ALTERNATIVES
Consideration of Different Extension Options
EPD identified 15 hectares of land in TKO Area 137 together with an adjoining narrow strip of land within the Clear Water Bay Country Park (CWBCP) as a potential site for the extension of the SENT Landfill. Five extension options have been identified and examined.
Please click on Option Buttons to view the proposed project sites:Options Evaluation
Characteristics |
 No Sharing of Infrastructure |
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Net Void Space (million m3) |
1.3 | 1.6 | 10 | 15 | 17 |
Encroachment into CWBCP (hectares) |
0 | 0 | 0 | 3 | 5 |
Estimated Construction Cost (HK$ per tonne of Waste) |
350 | 200 | 80 | 60 | 50 |
Additional Lifespan (Year) |
<1 | <1 | 4 | 5 | 6 |
The criteria used to evaluate the options include:
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Landfill capacity offered The stand-alone options (Option 1a and 1b) provide very low void capacity which is equivalent to less than one year's extended lifetime of the existing landfill. Option 3b provides the highest void capacity of 17Mm3 as compared with all other options evaluated. |
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Efficiency of use of land All options make use of the 15 hectares of land in TKO Area 137 that adjoins the southern end of the existing SENT Landfill. Option 3a and 3b requires additional 3 and 5 hectares of land from the CWBCP, respectively, with Option 3b delivering the greatest void capacity per unit site area and therefore representing the most efficient use of land. |
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Cost effectiveness The estimated capital costs for the stand-alone options for Option 1a and 1b are HK$350 and HK$200 per tonne, as compared to $HK50 per tonne for Option 3b. Option 3b has the lowest capital cost per tonne and represents the most cost-effective option. |
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Encroachment into Country Park Options 1a, 1b and 2 has no direct impact on the CWBCP as there will be no encroachment into the Country Park. Option 3a and 3b will encroach into the CWBCP by 3 hectares and 5 ha, respectively. The potential encroachment area is a relatively inaccessible cliff face dominated by shrubland and grassland of low to moderate ecological value. The area is not being used for educational and recreational purposes. For options with such encroachment, the encroached area can be developed for useful education and recreational uses following the closure and restoration of the Extension, providing an opportunity to enhance the public enjoyment of the area. |
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Key environmental impacts The small scale developments required by Options 1a and 1b impose the least environmental impacts at a local level, however, more environmental impacts at a territorial level due to shorter lifespan and the need for waste collection vehicles diversion to the more remote landfills for a longer period. Options 2 and 3a will have relatively greater environmental impacts at a local scale but lower environmental impacts at a territorial level as the period for waste collection vehicles diversion to the more remote landfills is less. Option 3b being the largest extension option will generate greater environmental impacts at the local scale including habitats within the CWBCP. Such impacts can be mitigated by compensatory planting and enhancing educational and recreational values with appropriate afteruse development. |
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Engineering measures considered The use of engineering measures to maximise the capacity of the Extension to avoid the need for encroachment into CWBCP has been considered. The building of an effective retaining wall around the waste mound at TKO Area 137 will have significant landscape and visual impact. The use of earth bund strong enough to support the weight of the waste to soften the landscape impact will in turn consume a significant portion of the landfill void space. Therefore, the use of engineering measures was not put forward for further consideration. |
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Additional land take in TKO Area 137 An option to increase landtake within TKO Area 137 to avoid the encroachment into the CWBCP was investigated. A significant increase in land take from 15 to approximately 34 hectares will be required and the allocation of land in the area is not considered feasible. |
Options Selection
Options without the encroachment into the CWBCP were considered first (Options 1a, 1b and 2). These options have the merit of relatively smaller environmental impact (for Options 1a and 1b) and no direct impact on natural habitat and wildlife in CWBCP. However, they are short in lifespan and when these landfills are closed, waste collection vehicles will have to be diverted to the more remote landfills, resulting in longer journey causing additional cost and environmental impacts. These options can only provide up to 10 Mm3 of void space and unable to provide adequate landfill capacity to meet the overall territory demand and to close the gap between the closure of existing SENT Landfill and the opening of the new waste management facility in the region. Engineering measures to increase void space for these options have also been considered. However, they are very expensive and visually undesirable. Additional landtake within TKO Area 137 have also been considered not feasible. With the consideration of the above, it is therefore necessary to consider options requiring temporary encroachment into the CWBCP.
The encroachment options (Options 3a and 3b) have the merit of longer landfill life, which will minimise the need for diversion of waste collection vehicles to the more remote landfills. They are more efficient in terms of cost and use of available land. These options will also provide opportunity to enhance the ecological value of the encroached area by compensatory woodland plantation upon full restoration. However, these options being larger in scale will generate relatively larger environmental impacts at local scale and will directly affect natural habitat within the CWBCP. Nevertheless, such environmental impacts can be mitigated by careful design, good site operation management and restoration arrangement at the Extension. It is also noted that the ecological impact at the directly affected area within the CWBCP is considered to be low to moderate. The wildlife within the area is highly mobile and there are similar habitat in the vicinity.
While both Options 3a and 3b will have similar environmental impacts, which can be mitigated, Option 3b can provide more void space, being more cost efficient and with a longer lifespan. When balancing all considerations and taking account of the benefits and disbenefits of all the options, Option 3b was chosen to be the preferred option, while avoiding prolonged adverse environmental impacts to the maximum practicable extent.