This Section presents the potential noise impacts associated with the
demolition of oil tanks, retrofitting of the Castle Peak Power Station “B”
Units (CPB) with emissions control facilities and the operation of the CPB.
4.2
Relevant
Legislation and Guidelines
4.2.1
Construction Noise
The principal legislation relating to the control of construction noise
is the Noise Control Ordinance (Cap. 400)
(NCO). A number of technical
memoranda (TMs) have been issued under the NCO to stipulate control approaches
and criteria and those which may be relevant to the demolition works and
retrofitting of CBP include the following:
·
Technical Memorandum on Noise from
Percussive Piling (PP-TM); and
·
Technical Memorandum on Noise from
Construction Work other than Percussive Piling (GW-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.
Percussive Piling
Under the PP-TM,
percussive piling is
prohibited at any time on Sundays and public holidays and during the weekday
evening and night-time hours (1900-0700 hours, Monday through Saturday). A Construction Noise Permit (CNP) is
required for such works during weekday daytime hours (0700-1900 hours, Monday
through Saturday).
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
4.1.
Table 4.1 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 4.2.
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 4.2 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 |
4.2.2
Operational Noise
Fixed plant noise is controlled under Section 13 of the NCO and the predictions will be undertaken in accordance with the Technical Memorandum on Noise from Places
other than Domestic Premises, Public Places or Construction Sites (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
4.3) as specified in the 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. Future check of prevailing noise levels
will be made during baseline noise measurement prior to construction of the
Project.
The criteria noise limits stipulated in
the IND-TM are dependent on the Area
Sensitivity Rating (ASR) of the NSRs, as shown in Table 4.3.
Table 4.3 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 |
As the site is located in a rural area and no
influencing factors affect the NSRs which are located at more than 1 km away
from the site, an ASR “A” has been assumed for the NSR located in the vicinity
of the proposed site. Baseline
noise measurement has been conducted to investigate the prevailing noise levels
at
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 assessment.
4.3
Baseline
Environmental Conditions and Noise Sensitive Receivers
4.3.1
Baseline Environmental
Conditions
The site will be located within the existing site of the Castle Peak Power
Station (Figure
4.1). The background noise environment is dominated
by the fixed plant noise from the operation of the existing Castle Peak Power
Station and the adjoining Green Island Cement Plant, and road traffic noise
from
4.3.1
Noise Sensitive Receivers
The nearest NSR is identified as the village house at
Sha Po Kong (N1) which is located at approximately 1.1 km away from the
site. A planned noise sensitive development is identified as
the Holiday Camp (PN1) located at approximately 1.2 km to the east of the
site. The locations of the NSRs are
shown in Figure
4.1 and presented in Table 4.4.
Table 4.4 Identified
Noise Sensitive Receivers
|
NSR |
Location |
Type of Uses |
|
N1 |
Village
house at Sha Po Kong |
Residential
(3-Storey) |
|
PN1 |
Planned |
Temporary
housing |
4.3.2
Baseline Noise Measurement
To investigate the prevailing noise levels at the NSRs in
The measurement results are summarised in Table 4.5 and a timeline chart showing the prevailing
noise levels is presented in Annex B-1. Since the measurement is a free field
measurement, an appropriate facade correction of 3dB(A) has been applied to the
noise measurement results.
Table 4.5 Measured
Prevailing Free-field Noise Level (with Facade Correction)
|
Period |
|
LAeq, 30min dB(A)
|
|
|
|
Minimum |
Average |
Maximum |
|
0700 – 2300
hours |
56 |
66 |
75 |
|
2300 – 0700
hours |
48 |
54 |
65 |
With the inclusion of facade 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.
4.4
Construction
Noise Assessment
4.4.1
Potential Sources of Impact
Potential impacts to the NSR during the construction phase of the CPB
will mainly arise from PME operating at construction work sites. The major construction work will include
the following key activities:
·
Demolition
of some existing facilities;
·
Relocation
of some existing facilities;
·
Installation
of new emissions control equipment and associated facilities; and
·
Extension
of the existing heavy load berth.
The construction noise from PME controlled under GW-TM is assessed in this EIA.
For the extension of the heavy load berth, percussive piling is
assumed. In accordance with the PP-TM, a CNP is required for all
percussive piling works. For this
season, a CNP application for the piling works of the berth extension will need
to be submitted to the Noise Control
Authority and the issue of a CNP will be governed by the procedures laid
down in the PP-TM when such an
application is made. The assessment of the
percussive piling noise impact associated with the construction of the berth
extension is therefore not included in this EIA.
Some of the construction works will be carried out simultaneously according to planned project
programme. It is anticipated that
the normal
working hours of the contractor will be between 0700 and 1900 hours from Monday
to Saturday (except public holidays).
Given the
site constraints and scale of the concurrent construction activities, there
will be limited plant items to be operating at the site. Construction noise assessment will be
undertaken based on construction programme and plant inventories summarized in Annexes B-2 and B-3 respectively.
4.4.2
Assessment Methodology
The methodology for the noise impact assessment is in accordance with
the procedures outlined in the GW-TM, which
is issued under the NCO and the EIAO-TM, and is summarized as follows:
·
Identifying
the likely type, sequence and duration of principal noisy construction
activities required for the implementation of the project;
·
Identifying
a list of plant likely to be required for each construction activity;
·
Calculating
the maximum total sound power level (SWL) for each construction activity using
the plant list and SWL data given for each plant in the technical memorandum;
·
Identifying
representative NSRs as defined by the EIAO-TM
based on existing and committed land uses in the Study Area that may be
affected by the worksite;
·
As a
conservative approach, calculating the distance attenuation to NSR from the
boundary of nearest worksite; and
·
Predicting
construction noise levels at NSRs in the absence of any mitigation measures.
Due to the large separation distance between the construction site and
the NSR (approximately 1 km), in accordance with ISO
9613-2 ([1]), the noise will be reduced due to energy
lost through atmospheric absorption during transmission. As a conservative approach to the assessment, the atmospheric absorption during transmission has
been omitted in the assessment. In
addition, it was assumed that all the construction plant will be operated
simultaneously for each activity.
The assessment has
taken into account the distance attenuation, barrier correction, and facade correction of +3 dB(A).
4.4.3
Evaluation of Impacts
The unmitigated construction noise levels at the NSR N1 (Village house
at Sha Po Kong) and PN1 (Planned Holiday Camp) have been predicted and are
presented in Annex B-4. The predicted construction noise levels
at N1 and PN1 are in the range of 43 - 51 dB(A), which are below the daytime
construction noise criterion of 75 dB(A) throughout the construction period and
utilized the conservative set of assumptions in the analysis.
Given that the predicted construction noise levels are well within the
stipulated noise criterion, mitigation measures are not required to alleviate
the noise impacts.
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.
4.5
Operational Noise
Assessment
4.5.1
Potential Sources of Impact
Noise associated with the operational
phase of the CPB would arise from the plant at the CPB. The dominant noise sources are mainly
from the machinery including the following equipment:
·
Flue Gas Desulphurisation (FGD) absorbers and associated duct works;
·
Various kind of fans and pumps;
·
Gas-gas heater;
·
Wastewater treatment plant; and
·
Loader/unloader of process reagents and by-products.
To minimise the noise impact to the environment,
most of the noise sources associated with the retrofit project will be housed
within individual enclosures or claddings.
In addition, Project
Proponent has advised that the maximum allowable measured free-field sound
pressure level (SPL) of 85 - 90 dB(A) at 1 m will be included in the tender
specification (Annex B-5). With such guarantee included in the FGD Supply Contract, the noise emission from
the equipment should comply with the tender specification.
As a conservative approach, it was assumed that all
equipment will be operated on a 24-hour basis.
4.5.2
Assessment Methodology
The methodology for the noise impact assessment is in
accordance with the procedures outlined in the IND-TM, which is issued under the NCO and the EIAO-TM.
The methodology for the fixed
plant noise assessment is presented below:
·
Identifying
types of equipment and the number of equipment;
·
Assuming
area sources with specified maximum SPL for each emission group;
·
Identifying
representative NSRs as defined by the EIAO-TM
based on existing and committed landuses in the Study Area that may be affected
by the worksite;
·
Calculating
the distance attenuation to the NSRs from the nearest noise sources; and
· Presenting the results in
terms of LAeq (30min) dB, as specified in the TM.
Due
to the large separation distance between the construction site and the NSR
(approximately 1 km), in accordance with ISO
9613-2 ([2]), the noise will be reduced due to energy
lost through atmospheric absorption during transmission. As a conservative approach to the assessment, the atmospheric absorption during
transmission has been omitted in the assessment.
The assessment has taken
into account the distance attenuation, barrier correction and facade correction of +3 dB(A).
4.5.3
Evaluation of Impacts
Based on the maximum specified sound pressure levels
for new equipment at the CPB, the NSR N1 and PN1 will be subject to noise level up to 35 dB(A), which
comply with the night-time (ANL-5) noise criterion (Annex B-6).
The
suppliers should guarantee the specified SPL by providing certificate of
measurement and verify the SPL during testing and commissioning in accordance
with international standard procedures.
If necessary, the suppliers should apply attenuation measures to achieve
the guaranteed noise levels during the detailed design stage.
4.6.1
Construction Phase
The predicted noise levels are within the stipulated noise criterion as
a result of the considerable
separation distance plus topography and existing building structures at CPB
located between the NSR and the Project.
Mitigation measures are not required.
4.6.2
Operational Phase
The predicted noise levels are below the daytime and night-time criteria
as a result of the considerable
separation distance plus topography and existing building structures at CPB
located between the NSR and the Project.
Mitigation measures are not required.
4.7
Environmental
Monitoring and Audit
4.7.1
Construction Phase
Given the compliance with the stipulated noise criterion, noise
monitoring is not required during the construction phase.
4.7.2
Operational Phase
Given
the compliance with the stipulated noise criterion, noise monitoring is not required
during the operational phase.
No noise sensitive receivers will be affected by the construction
activities to be undertaken at the site.
Predicted construction noise levels at the NSR, range from 43 – 51
dB(A), are within the stipulated noise criteria. In view of the insignificant
construction noise impact, mitigation measures are not required during the
construction phase.
Due to the large separation distance (approximately 1
km) and the use of enclosure/cladding plus topography
and existing building structures at CPB located between the NSR and the Project, the predicted operational noise levels
are up to 35 dB(A), which are within the daytime and night-time noise
criteria. Further mitigation
measures are therefore not required during the operational phase.
In view of the
anticipated insignificant noise impact in both construction and operational
phases, noise monitoring is therefore considered not necessary.