5.1.1
This section
identifies the types of wastes that are likely to be generated during the
construction and operation phases of the Project and evaluates the potential
environmental impacts that may result from these waste arisings. The main solid
waste management implications are related to construction and demolition
(C&D) material from site formation works for provision of new facilities
and units at the STW and demolition of existing facilities. Mitigation measures and good site practice,
including waste handling, storage and disposal have been recommended with
reference to the applicable waste legislation and guidelines.
5.2.1
The criteria
and guidelines for assessing waste management implications are outlined in
Annex 7 and Annex 15 respectively of the Technical Memorandum on Environmental
Impact Assessment Ordinance (EIAO-TM).
5.2.2
The following
legislation relates to the handling, treatment and disposal of wastes in the
Hong Kong SAR and was used in assessing potential impacts:
·
Waste
Disposal Ordinance (Cap. 354);
·
Waste
Disposal (Chemical Waste) (General) Regulation (Cap. 354);
·
Land
(Miscellaneous Provisions) Ordinance (Cap. 28); and
·
Public Health and Municipal Services Ordinance (Cap.
132) - Public Cleansing and Prevention of Nuisances Regulation.
Waste Management
5.2.3
The Waste
Disposal Ordinance (WDO) prohibits the unauthorised disposal of wastes. Construction waste is not directly defined
in the WDO but is considered to fall within the category of “trade waste”. Trade waste is defined as waste from any
trade, manufacturer or business, or any waste building, or civil engineering
materials, but does not include animal waste.
Under the WDO, wastes can be disposed of at sites licensed by the EPD.
5.2.4
The Public
Cleansing and Prevention of Nuisance Regulation provides control on illegal
tipping of wastes on unauthorised (unlicensed) sites.
Construction and Demolition (C&D)
Materials
5.2.5
The current policy related to the dumping of C&D material() is documented in the Works Branch Technical Circular No. 2/93,
‘Public Dump’. Construction and
demolition materials that are wholly inert, namely public fill, should not be
disposed of to landfill, but taken to public filling areas which usually form
part of reclamation schemes. The Land
(Miscellaneous Provisions) Ordinance requires that dumping licences are
obtained by individuals or companies who deliver public fill to public filling
areas. The licences are issued by the
Civil Engineering Department (CED) under delegated powers from the Director of
Lands.
5.2.6
In addition to the Works Branch Technical
Circular (WBTC), EPD and CED have produced a leaflet titled ‘New Disposal
Arrangements for Construction Waste’ (1992) which states that C&D
material with less than 30% by weight of inert material (that is, public fill)
will be accepted at landfill. If the
material contains more than 30% inert material, the waste must be sorted with
suitable material and sent to public filling area and the non-inert material
(that is, C&D waste) sent to landfill for final disposal.
5.2.7
Measures have
recently been introduced under Environment, Transport and Works Bureau (ETWB)
TC No. 33/2002 to enhance the management of C&D material including rock,
and to minimize its generation at source.
The enhancement measures include: (i) drawing up a Construction and
Demolition Material Management Plan (C&DMMP) at an early design stage to
minimize C&D material generation; (ii) vetting of the C&DMMP prior to
upgrading of the project to Category A in the Public Works Programme; and (iii)
providing the contractor with information from the C&DMMP in order to
facilitate him in the preparation of the Waste Management Plan (WMP) and to
minimize C&D material generation during construction. Projects generating less than 50,000m3
C&D material or importing less than 50,000m3 fill material are
exempt from the C&DMMP.
5.3.1
The criteria
for assessing waste management implications are outlined in Annex 7 of the
EIAO-TM. The methodology for assessing
potential waste management impacts during the construction and operation phases
of the Project follow those presented in Annex 15 of the EIAO-TM. Appropriate waste handling and on-site
storage practices, transportation and disposal routes have been recommended for
each type of waste arising, considering re-use options and waste reduction, and
the requirements of the Waste Control Ordinance and other relevant legislation
and guidelines. The assessment included
the following tasks:
·
estimation
of the types and quantities of wastes generated;
·
examination
of opportunities for waste reduction and re-use (both on-site and off-site) and
the required disposal options for each type of waste;
·
assessment
of potential environmental impacts from the management of solid wastes with
respect to potential hazards, air and odour emissions, noise and wastewater
discharges; and
·
identification
of impacts on the capacity of waste collection, transfer and disposal
facilities.
5.3.2
Mitigation
measures and good site practices have been recommended with reference to the
applicable waste legislation and guidelines.
Construction Phase
5.4.1
The
construction activities to be carried out for the proposed Project would
generate a variety of wastes that can be divided into distinct categories based
on their composition and ultimate method of disposal. The identified waste types include:
· C&D materials;
· general refuse; and
·
bentonite slurry.
5.4.2
During the
construction phase, the sludge handling arrangements would remain the same as
far as possible. The installation of temporary sludge handling arrangements
during the construction period is considered unnecessary at this stage.
5.4.3
The nature of
each type of waste arising is described in the following section, together with
an evaluation of the potential environmental impacts associated with these
waste arisings.
Construction and Demolition
(C&D) Materials
5.4.4
Excavated
material would be generated from site excavation works for the provision of new
treatment units and facilities. The
estimated volume of excavated material would be 152,000 m3. The excavated material would be mostly
general fill material. It was estimated
that approximately 5,300 m3 of excavated material could be reused
on-site (e.g. for backfilling of trenches), resulting in approximately 146,700
m3 of excavated material requiring off-site disposal to the
designated public filling area. A
review of the chemical testing results from the ground investigation works for
the land contamination assessment
showed that there is no exceedance in the Dutch B levels (i.e. soil clean-up
targets) for all soil samples, indicating that the area is not contaminated.
5.4.5
Construction
and demolition (C&D) material would also be generated from the demolition
of some of the existing facilities. The C&D material would comprise
reinforced concrete and other demolition wastes, such as brick, metallic
handrails/pipes, plastic products (e.g. PVC pipe) and general building waste
(e.g. door, window, building finishes).
Inert and non-inert demolition wastes would be sorted on-site and then
delivered to the designated recycling facility and landfill site accordingly.
The volume of C&D material was estimated to be approximately 12,100 m3
and would comprise mainly reinforced concrete.
5.4.6
The estimated
volumes of C&D material generated from the excavation and demolition works
are presented in Table 5.1 below, together with the estimated volumes of
C&D material to be disposed to public filling area designated
by the Civil Engineering and Development Department (CEDD) and to
landfill. The timing of these
construction activities are shown in the construction programme presented in
Appendix 7.3.
Table 5.1 Summary of Waste Volumes During
Construction Phase (In Bulk Volumes)
|
Construction
Activity
|
C&D
material (m3)
|
Inert
C&D material to be reused on site (m3)
|
C&D
waste to be disposed to landfill (1) (m3)
|
Inert
C&D material to be disposed to public filling area
designated by CEDD
(m3)
|
Inert
C&D material to be delivered to recycling facility (m3)
|
|
Phase 1 works :
|
|
Excavation
works
|
73,500
|
2,700
|
|
70,800
|
|
|
Demolition
of existing facilities
|
7,700
|
|
1,500
|
|
6,200
|
|
Phase 2 works :
|
|
Excavation
works
|
78,500
|
2,600
|
|
75,900
|
|
|
Demolition
of existing facilities
|
4,400
|
|
900
|
|
3,500
|
|
Bentonite Slurry
|
|
|
|
6,800 (2)
|
|
|
Total
|
164,100
|
5,300
|
2,400
|
153,500
|
9,700
|
Notes:
1.
The estimated amount of
general refuse produced is considered minimal when compared with the waste
generated from the demolition works and is deemed to be included in the
estimated amount of C&D waste to be disposed at landfill
2.
Used dewatered
bentonite slurry should be disposed to a public
filling area,and liquid bentonite slurry if mixed
with inert fill material should be disposed to a public filling areaor marine
dumping ground (as last resort).
General
Refuse
5.4.7
Throughout
the construction stage, the workforce would generate general refuse comprising
food scraps, waste paper, empty containers, etc. Release of general refuse into marine waters should not be
permitted as introduction of these wastes is likely to have detrimental effects
on water quality in the area. Effective
collection of site wastes would be required to prevent waste materials being
blown around by wind, flushed or leached into the marine environment, and odour
nuisance. The work sites may also attract pests and vermin if the waste storage
area is not well maintained and cleaned regularly. Disposal of refuse at sites
other than approved waste transfer or disposal facilities can also result in
similar impacts.
5.4.8
With the
implementation of the recommended waste management practices at the site,
adverse environmental impacts would not arise from the storage, handling and
transportation of refuse.
Bentonite Slurry
5.4.9
Bentonite
slurry may be used, depending on the construction method proposed by the
Contractor, during bored piling for the proposed structures under Tai Po STW
Stage V (refer to the construction programme presented in Appendix 7.3 for the
timing of piling work). It was
estimated that approximately 6,800 m3 of used bentonite slurry may
require off-site disposal.
Operation Phase
5.4.10
During the
operation phase of the Tai Po STW, the main waste arising would be dewatered
sludge cake. The sludge arising from
the sewage treatment process is thickened, digested and dewatered in the sludge
handling facilities within the Tai Po STW. The dewatered sludge cake is
currently disposed to the NENT landfill site, and the same disposal arrangement
would be followed after the upgrading works.
The estimated quantity of sludge after digestion would be 26,000
kg/day. The expected solids content of
dewatered sludge cake is 30%.
5.4.11
Screenings
and grit would also be generated at the inlet works during the operation phase
of the Tai Po STW. This waste would be discharged to storage containers and
trucked to an off-site solids disposal facility. Under the existing arrangement, screenings and grit are disposed
to the NENT landfill site and the same arrangement would be followed after the
upgrading works. Screenings from the
inlet works at the Stage I/II works would be compacted first and then
discharged to a storage container. The average total quantity of grit and
screenings from the Stage V works is estimated to be 2.6 m3/day and
2 m3/day, respectively.
5.4.12
Spent UV
lamps would also require disposal during the operation phase of the STW. Currently, the spent UV lamps are disposed
by the STW operation staff to landfill.
The total numbers of UV lamps that have been disposed are relatively
small and generally in small batches.
The spent UV lamps would be classified as chemical wastes and would
require special handling and storage arrangements before removal for disposal
to the designated landfill site.
Mitigation and control requirements for chemical wastes are detailed in
Section 5.5.9. Provided that the
handling, storage and disposal of the spent UV lamps are in accordance with
these requirements, adverse environmental impacts would not be expected.
Good Site Practices
5.5.1
Appropriate
waste handling, transportation and disposal methods for all waste arisings
generated during the construction works at the Tai Po STW should be implemented
to ensure that construction wastes do not enter the nearby coastal waters of
Tolo Harbour.
5.5.2
It is
expected that adverse impacts from waste management would not arise, provided
that good site practices are strictly followed. Recommendations for good site practices during construction
include:
·
nomination
of approved personnel, such as a site manager, to be responsible for good site
practices, and making arrangements for collection of all wastes generated at
the site and effective disposal to an appropriate facility;
·
training
of site personnel in proper waste management and chemical waste handling
procedures;
·
provision
of sufficient waste disposal points and regular collection for disposal;
·
appropriate
measures to minimise windblown litter and dust during transportation of waste
by either covering trucks or by transporting wastes in enclosed containers;
·
regular
cleaning and maintenance programme for drainage systems, sumps and oil
interceptors;
·
a
Waste Management Plan should be prepared and should be submitted to the
Engineer for approval. One may make
reference to ETWB TCW No. 15/2003 for details; and
·
a
recording system for the amount of wastes generated, recycled and disposed
(including the disposal sites) should be proposed.
5.5.3
In order to
monitor the disposal of C&D material at landfills and public filling areas,
as appropriate, and to control fly tipping, a trip-ticket system should be
included as one of the contractual requirements to be implemented by an
Environmental Team undertaking the Environmental Monitoring and Audit
work. One may make reference to WBTC
No. 21/2002 for details.
Waste Reduction Measures
5.5.4
Good management
and control can prevent the generation of significant amounts 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 include:
·
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;
·
separate
labelled bins shall be provided to segregate aluminium cans from other general
refuse generated by the work force, and to encourage collection of by
individual collectors;
·
any
unused chemicals or those with remaining functional capacity shall be recycled;
·
maximising
the use of reusable steel formwork to reduce the amount of C&D material;
·
prior
to disposal of C&D waste, it is recommended that wood, steel and other
metals shall be separated for re-use and / or recycling to minimise the
quantity of waste to be disposed of to landfill;
·
proper
storage and site practices to minimise the potential for damage or
contamination of construction materials;
·
plan
and stock construction materials carefully to minimise amount of waste
generated and avoid unnecessary generation of waste;
·
minimize
over ordering of concrete, mortars and cement grout by doing careful check
before ordering.
5.5.5
In addition
to the above good site practices and waste reduction measures, specific
mitigation measures are recommended below for the identified waste arisings to
minimise environmental impacts during handling, transportation and disposal of
these wastes.
General Refuse
5.5.6
General
refuse should be stored in enclosed bins or compaction units separate from
C&D material. A reputable waste collector should be employed by the
contractor to remove general refuse from the site, separately from C&D
material. An enclosed and covered area
is preferred to reduce the occurrence of 'wind blown' light material.
Construction and Demolition Material
5.5.7
The C&D
material generated from the site formation and demolition works should be
sorted on-site into inert C&D material (that is, public fill) and C&D
waste. In order to minimise the impact resulting from collection and
transportation of C&D material for off-site disposal, the excavated
material comprising fill material should be reused on-site as backfilling
material as far as practicable. C&D waste, such as wood, plastic, steel and
other metals should be reused or recycled and, as a last resort, disposed of to
landfill. A suitable area should be designated within the site for temporary
stockpiling of C&D material and to facilitate the sorting process. The stockpiling/sorting area should be
located as far away as possible from the identified NSR of the Tai Po STW Staff
Quarters.
Bentonite Slurry
5.5.8
Bentonite
slurries used in construction works should be reconditioned and reused wherever
practicable. Residual used bentonite
slurry should be disposed of from the site as soon as possible as stipulated in
Clause 8.56 of the General Specification for Civil Engineering Works which
states “Bentonite slurry which will not be reused shall be disposed of from the
Site as soon as possible.” The Contractor should explore alternative disposal
outlets for the residual used bentonite slurry and disposal at landfill should
be the last resort.Residual used dewatered
bentonite slurry should be disposed to a public
filling areaand liquid bentonite slurry if mixed
with inert fill material should be disposed to a public filling area,or marine
dumping ground (as the last resort).
Chemical Wastes
5.5.9
For the
disposal of spent UV lamps, the STW operator would be required to register with
the EPD as a Chemical Waste Producer and to follow the requirements stated in
the Code of Practice on the Packaging, Labelling and Storage of Chemical
Wastes. Good quality containers
compatible with the chemical wastes should be used. Appropriate labels should be securely attached on each chemical
waste container indicating the chemical characteristics of the chemical waste,
such as explosives, flammable, oxidizing, irritant, toxic, harmful, corrosive,
etc. Any specific requirements
regarding the disposal of spent UV lamps would be specified by EPD following
the provision of design information of the UV disinfection system at the
detailed design stage (should this disinfection option be selected). A licensed waste collector should be engaged
to transport and dispose of the chemical wastes in accordance with the Waste
Disposal (Chemical Waste) (General) Regulation.
5.6.1
With the
implementation of the recommended mitigation measures for the handling,
transportation and disposal of the identified waste arisings, residual impacts
would not be expected during the construction of the proposed upgrading works.
5.7.1
Waste
management would be the contractor’s responsibility to ensure that all wastes
produced during the construction of the Project are handled, stored and
disposed of in accordance with good waste management practices and EPD’s
regulations and requirements. The recommended mitigation measures should form
the basis of the site Waste Management Plan to be developed by the Contractor
at the construction stage.
5.8.1
Wastes generated by the construction
activities are likely to include C&D material from the site formation and
demolition works at the existing Tai Po STW site, general refuse from the
workforce and used bentonite slurry.
Provided that these identified waste arisings are to be handled,
transported and disposed of using approved methods and that the recommended
good site practices are strictly followed, adverse environmental impacts would
not be expected during the construction works.