4
Noise Impact
4.1
Introduction
4.1.1
This section
presents an assessment of the potential noise impact associated with the
construction and operation of Peng Chau Sewage Upgrade. Noise impacts during the
construction phase are mainly associated with the use of powered mechanical
equipment for the construction works. Noise impacts identified during the
operational phase are primarily from plant noise of the upgraded facilities.
The assessments are carried out based on standard acoustic principles.
4.2
Relevant
Legislation, Policies, Plans, Standards and Criteria
Construction Noise
General
4.2.1
The principal legislation to provide
statutory controls on environmental noise is the Noise Control Ordinance (Cap.
400) (NCO). Various Technical
Memoranda (TMs), which stipulate control approaches and criteria, have been
issued under the NCO. The
following TMs are applicable to the control of noise from construction
activities:
(a)
Technical Memorandum on Noise from
Percussive Piling (PP-TM);
(b)
Technical Memorandum on Noise from
Construction Work other than Percussive Piling (GW-TM)
4.2.2
The EIAO and the
TM-EIAP also provide guidelines for the assessment of noise impacts associated
with construction activities.
4.2.3
Regardless of any noise
impact description or assessment made in this EIA report, the Noise Control
Authority will be guided by the relevant TMs issued under the NCO in assessing
any application, once filed, for a Construction Noise Permit (CNP) for works
planned during restricted hours (i.e. 1900 to 0700 hours and any time on a
general holiday including Sundays). The Authority will consider all the factors
affecting its decision taking the then prevailing situations and conditions
into account. Nothing in this EIA Report shall bind the Authority in making its
decision and further, there is no guarantee that a CNP will be issued. If a
permit is to be issued, the Authority may include any conditions it considers
appropriate and such conditions must be followed during the execution of the
works covered by the permit. Failing to do so may lead to cancellation of the
permit and prosecution action under the NCO.
Percussive
Piling
4.2.4
Under the PP-TM,
percussive piling is prohibited at any time on Sundays and public holidays and
during evening and night-time hours (1900-0700 hours), Monday through Saturday.
A CNP is required in order to carry out such work during daytime hours
(0700-1900 hours), Monday through Saturday. As the issuance of a CNP by the
Noise Control Authority would depend on the submission of an application by the
Contractor, and therefore on the Contractor’s compliance with the percussive
piling noise limits set out within the PP-TM, the assessment of this type of
noise has not been included in this EIA. However, for completeness, the process
that would be followed in assessing a CNP application for percussive piling is
described below.
4.2.5
In evaluating a
CNP application for percussive piling, the Noise Control Authority would be
guided by the PP-TM. In assessing the potential noise impact, the EPD would
consider the difference between the Acceptable Noise Levels (ANLs), as
specified in the PP-TM and the Corrected Noise Levels (CNLs) predicted to
result from the proposed percussive piling activities. Depending on the projected
noise impacts at nearby Noise Sensitive Receivers (NSRs), the Noise Control
Authority would determine the allowable time periods for percussive piling
operations, as indicated in Table 4-1.
Table 4-1 Permitted
Hours of Operation for Percussive Piling (Note: the Use of Diesel, Pneumatic
and /or Steam Hammers is prohibited)
|
Amount by which CNL exceeds ANL
|
Permitted hours of Operation on
any day not being a holiday
|
|
|
0800 to 0900 and 1230
to 1330 and 1700 to 1800
|
|
Between 0 dB(A)
and 10 dB(A)
|
0800 to 0930 and
1200 to 1400 and 1630 to 1800
|
|
No exceedance
|
0700 to 1900
|
General
Construction Works During Restricted Hours
4.2.6
The NCO provides statutory
controls on general construction works during restricted hours (i.e. 1900 –
0700 hours Monday to Saturday and at any time on Sundays and public holidays).
The use of powered mechanical equipment (PME) for carrying out the construction
works during these restricted hours would require a CNP. The Noise Control
Authority will assess all CNP applications on a case by case basis and, in
doing so, it will be guided by the GW-TM.
4.2.7
When assessing an
application for the use of PME, the Noise Control Authority will compare the
ANLs specified in the GW-TM with the CNLs (adjusted for any barrier and
reflection effects) associated with the proposed PME operations. The NCO
requires that noise levels from construction at affected NSRs be less than a
specified ANL. The ANLs are related to the inherent noise sensitivity of the
noise receiver areas in question, which in turn relate to the background noise
characteristics of these areas. Each noise receiver area is then assigned an
Area Sensitivity Rating based on its predominant land use and the presence, if
any, of Influencing Factors such as nearby industrial areas, major roads or
airports. The relevant ANLs for evenings and holidays and for night-time are
provided in Table 4-2.
Table 4-2 Acceptable Noise Levels (ANLs, Leq, 5 min dB) for
General Construction Works to be Carried out During Restricted Hours
|
Time period
|
Area
Sensitivity Rating
|
|
A
|
B
|
C
|
|
All days during
the evening (1900-2300 hours) and general holidays (including Sundays) during
the day and evening (0700-2300 hours)
|
60
|
65
|
70
|
|
All days during
the night-time (2300 –
0700 hours)
|
45
|
50
|
55
|
4.2.8
Factors
influencing the outcome of a CNP application, such as the assigning of ANLs,
would be determined by the Noise Control Authority at the time of the
application review based on the then prevailing site conditions. It should be
noted that conditions around the site may change from time to time.
General
Construction Works during Normal Working Hours
4.2.9
Although the NCO
does not provide for the control of noise from construction activities during
normal working hours (0700 to 1900 hours, Monday to Saturday), Annex 5 of the
EIAO-TM specifies a limit of Leq (30 min) 75 dB(A) for residential
NSRs. Annex 5 also provides construction noise limits for schools of Leq
(30 min) 70dB(A) and 65 dB(A) during normal teaching periods and examination
periods respectively, as shown in Table
4-3.
Table 4-3 TMEIAP Construction Noise Standard
|
Use
|
Noise Standard (Leq
(30 min) dB(A))
|
|
Normal Working Hours
|
Restricted Hours
|
|
Domestic premises, including temporary housing
|
75
|
The NCO provides the statutory controls, a Construction
Noise Permit is required.
|
|
Hotel and hostels
|
75
|
|
Educational institutions including kindergartens,
nurseries and all other where unaided voice communication is required
|
normal periods
|
70
|
|
examination
periods
|
65
|
Restricted hours:
1900 to 0700 Monday to Saturday and any time on Sundays and public holidays
Operational Noise
4.2.10
Operational noise is
controlled under the NCO’s Technical Memorandum for the Assessment of Noise
from Places other than Domestic Premises, Public Places or Construction Sites.
Table 2 of the TM specifies the ANLs.
4.2.11
To plan for a better environment, the
TM-EIAP specifies the following requirements:
q
5dB(A) below the appropriate ANLs
shown in Table 2 of the Technical Memorandum for the Assessment of Noise from
Places other than Domestic Premises, Public Places or Construction Sites
(NCO-TM) ; or
q
the prevailing
background noise levels. (For quiet areas with 5dB(A) below the ANL).
4.2.12
Table 4-4 shows the two criteria stipulated in NCO-TM and TMEIAP.
Details of information on background noise measurements are provided in Section
4.3.
Table 4-4 Acceptable
Noise Levels from Fixed Points (ANL, Leq, 30min dB(A))
|
Time
Period
|
Criteria in NCO-TM
|
Criteria in TMEIAP
|
|
ASR A
|
ASR B
|
ASR C
|
ASR A
|
ASR B
|
ASR C
|
|
Day (0700 to 1900
hours)
|
60
|
65
|
70
|
55
|
60
|
65
|
|
Evening (1900 to
2300 hours)
|
60
|
65
|
70
|
55
|
60
|
65
|
|
Night (2300 to
0700 hours)
|
50
|
55
|
60
|
45
|
50
|
55
|
Note: According to the TM-EIAP, the level of the intruding
noise should be lower than the above TMEIAP criteria values and the background
level, whichever is lower.
4.3
baseline ENVIRONMENTAL
conditions
4.3.1
Peng Chau is a
sparsely populated island (largely village-type development). The Peng Chau STW
is located on Tai Lei Island and is connected to Peng Chau Island by Tai Lei
Bridge. The assessment area is 300m from both the construction and operational
phases of Peng Chau STW Upgrade. Most of the residential development and
village houses are located in the central part of the island. Some relatively
new low-rise apartment buildings are located on the northwestern tip of the
island near Tai Lei Island, where the STW is located. Peng Chau has no
conventional road system and is free from traffic noise source.
4.3.2
The noise climate
of Peng Chau Island, however, has been affected by the ongoing construction of
International Theme Park in Penny’s Bay of North Lantau together with its
essential associated infrastructure. Several noise monitoring programmes were
conducted in the vicinity of or at Sea Crest Villa of Peng Chau due to the
development at Penny’s Bay. Noise monitoring information from various stages of
Penny’s Bay development is depicted as follows:
4.3.3
A noise monitoring
survey was carried out from mid November to early December 1999 as part of the
EIA study for the Construction of an International Theme Park in Penny's Bay of
North Lantau together with Its Essential Associated Infrastructures.
The survey was carried out over three periods at Sea Crest
Villa near Tai Lei on the northwest shore of Peng Chau facing Penny’s Bay (Figure 4-1).
The results of these noise measurements are summarised in Table 4-5a.
Table 4-5a Noise Measurement Summary at Sea Crest Villa in 1999
|
Measurement Period
|
Weekday (1) (Leq)
|
Weekend (2) (Leq)
|
|
0700-1900 hours
|
50.5
|
49.3
|
|
1900 – 2300 hours
|
49.0
|
49.9
|
Note: (1) Weekday measurements
performed on 25 Nov 1999 (Thursday)
(2)
Daytime measurement on 4 Dec 1999 (Saturday) and evening
time measurement on 20 Nov 1999 (Sunday)
The finding of the survey showed that background noise levels
on the north-west shore of Peng Chau were controlled by natural sources (wind
and waves) and were found to be quite consistent during both the daytime and
evening. Since background noise levels at Peng Chau are controlled largely by
natural sources (wind and waves), it is expected that these noise levels would
be quite consistent from time to time. Night time noise level at the same
location is estimated to be similar to the weekend measured noise levels
49-50dB(A).
4.3.4
In 2001, a
baseline noise monitoring was carried out from August to October as part of the
Environmental Monitoring and Audit for the Infrastructure for Penny’s Bay
Development (CED, 2001-2003). One of the monitoring stations is at Sea Crest
Villa near Tai Lei Island on the northwest shore of Peng Chau facing Penny’s
Bay. Measurements of noise levels
during daytime, evening and night-time are presented in Table 4-5b below.
Table 4-5b Noise
Measurement Summary at Sea Crest Villa in 2001
|
Measurement Period
|
Leq
|
|
0700 – 1900 hours(1)
|
59.6
|
|
1900 – 2300 hours(2)
|
56.5
|
|
2300 - 0700 hours(2)
|
57.1
|
Note: (1) Measurement of Leq (30min) (2)
Measurement of Leq (5min)
4.3.5
Impact monitoring
of noise construction at the Penny’s Bay at Sea Crest Villa has been carried out
since December 2001. The Phase 1 construction work will be finished in
mid-2005. Phase 2 construction works were started in mid-2003 and will end in
2008/2009 and the impact monitoring locations are the same. Table 4-5c shows the impact monitoring
results at Sea Crest Villa up to October 2003.
Table 4-5c Noise
Measurement during Penny’s Bay Phase 1 Construction Work at Sea Crest Villa,
Peng Chau
|
Measurement
Period
|
Leq
|
|
0700 – 1900 hours(1)
|
60.1
|
|
1900 – 2300 hours(2)
|
56.9
|
|
2300 - 0700 hours(2)
|
56.2
|
Note: (1) Measurement of Leq (30min) (2)
Measurement of Leq (5min)
4.3.6
The operation of
Peng Chau STW Upgrade is anticipated to start in early 2008. In viewing of the completion
of Penny’s Bay construction in 2008/2009, the baseline noise levels recorded in
November and December 1999 best represent the prevailing background noise
levels of Sea Crest Villa shortly after the commissioning of Peng Chau STW
Upgrade.
4.3.7
Given the rural
setting of Peng Chau and Tai Lei, and no influencing factor is anticipated in
the area, the Area Sensitive Rating for the NSRs within the assessment area of
Peng Chau STW Upgrade could be classified as “A”. In any event, however, the
ASR assumed here 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 should bind the Noise Control Authority in assessing noise from these
sources upon the receipt of complaints. The Authority should assess the noise
impacts based on the contemporary conditions/situations.
4.3.8
The measured
lowest prevailing daytime level was 49.3dB(A), which is more than 5dB(A) below
the ANL stipulated in NCO-TM. The nighttime measurement was estimated to be 49
to 50dB(A). By comparing measured
noise levels with TMEIAP criteria, the following noise criteria are adopted for
this assessment (Table 4-6).
Table 4-6 Noise
Limit for the Operation of Peng Chau STW Upgrade
|
Time
Period
|
Noise Limit (dB(A))
|
Adopted from
|
|
|
49
|
Prevailing background noise measurement (round up value)
|
|
Night (2300 to
0700 hours)
|
45
|
TMEIAP
|
4.4
noise Sensitive
receivers
4.4.1
Noise Sensitive Receivers (NSRs) are identified
with reference to Annex 13 of the TMEIAP.
It is stated in Annex 13 that the potential NSRs could be, but are not
limited to, the following:
1. Residential uses -- all
domestic premises including temporary housing
2. Institutional
uses-- educational
institutions including kindergarten and nurseries
Hospitals
medical
clinics
homes
for the aged
convalescent
homes
places
of public worship
libraries
courts
of law
performing
art centres
auditoriums
amphitheatres
3. Others -- Hostels
country
parks
Construction Phase
4.4.2
The proposed works
for Peng Chau STW Upgrade would be carried out on Tai Lei Island and Tai Lei
bridge of Peng Chau Island. Residential developments in the vicinity are found mainly
along the western coast and central part of Peng Chau Island.
4.4.3
Noise sensitive
receivers identified within the 300m impact assessment zone from the
construction works boundary are Sea Crest Villa and Kam Peng Estate located on
Peng Chau Island (Figure 4-2). To the south of Sea Crest Villa a comprehensive residential
development including a commercial complex is under planning. The
implementation schedule of this development, as advised by the Planning
Department, is not available. It is not anticipated the land would be developed
during the construction stage from 2004-2007, the area is thus not considered
as an NSR during construction stage.
Nevertheless, the constructional noise impact at the identified NSRs in
Table 4-7 could still cover that at this planned NSR if built during the
construction period.
4.4.4
Table 4-7 presents the relevant information of the identified NSRs
during construction phase:
Table 4-7 Identified
NSRs during Construction Phase
|
NSRs
|
Name of
Buildings
|
Sensitive Uses
|
Ground Level
(mPD)
|
No. of Storey
|
|
|
|
N-C1
|
Sea
Crest Villa Block A
|
Residential
|
4.5
|
3
|
|
|
N-C2
|
Sea
Crest Villa Block B
|
Residential
|
4.5
|
3
|
|
|
N-C3
|
Sea
Crest Villa Block C
|
Residential
|
4.5
|
3
|
|
|
N-C4
|
Sea
Crest Villa Block D
|
Residential
|
4.5
|
3
|
|
|
N-C5
|
Kam
Peng Estate
|
Residential
|
4.7
|
7
|
|
Operational Phase
4.4.5
The operational
noise of Peng Chau STW Upgrade would be confined within the existing Peng Chau
STW. One of the identified noise
sensitive receiver is Sea Crest Villa. Although the implementation schedule of
the planned residential development to the south of Sea Crest Villa is not
certain, it is anticipated that it would be affected by the operation of Peng
Chau STW Upgrade when developed. It is thus considered as an operational NSR.
Kam Peng House, however, is not included in the 300m impact assessment zone (Figure 4-2). Table
4-8 presents the relevant information of the identified NSRs during
operational phase.
Table 4-8
Identified NSRs during Operational Phase
|
NSRs
|
Name
of Buildings
|
Sensitive
Uses
|
Ground
Level (mPD)
|
No.
of Storey
|
|
N-O1
|
Sea Crest Villa Block A
|
Residential
|
4.5
|
3
|
|
N-O2
|
Sea Crest Villa Block B
|
Residential
|
4.5
|
3
|
|
N-O3
|
Sea Crest Villa Block C
|
Residential
|
4.5
|
3
|
|
N-O4
|
Sea
Crest Villa Block D
|
Residential
|
4.5
|
3
|
|
N-O5
|
Planned
Residential Development
|
Residential
|
4.7
|
2*
|
Note: * as shown in
Peng Chau Outline Zoning Plan S/I-PC/4 dated August 03.
4.5
impact
identification
Construction Phase
4.5.1
Key noise generating activities during
Peng Chau STW Upgrade construction phase are:
(a)
construction of the twin rising mains;
(b)
construction of the components for the
Upgrade works and demolition of the old structures; and
(c)
construction of
submarine and emergency overflow outfalls.
4.5.2
Construction works
would be carried out during daytime construction period. No works would be
carried out during restricted hours.
4.5.3
Three main working
zones are identified for the construction phases stated in Section 4.5.1 (Figure 4-2). In order to assess the construction
noise impact on a particular NSR, the distances between the NSR and the
notional source position are defined. The notional source position, according
to GW-TM, is the position mid-way between the approximate geographical centre
of the construction site and its boundary nearest to the NSR, if the site is
somewhat a regular shape. The whole construction site is divided into three
parts according to the construction activities. Notional source positions for construction activities for
rising mains, STW upgrade works and outfalls are represented by X, Y and Z
respectively. Different power mechanical equipment (PME) would be used for twin
rising mains construction and two notional sources are defined (X1 and X2) for
construction impact assessment.
4.5.4
The approximate
distances of identified NSRs from the notional source positions and the
proposed NSRs are listed in Table 4-9.
Table 4-9 Approximate Distance of NSRs from Noise
Sources during Construction Phase
|
NSR
|
Description
|
Approximate
Distance (m)
|
|
From X1
|
From X2
|
From Y
|
From Z
|
|
N-C1
|
Sea Crest Villa
Block A
|
81
|
203
|
267
|
330
|
|
N-C2
|
Sea Crest Villa
Block B
|
80
|
202
|
279
|
344
|
|
N-C3
|
Sea Crest Villa
Block C
|
67
|
189
|
269
|
336
|
|
N-C4
|
Sea Crest Villa
Block D
|
37
|
159
|
245
|
316
|
|
N-C5
|
Kam Peng House
|
300
|
422
|
471
|
522
|
4.5.5
An inventory of
PME is developed for quantifying potential impact during each construction phase,
including the PME required for open trench submarine outfall construction. This
proposed PME list for construction, which has been agreed by the Project
Proponent, is provided in Appendix 4A.
4.5.6
The calculated sound
power levels (SWLs) for each construction stage are summarised in Table 4-10.
Table 4-10 Calculated
Sound Power Level at Each Key Construction Stage
|
Activities
|
Calculated
SWL (dB(A))
|
|
Extension of the Inlet Mains at X1
|
103.0
|
|
Extension of the Inlet Mains at X2*
|
122.0
|
|
Site Formation (earthworks and boulder/rock breaking) at Y
|
124.0
|
|
Piling and Foundation Works at Y
|
115.3
|
|
Concreting Works at Y
|
119.9
|
|
Modification and Demolition Works at Y
|
123.1
|
|
Submarine Outfall Construction at Z
|
119.7
|
Note: *The
highest SWL of different construction phase for mainlaying works at X2 is
adopted. See Appendix 4A for explanations.
Impact from Package H
4.5.7
The construction period
of Peng Chau STW Upgrade is scheduled to begin in early 2005 while the Package
H aims at completion in mid-2005. However, by the time the Peng Chau STW
Upgrade construction works start, the main laying works of Package H would have
been finished substantially. The remaining works before mid- 2005 would be
testing and commissioning of the pumping station, which is distant away from
the STW upgrade construction site. Cumulative noise impact is not anticipated.
Impact from Peng Chau Helipad
4.5.8
The construction
activities of Peng Chau Helipad are scheduled to be started in March 2005 and
will last for one year. These construction activities would be coincided with
the proposed construction activities including site formation, piling and
foundation works, concreting works, and excavation and mainlaying works.
Cumulative noise impact is inevitable on the common noise sensitive receivers
at Sea Crest Villa. Assessments on the noise cumulative impact are given in the
later sections.
Operational Phase
4.5.9
The major noise
generating equipment for operational phases are air blowers, ventilation fans
and water pumps. Given the design capacity required, the number of equipment
and their respective sound power levels are shown in Table 4-11. The proposed noisy equipment list has been agreed and
accepted by the Project Proponent. The referenced sound power level for each
equipment is provided in Appendix 4G.
Table 4-11 Plant
Inventory for the Operation of the STW Upgrade
|
Location
|
Equipment Used
|
Number of Units
|
SWL
(dB(A))/unit
|
Sub-total SWL (dB(A))
|
|
Blower Room
|
Blowers for SBR
|
4
|
104
|
110
|
|
|
1
|
104
|
104
|
|
Deodourization Unit
|
Deodourization Fans
|
4
|
96
|
102
|
|
Plant Rooms
|
Ventilation Fans
|
10 (total)
|
90
|
100
|
|
Total SWL dB(A)
|
111.8
|
4.5.10
Standby equipment
would be used in case of failure or maintenance of duty units. Concurrent
operation of both duty and standby equipment are not anticipated. It is
anticipated that the maximum sound power levels during operation would not
exceed that value stated in the above table.
4.5.11
All the operations
of Peng Chau STW Upgrade would be confined within the existing STW site
boundary, the same notional source position as Y is therefore identified (Figure 4-3).
The distances between the notional source position of the operational area
(denoted as X in Figure 4-3) and the identified NSRs are measured
and presented in Table 4-12.
Table 4-12 Approximate Distance of NSRs from Noise Sources during
Operational Phase
|
NSR
|
Description
|
Approximate
Distance (m)
|
|
N-O1
|
Sea Crest Villa Block A
|
267
|
|
N-O2
|
Sea Crest Villa Block B
|
279
|
|
N-O3
|
Sea Crest Villa Block C
|
269
|
|
N-O4
|
Sea Crest Villa Block D
|
245
|
|
N-O5
|
Planned Residential Development
|
317
|
4.5.12
All equipment are
likely to be operated at the same time during operational phase. However, most of these equipment will
be enclosed and noise impact would be reduced. The presence of STW plant
buildings and other facilities may provide noise shielding for identified noise
sensitive receivers.
Impact from Package H
4.5.13
The noise impact on
the surrounding are from the pumping station (Package H) is not expected to be
significant since it is enclosed in a concrete structure. No cumulative
operational impact is envisaged.
Impact from Peng Chau Helipad
4.5.14
Operational noise
from the helipad will mainly originate from helicopters transporting patients
during an medical emergency. As
this type of emergency will not take place often or regularly, cumulative
operational noise impact from the two projects is unlikely be an issue to the
residents living nearby. The cumulative operational noise impact is thus
considered insignificant.
4.6
impact assessment
Construction Phase
4.6.1
The following assumptions are made in
the assessment of noise impact:
(a)
The notional sources are in the direct
sight of the identified noise sensitive receivers;
(b)
Given the openness of the environment,
no correction for acoustic reflection is taken into account for the assessment;
and
(c)
Nearest NSRs of
each residential block at ground level are assessed.
4.6.2
The prediction of the
sound pressure levels at identified sensitive receivers is carried out by the
following equation:
SPL = SWL – DA + Façade correction
Where
SPL = Sound Pressure Level at
Noise Sensitive Receiver (dB(A))
SWL
= Sound Power Level at Source (dB(A))
DA = Distance Attenuation (dB(A))
4.6.3
The distance
attenuation calculation follows the following standard equation:
DA = 20 log d + 8
Where
d = Distance between the
noise source and sensitive receivers
4.6.4
The summary of the
worst predicted noise levels is given in Table
4-13 and the detailed assessment is provided in Appendix 4B.
Table 4-13 The Worst Predicted Noise Levels at Identified Noise
Sensitive Receivers
|
NSR
|
Description
|
Worst
Predicted Noise Levels dB(A)
|
|
N-C1
|
Sea Crest Villa Block A
|
72.2
|
|
N-C2
|
Sea Crest Villa Block B
|
72.1
|
|
N-C3
|
Sea Crest Villa Block C
|
72.6
|
|
N-C4
|
Sea Crest Villa Block D
|
74.0
|
|
N-C5
|
Kam Peng House
|
66.2
|
4.6.5
The predicted results
show that noise levels perceived by the identified NSRs comply with the daytime
construction limit of 75dB(A).
Cumulative
Construction Noise Impact
4.6.6
The worst case
noise levels calculated from construction activities, however, do not include
the construction works of Peng Chau helipad which would be carried out
concurrently for the first year of project construction. Elevated cumulative
noise impacts at the identified noise sensitive receivers would be inevitable. Appendix 4C
shows the predicted cumulative noise levels at the closest NSR N-C4 at Sea
Crest Villa. Cumulative noise levels from STW upgrade and helipad during the
concurrent construction period is provided in Table 4-14.
Table 4-14 Cumulative
Construction Noise Impact at N-C4
|
Description
|
STW Upgrade Predicted Noise
Levels dB(A)
|
Helipad Predicted* Worst Noise Levels dB(A)
|
Cumulative Noise Levels dB(A)
|
|
Year 2005
|
|
02 May to 19 May
|
71.2
|
72.1
|
74.7
|
|
20 May to 04 Jun
|
71.2
|
74.6
|
76.2
|
|
05 Jun to 02 Jul
|
71.2
|
71.2
|
74.2
|
|
03 Jul to 02 Aug
|
71.2
|
71.6
|
74.4
|
|
03 Aug to 22 Aug
|
73.3
|
62.9
|
73.7
|
|
23 Aug to 24 Aug
|
73.3
|
65.5
|
74.0
|
|
25 Aug to 21 Sept
|
73.3
|
65.0
|
73.9
|
|
22 Sept to 22 Sept
|
73.3
|
65.3
|
74.0
|
|
23 Sept to 06 Oct
|
73.3
|
62.6
|
73.7
|
|
07 Oct to 30 Oct
|
73.3
|
68.1
|
74.5
|
|
31 Oct to 07 Nov
|
73.3
|
69.6
|
74.9
|
|
08 Nov to 11 Nov
|
73.3
|
69.6
|
74.9
|
|
12 Nov to 23 Nov
|
73.3
|
67.9
|
74.4
|
|
24 Nov to 29 Nov
|
73.3
|
67.8
|
74.4
|
|
30 Nov to 04 Dec
|
74.0
|
68.2
|
75.0
|
|
05 Dec to 05 Dec
|
74.0
|
67.0
|
74.8
|
|
06 Dec to 18 Dec
|
74.0
|
68.8
|
75.1
|
|
19 Dec to 29 Dec
|
74.0
|
69.3
|
75.2
|
|
30-Dec
|
74.0
|
69.3
|
75.2
|
|
Year 2006
|
|
01 Jan to 05 Jan
|
74.0
|
69.3
|
75.2
|
|
06 Jan to 10 Jan
|
74.0
|
66.2
|
74.6
|
|
11 Jan to 25 Jan
|
74.0
|
61.7
|
74.2
|
|
26 Jan to 28 Jan
|
74.0
|
59.5
|
74.1
|
|
29 Jan to 28 Feb
|
74.0
|
64.3
|
74.4
|
Note: *
predicted noise levels adopted from draft Final EIA for Construction of Helipad
at Peng Chau and Yung Shue Wan, Lamma Island (May 2004)
4.6.7
The predicted
results show that exceedance of recommended daytime construction noise limit of
75dB(A) are predicted from May to June 2005. The corresponding construction
works are shown in Appendix 4C.
4.6.8
It is proposed
that a more stringent daytime construction limit of 72dB(A) should be observed
by both construction sites when construction activities are carried out. The
resultant noise level from both construction sites would then comply with the
recommended 75dB(A) daytime construction limit if the more stringent limit is
complied.
4.6.9
As shown in Table
4-13, the worst predicted noise levels at N-C3 and N-C4 exceeded 72dB(A). Noise
mitigation measures are recommended to reduce noise impacts at these identified
NSRs.
Construction Noise Mitigation Measures
4.6.10
The elevated noise levels are mostly
contributed by PME with high sound power levels. It is recommended that quiet
equipment is used to reduce the construction noise impact. Quiet equipment specifically
recommended for this Project include:
(a)
Excavated Mounted Hydraulic Breaker,
with reference to BS 5228 (British Standard, 1997), Table C.8, item 13, SWL of
110dB(A); and
(b)
Hand Held Electric
Vibratory Poker, with reference to BS 5228, Table C.6, item 32, SWL of
100dB(A);
4.6.11
The PME inventory
of using specified silencing equipment is shown in Appendix 4D. Detailed predicted noise
levels after adopting the quiet equipment are given in Appendix 4E. Summary of the worst
predicted noise levels after incorporating quiet equipment are shown in Table 4-15.
Table 4-15 The
Worst Predicted Noise Levels at Identified Noise Sensitive Receivers (Mitigated
Scenario)
|
NSR
|
Description
|
Worst Predicted Noise Levels
dB(A)
|
|
N-C1
|
Sea Crest Villa Block A
|
68.0
|
|
N-C2
|
Sea Crest Villa Block B
|
67.7
|
|
N-C3
|
Sea Crest Villa Block C
|
68.2
|
|
N-C4
|
Sea Crest Villa Block D
|
70.3
|
|
N-C5
|
Kam Peng House
|
63.0
|
4.6.12
With the use of recommended
silencing and replacement equipment, the predicted noise level at all
identified noise sensitive receivers would comply with the more stringent limit
of 72dB(A).
4.6.13
It is shown in the
above tables that the highest noise construction noise levels would be
perceived by residents at Sea Crest Villa Block D (N-C4). Cumulative noise
levels at this NSR from both Peng Chau STW Upgrade and Peng Chau Helipad
construction activities are provided in Appendix 4F and summarised in Table 4-16.
Table 4-16 Cumulative
Construction Noise Impact at N-C4 (Mitigated Scenario)
|
Description
|
STW Upgrade Predicted Noise
Levels dB(A)
|
Helipad Predicted* Worst Noise Levels dB(A)
|
Cumulative Noise Levels dB(A)
|
|
Year 2005
|
|
02 May to 19 May
|
67.4
|
72.1
|
73.3
|
|
20 May to 04 Jun
|
67.4
|
74.6
|
75.3
|
|
05 Jun to 02 Jul
|
67.4
|
71.2
|
72.7
|
|
03 Jul to 02 Aug
|
67.4
|
71.6
|
73.0
|
|
03 Aug to 22 Aug
|
65.8
|
62.9
|
67.6
|
|
23 Aug to 24 Aug
|
65.8
|
65.5
|
68.6
|
|
25 Aug to 21 Sept
|
65.8
|
65.0
|
68.4
|
|
22 Sept to 22 Sept
|
65.8
|
65.3
|
68.5
|
|
23 Sept to 06 Oct
|
65.8
|
62.6
|
67.5
|
|
07 Oct to 30 Oct
|
65.8
|
68.1
|
70.1
|
|
31 Oct to 07 Nov
|
65.8
|
69.6
|
71.1
|
|
08 Nov to 11 Nov
|
65.8
|
69.6
|
71.1
|
|
12 Nov to 23 Nov
|
65.8
|
67.9
|
70.0
|
|
24 Nov to 29 Nov
|
65.8
|
67.8
|
69.9
|
|
30 Nov to 04 Dec
|
67.1
|
68.2
|
70.7
|
|
05 Dec to 05 Dec
|
67.1
|
67.0
|
70.0
|
|
06 Dec to 18 Dec
|
67.1
|
68.8
|
71.0
|
|
19 Dec to 29 Dec
|
67.1
|
69.3
|
71.3
|
|
30-Dec
|
67.1
|
69.3
|
71.3
|
|
Year 2006
|
|
01 Jan to 05 Jan
|
67.1
|
69.3
|
71.3
|
|
06 Jan to 10 Jan
|
67.1
|
66.2
|
69.6
|
|
11 Jan to 25 Jan
|
67.1
|
61.7
|
68.2
|
|
26 Jan to 28 Jan
|
67.1
|
59.5
|
67.8
|
|
29 Jan to 28 Feb
|
67.1
|
64.3
|
68.9
|
Note: predicted
noise levels adopted from draft Final EIA for Construction of Helipad at Peng
Chau and Yung Shue Wan, Lamma Island (May 2004)
4.6.14
With
implementation of silencing equipment as noise mitigation measures, no
exceedance of 72dB(A) is predicted from the construction of the STW upgrade at
all time. Despite that elevated
noise levels up to 74.6 dB(A) is predicted from the construction of Helipad,
cumulative noise impact at the worst identified NSR still comply with the
daytime recommended noise level of 75dB(A).
Operational Phase
4.6.15
For the assessment
of operational noise, it is assumed that all the equipment proposed in Table
4-11 would be operated at the same time are located outdoor without shielding.
The total sound power level during operational phase is calculated to be 111.8
dB(A) (See Appendix 4G). To simplify the
assessment, a notional source position is assigned (Figure 4-2). The prediction of noise levels at
the identified sensitive receivers follows the equation shown in Section 4.5.2.
4.6.16
The predicted
noise levels during operational phase at the identified NSRs are shown in Table 4-17.
Table 4-17 Predicted
Noise Level during Operational Phase (without Shielding)
|
NSR
|
Description
|
Predicted Noise Level dB(A)
|
|
N-O1
|
Sea
Crest Villa Block A
|
58.3
|
|
N-O2
|
Sea
Crest Villa Block B
|
57.9
|
|
N-O3
|
Sea
Crest Villa Block C
|
58.2
|
|
N-O4
|
Sea Crest
Villa Block D
|
59.0
|
|
N-O5
|
Planned
Residential Development
|
56.8
|
4.6.17
It is shown that
if all the noisy equipment for STW are located outdoor without shielding, the
predicted noise levels would exceed the recommended noise limit at all time
(49dB(A) during daytime/evening and 45dB(A) during night time).
4.6.18
However these
noisy equipment are designed to be enclosed inside their respective treatment
buildings.A
reduction of 20dB(A) can be achieved if the building enclosures are built using
suitable material such as concrete with surface density of 25kg/m2.
With the proposed enclosure, the predicted noise levels during operational
phase at identified noise sensitive receivers are reduced and the results are
shown in Table 4-18.
Table 4-18 Predicted
Noise Level during Operational Phase (with concrete building enclosure)
|
NSR
|
Description
|
Predicted Noise Level dB(A)
|
|
N-O1
|
Sea Crest Villa Block A
|
38.3
|
|
N-O2
|
Sea Crest Villa Block B
|
37.9
|
|
N-O3
|
Sea Crest Villa Block C
|
38.2
|
|
N-O4
|
Sea Crest Villa Block D
|
39.0
|
|
N-O5
|
Planned Residential Development
|
36.8
|
4.6.19
With the
implementation of mitigation measures, the predicted noise levels at identified
noise sensitive receivers comply with the daytime/evening and night time
operation noise limit of 49dB(A) and 45dB(A), respectively. Operational noise impacts are
insignificant.
Cumulative Operational Noise Impact
4.6.20
As identified in
Section 4.5, no additional noise sources are identified during the operational
phase of the STW Upgrade. The cumulative
operational noise impacts .are predicted to be the same as the
operational noise shown in Table 4-18, and are in compliance with both
daytime/evening and night time operation noise limit.
4.7
mitigation
MEASURES
Construction Phase
4.7.1
Noise mitigation measures during
construction phase are recommended to reduce the potential cumulative noise
impacts with Peng Chau Helipad project. Recommended measures include adoption
of the following silencing equipment:
(a)
Excavated Mounted Hydraulic Breaker,
with reference to BS 5228 (British Standard, 1997), Table C.8, item 13, SWL of
110dB(A); and
(b)
Hand Held Electric
Vibratory Poker, with reference to BS 5228, Table C.6, item 32, SWL of
100dB(A);
4.7.2
In addition to using quiet PME, good
site practices are recommended, as follows:
(a)
Only well-maintained plant should be
operated on-site and plant should be serviced regularly during the construction
program;
(b)
Mobile plant, if any, should be sited
as far away from NSRs as possible;
(c)
Machines and plant that may be in
intermittent use should be shut down between work periods or should be
throttled down to a minimum;
(d)
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
(e)
Material stockpiles and other
structures should be effectively utilized, wherever practicable, in screening
from on-site construction activities.
4.7.3
As shown in
Section 4.6, no identified NSR would exceed the daytime construction noise
limit from the construction of the proposed Peng Chau STW Upgrade. The elevated
construction noise levels predicted are from the cumulative impacts of both the
Peng Chau STW Upgrade and Peng Chau Helipad and the most affected residential
NSRs are Sea Crest Villa (where predicted noise levels from Peng Chau STW
upgrade exceed 72dB(A)). The Sea Crest Villa consist of 42 residential units.
With the implementation of the proposed mitigation measures, a minimum of 42
residential units would be benefited from the provision of mitigation measures.
Operational Phase
4.7.4
Enclosure of noisy
equipment are proposed as noise mitigation measures for operational phase. These measures are to be incorporated
into design of the STW Upgrade.
4.7.5
The identified
operational NSRs include the Sea Crest Villa and a planned residential development.
It is anticipated that at least 42 residential units would be benefited by the
proposed noise mitigation measures during operational phase.
4.8
Residual Impacts
4.8.1
With the
implementation of recommended mitigation measures for construction phase and operational
phases, no residual adverse noise impacts are anticipated.
4.9
Environmental
Monitoring and Audit
Construction Phase
4.9.1
With the
implementation of recommended mitigation measures during the construction of the
STW Upgrade and Helipad, noise impact at the identified NSRs comply with the
recommended standard.
Nevertheless, EM&A is recommended to ensure the noise level
compliance.
Operational Phase
4.9.2
Insignificant
impact from operational phase would be expected. EM&A during operational
phase is not required.
4.10
conclusions and
recommendations
Construction Phase
4.10.1
Construction noise
impacts from STW upgrade was evaluated.
Key noise generating activities include construction of pumping mains,
treatment works upgrade and demolition of old units, as well as outfall
construction.
4.10.2
The predicted
results show that the construction noise standard of 75 dB(A) stipulated in
TMEIAP is complied at all identified NSRs from the proposed construction
activities at all phases. However, the construction of Peng Chau Helipad would
be taken place concurrently during the first year of construction when most
noisy equipment plants are scheduled to be operated. To minimise the cumulative
noise impact, a more stringent noise level of 72dB(A) is recommended to be
observed by both construction sites.
4.10.3
Noise mitigation
measures are proposed for the construction of STW upgrade. Two types of
silencing PME are recommended to reduce the noise impact. Noise levels at
identified NSRs after mitigating are all well below the proposed noise level of
72dB(A).
4.10.4
Exceedance of
72dB(A) noise level would occur by Helipad construction activities at the worst
identified NSR with the implementation of mitigation measures. Scheduling of
the STW construction have been properly arranged to avoid the elevated
cumulative noise impact at the worst identified NSR. No exceedance of cumulative noise level of 75dB(A) would be
resulted within the concurrent construction period of both projects.
4.10.5
No unacceptable/adverse
residual impacts are anticipated during the construction phase.
Operational Phase
4.10.6
The major noise
generating equipment for operational phases are air blowers, ventilation fans
and water pumps. Operational noise prediction is carried out assuming all the
noisy equipment would be located outdoor without shielding. The predicted noise
levels at identified NSRs exceed the daytime/evening and night time operational
noise standard of 49d(B)A and 45dB(A), respectively.
4.10.7
However these
noisy equipment are designed to be enclosed inside their respective treatment
buildings. A reduction of 20dB(A) can be achieved if the building enclosures
are built using suitable material such as concrete with surface density of
25kg/m2. With the proposed enclosure, the predicted noise levels
during operational phase at identified NSRs are reduced and would comply with
the operational noise standard during both daytime/evening and night time.
4.10.8
No adverse residual
operational noise impacts are encountered after implementation of mitigation
measures.