TABLE OF CONTENTS

2. Project description.. 2-1

2.1 Project Location and Description. 2-1

2.2 Need of the Project 2-2

2.3 Consideration of Alternative Locations and Design Options. 2-3

2.4 Considerations of Construction Methods and Sequences of Works 2-12

2.5 Selection of Preferred Scenario. 2-14

2.6 Construction Programme. 2-14

2.7 Concurrent Project 2-14

List of Tables

Table 2.1 Environmental Considerations for the Alternative Locations

Table 2.2 Comparison of Alternative Location Options

List of Figures

Figure 2.1 Location of the Proposed Sai O Trunk Sewer Sewage Pumping Station

List of Appendices

Appendix 2.1 General Layout and Sections of the Proposed Sai O Trunk Sewer Sewage Pumping Station

Appendix 2.2 Confirmation of No Change in EIA Study Brief

Appendix 2.3 Alternative Locations of the Proposed Sai O Trunk Sewer Sewage Pumping Station

Appendix 2.4 Alternative Design Options of the Proposed Sai O Trunk Sewer Sewage Pumping Station

Appendix 2.5 Tentative Construction Programme

2. Project description

2.1 Project Location and Description

2.1.1.1 The Project is to construct and operate the proposed Sai O Trunk Sewer Sewage Pumping Station (SPS) which is located at the north of Sai O and within “Government, Institution or Community” (G/IC) zone on the draft Ma On Shan Outline Zoning Plan (OZP) No. S/MOS/23. Based on the latest design, the installed capacity per day of the proposed Sai O Trunk Sewer SPS is about 20,600 m³ for coping with the sewerage needs of both existing and future developments. Location of the proposed Sai O Trunk Sewer SPS is shown in Figure 2.1.

2.1.1.2 The proposed Sai O Trunk Sewer SPS include the following main components:

Ÿ Loading/unloading bay

Ÿ Inlet chamber

Ÿ Coarse screen channel

Ÿ Distribution chamber

Ÿ Wet wells

Ÿ Valve chamber

Ÿ Emergency storage tank

Ÿ Deodorizing unit

Ÿ Switch room

Ÿ Transformer room

2.1.1.3 The footprint of the proposed SPS and switch room & transformer room would be approximately 980 m² and 200 m² respectively whilst the total site area of the Project is approximately 3,500 m². The proposed SPS is located on a site with a level 6.5 mPD similar to the adjacent Nin Ming Road. The design building height of the proposed SPS would be approximately 9.0 m with 1.2 m high steel parapet. All the above main components would be enclosed and covered by a green roof. Approximately 2.5 m high fence wall with vertical greening would be constructed along the site boundary of the proposed SPS. The general layout and sections of the proposed Sai O Trunk Sewer SPS are shown in Appendix 2.1.

2.1.1.4 Same as other existing unmanned sewage pumping stations in Hong Kong (e.g. Ma On Shan and Ma On Shan 108 SPSs in Ma On Shan / Wu Kai Sha areas), the operation of the proposed SPS would be monitored by Sha Tin Sewage Treatment Works (Sha Tin STW) and communication channels for public enquiries / contact on the operation of the unmanned SPS would be displayed at a conspicuous place outside the SPS.

2.1.1.5 Subsequent to the issue of the EIA Study Brief (No. ESB-281/2014), the proposed installed capacity per day has to be changed from 12,000 m³ to 20,600 m³ due to the need of catering for the additional / changes in sewage flow generated from the developments within the sewerage catchment boundary of the proposed Sai O Trunk Sewer SPS, such as planned developments in Lok Wo Sha Lane, Cheung Muk Tau, Shap Sz Heung and etc. Furthermore, the site location and footprint of the proposed SPS has been altered to allow the proposed SPS to be sit alongside the aboveground structures of Sai O Offtake and Pigging Station at the corner of the preferred vacant land and further away from Nin Ming Road. In accordance with Clause 6.2 of the EIA Study Brief, it was checked if there was any key change in the scope of the Project mentioned in Section 1.2 of the EIA Study Brief and in Project Profile (No. PP-517/2014), confirmations have been sought from the Director of Environmental Protection in writing on whether or not the scope of issues covered by the EIA Study Brief can still cover the key changes, and the additional issues, if any, that the EIA report must also address. It was demonstrated that the changes due to revised scheme of installed capacity of 20,600 m³/day and the minor change in site location and footprint would not fundamentally alter the key scope of the EIA Study Brief. The EIA Study Brief is still valid for the preparation of the EIA Report (Appendix 2.2 refers).

2.2 Need of the Project

2.2.1 Purpose and Objectives of the Project

2.2.1.1 The proposed Sai O Trunk Sewer SPS, as part of “Public Works Programme Item 4125DS – Tolo Harbour Sewerage of Unsewered Areas, Stage II” that originated from the findings of the Study “Review of North District and Tolo Harbour Sewerage Master Plans” completed by Environmental Protection Department (EPD) in 2002, is a core component of the planned trunk sewerage system in Ma On Shan along Sai Sha Road. It is required to receive all sewage flows collected from the planned sewered area along Sai Sha Road from Kei Ling Ha Lo Wai to Cheung Muk Tau, as well as the adjacent residential development, health care and education institutions (including Villa Concerto, Villa Rhapsody, Helping Hand Father Sean Burke Care Home for The Elderly, Holiday Centre for the Elderly, Hong Kong Baptist Theological Seminary and Li Po Chun United World College) and then convey the sewage to Ma On Shan Sewage Pumping Station and ultimately to Sha Tin Sewage Treatment Works.

2.2.2 Environmental Benefits and Dis-benefits of the Project

2.2.2.1 At present, the sewage from the existing village houses in unsewered area at Sai Sha is preliminarily treated by private treatment facilities, i.e. septic tanks / and soakaway systems, the performance of which could be affected by high development density, poor design and inadequate maintenance and could cause pollution of the environment and poor hygiene. While the sewage from existing residential developments is treated by local private treatment plants, the nearby residents are suffering from the nuisance from the aging treatment plants. The Sai Sha trunk sewerage system together with the proposed Sai O Trunk Sewer SPS are designed to serve the existing and planned developments in the Sai Sha area by collecting and conveying the sewage generated from these developments to Shatin Sewage Treatment Works for proper treatment. The proposed trunk sewerage system is generally supported by the local communities. As an essential component for the operation of the proposed trunk sewerage system, the Project plays an important role to improve the environment and hygiene conditions of the area.

2.2.2.2 The implementation of the Project would inevitably induce some potential environmental impacts during construction and operational phases. Nevertheless, with careful consideration of various locations and design options for the Sai O Trunk Sewer SPS, the preferred option would maximise environmental benefits and avoid / minimise adverse environmental effects to the maximum practicable extent while achieving the objectives of this Project. The potential environmental impacts associated with the Project have been assessed in Section 3 to Section 11 and mitigation measures have been recommended if necessary, to alleviate the impacts to acceptable levels.

2.2.3 Scenarios With and Without the Project

2.2.3.1 As discussed in Section 2.2.2.1, the proposed Sai O Trunk Sewer SPS is a core component of the planned trunk sewerage system along Sai Sha Road that collects and conveys the sewage from the existing and planned developments in the area to Shatin Sewage Treatment Works for treatment, hence eliminating the environmental and hygienic nuisance caused by aging or inadequate performance of the existing private treatment facilities / plants. With the Project, the environment and hygiene conditions in Sai O area would be improved.

2.2.3.2 Without the Project, the whole sewerage system along Sai Sha Road could not function. Without proper collection of the sewage from the existing developments to Shatin Sewage Treatment Works for treatment, the environmental and hygiene nuisance resulting from the potential inadequate performance of the private treatment facilities / plants due to aging, increasing village density, poor maintenance etc. could not be rectified or improved. Moreover, the planned developments cannot be implemented and potential supply of housing units within the catchment, e.g. the “Comprehensive Development Area” (“CDA”) zone on the approved Shap Sz Heung OZP No. S/NE-SSH/11, will be seriously affected, which will aggravate the shortage of housing supply in Hong Kong.

2.3 Consideration of Alternative Locations and Design Options

2.3.1 Site Selection

2.3.1.1 The proposed Sai O Trunk Sewer SPS is a core component of the proposed trunk sewerage system in Ma On Shan along Sai Sha Road and its prime objective is to collect and convey sewage from the existing and planned developments along Sai Sha Road to Shatin Sewage Treatment Works for treatment. Major environmental issues associated with the operation of SPS is expected to be potential odour, noise and visual impacts. Hence, apart from the avoidance of encroaching onto area of conservation importance (e.g. Site of Special Scientific Interest (SSSI), Country Park, Conservation Area), avoidance and minimisation of these potential adverse environmental impacts has been taken into account in deriving the preferred location of the Sai O Trunk Sewer SPS while the operation requirements were not compromised.

Selection and Optimisation of Preferred Location for the Sai O Trunk Sewer SPS

Site Selection for the Sai O Trunk Sewer SPS

2.3.1.2 Under the Assignment, a search of various sites within the catchment was conducted for a suitable location of the SPS. Eight possible locations were identified and considered in the site selection process. The locations are listed below and their indicative positions are shown in Appendix 2.3A.

· Location 1: On footpath next to existing public toilet and Nai Chung Bus Terminus

· Location 2: Vacant land in between Nai Chung Bus Terminus and Nai Chung Village

· Location 3: Vacant land to the east of Hong Kong Baptist Theological Seminary (HKBTS)

· Location 4: Vacant land to the east of Nai Chung Village and opposite to Nai Chung Barbecue Site

· Location 5: Open area at Lok Wo Sha Lane and to the west of The Entrance

· Location 6: Nai Chung Barbecue Site

· Location 7: Chek Kok

· Location 8: Vacant land next to Sai O Offtake and Pigging Station

2.3.1.3 The environmental benefits and dis-benefits of each of the above locations have been reviewed with respect to the following environmental considerations and the findings are presented in Table 2.1:

· Conservation and Ecology - Avoidance of Recognised Sites of Conservation Importance and Natural Habitats with Higher Ecological Values: Several recognised sites of conservation importance and natural habitats with higher ecological values, including Ma On Shan Country Park (CP), Nai Chung Coast Site of Special Scientific Interest (SSSI), Tseng Tau Coast SSSI, Coastal Protection Area (CPA), mangrove, mudflat and woodland, fall within the catchment. In order to avoid any irreversible adverse impact on ecology and conservation, encroachment on these recognised sites of conservation importance and natural habitats with higher ecological values should be avoided as far as practicable. Also, the location should not be situated in close proximity to these recognised sites of conservation importance and natural habitats so as to avoid/minimize potential impacts on these valuable sites/habitats.

· Air Quality and Noise - Minimisation of Air and / or Noise Sensitive Receivers to be Affected: Construction dust and noise impacts may arise from the construction of the proposed SPS while potential odour and fixed plant noise impact would arise during the operational phase. While mitigation measures recommended in this EIA would be implemented during both construction and operational phases, in order to avoid and minimise the potential adverse environmental impacts on the nearby sensitive receivers, it would also be more preferable if the proposed SPS is situated in a location with less air / noise sensitive receivers nearby.

· Visual - Lower Visibility to Public: Adoption of aesthetic and sophisticated architectural and landscape designs could minimise potential landscape and visual impacts. Nonetheless, locations that are less visible to public would be more preferable.

· Better Environmental Performance (e.g. higher energy efficiency, less waste generation, impact on less sensitive receivers): It would be more preferable if the location of the proposed SPS favours a better environmental performance in terms of waste generation, energy efficiency and impact on sensitive receivers during its construction and operation. When the proposed SPS is located at a relatively higher level of the catchment, additional pumping facilities at a lower level of the catchment or deeper gravity sewerage pipe would be required to collect and/or pump the sewage to the proposed SPS. If the additional pumping facilities option is adopted, this would inevitably lead to higher energy consumption, more construction and demolition (C&D) materials generation, and impact on additional sensitive receivers in the vicinity of the additional pumping facilities. Alternatively, if a deeper gravity sewerage pipe option is adopted, the inlet level of the proposed SPS will have to be further deepened for the sewer connection and deep excavation for the SPS as well as the sewerage system would be required, hence generating more C&D materials, resulting in lower energy efficiency and adding more difficulties to maintenance works.

· Minimisation of Septic Sewage and the Associated Odour Issue due to Long Retention Time: It would also be more preferable if the location favours a shorter pumping distance so as to minimise the retention time of sewage within the pumping system, which could in turn decrease the likeliness of sewage becoming septic and causing odour problems.

Table 2.1 Environmental Considerations for the Alternative Locations

Location	Environmental Benefits	Environmental Disbenefits
Location 1	· No encroachment on or in close proximity to any recognized sites of conservation importance and habitats with high ecological value. · Located at low point of the catchment. Since no additional pumping facilities or deep excavation for the SPS to facilitate connection with deeper gravity sewerage pipe is required, better environmental performance could be achieved with higher energy efficiency in operation and less C&D materials generation. · Medium pumping distance that reduces the retention time of sewage within the pumping system and in turn decreases the likeliness of sewage becoming septic and causing odour problems.	· Affects more nearby existing or planned air / noise sensitive receivers within 150m* of the location, including HKBTS, Sai O Village, Nai Chung Village, Sai Sha Villa, planned sitting out area and playground, and Zessa Vista · High visibility to public.
Location 2	· Located at low point of the catchment. Since no additional pumping facilities or deep excavation for the SPS to facilitate connection with deeper gravity sewerage pipe is required, better environmental performance could be achieved with higher energy efficiency in operation and less C&D materials generation. · Medium pumping distance that reduces the retention time of sewage within the pumping system and in turn decreases the likeliness of sewage becoming septic and causing odour problems.	· Encroachment on woodland and in close proximity to mudflat and mangrove of higher ecological value. · Affects more nearby air / noise sensitive receivers within 150m* of the location, including Sai O Village, Nai Chung Village, Zessa Vista, HKBTS and Sai Sha Villa · Medium to high visibility to public
Location 3	· Affect not as many nearby air / noise sensitive receivers within 150m* of the location, including planned sitting out area and playground, HKBTS, Zessa Vista and Nai Chung Village · Located at low point of the catchment. Since no additional pumping facilities or deep excavation for the SPS to facilitate connection with deeper gravity sewerage pipe is required, better environmental performance could be achieved with higher energy efficiency in operation and less C&D materials generation. · Medium pumping distance that reduces the retention time of sewage within the pumping system and in turn decreases the likeliness of sewage becoming septic and causing odour problems.	· Close to woodland, mudflats and mangrove habitats of higher ecological value. · Medium visibility to public.
Location 4	· Affects not as many nearby existing or planned air / noise sensitive receivers within 150m* of the location, including Nai Chung Village, Kwun Hang Village, Nai Chung barbecue area and the “CDA” zone on the approved Shap Sz Heung OZP No. S/NE-SSH/11 · Medium pumping distance that reduces the retention time of sewage within the pumping system and in turn decreases the likeliness of sewage becoming septic and causing odour problems.	· Encroachment on woodland of higher ecological value. · Medium visibility to public. · Located at high point of the catchment. Since additional pumping facilities or deep excavation for sewer/SPS at depth of approx. 21 m would be required, poor environmental performance would be expected with lower energy efficiency in operation, more C&D materials generation and impact on additional sensitive receivers in the vicinity of the additional pumping facilities.
Location 5	· No encroachment on or in close proximity to any recognized sites of conservation importance and habitats with high ecological value. · Short pumping distance that reduces the retention time of sewage within the pumping system and in turn decreases the likeliness of sewage becoming septic and causing odour problems.	· Affects more nearby existing or planned air / noise sensitive receivers within 150m* of the location, including the Entrance, Double Cove, Li Po Chun United World College, Lake Silver and “Residential (Group A)” zone on the draft Ma On Shan OZP No. S/MOS/23 · High visibility to public. · Located at high point of the catchment. Since additional pumping facilities or deep excavation for sewer/SPS at depth of approx. 25 m would be required, poor environmental performance would be expected with lower energy efficiency in operation, more C&D materials generation and impact on additional sensitive receivers in the vicinity of the additional pumping facilities.
Location 6	· Affect not as many nearby air / noise sensitive receivers within 150m* of the location, including Nai Chung barbeque area, Kwun Hang Village, Nai Chung Village and “CDA” zone on the approved Shap Sz Heung OZP No. S/NE-SSH/11 · Low to medium visibility to public. · Medium pumping distance that reduces the retention time of sewage within the pumping system and in turn decreases the likeliness of sewage becoming septic and causing odour problems.	· Encroachment on Ma On Shan Country Park and woodland. · Located at high point of the catchment. Since additional pumping facilities or deep excavation for sewer/SPS at depth of approx. 21 m would be required, poor environmental performance would be expected with lower energy efficiency in operation, more C&D materials generation and impact on additional sensitive receivers in the vicinity of the additional pumping facilities.
Location 7	· Situated far away from air and noise sensitive receivers (over 500m). · Low visibility to public. · Located at low point of the catchment. Since no additional pumping facilities or deep excavation for the SPS to facilitate connection with deeper gravity sewerage pipe is required, better environmental performance could be achieved with higher energy efficiency in operation and less C&D materials generation.	· Encroachment on Tseng Tau Coast SSSI. · Long pumping distance (>3km) would result in longer retention time of sewage within the pumping system which would in turn increase the likeliness of sewage becoming septic and causing odour problems. · There is no existing access road to this location. Potential adverse environmental impact would likely be induced by formation of a new public access road leading to the site.
Location 8	· Situated on a fence-off vacant land surrounded by developed area that was under constant human disturbance. No encroachment on or in close proximity to any recognized sites of conservation importance and habitats with high ecological value. · Affect not as many nearby existing or planned air / noise sensitive receivers within 150m* of the location, including HKBTS, the planned school with recreational area under approved planning application no. A/MOS/125 and planned sitting out area and playground · Located at low point of the catchment. Since no additional pumping facilities or deep excavation for the SPS to facilitate connection with deeper gravity sewerage pipe is required, better environmental performance could be achieved with higher energy efficiency in operation and less C&D materials generation. · Medium pumping distance that reduces the retention time of sewage within the pumping system and in turn decreases the likeliness of sewage becoming septic and causing odour problems.	· Medium visibility to public.

Note:

* – As described in Section 1.1.1.4, the proposed SPS is considered as a DP by virtue of Item F.3(b) of Part I, Schedule 2 of EIAO as it has an installed capacity of more than 2 000 m³ per day and a boundary of which is less than 150 m from existing or planned uses that would be potentially affected by development of SPS (including residential area, place of worship, and educational institution).

2.3.1.4 Based on the environmental benefits and dis-benefits of each location listed in Table 2.1, a comparison of the eight alternative locations have been conducted and is presented in Table 2.2.

Table 2.2 Comparison of Alternative Location Options

Factors	Alternative Location Options
	1	2	3	4	5	6	7	8
Conservation & Ecology	Preferable No encroachment on or in close proximity to any recognized sites of conservation importance and habitats with high ecological value.	Not Preferable Encroachment on and in close proximity to natural habitats of higher ecological value, including woodland, mudflat and mangrove.	Less Preferable No encroachment on any recognized sites of conservation importance and habitats with high ecological value, but located close to habitats of higher ecological value, e.g. mangrove, mudflat and woodland.	Not Preferable Encroachment on woodland of higher ecological value.	Preferable No encroachment on or in close proximity to any recognized sites of conservation importance and habitats with high ecological value.	Not Preferable Encroachment on Ma On Shan Country Park and woodland.	Not Preferable Encroachment on Tseng Tau Coast SSSI.	Preferable No encroachment on or in close proximity to any recognized sites of conservation importance and habitats with high ecological value.
Air Quality & Noise	Less Preferable Affects more nearby existing or planned air / noise sensitive receivers within 150m* of the location including HKBTS, Sai O Village, Nai Chung Village, Sai Sha Villa, planned sitting out area and playground, and Zessa Vista.	Less Preferable Affects more existing or planned air / noise sensitive receivers within 150m* of the location, including Sai O Village, Nai Chung Village, Zessa Vista, HKBTS and Sai Sha Villa	Preferable Affects not as many nearby air / noise sensitive receivers within 150m* of the location, including the planned sitting out area and playground, HKBTS, Zessa Vista and Nai Chung Village.	Preferable Affects not as many nearby existing or planned air / noise sensitive receivers within 150m* of the location, including Nai Chung Village, Kwun Hang Village, Nai Chung barbecue area and the “CDA” zone on the approved Shap Sz Heung OZP No. S/NE-SSH/11.	Less Preferable Affects more nearby existing or planned air / noise sensitive receivers within 150m* of the location, including the Entrance, Double Cove, Li Po Chun United World College, Lake Silver and “Residential (Group A)” zone on the draft Ma On Shan OZP No. S/MOS/23.	Preferable Affects not as many nearby existing or planned air / noise sensitive receivers within 150m* of the location, including Nai Chung barbeque area, Kwun Hang Village, Nai Chung Village and “CDA” zone on the approved Shap Sz Heung OZP No. S/NE-SSH/11.	More Preferable Far away from air and noise sensitive receivers (over 500m).	Preferable Affects not as many nearby existing or planned air / noise sensitive receivers within 150m* of the location, including HKBTS, the planned school with recreational area under approved planning application no. A/MOS/125 and planned sitting out area and playground.
Visual	Less Preferable High visibility to public	Less Preferable Medium to high visibility to public	Preferable Medium visibility to public	Preferable Medium visibility to public	Less Preferable High visibility to public	More Preferable Low to medium visibility to public	More Preferable Low visibility to public	Preferable Medium visibility to public
Environmental Performance	Preferable Since the site is located at low point of the catchment, no additional pumping facilities or deep excavation for the SPS to facilitate connection with deeper gravity sewerage pipe is required, better environmental performance could be achieved with less C&D materials generation and higher energy efficiency in operation.	Preferable Since the site is located at low point of the catchment, no additional pumping facilities or deep excavation for the SPS to facilitate connection with deeper gravity sewerage pipe is required, better environmental performance could be achieved with less C&D materials generation and higher energy efficiency in operation.	Preferable Since the site is located at low point of the catchment, no additional pumping facilities or deep excavation for the SPS to facilitate connection with deeper gravity sewerage pipe is required, better environmental performance could be achieved with less C&D materials generation and higher energy efficiency in operation.	Less Preferable Since the site is located at high point of the catchment, additional pumping facilities or deep sewer/SPS would be required, poorer environmental performance would be anticipated with more C&D materials generation and lower energy efficiency in operation.	Less Preferable Since the site is located at high point of the catchment, additional pumping facilities or deep sewer/SPS would be required, poorer environmental performance would be anticipated with more C&D materials generation and lower energy efficiency in operation.	Less Preferable Since the site is located at high point of the catchment, additional pumping facilities or deep sewer/SPS would be required, poorer environmental performance with more C&D materials generation and lower energy efficiency in operation.	Preferable Since the site is located at low point of the catchment, no additional pumping facilities or deep excavation for the SPS to facilitate connection with deeper gravity sewerage pipe is required, better environmental performance could be achieved with less C&D materials generation and higher energy efficiency in operation.	Preferable Since the site is located at low point of the catchment, no additional pumping facilities or deep excavation for the SPS to facilitate connection with deeper gravity sewerage pipe is required, better environmental performance could be achieved with less C&D materials generation and higher energy efficiency in operation.
Septic Sewage & Odour	Preferable Medium pumping distance that decrease the likeliness of septic sewage and hence causing odour problems	Preferable Medium pumping distance that decrease the likeliness of septic sewage and hence causing odour problems	Preferable Medium pumping distance that decrease the likeliness of septic sewage and hence causing odour problems	Preferable Medium pumping distance that decrease the likeliness of septic sewage and hence causing odour problems	More Preferable Short pumping distance that decrease the likeliness of septic sewage and hence causing odour problems	Preferable Medium pumping distance that decrease the likeliness of septic sewage and hence causing odour problems	Less Preferable Long pumping distance that increase the likeliness of septic sewage and hence causing odour problems	Preferable Medium pumping distance that decrease the likeliness of septic sewage and hence causing odour problems

Note:

* – As described in Section 1.1.1.4, the proposed SPS is considered as a DP by virtue of Item F.3(b) of Part I, Schedule 2 of EIAO as it has an installed capacity of more than 2 000 m³ per day and a boundary of which is less than 150 m from existing or planned uses that would be potentially affected by development of SPS (including residential area, place of worship, and educational institution).

2.3.1.5 As shown in Table 2.2, Locations 2, 4, 6 and 7 are not recommended for the proposed SPS as all of them would encroach on recognised sites of conservation importance and / or natural habitats with higher ecological values that irreversible adverse impact on ecology and conservation could not be avoided. While Location 3 would not encroach on these valuable sites/habitats, it is less preferable due to its relatively close proximity to habitats with higher ecological values (including woodland, mudflats and mangrove). For the remaining 3 locations (Locations 1, 5 and 8), they are all considered preferable with respect to conservation and ecology aspects as they would not encroach on or in the close proximity to any recognised sites of conservation importance and/or natural habitats with higher ecological values.

2.3.1.6 In regard to air quality and noise aspects, amongst the remaining 3 locations (Locations 1, 5 and 8), Location 8 is considered more preferable as the proposed SPS at this location would affect relatively less nearby air and noise sensitive receivers.

2.3.1.7 In regard to visual aspect, Location 8 is also comparatively less visible to public than Locations 1 and 5.

2.3.1.8 In regard to environmental performance and septic sewage and odour aspect, Location 8 is also considered preferable. Extra pumping facilities or deep gravity sewer/SPS would not be required and hence would result in less C&D materials generation, higher energy efficiency in operation, and avoidance of impact on additional sensitive receivers near the extra pumping facilities. In addition, the likeliness of septic sewage that cause odour problem would be reduced.

2.3.1.9 Based on the above comparison of the eight locations, the vacant land next to Sai O Offtake and Pigging Station is considered the most preferred site for the Sai O Trunk Sewer SPS given the environmental benefits and comparatively less environmental dis-benefits.

Optimisation of Preferred Location for the Sai O Trunk Sewer SPS

2.3.1.10 In the process of developing the preferred design option for the SPS (Section 2.3.2 refers), the site footprint and location of the proposed SPS building have been modified from Location 8 into Location 8A as indicated in Appendix 2.3A. In order to optimise the preferred location, the SPS building has been moved further away from Nin Ming Road and sit alongside the aboveground structures of Sai O Offtake and Pigging Station at the corner of the preferred vacant land as detailed in Section 2.3.2.4. Location 8A allows the SPS building to be positioned in such a way that is most compatible with the surrounding landscape and visual context and greater room for landscape planting to enhance the landscape quality and block the view from the main road as detailed in Section 2.3.2.5, which could in turn minimise the landscape and visual impact to the maximum practicable extent. Location 8A has therefore been selected as the preferred location for the Sai O Trunk Sewer SPS that could best avoid impacts on area of conservation importance and natural habitats of higher ecological value, and avoid / minimise the potential adverse environmental impacts associated with the SPS (e.g. noise, odour, visual) while achieving a comparatively better environmental performance.

Alternative Site and Sewage Conveyance Scheme Put Forward by Public

2.3.1.11 During the course of the EIA study, an alternative site at Pak Shek (Whitehead) and reconsideration of Location 5 for SPS, together with alternative sewage conveyance scheme to Whitehead / Location 5, were put forward by the public. In response to this request, a further review of the alternative site at Pak Shek and Location 5 was conducted. The indicative position of alternative site at Pak Shek is illustrated in Appendix 2.3B.

Reconsideration of Location 5

2.3.1.12 As discussed in Sections 2.3.1.6 and 2.3.1.7, Location 5 is considered less preferable as the SPS at this location would affect more nearby existing or planned air & noise sensitive receivers and would be more visible to public compared to Location 8A (Table 2.2 refers). Furthermore, Location 5 is located at a high point of the catchment (up to around +21.7 mPD) and thus considered less preferable for this Project given its comparatively undesirable environmental performance (e.g. lower energy efficiency, more C&D materials generation) due to the need for an extra pumping facility in a lower level site in Sai O to support the operation of the SPS or deep excavation at the SPS to facilitate deeper gravity sewerage connection.

2.3.1.13 Concerning the undesirable environmental performance due to the large elevation differences between the catchment and Location 5 as described in Section 2.3.12, the public also put forward an alternative scheme to convey sewage to Location 5 in the form of a sewer tunnel that is similar to the Harbour Area Treatment Schemes (HATS) along Sai Sha Road, with a view to eliminating the need for an extra pumping facility in a lower level site in Sai O to support the provision of a SPS at Location 5. However, as further reviewed, if the sewage is to be conveyed to the SPS at Location 5 via a sewer tunnel that is similar to the HATS, there is still a need to provide a preliminary treatment works (PTW) / desilting facilities in low laying area (e.g. Sai O) before the sewage can be discharged to the sewer tunnel in order to remove large solids and grits to avoid deposition in the tunnels and to protect downstream facilities from damage or blockage. Apart from the extensive excavation works for the tunnel construction that would generate substantial amount of excavated materials, the required PTW/desilting facilities would also induce environmental impacts (e.g. odour, noise, visual) similar to the SPS to additional sensitive receivers in low laying area of the catchment (e.g. Sai O). The sewer tunnel option is therefore not recommended as it would not enhance the environmental performance of Location 5 or other alternative location at high point of the catchment.

Alternative Site at Whitehead

2.3.1.14 For the alternative site at Whitehead, the site and its surrounding areas are mainly zoned for recreational and residential developments as well as “Conservation Area”. The nearby existing air / noise sensitive receivers include St. Barths, Altissimo, Cycle Velodrome, Whitehead Club Golf Driving Range and Whitehead Barbecue. There is a large elevation difference between the alternative site at Pak Shek (+8.0 mPD) and the area near the Entrance (up to around +21.7 mPD).

2.3.1.15 Similar to Location 5, if the sewage is to be conveyed to a pumping station in Whitehead via deep sewer or rising mains along Sai Sha Road, Nin Wah Road and Lok Wo Sha Lane, an extra pumping facility or deep excavation at the SPS to facilitate connection with deeper gravity sewerage pipe would be required; if the sewage is to be conveyed via a sewer tunnel that is similar to the HATS, a PTW / desilting facilities in low laying area (e.g. Sai O) would be required as detailed in Section 2.3.1.12. Considering the topography of the areas, in order to avoid the provision of extra pumping facilities, PTW or desilting facilities in Sai O, or deep gravity sewer/SPS, provision of gravity sewers along the coastline would be required to convey sewage from Sai O area to Whitehead, which would encroach onto recognized sites of conservation importance (i.e. Nai Chung Coast SSSI and the “Conservation Area”) (Appendix 2.3B refers).

2.3.1.16 As summarised below, the alternative site at Whitehead is considered environmentally unfavourable as it could not avoid impacts on area of conservation importance and natural habitats of higher ecological value nor avoid / minimise the potential adverse environmental impacts associated with the SPS (e.g. noise, odour, visual) while having a comparatively undesirable environmental performance.

· Conservation and Ecology: The alternative site is considered environmentally unfavourable in regard to conservation and ecology as the site is situated in close proximity to and would likely encroach onto the “Conservation Area” while the gravity sewer alignment would also encroach onto recognized sites of conservation importance (i.e. Nai Chung Coast SSSI and the Conservation Area) that irreversible adverse impact on ecology and conservation could not be avoided.

· Air Quality, Noise and Visual: The alternative site is considered environmentally less preferable in regard to air quality and noise, as well as visual aspects as the site is surrounded by recreational and residential developments that the SPS at this location would affect more nearby existing or planned air & noise sensitive receivers (particularly existing or planned residential area) and have a high visibility to public.

· Environmental Performance: The alternative site is considered less favourable given its comparatively undesirable environmental performance (e.g. sensitive receivers in both Pak Shek and Sai O area would be affected, lower energy efficiency in operation, more C&D materials generation) due to the need for an extra pumping facility, deep excavation for the SPS to facilitate connection with deeper gravity sewerage pipe or extra PTW / desilting facility.

2.3.2 Design Options

2.3.2.1 The major environmental impacts associated with the Sai O Trunk Sewer SPS would be odour and fixed plant noise impacts from its operation and visual impact from the aboveground structures. Different design features (e.g. underground plant facilities, minimising the building bulk, appropriate façade and boundary treatments, etc) were considered in the process of developing the preferred design option for the SPS from the original design option presented in the Project Profile submitted for the Application for EIA Study Brief (Application No. ESB-281/2014) (Appendix 2.4), with an aim to avoid / minimise the potential impacts on the nearby sensitive receivers to the maximum practicable extent without compromising operational requirements of the proposed SPS.

2.3.2.2 The preferred design option adopted was optimised from the original design that it has retained beneficial features of the original design that could improve the overall environmental performance of the SPS and also incorporated other advantageous features (as discussed below in Section 2.3.2.3 to Section 2.3.2.5) in order to minimise the potential environmental impacts on the nearby sensitive receivers to the maximum practicable extent. Key design features considered and adopted in preferred design option are described below.

Submersible and Enclosed Design of Pumping Station

2.3.2.3 Similar to the original design option, the preferred design option has adopted the typical design of submersible type pumping station to reduce the scale and size of above-ground structure of the SPS. All submersible equipment / components, such as inlet chamber, coarse screen chambers, dry and wet wells, sewage pumps, valve and flowmeter chamber, will be placed underground with cover. The above-ground structure of the SPS is only for the equipment, such as electrical and mechanical (E&M) equipment, control panels, deodorization unit and exhaust, that has to be placed above ground and flooding levels. Furthermore, all the underground and aboveground equipment / components of the SPS will be enclosed within reinforced concrete structure with soundproof door and ventilated via deodorising unit and equipped with silencers or other acoustic treatment equipment at ventilation openings to avoid adverse odour and fixed plant noise impacts during its operation. In addition, enclosed design of the loading/unloading area has also been adopted in the preferred design option to confine any potential environmental nuisances from the loading and unloading activities during the SPS operation.

Compacted Design of Pumping Station with Deeper Structure, Smaller Plan Area and Limited Headroom

2.3.2.4 In order to avoid/minimise the potential landscape and visual impacts to the maximum practicable extent, under the preferred design option, the plan area of the SPS has been reduced by deepening the underground structures and the SPS components has been reconfigured. With this compacted design, building bulk of the SPS could be reduced by about 16% compared to the original design option, which could then allow the SPS building to be moved further away from Nin Ming Road and sited alongside the aboveground structures of Sai O Offtake and Pigging Station at the corner of the vacant land. In addition, the proposed height of SPS had been minimized by lowering the ground level to match with the existing carriageway and slope. The height of SPS has also been designed with limited headroom by skipping double slab and allow minimum headroom for lifting operation etc. With these design features in place, the building bulk of the SPS could be minimised and be positioned in such a way that is most compatible with the surrounding landscape and visual context, hence minimising the potential landscape and visual impact from the new superstructure. Furthermore, since deeper underground structures with smaller plan area would be adopted in the design, the area of excavation works required for the underground wells/chambers would be reduced as compared to the original design and hence would also minimise the potential visual impact from the excavation works.

Appropriate and Aesthetic Façade and Boundary treatments with Area Reserved for Landscape Planting

2.3.2.5 Similar to landscape and aesthetic design of the original design option, the preferred design option has been designed to blend into the existing environment of the Project site and screen the view of proposed SPS from the public path with aesthetically designed fence wall treated with planters and vegetation. Building façades, roof slab and fence walls would be treated with planters and vegetation, while the surface of the SPS would be covered with wall tiles to harmonize with the earthy landscape to echo with the surrounding natural environment. In addition to the landscape design of the original design option, under the preferred design option, the whole SPS building has been moved to the northern part of the site alongside the northern boundary wall of the existing Sai O Offtake and Pigging Station for better compatibility with the surrounding landscape and visual context as detailed in Section 2.3.2.4, the southern part of the site (next to Nin Ming Road) could therefore be preserved for landscape planting to enhance the existing landscape quality and provide further screen planting to block the view of the SPS from the main road.

2.4 Considerations of Construction Methods and Sequences of Works

2.4.1 Construction Methods

2.4.1.1 There are two approaches for the SPS superstructure construction, including conventional cast in-situ construction method and pre-cast structure. In view of the small scale and relatively simple structure of the proposed SPS (i.e. single storey building with basement), there is limited advantage from the pre-cast method which is usually more efficient for structure with repeating blocks (e.g. standardised flats in high-rise residential development, segments of bridge). On the contrary, since pre-cast structure is prefabricated, modification to the pre-cast structure is inevitable due to the actual site constrains and construction procedure such as E&M equipment installation. Utilisation of powered mechanical equipment (PME) such as breaker would be required and hence, the environmental impacts for both approaches would be similar. Alternatively, if a new precast structure is adopted instead of on-site modification, detailed and prolonged coordination between different parties including structural, architectural, E&M, pumping specialist etc. would be required so that the whole construction period might be prolonged and would result in wastage of construction material.

2.4.1.2 Considering the traditional cast in-situ construction method could allow more flexibility in on-site alteration for E&M equipment and pumping system installation, and is the most straightforward method for this Project to avoid prolonged construction duration and hence reduce potential disturbance to the environment and local public, the cast in-situ construction method would be adopted for the superstructure construction.

2.4.1.3 Two foundation approaches were considered for the proposed SPS, including percussive piling and shallow foundation (e.g. footing foundation). While percussive piles require shorter construction time and could reduce the duration of environmental impacts from foundation works, it would induce a relatively high disturbance in term of noise level during the construction stage. Although shallow foundation would require longer construction period, it is a quieter foundation method. Considering the relatively small scale of works, shallow foundation would therefore be adopted for the proposed SPS.

2.4.2 Construction Sequences

2.4.2.1 The sequence of construction works is defined by the need to meet the constraints of the programme as well as engineering requirements. Two approaches are generally adopted for arranging the sequences of works, including the concurrent construction sequence and phased construction sequence. The concurrent construction sequence involves various construction activities occurring at the same time. The environmental benefit of this approach would result in a shorter construction period and hence the duration of impact due to the construction activities. However, the magnitude of overall environmental impact would be higher. The phased construction sequence involves construction activities being carried out one followed by another that would reduce the magnitude of the overall impacts but at the expense of prolonged construction period. As the two approaches have their environmental benefits and drawbacks, a balancing approach with a combination of both has been considered in deriving the construction sequence so as to avoid/minimise prolonged disturbance to the environment and local public.

2.4.2.2 Construction of the Project generally includes the following activities:

· Site clearance;

· Excavation and lateral supports for basement excavation;

· Bulk excavation;

· Steel fixing and casting of concrete structure;

· Backfilling;

· E&M equipment installation and pipeworks; and

· Finishing and landscaping works.

2.4.2.3 As shown in Appendix 2.5, the above construction activities would be carried out in phased sequence in conjunction with the overlapping of some activities such that the construction duration could be shortened and potential adverse cumulative impacts from concurrent construction activities would be avoided.

2.5 Selection of Preferred Scenario

2.5.1.1 Due consideration of alternative options for location, design, construction method and sequence of the Project have been conducted (as detailed in Sections 2.3 and 2.4) to arrive at the preferred scenario that the potential adverse environmental impacts on the nearby sensitive receivers would be avoided / minimised to the maximum practicable extent. The selected and optimised preferred location (Location 8A) would maximise the environmental benefits in terms of no encroachment onto any area of conservation importance (e.g. SSSI, Country Park, Conservation Area), minimisation of air and / or noise sensitive receivers to be affected, lower visibility to public and better environmental performance (including higher energy efficiency, less waste generation, impact on less sensitive receivers) for SPS operation. Together with the adoption of the preferred option in design, construction method and sequence, such as adoption of compacted design to minimise the building bulk of SPS and to position the SPS building in such a way that is most compatible with the surrounding landscape and visual context, enclosed loading/unloading area to avoid environmental nuisances during loading/unloading activities, and preserving the southern part of the site for landscape planting to improve the existing landscape quality and minimise the visual impact, the potential environmental impacts would be avoided / minimised to the maximum practicable extent.

2.6 Construction Programme

2.6.1.1 The construction of the Project is planned to commence in year 2021 Q4 for completion, and commissioning and operation in year 2024 Q2. The tentative construction programme is presented in Appendix 2.5.

2.7 Concurrent Project

2.7.1.1 Based on the available information at the time of this EIA preparation, “Sai Sha Road Widening” would be carried out adjacent to the Project site from Q1 of 2018 to Q4 of 2023, as such cumulative construction phase environmental impacts are expected. Potential cumulative environmental impacts arising from this concurrent project during the construction phase of the Project have been assessed in the EIA Report.

2.7.1.2 A school with recreational area is proposed at various lots in D.D.167 and adjoining government land, Nai Chung to the north of Nin Ming Road under the approved planning application No. A/MOS/125. Since no confirmed construction programme of the planned educational development is available at the time of the preparation of this EIA, potential cumulative environmental impacts associated with this planned development have not been taken into account.

2.7.1.3 Comprehensive Residential and Commercial Development with Government, Institution or Community Facilities is proposed along Sai Sha Road at Tai Po Town Lot 157 and Various Lots in D.D. 165, D.D. 207 and D.D. 218 and Adjoining Government Land, Sai Sha, Shap Sz Heung under the approved planning application Nos. A/NE-SSH/120 and A/NE-SSH/120-1. Since no confirmed construction programme of the planned comprehensive development is available at time of the preparation of this EIA, potential cumulative environmental impacts associated with this planned development have not been taken into account.