7.1. This section identified the types of wastes that would likely be generated during the construction phase and the operation of the STW, and evaluates the potential environmental impacts that would likely result from these waste arisings. Mitigation measures and good site practices, including waste handling, storage and disposal, were recommended with reference to the applicable waste legislation and guidelines.

Environmental Legislation, Policies, Plans, Standards and Criteria

7.2. The principal legislation controlling waste materials in Hong Kong is the Waste Disposal Ordinance [Cap.354] (WDO). Enacted in 1980, this ordinance generally encompasses all stages of the waste management chain, from place of arising to final disposal point.

7.3. There are a number of provisions under the WDO for dealing with certain types of waste. They include the Waste Disposal (Chemical Waste) (General) Regulation, which is relevant to this Project. Enacted in 1992, this regulation controls all aspects of chemical waste disposal, including storage, collection, transport, treatment and final disposal. Technical Circulars include the Environment, Transport and Works Bureau Technical Circular (Works) No. 33/2002 on the management of construction and demolition material including rock is also relevant to this Project for the management of construction and demolition (C&D) material.

7.4. Annex 15 of TMEIA sets out guidelines for assessment of waste management implications.

Description of the Environment

Baseline Conditions

7.5. According to the Consultancy Study for Outlying Islands Refuse Transfer Facilities Initial EIA Report, September 1993, the projected current waste arisings were estimated to be 2 tonnes per day, which mainly consists of domestic and commercial waste. There is no sewage treatment works in Sok Kwu Wan at present and therefore there is no sewage sludge arisings. The domestic and commercial waste arisings are currently collected in plastic sacks and transferred to barging points operated by the Leisure and Cultural Services Department for the final disposal at the WENT Landfill.

7.6. A refuse transfer station is located adjacent to the footpath connecting the villages of Sok Kwu Wan and Mo Tat Wan. The refuse transfer station receives publicly collected domestic and commercial wastes and undertakes waste compaction and containerisation. The containerised waste is delivered to Mui Wo by boat and transferred by marine transport for disposal at the WENT Landfill. The refuse transfer station was designed to accommodate the anticipated population and economic growth over a 15-year period from year 1993 and it was taken into account the fluctuations in waste arisings from weekends and at holiday and festival periods.

Assessment Methodologies

7.7. Types of waste arising from the construction activities and the operation of the STW were identified. If possible, these wastes were also quantified. Suitable methods were recommended for proper disposal of these wastes.

Environmental Impact Identification, Prediction and Evaluation

Construction Phase

7.8. Construction activities of the proposed development would include the following:

· trench excavation for sewer pipe laying;

· excavation for substructures of pumping stations and STW;

· formwork for concreting works; and

· operation/maintenance of construction plant and material storage facilities.

7.9. The pipe laying activities would generate various types of wastes, including soft and rock spoils. Due to the limited areas involved in the construction works it was anticipated that relatively small quantities of spoil would be generated as a result of the excavation works. It was estimated that a total bulk of 380 m³ of rock spoil and 6,250 m³ of soft spoil would be generated. Of the soft spoil, approximately 3,360 m³ would be re-reused on site as fill material.

7.10. The construction equipment would require regular maintenance and servicing which would use and generate chemical waste. Substances generated would likely include oil, lubricants, cleaning fluid, solvents and rags. This chemical waste should be handled, collected, and disposed of according to the Waste Disposal (Chemical Waste) (General) Regulation under the Waste Disposal Ordinance and disposed of by a licensed contractor at Tsing Yi Chemical Waste Treatment Facility.

7.11. Finally, throughout the construction, the workforce on site would generate general refuse, comprising food scraps, paper and empty containers, etc. For the handling of general refuse, on-site refuse collection points should be provided.

7.12. Different types of construction waste should be segregated, stored and transported and disposed separately in accordance with the relevant legislative requirements and guidelines.

*Operational Phase***

7.13. Wastes generated during normal STW operations would include screenings grit, and sewage sludge. The sewage sludge would be stabilized on-site by aerobic digestion. The quantity of digested sludge generated from the operations at design capacity would be approximately 184 kg of dry solids per day. The sludge would be dewatered on-site and the sludge cake would be delivered to Sok Kwu Wan refuse transfer station for disposal to nearby landfill site. It was estimated that the sludge cake production per week is approximately 4.3 tonnes.

Mitigation of Adverse Environmental Impacts

Construction Phase

7.14. It was anticipated that adverse waste management related impacts would not arise, provided that good site practices are adhered to. Recommendations for good site practices for the construction waste arising include:

Ÿ Nomination of an approved person, such as a site manager, to be responsible for the implementation of good site practices, arranging for collection and effective disposal to an appropriate facility, of all wastes generated at the site.

Ÿ Training of site personnel in proper waste management and chemical handling procedures.

Ÿ Appropriate measures to minimize windblown litter and dust during transportation of waste by either covering trucks or by transporting wastes in enclosed containers.

Ÿ Provision of sufficient waste disposal points and regular collection for disposal.

Ÿ Separation of chemical wastes for special handling and appropriate treatment at the Chemical Waste Treatment Facility.

Ÿ Regular cleaning and maintenance programme for drainage systems, sumps and oil interceptors.

Ÿ Maintain records of the quantities of wastes generated, recycled and disposed.

7.15. In order to monitor the disposal of C&D waste at landfills and to control fly tipping, a trip-ticket system should be included as one of the contractual requirements and implemented by an Environmental Team undertaking the Environmental Monitoring and Audit work. An Independent Environmental Checker should be responsible for auditing the results of the system.

7.16. Good management and control could prevent the generation of significant amount of waste. Waste reduction is best achieved at the planning and design stage, as well as by ensuring the implementation of good site practices. Recommendations to achieve waste reduction 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;

· use of reusable non-timber 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.

7.17. In addition to the above good site practices and waste reduction measures, specific mitigation measures were recommended below for the identified construction waste arisings to minimise environmental impacts during the handling, transportation and disposal of these wastes:

a) General Site Wastes

7.18. A collection area should be provided where waste can be stored prior to removal from site. An enclosed and covered area is preferred to reduce 'wind blow' of light material.

b) Chemical Wastes

7.19. After use, chemical waste (eg. 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. Any unused chemicals or those with remaining functional capacity should be recycled. Spent chemicals should be properly stored on site within suitably designed containers, and should be collected by an approved operator for disposal at the Chemical Waste Treatment Facility or other licenced facility in accordance with the Waste Disposal (Chemical Waste) (General) Regulation under the Waste Disposal Ordinance

7.20. Any service shop and minor maintenance facilities should be located 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 leakages and spillage should only be undertaken within the areas appropriately equipped to control these discharges.

c) Construction and Demolition Material

7.21. The C&D material should be separated on-site into three categories: (i) public fill, the inert portion of the C&D material (e.g. concrete and rubble), which should be re-used on-site or disposed of at a public filling area; (ii) C&D waste for re-use and/or recycling, the non-inert portion of the C&D material, (e.g. steel and other metals, wood, glass and plastic); (iii) C&D waste which cannot be re-used and/or recycled. The waste producers are responsible for its disposal at strategic landfills.

7.22. In order to minimise the impact resulting from collection and transportation of material for off-site disposal, it was recommended that inert material should be re-used on-site where possible. Prior to disposal of C&D material, it was also recommended that steel and other metals should be separated for re-use and/or recycling where practicable to minimise the quantity of waste to be disposed of to landfill.

7.23. When disposing C&D material at a public filling area, it should be noted that the material should only consist of earth, inert building debris and broken rock and concrete. The material should 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 public filling supervisor. Small quantities of timber mixed with otherwise suitable material would be permitted.

Operational Phase

7.24. Wastes generated during normal STW operations would include inlet screenings, grit from detritors and dewatered sludge. It was proposed that the sewage sludge generated from the STW would be dewatered on-site and the sludge cake would be delivered to Sok Kwu Wan refuse transfer station for disposal to nearby landfill. It is expected that the handling and disposal of the sludge generated from this small-scale STW (< 1000 m³/d of effluent flow) would not induce unacceptable impacts compared to other large-scale sewage treatment works operating in the territory.

Summary

7.25. Table 7.1 provides a summary of the various waste types likely to be generated during construction and operational phases, together with the recommended handling and disposal methods.

Table 7.1 Summary of Waste Handling Procedures and Disposal Routes

Waste Type	Handling	Disposal
Construction
Construction & Demolition Material	Where possible should be re-used on-site	On-site for pavement re-instatement
	If off-site disposal required, separate into: · Public fill (e.g. concrete and rubble) · C&D waste for re-use and/or recycling (e.g. steel and other metals, wood, plastic) · C&D waste which cannot be re-used and/or recycled	Public filling area or reclamation Steel and other metals should be separated for re-use and/or recycling where practicable before disposal of at landfill. Landfill
Maintenance and Chemical Wastes	Recycle on-site or by licensed companies Stored on-site within suitably designed containers	By licenced contractor to Chemical Waste Treatment Facility
Workforce Wastes	Provide on-site refuse collection facilities	Landfill, collection by private hygiene company
Operation
Sewage sludge	Dewatered on-site	Landfill

Definition and Evaluation of Residual Environmental Impacts

Construction Phase

7.26. Given that all the recommended mitigation measures on waste management practices are adopted, it is expected that the residual impacts from the generation of construction and demolition material, workforce wastes and chemical/maintenance wastes on-site would not be significant.

Operational Phase

7.27. The preliminary assessment has identified that approximately 6 m³/week of sludge would be generated from the STW for ultimate disposal at the WENT Landfill. It was recommended that possible environmental impacts arising from the dewatering and disposal arrangement of sludge should be addressed later during the design stage of the Project.

Environmental Monitoring and Audit

7.28. It was recommended that auditing of each waste stream be carried out periodically to determine if waste is being managed in accordance with approved procedures and the site waste management plan. The audits should look at all aspects if waste management including waste generation, storage, recycling, treatment, transport, and disposal. An appropriate audit programme would be undertaken a first audit at the commencement of the construction works, and then to audit monthly thereafter.