4.1
This section presents an
assessment of potential airborne noise impacts during the construction of the
Project, and recommends appropriate mitigation measures, where necessary.
Environmental
Legislation, Standards and Guidelines
4.2
Noise impacts have been assessed in
accordance with the criteria and methodology given in the Technical Memoranda
(TMs) under the Noise Control Ordinance (NCO), and Annexes 5 and
4.3
The NCO, Cap. 400 and Environmental Impact
Assessment Ordinance, Cap. 499 (EIAO) provide the statutory framework for noise
control. Assessment procedures and
standards are set out in the following TMs:
Ÿ Technical Memorandum on Environmental Impact Assessment Process
Ÿ Technical Memorandum on Noise from Construction Work other than Percussive Piling (GW-TM)
Ÿ Technical Memorandum on Noise from Percussive Piling (PP-TM)
Ÿ Technical Memorandum on Noise form Construction Work in Designated Areas (DA-TM)
Ÿ Technical Memorandum for the Assessment of Noise from Places Other Than Domestic Premises, Public Places or Construction Sites (IND-TM)
4.4
Percussive piling is governed under the PP-TM
and a construction noise permit (CNP) is required in order to carry out such
work. As the issuance of a CNP by the
Noise Control Authority would depend on the compliance of percussive piling
noise impact with the limits set out within the PP-TM, the assessment of this
type of noise would not be covered in the EIA Report.
Construction Noise during Non-restricted Hours - EIAO-TM
4.5
Daytime general construction works (excluding
percussive piling) between the hours 0700 – 1900 on weekdays, i.e.
non-restricted hours, is controlled under the EIAO. Annex 5 of the EIAO-TM sets out the
construction noise assessment criteria, which are Leq(30
min) 75dB(A) for domestic premises, hotels and hostels; and Leq(30 min) 70dB(A) for schools
during normal hours (65dB(A) during examination periods) and all other places
where unaided voice communication is required. The criteria are summarized in Table 4.1.
Table
4.1 Air-borne Daytime Construction Noise
Criteria
|
Uses |
Daytime Noise Criteria, (Leq, 30min, dB(A)) |
|
|
Domestic
premises, hotel, hostel |
75 |
|
|
Educational
Institution |
70 |
|
|
Educational
Institution (during examination) |
65 |
|
Note: The
above standards apply to uses which rely on opened windows for ventilation
Construction Noise Standard during Restricted Hours
4.6
Between
1900 and 0700 hours and all day on Sundays and public holidays, activities
involving the use of powered mechanical equipment (PME) for the purpose of
carrying out construction work is prohibited unless a CNP has been obtained. A CNP may be granted in cases where the noise
can be contained within the Acceptable Noise Level (ANL) at the NSRs. ANLs are assigned depending upon the Area
Sensitivity Ratings (ASRs). The
corresponding basic noise levels (BNLs) for evening and night-time periods are
given in Table 4.2.
Table 4.2 Construction Noise Criteria for
Activity other than Percussive Piling during Restricted Hours
|
Time Period |
ANL on Different ASR During Restricted Hours (Leq,
30min, dB(A)) |
||
|
ASR A |
ASR B |
ASR C |
|
|
Evening (1900 to 2300 hours) [a] |
60 |
65 |
70 |
|
Night (2300 to 0700 hours) |
45 |
50 |
55 |
Notes: [a] Includes Sundays and Public Holidays
during daytime and evening
4.7
Despite
any description or assessment made in this EIA Report on construction noise
aspects, there is no guarantee that a CNP will be issued for the project
construction. The Noise Control Authority will consider a well-justified CNP
application, once filed, for construction works within restricted hours as
guided by the relevant TMs issued under the NCO. The Noise Control Authority
will take into account contemporary conditions/ situations of adjoining land
uses and any previous complaints against construction activities at the site
before deciding whether to grant a CNP.
Nothing in the EIA Report should bind the Noise Control Authority in
making its decision. If a CNP is to be
issued, the Noise Control Authority should include in the permit any condition
it thinks fit. Failure to comply with
any such conditions will lead to cancellation of the CNP and prosecution under
the NCO.
4.8
Under
the DA-TM, the use of five types of Specified Powered Mechanical Equipment
(SPME) and three types of Prescribed Construction Work (PCW) within a
designated area during restricted hours would require a valid CNP (The Project
falls within DA). The SPME includes
hand-held breaker, bulldozer, concrete lorry mixer, dump truck and hand-held
vibratory poker. The PCW are:
Ÿ Erecting or dismantling of formwork or scaffolding;
Ÿ Loading, unloading or handling of rubble, wooden boards, steel bars, wood or scaffolding material; and
Ÿ Hammering
4.9
In
general, it should not be presumed that a CNP would be granted for carrying out
PCW within a designated area during restricted hours. The CNP may be granted for the execution of
construction works during restricted hours involving the use of PME and/or SPME
if the relevant Acceptable Noise Levels and criteria stipulated in the GW-TM
and DA-TM can be met. The construction noise criteria are presented
in Table 4.3.
Table
4.3 Construction Noise Criteria for SPME
|
Time Period |
Basic Noise Level (BNLs) |
||
|
ASR
‘A’ |
ASR
‘B’ |
ASR
‘C’ |
|
|
Evening (1900 to 2300 hours) (1) |
45 |
50 |
55 |
|
Night (2300 to 0700 hours) |
30 |
35 |
40 |
Note: (1) Includes
Sundays and Public Holidays during daytime and evening
Description of the Existing Environment
4.10
The SCL Protection Works is located entirely offshore within the
CBTS. Dredging would be carried out at
the southeast corner of the CBTS.
4.11
The proximities of the Project area include a mix of commercial,
Government/Institution/Community and residential uses. Traffic noise from
4.12
Existing and planned/committed noise
sensitive receivers within
4.13
Only the first
layer of Noise Sensitive Receivers (NSRs) was identified for assessment because
it would provide acoustic shielding to those receivers at further distance
behind, and would represent the worst-case scenario. The assessment points have been agreed with
EPD. Locations of the representative NSRs for the construction noise
impact assessment are shown in Figure Nos. NEX2213/C/331/ENS/M52/501 and NEX2213/C/331/ENS/M52/502. Details of the representative NSRs are presented in Table 4.4.
Table 4.4 Representative
Noise Sensitive Receivers for Noise Impact Assessment
|
NSR ID |
Description |
Land Use |
No. of storey |
|
N11 |
|
Residential |
24 |
|
N13 |
Belle House |
Residential |
24 |
|
CH1 |
|
Residential |
17 |
|
CH2 |
|
Residential |
19 |
|
CH3 |
Elizabeth House, Block C |
Residential |
21 |
|
CH4 |
|
Residential |
15 |
4.14
The
Project is scheduled to be commenced in early 2012 and to be completed by early
2014. According to the construction programme (Appendix
2.3
refers), there are three major construction tasks. All construction tasks are planned
to be carried out during unrestricted hours.
4.15
The
methodology for the noise impact assessment is in accordance with the
procedures outlined in the GW-TM. The general approach is summarized below:
Ÿ Locate the NSRs which would most likely be affected by noise from the construction work;
Ÿ Determine the items of PME for each discrete construction activity, based on available information or agreed plant inventories;
Ÿ Assign sound power levels (SWLs) to the proposed PME according to the GW-TM or other sources;
Ÿ Calculate distance attenuation to NSRs from notional noise source;
Ÿ Apply corrections in the calculations such as potential screening effects and acoustic reflection, if any;
Ÿ Predict construction noise levels at NSRs in the absence of any mitigation measures;
Ÿ Consider cumulative impact from the concurrent projects within
Ÿ Compare the cumulative construction noise level against the noise criteria and propose suitable mitigation measures;
4.16
SWLs
of the equipment from Table 3 of GW-TM were used for the assessment. Where no relevant SWL to be found in the
GW-TM, reference was made to British Standard 5228:Part
1:2009 Noise Control on Construction and Open Sites and previous similar
studies or from measurements taken at other sites in
4.17
The
construction programme and plant inventory as presented in Appendices
2.3 and 4.1 respectively for
various construction activities were developed by the engineering consultants
of the Project Proponent. Highways Department (HyD)
has confirmed the proposed plant inventory as being
practical and adequate for completing the works within the scheduled timeframe.
4.18
It was
assumed that all PME items required for a particular construction activity
would be located at the notional or probable source position of the segment
where such activity is to be performed.
The assessment was based on the cumulative SWL of PME likely to be used
for each location, taking into account the construction period in the vicinity
of the receiver location. To predict the
noise level, PME was divided into groups required for each discrete
construction task. The objective was to identify the worst case scenario
representing those items of PME that would be in use concurrently at any given
time. The sound pressure level of each construction task was calculated,
depending on the number of plant and distance from receivers. The noise levels
at NSRs were then predicted by adding up the SWLs of all concurrent
construction tasks. Noise sources from the areas greater than
4.19
A
positive 3 dB(A) façade correction was added to the
predicted noise levels in order to account for the facade effect at each NSR.
The unmitigated construction noise impacts at the identified NSRs were
predicted accordingly. Practicable direct mitigation measures including use of
quieter equipment, movable barriers, enclosures and quieter alternative methods
were considered if exceedance of relevant criteria
was predicted. In case where the mitigated noise levels still exceeded the
relevant criteria, the duration of the noise exceedance
would be estimated.
Identification
of Environmental Impacts
4.20
The potential source of noise impact during
the construction phase of the Project would mainly be the use of PME for
various construction activities. Major
construction works that would contribute to air-borne construction noise
impacts would include temporary reclamation, relocation of
temporary RHKYC jetty, and dredging works.
4.21
The key elements involved for air-borne
construction noise at different works sections are summarized in Table 4.5
Table
4.5 Construction Phase Elements
|
Sections |
Key
Construction Items |
Nearby
Representative NSR |
|
Protection
Works at |
§
Dredging works at southeast corner of
CBTS to provide space for relocation
of anchorage area |
§ Bella
House § |
|
|
§
Marine piling for the temporary
relocation of jetty at RHKYC §
Temporary
reclamation §
Diaphragm walls §
Seawalls §
Approximately 160m long cut-and-cover
tunnel §
Bottom-up construction §
Removal of temporary Reclamation (Same construction method as CWB) |
§ § § Elizabeth
House, Block C § |
4.22
Since the
Project would be constructed together with the CWB project at the CBTS,
potential cumulative noise impact arising from the CWB project and the Project
would be expected. The potential cumulative noise impact arising from the construction of the Project and CWB project was therefore considered in this assessment.
4.23
Based
on the available construction programme of the SCL (HUH-ADM) at the time of this EIA study, the SCL (HUH-ADM) would not interface with the Project. As such, cumulative noise
impact from the construction
activities of the SCL
(HUH-ADM) is not expected.
Prediction and Evaluation
of Environmental Impacts
Construction Phase during
4.24
To strike a
balance between the need for providing a railway system to the public and the
public concerns on the adverse impacts, the following key features have been
considered during the design of the Project to alleviate the construction noise
impacts as far as practicable:
·
Minimisation of
number of PME; and
·
Works would be
implemented in phases, where possible, in order to reduce the number of PME
required to be on-site.
4.25
The unmitigated
noise levels at representative NSRs were predicted and presented in Table 4.6 based on the construction
programme and plant inventory (Appendices
2.3 and 4.1). Locations of
notional sources and distance to NSRs are shown in Appendix 4.3 and corresponding
figure.
4.26
Sample
calculations and a summary of unmitigated construction noise levels during
normal daytime working hours for the representative NSRs are presented in Appendix 4.4 and 4.5, respectively.
Table
4.6 Unmitigated Construction
Noise Levels due to construction of the Project
|
NSR ID |
Description |
Predicted Unmitigated Construction Noise
Levels, dB(A) |
EIAO-TM Noise Criteria, dB(A) |
|
N11 |
|
64 |
75 |
|
N13 |
Belle House |
70 |
75 |
|
CH1 |
|
64 - 84 |
75 |
|
CH2 |
|
63 - 83 |
75 |
|
CH3 |
Elizabeth House, Block C |
65 - 79 |
75 |
|
CH4 |
|
67 - 81 |
75 |
Note:
Bold figures indicate exceedances of the EIAO-TM noise criteria
4.27
The predicted noise
levels at the representative NSRs would range from 63 to 84 dB(A),
and some of which would exceed the EIAO-TM noise criterion of 75 dB(A). Mitigation measures would be required to
abate the construction noise impacts.
Construction Phase during
Restricted Hours
4.28
According to the
construction programme, no construction works would be carried out during
non-restricted hours. In case of any
construction activities during restricted hours (1900 – 0700), it is the
Contractor’s responsibility to ensure compliance with the NCO and the relevant
TMs. The Contractor will be required to submit CNP application to the Noise
Control Authority and abide by any conditions stated in the CNP, should one be
issued.
Mitigation
of Adverse Environmental Impacts
4.29
The construction noise assessment indicated
that, in the absence of any mitigation measures, there would be exceedance of the construction noise criteria at some of
the NSRs. Various mitigation options have thus been considered in accordance
with the guidelines laid down in the Environmental Impact Assessment Ordinance,
Guidance Note No. 9/2004 “Preparation of Construction Noise Impact Assessment
under the Environmental Impact Assessment Ordinance” (GN 9/2004). It should be noted that the assumptions used
in formulating mitigation measures and their practicality were based on the
best available information at the preliminary design stage of the Project.
Alternative mitigation proposals which could achieve the same noise reduction
effect may be considered in the detailed design stage. The recommended
mitigation measures are discussed below.
Good Site Practice
4.30
Although the noise mitigation effects are
easily quantifiable and the benefits may vary with site conditions and operating
conditions, good site practices are easy to implement and do not impact upon
the works schedule. The site practices
listed below should be followed during each phase of construction:
Ÿ Only well-maintained plant should be operated on-site and plant should be serviced regularly during the construction program;
Ÿ Silencers or mufflers on construction equipment should be utilized and should be properly maintained during the construction program;
Ÿ Mobile plant, if any, should be sited as far from NSRs as possible;
Ÿ Machines and plant (such as trucks) that may be in intermittent use should be shut down between work periods or should be throttled down to a minimum;
Ÿ Plant known to emit noise strongly in one direction should, wherever possible, be orientated so that the noise is directed away from the nearby NSRs; and
Ÿ Material stockpiles and other structures should be effectively utilized, wherever practicable, in screening noise from on-site construction activities.
Adoption of Quiet PME
4.31
In order to reduce the excessive noise
impacts at the affected NSRs during normal daytime working hours, quieter PME
are recommended. The Contractors may use
other types of quiet plant instead of specific items of quiet plant adopted in
this assessment, which have the same total SWL, to meet their needs. Quiet PME adopted in the assessment were
taken from the BS5228: Part 1:2009. It
should be noted that the selected quiet PME for assessment could be found in
4.32
A list of quiet PME recommended for adoption
during the construction phase is presented in Table 4.7.
Table 4.7 Quiet
PME Recommended for Adoption during Construction Phase
|
PME |
Reference |
SWL,
dB(A) |
|
Air
Compressor |
BS D7/16 |
96 |
|
Concrete Pump |
BS D6/36 |
106 |
|
Crane |
BS D7/113 |
101 |
|
Dump Truck |
BS D9/27 |
105 |
|
Excavator |
BS D3/97 |
105 |
|
Generator |
CNP 103 |
95 |
|
Hand-held Breaker |
BS D2/10 |
110 |
|
Air
Compressor* |
Table C7/16 |
96 |
|
Bulldozer* |
Table C9/2 |
104 |
|
Concrete
Lorry Mixer* |
Table C6/35 |
100 |
|
Concrete
Pump* |
Table C6/36 |
106 |
|
Crane* |
Table C7/114 |
101 |
|
Dump
Truck* |
Table C9/27 |
105 |
|
Excavator* |
Table C3/97 |
105 |
|
Poker
Vibrator* |
Table C6/32 |
100 |
|
Roller* |
TableC8/27 |
104 |
|
Trucks* |
TableC9/27 |
105 |
Remark:
* Reference has been made to the approved WDII & CWB EIA Report
Use
of Movable Noise Barrier
4.33
The use of movable barrier for certain PME
could further alleviate the construction noise impacts. In general, 5dB(A)
reduction for movable PME and 10dB(A) for stationary PME can be achieved
depending on the actual design of movable noise barrier.
4.34
Table 4.8 shows the
assumed noise reduction effects achieved by the movable noise barrier for
certain items of PME. The Contractor shall
be responsible for design of the movable noise barrier with due consideration
given to the size of the PME and the requirement of intercepting the line of
sight between the NSRs and PME. Barrier
material of surface mass in excess of 10 kg/m2 is recommended to
achieve the predicted screening effect.
4.35
A
summary of the
assumed noise reduction effects achieved by the use of movable noise barrier for certain item of PME
is presented in Table 4.8.
Table
4.8 Noise Mitigation Measures for
Certain PME during Construction Phase
|
PME |
Mitigation
Measures Proposed |
Noise
Reduction, dB(A) |
|
Air
Compressor* |
Movable
Barrier |
10 |
|
Bar
Bender* |
Movable
Barrier |
10 |
|
Bentonite Plants* |
Movable
Barrier |
5 |
|
Concrete
pump* |
Movable
Barrier |
10 |
|
Diaphragm
Wall Rigs* |
Movable
Barrier |
5 |
|
Excavator* |
Movable
Barrier |
5 |
|
Poker
Vibrator* |
Movable
Barrier |
5 |
Remarks:
* Reference has been made to the approved
WDII&CWB EIA Report
Mitigated
Construction Noise Impacts
4.36
Having
taken into account the noise reduction achieved by the above-mentioned
mitigation measures, the total SWLs of each activity were predicted, and are
presented in Appendix 4.6. Predicted mitigated noise levels from the Project itself
at all the representative NSRs would comply with the EIAO-TM noise
criteria. Table 4.9 summarises the mitigated levels at the representative
NSRs. The sample calculations and the summary of mitigated construction noise
levels during normal daytime working hours are presented in Appendices 4.7 and 4.8, respectively.
Table 4.9 Mitigated
Construction Noise Levels due to construction of the Project
|
NSR ID |
Description |
Predicted Mitigated Construction Noise
Levels, dB(A) |
EIAO-TM Noise Criteria, dB(A) |
|
N11 |
|
64 |
75 |
|
N13 |
Belle House |
70 |
75 |
|
CH1 |
|
61 – 73 |
75 |
|
CH2 |
|
60 – 73 |
75 |
|
CH3 |
Elizabeth House, Block C |
60 – 68 |
75 |
|
CH4 |
|
61 - 70 |
75 |
Cumulative
Construction Noise Impact
4.37
The
concurrent project in the vicinity of the Project works area is CWB project.
Construction of the CWB project in the vicinity would involve the temporary
reclamation and cut and cover tunnel works at Ex-Public Cargo Working Area and
CBTS.
4.38
Cumulative
construction noise impacts from the CWB project were
assessed by using the maximum mitigated
construction noise levels predicted in the approved WDII & CWB EIA Report during the overlapping period.
4.39
Table 4.10 summaries the cumulative noise levels from the Project and
CWB project. Detailed calculation of the cumulative noise impacts are presented
in Appendix 4.9. The results indicate that the cumulative noise levels at
all the NSRs would comply with the EIAO-TM noise criteria.
Table
4.10 Cumulative Construction Noise
Levels from Other Concurrent Projects (Mitigated)
|
NSR ID |
EIAO-TM Noise Criteria, dB(A) |
Predicted Mitigated Noise Levels, dB(A) |
Cumulative Noise Level, dB(A) |
|
|
The Project |
CWB Project[*] |
|||
|
N11 |
75 |
64 |
64 |
64 – 67 |
|
N13 |
75 |
70 |
67 |
67 – 72 |
|
CH1 [a] |
75 |
61 – 73 |
68 [a] |
68 – 74 |
|
CH2 [a] |
75 |
60 – 73 |
68 [a] |
68 – 74 |
|
CH3 |
75 |
60 – 68 |
68 |
68 – 71 |
|
CH4 |
75 |
61 - 70 |
73 |
73 – 75 |
Note:
[*] Maximum
mitigated construction noise level from CWB project at the particular NSR
within the overlapping period is based on the approved WDII & CWB EIA
Report.
[a] Since no construction noise level was
predicted at CH1 and CH2 in the approved WDII & CWB EIA Report, the maximum
mitigated construction noise level at the nearest NSR (CH3) was adopted to
predict the cumulative construction noise levels from CWB project.
Evaluation
of Residual Impacts
4.40
With the use of quiet PME and movable noise
barriers, the predicted construction noise levels at all representative NSRs
would comply with the noise criteria stipulated in the EIAO-TM.
Environmental Monitoring and Audit
4.41
An EM&A programme is recommended
to be established according to the predicted occurrence of noisy activities.
All the recommended mitigation measures for daytime normal working activities
should be incorporated into the EM&A programme for implementation during
construction. Details of the programme are provided in a stand-alone EM&A
Manual.
4.42
Noise
arising from the construction activities of the project would have unavoidable
potential impact on the NSRs located in the vicinity of the works areas.
Unmitigated construction noise levels at the representative NSRs have been
predicted, which are found to be in the range of 63 to 84 dB(A).
4.43
Mitigation
measures including good site practices, quieter plant, and movable noise barrier
are recommended to reduce the noise levels so as to meet the EIAO-TM noise
criterion. With the recommended
mitigation measures in place, noise levels due to the Project and the cumulative impact with
CWB project at all representative NSRs
are predicted to comply with the EIAO-TM daytime construction noise
criterion. No adverse residual impact
would be envisaged.