5                        Waste management implications

5.1                 Introduction

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                 Environmental Legislation, Policies, Plans, Standards and Criteria

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([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 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                 Assessment Methodology and Criteria

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.

5.4                 Identification and Evaluation of Environmental Impacts

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[2] 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


Inert C&D material to be delivered to recycling facility (m3)

Phase 1 works :

Excavation works






Demolition of existing facilities






Phase 2 works :

Excavation works






Demolition of existing facilities






Bentonite Slurry




6,800 (2)









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.

5.5                 Mitigation Measures

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                 Evaluation of Residual Impacts

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                 Environmental Audit Requirements

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                 Conclusions

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.

([1])      “C&D material” contains a mixture of inert and non-inert material.  The inert portion is the “public fill” and the non-inert portion is the “C&D waste”.

[2]        Tai Po Sewage Treatment Works, Stage V, Contamination Assessment Report, August 2003.  Sewerage Projects Division, Drainage Services Department.