4.1
This
Section presents an assessment of the potential noise impacts pertinent to the
construction and operation phase of the Project, and recommends appropriate mitigation
measures, where necessary.
Environmental Legislation, Standards and Guidelines
4.2
The
Noise Control Ordinance (NCO) and Environmental Impact Assessment Ordinance
(EIAO) provide the statutory framework for noise control. Assessment procedures and standards are set
out in the five Technical Memoranda (TMs) listed below:
Ÿ
TM
on Environmental Impact Assessment Process (EIAO-TM)
Ÿ
TM
on Noise from Construction Work other than Percussive Piling (GW-TM)
Ÿ
TM
on Noise from Percussive Piling (PP-TM)
Ÿ
TM
on Noise form Construction Work in Designated Areas (DA-TM)
Ÿ
TM
on Noise from Places other than Domestic Premises, Public Places or
Construction Sites (IND-TM)
Construction Noise
4.3
Daytime
construction noise (excluding percussive piling) between the hours 0700 – 1900
on weekdays, is controlled under the EIAO.
Annex 5 of the EIAO-TM sets out the construction noise limits, which are
Leq(30 min) 75dB(A) for domestic premises 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.
4.4
Construction
activities other than percussive piling using powered mechanical equipment
(PME) undertaken at other times (i.e. during restricted hours) are under the
control of the NCO.
Fixed Plant Noise
4.5
Operational
noise emitted from the fixed noise source is controlled under the NCO and
IND-TM. According to the TM, the
acceptable Noise Levels (ANLs) for different Area Sensitivity Ratings (ASRs)
are given in Table 4.1.
4.6
The ANL
is a function of the type of area within which the NSR is located, and the
degree of the effect on the NSR of influencing factors such as major roads and
industrial areas. The ANLs for all ASRs
are provided in Table
4.1.
Table 4.1 Acceptable
Noise Levels (ANLs)
(dB(A))
|
Time Period |
ASR A |
ASR B |
ASR C |
|
Day (0700 to 1900 hours) |
60 |
65 |
70 |
|
Evening (1900 to 2300 hours) |
|||
|
Night (2300 to 0700 hours) |
50 |
55 |
60 |
4.7
The
EIAO-TM states that all fixed noise sources should be so located and designed
so that when assessed in accordance with the IND-TM, the level of the intruding
noise at the facade of the nearest sensitive use should be at least 5 dB(A)
below the appropriate ANL shown in Table 2 of the IND-TM or, in the case of the
background being 5 dB(A) lower than the ANL, the predicted noise level should
not exceed the background.
4.8
The
Project site is located in the North Wan Chai District, and is bounded by
4.9
Major
noise sources identified within this area include traffic noise from nearby
road networks, e.g.
4.10
Representative
Noise Sensitive Receivers (NSRs) were selected in accordance with the criteria
in the EIAO-TM to evaluate the potential noise impacts. Table 4.2 summarises the selected NSRs for the noise impact
assessment. The locations of
representative NSRs in the vicinity of the proposed work areas are illustrated
in Figure 4.1.
Table 4.2 Representative Noise Sensitive Receivers
|
NSR |
Description |
Land Use |
Distance(1) |
Remarks |
|
N1 |
|
Government /
Institution / Community |
180 |
With A/C(3) |
|
N2 |
Causeway
Centre |
Residential |
250 |
- |
|
N3 |
Renaissance
Harbour View Hotel |
Other Specified Uses |
-(2) |
With A/C(3) |
|
N4 |
Grand
Hyatt Hotel |
Other Specified Uses |
-(2) |
With A/C(3) |
Note:
(1)
Horizontal distance between NSR to the nearest project boundary
(2) NSR is
located next to the Project Site
(3) With
central ventilation system
4.11
As noted
from site visits, the identified NSRs except NSR N2 are provided with central
ventilation systems. As such, they do not rely upon opened windows for
ventilation, and are therefore less noise sensitive. The noise criteria as
stipulated in the EIAO-TM only apply to NSRs which rely on opened windows for
ventilation. Thus, the EIAO-TM criteria would not be applicable to those NSRs
with central ventilation systems (i.e. NSR N1, N3 and N4), and these NSRs will
be excluded in this assessment.
4.12
As shown
in Figure 4.1, the NSR N2 is located
in urban area of Wan Chai with an annual average daily traffic flow in excess
of 30,000 running through the nearby
Construction Phase
4.13
The
potential source of noise impact during the construction phase of the Project
would be the use of PME for various construction activities as described in
Section 2. As indicated in Table 2.1, the proposed Project will last from May
2006 to March 2009. The major construction activities for the Project which
would be potential sources of construction noise in the Study Area include
construction of temporary footbridge/working platform/superstructure for atrium
link extension, demolition of existing atrium link, piling and foundation
works. The construction noise impacts arising from the proposed project are
discussed in Sections 4.17 to 4.20.
4.14
Generally,
the construction activities of the Project would be carried out in
non-restricted hours (0700-1900 hours) during normal working days. In case of
any construction activities during restricted hours, 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.
4.15
Based on
the preliminary design information, percussive pilling would be used for the
driving of temporary marine piles into the seabed. Percussive piling is
prohibited between 1900 and 0700 hours on any weekday not being a general
holiday and at any time on Sunday or general holiday. A CNP is required for carrying out of
percussive piling between 0700 and 1900 hours on any day not being a general
holiday. The Contactor will be responsible to apply to the EPD for a CNP under
the NCO. When assessing a CNP application for carrying out percussive piling,
the Noise Control Authority is guided by the PP-TM.
Operation Phase
4.16
To cope
with the building service requirement, plant rooms will be constructed and
located at the north-eastern corner of the ALE on Level 2 and Level 3 (Figure 4.2 refers). They will
accommodate chiller plant, chiller pump and flushing tank which are considered
to be the major sources of fixed plant noise. The Sound Power Level (SWL) of
the chiller plant are typically in range of 100 to 109 dB(A) with reference to
the Good Practices on Ventilation System on Noise Control. The noise Impact
arising from the operation of the identified fixed plant will be assessed in
Sections 4.21 to 4.23.
Prediction and Evaluation of Impacts
Construction Phase
4.17
The
major construction activities for the Project which would be potential sources
of construction noise in the Study Area include construction of temporary
footbridge/working platform/superstructure for atrium link extension,
demolition of existing atrium link, piling and foundation works. PME likely to
be used include breaker, crane, lorry, excavator, air compressor, generator and
pilling machines, etc for these major construction activities. With reference
to the GW-TM, the SWL of PME is typically in range of 108 to 122 dB(A). For a
conservation estimation, the maximum SWL of the construction activities
throughout the construction period would be estimated to be about 127 dB(A) by
assuming two sets of typical PMEs operated concurrently.
4.18
As shown
in the Figure 4.1, the nearest NSR
rely on openable window for ventilation is the Causeway Centre (NSR N2). The
distance from the NSR N2 to the nearest boundary of the work site is about
4.19
Taking
into account the noise reduction provided by the large separation distance and
the screening from the nearby office buildings, the construction noise levels
at NSR N2 would be about 64 dB(A) which would be well within the EIAO-TM
daytime construction noise criteria of 75dB(A). Therefore, adverse construction
noise impact on Causeway Centre would not be anticipated. Good site practices
and weekly environmental audit will be implemented properly during construction
of the Project to check on compliance with the assessment criteria.
4.20
The
construction of Central Reclamation Phase III (CRIII) would likely coincide
with the construction of the Project.
Nevertheless, the nearest worksites of the CRIII are located more than
Operation Phase
4.21
With
reference to the SWL of the typical building service equipment, the dominant
noise source would be mainly due to the operation of chiller plants. Based on
preliminary design information provided by the Engineer, there would be five
chiller plants to be operated. Assuming all chiller plants with SWL of 109 to
be operated at the same time, the total SWL of the equipment in plant rooms was
estimated to be 116 dB(A) as a conservative assumption. As all the building
service equipment will be housed in building structure, a 10 dB(A) noise
reduction of noise emitted from the sources due to transmission loss of wall
can be achieved.
4.22
As shown
in Figure 4.1, Causeway Centre is
substantially screened by two office buildings (i.e. Great Eagle Centre and
Harbour Centre) in between. The project site would be screened from the
line-of-sight of NSRs by building or the structures. This allowed a reduction
in the predicted noise level by 10 dB(A) in accordance with the GW-TM. The predicted noise levels at NSR N2 would be
about 43 dB(A) taking into account the separation distance and the
above-mentioned noise reduction. This predicted noise levels would be
conservative because a well-designed building can have more than 10 dB(A) noise
reduction due to transmission loss of building walls.
4.23
Insurmountable
noise impact associated with the fixed noise sources from the Project would not
be envisaged having regard to the fact that the separation distance between the
Project Site and the nearest NSR N2 would be large and the line of sight of the
NSR to the Project Site would be limited.
Mitigation of Adverse Environmental Impacts
Construction Phase
4.24
Although
adverse noise impact would not be expected during the construction phase of the
Project, good site practices will be implemented by the Contractor to minimize
noise emission. 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 utilised, wherever
practicable, in screening noise from on-site construction activities.
Operation Phase
4.25
Although
no adverse noise impact would be expected during the operation phase of the
Project, it is recommended that the following noise reduction measures should
be considered as far as practicable during detailed design:
Ÿ
Choose
quieter plants such as those which have been effectively silenced.
Ÿ
Include
noise levels specification when ordering new plants.
Ÿ
Locate
fixed plants away from any NSRs as far as practicable.
Ÿ
Locate
fixed plants in plant rooms with thick walls or specially designed enclosure
Ÿ
Locate
noisy machines in basement or a completely separate building
Ÿ
Develop
and implement a regularly scheduled plant maintenance programme so that plants
are properly operated and serviced in order to maintain controlled level of
noise. The programme should be implemented by properly trained personnel.
Evaluation of Residual Impacts
4.26
No
adverse residual impact would be envisaged.
Environmental Monitoring and Audit
Construction Phase
4.27
To
ensure all the recommended mitigation measures to be fully implemented during
the construction stage, environmental audit is recommended. Details of the
EM&A requirements are provided in a stand-alone EM&A Manual.
Operational Phase
4.28
No
operation noise monitoring for fixed plant would be considered necessary.
4.29
Noise
arising from the construction activities for Atrium Link Extension and
operation of the fixed plant would not have significant impact on the NSRs
located in the vicinity of the work sites. The nearest NSR which rely on
openable window for ventilation is Causeway Centre (NSR N2) and it will be
separated from the Project site for