This Section presents the assessment of
potential air quality impact associated with the demolition of the CCPP at the
GICP. Dust generating from the
construction activities would be the major air polluting concern during the
demolition of the CCPP.
In view of the
nature of the structures (mainly steel structure and equipment) and small scale
(pilot demonstration) of the CCPP and large separation distance from the identified
Air Sensitive Receivers (ASRs) (see Figure
3.4a), it is anticipated that with the implementation of the control
measures described in the Air Pollution Control (Construction Dust)
Regulation the potential dust impacts to the ASRs due to the demolition
works will be minimal and controlled within the relevant standards as
stipulated in Section 1 of Annex 4 of the Technical Memorandum on Environmental Impact
Assessment Process (EIAO-TM).
Hence, a quantitative air quality impact assessment will not be
required.
A site audit programme (see Section 3.7) will be
implemented during the demolition works to ensure that the control measures are
properly implemented.
3.2
Legislation Requirements and Evaluation Criteria
The principal
legislation for management of air quality in
Table 3.2a Hong
Kong Air Quality Objectives (µg m-3) (a)
|
Air Pollutant |
Averaging Time |
|||
|
|
1 Hour (b) |
24 Hour (c) |
3 Months (d) |
1 Year (d) |
|
Total Suspended Particulates (TSP) |
- |
260 |
- |
80 |
|
Respirable Suspended Particulates (RSP) (e) |
- |
180 |
- |
55 |
|
|
800 |
350 |
- |
80 |
|
Nitrogen Dioxide (NO2) |
300 |
150 |
- |
80 |
|
Carbon Monoxide (CO) |
30,000 |
- |
- |
- |
|
Photochemical Oxidants (as ozone (O3)) (f) |
240 |
- |
- |
- |
|
Lead (Pb) |
- |
- |
1.5 |
- |
|
Notes: (a)
Measured
at 298K (25°C) and 101.325 kPa (one
atmosphere) (b)
Not
to be exceeded more than three times per year (c)
Not
to be exceeded more than once per year (d)
Arithmetic
means (e)
Suspended
airborne particulates with a nominal aerodynamic diameter of 10 micrometres
or smaller (f)
Photochemical
oxidants are determined by measurement of ozone only |
||||
For
construction dust impact assessment, the EIAO-TM also stipulates
an hourly TSP criterion of 500 µg m-3.
The dust control measures set out in the Air Pollution Control (Construction Dust)
Regulation will be implemented to reduce dust impacts associated with the
demolition works.
3.3
Baseline
Conditions and Background Air Quality
The CCPP is located within the GICP which
is surrounded by the CLP Castle Peak Power Station and Shui
The existing air quality in the vicinity of
the CCPP is mainly contributed by the emissions from the adjacent industrial
premises (including the Castle
Peak Power Station, the operations of the GICP and Shui
There is currently
no Air Quality Monitoring Station (AQMS) operated by the EPD in the immediate
vicinity. The nearest EPD AQMS is
located in Tung Chung (TC), which is to the north of
3.4
Identification of
Air Sensitive Receivers
The Study Area
is generally defined by an area within 500m from the boundary of CCPP. ASRs within 500m from the CCPP boundary were
identified in line with the definition defined in the Annex 12 of the EIAO-TM. Their descriptions are
presented in Table 3.4a and the
locations are illustrated in Figure 3.4a. No residential dwellings (both existing
and planned) were identified within the Study Area.
Table 3.4a Identified Air
Sensitive Receivers
|
ASR |
Description |
Type of Uses |
Approximate Distance from CCPP Site Boundary (m) |
Approximate Maximum Height of Building above Ground (m) |
|
A1-1 |
|
Office |
210 |
3 |
|
A1-2 |
|
Office |
300 |
20 |
|
A2-1 |
Shui
|
Office |
180 |
10 |
|
A2-2 |
Shui |
Workshop |
145 |
6 |
|
A3 |
Permanent
Aviation Fuel Facility – |
Office |
410 |
6 |
|
A4 |
EcoPark |
Office |
560 |
6 |
|
A5-1 |
GICP - Site Office |
Office |
90 |
20 |
|
A5-2 |
GICP - Guard House |
Office |
160 |
6 |
The number of construction plant and
equipment (1 to 2 mobile cranes, and 1 to 2 backhoe (with pneumatic drill
mounted on the backhoe) used for the demolition works will be limited. Only a few dump trucks/lorries will be working
on site at any one time to remove the demolished concrete and scrap
metals. The air emissions from the
operation of these plant and equipment will be minimal. Besides, the additional road traffic
generated during the decommissioning of the CCPP will also be small (ie a maximum of 10 truck trips per day associated with the
disposal of C&D materials). It
is therefore anticipated that the operation of construction plant and equipment
on-site and additional road traffic generated during the decommissioning work
will not cause adverse air quality impact to the identified ASRs.
The demolition method is described in Section 2.3. GIC will implement good site practices
and dust control measures stipulated in the Air
Pollution Control (Construction Dust) Regulation (as listed in Section 3.6) throughout the demolition
works. According to the Hong
Kong Planning Standards and Guidelines (HKPSG), fugitive dust will be localised to an area within 100m
from the site boundary. With respect
to the nature of the demolition works (dismantling of the plant and equipment
using powered mechanical hand tools and
mobile cranes) and the small scale of the concrete structures (a small fire
services water tank and foundation block (to about 1.5m below ground)), the
demolition works will not cause adverse dust impact to the identified ASRs
which are located more than 90m from the CCPP site.
The chemical analysis of the Co-Combustion
residues contains very low concentration of heavy metals and extremely low
concentration (in part per trillion levels) of dioxins and furans (please refer
to Tables 5.5b, 5.5c, 5.5g and 5.5h for
the chemical analysis results). As
discussed in Section 2.3, the
proposed demolition method has carefully designed to minimise potential release
of residues during the dismantling and cleaning of the plant and
equipment. Together with
the implementation of effective control measures recommended in Section 3.6, the emissions of the
residues will be effectively controlled and hence the emissions of dioxins and
heavy metals during the
demolition and cleaning process will be minimal and will not cause air quality
impact to the vicinity.
The evaluation
of the potential air quality impacts during decommissioning works, particularly
how to control the emission of dust within the Co-Combustion unit are further
discussed in the following sections.
3.5.1
Dismantling and Demolition of Equipments
and Steel Structures
The materials recovery/recycling equipment
(including shredder, conveyor belts, picking station, magnetic separator, eddy
current separator, etc) in the MRRF building will be disassembled using powered
mechanical hand tools. No
significant dust and air emissions will be generated from this activity.
After removal
of the materials recovery equipment from the MRRF building, the MRRF will be
used as the cleaning workshop for the Co-Combustion unit. The cleaning workshop will be provided
with forced ventilation and maintained with a slight negative pressure during
the cleaning works. The exhaust air
will be cleaned with a High Efficiency Particulate Air (HEPA) filter prior to
discharge to the atmosphere.
Further details of the cleaning procedures are provided in Section 2.4.
The duct works of the secondary combustion
unit and the gas cooler will be dismantled by removal of the bolts or cutting
at the joints. The openings (both
ends of ducts) will be immediately sealed with 2 layers of fire retardant
polyethylene sheets to prevent escape of any dust from the duct. The sheets will be secured
with duct tapes. The capped equipment sections/pieces will be
lowered to ground level. Where
necessary, the sections may be cut into smaller size to facilitate cleaning and
transportation. The segments of
the equipment will be transported to the cleaning area within the MRRF
building. The internal wall of the ducts will be damped with
water spray and properly cleaned with wet cloths. The cleaning materials will be collected
and placed in sealed containers lined with plastic sheeting and disposed of at
a designated landfill.
The refractory bricks of the rotary kiln
will be removed before lifting the whole equipment down to the ground. The refractory bricks will be placed in
sealed bags and then in drum for disposal at a designated landfill. The internal lining of the secondary
combustion chamber will be damped down and properly cleaned with wet
cloths. The lining material will be
removed and placed together with the cleaning materials in sealed containers
lined with polyethylene sheeting and disposed of at a designated landfill. The cleaned steel frame of the equipment will then be
cut into manageable sections and sold to scrap metal recyclers.
The filter bags from the dust collector
will be removed in accordance with manufacturer’s instructions and placed in sealed bags or
containers for disposal. The metal
casing of the dust collector will be properly cleaning using the same
procedures for the duct works. The
cleaned dust collector will then be sold as scrap metal.
After the completion
of the cleaning of the Co-Combustion unit, the cleaning workshop will be
removed. The steel frame structure of the MRRF building will then demolished in accordance with the Code
of Practice for Demolition of Buildings and generally in the reverse order
to that of their construction. The
structures will be demolished progressively from top to bottom. The external non-loading bearing
cladding or any non-structural elements will be removed first. Crane and lifting gear will be used
where possible to support the structural beams and columns whist they are being
cut and lowered to the ground.
Air-powered wrenches, cutting torches, cranes and similar industrial
equipment will be used. The steel
beams and column will be cut to manageable size to facilitate
transportation. No significant dust
and air emissions will be generated from this activity.
With the implementation of the proposed
control measures, it is not
anticipated that the dismantling and demolition of equipments and steel structures
will cause adverse dust impacts to the identified ASRs. The release of dust from the
Co-Combustion unit will be minimal.
3.5.2
Dismantling of Concrete Structures
The concrete structures (fire services
water tank and pump house, concrete slab and foundation) will be sprayed with
water immediate prior to and regularly during the demolition works to control
potential of dust and air emissions. The broken concrete and
scrap metals will be placed in separate skips and removed off-site as soon as
practicable.
With the implementation of the proposed dust and air control measures, it is not anticipated that the demolition
of the concrete structures will cause adverse dust impacts to the identified
ASRs.
3.5.3
Backfilling of the CCPP Site with Soil
The CCPP Site will
be backfilled with imported clean soil
and restored into an open area. Due
to the relative small area of the CCPP site (about 4,000 m2) and the
volume of soil to be handled on site at any one time will be small, it is not anticipated that the minor earthworks will cause adverse dust impact to the identified
ASRs with the implementation of the dust control measures described in the Air
Pollution (Construction Dust) Regulation.
It is not anticipated that the demolition of
the CCPP will cause adverse air quality and dust impacts to the identified
ASRs. However, GIC will implement
the following good site practices and dust control measures stipulated in the Air Pollution Control (Construction Dust)
Regulation. Special care will
be taken when dismantling the Co-Combustion unit of the CCPP and removal of any residual dust
attached to the internal lining or surface of the equipment so that potential dust releases to the
atmosphere will be minimal.
·
The
engine of idling construction plant will be switched off;
·
Construction
plant will be regularly checked and maintenance to avoid emission of black
smoke;
·
Wheel
washing facilities will be provided at the exit of the CCPP Site;
·
Both
ends of the individual section of the duct works of the Co-Combustion unit will
be sealed with two layers of polyethylene sheet immediately after dismantle and
prior to lower down to the ground level;
·
Internal
lining or surface of the Co-Combustion unit (including duct works, and chambers
of the rotary kiln, secondary combustion unit, gas cooler, and dust collector)
will be damped down followed by wet wiping to remove any residual dust. Cleaning materials will be placed in
sealed containers and disposed of at a designated landfill by the EPD;
·
Filter
bags of dust collector will be removed in accordance with the manufacturer’s
procedures and placed in sealed bags/containers and disposed of with the
cleaning materials at a designated landfill;
·
The
concrete structures and slab will be damped down prior to and during the
demolition works to minimal dust generation;
·
Broken
concrete and scrap metals will be placed in separate skips. The skips storing broken concrete will
be covered with impervious sheet at the end of each working day and where
necessary during windy days; and
·
The
dropping height of the imported soil during material handling or will be
minimised as much as practicable to minimise dust generation.
3.7
Environmental
Monitoring and Audit
Due to the small scale of the demolition works,
it is not anticipated that the works will cause adverse air quality and dust
impacts to the identified ASRs. No dust monitoring will be required.
The cleaning of the Co-Combustion units
will be carried out in the enclosed cleaning workshop within the MRRF
building. The proposed cleaning
method will effectively control dust emission. The cleaning workshop will be provided
with forced ventilation and maintained a slight negative pressure, and the
exhaust air will be cleaned with a HEPA filter. As the cleaning activities will not
cause adverse dust impacts to the ASRs, no dust monitoring will be
required.
Regular environmental site audit will also
be conducted to ensure that recommended dust control measures are implemented
accordingly.
No residential dwellings (both existing
and planned) were identified within the Study area (ie
500m from the CCPP Site boundary). The nearest Air Sensitive Receiver (ASR)
is located at about 90m from the CCPP Site boundary.
The number of construction plant and
equipment to be used for the demolition works will be limited. Only a few dump trucks/lorries will be
working on site at any one time to remove the demolished concrete and scrap
metals. Air emissions from the
operation of these plant and equipment will be minimal and it is therefore not anticipated that it will cause adverse
air quality impact to the identified ASRs.
GIC will implement good site practices and
dust control measures stipulated in the Air
Pollution Control (Construction Dust) Regulation (as listed in Section 3.6) throughout the demolition
works. Special care will be taken
when dismantling the Co-Combustion unit of the CCPP and removal of any residual dust
attached to the internal lining or surface of the equipment so that the potential dust releases to
the atmosphere will be minimal.
With the implementation of the recommended
control measures described in the EIA and
those stipulated in the Air Pollution
Control (Construction Dust) Regulation, the potential air quality impacts
to the identified ASRs will be controlled within the relevant standards as
stipulated in Section 1 of Annex 4 of the EIAO-TM. No adverse air quality impact is
anticipated.