4.1.1
This section
presents an assessment of the potential noise impacts associated with the
construction and operation of the proposed Project.
4.1.2
In view of the
project area of Siu Ho Wan WTW extension and Siu Ho Wan Raw Water Booster Pumping
Station, no noise sensitive receivers identified within 300m of the study area,
therefore, no assessment was carried out during construction phase and
operation phase of the study area at Siu Ho Wan. Regarding the study area at Pui O, uprating of Pui O No. 2 Raw
Water Pumping Station (RWPS) would involve the installation of the equipment
within the station, as only two trimmer pumps will be installed in the reserved
pumps
bays of Pui O No. 2 RWPS, no adverse construction noise impact would be
expected. The potential noise impact
arising from laying of raw
water mains at Pui O, demolition and construction of Pui O RWPS was
assessed. The potential operational
noise impacts from Pui O RWPS and Pui O No. 2 RWPS were also evaluated. Appropriate mitigation measures would be
recommended, where necessary, to mitigate the potential noise impacts to
acceptable levels.
4.2.1
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.
4.2.2
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).
4.2.3
The NCO and the
accompanying Technical Memoranda provide a mechanism for assessing noise levels
and the statutory power to control noise.
4.2.4
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 characterisation 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 therefore the
acceptable noise level (see Table 4.1).
Table 4.1 Area
Sensitivity Ratings
|
Type
of Area Containing NSR |
Degree
to which NSR is affected by Influencing Factor |
||
|
Not
Affected |
Indirectly
Affected |
Directly
Affected |
|
|
Rural
Area |
A |
B |
B |
|
Urban
Area |
B |
C |
C |
|
Low
density residential area consisting of low-rise or isolated high-rise
developments |
A |
B |
C |
|
Area
other than those above |
B |
B |
C |
Construction Activities
4.2.5
Under the GW-TM,
noise from construction activity is not restricted during the period 0700 -
1900 hours on weekdays, except public holidays. However, the EIAO-TM identifies
a daytime general construction noise limit of 75 dB(A) Leq (30
minutes) for domestic premises, 70 dB(A) Leq (30 minutes) for
educational institutes and places where unaided voice communication is required
and 65dB(A) Leq (30 minutes) is allowed for school during
examination period. This standard was used as assessment criteria in the
construction noise assessment.
4.2.6
Between 1900 and
0700 hours and all day on Sundays and public holidays, activities involving the
use of powered mechanical equipment (PME) for construction work are prohibited
unless a construction noise permit (CNP) has been obtained. The Noise Control Authority would consider a
well-justified CNP application, once filed, for construction works within
restricted hours as guided by the relevant technical memorandum issued under
the NCO. The Noise Control Authority
would take into account of contemporary conditions / situations of adjoining
land uses and any previous complaints against construction activities at the
site before making the decision to grant a CNP. Nothing in this EIA Report shall bind the Noise Control Authority
in making its decision. If a CNP is to
be issued, the Noise Control Authority shall include in the permit any
condition he thinks fit. Failure to
comply with any such conditions would lead to cancellation of the CNP and
prosecution action under the NCO. A CNP
could be granted provided that the Acceptable Noise Level (ANL) for the NSRs
could be complied with. ANLs are
assigned depending upon the ASR. The
corresponding basic noise levels (BNLs) for evening and nighttime periods,
together with a daytime standard, are given in Table 4.2.
Table 4.2 Construction
Noise Criteria for Activity other than Percussive Piling
|
Time
Period |
Basic
Noise Level (BNLs) (dB(A)) |
||
|
ASR
A |
ASR
B |
ASR
C |
|
|
Evening (1900
to 2300 hours) (1) |
60 |
65 |
70 |
|
Night (2300 to 0700
hours) |
45 |
50 |
55 |
Notes: (1) includes Sundays and Public Holidays during
daytime and evening
4.2.7
It is considered
that the construction programme is practical and engineering feasible without
works within the restricted hours. Only
the daytime (0700 to 1900) non-statutory criterion of 75 dB(A) for residential
dwellings, 70 dB(A) for education institutes and 65 dB(A) during examination
period would be applicable in the assessment.
Besides, statutory criteria in DA-TM are not applicable to this Project
as well. If percussive piling is
required for the Project in future, the Contractor shall obtain a valid CNP
before undertaking.
4.2.8
Operational
noise emitted from the Pui O RWPS and Pui O No. 2 RWPS is controlled under the
IND-TM.
4.2.9
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 4.3.
Table 4.3 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 |
4.2.10
The EIAO-TM states
that all fixed noise sources should be so located and designed that when
assessed in accordance with the IND-TM, the level of the intruding noise at the
facade of the nearest sensitive building 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 noise
level being 5 dB(A) lower than the ANL, the predicted noise level should
not exceed the background noise level.
4.2.11
The study area
containing NSRs were regarded as rural in nature, and all potential NSRs would
not be affected by “influencing factors”.
Therefore, the study area is defined as ASR “A”, i.e. its planning
criteria for NSRs would be 55 dB(A) for daytime operations and 45 dB(A) for
nighttime operations. In any event, the
ASR assumed in the EIA is for indicative assessment only. It should be noted that fixed noise sources
are controlled under section 13 of the NCO.
Nothing in this Report shall bind the Noise Control Authority in
assessing noise from these sources upon the receipt of complaints. The Authority shall assess the noise impacts
based on the contemporary conditions / situations.
4.2.12
The operation
noise impacts arising from the new proposed equipment were evaluated against
the relevant noise criteria. As the Pui O RWPS will be demolished and
re-constructed, the reprovisioned Pui O RWPS is considered as a new proposed station raw water pumping station.
4.2.13
On the other hand,
uprating of Pui O No. 2 RWPS would involve the installation of the equipment
within the station. There
are four main pumps installed at the existing Pui O No. 2 RWPS and Ttwo trimmer pumps
would be installed in the reserved pumps bays of Pui
O No. 2 RWPS as standby pumps. The
capacity of two new standby trimmer pumps would be equal to one main pump and
the sound power level of the two trimmer pumps would not be higher than that of
the existing main pump, therefore, there will be no
increase in operation noise generated from the existing Pui O No. 2 RWPS. And, the number of the
equipment to be used during the operation of the Pui O No. 2 RWPS would remain
unchanged. Therefore, tThe noise impact arising from the four main pumps at the existing
raw water pumping
station, Pui O No. 2 Raw Water Ppumping
Station, which would be the worst-case scenario, would
only be assessed for the cumulative noise impact assessment.
4.2.14
A noise survey was
undertaken at Pui O study area in February 2004 to determine the background
noise levels. The measured noise levels are summarised in Table 4.4.
Results indicated that the measured daytime and evening time noise level was in
the range of 50 – 67 dB(A); and the measured night time noise level was in the
range of 49 – 61 dB(A) at the selected stations as shown in Figure 4.1.
Table
4.4 Noise Criteria for Operation
Noise Impact due to New Proposed Equipment
|
Location
ID |
Description |
Measured Noise Level(1) |
|
Recommended Noise Criteria |
|
LWT2 |
Village house
along South Lantau Road |
Daytime: 55-67 Night-time: 56-61 |
55 45 |
55 45 |
|
LWT3 |
Village
house next to Pui O Raw Water Pumping Station |
Daytime: 50-5 Night-time: 49-50 |
55 45 |
50 45 |
|
ALWT2 |
Village
house along South Lantau Road |
Daytime: 53-64 Night-time: 51-60 |
55 45 |
53 45 |
|
ALWT1 |
Village
house along South Lantau Road |
- |
55 45 |
53 45 |
Note: (1) Measured Noise Levels in Leq (30-mins) dB(A) according to the measurements conducted on 1 & 2 February 2004.
4.2.15
According to the
noise survey result, the assessment criteria for NSR LWT2 are recommended to
adopt the daytime & evening time ANL-5dB(A) criterion planning criteria,
which are lower values. The background
noise levels for daytime & evening time at NSRs LWT3 and ALWT2 is lower
than the planningANL-5dB(A) criteriaon. Thus, the background noise levels measured
of 50 dB(A) and 53 532 dB(A)
are adopted for NSRs LWT3 and ALWT2 as daytime & evening time assessment
criterion. On the other hand, as the
background noise level measured at night-time is higher than the planningANL-5dB(A) criteriaon, planning
criteria of 45 dB(A) would be adopted as night-time criterion for all representative
NSRs. As NSR ALWT13
is located in the vicinity of the ALWT2 and would have noise environment similar to that
of ALWT2, same noise criteria would be used for the fixed noise
assessment. The recommended assessment
criteria for the NSRs are summarised in Table 4.4.
4.3.1
The existing Pui O
RWPS and Pui O No. 2 RWPS are located along South Lantau Road at Pui O Lo Wai
Tsuen. The proposed raw water mains alignment would be
across Lo Uk Tsuen, San Wai Tsuen, Lo Wai Tsuen. The site is a rural area with agricultural land and low-density
population residential area. Most residential
buildings are 2 or 3-storeys
village houses. Based on on-site
observation, traffic noise from South Lantau Road is dominant noise source to
the NSRs in the study area.
4.3.2
Baseline noise
surveys were carried out at three selected locations (as shown in Figure 4.1)
within the study area on 1 and 2 February 2004. The selected locations are located near the raw water pumping
stations, which are representative to reflect the background noise levels. All the noise measurements were conducted in
accordance with IND-TM. The measured
noise levels in terms of Leq (30-minutes) are shown in Table
4.4. Detailed methodology and results
were presented in Appendix 4.1. The
measured noise levels at the selected locations range from 49 to 67 dB(A). The
major noise source was from dog barking, traffic noise from South Lantau Road
and operation of existing raw water pumping stations. The results indicated that the noise environment for the Project
site was representative of quiet rural areas due to its remote locations and
lack of large scale industrial and transport infrastructure developments. Therefore, the site was sensitive to any
increase in noise levels.
4.4.1
As no noise
sensitive receiver (NSR) was located within 300m of the study area of the
Project at Siu Ho Wan, no assessment would be taken at Siu Ho Wan study
area. Referring to the Siu Ho Wan
Layout Plan – Lantau Island (Plan No.L/I-SHW/1), no planned NSRs would be
developed within 300m from the Project boundary in future.
4.4.2
NSRs in the
vicinity of the Pui O raw water pumping stations at Pui O were likely to
be adversely affected during construction and operation phases. Most existing
NSRs within 300m of the study area were low-rise (2 to 3-storey high)
residential development. Among all the affected NSRs within the study area, Pui
O Lo Wai Tsuen is the nearest, located at about 50m from the Pui O raw
water pumping stations at
Pui O. Other affected NSRs include Lo UK Tsuen, Pui O San Wai Tsuen, Pui
O Au Lo Wai Tsuen and Bui O Public School.
4.4.3
NSRs were
identified for this assessment, in accordance with the criteria stipulated in
the EIAO-TM. Domestic premises, hotel, hostel, temporary housing accommodation,
hospital, medical clinic, educational institution, place of public worship,
library, court of law or performing arts centre shall be considered to be a
NSR. The worst affected NSRs for this noise assessment are listed in Table 4.5
and its locations are shown in Figure 4.1. Distance between the NSRs, the
Proposed Raw Water Mains and/or the Pui O Raw Water Pumping Station are also
summarised in Table 4.5.
4.4.4
According to the Outline Zoning
Plan (Plan No. S/SLC/132 and L/I-SHW/1)
issued in 2002
South Lantau Coast Outline Zoning Plan No.S/SLC/13 gazetted on 26 Marchissued
in 2004, the area in
the close vicinity of the proposed facilities has been zoned for Green Belt
(“GB”), Other Specified Use (“OU”), Coastal Protection Area (“CPA”), Country
Park (“CP”) and Government (“G”). Thus, no planned noise sensitive uses receivers are identified
within the study area.
Table 4.5 Representative Noise Sensitive
Receivers
|
NSR |
mPD above ground
|
Description (Uses) (Floors of Building) |
Horizontal
Distance from the Nearest Boundary |
||
|
|
|
Proposed
Raw Water Mains |
Pui
O |
Pui O No. 2 RWPS |
|
|
LUT |
|
Lo Uk Tsuen (Residential) (3 Floors) |
15 |
- |
- |
|
BOS |
+6.5 mPD |
Bui O Public School (Educational Institution) (2 Floors) |
25 |
- |
- |
|
LWT1 |
+7 mPD |
Pui O Lo Wai Tsuen facing South Lantau Road (Residential) (3 Floors) |
13 |
- |
- |
|
LWT2 |
+8 mPD |
Pui O Lo Wai Tsuen facing South Lantau Road (Residential) (3 Floors) |
29 |
91 |
88 |
|
LWT3 |
+14 |
Pui O Lo Wai Tsuen facing the Pumping Station (Residential) (3 Floors) |
121 |
42 |
105 |
|
ALWT1 |
+32 mPD |
Pui O Au Lo Wai Tsuen facing the Pumping Station (Residential) (3 Floors) |
65 |
89 |
96 |
|
ALWT2 |
+26 mPD |
Pui O Au Lo Wai Tsuen facing South Lantau Road (Residential) (3 Floors) |
34 |
128 |
109 |
Construction
Phase
4.5.1
The assessment
followed the procedures given in the GW-TM.
For the assessment of noise from PME, the distance attenuation was
estimated using the standard formula:
Distance Attenuation in dB(A) = 20 log D
+ 8 [where D is the distance in metres]
4.5.2
Sound Power Levels
of the equipment were taken from Table 3 of the GW-TM. Where no SWL is supplied in the TM,
reference was made to BS 5228, previous similar studies or information from the
contractors. Equipment likely to be
employed for laying of raw water mains at Pui O, demolition of existing Pui O
Raw Water Pumping Station and reconstruction of the station are presented in
Appendix 4.2. For each construction
activity, PME was grouped according to likely concurrent usage. It was considered that the plant inventory
and on-time operation of the plant for the assessment was practical for the
proposed works as
confirmed by the Project Proponent.
4.5.3
Noise impact was
assessed on the basis of the following assumptions:
·
All PME items required for a particular construction
activity would be located at the notional source position, which was at a
position mid-way between the appropriate geographical centre of the
construction site and its boundary nearest to the NSR at ground floor.
·
A +3 dB(A) façade correction was added to the predicted
noise levels to account for the façade effect at each NSR.
·
Noise impacts at the nearest sensitive façades of the
residential buildings to the source positions were assessed.
4.5.4
Given the openness
of the immediate locality of the construction site and the NSRs under consideration,
correction for opposite façade reflection would not apply to the assessment. The representative NSRs are all 2 – 3
storeys high
buildings, the
assessment
points at ground floor, which are the shortest distance between the
NSRs and the noise sources, were selected for assessment.
4.5.5
Within 300 m from
the Pproject
boundary, there were no construction activities of other projects undertaken
concurrently with this Project during construction period. Therefore, no cumulative construction noise
impact from other projects was anticipated.
Operation
Phase
4.5.6
The assessment
followed the procedures given in the IND-TM.
For the assessment of noise from raw water pumping stations at Pui O,
the distance attenuation was estimated using the standard formula as mentioned
in Section 4.5.1. The representative NSRs at ground floor,
which are the shortest distance from the noise sources, were selected for
assessment.
4.5.7
For this
assessment, the sound power levels (SWLs) of the plant at the pumping stations
would make reference to the noise data for the equipment being used in the
concerned pumping stations or other pumping stations or published data for
proposed equipment provided by WSD. The
plant inventories of the Pui O RWPS and Pui O No. 2 RWPS are presented in Appendix 4.3.
4.5.8
Noise impact was
assessed on the basis of the following assumptions:
·
All items of operational plant required
for operation of the pumping stations would be located at the actual source
position.
·
A +3 dB(A) façade correction was added to the predicted
noise levels to account for the façade effect at each NSR.
·
Noise impacts at the nearest sensitive façades of the
residential buildings to the source positions were assessed.
Construction
Phase
4.6.1
Major potential
construction noise impacts arising from the Project would be:
·
Construction of
the extension parts of the existing Siu Ho Wan WTW within its existing site;
·
Construction of
the proposed Siu Ho Wan Raw Water Booster Pumping Station and the laying of the
associated water mains;
·
Demolition and
reprovisioning of the Pui O Raw Water Pumping
Station; and
·
Laying of two
sections, approximately 2km long, of 1200mm diameter raw water mains at Pui O.
4.6.2
No construction
noise impact would be expected in the area of the Project at Siu Ho Wan as no
NSR is identified in that area.
4.6.3
No cumulative
construction noise impact would be expected within the study area at Pui O as
there were no construction activities of other projects undertaken concurrently
within 300m from the Project boundary.
Operation
Phase
4.6.4
No operation noise
impact would be expected in Siu Ho Wan WTW extension and Siu Ho Wan Raw Water
Booster Pumping Station as no NSR was identified in that area.
4.6.5
Operation noise
would be generated during the operation of the Pui O RWPS and Pui O No. 2 RWPS.
The major fixed noise source would be the raw water pumps, transformers, the
blowers and ventilation fans. There is
no generator would be installed for the reprovisioned Pui O Raw Water Pumping
Station. A standby generator is
installed at Pui O No. 2 Raw Water Pumping Station but it would only be used
when there is no electricity supply.
Since the raw water pumps will be installed in the basement
(underground) of the pumping stations, and the transformers and blowers would
be enclosed by the pumping station building, no insurmountable operational
noise impact is expected at the identified NSRs. The layouts of Pui O raw water pumping stations are shown in
Figure A4.1 of Appendix 4.3.
4.6.6
It is expected
that no other fixed noise source would be identified within the study area
except the operation of the Pui O raw water pumping stations at Pui O.
4.7.1
All works would be
carried out in the non-restricted hours.
No works was anticipated to occur at night and on Sundays and public
holidays. According to the tentative
construction programme, each construction activity for laying raw water mains
at Pui O would not be carried out concurrently within 300m as confirmed with the
Project Proponent. Construction
tasks for Pui O Raw Water Pumping Station would also be undertaken
separately. However, cumulative
construction noise impacts arising from the activities initiated by laying raw
water mains and construction of pumping station would be considered in the
assessment as a worst-case scenario.
Predicted construction noise levels at the representative NSRs were
calculated and are presented in Tables 4.6. A positive facade correction of 3 dB(A) was added to predicted
noise levels. Detail calculation is
presented in Appendix 4.2.
Table 4.6 Predicted Construction Noise Levels–
Unmitigated Scenario
|
NSR |
Predicted
Noise Levels, dB(A) |
||
|
Laying
of Raw Water Mains at Pui O |
Demolition/Reprovision
of Pui O R |
Cumulative
Noise Impact |
|
|
LUT |
80 – 89 |
- |
- |
|
BOS |
75 – 84 |
- |
- |
|
LWT1 |
81 – 90 |
- |
- |
|
LWT2 |
73 – 81 |
80 / 69 – 80 |
80 – 83 / 74 – 83 |
|
LWT3 |
51 – 59 |
85 / 75 – 85 |
85 / 75 – 85 |
|
ALWT1 |
67 – 75 |
80 / 69 – 80 |
80 – 81 / 71 – 81 |
|
ALWT2 |
73 – 81 |
77 / 66 – 77 |
78 – 83 / 74 – 83 |
Note:
1. The
noise criterion is 75 dB(A) for all representative residential NSRs and 70
dB(A) for educational NSR BOS (65 dB(A) during examination periods)
4.7.2
As indicated in
Table 4.6, the unmitigated noise levels at the representative residential NSRs would not
comply with the daytime noise criterion of 75 dB(A) for domestic dwellings and 70 dB(A)
for educational institutes.
Mitigation measures would be required to alleviate the impacts.
4.7.3
The results also indicated that
the unmitigated noise levels at educational NSR BOS would not comply with the
noise criteria of 70 dB(A) during normal teaching periods and 65 dB(A)
during examination period. As more stringent criteria need to be complied at the educational NSR, the following arrangements would
be adopted to minimize
the construction
noise impact at this educational NSR BOS (Appendix 4.2 refers) during examination period:
·
Excavation of Trench / Breaking up Pavement –mini-robot mounted breaker would not be operated during
examination period;
·
Reinstating Road Surface during raw water mains Cconstruction - 50 % On-time percentage would be used for
lorry; and
·
Installation of Pipes and Bedding – One mobile
crane would be used only.
4.7.4
As confirmed with the Project Proponent, the above arrangements
are practicable and feasible in the context of construction programme and
method.
4.7.5
With the adoption of the above arrangement, the
noise levels at NSR BOS would still exceed the noise criteria. Mitigation measures would
therefore be required to abate the construction noise impacts.
4.7.6
Assessment was
carried out based on the SWLs of new and replacement plant in Pui O RWPS likely
to be installed under the works of the Project. 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.
4.7.7
The
structure material of the existing Pui O No. 2 RWPS is 150 mm reinforced
concrete. As the acoustic louvers are provided at
the Raw Water Pump Hall of Pui O No. 2 RWPS are provided with
acoustic panels and the representative NSRs have no direct line of
sight to the pump sets which are all located at the basement of the structure,
noise attenuation of 20 dB(A) would be expected for the noise emitted from the
pump sets. The blowers
would be fully enclosed within the blower room which is no any openings (the door should be closed during operation of
the blower)
and its building materials are 150mm reinforced concrete and 225mm brick walls,
at least 30 dB(A) of noise attenuation was assumed in the assessment.
4.7.8
The ventilation
fans and roof extractor installed at Pui O No. 2 RWPS are all considered in the
assessment. The ventilation fans
installed at the north side of the raw water pumping station have been provided
with acoustic panellouvers and. 20 dB(A) of noise attenuation was assumed for
the NSRs which have no direct line of sight to these ventilation fans. If the
NSRs can view these ventilation fans, 10 dB(A) of noise reduction was assumed in
the calculation. The transformers at
the pumping station are fully enclosed and insertion loss of 10 dB(A) was
considered in the assessment.
4.7.9
The reprovisioned
Pui O RWPS would apply the existing structure material, i.e. 150 mm reinforced
concrete. As the four main pump sets
would be located at the basement and the representative NSRs have no direct
line of sight to the sources (pumps), 10 dB(A) of noise attenuation would be
expected at the representative NSRs.
The building materials for blower room at reprovisioned Pui O RWPS would
be 150mm reinforced concrete and 225mm brick walls. As the blower would also be enclosed within the blower room
without any openings (the door should be closed during operation of the
blower), sound reduction of 30 dB(A) would be expected. Ventilation fans would also be installed at
the pumping station. 10 dB(A) of noise
attenuation would be expected at the NSRs if they have no direct line of sight
to these ventilation fans.
4.7.10
Due to the facade
effect, a positive 3 dB(A) has been added to predict noise levels at the
NSRs.
4.7.11
For determining
the distance correction factors, the distances between the probable source
positions and the NSRs were considered.
Appendix 4.3 presents the results of the operational noise impacts
from the Pui
O raw water pumping stations at Pui O.
The predicted noise levels at the representative NSRs were presented in Table
4.7.
4.7.12
According to Table
4.7, the predicted cumulative noise levels at the representative NSRs would
be in the range of 46 to 51 dB(A), which would not comply with their relevant
recommended noise criteria stated in Table 4.4. Thus, mitigation
measures would be required for the new equipment at reprovisioned Pui O Raw Water Pumping
Station.
Table 4.7 Predicted Unmitigated Operational
Noise Levels from Pui O Raw
Water Pumping Station & Pui O No. 2 Raw Water Pumping Station
|
|
Predicted
Noise Levels, dB(A) |
||
|
NSR |
Pui
O RWPS (New
Proposed Equipment) |
Pui
O No. 2 RWPS (Existing
Equipment) |
Cumulative |
|
LWT2 |
46.3 |
43.5 |
48.2 |
|
LWT3 |
50.7 |
42.3 |
51.3 |
|
ALWT1 |
47.4 |
|
48.7 |
|
ALWT2 |
44.5 |
|
46.4 |
4.8.1
To reduce
construction noise impacts on the affected NSRs during construction, silenced
PME, which were in accordance with BS 5228: Part 1, 1997, were
recommended. It was consideredThe Project Proponent
confirmed that these quiet construction equipment were commercially
available in the market and have been used in other similar projects before.
4.8.2
With the adoption
of quiet plants, the predicted noise levels of the residential representative
NSR LUT and LWT1, and educational NSR BOS would still not comply with the noise
criteria. Results indicated that the
residential dwellings located less than 25 m away from the site for laying raw
water mains would be affected even with adoption of quiet plant. Further mitigation measures should be
considered.
4.8.3
To further
alleviate the construction noise impacts at the NSR BOS and the residential
dwellings located less than 25m away from the work site for raw water mains
construction, movable noise barriers, which were free from gaps or openings,
would be provided for particular plants. As the
residential dwellings are 2 –3 storeys village houses, according to GW-TM,
movable noise barrier located as close to the noise generating part of the PME
would reduce noise by 5 - 10 dB(A). The
material for the movable noise barriers should be at least 7 kgm-2. The noise screening benefit for each plant
considered in this assessment is listed as follows:
·
Stationary plant – assuming 10 dB(A) reduction: air
compressor, concrete mixer, vibrator poker, compactor and generator during raw
water mains construction at Pui O;.
·
Mobile plant – assuming 5 dB(A) reduction: mini excavator,
wheeled excavator fitted with hydraulic rock breaker and mobile crane during
raw water mains construction at Pui O.
4.8.4
With the use of
movable noise barriers and silenced PME, the predicted construction noise
levels at all representative NSRs for different construction tasks would then
comply with the daytime noise criteria.
·It is
considered that in theExcavation of Trench / Breaking up Pavement –
wheeled excavator/loader fitted with hydraulic breaker would not be operated
during examination period;
·Reinstating
Road Surface during raw water mains Construction - Reduction of 50% operated On-time percentage of lorry;
·Installation of
Pipes and Bedding – Reduction of number of operated mobile crane (i.e use one
mobile crane only).
4.8.5
The mitigated
construction noise levels are shown in Table 4.8. Detail calculation is
presented in Appendix 4.2.
Table 4.8 Predicted Construction Noise Levels –
Mitigated Scenario
|
NSR |
Predicted
Noise Levels, dB(A) |
||
|
Laying
of Raw Water Mains at Pui O |
Demolition/Reprovision
of Pui O R |
Cumulative
Noise Impact |
|
|
LUT |
70 – 74 (2) |
- |
- |
|
BOS (1) |
65 – 70 (2)(normal) 64 – 65(4) (examination) |
- |
- |
|
LWT1 |
71 – 75 (2) |
- |
- |
|
LWT2 |
67 – 73 (3) |
69 / 57 – 68 (3) |
71 – 74 / 67 – 74 (3) |
|
LWT3 |
45 – 51 (3) |
75 / 62 – 74 (3) |
75 / 63 – 74 (3) |
|
ALWT1 |
61 – 67 (3) |
70 / 57 – 68 (3) |
70 – 71 / 63 – 71 (3) |
|
ALWT2 |
67 – 73 (3) |
67 / 54 – 65 (3) |
70 – 74 / 68 – 74 (3) |
Note:
1.
The noise
criterion is 75 dB(A) for all representative residential NSRs and 70 dB(A) for
educational NSR BOS (65 dB(A) during examination periods).
2.
Adoption of quiet
PME and movable noise barrier
3.
Adoption of quiet
PME
Adoption of quiet PME,
movable noise barriers and further mitigation measuresarrangementsassumptions as
described in Section 4.78.3 4 for
BOS during
examination periodduring examination period
4.8.6
In addition to the
use of movable noise barriers, silenced PME and scheduling of operation of some
PMEs, 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 programme.
·
Silencers or mufflers on construction equipment should be utilised and
should be properly maintained during the construction programme.
·
Mobile plant, if any, should be sited as far away 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.
·
Material stockpiles and other structures should be effectively utilised,
wherever practicable, in screening noise from on-site construction activities.
4.8.7
Since the
predicted operation noise levels at all closest representative NSRs would not
comply with the night time criteria, mitigation measures would be
required. It was recommended to install
silencers acoustic louvers for
the ventilation fans at Pui O RWPS, which would provide a minimum
insertion loss of 2010dB(A). Higher noise reduction (up to 20 dB(A))
would be expected at the NSRs who have no direct line of sight to these
ventilation fans. In
addition, it was recommended to install acoustic louvres at the ventilation
openings of the pump hall at reprovisioned Pui O RWPS. As the main pump sets would be located at
the basement, a minimum noise attenuation of 20 dB(A) would be expected.
4.8.8
With the
implementation of the proposed mitigation measures, the predicted noise levels
at representative NSRs would comply with daytime and night-time criteria. The mitigated results are summarised in
Table 4.9 and detail assessment results are presented in Appendix 4.3.
Table 4.9 Predicted
Mitigated Operational Noise Levels from Pui O Raw Water
Pumping Station & Pui O No. 2 Raw Water Pumping Station
|
|
Predicted
Noise Levels, dB(A) |
||
|
NSR |
Pui
O RWPS (New
Proposed Equipment) |
Pui
O No.2 RWPS (Existing
Equipment) |
Cumulative |
|
LWT2 |
37.0 |
43.5 |
44.4 |
|
LWT3 |
41.8 |
42.3 |
45.1 |
|
ALWT1 |
|
|
|
|
ALWT2 |
|
|
|
4.9.1
No adverse
construction noise impact from the Project would be expected with the
implementation of proposed mitigation measures and good site practices.
4.9.2
With provision of
appropriate noise control measures for reprovisioned Pui O RWPS, such as
acoustic louvres at ventilation openings of pump hall and silencers at ventilation
fans, the fixed noise sources from the operation of the Pui O Raw Water Pumping
Station and Pui O No. 2 RWPS would not pose
any unacceptable residual noise impact on nearby NSRs.
4.10.1
An Environmental
Monitoring and Audit (EM&A) programme was recommended to be established
according to the predicted occurrence of noisy activities. The recommended mitigation measures should
be incorporated into the EM&A programme for implementation during
construction. No operational
noise monitoring was recommended.
Details of the programme are provided in a stand-alone EM&A Manual.