6.1.1
This section identifies the types of
wastes that are likely to be generated during the construction of the drainage
improvement works and evaluates the potential environmental impacts that may
result from the handling and disposal of these waste arisings. The main solid
waste management implications are related to excavated materials from
earthworks for the river improvement works.
Mitigation measures and good site practices, including waste handling,
storage and disposal have been recommended with reference to the applicable
waste legislation and guidelines.
6.2.1
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);
·
Public Health and Municipal Services
Ordinance (Cap. 132) - Public Cleansing and Prevention of Nuisances Regulation;
and
·
Dumping
At Sea Ordinance (Cap. 466).
Waste Management
6.2.2
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
Environmental Protection Department (EPD).
6.2.3
Under the regulation of WDO, the Chemical
Waste (General) Regulation 1992 provides regulations for chemical waste control,
and administers the possession, storage, collection, transport and disposal of
chemical wastes. The EPD has also
issued a ‘guideline’ document, the Code of Practice on the Packaging,
Labelling and Storage of Chemical Wastes (1992), which details how the
Contractor should comply with the regulations on chemical wastes.
6.2.4
The Public Cleansing and Prevention of
Nuisances Regulation provides control on illegal tipping of wastes on
unauthorised (unlicensed) sites.
Construction and Demolition
(C&D) Materials
6.2.5
The current policy related to the
dumping of C&D material([1])
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 individual
or companies who deliver public fill to public filling areas. The licences are issued by the Civil
Engineering and Development Department (CEDD) under delegated powers from the
Director of Lands.
6.2.6
In addition to the Works Branch
Technical Circular (WBTC), EPD and CEDD 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.
6.2.7
Measures have been introduced under Environment,
Transport and Works Bureau (ETWB) TCW No. 33/2002 to enhance the management
of C&D material including rock, and to minimise 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 minimise 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 minimise 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. A new technical circular
ETWB TCW 15/2003 was recently issued to introduce additional measures to
enhance waste management on construction sites. The circular sets out the policy and procedures requiring
contractors to prepare and implement an enhanced WMP to encourage on-site sorting
of C&D material and to minimise their generation during the course of
construction.
6.2.8
The ETWB TCW No. 34/2002 sets out the
management framework for dredged/excavated sediment. This Technical Circular outlines the procedures to be followed in
assessing and classifying sediment and explains the marine disposal arrangement
for the classified material. The
sediment quality criteria for the classification of sediment are presented in Table
6.1. Dumping permits from EPD are required for marine disposal of
dredged/excavated materials.
General
6.3.1
The methodology for assessing
potential waste management impacts during the construction phase of the Project
included the following tasks:
·
estimation
of the types and quantities of wastes to be generated as a result of construction
activities;
·
assessment
of potential impacts from the management of solid wastes with respect to
potential hazards, air and odour emissions, noise and wastewater discharges;
·
evaluation
of the opportunities for reducing waste generation;
·
identification
of disposal options for each type of waste;
·
assessment
of impacts on the capacity of waste collection, transfer and disposal
facilities.
Excavated Riverbed Material
6.3.2
A sediment quality characterization
survey was carried out in February 2003 to characterise the level of
contamination in the riverbed material of Sai Kung River, Pak Kong River and Ho
Chung Channel for the purpose of this EIA. The works comprised sampling by
hand-auger at a total of eight locations within the three river channels to obtain
samples for chemical testing (Figure 6.1). The methodology for the sampling and laboratory testing of the
riverbed samples was agreed with EPD prior to the commencement of the survey.
6.3.3
The riverbed samples were tested in
the laboratory for the following parameters:
(i)
Metals concentrations including chromium (Cr), copper (Cu),
mercury (Hg), lead (Pb), cadmium (Cd), nickel (Ni), zinc (Zn), silver (Ag) and
arsenic (As).
(ii)
Concentrations
of organic compounds: total polychlorinated biphenyls (PCBs) and polyaromatic
hydrocarbons (PAHs).
6.3.4
The chemical contaminant criteria
under the management and classification system for excavated material destined
for marine disposal are listed in Table 6.1 below.
Table
6.1 Sediment Quality Classification
Criteria
|
Contaminants
|
LCEL
|
UCEL
|
|
Heavy
Metal (mg/kg dry weight)
|
|
Cadmium
(Cd)
|
1.5
|
4
|
|
Chromium
(Cr)
|
80
|
160
|
|
Copper
(Cu)
|
65
|
110
|
|
Mercury
(Hg)
|
0.5
|
1
|
|
Nickel
(Ni)
|
40
|
40
|
|
Lead
(Pb)
|
75
|
110
|
|
Silver
(Ag)
|
1
|
2
|
|
Zinc
(Zn)
|
200
|
270
|
|
Metalloid
(mg/kg dry weight)
|
|
Arsenic
|
12
|
42
|
|
Organic-PAHs
(µg/kg dry weight)
|
|
PAHs
(Low Molecular Weight)
|
550
|
3160
|
|
PAHs
(High Molecular Weight)
|
1700
|
9600
|
|
Organic-non-PAHs
(µg/kg dry weight)
|
|
Total
PCBs
|
23
|
180
|
Source: Appendix A of ETWB TCW No. 34/2002 Management
of Dredged / Excavated Sediment
Note: LCEL – Lower
Chemical Exceedance Level
UCEL – Upper Chemical Exceedance Level
6.3.5
Sediments are categorised with
reference to the LCEL and UCEL, as follows:
Category L Sediment with
all contaminant levels not exceeding the LCEL.
The material must be dredged, transported and disposed of in a manner
that minimises the loss of contaminants either into solution or by suspension.
Category M Sediment with any one or more contaminant levels exceeding
the LCEL and none exceeding the UCEL.
The material must be dredged and transported with care, and must be
effectively isolated from the environment upon final disposal unless appropriate
biological tests demonstrate that the material will not adversely affect the
marine environment.
Category H Sediment with any one or more
contaminant levels exceeding the UCEL.
The material must be dredged and transported with great care, and must
be effectively isolated from the environment upon final disposal.
6.3.6
For projects with disposal
requirements of less than 50,000 m3 Category L sediment, the
allocation of sediment disposal space had been delegated to Director of
Environmental Protection (DEP) in accordance with ETWB TCW No. 34/2002.
6.3.7
The chemical testing results of the
riverbed samples as compared with the classification criteria are presented in Table
6.2. The chemical testing results
indicate that Category L material was found at all sampling locations apart
from SK1, HC1 and PK3. Category M
material was found at sampling location SK1 in terms of PAHs and zinc, at
sampling location HC1 in terms of copper and zinc, and at sampling location PK3
in terms of lead.
Table 6.2 Contaminant
Levels of Riverbed Soil Samples and their Categories
|
Sampling Station No.
|
LMW
|
HMW
|
Total
PCBs
|
Metals
|
Overall Category
|
|
PAHs
|
PAHs
|
mg/kg
|
|
µg/kg
|
µg/kg
|
µg/kg
|
Ag
|
As
|
Cd
|
Cr
|
Cu
|
Ni
|
Pb
|
Zn
|
Hg
|
|
HC1
|
<550
|
<1700
|
<3
|
<0.1
|
5.8
|
0.07
|
12.7
|
70
|
6.4
|
24.2
|
262
|
0.05
|
M
|
|
HC2
|
<550
|
<1700
|
<3
|
<0.1
|
2.2
|
<0.02
|
4
|
3.7
|
2.5
|
6.5
|
36.6
|
0.02
|
L
|
|
HC3
|
<550
|
<1700
|
<3
|
<0.1
|
3.2
|
0.09
|
5.3
|
8.7
|
2
|
18.3
|
70.7
|
0.04
|
L
|
|
PK1
|
<550
|
<1700
|
<3
|
<0.1
|
3.8
|
0.7
|
31.9
|
31.2
|
8.3
|
21.7
|
118
|
0.05
|
L
|
|
PK2
|
<550
|
<1700
|
<3
|
<0.1
|
3.5
|
0.07
|
8.7
|
14.8
|
4.1
|
25.5
|
69
|
0.03
|
L
|
|
PK3
|
<550
|
<1700
|
<3
|
<0.1
|
4.2
|
0.22
|
11.1
|
33.7
|
7.3
|
76.9
|
171
|
0.1
|
M
|
|
SK1
|
910
|
3680
|
<3
|
<0.1
|
7.7
|
0.22
|
11.9
|
23
|
19.8
|
44.7
|
222
|
0.06
|
M
|
|
SK2
|
<550
|
<1700
|
<3
|
<0.1
|
3.2
|
0.07
|
5.6
|
4.6
|
1.4
|
14.8
|
64.8
|
0.03
|
L
|
Notes:
1.
LMW = Low molecular weight PAHs, that is, acenaphthene, acenaphthylene,
anthracene, fluorene, naphthalene and phenanthrene.
2.
HMW = High molecular weight PAHs, that is, benzo[a]anthracene,
benzo[a]pyrene, chrysene, dibenzo[a,h]anthracene, fluoranthene, pyrene,
benzo[b]fluoranthene, benzo[k]fluoranthene, indeno[1,2,3-c,d]pyrene and
benzo[g,h,i]perylene.
3.
Values in underline indicate Category M sediment under ETWB TCW
No. 34/2002.
6.4.1
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:
·
construction
and demolition (C&D) materials;
·
chemical
waste; and
·
general
refuse.
6.4.2
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
6.4.3
Construction of the river improvement
works would involve earthworks for the new river channel to the required
profile and formation levels. The excavated materials would comprise mostly
soil, sand, gravel and small rocks from the fields and river/stream
channels. Based on the proposed design
of the river improvement works, the total volume of excavated materials to be
generated from the construction of the Project was estimated by the Project
Engineer to be approximately 67,200 m3.
6.4.4
The results of the sampling and
laboratory testing provided information on the characteristics of the excavated
materials from the riverbed. The
samples collected at all 8 sampling locations were described as alluvial sand,
and some gravel was described in the samples from the Pak Kong River. A
possible cause for the moderate levels of copper and zinc recorded at sampling
location HC1 in the Ho Chung Channel and zinc recorded at sampling location SK1
in the Sai Kung River could be livestock waste discharges. Construction works were observed in close
proximity to SK1 and a possible cause for the moderate level of PAHs recorded
could be localised spillage or leakage of vehicle or equipment oil. Road re-surfacing works have also been
carried out recently for Tai Mong Tsai Road, immediately adjacent to SK1. Sampling location PK3 was located adjacent
to village houses and a small vehicle workshop.
6.4.5
Uncontaminated excavated materials
from the river improvement works would be suitable for disposal to a public
filling area. The reported levels of
zinc, copper, lead and PAHs in the samples collected at sampling locations SK1,
HC1 and PK3 did not exceed the Dutch B level for soil,([2])
and therefore the riverbed material is considered to be not contaminated in this
regard. The excavated riverbed soil at sampling location HC1 is proposed to be
re-used on-site as far as practicable, with surplus excavated materials
disposed to a public filling area. (SK1
and PK3 are located outside the excavation area for the proposed new channels
for the drainage improvement works to the Sai Kung River and Pak Kong River,
respectively).
6.4.6
It was estimated by the Project
Engineer that approximately 13,700 m3 of the excavated materials from
the river improvement works would be of suitable characteristics for reuse
on-site for backfilling of temporary drainage channels and as fill material in
the construction of embankments.
Temporary stockpiles of excavated materials would be required on-site
before disposal. Considering the
unpolluted nature of the excavated materials, reuse on-site would not result in
any unacceptable environmental impact.
It is proposed that small cobbles and rocks from the existing rivers be
re-used in the recreated channel beds as far as possible, subject to suitable
size requirements. Surplus excavated
soil, sand, gravel and rock would be transported by trucks to the designated
barging point for disposal at the designated public filling area, or
transported directly to the public filling area.
6.4.7
C&D material would also be
generated from the demolition of existing crossings over the river channels and
structures. The volume of C&D
material was estimated by the Project Engineer to be approximately 9,900m3
and would comprise mostly concrete, brick and cement plaster/mortar. C&D
waste would be generated during site clearance and the estimated volume of
C&D waste for a contract of this size was approximately 26,700 m3. These C&D wastes would comprise
vegetation and top soil and would be delivered to a designated landfill site
for disposal. A summary of the
estimated volumes of excavated material generated from earthworks for the new
river channels, as well as C&D material generated from the demolition of
existing crossings and structures and from site clearance is presented in Table
6.3 below.
Table 6.3 Summary
of C&D Material Volumes (Bulk Volumes)
|
Improvement Works
|
C&D
Material (m3)
|
|
Inert
(Disposal
to public filling area)1
|
Non-inert
(Disposal
to landfill)2
|
|
Excavated material from
earthworks for river channels:
Sai Kung River/Sha Ha
Stream
Pak Kong River
Ho Chung Channel
|
67,200
(13,700 m3 to
be re-used on-site)
|
|
|
Demolition of existing
river crossings and structures
|
7,600
|
2,300
|
|
Site clearance
|
--
|
26,700
|
Notes:
1) The proposed public fill site is fill bank at Tseung Kwan O Area 137
2) The proposed landfill site is South East New
Territories (SENT) Landfill
Chemical Waste
6.4.8
The maintenance and servicing of construction
plant and equipment may possibly generate some chemical wastes, for instance,
cleaning fluids, solvents, lubrication oil and fuel. Maintenance of vehicles
may also involve the use of a variety of chemicals, oil and lubricants.
6.4.9
Since a large number of the
construction activities will be carried out in close proximity to river and
stream channels and residential dwellings, chemical wastes arising during the
construction phase may pose environmental, health and safety hazards if not
stored and disposed of in an appropriate manner as stipulated in the Waste
Disposal (Chemical Waste) (General) Regulations. The potential hazards include:
· toxic effects
to workers;
· adverse impacts
on water quality from spills and associated adverse impacts on fresh water
biota; and
· fire hazards.
6.4.10
Materials classified as chemical
wastes will require special handling and storage arrangements before removal for
appropriate treatment at the Chemical Waste Treatment Facility at Tsing
Yi. Wherever possible opportunities
should be taken to reuse and recycle materials. Mitigation and control requirements for chemical wastes are
detailed in Section 6.5.10. Provided
that the handling, storage and disposal of chemical wastes are in accordance
with these requirements, adverse environmental impacts are not expected to
result.
General Refuse
6.4.11
Throughout the construction stage, the
workforce would generate general refuse comprising food scraps, waste paper,
empty containers, etc. Release of
general refuse into the river and stream channels 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 aquatic 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.
6.4.12
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.
Good Site Practices and
Waste Reduction Measures
6.5.1
Appropriate waste handling,
transportation and disposal methods for all waste arisings generated during the
construction works should be implemented to ensure that construction wastes do
not enter the river and stream channels.
6.5.2
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;
·
separation
of chemical wastes for special handling and appropriate treatment at the
Chemical Waste Treatment Facility;
·
regular
cleaning and maintenance programme for drainage systems, sumps and oil
interceptors;
·
A
recording system for the amount of wastes generated, recycled and disposed
(including the disposal sites) should be proposed; and
·
A
Waste Management Plan should be prepared and submitted to the Engineer for
approval. One may make reference to
ETWB TCW No. 15/2003 for details.
6.5.3
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 ETWB TCW No. 31/2004 for details.
6.5.4
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;
·
to
encourage collection of aluminium cans by individual collectors, separate
labelled bins shall be provided to segregate this waste from other general
refuse generated by the work force;
·
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; and
·
plan
and stock construction materials carefully to minimise amount of waste
generated and avoid unnecessary generation of waste.
6.5.5
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.
Construction and Demolition
Material
6.5.7
When disposing C&D material at a
public filling area, it shall be noted that the material shall only consist of
soil, rock, concrete, brick, cement plaster/mortar, inert building debris,
aggregates and asphalt. The material
shall be free from marine mud, household refuse, plastic, metals, industrial
and chemical waste, animal and vegetable matter, and other material considered
to be unsuitable by the Filling Supervisor.
6.5.8
The C&D material generated from
demolition of existing structures should be sorted on-site into inert C&D
material (that is, public fill) and C&D waste. Suitable areas should be designated within the works site
boundaries for temporary stockpiling of C&D material. Within stockpile areas, the following
measures should be taken to control potential environmental impacts or
nuisance:
·
covering
material during heavy rainfall;
·
locating
stockpiles to minimise potential visual impacts; and
·
minimising
land intake of stockpile areas as far as possible.
Excavated
Riverbed Material
6.5.9
It is anticipated that the excavated riverbed
material may need to be temporarily stockpiled on-site prior to disposal
off-site. Details of environmental
control measures to be taken at the stockpiling area to prevent water pollution
are discussed in Section 5. Use
of water-tight trucks would be required for the transportation of excavated
riverbed material to the designated barging point for disposal at the
designated public filling area, or transported directly to the public filling
area.
Chemical Wastes
6.5.10
If chemical wastes are produced at the
construction site, the Contractor would be required to register with the EPD as
a Chemical Waste Producer and to follow the guidelines 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, and
incompatible chemicals should be stored separately. Appropriate labels should be securely attached on each chemical
waste container indicating the corresponding chemical characteristics of the
chemical waste, such as explosives, flammable, oxidizing, irritant, toxic,
harmful, corrosive, etc. The Contractor
shall use a licensed collector to transport and dispose of the chemical wastes
generated at the Chemical Waste Treatment Centre at Tsing Yi, or other licensed
facility, in accordance with the Waste Disposal (Chemical Waste) (General)
Regulation.
General Refuse
6.5.11
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.
6.6.1
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 drainage improvement works.
6.7.1
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 and implemented by the Contractor at the
construction stage.
6.8.1
The main waste arising during the
construction phase would be the excavated materials from the river improvements
works at Sai Kung River, Pak Kong River and Ho Chung Channel. The excavated
materials would comprise soil, sand, gravel and small rocks. It was recommended
that the excavated materials with suitable characteristics be reused on-site,
as far as practicable, such as for fill material for backfilling of temporary
drainage channels or construction of embankments. Surplus excavated soil, sand, gravel and rock material would
require disposal to a public filling area.
6.8.2
Other wastes generated by the
construction activities are likely to include general refuse from the
workforce, chemical wastes from plant and vehicle maintenance, and C&D
material from the demolition of existing structures and site clearance. Provided that these identified waste
arisings are to be handled, transported and disposed of using the recommended
methods and good site practices are to be strictly followed, adverse
environmental impacts would not be expected during the construction works. The recommended mitigation measures should
form the basis of the Waste Management Plan to be developed by the Contractor.