Environmental Impact Assessment - Ch.13 Summary of Environmental Outcome

13.1 Environmental Designs Recommended and Environmentally Friendly Options Considered 13-1

13.2 Key Environmental Problems Avoided. 13-4

13 SUMMARY OF ENVIRONMENTAL OUTCOME

13.1 Environmental Designs Recommended and Environmentally Friendly Options Considered

Environmental Enhancement Project by Nature

13.1.1 The proposed sewerage works in Po Toi O is an environmental enhancement project by nature. Through replacement of septic tanks/soakaway systems (STS) by a public sewerage system, hygiene and associated odour nuisance from routine desludging will be eliminated. In addition, the provision of sewerage is a preventive measure to avoid potential environmental problems due to insufficient desludging or structural defect of the STS. This can also relieve villagers’ burden to maintain their STS (e.g. desludging).

13.1.2 Sewage will be properly collected and treated by membrane bioreactor process (MBR) up to the effluent discharge standard of Port Shelter Water Control Zone. Treated effluent will be discharged via a submarine outfall at a diffuser installed at seabed in outer Po Toi O Bay, which will be at least 326m, 185m and 100m away, respectively, from the nearest fish culture zone, a coral-lined rocky shore and an amphioxus habitat.

Various Green Measures in the Project (Mainly by Avoidance and Minimization of Potential Impacts)

13.1.3 Po Toi O has scenic seashore embraced by hilly terrain overgrown with shrubs and trees. Village settlements along the shore and fish farming in the bay give Po Toi O a unique rural landscape. This EIA Study has identified and fully considered the potential constraints imposed by this special environ, and has developed a number of green initiatives at this planning stage. In addition to improving environmental hygiene in the Po Toi O area, this Project targets to achieve environmental friendliness in sewerage, construction and operation designs. The green measures and the associated environmental benefits of this Project are summarized as follows:

Green Measures in Sewerage System Design

· Minimization of loss of ecologically sensitive habitats by locating the STP on a cut slope (disturbed shrubland) and laying gravity sewers and rising mains along existing footpaths as far as possible from developed area;

· Avoidance of destruction of coral-lined rocky shore and major amphioxus habitat by locating the treated effluent discharge location over 100m away from the coral-lined shore and species of conservation importance (amphioxus);;

· Minimization of fisheries impact by discharging the treated effluent at about 326m away from the fish culture zone;

· Maximizing effluent dispersion by placing the diffuser on seabed at >10m depth and at outer Po Toi O bay where current flows are fast;

· Minimization of the footprint of the STP by constructing most of the STP structure underground and adopting a less land demanding sewage treatment technology (MBR);

· Minimization of odour and noise nuisance by keeping a sufficient buffer distance between the STP and village houses;

· Minimization of visual impact by embedding the STP into the existing cut slope;

· Maintenance of visual entity with surrounding undisturbed landscape by provision of appropriate façade treatment (e.g. adopting recessive colours on STP wall that blend in with the natural tones of the landscape backdrop), compensatory tree planting and vertical greening;

· Avoidance of impact on built heritage resources (e.g. Grade 3 historic building Hung Sing Temple) by laying gravity sewers and rising mains over 5m away from its footprint;

Green Measures in Construction Design

· Avoidance of open dredging to minimize water quality, marine ecological and fisheries impacts by adopting (1) horizontal directional drilling for submarine outfall below seabed and (2) enclosed dredging within a cofferdam for the diffuser;

· Avoidance of concurrent construction activities by designing a separate works programme for noisy works (carrying out rock breaking works for STP prior to laying of gravity sewer and rising mains and drilling for submarine outfall). Also, adopting three workfronts during pipe laying in village, each of short section and at least 100m away from each other.

Green Measures in Operation Design

· Improvement of environmental hygiene and removal of associated odour nuisance in the Po Toi O area by eliminating the need of desludging STS;

· Avoidance of emergency discharge of raw sewage into waterbodies by a number of design features or arrangements in case of emergency plant failure, such as notification to the operator by a supervisory control and data acquisition (SCADA) system, provision of standby equipment in the STP, provision of sufficient capacity of emergency storage of incoming sewage and provision of tankers for continuous removal of sewage to other STP for treatment.

· Minimization of odour nuisance from STP by provision of an odour removal system with 99.5% efficiency in the STP;

· Minimization of noise disturbance from STP by storing noisy plant equipment underground.

13.2 Key Environmental Problems Avoided/Minimized

13.2.1 A summary of the key environmental problems avoided/minimized for each aspects in this Project is listed in Table 13-1 below:

Table 13-1 Key Environmental Problems Avoided/Minimized

Aspects	Key Environmental Problems Avoided/Minimized
Air Quality	Benefits of Environmental Protection Measures Recommended Construction phase - Minimization of air quality impact (TSP, RSP and FSP emission) by adopting dust control measures stipulated in the Air Pollution Control (Construction Dust) Regulation (e.g. watering of exposed grounds and proper stockpiling). Operational phase - Minimization of air quality impact (odour) by pointing exhaust from the deodorizer of the STP upward to allow maximum dispersion. - Minimization of air quality impact (odour) by proper maintenance of deodorizer to ensure that the overall H₂S (i.e. odour source) removal efficiency of 99.5% or higher. Environmentally Sensitive Areas and Estimated Population Protected Existing residential village buildings, recreation area and temple in the vicinity of the Project Site (within work boundary in Figure 1-1). Compensation Included N/A
Noise	Benefits of Environmental Protection Measures Recommended Construction phase - Avoidance of concurrent construction activities by designing separate work programme for noisy works (carrying out rock breaking works for STP prior to laying of gravity sewer and rising mains and drilling for submarine outfall). Also, adopt three workfronts during pipe laying in village, each of short works section and at least 100m away from each other. - Minimization of noise disturbance by implementing mitigation measures such as adoption of good site practice, use of quieter PMEs and mobile noise barrier. Operational phase - Minimization of noise disturbance by storing most noisy plant equipment underground. Environmentally Sensitive Areas and Estimated Population Protected Existing residential village buildings in the vicinity of the Project Site. Compensation Included N/A
Water Quality	Benefits of Environmental Protection Measures Recommended Construction phase - Minimization of water quality impact by dredging within fully enclosed cofferdam or using horizontal directional drilling (HDD) instead of carrying out open dredging. - Avoidance of disturbance on watercourse by placing sand bag along work zones which are close to watercourse. Operational phase - Minimization of water quality impact by placing the diffuser in a deeper sea which allows better dispersion of effluent. - Avoidance of water quality impact on Po Toi O Bay by not discharging raw sewage into Po Toi O Bay in case of plant failure. Environmentally Sensitive Areas and Estimated Population Protected Water bodies in Po Toi O & Clear Water Bay, which include Po Toi O Fish Culture Zone, coral & amphioxus habitats, Clear Water Bay First & Second Beaches, Secondary contact recreation sub-zones, and shorelines at the Coastal Protection Zone at Po Toi O. Compensation Included N/A
Terrestrial Ecology	Benefits of Environmental Protection Measures Recommended Construction phase - Avoidance of disturbance on sensitive habitats (e.g. woodland in Conservation Area) and natural habitats by locating the STP on a man-made cut-slope. - Avoidance/minimization of disturbance on other habitats and protected species in the vicinity of the Project Site by erecting hoarding around construction site and bright colour fencing around the protected shrub Diospyros vaccinioides near the work boundary. - Avoidance of disturbance on freshwater habitat by placing sand bag along watercourse near work-zone. - Minimization of impact on all disturbed habitats (e.g. rocky shore in “Coastal Protection Area” where HDD entry pit is located) by habitat reinstatement as far as possible after construction works. Operational phase N/A Environmentally Sensitive Areas and Estimated Population Protected Habitat, vegetation and wildlife within the Study Area Compensation Included Compensatory planting for felled trees of at least 1:1 by number in accordance with DEVB TCW No. 7/2015, which requires future application to Lands Department for final approval.
Marine Ecology	Benefits of Environmental Protection Measures Recommended Construction phase - Minimization of impact on species with conservation importance (i.e. coral & Amphioxus communities) by locating the submarine outfall further away from them. - Minimization of impact on water quality (hence marine ecology) by dredging within fully enclosed cofferdam or using horizontal directional drilling (HDD) instead of carrying out open dredging. - Avoidance of impact on intertidal habitat and the associated fauna by designing no works area in intertidal zone. Operational phase - Avoidance of impact on water quality (hence marine ecology) by not discharging raw sewage into Po Toi O Bay in case of plant failure. Environmentally Sensitive Areas and Estimated Population Protected Habitat and wildlife within the Study Area Compensation Included N/A
Fisheries	Benefits of Environmental Protection Measures Recommended Construction phase - Minimization of impact on Po Toi O Fish Culture Zone by locating the submarine outfall further away from the Fish Culture Zone. - Minimization of impact on water quality (hence fisheries resources) by dredging within fully enclosed cofferdam or using horizontal directional drilling (HDD) instead of carrying out open dredging. Operational phase - Avoidance of impact on water quality (hence fisheries resources) by not discharging raw sewage into Po Toi O Bay in case of plant failure. Environmentally Sensitive Areas and Estimated Population Protected Fisheries resources in the Study Area, e.g. Po Toi O Fish Culture Zone Compensation Included N/A
Waste Management and Land Contamination	Benefits of Environmental Protection Measures Recommended Construction phase - Minimization of impact due to waste management by preparing a specific waste management plan by future contractor (required for public works under ETWB TCW No. 19/2005 Environmental Management on Construction Sites) and adopting good site practice (e.g. avoiding over-purchase of construction materials by careful planning). - Minimization of environmental nuisance by storing and delivering waste properly (e.g. in enclosed container) to designated disposal sites. Operational phase - Minimization of environmental nuisance by storing and delivering waste (including sludge, worn filters and general refuse) properly and disposing of at designated facilities (e.g. dispose of sludge to sludge treatment facilities) by licensed contractor where applicable. Environmentally Sensitive Areas and Estimated Population Protected Air and water sensitive receivers near the Project Site and along transportation routes. Compensation Included N/A
Landscape and Visual	Benefits of Environmental Protection Measures Recommended Construction phase - Minimization of impact on adjacent landscape by minimizing temporary works areas as possible. - Minimization of visual impact by using decorative mesh screens, construction hoardings and/or temporary noise barriers around works areas which are in visually unobtrusive colours as possible. Operational phase - Reinstatement the landscape which are appropriate to the context, by tree and shrub planting, and vertical greening. Environmentally Sensitive Areas and Estimated Population Protected Landscape resources, landscape character areas and visual sensitive receivers surrounding the Project Site. Compensation Included Compensatory planting for felled trees of at least 1:1 by number in accordance with DEVB TCW No. 7/2015, which requires future application to Lands Department for final approval.
Built Heritage	Benefits of Environmental Protection Measures Recommended Construction phase - Prevention of direct damage on built heritages (see below) by machine or dirt by providing protective covering on a movable fence. - Prevention of indirect damage by mechanical vibration and settlement by carrying out vibration and settlement monitoring. Operational phase N/A Environmentally Sensitive Areas and Estimated Population Protected Hung Shing Temple (i.e. Grade 3 historic building), historic built structures (e.g. Sir Ho Tung Recreation Centre), & cultural landscape features (e.g. Earth God Shrine) Compensation Included N/A