3                                            Description of the Extension

3.1                                      Site Description

The Extension Site is located at TKO Area 137 with a piggyback area occupying the southern slope of the existing SENT Landfill and its infrastructure area and extends over the boundary of the Clear Water Bay Country Park (CWBCP).  Figure 3.1a shows the location of the Extension Site.

The Extension Site is surrounded by existing and future developments on the northern, southern and western sides.  To the north of the Site is the existing SENT Landfill.  To the south and west of the Site is a reclaimed area currently used by the Civil Engineering and Development Department (CEDD) for a fill bank operation.  The eastern side of the Site is bounded by the natural headland of the CWBCP.  The sides of the natural headland adjoining the Site are steep, undeveloped and support grassland or shrub vegetation.  This headland forms a natural screen between the Extension and the largely undeveloped environments of Clearwater Bay and Port Shelter further to the east.  The TKO New Town lies approximately 3.5km to the north of the Extension Site.

The nearest existing development to the Extension Site is the industrial development within TKOIE located to the northwest and separated by Wan Po Road.  The main access route to the SENT Landfill and the Extension Site is via Wan Po Road. 

3.2                                      Site History

In the 1990s, the SENT Landfill and the surrounding area were relatively remote and lightly populated.  In the intervening years, there has been considerable development nearby.  Further reclamation has occurred on the seaward side of the SENT Landfill.  This reclamation is now occupied by the TKOIE and the TKO Area 137, where the Extension Site will be located.  The majority of TKO Area 137 is currently occupied by the temporary public fill bank.  The fill bank is used for storage of inert construction and demolition material, pending its beneficial reuse in construction projects elsewhere.

The Extension Site area within the CWBCP, designated in 1979, is undeveloped.  Part of the natural coastline of the CWBCP was lost due to the development of the SENT Landfill and the reclamation of TKO Area 137.

3.3                                      Design of the Extension

The Extension is a piggyback landfill, occupying the existing SENT Landfill infrastructure area, 15 ha of TKO Area 137 and approximately 5 ha of the CWBCP.  A layout plan of the Extension is shown in Figure 3.3a.  The new infrastructure area will be located to the south of the waste filling area.  Figure 3.3b shows the layout of the infrastructure area, which houses the landfill gas treatment facility and leachate treatment plant, offices, maintenance workshops, etc.

The Extension covers an area of around 50 ha (including all site infrastructure).  Discounting the void space required for miscellaneous engineering works and daily and intermediate covers, the total net void capacity for waste is estimated to be around 17 Mm3.  The lifespan of the Extension is estimated to be around 6 years, commencing operation in 2013 ([1]). 

The design of the Extension comprises the following key components:

·           Landfill liner and capping;

·           Landfill gas management system;

·           Leachate management system;

·           Surface water management system;

·           Groundwater management system; and

·           Site infrastructure.

The design of these components is described in the following sections.

3.3.1                                Landfill Liner and Cap

The Extension will be designed and constructed as a fully contained facility incorporating multilayer composite liner systems covering the entire surface area of the Extension Site where waste will be deposited.  Four different liner systems will be used for the different areas of the Extension Site, as follows:

·           Basal;

·           Rock slope;

·           Soil slope; and

·           Piggyback

Sections of the liner systems are shown in Figure 3.3c.  In general, the design of all liner systems contains at least one impermeable layer, ie HDPE liner, a geocomposite clay liner (GCL), a geotextile cushion, and leachate and groundwater drainage layers.

After final levels of waste are reached, a protective soil layer will be placed over the waste before placing the final cap.  The final cap comprises non-woven geotextile, HDPE liner (impermeable layer), a drainage layer and a soil layer.  The impermeable liner and cap will form a containment of void for waste so as to ensure that the waste is completely separated from the surrounding environment.  Hence, this containment system will ensure minimal runoff and groundwater entering the waste and prevent off-site migration of leachate and landfill gas.

3.3.2                                Landfill Gas Management

Landfill Gas Collectors at the Extension

Three types of collectors are proposed to be included to provide effective collection of landfill gas at the Extension as soon as possible:

·           Horizontal collectors above the leachate drainage layer – these have been allowed for at approximately 100m intervals above the basal liner system;

·           Horizontal collectors in the waste mass – these have been allowed for at approximately 75m centres; and

·           Vertical drilled wells – at 40m centres on the perimeter of the waste boundary and 80m centres within the body of the waste nass.

The locations of these collectors are shown in Figure 3.3d.  Together with the impermeable liner as part of the intermediate cover system, and the final capping system, these types of collector effectively minimise landfill gas emissions from the Extension at any time during the operation. 

Landfill Gas Collectors at the Existing SENT Landfill

To avoid damaging the liner system of the Extension, modifications to the landfill gas collection wells at the southern waste slope of the existing SENT Landfill will be required.  The modification work will include removal of well pipes, placement of a concrete cap over the top of the affected wells and installing a short length of pipe to connect the affected wells to the existing gas collection system of the SENT Landfill (see Figure 3.3e).  If the existing landfill gas collection wells are damaged beyond economical repair and rendered useless or it is considered that there is a need to have greater collection ability during the construction of the Extension, new wells can be drilled to enhance gas collection.

As part of the liner design, a landfill gas drainage layer will be sandwiched between the SENT Landfill cap and the Extension liner (see Figure 3.3f).  This gas drainage layer comprises a layer of granular fill over the landfill surface and to collect gas emanating from the surface should leakage in the capping system and around the damaged gas wells occur.  It also serves a secondary function to provide a mean of collection which may be beneficial after a period, when settlement is or has occurred, and the existing and interim gas collection system and/or cap has suffered damage.

Landfill Gas Collection Pipework

Interim pipework will be required to connect the various collector types in both the Extension and the existing SENT Landfill.  The pipework will be laid using either welded HDPE pipes laid over the surface, or a system of reasonable flexible convoluted polypropylene pipe with suitable robust connection methods.  The interim pipework can be laid to connect the landfill gas treatment facility at the infrastructure area or to localised temporary gas flares.

Permanent pipework will be installed to eventually connect all gas collectors and allow the gas extracted to be delivered to the landfill gas treatment facility.  It will be laid over the surface, provided that the polymer used contains sufficient UV inhibitors to prevent degradation occurring.  Alternatively, the pipework will be buried within the landfill cap.

The landfill gas collected from the existing SENT Landfill will be delivered to the landfill gas utilisation plant proposed by GVL and the remaining gas will be delivered to the landfill gas treatment facility located at the new infrastructure area.  The landfill gas collected from the Extension will be transferred to the landfill gas treatment facility located in the infrastructure area.

Landfill Gas Treatment Facility

The landfill gas treatment facility will be located in the infrastructure area and will comprise the following key components:

·           Condensate knockout pot to remove moisture droplets;

·           Gas boosters to provide suction to the well field and pressure to downstream facilities;

·           Enclosed flares to efficiently destroy the methane and trace components;

·           A control system to ensure safe initiation of the flare burn and subsequent operation; and

·           Connections to permit an off-take for utilization of the landfill gas.

The predicted gas yield indicates that a peak combined gas flow from both the Extension and the existing SENT Landfill of approximately 16,600 m3 hr-1 is expected in year 2020, whilst the flow is anticipated to be over 10,000 m3hr-1 over a twenty year period, between 2008 and 2028.  The design will include two identical enclosed flares with a capacity of 10,000 m3 hr-1 each, to provide a maximum handling capacity of 20,000 m3 hr-1. 

Landfill Gas Utilisation

Landfill gas is flammable, which has value as a renewable fuel and has utilised as such around the world in many applications.  The potential utilisation options which may be considered for the landfill gas collected from the Extension include:

·            On site utilisation in the leachate treatment plant;

·            On-site utilisation for site power requirements;

·            Delivery to the proposed landfill gas utilisation plant at the existing SENT Landfill;

·            On-site Combined Heat and Power (CHP);

·            Dedicated use in the adjacent industrial area. Uses include direct firing in boilers for process heat, or in an absorption chiller to provide for air conditioning or CHP schemes; and

·            Power generation for export to the CLP grid.

The precise type of utilisation will be determined during the detailed design stage by the Extension Contractor.  For the purpose of the assessment, it is assumed that landfill gas will be used to fuel the LTP while the remaining gas will be flared.

3.3.3                                Leachate Management

With the proposed design of the liner and capping systems, water ingress into the Extension will be minimized and off-site migration of leachate will be negligible.  Leachate will be contained and collected via the collection system to the LTP in the new infrastructure area.  The main features of the leachate management system are:

·           Leachate collection system comprising aggregate and geosynthetic drainage layers;

·           Leachate extraction system comprising HDPE sideslope risers and collection sumps; and

·           The LTP.

Location of the main features of the leachate management system is shown in Figure 3.3g. 

Leachate Collection System

The leachate collection layer is designed to collect and drain leachate which percolates downwards from the waste.  The layer, comprising aggregate (a minimum depth of 300mm) in the basal liner or geosynthetic drainage layer (in the slope and piggyback liners) will be placed on top of the impermeable liner with a layer of cushion (eg geotextile) between the two.  Drainage pipework will be installed within the leachate collection layer in the basal liner.  At the piggyback and side slope area, leachate will be collected at the geosynthetic drainage layer and flow by gravity to the basal liner where leachate will be collected by the pipwork.  The pipework will be manufactured from either HDPE, u-PVC or polypropylene, and will be perforated (with slots or holes) except for the lower 120o of the pipe cross-section, which will be solid to allow for flow of leachate.  The leachate drainage pipework will be designed such that the maximum head of leachate above the basal lining system does not exceed 1m.  The maximum pipe spacing will be 50m, and the gradient should be at least 1(v) : 50(h).  The pipework will collect leachate from the waste and drain it to the collection sumps.

Leachate Extraction System

Leachate will be extracted from the landfill via four collection sumps around the western and southern perimeter of the Extension Site (see Figure 3.3g).

The leachate collection sumps will be constructed of pre-cast concrete and will be equipped with submersible pumps to enable leachate to be pumped from the base of the landfill to the leachate collection main, which will transfer leachate to the LTP in the new infrastructure area.

The leachate collection sumps will be accessed by HDPE upslope risers along the toe bund of the Extension, and therefore will not be prone to damage due to movements of the waste mass.

Leachate Treatment Plant

The process flow diagram of the proposed leachate treatment process is shown in Figure 3.3h.  All processing tanks, except the SBR tanks, will be covered.

The predicted average daily leachate flow from the Extension during its period of operation is 332 m3 d-1.  However, the daily flow rate will vary according to seasonal rainfall.  The predicted average daily flow from the existing SENT Landfill following restoration is 23 m3 d-1.

The proposed leachate treatment option is to provide an LTP with maximum design flow rate of 1,500 m3 d-1, coupled with a buffer storage capacity of 22,000 m3.  This capacity will be able to cope with the anticipated peak leachate treatment requirement during the last year operation of the existing SENT Landfill when the existing Bioplant will be demolished, and subsequently during the Extension operation.  Following full restoration of the existing SENT Landfill, the buffer storage capacity could be reduced, subject to further review, as the leachate generation from the Extension is smaller.  Table 3.3a summarises the design leachate flow and quality of the LTP.

Table 3.3a      Summary of Design Leachate Flow and Quality Used in Plant Sizing

Design Flow Rate





Design effluent limits





Total inorganic nitrogen (TIN)





Total nitrogen (TN)










Design Raw Leachate Quality





Influent NH4-N





Influent COD





Hard COD





Hard TKN





From the buffer storage tanks, leachate will be pumped to the metal precipitation system and then to ammonia stripping plant which consisting of two stripping towers, two thermal oxidizer towers (one operating and one on standby), heat exchangers and ancillary equipment.  The two ammonia stripping towers, each with a capacity of 750 m3 d-1 can operate alternately to allow for regular maintenance.  The stripping process would be operated to remove approximately 92 to 98% of the ammonia, leaving approximately 100 to 200 mg L-1 of ammonical nitrogen (NH4-N) to be removed biologically together with the degradable chemical oxygen demand (COD).  The ammonia-laden air then passes to the thermal oxidizer where the ammonia will be oxidized to nitrogen gas prior to discharge to atmosphere. 

Stripped effluent will be stored in a holding tank from where it will be fed to the Sequential Batch Reactor (SBR) tanks.  The SBRs will operate on a 24-hour cycle with denitrification.  From the SBRs, treated leachate is decanted, after a settling period, into the final effluent holding tank.  This allows continuous discharge of the treated effluent to the receiving foul sewer.  The Sewerage Impact Assessment has confirmed that the existing sewage infrastructure is adequate for the predicted flows.

The LTP will be commissioned during the last year of operation at the SENT Landfill and will replace the existing Bioplant of the SENT Landfill.  The LTP is capable of treating leachate to comply with the discharge standard stipulated in the existing discharge license of the SENT Landfill.  Following closure and restoration of the existing SENT Landfill, leachate generation at the existing SENT Landfill will be reduced significantly.  It is estimated that the averaged combined leachate flow from the restored SENT Landfill and the operating Extension will be around 355 m3 d-1 while the peak treated effluent flow will be limited to 1,000 m3 d-1.  The LTP is capable of treating leachate to comply with discharge standards stipulated in EPD’s Technical Memorandum Standards for Effluents Discharged into Drainage and Sewage Systems, Inland and Coastal Waters. 

3.3.4                                Surface Water Management

The surface water management system for the Extension is designed to minimise surface water entering the Extension Site from the upgradient area of CWBCP and the restored slope of the existing SENT Landfill.  It also controls contaminated runoff from the Extension Site entering the surrounding area.  Key features of the surface water management system include:

·           Permanent perimeter cut-off channel and drainage tunnels;

·           Temporary cut-off channels; and

·           Sediment traps and oil separator.

The location of these features is shown in Figure 3.3i.

Permanent Perimeter Cut-off Channel

A permanent cut-off channel will be constructed along the waste boundary of the Extension and will connect with the drainage features that are incorporated into the SENT Landfill restoration design.  The southern part of this cut-off channel will drain by gravity to the south-eastern corner of the Extension.  The northern part of this cut-off channel falls to the north, to a low point near the south-eastern corner of the existing SENT Landfill, where it will meet up with the existing cut-off channel for the existing SENT Landfill.

At present, the existing SENT Landfill cut-off channel traverses the eastern edge of the landfill, and then turns to the west, towards the existing SENT Landfill infrastructure area.  As part of the Extension development, this portion of the channel will be covered by waste.  The design of the surface water management system has therefore included the construction of a twin drainage tunnel (2,000mm diameter) to drain surface water collected at the low point near the south-eastern corner of the existing SENT Landfill to TKO Area 137.  The outfall of the twin drainage tunnels will join the perimeter cut-off channel at the eastern boundary of the Extension in TKO Area 137.

Following completion of the Extension, an additional channel will be constructed around the eastern flank of the Extension and then to the west, to convey flows directly to the western boundary of the Extension Site avoiding the low point to the east. 

Temporary Cut-off Channel

Prior to completion of the Extension, temporary collection and pumping of surface water (at low points) will be required as part of the surface water management plan, to avoid any discharge of stormwater eastwards into Clear Water Bay.

Run-off that has been in contact with waste will be treated as leachate and collected for treatment at the LTP.

Rain falling onto the restored slopes of the Extension will be collected by surface water channels on the slopes, and drained to the perimeter of the Extension Site.

Rain falling onto areas of active tipping and daily cover areas will infiltrate into the waste and be collected by the leachate collection system, for treatment prior to discharge into the foul sewer.

A series of temporary cut-off channels will be constructed on the side slopes and on the southern waste slopes of the existing SENT Landfill that lie within the Extension.  These channels will intercept rain falling on areas above the active tipping face, and divert it to the perimeter cut-off channels.

Within each development phase, areas outside the active tipping face will be covered with intermediate cover.  In order to minimise odour emission, leachate generation and to control contamination of surface water runoff, the intermediate cover will include an impermeable liner.  Temporary surface water management will be provided in order to collect rain falling onto areas of intermediate cover, and divert the clean runoff to the perimeter cut-off channels.

Sediment Traps and Oil Separator

All surface water drainage channels that discharge either directly or indirectly to surface watercourses or to the sea will be provided with sediment traps, stilling basins and oil separators to control suspended solid concentrations and oil in the surface water discharged from the Extension Site. 

3.3.5                                Groundwater Management

Groundwater will be managed to prevent a hydrostatic build-up of water below the base liner and to prevent contamination by leachate.  The basal liner has been designed to contain two impermeable layers to avoid leachate migrating out of the lining system.  The design of the leachate collection system will also minimise the leachate head and thus minimise the driving force of leachate migration through any holes in the base and sideslope liner system.  A geocomposite drainage layer below the base liner (see Figure 3.3c) will collect and transport groundwater away from the liner.  The base of the Extension has been kept above the groundwater level, in order to minimise difficulties during construction, and minimise the consequences of any leakage from the lining system. 

The groundwater collection layer on the side slopes of the Extension will be connected to groundwater diversion pipe trenches, and groundwater flows will be diverted to a series of groundwater collection sumps along the western boundary of the Extension adjacent to the leachate sumps before discharge off-site (see Figure 3.3j).  The design has allowed for the provision of a submersible pump in the sump for pumping to the leachate collections sumps (adjacent) in the event of contamination being detected.

3.3.6                                Site Infrastructure

The new infrastructure area is located south of the waste filling area.  This area is occupied by offices, maintenance workshops, landfill gas treatment facility and the LTP, as shown in Figure 3.3b.  A loop road system is designed to provide access to all tanks and equipment within the infrastructure area.  A 5m wide landscape planting strip has been allowed along the boundary to screen the access road and the infrastructure area.

Other site infrastructure includes the weighbridge and vehicle washing facility, located to the north of the new infrastructure area.  The weighbridges will be enclosed and will be maintained at a slight negative pressure.  Air extracted from the enclosed area will pass through the air scrubbing system prior to discharge to the atmosphere.

The vehicle washing facility will be located just before the out-weighbridge.  The water spray at the facility will ensure that the outside of the whole vehicle to be washed so as to minimize potential odour impacts from the RCVs leaving the Extension Site.  The wash water will be drained to the LTP for treatment.

3.4                                      Extension Development Programme

The key tasks of the Extension development are shown in Figure 3.4a.   Construction works will commence two years prior to commencement of waste filling.  The Extension will be developed and operated under six phases, each will last for about one year.  Upon the completion of each phase, the areas that reached the final profile will be restored immediately. 

3.5                                      Construction of the Extension

Construction works will commence in early 2011, two years before the Extension starts operation.  During the first year of construction, works including site formation and construction of superstructure will be carried out in the new infrastructure area.  Pipes will be constructed to transfer the leachate and landfill gas collected from the existing SENT Landfill to the treatment facilities at the new infrastructure area.  Waste reception facilities, including the site access road and weighbridges and monitoring wells will also be constructed.

Formation of side slopes on the eastern side of the Extension will begin in the third quarter of 2011.  The formation of side slopes will require blasting of the rock slopes.  The total volume of rock to be excavated for the Extension is around 320,000 m3.  With the assumption that there will be one blast per day and a volume of 3,000 m3 per blast, the total blasting period would be around 107 days.   The quantity of explosive used and the dimensions and spacings of shotholes will be carefully designed to minimize air overpressure, flyrock generation and ground-borne vibration.  To minimize environmental impacts and ensure safe operation, loose material and stones in the Site will be removed prior to the blast operation.  The area within 30m from the blasting area will be wetted prior to blasting to minimize dust generation.  During blasting, blast nets, screens and other protective covers will be used to prevent the projection of flying fragments and other material resulting from blasting.

The rock obtained from blasting will be crushed on-site for reuse as leachate stone and subsequent site formation and engineering works.

The construction of the surface cut off drain and the 2,000mm twin drainage tunnels will commence in the third quarter of 2011 and will last for about 6 months.  The tunnels will be constructed using micro-tunnelling techniques (using a tunnel boring machine (TBM)).  The tunnel will be constructed from the lower end, ie at TKO Area 137. 

In the second year, plant and equipment in the new infrastructure area will be commissioned, followed by demolition of the existing infrastructure at the SENT Landfill.  This arrangement will ensure that treatment of leachate and landfill gas from the existing SENT Landfill is not interrupted. 

The base grades of the waste filling area will be formed, followed by laying of base liner and the groundwater and leachate collection system.  The formation of side slopes with blasting will continue throughout the second year and be completed by 2012.

The waste filling area will be ready for tipping operations in 2013.

3.6                                      Operation of the Extension

The Extension will be developed in six phases (see Figures 3.6a to 3.6k).  Towards the end of each phase, liner will be installed on the side slope for the next phase.

Based on the waste arisings forecast, the Extension will receive on average around 8,600 tonnes per day throughout its operational life time, generating around 1,500 vehicle per day ([2]).  It is anticipated that the Sludge Treatment Facilities (STF) will commence operation in 2012, before the commissioning of the Extension.  The incineration ash generated by the Integrated Waste Management Facilities (IWMF) planned to be in operation by 2014 will also be disposed of at the Extension.  Hence, the type of waste to be received by the Extension will include MSW, construction waste and special waste (without sludge from the sewage treatment facilities ([3]) but including the residues from the STF and IWMF).

Similar to the existing practice, the Extension will be receiving waste from 8:00am till 11:00pm.  Preparation of the daily tipping face will start before 8:00am.  The preparation work includes mobilizing equipment to the tipping face and removal of cover soil.  The special waste trench will be constructed after 8:00 am.

When a waste collection vehicle arrives at the site, it will go through the in-weighbridge and then heading to the designated tipping face.  The size of the active tipping face will be around 1,200 m2.  The waste collection vehicle will unload the waste in the designated areas, depending on the type of waste it is carrying.  In general, MSW and the non-inert waste are unloaded in the “wet waste” tipping area, the inert waste and construction waste are unloaded in the “dry waste” tipping area and selected special waste ([4]) is unloaded in the special waste trench, approximately 15 m2 in size.  Waste unloaded in the “wet waste” tipping area will be immediately covered by the construction waste from the “dry waste” tipping area.  Waste will then be compacted by landfill compactors and dozers.  When the waste collection vehicle leaves the tipping area, it will go through the vehicle wash facility and the out-weighbridge before leaving the Extension Site.

Towards the end of each working day the whole tipping face will be covered with 300mm of soil and compacted.  The special waste trench will be opened from 9:00am to 6:00pm and will be covered with soil immediately after closure.

To control odour emission and reduce leachate generation in areas not actively used for tipping (ie the intermediate covered area), an impermeable liner will be placed on top of the 600mm thick cover soil ([5]).  When the area is to be used for tipping, the impermeable liner and the cover soil will be removed. 

It is expected that the landfill operation will last for about six years.  The Extension will be operated to comply with international best practice for landfill operation.

3.7                                      Restoration of the Extension

Areas filled to final grades will be restored as soon as possible.  Restoration will be carried out in stages as phases are progressively filled with waste.  After final levels are reached within a given phase, a 300mm protective soil layer will be placed over the waste.  The final cap, comprising a non-woven geotextile, a HDPE geomembrane, a high permeability geocomposite drainage layer and a 1,500mm fill layer, will then be placed (see Figure 3.3c).

The first 1,200mm of fill directly above the drainage layer will be compacted to reduce surface water infiltration.  The thickness of the fill layer will be increased in some planting areas to provide depth sufficient to prevent damage to the liner from vegetation rooting.  After placement of the final cover system, the areas will be landscaped.

Vertical landfill gas extraction wells will be drilled during restoration.  The restoration work will also include the construction of permanent surface water drains.

3.8                                      Aftercare of the Extension

Upon completion of final filling and site restoration, the period of aftercare will begin and last for 30 years.  During this period, by-products from waste disposal will continue to be generated including leachate and landfill gas.  The established leachate and landfill gas management control and treatment facilities will continue to operate throughout the aftercare period.

Regular site maintenance will be required during the aftercare period to keep the incorporated systems functioning as designed.  Site monitoring during the aftercare period will continue in accordance with the monitoring plan, but may be decreased if warranted and approved by the EPD. 

During the aftercare period, afteruse(s) could be developed on the restored landfill for beneficial uses.  However, the definition of the afteruse development is outside the scope of the current assessment and the Extension contract.  A separate feasibility study and environmental impact assessment (if required) will be carried out for the development of the afteruse(s).

3.9                                      Concurrent Projects

3.9.1                                Interfacing with the Existing SENT Landfill Operation

There will be an overnight switch of tipping areas from the existing SENT Landfill to the new tipping area at the Extension.  During the first quarter of the operation at the Extension, restoration at the last filling area at the existing SENT Landfill will be undertaken.  Based on the phasing plan from the existing SENT Landfill operator, the last filling area will be located at the northern end of the existing SENT Landfill, as shown in Figure 3.9a.  Since the distance between the last filling area at the SENT Landfill and the new active tipping face at the Extension is over 1km, cumulative impacts are not anticipated.

3.9.2                                Development in TKO Area 137

The rest of the area in TKO Area 137 is currently planned for Deep Water Front Industrial uses.  With reference to the Engineering Feasibility Study of Development of TKO Area 137 (March 1993), potential hazardous installation (PHI) may be developed in the area and hence there is a worker density restriction imposed in TKO Area 137, although there is no committed PHI development at presence.  The risk assessment as part of that Engineering Feasibility Study recommended a worker density of 30 persons/ha within the Consultation Zone in Area 137.  As the worker density at the Extension during both construction and operation phases will not exceed this recommendation, it is expected that risk to the workers within the Extension Site due to the potential PHI development is acceptable.

While the planning of landuses within TKO Area 137 is still ongoing, a Construction and Demolition Material Handling Facility is committed to be located at the TKO Area 137 (see Figure 3.9b).  The Facility is planned to start operation in phases in 2009.  The capacity of the Facility is 20,000 tpd.  The potential cumulative dust impact is addressed in Section 4.

The programme of developing other uses in TKO Area 137 is uncertain at the moment.  Hence, cumulative impacts cannot be assessed in this EIA.  Nevertheless, these uses have been considered as sensitive receivers, where appropriate, in this EIA.


([1])     It is based on the assumption that the existing SENT Landfill will be closed by about 2012 and the Extension will commencement operation in 2013.  However, this commencement year is subject to changes and will follow immediately after the closure of the existing SENT Landfill.

([2])     The additional waste tonnage is mainly coming from inert incineration residues which will be stablised before before delivering to the landfill.  At present, only the SENT Landfill is designed to accept residues from thermal treatment facilities.  For conservative assumption, it is assumed that all residues of the STF and IWMF will be disposed of at the Extension.  However, it is understood that the disposal location of the residues will also depend on the location of the STF and the IWMF.

([3])      The Extension will however receive insignificant amount of sludge generated from the on-site leachate treatment plant.

([4])     Including animal carcasses, asbestos waste, chemical waste and clinical waste.

([5])      The use of impermeable liner has been adopted at the existing NENT and WENT Landfill operations.