5.1.1.1 Impacts from waste generation throughout construction and operation of San Wai STW and Ha Tsuen PS would be minimised by implementation of suitable mitigation measures through waste management. Requirements in waste management are summarised in this section.
5.2 Mitigation of Adverse Impacts during Construction Phase
5.2.1 Waste Management Plan
5.2.1.1 A proper Waste Management Plan (WMP) for the construction of the project should be submitted to the 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.
5.2.1.2 For the purpose of enhancing the management of C&D material including rock, and to minimize its generation at source, a C&D Material Management Plan (C&DMMP) has been prepared for this project and would be processed in accordance with the Environment, Transport and Works Bureau Technical Circular (Works) No. 33/2002 - Management of Construction and Demolition Material Including Rock and is included in Appendix 6A of the EIA Report. The management measures stipulated in the C&DMMP should be incorporated into the WMP.
5.2.2 Waste Reduction Measures
5.2.2.1 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
The project proponent will try every endeavours in minising the generation and maximising the reuse/recycle of the construction and demolition material. The measures that will be taken are as follows:
· Use the excavated materials for earthfilling as far as
possible;
· Use the excavated soft materials for landscaping works;
· Reuse the C&D materials for as pipe bleeding; and
· Use precast units to minimise the amount of C&D materials generated on
site.
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.
5.2.3 Good Site Practices
5.2.3.1 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;
· Separation of chemical wastes for special handling and appropriate treatment
at the Chemical Waste Treatment Facility; and
· Regular cleaning and maintenance programme for drainage systems, silt traps,
sumps and oil interceptors.
5.2.3.2 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. 21/2002 Trip-ticket System for Disposal of Construction and Demolition Material should be included as one of the contractual requirements and implemented by the contractor.
5.2.3.3 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.
5.2.3.4 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.
5.2.4 General Site Wastes
5.2.4.1 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.
5.2.5 Maintenance and Chemical Wastes
5.2.5.1 The chemical waste generated should be labelled, stored and disposed of according to the Waste Disposal (Chemical Waste) (General) Regulation. Registration as a chemical waste producer is required if chemical wastes would be produced. Relevant regulations should be observed and complied with for control of chemical wastes. Proper storage area should be allocated on site for storage of chemical waste. The chemical waste should only be collected by a licensed collector. An updated list of licensed chemical waste collector can be obtained from EPD.
5.2.5.2 The construction contractors/facility operator should adopt the necessary mitigation measures to prevent the uncontrolled disposal of chemical and hazardous waste into air, soil, surface waters and ground waters. Spill adsorbent material and emulsifiers should be available on site in case of spillage. Any contaminated material such as absorbent or cleaning stuffs should be properly disposed of.
5.2.6 C&D Material
5.2.6.1 Components of C&D material such as steel and other metals should be segregated and recycled as far as possible before disposal to landfill.
5.2.6.2 The inert C&D material should be re-used on-site or recycled as far as possible before arranging for disposal of at public filling area.
5.2.6.3 For surplus inert C&D material required to be disposed of at public filling area, it should be noted that the public filling materials should only consist of earth, building debris and broken rock and concrete. They should be free from marine mud, household refuse, plastic, metals, industrial and chemical waste, animal and vegetable matter, and other material considered unsuitable by the public filling Supervisor.
5.3 Mitigation of Adverse Impacts during Operational Phase
Sludge
5.3.1.1 All the sludge generated in San Wai STW should be dewatered onsite to more than 30% dry solids content before transporting to the designated landfill site for disposal and should be stored in covered container along the transporting route to avoid the possible odour impact on nearby sensitive receivers.
Spent UV disinfection lamps
5.3.1.2 The operators of future UV disinfection facility should work with the supplier/manufacturer on recycling and reuse of the defective UV lamps as far as possible. Should the disposal of UV lamps be unavoidable, the operators should identify the content 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 Waste Disposal (Chemical Waste) (General) Regulation. In handling the UV lamps, cautions should be exerted to avoid breakage of lamps and release of contaminants.
Deodourisation unit waste
5.3.1.3 Depending on the technology to be used for the proposed deodourisation unit at the expanded San Wai STW and Ha Tsuen PS, different kinds of waste streams may be produced from the deodourisation process. The two likely technologies would be adsorption of odourous chemicals by granulated activated carbon (GAC) and scrubbing of odourous air stream with chemical oxidants in a chemical scrubber.
5.3.1.4 The spent GAC and scrubbing fluids from the chemical scrubber are likely to be categorised as chemical waste due to their characteristics as strong alkalis and oxidants. The handling, storage and disposal of the spent scrubbing fluids should follow the requirements under the CWR. Unless the spent fluids are treated to meet discharge standards as stipulated in the Technical Memorandum under Water Pollution Control Ordinance, direct discharge into local sewerage systems should not be allowed.