This Section presents the potential noise impacts associated with the
demolition of oil tanks, retrofitting of Flue Gas Desulphurisation (FGD) plant
to two existing 350MW coal-fired generating units L4 and L5 of Lamma Power
Station, construction of equipment building and the cumulative noise impacts
associated with operation of proposed FGD plant and existing units.
6.2
Relevant Legislation and Guidelines
6.2.1
Construction Noise
The principal legislation relating to the control of construction 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:
·
Technical Memorandum
on Noise from Percussive Piling (PP-TM);
·
Technical Memorandum
on Noise from Construction Work other than Percussive Piling (GW-TM);
and
·
Technical Memorandum
on Noise from Construction Work in Designated Areas (DA-TM).
Apart from
the above, the Environmental Impact
Assessment Ordinance (EIAO) (Cap. 499) also provides means to assess
construction noise impacts. The Technical Memorandum on Environmental Impact
Assessment Process (EIAO-TM),
issued under the EIAO, provides
guidelines and noise criteria for evaluating construction noise impacts.
General
Construction Works
Under the EIAO, noise impact
arising from general construction works during normal working hours (i.e. 0700
to 1900 hours on any day not being a Sunday or public holiday) at the openable
windows of buildings is to be assessed in accordance with the noise criteria as
given in the EIAO-TM. The EIAO-TM
noise standards are presented in Table
6.1.
Table 6.1 EIAO-TM
Daytime Construction Noise Standard (Leq, 30 min dB(A))
|
Use |
Noise Standard |
|
Domestic Premises |
75 |
|
Educational
Institutions (normal periods) Educational
Institutions (during examination periods) |
70 65 |
When
assessing a CNP application for the use of Powered Mechanical Equipment (PME)
during restricted hours, the Noise Control Authority will compare the ANLs, as
promulgated in GW-TM, and the CNLs (after accounting for factors such as
barrier effects and reflections) associated with the proposed PME
operations. The ANLs are related
to the noise sensitivity of the area in question and different Area Sensitivity
Ratings have been established to reflect the background characteristics of
different areas. The relevant ANLs
are shown in Table 6.2.
The Noise Control Authority will consider a well-justified Construction
Noise Permit (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 will take into account adjoining land uses and any previous
complaints against construction activities at the site before making a decision
in granting a CNP. Nothing in this
EIA Report shall bind the Noise Control Authority in making his decision. The Noise Control Authority may include
any conditions in a CNP that it considers appropriate. Failure to comply with any such
conditions may lead to cancellation of the CNP and prosecution action under the
NCO.
Table 6.2 Acceptable
Noise Levels (ANL, Leq, 5 min dB(A))
|
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 |
In addition to the general controls on the use of PME during restricted
hours, the EPD has implemented a more stringent scheme via the DA-TM. The DA-TM regulates the use of
five types of Specified Powered Mechanical Equipment (SPME) and three types of
Prescribed Construction Work (PCW), which are non-PME activities, in primarily
densely populated neighbourhoods called Designated Areas (DAs). The SPME and PCW are:
SPME:
·
hand-held breaker;
·
bulldozer;
·
concrete lorry mixer;
·
dump truck; and
·
hand-held vibratory poker.
PCW:
·
erection or dismantling of formwork or scaffolding;
·
loading, unloading or handling of rubble, wooden boards, steel bars,
wood or scaffolding material; and
·
hammering.
A CNP will be required for works during the time between 1900 and 0700
hours and any time on a general holiday, including Sunday, and the noise
criteria for evaluating noise impact laid down in relevant TM issued
under the NCO must be met.
As the study area is located outside a designated area, the noise
criteria stipulated under the DA-TM are not applicable in this study.
6.2.2
Operational Noise
The EIAO-TM and Technical Memorandum on Noise From Places
Other than Domestic Premises, Public Places or Construction Sites (IND-TM)
specifies the applicable Acceptable Noise Levels (ANLs) for the cumulative
noise impacts from the operation of Project and existing power station
equipment. The ANLs are dependent
on the Area Sensitivity Rating (ASR) and the time of the day and are presented
in Table 6.3.
Table 6.3 ANLs
to be used as Operation Noise Criteria
|
Time Period |
LAeq
30min (dB(A)) |
||
|
ASR
“A” |
ASR
“B” |
ASR
“C” |
|
|
Daytime 0700-1900 |
60 |
65 |
70 |
|
Evening 1900-2300 |
60 |
65 |
70 |
|
Night-time 2300-0700 |
50 |
55 |
60 |
Fixed
Plant Noise
Fixed plant noise is controlled under Section 13 of the NCO
and the predictions will be undertaken in accordance with the IND-TM. The criteria noise limits are set out
in the EIAO-TM as follows:
·
the total fixed source noise level at the facade of the nearest NSR is
at least 5 dB(A) lower than the appropriate ANL (as shown in Table 6.3)
as specified in the Technical Memorandum on Noise from Places other than
Domestic Premises, Public Places or Construction Sites (IND-TM); or,
·
where the prevailing noise level in the area is 5 dB(A) or more below
the appropriate ANL, the total fixed source noise level must not exceed this
noise level.
The criteria noise limits stipulated in the IND-TM are dependent
on the Area Sensitivity Rating (ASR) of the NSRs as shown in Table 6.3.
As the site is located in a rural area
and no influencing factors affect the NSRs, an ASR “A” has been assumed for the
NSRs located at Ko Long and Hung Shing Ye. With the inclusion of façade correction, the measured
prevailing noise level will be higher than the (ANL-5) criterion, and therefore
the (ANL – 5) criterion, i.e. 45 dB(A) LAeq, 30min for night-time
period will be considered as the stipulated noise limit for the assessment of
operational noise impact. Detail
of the noise measurement will be further discussed in Section 6.3.3.
In any event, the Area Sensitive Rating assumed in this Report is for
indicative assessment only given that there are currently no influencing
factors assumed in the vicinity of the NSRs. 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 / situations of adjoining land uses. Nothing in this Report shall bind the
Noise Control Authority in the context of law enforcement against all the fixed
noise sources being assessed.
6.3
Baseline Environmental Conditions and Noise
Sensitive Receivers
6.3.1
Noise Sensitive
Receivers
Settlement on the northern end of Lamma Island is largely concentrated
around the harbour at Yung Shue Wan and in the adjacent villages of Yung Shue
Long, Sha Po, Ko Long, Wang Long and Tai
Wan San Tsuen. These residences
are shielded from plant noise to varying degrees by the intervening hill (Kam
Lo Hom) which defines the plant’s northern site boundary. The villages of Long Tsai Tsuen and
Hung Shing Ye, although lie outside the area
which is shielded by the hill (Kam Lo Hom), are shielded from the new plants by the existing plants. The most affected NSRs are identified and summarised in Table 6.4 and
the locations of the NSRs are shown in
Figure
6.1. No planned NSRs are
identified within the study boundary.
Table 6.4 Identified
Noise Sensitive Receivers
|
NSR |
Location |
Type of Use |
|
NSR 1 |
Hung Shing Ye / Tai
Wan To |
Residential Use
(3-storey) |
|
NSR 2 |
Ko Long |
Residential Use
(3-storey) |
6.3.2
Baseline Environmental
Conditions
The proposed Project is located at the northern section of the existing
Lamma Power Station. The
residential buildings located to the north and north-east of the Lamma Power
Station are screened by the existing equipment units and natural
topography. Background noise is
generally low and there are no private vehicles or industrial facilities within
the Study Area. The major noise
source is identified as the community noise from the residents and the construction of the extension to the existing Lamma Power Station.
6.3.3
Baseline Community
Noise Monitoring
Existing local acoustic environment at the NSRs is currently affected
by the construction activities of extension works conducted at the Lamma Power
Station, and therefore to allow a worst case scenario, the ambient noise levels
at the NSRs are made reference to Sections
6.3.3 and 6.3.4 of the Lamma Extension EIA Report ([1]). The ambient noise levels were
contributed by the operational noise from the existing Lamma Power Station and
the ambient community noise.
With reference to the noise monitoring conducted in 1997, the noise
data collected at Tai Wan To (TWT) were considered to be a more stringent
representation of the background as the results were manually screened to
eliminate certain particular extraneous noise sources present in the
environment. The background noise
levels are summarised in Table 6.5.
Table 6.5 Seasonal
Background Noise at TWT in 1997
|
Period |
LAeq(1),
30min dB(A) |
|
|
|
Summer |
Winter |
|
Daytime |
52 |
49 |
|
Night-time |
49 |
45 |
|
Remark: (1)
The measured noise levels were not affected by the construction noise
from the Lamma Extension, and therefore the noise levels represent a quieter
ambient condition and a more stringent noise limit for the operational
assessment. (2)
There is no major change on site condition/environment of the study
area so that the background noise
levels obtained in 1997 can still be applicable |
||
6.4
Construction
Noise Assessment
6.4.1
Potential Sources of
Impact
The major construction activities associated with the Project that may
cause noise impacts to the NSRs are:
·
Demolition
of two existing Nos. 4 & 5 Light Oil tanks, each of 50m3; and
·
Retrofit of
FGD plants to two existing 350MW coal-fired Units L4 & L5 of the Lamma
Power Station.
According to planned project programme, the
demolition and retrofit works will be carried out
in phases without overlapping.
6.4.2
Evaluation of Impacts
The proposed Project is in small scale. Additionally, in the view that the
residential developments are shielded from construction noise to varying
degrees by the intervening hill (Kam Lo Hom) and the existing plants, and
considerable separation distance between the NSR and the Project, the noise
generated during the construction stage is not expected to be a concern. In accordance with the EIA Study Brief,
a quantitative construction noise assessment is therefore not required.
The normal working hours of the contractor will be between 0700 and
1900 hours from Monday to Saturday (except public holidays). Should evening and night works between
1900 and 0700 hours or on public holidays (including Sunday) be required, the
contractor should submit a CNP application and will be assessed by the Noise
Control Authority. Conditions
stipulated in CNPs should be strictly followed.
6.4.3
Mitigation Measures
In accordance with the EIA Study Brief, the following good site practice
and noise management are
recommended to ensure that construction noise is controlled within the relevant criteria:
·
Use of quiet plants should be considered for replacing the use of noisy
plant;
·
Only well-maintained plant should be operated on-site and plant should
be serviced regularly during the construction works;
·
Machines and plant that may be use intermittently, such as vibratory
poker, 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, where
possible, be orientated to direct noise away from nearby NSRs; and
·
Mobile plant should be sited as far away from NSRs as possible.
6.5
Operational
Noise Assessment
6.5.1
Potential Sources of
Impact
Additional equipments to be installed for the existing FGD plant at
Lamma Power Station are given below:
·
Two sets of FGD absorbers and associated duct works;
·
Two sets of booster fans;
·
Two sets of gas-gas heater;
·
FGD switchgear and equipment building; and
·
Gypsum dewatering system comprising two sets of hydrocyclones and belt
filter.
With reference to the operation mode of existing FGD units in Lamma
Power Station, the potential noise sources and their sound power levels are
presented in Table 6.6.
To minimise the noise impact to the environment, most of the noise
sources associated with the retrofit project will be housed within individual
acoustic enclosure.
Table 6.6 Noise
data Collected from Existing FGD Units
|
Equipment |
No. of Unit for Each FGD Unit |
Sound Power Level(1) per unit,
dB(A) (with the provision of mitigation measures) |
Mitigation Measures(2) Provided
to the equipment |
|
Absorber |
1 |
107 |
- |
|
Absorber
Recirculation Pump |
4 |
88 |
In enclosure |
|
Oxidation Air Blower |
2 |
100 |
In enclosure |
|
Booster Fan |
1 |
99 |
In enclosure |
|
Booster Fan Motor |
1 |
90 |
In enclosure |
|
Gas-Gas Heater
(untreated side) |
1 |
95 |
Reinforced lagging |
|
Gas-Gas Heater
(treated side) |
1 |
85 |
- |
|
Total Sound Power Level |
112 for L4 & L5
FGD Units |
|
|
|
Remark: (1) Sound Power
Levels of the equipment were provided by the FGD Suppliers. (2) Mitigation
measures will also be provided for the future equipment of the proposed
Project. |
|||
The figures presented in above Table 6.6 are guarantee figures from existing units provided by the
FGD suppliers. For the new L4
& L5 FGDs, same guarantee would also be included in the FGD Supply Contract
and the suppliers are required to provide enclosures to ensure noise emission
comply with the above requirements.
The equipment that will be installed inside the
switchgear equipment building and the gypsum dewatering house are of low noise
levels. Certain equipment will
also be fully enclosed inside concrete structures, and hence the equipment are
of negligible noise impact and need not be included in the assessment.
6.5.2
Assessment Methodology
The methodology for the noise impact assessment is in accordance with
the procedures outlined in the ISO 9613([2]) and IND-TM, which is issued under the NCO
and the EIAO-TM. The assessment will take into account
the distance attenuation, atmospheric absorption and barrier correction.
Based on the noise data collected from the existing operating units in
the Lamma Power Station, the facade noise levels at the identified NSRs (Hung
Shing Ye/Tai Wan To) are predicted and summarised in Table 6.7. Results indicate that the identified
NSRs will be subject to noise level of up to 38 dB(A), which will comply with
the stipulated noise criterion of 45 dB(A). For the NSR at Ko Long, which is located the north of the
proposed plants, the existing buildings and terrain act as barriers and
significantly reduce the noise levels due to the new plant, and therefore these
NSRs will be subject to even lower noise level than the NSRs at Hung Shing Ye
and Tai Wan To.
Table 6.7 Predicted
Facade Noise Levels at Hing Shing Ye/Tai Wan To and Ko Long
|
NSR |
Total
Sound Power Level, dB(A) |
Horizontal
Distance to the NSRs(1), m |
Correction Factor, dB(A) |
Predicted
Facade Noise Level, dB(A) |
|||
|
|
|
|
Distance |
Barrier(2) |
Facade |
Air
absorption(3) |
|
|
NSR1 |
112 |
1071 |
68.6 |
-5 |
+2.5 |
-3.0 |
38.0 |
|
NSR2 |
112 |
348 |
58.8 |
-20 |
+2.5 |
-1 |
35 |
|
Remark: (1) For a worst case scenario assessment, the
distance from the nearest plant to the NSR is used to assess the operational
noise impact at the NSRs (2) A negative correction of 5 dB(A) has been
included for the NSR screened by the existing equipment units and 20 dB(A)
has been included for the NSRs screened by the existing equipment units and
natural topography (Kam Lo Hom). (3) A sound
absorption by the atmosphere (assumed at 500 Hz, 20°C, RH 70%) has been accounted for in
accordance with ISO 9613-1 Acoustics – Attenuation of Sound During
Propagation Outdoors – Part 1: Calculation of the Absorption of Sound by the
Atmosphere. |
|||||||
As NSR 1 will be subject to highest facade noise level, the cumulative
operational noise levels from the existing Lamma Power Station, Extension Plant
and proposed Project at NSR 1 are predicted and summarised in Table 6.8.
Table 6.8 Predicted
Cumulative Noise Levels at Hung Shing Ye / Tai Wan To
|
Period |
Existing Plant and Extension Plant(1),
Leq, 30min dB(A) |
New L4 and L5, Leq,
30min dB(A) |
Cumulative Noise Impact, (Leq, 30min
dB(A) |
|
Daytime |
54.7 (summer) |
38.0 |
55 |
|
|
52.2 (winter) |
38.0 |
52 |
|
Night-time |
49.5 (summer) |
38.0 |
50 |
|
|
49.5 (winter) |
38.0 |
50 |
|
Remark: |
|
|
|
|
(1) Reference was
made from the prediction results (Table 6.5b) of Environmental Impact
Assessment of a 1,800 MW Gas-Fired Power Station at Lamma Extension, February
1999, ERM-Hong Kong. |
|||
The additional equipment to be installed will have insignificant
contribution when compared with the cumulative operational noise of the Lamma
Power Station. Therefore, the
plant noise associated with the retrofit plant is not expected to give rise
unacceptable environmental impacts.
6.5.4
Mitigation Measures
The noise assessment indicated that, based on a worst-case scenario,
the predicted facade noise levels will comply with the daytime, evening and
night-time noise criterion at all NSRs.
In addition, most of the noise sources associated with the retrofit
project will be housed within individual acoustic enclosure to minimise the
noise impact to the environment (Table 6.6). Hence, no further mitigation measures
are required.
6.6
Environmental Monitoring and Audit
In view of the anticipated
insignificant noise impact in both construction and operational phases,
additional noise monitoring work for this Project is considered not
necessary.
The proposed Project is in small scale. Additionally, in the view that the residential developments
are shielded from construction noise to varying degrees by the intervening hill
(Kam Lo Hom) and the existing plants, and considerable separation distance
between the NSR and the Project, it is envisaged that the construction noise of
the Project will not be a concern for the NSRs located at a considerable
distance from the proposed site.
However, in order to ensure that the construction noise levels at the
NSRs controlled within the relevant criteria, good site practice and noise
management is recommended during the construction phase.
Based on a worst-case scenario, the operational noise levels due to
additional equipment will comply with the noise criterion and will have
insignificant contribution to the cumulative operational noise of the Lamma
Power Station. Therefore, the
plant noise associated with the retrofit plant is not expected to give rise to
unacceptable environmental impacts.
In addition, most of the noise sources associated with the retrofit
project will be housed within individual acoustic enclosure to minimise the
noise impact to the environment.
In view of the anticipated
insignificant noise impact in both construction and operational phases,
additional noise monitoring work for this Project is considered not necessary.