Key mitigation measures are presented below. For full details on mitigation measures, please refer to the EIA Report.

Avoidance
An options evaluation exercise was conducted to identify a technically feasible, cost-effective, environmentally and socially acceptable option for the Stage 4 regulation works. The hydraulics model MIKE 11was used to assess the effects of different design options on the hydrology and hydraulics of the Shenzhen River. Land requirements, environmental considerations and management and maintenance during operation as well as cost were considered to decide on the preferred design option.

This option maintains the existing alignment of the concerned section of the Shenzhen River as far as possible to minimise alternation to the existing river profile and meandering nature, minimise landtake and avoid large amounts of excavation, dredging or filling. The design principle of the works is to protect the livelihood of residents on both sides of the river with an ecological sensible design, which should maintain the naturalness of the river and riparian habitats and hence protect the biodiversity. The designed alignment will follow the existing watercourse as far as possible.

Minimise
Potential ecological impacts associated with the Project during the construction phase are the disturbance of mainly low quality habitats (Developed Area, Low-lying Grassland, Cultivated Land and Channel) (approximately 13 ha) and their associated wildlife. Just over 11 ha of low to moderate quality habitats (Marshy Low-lying Grassland, Abandoned Agricultural Land, Plantation and the Shenzhen River) and their associated wildlife will also be affected.

Approximately 0.4 ha of the secondary woodland which was located within the works area may be disturbed during the construction phase, but such loss is considered as the worst case scenario for the purpose of the assessment and the Project will preserve/avoid such habitat as far as possible. If this small patch of woodland could not be avoided due to the project works, it will be reinstated after construction.

Approximately 1.9 ha of the Shenzhen River and approximately 5.9 ha of the marshy low-lying grassland will be disturbed due to the Project but approximately 1.6 ha of the stream/river habitat and approximately 1.9 ha of the marshy low-lying grassland will be reinstated respectively after the construction works.

Additional secondary woodland habitat (~0.5 ha) and stream/river habitat (~2.1 ha) will be formed after the advanced works and river modification works. As discussed in Section 7.10, the potential ecological impact caused by the Project is anticipated to be low to moderate and the suggested mitigation measure would further reduce the possible ecological impacts:

Implementation of good construction practices as follows:

	Avoid potential impacts on the trees/ secondary woodland habitat whenever possible during the detailed design stage. Where possible, the retained trees/ woodland will be fenced off as protection from the construction works. If the trees cannot be avoided due to the engineering constraint, the affected individual(s) will be transplanted to compensatory woodland planting site near Pak Fu Shan or a similar habitat in the vicinity of the Project Site if considered suitable (subject to the detailed assessment of the feasibility of transplantation). A detailed vegetation survey on the trees within the impacted area would be conducted by a suitably qualified botanist/ ecologist to identify and record the affected individuals prior to the commencement of site clearance works. Feasibility and suitability of transplanting the affected plant species of conservation interest would be carefully studied and suitable receptor sites would be identified during Tree Felling Application;
	Avoid any damage and disturbance, particularly those caused by filling and illegal dumping, to the surrounding habitats through proper management of waste disposal;
	Arrange river excavation works to be conducted in dry season (November to March) in order to minimize the potential water quality impacts on downstream areas of high ecological value. Impacts due to the excavation works on the habitat and associated wildlife during dry season can be minimised through phase implementation of works and adoption of good site practices.
	Regularly check the Site boundaries to ensure that they are not breached and that no damage occurs to surrounding areas;
	Regularly check the performance and/ or effectiveness of the cofferdam and "diversion dyke" in order to minimise surface runoff and the chance of soil erosion;
	Prohibit and prevent open burning within the site boundary during construction and provide temporary fire fighting equipment in the work areas; and
	Reinstate temporary work sites/disturbed areas (including approximately 1.6 ha of the Shenzhen River, approximately 0.4 ha secondary woodland and approximately 1.9 ha of the marshy low-lying grassland, immediately after completion of the construction works.

Compensation
Since approximately 0.4 ha of secondary woodland will be disturbed and 0.03 ha of plantation habitat will be lost as a result of the Project’s advanced construction works, approximately 0.5 ha of compensatory woodland planting (in addition to the reinstatement of the 0.4 ha secondary woodland) will be provided within the Project Site near Pak Fu Shan. The proposed compensatory woodland planting site will locate adjoining to the reinstated and existing (undisturbed by the Project) secondary woodland. The compensatory woodland planting will provide ecological linkage to the existing secondary woodland therefore avoided/ minimised habitat fragmentation. The selection of planting species shall be made with reference to the species identified in the Tree Survey and be native to Hong Kong or the South China region. In view of the presence of the rare butterfly species (Courtesan) within the Study Area and the potential loss of its larval food plant in the low-lying grassland habitat (even it can also be recorded in various habitats within the Study Area), it is recommended that the compensatory planting species shall include their larval food plants (Trema sp.) within the compensatory woodland. The arrangement of the on-site compensatory planting, ie tree/ shrub mix and Trema sp., will be subject to detailed landscape design and planting plan, and recommended to be implemented prior to the construction activities as far as practical.

Approximately 4.0 ha of stream/river habitat and 4.1 ha of riverbank landscape areas will be formed after the advanced works and river modification works. The river bed will be retained as natural bottom while the stream bank will be modified by adopting a sloping landscape where suitable native riparian vegetation will be planted to resemble the naturalness of the river.

Proper ecological design will be adopted for the landscape works along the river banks, including the floodplains (the 1.9ha marshy low-lying grassland will be reinstated in the floodplains at Hong Kong side; which is in addition to the small potion of approximately 0.4 ha at Shenzhen side). With the adoption of ecological design, the landscaping works at the river banks of the modified Shenzhen River (aimed at providing similar habitat as the marshy low-lying grassland) could provide ecological function and linkage to the surrounding habitats even the Advanced Works areas will still be fenced as the current practice. Provision of approximately 4.1 ha of riverbank landscape planting can therefore compensate the loss of approximately 4 ha of marshy low-lying grassland (of low to moderate ecological value) in certain extent. The details will be developed during Detailed Design Stage.

	Riverbank landscaping planting works will be carried out after the completion of the embankment construction and slope protection works. The landscape characters along the river course will be designed in view of mitigating any potential environmental or landscape impacts, and taking into consideration the local characteristics and the landuse planning in the adjacent area. The works will be carried out under the supervision of qualified landscape professionals.
	The overall objectives for the landscaping works will be mainly concerned with ecological enhancement but also include landscape enhancement. Further details will be developed during Detailed Design Stage. The river bank will be designed in order to: The overall objectives for the landscaping works will be mainly concerned with ecological enhancement but also include landscape enhancement. Further details will be developed during Detailed Design Stage. The river bank will be designed in order to: - re-establish the natural riparian ecosystem and enhance local biodiversity; - provide similar habitat for marshy low-lying grassland; - protect the water resources; and - avoid erosion.
	The arrangement of the planting, ie tree/ shrub/ grass mix, will be subject to detailed landscape design and in line with the landscape planting in Shenzhen side. Vegetation chosen for the landscaping works will be based on the following: - Well adapted to the environment – mainly use native species supplement by suitable exotic plants; - Able to contribute to enhancing the local biodiversity (mixed vegetations of trees, groundcovers and grasses will be placed along the river bank); and - Low management requirements - those species with low management requirements will be chosen to minimize the maintenance cost; and - Prevent obstruction of sight view - design should fulfil the security requirements for boundary patrolling and therefore should not obstruct the sight view along the boundary patrol road.

Additional Ecological Measures
With the implementation of the above mitigation measures, no adverse residual impacts due to the construction and operation of the Project are expected. The following additional ecological measure will provide added ecological value for the Project:

In addition to the recommended mitigation measures, proper ecological design will be adopted for the flood retardation pond (at Shenzhen side). A flood retardation pond will be constructed at chainage 14+778 to 15+183 within the Shenzhen boundary of the Project Site to further enhance the ecological function of the area, which can serve as a wetland habitat for flora and fauna. It will have a total area of approximately 2.2 ha and a water depth of usually not more than 1.2m. Two weirs with penstocks will the used to control water level during the dry season. Areas of water depth of 0.3-0.8m will have ‘emergent plant’ such as native Phragmites australis and exotic Lepironia articulata planted in it. Areas of water depth of 0.8-1.2m will have ‘submerged and floating plants’ such as the native Vallisneria natans, Euryale ferox andTrapa spp. planted. Further details will be developed during Detailed Design Stage.