15.1.1 The avoidance and minimisation of environmental impacts as far as practicable has been a major objective during the assessment and selection of the preferred route and through the progressive design of the selected alignment. The development of the project and the mitigation measures recommended have allowed key environmental problems to be avoided and environmentally sensitive areas and populations to be protected by the integration of environmentally friendly designs. This section serves to highlight and summarise these factors.
15.1.2 The proposed alignment runs through an area of natural landscape and ecological importance and thus, a key aspect of the scheme was to minimise the loss of natural habitat as far as possible. Thus, 2200m or 35% of the total road alignment will be widened on-line between Lung Tseng Tau and Tai Tung Shan in order to minimise habitat loss. In addition, the haul road has been specified along the same alignment as the main route as far as practicable to reduce the extent of temporary habitat loss and the alignment has been designed on viaduct and retaining walls used where appropriate in order to significantly reduce the extent of cut slopes required, having environmental benefits.
15.1.3 The on-line section of the road has been designed to be widened on the eastern side of the road as far as possible, such that the existing road provides a buffer zone from site run-off between the works and the ecological important Tung Chung stream. The selected alignment is also the furthest away from the Cheung Sha stream.
15.1.4 Protection of the streams and water gathering grounds within the study area has been a key issue for the project. The alignment has been designed to cross all key ecologically sensitive streams on structure during both the construction and operational stages to avoid direct impacts on the aquatic environment. Also works on streams, including stream diversions, culverting, widening or bank strengthening works have been avoided as far as possible at ecologically important streams with the road passing over the water courses on structure in the majority of cases.
15.1.5 In order to avoid indirect impacts, a drainage system has been devised to avoid / minimise water quality impacts as far as possible. During the construction phase, for the northern section of the new road, it is proposed that the operational drainage system be constructed ahead of the main roadworks such that it may be used to discharge the construction site runoff, thus avoid discharging construction site runoff into the streams all together. The discharge outfall for the northern section’s drainage system will be located in the Wong Lung Hang nullah near Ha Ling Pei and all discharge will be treated via a sedimentation tank in order to minimise impact on Tung Chung Bay and the San Tau SSSI seagrasses. South of the crest, it is proposed to use a series of peripheral surface channels to encase sections of the works site to intercept and divert the surface runoff from the hinterland and the construction site. All run-off will be treated by a series of sedimentation tanks prior to discharge into adjacent streams. Oil interceptors will also be used above the catchwater to further protect the water gathering grounds.
15.1.6 The key aspects of the proposed temporary drainage system which will be adopted to ensure the protection of the water quality in the inland streams, Tung Chung Bay and Pui O Wan during construction are as follows:
¨ system designed to have no discharge of site run-off into Tung Chung Stream;
¨ northern temporary drainage system will avoid discharge into any steams;
¨ system in the southern area divided into small sub-catchments to enhance control and minimise impacts;
¨ all run-off treated via a sedimentation tank prior to discharge either into streams in southern area or marine environment;
¨ oil interceptors used above catchwater to protect water gathering grounds;
¨ all parts of system will be regularly cleaned and maintained;
¨ hinterland runoff separated to protect from contamination; and
¨ system must be operational before the commencement of the permanent works.
15.1.7 Other measures proposed to protect both the ecologically sensitive streams and the water gathering grounds include:
¨ no major stockpiles in the Country Park;
¨ no storage of fuel or oil in the Country Park or water gathering grounds;
¨ no chemical wastes shall be stored in the water gathering grounds;
¨ no canteen facilities shall be located within the water gathering grounds;
¨ the Contractor shall comply with WSD’s General Conditions for Working within Water Gathering Grounds;
¨ the Contractor will be required to prepare a response plan to define procedures for the control, containment and clean-up of any spillage that could occur on the construction site;
¨ no maintenance activities which may generate chemical wastes shall be undertaken in the water gathering grounds;
¨ using on-site chemical treatment and storage facilities for wastewater from the site offices and toilet facilities; and
¨ washing vehicle wheels prior to entering and leaving the construction site.
15.1.8 During the operational phase, a specially designed carrier pipe along the length of the road will collect and transport all road drainage to either end of the alignment prior to discharge into the nullah at Tung Chung and Pui O Wan. Thus, operational discharge into all streams along the route, and thus the water gathering grounds, has been avoided.
15.1.9 Also, in order to protect the streams and water gathering grounds in the event of an accident, a road parapet has been proposed over much of the road’s length to prevent a vehicle from leaving the road. In addition, in the event that a major spill occurs on Tung Chung Road, a defined response plan has been recommended in order to minimise effects on the local ecological resources and water gathering grounds. In order to protect the mangroves and seagrass beds in Tung Chung Bay in the event of a spillage, an oil interceptor has been proposed for the discharge at the northern end of the alignment.
15.1.10 The permanent drainage system has also been designed to avoid direct impacts on Fong Yuen Marsh and the channelised section of Tung Chung stream which is proposed to be upgraded in the north by following an alignment parallel to the road which is more than 20m from the marsh. In the south, the operational drainage system discharges at Pui O Wan. The outfall will be over 1.0 km away from the gazette boundary of Cheung Sha Beach to the west, and over 1.2 km away from the gazette boundary of Pui O Beach to the east.
15.1.11 Key ecological resources are present in the study area and these include various habitats and species of conservation importance. Some of the key habitats and species of concern which may be affected and for which varying degrees of mitigation will be required include:
¨ secondary woodland along the alignment;
¨ streams and associated aquatic fauna along the route;
¨ shrub Pavetta hongkongensis, orchids Acampe rigida and Liparis viridiflora and tree Artocarpus hypargyreus; and
¨ habitats of amphibians and reptiles along the route including the Romer’s Tree Frog.
15.1.12 Mitigation measures to protect against both direct and indirect impacts on the streams have been highlighted above. However, other measures to protect and enhance key ecological species and areas are as follows:
¨ transplantation of the shrub Pavetta hongkongensis, orchids Acampe rigida and Liparis viridiflora and tree Artocarpus hypargyreus;
¨ special design of new culverts and culvert inlet and outlets for streams 19 and 21 (Figure 6.1) and culvert inlet and outlets for Stream 18 to reduce fragmentation effects;
¨ translocation of Hong Kong Newt, Lesser Spiny Frog and Romer’s Tree Frog from streams 15, 18, 19 and 21;
¨ scheduling of works in streams 15, 18, 19 and 21 to avoid the period April to June which is the key breeding period for fish, amphibians and odonates;
¨ translocation of Romer’s Tree Frog between Lung Tseng Tau and Shek Mun Kap prior to the works to prevent disturbance;
¨ provision of water filled pots as habitats for the Romer's Tree Frog between Lung Tseng Tau and Shek Mun Kap to enhance breeding and compensate for disturbance;
¨ translocation of isolated population of Beijiang Thick-lipped Barb in Stream 15 to tributary of Tung Chung Stream;
¨ provision of slope surfaces at step channels for aquatic fauna to move up and down stream at the existing bridge at stream 15;
¨ provision of escape routes from drainage channels for amphibians;
¨ provision of wildlife tunnels for faunal transfer;
¨ compensatory planting of 25.5ha to mitigate for vegetation loss; and
¨ reinstatement of land temporarily required during construction.
15.1.13 As the project will be located adjacent to both existing and future sensitive receivers in Tung Chung and Cheung Sha, measures to protect the residents have been proposed during both the construction and operational phases. During the construction phase, mufflers on equipment, reduction in the numbers of equipment, scheduling of noisy operations and the use of temporary noise barriers will be able to protect 44 existing dwellings.
15.1.14 During the operational phase, 127m of vertical reflective noise barriers of heights between 1.5 and 4.5m in Lung Tseng Tau in Tung Chung will protect all 10 dwellings that are affected by the project. In addition, in order to protect a future school proposed as part of the Tung Chung Valley development, a 4m landscaped bund between the school site and the Tung Chung Road has been proposed. A 2m landscaped bund, combined with a 4m non-building area, has also been designed to protect the future sensitive receivers of the proposed sale sites in Cheung Sha from operational traffic noise.
15.1.15 In summary, the following environmentally friendly designs have been included:
¨ on-line widening of 35% of road to minimise habitat loss;
¨ widening of road on east to provide buffer for Tung Chung Stream;
¨ use of bridge structures and retaining walls to minimise habitat loss and protect key streams;
¨ construction drainage system to avoid discharge to Tung Chung Stream and water gathering grounds;
¨ use of sediment tanks and oil interceptors to minimise impacts on streams and water gathering grounds, Pui O Wan and Tung Chung Bay during construction and operation;
¨ operational drainage to discharge at Pui O Wan to avoid the gazetted Cheung Sha Beach;
¨ operational drainage system to avoid Fong Yuen marsh;
¨ parapet to reduce risk of vehicles leaving the road;
¨ culverts and culvert inlet/outlet designs that minimise fragmentation for fish and other species;
¨ the incorporation of wildlife tunnels under the at-grade sections of road to minimise fragmentation for mammals and amphibians;
¨ provision of escape ramps in drainage channels for amphibians; and
¨ provision of water filled pots as habitats for the Romer's Tree Frog.
15.1.16 Also, the following sensitive populations and areas have been protected by the scheme. The areas and populations protected are presented in Figure 15.1 for reference.
¨ Tung Chung stream by widening to the east to create buffer, use of bridge structures to reduce direct stream impacts and down stream effects, construction and operational drainage system avoiding discharge, operational parpapet to contain accidents;
¨ Cheung Sha stream by selecting alignment furthest away, use of bridge structures to reduce direct stream impacts and down stream effects, construction and operational drainage system comprisng sedimentation tanks;
¨ key streams of high ecological value and the water gathering grounds by the use of bridge structures, construction and operational drainage system comprising sedimentation tanks and oil interceptors, operational parpapet to contain accidents;
¨ water gathering grounds by use of construction and operational drainage system comprising sedimentation tanks and oil interceptors, operational parpapet to contain accidents; proposing all works involving fuels, chemical waste and major stockpiles outside the water gathering grounds;
¨ Fong Yuen Marsh by designing operational drainage system 20m away;
¨ Tung Chung Bay by treating construction and operational discharge with sedimentation tanks and oil interceptors;
¨ Pui O Wan by treating construction phase discharge with sedimentation tanks
¨ Cheung Sha gazetted beach by discharging at Pui O Wan;
¨ habitats by minimising vegetation loss through on-line widening and use of bridge structures and retaining walls;
¨ key floral species by transplantation prior to the works;
¨ Romer’s Tree Frog by translocation prior to the works, provision of breeding pots, scheduling of works to avoid breeding season, compensatory planting, faunal access tunnels, drainage channel escape ramps and culvert design to allow access;
¨ Lesser Spiny Frog by translocation prior to the works and scheduling of works to avoid breeding season, faunal access tunnels, drainage channel escape ramps and culvert design to allow access;
¨ Hong Kong Newt by translocation prior to the works, faunal access tunnels, drainage channel escape ramps and culvert design to allow access;
¨ Beijiang Thick-lipped Barb by translocation prior to the works, culvert design to allow access and other fish species of conservation interest by avoidance of direct impacts on Cheung Sha Stream and Stream 40;
¨ all ASR’s during construction and operation by the recommendation of mitigation measures;
¨ 44 existing dwellings in Tung Chung and Cheung Sha during the construction phase by construction equipment mitigation;
¨ 10 dwellings in Tung Chung by the provision of 127m of noise barriers;
¨ future school in Tung Chung Valley by the provision of a landscaped earth bund; and
¨ future residents of the sale site in Cheung Sha by the provision of an earth bund and 4m non building area.
15.1.17 Thus, it can be seen that the project has aimed to protect key environmental areas and populations through sensitive design and the integration of environmentally friendly measures during both the construction and operation of the project.