Table
of Contents
4.2 Statutory
Requirements and Evaluation Criteria
4.4 Study Area and
Identification of air Sensitive Receivers
4.5 Potential Sources
of Impacts
4.10 Environmental
Monitoring and Audit
This
Section presents an assessment of the
potential air quality impact arising from the construction and operation of the
desalination plant at Tseung Kwan O (TKO) Area
137. Dust is the key potential concern
during the construction phase. In
operational phase, potential concern is related to air and odour emissions from
desalination process. Representative air
sensitive receivers (ASRs) have been identified with control measures
recommended to minimise the potential impacts.
The
principal legislation for the management of air quality in Hong Kong is the Air Pollution Control Ordinance (APCO) (Cap 311). The APCO Amendment was passed in July 2013
and a set of new Air Quality Objectives (AQOs) has been effective from 1
January 2014. The new AQOs stipulate
statutory ambient limits for air pollutants and the maximum allowable number of
exceedances over specific averaging periods.
The new AQOs are presented in Table 4.1 and they were used as the evaluation
criteria for this assessment. As
stipulated in Annex 4 of the Technical Memorandum on Environmental Impact
Assessment Process (EIAO-TM), the
AQOs and other relevant standards established under the APCO should be met.
Table 4.1 Hong Kong Air Quality Objectives (mg m-3)
(a)
|
Air
Pollutant |
Averaging Time |
Concentration
(mgm-3) (a) |
No.
of Exceedances Allowed per Year |
|
Sulphur Dioxide (SO2) |
10 minute |
500 |
3 |
|
|
24-hours |
125 |
3 |
|
Respirable
Suspended Particulates (RSP) (b) |
24-hours |
100 |
9 |
|
Annual |
50 |
- |
|
|
Fine Suspended Particulates (FSP) (c) |
24-hours |
75 |
9 |
|
Annual |
35 |
- |
|
|
Nitrogen Dioxide (NO2) |
1-hour |
200 |
18 |
|
|
Annual |
40 |
- |
|
Ozone (O3) |
8-hours |
160 |
9 |
|
Carbon Monoxide (CO) |
1-hour |
30,000 |
- |
|
|
8-hours |
10,000 |
- |
|
Lead |
Annual |
0.5 |
- |
|
Notes: (a)
Measured at 293K and 101.325 kPa. (b)
Suspended particles in air with a
nominal aerodynamic diameter of 10 μm or less (c)
Suspended particles in air with a
nominal aerodynamic diameter of 2.5 μm or less |
|||
A
maximum hourly TSP level of 500 mg m-3
at ASRs is also stipulated in Annex 4
of the EIAO-TM to assess potential
construction dust impacts. The measures
stipulated in the Air Pollution Control
(Construction Dust) Regulation
should also be followed to ensure that any dust impacts are minimised.
Annex 4 of
the EIAO-TM also stipulates that any
predictive assessment of the odour impact should meet 5 odour units based on an
averaging time of 5 seconds.
The proposed site for the
desalination plant is located in the southeast of TKO Area 137 with a reserved
site area of about 10 hectares. TKO Area
137 is located to the south of the Southeast New Territories (SENT) Landfill
and the Tseung Kwan O Industrial Estate. TKO Area 137 Fill Bank is located to the west
of the proposed plant while SENT Landfill, the proposed SENT Landfill Extension
and the TKO Industrial Estate are located to the north of the proposed plant. Furthermore, as part of the Project, there is
a proposed fresh water main along Wan Po Road and Po Hong Road, connecting the
proposed desalination plant with the existing Tseung
Kwan O Fresh Water Primary Service Reservoir (TKOFWPSR). Therefore, the local air quality is
influenced mainly by dust emissions from TKO Area 137 Fill Bank and SENT
Landfill, vehicle emissions from nearby roads (i.e. Wan Po Road), and
industrial emissions from the Tseung Kwan O
Industrial Estate.
The
nearest EPD’s Air Quality Monitoring Station (AQMS) is located in Kwun Tong. The
latest 5 years annual averaged concentrations (2009 - 2013) of RSP, FSP, NO2
and SO2 recorded at this AQMS are presented in Table 4.2.
Table 4.2 Baseline Air Quality (a)
|
Air Pollutant |
Annual Averaged
Concentration (mg m-3) in the Recent 5 Years |
||||||
|
|
2013 |
2012 |
2011 |
2010 |
2009 |
5-year average |
Annual AQOs |
|
SO2 |
12 |
11 |
12 |
10 |
11 |
11 |
- (b) |
|
NO2 |
59 |
59 |
63 |
59 |
58 |
60 |
40 |
|
RSP |
52 |
43 |
49 |
47 |
48 |
48 |
50 |
|
FSP (c) |
33 |
28 |
-- |
-- |
-- |
31 (d) |
35 |
|
Notes: (a)
5
years annual average concentrations (2009 - 2013) of air pollutants measured
at EPD’s AQMS in Kwun Tong. (http://www.aqhi.gov.hk/en/download/air-quality-reportse469.html?showall=&start=1) (b) No annual
AQO for SO2 Concentration. (c) FSP
monitoring data at the EPD Kwun Tong AQMS are
publicly available since 2012. (d) It is the
average of two year averaged values. |
|||||||
The
aforementioned monitoring results are indicative of the prevailing baseline air
quality at the Site. The 5-year averages
of RSP and FSP concentrations in 2009 - 2013 are below their respective AQOs (ie 50mg m-3
and 35 mg m-3,
respectively), while the 5-year average of NO2 concentration (60 mg m-3)
has exceeded the AQO (i.e. 40 µg m-3).
In accordance with the EIA Study Brief Section 3.4.2.2 of the Project,
the Study Area for the air quality impact assessment is generally defined by a
distance of 500m from the boundary of the Project Site. Air Sensitive Receivers (ASRs) were identified
within the Study Area in accordance with Annex
12 of EIAO-TM. Latest Outline Zoning Plans (OZP), Outline
Development Plan (ODP) and relevant land use plans published by Lands
Department were also reviewed to identify future or committed ASRs. Representative ASRs have
been identified within the Study Area during construction and operation phases
of the Project and are summarised in Table 4.3. The Study Area and the identified representative ASRs are shown
in Figure
4.1.
Table 4.3 Identified Representative Air Sensitive
Receivers
|
ASR |
Description |
Type
of Use |
Approximate
Maximum Height |
Approximate
Separation Distance from the Nearest Pipe Works (m) |
Approximate
Separation Distance from the Nearest Plant Works (m) |
Construction
Phase |
Operational
Phase |
|
A1 |
Offices
at SENT Landfill Extension |
Office |
5 |
45 |
200 |
P |
P |
|
A2 |
Offices
at Existing SENT Landfill |
Office |
5 |
90 |
680 |
P |
|
|
A3 |
TVB
City |
Commercial |
50 |
45 |
1000 |
P |
|
|
A4 |
Apple
Daily |
Industrial |
20 |
35 |
1450 |
P |
|
|
A5 |
Next
Media Ltd. |
Office |
15 |
25 |
1700 |
P |
|
|
A6 |
LOHAS
Park – La Splendur |
Residential |
180 |
100 |
2750 |
P |
|
|
A7 |
The
Beaumount |
Residential |
114 |
175 |
3000 |
P |
|
|
A8 |
Shaw
Tseung Kwan O Film Studios |
Industrial |
20 |
80 |
3300 |
P |
|
|
A9 |
Creative
Secondary School |
Educational |
24 |
35 |
4250 |
P |
|
|
A10 |
Oscar
By the Sea |
Residential |
175 |
85 |
4320 |
P |
|
|
A11 |
Tseung Kwan O Plaza Tower 1 |
Residential |
135 |
20 |
4600 |
P |
|
|
A12 |
Beverly
Garden |
Residential |
120 |
45 |
4730 |
P |
|
|
A13 |
Kwong Ming Court |
Residential |
110 |
45 |
5000 |
P |
|
|
A14
|
Haven
of Hope Hospital |
Hospital |
18 |
100 |
5480 |
P |
|
|
A15 |
Po
Hong Park |
Recreational |
0 |
60 |
5800 |
P |
|
|
A16 |
Verbena
Heights |
Residential |
169 |
45 |
6060 |
P |
|
|
A17 |
Serenity
Garden |
Residential |
9 |
25 |
6320 |
P |
|
|
A18 |
Tseung Kwan O Village |
Residential |
9 |
25 |
6780 |
P |
|
|
A19 |
King
Ming Court |
Residential |
105 |
20 |
6600 |
P |
|
|
A20 |
School
of Continuing and Professional Studies of the Chinese University of Hong
Kong |
Educational |
24 |
20 |
6500 |
P |
|
The construction of the proposed
desalination plant, fresh water main and other associated works has the
potential to cause dust nuisance if not properly managed. Dust in terms of Total suspended particulates
(TSP), respirable suspended particulates (RSP) and
fine suspended particulates (FSP) are the key air pollutants during
construction.
The key construction
activities for the Project are listed below:
·
Construction of the desalination plant – foundation and
piling, building works, submarine intake and outfall, installation of electrical
and mechanical plant and equipment, testing and commissioning;
·
Natural slope mitigation works – construction of flexible
barrier and soil nailing at the toe of the rock slope and stabilisation
of natural slopes and boulders on the natural slope within the Clear Water Bay
Country Park;
·
All the associated civil, structural, geotechnical,
landscaping, electrical and mechanical works; and
·
Construction of trunk feed system.
The site for the Project
has been formed and no major earthworks or site formation works will be
required.
Soil excavation, materials
handling, truck movements on unpaved roads and wind erosion from open
stockpiling of dusty materials within the Project Site are identified to be the
potential dust generating activities.
Tentatively, the
construction of the Project will last for about 54 months and is scheduled to
commence in 2nd quarter of 2016.
The normal working hours will be between 07:00 and
19:00 hrs from Monday to Saturday (except public holidays).
No
gaseous emission is anticipated during the operation of the desalination
plant. However, there is potential
gaseous emission from the standby generator and potential odour
nuisance may be resulted from the transportation, storage and handling of
sludge produced during the desalination process.
Construction of the Desalination Plant, Slope Mitigation Works
within Clear Water Bay Country Park, Associated Civil Works
The construction of the desalination
plant, including slope mitigation works and other associated works, will take
approximately 39 months.
Hoarding will be erected around the
site prior to the commencement of the foundation work. Pile foundation with reinforced concrete pile
caps will be used for the foundations of the buildings. Reinforced concrete slab and raft foundation
will be built for the desalination plant.
The majority of excavation materials will be generated during piling works
and construction of the basement and concreting works. With reference to the detailed estimation on
the quantities of excavated materials generated during construction phase in Section 8.3.2, a total of about 183,720
m3 of excavated materials will be generated from the construction of
desalination plant. About 180,117 m3,
2,744m3 and 859m3 of the excavated materials will be
disposed of at fill bank as public fill, at landfill as construction waste, and
as marine sediments, respectively. The
nearest ASR – A1 is located about 200 m from the nearest works boundary of the
building construction works, therefore, the fugitive dust impact is minor.
Open onshore intake or submerged intake
and outfall pipes will also be constructed.
The location of the worksite is more than 700 m from the nearest ASR –
A1, therefore, the fugitive dust impact from the works are minor.
Construction of flexible barriers and
soil nailing at the toe of the natural slope within the Clear Water Bay Country
Park for slope mitigation works and other associated civil works will also be
carried out. These works will involve
very minor excavation works which are expected to result in 56 m3 of
excavated materials. About 55 m3
and 1 m3 of the excavated materials will be disposed of at fill bank
as public fill and at landfill as construction waste, respectively. The nearest worksite is about 250 m from the
nearest ASR – A1, therefore, very limited fugitive
dust emission is anticipated.
With the implementation of dust control
measures stipulated under the Air
Pollution Control (Construction Dust) Regulation and those recommended in Section 4.8.1, together with proper site
management and good housekeeping, no adverse fugitive dust emission is expected
from the construction works.
A concrete batching plant (CBP) with
production rate of about 30 m3 per hour is proposed to be erected on
site for concreting works of the desalination plant construction. As indicated in Figure 4.1, the proposed on-site concrete batching plant will be
located more than 500m away from the nearest existing ASR (i.e. A1) and hence
the impact arising from the operation of the CBP would be minimal. Should the total silo installed capacity of
the CBP exceeds 50 tonnes, a licence
under Air Pollution Control (Specified
Process) Regulation is required.
Construction of the Trunk Feed System
The trunk feed system
includes the construction of a 9 km long and 1,200 mm in diameter fresh water
main for the transfer of fresh water output from the desalination plant to the
existing TKOFWPSR. The laying of the
entire fresh water mains will be divided into 3 sections, Section A from
desalination plant to Shek Kok Road, Section B from Shek Kok Road to Po Shum Road, and Section C from Po Shun
Road to TKOFWPSR. The system also
consists of a new pumping station, a new treated water storage tank and the associated
pipeworks and ancillary facilities including
fittings/valves, leakage, flow and pressure monitoring facilities in the
proposed desalination plant. The
construction of the trunk feed system will be carried out for about 45 months. The fresh water main will be constructed in
small sections using open cut method and trenchless method using pipe
jacking. The open cut method involves
soil excavation works and backfilling, which may have the potential to cause fugitive
dust emissions, and negligible dust emissions are expected from the trenchless
method. As the fresh water main will be
constructed in small sections (ie, 40 m), the
excavated materials generated will be limited (42,733 m3) and
limited number of construction plant will be deployed for the works. With such a
small construction site and the implementation of dust control measures
recommended in Section 4.8.1 during
works, potential dust emissions from the
aforementioned works will be minimal and hence, no adverse dust impact on
nearby ASRs is anticipated.
A typical process of
desalination has been described in Section
3.5. By reviewing the desalination
process, no gaseous emission is anticipated.
It is understood that the sludge
produced is primarily chemical in nature and would cause limited odour emissions. The sludge produced in the desalination plant is similar to
sludge produced in water treatment works in Water Supplies Department, with
very low content in organic sulfate, hence the potential for odour (such as H2S) generation from biochemical
process is low. Forced ventilation
system with sufficient air change rate would be equipped at the sludge
treatment and storage building and the exhaust discharge should be directed
away from ASRs as far as practicable. In
accordance with the Waste Disposal
Ordinance (WDO), the chemical sludge produced will be thickened and
dewatered to 30% dry solids prior to disposal at the landfill. With the provision of ventilation system with
sufficient air change rate and proper handling and disposal of the chemical
sludge as discussed in Section 4.8.2,
no adverse odour nuisance to nearby ASRs is
envisaged. In addition, there is
considerable separation distance between the nearest ASR (i.e. A1) and the
sludge building, which is about 250m.
Hence, no adverse odour impact is anticipated.
A
standby generator will be provided and located at the southeast corner of the
proposed plant. As the standby generator
will only operate when CLP’s grid is suspended, the operating time of the
generator is very rare and adverse air quality impact caused by gaseous
emissions from the generator is not expected.
As mentioned in Section 3.8, potential concurrent projects
during the construction phase of the Project include Cross Bay Link (CBL), Tseung Kwan O – Lam Tin Tunnel and Associated Works (TKO –
LTT), Trunk Road T2, South East New Territories (SENT) Landfill Extension and
Fill Bank at TKO Area 137. TKO – LTT and
Trunk Road T2 are all more than 1.5 km and 4 km away from the nearest
construction site boundary and any cumulative impact from these projects is
considered negligible. CBL,
SENT Landfill Extension and Fill Bank at TKO Area 137 are located
within 500 m of the Project Site during construction. As discussed in Section 4.6.1, the construction work of this Project is minor and
dust mitigation measures and good site practices will be adopted, therefore, it
is anticipated that no adverse cumulative dust impact is expected.
Since CBL, TKO – LTT and
Trunk Road T2 are located more than 3 km away from the Project Site in
operation phase, the cumulative impact is not anticipated. It is understood that the existing Fill Bank
at TKO Area 137 will cease to operate after 2018. With the anticipated operation year of the
desalination plant after 2020, there will be no cumulative impact from Fill
Bank at TKO Area 137. The SENT Landfill
Extension is located within 500m of the Project Site. As discussed in Section 4.6.2, the chemical sludge produced in the desalination
plant will cause very limited odour emissions, if
any. Therefore, no adverse cumulative odour impact is anticipated during the operation phase of
the Project.
The
following dust control measures stipulated in the Air Pollution Control (Construction Dust) Regulations and good site
practices will be incorporated into the Contract Specifications and implemented
throughout the construction period:
·
Impervious
dust screen or sheeting will be provided to enclose scaffolding from the ground
floor level of building for construction of superstructure of the new
buildings;
·
Impervious
sheet will be provided for skip hoist for material transport;
·
The
area where dusty work takes place should be sprayed with water or a dust
suppression chemical immediately prior to, during and immediately after dusty
activities as far as practicable;
·
All
dusty materials should be sprayed with water or a dust suppression chemical
immediately prior to any loading, unloading or transfer operation;
·
Dropping
heights for excavated materials should be controlled to a practical height to
minimise the fugitive dust arising from unloading;
·
During transportation by truck, materials should not
be loaded to a level higher than the side and tail boards, and should be
dampened or covered before transport;
·
Wheel
washing device should be provided at the exits of the work sites. Immediately before leaving a construction
site, every vehicle shall be washed to remove any dusty material from its body
and wheels as far as practicable;
·
Road sections between vehicle-wash areas and vehicular
entrance will be paved;
·
Hoarding
of not less than 2.4m high from ground level will be provided along the length
of the Project Site boundary;
·
Haul
roads will be kept clear of dusty materials and will be sprayed with water so
as to maintain the entire road surface wet at all times;
·
Temporary
stockpiles of dusty materials will be either covered entirely by impervious
sheets or sprayed with water to maintain the entire surface wet all the time;
·
Stockpiles
of more than 20 bags of cement, dry pulverised fuel ash and dusty construction
materials will be covered entirely by impervious sheeting sheltered on top and
3-sides;
·
All
exposed areas will be kept wet always to minimise dust emission;
·
Ultra-low-sulphur
diesel (ULSD) will be used for all construction plant on-site, as defined as
diesel fuel containing not more than 0.005% sulphur by weight) as stipulated in
Environment, Transport and Works Bureau
Technical Circular (ETWB-TC(W)) No 19/2005 on Environmental Management on
Construction Sites;
·
The
engine of the construction equipment during idling will be switched off;
·
Concrete
batching plant will be required on site.
The control measures recommended in the Guidance Note on a Best Practicable Means for Cement Works (Concrete
Batching Plant) (BPM 3/2 (93)) will be implemented; and
·
Regular
maintenance of construction equipment deployed on-site will be conducted to
prevent black smoke emission.
Odour mitigation measures may be
implemented during the operation of the desalination plant. The treatment and storage of the chemical
sludge should be enclosed inside building structure. Forced ventilation system with sufficient air
change rate would be equipped at the sludge treatment and storage building and
the exhaust discharge should be directed away from ASRs as far as
practicable.
The chemical sludge
produced at the desalination plant should be removed off-site regularly to
avoid accumulation of potentially odourous materials
on site. Proper handling and
transportation of the dewatered sludge to landfill will be conducted to minimise odour nuisance to nearby
ASRs. Trucks transporting the dewatered
sludge to the landfill would be fully enclosed to minimise
any off-site odour impact during the transportation
process.
No
adverse residual impact is anticipated from the construction and operation of
the Project with the implementation of the recommended mitigation measures and
good construction site practices.
No adverse fugitive dust
impact is anticipated during the construction period, dust monitoring is
considered not necessary. However, it is
recommended to conduct regular environmental site audit, ie,
on weekly basis, to ensure the implementation of the dust control measures and
good site practices as recommended in Section
4.8.1 throughout the construction period.
No adverse air quality or odour impact is anticipated during the operation of the
desalination plant, therefore, no air quality or odour
monitoring is considered necessary.
Potential
dust generating activities, including excavation and filling, materials
handling, truck movements on unpaved roads and wind erosion of temporary
stockpile of dusty materials have the potential to cause adverse fugitive dust
impacts to the nearby ASRs if not properly managed. As the site has been formed, only minor
excavation from the foundation and piling works are required. No fugitive dust emission is anticipated from
the building construction and civil works.
The worksite of open onshore intake or submerged intake and outfall
pipes and also slope stabilization works are located more than 250 m from the
nearest ASR, therefore, fugitive dust emission is minor. With the implementation of the recommended
dust control measures and adoption of good construction site practices, no
adverse fugitive dust impact is anticipated.
The fresh water mains will be
laid in small sections using open-cut method and small-scale excavation works
will be required. Since the excavated
materials generated will be relatively small and the worksite is small, no
adverse fugitive dust impact is envisaged provided that the recommended dust
control measures are properly implemented.
No cumulative impact is anticipated during the construction phase of the
Project.
To
ensure proper implementation of the recommended dust mitigation measures and
good construction site practices during the construction phase, environmental
site audits on weekly basis is recommended throughout the construction
period.
By reviewing the process
flow, no gaseous emission during operation is anticipated. Potential
gaseous emission from the standby generator within the desalination plant is
infrequent and transient. Hence, no adverse
air quality impact is anticipated.
Sludge produced from the desalination process is chemical sludge and the
potential to cause odour nuisance is low. With the implementation of proper odour control measures and good management practices, no
adverse odour impact is anticipated during the
operation of the desalination plant. As
no adverse air quality or odour impact is anticipated
during the operation of the desalination plant, therefore, no air quality or odour monitoring is considered necessary.