1
Introduction
1.1
The
Organic Waste Treatment Facilities (OWTF) Phase I development (hereinafter
referred to as “the Project”) is to construct and operate a biological
treatment facility with a capacity of about 200 tonnes per day (tpd) at Siu Ho
Wan, North Lantau to convert source-separated organic waste into compost and
biogas through proven biological treatment technologies.
1.2
The
Project is a designated project under Item G.4 of Part 1, Schedule 2 of the
Environmental Impact Assessment Ordinance (EIAO) (Cap. 499): “A waste disposal facility (excluding any
refuse collection point), or waste disposal activities, for (a) refuse; or (b)
chemical, industrial or special wastes.” An environmental permit is required for
the implementation of the Project under the EIAO.
1.3
An
Environmental Impact Assessment (EIA) Study was undertaken in accordance with
the EIA Study Brief No.ESB-172/2007 issued by the Environmental Protection
Department (EPD) in December 2007.
The EIA Study was also conducted based on the reference design of the
OWTF Phase I development so as to provide information on the nature and extent
of environmental impacts arising from the construction and operation of the
Project and related activities that take place concurrently.
2
Project Description
Need of the
Project
2.1
The
Project is important, not only to mitigate landfill space depletion, but
because resources are conserved, and valuable products such as composts and
biogas (a renewable energy) can be generated. The compost could be used as organic
fertilizer for farming and horticulture.
The biogas, if employed to generate electricity, could meet the
electricity demand of some 2,000 households, thereby contributing to reduction
in use of fossil fuel and reduction in greenhouse gas emission. In addition, organic waste diversion
from landfills reduces leachate and landfill gas generation. The Project would positively contribute
to the Hong Kong SAR Government’s MSW Management Policy.
Location of the
Project
2.2
The
Project is proposed to be located in the Siu Ho Wan, North
Lantau. The total area of the proposed project site comprises a total
area of approximately 2 hectares with no nearby residential development. As shown in Figure 1,
infrastructure facilities such as refuse transfer station, sewage treatment
works, water treatment works and vehicle pound/vehicle examination and weigh
station are located in the vicinity of the proposed site.
Scale of the Project
2.3
The
Project site boundary is shown in Figure 2. Key elements of the proposed OWTF Phase
I development include:
·
Pre-treatment facilities – The collected
source-separated organic waste would be transported to the Project site by
enclosed waste vehicles. The
incoming waste would be delivered to the enclosed waste reception area and
pre-treated through a trommel screen, overhead magnets and shredder, etc.
·
Anaerobic digestion process – The pre-treated
material would be fed into the buffer tanks to start the hydrolysis stage of
the anaerobic digestion. The mixed
organic waste with high moisture content will be directed to the individual
vertical cylindrical digesters.
·
Post-treatment of digestate – After digestion,
the material from digesters would be pumped to dewatering facility and further
treated by tunnel composting. All
the post-treatment facilities would be located in an enclosed building with air
extraction system.
·
Energy recovery system – Cogeneration units
would be installed to convert the energy contained in the biogas to electricity
and heat. The biogas generated from the digesters would be firstly treated by a
biological desulphurization process and the treated biogas would be temporarily
stored in the gas buffer prior to feeding to the cogeneration units. A stand-by flare would be installed in
the Project site for emergency use only.
·
Air and wastewater treatment facilities – A
centralized air pollution control unit would be provided to treat the vented
air extracting from a number of operation units, including the pre-treatment
and post-treatment facilities. All
the wastewater generated from the Project would be properly treated by the
wastewater treatment unit.
Project Programme
2.4
The Project is planned to be
implemented through a Design, Build and Operate (DBO) contract arrangement. The construction of the Project is
scheduled for commencement in late 2011 for completion and commissioning in
early 2013.
Consideration of
Alternatives
Site Selection
2.5
The
following potential sites for the OWTF Phase I development were identified and
evaluated:
·
Sha Ling Livestock Waste Composting Plant,
Sheung Shui;
·
EcoPark Phase II, Tuen Mun;
·
Siu Ho Wan, North Lantau;
and
·
Tseung Kwan O (TKO) Area 137, Tseung Kwan O.
2.6
The
proposed site in Siu Ho Wan was considered as the most suitable site for the
OWTF Phase I development in consideration of the following advantages:
·
No nearby residential development was found and
the site is presently reserved for deployment as waste treatment facility and
thus the proposed development of OWTF is in line with the planning intention
for the site.
·
Infrastructure facilities such as sewage and
water treatment works, refuse transfer station, etc are found in the vicinity
of the site. These infrastructural facilities are considered as potential users
of the electricity generated from the Project.
·
The site is accessible via Cheung Tung Road and Sham Fung Road adjacent to the North Lantau Highway.
Technology Selection
2.7
A review
of international organic waste treatment practices was carried out. In consideration of the objectives and
scale of the Project, and the future development of waste management facilities
in Hong Kong, it was concluded that anaerobic
digestion (AD) was the most preferable option with the following merits:
·
Highly applicable for organic waste including
food waste;
·
Production of considerable amounts of energy
from waste;
·
Reduction in greenhouse gas emission; and
·
Good odour control.
3
Key Findings of the
Environmental Study
Air Quality
Construction Phase
3.1
Air quality impacts from the
construction works of the Project would mainly be related to construction dust
from excavation, materials handling, spoil removal and wind erosion. With the implementation of mitigation
measures specified in the Air Pollution Control (Construction Dust) Regulation
and good site practices, dust impacts on nearby air sensitive receivers would
be minimal.
Operation Phase
3.2
During the operation of the
OWTF, a centralized air pollution control unit would be used to remove air
pollutants, dust and odorous gas in the air extracted from the main buildings
of OWTF and the wastewater treatment unit.
The potential major sources of air quality impacts arising from the OWTF
would be the air emissions from the stacks of centralized air pollution control
unit and cogeneration units. Flaring emissions may be emitted if there is a
failure in the cogeneration units.
3.3
The air quality background
level for the operation year of the OWTF has been predicted using the PATH model
and has taken into account key pollution sources such as power stations,
aviation, marine traffic, vehicular traffic, industrial chimneys within HKSAR
as well as emissions within Pearl River Delta Economic Zone.
3.4
Modelling for air emissions
from the stacks of centralized air pollution control unit and cogeneration
units or standby flaring gas unit of OWTF, as well as vehicular emissions and
marine emissions within the study area has been undertaken and the results have
been combined with the air quality background levels. The predicted maximum hourly, daily and
annual average nitrogen dioxide (NO2) concentrations at the
representative air sensitive receivers (ASRs) would be 273, 145 and 53 µg/m3. The predicted maximum daily and annual
average respirable suspended particulates (RSP) concentrations at the
representative ASRs would be 123 and 47 µg/m3. The predicted hourly, daily and
annual sulphur dioxide (SO2) concentrations would be 379, 76 and 12
µg/m3. The predicted
cumulative air pollutants levels would comply with Air Quality Objectives.
3.5
Assessment has also been
conducted for potential odour impacts arising from the OWTF, taking into
account of cumulative odour impacts from North Lantau Refuse Transfer Station
and Siu Ho Wan Sewage Treatment Works.
The predicted cumulative odour concentrations at the representative ASRs
are in the range of 0.5 – 4.6 odour units based on an averaging time of 5
seconds and thus comply with the EIAO-TM criteria (i.e. 5 odour units based on
an averaging time of 5 seconds).
3.6
Commissioning tests would be
conducted for emissions from the stacks of the centralized air pollution
control unit, cogeneration units and standby flaring gas unit. During operation phase, stack monitoring
would be installed for the OWTF to ensure that the air emissions from the OWTF
will meet the design emission limits as well as EPD criteria. Odour patrol at the plant boundary is
also proposed to monitor any odour impact arising from the operation of the
OWTF. The predicted air quality
impact from the operation of the OWTF would be insignificant.
Hazard to Life
3.7
A hazard
assessment has been carried out to evaluate the risk to construction workers
and operational staff of the OWTF due to the transport, storage and use of
chlorine associated with the operations at Siu Ho Wan Water Treatment Works
(SHWWTW).
3.8
Hazardous
scenarios associated with the operations at SHWWTW have been identified and
assessed in this study. Hazardous events for biogas storage have been
investigated through consequence analysis. These hazardous events would not
escalate to additional chlorine release scenario at SHWWTW. Thus, no hazardous scenario associated
with the operations at SHWWTW due to impact from biogas storage is found.
3.9
A
quantitative risk assessment has been conducted to determine the impact of the
identified hazardous scenarios on the surrounding population during
construction and operation phases of the OWTF in terms of individual and
societal risks. Individual risk at
the Project site is found to be at the order of 1E-06 per year which is
acceptable in comparison with the criteria (1E-05 per year) in the Risk
Guidelines. Both individual and
societal risks comply with the risk guidelines stipulated in Annexes 4 and 22
of the Environmental Impact Assessment Ordinance Technical Memorandum
(EIAO-TM).
3.10
An As Low
As Reasonably Practicable (ALARP) assessment has been carried out by
identifying all practicable mitigation measures and assessing the cost
effectiveness of each measure in terms of the risk reduction achieved and the
cost of implementing the measures. Societal risk curves for both construction
and operation phases with the implementation of the proposed mitigation
measures are indicated in Figure 3. The results
show compliance with the ALARP principles and the Risk Guidelines (EIAO-TM
Annex 4) provided recommendations are implemented.
Water Quality
3.11
Potential sources of water
quality impact associated with the construction of the Project would be site
run-off, sewerage effluent from the workforce, accidental spillage and
discharge of wastewater from various construction activities. With the implementation of recommended
mitigation measures and good site practices, water quality impacts from the
land-based construction works can be controlled to comply with the Water
Pollution Control Ordinance (WPCO) standards. No adverse water quality impacts would
be expected during the construction phase of the Project.
3.12
The operation of OWTF is to
convert organic waste into compost and biogas. All sewage or wastewater generated from
the operation of the Project will be adequately treated in the on-site
wastewater treatment plant before reused on-site or discharged to the public
sewerage system. Wastewater to be
discharged to the public sewerage will comply with the Technical Memorandum on
Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland
and Coastal Waters (TM-DSS) under WPCO. No adverse water quality impacts would
be anticipated.
Waste Management
3.13
Waste
types to be generated during the construction of the Project would likely
include excavated material, construction and demolition materials, chemical
waste and general refuse. Waste
sorting from pre-treatment process, chemical waste and general refuse are
expected to be the major types of waste arising from the operation of the OWTF.
3.14
With
effective implementation of good practices and mitigation measures, it is
anticipated that the impacts on the environment and the potential impacts on
the capacity of waste collection, transfer and disposal facilities will be
insignificant during both construction and operation phases of the Project.
3.15
Limited
amount of chemicals or chemical wastes would be used or generated for the
operation of the OWTF. With proper implementation of the recommended
practices and response procedures for contamination prevention, the potential
for contamination due to the OWTF operation is expected to be minimal.
Landscape and
Visual
3.16
A landscape and visual impact
assessment has been carried out in accordance to the criteria and guidelines as
stipulated in Annexes 10 and 18 of EIAO-TM and EIAO Guidance Note No.8/2002.
3.17
Three
landscape resources and seven landscape character areas were identified within 500m radius area from the OWTF site.
The impact to these landscape resources and landscape character areas would be
insubstantial or slight, except for the tree covered hill slope located at the
east and north-east of the OWTF site. For the visual impact, fifteen
visual sensitive receivers (VSRs) were identified within the Zone of Visual
Influence (ZVI). Most of these VSRs have low sensitivity, and the
magnitude of impact to them would be negligible or small. Only the visual
impact to the site staff in Siu Ho Wan Water Treatment Works, passengers on North Lantau Highway
and hikers in Lantau North (Extension) Country Park
would be moderate.
3.18
To mitigate the potential
landscape and visual impacts associated with the construction of the Project,
it is recommended that topsoil should be stripped and stored for re-use in the
construction of the soft landscape works; compensatory tree planting should be
provided to compensate for felled trees; night-time lighting should be
controlled; and decorative screen hoarding should be erected. With the implementation of these
mitigation measures, no adverse landscape and visual impacts would be expected
during the construction phase of the Project.
3.19
During the operation of the
OWTF Phase I development, with the implementation of the proposed mitigation
measures shown in Figures 4a and 4b, such as aesthetic
design of the proposed OWTF matching with adjacent landscape setting of the
site, green roofing, tree planting along the site boundary to provide
screening, the Project will not only be complimentary to the existing
neighbours and surrounding areas, but will also be Beneficial as it will
provide the much needed visual relief to offset and alleviate much of the
existing negative elements within the Study Area. In addition, it will also greatly
improve and increase the value of the existing landscape character.
3.20
Overall, it is considered that
the residual landscape and visual impacts of the proposed OWTF development
would be acceptable with mitigation measures during construction phase and
beneficial during operation phases.
Noise
3.21
No existing or planned
sensitive receivers were identified within 300m from the Project boundary. The Discovery Bay, located at the distance of over 1km away from the Project site, was
identified as the nearest existing noise sensitive receiver (Figure 5). Since the nearest noise sensitive
receiver is located considerably distant from the Project and is substantially
screened by natural terrain, the noise impact caused by the Project itself and
any cumulative noise impact associated with
the Project is thus considered insignificant.
Environmental
Monitoring and Audit
3.22
Environmental
monitoring and audit (EM&A) requirements for the Project have been
specified in an EM&A Manual.
The EM&A Manual contains details of proposed baseline and compliance
monitoring programme, implementation schedule of the environmental protection /
mitigation measures, EM&A reporting procedures and compliant handling
procedures.
4
Conclusion
4.1
The EIA
Study has determined the likely nature and extent of environmental impacts
predicted to arise from the Project. Where necessary and practicable, the EIA
Study has specified mitigation and control measures to reduce the environmental
impacts to acceptable levels.
4.2
With the
recommended mitigation measures applied, the Project would be environmentally
acceptable and no unacceptable residual impacts are anticipated. The schedule of implementation of the
recommended mitigation measures has been provided in the EIA report. Monitoring requirements have also been
specified in a separate EM&A Manual to ensure proper implementation of the
recommended mitigation measures.
