2.1 The baseline ecological surveys in the EIA Report identified that 4 habitats, including natural woodland, shrubland, developed area and freshwater habitat, were found within the assessment area. About 80% of the assessment area, particularly the area to be directly affected by the proposed Project, is natural woodland. Eight species of flora and 8 fauna of conservation interest have been recorded from the assessment area during the surveys. In which, two plant species of conservation interest, Small Persimmon and Common Tutcheria, would be directly affected by the Project. A habitat map of the assessment area is given in Figure 2.1 (Sheet 1) (Sheet2).
2.2 The ecological impact assessment in the EIA Report identified that ecological impacts resulting from the proposed landslide preventive works are anticipated to be minor in scale. Nevertheless, measures were identified in the EIA Report that would minimise any potential ecological impact. Ecological mitigation measures are detailed in the following sections.
Ecological Mitigation Measures
2.3 Following EIAO-TM Annex 16 guidelines, mitigation measures are proposed in this section to avoid, minimise and compensate for identified ecological impacts.
Avoidance/ Minimising
2.4 The location of the soil nail installation should be carefully selected and adjusted on-site to avoid/minimise the damage of root system to the existing plants on slope surface. No tree felling is required.
2.5 The following measures should be implemented to minimise identified ecological impacts during the construction and operation phases.
Construction Phase
2.6 Fences should be erected and installed along the boundary of the proposed works area before the commencement of works in order to minimise the disturbance to the natural woodland and shrubland habitats by preventing tipping, vehicle movements and encroachment of personnel onto the adjacent areas.
2.7 To minimise the indirect impacts to the nearby stream course and drainage culvert, the following measures should be implemented:
· Any runoff and drainage water with high levels of suspended solids should be prevented from entering the nearby water-bodies.
· Site runoff should be directed towards regularly cleaned and maintained silt traps and oil/grease separators to avoid and minimise the risk of sedimentation and pollution of the nearby stream courses and drainage culvert. The silt and oil/grease separators should be appropriately designed for the local drainage and ground conditions.
· An outlet pipe extending above the slope surface should be installed to facilitate collection of discharge of air, water and grout from the drillhole inserted with soil nail during grouting.
· Air should be used as the flushing medium of the drilling equipment to avoid the groundwater being affected by the flushing medium.
· Permanent casing should be provided to the drillhole of soil nail within the permeable colluvium layer as instructed by the Engineer.
· Debris and rubbish generated on-site should be collected, handled and disposed of properly.
2.8 It has been identified in the EIA report that two plant species of conservation interest (Hong Kong Pavetta, Pavetta hongkongensis and Common Tutcheria, Tutcheria spectabilis) (Appendix 2.2) would be potentially affected by the proposed construction of soil nailing. In view of this, specific mitigation measures have been recommended for these species:
· A detailed vegetation survey of the affected species of conservation interest should be conducted by a suitably qualified botanist/ecologist with over 7 years relevant experience to identify the affected individuals of the floral species of conservation concern, including but not limited to Small Persimmon, Common Tutcheria, Bird-nest Fern and Chinese Pholidota. These species should be labelled on site prior to the commencement of works for better protection.
2.9 To minimise disturbance to habitats adjacent to the works areas and the wildlife inhabiting, noise mitigation measures as listed below should be implemented:
· Quieter powered mechanical equipment should be used during the construction phase.
· Insulating fabric should be used for drill rigs during the drilling process in the construction of soil nailing.
· Noise generating construction works should be implemented at daytime only.
· Measures such as noise barriers should be used to minimise disturbance to the bat roost identified close to the western side of the works area.
2.10 To minimise the construction dust impact to the vegetation within and in vicinity of the proposed works area, the following mitigation measures as listed below should be implemented:
· Regular watering should be used during the construction of soil nailing.
· Any aggregate or dusty material storage piles should be completely covered.
· Dusty activities should be re-scheduled if high-wind conditions encountered.
2.11 Standard good site practice measures should be implemented throughout the construction phase. The measures should include:
· Placement of equipment or stockpile in designated works areas and access routes selected on existing disturbed land to minimise disturbance to natural or moderate-high ecological value habitats.
· Construction activities should be restricted to work areas that should be clearly demarcated. The work areas should be reinstated after completion of the works.
· Waste skips should be provided to collect general refuse and construction wastes. The wastes should be disposed of timely and properly off-site.
· General drainage arrangements should include sediment and oil traps to collect and control construction site run-off.
· Open burning on works sites is illegal, and should be strictly prohibited.
· Any soil contamination with fuel leaked from construction plants should be removed off-site.
· Disturbance to existing vegetation should be minimised wherever possible. In particular, adequate protection should be provided for mature trees located within or adjacent to the proposed works area.
Operation Phase
2.12 No substantial increases in direct or indirect ecological impacts are expected and ecological monitoring will not be required.
Compensation
2.13 Compensatory planting as listed below would be required due to the loss of trees and vegetations:
· Planting of suitable shrubs/herbs, including the Small Persimmon, should be provided within the within the impacted areas under this Project to compensate for the loss of understorey vegetation of the woodland habitat due to the construction of landslide preventive works.
· Chinese Fan-palm (Livistona chinensis) near the existing bat roost in the project area should be planted to provide suitable habitat for the Short-nosed Fruit Bat (Cynopterus sphinx) after the completion of landslide preventive works.
Ecological Monitoring and Audit Requirements
2.14 The proper implementation of mitigation measures during construction phase recommended in Sections 2.6 to 2.13 should be monitored and audited.
2.15 A suitably qualified local ecologist(s) with over 7 years relevant ecological experience as a member of the ET shall be responsible for carrying out a specific monitoring programme of the plant individuals of conservation interest identified within the proposed works area during the detailed vegetation survey. Regular monitoring of the trees, shrubs and herbs should be conducted to check on the health and condition of the plants. Monitoring should be conducted twice a month cover the whole construction period.