2.1
Purposes and Objectives of the Project
2.1.1.1
As
discussed in Section 1.1, the
Project aims to upgrade the facility standards of Lai Chi Wo (LCW) Pier for safe pier usage by local villagers, mariculturists, visitors and
tourists.
2.1.1.3
This Project will address these
operational and safety problems and provide opportunities to bring benefits in
enhancing LCW Pier with upgraded facilities such as barrier-free facilities, canopy,
seats, etc.
2.2.1
Description of the Existing Pier
2.2.1.1
The existing LCW Pier (Marine
Structure No. NP079) is a straight solid concrete finger pier of about 64m long
and 2.5m wide, and orientates at a bearing angle of approximately 103°. The pier top level is about 3m above
the Principal Datum (mPD). A 4.2m long flight of steps is at the sea end of the
pier. Another 4.2m long and 1.2m wide flight of steps is at 25-30m from the
pier end and normal to the pier. In addition, a navigation light is at the head
of the pier and a row of bollards is on each side of the pier. Two sets of 1m
high galvanised steel tubular railing are along the southwestern edge of the
pier. A general view of the pier is shown in Image 2.1.
Image 2.1 Layout of the existing LCW Pier
2.2.1.2
A hydrographic survey was conducted
in July 2019 and the seabed level at the existing pier head was about -1.0mPD.
2.2.2
Safety Concerns
2.2.2.1
As described in Section 2.1.1.2, there are safety concerns for vessels and passengers using the LCW
Pier. These concerns are listed as follows and are elaborated in the following
paragraphs.
(1)
Deteriorating structural
conditions;
(2)
Insufficient water depth for
berthing and manoeuvring;
(3)
Low pier level;
(4)
Undesirable berthing
arrangement; and
(5)
Non-fully restrained narrow
pier.
Deteriorating
Structural Conditions
2.2.2.2
Historical aerial photos show
that the existing LCW Pier has been in operation since at least Year 1956.
There is however no information as to what design standards or conditions that
the existing pier had been designed for. Nevertheless, the existing LCW Pier
has been in service for more than 50 years, and the pier would have reached the
end of its design life even if the pier was designed according to current
standards.
2.2.2.3
The pier is currently
maintained by the Home Affairs Department, and maintenance and repair works are
regularly undertaken. Notwithstanding the continuous efforts by government
departments in regular maintenance and inspection over the years, the aging
condition of the LCW Pier is still deteriorating and cannot be completely fixed.
2.2.2.4
The pier is deemed to be
primitive and aging. Cracks and bulging are found on the side faces of the existing
pier. Structural integrity of the existing pier is a key issue in maintaining
the function of the pier.
Insufficient
Water Depth for Berthing and Manoeuvring
2.2.2.5
The seabed level around the existing
LCW Pier is generally very shallow. Based on the latest sounding survey
undertaken in 2019, the approximate seabed levels at the existing pier head is
around -1.0mPD. The water depth is just about 1.5m during some low tide
condition when the Mean Lower Low Water (MLLW) level of +0.5mPD recorded at the
nearest tide station at Ko Lau Wan is considered. The water depth is even
shallower when the Lowest Astronomical Tide (LAT) occurs.
2.2.2.6
Vessels that currently use LCW
Pier include licenced Kaito ferries and government vessels such as Agriculture,
Fisheries and Conservation Department (AFCD) patrol boats. The drafts of these
vessels could be up to 2m. Thus, the water depth at the existing pier head
could be too low for berthing and manoeuvring of these vessels at low tide
conditions. These vessels may not be able to access the pier during low tides
and could be grounded if they moor at the existing pier at low tide.
2.2.2.7
Berthing and manoeuvring safety
is important for safe usage of the pier by vessels. Based on the Berthing
Guideline published by the Marine Department (MD), to ensure safe navigation
and berthing, 10% of underkeel clearance (UKC) at berth shall be provided.
Considering all time berthing, the required seabed level at the berth should be
about -2.1mPD or lower. To ensure sufficient water depth at the berths and
avoidance of potential spillage of water suspended solid of seabed sediment, the
pier berths shall be better located at seabed of about -2.4mPD or lower.
Low Pier
Level
2.2.2.8
The existing pier top level is
about +3.0mPD. During high tides, the sea level can rise higher than the pier
top level, and completely floods the pier. It poses safety concerns for pier
users and vessels.
2.2.2.9
Pier users might have to walk
on the “flooded” pier to access the pier head, and to board on or disembark
from the vessels. Vessels fendering and mooring systems would become less effective
or even ineffective when the pier structure was below water.
2.2.2.10
These conditions would be
exacerbated when sea level rises due to the effects of climate change in the
future. According to the Port Works Design Manual Corrigendum No. 1/2018, the mean
sea level will rise by about half a metre by the end of century.
Undesirable
Berthing Arrangement
2.2.2.11
The pier head is only about
4.2m long compared to the licenced Kaito ferries which are typically 25m to 30m
long. The ferries cannot berth alongside of the vessels for boarding. Hence,
there are safety concerns for passengers boarding from the bow of the ferry.
Non-Fully
Restrained Narrow Pier
2.2.2.12
The existing pier is only 2.5m
wide and is only restrained by tubular handrail on one side of the pier for some
sections of the pier.
2.2.2.13
There is not adequate space on
the pier for Kaito ferry patrons waiting or queuing at the pier for the Kaito
ferry service. The space is quite limited for single file queuing and passage
of other pier users. The risk of falling into water could be very high when the
pier was crowded with people.
2.2.2.14
Crowd management is therefore difficult
to be implemented in such a narrow pier when bi-directional movements of people
along the pier and boarding on /disembarkation off vessels occur concurrently.
2.2.3
Barrier-Free Facilities
2.2.3.1
It has been the Government's
established policy to provide barrier-free facilities for people in need with a
view to enabling them to freely access premises and make use of community
facilities and services on an equal basis with others. Accessible facilities
would provide opportunities for these people to live independently, participate
in various social activities and integrate into the community.
To improve accessibility of public pier, the accessibility (1) between the
vessel and the pier, and (2) within the pier shall be improved.
2.2.3.2
The sea level is changing due to tides and other
meteorological effects creating a varying level difference between the deck of
vessels and the pier. To enhance the accessibility between the deck of vessels
and the pier, their level difference should be maintained at a fixed height to
enable embarking/disembarking via a movable plank (gangplank). This can be
achieved by berthing against a floating pontoon, which rises and falls with the
vessels when sea level changes.
2.2.4
Sustainable Development of the
Geopark
2.2.4.1
As mentioned in Section
1.2.1.1, Lai Chi Wo Pier is located within the Hong Kong UNESCO Global
Geopark (Double Haven Geo-Area). The Hong Kong UNESCO Global Geopark is
currently a member of the Global Geoparks Network (GGN), of which one of the key features is to
promote earth science and sustainable development through geo-tourism and
education. According to the protection level of Geopark, Lai Chi Wo belongs to “Integrated Protection Area”, because it carries function for geo-tourism
because its carrying capacity is relatively higher than that in other areas of
Geopark. With the implementation of the proposed pier improvement works, Lai
Chi Wo Pier would provide safer access for the public to visit Lai Chi Wo, so as to improve the experience of the public
visiting the geopark and thus supporting the sustainable development of the
geopark.
2.2.5
Villagers’ / Pier User’s
Concerns
2.2.5.1
There have been repeated
requests from Village Representatives (VRs) of Lai Chi Wo Village, Sha Tau Kok District Rural Committee (STKDRC) members and North
District Council (NDC) members over the years to improve the safety and accessibility of
the pier. During the consultation meetings held with elected-by-villagers VRs,
STKDRC members and NDC councillor in May 2019, they shared the inconvenience that
vessels could only berth at specific time due to inadequate water depth at the
pier, and hence they fully support the Project and urge the earlier
implementation of the improvement works.
2.3
Scenarios “With” and “Without” the Project
2.3.1.1
Without the Project, the current
users including villagers and visitors still have to rely on the existing LCW
Pier for waterborne transport to access Lai Chi Wo village and the adjacent
area. The Lai Chi Wo area is not accessible via any vehicular road, and hence the
existing LCW Pier is the only transport infrastructure in the vicinity of Lai
Chi Wo. Regular inspection and maintenance by the Government departments will
still be carried out at the pier to identify any damage of the pier visually or
by using instruments, and to repair cracks and damaged area. However, these
maintenance and repair works are minor in nature, and can only fix the problems
observed or noted near the external surface of the structure. These minor works
cannot provide significant improvement to abate the aging problem of the structure.
2.3.1.2
Considering that the pier has
already reached the end of its design life in current design standards, the condition
of the aging internal structure could have deteriorated and be hazardous to
pier users. Moreover, the safety issues such as insufficient water depth for berthing
and manoeuvring, low pier level, undesirable berthing arrangement and non-fully
restrained narrow pier would continue to exist and pose threats to pier users,
especially those with special needs. Enhancing accessibility using barrier-free
facilities would not be possible if the Project was not implemented.
2.3.1.3
There is currently one licenced
Kaito service between Ma Liu Shui and Lai Chi Wo. The service only operates on
Sundays and public holidays; the current operator is Best Sonic Industrial
Limited. Ferries are scheduled to depart at 9:00 am from Ma Liu Shui to Lai Chi
Wo and return at 3:30pm from Lai Chi Wo. The largest vessel of the Kaito
service is about 26m long and 7.3m wide with 2m draft. Other than licenced Kaito
ferries, government vessels for AFCD and FEHD also access Lai Chi Wo area using
the pier in weekdays and weekends.
2.3.1.4
From environmental
perspectives, the amenity and visual aesthetic of the existing aging pier cannot
be enhanced without the Project. In addition, the water depth at the existing
pier is insufficient for berthing and manoeuvring of vessels safely. This
inevitably causes disturbance to the seabed and therefore result in release of
suspended solids to the water column. This situation could not be improved
unless sufficient water depth is provided for vessel berthing and manoeuvring
via the implementation of the Project.
With Project Scenario
2.3.1.5
With the Project, the LCW Pier
will be upgraded to be integrated with a new pier structure extending to a
location that can allow safe access, manoeuvring and berthing of vessels, and providing
safe means of access for the patrons and pier users. Other enhancement
facilities such as barrier-free facilities, canopy, seats, etc. could enhance
the convenience, pleasures and satisfaction of pier users.
2.3.1.6
From the environmental
perspectives, the pier improvement works can also benefit the coral communities
in the long term by increasing the surface area of hard substrate for the
attachment of corals. Through this Project, a pier with modern design and more
compatible colour scheme and texture can be provided. This enhances the visual
amenity of the pier. More comfortable environment would also be offered to the
passengers waiting for ferries and vessels. In addition, the proposed pier will
be extended so that the berthing area will be located further away from the air
sensitive receivers and noise sensitive receivers. Besides, by increasing the
water depth of the berthing area, disturbance to the seabed by the vessels
could be minimised. Further details are provided in Section 2.4.
2.3.1.7
The implementation of the
Project would not cause adverse environmental impacts during the construction
phase if mitigation measures and good site management practices are properly
adopted. Those potential impacts include water
quality, marine ecological and fisheries impacts from the marine-based construction
works, air quality impact from fugitive dust emission, noise impact from the use
of powered mechanical equipment and waste and environmental hygiene
implications. Environmental impacts are therefore duly assessed throughout the
EIA stage. A series of mitigation measures and good site management practices
are recommended to avoid, minimise and mitigate, where practicable, the
potential adverse environmental impacts (see Section 12 and Section 13
for details). A comprehensive and effective environmental
monitoring and audit programme is also proposed to ensure the mitigation
measures and good site practices are properly implemented.
2.4
Environmental Benefits of the Project
2.4.1
Increased Surface Area for
Corals
2.4.1.2
As discussed in Section 2.2, the Project will extend
the LCW Pier to deeper water, and the new pier structures comprise underwater hard
structural elements, thus providing additional hard surface area for corals to
attach and grow. In the current preliminary design (Section 2.6), there would be about 57 nos. piles with an average
diameter of about 0.8m to 1m. This would provide an additional surface area of around
220m2 below the Mean Lower Low Sea Level (i.e. +0.5mPD) and hence
would provide an additional surface area for corals. Nevertheless, the total number of piles and
the actual diameter of the piles would be subject to detailed design.
2.4.2
Enhance Visual Amenity of the
Pier
2.4.2.1
The existing pier is in poor physical
and amenity condition. By the implementation of the pier improvement works with
modern design and more compatible colour scheme and texture, the visual
appearance of the LCW Pier can be better enhanced. Hence, the status of Lai Chi
Wo as a popular destination for eco-tourism can be further uplifted.
2.4.3
Reduce Air Quality and Noise
Impacts during Operational Phase
2.4.3.1
As discussed in Section 2.2, the length of the pier
will increase from 64m to approximately 155m with the landing steps shifted
seawards. Hence, the proposed berthing locations associated with the marine
traffic emissions and marine traffic noise will be further away from the coast
and the residential sensitive receivers at Lai Chi Wo village as compared with
the current condition without pier improvement. Hence, the Project may result
in some improvement in air quality and noise impacts at the sensitive receivers.
Details will be further discussed in Section 3.5
and Section 4.5.
2.4.4
Sufficient Water Depth to avoid
Seabed Disturbance
2.4.4.1
As discussed in Section 2.2, the approximate seabed
levels at the existing pier head is around -1mPD. Hence, the water depth is
just about 1.5m during some low tide condition when the MLLW level of +0.5mPD
recorded at the nearest tide station at Ko Lau Wan is considered. Vessels
currently using the LCW Pier include licenced Kaito ferries and government
vessels such as AFCD patrol vessels, the required draft of these vessels could
be up to 2m. Though there are speed limitation within the Marine Park waters,
it is possible that the vessels manoeuvring at the shallow region of the
existing LCW Pier would most likely stir up the sediment from the seabed,
resulting in local rise of suspension solids.
2.4.4.2
With the proposed pier
improvement works, the pier berth would be located at the seabed level of about
-2.4mPD or lower (i.e. 2.9m depth at MLLW) which would be sufficient for
vessels to manoeuvre. Seabed disturbance could therefore be minimised during
the operation of the Project. Re-suspension of suspension solids could also be
minimised.
2.5
Tackling Environmental Challenges and Options Considered
2.5.1.1
Due consideration has been given
in formulating the pier design to overcome environmental challenges faced by
the Project. The hierarchy of “Avoid, Minimise and Mitigate” has been adopted
during the process to protect the environment as much as practicable. The key principles adopted to tackle all the
environmental challenges are discussed in the following sections.
2.5.2
Environmental Challenges Posed
by Ecological Resources
2.5.2.1
According to the literature
review and the comprehensive ecological surveys conducted as part of this EIA
(see Section 8 for details), the
areas in the neighbourhood of the Project accommodate a number of ecological
resources including those in marine and those on land. These key ecological
resources include:
·
Corals in the vicinity of the Project;
·
Yan Chau Tong Marine Park;
·
Lai Chi Wo Beach SSSI;
·
Lai Chi Wo Special Area; and
·
Plover Cove Country Park.
2.5.3
Avoidance of Open Sea Dredging
Works
2.5.3.1
As discussed in Section 8, the Project is located
within the Yan Chau Tong Marine Park and next to the seagrass bed. The
ecological surveys conducted have concluded that the ecological value of the seagrass
bed is High (see Section 8.4.4 for
the ecological evaluation). The seagrass bed is sensitive to any suspended
solids that may be generated during the construction phase of the Project.
2.5.3.2
In order to avoid any adverse
water quality impacts and hence ecological impacts on the seagrass bed in the close
proximity to the Project site, the study team has been very mindful on the
configuration and design of the pier. Open sea dredging works will be totally
avoided during the construction phase. By avoiding open sea dredging works, any
adverse water quality impacts and hence impacts on marine ecological resources
during the construction phase would be minimised as much as practicable.
2.5.4
Avoidance of Wastewater
/ Effluent Discharge During both Construction and Operational Phases
2.5.4.1
Given that the Project is within
the Yan Chau Tong Marine Park which is a Water Sensitive Receiver (see Section 5.3), it is important to
implement all practicable measures to avoid any discharge of waste water /
effluent discharge into Yan Chau Tong Marine Park during both the construction
and operational phases.
2.5.4.2
During the construction phase,
the potential impacts that would be generated by the construction team has been
assessed in detail (see Section 5.4.2).
The Contractor will be prohibited to discharge any wastewater and effluent into
the Yan Chau Tong Marine Park. Any wastewater and effluent that would be
generated during the construction activities would be transported away for proper
treatment and disposal.
2.5.4.3
During the operational phase, the
Project has been designed to avoid any need for using detergents/chemicals
during routine maintenance (see Section
5.5). This would therefore avoid any potential water quality impacts on the
Yan Chau Tong Marine Park.
2.5.5
Avoidance of Solid
Pier Design
2.5.5.1
The
Project is located at the eastern coastal area of Crooked Harbour near Lai Chi
Wo. The cove is partly surrounded by the natural terrain with a wide coastal
inlet of about 800m.
2.5.5.2
The existing pier is a straight
solid concrete structure. In order to minimise any additional impacts caused by
the proposed pier improvement works, the structure of the proposed pier would
adopt concrete decks on top supported by piled foundation. The proposed pier is
extending from the existing pier towards the area with deeper water region of
about -2.4mPD to the east. The diameter of the foundation would be
approximately 0.8m to 1m and the column-to-column spacing is approximately 5m
to 8m. Such a configuration is typical for other similar piers in Hong Kong,
for instance, Sai Kung Public Pier.
2.5.5.3
Due to small footprint of the
new supportive piles, changes in the flow regime and hydrodynamic in the
eastern coastal area of Crooked Harbour are limited. The proposed pier
improvement works have minimised any impacts on hydrodynamics as much as
practicable. Details are provided in Section
5.5.
2.5.6
Minimisation
of Works in Country Park
2.5.6.1
As discussed in Section 1.2, the Plover Cove Country
Park is located immediately next to Yan Chau Tong Marine Park at Lai Chi Wo.
The existing connecting walkway between the pier and the footpath to Lai Chi Wo
falls within the Country Park.
2.5.6.2
Due to the pier improvement
works, the connecting walkway made of concrete will be inevitably constructed
between the proposed LCW pier and the existing footpath to Lai Chi Wo due to the level difference in
between. The connecting walkway partly falls within the intertidal shore of Plover
Cove Country Park (PCCP) (occupied around 0.0054
ha) as illustrated in Figure 1.3.
2.5.6.3
During the pier improvement works,
depending on the construction method to be proposed by the Contractor, it might
not be possible for the vessels to berth the existing pier, and hence a
temporary pier will then be constructed or provided to maintain the pier
operation during construction works. A temporary connecting walkway will also need
to be constructed to connect the temporary pier and the existing footpath to
Lai Chi Wo and located within the intertidal shore within the boundary of PCCP
(occupied around 0.0026 ha).
2.5.6.5
Based on the ecological survey
results, the ecological values within the occupied area of intertidal shore at
the boundary of the PCCP are ranked as Low to Moderate.
2.5.7
Minimisation of
Waste Generation During Construction Phase
2.5.7.1
The pier improvement works for LCW
Pier endeavour to minimise the waste generation in relation to integrate the structures
of the existing pier to the new pier structures. It therefore minimises the
generation of over 400 m3
construction and demolition (C&D) materials disposed of to the
landfills/public fill banks if the whole pier was demolished and reconstructed.
2.5.7.2
The Project will limit works on
land and avoids tree felling during the construction of pier. Hence, it
minimises vessel trips required for the delivery of C&D materials and waste
from the remoted Project site to the disposal sites. As such, disturbance from
the marine vessels to the marine park can be minimised.
2.5.7.3
In order to minimise the waste
generation at the Project site during construction phase, the most effective
approach is to adopt pre-cast elements for the deck as much as practicable. By
adopting this approach, most of the elements for the deck would be pre-cast
off-site and then transported to the site for final assembly.
2.5.8
Minimisation of Construction
Vessels During Construction Phase
2.5.8.1
As open sea marine dredging
would be avoided and pre-cast elements would be adopted as much as practicable,
the number of construction vessels during the construction phase would also be
minimised. Since the Project is located
within the Yan Chau Tong Marine Park, it is inevitable that the construction
vessels will travel within the marine park.
Hence, by minimising the number of construction vessels required, any
indirect impacts caused by those vessels on the marine park would also be
minimised as well. Nevertheless,
appropriate good practices would be adopted by the Contractor to operate the
construction vessels.
2.5.9.1
Due considerations have been
given in formulating the pier design to address environmental challenges in
this Project. The hierarchy of “Avoid, Minimise and Mitigate” has been fully
adopted in the process to protect the environment as much as practicable. Hence,
the design has given due consideration on the locations of the pier improvement
works to minimise the environmental impacts.
1. Options Considered for Pier Locations
2.5.9.2
The options that have been duly
considered include the following (Image 2.2):
·
Option 1: A
new pier to the north of the existing LCW Pier;
·
Option 2:
Extension of the existing LCW Pier to provide a new structure for construction
of landing steps and incorporation of floating pontoon; and
·
Option 3: A
new pier to the south of the existing LCW Pier.
-2mPD -3mPD -4mPD
Image
2.2 Location
Options of LCW Pier Improvement
Engineering Considerations
2.5.9.3
For Option 1, a new pier will
be constructed to the north of the existing LCW Pier. No temporary pier is required
to be constructed or provided as the existing pier can be used for berthing
during the construction of the new pier. The existing LCW Pier would need to be
demolished for safety reason after the pier improvement works. The demolition
works of the existing LCW Pier solid pier might involve wire saw cutting or
blade saw cutting above seabed level. Solid wastes including inert and
non-inert C&D materials are expected to be generated from the demolition work
of the existing pier.
2.5.9.4
For Option 2, pier improvement
works will be taken place over and on the seaside of the existing LCW Pier. As
the design of the new pier will integrate with the existing pier structure, no
demolition works of the existing pier will be required for this option. Provision
of a temporary pier is however required prior to construction of the new pier.
This temporary pier is likely to be at the location to the north of the
existing pier (see Section 2.6). Piles are required to support both the new pier and the
temporary pier, and these pile foundations will likely be bored piles. Casings
will be installed to separate the pile arisings from the water body to minimise
any risk of water pollution. After the completion of the construction of
the new pier, the piles for the temporary pier will then be removed by wire saw
cutting, blade saw cutting or similar method as close to the seabed as
practicable.
2.5.9.5
For Option 3, a new pier will
be constructed to the south of the existing LCW Pier. No temporary pier is required
as the existing pier can be used for berthing during the construction of the
new pier. However, due to the shallower water at the inner shore area near Lai
Chi Wo, the pier extension for Option 3 is anticipated to be the longest among
all the 3 options. The existing LCW Pier will need to be demolished for safety
reason after the pier improvement works. The demolition works of the existing
LCW Pier solid pier might involve wire saw cutting or blade saw cutting above
seabed level. Solid wastes including inert and non-inert C&D materials are
expected to be generated from the demolition work of the existing pier.
Environmental Considerations
2.5.9.6
For Option 1, the new pier will
be located closer to the coral colonies at Kau Lo Tau at 350m away. Though this
option will not require the construction and demolition of the temporary pier,
it requires the demolition of the existing pier for safety reason as mentioned
above. However, the existing pier is in solid structure. Though the new pier
will be located the farthest away from Lai Chi Wo Beach SSSI where seagrass bed
and mangrove stand with high ecological values are located, the demolition of the existing pier would inevitably
involve larger scale of marine works which would generate more C&D
materials to be delivered for off-site disposal as well as potential water
quality impacts. Nevertheless, amongst the three options, Option 1 will be
located at 490m (see Table 2.1) and
the farthest, albeit small difference, away from the LCW village where the
sensitive receivers are located. Air quality and noise impacts during
construction and operation on the sensitive receivers would be the best amongst
the three options, though the difference would not be very significant.
Furthermore, direct encroachment of the PCCP under this option would be the
largest one (around 0.0084ha) (see Table
2.2).
2.5.9.7
For Option 2, the Project will
not require the demolition of the existing pier and hence minimise the scale of
marine works and generation of C&D materials. Though the new pier will
require the construction and demolition of the temporary pier, the temporary
pier will be supported by piles where the scale of works will be smaller than
the demolition of the existing solid pier. Water quality impact is anticipated
to be the least among the three options during construction. Direct
encroachment of the PCCP under this option (extracted area of existing pier
which is already encroached upon PCCP) would be around 0.0064 ha (see Table 2.2), lesser than that of Option
1 but more than that of Option 3.
2.5.9.8
For Option 3, the new pier will
be located at 120m and closest to the seagrass bed and mangrove stands at Lai
Chi Wo Beach SSSI (see Table 2.1).
As the water depth is much shallower in the southern region of the cove, the
length of the pier will need to be increased to achieve sufficient water depth
for berthing. In addition, construction of the pier at the shallower region may
cause higher hydrodynamic impact and may affect the water quality of the SSSI.
The longer pier will also bear higher visual impact. Furthermore, similar to
Option 1, the Project will also involve the demolition of the existing pier
which would arise more C&D materials and cause potential water quality
impacts. In addition, amongst the three options, the new pier will be the
closest, albeit small difference, to Lai Chi Wo village residential receivers.
It would therefore cause more air quality and noise impacts on the local
villagers amongst the three options, though the difference would not be very
significant. Direct encroachment of the PCCP under this option would be the
least (around 0.0037 ha) (see Table 2.2).
2.5.9.9
The distances between the pier
options and the major sensitive receivers are summarised in Table 2.1, while the relative locations
of the piers and the sensitive receivers are shown in Image 2.3. As
discussed in Section 2.5.5, all
three options would be inevitably encroached upon PCCP, the corresponding
approximate area of encroachment (long-term) are summarized in Table 2.2.
Table 2.1 Distances
from the pier options to sensitive receivers
|
Major
Sensitive Receivers |
Type |
Approximate
Separation Distances |
||
|
Option 1 |
Option 2 |
Option 3 |
||
|
Lai
Chi Wo Village |
Air/Noise Sensitive Receiver |
430 |
400 |
370 |
|
Lai Chi Wo Beach SSSI |
Water/Ecological Sensitive Receiver |
190 |
150 |
120 |
|
Coral colonies at Kau Lo Tau |
Water/Ecological Sensitive Receiver |
350 |
380 |
420 |
Table 2.2 Area of encroachment
upon PCCP for the pier options
|
Major
Sensitive Receivers |
Approximate
Area of Encroachment (Long-term), ha |
||
|
Option 1 |
Option 2 |
Option 3 |
|
|
Plover Cove Country Park (PCCP) |
0.0084 |
0.0067 [1] |
0.0038 |
|
Note: [1] The area of existing pier which was encroached
upon PCCP was excluded. |
|||
Image
2.3 Locations
of Pier Options and Nearby Sensitive Receivers
Preferred Option
2.5.9.10
Taking the potential
environmental impacts into consideration, Option 2 has been selected as the
preferred option. Though this Option will require the construction of a temporary
pier, it avoids the demolition of the existing solid pier. Conversely, for
Option 1 and Option 3, notwithstanding that the construction or provision of
the temporary pier is not required, the existing pier will need to be
demolished after the completion of the construction of the new pier due to its
aging condition. When comparing the potential water quality impact from the demolition
of temporary pier, which is supported by pile columns, with the demolition of
the existing pier, which is a solid finger pier, the demolition of the solid
finger pier for Option 1 and Option 3 will involve more marine works than the
cutting of the pile columns by wire saw, resulting in higher water quality
impact. In terms of waste generation, the demolition of the existing solid pier
will generate more C&D materials for offsite disposal, and therefore
increase the number of trips required to deliver the C&D material offsite.
2. Options Considered for Pier
Arrangement
2.5.9.11
The pier arrangement of L-shape and linear extension have been
preliminarily considered. The arrangement of T-shape has not been considered as
the water depth is swallow at the south of the pier, T-shaped pier arrangement
is not feasible. By considering the provision of barrier-free facilities,
sufficient water depth and appropriate size to allow side berthing of the Kaito
ferries and other typical vessels, the tentative preliminary layout of a
L-shape and linear extension pier arrangement were preliminarily studied and
shown in Image 2.4 and Image 2.5.
Image
2.4 Preliminary
Layout of L-shape Pier Arrangement
Image
2.5 Preliminary
Layout of Linear Extension Pier Arrangement
Engineering Considerations
2.5.9.12
As discussed in Section 2.2, the water depth at the
head of the existing LCW Pier is very shallow and could be unsafe for berthing
and manoeuvring of vessels during low tide. Therefore, it is proposed to
improve the safety of using the pier by extending the LCW Pier to a deeper water
area of seabed at about -2.4mPD.
2.5.9.13
The dominant wave direction is
easterly in Crooked Harbour near Lai Chi Wo. A T-shape pier has been considered
but is not preferred as vessels berthing at the pier head could be subjected to
boardside wave, i.e. waves directing on the sides of vessels inducing repeated
bouncing of vessels against the pier. The tentative footprint of the L-shape
and linear extension of pier arrangement are around 0.17ha and 0.15ha
respectively. L-shape pier arrangement would result in a footprint larger than
that of the linear extension one, more piled foundation would be anticipated.
Environmental Considerations
2.5.9.14
As the L-shape pier arrangement
would result in a larger footprint, more piled foundation and hence more seabed
loss is anticipated when compared with the linear extension arrangement.
Preferred Pier Arrangement
2.5.9.15
Taking the potential
engineering and environmental impacts into consideration, linear extension
arrangement would be selected as the preferred arrangement.
3. Options Considered for Size of
Pier
2.5.9.16
For the linear extension pile arrangement, the size of the proposed pier
has been carefully studied in consideration of several factors including water
depth, size of improvement works, barrier-free facilities provision and potential
ecological impact. An initial preliminary layout (Option A) was established and
is shown in Image 2.6.
Image
2.6 Initial Preliminary Pier
Layout (Option A)
Water Depth of Lai Chi Wo
2.5.9.17
Based on the hydrographic
survey at Lai Chi Wo in July 2019, the seabed level at the existing pier head
is about -1mPD and thus the water depth during low tide is only 1m to 1.5m. As
the required draft of the existing Kaito ferries and other typical vessels
could be up to 2m, the current water depth especially during low tide period is
insufficient for these vessels to berth.
2.5.9.18
Therefore, the proposed pier
head shall be located in the area with sufficient water depth for Kaito ferries
and other typical vessels to berth (e.g. area with seabed level of about
-2.4mPD). The proposed pier is anticipated to be extended at least 80m from the
existing pier head (as shown in Image
2.6). By providing sufficient depth for vessels to manoeuvre, seabed
disturbance could be minimised during operation of the Project.
Appropriate Size of Improvement Works
2.5.9.19
The existing pier is only 2.5m
wide and 4.2m long at the pier head which cannot allow complete alongside berthing
of the full length of Kaito ferry vessels which are typically 20m to 25m long. Therefore,
the proposed pier head shall at least cater for side berthing of the Kaito
ferries and other typical vessels; 30m long pier head is sufficient for more
safety side berthing arrangement.
2.5.9.20
Furthermore, there is inadequate
space on the pier for Kaito ferry patrons waiting or queueing at the LCW Pier.
The proposed improvement works shall consider providing sufficient space
(ideally with cover) to allow pier users to wait and queue for the Kaito ferry
service, which is also a common provision in other existing piers in Hong Kong.
The existing 2.5m wide catwalk shall also be widened to an appropriate width as
there is a high risk of falling into water when the pier was crowded with
people, especially during boarding/disembarkation time.
2.5.9.21
Based on the above
considerations, the initial preliminary pier design (as shown in Image 2.6) reflected such requirement.
By taking into account the patronage in peak hours of the LCW Pier, the
proposed size of improvement works could also cater for the needs of users and
largely reduce the risk of safety issue.
Barrier-free
Facilities Provision
2.5.9.23
Compared to a traditional pier
head, the floating pontoon might be subject to relatively higher maintenance
frequency. During the maintenance works of floating pontoon, the traditional
pier head can provide normal service for daily operation of the pier.
Therefore, both traditional pier head and floating pontoon with ramps will be
provided at the proposed pier. The initial preliminary pier layout (Option A)
incorporates the idea of barrier-free facilities provision.
Preliminary Ecological Review
2.5.9.24
Therefore, the initial preliminary
pier layout was revised to minimise the size of proposed improvement work to
form the revised preliminary pier layout (Option B). Considerations revisited
include the size of pier deck, ramp and pontoon structures, modification of
existing pier to provide sufficient length for vessels to berth etc. The
revised preliminary pier layout is shown in Image 2.7.
Image
2.7 Revised
Preliminary Pier Layout (Option B)
2.5.9.25
The revised preliminary pier
layout (Option B) has largely been reduced in size (~240m2) while
still maintains the requirements for the pier improvement. Due to the provision
of the desirable length of safe berthing, part of the existing pier head has
been modified as shown in Image 2.8.
2.5.9.26
After incorporating this
revised arrangement, the number of piles required to be constructed will
decrease to around 52 piles (plus 5 piles constructed at existing pier
footprint). The seabed loss for piles will be minimised to around 0.003ha. The
revised preliminary pier layout has therefore achieved an optimum option in
view of different considerations.
2.5.9.27
The proposed pier shall provide
berths at locations with sufficient water depth to enhance safety for berthing
and manoeuvring. Therefore, a minimum length of 95m from the existing pier head
towards south-east direction is maintained to provide adequate water depth of at
least 2.9m.
Summary of Options Considered
2.5.9.28
A summary of the above options
is given in Table 2.3 with the
preferred option identified for ease of reference.
Table 2.3 Summary of Options Considered
|
Options |
Pros |
Cons |
Preferred Option (Y/N) |
|
1.
Pier Locations |
|||
|
Option 1 |
Engineering
Considerations |
N |
|
|
· No
additional temporary pier will be required. |
· Demolition
works will be required for the existing pier. |
||
|
Environmental
Considerations |
|||
|
· Amongst
the three options, the new pier will be located the farthest away, albeit
small difference, from the LCW village where the residential sensitive
receivers are located. Environmental impacts during construction and
operation on the residential sensitive receivers will be the least among the
three options. |
·
Though the new pier will be
located the farthest from Lai Chi Wo Beach SSSI where seagrass bed and
mangrove stand with high ecological values are located, demolition
of existing pier shall be carried out for safety reason. Hence, it will generate
larger quantity of waste and more marine works, which may cause water quality
impact. · Largest
encroachment upon PCCP among all 3 Options. Hence, it will generate the
greatest potential impact upon the Country Park. |
||
|
Option 2 |
Engineering
Considerations |
Y |
|
|
· No
demolition works will be required for the existing pier. |
· Additional
temporary pier will be required during construction phase. |
||
|
Environmental
Considerations |
|||
|
· No
demolition works will be carried out on existing pier, hence largely reduce
quantities of waste generated. Without the demolition works, the water
quality impact on the neighbouring water sensitive receivers such as Lai Chi
Wo Beach SSSI is anticipated to be the least. |
· Area
of encroachment upon PCCP of this option is smaller than that of Option 1,
but more than that of Option 3. |
||
|
Option 3 |
Engineering
Considerations |
N |
|
|
· No
additional temporary pier will be required. |
· Demolition
works will be required for the existing pier · The
water depth is the shallowest among the three options. Hence, the pier length
is the longest among the three options to provide sufficient water depth for
berthing. |
||
|
Environmental
Considerations |
|||
|
· Area
of encroachment upon PCCP of this option is the smallest one. The potential
impact upon the PCCP is considered to be the least. |
· Demolition
of existing pier shall be carried out for safety reason. Hence, it will
generate larger quantity of waste and potential water quality impact. · Amongst
the three options, the proposed pier will be the closest to Lai Chi Wo Beach
SSSI, where the seagrass bed and mangrove with high ecological value are
identified. ·
Amongst the three options, the new pier will be
the closest, albeit small difference, to Lai Chi Wo village residential
receivers. It would therefore cause more air quality and noise impacts on the
local villagers amongst the three options, though the difference would not be
very significant. |
||
|
2.
Pier Arrangements |
|||
|
L-Shape |
Engineering Considerations |
N |
|
|
N/A |
· Wave
direction will be perpendicular to the berthing vessel and repeating bouncing
of vessel against the pier is anticipated. Hence, it is more dangerous for
pier users when boarding. · In
order to achieve sufficient water depth at the proposed pier head, the
footprint of T-shaped pier will be larger compared with the Liner
arrangement. |
||
|
Environmental Considerations |
|||
|
N/A |
· More
permanent marine habitat loss is anticipated due to more footprint when
compared with the linear extension arrangement. |
||
|
Linear |
Engineering Considerations |
Y |
|
|
· As
wave direction will be in parallel to vessel berthing, less bouncing of
vessel against the pier is anticipated. Hence, it enhances the safety
boarding pier users. · Smaller
footprint area is envisaged. Less piled foundation is anticipated. |
N/A |
||
|
Environmental Considerations |
|||
|
· Less
permanent marine habitat loss is anticipated due to lesser footprint when
compared with the L-shape pier arrangement. |
|
||
|
3.
Pier Sizes |
|||
|
Option A |
· More
space will be provided on pier for pier users to wait or queue for Kaito
service. · A
widen catwalk will cause fewer safety problems. |
· More
piled foundation to support to pier structure is anticipated. Hence, there
will be more seabed loss compared with Option B. |
N |
|
Option B |
· Less
piled foundation is envisaged. Therefore, there will be less seabed loss
compared with Option A. |
· Less
space and narrower walkway will be provided for the pier users. |
Y |
2.5.10
Consideration of Construction
Methodologies
2.5.10.1
Various
construction methodologies have been considered in view of avoidance and
minimisation of potential environmental impacts.
Solid Pier
Construction vs. Pile-Supported Pier Construction
2.5.10.3
To
avoid the potential water quality impact, the foundations of the proposed LCW
Pier and the temporary pier will be composed of in-situ bored piles or similar pile types (e.g. rock socketed
Steel H-pile). As the marine piles will be
constructed with a pile casing system (see Section 2.6.3), sediment and
drilling fluid during the pile construction will be confined in the pile casing,
and isolated from the external water bodies. The
proposed construction method has totally avoided the need of open sea dredging.
The pile-supported pier allows water flow underneath the pier structures. It
has much smaller hydrodynamic impact during operation phase.
On-site
Construction vs. Prefabrication Construction
2.5.10.4
Prefabrication construction method
has been proposed for the construction of deck structures of the pier. Selected
concrete superstructures
will be formed by pre-cast concrete offsite in a controlled environment and
installed onsite when ready. This can avoid on-site casting activities that may
affect water quality by minimising the storage of casting materials. Moreover,
this approach can minimise the extent and duration of on-site construction
activities. The time of on-site construction activities
could be reduced by 10% when compared with typical in-situ construction method.
The prefabrication method also minimises the waste generation
on-site during the construction phase. As a result, the air quality, noise,
water quality impacts and waste implications associated with these construction
activities including emissions, site run-off, accidental spillage of chemicals
and sewage from workforce could thus be avoided or minimised in comparison with
on-site casting method.
Conventional Demolition vs. Wire Saw Demolition
2.5.10.5
The temporary pier will be
decommissioned after the completion of pier improvement works. Piled foundation
of temporary pier will be cut by wire saw or similar method as close to the
seabed as possible. The wire saw is a saw that uses a metal wire or similar
material for cutting structure from its parent structure in a safe and
efficient way with limited vibration.
2.5.10.6
Compared to the conventional
demolition work in mechanical mean (e.g. using chisel and grab) to remove the
piled foundation, wire saw cutting would cause less vibration, limited
suspended solid and hence cause less adverse impacts to the environment.
Summary of Construction Methodology Considered
2.5.10.7
A summary of benefits and
disbenefits of construction methodology considered is given in Table 2.4.
Table 2.4 Summary of Construction Methodology
Considered
|
Options |
Pros |
Cons |
Preferred Option (Y/N) |
|
Solid
Pier Construction vs. Pile-Supported Pier Construction |
|||
|
Solid Pier Construction |
N/A |
·
Soft
materials on the seabed will need to be dredged. There will be great impacts
on the water quality, hydrodynamic and marine ecology issues in both
construction and operation phases |
N |
|
Pile-Supported Pier Construction |
· This
construction method totally avoids the need of open sea dredging and thus
safeguard water quality impact during construction phase. |
N/A |
Y |
|
On-site
Construction vs. Prefabrication Construction |
|||
|
On-site Construction |
N/A |
· Require
storage of more construction materials and generate more construction waste
on-site · There
will be more construction activities and more PME items on-site. Hence, the
construction activities and use of PME may incur more air quality, noise and
water quality impacts |
N |
|
Prefabrication Method |
· Minimise
on-site construction activities and the use of PME on-site, which may incur
air quality, noise and water quality impacts · Minimise
storage of construction materials on-site and generation of waste on-site |
N/A |
Y |
|
Conventional
Demolition vs. Wire Saw Demolition |
|||
|
Demolition work in mechanical mean |
N/A |
· More
vibration and suspended solid are anticipated if adopting demolition work in
mechanical mean. Hence, cause more impact to the environment. |
N |
|
Wire-saw cutting |
· Less
vibration, limited suspended solids and hence cause less impacts to the
environment. |
N/A |
Y |
2.5.11
Consideration of Construction
Sequence
2.5.11.1
As
the Project is located within the Yan Chau Tong Marine Park, the construction
sequence has also been duly arranged during the EIA study.
Overlapping vs. Non-overlapping
of Construction Stages
2.5.11.2
Construction
will be conducted phase to phase to avoid environmental impacts. The
construction of the proposed pier will only be commenced after the completion
of the temporary pier. Likewise, the demolition of temporary pier would only be
commenced when the proposed LCW pier has completed.
Successive vs.
Concurrent Construction/Demolition of Structures
2.5.11.3
Construction
of pier structures and demolition of temporary pier structures will be
conducted successively. During the construction of marine bored piles, there
will only be one to two piles constructed concurrently within the Project site.
During demolition of the piles for the temporary pier, marine piles will be cut
one by one to minimise the impact. This avoids large quantities of PME
operating concurrently within the Project site, and therefore reduces the
potential noise and air quality impacts.
Summary of Construction Sequence Considered
2.5.11.4
A summary of benefits and
disbenefits of construction methodology considered is given in Table 2.6.
Table 2.6 Summary of Construction Sequence
Considered
|
Options |
Pros |
Cons |
Preferred Option (Y/N) |
|
Overlapping
vs. Non-overlapping of Construction Stages |
|||
|
Non-overlapping of different
construction stages |
·
Less
amount of construction activities occurred and less PME used in the Project
site concurrently ·
Reduce
the magnitude of negative environmental impacts |
·
Longer
duration of construction |
Y |
|
Overlapping of different
construction stages |
· Shorter
duration of construction |
·
More
amount of construction activities occurred and more PME used in the Project
site concurrently · Potentially
more environmental impacts |
N |
|
Concurrent
vs. Successive Construction/Demolition of Structures |
|||
|
Concurrent construction /demolition
of structures |
·
Less
amount of construction/ demolition activities occurred and less PME used in
the Project site concurrently · Reduce the magnitude of negative environmental
impacts |
· Longer duration of construction/demolition |
Y |
|
Successive construction /demolition
of structures |
· Shorter
duration of construction/demolition |
·
More
amount of construction/ demolition activities occurred and more PME used in
the Project site concurrently · Potentially more environmental impacts |
N |
2.6
Proposed Development Scheme
Proposed LCW Pier
2.6.1.1
The existing LCW Pier extends
from the land towards the sea in the east-southeast direction. The proposed LCW
Pier will be constructed on top of the existing LCW Pier, and will be
integrated with it. The proposed LCW Pier will align in the same direction as
the existing pier, and extend to deeper water. The location of the proposed LCW
Pier is shown in Image 2.8.
|
Plover Cove Country Park |
Image 2.8 Location of Proposed LCW
Pier and Proposed Temporary Pier
2.6.1.2
The proposed LCW Pier will be a
piled deck structure in order to minimise any impact on environment and
hydrodynamics. The piled deck structure will be of a length of about 155m and
widths ranging from 6m to 8m increased to 15m at the pier head for both
traditional pier head and floating pontoon provision. The proposed LCW Pier
will consist of a floating pontoon and a gangway for barrier-free facilities,
and PV panels if applicable.
Proposed Temporary Pier
2.6.1.3
During construction of the proposed LCW Pier, concurrent undertaking of
improvement works at the existing pier and berthing of vessels is not spatially
feasible, and it would not be safe. A temporary pier will be provided to
maintain operation of the licenced Kaito service and to serve other public
vessels.
2.6.1.4
The temporary pier will be located at about 30m
north from the existing LCW Pier. The proposed temporary LCW Pier will align in
the same direction as the existing one. The proposed temporary LCW Pier will be
about 70m long and 3m wide, and will largely be in the form of floating pontoon and/or steel structures
supported by piles to minimise any environmental
impact. The location of the
proposed temporary LCW Pier is shown in Image 2.8.
Ramp Width
2.6.1.5
According to the Barrier Free
Access Design Manual published by the Buildings Department, the width of a ramp
should be at least 1.5m to allow 2 wheelchairs to pass. The pier improvement
provides a 2m of clearance for passage of 2 wheelchairs and a 0.5m of width for
the installation of handrails and fenders on both sides.
2.6.2
Construction Sequence
2.6.2.2
Prefabrication method will, if
possible and applicable, be used for the construction of the proposed LCW Pier.
The preliminary construction sequence for the proposed LCW Pier is as follows:
Construction
of Temporary Pier
(1)
Install pile foundation;
(2) Install working barge
and/or temporary steel structures; and
(3)
Connect the temporary pier to existing footpath by mass concrete block.
Pile
Foundation
(1)
Install pile foundation/guide piles for the new pier;
(2) Erect temporary bracing to
stabilise piles; and
(3) Install precast pile caps.
2.6.2.3
Due to the location of the
site, construction materials will be delivered via marine access. They will be
transported by barges and installed using derrick barge and/or multi-purpose
jack-up barge and/or temporary steel structures.
Construction
of Pier Superstructure
(1)
Install precast beams;
(2)
Install prefabricated reinforcement cages;
(3)
Install precast fender blocks;
(4)
Install precast slab panels;
(5)
Install precast staircase;
(6)
Install prefabricated rebar for top slab and connect the top slab and
the fender blocks; and
(7) Install bollards, fenders
and remaining works and provide associated facilities.
2.6.2.4
All the precast units will be delivered
via marine access. They will be transported by barges and/or derrick barge, and
will be installed on site.
Installation
of Floating Pontoon/ Gangway
(1)
Transport the prefabricated floating pontoon;
(2)
Install the guide pile frame on the prefabricated floating pontoon to
the guide pile for mooring;
(3)
Transport the prefabricated gangway; and
(4)
Fix the gangway on the landing and rest on the floating pontoon.
(1) Demolish the steelworks and
mass concrete block of temporary pier in pieces;
(2) Transport the demolished
steelworks and concrete block off site;
(3) Cut and remove the piles as
close as possible to the seabed; and
(4) Transport the removed piles
off site.
2.6.3
Consideration of
Environmentally Conscious Construction Methodologies
Use
of Pile Casing and Silt Curtain to Confine Pollutants during Pile Construction
2.6.3.2
To avoid the potential water
quality impact, the foundations of the proposed LCW Pier and the temporary pier
will be composed of in-situ bored
piles or similar pile types
(e.g. rock socketed Steel H-pile). The proposed construction method has
totally avoided the need of open sea dredging.
2.6.3.3
For each pile construction, pile
casing shall be first slowly drilled through the seabed and would disturb small
areas of seabed, only limited resuspension of sediment is expected. Once the
pile casing penetrates the layers of marine sediment, all excavation work would
be carried out inside the pile casing to avoid spillage of sediment and water
containing suspended solids (SS) during piling works. All grabbed material will
be conveyed to and be settled in the sedimentation tank, and will be
sequentially delivered to the designated disposal outlets by marine
transportation. Hence, the practical measures to avoid grabbed material making
in direct contact with the open sea water would be implemented. To further
eliminate the probability of release of fines to the surrounding water body
during construction works, installation of silt curtain to confine the site
activities shall be adopted. An illustrative figure of the setup of a marine
bored pile construction is shown in Image 2.9.
Image 2.9 Pile Casing and Silt
Curtain for Marine-based Pile Construction
Prefabrication Construction Method for Pier Deck
Structures
2.6.4
Preferred Construction
Methodology for Site Investigation Work
2.6.4.2
Illustrative diagram of the
setup of a vertical borehole drilling rig on the barge is shown in Image 2.10. An outer casing shall be
first placed on the seabed level to avoid spillage of sediment and water
containing suspended solids (SS) during drilling work. Throughout the drilling
process, a rotary core with a drill bit is advanced inside the outer casing to
the seabed and the soil sampler cuts and collects the soil cores. After that,
an inner casing (around 168mm dia.) will be advanced to the drill bit tip level
to support the ground and seal off the open fissures. The drill bit with the
sampler with then be brought to the barge and the soil samplers would be
collected for further laboratory tests. After removal of the sample, the rotary
core with the drill bit will be once again returned to the base of the hole for
subsequent sampling works.
Image 2.10 Illustrative Diagram of Vertical Boreholes
2.6.5
Preferred Construction
Methodology for the Proposed LCW Pier
Pile Installation Works
2.6.5.2
The foundations of the proposed
LCW Pier and the temporary pier will be composed of in-situ bored piles or
similar pile types (e.g. rock socketed Steel H-pile). A
working platform in form of a working barge and/or temporary steel structure
supported by mini-piles (~219 or 273mm dia.) will be adopted to facilitate the
pier construction works. Working barge will be fixed
in a position by anchoring onto the seabed while the mini-piles used to support
the temporary steel structure would follow the pile casing and silt curtain method as
discussed in Section 2.6.3.2 to 2.6.3.4 in order to control the water quality and ecological impacts. Minimal disturbance of existing seabed would be resulted but
significant dispersion of suspended solids is not expected.
2.6.5.3
For each pile construction, pile casing and silt
curtain method as discussed in Section 2.6.3.2 to 2.6.3.4 would
also be followed. Pile casing of approximately 0.8-1.0m in
diameter will be installed into the seabed by using hydraulic oscillator from a
working platform. Pile shaft excavation by using hammer grab will be carried
out within the casing. Grab excavator will be deployed to minimise the leakage
of material collected during the process. The grabbed material will be bought
to and be settled in the sedimentation tank. The pile casing will then be
jacked down into the ground by oscillator prior to carry out next grabbing
process until reaching rockhead. Reverse Circulation Drill (RCD) will be
deployed to drill through the bedrock and any hard material encountered until
reaching the required level. No grabbed material will made in direct contact
with the open sea water.
Pier Deck Structures Construction
2.6.5.5
Once the piles are installed, the precast elements of the pier structure
including precast pile caps, beams, walls and slabs will be transported to the
site by barges for subsequent erection, installation and in-situ stitching/casting. These precast
elements could be shells of the elements to enable in-situ casting of the remaining concrete portions without the need
of formwork and avoiding leakage of wet concrete out of conventional formwork.
2.6.5.6
Following the completion of the
deck structure, other superstructure and ancillary elements including the
canopy, handrailing and seats can be transported to the site for installation.
The canopy structure can be partly prefabricated off site. Silt curtain would then be
removed after completion of proposed pier construction work.
2.6.6
Preferred Construction
Methodology for the Proposed Temporary Pier
2.6.6.1
Piled foundation for the proposed temporary
pier will be installed in the similar fashion as the piled foundation for the new
pier as described in Section 2.6.5.1 to Section 2.6.5.4.
2.6.6.2
Temporary pier might be
in a form of floating pontoon and/or steel structures supported by piles to
maintain the marine access to Lai Chi Wo and subject to the Contractor’s
proposal.
2.6.7
Demolition of the Proposed Temporary
Pier
2.6.7.2
Pile foundations for temporary use will be cut by wire saw, blade saw or
similar method as close as possible to the seabed, and
the demolished portions of the pile foundations will be removed off site. The portions of the piles embedded in the ground will be
left untouched below the seabed. The estimated length of pile below seabed is
about 20m to 30m.
2.6.8
Maintenance Dredging
2.6.8.1
It is not expected to carry out
maintenance dredging during both construction and operational phases as the
proposed LCW Pier would be extended to a location with sufficient water depth
for vessels to berth. The adoption of pile foundation supporting pier deck
structure minimizes the accumulation of sediment when compared with adopting
solid pier structure and reduces the need of maintenance dredging.
2.7.1.1
Whilst
a number of design initiatives have been proactively implemented to tackle
various environmental challenges, the Project aims to achieve more than the
statutory requirements. Thus, various
environmental initiatives have been identified for the Project. These initiatives cover different aspects
including:
·
Clean energy / energy saving;
·
Waste minimisation; and
·
Enhance biodiversity /
greening.
2.7.1.2
However, whilst these
initiatives are generally considered as practicable at this stage, the extent
of applications and other details have to be revisited and further established
during the detailed design stage when the engineering design is further
developed. Table 2.7 summarises all those environmental initiatives envisioned
at this stage.
Table 2.7 Environmental initiatives to be further
developed during detailed design stage
|
Aspect |
Environmental Initiatives |
Environmental Benefits |
|
Enhance
biodiversity |
·
Priority
using eco-tiles or eco-concrete for the surface of the foundation. |
·
Promote
seamless integration of biodiversity into the pier design |
|
Clean
energy / energy saving |
·
PV
panels (e.g. for lights at waiting area) ·
Priority
using of LED lighting |
·
Use of
solar energy and energy-saving equipment to minimise energy consumption |
|
Waste
minimization |
·
Use
recycle glass bricks for pavement |
·
Promote
the use of recycled materials / products |
2.7.1.3
Subject to the detailed
design of the Project, eco-tile or eco-concrete is recommended for the
provision of hard surfaces for vitalising the ecological functions at sub-tidal
artificial pier structures such as the downstand
wall and piles. The uneven surfaces or
selected patterns of eco-tiles provide microhabitats for various marine
organisms to colonise and grow, and develop into communities to provide feeding
and hiding habitats for juveniles of marine fauna, and thereby effectively
enhance biodiversity and ecosystem functions of the new man-made structures. During the detailed design of the Project, the feasibility,
detailed design and the implementation programme of the eco-tile or
eco-concrete will be submitted for the approval of the authority before
commencement of the works.
2.8
Collating and Addressing Public
Views
Support from Lai Chi Wo
Village Representatives and Sha Tau Kok District Rural Committee
2.8.1.1
This
Project has been fully discussed with the members of Sha Tau Kok District Rural
Committee (STKDRC) and the village representatives of Lai Chi Wo Village. Site
visit and consultation meeting were held in 2018 and 2019 respectively to
explain the proposed design and collate views from the stakeholders. They have
fully supported to the project.
2.8.1.2
Vessels can only berth at
particular time in accordance to the tidal condition because of the insufficient
of water depth. The situation does not flavour villagers/fishermen to berth at
the existing pier and therefore, they fully supported to the Project in order
to provide a pier with standardize water depth and berthing facilities.
Support from North District Council
2.8.1.3
Lai Chi Wo
Pier Improvement Works was first discussed on District Minor Works and
Environmental Improvement Committee of North District Council (NDC) on 15 May
2017 under Pier Improvement Program (Ref. Paper No. DMWEIC 22/2017). Councilors supported the improvement works and stated
that due to the safety issues, Lai Chi Wo Pier showed strong needs to be
revamped.
2.8.1.4
In May
2019 and April 2020, there were a few meetings with related District Councilors.
The councilors all showed their support to the improvement works. On 18 May
2020, the Project was discussed on Land Development, Housing and Works
Committee (LDHWC) of NDC (Ref. Paper No. LDHWC 7/2020). There were
councilors asked about the structure safety under strong wind and wave
situation, the safety of pontoon and gangway design and works schedule under
EIA process.
2.8.1.5
Project
proponent confirmed that guiding piles would control the movement of pontoon as
upward and downward and there was wind and wave modeling tested during the pier
design. They also pointed out that the improvement works would only commence upon
the Environmental Permit granted by the authority and the works duration would
be around 2 to 2.5 years.
2.8.1.6
There was
no concern on environmental issues and gave endorsement to the Project for way
forward.
Consultation
with Green Groups
2.8.1.7
In August and October 2019,
there were two consultation meetings held with green groups. They raised
concerns about the land area within the proposed works boundary and if so, how
the trees nearby would be affected, water quality monitoring during
construction works and demolishing the existing pier. Members of green groups
also supported the pile-deck design and pre-cast construction method.
2.8.1.8
The Project Proponent responded
that most of the works will be carried out on a work barge. Therefore, no trees
are required to be felled by the Project. The closest distance to land would be
the temporary pier and tree protection measures will be implemented to ensure
sufficient distance between the trees and works area, and the temporary pier.
2.8.1.9
Regarding the water quality
during construction works, two monitoring stations will be implemented during
construction phase. Once the readings exceed the limitation, works will be
suspended. Besides, there is no plan to demolish the existing pier as removing
the existing pier structures may require more marine works including demolition
of concrete structures, which may bear potential water quality impact during
the construction phase. The proposed construction methodology avoids the
demolition of the existing pier to minimise the construction period, marine
works required and waste generation.
Comments Received During the EIA Process
2.8.1.10
In December 2019, the Project
was discussed in Marine Park Committee (MPC). The comments obtained from
consultations with MPC, green groups and members of the public have been duly
revisited and were incorporated in the design, construction and operation of
the Project where appropriate. Table 2.8
summarises all these comments and how the Project Proponent has addressed them
suitably.
Table 2.8 Summary
of key comments and approaches adopted to address comments collated
|
Issues |
Comments |
Responses & Approaches Adopted |
|
Project Design |
The proposed extension of
Lai Chi Wo Pier would lead to a longer walking distance which would not be beneficial
to villagers and fishermen. Project Proponent should consider providing
additional lading facilities near the shore. |
The landing steps of the existing Lai Chi Wo Pier
would be retained considering the high usage rate. Repairing works on the
landing steps would be carried out then merge into the new pier structure.
Continue liaison with concerned parties will be made during design
development. |
|
Ecology |
The details of coral
colonies near the pier structure shall describe clearly. |
Low coverage of common
hard coral (less than 1%, equivalent to 0.006m2) were found on
pier head while the surroundings have no record due to the soft clay substrate
of the seabed. Details of coral colonies recorded during coral survey, please
refer to Section 8. |
|
|
Patches of mangrove
stands and seagrass are recorded inside the bay of Lai Chi Wo, which are in
close vicinity to the location of the newly proposed pier. Heavy sediment
load from the pier construction would pose adverse impacts to both mangrove
stand and seagrass patches, so smart design of the pier, clear construction
procedures and installation of silt curtains are crucial in order to protect
these habitats. |
Seagrass bed, mangrove
and tidal pond habitats were identified in the vicinity of the Lai Chi Wo
assessment area. No seagrass bed and mangrove will directly be affected. Silt curtain will be adopted during piling
works at construction phase. Also, silt curtain will be installed, and pre-cast
construction method will be adopted to minimise the possibility of water
pollution. |
|
Tree Preservation |
Noting that there would be a temporary pier
throughout the construction period, Project Proponent should ensure an
adequate distance provided between trees and the temporary pier. |
A tree survey has been conducted during the
EIA study. No trees are required to be felled by the Project. Tree protection
measures as discussed in Section 9
will be implemented to ensure sufficient distance between the trees and works
area, and the temporary pier. |
|
Water Quality |
The existing pier
structure would block the water current. Hence, it is suggested Project
Proponent to remove the entire structure. |
Removing the existing
pier structures may require more marine works including demolition of
concrete structures, which may bear potential water quality impact during the
construction phase. The proposed construction methodology avoids the
demolition of the existing pier to minimise the construction period, marine
works required and waste generation. Details are provided in Section 2.5.7. |
|
Nothing that the waters around
the pier is sensitive to water quality, Project Proponent should monitor the
water quality during construction works and suspend the works if the readings
exceed the certain standard. |
There will be two pairs
of monitoring stations implemented during construction phase. Once the
readings exceed the limitation, construction works will be suspended. Details
are provided in Section 5. |
|
|
Noise and Vibration |
It is concerned that vibrations from the piling
works would affect the marine species around the area. |
Instead of adopting percussive piling for
pile construction, bored piling method will be adopted to minimise the noise
and vibration from the piling works of the Project. |
|
Project Operations |
The number of visitors
may increase and therefore burden the handling capacity of the island so as
the increase of man-made pollution. |
After consulting related
Government Departments, there is no plan to increase the frequency of
licensed Kaito services. |
|
Sustainability |
Renewable energy should
be deployed as much as possible in this development project. |
Renewable energy has been
explored during the EIA study. Environmental initiatives including but not
limited to renewable energy will be implemented during detailed design of the
Project. Details are provided in Section
2.7. |
2.9
Tentative
Implementation Programme
2.9.1.1
A tentative programme for the
construction of the project is shown in
Appendix 2.1. Site Investigation works for detailed design will be
carried out in mid-2021. Prefabrication method will be adopted as far as
practicable for the construction works. Construction is scheduled to commence in
Year 2023 and completed by Year 2025.
Construction works are planned to be carried out during non-restricted hours
(i.e. 0700-1900 hours from Monday to Saturday other than public holidays). The
exact schedule of construction depends upon factors such as the granting of
necessary permit for its construction and the awarding of the contract to the
contractor.
2.10.1.1
There is only one concurrent
project which may bear potential environmental impacts during the construction
and operational phases of the proposed Project. This concurrent project is identified
as follows.
·
Improvement of Trails and Provision of
Facilities in Sha Tau Kok.
2.10.1.2
Detailed justifications on consideration of various environmental
cumulative impacts from the concurrent project has been included in
corresponding sections.
Improvement of Trails and Provision of Facilities in Sha Tau Kok
2.10.1.3
This concurrent project
involves improvement works of facilities along the trail straddling the PCCP
and the Northeast New Territories Sedimentary Rock Region of Hong Kong Global
Geopark of China (HKGCC). A number of sites to be improved have been selected.
Among three sites, namely T24, T25 and T26, of those sites are at LCW as shown
in Image 2.11. Minor replacement, renovation and conservation works will be
carried out on these three sites. Works at these three sites have been
completed in September 2019. In general, only a limited extent of environmental
impact is anticipated from the construction of this concurrent project. During
the operation, there will be neither emission nor discharge from this
concurrent project. Cumulative environmental impacts from the concurrent
project is not anticipated according to Table
2.9.
Image 2.11 Location of the Concurrent Project –
Improvement of Trails and Provision of Facilities in Sha Tau Kok
Table 2.9 Potential
impacts of concurrent projects
|
Project
Proponent |
Programme |
Potential Cumulative Impacts (Construction Phase) |
Potential Cumulative Impacts (Operational Phase) |
||
|
Start |
Complete |
||||
|
Present Project (Site Investigation Works for
Detailed Design) |
CEDD |
Mid-2021 |
End-2021 |
NA |
NA |
|
Present Project (Pier Improvement Works) |
CEDD |
2023 |
2025 |
NA |
NA |
|
Improvement
of Trails and Provision of Facilities in Sha Tau Kok |
Home Affairs
Department |
2015 |
2019 |
As the works area near the Project have completed
before the start of the Project, no cumulative impacts are anticipated. |
No environmental impacts are expected from the
concurrent project. No cumulative impacts are anticipated. |
Note:
[1] NA – Not Applicable
2.11
Summary of Environmental
Benefits and Environmental Achievements of the Project
2.11.1.1
Throughout
the EIA study, site constraints and impacts have been identified and assessed
and mitigation measures/good site practices/ enhancement measures, if necessary, have been recommended to avoid negative environmental
impacts to the surroundings. In addition, comments from district councils, residential, communities,
green groups and other stakeholders have also been reviewed and incorporated
where practicable. A number of environmental initiatives covering good managing
practices, waste minimisation and natural conservation have been recommended
for incorporation in the detailed design.
2.11.1.2
A
summary of the key environmental benefits and achievements of the Project is
given in Table 2.10 for reference:
Table 2.10 Key Recommended Mitigation Measures/Good
Site Practices/ Enhancement Measures and their Associated Benefits
|
Key
recommended mitigation measures/good site practices/enhancement measures |
Associated
Benefits |
|
|
Air Quality |
·
Routing
of barges used for delivery of goods should be as far away from the
identified ASRs as practicable. ·
The
number of boat trips should be minimised as far as practicable by appropriate
planning. |
·
Protect air
sensitive receivers by reducing fugitive dust emission |
|
Noise |
·
Use of Quality Powered Mechanical Equipment
(QPME). ·
Use of temporary noise barriers to screen
noise from relatively static Powered Mechanical Equipment (PME). ·
Alternative use of plant items within one
worksite, wherever practicable. |
·
Protect noise
sensitive receivers by reducing construction noise impact |
|
Water Quality |
·
Water quality monitoring. ·
Adoption of good site practices for
foundation works, such as use of silt curtains and pile casings, to avoid and
minimise water quality impacts. ·
Excavation should
only be conducted inside pile casing. Only one grab should be used at the
same time. ·
Only 1-2 piles to be
constructed at the same time. ·
Prefabrication
construction method should be adopted as far as practicable. ·
Contractor to prepare Emergency Spillage
Plan for accidental spillage of chemicals. |
·
Protect the
neighbouring water sensitive receivers such as coral, seagrass and mangrove |
|
Waste Management |
·
Good waste management and control
practices to avoid generation of excessive amount of waste materials. ·
Employ waste collectors for
disposal of general refuse to prevent potential nuisance caused by
mistreating general refuse, such as windblown, vermin, water pollution and
visual impact. ·
Good management practices for handling and
disposal of marine sediments at dedicated marine disposal sites. |
·
Minimise
waste generation ·
Ensure
proper handling of chemical waste |
|
Land Contamination |
·
No
mitigation measures would be required. |
·
No land contamination
anticipated |
|
Ecology |
·
Seagrass monitoring ·
Pre-construction dive survey to verify the
conditions of small coral colonies on the existing LCW pier before
construction works ·
Avoidance of encroaching the trees
in particular within the country park. ·
Priority using eco-tiles or eco-concrete for
the surface of the foundation to promote seamless integration of biodiversity
into the pier design. |
·
Minimise
the impact to coral, seagrass bed and mangrove stand in proximity to the
Project ·
Protect
trees in country park ·
Enhance
biodiversity of the site |
|
Landscape and Visual |
·
Sensitive design and disposition of the pier
structures to minimise visual intrusion to VSRs as far as practicable. |
·
Enhance the visual
appearance for the operational phase |
|
Fisheries |
·
Avoidance of mariculture site and waters of
high fisheries production ·
Adoption of good
site practices for water quality in marine works to ensure no adverse
fisheries impact would be anticipated. |
·
Protect
fisheries resources |
|
Cultural Heritage |
·
No mitigation
measures would be required. |
·
No impact
of cultural heritage anticipated |