TABLE OF CONTENTS

Page

15           Conclusions. 15-2

15.1        Impact Summary. 15-2

15.2        Benefits of the Project 15-2

15.3        Air Quality Impact 15-3

15.4        Noise Impact 15-3

15.5        Water Quality Impact 15-4

15.6        Land Contamination. 15-6

15.7        Hazard to Life. 15-6

15.8        Ecological Impact 15-7

15.9        Fisheries Impact 15-8

15.10     Landscape and Visual Impact 15-9

15.11     Cultural Heritage Impact 15-10

15.12     Waste Management Implications. 15-10

15.13     Health Impact 15-10

15.14     Environmental Outcomes. 15-11

15.15     Overall Conclusion. 15-17

 

LIST OF TABLES

Table 15.1       Summary of Key Environmental Outcomes / Benefits. 15-11

 

 

15                   Conclusions

15.1                Impact Summary

15.1.1.1         The Project covers the following DP elements of Schedule 2 under the EIAO (Cap.499):

·         DP1 –

Sewage treatment works with an installed capacity of more than 15,000 m3 per day under Item F.1 in Schedule 2 Part I;

 

·         DP2 –

Sewage treatment works under Item F.2 in Schedule 2 Part I---

§  With an installed capacity of more than 5,000 m3 per day; and

§  A boundary of which is less than 200m from the nearest boundary of an existing or planned residential area, educational institution and health care institution.

 

·         DP3 –

An activity for the reuse of treated sewage effluent from a treatment plant under Item F.4 in Schedule 2 Part I;

 

·         DP4 –

Underground rock caverns under Item Q.2 in Schedule 2 Part I;

 

·         DP5 –

An explosives depot in a stand‑alone, purpose built building under Item K.10 in Schedule 2 Part I; and

 

·         DP6 –

Decommissioning of an explosives depot under Item 11 in Schedule 2 Part II.

15.1.1.2         This EIA report has provided an assessment of the potential environmental impacts associated with the construction and operation of the Project based on the preliminary engineering design information available.  The assessment has been conducted, in accordance with the Study Brief No. ESB-273/2014 under the EIAO for the Project, covering the following environmental issues.

·         Air Quality Impact

·         Noise Impact

·         Water Quality Impact

·         Land Contamination

·         Hazard to Life

·         Ecological Impact

·         Fisheries Impact

·         Landscape and Visual Impact

·         Cultural Heritage Impact

·         Waste Management Implications

·         Health Impact

15.1.1.3         The findings of this EIA Study have determined the likely nature and extent of environmental impacts predicted to arise from the construction and operation of the Project.  During the EIA process, specific environmental control and mitigation measures have been identified and incorporated into the planning and design of the Project in order to achieve compliance with environmental legislation and standards during both the construction and operation phases.  An EM&A programme has also been developed.  The Implementation Schedules listing the recommended mitigation measures are presented in the Section 16.  A summary of the environmental impacts are presented in the sections below.

 

15.2                Benefits of the Project

15.2.1.1         Upon relocation of the STSTW to caverns, 28 ha of land in Sha Tin with sea frontage can be released for re-development to meet the needs of the society.

15.2.1.2         The living environment of the surrounding area would be improved. The common potential impacts of a sewage treatment works, particularly odour and visual impacts, can be very effectively controlled and minimised.  Odour management of the STSTW would be greatly enhanced since the caverns would serve as very effective natural barriers. 

15.2.1.3         Advanced technologies can be adopted for the new sewage treatment facilities to enhance operation process performance, resilience and reliability, as well as operation efficiency.

15.2.1.4         Subject to subsequent planning, the released STSTW site will provide opportunities for developing a green and vibrant waterfront living environment with ample open space, a continuous promenade and recreational facilities such as amenity areas, cycle tracks and other leisure purposes could be created.

15.2.1.5         The development opportunities of the surrounding area adjacent to the existing STSTW site would be enhanced after completion of the Project and the accessibility of the area would be improved by improving transport infrastructure at the area.

15.2.1.6         The project location is rich in granite.  Excavation of caverns will produce a large amount of hard granitic rocks, which are valuable natural resources for construction use.  Rocks produced under this Project would become a local source to support the construction industry.

 

15.3                Air Quality Impact

15.3.1.1         The assessment shows that the potential construction dust impacts from the construction works of the Project would mainly be related to construction dust from excavation, materials handling, spoil removal and wind erosion.  With the implementation of mitigation measures specified in the Air Pollution Control (Construction Dust) Regulation together with the recommended dust suppression measures including watering 8 times a day on active works areas, exposed areas and unpaved haul roads, and dust collector with 99% removal efficiency for rock crusher, good site practices, the predicted dust impact at ASRs would comply with the hourly, daily and annual particulate criteria stipulated in the AQOs and EIAO-TM.  An EM&A programme during construction phase is recommended to ensure that the mitigation measures are to be properly implemented.

15.3.1.2         Potential operational air quality impacts would come from odour emission from the ventilation shaft of CSTW after the deodourisation treatment at design odour removal efficiency of 80 – 97%.  The odour impact assessment results show that the predicted odour concentration at all ASRs located in the vicinity of CSTW would comply with the odour criterion (5 odour units based on an averaging time of 5 seconds) stipulated in the EIAO-TM.  No further mitigation measures are required.  A commissioning test on deodorisers is however recommended to ensure the effectiveness of the deodorisation treatment implemented in the Project.

 

15.4                Noise Impact

Construction Phase

15.4.1.1         This assessment has presented construction noise impacts of the Project during construction of relocated STSTW including water reclamation facilities, decommissioning and demolition of the existing STSTW and the temporary explosives magazine.  The predicted maximum unmitigated noise levels at representative NSRs would range from 70 to 89 dB(A).  With the adoption of quiet PME, use of movable noise barrier/acoustic mat, and limitation of the number of on-time operating PMEs within 120m of the Neighbourhood Advice-Action Council Harmony Manor during construction of access road, the noise levels due to the Project itself at all representative residential NSRs would comply with the EIAO-TM criterion of 75 dB(A).  All representative educational NSRs would also comply with the noise criteria except that occasional exceedances of noise criterion during examination period are predicted at educational NSR NR-C07 due to construction activities at the main portal and at Area 73.  As this NSR is located in close vicinity of these work areas, all practical mitigation measures have been exhausted.  As the affected period would be limited to examination periods and the affected educational NSR has been noise insulated with air conditioners, it is considered that the residual noise impact is in short term period and would be minimised by keeping the windows closed during the affected examination periods.  Notwithstanding this, it is recommended that particularly noisy construction activities should be scheduled to avoid examination periods of this NSR as far as practicable.  The Contractor should liaise with the school representative(s) to obtain the examination schedule so as to avoid noisy construction activities during school examination period. During the actual construction period, as much as practically possible should be done to reduce the construction noise, and on-going liaison with all concerned parties and site monitoring should also be conducted during the course of the construction period.  A construction noise EM&A programme is recommended to check the compliance of the noise criteria during normal daytime working hours. 

15.4.1.2         Ground-borne construction noise impacts pertinent to the use of hydraulic breaker, hand-held breaker, drill rig and TBM would comply with criteria of EIAO-TM.  No adverse ground-borne construction noise impacts is predicted and therefore no noise mitigation measure and noise monitoring are proposed.

15.4.1.3         For the temporary modification works at the merging point of Ma On Shan Road and temporary access haul road, the provision of 220m length of noise barrier of a height at 10mPD on the temporary access haul road to replace the existing 150m length of noise barrier at 9.2mPD to 10mPD height on Ma On Sha Road would pose negligible difference in the overall traffic noise level at the sensitive facades in the vicinity.  Once the construction work is completed, the noise barrier on the concerned road section of Ma On Shan Road would be re-installed according to the existing configuration.  

Operational Phase

15.4.1.4         The noise impact associated with the operation of the Project has been assessed.  The predicted fixed plant noise levels at the representative NSRs would comply with the criteria based on the plant design information provided by the Engineer at the time of the assessment.  If there is any change in engineering design information during detailed design stage or fitting-out stage, the fixed source noise design should be reviewed by the Engineer/Contractor to ensure that both the NCO and EIAO-TM criteria at the NSRs can be met in the future.  Prior to the operational phase of the Project, a commissioning test for the ventilation buildings, the ventilation shaft,  ventilation fan for chiller plant room and cooling tower at the administration building would be conducted to ensure compliance with the relevant allowable maximum sound power levels.

 

15.5                Water Quality Impact

Construction Phase

Land-based Construction

15.5.1.1         Minor water quality impact would be associated with land-based construction. Impacts may result from the surface runoff, accidental spillage, sewage from on-site construction workers and groundwater infiltration.  Impacts could be controlled to comply with the WPCO standards by implementing the recommended mitigation measures.

Tolo Harbour Effluent Export Scheme (THEES) Connection Works

15.5.1.2         Both the TPSTW and existing STSTW are secondary treatment plants with disinfection process. Under normal operation of the THEES, the TPEPS would pump the secondarily treated and disinfected effluent of TPSTW via a rising main and a submarine pipeline to the STEPS. The STEPS would receive the secondarily treated and disinfected effluent from both TPSTW and STSTW for combined discharge to the KTN in the Victoria Harbour WCZ via the THEES effluent tunnel.

15.5.1.3         In order to maintain the current arrangement in discharging effluent to KTN through THEES tunnel, the provision of a dry construction zone within the THEES tunnel to allow connection from the CSTW would be essential for the Project. During the connection works, the THEES tunnel needs to be temporarily suspended from its normal operation with effluent bypass into the Tolo Harbour.

15.5.1.4         Under the existing practice, regular inspection and repair of the THEES would be carried out when necessary to maintain proper functioning and integrity of the THEES. During each THEES maintenance event, secondarily treated and disinfected effluent from TPSTW and STSTW would be temporarily discharged to the Tolo Harbour to provide a dry zone within the THEES tunnel for a maximum duration of 4 weeks. To minimize water quality impact to Tolo Harbour, the necessary THEES connection works required for this Project will be split into a number of steps for sequential and synchronized implementation with THEES maintenance, thereby avoiding the need for additional temporary suspension of the THEES. Each suspension will not be longer than 4 weeks and will be outside the algae blooming season (January to May), and the frequency will be no more than once per year during the construction phase of the Project.  Therefore, no additional water quality effect on the Tolo Harbour waters would result from the proposed THEES connection works.  No cumulative or residual impact would be expected during the construction phase of the Project with the recommended mitigation measures properly implemented.

Operational Phase

15.5.1.5         The CSTW effluent together with the TPSTW effluent will be discharged to the Victoria Harbour via the THEES during normal operation. Compared with the existing STSTW, the CSTW has the same design flow capacity (340,000m3 ADWF) per day) and effluent standard.  Hence, this Project will not induce any change to the flow and loading of THEES effluent to the Victoria Harbour. 

15.5.1.6         Maintenance of the THEES tunnel is required to ensure proper functioning and integrity of the tunnel. During the inspection or maintenance of the THEES tunnel, temporary suspension of the normal THEES operation with effluent bypass into the Tolo Harbour is unavoidable in order to provide a safe and dry zone within the THEES tunnel. It should be noted that such temporary effluent bypass during THEES maintenance is part and parcel of the existing THEES regardless of whether the Project is implemented or not. 

15.5.1.7         Mathematical modelling was undertaken under this EIA to study the water quality impact arising from a 4-week THEES maintenance discharge.  The model results indicated that even for such a discharge in the algae blooming season (January to May) under the ultimate development scenario, the increase in pollution level in Tolo Harbour would still be transient and reversible. 

15.5.1.8         With the design capacity, effluent standards and effluent discharge points being the same as those of the existing STSTW, this Project will not change the flow, load and discharge point of the THEES effluent to Victoria Harbour and Tolo Harbour. 

15.5.1.9         In order to further minimize water quality impact, it is recommended under this Project to schedule the THEES maintenance outside the algae blooming season (January to May).  Water quality modelling indicates that the pollution elevation in Tolo Harbour and the associated recovery period would be significantly reduced and alleviated as compared to the case of inside the algae blooming season (January to May).   An event and action plan and a water quality monitoring programme (presented in the standalone EM&A Manual) is proposed for the THEES maintenance events during both construction and operational phases to minimize water quality impacts.

15.5.1.10      Emergency discharges from the Project would possibly be the consequence of pump failure, interruption of the electrical power supply or failure of treatment units. Mitigation measures, including dual power supply or ring main supply from electric company, standby pumps, treatment units and equipment, would be provided to avoid the occurrence of any emergency discharge.  A contingency plan has also been formulated to minimize the impact of emergency discharges and facilitate subsequent management of the situation emergency.  An event and action plan and a water quality monitoring programme (presented in the standalone EM&A Manual) is proposed for the emergency discharge events during operational phase to minimize water quality impacts.  No cumulative or residual impact would be expected during the operational phase of the Project with the recommended mitigation measures properly implemented.

 

15.6                Land Contamination

15.6.1.1         Site appraisal was carried out in the period from November 2014 to March 2015 with site walkovers conducted in November 2014 and January / July / November 2015.  Based on the site appraisal, within the Project boundary, the existing STSTW and the temporary works area on Area 73, currently part of a VDC, are considered to be areas with potential land contamination concerns.

15.6.1.2         A sampling and testing programme, targeting the existing STSTW and the temporary works area on Area 73, has been proposed.  Since the sites will continue to be in use until the full commissioning of the relocated STSTW, the proposed SI works and any necessary remediation action are recommended to be carried out after decommissioning of the existing STSTW and when the temporary works area on Area 73 is vacated, but prior to re-development.

15.6.1.3         In addition, two sites (the David Camp and proposed A Kung Kok Shan Road surface magazine site) within the Project boundary are inaccessible or yet to be constructed. Further site walkover is recommended within the sites when access to the camp site is available and before the decommissioning of the surface magazine site to confirm the presence of any land contamination. If land contamination were presence, detailed land contamination assessment and remediation would be required prior to the re-development.

15.6.1.4         Further site walkover, assessment and remediation (if necessary), including the submission of Supplementary CAP(s), CAR(s)/RAP(s) and RR(s) would follow EPD’s prevailing guidelines and recommendation in the EIA Study.

15.6.1.5         With the implementation of further site walkover, land contamination assessment and, if required, remediation works for the Project Site, any soil/groundwater contamination would be identified and properly treated prior to re-development.  Land contamination impacts are therefore considered surmountable to future occupants.

 

15.7                Hazard to Life

Storage, Transport and Use of Explosives

15.7.1.1         A QRA has been carried out to assess the hazard to life issues arising from the storage, transport and use of explosives during the construction of the Project.

15.7.1.2         The criterion of Annex 4 of the EIAO-TM for Individual Risk would meet with regards to the hazard to life posed by storage, transport and use of explosives.  The assessment results show that the societal risk for the storage and use of explosives lies within the acceptable region, and the transport of explosives lies within the lower ALARP region when compared to the criteria stipulated in the EIAO-TM.   A detailed ALARP assessment has been undertaken considering a range of mitigation measures and the results show compliance with the ALARP principles provided that the recommendations in Section 7.14 are followed.

HP Underground Town Gas Transmission Pipelines

15.7.1.3         The transport route of explosives is close to an HP underground town gas transmission pipelines. A QRA has therefore been conducted to assess the increased societal risk arising from the incremental population during both construction and operational phases of the Project.

15.7.1.4         The criterion of Annex 4 of the EIAO-TM for Individual Risk would meet with regards to the hazards to life posed by the HP underground town gas transmission pipelines during both construction stage and operational stage.  The assessment results show that the societal risk lies within the lower ALARP region of the HKRG.  However, with the comparison of the ‘without Project’ scenarios, it is found that the ALARP is due to the background population instead of the population induced by the Project.

 

15.8                Ecological Impact

15.8.1.1         Ecological impact assessment for the relocation of STSTW has been conducted following the guidelines of the EIAO-TM Annex 8 and Annex 16.

15.8.1.2         Terrestrial habitats identified within the assessment area include woodland, fung shui wood, plantation, shrubland, cultivated land, developed area, and stream.  Marine habitats within the assessment area include subtidal hard substrata, soft bottom habitats, and intertidal habitats.  The ecological values of the identified habitats are rated between low and moderate to high.  No sites of conservation importance will be directly affected. 

15.8.1.3         Direct impacts arising from the proposed land-based works include permanent loss and temporary loss of some woodland, plantation, and shrubland, as well as minor habitat fragmentation of woodland and plantation in Nui Po Shan.  Given the relatively low to moderate ecological values of the habitats and the small area affected, impacts are anticipated to be generally minor in nature.  The permanent loss of woodland (0.65 ha) will be mitigated by compensatory planting (approximately 0.92 ha) of native species, while all temporarily affected works area will be reinstated.  A Woodland Compensation Plan should be prepared to form the basis (e.g. implementation details, management requirement, and monitoring requirements) and submitted for approval from EPD at least three months before commencement of compensatory woodland planting.  All temporarily affected works area will be reinstated.  Avoidance measures would be implemented to preserve a natural stream in vicinity of the proposed access road on Nui Po Shan (e.g. provision of an elevated section at the stream crossing). 

15.8.1.4         Some plant species of conservation importance were recorded within the Project boundary.  To minimise the loss, a Detailed Vegetation Survey should be conducted prior to the commencement of construction works to identify potentially affected plant species.  All identified species would be labelled and fenced off on site for better preservation, or in case of unavoidable loss, for transplantation according to the Protection and Transplantation Proposal.

15.8.1.5         Construction site runoff and other disturbance impacts resulting from the proposed aboveground works may potentially result in indirect impact on the streams, wildlife, and some fauna species of conservation importance (amphibian Lesser Spiny Frog and freshwater crab Cryptopotamon anacoluthon) recorded at stream S2 at Nui Po Shan.  Standard mitigation measures such as good site practice, control of glare / lighting, minimisation of groundwater infiltration, and water quality impact control measures are proposed. 

15.8.1.6         There would be no disturbance to marine or riverbed sediments under the Project and hence loss of marine habitat is avoided.  According to the water quality impact assessment, no unacceptable ecological impact is anticipated on marine ecological resources.  Nevertheless, an event and action plan and a water quality monitoring programme should be implemented during construction and operation phases to verify whether or not impact predictions are representative, and to ensure that it would not result in unacceptable impacts.  During operation phase, monitoring of the treated effluent quality from the CSTW should be carried out to ensure that the effluent quality would comply with the design standards.

15.8.1.7         Excavation in rock would have relatively minor potential impacts on groundwater as compared to excavation in soft ground.  The rock itself is a natural barrier with very low permeability which can prevent potential groundwater drawdown in any soil and aquifer layers above the rock stratum.  Thus it would not adversely affect the groundwater level within the soil layer as well as the water level of the adjacent streams.  Since the majority of the CSTW is situated in very competent rock stratum in Nui Po Shan, the impact on groundwater would be minor.  Nonetheless, precautionary measures would be taken in cavern design and construction to minimize the potential impacts from the change in groundwater level.  Preventive measures such as pre-grouting and post-grouting, which have been successfully applied in other tunnel projects in Hong Kong, would be conducted to minimize any impact from the cavern construction activities to the adjacent groundwater table.  Surface water level or groundwater level near the caverns will be closely monitored during the construction stage to ensure that the surrounding groundwater level will not be adversely affected due to the cavern construction activities and presence of the caverns.  Post-construction monitoring of groundwater for 1 year will also be carried out after completion of excavation works.

15.8.1.8         With proper implementation of mitigation measures, no adverse residual ecological impacts are expected from the Project.  The implementation of mitigation measures would be subject to regular audit as part of the EM&A programme.

 

15.9                Fisheries Impact

15.9.1.1         A study based on existing information on commercial fisheries resources and fishing operations within the waters of the assessment area has been undertaken, following the criteria and guidelines for evaluating and assessing fisheries impact as stated in Annexes 9 and 17 of the EIAO-TM.  Sites of fisheries importance have been identified, where present.

15.9.1.2         No important spawning or nursery grounds were identified in the immediate vicinity of the existing STSTW, while the nearest important nursery area for commercial fisheries resources is located in Three Fathoms Cove in Tolo Channel (approximately 6.5 km from the existing STSTW).  The nearest FCZs (Yim Tin Tsai FCZ and Yim Tin Tsai (East) FCZ) are located approximately 4.5 km away from the existing STSTW.  The importance of capture fisheries resources in the vicinity of the existing STSTW was identified as low in terms of both production weight and value.  Fish fry production was low in the immediate vicinity of the existing STSTW in Tolo Harbour.

15.9.1.3         The Project will only involve land-based construction works.  There will be no disturbance to marine or riverbed sediments.  Under the Project design, any Project effluent bypass to the Tolo Harbour will be discharged separately through the existing emergency outfalls of the TPSTW and STSTW.  Construction of connection pipes to existing emergency outfall of STSTW was proposed to be by trenchless method underneath Shing Mun River.  This construction method would not cause disturbance to the marine sediment and hence no impact to or loss of fishing ground is anticipated.

15.9.1.4         During the construction phase, THEES connection works required for this Project will be arranged to be synchronized within the THEES maintenance.  Such that no additional water quality impact, and hence, fisheries impact from changes of water quality will be induced by the proposed THEES connection works. 

15.9.1.5         Despite not being specifically induced by this Project, the scenario of THEES maintenance or bypass under extreme emergency situations during the operation phase of the Project have been considered.  Indirect fisheries impacts due to deterioration of water quality are expected during these abnormal operation periods.  Changes in water quality (e.g. SS, DO, TIN, chlorophyll-a) at Yim Tin Tsai FCZ, Yim Tin Tsai (East) FCZ, potential subzone of Yim Tin Tsai FCZ, Yung Shue Au FCZ, Lo Fu Wat FCZ and the nursery area for commercial fisheries resources at Three Fathoms Cove are expected during these scenarios.  However, no significant changes in water quality parameters are predicted as the pollution elevation associated with the discharge would be reversible and hence no unacceptable water quality impacts are expected.  With the implementation of mitigation measures for water quality, no unacceptable fisheries impacts are expected.    

 

15.10              Landscape and Visual Impact

15.10.1.1      The Project will inevitably result in some landscape and visual impacts during construction and operation phases.  These impacts have been minimised through careful consideration of alternatives, minimisation of works areas, and incorporation of aesthetic external designs and landscape treatments of proposed aboveground structures. 

15.10.1.2      The Project is generally located within GB Zones of the Approved Sha Tin OZP No. S/ST/32 (11.12.2015) and, for a small part, on the Approved Ma On Shan OZP No. S/MOS/22 (15.1.2016).  It is recommended that both the Sha Tin OZP and Ma On Shan OZP shall be amended to incorporate the latest changes arising from the Project.  The demolition of decommissioning of existing STSTW is located within the OU under the Approved Sha Tin OZP No. S/ST/32 (11.12.2015).  Since the future developments at the site of the existing STSTW after its decommissioning are under a separate project, any recommendation to the change in OZP shall be made later.

15.10.1.3      Based on a broad brush estimate, approximately 828 existing trees in the Amenity Planting Area in the Existing STSTW (LR-01), Roadside Planting Areas along Ma On Shan Road (LR-07) and Woodland on Slopes of Nui Po Shan (LR-08) will be affected by the proposed works.  The affected trees shall be considered for transplanting in accordance with DEVB TCW No. 7/2015 - Tree Preservation and the latest Guidelines on Tree Preservation during Development issued by DEVB.  Many of the affected trees are of semi-mature to mature size.  None of these are Registered Old and Valuable Trees.  Under the proposed scheme for the Project, opportunities for tree compensation within the Project boundary has been fully explored and incorporated in the proposed mitigation measures as much as practicable.  Approximately 330 nos. of heavy standard trees and 10,000 nos. of tree whips can be compensated for the loss of existing trees due to the Project.  Tree Preservation and Removal Proposals including compensation planting scheme shall be submitted in accordance with DEVB TCW No. 7/2015 - Tree Preservation. 

15.10.2          Under the Project, there would be temporary loss of 59,900m2 of existing vegetation on Slopes of Nui Po Shan.  With the proposed compensation and reinstatement woodland mix planting proposals (approximately 34,700m2), there would be a net permanent loss of 25,200m2 of vegetation in Woodland on Slopes of Nui Po Shan. 

15.10.2.1      With the implementation of proposed mitigation measures it is predicted that there would be substantial to slight residual impact on existing landscape resources (LR-01, LR-07 and LR-08) during construction, and moderate to insubstantial impact on day 1 of operation.  The residual impact on these landscape resources would be further reduced to slight to insubstantial when the proposed compensatory planting, buffer planting and woodland mix planting become mature in year 10 of operation. 

15.10.2.2      It is predicted that there would be substantial to slight residual impact on landscape character areas (LCA-01, LCA-04, LCA-05 and LCA-07) during construction and moderate to insubstantial impact on day 1 of operation.  The residual impact on these landscape character areas would be further reduced to slight to insubstantial when the proposed compensatory planting, buffer planting and woodland mix planting become mature in year 10 of operation. 

15.10.2.3      Regarding visual impact, it is predicted that there would be moderate residual impact on residential VSRs in Chevalier Garden (R-01) Kam Tai Court (R-12).  The residual impact on these VSRs would remain moderate on day 1 of operation and would be reduced to slight when the proposed tree planting becomes mature in year 10 of operation.  There would be slight to insubstantial residual impact on other VSRs within the visual envelope during the construction and operation of the Project. 

15.10.2.4      As a whole, the residual landscape and visual impacts of the proposed Project is considered acceptable with the proposed mitigation measures implemented during construction and operation phases. 

 

15.11              Cultural Heritage Impact

15.11.1.1      The CHIA has assessed current condition and potential impact on cultural heritage resources within the study area.  As no terrestrial and marine archaeological potential is identified, it is considered that there is no impact on archaeology and mitigation measures are not required.

15.11.1.2      Two built heritage resources in Tai Shui Hang (both are Grade 3 historic buildings) as well as the Pak Kong-Mui Tsz Lam Trackway (Site of Archaeological Interest) are identified outside the 50m study area from the site boundary of the Project.  Thus, no potential direct or indirect impact to these cultural heritage resources is anticipated, and therefore no mitigation measures are required.

 

15.12              Waste Management Implications

15.12.1.1      Different types of waste generated from the Project during the construction phase are likely to include C&D materials from demolition, excavation and site formation works, general refuse from workforce, and chemical waste from the maintenance of construction vehicles and equipment.  During the operation phase, the major types of waste would be grit and screenings, and sewage sludge.

15.12.1.2      Approximately 6,000,000m3 of inert materials and 124,000 m3 of non-inert materials would be generated during the construction phase of the Project.  About 3,740,000 m3 of total excavated materials is rock generated from the caverns excavations.  An estimated volume of 595,000 m3 is soft materials while 1,669,000 m3 would be AHM.  Soft inert C&D materials from the above construction works will be sorted and reused as filling material as much as possible.  The surplus will be transported and disposed at Tuen Mun Area 38 Fill Bank. Hard inert C&D material includes Grade III granitic rock and Grade I & II granitic rock.  The Grade III granitic rock and AHM will be re-used as much as possible and the surplus will be transported to Tuen Mun Area 38 Fill Bank for reuse by other projects.  The Grade I & II rock will be transported to Lam Tei Quarry for recycling as useful aggregates.  Non-inert waste will be recycled as far as possible before disposed to landfill.  Opportunities in minimisation of generation and maximisation of reuse would be continually investigated during the detailed design and construction phases.  With the implementation of the recommended good site practices and mitigation measures for the handling, transportation and disposal of the identified waste arising, adverse environmental impacts is not anticipated.

15.12.1.3      The waste management assessment has recommended good waste management practices to ensure that adverse environmental impacts are prevented.  The assessment concluded that no unacceptable environmental impacts would result from the storage, handling, collection, transport and disposal of wastes arising from the construction and operation of the Project.

 

15.13              Health Impact

15.13.1.1      The risk arising from exposure to TAPs associated with the emissions of the relocated STSTW is evaluated. The non-carcinogenic and carcinogenic health impact of the TAPs imposed to the impacted HRs were assessed and compared with international guideline levels. The assessment findings revealed that the levels of TAPs at HRs would be extremely small when compared to the derived reference levels. The highest incremental cancer risk arising from the operation of CSTW is predicted to be 7.1E-08 which is far below the guidance level of 1E-06 adopted by USEPA and it is considered that the Project would not present an unacceptable risk and no further analysis is necessary. For the criteria air pollutants, while it is not possible to rule out the additional potential health effects from the operation of CSTW with complete certainty, the impact on health from extremely small additional air pollutants is likely to be very small and unlikely to be quantifiable.

15.13.1.2      A minor portion of treated effluent would be reused but would be limited to non-potable uses inside the plant and therefore the general public is not expected to be exposed to the treated effluent. Thus, there is no health risk to the general public caused from the reuse of treated effluent.

 

15.14              Environmental Outcomes

15.14.1.1  The EIA Study for the STSTW to Caverns has predicted that the Project, with the implementation of the proposed environmental control and mitigation measures, the environmentally sensitive receivers within the Study Area would be protected from adverse environmental impacts arising from the proposed Project. Table 15.1 summarises the environmental outcomes/benefits that have accrued from the environmental considerations and analysis during the EIA process and the implementation of environmental control measures of the Project.

Table 15.1     Summary of Key Environmental Outcomes / Benefits

Area/Issue

Environmental Outcomes / Benefits and Mitigation Measures

Environmental Benefits of the Project

·         Release of 28ha of land in Sha Tin with sea frontage for a re- development to meet the needs of the society.

·         Subject to subsequent planning, the released STSTW site will provide opportunities for developing a green and vibrant waterfront living environment

·         The living environment of the surrounding area would be improved upon relocation of the existing STSTW to caverns.  The common potential impacts of a sewage treatment works, i.e. odour and visual impacts, can be very effectively controlled and minimised. 

·         Advanced technologies can be adopted for the new sewage treatment facilities to enhance operation process performance, resilience and reliability, as well as operation efficiency

·         The development opportunities of the surrounding area adjacent to the existing STSTW site would be enhanced after completion

·         Produce large amount of hard granitic rocks to support the construction industry as a local source.

 

Environmentally Friendly Design Considered and key environmental problems avoided and any compensation area

·         The layout of sewage and sludge treatment units are optimised to have the best hydraulic performance with minimum construction and demolition materials, footprint and energy requirements, as well as to facilitate plant operation and maintenance.

·         Impacts to ecological sensitive areas have been minimised through putting the sewage treatment system into caverns as much as possible.

·         Engineering design for fixed plant complies with day-time, evening time and night time noise criteria.

·         The adoption of new carven sewage treatment system will reduce the public nuisance from odorous gas.

·         Adoption of aesthetically pleasing and green design of aboveground structures to blend into the adjacent landscape and visual context.

 

Population and Environmentally Sensitive Areas Protected

With the adoption of environmentally friendly design mentioned above, major environmentally sensitive receivers would be protected.

Air Quality Impact

Environmental benefits of environmental protection measures recommended:

Construction

Watering 8 times a day on active works areas, exposed areas and unpaved haul roads to reduce dust emission by 87.5% and dust collector with 99% removal efficiency for rock crusher.

Dust suppression measures stipulated in the Air Pollution Control (Construction Dust) Regulation.

Operation

Relocate the STSTW into caverns will allow effective control of odour arising from the sewage treatment process and will significantly reduce the potential odour impacts. The exhausted odorous air will be conveyed to four deodourisers (with 80 – 97% odour removal efficiency) for treatment before discharge to the environment. Predicted odour concentrations at the ASRs are well below the criteria.

 

Compensation areas included:

N/A

 

Population and environmentally sensitive receivers protected:

Existing ASRs within 500m of the project boundary, including residential premises, schools, hospital and institutional uses.

 

Noise Impact

Environmental benefits of environmental protection measures recommended:

Construction

Residential NSRs and educational NSRs are protected with implementation of quiet PME, movable barriers and acoustic mats, and limitation of on-time operating PMEs as well as good site practices during construction of relocated STSTW and demolition of existing STSTW and temporary explosives magazine, except occasional exceedance of noise criterion for examination period by 1 dB(A) at S.K.H. Ma On Shan Holy Spirit Primary School during examination period.

For the temporary modification works at the merging point of Ma On Shan Road and temporary access haul road, the provision of 220m length of noise barrier of a height at 10mPD on the temporary access haul road to replace the existing 150m length of noise barrier at 9.2mPD to 10mPD height on Ma On Sha Road would pose negligible difference in the overall traffic noise level at the sensitive facades in the vicinity.  Once the construction work is completed, the noise barrier on the concerned road section of Ma On Shan Road would be re-installed according to the existing configuration.  

Operation

The fixed plant noise impact from operation of ventilation shaft, cooling tower and ventilation fan for chiller plant room at administration building, and ventilation buildings at main portal and secondary portal of the CSTW has been assessed.  The predicted fixed plant noise levels at the representative NSRs would comply with the noise criteria based on the noise emission inventory provided by the Engineer. 

 

Compensation areas included:

N/A

 

Population and environmentally sensitive receivers protected:

Existing and planned NSRs within 300m of the project boundary, including residential premises, schools and institutional uses.

Water quality 

Environmental benefits of environmental protection measures recommended:

Construction Phase

 

The key issue from the land-based construction activities would be the potential for surface runoff, accidental spillage, sewage from on-site construction workers and groundwater infiltration. Impacts can be controlled to comply with statutory standards by implementing mitigation measures such as on-site drainage and sediment traps to control run-off.

 

During the connection works of the relocated STSTW to the existing THEES tunnel, the THEES tunnel needs to be temporarily suspended from its normal operation with treated effluent bypass into the Tolo Harbour to provide a dry construction zone.  To minimise water quality impact to Tolo Harbour, the necessary THEES connection works required for this Project will be split into a number of steps for sequential and synchronized implementation with THEES maintenance. Each suspension will not be longer than 4 weeks and will be outside the algae blooming season (January to May), and the frequency will be no more than once per year.  No cumulative or residual impact would be expected.

 

Operation Phase

The main operational impact from the Project would come from the emergency discharge from the CSTW in case of complete failure of plant or power supply.  Mitigation measures, including dual power supply or ring power main supply, standby pumps, treatment units and equipment, would be provided to avoid the occurrence of any emergency discharge.  A contingency plan has also been formulated to minimise the impact of emergency discharges and facilitate subsequent management of the situation.

 

Compensation areas included:

N/A

 

Population and environmentally sensitive receivers protected:

Water sensitive receivers in Victoria Harbour and Tolo Harbour

 

Land Contamination

 

Environmental benefits of environmental protection measures recommended:

Further site walkover, land contamination assessment and, if required, remediation works would be carried out prior to the re-development for the existing STSTW site and part of VDC within the Project boundary. Land contamination impacts are considered surmountable to future occupants if the recommended actions were followed and contaminated soil and groundwater (if any) were properly treated using appropriate remediation methods and according to EPD’s approved RAP.

Compensation areas included:

N/A

 

Population and environmentally sensitive receivers protected:

Future occupants within the concerned sites.

 

Hazard to life

Environmental benefits of environmental protection measures recommended:

With the implementation of the proposed mitigation measures as proposed, no insurmountable environmental impact would be expected during construction phase.

 

Compensation areas included:

N/A

 

Population and environmentally sensitive receivers protected:

Existing and planned sensitive receivers in the vicinity of the Project sites, the temporary magazine and the transport route of explosives.

 

Ecology 

Environmental benefits of environmental protection measures recommended:

The current proposed locations of both main portal and secondary portal areas are situated adjacent to woodland habitats, while the proposed alignment of the access road runs along woodland, plantation and shrubland habitats.  The layout of the portal areas and the access road alignment have been designed to minimise encroachment into adjacent woodland habitats, avoid potential extensive excavation works of hilly terrain, and minimising the slope cutting and vegetation removal potentially needed.

Construction of the connection pipes to emergency outfall by trenchless method underneath Shing Mun River was proposed.  With the adoption of trenchless method, no permanent / temporary loss of marine habitat is anticipated.

 

Compensation areas included:

In view of the inevitable permanent loss of woodland habitat, mitigation measure by compensatory planting (approximately 0.92 ha) of native species would be provided at the main and secondary portal areas, and along the access road.  

 

Population and environmentally sensitive receivers protected:

Direct loss of woodland, plantation and shrubland habitats have been minimised with the layout design.  Loss of marine habitat has been avoided as trenchless method would be adopted. 

 

Fisheries impact 

Environmental benefits of environmental protection measures recommended:

Under the Project design, any Project effluent bypass to the Tolo Harbour will be discharged through the existing emergency submarine outfall of the STSTW, which is located in Sha Tin Hoi. Construction of connecting pipes between the relocated STSTW and the existing outfall by trenchless method across Shing Mun River was proposed.   No loss of fishing ground is anticipated. 

 

Compensation areas included:

N/A

 

Population and environmentally sensitive receivers protected:

Loss of fishing ground has been avoided as trenchless method would be adopted. 

Landscape and visual

Environmental benefits of environmental protection measures recommended:

Implementation of the proposed mitigation measures would minimise and reduce the potential adverse landscape and visual impacts during the construction and operation phase of the Project to an acceptable level.

 

Compensation areas included:

Based on a broad brush estimate, approximately 828 existing trees will be removed.  The affected trees shall be considered for transplanting in accordance with DEVB TCW No. 7/2015 - Tree Preservation and the latest Guidelines on Tree Preservation during Development issued by DEVB.  Under the proposed scheme for the Project, opportunities for tree compensation within the Project boundary has been fully explored and incorporated in the proposed mitigation measures as much as practicable.  Tree Preservation and Removal Proposals including compensation planting scheme shall be submitted in accordance with DEVB TCW No. 7/2015 - Tree Preservation.

 

Population and environmentally sensitive receivers protected:

With the implementation of proposed mitigation measures, the landscape resources, character areas and visually sensitive receivers identified within the assessment boundary will be protected.

 

Cultural Heritage 

Environmental benefits of environmental protection measures recommended:

No potential direct or indirect impact to cultural heritage resources is anticipated, and therefore no mitigation measures are required.

 

Compensation areas included:

N/A

 

Population and environmentally sensitive receivers protected:

Cheung Village House, No. 6 and Nos. 16-18 Tai Shui Hang; Pak Kong-Mui Tsz Lam Trackway

 

Waste Management Implication

Environmental benefits of environmental protection measures recommended:

Implementation of the proposed waste control and mitigation measures would avoid the potential water quality, dust, odour, and noise impacts associated with handling, transportation and disposal of the identified wastes arising from the construction phase of the Project.

It is estimated that approximately 6,000,000 m3 of inert C&D materials would be generated from the Project, which are proposed to be transported to Tuen Mun Area 38 Fill Bank for reuse by other projects. About 124,000 m3 of non-inert C&D materials would be generated and recycled or disposed of at landfill.

With the implementation of the recommended mitigation measures, no adverse environment impacts would be expected.

 

Compensation areas included:

N/A

 

Population and environmentally sensitive receivers protected:

Water quality, air, and noise sensitive receivers in the vicinities of Project sites, the waste transportation routes and the waste disposal site(s).

 

Health Impact

Environmental benefits of environmental protection measures recommended:

The non-carcinogenic and carcinogenic health impact of the TAPs imposed to the human receptors would be negligibly small when compared to the international guideline levels.

The treated effluent from the Project would be limited to non-potable use inside the plant for polymer preparation. No direct human contact is involved and the health impact to humans is not expected.

 

Compensation areas included:

N/A.

 

Population and environmentally sensitive receivers protected:

Existing ASRs within 500m of the project boundary, including residential premises, schools, hospital and institutional uses.

 

 

15.15              Overall Conclusion

15.15.1.1      The findings of this EIA have provided information on the nature and extent of environmental impacts arising from the construction and operation of the Project.  The EIA has, where appropriate, identified mitigation measures to ensure compliance with environmental legislation and standards.

15.15.1.2      Overall, the EIA Report has predicted that the Project would be environmentally acceptable with the implementation of the proposed mitigation measures for construction and operation phases.  An EM&A programme has been recommended to ensure the effectiveness of recommended mitigation measures.

 

<End of Section 15>