7.1.1 This Section presents the findings of an assessment of the potential ecological impacts associated with the construction and operation of the proposed Project at Sha Tau Kok. It summarises baseline information gathered from the literature review and baseline ecological surveys on the terrestrial and marine ecological resources in the Study Area, and describes the ecological importance of this area. The assessment area for the purpose of the terrestrial ecological impact assessment includes areas within 500m distance from the boundary of the Project (Figure 7.1a). For aquatic ecology, the assessment area is the same as the water quality impact assessment, which is within 7 km from the boundary of the proposed expansion of the STKSTW and the submarine outfall (Figure 7.1).
7.2.1
The local ordinances,
regulations and guidelines relevant to protection of species and habitats of
ecological importance include the following:
·
Environmental Impact Assessment Ordinance
("the EIAO", Cap. 499) and the associated Technical Memorandum
(EIAO-TM)
·
EIAO Guidance Note No. 6/2010
·
EIAO Guidance Note No. 7/2010
·
EIAO Guidance Note No. 10/2010
·
EIAO Guidance Note No. 11/2010
·
Hong Kong Planning Standards and
Guidelines Chapter 10 (HKPSG)
·
Forests and Countryside Ordinance (Cap.
96) and its subsidiary legislation, the Forestry Regulations
·
Wild Animals Protection Ordinance (Cap.
170)
·
Protection of Endangered Species of
Animals and Plants Ordinance (Cap. 586)
·
Country Parks Ordinance (Cap. 208) and
its subsidiary legislation
·
Town Planning Ordinance (Cap. 131)
·
China Red Data Book of Endangered Animals
·
IUCN Red List Categories and Criteria
·
United Nations Convention on Biological
Diversity (1992)
·
The Convention on International Trade in
Endangered Species of Wild Fauna and Flora (CITES)
7.2.2
These
are described in detail in Annex
7A.
7.3.1
The
baseline conditions of both terrestrial and marine ecological resources of the
habitats in the Study Area are reviewed by desktop literature review and dedicated
field surveys. The methodology and
findings of this review are presented in detail in Annex
7A.
7.3.2
The key
ecologically sensitive areas of the Study Area include the A Chau Site of Special
Scientific Interest (SSSI) and coastal habitats including mangrove
stands, sandflats and mudflats at Sha Tau Kok Hoi, where species of conservation
interest have been recorded. A Chau SSSI is located more than 2km away from the Project site. The location of A Chau SSSI is shown in Annex
7A. The Study Area for ecological field surveys
included areas within 500 m of the boundary of the Project Site and other areas
that may be impacted by the Project (e.g. A Chau egretry). Surveys identified both terrestrial and marine
ecological habitats and communities in the Study Area, and focused on the areas
where direct impact of the Project might be experienced i.e. the Project
footprint. Marine ecological surveys were also conducted
to cover the eastern coast of Starling Inlet from near Kuk Po to Ah Kung Tsui
and near Ah Kung Au in the vicinity of the proposed location of the submarine
outfall diffuser.
7.3.3
In
accordance with the requirements of the EIA Study Brief, focused field surveys
of more than nine (9) months covering both wet and dry seasons were completed
in 2014. The surveys included habitat and
vegetation surveys, wildlife surveys, egretry surveys, freshwater aquatic
assemblage surveys, horseshoe crab and seagrass surveys, intertidal surveys,
subtidal coral surveys and subtidal benthos surveys. Detailed findings of the field surveys are
presented in Annex
7A which also indicate the ecological profiles and existing wildlife
uses of the various habitats of the Study Area. A supplementary coral survey was conducted
in February 2016 at the eastern coast of Starling Inlet near the proposed location of the submarine
outfall diffuser at Sha Tau Kok and the survey details are presented
in Annex
7B.
7.3.4
The
ecological values of the habitats recorded within the Study Area have been
evaluated in accordance with the criteria stipulated in Table 2 of Annex 8 of EIAO-TM.
Details of the evaluation are provided in Annex
7A.
The overall ecological values of the habitats recorded in the Study Area
are summarized in Table 7.1.
Table 7.1- Habitat Evaluation
|
Habitat |
Overall Ecological
Value |
Habitat found in
Project Site? |
|
Woodland |
High |
û |
|
Shrubland |
Low |
û |
|
Abandoned Agricultural Land/Low-lying
Grassland |
Low |
û |
|
Marsh |
Moderate |
û |
|
Mangrove |
Moderate-high |
û |
|
Pond |
Moderate-low |
û |
|
Stream/River |
Moderate-low |
û |
|
Developed Area |
Low |
ü |
|
Artificial Seawall |
Low |
û |
|
Rocky Shore |
Low |
û |
|
Mudflat |
Moderate-high |
û |
|
Sandy Habitats |
Moderate-low |
û |
|
Subtidal Benthic Habitat within Sha Tau Kok Hoi |
Moderate-low |
û |
|
Subtidal Benthic Habitat in Starling Inlet |
Low |
ü |
7.3.5
The field surveys showed that approximately 40% of the Study Area consists
of man-made habitats (i.e. Developed Area and Artificial Seawall) with low
ecological values. The Project Site (except the proposed outfall) is entirely located within
the Developed Area. Within the Study Area, three (3) floral
species of conservation interest were identified (Portia Tree Thespesia populnea, Common
Zeuxine Zeuxine strateumatica and
Water Fern Ceratopteris
thalictroides) but none of these were recorded
within the Project Site. All mammal,
herpetofauna, butterfly, odonate and aquatic species recorded during surveys were
recorded outside of the Project Site boundary. A total
of sixteen (16) avifauna species of conservation interest were recorded in the
Study Area, and again none of these was recorded within the Project Site
boundary. Avifauna surveys suggested
that several habitats within the Study Area and other areas within the Starling
Inlet such as Kuk Po and Luk Keng are of importance to ardeid species as
stopover point for wintering birds. A Great Egret Night Roosting Site
was recorded at about 250 m east of the Project Site.
7.3.6
The Mangrove
horseshoe crab Carcinoscorpius
rotundicauda (both juveniles and adults) were recorded at the mangrove edge
and on the mudflat in STK within the Study Area (i.e. at intertidal areas). No horseshoe crab species were recorded along the
eastern coast of Starling Inlet. A very small patch (area approximately 1 m2) of seagrass (Halophila ovalis) was found on the
mangrove edge and the sandflats during the seagrass walk-through surveys in
June 2014. Several patches of Halophila ovalis of various sizes (1 m2 to 120 m2)
were also found on the sandflats during the surveys from March to June 2014 but
no Halophila ovalis was found between
July and September 2014 at any survey location, indicating a seasonal presence of
Halophila ovalis. One common hard coral species Oulastrea crispata with very low
percentage cover (< 1%) was recorded at the eastern coast of Starling Inlet
within the Study Area. Furthermore, no
species of conservation interest were found from the benthic
grab sampling
except the Horseshoe Crab Carcinoscorpius rotundicauda. Intertidal surveys conducted on both
hard-bottom and soft-bottom intertidal habitats including artificial seawall,
mudflat, mangrove and sandy shore within the Study Area also did not record any
species of conservation interest.
7.3.7
Overall, a
total of 3 flora and 26 fauna taxa (including both terrestrial and aquatic
taxa) of conservation interest were recorded in the Study Area. None of these was recorded within the
Project works Site (both land and marine). The ecological values of species of
conservation interest were assessed in accordance with Table 3, Annex 8 of the EIAO-TM in terms of protection status (e.g.
fauna protected under Wild Animals Protection Ordinance (except birds), and flora and fauna
protected under regional/global legislation/conventions), species distribution
(e.g. endemism), and rarity (e.g. rare or restricted). Details of the evaluation are provided in Annex
7A.
7.4.1
Potential impacts to ecological
resources can arise from both the construction and operation phases. Each is discussed in turn below.
7.4.2
Construction Phase
Land-based
construction activities and marine construction works of this Project have the
potential to affect ecological resources by:
·
Direct loss of habitats and vegetation
removal within the footprint of the land-based works area, including potential reduction
of species abundance/diversity, loss of feeding grounds, reduction of
ecological carrying capacity;
·
Direct disturbances to benthic habitat
within the marine works area;
·
Potential disturbance to the recognized
site of conservation importance at the A Chau SSSI;
·
Potential disturbance to species of
conservation interest;
·
Habitat fragmentation and isolation,
including potential restriction of wildlife utilisation of the area (i.e.
transit, feeding and roosting) especially for those inactive/ less mobile/
habitat-specific wildlife nesting/inhabiting the habitats, and degradation of
habitat quality/ ecological function;
·
Physical disturbance to the surrounding
habitats and associated wildlife due to noise and increased human activities,
etc.; and,
·
Potential indirect impact, potential
changes in the water quality, hydrodynamics properties, sedimentation hydrology.
7.4.3
Operation
Phase
The potential
impacts of the operational phase of the Project on the ecology of the Study
Area are mainly due to perturbations to key water quality parameters from the
effluent discharge at the diffuser of the proposed submarine outfall at the
mouth of Starling Inlet.
Terrestrial
ecological resources are not expected to be impacted by the Project’s
operational activities.
7.5.1
Assessment Methodology
Potential
impacts that may arise from the construction and operational phases for the
development of the Project are assessed following the EIAO-TM Annex 16 guidelines, and the impacts evaluated based on the
criteria in EIAO-TM Annex 8.
7.5.2
Terrestrial Ecology
(Construction Phase Only)
As the land-based
Project site is entirely located on developed areas of low ecological value and
with limited wildlife usage, the terrestrial ecological impacts (including
habitat and vegetation loss, reduction of species abundance/diversity, loss of feeding grounds,
reduction of ecological carrying capacity, as well as impacts
on the recognized
site of conservation importance at the A Chau SSSI which is located at least 2
km from the Project site) due to the Project, is
expected to be low. According to the
flight data, most of the ardeids were observed flying out of A Chau SSSI
towards the southwest directions (mangroves area, approximately 40.8%) and the
eastern directions (coastal areas, approximately 8.3%). Only approximately 10.3% of the breeding ardeids
was observed flying towards northeast directions (the Sha Tau Kok area), which
cover various habitats and areas including the Study Area and Project Site. Only a small portion of the breeding ardeids
from A Chau SSSI is expected to forage inside the Study Area. The baseline data demonstrated that the
ardeids also mainly utilise the coastal areas and habitats, ie mangroves,
mudflat and ponds, but not the Project Site. Therefore, potential impacts on the A Chau
SSSI are not expected during the construction of the Project. There will also be no direct impacts on the
woodland (habitat of high overall ecological value), mudflat and mangrove
habitats (both of moderate-high overall ecological value) due to the Project. Except the Night Roosting Site for Great
Egret (location refer to Figure 7.1a) that may be affected by
the nearby work activities, i.e. decommission of existing rising main,
demolition of existing Sewage Pumping Station, diversion works of existing
sewer and trench works of gravity sewer, impacts on wildlife and species of
conservation interest are not expected, even there are some occasional records
of White-cheeked Starling, Grey Heron and Little Egret as well as Comma Polygonia c-aureum c-aureum nearby. It should be noted
that the existing outfall will be abandoned by grouting or foam concreting, in
order to avoid dredging and backfilling activities which may disturb the
mudflat (where of some records of waterbirds and ardeids) and coastal/ marine
ecology. The grouting or foam concreting
works will be confined within the STKSTW, and therefore potential impacts on
the waterbirds and ardeids (i.e.
on the mudflat or in the open waters, as well as the Night
Roosting Site for Great Egret) are not expected.
There will only be demolition of STKSPS and decommission of the existing rising main to be undertaken near the Night Roosting Site of Great Egrets. The Night Roosting Site of Great Egrets is located within an urban area and adjacent to the existing bus terminal where a certain degree of human activities, particularly during daytime. The demolition and decommissioning works, as well as increased human activities may potentially disturb the usage of the Great Egrets on the Night Roosting Site. According to the results of baseline surveys, the earliest arrival of Great Egrets to the Night Roosting Site is around 16:00 and settled by 17:00. It is expected that the demolition and decommissioning work activities will mainly be undertaken during normal working hours (07:00 to 19:00), there may be potential disturbance to the Great Egrets in the last three working hours (16:00 to 19:00). The potential disturbance could be avoided by restricting work hours, ie no works in close vicinity of the Night Roosting Site from 16:00 to 07:00 of the following day. In addition, strong artificial lighting should not be used in the area at night to avoid disturbance to the roosting ardeids. Given the short period of the demolition of STKSPS as well as the nearby decommission of the existing rising main (~6 months) and with the implementation of recommended measures, unacceptable adverse impacts on the Night Roosting Site for Great Egret due to the demolition and decommissioning activities are not expected.
7.5.3
Marine
Ecology
As the
submarine outfall would be constructed at around 90m below the seabed [RC1] using
Horizontal Directional Drilling (HDD) method, it is not expected to have
adverse impact to the aquatic environment, particularly the shrubland and
sandflat above the submarine outfall. As
indicated by the findings of the water quality impact assessment and water
quality modelling results (Section 5 refers), the predicted zone of influence
of the Project is limited to the immediate vicinity of the submarine
outfall. In this context, the marine
ecological impact assessment in this section focuses on the area around the
development footprint around the submarine outfall diffuser at the mouth of Sha
Tau Kok Hoi.
7.5.4
Construction Phase
Potential
impacts of the construction activities on marine ecological resources are
presented in Section 7.4.2.
7.5.5 Habitat Loss/Disturbance
The direct impacts of the marine construction activities will be the loss of subtidal soft bottom habitats during the installation of the cofferdam for the submarine outfall diffuser and the removal of organisms associated with the habitats. With the use of HDD method for the construction of submarine outfall alignment, it is anticipated that habitat loss would be minimised to about 0.18 ha only. It is important to determine whether the area of disturbance contain species of conservation interest or noteworthy benthic assemblages, which will be lost during the marine works. Findings from the literature review and the baseline subtidal benthos survey indicated that the benthic assemblages within and in the vicinity of the works areas were dominated by polychaetes. All species recorded are found to be common in Hong Kong and no rare species were observed. As a result, the assemblages were regarded as low ecological value. In addition, marine construction works are expected to cause temporary disturbance (about 3 months for the construction of cofferdam) to a marginally larger marine construction works area. Considering the very small extent and low ecological value of the habitat of concern, no unacceptable impact is expected.
Demolition of the existing submarine outfall is considered not
necessary. The opening of the abandoned
submarine outfall will be sealed and no other action would be required. As such, no unacceptable impact is expected
due to the abandonment of the existing submarine outfall.
7.5.6 Changes in Water Quality
Suspended Solids
Subtidal Soft Bottom
Habitat
The subtidal
benthos within and around the submarine outfall diffuser are considered to be
of low ecological value. Sessile
organisms will be susceptible to the effects of increased sediment loads
through burial. Sediment may be
deposited on the seabed within and near the works areas due to the dispersion
of sediments from habitat disturbance during sheetpiles installation and
removal. Temporary impacts are expected
to be the largest in the immediate vicinity of the sheetpiles (i.e. in the
mixing zone) when the works are underway, while impacts on the wider marine
environment (>1 km away from the works area) expected to be very low due to
gradual deposition of SS over a short distance.
Owing to the
small scale and the low level of sedimentation associated with the marine construction
works, the indirect disturbance on benthic assemblages in the vicinity of the
works area are expected to be of low severity and localized. With the assumption that the temporarily
affected subtidal soft bottom habitats due to marine construction works could
be recolonised by fauna which is typical to that area, the temporary
disturbance to these low ecological value assemblages is not considered to be
unacceptable.
Subtidal Hard Bottom Habitat
One hard coral species Oulastrea crispata with < 1% cover was
recorded in the subtidal hard bottom habitat at a distance of > 350 m of the
proposed submarine outfall. This coral
species is a common species found throughout Hong Kong waters ([1]). Oulastrea
crispata is adaptable to different environmental conditions (including
those unfavourable to corals) as well as geographic locations, which is a
result of its stress-tolerant ability ([2]). With an opportunistic life history trait, Oulastrea crispata is able to colonise a
variety of substrata and flourish as a pioneer coloniser of newly immersed
structures ([3])([4]). No other rare or species of conservation
importance were recorded during the surveys.
As such, the shallow subtidal hard bottom habitat is regarded as low ecological
value. The transient nature of any
increase in suspended sediment arising from marine construction works will have
no unacceptable adverse impacts on this habitat and this is confirmed by
results of the water quality modelling (Section
5.8).
Intertidal Habitats
Intertidal
habitats within the Study Area which can be affected by the marine construction
works include artificial seawall, mudflat, sandflat,
mangrove and sandy shore. Sediment dispersion modelling results predict
that the SS elevations due to sheetpile installation/removal will be transient
and will be confined to the proposed works area. Thus, it is expected that unacceptable
impacts would not be resulted from elevated SS levels to the intertidal
assemblages which are over 1km from the proposed works area.
Coastal / Marine Water Habitats
The minor marine
construction works may cause deterioration to water quality, which may
potentially impact marine ecological resources.
Information from the water quality impact assessment (Section 5.8) indicates that indirect
impacts are not predicted to impact these resources adversely as the elevation
of suspended sediments due to sediment plume will be transient and localized to
the works area. As a result,
unacceptable impacts to open water habitats due to increased suspended sediment
levels will not occur.
Dissolved Oxygen
The assessment
examining potential impacts of elevated SS levels associated with the proposed
marine dredging works showed that the impacts are likely to be minor, localised
to the mixing zone and transient.
Consequently, DO depletion as a result of dispersion of sediment plumes
associated with marine works of the Project is expected to be within acceptable
levels and its effect on marine ecological resources is also likely to be very
limited.
Elevation of Nutrient, Heavy Metals and
Micro-organic Pollutants
According to the
water quality impact assessment in Section
5, no unacceptable water quality impacts due to the potential elevation of
TIN and UIA as well as leaching of metals and micro-organic pollutants from the
disturbed sediments into the water column are expected to occur during proposed
sheetpiles installation/removal operation.
Vessel Operational Discharge
As discussed in Section 5, construction vessels have the
potential for the liquid discharges of uncontaminated deck drainage,
potentially contaminated drainage from machinery spaces, and sewage/grey
water. These waste streams are all
readily amenable to control as part of appropriate practice on vessels (detailed
in Section 5.9). Possible impacts
associated with construction vessel discharges are therefore considered to be
negligible.
Site Runoff from Land-based Construction
Activities
Discharges and
runoff from the land-based sites during the construction phase, particularly during
the site formation, excavation and backfilling works, will contain SS which
could be a source of water pollution, causing short-term degradation of habitat
quality. However, considering that the
scale of the construction works and with effective implementation of good site
management practices as well as mitigation measures mentioned in Section 5, site run-off is not predicted
to have an adverse impact on the coastline.
In summary,
unacceptable impacts (elevated SS, nutrient and contaminant levels and DO
depletion) on sensitive receivers from sediment release associated with marine
construction works are not expected to occur.
Potential impacts arising from vessel operational discharges and
land-based site runoff during construction stage are also considered to be
negligible.
7.5.7
Operation Phase
No unacceptable adverse impacts due to operational effluent discharge from the TSTP/ expanded STKSTW on marine ecological resources are expected as the discharge will satisfy the relevant requirements of WPCO-TM effluent discharge standards (details refer to Section 5) and will be in compliance with the relevant assessment criteria which are of relevance for the protection of marine ecological resources (see Section 5). Overall, whilst the operation of the expanded STKSTW slightly affects the water quality at marine ecological sensitive receivers which are close to the proposed submarine outfall, the operation of the expanded STKSTW would in general result in an overall improvement in DO, TIN and UIA levels for marine ecological WSRs within Starling Inlet, and no exceedance in the corresponding criteria of the WQO is predicted at all marine ecological sensitive receivers.
A number of precautionary measures
have been taken into account in the design of the expanded STKSTW to minimize
the risk of discharge of untreated or incompletely-treated sewage into the
marine waters of Starling Inlet under emergency situation as discussed in Section 5. In the event that such situation occurs, it
is predicted that the change in levels of DO, SS, UIA
and E. coli is localised around the
safety outlet of the TSTP and expanded STKSTW after a 2-hour emergency
discharge and the water quality would recover to ambient levels within a short
period of time (3 to 10 days) after such emergency discharge (see Section 5). Therefore, the impact from the emergency
discharge of the TSTP and the expanded STKSTW on marine ecological resources is
considered to be temporary and insignificant.
Given the unlikely occurrence of emergency discharge with the
application of the precautionary measures and the temporary change in water
quality after an emergency discharge, there would be no unacceptable impact on
the marine ecological resources, including mangrove horseshoe crabs, under such
situation.
7.6.1
Terrestrial Ecology
(Construction Phase Only)
Disturbance of 72.4 ha of the developed area is anticipated for the Project but its habitat nature would not be changed during and after construction. No species of conservation interest was recorded within the affected area. In view of its low ecological value and artificial nature that results in a high recreatability, it is considered that the overall impact would be of negligible significance (see Table 7.1).
Table 7.1 Impact
of Habitat Loss on Urbanised/Disturbed Area during Construction Phase
|
Evaluation Criteria |
Developed
Area |
|
Habitat Quality |
The habitat quality
is low. |
|
Species of
Conservation Interest |
No plant species of
conservation interest was recorded within the affected area. Night Roosting Site for Great Egret was
recorded near the temporary affected area.
Limited number of breeding ardeids from A Chau
SSSI is expected to utilise the developed area. |
|
Size/Abundance |
Loss of
approximately 72.4 ha for the Project |
|
Duration |
The impact will
persist during construction phase. |
|
Reversibility |
The loss of this
habitat is considered reversible since the STKSTW is also part of developed
area. |
|
Magnitude |
The scale of the
habitat loss is small and the identified impacts are also expected to be
minor. |
|
Overall Impact
Before Mitigation |
Negligible |
Given the low ecological value of the affected area, the small scale and temporary nature of the construction phase, terrestrial ecological impacts due to the Project is expected to be low.
Increased human activities and disturbances due to the Project construction have the potential to affect Great Egret’s usage of the Night Roosting Site. These potential impacts are expected to be low, due to its small scale, temporary nature of construction activities and with the implementation of recommended measures (restriction of working hours and strong artificial lighting).
7.6.2
Marine
Ecology
The following
section discusses and evaluates the impacts to marine ecological resources as a
result of the resources identified in the previous sections. Based upon the information presented above,
the significance of the marine ecological impact associated with the
construction and operation of the submarine outfall has been evaluated in
accordance with the EIAO-TM (Annex 8, Table 1) as follows.
Habitat Quality:
Direct
impacts are only predicted to occur to habitat of low ecological value
(i.e. subtidal soft bottom habitats) at the footprint of submarine outfall
diffuser. The selection of trenchless
method will avoid direct impacts to subtidal soft bottom habitats which are of
low to moderate ecological value.
Operation phase impacts are not expected to impact habitats of high
ecological value.
Species: Based on literature and baseline surveys, Mangrove
horseshoe crab Carcinoscorpius
rotundicauda, seagrass Halophila ovalis and hard coral Oulastrea
crispata are found on mudflats, sandflats and subtidal hard bottom habitats,
respectively. As discussed in Section 5, horseshoe crabs are particularly adapted to environment with
high ambient SS level as a result of sand- or mud-burrowing behaviours and
therefore not sensitive to SS ([5]). The predicted
increase of SS at the seagrass habitat during construction and operation phases
is below the allowed 30% elevation stipulated in the WQO. In addition, Oulastrea crispata is a common hard coral species with
stress-tolerant ability and can be adapted to different environmental
conditions ([6]). As their location is not under the footprint
of marine construction site (i.e. cofferdam), no significant construction or
operation phase impacts are expected to these sensitive receivers. The predicted change in water quality from the operation of the expanded
STKSTW would be within the limit stipulated in the WQO which
are of relevance for the protection of marine ecological resources. In the event of an emergency discharge of untreated or
incompletely-treated sewage into the marine waters of Starling Inlet, which is
very unlikely to occur given the precautionary measures in place, only
localised and temporary changes in water quality is predicted. Thus, no significant
construction or operation phase impacts are expected.
Size: The maximum size of sediment disturbance of
subtidal soft bottom habitats due to the marine construction works is
approximately 0.18 ha. The impact to
such a small area of low ecological value of benthic assemblages is expected to
be acceptable.
Duration: The construction
of cofferdam) will approximately last for a period of 3 months while the whole
marine construction will last for 27 months.
Increases in suspended sediments are expected to be low and transient,
and within acceptable environmental limits.
The operation phase of the submarine outfall diffuser will be long term
but the impacts to marine ecological resources would be acceptable.
Reversibility: Impacts to
the benthic assemblages on the subtidal soft bottom habitats within the marine
construction areas are irreversible, but which are regarded as low ecological
value. Disturbance from marine
construction activities and associated water quality changes are expected to be
relatively short term and recolonisation of the disturbed areas is expected to
occur.
Magnitude: No unacceptable
impacts to marine ecological resources are predicted to occur. Operation phase impacts are not expected to
cause any adverse impacts and are considered to be of low magnitude.
The impact
assessment presented above indicates that no unacceptable impacts to various
marine ecological resources mentioned in the above sections would be expected.
7.7.1
General
In accordance with the guidelines in the EIAO-TM Annex 16 on ecological impact assessment, the policy adopted in this EIA for mitigating significant impacts to ecology, in order of priority, is:
·
Avoidance:
Potential impacts should be avoided to the maximum extent practicable by
adopting suitable alternatives;
·
Minimisation: Unavoidable impacts should be minimised by
taking appropriate and practicable measures such as constraints on intensity of
works operations or timing of works operations; and
·
Compensation: The
loss of important species and habitats may be provided for elsewhere as
compensation. Enhancement and other conservation measures should always be
considered whenever possible.
7.7.2
Avoidance
The above impact assessment demonstrates that the Project will minimize encroachment onto any habitat of low to moderate, moderate or high ecological value during its construction, particularly to those key ecological sensitive receivers such as the A Chau SSSI and coastal habitats including mangrove stands, sandflats and mudflats at Sha Tau Kok Hoi. Direct impacts on plant and wildlife species of conservation interest, as well as the Night Roosting Site for Great Egrets, will also be avoided.
Construction impacts to marine ecological resources have largely been avoided by optimizing the length and alignment of the submarine outfall to avoid key ecologically sensitive areas, and by applying the trenchless method for installing submarine outfall and through proper planning design and execution of the works (i.e. optimisation of project construction schedule/ sequence, using good engineering/ industry practice, timely completion of construction works to reduce impact duration, etc.). The construction activities are separated into several phases as shown in Pane 5.1, with marine construction confined to be within 27 months (September 2018 – November 2020).
Indirect impacts on marine sensitive receivers due to the dispersion of sediment plume can be avoided as the marine construction works will be designed to confirm compliance with the assessment criteria at sensitive receivers and control water quality impacts to within acceptable levels, and water quality mitigation measures will be developed and implemented when required to further avoid/ reduce potential impacts (See Section 5).
To summarise, this initial assessment of impacts demonstrates that impacts will largely be avoided during the construction and operation of the proposed Project, particularly to the key terrestrial and marine ecological sensitive receivers through the avoidance of direct and indirect impacts to ecological sensitive habitats and wildlife/ species of conservation interest.
7.7.3
Minimisation
Trenchless construction method has been considered for laying the proposed submarine pipeline. The present alignment of the pipeline is more favourable for effluent mixing as the current velocity is generally stronger than that of the original proposed outfall location. The revised location could minimize environmental impact and meet the WQO.
The use of trenchless method (i.e. HDD) is particularly suitable for the construction of the proposed submarine outfall of STKSTW because marine construction works would be minimal without the need of dredging along the submarine outfall alignment. The trenchless method will minimise the potential impacts on water quality and marine ecological resources. Since the sediment removal at outfall structure would be conducted in dry condition after cofferdam construction is completed and inside of the cofferdam be drained, no sediment release into the water column would be expected from the sediment removal under this Project.
To minimize the other disturbances of the construction works to the surrounding habitats and associated wildlife such as the A Chau SSSI (Egretry), the following appropriate construction practices should be implemented as far as practicable.
·
Erect fences along the boundary of the
works area before the commencement of works to prevent vehicle movements and
encroachment of personnel onto adjacent areas;
·
Regularly
check the work site boundaries to ensure that they are not breached and that
damage does not occur to surrounding areas; and
·
Avoid any damage and disturbance,
particularly those caused by filling and illegal dumping, to the surrounding
habitats through proper management of waste disposal.
The following precautionary measures shall be implemented as far as practicable for the protection of the identified Night Roosting Site for Great Egret:
·
To avoid/ minimise the potential
disturbance on the Night Roosting Site for Great Egret if confirmed to be
continuing their usage before the construction activities, no work shall be
undertaken within an area of 100m from the Night Roosting Site after 16:00 under
normal working hours (i.e. 16:00 to 07:00 of the following day) (refer to
Section 2.3.2 of Annex
7A). In addition, strong artificial
lighting should not be used in the area at night to avoid disturbance to the
roosting ardeids. Clear signs should be
erected on site to alert all site staff and workers about the requirement.
7.7.4 Compensation
Since habitat
loss due to other land-based construction and marine construction works for
laying the submarine outfall of the Project only occurs on the habitats of low
ecological value where no species of conservation interest will be lost,
ecological compensation is not required.
7.8.1
Information from publicly
available sources suggested that the construction/ implementation programmes of
the major projects identified in Section
2.10 would coincide with the construction of this Project. In particular, the sediment removal project
at Sha Tau Kok Fish Culture Zone, Boat Shelter and Approach Channel (tentative
without confirmed programme) could be the concurrent marine construction works
that involves dredging operation at Starling Inlet which is located > 1 km
away from the diffuser of the proposed outfall.
The sediment removal project is scheduled to commence in the
1st half of 2017 for completion in the 1st half of 2018 tentatively, which
would potentially be concurrent with the marine construction period under this
Project.
However, as discussed in Section 5
regarding potential cumulative water quality impacts arising from concurrent
projects, it is anticipated that water quality mixing zone of this Project is
unlikely to overlap with those of other concurrent projects in this part of Hong
Kong, it is thus concluded that cumulative impacts on water quality impacts and
consequently on marine ecology are not predicted to occur.
7.8.2
Given that the no operational
impacts on ecological resources are anticipated from the concurrent projects,
operational cumulative impacts with other development in and around Sha Tau Kok
are not predicted to occur.
7.9.1
As the Project is on existing
developed land, the affected habitats are considered to be low ecological
value. With the implementation of the recommended mitigation measures discussed
in Section 7.7, it is anticipated
that all potential ecological impacts will be reduced to an acceptable level.
Therefore, no adverse residual impact due to the construction of proposed
STKSTW and the proposed submarine outfall is expected from the aspect of
terrestrial ecology.
7.9.2
In terms of marine-based
construction works, approximately 0.18 ha of subtidal soft bottom habitats of
low ecological value will be disturbed due to the sheetpiles
installation/removal during the construction of cofferdam. Since the loss of subtidal soft bottom
habitat is very small in size in the context of surrounding similar habitat,
therefore no unacceptable residual impacts are anticipated from the aspect of
marine ecology.
7.10.1
Terrestrial
Ecology
7.10.2
The
assessment presented above indicates that unacceptable construction phase
impacts and operation phase impacts are not expected to occur to terrestrial
ecological resources. The implementation of the ecological mitigation measures
described in Section 7.7 will be
inspected regularly as part of the EM&A procedures during the construction
period.
The following precautionary measures shall be
implemented as far as practicable for the protection of the identified Night
Roosting Site for Great Egret:
Ÿ Undertake Pre-construction survey
to reconfirm the usage of the Night Roosting Site for Great Egret. If the Night Roosting Site is used by Great
Egrets or other ardeids species, no work shall be undertaken within an area of
100m from the Night Roosting Site from 16:00 to 07:00 of the following day (Figure
7.2). In addition, strong
artificial lighting should not be used in the area at night to avoid
disturbance to the roosting ardeids. Clear
signs should be erected on site to alert all site staff and workers about the
requirement.
7.10.3
No operational phase monitoring
is considered necessary.
7.10.4
Marine
Ecology
7.10.5
Construction
Phase
During the
construction phase, the following EM&A measures will be undertaken to
verify the predictions in the EIA and ensure the environmental acceptability of
the construction works. Water quality
impacts will be monitored and checked through the implementation of a Water
Quality EM&A programme (refer to EM&A
Manual for details). The monitoring
and control of water quality impacts will also serve to avoid unacceptable
impacts to marine ecological resources.
7.10.6
Operation Phase
To ensure compliance to the effluent standard specified in Section 5 (or other standard stipulated in the WPCO Discharge Permit), regular monitoring of effluent quality is recommended during normal operation. The monitoring and control of water quality impacts will also serve to avoid unacceptable impacts to marine ecological resources.
7.10.7
Details environmental
monitoring procedures and audit requirements are provided in the standalone EM&A manual.
7.11.1
This Section of the EIA has
described the potential terrestrial and marine ecological impacts associated
with the construction and operation of the Project at Sha Tau Kok. The purpose of the assessment is to evaluate
the acceptability of predicted impacts to terrestrial and marine ecological
resources and sensitive receivers.
Findings of literature review and dedicated baseline field surveys have
provided information for the evaluation of species of conservation interest and
ecological importance of various habitats within the Study Area as well as in
the Project Site.
7.11.2
A total of 13 habitat types
were identified within the Study Area.
They are terrestrial habitats (i.e. woodland, shrubland, abandoned
agricultural land/low-lying grassland, marsh, mangrove, pond, stream/river and
developed area) and coastal habitats (i.e. artificial seawall, rocky shore,
mudflat, sandy habitats, and subtidal benthic habitat within Study Area of Sha
Tau Kok and in Starling Inlet). All of
the habitats are of low to moderate-low ecological values, except for woodland,
marsh, mangrove and mudflat. The A Chau SSSI and coastal habitats
including mangrove stands, sandflats and mudflats at Sha
Tau Kok Hoi are the recognized ecologically important / sensitive sites located
within the Study Area.
7.11.3
Regarding to the species of
conservation interest, three flora species, one mammal species, sixteen bird species,
five butterfly species, one odonate species, one aquatic fauna, one horseshoe
crab species and one seagrass species from mudflat habitat were recorded during
the field baseline surveys. None of
these species were found within the Project Site.
7.11.4 Increased human activities and disturbances due to the Project construction have the potential to affect Great Egret’s usage of the Night Roosting Site. These potential impacts are expected to be low, due to the small scale and temporary nature of construction activities. Hence, no construction activities will be undertaken within an area of 100 m from the Night Roosting Site from 16:00 to 07:00 of the following day. In addition, strong artificial lighting should not be used in the area at night to avoid disturbance to the roosting ardeids. Clear signs should be erected on site to alert all site staff and works regarding the requirements.
7.11.5
For marine ecological impact,
habitat loss of subtidal soft bottom habitat which is of low ecological value
(within the Project footprint) will also arise from marine construction
activity for installing the submarine outfall and there will be potential
burial of benthic organisms, which are dominated by common polychaete species
with no conservation importance.
Intertidal and subtidal habitats will be impacted temporarily due to the
deterioration of water quality arising from marine construction works.
7.11.6
With
the implementation of the proposed mitigation measures, no adverse residual
impact due to the land-based and marine-based construction of proposed STKSTW
and submarine outfall pipelines is anticipated.
([1]) Chan, AKL, Chan, KK, Choi, CLS, McCorry, D,
Lee, MW, Ang, P Jr, Li, SSF (2005).
Field Guide to Hard Corals of Hong Kong. Friends of the Country Parks
and Cosmos Books Ltd, Hong Kong.
([3])
Lam, KK (2000a). Sexual reproduction of a low temperature
tolerant coral, Oulastrea crispata,
in Hong Kong, China. Marine Ecology Progress Series, 205, 101-111.
([4])
Lam, KK (2000b). Early growth of a pioneer recruited coral Oulastrea crispata on PFA-concrete
blocks in a marine park in Hong Kong, China. Marine Ecology Progress Series,
205, 113-121
[RC1]BV to include the 90m information at the Project Description section