5.
NOISE
IMPACT ASSESSMENT
5.1
Introduction
5.1.1
This chapter addresses the potential
noise impacts associated with construction and operation phases of the proposed
Hong Kong West Drainage Tunnel.
5.1.2
The main noise impacts are identified as
follows:
(i) Construction
Phase – the noise generated from construction activities in particular those
requiring the use of powered mechanical equipment has the potential to pose
adverse noise impacts to surrounding noise sensitive receivers (NSRs). The ground-borne noise / vibration impact may also
pose noise impacts at the NSRs during the
construction phases while the tunnel is excavated using a TBM (tunnel boring
machine).
(ii) Operation
Phase – the operation impact is not expected to pose any adverse noise impact
to the environment, as there will not be any noisy electrical or mechanical
equipment to be operated during operation.
5.1.3
The scope of this noise impact
assessment follows the requirement under Section 3.4.2 of the EIA Study Brief
issued in May 2001.
5.2
Construction
Noise Assessment
Introduction
5.2.1
This section presents the methodology,
representative sensitive receivers and relevant assessment criteria.
5.2.2
The Study Area is characterized by the
suburbs of eastern and western mid-levels of Hong Kong Island, where district
distributors interlace low-density or mid-density residential areas located at
the edge of Country Parks. While the noise environment of these areas is
dominated by traffic noise generated by relatively low
traffic volume. Therefore, background noise is generally low. There are no
major commercial or industrial premises in the Study Area, whereas some of the
sensitive receivers are schools and educational institutions.
5.2.3
In this assessment, the worst case
scenarios have been adopted to examine the noise impacts and where necessary
appropriate mitigation measures have been recommended.
Construction Noise Assessment Criteria
5.2.4
Noise impacts
were assessed in accordance with the criteria and methodology given in the
Technical Memoranda made under the Noise Control Ordinance (NCO), and EIAO-TM.
5.2.5
The NCO provides
the statutory framework for noise
control. This defines statutory
limits applicable to equipment used during the construction and operation
phases of the proposed works in the
study area. The NCO invokes four
Technical Memoranda, which define the technical means for noise assessment:
Technical
Memorandum on Noise from Places other than Domestic Premises, Public Places or
Construction Sites (IND-TM);
Technical
Memorandum on Noise from Construction Work in Designated Areas (DA-TM);
Technical
Memorandum on Noise from Construction Work other than Percussive Piling
(GW-TM); and
Technical
Memorandum on Noise from Percussive Piling (PP-TM).
5.2.6
The NCO and the
accompanying Technical Memoranda provide a mechanism for assessing noise levels
and the statutory power to control noise.
5.2.7
With regard to
the assessment of the operation noise impacts, the NCO designates acceptable
noise levels for Noise Sensitive Receivers (NSRs) on
the basis of an Area Sensitivity Rating (ASR),
based on the characterisation of the area within which they are located such as
rural, village, low-density residential, or urban. Within these areas, the presence of
"influencing factors" (such as the presence of industrial activities
or major roads) can further affect the ASR
and therefore the acceptable noise level (see Table 5.1).
Table
5.1 Area Sensitivity Ratings
|
Type of Area Containing NSR
|
Degree to which NSR is affected by Influencing
Factor
|
|
Not Affected
|
Indirectly Affected
|
Directly Affected
|
|
Rural Area
|
A
|
B
|
B
|
|
Urban Area
|
B
|
C
|
C
|
|
Low density residential area consisting of low-rise
or isolated high-rise developments
|
A
|
B
|
C
|
|
Area other than those above
|
B
|
B
|
C
|
Construction Activities
5.2.8
Under the GW-TM,
noise from construction activity is not restricted during the period 0700 -
1900 hours on weekdays, except public holidays. However, the EIAO-TM identifies
a daytime general construction noise limit of 75 dB(A) Leq
(30 minutes) for domestic premises, 70 dB(A) Leq
(30 minutes) for educational institutes and places where unaided voice
communication is required and 65dB(A) Leq
(30 minutes) is allowed for school during examination period. This standard was
used as assessment criteria in the construction noise assessment. The noise standards are present in Table
5.2.
Table 5.2 EIAO-TM Daytime Construction
Noise Standards
|
Uses
|
Noise Standard
(Leq, 30 min
dB(A))
|
|
|
75
|
|
|
70
|
|
Educational
Institutions (during examination periods)
|
65
|
5.2.9
The NCO provides
statutory controls on general construction works
during the restricted hours (i.e. 1900 to 0700 hours Monday to Saturday and at
any time on Sundays and public holidays). The use of powered mechanical
equipment (PME) for carrying out
of construction works during the
restricted hours will require a CNP. The Noise Control Authority is
guided by the GW-TM when assessing such an application. A CNP may be
issued if the CNL is equal to or
less than the ANL. The ANLs are related to the noise sensitivity of the area in
question and the Noise Control Authority will judge these at the time of the
CNP application. As conditions may vary between the time of the EIA for a
project and the time of a CNP application, the assignment of any Area
Sensitivity Ratings in the EIA is not binding upon the Noise Control
Authority. The relevant ANLs are shown in Table
5.3, which are determined by Area Sensitive Ratings (ASRs).
Table 5.3 Acceptable Noise Levels (ANL, Leq, 5min dB(A))
|
Time
Period
|
Area
Sensitivity Rating
|
|
A
|
B
|
C
|
|
All days during the evening (1900-2300
hours) and general holidays (including Sundays) during the day and evening
(0700-2300 hours)
|
60
|
65
|
70
|
|
All days
during the night-time (2300-0700 hours)
|
45
|
50
|
55
|
5.3
Representative
Noise Sensitive Receivers
5.3.1
A site survey and desk study of
government survey maps were conducted to determine the location of existing
noise sensitive receivers within 300m from the boundary of the Study Area.
There are a number of residences in the vicinity of the work
areas; the most representative of these are chosen as Representative Noise
Sensitive Receivers (RNSRs). RNSRs
were selected to represent both existing and future land uses based on the
consideration of their respective distances from construction activities.
5.3.2
For assessment of construction noise, RNSRs are selected near the tunnel portals and intake
shafts where Powered Mechanical Equipment (PME)
will be used during construction. The choice of the locations for the tunnel portals
and intake shafts are given in Chapter 2 of this report. RNSRs are
not selected along tunnel sections where PME
is used underground. Ground-borne noise during construction tunnel has been
taken into account during the construction phase.
5.3.3
Figures 5.1-5.32 present the locations
of the selected RNSRs. Table 5.4 gives the details of
each of these RNSRs and the type of land use they
represent.
Table 5.4 Details of Representative Noise Sensitive Receivers
|
NSR
No.
|
Figure
no.
|
Descriptions
|
Status
|
No. of Floors
|
No. of stories of non-sensitive structure
|
Shortest distance to RNSR (m)
|
|
Eastern Portal
|
5.1
|
|
|
|
|
|
|
EP/1
|
|
Blk B Lai Sing Court
|
Residential
|
22
|
|
61
|
|
EP/2
|
|
Future
Residential Development (Tower 1, The Legend)
|
Residential
|
40
|
6 floors of Car
Park
|
48
|
|
EP/3
|
|
True
Light Middle School of Hong Kong
|
School
|
5
|
|
40
|
|
Western Portal
|
5.2
|
|
|
|
|
|
|
WP/1
|
|
Point
Breeze
|
Residential
|
2
|
|
175
|
|
WP/2
|
|
Aegean
Terrace
|
Residential
|
3
|
|
140
|
|
Intake shafts B2(P)
|
5.3
|
|
|
|
|
|
|
B2(P)/1
|
|
Borrett Mansions
|
Residential
|
21
|
|
37
|
|
B2(P)/2
|
|
Carmel
School
|
School
|
4
|
|
95
|
|
B2(P)/3
|
|
Glory
Mansion
|
Residential
|
10
|
|
45
|
|
B2(P)/4
|
|
Grand
House
|
Residential
|
10
|
|
45
|
|
Intake shafts BR3(P)
|
5.4
|
|
|
|
|
|
|
BR3(P)/1
|
|
Greenville
Garden Block D
|
Residential
|
23
|
5 floors of Car
Park
|
85
|
|
Intake shafts BR4(P)
|
5.5
|
|
|
|
|
|
|
BR4(P)/1
|
|
Kennedy
Court
|
Residential
|
5
|
|
110
|
|
BR4(P)/2
|
|
St. James' Primary School
|
School
|
4
|
1 floor of Hall
|
141
|
|
BR4(P)/3
|
|
Grandview
Tower
|
Residential
|
29
|
|
120
|
|
Intake shafts BR5(P)
|
5.6
|
|
|
|
|
|
|
BR5(P)/1
|
|
Sakura
Court
|
Residential
|
12
|
1 floor of Car
Park
|
90
|
|
BR5(P)/2
|
|
Camelot
Height
|
Residential
|
20
|
|
96
|
|
BR5(P)/3
|
|
HK
Tang King Po College
|
School
|
6
|
|
160
|
|
Intake shafts
BR6(P)
|
5.7
|
|
|
|
|
|
|
BR6(P)/1
|
|
16 Caronia
|
Residential
|
2
|
|
30
|
|
BR6(P)/2
|
|
Man
Yuen Garden
|
Residential
|
12
|
|
45
|
|
BR6(P)/3
|
|
15 Carionia
|
Residential
|
2
|
|
90
|
|
Intake shafts BR7(P)
|
5.7
|
|
|
|
|
|
|
BR7(P)/1
|
|
16 Caronia
|
Residential
|
4
|
|
23
|
|
BR7(P)/2
|
|
15 Caronia
|
Residential
|
2
|
|
28
|
|
BR7(P)/3
|
|
12 B
Bowen Road
|
Residential
|
5
|
|
70
|
|
BR7(P)/4
|
|
Monticello
|
Residential
|
20
|
|
61
|
|
BR7(P)/5
|
|
Man
Yuen Garden
|
Residential
|
12
|
|
75
|
|
Intake shafts DG1(P)
|
5.8
|
|
|
|
|
|
|
DG1(P)/1
|
|
Rosaryhill School
|
School
|
6
|
2 floors of
Hall
|
62
|
|
DG1(P)/2
|
|
Blk C Villa Monte Rosa
|
Residential
|
20
|
1 floor of Car
Park
|
34
|
|
DG1(P)/3
|
|
Evergreen
Villa
|
Residential
|
16
|
3 floors of
Cark Park
|
75
|
|
Intake shafts E5(A)(P)
|
5.9
|
|
|
|
|
|
|
E5(A)(P)/1
|
|
Buddist Li Ka Shing
Care & Attention Home for the Elderly
|
Elderly Home
|
9
|
2 floors of Car
Park
|
15
|
|
E5(A)(P)/2
|
|
Blk 10, 135 Tai
Hang Road
|
Residential
|
20
|
2 floors of Car
Park
|
23
|
|
Intake shafts E5(B)(P)
|
5.9
|
|
|
|
|
|
|
E5(B)(P)/1
|
|
Blk 9 Aurizon
|
Residential
|
20
|
2 floors of Car
Park
|
32
|
|
E5(B)(P)/2
|
|
Blk 1 Cavendish Heights
|
Residential
|
32
|
4 floors of Car
Park
|
27
|
|
E5(B)(P)/3
|
|
Blk 10, 135 Tai
Hang Road
|
Residential
|
20
|
2 floors of Car
Park
|
37
|
|
Intake shafts E7(P)
|
5.10
|
|
|
|
|
|
|
E7(P)/1
|
|
Marymount Secondary School
|
School (School hall)
|
7
|
|
19
|
|
E7(P)/2
|
|
French
International School
|
School (School hall)
|
6
|
|
87
|
|
E7(P)/3
|
|
117
Blue Pool Road
|
Residential
|
3
|
1 floor of Car
Park
|
20
|
|
E7(P)/4
|
|
Blk J Villa Dorada
|
Residential
|
2
|
|
51
|
|
E7(P)/5
|
|
Blk 1 Green Lane Court
|
Residential
|
3
|
1 floor of Car
Park
|
52
|
|
Intake shafts GL1(P)
|
5.11
|
|
|
|
|
|
|
GL1(P)/1
|
|
Green
Lane Hall
|
Residential
|
15
|
|
29
|
|
Intake shafts HKU(P)
|
5.12
|
|
|
|
|
|
|
HKU1(P)/1
|
|
WSD
Staff Quarters
|
Residential
|
2
|
|
44
|
|
Intake shafts HR1
|
5.13
|
|
|
|
|
|
|
HR1/1
|
|
Shuk Yuen Terrace
|
Residential
|
3
|
|
52
|
|
HR1/2
|
|
16-20
Broom Road
|
Residential
|
4
|
|
33
|
|
Intake shafts M3(P)
|
5.14
|
|
|
|
|
|
|
M3(P)/1
|
|
May
Fair
|
Residential
|
29
|
9 floors of Car
Park /Hall
|
65
|
|
Intake shafts MA13(P)&MA14(P)
|
5.15
|
|
|
|
|
|
|
MA13(P) & MA14(P)/1
|
|
The Harbour View
|
Residential
|
25
|
4 floors of
Club/ Car Park
|
31
|
|
MA13(P) & MA14(P)/2
|
|
Magazine
Gap Towers
|
Residential
|
12
|
|
31
|
|
MA13(P) & MA14(P)/3
|
|
Magazine
Heights
|
Residential
|
13
|
4 floors of
Platform
|
75
|
|
Intake shafts MA15(P)
|
5.15
|
|
|
|
|
|
|
MA15(P)/1
|
|
The Harbour View
|
Residential
|
25
|
6 floors of
Club/ Car Park
|
35
|
|
MA15(P)/2
|
|
Magazine
Gap Towers
|
Residential
|
12
|
|
105
|
|
MA15(P)/3
|
|
Rose
Gardens
|
Residential
|
12
|
|
56
|
|
MA15(P)/4
|
|
Magazine
Court
|
Residential
|
12
|
1 floor of Car
Park
|
85
|
|
Intake shafts MA17(P)
|
5.16
|
|
|
|
|
|
|
MA17(P)/1
|
|
Blk A Grenville House
|
Residential
|
12
|
1 floor of Car
Park
|
51
|
|
MA17(P)/2
|
|
Magazine
Court
|
Residential
|
12
|
7 floors of
Platform
|
65
|
|
MA17(P)/3
|
|
Rose
Gardens
|
Residential
|
12
|
|
95
|
|
Intake shafts MB16(P)
|
5.17
|
|
|
|
|
|
|
MB16/1
|
|
Clement
Court
|
Residential
|
3
|
1 floors of
Platform
|
37
|
|
MB16/2
|
|
81
Perkins Road
|
Residential
|
2
|
|
28
|
|
MB16/3
|
|
83
Perkins Road
|
Residential
|
2
|
|
27
|
|
Intake shafts MBD2
|
5.18
|
|
|
|
|
|
|
MBD2/1
|
|
Amber
Lodge
|
Residential
|
2
|
1 floor of
Ground Story
|
40
|
|
Intake shafts P5(P)
|
5.19
|
|
|
|
|
|
|
P5(P)/1
|
|
24
Po Shan Road
|
Residential
|
1
|
1 floor of Car
Park
|
20
|
|
P5(P)/2
|
|
23
Po Shan Road
|
Residential
|
10
|
1 floor of Car
Park
|
45
|
|
P5(P)/3
|
|
Haddon
Court
|
Residential
|
4
|
|
57
|
|
Intake shafts PFLR(P)
|
5.20
|
|
|
|
|
|
|
PFLR(P)/1
|
|
Honey
Court
|
Residential
|
9
|
1 floor of Car
Park
|
28
|
|
PFLR(P)/2
|
|
Pokfulam Heights
|
Residential
|
4
|
1 floor of Car
Park
|
29
|
|
Intake shafts RR1(P)
|
5.21
|
|
|
|
|
|
|
RR1(P)/1
|
|
Primrose
Court
|
Residential
|
28
|
1 floor of Hall
|
27
|
|
RR1(P)/2
|
|
Scenic
Heights
|
Residential
|
24
|
8 floors of Car
Park/ Hall
|
33
|
|
RR1(P)/3
|
|
Ying
Wa Girl's School
|
School
|
6
|
1 floor of Car
Park
|
77
|
|
RR1(P)/4
|
|
Peaksville Court
|
Residential
|
14
|
2 floors of Car
Park
|
35
|
|
Intake shafts THR2(P)
|
5.22
|
|
|
|
|
|
|
THR2(P)/1
|
|
Hong
Chi Lions Morninghill School
|
School (School hall)
|
2
|
|
45
|
|
THR2(P)/2
|
|
Hong
Kong Japanese School
|
School
|
5
|
1 floor of Hall
|
41
|
|
THR2(P)/3
|
|
Wan
Chui Chuen
|
Residential
|
5
|
|
30
|
|
THR2(P)/4
|
|
Marymount Primary School
|
School
|
5
|
|
97
|
|
Intake shafts TP4(P)
|
5.23
|
|
|
|
|
|
|
TP4(P)/1
|
|
Tregunter Tower 1
|
Residential
|
34
|
1 floor of Hall
|
41
|
|
TP4(P)/2
|
|
Tregunter Tower 2
|
Residential
|
32
|
1 floor of Hall
|
40
|
|
Intake shafts TP5(P)
|
5.23
|
|
|
|
|
|
|
TP5(P)/1
|
|
Tavistock II
|
Residential
|
34
|
1 floor of Hall
|
61
|
|
Intake shafts TP789(P)
|
5.24
|
|
|
|
|
|
|
TP789(P)/1
|
|
Tavistock
|
Residential
|
13
|
1 floor of Hall
|
48
|
|
TP789(P)/2
|
|
Branksome
|
Residential
|
23
|
|
64
|
|
Intake shafts WO(P)
|
5.25
|
|
|
|
|
|
|
WO(P)/1
|
|
Sir
Ellis Kadoorie Secondary School (Edward Hall)
|
School (School hall)
|
4
|
|
36
|
|
WO(P)/2
|
|
Goodview
Garden
|
Residential
|
2
|
2 floors of Car
Park
|
51
|
|
WO(P)/3
|
|
Kui Yuen
|
Residential
|
3
|
|
72
|
|
Intake shafts W1(P)
|
5.26
|
|
|
|
|
|
|
W1(P)/1
|
|
74
Bamboo Grove
|
Residential
|
33
|
1 floor of Hall
|
81
|
|
W1(P)/2
|
|
Blk B Merry Garden
|
Residential
|
12
|
1 floor of Hall
|
76
|
|
W1(P)/3
|
|
St James's Primary School
|
School
|
4
|
1 floor of Hall
|
122
|
|
W1(P)/4
|
|
Caine Terrace
|
Residential
|
4
|
1 floor of Hall
|
72
|
|
Intake shafts W3(P)
|
5.27
|
|
|
|
|
|
|
W3(P)/1
|
|
Regent
on the Park
|
Residential
|
36
|
1 floor of Hall
|
75
|
|
W3(P)/2
|
|
Carmel
School
|
School
|
3
|
|
174
|
|
W3(P)/3
|
|
Green
Villa
|
Residential
|
4
|
|
128
|
|
Intake shafts W5(P)
|
5.28
|
|
|
|
|
|
|
W5(P)/1
|
|
Raimondi
College
|
School
|
7
|
3 floors of
Platform
|
13
|
|
W5(P)/2
|
|
Raimondi
Primary School
|
School
|
10
|
3 floors of
Platform
|
12
|
|
W5(P)/3
|
|
Caritas
House
|
Residential
|
9
|
|
30
|
|
W5(P)/4
|
|
Canossa
Hospital
|
Hospital
|
6
|
|
76
|
|
Intake shafts W8(P)
|
5.29
|
|
|
|
|
|
|
W8/1
|
|
Blk1,
80 Robinson Road
|
Residential
|
28
|
11 floors of
Platform
|
11
|
|
W8/2
|
|
Bonham
Court
|
Residential
|
27
|
1 floor of Hall
|
17
|
|
W8/3
|
|
Hong
Kong Institute of Technology
|
School
|
6
|
2 floors
including G/F
|
5
|
|
Intake shafts W10(P)
|
5.30
|
|
|
|
|
|
|
W10/1
|
|
Future
Residential Development
|
Residential
|
12
|
|
24
|
|
W10/2
|
|
Blk 2 Po Shan Rd
|
Residential
|
10
|
7 floors of
Platform
|
29
|
|
W10/3
|
|
University
Lodge
|
School
|
1
|
|
60
|
|
W10/4
|
|
Blk A-B University Heights
|
Residential
|
12
|
1 floor of Hall
|
56
|
|
Intake shafts W11(P)
|
5.31
|
|
|
|
|
|
|
W11(P)/1
|
|
17
Hatton Road
|
Residential
|
3
|
1 floor of Car
Park
|
48
|
|
W11/(P)/2
|
|
Block
B Hatton Place
|
Residential
|
10
|
1 floor of Car
Park
|
74
|
|
Intake shafts W12(P)
|
5.32
|
|
|
|
|
|
|
W12(P)/1
|
|
Sylvanbrook
|
Residential
|
4
|
1 floor of Car
Park
|
10
|
|
W12(P)/2
|
|
94A Pok Fu Lam Road
|
Residential
|
3
|
1 floor of Car
Park
|
11
|
|
W12(P)/3
|
|
Blk A La Clare Mansion
|
Residential
|
12
|
3 floors of
Platform
|
43
|
5.4
Airborne
Construction Noise Assessment
Potential
Sources of Impacts
5.4.1
The major construction
activities that
are anticipated at tunnel portals and intake are summarised
in Table 5.5. All
proposed intakes and portals locations are outside Country Parks. The proposed intakes locations and
alternative have been considered and discussed in Chapter 2.
Table
5.5 Construction activities at portals and intakes
|
Eastern/Western
Portals
|
Intakes (35 in total)
|
Remarks
|
|
Site clearance and surface breaking
|
Site clearance and surface breaking
|
use of earthmoving
machinery and vehicles
|
|
Drilling
|
Initial Excavation
|
use of excavators,
loaders, dump trucks, rock drill
|
|
Loading
|
Rock drilling for manhole construction
|
|
Site formation
|
Excavation
|
|
TBM supporting activities
|
-
|
Conveyor belt, gantry,
dump truck, muck train
|
|
Finalized stage – General works
|
Finalized stage – General works
|
Dump trucks, conveyor
belts
|
|
Finalized stage – Concreting works
|
Finalized stage – Concreting
|
Concrete lorry mixer,
poker
|
|
Finalized stage – Marine Transport
|
-
|
Barge, Tug boat
|
5.4.2
All concrete to be used will be
transported to the work sites.
Therefore, there will be no concrete batching plant on-site. All sites except Western Portal will
be accessed
mainly via existing roads.
Construction
Equipment
5.4.3
The type and quantity of Powered
Mechanical Equipment (PME) likely
to be used in each construction works
described above and their Sound Power Level (SWL) are listed in Tables 5.6a-b.
It should be noted that this is an assumption of the most likely equipment to
be used. The actual construction equipment will be determined by the Contractor
performing the works.
Table 5.6a Equipment List for each
Construction Activity for Eastern and Western Portals
|
Activity /
Equipment
|
Date
|
Duration
|
TM Code
|
SWL,
dB(A)
|
Quantity
|
Summation
of SWL, dB(A)
|
Total SWL
dB(A), Eastern Portal
|
Total SWL
dB(A), Western portal
|
|
Site clearance
|
May 2007 to Jun
2008
|
56 weeks
|
|
|
|
|
|
|
|
Bulldozer
|
030
|
115
|
1
|
115
|
115
|
115
|
|
Surface breaking
|
|
|
|
|
|
|
|
Breaker, excavator mounted
|
028
|
122
|
1
|
122
|
122
|
122
|
|
Drilling
|
|
|
|
|
|
|
|
Rock drill, hand-held (pneumatic)
|
183
|
116
|
1
|
116
|
116
|
116
|
|
Air compressor
|
003
|
104
|
1
|
104
|
|
|
|
Loading
|
|
|
|
|
|
|
|
Wheeled Loader
|
081
|
112
|
1
|
112
|
118
|
118
|
|
Dump Truck
|
067
|
117
|
1
|
117
|
|
|
|
Site formation
|
|
|
|
Excavator
|
081
|
112
|
1
|
112
|
118
|
118
|
|
Dump Truck
|
067
|
117
|
1
|
117
|
|
|
|
TBM Supporting
Activities
|
Jun 2008 to Jun
2011
|
Eastern Portal
-
208 weeks
Western
Portal - 212 weeks
|
|
|
|
Gantry
|
122
|
95
|
1
|
95
|
118
|
119
|
|
Ventilation fan
|
241
|
108
|
1
|
108
|
|
|
|
Conveyor belt
|
041
|
90
|
1
|
90
|
|
|
|
Muck train
|
#
|
105
|
1
|
105
|
|
|
|
Dump Truck
|
067
|
117
|
1
|
117
|
|
|
|
Air compressor
|
003
|
104
|
1
|
104
|
|
|
|
Tug Boat (Western portal only)
|
221
|
110
|
1
|
110
|
|
|
|
Crane, barge mounted (Western portal only)
|
048
|
112
|
1
|
112
|
|
|
|
Finalized stage - General Works
|
Apr 2011 to Nov
2011
|
Eastern Portal
-
12 weeks
Western Portal
-18 weeks
|
|
|
|
Excavator
|
081
|
112
|
1
|
112
|
118
|
117
|
|
Dump Truck
|
067
|
117
|
1
|
117
|
|
|
|
Finalized stage - Concreting
|
|
|
|
|
|
|
|
Concrete lorry mixer
|
044
|
109
|
1
|
109
|
114
|
114
|
|
Poker, vibratory, hand-held
|
170
|
113
|
1
|
113
|
|
|
|
Finalized stage - Marine Transport
|
|
|
|
|
|
|
|
Tug Boat (Western portal only)
|
221
|
110
|
1
|
110
|
|
114
|
|
Crane, barge mounted (Western portal only)
|
048
|
112
|
1
|
112
|
|
|
SWL – Sound Power Level;
# - Information from supplier
Table
5.6b Equipment List for each Construction Activity for Intakes
|
Activity / Equipment
|
Date
|
Duration per intake
|
TM Code
|
SWL,
dB(A)
|
Quantity
|
Summation
of SWL, dB(A)
|
Total SWL dB(A),
|
|
Site clearance
|
Aug 2008 to Jun 2011
|
2 weeks
|
|
|
Excavator
|
081
|
112
|
1
|
112
|
112
|
|
Surface breaking
|
|
|
Breaker,
excavator mounted
|
028
|
122
|
1
|
122
|
122
|
|
Initial Excavation
|
4
months
|
|
|
Excavator
|
081
|
112
|
1
|
112
|
112
|
|
Water
pump, submersible (electric)
|
283
|
85
|
1
|
85
|
|
|
Generator,
silenced
|
102
|
100
|
1
|
100
|
|
|
Rock drill for manhole
|
1 month
|
|
|
Breaker,
excavator mounted
|
028
|
122
|
1
|
122
|
122
|
|
Excavation method I
|
5 months
|
|
|
Raise
boring machine
|
166
|
100
|
1
|
100
|
103
|
|
Hydraulic
power pack
|
102
|
100
|
1
|
100
|
|
|
Excavation method II*
|
|
|
|
|
|
|
Reverse
circulation drill (50% on time)
|
166
|
100
|
1
|
97
|
110
|
|
Water
pump, submersible (electric)
|
283
|
85
|
1
|
85
|
|
|
Generator,
silenced
|
102
|
100
|
1
|
100
|
|
|
Lorry
with grab (50% on time)
|
141
|
112
|
1
|
109
|
|
|
Finalized stage - General Works
|
1.5 months
|
|
|
|
|
|
|
Lorry
with crane
|
141
|
112
|
1
|
112
|
112
|
|
Finalized stage - Concreting
|
|
|
|
|
|
|
Concrete
lorry mixer
|
044
|
109
|
1
|
109
|
114
|
|
Poker,
vibratory, hand-held
|
170
|
113
|
1
|
113
|
|
SWL – Sound Power Level
For raise boring SWL, it is assumed the sound
power level for raise boring machine is close to reverse circulation drill. Most of intakes shafts will be
constructed by Excavated Method I (raise boring) except W8, W5, RR1, THR2, WO
and HR1 (Excavated method II – reverse circulation drill). The Method I is
only applicable for site with high rock level while Method II is applicable for
site with thick soil stratum.
5.4.4
The equipment list was reviewed by the
Project Proponent and was considered reasonable in terms of the types and
numbers based on the tentative construction programme.
Construction
Schedule and Program
5.4.5
Only a tentative
construction programme is available at the time of assessment. Work is schedule
to commence in May 2007 and will be completed in Nov 2011.
Construction
Works during Restricted Hours
5.4.6
Construction of intakes will not be
carried out during restricted hours.
For the underground adits and tunnel, it will
be carried out during restricted hours subject to CNP applications.
5.4.7
No movement of spoil off-site will be
carried out during restricted hours at both portals. Spoil arising from the
tunneling activities will be moved to muck pit for overnight stock piling using
a conveyor system. Full enclosure should be provided at muck pit area enclosing
air compressor, muck train, conveyor belt system and ventilation fan during the
TBM support construction stage at the Eastern portal.
5.4.8
Construction works
within restricted hours will be under the control of the statutory conditions
of the CNP. The assessment of these works
is outside the current scope of the EIA brief. The contractor shall have
responsibility of meeting the requirements from the Noise Control
Ordinance. They will have the
responsibility for applying for the necessary CNPs
and demonstrating the predicted noise impacts for their proposed construction
activities during the restricted hours and the effectiveness of the proposed
mitigation, if any.
Assessment
Methodology and Assumptions
5.4.9
The construction noise assessment has
been conducted based on standard acoustic principles, the methodology stated in
the Technical Memorandum on Noise from
Construction Works Other Than Percussive Piling and Sections 5.3 & 5.4
of Annex 13 of the Technical Memorandum on EIA Process. The assessment also
makes reference to the British Standards
(BS) 5228: Part 1.
5.4.10
In general terms, the methodology used involves the following steps:
(i) identification of the most likely worst case scenario from
the construction program;
(ii) identification of
the nearest representative NSRs to the work site;
(iii) calculation of the total
Sound Power Level (SWL) of equipment to be used;
(iv) calculation of distance
attenuation to NSRs from work
site notional noise source point; and
(v) comparison of the
Predicted Noise Levels (PNLs) with the relevant noise
criteria.
5.4.11
All PME
are assumed to be stationary while performing the noisiest activity, such as
loading/off-loading, lifting and ground breaking at different Notional Noise
Sources (NNS) attributed to
various construction activities.
5.4.12
The assessment has been undertaken on
the basis of the assumption that all construction equipment will be located on
a notional noise source point (in accordance with the Technical Memorandum on
Noise from Construction Works Other Than Percussive Piling) and is operating at
the same time. Shielding effect from existing building structures, topographic
features and/or neighboring construction sites have not been considered to
simulate worst-case effect. A façade correction of +3 dB(A)
is added to account for the sound reflection from the building’s surface of a
NSR.
5.4.13
For the construction of intake shafts
along the proposed tunnel, the construction activities will take place
sequentially. For the construction of the two tunnel portals and the stilling
basin, some of the construction activities may take place at the same time. The
total predicted sound power levels attributed to each construction activity and
the scenarios for assessing concurrent construction noise impact are analysed.
Assessment
Results
5.4.14
Predicted noise levels at the closest
identified NSRs without mitigation measures are given
in Tables 5.7a-b for Eastern/Western Portals and Intakes respectively. The results show that the construction
noise will exceed the daytime noise criteria at most of the RNSRs
in view of their close proximity to the site. Suitable mitigation measures are
thus required. The recommended mitigation measures for the construction works are discussed in the following section.
Table 5.7a Predicted Noise Level (Unmitigated) at RNSRs for
Eastern Portals and Western Portals
|
|
Site clearance
|
Surface
Breaking
|
Drilling
|
Loading
|
Site Formation
|
TBM Support
|
Finalized Stage
- General Works
|
Finalized
Stage- Concreting
|
Finalized Stage
- Marine Transport
|
|
Approximate
Duration (weeks)
|
2
|
2
|
8
|
208
|
8
|
212
|
18
|
18
|
18
|
|
Educational
institutions
|
|
EP/3
|
78
|
85
|
79
|
81
|
81
|
81
|
81
|
77
|
|
|
Domestic
premises/hotels/hostels
|
|
EP/1
|
75
|
81
|
76
|
77
|
77
|
77
|
77
|
74
|
|
|
EP/2
|
76
|
83
|
77
|
79
|
79
|
79
|
79
|
75
|
|
|
WP/1
|
64
|
71
|
66
|
68
|
68
|
69
|
68
|
64
|
64
|
|
WP/2
|
66
|
73
|
67
|
69
|
69
|
71
|
69
|
66
|
65
|
Remarks:
|
> 70 dB (Educational Institution)
|
|
> 75 dB (Domestic premises/hotels/hostels)
|
Table 5.7b Predicted Noise Level (Unmitigated) at RNSRs for Intakes
|
|
Site clearance
|
Surface
breaking
|
Initial
Excavation
|
Rock Drilling
for Manhole
|
Excavation
|
Finalized
stage - General Works
|
Finalized
stage - Concreting
|
|
Approximate
Duration
|
1 week
|
1 week
|
4 months
|
1 month
|
< 5 months
|
1 month
|
2 weeks
|
|
Educational
institutions
|
|
B2(P)/2
|
67
|
77
|
67
|
77
|
58
|
67
|
70
|
|
BR4(P)/2
|
64
|
74
|
64
|
74
|
55
|
64
|
66
|
|
BR5(P)/3
|
63
|
73
|
63
|
73
|
54
|
63
|
65
|
|
DG1(P)/1
|
71
|
81
|
71
|
81
|
62
|
71
|
74
|
|
E7(P)/1
|
80
|
90
|
80
|
90
|
71
|
80
|
83
|
|
E7(P)/2
|
67
|
77
|
67
|
77
|
58
|
67
|
69
|
|
RR1(P)/3
|
69
|
79
|
69
|
79
|
67
|
69
|
72
|
|
THR2(P)/1
|
64
|
74
|
64
|
74
|
62
|
64
|
66
|
|
THR2(P)/2
|
64
|
74
|
64
|
74
|
62
|
64
|
66
|
|
THR2(P)/4
|
67
|
77
|
68
|
77
|
65
|
67
|
70
|
|
WO(P)/1
|
76
|
86
|
76
|
86
|
73
|
76
|
78
|
|
W1(P)/3
|
65
|
75
|
66
|
75
|
56
|
65
|
68
|
|
W3(P)/2
|
61
|
71
|
61
|
71
|
52
|
61
|
64
|
|
W5(P)/1
|
83
|
93
|
83
|
93
|
80
|
83
|
85
|
|
W5(P)/2
|
83
|
93
|
83
|
93
|
81
|
83
|
86
|
|
W8/3
|
88
|
98
|
88
|
98
|
86
|
88
|
91
|
|
Domestic
premises/hotels/hostels
|
|
B2(P)/1
|
74
|
84
|
75
|
84
|
65
|
74
|
77
|
|
B2(P)/3
|
74
|
84
|
74
|
84
|
65
|
74
|
76
|
|
B2(P)/4
|
74
|
84
|
74
|
84
|
65
|
74
|
76
|
|
BR3(P)/1
|
68
|
78
|
69
|
78
|
59
|
68
|
71
|
|
BR4(P)/1
|
66
|
76
|
66
|
76
|
57
|
66
|
69
|
|
BR4(P)/3
|
65
|
75
|
66
|
75
|
56
|
65
|
56
|
|
BR5(P)/1
|
68
|
78
|
68
|
78
|
59
|
68
|
70
|
|
BR5(P)/2
|
67
|
77
|
68
|
77
|
58
|
67
|
70
|
|
BR6(P)/1
|
77
|
87
|
77
|
87
|
68
|
77
|
79
|
|
BR6(P)/2
|
74
|
84
|
74
|
84
|
65
|
74
|
76
|
|
BR6(P)/3
|
68
|
78
|
68
|
78
|
59
|
68
|
70
|
|
BR7(P)/1
|
79
|
89
|
79
|
89
|
70
|
79
|
81
|
|
BR7(P)/2
|
78
|
88
|
78
|
88
|
69
|
78
|
81
|
|
BR7(P)/3
|
70
|
80
|
70
|
80
|
61
|
70
|
72
|
|
BR7(P)/4
|
71
|
81
|
72
|
81
|
62
|
71
|
74
|
|
BR7(P)/5
|
69
|
79
|
70
|
79
|
61
|
69
|
72
|
|
DG1(P)/2
|
76
|
86
|
77
|
86
|
67
|
76
|
79
|
|
DG1(P)/3
|
69
|
79
|
70
|
79
|
61
|
69
|
72
|
|
E5(A)(P)/1
|
83
|
93
|
83
|
93
|
74
|
83
|
85
|
|
E5(A)(P)/2
|
79
|
89
|
80
|
89
|
70
|
79
|
82
|
|
E5(B)(P)/1
|
-7
|
83
|
73
|
83
|
64
|
73
|
75
|
|
E5(B)(P)/2
|
73
|
83
|
74
|
83
|
64
|
73
|
76
|
|
E5(B)(P)/3
|
73
|
83
|
73
|
83
|
64
|
73
|
75
|
|
E7(P)/3
|
81
|
91
|
81
|
91
|
72
|
81
|
83
|
|
E7(P)/4
|
73
|
83
|
73
|
83
|
64
|
73
|
75
|
|
E7(P)/5
|
73
|
83
|
73
|
83
|
64
|
73
|
75
|
|
GL1(P)/1
|
78
|
88
|
78
|
88
|
69
|
78
|
80
|
|
HKU1(P)/1
|
74
|
84
|
74
|
84
|
65
|
74
|
76
|
|
HR1/1
|
72
|
82
|
72
|
82
|
70
|
72
|
75
|
|
HR1/2
|
75
|
85
|
75
|
85
|
73
|
75
|
77
|
|
M3(P)/1
|
71
|
81
|
71
|
81
|
62
|
71
|
73
|
|
MA13(P) & MA14(P)/1
|
76
|
86
|
77
|
86
|
67
|
76
|
79
|
|
MA13(P) & MA14(P)/2
|
77
|
87
|
77
|
87
|
68
|
77
|
80
|
|
MA13(P) & MA14(P)/3
|
69
|
79
|
70
|
79
|
60
|
69
|
72
|
|
MA15(P)/1
|
75
|
85
|
75
|
85
|
66
|
75
|
77
|
|
MA15(P)/2
|
67
|
77
|
67
|
77
|
58
|
67
|
69
|
|
MA15(P)/3
|
71
|
81
|
72
|
81
|
62
|
71
|
74
|
|
MA15(P)/4
|
68
|
78
|
69
|
78
|
59
|
68
|
71
|
|
MA17(P)/1
|
73
|
83
|
73
|
84
|
65
|
74
|
75
|
|
MA17(P)/2
|
69
|
79
|
69
|
79
|
60
|
69
|
71
|
|
MA17(P)/3
|
66
|
76
|
67
|
76
|
57
|
66
|
69
|
|
MB16/1
|
76
|
86
|
76
|
86
|
67
|
76
|
78
|
|
MB16/2
|
78
|
88
|
78
|
88
|
69
|
78
|
81
|
|
MB16/3
|
78
|
88
|
79
|
88
|
69
|
78
|
81
|
|
MBD2/1
|
75
|
85
|
75
|
85
|
66
|
75
|
77
|
|
P5(P)/1
|
81
|
91
|
81
|
91
|
72
|
81
|
83
|
|
P5(P)/2
|
74
|
84
|
74
|
84
|
65
|
74
|
76
|
|
P5(P)/3
|
72
|
82
|
72
|
82
|
63
|
72
|
74
|
|
PFLR(P)/1
|
76
|
86
|
76
|
86
|
67
|
76
|
78
|
|
PFLR(P)/2
|
76
|
86
|
76
|
86
|
67
|
76
|
78
|
|
RR1(P)/1
|
74
|
84
|
74
|
84
|
72
|
74
|
76
|
|
RR1(P)/2
|
73
|
83
|
73
|
83
|
71
|
73
|
76
|
|
RR1(P)/4
|
76
|
86
|
76
|
86
|
74
|
76
|
78
|
|
THR2(P)/3
|
77
|
87
|
77
|
87
|
75
|
77
|
80
|
|
TP4(P)/1
|
75
|
85
|
75
|
85
|
66
|
75
|
77
|
|
TP4(P)/2
|
75
|
85
|
75
|
85
|
66
|
75
|
77
|
|
TP5(P)/1
|
71
|
81
|
72
|
81
|
62
|
71
|
74
|
|
TP789(P)/1
|
73
|
83
|
74
|
83
|
75
|
73
|
76
|
|
TP789(P)/2
|
71
|
81
|
71
|
81
|
62
|
71
|
73
|
|
WO(P)/2
|
73
|
83
|
73
|
83
|
71
|
73
|
75
|
|
WO(P)/3
|
69
|
79
|
69
|
79
|
67
|
69
|
71
|
|
W1(P)/1
|
69
|
79
|
69
|
79
|
60
|
69
|
71
|
|
W1(P)/2
|
69
|
79
|
70
|
79
|
60
|
69
|
72
|
|
W1(P)/4
|
70
|
80
|
70
|
80
|
61
|
70
|
72
|
|
W3(P)/1
|
67
|
77
|
67
|
77
|
58
|
67
|
69
|
|
W3(P)/3
|
65
|
75
|
65
|
75
|
56
|
65
|
67
|
|
W5(P)/3
|
77
|
87
|
78
|
87
|
75
|
77
|
80
|
|
W5(P)/4
|
68
|
78
|
68
|
78
|
66
|
68
|
70
|
|
W8/1
|
76
|
86
|
76
|
86
|
74
|
76
|
78
|
|
W8/2
|
82
|
92
|
82
|
92
|
80
|
82
|
85
|
|
W10/1
|
79
|
89
|
80
|
89
|
70
|
79
|
82
|
|
W10/2
|
76
|
86
|
76
|
86
|
67
|
76
|
78
|
|
W10/3
|
71
|
81
|
72
|
81
|
62
|
71
|
74
|
|
W10/4
|
72
|
82
|
72
|
82
|
63
|
72
|
74
|
|
W11/1
|
73
|
83
|
73
|
83
|
64
|
73
|
75
|
|
W11/2
|
69
|
79
|
70
|
79
|
60
|
69
|
72
|
|
W12(P)/1
|
84
|
94
|
84
|
94
|
75
|
84
|
86
|
|
W12(P)/2
|
84
|
94
|
84
|
94
|
75
|
84
|
87
|
|
W12(P)/3
|
73
|
83
|
73
|
83
|
`64
|
73
|
75
|
Remarks:
|
> 70 dB (Educational Institution)
|
|
> 75 dB (Domestic premises/hotels/hostels)
|
Mitigation
Measures
Good Site
Practices
5.4.15
In general, potential construction noise
impact can be minimized or avoided by imposing a combination of the following
good site practices:
(a)
Noisy equipment and
activities should be sited by the Contractor as far from close-proximity
sensitive receivers as practical. Prolonged operation of noisy equipment close
to dwellings should be avoided.
(b)
The Contractor
should minimise construction noise exposure to the schools (especially during
examination periods). The Contractor should liaise with the school and the
Examination Authority to ascertain the exact dates and times of all examination
periods during the course of the works
contract and to avoid noisy activities during these periods.
(c)
Noisy plant or
processes should be replaced by quieter alternatives. Silenced diesel and gasoline
generators and power units, as well as silenced and super-silenced air
compressors, can be readily obtained.
(d)
Noisy activities
should be scheduled to minimise exposure of nearby sensitive receivers to high
levels of construction noise. For example, noisy activities can be scheduled
for midday, or at times coinciding with periods of high background noise (such
as during peak traffic hours).
(e)
Idle equipment
should be turned off or throttled down. Noisy equipment should be properly
maintained and used no more often than is necessary.
(f)
The power units
of non-electric stationary plant and earth-moving plant should be quietened by
vibration isolation and partial or full acoustic enclosures for individual
noise-generating components.
(g)
Construction
activities should be planned so that parallel operation of several sets of
equipment close to a given receiver is avoided, thus reducing the cumulative
impacts between operations. The numbers of operating items of powered
mechanical equipment should be minimised. Noise can be reduced by increasing
the distance between the operating equipment and the NSRs
or by reducing the number of items of equipment and/or construction activity in
the area at any one time.
(h)
The use of quiet
plant and working methods can
further reduce noise level. Quiet plant is defined as Powered Mechanical
Equipment (PME) whose actual sound
power level is less than the value specified in the TMs
for the same piece of equipment. To allow the Contractor some flexibility to
select equipment to suit his needs, it is considered too restrictive to specify
which specific items of silenced equipment to be used for the construction
operations. It should be noted that various types of silenced equipment can be
found in Hong Kong and are readily available on the market. BS 5228 also
provides examples of quiet construction plant and their SWL.
(i)
Construction
plant should be properly maintained (well-greased, damage and worn parts
promptly replaced) and operated. Construction equipment often has silencing
measures built in or added on, e.g. bulldozer silencers, compressor panels, and
mufflers. Silencing measures should be properly maintained and utilised. Rubber
or damping materials should be introduced between metal panels to avoid rattle
and reverberation of noise.
(j)
Equipment known
to emit sound strongly in one direction, should be
oriented so that the noise is directed away from nearby NSRs.
(k)
Material
stockpiles and other structures (such as site offices) should be effectively
utilised to shield construction noise. Noise can also be reduced by
construction of temporary noise barriers which screen the lower floors from
viewing the sites. Temporary noise barriers should be installed at active parts
of construction areas where construction equipment is being operated in close
proximity to NSRs.
(l)
It is noted that
under the WBTC No. 19/2001, all construction sites are required to use metallic
site hoarding to reduce the amount of timber. This metallic hoarding can be
slightly modified (with the addition of steel backings) into temporary noise
barriers. These barriers should be gap free and have a surface mass density of
at least 7 kg/m2.
(m)
All hand-held percussive breakers and
air compressors should comply the Noise Control (Hand-held Percussive Breakers) Regulations and Noise Control (Air Compressors) Regulations
respectively under the NCO (Ordinance No.
75/88, NCO Amendment 1992 No.6).
5.4.16
The Contractor shall devise, arrange
methods of working and carry out the
works in such manner as to minimise noise impacts on the surrounding environment, and
shall provide experienced personnel with suitable training to ensure that these
measures are implemented properly.
5.4.17
The predicted unmitigated noise levels
showed that construction works would
give rise to adverse daytime noise impacts to most of the RNSRs.
Mitigation measures are required and the following types of mitigation measures
are recommended.
Site Specific
Direct Technical Measures
5.4.18
The Contractor is required to adopt
Levels 1 and 2 site specific direct technical measures as specified below
during the construction phase.
(a) Use of Quiet Plant (Level 1 mitigation)
5.4.19
Level 1 direct technical measures are proposed to mitigate potential construction
noise impacts. Level 1 measures include limiting the
concurrent use of construction equipment and using silenced and quiet
equipment, without delay to the construction programme.
5.4.20
It has been confirmed with Project
Proponent that site clearance, surface breaking, rock drilling for manhole,
loading, site formation, excavation and finalized stage (e.g. reinstatement and
landscaping works) will be carried out in a non-concurrent sequence for any
given locations.
5.4.21
Appendix C (Table C-1b) presents the
noise level generated due to the combinations of silenced equipments of PME.
All proposed silenced equipments are available in the market of Hong
Kong. Predicted noise levels at the
closest identified NSRs with Level 1 mitigation
measures are given in Tables 5.8a & b for Eastern/Western Portals and
Intakes respectively.
Table 5.8a Predicted Noise Level (Silenced Equipment) at RNSRs for
Eastern Portals and Western Portals
|
|
Site clearance
|
Surface
Breaking
|
Drill
|
Loading
|
Site Formation
|
TBM Support
|
Finalized Stage
- General Works
|
Finalized
Stage- Concreting
|
Finalized Stage
- Marine Transport
|
|
Approx.
Duration
|
2 weeks
|
2 weeks
|
8 weeks
|
208 weeks
|
8 weeks
|
212 weeks
|
18 weeks
|
18 weeks
|
18 weeks
|
|
Education
institution
|
|
EP/3
|
67
|
73
|
79
|
73
|
71
|
75
|
71
|
69
|
|
|
Domestic
premises/hotels/hostels
|
|
EP/1
|
67
|
69
|
76
|
69
|
67
|
71
|
67
|
65
|
|
|
EP/2
|
65
|
71
|
77
|
70
|
69
|
73
|
69
|
67
|
|
|
WP/1
|
53
|
59
|
66
|
59
|
57
|
64
|
57
|
56
|
61
|
|
WP/2
|
55
|
61
|
67
|
61
|
59
|
66
|
59
|
57
|
63
|
Remarks:
|
> 70 dB (Educational Institution)
|
|
> 75 dB (Domestic premises/hotels/hostels)
|
Table 5.8b Predicted Noise Level (Silenced Equipment) at RNSRs for Intakes
|
Intakes
|
Site clearance
|
Surface
breaking
|
Initial
Excavation
|
Rock Drilling
for Manhole
|
Excavation
|
Finalized
stage - General Works
|
Finalized
stage - Concreting
|
|
Approximate
Duration
|
1 week
|
1 week
|
4 months
|
1 month
|
< 5 months
|
1 month
|
2 weeks
|
|
Education
institution
|
|
B2(P)/2
|
60
|
65
|
61
|
65
|
58
|
60
|
61
|
|
BR4(P)/2
|
57
|
62
|
58
|
62
|
55
|
57
|
58
|
|
BR5(P)/3
|
56
|
61
|
57
|
61
|
54
|
56
|
57
|
|
DG1(P)/1
|
64
|
69
|
65
|
69
|
62
|
64
|
65
|
|
E7(P)/1
|
73
|
78
|
74
|
78
|
71
|
73
|
74
|
|
E7(P)/2
|
60
|
65
|
61
|
65
|
58
|
60
|
61
|
|
RR1(P)/3
|
62
|
67
|
63
|
67
|
62
|
62
|
63
|
|
THR2(P)/1
|
57
|
62
|
58
|
62
|
57
|
57
|
58
|
|
THR2(P)/2
|
57
|
62
|
58
|
62
|
57
|
57
|
58
|
|
THR2(P)/4
|
60
|
65
|
61
|
65
|
60
|
60
|
61
|
|
WO(P)/1
|
69
|
74
|
70
|
74
|
69
|
69
|
70
|
|
W1(P)/3
|
58
|
63
|
59
|
63
|
56
|
58
|
59
|
|
W3(P)/2
|
54
|
59
|
55
|
59
|
52
|
54
|
55
|
|
W5(P)/1
|
76
|
81
|
77
|
81
|
76
|
76
|
77
|
|
W5(P)/2
|
76
|
81
|
77
|
81
|
76
|
76
|
77
|
|
W8/3
|
81
|
86
|
82
|
86
|
81
|
81
|
82
|
|
Domestic
premises/hotels/hostels
|
|
B2(P)/1
|
67
|
72
|
69
|
72
|
65
|
67
|
69
|
|
B2(P)/3
|
67
|
72
|
68
|
72
|
65
|
67
|
68
|
|
B2(P)/4
|
67
|
72
|
68
|
72
|
65
|
67
|
68
|
|
BR3(P)/1
|
61
|
66
|
63
|
66
|
59
|
61
|
63
|
|
BR4(P)/1
|
59
|
64
|
60
|
64
|
57
|
59
|
60
|
|
BR4(P)/3
|
58
|
63
|
60
|
63
|
56
|
58
|
60
|
|
BR5(P)/1
|
61
|
66
|
62
|
66
|
59
|
61
|
62
|
|
BR5(P)/2
|
60
|
65
|
62
|
65
|
58
|
60
|
62
|
|
BR6(P)/1
|
70
|
75
|
71
|
75
|
68
|
70
|
71
|
|
BR6(P)/2
|
67
|
72
|
68
|
72
|
65
|
67
|
68
|
|
BR6(P)/3
|
61
|
66
|
62
|
66
|
59
|
61
|
62
|
|
BR7(P)/1
|
72
|
77
|
73
|
77
|
70
|
72
|
73
|
|
BR7(P)/2
|
71
|
76
|
72
|
76
|
69
|
71
|
72
|
|
BR7(P)/3
|
63
|
68
|
64
|
68
|
61
|
63
|
64
|
|
BR7(P)/4
|
64
|
69
|
66
|
69
|
62
|
64
|
65
|
|
BR7(P)/5
|
62
|
67
|
64
|
67
|
61
|
62
|
64
|
|
DG1(P)/2
|
69
|
74
|
71
|
74
|
67
|
69
|
70
|
|
DG1(P)/3
|
62
|
67
|
64
|
67
|
61
|
62
|
64
|
|
E5(A)(P)/1
|
76
|
81
|
77
|
81
|
74
|
76
|
77
|
|
E5(A)(P)/2
|
72
|
77
|
74
|
77
|
70
|
72
|
74
|
|
E5(B)(P)/1
|
66
|
71
|
67
|
71
|
64
|
66
|
67
|
|
E5(B)(P)/2
|
66
|
71
|
68
|
71
|
64
|
66
|
67
|
|
E5(B)(P)/3
|
66
|
71
|
67
|
71
|
64
|
66
|
67
|
|
E7(P)/3
|
74
|
79
|
75
|
79
|
72
|
74
|
75
|
|
E7(P)/4
|
66
|
71
|
67
|
71
|
64
|
66
|
67
|
|
E7(P)/5
|
66
|
71
|
67
|
71
|
64
|
66
|
67
|
|
GL1(P)/1
|
71
|
76
|
72
|
76
|
69
|
71
|
72
|
|
HKU1(P)/1
|
67
|
72
|
68
|
72
|
65
|
67
|
68
|
|
HR1/1
|
65
|
70
|
66
|
70
|
65
|
65
|
66
|
|
HR1/2
|
68
|
73
|
69
|
73
|
68
|
68
|
69
|
|
M3(P)/1
|
64
|
69
|
65
|
69
|
62
|
64
|
65
|
|
MA13(P) & MA14(P)/1
|
69
|
74
|
71
|
74
|
67
|
69
|
71
|
|
MA13(P) & MA14(P)/2
|
70
|
75
|
71
|
75
|
68
|
70
|
71
|
|
MA13(P) & MA14(P)/3
|
62
|
67
|
64
|
67
|
60
|
62
|
64
|
|
MA15(P)/1
|
68
|
73
|
69
|
73
|
66
|
68
|
69
|
|
MA15(P)/2
|
60
|
65
|
61
|
65
|
58
|
60
|
61
|
|
MA15(P)/3
|
64
|
69
|
66
|
69
|
62
|
64
|
66
|
|
MA15(P)/4
|
61
|
66
|
63
|
66
|
59
|
61
|
63
|
|
MA17(P)/1
|
66
|
71
|
67
|
72
|
65
|
67
|
67
|
|
MA17(P)/2
|
62
|
67
|
63
|
67
|
60
|
62
|
63
|
|
MA17(P)/3
|
59
|
64
|
61
|
64
|
57
|
59
|
61
|
|
MB16/1
|
69
|
74
|
70
|
74
|
67
|
69
|
70
|
|
MB16/2
|
71
|
76
|
72
|
76
|
69
|
71
|
72
|
|
MB16/3
|
71
|
76
|
73
|
76
|
69
|
71
|
73
|
|
MBD2/1
|
68
|
73
|
69
|
73
|
66
|
68
|
69
|
|
P5(P)/1
|
74
|
79
|
75
|
79
|
72
|
74
|
75
|
|
P5(P)/2
|
67
|
72
|
68
|
72
|
65
|
67
|
68
|
|
P5(P)/3
|
65
|
70
|
66
|
70
|
63
|
65
|
66
|
|
PFLR(P)/1
|
69
|
74
|
70
|
74
|
67
|
69
|
70
|
|
PFLR(P)/2
|
69
|
74
|
70
|
74
|
67
|
69
|
70
|
|
RR1(P)/1
|
67
|
72
|
68
|
72
|
67
|
67
|
68
|
|
RR1(P)/2
|
66
|
71
|
67
|
71
|
66
|
66
|
67
|
|
RR1(P)/4
|
69
|
74
|
70
|
74
|
69
|
69
|
70
|
|
THR2(P)/3
|
70
|
75
|
71
|
75
|
70
|
70
|
71
|
|
TP4(P)/1
|
68
|
73
|
69
|
73
|
66
|
68
|
69
|
|
TP4(P)/2
|
63
|
68
|
63
|
68
|
56
|
63
|
64
|
|
TP5(P)/1
|
59
|
64
|
59
|
64
|
52
|
59
|
60
|
|
TP789(P)/1
|
66
|
71
|
68
|
71
|
68
|
66
|
68
|
|
TP789(P)/2
|
64
|
69
|
65
|
69
|
62
|
64
|
65
|
|
WO(P)/2
|
66
|
71
|
67
|
71
|
66
|
66
|
67
|
|
WO(P)/3
|
62
|
67
|
63
|
67
|
62
|
62
|
63
|
|
W1(P)/1
|
62
|
67
|
63
|
67
|
60
|
62
|
63
|
|
W1(P)/2
|
62
|
67
|
64
|
67
|
60
|
62
|
64
|
|
W1(P)/4
|
63
|
68
|
64
|
68
|
61
|
63
|
64
|
|
W3(P)/1
|
60
|
65
|
61
|
65
|
58
|
60
|
61
|
|
W3(P)/3
|
58
|
63
|
59
|
63
|
56
|
58
|
59
|
|
W5(P)/3
|
70
|
75
|
72
|
75
|
70
|
70
|
72
|
|
W5(P)/4
|
61
|
66
|
62
|
66
|
61
|
61
|
62
|
|
W8/1
|
69
|
74
|
70
|
74
|
69
|
69
|
70
|
|
W8/2
|
75
|
80
|
76
|
80
|
75
|
75
|
76
|
|
W10/1
|
72
|
77
|
74
|
77
|
70
|
72
|
74
|
|
W10/2
|
69
|
74
|
70
|
74
|
67
|
69
|
70
|
|
W10/3
|
64
|
69
|
66
|
69
|
62
|
64
|
66
|
|
W10/4
|
65
|
70
|
66
|
70
|
63
|
65
|
66
|
|
W11/1
|
66
|
71
|
67
|
71
|
64
|
66
|
67
|
|
W11/2
|
62
|
67
|
64
|
67
|
60
|
62
|
63
|
|
W12(P)/1
|
77
|
82
|
78
|
82
|
75
|
77
|
78
|
|
W12(P)/2
|
77
|
82
|
78
|
82
|
75
|
77
|
78
|
|
W12(P)/3
|
66
|
71
|
67
|
71
|
64
|
66
|
67
|
Remarks:
|
> 70 dB
(Educational Institution)
|
|
> 75 dB
(Domestic premises/hotels/hostels)
|
5.4.22
After implementation of Level 1
mitigation measures, most of the noise exceedances
are mainly during surface breaking and rock drilling for manhole at
intakes. Eastern Portal, E7(P), WO(P), W5(P), BR7(P), E5(A)(P), GL1(P), MB16, P5(P),
W8, W10 and W12(P) (12 locations out of 37 locations including both portals)
cannot be controlled effectively by the use of quiet plant mitigation. Further mitigation measures should be
applied for these sites.
(b) Use of
Barriers (Level 2 mitigation)
5.4.23
The use of full enclosure, movable
barriers and cantilevered-type site hoarding barrier are proposed to mitigate
the noise impacts during construction to an acceptable level. The proposed
cantilevered-type site hoarding barrier will be built at W5(8)
and W8 with maximum 5 m height. In
general, this would provide a minimum 10 dB(A)
attenuation for the low level receivers.
Since some of the construction sites is closed to the NSRs, it may not be effective to use movable barrier for
mitigate the noise impact in some specific sites. It would be possible for the Contractor
to provide these in the form of site hoardings to achieve this attenuation
effect, provided that the barriers have no openings or gaps and have a
superficial surface density of at least 10kg/m2. Good site practice shall also be adopted
by the Contractor to ensure the conditions of the hoardings are properly
maintained throughout the construction period.
5.4.24
Use of movable barriers located close to
noisy plant especially breaker (excavator mounted) can be
very effective mitigation measures in screening RNSRs.
Movable barriers of 3 to 5 m height with a small cantilevered upper portion and
skid footing can be located within about 5 m or more for mobile equipment such
that the line of sight is blocked. It would be possible for the Contractor to
provide purpose-built noise barriers or screens constructed of appropriate
material (minimum superficial density of 10 kg/m²) located close to operating PME. Certain types of stationary equipment, such as
generators and compressors, can be completely screened by movable barriers
giving a total noise reduction of 10 dB(A) or more.
5.4.25
For this assessment, it was estimated
that movable noise barriers can achieve a 10 dB(A)
noise reduction for stationary plant and 5 dB(A) reduction for mobile plant.
5.4.26
Due to the limited available space at
intake areas during construction, it is not suitable to place a movable barrier
as the distance between the site hoarding to notional
noise source being less than 5m or line of sight is not effectively shielded
from notional noise source to the high rise building (RNSRs). The application of movable barriers to
the following intakes is, therefore, not recommended. They are W5(P),
BR7(P) and W8.
5.4.27
The proposed full enclosure will be
built at Eastern Portal due to the longer construction period at these location. The
construction material for the enclosure shall have a surface density not less
than 10 kg/m². The noise enclosure shall be gap free apart from necessary
entrance/exits. The entrance/exit
shall face away from the nearest RNSRs especially
schools in order to minimize the noise impact. Acoustic screen doors shall be
provided for entrance/exit and shall be remained closed throughout the
construction period. If there is a
need for window opening or exhaust opening for ventilation, opening should not
face towards the school. For the
partial enclosure, it should be designed such that there shall have no direct
line of sight from the open side (i.e. entrance/exit point) of the partial
enclosure to the NSRs.
5.4.28
The predicted noise levels after
implementation of Levels 1 and 2 mitigation measures are effective only for
noise impacts generated especially from surface breaking, rock drilling for
manhole and rock drilling at Eastern Portal. Appendix C (Table C-1c) presents the
expected noise level generated by PME
due to the combination use of silenced equipments, movable
barrier and full enclosure.
5.4.29
Predicted noise level at identified NSRs with Level 1 and Level 2 mitigation measures are summarised in Tables 5.9a & b for Eastern Portal and
Intakes respectively. The predicted
noise level at 6 intakes E7(P), E5(A)(P), W5(P),
BR(7), W8 and W12 may exceed noise level limit due to close proximity to the
construction sites.
Table 5.9a Predicted Noise Level at RNSRs
for Eastern Portal
[With Level 1 and Level 2 (Movable / Cantilevered-type /Full
enclosure barrier) Measures]
|
|
Site clearance
|
Surface
Breaking
|
Drill
|
Loading
|
Site Formation
|
TBM Support
|
Finalized Stage
- General Works
|
Finalized
Stage- Concreting
|
|
Approximate Duration
(weeks)
|
2
|
2
|
8
|
208
|
8
|
212
|
18
|
18
|
|
Educational institutions
|
|
EP/3
|
62
|
68
|
64
|
68
|
66
|
65
|
66
|
64
|
|
Domestic premises/hotels/hostels
|
|
EP/1
|
62
|
64
|
61
|
64
|
62
|
62
|
62
|
60
|
|
EP/2
|
60
|
66
|
62
|
65
|
64
|
63
|
64
|
62
|
Remarks:
|
> 70 dB (Educational Institution)
|
|
> 75 dB (Domestic premises/hotels/hostels)
|
Table 5.9b Predicted Noise Level at RNSRs
for Intakes
[With Level 1 and Level 2 (Movable / Cantilevered-type Barrier)
Measures]
|
Intakes
|
Site clearance
|
Surface
breaking
|
Initial
Excavation
|
Rock Drilling
for Manhole
|
Excavation
|
Finalized
stage - General Works
|
Finalized
stage - Concreting
|
|
Approximate
Duration
|
1 week
|
1 week
|
4 months
|
1 month
|
< 5 months
|
1 month
|
2 weeks
|
|
Educational institutions
|
|
E7(P)/1
|
68
|
73
|
68
|
73
|
61
|
68
|
69
|
|
E7(P)/2
|
55
|
60
|
55
|
60
|
48
|
55
|
56
|
|
WO(P)/1
|
64
|
69
|
64
|
69
|
64
|
64
|
65
|
|
W5(P)/1
|
66
|
71
|
66
|
71
|
68
|
66
|
67
|
|
W5(P)/2
|
66
|
71
|
66
|
71
|
68
|
66
|
67
|
|
W8/3
|
71
|
76
|
71
|
76
|
73
|
71
|
72
|
|
Domestic premises/hotels/hostels
|
|
E5(A)(P)/1
|
71
|
76
|
71
|
76
|
64
|
71
|
72
|
|
E5(A)(P)/2
|
67
|
72
|
67
|
72
|
60
|
67
|
69
|
|
E7(P)/3
|
69
|
74
|
69
|
74
|
62
|
69
|
70
|
|
E7(P)/4
|
61
|
66
|
61
|
66
|
54
|
61
|
62
|
|
E7(P)/5
|
61
|
66
|
61
|
66
|
54
|
61
|
62
|
|
GL1(P)/1
|
66
|
71
|
66
|
71
|
59
|
66
|
67
|
|
MB16/1
|
64
|
69
|
64
|
69
|
57
|
64
|
65
|
|
MB16/2
|
66
|
71
|
66
|
71
|
59
|
66
|
67
|
|
MB16/3
|
66
|
71
|
66
|
71
|
59
|
66
|
68
|
|
P5(P)/1
|
69
|
74
|
69
|
74
|
62
|
69
|
70
|
|
P5(P)/2
|
62
|
67
|
62
|
67
|
55
|
62
|
63
|
|
P5(P)/3
|
60
|
65
|
60
|
65
|
53
|
60
|
61
|
|
W10/1
|
67
|
72
|
67
|
72
|
60
|
67
|
69
|
|
W10/2
|
64
|
69
|
64
|
69
|
57
|
64
|
65
|
|
W10/3
|
59
|
64
|
59
|
64
|
52
|
59
|
61
|
|
W10/4
|
60
|
65
|
60
|
65
|
53
|
60
|
61
|
|
W12(P)/1
|
72
|
77
|
72
|
77
|
65
|
72
|
73
|
|
W12(P)/2
|
72
|
77
|
72
|
77
|
65
|
72
|
73
|
|
W12(P)/3
|
61
|
66
|
61
|
66
|
54
|
61
|
62
|
|
W5(P)/3
|
60
|
65
|
60
|
65
|
63
|
60
|
62
|
|
W8/2
|
65
|
70
|
65
|
70
|
67
|
65
|
66
|
Remarks:
|
> 70 dB (Educational Institution)
|
|
> 75 dB (Domestic premises/hotels/hostels)
|
Residual
Impacts
5.4.30
Residual construction noise impact is
expected after implementation of Levels 1 and 2 (use of mobile/partial/full
enclosures), site specific measures as well as the general mitigation measures as
specified above. Table 5.10
summaries the predicted noise level with the implementation of proposed
mitigation measures.
Table 5.10 Predicted
Residual Noise Impact (After Mitigation) at Intakes
|
|
Site clearance
|
Surface
breaking
|
Initial
Excavation
|
Rock Drilling
for Manhole
|
Excavation
|
Finalized
stage - General Works
|
Finalized
stage - Concreting
|
|
Approximate
Duration
|
1 week
|
1 week
|
4 months
|
1 month
|
< 5 months
|
1 month
|
2 weeks
|
|
Educational institutions
|
|
E7(P)/1
|
68
|
73
|
68
|
73
|
61
|
68
|
69
|
|
W5(P)/1
|
66
|
71
|
66
|
71
|
68
|
66
|
67
|
|
W5(P)/2
|
66
|
71
|
66
|
71
|
68
|
66
|
67
|
|
W8/3
|
71
|
76
|
71
|
76
|
73
|
71
|
72
|
|
Domestic premises/hotels/hostels
|
|
BR7(P)/1
|
72
|
77
|
73
|
77
|
70
|
72
|
73
|
|
BR7(P)/2
|
71
|
76
|
72
|
76
|
69
|
71
|
72
|
|
E5(A)(P)/1
|
71
|
76
|
71
|
76
|
64
|
71
|
72
|
|
W12(P)/1
|
72
|
77
|
72
|
77
|
65
|
72
|
73
|
|
W12(P)/2
|
72
|
77
|
72
|
77
|
65
|
72
|
73
|
5.4.31
For the domestic premises NSRs at BR7(P), E5(A)(P) and W12
and schools NSRs at E7(P), W5(P) and W8, the exceedance of noise limit level (1dB(A) to 6 dB(A) are
mainly contributed during the surface breaking and rock drilling
activities. The expected
construction period for surface breaking and rock drilling at manhole are less
than 1 week and 1 month respectively, noise impacts to these RNSRs would be considered low. Pre-drilling followed by chemical
splitting to replace the use of excavator mounted breaker should be used at BR7(P), E7(P), E5(A)(P), W5(P), W8 and W12 as an mitigation
measures for rock breaking and rock drilling at manhole construction
activities.
5.4.32
For the schools NSRs
at Eastern Portal, DG1(P), E7(P), RR1, W0(P), W5(P)
and W8, the noise level may exceed the noise criteria during examination period. The exceedance
is mainly contributed by the surface breaking, rock
drilling and excavation construction activities (see Tables 5.10a &
5.10b). To be conservative, it is
recommended that no construction activity at these sites is allowed during the
examination period. The most noisy construction
activity (surface breaking and rock drilling at manhole) should be programmed
at summer vacation or school holidays to reduce the noise impact to an
acceptable level.
5.4.33
It should be noted that the construction
noise assessment presented above simulates a worst possible scenario whereby
all the works under this Project is
assumed to be under construction simultaneously for the entire construction
phase. In reality, the actual implementation programme
is not working according to the
worst case scenario.
Therefore such an assessment approach will ensure that the proposed
mitigation measures could protect the RNSRs even in
the event of any future slippage or rearrangement of implementation programme.
Noise Impact due to
Erection and Dismantle of Full Enclosure or Cantilevered-type Noise Barrier
5.4.34
The erection and dismantle of full
enclosure or cantilevered-typed noise barrier at Eastern Portal, W5(P) and W8 will inevitably give a short term noise impact
to the nearby NSRs. The erection of the full
enclosure or cantilevered-type noise barriers involves the use of a hand held
rock drill, a crane, a generator and a concrete truck. An acoustic shed should be provided
during the drilling activities to minimize the noise impacts. During dismantling the noise barriers, a
crane and a lorry will be used.
5.4.35
The predicated noise levels at the NSRs near Eastern Portal and Intakes W5(P)
and W8 during erection and
dismantle of full enclosre or cantilevered-typed
noise barriers are presented in Table 5.11(a).
(a) Eastern Portal
The time for erection
of Stage A and Stage B noise enclosure will last for approximately two weeks
and four weeks respectively and the dismantling activity will last for
approximately one week for both stages.
The locations for the Stage A & B full
enclosures are shown in Figure 5.33.
No exceedance of the daytime noise criteria is
predicted for NSRs at Eastern Portal during normal
day but noise exceedance at the educational NSR EP/3
may be recorded during the examination period. It is recommended to carry out
the noise barrier erection/dismantle construction work outside the examination period. Thus, no residual impact resulting from
the erection and dismantling of noise barriers at Eastern Portal are
expected.
(b) Intakes
5.4.36
The use of cantilevered-type noise
barrier at the intakes [W5(P) and W8 only] would
result in elevation of noise levels during its erection and dismantling. The predicted noise levels at the
educational NSR W8/3 exceed the criteria by a maximum 14 dB(A)
and 12 dB(A) during the erection and dismantle period. It is recommended to schedule the noise
barrier erection to the non sensitive periods, e.g. during summer holiday, to
avoid the adverse impact. At the
residential NSR W8/2, the noise levels is expected to exceed the criteria by 3 dB(A) and 1 dB(A) during the erection and dismantle period.
5.4.37
Although residual impacts from the erection
and dismantling of noise barriers at intakes W5(P) and W8 are predicted, the
periods of exceedance are comparatively short
considering the noise barriers is protecting the NSRs
from construction noise for the remaining construction period. The erection of noise barriers will last
for approximately two weeks and the dismantling activity will last for
approximately one week. Without the
noise barriers, exceedance is expected during the
surface breaking, initial excavation, rock drilling for manhole and the
concreting works which will last for
over 20 weeks. Similar to Eastern
Portal, it is therefore also more beneficial to construct the cantilevered-type
noise barriers at these intakes.
Table 5.11 Predicted
Noise Level for Full Enclosure / Cantilevered-type Barrier
Erection and Dismantling at RNSRs for
Eastern Portal, Intakes W5(P) and W8
|
Intakes
|
Noise Barrier Erection
|
Noise Barrier Dismantling
|
|
EP/1
|
67
|
65
|
|
EP/2
|
68
|
67
|
|
EP/3
|
70
|
69
|
|
W5(P)/1
|
78
|
77
|
|
W5(P)/2
|
78
|
77
|
|
W5(P)/3
|
73
|
72
|
|
W5(P)/4
|
63
|
62
|
|
W8/1
|
71
|
70
|
|
W8/2
|
78
|
76
|
|
W8/3
|
84
|
82
|
Remarks:
|
> 70 dB (Educational Institution)
|
|
> 75 dB (Domestic premises/hotels/hostels)
|
Summary of Mitigation Measures at Portals and
Intakes
(a) Eastern
Portal
5.4.38
The major construction activities for
Eastern Portal are generally divided into three main phases. To minimize the noise impacts to the
nearby NSRs during construction, all the necessary
noise control measures as depicted below would be adopted :
Phase I
(i)
Site formation phase includes site
clearance, surface breaking, drilling, loading and site formation. The duration for this phase of works will be about one year. Even with the use of quiet plant (Level
1 mitigation measures), the assessment identified that the noise impact may
still exceed the daytime noise criteria.
In light of this, Level 2 mitigation measures are required. Considering the relatively longer
construction period at Eastern Portal, both the partial and full enclosures at
Eastern portal are adopted for different stages of works
to ensure compliance with the requirements during the construction phase.
Stage A full enclosure is provided
at the tunnel portal to mitigate the noise due to rock drilling at portal for
the preparation of TBM launching.
The enclosure is a gap free enclosure with acoustic door for access
purpose. The door should be kept
closed during the drilling operation;
Phase II
(ii)
TBM supporting activities phase includes
delivery of excavated spoil, tunnel segments, and TBM spare parts to facilitate
the TBM tunnel construction. The
duration for this phase of works
will be about three years. During
this phase of works, all the tunnel
excavation works will be carried out
deep inside the tunnel but delivery of tunnel lining segments for installation
and excavated material for disposal off site is required.
Stage B full enclosure is an extension of the Stage A full
enclosure to mitigate the noise arising from tunnel operation including the
transportation of excavated spoil to the muck out area for temporary
storage. The Stage B full enclosure
will cover the muck pit area, the works
area where air compressor and air ventilation system are located; and
The Stage B full enclosure to cover the muck pit area will
be in place until all tunnel excavation and adit
construction works are complete. To
reinforce the noise mitigation measures, the loading and unloading area for the
trucks operation will be partially enclosed. Figure 5.33 shows the site layout at
Eastern Portal;
Phase III
(iii)
Finalization stage includes general
civil works, concreting and
landscaping works. The works will take about 7 months to complete. Both
quite plant and movable noise barriers will be used at Eastern Portal to limit
the noise impacts within the daytime noise critieria.
5.4.39
The noise enclosure shall be gap free and
constructed of material with surface density not less than 10kg/10 kg/m² . Acoustic screen doors shall be provided for
entrance/exit. The entrance/exit shall face away from
the nearest NSRs especially schools (e.g. True Light
Middle School of Hong Kong) such that there shall have no direct line of sight
to the NSRs. If there is a need for openings for
ventilation, opening should not face towards the school.
5.4.40
After implementation of the above
measures, it is predicated that the noise levels at all NSRs
during different phases of construction at Eastern Portal shall comply with the
noise criteria.
(b) Western
Portal
5.4.41
The assessment indicates that after
implementation of the Level 1 mitigation measures the predicted noise level
complies with the daytime noise criteria at the nearest noise sensitive
receivers
during construction of
the Western Portal. Level 2 mitigation measures (i.e. provision of
noise barrier) are not required at Western Portal as a mitigation measures.
5.4.42
For Western portal, excavated spoil from
TBM tunnel will be discharged to barge by a conveying system for proper
disposal. A three-side roofed
enclosure with a flexible curtain across the entry shall be provided. Exhaust
fan shall be provided for this enclosure and vented to a suitable filter
system. As a result, noise impact generated from vehicular traffic required for
spoil disposal could be greatly reduced.
A muck pit area is also required for temporary storage of excavated
spoil and an indicative layout is shown in Figure 5.34.
(c) Intakes
5.4.43
After implementation of Level 1
mitigation measures, the noise impacts at E7(P), WO(P), W5(P), BR7(P),
E5(A)(P), GL1(P), MB16, P5(P), W8, W10 and W12(P) will be effectively
controlled by the use of quiet plant but noise level exceedence
at these locations are still predicated.
Level 2 (use of movable barriers) mitigation measures are therefore
required to further mitigate the noise impacts.
5.4.44
Use of movable barriers at W5(P) and W8 is
impractical due to the space constraints and the proximity of the nearby
sensitive receivers. Cantilevered-type
noise barriers are proposed at W5(P) and W8. The assessment indicated that the
predicated noise levels at BR7(P), E7, E5(A), W5(P),
W8 and W12 may exceed the daytime construction noise criteria after Level
2 mitigation measures are
implemented. The noise exceedance are mainly
contributed by surface breaking and rock drilling. Erection of full enclosure at these
locations is not practicable due to space constraints. Further mitigation measures are proposed
such as the use of pre-drilling followed by chemical splitting to replace the
use of excavator mounted breaker and re-schedule the works
programme to avoid the sensitive period.
5.4.45
Although the
construction programme of the entire Project could
last for 4 years, the scale of the construction works
at intakes is relatively small and straight forward when it compares to the
Portal areas. The maximum period
for intake construction is only up to 12 months (the deepest shaft). Therefore, there is a mark difference
between the construction time required at portals and intakes. The estimated maximum duration for each
construction activities at intake is shown in Table 5.12.
Table 5.12 Estimated Duration of Each Construction Activities at Intakes
|
Construction activities
|
Duration
|
|
Site clearance
|
1 week
|
|
Surface Breaking
|
1 week
|
|
Initial Excavation
|
4 months
|
|
Rock drilling for
manhole
|
1 month if
rock present at the proposed site
|
|
Excavation
|
Not more
than 5 months
|
|
Finalized stage –
General Works
|
1 month
|
|
Finalized stage –
concreting
|
2 weeks
(only 1 hour duration for each day)
|
|
Maximum Duration
|
12 months
|
Table 5.13a – List of Quiet Equipment
|
Quiet Equipment
|
Code
|
Sound Power Level dB(A)
max.
|
|
Air
compressor
|
BS5228:
Tab. C7-44
|
103
|
|
Bulldozer
|
BS5228:
Tab. C9-2
|
104
|
|
Breaker, excavator mounted.
|
BS5228:
Tab. C8-13
|
110
|
|
Wheeled
loader
|
BS5228:
Tab. C3-4
|
108
|
|
Dump
truck
|
BS5228:
Tab. C9-27
|
105
|
|
Excavator
|
BS5228:
Tab. C3-97
|
105
|
|
Crane,
barge mounted (Western portal only)
|
BS5228:
Tab. C7-113
|
107
|
|
Concrete
lorry mixer
|
BS5228:
Tab. C6-35
|
100
|
|
Poker,
vibratory, hand-held
|
BS5228:
Tab. C6-43
|
105
|
|
Lorry
with grab
|
BS5228:
Tab. C9-27
|
105
|
|
Lorry
with crane
|
BS5228:
Tab. C9-27
|
105
|
5.4.47
Therefore all practical effective noise
mitigation measures (e.g. Level 1 and Level 2 mitigation measures and good site
practices) have been exhausted to reduce the nuisance to the public arising
from the construction works.
Cumulative Impacts
5.4.48
The construction
of some of the intakes of the proposed drainage tunnel due to their close proximity
would likely coincide during the construction phase. The main concurrent projects that would
have potential cumulative impacts to intakes BR6(P),
E5(B)(P), MA15(P) and TP4(P) are shown as following Table 5.14.
Table 5.14 Concurrent
Project respect to Intakes
|
Intakes
|
Concurrent Project (Intakes)
|
RNSRs
selected
|
|
BR6(P)
|
BR7(R)
|
BR6(P)/2
|
|
E5(B)(P)
|
E5(A)(P)
|
E5(B)(P)/1
|
|
MA15(P)
|
MA13(P)&MA14(P)
|
MA15(P)/2
|
|
TP4(P)
|
TP5(P)
|
TP4(P)/1
|
5.4.49
Intakes will assume to be constructed at the same period of
time as a worst case scenario. A RNSR at each intake have been used to assess
the potential cumulative noise impacts from the concurrent projects. These RNSRs
have been carefully selected to represent the worst affected NSRs from a cumulative noise impact point of view.
5.4.50
Summary of the
mitigated cumulative noise levels from various construction activities of the
intakes at the representative NSRs is tabulated below
in Table 5.15. The highest
noise level of the construction works
was selected for the assessment, therefore, surface breaking.
Table 5.15 Predicted
Cumulative Construction Noise Level
|
NSR
|
Unmitigated Noise Level, dB(A)
|
Mitigated Noise Level, dB(A)
|
|
Level 1 Mitigation
|
Level 2 Mitigation
|
|
BR6(P)/2
|
85
|
73
|
*
|
|
E5(B)(P)/1
|
86
|
74
|
Not requiredD
|
|
MA15(P)/2
|
88
|
76
|
71
|
|
TP4(P)/1
|
86
|
74
|
Not requiredD
|
Note:
Bold value indicates the exceedance
of noise criteria of 75 dB(A) for residential uses
* -
Movable barrier is not a mitigation measures due to the site area limitation.
Not required D - Level 1 is sufficient to mitigate the
noise impact, i.e. Level 2
mitigation measure is not required.
5.4.51
There is no
cumulative impact for construction sites between (i)
BR6(P) and BR7(P), (ii) E5(B)(P) and E5(A)(P) and (iii) TP4(P) and TP5(P), the
proposed level 1 mitigation measures (quite plant) could effectively mitigate
the noise impact within the daytime construction noise criteria. Exceedances of
the EIAO-TM noise criterion at MA15(P)/2 is predicted
with implementation of the level 1 mitigation measure (quiet plant). In order to mitigate the noise impact,
either (i) use of movable barriers (level 2
mitigation measure) for both MA15(P) and MA13(P)&MA14(P) construction sites
or (ii) the construction programme for intakes MA15(P) and MA13(P)&MA14(P)
should be scheduled in different construction time period, thus no concurrent work for these two intakes is recommended.
Monitoring and
Audit Requirement
5.4.52
Noise monitoring should be carried out
at selected representative NSR during the construction period to monitor
compliance with permissible noise levels of the construction activities. Monitoring is also required to check the
effectiveness of the recommended mitigation measures. Ad-hoc monitoring and audit should also
be carried out at other NSRs in case of complaints,
and measures taken to ensure acceptable noise levels are met as far as
possible.
5.4.53
It is proposed that the following
representative NSRs be monitored during the
construction stage of the proposed Project. These NSRs are
selected to represent a particular area likely to be worst affected by the
construction works and where
applicable to monitor potential cumulative noise impacts form concurrent
project.
School
EP/3 : True Light Middle School of
Hong Kong
DG1(P)/1 : Rosaryhill School
E7(P)/1 : Marymount Secondary School
RR1(P)/3 : Ying Wa Girl’s School
THR2(P)/1 : Hong Kong
Japanese School
W0(P)/1 : Sir Ellis
Kadoorie Secondary School
W5(P)/1 : Raimondi
College
W8/3 : Hong Kong Institute of
Technology
Domestic Premises
EP/2 : The
Legend (Future development, complete construction before proposed project)
BR6(P) /1
: Man Yuen Garden
BR7(P)/1
: 16 Caronia
DG1(P)/2
: Blk C Villa Monte Rosa
E5(A)(P) : Buddist Li Ka Shing Care &
Attention Home for the elderly
E7(P)/3 : 117 Blue
Pool Road
MA13(P)&MA14(P)/1
: The Harbour View
P5(P)/1 : 24 Po
Shan Road
PFLR(P)/1 : Honey
Court
RR1(P)/4 : Peaksville Court
W8/1 : Blk 1, 80
Robinson Road
W12(P)/1 : 92A-92C Sylvanbrook
WP/2: Aegean Terrance
5.4.54
Details of the monitoring and audit for
construction noise are presented in the separate EM&A Manual.
Public Relationship Strategy
5.4.55
Having a good public relation with the
local communities during the construction stage of the works
is indispensable for smooth implementation of the Project. Prior to
commencement of the construction, visits to the possibly affected local
communities including the district councils, nearby residents, schools and
property owners will be carried out.
The purpose of the visits is to advise the public the following
information in relation to the Project:
·
the implementation programme of the works;
·
the planned construction activities that will be involved;
·
the possible impacts to the affected communities;
·
the measures to avoid or mitigate any adverse impacts;
·
the monitoring programme to check the
efficiency of the measures; and
·
the communication channels between the local
communities and the project office for better understanding the efficiency of
the measures taken and the necessity for enhancement of the measures.
5.4.56
Public support is essential for
successful implementation of the project. To maintain an effective
communication channel with the public, a 24-hour hotline system will be
established by the Contractor to receive any enquiry and complaint lodged by
the public in respect of the project.
Upon receipt enquiry/complaint, the Contractor will investigate the
causes of the incident and take the appropriate action to rectify the
situation. Periodic news letters
will also be distributed to the nearby residence, advising them the current
progress, and the schedule of works in future, the potential environmental
impacts arising from the works and the corresponding mitigation measures. It is
considered that such a close relation between the local communities and the
project site office could ensure speedy resolution of any environmental
non-compliance and maintain an environmental standard acceptable to the
communities during construction.
Summary
5.4.57
The use of powered mechanical equipment
during the construction phase of the Project is expected to create construction
noise nuisance given the proximity of the noise sensitive receivers to the
construction site. Mitigation
measures are available to reduce the construction noise impacts to acceptable
levels for most of the construction site.
The recommended mitigation measures include use of quiet plant and the
use of noise barrier and good site practices. With the implementation of the
recommended mitigation measures, the residual impacts of construction noise
levels can be kept at reasonable levels all times.
5.4.58
Noise monitoring is recommended at
selected representative NSRs during the construction
period to monitor compliance with daytime construction noise levels for the
construction activities being undertaken for the proposed Project.
5.5
Ground
Borne Construction Noise Assessment
Legislation and
Standards
5.5.1
Construction noise is controlled and
governed by Noise Control Ordinance (NCO), the EIAO and their subsidiary
requirements. Noise arising from
general construction works during
normal working hours is governed by
the EIAO-TM under the EIAO as shown in Table 5.2. TM for the Assessment of Noise from
Place other than Domestic Premises, Public Places or Construction Sites (IND-TN) under the NCO stipulates that noise
transmitted primarily through the structural elements of building, or
buildings, shall be 10 dB (A) less than the relevant ANLs. This approach to deriving ground borne
noise limits is pragmatic given the temporary nature of the construction works and the practical difficulty to abate the
inherently noise construction activities (e.g. rock drilling/breaking).
5.5.2
A daytime ground borne construction
noise limit of 60dB(A) applies with reference to EIAO-TM 70 dB(A) criterion for
schools and taking account of the minus 10 dB(A) requirement under the NCO TM-Places. Under the same principle, domestic
premises will be limited to 65 dB(A) which refers to
the daytime airborne noise criterion of 75 dB(A) in accordance with EIAO-TM.
5.5.3
The use of PME
for carrying out of construction works
during restricted hours requires a CNP issued under the NCO. The Noise Control
Authority is guided by the GW-TM when assessing such an application regardless
of the results of the construction noise impact assessment for restricted hours
in the EIA Report and the assessment in the EIA Report, according to the study
brief, are for the evaluation of whether construction works
in restricted hours are feasible or not in the context of programming
construction works only. Also, the
ground borne noise criteria during restricted hours (daytime during holidays,
all evenings and night time) presented in Table 5.16 only refer to areas with ASR “B” for demonstration purpose.
Table 5.16 Construction
Ground Borne Noise Standards
|
|
Ground Borne Noise Criteria, dB(A) (Leq, 30
mins)
|
|
|
Daytime
(except General Holidays and Sundays)*
|
Daytime during general holidays and Sundays and all days during
Evening
(1900 to 2300 hrs)**
|
Night time
(2300 to 0700 hrs)**
|
|
|
65
|
55
|
40
|
|
Educational Institutions (normal
periods)
|
60
|
55
|
[1]
|
|
Educational Institutions (during examination periods)
|
55
|
55
|
[1]
|
* 10 dB(A) below the noise criteria
stipulated in EIAO-TM
** 10 dB(A) below the noise criteria
stipulated in GW-TM
[1] No sensitive uses usually present during these periods
Potential Source
of Impact
5.5.4
Tunnel boring machine (TBM) and rock
breaking activities will be used to excavate rock in the main tunnel and at the
adits respectively. The potential for noise impact caused by
possible transmission and magnification of vibration from TBM or rock breaker
through the ground and structures (such as buildings) to RNSRs
has been reviewed. The path of the
potential noise impact will be as follows:
l
Source - vibration of the rock surface
of the tunnel due to cutting action of TBM and rock breaker
l
Path - vibration is transmitted through
the bed rock, ground soil and the foundation of RNSR building to the walls of
overlying rooms.
l
Receiver - vibration of walls excite the
air inside the rooms to form noise. Reflection of the walls may also increase
the noise level
5.5.5
The residents will not receive noise
from the airborne path through the tunnel air passage. Thus the ground-borne
path is a potential source of noise impact.
5.5.6
It should be noted that during tunneling
construction other powered mechanical equipment will generate much less
vibration. Also, construction works
near the ground surface other than tunneling may generate more airborne noise
than ground-borne noise. Thus it is adequate to assess only the ground borne
vibration from the TBM or rock breaking operation for this project.
5.5.7
Raising boring machines will be used for
construction of the vertical shaft at intake shaft locations during normal
daytime working hours. It is expected that during the operating
period the airborne noise intrusion through the above ground fabric of the
building from other ambient sources will dominate over any noise reradiated by
ground borne vibration sources.
Duration of Impact and Specification of Tunnel Boring Machine
5.5.8
It is assumed that the duration of
potential structure borne impact could last throughout the construction period
for the tunnel and portal works. According to the proposed construction
period, this will be from mid 2008 to end 2010.
Assessment Methodology and Assumption
5.5.9
Field investigation and literature
review have been carried out to collect the necessary background information
including site underground data, data on various construction
equipment to be used in the project, and various theoretical analysis
methodologies for groundborne noise and vibration
assessment. Some of the data are site specific and may have a variation
for the predicated ground borne noise levels for the operation of TBM. Prior to the use of the data, the
validity of the above information on site is required.
5.5.10
The representative NSRs
were identified based from the existing and committed land uses in the study
area that may be affected by the worksite.
For the purpose of this study, NSRs within 100m from
the main tunnel alignment and 15m from the adits
alignment have been considered.
5.5.11
With a ground borne noise and vibration
prediction model, the known underground condition, the separation distance
between the vibration source and RNSRs, the ground
borne noise levels due to each construction activities at NSRs
are predicated. The mathematical
prediction model was developed with reference to the following technical paper in Hong Kong Institute
of Engineers Transaction
Yeung, A.,
Tam K and Ng. C.F (2001) “A Practical
Methodology for Impact Assessment of Tunnel Boring Machine Generated noise” . HKIE Transaction Vol.
8 (3), pp. 26-30.
The prediction was also referred to data
from the reference "Transient Noise and Vibration Impact Assessment",
Final Report, April 1995, prepared by Harris Miller Miller
& Hanson Inc. 15 New England Executive Park Burlington, Massachusetts
01803.
5.5.12
The vibration level, VL, 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 groundborne noise level is determined by the following
steps. .
Step 1 – Determination of vibration level
at sources
5.5.13
The excitation force and vibration of
the soil due to the TBM and Beaker vibration has been obtained from the rock
excavation works during the
construction of the Lok Ma Chau
Spur Line tunnel contract and other performance related reports
on construction plant. The plant
inventory data is presented in Annex I to Appendix D.
The vibration
level at sources is determined by the following equation:
VL= 20log(velocity
at reference distance from sources/0.000001mm/s )
Step 2 – Vibration transmission across the geological media
5.5.14
Several on-site vibration measurements
were conducted during borehole drilling operation for the Project ground
investigation. The purpose of the
site measurement is to determine
the
attenuation constant applicable to the Project conditions. The site measurement
data is in Annex II to Appendix D. The effect of distance attenuation during
the course of propagation of the vibration waves across the geological media is
established by using the following empirical formula :
d
= 20log(r/10) – a ( r-10)
where d= distance attenuation;
r = separation distance between the
source and the building foundation;
a= attenuation constant determined by the
on-site test
Therefore the soil vibration level near
building foundation is obtained by the following equation:
VL(building
foundation)= VL – d
Step 3 – Soil-Foundation Coupling
5.5.15
There is a change in the incident
ground-surface vibration due to the presence of the pile supported building
foundation. This is represented by
the coupling loss into building foundation. The empirical values from previous work based on the guidance as set out in the
reference book “ Transient Noise and Vibration Impact Assessment” are used to
predict the soil/foundation interaction are used to determine the coupling loss
factor for the transmission of vibration from the soil to the foundation. Annex IV to the Appendix D presents the
empirical values used for this assessment.
Therefore the vibration level of the building at ground level is
represented by the following equation:
VL(building ) = VL(building foundation) - c
where c =
coupling loss into building foundation
Step 4 – Building Vibration
5.5.16
A finite element analysis method is used
to predict the mode shape and longitudinal and lateral resonance frequencies of
the floors and walls of the residential buildings. Annix
V to the Appendix D gives the details of the finite element analysis. The vibration level of the walls of the
rooms is calculated by the following equation:
VL(building wall ) = VL(building) - b
where b =
attenuation determined by finite element analysis method
Step 5 – Acoustic Power and Sound Pressure Level
5.5.17
The sound power level of the noise
generated due to vibration of the floors and walls of a building is dependent
on the vibration response, radiation efficiency in 1/3 octave band and the
surface areas of the room. The acoustic
power can be calculated using the following formula:
Sound
power level SWL = VL(building wall) +S1
where S1 = 10logAe
A = surface area of the room
e = radiation efficiency factor
5.5.18
The sound pressure level inside a
typical room was calculated using an in-house software
STRUCTURAL ACOUSTIC ANALYSIS to predict the sound power level and the
corresponding sound pressure level with allowance for the effect of
reverberation.
SPL=SWL +S2
where S2 = 10log(1/S + 4/R)
S
= area of free field waves from the plane source of wall,
R = room constant
From the above steps, the SPL inside a residential room is
given by the following equation.:
SPL=VL-d-c-b+S1+S2
Based on the above method, the error of prediction for the
worst case scenarios will be in the order of +/- 5dB. is
the range of error mainly due to the uncertainty of the acoustic absorption of
the rooms.
5.5.19
The steps in the ground borne noise model can be in
summary as the diagram below.
Screening procedure
5.5.20
To identify the area that may be
affected by the ground-borne noise, first screening process was first carried
out to identify, if any, NSRs that may potentially be
affected and warrant for detailed consideration. The screening is based on a worst case
scenario which is assumed that the noise source and transmission path are
within a rock stratum without soil damping effect. The potential noise sensitive receivers
are on ground floor which rests on piled foundation being in direct contact
with the surface of the bedrock. Therefore, the screening process is a conservative
one without taking account of site specific attenuations. The assessment
results in Annex VI to Appendix D shows that ground borne noise level arising
from TBM operation in main tunnel will be below night-time limit of 40 dB(A)
for NSRs at distance above 100m and below day-time
limit of 55 dB(A) at distance above 20m. A geology profile along the centerline
of the main tunnel is in Annex VII
to Appenidx D.
It shows that the following sections of main tunnel have a rock cover
less than or equal to 100m:
·
Eastern portal tunnel section (CH+0 to
CH+500) – with rock cover less than 100m;
·
Location 1 (CH+1,950) – with rock cover
equal to 80m;
·
Location 2 (CH+4,310) – with rock cover
equal to 100m;
·
Location 3 (CH+4,900) – with rock cover
equal to 100m; and
·
Western portal tunnel section (CH+9,650
to CH+10,504) – with rock cover less than 100m
Therefore the impact of the ground borne noise to the NSRs within the above areas will be examined in more detail
in the following sections.
5.5.21
A similar screening has been performed
for the horizontal adits to identify the area that
may be affected by the ground borne noise during rock breaking operation inside
the adits.
The assessment results in Annex VI to Appendix D demonstrates that the
ground borne noise level will be below night-time limit of 40 dB(A) for NSRs at distance above 15m and below day-time limit of 55
dB(A) at a distance above 3m. A
table showing the rock depth for each adit is in
Appendix D (annex VIII). It is found that the following adits
have rock cover less than 15m:
·
Adit with
vertical intake shaft HR1;
·
Adit with
vertical intake shaft W0;
·
Adit with
vertical intake shaft W3; and
·
Adit with
vertical intake shaft W5
Therefore the impact of the ground borne noise to the NSRs along the above mentioned adit
will be studied in more details in the following sections.
Results of predictions
5.5.22
Six NSRs have
been identified as the nearest to the main tunnel alignment in the western
portal tunnel section and the eastern portal tunnel section. They are namely as NSR1, NSR1a, NSR2,
NSR3, NSR3b and NSR3b. NSR1, NSR1a,
NSR3 and NSR3a are domestic premises whereas NSR 2 and NSR3b are for
educational use. The locations of
the NSR are shown in Figures 5.1 and 5.2. Other NSRs
in the western portal and eastern portal sections are not selected for detailed
examination since the separation distance between the NSRs
and the works is much greater than
the selected NSRs. The details of the selected NSRs are given in Table 5.17.
Table 5.17 – Details of Selected Noise Sensitive Receivers
|
NSR
|
Name
|
Use
|
|
1
|
Aegean Terrace
|
Domestic use
|
|
1a
|
Carriana Sasson
|
Domestic use
|
|
2
|
Proposed
building by HKU
|
Educational
Institution
|
|
3
|
Lai Shing Court
|
Domestic use
|
|
3a
|
The Legend
(future development)
|
Domestic use
|
|
3b
|
True light
middle school of Hong Kong
|
Educational
Institution
|
5.5.23
In examination of the NSRs at locations 1, location 2 and location 3 along the
main tunnel sections, it is found that one school NSR4 (French International
School) at location 1 is located with rock cover about 80m above the
tunnel. No other NSRs are located at locations 2 and 3. Figures 5.35 to 5.37 show the
extent of the ground borne noise influence zone and the identified NSR within
the areas.
5.5.24
Figures 5.38 to 5.41 show the extent of
the ground borne noise influence zone along the alignments of adit with vertical intake shaft HR1, W0, W3 and W5
respectively. It is noted that
NSR5, NSR6 and NSR7 are within the influence zone near to the alignments of adit with vertical intake shaft HR1, W3 and W5
respectively. Both NSR5 and NSR6 are domestic premises whereas NSR7 (Raimondi
College) is for educational use.
Based on the site investigation data, the rock head is below the invert
of the adit with vertical intake shaft HR1. The
borehole records at shaft HR1 are in Annex III
to Appendix D. Excavation in soil
stratum is expected and therefore no further structural borne noise assessment
is required for this adit. The rock head is about 11m and 7m above
the adits with vertical intake shaft W3 and W5. The details of the selected NSR as
mentioned in paragraphs 5.5.23 and 5.5.24 are summarised
in Table 5.18.
Table 5.18 – Details of Selected Noise Sensitive Receivers
|
NSR
|
Name
|
Use
|
|
4
|
French
International School
|
Educational
Institution
|
|
5
|
Builidngs at Broom Road 9-20
|
Domestic
use
|
|
6
|
Green
Villa
|
Domestic
use
|
|
7
|
Raimondi
College
|
Educational
Institution
|
5.5.25
On site vibration measurement tests were
conducted at the following locations to determine a situational attenuation
constant for step 2 of the calculation method:
·
a borehole drilling site VH10 near to
NSR2 (Educational Institute of Hong Kong University) in the close proximity of
the Western Portal (Figure 5.2)
·
a borehole drilling site VH1 near to
NSR3 (Block B of Lai Sing Court) in the close proximity of the Eastern Portal (Figure
5.1)
The site measurement data at VH1 is inconclusive and is not
used for the assessment. Detail of the testing configurations and test results
measured at VH10 are given in Annex II to Appendix D. Based on the results, a
low attenuation is recorded due to the presence of solid rocks for 90% of the
path from the source to the receivers. It is verified by logging records for
the boreholes at point VH10. The
relevant borehole records are in Annex III
to Appendix D. In the absence of similar vibration tests at other sensitive
receiver locations, the attenuation for others NSRs
is assumed to be zero taking as the worst scenario case.
5.5.26
Most of the buildings are on piles. These generally give lower coupling loss
in the frequency range around 31.5 Hz but higher coupling loss in the frequency
range 63 Hz –500 Hz (ref. Appendix D (Annex IV)).
5.5.27
Finite element analysis package SAP 2000 was used to predict the mode shape and
longitudinal and lateral resonance frequencies of the floors and walls of the
buildings. Typical results are given in Annex V to Appendix D and these
indicate that the resonant frequencies are in the octave bands of 31.5 Hz to 63
Hz. The amplification of vibration due to resonance is in the range of 6-10 dB.
5.5.28
The predicted noise levels at the RNSRs along the main tunnel are shown in Table 5.19 below:
Table 5.19 Predicted Ground Borne Noise Level
|
NSR
|
Uses
|
Predicted Noise Level ^
|
Day-time Limit Level
(except General Holidays and Sundays)*
|
Daytime during
general holidays and Sundays and all days during Evening
(1900
to 2300 hrs)**
|
Night time Limit Level
(2300 to 0700 hrs)**
|
|
1 - Aegean Terrace
|
Domestic premises
|
42 dB (A)
|
65 dB (A)
|
55 dB (A)
|
40 dB (A)
|
|
2 - HKU
|
Educational Institute
of Hong Kong University
|
41 dB (A)
|
60 dB (A)
|
55 dB (A)
|
[1]
|
|
3a - The Legend
|
Future domestic
development
|
43dB (A)
|
65 dB (A)
|
55 dB (A)
|
40 dB (A)
|
|
3b - True light middle
school of Hong Kong
|
School
|
45 dB (A)
|
60 dB (A)
|
55 dB (A)
|
[1]
|
*
10 dB(A) below the noise criteria stipulated in
EIAO-TM
** 10 dB(A) below the
noise criteria stipulated in GW-TM; Noise limits during restricted hours only
refer to areas with ASR “B” for
demonstration purpose.
[1] No
sensitive uses during these period
^ The
noise levels are predicted based on particular site data subject to be verified
for each specific site.
Mitigation
Measures
5.5.29
The mitigation
measures proposed are to study the feasibility to carry out the construction
works during restricted hours or in the context of programming construction
works only. The construction works
during restricted hours are still under control of NCO by a permit system. The
use of PME (including TBM) for
carrying out construction work
during the restricted hours will require a CNP. There are some factors
affecting the assessment results of a CNP application, such as the assigning of Area
Sensitivity Rating. As the
situations/conditions around the sites may change from time to time, the Noise
Control Authority would decide these at the time of assessment of such an
application based on the contemporary situations/conditions.
Area
near NSR1
5.5.30
NSR1 and NSR1a has the same horizontal
distance from the tunnel path, thus it is assumed that they will receive the
same structure borne noise level of 42 dB(A). The assessment show that noise levels at NSR1 and NSR1a
may marginally above the night time noise limit level.
5.5.31
The assessment
predicated that TBM operation work can
therefore proceed during the daytime when tunnelling through the tunnel section
between Western Portal and point B as shown in Figure 5.2. The ground borne
noise received by other potential NSRs are expected
to be within the day time noise limit since they are much further away from the
tunnel alignment as compared with NSR1 and NSR1a.
5.5.32
Based on the
assessment, the TBM construction work
can be performed during both day and night time when TBM is operating through
the tunnel section beyond point D at where rock cover is greater than 100m as
shown in Figure 5.2.
5.5.33
Noise monitoring
should be performed at the following locations:
·
at NSR1 when TBM
is operating through the tunnel section between Western portal and point A; and
·
at NSR1a when TBM is operating
through the tunnel section between points A and B.
5.5.34
The noise level
should be measured on the ground floor inside the nearest building during the
TBM construction work in the
daytime. If the daytime monitored
ground borne noise exceeds the relevant evening/night ground borne noise
criteria, evening/night construction work
could not be carried out for the concerned tunnel section.
Area
near NSR2
5.5.35
The prediction
shows that the noise level at NSR2 due to TBM operation will be marginally
above night time limit level but well below the day time limit level. It is
expected therefore that a lower ground borne noise level will be received by
other sensitive receivers around NSR2 since they are located higher and further
away from the alignment of the tunnel.
5.5.36
Based on the
assessment, the TBM construction work
can be performed during both day and night time when TBM is operating through
the tunnel section beyond point D where rock cover is greater than 100m (Figure
5.2).
5.5.37
Noise monitoring
should be performed in tunnel section between path CD
near NSR2.
5.5.38
The noise level
should be measured on the ground floor inside the nearest building during the
TBM construction work in the
daytime. If the daytime monitored
ground borne noise exceeds the relevant evening/night ground borne noise
criteria, evening/night construction work
could not be carried out for the concerned tunnel section.
Area
near NSR3
5.5.39
NSR3 and NSR3b
have the similar horizontal distance to the tunnel path thus it is assumed that
they will receive the same structural borne noise. The predicated ground borne noise level
is below the day and night time limit levels. The structural borne noise level
at NSR3a (the future residential building - The Legend) is expected to be
higher than the night time limit level.
5.5.40
Based on the
assessment, the TBM can be operated during both the day-time and night time
periods when it is working beyond
point D which is 100m from NSR3a. Day-time construction will only be
permissible for the section of tunnel between the Eastern portal (i.e. point E)
and point D as shown by Figure 5.1.
5.5.41
Noise monitoring
at NSR3a during daytime should be performed when TBM is operating along the
tunnel section between points D and E which is nearest to RNSRs.
Area near NSR4
5.5.42
NSR4 is for
educational use purpose and therefore no night time sensitive use is
expected.
5.5.43
Based on the
available information, rock head is about 80m above the main tunnel at location
near NSR4. The predicated noise
level at NSR4 would be below the daytime limit based on the screening process
mentioned in 5.5.20. No sensitive
use at NSR4 during the night time and if the daytime ground borne noise limit
could be met, the TBM construction work
could be operated on daily basis if necessary.
5.5.44
Noise monitoring
at NSR4 during daytime should be performed when TBM is operating along the
tunnel section within the influence zone as shown in Figure 5.35.
Area near NSR5
5.5.45
As stipulated in
paragraph 5.5.24, the excavation inside the adit with
vertical shaft HR1 will be carried out in soil stratum. No ground borne noise impact is
expected. Therefore no mitigation
measures or monitoring works for
ground borne noise impact is expected.
Area near NSR6
5.5.46
NSR6 is the
nearest domestic sensitive receiver along the alignment of the horizontal adit with vertical shaft W3 (Figure 5.40).
5.5.47
The rock head
above the section of adit near NSR6 is about
11m. According to the screening
criteria as stipulated in paragraph 5.5.21, the predicated noise level at NSR6
will be higher than the night-time limit level but below the day-time
limit. The rock breaking operation
inside the adit should be carried out during the
day-time.
5.5.48
Noise monitoring
should be carried during daytime when the breaker is operating along the adit section between points F and G at NSR6. If the daytime monitored ground borne
noise exceeds the relevant evening/night ground borne noise criteria,
evening/night construction work could
not be carried out for the concerned tunnel section.
Area near NSR7
5.5.49
NSR7 is the
nearest receiver along the alignment of the horizontal aidt
with vertical shaft W5 (Figure 5.41).
It is used for educational purpose and therefore no sensitive use during
the night-time is expected.
5.5.50
The rock head
above the section of adit near NSR7 is about 7m. According to the screening criteria as
stipulated in paragraph 5.5.20, the predicted noise level at NSR7 will be
higher than the night-time limit level but below the day-time limit. No sensitive use during the night-time
at NSR7 is expected.
5.5.51
Noise monitoring
should be carried out during daytime when the breaker is operating along the adit section between points H and I at NSR7.
5.6
Operation
Noise
5.6.1
Operation noise impact is not expected
as there will not be any electrical or mechanical equipment operating inside
the main tunnel and adits after commissioning of the
facilities. Maintenance of the intake shafts and stilling basin will only
involve the removal of trapped gravels by hand. No operation vibration sources have been
identified.
5.7
Monitoring
and Audit Requirements
5.7.1
Airborne and ground borne noise
monitoring will be carried out at selected representative RNSRs
during the construction phase. The objectives of monitoring are to:
1)
check for
compliance to acceptable noise levels during construction phase.
2)
check the
effectiveness of the recommended mitigation measures. Ad-hoc monitoring and
audit will also be carried out at other NSRs in case of
complaints, and measures taken to ensure acceptable noise levels are met.
5.7.2
Details of the noise monitoring are
presented in a separate Environmental Monitoring and Audit (EM&A) Manual.
5.8
Conclusion
5.8.1
The unmitigated construction noise
activities would cause exceedance of the daytime
construction noise criterion at most of the nearby sensitive receivers during
normal working hours. In addition to good site practices, use
of mitigation measures such as provision of on-site movable noise barrier, cantilevered
type barriers, full enclosure at strategic locations, quiet plant and limiting
the number of plant operating concurrently have been recommended. With the implementation of these
measures, the residual impacts of construction noise levels can be kept at reasonable
levels at all times.
5.8.2
Predicted ground
borne construction noise levels at all NSRs will not
exceed the daytime ground borne noise criteria with a margin of over 15 dB(A).
5.8.3
Regular monitoring of construction noise
at selected representative NSRs will be required
during the daytime construction phase to monitor the compliance and
effectiveness of the proposed mitigation measures and has been presented in a
separate EM&A manual.
5.8.4
No operation phase noise impacts are
expected.
