Common use of Operational Phase Clause in Contracts

Operational Phase. 5.12.2.1 The potential sources of water quality impacts during the operational phase would be related to non-point source surface / irrigation runoff, routine maintenance works (maintenance desilting and minor maintenance to DWFI system), potential changes in hydrodynamics properties and hydrology, and water quality impact from riparian public open space (including operation of UV disinfection system and water play features in amenity area). Adequate drainage system with silt traps and oil interceptors should be be incorporated into the proposed works to collect the surface / irrigation runoff or runoff from riparian public open space. With proper design of drainage system and implementation of the recommended pollution control measures, no adverse water quality impact from non-point source surface / irrigation run-off or runoff from riparian public open space would be expected. No adverse water quality impacts would be expected to occur at any identified WSRs due to the small- scale and infrequent routine maintenance works to remove excessive silts, debris and any obstructions for safeguarding the hydraulic capacity of the nullah, which practices and frequencies would be similar to the ones undertaken by DSD along TWN under existing arrangement. 5.12.2.2 Despite the reduced environmental baseflow at the nullah due to the interception of the flow with polluted discharges by the DWFI system, owing to the natural sloping gradient along TWN and the water retention and replenish designs and ecological enhancement features (e.g. wetland habitats created) within the nullah, average flow rate would remain similar to baseline condition and no unacceptable impacts on hydrodynamics properties and hydrology would be anticipated. No adverse water quality impact during the operational phase would therefore be anticipated. 5.12.2.3 While the Project is expected to improve the overall water quality of TWN and environmental monitoring and audit for water quality is not considered necessary for the operational phase under this EIA study, a post-revitalisation water quality monitoring programme to review compliance with the Water Quality Goals as stipulated in DSD PN No. 3/2021 will be establised and implemeneted by the DSD.

Operational Phase. 5.12.2.1 The potential sources of water quality impacts during 3.6.2.1 As mentioned in Section 3.5.2.2, similar to the operational phase would be related to non-point source surface / irrigation runoffexisting practices by the DSD, routine regular maintenance works (for the drainage and sewerage systems along TWN, including maintenance desilting at the nullah and minor maintenance to the DWFI system), potential changes in hydrodynamics properties and hydrology, and water quality impact from riparian public open space (including operation of UV disinfection system and water play features in amenity area). Adequate drainage system with silt traps and oil interceptors should be be incorporated into the proposed works to collect the surface / irrigation runoff or runoff from riparian public open space. With proper design of drainage system and implementation of the recommended pollution control measures, no adverse water quality impact from non-point source surface / irrigation run-off or runoff from riparian public open space would be expected. No adverse water quality impacts would be expected to occur at any identified WSRs due to the small- scale and infrequent routine maintenance works to remove excessive silts, debris and any obstructions for safeguarding obstruction to safeguard the hydraulic capacity of the nullahnullah would be required. Maintenance desilting of the nullah should be carried out on an annual basis during dry season (November to March) when the water flow is low, which except during emergency situations where the accumulated silt would adversely affect the hydraulic capacity of the nullah or where flooding risk is imminent, or when complaints on environmental nuisance associated with the accumulated silt are received. Moderate siltation would generally be allowed to accumulate, and removal of excess silt would be carried out at locations where it would impede water flow. Maintenance works would also be undertaken for the DWFI system on an as-needed basis and frequent maintenance (i.e. monthly) would not be required. The maintenance practices and frequencies frequency would be similar to the ones existing maintenance works undertaken by DSD along TWN under existing arrangementthe DSD. Such small-scale maintenance would require only light mechanical equipment such as a small loader and/or a small crane truck. Hand-held equipment would be used for vegetation removal. Therefore, adverse impacts from dust and gaseous emission are not expected. 5.12.2.2 Despite 3.6.2.2 While the reduced environmental baseflow at odour nuisance of TWN is anticipated to be alleviated with the nullah implementation of DWFI system under the Project and treatment wetlands to intercept / polish the polluted discharges from drainage outlets along the nullah, as well as with the modification of channel bed downstream of TWN’s low flow channel near its confluence with ▇▇▇▇▇ ▇▇▇ River near Man Lai Court to improve the excessive accumulation of silt brought by tidal influence due to the interception flat and uneven nullah bed in front of the flow broad-crested ▇▇▇▇, desilted materials from the maintenance/desilting works may be found to be odorous when exposed to air. While minor odour impact may arise from maintenance/desilting works, the desilted materials will be properly covered with polluted discharges tarpaulin / contained in watertight container on-site immediately and be located as far away from the ASRs as possible and be transported off-site by trucks for disposal of at strategic landfill within one day. As such, any odour impact during the DWFI system, owing maintenance would be temporary and confined to the natural sloping gradient along TWN and the water retention and replenish designs and ecological enhancement features (e.g. wetland habitats created) within the nullah, average flow rate areas of maintenance works that it would remain similar to baseline condition and no unacceptable impacts on hydrodynamics properties and hydrology be well-controlled through good site practices described in Section 3.7. No adverse odour impact would be anticipated. No adverse water quality impact during the operational phase would therefore be anticipated. 5.12.2.3 While the Project is expected to improve the overall water quality of TWN and environmental monitoring and audit for water quality is not considered necessary for the operational phase under this EIA study, a post-revitalisation water quality monitoring programme to review compliance with the Water Quality Goals as stipulated in DSD PN No. 3/2021 will be establised and implemeneted by the DSD.

Operational Phase. 5.12.2.1 3.5.2.1 The potential sources purpose of water the Project is to revitalise the existing concrete-lined TWN into a green space to connect the community with nature. The beautification and vegetating of the existing nullah would bring positive influence on the surrounding environment. In view of the Project nature, adverse air quality impacts during impact due to the operational phase operation of the Project is not anticipated. With the implementation of DWFI system under the Project and treatment wetlands, the existing dry weather flows from drainage outlets along TWN would either be intercepted and diverted to the existing sewerage system for conveying to Shatin Sewage Treatment Works for treatment by the DWFI system, or be discharged into the treatment wetlands installed at drainage outlets for in-situ polishing. Furthermore, with the modification of channel bed downstream of TWN’s low flow channel near its confluence with ▇▇▇▇▇ ▇▇▇ River near Man Lai Court, the excessive accumulation of silt brought by tidal influence due to the flat and uneven nullah bed in front of the broad-crested ▇▇▇▇ would be related greatly reduced. With the abovementioned designs, it is expected that the odour nuisance of TWN would be alleviated due to non-point source surface / irrigation runoffthe operation of the Project. 3.5.2.2 Similar to the existing practices by, routine regular maintenance works (for the drainage and sewerage systems along TWN, including maintenance desilting at the nullah and minor maintenance to the DWFI system), potential changes in hydrodynamics properties and hydrology, and water quality impact from riparian public open space (including operation of UV disinfection system and water play features in amenity area). Adequate drainage system with silt traps and oil interceptors should be be incorporated into the proposed works to collect the surface / irrigation runoff or runoff from riparian public open space. With proper design of drainage system and implementation of the recommended pollution control measures, no adverse water quality impact from non-point source surface / irrigation run-off or runoff from riparian public open space would be expected. No adverse water quality impacts would be expected to occur at any identified WSRs due to carried out by the small- scale and infrequent routine maintenance works DSD to remove excessive silts, debris and any obstructions for safeguarding obstruction to safeguard the hydraulic capacity of the nullahnullah would be required. Maintenance desilting of the nullah would be carried out on an annual basis during dry season (November to March) when the water flow is low, which except during emergency situations where the accumulated silt would adversely affect the hydraulic capacity of the nullah or where flooding risk is imminent, or when complaints on environmental nuisance associated with the accumulated silt are received. Minor maintenance to DWFI system would only be undertaken on an as-needed basis and frequent maintenance (i.e. monthly) would not be required. The maintenance practices and frequencies frequency would be similar to the ones existing maintenance works undertaken by DSD along TWN under existing arrangement. 5.12.2.2 Despite the reduced environmental baseflow at the nullah due to the interception of the flow with polluted discharges by the DWFI system, owing to the natural sloping gradient along TWN and the water retention and replenish designs and ecological enhancement features (e.g. wetland habitats created) within the nullah, average flow rate would remain similar to baseline condition and no unacceptable impacts on hydrodynamics properties and hydrology would be anticipated. No adverse water quality impact during the operational phase would therefore be anticipated. 5.12.2.3 While the Project is expected to improve the overall water quality of TWN and environmental monitoring and audit for water quality is not considered necessary for the operational phase under this EIA study, a post-revitalisation water quality monitoring programme to review compliance with the Water Quality Goals as stipulated in DSD PN No. 3/2021 will be establised and implemeneted by the DSD. Minor odour impact from maintenance desilting works may arise, yet not concerning and would be well-controlled through good site practices.

Operational Phase. 5.12.2.1 The potential sources of water quality impacts during Surface Run-off / Irrigation Run-off 5.7.2.1 Surface run-off / irrigation run-off to be generated from the operational phase would be related to Project is known as non-point source surface / irrigation runoffpollution. The paved and developed areas, routine maintenance works (maintenance desilting and minor maintenance to DWFI system), potential changes in hydrodynamics properties and hydrology, and water quality impact from riparian especially the new public open space (including operation e.g. viewing decks) / footpath will increase the quantity of UV disinfection system surface runoff. Irrigation run-off would also be anticipated from the routine maintenance of the proposed planting. Release of uncontrolled surface / irrigation run-off would increase the suspended solids levels and turbidity as well as fertiliser / pesticides (if required to sustain healthy growth of the proposed plantings) in the nearby waterbodies. However, impacts upon water play features in amenity area). Adequate quality would be minimal provided that proper drainage system with silt traps and oil interceptors should be would be incorporated into the proposed propsed works to collect the receive surface / irrigation runoff or runoff from riparian public open space. With proper design of to the drainage system at the planning and design stages. It is anticipated that with proper implementation of the BMPs as recommended pollution control measuresin Section 5.8, no adverse water quality impact from non-point source surface / irrigation run-off or runoff from riparian public open space is expected. 5.7.2.2 During the operational phase, similar to the existing practices, regular maintenance works for the drainage and sewerage systems along TWN, including desilting along the nullah and minor maintenance to the DWFI system, would be expected. No adverse water quality impacts would be expected to occur at any identified WSRs due to carried out by the small- scale and infrequent routine maintenance works DSD to remove excessive silts, debris and any obstructions for safeguarding to safeguard the hydraulic capacity of the nullah, which . The maintenance practices and frequencies frequency would be similar to the ones existing maintenance works undertaken by DSD the DSD. Such small-scale routine maintenance works would require only light mechanical equipment such as a small loader and/or a small crane truck. Hand-held equipment will be used for vegetation removal along TWN under existing arrangementthe nullah. 5.12.2.2 Despite the reduced environmental baseflow at 5.7.2.3 Maintenance desilting of the nullah should be carried out on an annual basis during dry season (November to March) when the water flow is low, except during emergency situations where the accumulated silt would adversely affect the hydraulic capacity of the nullah or where flooding risk is imminent, or when complaints on environmental nuisance associated with the accumulated silt are received. Whilst possible changes to water quality may be expected during the removal of excessive silt, vegetation, debris and obstructions within the nullah, such as increases in SS due to disturbance of nullah bed material and subsequently increased sedimentation onto the interception nullah bed, it is expected that these changes will be short- term and localised within the area of maintenance works and for a short distance downstream due to rapid settling out of any disturbed nullah bed material that no unacceptable adverse water quality impacts to WSRs downstream would be anticipated. Changes in SS concentrations would be expected to be within the typical ranges experienced under ambient conditions following heavy storms and increased sediment run-off. Therefore, no unacceptable water quality impacts are anticipated to occur as a result of the flow with polluted discharges by small-scale maintenance desilting works. 5.7.2.4 For the minor maintenance works for the DWFI system, owing it is expected that any maintenance will only be undertaken on an as-needed basis and frequent maintenance (i.e. monthly) will not be required. Diversion of the dry weather flow to the natural sloping gradient nearby sewerage system can be adopted during maintenance of DWFI system so that the water quality at TWN would not be adversely affected. Given the infrequent maintenance requirements and the collected solid wastes will be collected and disposed off-site properly, unacceptable water quality impact is not expected. 5.7.2.5 During operation of the Project, DWFI system will be in place along the nullah to intercept and convey the flow with heavily polluted discharges from some of the drainage outlets along the nullah to Sha Tin Sewage Treatment Works for treatment, which would inevitably lead to reduced flowrate and amount of freshwater input into TWN and downstream receiving water (▇▇▇▇▇ ▇▇▇ River Main Channel). With the provision of treatment wetland for in-situ polishing of non-intercepted flow with less polluted discharges as discussed in Section 2, the polished flow could serve as a part of the environmental flow to sustain the ecological function of the flora and fauna and habitat processes present within the revitalised TWN. Furthermore, with the incorporation of water retention and replenish designs and ecological enhancement features (e.g. wetland habitats created) within the nullahnullah (see Section 2), average flow rate would will remain similar to baseline condition and no unacceptable impacts on hydrodynamics properties and hydrology are anticipated. Furthermore, with the modification of channel bed and realignment of low flow channel at downstream TWN near its confluence with ▇▇▇▇▇ ▇▇▇ River near Man Lai Court, the sedimentation in front of the broad-crested ▇▇▇▇ caused by tidal influence and uneven surface and flat gradient of the existing channel in front of the broad- crested ▇▇▇▇, as well as the associated water quality issues and environmental nuisance, would be anticipated. No adverse water quality impact greatly reduced. 5.7.2.6 In addition, as all the identified natural watercourses within the assessment area are located at the upper catchment of TWN (see Section 8), no changes in hydrodynamic properties or hydrology are anticipated for the watercourses during the operational phase would therefore be anticipatedof the Project. 5.12.2.3 While 5.7.2.7 Relatively clean freshwater discharge from an existing drainage outlet of the Project is expected nullah near Pok ▇▇▇▇ ▇▇▇▇▇, which receives mainly clean river flow from upstream natural hillside catchment north to improve Peak One (i.e. WSR8 / S5 in Figure 5.1), were identified through the overall pollution source identification survey conducted under this Project. The clean freshwater discharge will be partially intercepted and directed to the proposed UV disinfection system for treatment and be used in the water quality play features (e.g. water spouts and fountains) in the riparian amenity area (fully seperated from the water body of TWN and environmental monitoring and audit for water quality is not considered necessary the revitalised TWN). Based on preliminary design, no additional stormwater collection facilities would be required for the operational phase under this EIA study, a post-revitalisation conveyance of freshwater for the proposed water quality monitoring programme play features. A more stringent treatment standard will be adopted for the proposed water play features that in addition to review compliance with fulfilling the Water Quality Goals relevant WQGs for primary contact recreation (type 3 designated use) as stipulated in DSD PN No. 3/2021 (Table 5.3 refers), E. coli bacteria should be non-detectable (in cfu/100 mL, calculated as the geometric mean of all samples collected in one calendar year) in the treated water. When the disinfection system is not under normal operation, under maintenance or when the treatment standard as specified in the post-revitalisation water quality monitoring programme established and implemented by DSD is not compiled with (detailed in Section 5.8.3), the water play features will be establised closed and implemeneted the water will be directly discharged into the low flow channel. Since UV treatment is a physical treatment process and the intercepted freshwater discharge would be relatively clean, no wastewater would be generated and no secondary water quality impact would be anticipated from its overall operation. 5.7.2.8 The riparian walkway and amenity areas would be properly designed to restrict public access / physical contact to the water body, i.e. the low flow channel, and to ensure safe and appropriate usage of the riparian public space and water play features (e.g. elevated walkway design, fencing, provision of warnings / signage, deployment of management personnel etc.). In particular, it should be noted that neither the water from the revitalised nullah with improved water quality or the water play features utilising treated freshwater shall be used for human or animal consumption, bathing or showering, food preparation / washing. As detailed in Section 2, access to the riparian walkway and amenity areas [provided with water play features] will be closed and evacuated in case of foreseeable flooding at the nullah bed or under extreme weather conditions. It is anticipated that with proper implementation of BMPs and the adoption of channel management system by the DSDDSD as detailed in Section 5.8, no adverse water quality impact from the operation of the riparian public open space is expected.