4.
CONSTRUCTION
NOISE IMPACT ASSESSMENT
4.1.1
This Chapter presents an assessment
of construction noise impacts associated with the construction of the proposed
drainage channels: MUP03, MUP04A, MUP04B,
MUP05 and LMH01 (the
Project).
4.1.2
Noise generated during the
construction phase by works activities and powered mechanical equipment would
pose potential impacts to the surrounding sensitive receivers. Appropriate
mitigation measures are recommended where necessary to mitigate such impacts.
4.1.3
Operational
phase of the channels would only involve small scale maintenance and is not
expected to generate any excessive noise.
Noise
Assessment Study Area
4.2.1
For the purpose of noise
assessment, the Study Area covers essentially 300 m from the boundary of each
of the work sites of the Project. This Study Area can be reduced if the first
layer of the noise sensitive receivers, closer than 300 m from the boundary,
provides acoustic shielding to those receivers at further distance behind.
Description
of the Existing
Noise Environment
MUP03, MUP04A, MUP04B, MUP05
4.2.2
The existing noise climate within
the Man Uk Pin and Loi Tung area
is dominated by the traffic on the existing roads – Sha Tau Kok Road (Wo Hang Section) and Wo Keng
Shan Road. These roads carry a substantial amounts of heavy goods vehicles and
container lorries utilising the nearby Sha Tau Kok border crossing, North East
New Territories (NENT) Landfill
and various open storage yards in the vicinity. As such, sensitive receivers facing these roads are affected by high
traffic noise.
4.2.3
The major landuse in the vicinity
is village environs and agriculture use. Some small-scale industrial
establishments, such as storage yards and workshops, can be found scattered
in and around the villages.
LMH01
4.2.4
Lin Ma
Hang is located within the Closed Area. The noise climate is quiet and mainly
dominated by local village activities.
4.3
Construction
Noise Criteria
4.3.1
There are currently no statutory
criteria for noise generated from construction work other than percussive
piling during the daytime hours of
4.3.2
The noise standards for general
construction works during normal working hours (i.e. 0700 to 1900 hours on any
day not being a Sunday or public holiday) stipulated in
Table 1B of Annex 5 of the
EIAO-TM are given
in Table 4.1.
EIAO-TM Daytime
Construction Noise Standards
|
Uses |
Daytime Construction Noise Standards, Leq (30
minutes) dB(A) |
|
Domestic Premises |
75 |
|
Educational
institutions (normal periods) |
70 |
|
Educational
institutions (during examination periods) |
65 |
Notes:
These standards assume the use of
open windows for ventilation. They are the maximum permissible noise levels
assessed at 1 m from the receiver’s external façade.
4.3.3
The principal legislation on the
control of construction noise during restricted hours is the Noise Control
Ordinance (NCO) (Cap.400) and its associated Technical Memoranda (TM). 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 Contractor shall comply with the NCO and all relevant
regulations under this Ordinance, including restrictions placed on noise from
construction work and the requirements to seek Construction Noise Permit (CNP).
At present, construction works during restricted hours are not expected.
However, should works have to be carried out during restricted hours, a CNP
must be obtained from the relevant Noise Control Authority (i.e. EPD) before
the works are allowed to take place. Percussive piling works are also subjected
to CNP licensing under the NCO. The Contractor is also required to display
these permits appropriately.
4.3.4
Despite the description or
assessment made in the subsequent sections, 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 by the relevant Technical Memorandum
(Memoranda) issued under the NCO. The Noise Control Authority will take into
account of contemporary situations/conditions of adjoining land uses and any
previous complaints against construction activities at the site before making
his decision in granting a CNP. Nothing in this Report shall bind the Noise
Control Authority in making his decision. If a CNP is to be issued, the Noise
Control Authority shall include in it any conditions that are considered
appropriate and such conditions are to be followed while the works covered by
the permit are being carried out. Failure to comply with any such conditions
will lead to cancellation of the CNP and prosecution action under the NCO.
4.4
Representative
Noise Sensitive Receivers
4.4.1
The Representative Noise Sensitive
Receivers (RNSRs) chosen for construction noise assessment are shown in Figures
4.1 – 4.3. These RNSRs are selected in accordance with the
criteria in Annex 13 of the EIAO-TM. Reference has been made to the following
Outline Zoning Plan (OZP): S/NE-MUP/10. No OZP is available for Lin Ma Hang. Based
on the available information at the time of assessment, there are no planned /
committed noise sensitive development and uses in the area. A
description of the RNSRs is
tabulated in Table 4.2.
Details of Representative NSRs close to the Project
|
Channels |
Representative NSR |
General Description |
No. of Floors |
Approximate Horizontal
Distance from Construction Activities (Notional Point Source), m |
|
MUP03 |
MUP03-1 |
Village house near |
2 |
36 |
|
MUP03 |
MUP03-2 |
Village house near |
1 |
17 |
|
MUP04A |
MUP04A-1 |
23 King Ngai Garden near |
3 |
52 |
|
|
MUP04A-2 |
Village house near |
3 |
10 |
|
MUP04B |
MUP04B-1 |
|
3 |
26 |
|
|
MUP04B-2 |
Village house near |
3 |
6 (to 1350mm pipe) |
|
MUP05 |
MUP05-1 |
Village house near |
2 |
22 |
|
|
MUP05-2 |
Village house at Loi Tung North |
2 |
41 |
|
|
MUP05-3 |
Village house at Loi Tung North |
2 |
18 |
|
|
MUP05-4 |
Village house at Loi Tung North |
2 |
22 |
|
|
MUP05-5 |
Village house near |
2 |
52 |
|
|
MUP05-6 |
Village house at Loi Tung North |
2 |
16 |
|
LMH01 |
LMH01-1 |
Village house at No. 166 Lin Ma Hang |
2 |
12 |
|
|
LMH01-2 |
Village house at No. 213A Lin Ma Hang |
3 |
10 |
|
|
LMH01-3 |
Village house at No. 139B Lin Ma Hang |
3 |
35 |
|
|
LMH01-4 |
Village house at No. 71 Lin Ma Hang |
2 |
12 |
|
|
LMH01-5 |
Village house at No. 1A Lin Ma Hang |
3 |
127 |
Note:
The location of the NSRs is
shown in Figures 4.1 – 4.3.
4.5
Construction
Noise Impact Assessment
Potential
Sources of Impacts
4.5.1
The main construction activities for the proposed drainage
channels include site clearance, excavation of channel to formation level, backfilling, followed by assembly of gabions and mattress lining
and other associated construction (box
culvert, vehicular bridges, footbridges, etc).
4.5.2
Dedicated
haul road is not anticipated for the project as access to the sites is readily available
from
4.5.3
Construction of the channels will
generally be carried out starting from the downstream end to the upstream to
facilitate simple draining of the works site. However, the Contractor may start
at isolated sections to suit his allocation of resources and to maintain access
across the channel banks.
4.5.4
Majority of the potential
construction noise impact may occur during the site clearance and excavation
works, when soil and stream bed sediments are excavated and transported out of
the site. The construction of the channel includes installation of gabion cages / mattress lining, pre-fabricated grasscrete
panels & U-channels and box culvert. Filling of
the gabions will be carried out either by hand or by machine depending on the
accessibility of the site,
hence the number of powered mechanical equipment being operated is expected to
be limited. Since gabion will be extensively used as channel
lining and base, the amount of concrete to be used on-site is also
expected to be limited. The proposed ‘two-stage’ channel design for MUP05
involves retaining sections of the stream bed or banks in-situ, as such
construction activities for MUP05 is expected to be significantly scaled down. Similarly,
the construction of maintenance access road and foot bridges will involve few
mechanical equipment.
4.5.5
Alternative solutions to flooding
problem at Lin Ma Hang instead
of a bypass channel have been recommended under this Project to avoid
impacts on the valuable ecological resources in the area. The revised works for
Lin Ma Hang comprise short section of gabion channel at the downstream end, local
improvement of stream
banks, reconstruction of vehicular
bridges as well as improvement to the existing security grille
at the outlet of Lin Ma Hang stream. It also includes the installation of several flood alarm system in the village. As a
consequence, construction activities are substantially scaled down. Given the
small scale works, construction equipment is expected to be limited.
Construction
Equipment
4.5.6
The type and quantity of Powered
Mechanical Equipment (
4.5.7
The equipment used in the noise
calculation was based on site experience and was reviewed by the design engineers.
It was considered reasonable in terms of the types and numbers to be used by
the Contractor for satisfactory completion of the Project based on the
tentative construction programme, though there may be variation in the actual
construction stage. A copy of DSD’s memo acknowledging the proposed
construction equipment is attached in Appendix B.
Construction Schedule and Programme
4.5.8
The
construction duration for this Project is expected to last for about 42 months
within the tentative construction timeframe of end 2007 to mid 2011.
The tentative construction programme for each channel is not available at this
preliminary design stage. Currently, construction work during
restricted hours is not anticipated.
Tentative Construction Programme for the Proposed Channels
|
Proposed Channel |
Tentative Construction Programme |
|
MUP03, MUP04A,
MUP04B, MUP05 and LMH01 |
End 2007 – Mid
2011 |
Note:
Tentative
construction programme and duration subject to further changes subject to land
resumption programme.
Assessment Methodology and Assumptions
4.5.9
The construction noise assessment
has been conducted based on standard acoustic principles, the methodology
stated in Sections 5.3 & 5.4 of Annex 13 of the EIAO-TM, and the Technical
Memorandum on Noise from Construction Work other than Percussive Piling
(TM-GW). The assessment also makes reference to the BS 5228: Part 1: 1997 Noise
and Vibration Control on Construction and Open Sites, Part 1: Code of Practice
for Basic Information and Procedures for Noise and Vibration Control (BS5228) as well as EIAO Guidance Note
No. 9/2004 – Preparation of Construction Noise Impact Assessment under the Environmental Impact Assessment
Ordinance.
4.5.10
In general
terms, the methodology used involves the following steps:
(i)
identification
of the most likely worst case scenario from the construction programme;
(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.
4.5.11
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 TM-GW) and is
operating at the same time. The various construction activities are not
expected to be carried out concurrently. Shielding effect from existing
building structures, topographic features and/or neighbouring 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.
Assessment Results
4.5.12
The unmitigated PNL at RNSRs, resulting from various
construction activities, are summarised below in Tables 4.4 – 4.5. Detailed calculations are
presented in Appendix B.
Predicted
Noise Level during Construction of MUP Channels - Unmitigated
|
RNSR |
Unmitigated Construction Noise Level, dB(A) |
||||
|
Site Clearance |
Excavation to Formation
Level |
Backfilling |
Construction of Channel
Base / Lining and other Works |
Concreting Works |
|
|
MUP03-1 |
82 |
82 |
77 |
82 |
78 |
|
MUP03-2 |
89 |
89 |
84 |
89 |
85 |
|
MUP04A-1 |
79 |
79 |
74 |
79 |
75 |
|
MUP04A-2 |
93 |
93 |
88 |
93 |
90 |
|
MUP04B-1 |
85 |
85 |
80 |
85 |
81 |
|
MUP04B-2 |
98 |
98 |
93 |
98 |
94 |
|
MUP05-1 |
86 |
86 |
82 |
86 |
83 |
|
MUP05-2 |
81 |
81 |
76 |
81 |
77 |
|
MUP05-3 |
88 |
88 |
83 |
88 |
85 |
|
MUP05-4 |
86 |
86 |
82 |
86 |
83 |
|
MUP05-5 |
79 |
79 |
74 |
79 |
75 |
|
MUP05-6 |
89 |
89 |
84 |
89 |
86 |
Notes:
Numbers in BOLD denote exceedance of daytime noise
standard: 75 dB(A) for residential premises, 70 dB(A)
for educational institution.
Predicted
Noise Level during Construction of LMH01 - Unmitigated
|
RNSR |
Unmitigated Construction Noise Level, dB(A) |
|||
|
Demolition Works |
Site Clearance
/ Excavation |
Reconstruction of
Vehicular Bridge / Bank Improvement |
Concreting Works |
|
|
LMH01-1 |
85 |
92 |
90 |
88 |
|
LMH01-2 |
86 |
93 |
92 |
90 |
|
LMH01-3 |
75 |
82 |
81 |
N/A
(see note 2) |
|
LMH01-4 |
N/A
(see note 1) |
92 |
90 |
N/A
(see note 2) |
|
LMH01-5 |
64 |
71 |
70 |
N/A
(see note 2) |
Notes:
Numbers in BOLD denote exceedance of daytime noise
standard: 75 dB(A) for residential premises, 70 dB(A)
for educational institution.
Note
1 Existing
natural banks, no demolition of shotcrete banks necessary.
Note
2 No
concrete necessary for bank improvement works.
4.5.13 Tables 4.4 – 4.5 show that unmitigated construction noise levels would exceed the daytime noise standards at most of the RNSRs. The predicted exceedance is due to the close proximity of the construction works to the NSRs. However, the likely overall exceedance with respect to each receiver is expected to be intermittent and not severe, as some part of the works would be carried out within the channel where the noise would be partially shielded. Moreover, as the available works area for some channels, pipes or box culvert are limited, the use of heavy construction machinery will be limited. Nonetheless, adequate mitigation measures will be required. The recommended mitigation measures for the construction works are discussed in the following section.
4.6.1 The predicted noise levels showed that construction works would give rise to daytime noise impacts to most of the RNSRs. The following types of mitigation measures are recommended.
Level 1 Mitigation - Use of
Quiet Plant
4.6.2
The use of quiet plant (also
referred as silenced equipment) can provide significant reduction in noise
level. Quiet plant is defined as PME whose actual sound power level is less
than the value specified in the TM-GW for the same piece of equipment. The
common source of these information is from international standard /
certification, e.g. BS 5228. To allow the Contractor some flexibility to select
equipment to suit actual needs, it is considered too restrictive to specify
which specified silenced equipment to be used for the construction works. Hence, it
is preferable and practical to specify the noise performance specification of
the plant on site in terms of the sound power level so that the Contractor is
allowed some flexibility. It should be noted that various types of silenced equipment
can be found in
4.6.3 The use of quiet plant is considered to be the most effective ways of alleviating construction noise impact. The Contractor should use quiet plant with sound power level lower than that stipulated in the TM-GW as the Level 1 mitigation for construction noise.
4.6.4 The use of mini or lower power rating equipment (e.g. mini excavator) should also be considered where practical. This technique would be feasible and practical at some locations given the limited space available for using large size construction equipment and the small scale works involved (e.g. localised bank improvement at LMH01, U-channel and drainage pipes at MUP 03 & MUP04B).
4.6.5 The Contractor should take note of ETWB TCW No. 19/2005 - Environmental Management on Construction Sites which sets out the policy and procedures requiring contractors to, among others, adopt Quality Powered Mechanical Equipment (QPME)[1].
4.6.6 With the use of quiet plant, most of the RNSRs are within the daytime noise criteria. Only RNSRs MUP03-2, MUP04A-2, MUP04B-2, MUP05-1, MUP05-3, MUP05-4, MUP05-6, LMH01-1, LMH01-2 and LMH01-4 will still require further mitigation measures.
Level 2 Mitigation - Use of
Temporary Noise Barriers
4.6.7 Since most of the NSRs within the Project area are typically low-rise village houses of not more than 3 storeys tall, it would be effective to have noise screening structures or temporary noise barriers purposely-built along the site boundary to provide additional protection to NSRs close to the construction site boundary. This could be in the form of purposely-built site hoarding constructed from appropriate materials with a minimum superficial density of 7 kg/m2. Noise barrier should be provided for noisy construction activities that would be undertaken close (about 25m or less) to NSRs. With the exception of NSRs MUP04A-2 and MUP05-6, the noise barrier should have a vertical height of at least 2.5 m or (depending on the height of the NSRs to be protected) a height ensuring that the operating equipment can be shielded from the view of the NSRs. For NSR MUP04A-2, the temporary noise barrier should have a minimum height of 3.5 m with a small cantilevered upper portion. For NSR MUP05-6, the temporary noise barrier should have a minimum height of 3 m with a small cantilevered upper portion. The temporary noise barrier should have no gaps or opening at joints. The Contractor should regularly inspect and maintain the noise barrier to ensure its effectiveness.
4.6.8 For the construction works which have the potential to exceed the noise standards on nearby NSR and whose line of sight cannot be effectively blocked by the temporary noise barrier, movable (mobile) barriers should be provided. This may also be applicable in situation where construction of a temporary noise barrier may not possible due to site / space constraints, for example blocking village or emergency vehicle access. Movable barriers of at least 2.5 m height with a small cantilevered upper portion and skid footing can be located within a few meters of stationary plant (e.g. generator, compressor) and within about 5 m or more of a mobile equipment (e.g. excavator), such that the line of sight to the NSR is blocked by the barriers.
4.6.9 The temporary noise barriers are expected to provide 10 dB(A) noise reduction for stationary equipment or 5 dB(A) noise reduction for mobile equipment.
4.6.10 The proposed noise barrier for the affected RNSRs is shown in Figures 4.4 – 4.6 respectively. A typical cross section view of the barrier showing line of sight could be shielded by the proposed barrier is included in Appendix B.
Good
Site Practices
4.6.11 In general, potential construction noise impact can be minimised or avoided by imposing a combination of the following good site practices as mitigation measures:
(a)
Only
well-maintained plant should be operated on-site and plant should be serviced
regularly during the construction period.
(b) Construction plant should be sited away from NSRs.
(c) Machines and plant that may be in intermittent use should be shut down between works periods or should be throttled down to a minimum.
(d) Equipment known to emit sound strongly in one direction should be orientated such that the noise is directed away from nearby NSRs.
(e) Material stockpiles and other structures (such as site offices) should be effectively utilised to shield on-site construction activities.
(f) Stationary equipment should be located within the channel when weather conditions permit (e.g. dry season).
(g) The Contractor shall devise, arrange methods of working and carrying 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.
(h) In the event that new schools are built near the works area, 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 contract and to avoid noisy activities during these periods.
4.6.12 The implementation of the above good site practices could be readily applied to construction sites and can, in theory, provide additional reduction in construction noise levels. However, such noise reduction is difficult to quantify and is therefore not considered in the calculations.
Public Relation Strategy
4.6.13 Having a good public relation with the local communities during the construction phase is indispensable for a smooth implementation of the Project. Prior to commencement of the construction, visits to the affected villages, local communities and property owners should 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 arising from the works;
§ 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.
4.6.14 To maintain an effective communication channel with the public, a 24-hour hotline system should be established by the project office for the Contractor to receive any enquiry and complaint lodged by the public in respect of the Project. Upon receipt of enquiry / complaint, the Contractor (or its ET) should investigate the causes of the incident and take the appropriate action to rectify the situation. Periodic newsletters, information leaflets, notices or other means of communication should be provided to the affected villages, communities, and residents advising them the current progress, 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 local communities during construction.
4.6.15 Tables 4.6 – 4.7 show predicted noise levels with the implementation of the proposed Level 1 mitigation measure (use of quiet plant).
Predicted
Noise Level during Construction of MUP Channels - Mitigated
(Level 1 mitigation : use of quiet plant)
|
RNSR |
Mitigated
Construction Noise Level, dB(A) |
||||
|
Site Clearance |
Excavation to Formation
Level |
Backfilling |
Construction of Channel
Base / Lining and other Works |
Concreting Works |
|
|
MUP03-1 |
71 |
71 |
71 |
71 |
68 |
|
MUP03-2 |
78 |
78 |
77 |
78 |
74 |
|
MUP04A-1 |
68 |
68 |
67 |
68 |
64 |
|
MUP04A-2 |
82 |
82 |
82 |
83 |
79 |
|
MUP04B-1 |
74 |
74 |
73 |
74 |
70 |
|
MUP04B-2 |
87 |
87 |
86 |
87 |
83 |
|
MUP05-1 |
76 |
76 |
75 |
76 |
72 |
|
MUP05-2 |
70 |
70 |
70 |
70 |
66 |
|
MUP05-3 |
77 |
77 |
77 |
77 |
74 |
|
MUP05-4 |
76 |
76 |
75 |
76 |
72 |
|
MUP05-5 |
68 |
68 |
67 |
68 |
64 |
|
MUP05-6 |
78 |
78 |
78 |
78 |
75 |
Notes:
Numbers in BOLD denote exceedance of daytime noise
standard: 75 dB(A) for residential premises, 70 dB(A)
for educational institution.
Predicted
Noise Level during Construction of LMH01 - Mitigated
(Level 1 mitigation : use of quiet plant)
|
RNSR |
Mitigated
Construction Noise Level, dB(A) |
|||
|
Demolition Works |
Site Clearance
/ Excavation |
Reconstruction of
Vehicular Bridge / Bank Improvement |
Concreting Works |
|
|
LMH01-1 |
82 |
81 |
77 |
77 |
|
LMH01-2 |
83 |
82 |
79 |
79 |
|
LMH01-3 |
72 |
72 |
68 |
N/A
(see note 2) |
|
LMH01-4 |
N/A
(see note 1) |
81 |
77 |
N/A
(see note 2) |
|
LMH01-5 |
61 |
60 |
57 |
N/A
(see note 2) |
Notes:
Numbers in BOLD denote exceedance of daytime noise
standard: 75 dB(A) for residential premises, 70 dB(A)
for educational institution.
Note
1 Existing
natural banks, no demolition of shotcrete banks necessary.
Note
2 No
concrete necessary for bank improvement works.
4.6.16 Tables 4.8 – 4.9 show predicted noise levels with the implementation of the proposed Level 2 mitigation measures (use of quiet plant + temporary noise barrier) for the affected RNSRs.
Predicted Noise Level during Construction of MUP
Channels - Mitigated
(Level 2
mitigation : use of quiet plant + use of noise barriers)
|
RNSR |
Mitigated
Construction Noise Level, dB(A) |
||||
|
Site Clearance |
Excavation to Formation
Level |
Backfilling |
Construction of Channel
Base / Lining and other Works |
Concreting Works |
|
|
MUP03-2 |
73 |
73 |
72 |
73 |
N/A |
|
MUP04A-2 |
77 |
77 |
77 |
77 |
73 |
|
MUP04B-2 |
82 |
82 |
81 |
82 |
78 |
|
MUP05-1 |
70 |
70 |
N/A |
70 |
N/A |
|
MUP05-3 |
72 |
72 |
72 |
72 |
N/A |
|
MUP05-4 |
70 |
70 |
N/A |
70 |
N/A |
|
MUP05-6 |
73 |
73 |
73 |
73 |
N/A |
Notes:
Numbers in BOLD denote exceedance of daytime noise
standard: 75 dB(A) for residential premises, 70 dB(A)
for educational institution.
N/A
= not applicable
Predicted
Noise Level during Construction of LMH01 - Mitigated
(Level 2 mitigation
: use of quiet plant + use of noise barriers)
|
RNSR |
Unmitigated Construction Noise Level, dB(A) |
|||
|
Demolition Works |
Site Clearance
/ Excavation |
Reconstruction of
Vehicular Bridge / Bank Improvement |
Concreting Works |
|
|
LMH01-1 |
76 |
76 |
72 |
72 |
|
LMH01-2 |
78 |
77 |
73 |
73 |
|
LMH01-3 |
N/A |
N/A |
N/A |
N/A
(see note 2) |
|
LMH01-4 |
N/A
(see note 1) |
76 |
77 |
N/A
(see note 2) |
|
LMH01-5 |
N/A |
N/A |
N/A |
N/A
(see note 2) |
Notes:
Numbers in BOLD denote exceedance of daytime noise
standard: 75 dB(A) for residential premises, 70 dB(A)
for educational institution.
N/A
= not applicable
Note
1 Existing
natural banks, no demolition of shotcrete banks necessary.
Note
2 No
concrete necessary for bank improvement works.
4.6.17 Although the proposed temporary noise barriers can shield the view of NSR MUP04A-2 to the construction site (see Figure B1 of Appendix B), there would still be slight exceedance of about 2 dB(A) as shown in Table 4.8 due to the close proximity of the NSR to the works. Further mitigation is recommended for this NSR by restricting concurrent usage of several equipment at the same time. As shown in Table 4.10, noise reduction of about 2 dB(A) is expected by such restriction. Detailed calculation is shown in Appendix B. The restriction should be applied to all construction works that are conducted within 20 m of NSR MUP04A-2. As the extent of restriction only confines to a small area near NSR MUP04A-2, such restriction is considered feasible and would not hinder the progress of the construction works. It is also recommended that this NSR be included in the EM&A programme during construction period to monitor the noise level and effectiveness of the mitigation measures.
4.6.18 Similarly, exceedance of about 7 dB(A) is expected for NSR MUP04B-2 (see Table 4.8). Further mitigation is recommended for this NSR by restricting concurrent usage of several equipment at the same time. The restriction should be applied to all construction works that are conducted within 20 m of NSR MUP04B-2. As the extent of restriction only confines to a small area near NSR MUP04B-2, such restriction is considered feasible and would not hinder the progress of the construction works. Moreover, the associated works involve laying of a 1350mm drainage pipe. Such small scale minor works could be carried out within a short period using a mini-excavator.
Predicted Noise Level during Construction of MUP
Channels - Mitigated
(Further mitigation A : use of quiet plant + use of noise barriers + restricting concurrent usage of equipment)
|
RNSR |
Mitigated
Construction Noise Level, dB(A) |
||||
|
Site Clearance |
Excavation to Formation
Level |
Backfilling |
Construction of Channel
Base / Lining and other Works |
Concreting Works |
|
|
MUP04A-2 |
75 |
75 |
75 |
75 |
N/A |
|
MUP04B-2 |
73 |
73 |
73 |
73 |
74 |
Notes:
Numbers in BOLD denote exceedance of daytime noise
standard: 75 dB(A) for residential premises, 70 dB(A)
for educational institution.
N/A
= not applicable
4.6.19 The use of purpose built temporary noise barriers would not be practicable for works at LMH01 as the works are small scale, short duration and within village environs with very limited working space. It may also hamper access causing inconvenience to the villagers. The process of installing and dismantling the noise barriers itself would create additional noise nuisance. The use of light-weight mobile barrier is considered more preferable.
4.6.20 As shown in Table 4.9, exceedance of about 1 – 3 dB(A) for demolition works of crossings and 1 – 2 dB(A) for excavation works are still predicted. Further mitigation is recommended by employing quiet working method (for demolition works of crossings) and restricting concurrent usage of several equipment at the same time.
4.6.21 It is recommended that demolition of the existing vehicular crossing should employ quiet working method such as mini concrete crusher, saw & lift, or other similar quiet method. In addition, it is recommended that dump truck and concrete lorry mixer should be parked outside the main village area at a location to be agreed with Engineer, ET Leader and if necessary the village representative. This restriction is considered reasonable and feasible given the ecological importance of the area and since most of the works area are within village environs which cannot be accessible by heavy machinery / vehicles. Moreover, the use of dump truck or concrete lorry mixer will be limited to only about 1 trip every few days. The restriction would not hinder the progress of the construction works. The contractor should submit to the Engineer for approval detailed working methods and mitigation measures with respect to noise (in addition to water quality and ecological impacts) before commencement of the works at LMH01.
4.6.22 As shown in Table 4.11, with the implementation of the above restriction, noise level will be within the acceptable noise level. Detailed calculation is shown in Appendix B. It is also recommended that noise monitoring should be carried out at LMH01 during construction period to monitor the noise level and effectiveness of the mitigation measures.
Predicted
Noise Level during Construction of LMH01 - Mitigated
(Further mitigation A : use of quiet plant + use of noise barriers + quiet working method & restricting
concurrent usage of equipment)
|
RNSR |
Unmitigated Construction Noise Level, dB(A) |
|||
|
Demolition Works |
Site Clearance
/ Excavation |
Reconstruction of
Vehicular Bridge / Bank Improvement |
Concreting Works |
|
|
LMH01-1 |
67 |
74 |
N/A |
N/A |
|
LMH01-2 |
69 |
75 |
N/A |
N/A |
|
LMH01-4 |
N/A
(see note 1) |
74 |
N/A |
N/A
(see note 2) |
Notes:
Numbers in BOLD denote exceedance of daytime noise
standard: 75 dB(A) for residential premises, 70 dB(A)
for educational institution.
N/A
= not applicable
Note
1 Existing
natural banks, no demolition of shotcrete banks necessary.
Note
2 No
concrete necessary for bank improvement works.
4.7.1 With the implementation of proposed mitigation measures, adverse residual noise impact would not be expected from the construction works.
4.8.1 There are a number of projects in the vicinity of the proposed drainage channels. These are described in Chapter 2. Many do not have significant influence on the Project, some are on-going projects that will be completed by the time works commences for this Project.
4.8.2 The major public works project in the area is the Fanling Bypass for the Ping Che / Ta Kwu Ling Development proposed under the NENT Study. However, there is still no programme for the preliminary design or implementation of this project and thus will not be considered in the cumulative impact assessment.
4.8.3 The only likely potential cumulative impact would be from construction works under this Assignment, including the DP channels in this EIA, the Non-DP channels at MUP 01&02 (which drains into MUP05) and the various improvement works at LMH01. Assuming that both DP and non-DP channels will be constructed at the same time, the likely cumulative impact is not expected to exceed the daytime construction noise standard (except for LMH01) provided the recommended mitigation measures are implemented during construction. The cumulative impact result is shown in Table 4.12 with details presented in Appendix B.
Cumulative
Construction Noise Impact
|
RNSR |
Distance to Channel, m |
Unmitigated |
Mitigated |
|||
|
PNL, dB(A) |
Total Cumulative PNL, dB(A) |
PNL, dB(A) |
Total Cumulative PNL, dB(A) |
|||
|
MUP03-1 |
MUP01/02 |
92 |
74 |
84 |
63 |
73 |
|
MUP03 |
36 |
82 |
71 |
|||
|
MUP05 |
53 |
79 |
68 |
|||
|
MUP03-2 |
MUP01/02 |
126 |
71 |
89 |
60 |
75 |
|
MUP03 |
17 |
89 |
73 |
|||
|
MUP04B |
64 |
77 |
66 |
|||
|
MUP05 |
62 |
77 |
67 |
|||
|
MUP04A-1 |
MUP04A |
52 |
79 |
84 |
68 |
73 |
|
MUP04B |
40 |
81 |
70 |
|||
|
MUP05 |
90 |
74 |
63 |
|||
|
MUP04A-2 |
MUP04A |
10 |
93 |
93 |
75 |
75 |
|
MUP04B |
125 |
71 |
61 |
|||
|
MUP05 |
165 |
69 |
58 |
|||
|
MUP04B-1 |
MUP03 |
39 |
81 |
87 |
71 |
74 |
|
MUP04A |
173 |
69 |
58 |
|||
|
MUP04B |
26 |
85 |
69 |
|||
|
MUP05 |
86 |
75 |
64 |
|||
|
MUP04B-2 |
MUP03 |
107 |
73 |
98 |
62 |
75 |
|
MUP04A |
103 |
73 |
62 |
|||
|
MUP04B |
6 |
98 |
74 |
|||
|
MUP05 |
70 |
76 |
66 |
|||
|
MUP05-2 |
MUP01/02 |
16 |
89 |
90 |
73 |
74 |
|
MUP03 |
82 |
75 |
64 |
|||
|
MUP04B |
170 |
69 |
58 |
|||
|
MUP05 |
41 |
81 |
65 |
|||
|
MUP05-3 |
MUP01/02 |
163 |
69 |
89 |
58 |
73 |
|
MUP03 |
100 |
73 |
63 |
|||
|
MUP04A |
182 |
68 |
57 |
|||
|
MUP04B |
100 |
73 |
63 |
|||
|
MUP05 |
18 |
88 |
72 |
|||
|
MUP05-4 |
MUP04A |
140 |
70 |
87 |
60 |
71 |
|
MUP04B |
156 |
69 |
59 |
|||
|
MUP05 |
22 |
86 |
70 |
|||
|
MUP05-5 |
MUP04A |
140 |
70 |
80 |
60 |
69 |
|
MUP04B |
155 |
69 |
59 |
|||
|
MUP05 |
52 |
79 |
68 |
|||
|
MUP05-6 |
MUP01/02 |
102 |
73 |
90 |
57 |
75 |
|
MUP03 |
50 |
79 |
69 |
|||
|
MUP04A |
230 |
66 |
55 |
|||
|
MUP04B |
76 |
76 |
65 |
|||
|
MUP05 |
16 |
89 |
73 |
|||
|
LMH01-1 |
V1 |
25 |
85 |
94 |
73 |
79 |
|
V2 |
12 |
92 |
74 |
|||
|
V3 |
22 |
86 |
74 |
|||
|
Bank |
93 |
74 |
67 |
|||
|
LMH01-2 |
V1 |
29 |
84 |
94 |
72 |
77 |
|
V2 |
10 |
93 |
75 |
|||
|
V3 |
34 |
83 |
70 |
|||
|
Bank |
105 |
73 |
66 |
|||
|
LMH01-3 |
V2 |
115 |
72 |
83 |
60 |
76 |
|
V3 |
88 |
74 |
62 |
|||
|
Bank |
35 |
82 |
75 |
|||
Notes:
- PNL: Predicted Noise
Level
- Channels MUP01 & 02 are Non-DPs
- Numbers in
- Shielding effect from
existing building structures, topographic features and
construction sites are not considered to simulate worst case scenario.
-
Mitigation: use of quiet plant, temporary noise barrier, restricting concurrent
usage of equipment.
4.8.4 As shown in Table 4.12, exceedance of construction noise level is expected in LMH01 when construction of the vehicular crossings (V1, V2 & V3) are being carried out at the same time. To minimize potential adverse cumulative noise impact, it is recommended that works programme should be scheduled such that only either one vehicular crossing or bank improvement works is constructed at any one time. This restriction is also in line with the measures to minimize potential water quality and ecological impacts and is not expected to hinder the progress of the construction works.
4.9
Summary
of Mitigation Measures
4.9.1 Table 4.13 summarises the mitigation measures proposed for the construction works. All these construction noise mitigation measures should be implemented by the contractor during the construction stage of the works. The location of the temporary noise barriers should be further reviewed during the detailed design stage by the detailed design engineer or by the Engineer during the construction stage based on the latest construction programme and contemporary conditions, including any changes with respect to NSRs. The contractor should design, construct, operate and maintain the mitigation measures throughout the construction stage and as required by the Engineer. Before commencement of the works, the contractor should submit to the Engineer for approval (as part of their method statement) details of the mitigation measures to be employed under the works. The contractor’s proposed mitigation measures should also be certified by the Environmental Team (ET) Leader and verified by the Independent Environmental Checker (IEC) to ensure the intended noise reduction effectiveness can be achieved.
Summary of Proposed Construction Noise Mitigation Measures
|
Proposed Mitigation Measures |
Location |
Timing / Duration |
Implementation Agent |
Specific Requirements |
|
Use of quiet
equipment including QPME |
All construction
works / sites |
During the
construction period |
Contractor |
Some examples of
quiet plant and QPME are shown in Appendix B. Contractor can propose other
suitable alternative equipment with similar or lower sound power level. |
|
Use of temporary
noise barrier (purpose-built site hoarding) and/or movable (mobile) noise
barrier |
The temporary
noise barrier shall be located as per Figures 4.4 to 4.6 or wherever noisy
construction works are being carried out close (25m or less) to NSRs |
During the
construction period |
Contractor |
Barriers should be
of at least 2.5 m high or able to shield construction equipment from
NSR’s view. For NSRs MUP04A-2 and MUP05-6, barrier should have a minimum
height of 3.5 m and 3 m respectively. These barriers should be constructed of
appropriate material with a minimum superficial density of 7 kg/m2, with no gaps or
openings. Also, regular inspection and maintenance should be carried out. Where barriers
cannot block line of sight, mobile barrier of 2.5 m high with a
cantilevered upper portion
should be provided. |
|
Good site
practices |
All construction
works / sites |
During the
construction period |
Contractor |
----- |
|
Public relation
strategy |
All construction
works / sites |
During the
construction period |
Project office
(Engineer) / Contractor |
Maintain a 24-hour
hotline for enquiry and complaint, periodic communication with affected
parties |
|
Restrict concurrent
usage of several construction equipment at the same time |
For construction
works within 20m of NSRs MUP04A-2 & MUP04B-2 and works at LMH01 |
During the
construction period |
Contractor |
Contractor to
propose details to the Engineer and ET Leader for approval |
|
Employ quiet
working method for demolition of crossings Dump truck and
concrete lorry mixer parked outside the main village area One vehicular
crossing or bank improvement to be constructed at any one time to minimize
cumulative impact |
For construction
works at LMH01 |
During the
construction period |
Contractor |
Contractor to
propose details to the Engineer and ET Leader for approval |
4.10
Monitoring
and Audit Requirement
4.10.1 Further information regarding construction noise monitoring and audit are broadly described in Chapter 10 of this Report. Key points are summarized in the following sections. Details of the monitoring and audit of construction noise will be presented in the separate EM&A Manual.
4.10.2 Noise monitoring should be carried out at selected representative NSRs during the construction period to check for compliance with permissible noise standards, and to verify the effectiveness of the recommended mitigation measures. Ad-hoc monitoring and audit should also be carried out at other NSRs if complaints are received. Measures should be taken by the Contractor to ensure compliance with the noise standards.
4.10.3
It is recommended that at least
the following representative NSRs (Table 4.14) should be monitored during the
construction stage. The representative sensitive receivers have been selected
for monitoring to represent a particular area likely to be most affected by the
construction works of this Project, and where the monitoring of potential
cumulative noise impacts from concurrent projects would be most feasible.
4.10.4 No monitoring is required during operational phase.
Representative NSRs chosen for Noise Monitoring during Construction Stage
|
Noise Monitoring Station |
NSR ID |
Representative for |
Secondary Channels |
|
MUP-N1 |
MUP05-2 |
Village north of Loi Tung |
MUP05 and potential concurrent
activities at MUP01, MUP02 and MUP03 |
|
MUP-N2 |
MUP05-4 |
Village north of Loi Tung |
MUP05 and potential concurrent activities at MUP04B |
|
MUP-N3 |
MUP05-6 |
Village north of Loi Tung |
MUP05 and potential concurrent
activities at MUP03 and MUP04B |
|
MUP-N4 |
MUP04A-2 |
Village house near Loi Tung |
MUP04A |
|
LMH-N1* |
LMH01-1, LMH01-2, LMH01-3,
LMH01-4 or LMH01-5 |
|
LMH01 |
Notes:
* Mobile
station subject to the location of the construction works and to be proposed by
the ET Leader.
4.11.1
The operation phase will not involve any stationary noise
source. No pumping station or electrical and mechanical infrastructure will be
established. Maintenance would be necessary for the proposed gabion channels to
remove excessive silts, vegetation, debris and obstructions in order to
maintain its hydraulic performance and structural integrity. Siltation will
generally be allowed to accumulate and removal of excess silt would be carried
out at locations where it would impede water flow. Such small scale maintenance
would require only light mechanical equipment such as a small loader and/or a
small crane truck. Hand-held equipment will be used for vegetation removal.
Little or no maintenance will be necessary for the ‘two-stage’ channel at MUP05
and the natural stream sections of LMH01. Therefore the operational phase of
this Project would unlikely cause any adverse noise impact.
4.12.1 The use of powered mechanical equipment during the construction phase of this drainage project is expected to create noise nuisance, due to the close proximity between the works areas and noise sensitive receivers. Assessment indicates that such noise impacts can be mitigated to acceptable levels by appropriate measures, such as the use of quiet plant, temporary noise barriers, restricting concurrent usage of equipment and the implementation of good site practices. The Contractor will be required to implement these measures when powered mechanical equipment is used during the construction phase. With these measures in place, residual noise impact would not be expected from the construction works.
4.12.2 Potential cumulative noise impact can be mitigated by restricting the number of concurrent works in addition to the above mitigation measures.
4.12.3
Noise monitoring is recommended
at selected representative NSRs during the construction period to check for
compliance with permissible noise levels and effectiveness of the proposed
mitigation measures.
4.12.4
The operation phase of the
Project is not expected to pose any noise impact to the surrounding area.
4.12.5
Overall, the potential noise
impacts associated with the construction of drainage channels MUP03, MUP04A, MUP04B,
MUP05 and LMH01 are not insurmountable and does not form a constraint to the
Project.
[1] QPME
are construction plant and equipment that are notably quieter, more
environmentally friendly and efficient. EPD has developed a system for the
registration of QPME that are used in