In response to the Hong Kong SAR
Government’s initiative to develop bulk waste reduction facilities to tackle
Hong Kong’s waste disposal crisis, Green Island Cement Company Limited (the
Project Proponent) established a pilot demonstration waste-to-energy facility
(consisting of a Materials Recovery/Recycling Facility (MRRF) and a
Co-Combustion Plant) (hereafter this facility is referred to as the
Co-Combustion Pilot Plant (CCPP)) within the Green Island Cement Plant (GICP)
site at Tap Shek Kok, Tuen Mun (see Figure 1.1a).
The aims of the CCPP were to determine the
technical and economic issues associated with the operation of a MRRF as part of
an integrated waste management system; to demonstrate that the CCPP will meet
the requirements of the Guidance Note on the Best Practical Means for
Incinerators (Municipal Waste Incineration) (BPM 12/1 (08)) issued by the
Environmental Protection Department (EPD); and to obtain engineering data to
refine the design of the Co-Combustion Plant.
The construction and installation of the
CCPP was completed in February 2005 and commissioning tests were carried out in
April and July/August 2005 in order to demonstrate its performance. Continuous operation of the CCPP was started
in early October 2005. During the
operation period, the cumulative operating time of the facility was 11 weeks
and no more than 24 tonnes per day of Municipal Solid Waste (MSW) were treated. After achieving the research objectives, the
operation of pilot plant was stopped on 17 December 2005.
The decommissioning of such municipal
waste incinerator is classified as a Designated Project under Item 3 of Part II
Schedule 2 of the Environmental Impact
Assessment Ordinance (EIAO) and
hence the decommissioning of the CCPP (hereafter referred to the Project) is
classified as a DP and requires an Environmental Permit (EP) prior to the
decommissioning works.
A Project Profile (PP-315/2007) for the
decommissioning of the CCPP was submitted to EPD for application of an EIA
Study Brief under the EIAO and Study
Brief (ESB-164/2007) was issued on 7 June 2007 which sets out the scope of the
work for this EIA Study.
An Environmental Impact Assessment (EIA)
Study has been conducted to evaluate the potential environmental impacts due to
the Project in accordance with the EIA Study Brief and the guideline on
assessment methodology provided in the Technical
Memorandum on Environmental Impact Assessment Process (EIAO-TM). The overall objectives of the EIA Study are
to provide information on the nature and extent of potential environmental
impacts arising from the Project; to recommend appropriate mitigation measures
to control the potential environmental impacts so that it complies with the
requirements of the EIAO-TM, and to confirm the environmental acceptability of
the Project. Key environmental issues identified in the EIA Study
Brief include air quality, land contamination, water quality and waste
management implications.
The general approach for the assessment
includes a description of the baseline environmental conditions, identification
and evaluation of potential impacts and recommendations for mitigation measures
and establishment of the environmental monitoring and audit requirements. The assessments in this EIA Study are
conducted using well-proven and internationally accepted methods based on
reasonable worst-case conditions.
The pilot plant to co-combust MSW with cement
production was developed by the Green Island Cement Company Limited (GIC) in
collaboration with the Chemical Engineering Department of the Hong Kong
University of Science and Technology (HKUST).
The pilot demonstration was funded by the Innovation and Technology Fund
under the University-Industry Collaboration Programme.
Continuous operation of the plant was started in
early October 2005 and completed in December 2005. No more than 24 tonnes of MSW were treated
per day during the pilot demonstration of the CCPP. During the operation of pilot plant, the GIC
and HKUST obtained satisfactory results and sufficient design and operational
data on the Co-Combustion technology.
All MSW delivered to the site was treated and no MSW is currently stored
on-site. All the Co-Combustion residues
(including bottom ash and fly ash) were securely packed in labelled sealed bags
and stored in the covered waste reception hall of the MRRF building.
The pilot demonstration has fulfilled its objectives
and the CCPP was closed down on 17 December 2005. It is necessary to demolish the whole pilot
plant so that the Project Site could be released for the operation and future
development of the GICP.
The CCPP
has been decommissioned after the completion of the pilot demonstration. All structures and the associated foundation,
and plant and equipment will be dismantled, cleaned (where necessary) and
removed from the Project Site for reuse, recycled or disposal. The concrete slab of the Project Site will be
demolished and the site will be backfilled with a layer of imported clean
soil. The Project Site area will be
levelled and landscaped. Figure 2.2a shows the general layout plan of the CCPP. Figures 2.2b to 2.2d show the details of the plant
and equipment and structure to be demolished.
The
selection of preferred demolition/dismantling methods has made reference to the
common demolition methods in
The
main system and MRRF building of the CCPP are mainly made of steel while the
fire service water tank and pump house are made of concrete. In a view of small size of the CCPP, the best
option for dismantling the steel structures (eg the
For the small concrete structures of the fire service
water tank and pump house, the structure will be demolished by jack hammer,
pneumatic or hydraulic breaker.
The
overall sequence of demolition works is as follow:
·
Cordon
off the site and erection of hoarding;
·
Disconnect
the utilities (except for the power and water supplies to the fire services
pump room and water tank);
·
Dismantling
and removal of all plant and equipment inside the MRRF building;
·
Dismantling
and removal of the Co-Combustion unit;
·
Cleaning
of the Co-Combustion unit within the enclosed cleaning workshop inside the MRRF
building;
·
Demolition
of the steel structure of the MRRF building;
·
Demolition
of the fires services pump room and water tank;
·
Demolition
of the concrete slab and shallow footing foundation;
·
Backfilling
the site with clean soil;
·
Provision
of surface water drains at the site;
·
Landscaping
the Project site area.
The whole demolition process will be conducted in a safe
manner for the protection of the workers and to minimise occupational health
and safety hazards.
The duct works of the Co-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 within the duct. The sheets will be secured with duct
tapes. The capped equipment sections/pieces will be lowered
to ground level by crane and transported to the cleaning workshop for
cleaning.
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 disposed of at a designated landfill. The internal wall will be properly cleaned
with wet cloths or other suitable absorbents to remove the loose dust
deposits. The steel frame of the
equipment will then be cut into manageable sections and sold to scrap metal
recyclers.
The pumps and control panels of the fire
services system will be dismantled and sold.
All water in the water tank will be drained out. The concrete wall of the water tank and the pump
house will be demolished and removed by a pneumatic drill mounted backhoe. The concrete structures will be damped down
before and during the demolition works to control dust. The steel reinforcement will be recovered as
far as practicable for recycling. The
broken concrete will be disposed of at the public fill reception facilities. The load will be properly covered with
tarpaulin to minimise dust during transportation.
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 and removed. Most
of the plant and equipment are still in good serviceable conditions and will be
sold to other MRRF operators or second hand equipment vendors. After the completion of the cleaning works
(see Section 2.3) the MRRF building
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. This together with the metal claddings and
scrap metals from the MRRF equipment will be sold to the scrap metal recyclers.
After
all the machinery and equipment were removed, half of the MRRF building will be
converted into a cleaning workshop for cleaning works. The cleaning workshop will be provided with forced ventilation and a slight
negative pressure would be maintained within the cleaning workshop during the
cleaning works. The exhaust air from the cleaning workshop
will be cleaned using a High Efficiency
Particulate Air (HEPA) filter prior to discharge to the
atmosphere.
It
is expected that a small quantity of residues (e.g. fly ash, bottom ash) will
remain inside the Co-Combustion unit since the operation of the CCPP was
completed. All residues remaining in the
CCPP system will be removed by a vacuum cleaner with a HEPA filter. Any residues attached within the equipments will
be removed by a combined method of scraping and cleaning. The internal surfaces of the equipments will
be cleaned by wet wiping. To minimise
the exposure of residues, the workers will wear appropriate personal protection
equipment (including face mask, protective gloves, overcoat, and safety boots).
The
scraped lining material will be placed in sealed bags and disposed of at a
designated landfill. The filtered
materials, and cloths used for wet wiping will be packed in sealed bags and
disposal of at a designated landfill.
With proper precautionary measures and handling procedures in place,
contamination of steel structure of the MRRF is not anticipated.
After completion of the cleaning process of the
Co-Combustion equipment and removal of the equipment, the cleaning workshop
will be vacuum cleaned and wet
wiping. The cleaning materials will be
disposed of at designated landfill.
2.4
Project Planning
and Implementation
The
tentative programme for the demolition, cleaning and disposal works is shown in
Table 2.4a.
Table 2.4a Tentative
Programme for the Demolition, Cleaning and Disposal Works of CCPP
|
Tasks |
Tentative Date |
|
Issue of Environmental Permit by EPD |
June 2009 |
|
Issue of Buildings Department Permit |
July 2009 |
|
Demolition Works Tendering |
June 2009 |
|
Site Preparation for Demolition Works |
July 2009 |
|
Demolition and Cleaning |
August to December 2009 |
|
Disposal of Scrap Materials |
September to December 2009 |
|
Backfilling & Re-surfacing |
December 2009 |
|
Completion of Demolition and Decommissioning |
December 2009 |
The
environmental outcomes associated with the demolition and cleaning of the CCPP
have been assessed in the EIA Study. The
key findings and recommendations are summarised below.
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 and
it is therefore not anticipated that it will cause adverse air quality impact
to the identified Air Sensitive Receivers (ASRs).
The
additional road traffic generated during the decommissioning of the CCPP will
be small (i.e. a maximum of 10 truck trips per day associated with the disposal
of C&D materials). The potential air
quality impacts due to vehicular emissions are therefore, expected to be
minimal.
The Co-Combustion unit will be dismantled by
removal of the bolts or cutting at the joints.
The openings (both ends of ducts) will be immediately sealed with two
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. The segments
of the equipment will be transported to the cleaning workshop within the MRRF
building. 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 HEPA filter prior to discharge to
the atmosphere. The internal wall of the ducts and equipment will be
damped with water spray and properly cleaned with wet cloths. The potential dust/residues release to the
atmosphere due to the cleaning process will be minimal.
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. The proposed
demolition method has been carefully designed to minimise potential release of
residues during the dismantling and cleaning of the plant and equipment. With the implementation of control measures
recommended in EIA Report, the
emissions of the residues will be effectively controlled. The emissions of dioxins and heavy metals
associated with the residues will therefore be minimal and will not cause
adverse air quality impact to the identified ASRs.
After the completion of the cleaning of the
co-combustion unit, the cleaning workshop will be cleaned. The MRRF building will be
disassembled. 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 air emissions from the operation of these
plant and equipment will be minimal and no adverse air quality impact is
anticipated.
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 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.
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 and small volume of soil to be handled on site at any one time, 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 Control (Construction Dust) Regulation.
GIC
will implement good site practices and dust control measures stipulated in the Air Pollution Control (Construction Dust)
Regulation and the recommended mitigation measures presented in the EIA Report throughout the demolition and
cleaning works. With respect to the nature of the
works and the small scale of the concrete structures, the demolition and
cleaning works will not cause adverse air quality impact to the identified
ASRs.
The
assessment of land contamination sources and the potential impacts to sensitive
receptors were investigated in accordance with the EPD’s
Guidance Manual for Use of Risk-based
Remediation Goals (RBRGs) for Contaminated Land
Management (the RBRG Guidance Manual), the associated Guidance Note for Contaminated Land Assessment and Remediation, and
the EPD’s
Guidance Notes for Investigation and Remediation of Contaminated Sites of
Petrol Filling Stations, Boatyards, and Car Repair/Dismantling Workshop.
Site
appraisal comprising a site visit, and a review of background information and
land history in relation to possible land contamination was conducted. Potential sources of contamination and
associated impacts, risks or hazards are identified in the Contamination Assessment Plan.
Land contamination assessment was carried out and results presented in
the Contamination Assessment Report. The results of the site investigation works
determined that:
·
Total
petroleum hydrocarbon (TPH)/ benzene, toluene, ethyl benzene, and xylene (BTEX) were below the reported detection limits in
any of the soil samples collected;
·
Concentrations
of priority pollutant metals detected were well below the RBRG standards; and
·
Levels
of PCBs, dioxins and furans analysed in all samples were well below the RBRG
values.
Excavation
works proposed for the demolition works will be limited to the concrete
sub-structures and underground storage tank.
No soil excavation or groundwater extraction will be required for the
Project and hence no off-site disposal of soil and groundwater will be
required.
The
substructure areas of the Project Site will be filled using clean imported fill
materials and rehabilitated as green lawn and open area. The potential for human contact with any
underlying contamination in the future is considered low. As the result of the above, no potential
impact from the contaminated soil is anticipated.
The
Project Site’s future use remains industrial (manufacture of cement and cement
related products) and is surrounded by remaining areas of the GICP. It is considered that the only potential
receptors at risk might be site workers involved in decommissioning and
demolition works. As the contaminants
analysed were either not detected or with concentrations well below the RBRG guideline
values, the potential risk to the workers due to demolition activities will be
minimal.
3.4
Waste Management
Implications
The
decommissioning of the CCPP will generate a variety of wastes (including public
fill (about 1,806 m3), scrap metals (about 369 tonnes),
Co-Combustion residues (about 200 tonnes), refractory bricks and lining (about
345 tonnes), general refuse (about 9.1 kg d-1) and sewage (about 2.1
m3 d-1)) and recyclables (MRRF Equipment , unused
reagents, etc). The waste management
implications and environmental impacts associated with the handling, storage
and disposal of these wastes have been assessed.
The
public fill will be disposed of at the Tuen Mun Area 38 Fill Bank.
The
physical properties and chemical analysis results show that the characteristics
of the Co-Combustion residues are similar to those of the typical clinker raw
materials. The residues contain very
low levels of heavy metals and extremely low levels of (in the order of part
per trillion) dioxins and furans, which will not have adverse impacts on the
gaseous emissions and the cement plant.
The residues will be used as an alternative feedstock for the cement
clinker production.
With
the proposed loading rate of 0.5% w/w of the Co-Combustion residue to other raw
materials for cement clinker production, it will not adversely affect the
environmental performance of the cement plant.
It will take about 7 days for the cement plant to consume all the
residues. There is no concern of
long-term environmental impacts associated with the proposed residue reuse
option. This will avoid the disposal of
residues at landfill.
As a
last resort, the residues will be disposed of at a landfill designated by the
EPD. The Toxicity Characteristic
Leaching Procedure (TCLP) tests indicate that the concentrations of heavy
metals in the leachate arising from the residues are
well below the respective limits for landfill disposal. The residues can therefore be disposed of at
the designated landfill without further treatment. An advance agreement should be obtained from
the Landfill Authority (EPD) for the disposal of the residues at landfill.
The
refractory bricks and lining of the Co-Combustion unit and waste generated from
cleaning of the Co-Combustion unit will be placed in sealed polyethylene bags
and disposed of at a landfill designated by the EPD.
The
MRRF equipment is still in good serviceable condition and will be sold to other
MRRF operators or second hand equipment vendors. Scrap metals and unused reagents will be
recycled.
Due
the small scale of the CCPP, the quantities of public fill, chemical waste,
general refuse, sewage to be generated will be small. With the implementation of the recommended
mitigation measures in this EIA Report,
the handling and disposal of these wastes will not cause adverse environmental
and traffic impacts.
Clean surface runoff from the Project Site will be
diverted to the existing drainage system of the GICP which will lead to the on-site stormwater
detention pond. Suspended solids will be
settled out in the pond before discharging into the stormwater
drainage. No unacceptable impact
to water sensitive receivers is anticipated.
The cleaning works will be
carried out inside the cleaning workshop of the MRRF building. During the cleaning process, wet wiping and
vacuum cleaning will be used to clean the internal lining of the
ducting/equipment and remove the loose dust particles deposited on the surface
of the ducts and equipment. Water
flushing will not be used to clean the plant and equipment of the Co-Combustion
unit and hence the wastewater generated from the cleaning works will be
minimal. All
wastewater will be treated in the existing on-site wastewater treatment plant
(WWTP) of the GICP.
A small quantity of sewage
(about 2.1 m3 per
day)
will arise from the demolition workforce.
The existing toilet facility of the GICP will be available to the
construction workforce. The sewage will
be discharged to the on-site WWTP. No adverse impact water quality is anticipated
due to the treatment and disposal of sewage generated from the workforce.
With the implementation of
general good site practices, the demolition of CCPP will not cause adverse
water quality impact.
3.6
Environmental
Monitoring and Audit
No environmental monitoring for air quality and water
quality will be required.
Monthly site audits will be undertaken jointly by the site representative of
GIC and the contractor during the Project to ensure that dust control,
construction waste and site runoff and are managed in accordance with the good
site practices recommended in EIA Report.
An Implementation Schedule, containing the
recommended mitigation measures, monitoring and audit requirements, and the
implementation agent are presented in Annex
C of the EIA Report.
In
accordance with the EIA Study Brief
and the guidance in the EIAO-TM, the
EIA Study has identified and assessed potential environmental impacts
(including air quality, land contamination, waste management and water quality)
associated with the Project.
The
study concludes that with the implementation of the recommended environmental
control measures during the Project, no unacceptable environmental impacts are
envisaged.
Regular
site audits are recommended to ensure proper implementation of the recommended
mitigation measures.