6. WASTE MANAGEMENT IMPLICATIONS
As described in Section 1, the Project is divided into three packages as follows:
Package 1 – Ngong Ping STW with tertiary treatment;
Package 2 – Ngong Ping main trunk sewer and effluent export pipeline; and
Package 3 – Ngong Ping village sewerage system.
This section discusses the waste management implications and management required as a result of the construction and operation of the Project. Impacts on water quality from wastewater and sewage generated during construction activities are discussed in Section 5, Water Quality Impact Assessment.
6.1 Legislation, Policies, Plans, Standards and Criteria
Legislation
6.1.1 The legislation on handling, treatment and disposal of wastes, which are of relevance to this Project, are:
| Waste Disposal Ordinance (Cap. 354) & relevant regulations; |
| Environmental Impact Assessment Ordinance (Cap. 499); and |
| Public Health and Municipal Services Ordinance (Cap. 132). |
6.1.2 The Waste Disposal Ordinance (WDO) 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 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.
6.1.3 There are a number of provisions under the WDO for dealing with certain types of waste. These include the Waste Disposal (Chemical Waste) (General) Regulation (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 waste 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.
6.1.4 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 (EIAO-TM) under the EIAO specifies the assessment criteria for evaluating waste management implications.
6.1.5 Public Health and Municipal Services Ordinance provides 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.
Other Waste Handling & Disposal Guidelines
6.1.6 A Waste Reduction Framework Plan (WRFP) was launched in November 1998. The WRFP sets out programme to avoid and minimise waste; promote recovery, recycling and reuse of materials; prolong the 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.
6.1.7 The Works Bureau 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 construction and demolition (C&D) waste. 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 Filling Sub-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.
6.1.8 The Works Bureau Technical Circular No. 5/98 - On Site Sorting of Construction Waste on Demolition 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.
6.1.9 The Works Bureau Technical Circular No. 5/99 and No. 5/99A- 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.
6.1.10 The Works Bureau Technical Circular No. 25/99, 25/99A and 25/99C- Incorporation of Information on Construction and Demolition Material Management in Public Works Subcommittee Papers promulgates the policy and guidelines for incorporating information on the management of construction and demolition material in Publics Works Subcommittee papers recommending the upgrading of projects to Category A of the Public Works Programme for the implementation of construction works.
6.1.11 The Works Bureau Technical Circular No. 29/2000 - Waste Management Plan introduces the requirement for contractors to prepare and implement a waste management plan (WMP). The requirement shall be included in all PWP contracts (including design and build contracts but excluding term contracts and contracts administered by Electrical and Mechanical Services Department).
6.1.12 The following guidelines should also be observed:
| Works Bureau Technical Circular No. 4/98 and No. 4/98A – Use of Public Fill in Reclamation & Earth Filling Projects |
| Works Bureau Technical Circular No. 19/99 – Metallic Site Hoardings and Signboards |
| Works Bureau Technical Circular No. 12/2000 – Fill Management |
6.2.1 The assessment on waste management implications follows the criteria and guidelines as stated in Annexes 7 and 15 of the EIAO-TM together with other relevant legislation, policies, and guidelines discussed in Section 6.1 above.
6.2.2 This assessment covered the analysis of activities and waste generation and proposal for waste management in the construction and operational stages of the proposed project.
6.3 Construction Waste Assessment
General Site Wastes
6.3.1 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 6.5 (including good site practices), the potential environmental impacts resulting from the storage, handling and transportation of general site wastes would be minimal.
Workforce Wastes
6.3.2 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 6.5), 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
6.3.3 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. Vehicle and 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. The cumulative effect of a potentially large number of small spillages during maintenance operations by faulty equipment, accidents, carelessness and deliberate discharge to drain may be significant.
6.3.4 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.
These hazards include:
| toxic effects to workers; |
| adverse impacts from spills on water gathering ground and other ecological sensitive areas such as Ngong Ping SSSI; and |
| fire hazards. |
6.3.5 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.
6.3.6 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 wastes are detailed in Section 6.5. 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
6.3.7 The construction of Ngong Ping main trunk sewer, Tai O effluent export pipeline, and the sewer laying in Ngong Ping village will be carried out by traditional open trench method. These construction activities, as well as the site formation and foundation works at the proposed Ngong Ping STW site, would generate construction and demolition (C&D) material. An initial estimate of the total volume of excavated material likely to be generated from the construction works is given in Table 6.1.
|
Construction Package |
Expected Time Frame |
Excavated Spoil (m3) |
Excavated Spoil to be Reused Onsite (m3) |
Excavated Spoil for Disposal (m3) |
Imported Fill Material (m3) |
|
1: Ngong Ping STW |
Sep 03-Sep 04 |
50,000 |
0 |
50,000 |
3,000 |
|
2: Ngong Ping main trunk sewer and effluent export pipeline |
Mar 03- Apr 05 |
19,000 |
5,200 |
13,800 |
0 |
|
3: Ngong Ping village sewerage system |
Sep 05-Apr 07 |
7,800 |
3,900 |
3,900 |
0 |
|
TOTAL |
76,800 |
9,100 |
67,700 |
3,000 |
6.3.8 The excavated spoil (rock and soil) is inert material and should not be disposed of to landfills but should be reused as fill material. Reuse of the excavated spoil on-site has been planned (Table 6.1). About 9,100 m3 of excavated spoil from construction of Packages 2 and 3 can be reused on-site to backfill pipeline trenches. However, there would be still a significant amount of surplus after reuse that requires off-site disposal. As shown in Table 6.1, most of the surplus excavated material (50,000 out of 67,700 m3) would be generated over the period from March 2003 to March 2004 during the construction of the STW. The surplus excavated spoil will be transported to the Public Fill Stockpiling Area at Mui Wo for reuse in suitable public filling areas or land formation projects. Nevertheless, on-site sorting of all C&D material should be provided prior to disposal. Non-inert portion of C&D material that cannot be reused or recycled should be disposed of to designated landfill sites.
6.3.9 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 5/99A should be followed closely.
6.3.10 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 temporarily before removal to disposal sites.
6.3.11 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.
6.4 Operational Waste Assessment
Sludge
6.4.1 Sludge will be produced from the secondary biological treatment of SBR. The volume of dewatered sludge cake production was estimated to be about 5.67 m3/day, which will be disposed of to landfill. All the sludge will be dewatered onsite to more than 30% dry solids content before transporting to the designated landfill site for disposal and will be stored in covered container along the transporting route to avoid the possible odour impact on nearby sensitive receivers. The transportation of the sludge by sea to the disposal location is recommended, as far as practicable, in order to reduce potential noise and air quality impacts from road transportation.
Spent UV Disinfection Lamps
6.4.2 At the UV disinfection plant, small quantities of spent or defective UV lamps may be produced from time to time. UV lamps may contain mercury and other heavy metals, and some older models may also contain polychlorinated biphenyls (PCBs). Heavy metal and PCB wastes are classified as chemical waste under Schedule 1 of the Chemical Waste Regulations (CWR). An initial estimate of a total of 70 spent low-pressure UV lamps would be generated each year during the operation of Ngong Ping STW.
6.4.3 Since virtually an entire fluorescent lamp can be recycled, including end caps, glass tube, wire, mercury, and phosphorus powder, recycling of spent UV lamps should be encouraged if the number of lamps warrants this practice. The recycled glass can be used as feedstock in the manufacture of glass products. The metallic portion can be used as scrap metal. Mercury can be reused in thermometers and electronic devices after further purification. However, there are currently no recyclable material collectors in Hong Kong that would handle
recycling of fluorescent lamps.
6.4.4 If recycling facilities are not available and spent lamps must be disposed
of as waste, special procedures would have to be followed. According to the Code
of Practice on the Handling, Transportation and Disposal of Polychlorinated
Biphenyl (PCB) Waste, "…small PCB capacitors have been used in the
starter units of fluorescent lights and …typically they contain about 50 g of
the lower chlorinated PCBs mostly absorbed in the windings. They normally carry
no label identifying the PCB content, and they are usually disposed of as part
of the redundant appliances at landfill sites. No special precautions need to be
taken in the disposal of small capacitors unless the landfill operator advises
that there is undue concentration at the landfill site. However, if sufficient
quantities are located, they should be handled in the same manner as the larger
electrical capacitors but need not be packaged as carefully because they contain
no free fluids. It is understood that non-PCB materials are gaining wider use in
capacitors for fluorescent light fittings, …" Therefore, the operators of
the future UV disinfection plant should identify the contents of the UV lamp and
confirm with EPD whether the UV lamps should be disposed of as chemical waste.
If so, the handling and disposal should follow the guidelines under the CWR. In
handling UV lamps, it is recommended that caution be exercised to avoid breakage
and contaminant release.
Wet Scrubber Chemical Wastes
6.4.5 A wet scrubber system has been proposed for deodorization at Ngong Ping STW. Spent scrubbing fluids may contain undesirable chemicals or extreme pH, which may be classified as chemical waste 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.
6.4.6 Approximately 450 m3 per year of 13% sodium hypochlorite and 140 m3 per year of 45% caustic soda will be generated and will be transported to the chemical waste treatment facility at Tsing Yi. These materials will need special handling and storage arrangements before removal for appropriate disposal or treatment, which should follow the requirements under the CWR.
Other Operational Wastes
6.4.7 Small amounts of domestic waste may be generated from site management offices, and of 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 6.5, are undertaken, no adverse impact is envisaged.
6.5 Mitigation of Adverse Impacts
Waste Management Plan
6.5.1 A proper Waste Management Plan (WMP) should be submitted to Engineer for approval and implemented. Where waste generation is unavoidable then the potential for recycling or reuse should be explored and opportunities taken. If wastes cannot be recycled, recommendations for appropriate disposal routes should be provided in the WMP. A method statement for stockpiling and transportation of the excavated material and other construction wastes should also be included in the WMP and approved before the commencement of construction. All mitigation measures arising from the approved WMP shall be fully implemented.
Waste Reduction Measures
6.5.2 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 are as follows:
Planning and Design Stage
| 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
| 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 should be provided to segregate this waste from other general refuse generated by the workforce; |
| Any unused chemicals or those with remaining functional capacity should be recycled; |
| 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 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. |
Good Site Practices
6.5.3 Recommendations for good site practices during the construction phase include:
| Nomination of approved personnel, such as a site manager, to be responsible for good site practices, arrangements for collection and effective disposal to an appropriate facility, of all wastes generated at the site; |
| Training of site personnel in proper waste management and chemical handling procedures; |
| Provision of sufficient waste disposal points and regular collection for disposal; |
| Appropriate measures should be employed to minimise windblown litter and dust during transportation of waste by either covering trucks or by transporting wastes in enclosed containers; |
| The storage of oils/chemicals/waste within the boundary of the water gathering ground should be limited to the absolute minimum volume and are to be removed from sites at the earliest opportunity; |
| Separation of chemical wastes for special handling and appropriate treatment at the Chemical Waste Treatment Facility; |
| Regular cleaning and maintenance programme for drainage systems, silt traps, sumps and oil interceptors; and |
| Any mud and debris should be removed from any waterworks access roads and associated drainage systems within the water gathering ground. |
6.5.4 In order to monitor the disposal of C&D material and solid wastes at public filling areas and landfills, and to control fly-tipping, a trip-ticket system as described in WBTC No. 5/99 and 5/99A should be included as one of the contractual requirements and implemented by the contractor. If surplus excavated spoil would be reused in land formation projects, the sites for such land formation projects must be clearly identified with written agreement from the relevant third party before such disposal. Assessment of potential environmental impact of such disposal has to be conducted and the above information has to be submitted to EPD for approval before action is taken.
6.5.5 A recording system for the amount of wastes generated, recycled and disposed (including the disposal sites) should be proposed. Quantities could be determined by weighing each load or other suitable methods.
6.5.6 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. The transportation of these wastes by sea to the disposal location is recommended, as far as practicable, in order to reduce potential noise and air quality impacts from road transportation.
General Site Wastes
6.5.7 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. The collection area for waste should be sited away from the Country Park and ecological sensitive areas.
Workforce Wastes
6.5.8 Suitable collection sites around site offices and canteen will be
required. It is recommended that for environmental hygiene reasons and to
minimise odour, refuse is not stored for a period exceeding 48 hours, however,
removal every 24 hours is preferable. No canteen should be provided within the
water gathering ground.
6.5.9 Provision of temporary toilet facilities within the water gathering ground
should be subject to the approval of Director of Water Supplies. All waste
should be cleared away daily and disposed outside the water gathering ground.
The toilet facilities should not be less than 30 m from any watercourses.
Maintenance and Chemical Wastes
6.5.10 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.
6.5.11 Any service shop and minor maintenance facilities should be located outside the water gathering ground and should be on hard standings within a bunded area, and sumps and oil interceptors should be provided. Maintenance of vehicles and equipment involving activities with potential for leakage and spillage should only be undertaken with the areas appropriately equipped to control these discharges. No storage and discharge of flammable or toxic solvents, petroleum oil or tar and other toxic substances shall be allowed within the water gathering ground. Any chemicals to be used including disinfectants and deodorants within the water gathering ground should be subject to the approval of the Director of Water Supplies.
C&D Material
6.5.12 No earth, building materials, soil and other materials should be stockpiled within the water gathering ground. All surplus spoil should be removed from the water gathering ground as soon as practicable. Stockpiles of excavated spoil outside the water gathering ground 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.
6.5.13 Any soil contaminated with fuel leaked from plant should be removed from the water gathering ground and the voids arising from removal of contaminated soil should be replaced by suitable material to the approval of the Director of Water Supplies.
6.6 Definition and Evaluation of Residual Environmental Impacts
6.6.1 If appropriate mitigation measures are implemented during the handling, collection, and disposal of waste material, the residual environmental impacts would be reduced to acceptable levels. These mitigation measures can be enforced by incorporating them into a waste management plan as part of the contract document. Environmental monitoring and audit will be necessary to ensure the implementation of correct disposal requirements for the various wastes generated from construction works.