7.1.1
This section identifies the waste
arising from the construction and operation of the Peng Chau STW Upgrade and
assesses the potential environmental impacts associated with the handling and
disposal of the waste. The options for reuse, minimisation, recycling,
treatment, storage, collection, transport and disposal of wastes arising from
the Project have been examined. Where appropriate, procedures for waste
reduction and management are considered and environmental control measures for
avoiding and minimising the potential impacts are recommended.
7.2
Relevant Legislation, Policies, Plans,
Standard and Criteria
Legislation
7.2.1
The legislation on handling, treatment
and disposal of wastes, which are of relevant to this Project, are:
o
Waste Disposal Ordinance (Cap. 354)
& relevant regulations:
o
Environmental Impact Assessment
Ordinance (Cap. 499);
o
Public Health and Municipal Services
Ordinance (Cap. 132); and
o
Dumping at Sea Ordinance (1995).
7.2.2
The Waste Disposal Ordinance (WDO)
(Cap 354) enacted in 1980 provides the statutory framework for the management
of all wastes from where they arise to the point of final disposal i.e. control
on the collection, treatment and disposal of waste. The WDO prohibits any
person from using any land or premises for the disposal of wastes unless the
person has been authorised by or has obtained a license from the waste disposal
authority. The ordinance was amended in early 1995 to enable a permit control
on import and export of wastes in line with the requirements under the Basel
Convention, and was in place in September 1996. The ordinance was further
amended in early 1997 to enable more effective implementation of waste disposal
charging.
7.2.3
There are a number of provisions under
the WDO for dealing with certain types of waste. This include the Waste
Disposal (Chemical Waste) (General) Regulation (Cap. 354) (CWR). This
Cradle–to-grave control of chemical wastes was implemented in May 1993 to
control all aspects of chemical waste disposal, including packaging, labelling,
storage, collection, transport, treatment and final disposal. Under the CWR,
any person who produces or causes to produce chemical waste must register with
the Environmental Protection Department (EPD). Each registered producer has the
obligation to inform the EPD as soon as practicable of any change in the
particulars of the registration. The CWR requires wastes producers to arrange
for proper disposal of their wastes at licensed facilities and to engage a
licensed collector to remove and transport the waste. It also requires that all
chemical waste must be properly stored, packaged and labelled.
7.2.4
The Environmental Impact Assessment
Ordinance (EIAO) came into operation in April 1998. Designated Projects
specified under Schedule 2 of the EIAO must follow the statutory EIA process
and apply for environmental permits for their construction and operation. Annex
7 of the Technical Memorandum on Environmental Impact Assessment Process
(TM-EIAP) under the EIAO specifies the assessment criteria for evaluating waste
management implications. The guidelines for assessment are provided in Annex
15.
7.2.5
Public Health and Municipal Services Ordinance
aprovides
for the control of the discharge of hazardous materials to sewers, and for the
control of littering. It also places restrictions on the storage of wastes in
buildings. This may be applicable to construction site offices.
7.2.6
The Dumping at Sea Ordinance empowers
the Director of Environmental Protection to control the disposal and
incineration of substances and articles at sea for the protection of the marine
environment. Under the Ordinance, a permit from the DEP is required for the
disposal of regulated substances within and outside the waters of the HK SAR.
The permit contains terms an conditions that includes the following
specifications:
o
Type and quantity of substances to be
dumped;
o
Location of the disposal grounds;
o
Requirement of equipment for
monitoring the disposal operations; and
o
The need for environmental monitoring.
Other Waste Handling &
Disposal Guidelines
7.2.7
A Waste Reduction Framework Plan
(WTFP) was launched in November 1998. The WRFP sets out programme to avoid and
minimise waste; promote recovery, recycling and reuse of materials; prolong to
life of existing landfills and reduce the increasing costs of waste transportation,
treatment and disposal. The WRFP also contains suggestions on how different
sectors can incorporate various waste reduction measures into their business
practices.
7.2.8
The Works Branch Technical Circular
No. 2/93 – Public Dumps and the Works Bureau Technical Circular No. 2/93B –
Public Filling Facilities outlines the policy relating to dumping of inert
construction and demolition (C&D) material. The circulars state the C&D
material suitable for use as fill material should not be disposed of to landfills,
but should be reused in public filling area or reclamation and land formation
projects. The Public Fill Committee together with Project Departments are
responsible for considering the suitability of a site as a public filling area.
In order to dispose of the inert portion of C&D material in a public
filling area, a license issued by the Civil Engineering Department is required.
7.2.9
The Environment, Transport and Works Bureau
Technical Circular (Works) No. 15/98 2003 – Waste Management
on Construction Sites outlines the requirement of demolitions works for on-site
sorting of all C&D material prior to disposal. This circular states a
particular specification clause to be included in the tender documents for
mandatory on-site sorting, processing and disposal of the same.
7.2.10 The Works Bureau Technical Circular No. /99 and No. 5/99A21/2002 – Trip-ticket
System for Disposal of Construction and Demolition Material promulgates the
policy to implement a trip-ticket system in Public Works Programme (PWP)
contracts for the proper disposal of C&D material at public filling
facilities or landfills.
7.2.11 The Environment,
Transport and Works Bureau Technical Circular (Works) No. 29/200015/2003 – Waste
Management on Construction Sites introduces the requirement for contractors to
prepare and implement a waste management plant (WMP). The requirement shall be
included in all PWP contracts (including design and build contracts but
excluding term contracts administered by Electrical and Mechanical Services
Department).
7.2.12 The following guidelines should also be observed:
o
Works Bureau Technical Circular No.
4/98 and No. 4/98A – Use of Public Fill in Reclamation & Earth Filling
Projects
o
Works Bureau Technical Circular No.
19/99
2001 –
Metallic Site Hoardings and Signboards
o
Works Bureau Technical Circular No.
12/2000 – Fill Management
General Site Wastes
7.3.1
Materials and equipment used on site
would produce packaging and container wastes. Mitigation measures should
include provision of a collection area where waste can be stored and loaded
prior to removal from the site. The volume of general site wastes generated
will be dependent on the Contractor’s operating procedure and practices and
cannot be quantified. With the implementation of the recommended mitigation
measures in Section 7.6 (including site practices), the potential environmental
impacts resulting from the storage, handling and transportation of general site
wastes would be minimal.
Workforce Wastes
7.3.2
Throughout construction, the workforce
would generate general refuse, comprising food scraps, paper, empty containers
etc. Rapid and effective collection of site wastes will be required to prevent
waste materials being blown around by wind, flushed or leached into the
environment, and odour nuisance. The amount of general refuse which is likely
to arise cannot be quantified at this time as it will be largely dependent on
the size of the workforce employed by the contractor. Though with the
implementation of waste management practices at the site (as recommended in
Section 7.6), it is not expected that there would be any adverse environmental
impacts arise from the storage, handling and transportation of workforce
wastes.
Maintenance and Chemical
Wastes
7.3.3
Construction plant and equipment will
require regular maintenance and servicing, which would generate waste.
Substances generated are likely to include some chemical wastes such as
cleaning fluids, solvents, lubrication oil and fuel. Equipment maintenance
activities would also involve the use of a variety of chemicals, oil and
lubricants, including heavy-duty cleaners, organic solvents, degreasers, brake
fluids, battery acid and soldering fluids.
7.3.4
Chemical wastes arising during the
construction phase may pose serious environmental, health and safety hazards if
not stored and disposed of in an appropriate manner as outlined in the Chemical
Waste Regulations (CWR). These hazards include:
(a) Toxic
effects to workers;
(b) Adverse impacts from spills on water gathering ground and other
ecological sensitive areas; and
(c) Fire hazards.
7.3.5
It is required to register as a
chemical waste producer if chemical wastes would be produced from the
construction activities. The Waste Disposal Ordinance (Cap 354) and its
subsidiary regulations in particular the Waste Disposal (Chemical Waste)
(General) Regulation should be observed and complied with for control of
chemical wastes.
7.3.6
Materials classified as chemical
wastes will need special handling and storage arrangements before removal for
appropriate treatment at the chemical waste treatment facility (CWTF) at Tsing
Yi. Wherever possible opportunities should be taken to reuse and recycle
materials. Mitigation and control requirements for chemical waste are provided
in Section 7.5. Provided that the handling, storage and disposal of chemical
wastes are in accordance with these requirements, adverse environmental impacts
should not result.
Construction and
Demolition (C&D) Material
7.3.7
The construction activities including
site formation and foundation works at the proposed Peng Chau STW Upgrade,
would generate construction and demolition material. An initial estimate of the
total volume of excavated material likely to be generated from the construction
works is given in Table 7-1.
Table 7-1 Types
and Quantities of Construction Waste
|
Categories
|
Estimated
Spoil Quantities –Mainlaying (m3)
|
Estimated
Spoil Quantities –Existing Structures Demolition and Site Formation
Activities (m3)
|
|
Generation
|
Insignificant
|
7,000
|
|
Reused Onsite
|
Insignificant
|
500
|
|
Reused in Public Filling Area
|
Insignificant
|
6,500
|
|
Disposal of at Landfill
|
Insignificant
|
Insignificant
|
7.3.8
The mainlaying construction activity
is scheduled from early 2005 while major structure demolition and site
formation activities are scheduled in 2005/2006. Given the relatively small scale of construction, the
quantities of C&D waste generated is not large. Inert C&D materials
should be disposed of at public filling area, such as Penny Bay Reclamation,
Central Reclamation or other CED designated public filling facilities.
Nevertheless, on-site sorting of all C&D materials should be provided prior
to disposal. Non-inert portion of C&D materials (i.e. C&D wastes) that
cannot be reused or recycled should be disposed of to designated landfill
sites.
7.3.9
The Contractor should be responsible
for ensuring that waste is collected by approved licensed waste collectors and
that appropriate measures are taken to minimise adverse impacts, such as dust
generation. The Contractor must also ensure that all necessary waste disposal
permits are obtained. The requirements stipulated in WBTC 5/99 and 5/99A21/2002 should be
followed closely.
7.3.10 No potential hazard is associated with handling and disposal of
excavated spoil. The excavated spoil will be tipped to spoil banks within the
construction site temporary before removal to disposal sites.
7.3.11 On completion of the construction works, site buildings and
facilities will be demolished and removed from site. Demobilisation of
infrastructure and site clearance will generate C&D material and scrap
material residues which will require disposal. Certain elements may need to be
disposed to landfill or public filling areas. However, recyclable materials
should be salvaged for reuse (such as wood and metal) and inert waste utilised
as public fill.
Marine Dredging for
Submarine Outfall
7.3.12 Dredged marine mud will be produced from the construction of
submarine outfall components. As
reviewed in Chapter 6 that the marine sediment quality in the surrounding Peng
Chau and Tai Lei Island is classified as Category L. Based on the current design, the estimated volume
of dredged material for marine disposal is about 22,000m3. As
the proposed dredged volume is less than 50,000m3, a dumping permit
would be required from the Territory Control Group (TCG) of EPD under the
Dumping at Sea Ordinance.
7.4
waste generated during operation phase
Sludge
7.4.1
Sludge will be produced from the
primary and secondary biological treatment of the sewage. Two arrangements of
sludge dewatering and disposal, namely sludge export scheme and onsite drying
bed dewatering scheme would be adopted (seeAppendix 2C). Sludge export scheme
would involve transporting of wet digested sludge at about 3-5% solids to other
designated sewage treatment works for centralised dewatering and disposal. The
wet sludge would be stored on site temporary and would be barged for further
treatment at regular intervals to prevent any excessive odour emission. The
estimated production of wet sludge is approximately 9.5m3/day. The
storage container would be covered to minimise the potential odour nuisance.
Sludge drying bed would be used as standby sludge dewatering device in the case
when sludge export is not feasible in the initial stage of STW Upgrade
operation.
7.4.2
Sludge
export scheme would become less cost effective when higher volume of sludge
would need to be barged away. In addition, this scheme would also be
constrained by the treatment capacity of the designated centralised dewatering
facility. In view of the above, DSD may consider switching the sludge export
scheme to on-site sludge drying bed scheme as the duty dewatering facility. Sludge drying bed is capable for sludge dewatering to a 30% dry
solid content. The estimated volume of dewatered sludge, based on the design
flow, would be approximately 1.0m3/day. The dewatered sludge would
be collected and stored on site before sea-transport to the designated landfill
site (via the nearby refuse transfer station) for disposal. Same as sludge
export scheme, the storage container would be covered to minimise the potential
odour nuisance.
Chemical Waste
7.4.3
If
wet scrubber system is used for odour control, it will generate chemical
wastes. Spent scrubber fluids may
contain undesirable chemicals or extreme pH, which may be classified as
chemical under Schedule 1 of the CWR, depending on the concentrations of the
fluid. Unless the spent fluids are
treated to meet discharge standards as stipulated in the Technical Memorandum
under Water Pollution Control Ordinance, they should not be discharged. These materials will need special
handling and storage arrangements before removal for appropriate disposal or
treatment, which should follow the requirements under the CWR. Due to relatively small scale of the
proposed Project, the Chemical wastes to be produced are anticipated to be
insignificant.
Other Operational Wastes
7.4.4
Small amounts of domestic waste may be
generated from site management offices, and chemical waste from equipment
maintenance. Improper storage of domestic waste onsite can give rise to adverse
environmental impact such as odour nuisance, vermin and pests, water quality
impacts, and adverse visual impacts. If proper handling and disposal measures,
as mentioned in the Section 7.5, are undertaken, no adverse impact is
envisaged.
7.5
Mitigation Measures
Construction Phase
7.5.1
A proper Waste Management Plan (WMP)
should be submitted to the Engineer for approval and implemented. The potential
for recycling or reuse should be explored and opportunities taken if waste
generation is unavoidable. The WMP
should provide recommendations for appropriate disposal routes if waste can not
be recycled. The WMP should include the method statement for stockpiling and
transportation of the excavated materials and other construction wastes. The
WMP should be approved before the commencement of construction. All mitigation
measures arising from the approved WMP should be fully implemented.
Waste Reduction Measures
7.5.2
Good management and control can
prevent the generation of significant amount of waste. Waste reduction is best
achieved at the planning and design stage, as well as by ensuring the
implementation of good site practices. Recommendations to achieve waste reduction
are as follows:
Planning and Design Stage
o
Excavated material to be generated
from construction works to be re-used on-site as far as practicable to reduce
off-site disposal.
Construction Stage
o
Segregation and storage of different
types of waste in different containers, skips or stockpiles to enhance reuse or
recycling of materials and their proper disposal;
o
To encourage collection of aluminium
cans by individuals collectors, separate labelled bins should be provided to
segregate this waste from other general refuse generated by the workforce;
o
Any unused chemicals or those with
remaining functional capacity should be recycled;
o
Prior to disposal of C&D waste, it
is recommended that wood, steel and other metals be separated for re-use and/or
recycling and inert waste utilised as fill material to minimise the quantify of
waste to be disposed of to landfill;
o
Proper storage and site practices to
minimise the potential for damage or contamination of construction materials;
and
o
Plan and stock construction materials
carefully to minimise amount of waste generated and avoid unnecessary
generation of waste.
Good
Site Practices
7.5.3
Minimisation of waste generation can
also be achieved by good site practices, which include:
(a) Nominating an approved personnel, such as a site manager, to be
responsible for good site practices, and arrangements for collection and
effective disposal to an appropriate facility of all wastes generated at the
site;
(b) Training of site personnel in proper waste management and chemical
handling procedures;
(c) Provision of sufficient trash bins and regular collection for
disposal;
(d) Implementing of appropriate measures to minimise windblown litter
and dust during transportation of waste by either covering trucks or by
transporting wastes in enclosed containers;
(e) Separating chemical wastes for special handling and appropriate
treatment at the Chemical Waste Treatment Facility;
(f)
Adopting regular cleaning and
maintenance programme for the drainage systems, silt traps, sumps and oil
interceptors;
(g) Bookkeeping of the amount of wastes generated, recycled and disposed
(including the disposal sites);
(h) Re-using of excavated material and C&D materials on-site as far
as practicable to reduce off-site disposal;
(i)
Using of non-timber formwork to reduce the amount of C&D
materials;
(j)
Recycling of any unused chemicals or
those with remaining functional capacity;
(k) Storing and sorting of different types of waste in different
containers, skips stockpiles to facilitate reuse or recycling of waste
materials and their proper disposal; and
(l)
Minimising the potential for damage or
contamination of construction materials by proper storage and site
practice.
7.5.4
In addition to the above good site
practices and waste reduction measures, specific mitigation measures are
recommended below for the identified waste arising to minimise environmental
impacts during the handling, transportation and disposal of these wastes.
General Site Wastes
7.5.5
A collection area should be provided
where waste can be stored and loaded prior to removal from site. An enclosed and
covered area is preferred to reduce the occurrence of 'wind blown' light
material. If an open area is unavoidable for the storage or loading/unloading
of wastes, then the area should be bunded and all the polluted surface run-off
collected within this area should be diverted into wastewater treatment system.
Maintenance and Chemical Wastes
7.5.6
After use, chemical wastes (e.g.
cleaning fluids, solvents, lubrication oil and fuel) should be handled
according to the Code of Practice on the Packaging, Labelling and Storage of
Chemical Wastes. Spent chemicals should be stored and collected by an approved
operator for disposal at the Chemical Waste Treatment Facility or other
licensed facility in accordance with the Chemical Waste (General) Regulation.
The Contractor should register as chemical waste producer if chemical waste is
produced.
C&D Material
7.5.7
Stockpiles of C&D material should
be covered to minimise run-off during heavy rainstorms and should be located to
minimise visual impacts and nuisance related to noise and dust. Appropriate
haul routes should be designated. Elevated levels of suspended solids in
surface water should be prevented through appropriate bunding, interceptors,
and direction of run-off into settling ponds.
C&D material should be separated on-site into three categories:
o
Inert portion of the C&D material
(e.g. concrete and rubble), which should be re-used as much as possible or
disposed of at designated public filling area.
o
Non-inert potion of the C&D
material (e.g. steel and other metals wood, glass and plastic), which is to be
recycled as much as possible.
o
Waste that can not be re-used or
recycled and should be disposed of at strategic landfills.
Dredged Marine Mud
7.5.8
Mitigation measures for handling,
transporting and disposal of the dredged marine mud is provided in Chapter 6.
The location of open sea disposal is to be recommended by the TCG on the
dumping permits to be issued. A marine mud transportation route will be
designed based on the dumping location. It is recommended that the Contractor
should avoid passing through the Fish Culture Zone at Cheung Sha Wan of
southern Lantau as far as practicable.
7.5.9
As a result of consultation with the
Peng Chau Fisherman Association, transportation route of dredged mud via the
direction of Sunshine Island (Chau Kung To) is recommended.
Operational Phase
7.5.10 Waste generated from the normal operation of the STW will include
screening and digested sludge.
Currently there is sufficient dewatering capacity in other outlying
islands sewage treatment works where centralised treatment can be implemented,
digested sludge would be collected and stored prior to export for dewatering
and disposal of. The estimated production of digested sludge is about 9.5 m3/day,
based on the design flow. Storage containers are recommended to be covered to
minimise the potential odour nuisance and would be barged away regularly.
7.5.11 In case sludge export becomes infeasible, digested sludge can be
dewatered on site by using sludge drying bed. Such dewatering device is capable
of producing sludge of 30% solid contents. Based on the design flow, the
estimated dry solid volume is 1.0 m3/day, which is not significant. Dewatered sludge can
be disposed of at designated landfill. It is also recommended to cover the
storage container before disposal to minimise the potential odour nuisance.
7.5.12 As mentioned in Clause 4.7.3 of Appendix 2C, the operation will be reversed (i.e. drying bed as duty unit and export as
standby unit) if the export option turns out to be expensive due to the build
up of sludge amount in the future.
7.6
residuAL Impacts
7.6.1
With the implementation of the
appropriate mitigation measures as discussed above during the handling,
collection, and disposal of waste material, the residual environmental impacts
would not be significant. These mitigation measures can be enforced by
specifying a waste management plan as part of the contract document.
Environmental monitoring and audit would be necessary to ensure the
implementation of correct disposal requirements for the various wastes generated
from construction works.
7.7
Environmental Monitoring and Audit
7.7.1
It was recommended that auditing of
each waste stream be carried out periodically to determine if waste is being
managed in accordance with approved procedures and the site waste management
plan. The audits should look at
all aspects of waste management including waste generation, storage, recycling,
treatment, transport and disposal.
An appropriate audit programme would include a first audit at the
commencement of the construction works and then to audit monthly thereafter.
7.8
conclusions and recommendations
Construction Phase
7.8.1
Waste generated by construction works
include workforce waste, maintenance and chemical waste and construction and
demolition material. With the implementation of appropriate mitigation measures
during the handling, collection and disposal of construction waste material,
the residual environmental impacts would be acceptable. The mitigation measures
can be enforced by incorporating them in to a waste management plan as part of
the contract document. Environmental monitoring and audit would be necessary to
ensure the implementation of correct disposal requirements for the various
waste generated from construction works.
7.8.2
Dredging activities would be occurred
at the proposed outfall. Approximately 22,000 m3 of marine mud would
be dredged and disposed of. It is
recommended to avoid the leakage of the dredged mud into the marine environment
by implementing appropriate mitigation measures. The residual impact would not
be significant given the small amount of dredged mud to be handled and disposed
of.
Operational Phase
7.8.3
Waste generated during operational
phase of Peng Chau STW Upgrade would mainly be sludge from secondary treatment
units. The digested wet sludge would be barged away for centralised treatment
and disposal. Sludge can also be dewatered on site by drying bed to 30% solid
content and for disposal of at designated landfill site when sludge export is
infeasible.
7.8.4
The operation will be reversed (i.e.
drying bed as duty unit and export as standby unit) when the export option
turns out to be expensive due to the build up of sludge amount in the future.