-150 |
51 |
+4.0 |
121 |
|
|
C |
-40 |
-150 |
77 |
+4.0 |
134 |
|
|
Grand Hyatt, Wan Chai |
C |
-40 |
-150 |
70 |
+4.0 |
130 |
|
|
M |
Merton Block 1, |
B |
-45 |
-120 |
6.5 |
+4.1 |
75 |
|
N |
SAGE Madam Ho Sin Hang Home for the Elderly |
A |
-25 |
-70 |
95 |
+5.4 |
105 |
|
P |
Wah Fu |
B |
-10 |
-80 |
17 |
+25 |
72 |
|
Le Meridien Hotel, Cyberport |
B |
-30 |
-75 |
31 |
+5.4 |
56 |
|
|
Q |
South Horizons Block 10, Ap Lei Chau |
B |
-20 |
-60 |
116 |
+14.3 |
123 |
|
Effluent Tunnel |
Ngong Shuen Chau Barracks |
C |
-30 |
-50 |
335 |
+4.0 |
336 |
Notes: Locations of the tunnel
sections can be referred to the Figure 2.9 in Section 2.
5.8 Not all foundation details of the above identified noise sensitive receivers were provided for the assessment during the study. Therefore, for conservative analysis, it is assumed that all NSRs are having piles rested on rock head level which give a worst case on vibration transmission path. Because of this, the distance from the piles to the tunnel is taken as the slant distance with shortest vibration path.
5.9 In this groundborne noise assessment, distance attenuation is the dominant factor affecting the predicted result. From Table 5.3 the shortest slant distance from tunnel to the foundation/piles appears in Le Meridien Hotel, Cyberport.
5.10 As mentioned above, TBM or D&B would be adopted for tunneling at most of the tunnel sections. However, D&B is not considered with respect to noise annoyance since the duration of blasting is very short and infrequent. Therefore, as the worst case scenario, TBM was assumed to be the construction method all along the tunnel alignment for groundborne noise assessment. In principle, vibration would be transmitted from the operation of TBM via bedrock or soil to the nearby foundations of the NSR, and it would then be transmitted primarily through the structural elements of the buildings, resulting in groundborne noise to the NSR.
5.11 HDD would be employed as micro-tunneling method for the tunnel section from Aberdeen PTW towards Ap Lei Chau PTW. It would start from the surface with maximum inclined angle of 25 degrees to the lowest level of about -76mPD under the sea. After keeping this level along the tunnel alignment, the HDD would then go upwards with the existing angle maximum of 25 degrees to the surface. The drilling process would be carried out in several stages, the first pilot hole with about 300 mm diameter would be firstly finished and then reamed to large hole by several stages up to approximately 1.5 m. Since the size of the HDD is relatively small when comparing with the TBM, and its alignment is about -76mPD under sea which is far away from residential buildings (around 100 m from the nearest South Horizon), it was predicted that groundborne noise generated from this activity would be minimal and hence was not considered in the groundborne noise assessment.
5.12 Other than tunneling, drop/riser/production shafts would also be constructed by mechanical excavation and boring. In particular, the lower shaft at the rock layer would be constructed by means of PME for rock breaking. Hydraulic breaker and RBM will be the major PME to generate groundborne noise affecting the nearby NSRs during lower shaft construction and tunnel drilling. Other construction activities such as lorry movement and concreting etc are unlikely to generate adverse groundborne noise.
5.13
In summary, the major vibration
generating equipment relevant to tunneling and shafting works would be TBM, RBM
and hydraulic breaker. However, at
the time of preparation of this report, there was no available information on
the relevant models and vibration source levels of both types of PME (i.e. TBM
and hydraulic breaker) from the tunnel design engineers. To assess the
groundborne noise generated from the PME, the most relevant source levels for
TBM and hydraulic breakers were derived by making reference to the vibration
source data from other similar tunneling project – ‘Kowloon Southern Link’ (KSL
EIA) by KCRC. The source level of the TBM extracted
from KSL EIA is shown in Appendix 5.1.
5.14 Groundborne construction noise was predicted based on the methodology as described in the US Department of Transportation “High-Speed Ground Transportation Noise and Vibration Impact Assessment”.
5.15 Groundborne noise was assessed by using the following formula taking into account relevant source data, geological profile and foundation structure of the NSR. The geological profile for selected NSR for calculation is shown in Figure 5.2.
5.16 The predicted groundborne noise level Lp inside the noise sensitive rooms is given by the following equation.
Lp = Lv,rms
+ Cdist + Cdamping + Cbuilding + Cfloor
+ Cnoise + Cmulti + Ccum
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
Soil
Damping
5.17 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[1]
V(R) = V(Ro)
´ e
5.18 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 5.4.
Table 5.4 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 |
5.19
No damping attenuation was
applied for propagation in rocks. If the vibration propagation through rock
with a distance more than
5.20 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 5.5.
Table 5.5 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 |
5.21 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.
5.22 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 is 26 dB(A) for residential units and 27 dB(A) for hotel guest rooms as mention in the KSL EIA report.
5.23
From
the formula in Section 5.13, groundborne noise was assessed based on the
following factors:
l
Vibration
source strength
l
Vibration
transmission media
l
Distance
from the source to the NSR
l
Floor
level of NSR
l
Standard
factors such as building coupling loss and acoustic conversion
5.24
The
NSR closest to each of the tunnel alignments was identified as shown in Table 5.3. It was assumed that greater
vibration impacts would be anticipated at the NSR with shorter distance from foundation
to the tunnel alignment. In this case, Le Meridien
Hotel at Cyberport
with distance of
|
Factors |
Description |
Worst Case Assumption |
|
Identification of NSR |
Le Meridien Hotel at
Cyberport |
In principal, the shortest
distance from the tunnel to the foundation of NSR would receive the worst
groundborne noise impact. According to the depth of the tunnel alignment and
the distance between the NSR’s foundation & the tunnel (see Table 5.3),
NSRs near Tunnel P running from Cyberport all along to |
|
Source Term |
The TBM working geology would be
granite which is similar to that of the |
The size of the TBM to be used for
this Project would be expected to be half of the KSL Project. Therefore, the
assumed vibration source term was sufficiently conservative. |
|
Soil Damping |
No damping attenuation was applied
to propagation in rocks. If the vibration propagation through rock with a
distance more than |
In this Project, the TBM will
operate in rock level and the vibration will transmit from rock to the
foundation pile of the NSR. Therefore, by assuming the whole transmission
process in rock media without faults and joints as the worst case scenario,
zero damping effect was therefore adopted. |
|
Floor to Floor
Attenuation |
Loss of 1 dB reduction
per floor |
The hotel guest rooms
were assumed to be located at the third level of the hotel. Therefore, a
floor to floor attenuation factor of -3dB(A) was applied in the calculation. |
|
Distance Attenuation |
Standard acoustic principle
for determining distance attenuation was adopted in the present assessment. |
Assuming the tunnel
alignment is directly under the NSR, no offset was applied. |
|
Building Coupling Loss |
Standard acoustic principle
for determining building coupling loss was adopted in the present assessment. |
Standard conversion |
|
Coupling Loss from
Bedrock to Pile |
In the KSL EIA, a 18
dB(A) reduction was applied for the coupling Loss from bedrock to pile. |
When the TBM is
drilling through the bed rock, the vibration will be transmitted along the
rock mass to the piles of nearby buildings if the piles rest on bed rock
directly. When the vibration hits
the piles of the buildings, it will be transferred without loss. Therefore, no bed rock to pile loss
was applied in this assessment. |
|
Conversion from
Vibration to Noise |
Standard acoustic
principle for converting vibration levels to noise levels was adopted in the
present assessment. |
Standard conversion |
|
Conversion to
A-weighted Noise |
Standard acoustic
principle for converting vibration levels to noise levels was adopted in the
present assessment. |
Standard conversion |
5.25
The
NSR closest to the drop shaft is Wah Ming House of Wah Fu Estate which is
around
|
Factors |
Description |
Worst Case Assumption |
|
Identification of NSR |
Wah Ming House of Wah
Fu Estate |
Wah Ming House is only |
|
Source Term |
Hydraulic Breaker - Refer to
Appendix 7-1 of EIA report of KSL project. RBM assumed to be the same as TBM
operation but working vertically. Reference is also to KSL project. |
The size of the RBM to be used for
this Project would be expected to be half of the KSL Project. Therefore, the
assumed vibration source term was sufficiently conservative. |
|
Soil Damping |
No damping attenuation was applied
to propagation in rocks. If the vibration propagation through rock with a
distance more than |
Assuming the whole transmission
process in rock media without faults and joints as the worst case scenario,
zero damping effect was therefore adopted. |
|
Floor to Floor
Attenuation |
Loss of 1 dB reduction
per floor |
The residential units
were assumed to be located at the second level of the hotel. Therefore, a
floor to floor attenuation factor of -2dB(A) was applied in the calculation. |
|
Distance Attenuation |
Standard acoustic principle
for determining distance attenuation was adopted in the present assessment. |
Horizontal plan
distance is assumed from the hydraulic breaker / RBM to the NSR |
|
Building Coupling Loss |
Standard acoustic
principle for determining building coupling loss was adopted in the present
assessment. |
Standard conversion |
|
Coupling Loss from
Bedrock to Pile |
In the KSL EIA, a 18
dB(A) reduction was applied for the coupling Loss from bedrock to pile. |
When the hydraulic breaker
/ RBM is breaking the rock, the vibration will be transmitted along the rock
mass to the piles of nearby buildings if the piles rest on bed rock
directly. When the vibration hits
the piles of the buildings, it will be transferred without loss. Therefore, no bed rock to pile loss
was applied in this assessment. |
|
Conversion from
Vibration to Noise |
Standard acoustic
principle for converting vibration levels to noise levels was adopted in the
present assessment. |
Standard conversion |
|
Conversion to
A-weighted Noise |
Standard acoustic
principle for converting vibration levels to noise levels was adopted in the
present assessment. |
Standard conversion |
5.26
Based
on the vibration source data and the existing geological profile available at
the time of reporting, a worst case scenario for potential groundborne
construction noise impact was assessed using methodology as presented above. Unmitigated groundborne noise levels
predicted at the worst affected NSR (Le Meridien Hotel
and Wah Ming House)
is shown in Table 5.8. Details calculations of groundborne
noise levels are presented in Appendix
5.2.
Table 5.8 Unmitigated Groundborne Construction Noise Levels at the Worst Affected NSR
|
Construction Activities |
NSR |
Predicted Groundborne Noise
Level at NSR, dB(A) |
Noise Criterion, dB(A) of ASR
“B” |
||
|
0700-1900 |
1900-2300 |
2300-0700 |
|||
|
Hydraulic Breaker at Wah Fu Drop Shaft |
Wah Ming House |
40 |
65 |
55 |
40 |
|
Raise Boring Machine at Wah Fu Drop Shaft |
Wah Ming House |
40 |
|||
|
TBM under Cyberport |
Le Meridien Hotel |
36 |
|||
Note: According to the
preliminary construction programme available at the time of reporting, no
simultaneous operations of the TBM, RBM and hydraulic breaker would be
expected.
5.27
As
shown in the table above, the predicted groundborne noise levels generated by
using TBM, RBM or hydraulic breaker during construction phase of the Project
would be below the relevant noise assessment criterion at the worst affected
NSR. Hence, adverse groundborne noise impact associated
with the construction of the Project would not be expected.
5.28
No
mitigation measures would be recommended as no adverse groundborne noise impact
was expected in the unmitigated scenario during construction stage of the
Project.
5.29
The
groundborne noise level at the worst affected NSR was predicted to be well
below the relevant noise criterion. No residual groundborne noise impact would
therefore be anticipated during the construction phase of the Project.
5.30
Potential
groundborne noise sources during the construction phase of the Project have
been identified. The major activities inducing potential groundborne noise
impacts are from operation of TBM, RBM and hydraulic breaker during tunneling
and rock breaking. The noise impact on the closest sensitive receiver was
assessed and the results indicated that the predicted impacts would be within the
statutory requirements. In other words, all NSRs along the proposed tunnel
alignment would not be adversely affected by groundborne noise generated by the
construction of the Project, and mitigation measures as well as monitoring
programme would not be necessary. Regardless of the results of the groundbornes
noise assessment for restricted hours (1900-0700), it is emphasis that a
construction noise permit must be applied in accordance to the Technical
Memorandum of NCO for any construction work within the restricted hours period.