4.1 This section presents an assessment of potential noise impact pertinent to the construction and operation phase of the Project. Appropriate mitigation measures have been recommended, where necessary, to alleviate the potential noise impacts to acceptable levels.
Environmental Legislation, Policies, Plans, Standards and Criteria
4.2
Noise
impacts were assessed in accordance with the criteria and methodology given in
the Technical Memoranda made under the Noise Control Ordinance (NCO), and
EIAO-TM.
4.3
The
NCO provides the statutory framework for noise control. This defines statutory
limits applicable to equipment used during the construction and operation
phases of the proposed works in the study area. The NCO invokes four Technical
Memoranda, which define the technical means for noise assessment:
•
Technical Memorandum on Noise from Places other than
Domestic Premises, Public Places or Construction Sites (IND-TM);
•
Technical Memorandum on Noise from Construction Work in
Designated Areas (DA-TM);
•
Technical Memorandum on Noise from Construction Work other
than Percussive Piling (GW-TM); and
•
Technical Memorandum on Noise from Percussive Piling
(PP-TM).
4.4
The
NCO and the accompanying Technical Memoranda provide a mechanism for assessing
noise levels and provide the statutory power to control noise.
4.5
The
NCO provides the statutory framework for noise control of construction work,
other than percussive piling, using powered mechanical equipment (PME) between
the hours of 1900 and 0700 hours or at any time on Sundays and general holiday
(that is, restricted hours). Noise
control on construction activities taking place at other times is subject to
the Criteria for Evaluating Noise Impact stated in Table
4.6
The
construction works would not be carried out during restricted hours, therefore,
the EIAO-TM standard was used as the assessment criteria in the construction
noise assessment.
4.7
Operational
noise emitted from the proposed Project is controlled under the IND-TM. With
regard to the assessment of the operational noise impacts, the NCO designates
acceptable noise levels for Noise Sensitive Receivers (NSRs) on the basis of an
Area Sensitivity Rating (ASR), based on the characteristics of the area within
which they are located such as rural, village, low-density residential, or
urban. Within these areas, the presence of "influencing factors"
(such as the presence of industrial activities or major roads) can further
affect the ASR and hence the acceptable noise level (see Table 4.1).
Table 4.1 Area Sensitivity Ratings (ASRs)
|
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 |
4.8
The
Acceptable Noise Level (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.
According to the TM, the ANLs for different Area Sensitivity Ratings
(ASRs) are given in Table 4.2.
4.9
The
Study Area for noise impact is defined by a distance of 300m from the boundary
of the Project site. The study area
is a rural area with low-density residential development. There is no industrial operation or
major roads are noted within the study area, therefore, the Area Sensitivity
Rating (ASR) of “A” is determined.
Table 4.2 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 |
4.10 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.
4.11 As stated in Section 4.9, the Area Sensitivity Rating (ASR) of “A” is determined for the study area, i.e. its planning criteria for NSRs would be 55 dB(A) for daytime operations and 45 dB(A) for night-time operations.
4.12
A
noise survey in the proximity of TM54SPS was undertaken on 13 November 2007 to
determine the background noise levels.
Four sets of noise data at each measurement period were collected, The measured minimum daytime
(measurement during 16:00 – 18:00), evening time (measurement during 21:00 –
23:00) and nighttime (measurement during 00:00 – 01:00) noise levels at Kei Lun
Wei were 51.5dB(A) (Leq (30 min)), 50.3 dB(A) (Leq (30 min))
and 51.7 dB(A) (Leq (5 min)) respectively. The recommended daytime, evening time
and nighttime noise criteria in the assessment are therefore 51.5dB(A), 50.3
dB(A) and 45 dB(A) respectively.
4.13
In
any event, the Area Sensitivity Rating assumed in this EIA Report is for indicative
assessment only. It should be noted that fixed noise sources are controlled
under section 13 of the NCO. At the time of investigation, the Noise Control
Authority shall determine noise impact from concerned fixed noise sources on
the basis of prevailing legislation and practices being in force, and taking
account of contemporary conditions/ situation of adjoining land uses. Nothing
in this EIA Report shall bind the Noise Control Authority in the Context of law
enforcement against all the fixed noise sources being assessed.
Description of the Environment
4.14
TM54SPS
will be constructed in the central part of Site
4.15
In order to evaluate the
construction and operational noise impacts likely to arise from the Project,
representative existing noise sensitive receivers (NSRs) and planned NSRs (in
accordance with the Tuen Mun OZP No. S/TM24) within
Table 4.3 Details of Noise Sensitive Receivers
|
NSR |
Description |
Uses |
Distance between
NSR and nearest Project Boundary (m) |
|
N1 |
|
Residential |
95 |
|
N2 |
Kei Lun Wei |
70 |
|
|
N3 |
Siu Hang Tsuen |
140 |
|
|
N4 |
Planned Secondary School |
Educational Institution |
10 |
|
N5 |
Planned Secondary School |
35 |
|
|
N6 |
Planned Primary School |
20 |
4.16 The construction work for TM54SPS would be completed in early 2014. The operation year of the planned schools (NSR N4 – N6) would be beyond 2016. Therefore, the construction noise impact assessment would be focused on the representative NSRs N1 – N3. For the operation phase impact assessment, the planned primary and secondary schools would not be operated during nighttime, the fixed plant noise impact on the planned schools during daytime and evening time would be assessed only.
Identification of Environmental Impacts
4.17 The potential source of noise impact during the construction phase of the Project would be the use of PME for various construction activities. As shown in Figure 2.3, the construction of the Project (including testing & commissioning) has been scheduled to commence in early 2011 and to be completed in early 2014. The Project would involve the following major construction activities.
·
Site Clearance
·
Bulk Excavation for Sub-Structure and Site Formation
·
Steel Fixing Concreting of Sub-Structure
·
Steel Fixing and Concreting of Roof and Columns
·
Brick Work and Finishing
·
M&E Installation and Pipeworks
·
Landscape Works and Roadworks
4.18 Referring to the construction programme, the following construction activities would be undertaken concurrently. Cumulative noise impacts on the representative NSRs were also assessed.
·
Brick Work & Finishing and M&E Installation &
Pipeworks
·
Brick Works & Finishing, M&E Installation &
Pipeworks, Landscape Works & Roadworks
4.19 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.
4.20
There
would have two other projects to be undertaken concurrently within 300m of the
study area. The concurrent
activities includes (i) site formation and infrastructural works for Site 2
under the project “Formation, Roads and Drains in Tuen Mun Area 54 – Phases 1
and 2, Private and Public Rental Housing Development in Tuen Mun Area 54” (be commenced in September 2010 and
completed in September 2013); and (ii) Village sewerage works under the project “Sewerage Upgrading Works in Tune Mun under Agreement No. CE 38/2006
(DS)” (be commenced in mid 2009 for completion in end 2015). The project proponent of the village
sewerage’s works agreed that the construction of the proposed village sewerage
works at Kei Lun Wai and Unicorn Garden within 300m of the study area would be
scheduled with the consideration of the construction of TM54SPS (i.e. no
overlap with the construction of TM54SPS) so as to minimize the cumulative
noise impact to the sensitive receivers. Therefore, only cumulative
construction noise impacts from site formation and infrastructural works for
Site 2 were assessed in the study.
4.21
The potential sources of noise
impact during the operation phase of TM54SPS would be the operation of pumps,
mechanically racked screens, transformer and ventilation fan of deodourization
unit. Four main pump sets (3
operations and 1 standby), two mechanically racked screens and one transformer
would be installed in TM54SPS. A
ventilation fan of the deodourization unit would also be installed.
4.22
The transformer would be
located in an enclosed reinforced concrete structure while the pump sets and
mechanically racked screens would be located in the underground level and
housed in a reinforced concrete structure with acoustic louvers . The structure material of TM54SPS would
be
4.23
In accordance with the EIAO-TM,
the methodology outlined in the GW-TM was used for the construction noise assessment.
The general approach is summarized below:
·
Locate the NSRs which would most likely be affected by noise
from the construction work
·
Determine the items of Powered Mechanical Equipment (PME) for
each discrete construction activity, based on available information or agreed
plant inventories
·
Assign sound power levels (SWLs) to the proposed PME
according to the GW-TM or other sources
·
Calculate distance attenuation and screening effects to NSRs
from notional noise source
·
Predict construction noise levels at NSRs in the absence of
any mitigation measures
·
Include a 3 dB(A) façade correction to the predicted noise
levels in order to account for the façade effect at each NSR.
4.24 Sound power levels (SWLs) of the equipment were taken from Table 3 of GW-TM. Groups of PME were assigned for various construction activities of the proposed Project. The proposed plant inventory for the construction of the Project is presented in Appendix 4.1a. The Project Proponent has confirmed the proposed plant inventory as being practical and adequate for completing the works within the scheduled timeframe.
4.25 For assessing cumulative construction noise impacts, the plant inventories in the approved EIA Report “Planning and Development Study of Potential Housing Site in Area 54, Tuen Mun (Agreement No. CE 21/97)” were used for calculation. The plant inventories of this project are presented in Appendix 4.1e.
4.26
For the assessment of noise
from equipment, the noise level at NSR was predicted using the standard
acoustic principles:
Predicted Noise Level = Sound Power
Level of Equipment - Distance Attenuation - Enclosure Reduction (if any) -
Screening Reduction (if any) + Facade Correction
where Distance Attenuation = 20 log D + 8 [where D is the distance in
meters]
Façade Correction =
3 dB(A)
4.27
The SWL of the pumps and motors
were taken with reference to the Central
and Wan Chai East Pumping Stations and Screening Plants – Operation and
Maintenance Manual Volume 1 (Contract No. DE/95/12) published by DSD. The SWL of the ventilation fan was in
accordance with Good Practices on
Ventilation System Noise Control published by EPD.
4.28 Noise impact was assessed on the basis of the following assumptions:
·
All items of operational plant required for operation of the
proposed facilities would be located at the actual source position.
·
A +3 dB(A) façade correction and a +6dB(A) for tonal
correction were added to the predicted noise levels to account for the facade
effect at each NSR.
·
Noise impacts at the nearest facades of the NSRs to the
source positions were assessed.
Prediction and Evaluation of Environmental Impacts
4.29 Noise impacts arising from different construction activities have been predicted and are shown in Appendix 4.1a – 4.1b.
4.30 The predicted noise levels at the three existing representative NSRs were in the range of 63 to 80 dB(A). The predicted noise levels at NSR N1 and N2 would exceed the daytime noise criteria of 75 dB(A) during the following construction activities. Noise mitigation measures are required to alleviate the adverse impact arising from the Project.
·
Bulk excavation for sub-structure and site formation
·
Landscape works & roadworks
·
Brick Works & Finishing + M&E Installation &
Pipeworks + Landscape Works & Roadworks
4.31
The plant inventory and the
corresponding SWL are summarised in Appendix
4.2. As confirmed by the
Project Proponent, the plant inventory used for prediction of operation noise
impact is practical and realistic. To represent the worst case scenario, all
items of equipment were assumed to operate concurrently 24 hours a day and the
directivity was not included in the calculation.
4.32
The
transformer would be housed in an enclosed
4.33
According to the plant
inventory for TM54SPS as shown in Appendix 4.2, the predicted noise
levels at the residential NSR N1 and N2 would be 36 dB(A) and 40 dB(A)
respectively. The predicted noise
levels at the educational institutes including NSR N4, N5 and N6 would be in
the range of 39 dB(A) and 44 dB(A).
The predicted noise levels at all representative NSRs would comply with
daytime and evening time noise criteria of 51.5 dB(A) and 50.3 dB(A) respectively. The predicted noise levels at the
existing residential NSRs would also comply with the night time criteria of 45
dB(A). Thus, mitigation measures
would not be required for TM54SPS. Details of the calculation are presented in Appendix 4.2.
4.34
Referring
to Figure 4.1, the distance of NSR
N3 to TM54SPS is much farther than that of NSRs N1 and N2. Since the predicted noise level is
distance dependent and the predicted noise levels of NSRs N1 and N2 did not
exceed the noise criteria even for their shorter distances than NSR N3. Hence, NSR N3 was not assessed as noise
exceedance at NSR N3 would not be expected.
Mitigation of Adverse Environmental Impacts
4.35
In
order to reduce construction noise impacts on the NSRs, silenced types of PME,
which are in accordance with BS 5228:
Part 1, 1997, are recommended. The total Sound Power Level (SWL) of PME for
each construction activity was calculated and is summarized in Appendix 4.1c.
4.36 With the use of quiet PME for these construction activities, a noise reduction of up to 13 dB(A) at the NSRs could be achieved. A detailed calculation of construction noise impact for the mitigated scenario is presented in Appendix 4.1c – 4.1d. The results indicate that the mitigated maximum noise levels predicted at NSR N1, N2 and N3 due to this Project would be ranged from 59 to 69 dB(A), complying with the daytime noise standard of 75 dB(A).
4.37 In addition to adoption of quiet PME, good site practices listed below should be adopted to further abate any residual impacts during the construction phase of the Project and should be included in the contract document:
·
Only well-maintained plant should be operated on-site and plant
should be serviced regularly during the construction program;
·
Silencers or mufflers on construction equipment should be
utilized and should be properly maintained during the construction program;
·
Mobile plant, if any, should be sited as far from NSRs as
possible;
·
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;
·
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
·
Material stockpiles and other structures should be
effectively utilised, wherever practicable, in screening noise from on-site
construction activities.
4.38 As mentioned in Section 4.20, the site formation and infrastructural works for Site 2 under the project “Formation, Roads and Drains in Tuen Mun Area 54 – Phase 1 and 2, Private and Public Rental Housing Development in Tuen Mun Area 54” would be undertaken concurrently within 300m of the study area. The detail calculation for cumulative construction noise impacts is presented in Appendix 4.1e. The predicted cumulative noise levels at NSR N1, N2 and N3 would be 70 dB(A), 70 dB(A) and 67 dB(A), which would comply with the EIAO TM construction noise criterion of 75 dB(A). Therefore, no further mitigation measures would be proposed for this Project.
4.39
As the predicted noise levels
at representative NSRs would comply with the daytime, evening time and
nighttime noise criteria, no mitigation measures are proposed.
Evaluation of Residual Impacts
4.40
No
adverse residual construction noise impact from the Project is expected with the
use of silenced PME and implementation of good site practices. The mitigated cumulative construction
noise impact at NSRs N1 and N2 would also complied with the construction noise
criteria.
4.41
No
adverse residual operation noise impact from TM54SPS is expected.
Environmental Monitoring and Audit
4.42
It
is recommended to establish an Environmental Monitoring and Audit (EM&A)
programme for control of construction noise. The recommended mitigation
measures should be incorporated into the EM&A programme for implementation
during the construction period. Details of the programme are provided in a
stand-alone EM&A Manual.
4.43 The EIA findings confirmed that proper designs of TM54SPS (i.e. the pump sets and mechanically racked screens to be located at underground and housed in 200mm reinforced concrete structure with soundproof door, the transformer to be housed in enclosed reinforced concrete structure with soundproof door, provision of acoustic silencer for louvers of pump house and exhaust fan of deodourizing unit, and specify the maximum allowable sound power levels of noisy equipment) would control the potential noise impact at noise sensitive receivers within acceptable levels, no operational noise monitoring would be conducted after commissioning of the TM54SPS.
4.44 The potential noise impact arising from construction of TM54SPS on the nearest representative NSRs was assessed. Results indicated that noise exceedance was predicted at the NSRs N1 and N2 during some construction activities of the Project. With the adoption of quiet PME during these construction activities, the predicted construction noise levels at representative NSRs would all comply with the relevant noise criteria. Good site practices were also proposed to further abate the impacts on the NSRs. Taking into account of concurrent construction activities undertaken by other projects within 300m of the study area, the predicted noise levels at NSRs N1, N2 and N3 would still comply with the construction noise criterion. The mitigated impact at NSRs N1, N2 and N3 are therefore considered acceptable.
4.45
The noise impacts associated
with the operation of the Project were assessed. In view of proper design of
TM54SPS as mentioned in S4.43, the operation noise levels at representative
NSRs would comply with the daytime, evening time and night time noise
criteria. No mitigation measures
were proposed.