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
5.2.5
The NCO provides
the statutory frame
Technical
Memorandum on Noise from Places other than Domestic Premises, Public Places or
Construction Sites (
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 (
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)) |
Domestic Premises |
75 |
Educational Institutions (normal
periods) |
70 |
Educational
Institutions (during examination periods) |
65 |
5.2.9
The NCO provides
statutory controls on general construction
Table 5.3 Acceptable Noise Levels (
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
5.3.2
For assessment of construction noise, RNSRs are selected near the tunnel portals and intake
shafts where Powered Mechanical Equipment (
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. |
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 |
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 |
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 |
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
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 |
Finalized stage – General |
Dump trucks, conveyor
belts |
Finalized stage – Concreting |
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
5.4.3
The type and quantity of Powered
Mechanical Equipment (
Table 5.6a Equipment List for each
Construction Activity for Eastern and Western Portals
Activity /
Equipment |
Date |
Duration |
TM Code |
SWL, |
Quantity |
Summation |
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, |
Quantity |
Summation |
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.
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.
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
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
(iii) calculation of the total
Sound Power Level (SWL) of equipment to be used;
(iv) calculation of distance
attenuation to NSRs from
(v) comparison of the
Predicted Noise Levels (PNLs) with the relevant noise
criteria.
5.4.11
All
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.
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
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 |