10.1 This EIA study has provided an assessment of the potential environmental impacts associated with the construction and operation of the Project according to the latest information available.
10.2 The environmental issues below have been assessed in the EIA Study, in accordance with the EIA Study Brief (No. ESB-158/2006) registered under the EIAO for the Project:
· Ecological Impact
· Landscape and Visual Impacts
· Construction Noise Impact
· Construction Water Quality Impact
· Construction Air Quality Impact
· Waste Management Implications
10.3 Specific mitigation measures necessary for avoiding or reducing impacts from the Project to acceptable levels, as well as environmental monitoring auditing procedures to ensure full implementation of all mitigation measures, as well as compliance with relevant standards and guidelines, have been developed during the detailed assessments.
10.4 A summary of the environmental impacts associated with the Project are presented in Appendix 10.1. For each key environmental issue, the predicted impact level, relevant criteria, recommended mitigation measures and residual impact at the sensitive receivers have been clearly summarised.
10.5 The key assessment assumptions, limitation of assessment methodologies and all relevant prior agreements with the EPD on individual environmental media assessment components are given in Appendix 10.2.
10.6 The key issue arising from the landslide preventive works during the construction stage would include the direct impact on 2 plant species of conservation interest, Small Persimmon and Common Tutcheria, the disturbance impacts to habitats and associated communities within and adjacent to the proposed works areas, particular the bat roost of Short-nosed Fruit Bat within the proposed works area, dumping of construction wastes and dust deposition, and sediment and water quality impacts.
10.7 To avoid/minimize potential impacts on plant species of conservation interest, the construction design has been considered to avoid impact to these species. Also, given that the Small Persimmon are locally common and widespread and are not threatened in Hong Kong, the potential loss or damage of a relatively small number of individuals would be a minor impact and hence no transplantation works was required. Nevertheless, planting of suitable plant species including Small Persimmon would be provided to reinstate the impact understorey habitat.
10.8 A detailed search for the floral species of conservation concern, including but not limited to Small Persimmon, Common Tutcheria, Bird-nest Fern and Chinese Pholidota, would be conducted. These species would be labelled on site prior to the commencement of works to avoid or minimize the damage to the floral species of conservation importance present in the proposed works area.
10.9 With the implementation of the recommended mitigation measures including the use of effective quiet machinery, the control of soil nail installation work hours, construction works would not result in unacceptable disturbance impacts on the bat and bird populations.
10.10 With the implementation of standard good site practice, construction works would not result in unacceptable impacts of dumping and dust deposition on vegetation adjacent to the proposed works area.
10.11 With the implementation of the recommended mitigation measures including adequate construction site drainage and provision of sediment removal facilities, construction works would not result in unacceptable water quality impacts on the two streams, drainage culvert and the associated fauna including Lesser Spiny Frog, Hong Kong Cascade Frog and Mountain Crab.
10.12 Fences would 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.
10.13 No substantial increases in direct and indirect ecological impacts during operation stage are expected.
10.14 A specific monitoring programme of the plant individuals of conservation interest identified within the proposed works area during the detailed vegetation survey should be carried out by a suitably qualified local ecologist(s) with over 7 years relevant ecological experience. 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.
10.15 There is expected to be some minor impact upon the existing woodland, which is approximately 2000m2, within the works area. The Engineer confirmed that no trees will be felled or requires transplanting due to the proposed landslide preventive works. However, the rest of groundcover / scrub will be affected. With the proposed mitigation measures, residual impacts are expected to be insubstantial after year 10.
10.16 Residents in the medium rise development along
10.17 After the proposed mitigation measures have been implemented and the proposed tree planting has matured over 10 years, all residual adverse landscape and visual impacts in operation phase will be of insubstantial significance.
10.18 The potential noise impact arising from daytime construction activities on the noise sensitive receivers (NSRs) located in the vicinity of the work sites was assessed. Noise generated from the use of powered mechanical equipment (PME) associated with the construction activities proposed for the Project would be the main concern.
10.19 The assessment results indicated that in the absence of mitigation measures, cumulative noise levels at the NSRs at Po Shan Mansions would likely exceed the EIAO-TM noise criterion during construction.
10.20 In order to alleviate the predicted construction noise impacts, noise reduction measures including the adoption of good site practices, the use of quieter plant, noise barrier/enclosure and noise insulating fabric would be necessary. With the recommended mitigation measures in place, noise levels at all NSRs are predicted to comply with the EIAO-TM daytime construction noise criterion. No adverse residual construction noise impact is expected.
Construction Water Quality Impact
10.21 The key issue in terms of water quality during the construction phase of the Project would be the potential for release of sediment-laden water from works areas during site clearance and the proposed soil nailing and rock slope stabilization works. Minimisation of water quality deterioration could be achieved through implementing adequate mitigation measures such as control measures on site runoff and drainage from the works areas to minimise construction runoff, and on-site treatment of site runoff and drainage prior to discharge. Proper site management and good housekeeping practices would also be required to ensure that construction wastes and other construction-related materials would not enter the drainage culvert. Sewage effluent arising from the construction workforce would also be handled through provision of portable toilets.
10.22 The installation of the soil nails and raking drains would not involve any pumping or discharge of groundwater and air would be used as the flushing medium. Hence, the groundwater would not be affected by the flushing medium of the drilling equipment. In addition, permanent casing may be provided to the drillhole of soil nail within the permeable colluvium layer as instructed by the Engineer. This extra measure would also minimize the impact to the groundwater table situated at the permeable soil stratum.
10.23 Potential sources of pollution from the construction and installation of the soil nails may include: effluent discharge during grouting and wash water from dust suppression sprays. An outlet pipe extending above the slope surface would be installed to facilitate collection of discharge of air, water and grout from the drillhole inserted with soil nail during grouting. With this appropriate setup, spillage during the grouting operation would be effectively controlled.
10.24 With the implementation of these recommended mitigation measures, the construction works for the Project would not be expected to result in unacceptable impacts on water quality. Site inspections should be undertaken routinely to inspect the works areas in order to ensure the recommended mitigation measures are properly implemented.
Construction Air Quality Impact
10.25 With the implementation of effective dust suppression measures, no adverse construction dust impact would be expected in the vicinity of the project.
10.26 Wastes generated by the construction activities are likely to include C&D material, general refuse from the workforce and chemical waste from the maintenance of construction plant and equipment. Provided that these identified waste arisings are handled, transported and disposed of using approved methods and that the recommended good site practices are strictly followed, adverse environmental impacts would not be expected during the construction phase.