2.1.1.1
The Project is situated at North Lantau and Tsing
Yi. It consists of a cable-supported bridge which spans over the Ma Wan Fairway
(MWF) and Kap Shui Mun
Fairway (KSMF). The areas in close
vicinity of the Project site in Tsing Yi are mainly occupied by industrial uses
(e.g. cement works, dockyard, oil depots, etc.), while the project area in
North Lantau is zoned as green belt where North Lantau Highway is located in the
vicinity with some
village houses or temporary structures scattering in San Po Tsui, Yi Chuen and
Tso Wan.
2.1.1.2
The
2017 and 2018 Policy Addresses indicated that a Feasibility Study on Route 11
(between Yuen Long and North Lantau) shall be commenced as soon as possible for
the long-term development of Northwest New Territories (NWNT), and to enhance the road network
connecting to Hong Kong International Airport (the airport) and cope with the long-term development of
Lantau Island. The findings of the Traffic Impact Assessment (TIA) Study
indicated that Route 11, serving as an additional route for the urban-bound
vehicles from NWNT, would attract more traffic to Lantau Link, thus causing delays for access to
the major developments on Lantau Island, including the airport. Hence, the TIA Study recommended
that a new highway infrastructure downstream of Route 11, i.e. Tsing Yi -
Lantau Link (TYLL), should be completed in tandem with Route 11.
2.1.1.3
HyD
commissioned another consultancy study titled “Feasibility Review of Tsing Yi -
Lantau Link – Feasibility Study” (hereinafter referred to as “TYLL FS”) under
Agreement No. CE 50/2020 (HY) in March 2021 to ascertain the technical
feasibility of TYLL and determine a preferred alignment, taking account of the
latest planning and development parameters.
2.1.1.4 Subsequently,
HyD commissioned an Investigation, Design and Construction consultancy of the
Project in May 2023, to review the findings of previous feasibility study,
identify the recommended alignment, conduct impact assessments on environment,
traffic, marine, land and other related aspects, and carry out site
investigation, detail design and supervision on construction works for
TYLL.
2.2.1
Objective of the Project
2.2.1.1
The
objective of the Project is to provide a new road connecting Route 11 on Lantau
Island and Tsing Sha Highway at Tsing Yi serving as an alternative route to
Lantau Link for the vehicles commuting between NWNT and urban areas, thus
improving the traffic condition of Lantau Link which is the vital road
connection between developments / infrastructures (including the airport and
Hong Kong-Zhuhai-Macao Bridge (HZMB)) on Lantau Island and the urban areas.
2.2.2
Need of the Project
2.2.2.1 To meet the traffic demands arising
from developments in the NWNT (including the Hung Shui Kiu / Ha Tsuen New
Development Area (NDA) and the Yuen Long South Development), a group of major
roads are earmarked for future developments, which comprises Route 11 (section
between Yuen Long and North Lantau), Tuen Mun Bypass, TYLL and Widening of Yuen
Long Highway (section between Lam Tei and Tong Yan San Tsuen).
2.2.2.2 According
to the traffic impact assessment carried out as part of
the TYLL FS, the traffic capacity of the Lantau Link will not be able to cope with
the additional traffic commuting between the NWNT/ Lantau and the urban areas
via Route 11 and Lantau Island after the completion of Route 11. Hence, TYLL is required to ameliorate future
traffic condition on Lantau Link.
2.2.2.3 The
Project serves as a major carriageway connecting North Lantau, the proposed
Route 11 (section between Yuen Long and North Lantau), and Tsing Yi. It is expected the
Project will greatly improve the traffic conditions on Lantau Link which
is the vital road connection between developments / infrastructures (including
the airport and HZMB) on Lantau Island and the urban areas.
2.2.2.4
Furthermore, the
Project can serve as an alternative route to the existing Lantau Link for
vehicles commuting between Lantau Island and the urban areas. This will improve
the resilience of the NWNT traffic network in the event of traffic incidents or
emergencies in major roads. By providing
multiple access points and connections to major roads in NWNT, the Project and
Route 11 will serve as a reliable pathway for redirecting traffic towards urban
areas during such events. Moreover, the
Project and Route 11 will act as a strategic route connecting NWNT and urban
areas to Lantau, thereby enhancing the overall resilience of the road network
connecting to the airport and HZMB.
2.3
Consideration of “With” and “Without” Project Scenarios
2.3.1
Consideration of “Without” Project
Scenario
2.3.1.1
Without the
implementation of the Project, substantial amount of traffic load from new and
existing developments in NWNT heading towards Tsuen Wan, West Kowloon, Lantau
Island and Hong Kong Island, etc. would have to rely on the existing Tuen Mun
Road or Lantau Link. The traffic impact assessment indicates that the Tuen Mun
Road and Lantau Link would not have sufficient capacity to handle the future
traffic demands, resulting in traffic congestion anticipated during peak hours, consequently leading to
higher vehicular emissions from decreased traffic speeds.
2.3.2
Consideration of “With” Project
Scenario
2.3.2.1
Upon completion of the
Project, TYLL is expected to ameliorate the forecast traffic condition on Lantau Link and major roads
connecting the NWNT and the urban areas, increase route choices and strengthen
the resilience of the entire road network.
Together with other road projects that are currently under
implementation, TYLL is also expected to help create traffic capacity to
effectively unleash the development potential of the NWNT and Lantau Island
effectively.
2.3.2.2
The implementation of
the Project results in a significant improvement in the traffic conditions
between NWNT and urban areas, including Tsing Yi, NWNT and Lantau Island. Additionally, it brings benefits to the overall
transport system by introducing alternative route choices for commuting
traffic, ameliorating the traffic condition of
Lantau Link. Through the optimisation of
the Project's alignment, it achieves more than just reducing travel time for
road users; it also effectively reduces energy consumption and minimises
environmental impact on the neighbourhood.
2.4.1.1
As mentioned in the
above sections, the existing major roads such as Tuen Mun Road and Lantau Link
would experience traffic congestion during peak hours. The Project would
ameliorate the traffic conditions on these major roads and reduce the potential
air quality and noise impacts to the neighbouring sensitive receivers.
2.4.1.2
Furthermore,
eco-shoreline features would also be incorporated on newly established coastal
structures and shorelines. It is
expected that these features will facilitate the recruitment, settlement and
colonisation of marine benthos, thereby enhancing the overall quality and
diversity of associated marine ecosystems in the vicinity.
2.5.1
Location and Scope of the Project
2.5.1.1
The location of the
Project is shown in Figure 2.1.1. The scope of the Project comprises the following:
(a) construction
of the cable-supported bridges crossing the MWF and KSMF (hereinafter referred
to as the “Main Bridges”) including:
(i) a
dual three-lane 3-span continuous and earth-anchored suspension bridge crossing
the MWF between Ma Wan and Tsing Yi with a main span of about 1400m;
(ii) a
dual three-lane earth-anchored single-tower suspension bridge crossing the KSMF
between North Lantau and Ma Wan with a main span of about 500m;
(b) construction
of North Lantau Interchange, consisting of slip roads, tunnel and viaducts at
North Lantau to connect the cable-supported bridge crossing the KSMF to North
Lantau Highway, the proposed Tsing Lung Bridge under Route 11 and the proposed
Hong Kong Island West – Northeast Lantau Link (HKIW-NEL Link);
(c) construction
of Tsing Yi Connection, consisting of extension of the TYLL mainline from the
proposed cable-supported bridge crossing the MWF to connect with the Tsing Sha
Highway at the west of Nam Wan Tunnel and provision of slip roads and viaducts
to connect with the local roads in Tsing Yi;
(d) construction
of viaduct at Ma Wan South to connect the cable-supported bridges;
(e) modification
/ realignment of Tsing Sha Highway and Cheung Tsing Highway northbound; and
(f)
associated works including civil, marine, drainage,
sewerage, road works, traffic aids, street lighting, traffic control and
surveillance system (TCSS), toll collection facilities, bridge facilities, fire
services works, electrical and mechanical (E&M) works, re-provisioning of
facilities affected and utility diversion, environmental mitigation works,
landscaping works, site clearance and demolition, earth works, slope works,
geotechnical works, natural terrain hazard mitigation works, reclamation works,
etc.
2.6
Design Changes to the Project
2.6.1
General
2.6.1.1
Subsequent to the issue of the EIA Study Brief (No.
ESB-359/2023) in June 2023, the Project Proponent has been optimising the
alignment and design of the Project proactively to avoid and minimise
environmental impacts where practicable. The Project Proponent had sought and
received confirmation that a fresh study brief is not required due to these
changes in accordance with Section 6.2 of the study brief. The assessments to
these changes have been included under this EIA Study and the summary of the
key project design changes are summarised in the sections below. Details of alignment are shown at Figure 2.1.1 to Figure 2.1.4.
2.6.2
Exclusion of Tsing Yi Road West
Connection Viaduct (TYRWV)
2.6.2.1
Under
the original planning of the Project in the feasibility study, a slip road in
the form of a viaduct, i.e. TYRWV, was proposed to connect the mainline of the
Project with Tsing Yi Road West. The construction of this around 1.7km long
TYRWV abutting Sai Tso Wan Road will require slope works/retaining structures
and temporary works, which will generate construction and demolition materials
and cause impact to nearby sensitive receivers. In this design development, it
was found that this TYRW could be excluded while maintaining necessary
connection with minor adjustment to the interchange.
2.6.2.2
This arrangement will also
increase the horizontal
distance between the proposed road under the Project and the sensitive
receivers along Sai Tso Wan Road. To
illustrate this point, the closest distance between the proposed roads and the
existing Potentially Hazardous Installation (PHI), namely Shell Tsing Yi
Installation, will increase from 20m in the Project Profile to 60m in the
current scheme. This would not only reduce the risk to road users but also
minimise the environmental impacts such as air quality impact in both
construction stage and operation stage.
2.6.3
Reduction in Total Reclamation Area
2.6.3.1
Earlier design of the Project
as shown in the Project
Profile included reclamations in North Lantau, Ma Wan and Tsing Yi to
accommodate the towers and anchorages of long span bridges. Subsequently, the
alignment has been refined and the bridge form has
been changed, the
extent of the proposed reclamation works has also been reviewed with due
consideration to the engineering, environmental and marine operation aspects.
As a result, the footprints of the proposed reclamations are reduced. One of
the refinements include the avoidance of reclamation at North Lantau by
adopting a pile-supported Vessels Impact Protection System (VIPS) at the existing shoreline at North
Lantau. The VIPS provides protection to the bridge pier against vessel impact,
hence eliminating the need for reclamation. As a result, the total reclamation
area in the current scheme (about 19.8 hectares) is reduced by about 4.1
hectares (17%) when compared with the original scheme in the Project Profile
(about 23.9 hectares).
2.6.4
Rearrangement of the slip road
tunnel connecting to the proposed HKIW-NEL Link to separate tunnel tubes and
confirmed layout of slip roads connecting to North Lantau Highway
2.6.4.1
The
scope of the Project includes the construction of slip roads, viaducts
and a road tunnel at North Lantau connecting the mainline of the Project to the
proposed HKIW-NEL Link and North Lantau Highway. During
the preparation of the Project Profile, the planning and design of the proposed
HKIW-NEL Link and the road alignment of the Project was still at a very
preliminary stage. Therefore, we could only include an indicative arrangement
of such connection in the Project Profile.
2.6.4.2
Further
to the preliminary design of the Project, rearrangement of the slip road tunnel
as two distinct tunnel tubes (one for each traffic bound) less than 800 m in
length between portals was found to be required in order to
maintain sufficient vertical clearance from the mainlines of the Project and
the HKIW-NEL Link. Nevertheless, the tunnel portals at both ends would stay at
a similar location.
2.6.4.3
The
current scheme of the road alignment design also includes two slip roads
connecting to North Lantau Highway (eastbound and westbound). In the design, the routing and elevation were
adjusted to minimise the required slope cutting works.
2.6.4.4
Similar
ecological profile, habitat compositions and conditions to the original scheme
are observed in the concerned areas (such as shrubland of low to moderate
value, developed area and plantation of low ecological value). The scope of key
environmental issues such as noise impact, air quality impact, terrestrial
ecological impact, etc. need to be assessed as identified in the Project
Profile are still covered in the current scheme. While the assessment area of the applicable
impact assessments in the EIA study had been adjusted according to the revised
boundary of the revised road and tunnel alignment, there is no additional
environmental issue associated with the proposed changes presented in the
current scheme.
2.7
Consideration of Alignment Options
2.7.1
General
2.7.1.1
Having
thoroughly reviewed the possible alignment options of the TYLL mainline
investigated in the TYLL FS, recommendations from the public, and other
alternative options, the recommended alignment option (Figure 2.1.1 refers) is still considered as the
most cost effective and environmentally friendly alignment option of the TYLL
mainline for connecting North Lantau and Tsing Yi. It was therefore selected based on various
engineering and environmental factors and will be taken forward for design and
construction of the Project.
2.7.1.2
The
following sections present the key elements and construction methodologies
adopted in determining the most cost effective and environmentally friendly
alignment option.
2.7.2
Tunnel Options for Crossing Fairways
under Previous Stages of the Project
2.7.2.1
The
tunnel options crossing both the KSMF and MWF near the fairway junction area in either immersed
tube tunnel or tunnel boring machine form, followed by various landing points
at Tsing Yi and Lantau in different structural forms were reviewed and
evaluated in the previous stages of the Project. All tunnel options for crossing the fairways were not recommended
after considering their traffic planning, engineering and constructability, environmental
issues, marine aspect, programme, cost as well as impact on local community and
public acceptance.
2.7.3
Landing
Point Options in Tsing Yi and Lantau
2.7.3.1 Other
than the current recommended alignment, three alternative landing options are considered for
this section of the Project, namely Alternative Landing Option 1, Alternative
Landing Option 2 and
Alternative Landing Option 3 (see Figure 2.1.5).
2.7.3.2
The current recommended alignment connects North Lantau
Highway and Route 11 via an interchange at Ng Kwu Leng, crosses the KSMF and
MWF by long span bridges, lands at the Hongkong United Dockyards (HUD) at Tsing
Yi west, and connects to Tsing Yi North coastal Road, Cheung Tsing Highway and
Tsing Sha Highway via slip roads.
2.7.3.3
Alternative Landing Option 1 connects North Lantau
Highway and Route 11 via an interchange at Ng Kwu Leng, crosses the KSMF and
MWF both at a skewed angle by two long span bridges, followed by slip roads and
a land tunnel after landing at the south-west of Tsing Yi, and finally connects
with Cheung Tsing Tunnel via Tsing Yi Road West and Tsing Sha Highway. For
Alternative Landing Option 1, additional reclamation works would be required
near Tang Lung Chau and Tsing Yi west.
In addition, considerable amount of slope works
and tunnel works associated with the proposed slip roads in Tsing Yi west would
be involved, leading to
a higher volume of excavated materials and associated construction dust
impacts.
2.7.3.4
Alternative Landing Option 2 connects North Lantau
Highway and Route 11 via San Po Tsui, crosses the KSMF and MWF by two long span
bridges, lands at Wok Tai Wan, and connects to Tsing Yi North Coastal Road,
Cheung Tsing Highway and Tsing Sha Highway via slip roads. For Alternative Landing Option 2, similarly,
additional reclamation works at Tsing Yi west would be required for supporting
the slip roads connecting to Tsing Yi North Coastal Road and the back span at the
eastern end of the long span bridge. Moreover,
the alignment is in close proximity to Ma Wan
residential areas, a theme park and the Ma Wan Tung Wan Beach. Major visual and environmental impacts to the
residents, visitors and beach users are expected.
2.7.3.5
Alternative Landing Option 3 connects North Lantau
Highway and Route 11 via an interchange at Ng Kwu Leng, crosses the KSMF and
MWF by long span bridges, lands at the Shell Tsing Yi Installation at Tsing Yi
west, and connects to Cheung Tsing Highway and Tsing Sha Highway via slip
roads. Alternative Landing Option 3 might require the
shifting of Cheung Tsing Highway towards northeast into existing slope. Therefore, substantive slope works, including
significant additional construction and demolition material, as well as
environmental impact. The landing point
is located at a reduced distance to the air sensitive receivers (ASRs) in Sai Tso Wan and the two existing PHIs, namely Chevron Hong
Kong Limited Tsing Yi Terminal and Shell Tsing Yi Installation. This would result in relatively greater
potential direct impacts and long-term indirect disturbances to the
environmental sensitive receivers.
Besides, Alternative Landing Option 3 is located right beside Shell
Tsing Yi Installation and is susceptible to higher risk to life of the road
users in case of fire in oil depot.
Table 2.1 Summary
of Landing Options
|
Alignment
Option
|
Pros
|
Cons
|
Recommended
Option (Y/N)
|
|
Engineering
Factors
|
|
Recommended Alignment
|
·
Connection to the Tsing Yi North Coastal Road, Cheung Tsing Highway
and Tsing Sha Highway.
·
Adequate separation between TYLL and Tsing Ma Bridge to prevent
aerodynamic interference.
· Smaller reclamation
extent compared to Alternative Landing Options 1 and 2.
|
|
Y
|
|
Alternative Landing Option 1
|
|
·
No connection to the Tsing Yi North Coastal Road.
·
Travelling distance is about 40% longer than the Recommended Alignment
and may degrade the traffic performance and affect its utilisation, which may
in turn undermine its intended function to divert traffic from other existing
routes such as Tuen Mun Road and the Lantau Link.
·
Additional reclamation works near Tang Lung Chau and Tsing Yi west and
considerable amount of cut slopes and tunneling works associated with the
proposed slip roads in Tsing Yi west would be required, hence resulting in
higher capital and long-term maintenance cost.
|
N
|
|
Alternative Landing Option 2
|
|
· Aerodynamic
interference of two closely-spaced long-span bridges
would cause road safety concerns on both Tsing Ma Bridge and TYLL.
· Additional
reclamation works near Tsing Yi west and realignment of MWF would be
required, hence resulting in higher capital and long-term maintenance cost.
|
N
|
|
Alternative Landing Option 3
|
|
·
Inadequate space and headroom for proposed slip road connection to
Cheung Tsing Highway and Tsing Sha Highway due to the presence of several
layers of existing viaducts at merging / diverging points.
|
N
|
|
Environmental
Factors
|
|
Recommended Alignment
|
·
Smaller reclamation extents when compared with Alternative Landing
Options 1 and 2.
·
Adequate distance maintained between the project and PHIs.
|
|
Y
|
|
Alternative Landing Option 1
|
|
·
Additional reclamation works near Tang Lung Chau and Tsing Yi west and
considerable amount of cut slopes and tunneling works associated with the
proposed slip roads in Tsing Yi west would be required.
·
Generate large amount of construction
and demolition materials.
|
N
|
|
Alternative Landing Option 2
|
|
·
Proposed alignment and its associated reclamation would be very close
to the existing residential blocks of Ma Wan and Ma Wan Tung Wan beach,
resulting in significant visual and environmental impacts.
|
N
|
|
Alternative Landing Option 3
|
|
·
Proposed alignment is close to the existing oil depot and there might
not be adequate space for constructing hazard mitigation measures.
|
N
|
2.7.4
Tsing Yi Option 1 selected from
previous stages of the Project
2.7.4.1
The
Tsing Yi Option 1 selected from previous stages (alignment
shown on Project Profile) connects with North Lantau Highway and Route 11 via an
interchange at Ng Kwu Leng, crosses the KSMF and MWF, and finally connects with
Tsing Sha Highway on the west of Nam Wan Tunnel after landing on Tsing Yi. This Tsing Yi Option 1 in bridge form
excelled in engineering and constructability, environmental issues, programme,
cost, impact on local community, public acceptance criteria, transport planning
and marine aspect.
2.7.4.2
The
Tsing Yi Option 1 has been reviewed and the following
design refinements and / or modifications were considered, refined or explored:
-
(a)
Appropriate widening of the marginal strips or hard
shoulders to ensure adequate forward traffic visibility, which would affect the
road design shown in the Tsing Yi Option 1 and require shifting the Cheung
Tsing Highway northbound further west;
(b)
Eliminate the Tsing Yi Road West viaduct by
incorporating it into the Cheung Tsing Highway;
(c)
Provide access for traffic from CTT westbound to TYLL westbound;
(d)
Minimise retaining wall height at Tsing Yi;
(e)
Provide similar connectivity for TYLL and Lantau Link
at Tsing Yi;
(f)
Consider the local geological fault line at Ma Wan;
(g)
Reduce of cut slope extent at TYLL interface with
Route 11 and North Lantau Highway; and
(h)
Provide minimum 270m separation from Tsing Ma Bridge
from the aerodynamic performance viewpoint.
2.7.4.3
In
view of the above, other alignment options comprising sections of tunnels,
viaducts, at-grade roads and cable-supported bridge have been considered for
the Project. In consideration of the
alignment options, the Project is presented in the following two sections: -
(a)
Tsing Yi Connection; and
(b)
Main Bridges cum North Lantau Interchange.
2.7.4.4
The
alignment options for the two sections of the Project are discussed in the
sections below.
2.7.5
Tsing Yi Connection
General
2.7.5.1
Tsing
Yi Connection of the TYLL is located at the west of the Nam Wan Tunnel and the
CTT. Being west of these two tunnels
provides better opportunities to merge with and diverge to the existing road network on the
western side of Tsing Yi.
2.7.5.2
The
alignment of TYLL is restricted by the landing points on Tsing Yi, where oil
depots and shipyards are located.
Furthermore, the location of the TYLL should be on the south side of the
existing Tsing Ma Bridge such that direct connectivity with the HKIW-NEL Link,
CTT, and Nam Wan Tunnel can be developed.
The TYLL will connect with Tsing Sha Highway at the Tsing Yi Connection.
2.7.5.3
There
are three alignment options considered for this section of the Project, namely
Tsing Yi Option 1, Tsing Yi Option 2 and Tsing Yi Option 3 (Recommended) (see Figure 2.3, Figure 2.4 and Figure 2.5, respectively). The comparison of these three options is
presented in Figure
2.9.
Tsing Yi Option 1
2.7.5.4
Realignment
of Tsing Sha Highway northbound lanes proposed in this option requires a high
and few hundred metres long retaining wall structure at a steep slope. Construction of the high and long retaining
wall would pose construction and programme risks to the Project and therefore
should be reviewed.
2.7.5.5
Tsing
Yi Road West viaduct connection to TYLL Bridge (hereafter referred to as
TYRW-TYLL Viaduct) into Tsing Sha Highway under the Tsing
Yi Option 1 requires ground-level space for columns / foundations, which
may obstruct current and future land uses adjacent to Sai Tso Wan Road. The eastbound TYLL diverging to the TYRW-TYLL
Viaduct should take into account the cable arrangement of the TYLL
Main Bridge design.
2.7.5.6
There
is no connection between the CTT westbound and the TYLL westbound proposed
under the Tsing Yi Option 1.
2.7.5.7
The
existing slip road connections at Northwest Tsing Yi Interchange and Tsing Sha
Highway near Liu To Shan connecting CTT, Nam Wan
Tunnel, Tsing Yi Road West, Tsing Yi North Coastal Road, Ting Kau Bridge and
Tsing Ma Bridge are complicated with various merging, diverging and weaving
movements. It is noted that the existing connectivity needs to
be maintained and the TYLL Main Bridge should have the same or similar
connectivity to the existing road network.
2.7.5.8
The
TYLL will not connect with CTT directly.
To provide a connection between TYLL and CTT, widening towards the east
side is feasible but should be avoided (subject to engineering design) to avoid deep cutting
of the existing slope adjacent to Cheung Tsing Highway eastbound. There would also be insufficient weaving
length for the traffic from TYLL eastbound to CTT eastbound; and the traffic
from Tsing Sha Highway to Tsing Yi Road West.
Therefore, the alignment should be widened towards the west side. This widening would increase slope works in
Tsing Yi, leading to a higher volume of excavated materials and associated
construction dust impacts. It would also
reduce the distance from the proposed roads to the ASR in Sai Tso Wan and
the two existing PHIs, namely Chevron Hong Kong Limited Tsing Yi Terminal and
Shell Tsing Yi Installation to approximately 20m. This would result in
relatively greater potential direct impacts and long-term indirect disturbances
to the environmental sensitive receivers.
Tsing Yi Option 2
2.7.5.9
Tsing
Yi Option 2 is developed and refined from Tsing Yi Option 1. A new slip road was
proposed to connect Nam
Wan Tunnel and TYLL westbound lane directly, removing a two-lane width spatial
requirement on the existing Tsing Sha Highway and eliminating the need for extensive slope work in
Tsing Yi. This option would increase
slope works along Cheung Tsing Highway, require more land lot areas for
construction of elevated roads and vehicles movement would be closer to air and
noise sensitive receivers.
Tsing Yi Option 3 (Recommended)
2.7.5.10
Tsing
Yi Option 3 (Recommended) is developed based on the Tsing Yi Option 1 and Tsing
Yi Option 2. Tsing Yi Option 3
(Recommended) has the same connectivity as the Tsing Yi Option 1 with less extensive slope work in
Tsing Yi and accommodating the following modifications: -
(a)
TYRW-TYLL
Viaduct incorporated into the Cheung Tsing Highway, this modification
will reduce the total number of retaining walls and temporary working
platforms, thereby minimising land impact; and
(b)
Provision
of direct traffic connection from CTT westbound to TYLL westbound as an
alternative route to the Lantau Link to improve traffic resilience.
Summary of Alignment Option Considered
2.7.5.11
A
summary of the above options for Tsing Yi Connection is given below with the
recommended option identified.
Table 2.2 Summary
of alignment options for Tsing Yi Connection
|
Alignment
Option
|
Pros
|
Cons
|
Recommended
Option (Y/N)
|
|
Engineering
Factors
|
|
Tsing Yi Option 1
|
·
Direct connection to Tsing Yi Road West.
|
· TYRW-TYLL
Viaduct requires land adjacent to Sai Tso Wan Road.
· No
direct connection between TYLL and CTT.
·
Large temporary working platforms are anticipated
for the construction of bored pile wall along existing slopes.
|
N
|
|
Tsing Yi Option 2
|
· The
amount of retaining structures is less than the Tsing Yi Option 1.
|
· TYRW-TYLL
Viaduct requires land adjacent to Sai Tso Wan Road.
· Appropriate
widening of the marginal strips or hard shoulders to satisfy adequate forward
visibility distance.
·
No direct connection between TYLL and CTT.
|
N
|
|
Tsing Yi Option 3 (Recommended)
|
· The
amount of retaining structures is fewer than the Tsing Yi Option 1 and 2.
· The
modification of existing road is less than Tsing Yi Option 2 by approximately 4.3km.
· Direct
connection of TYLL westbound and CTT westbound.
· TYRW-TYLL
Viaduct incorporated into Tsing Sha Highway.
|
· Appropriate
widening of the marginal strips or hard shoulders to satisfy adequate forward
visibility distance.
· Large
temporary working platforms are anticipated for the construction of bored
pile wall along existing slopes.
|
Y
|
|
Environmental
Factors
|
|
Tsing Yi Option 1
|
|
· Affect
large number of trees (~909 nos. of trees) at
existing slope.
· Closer
to the two existing PHIs (~20m) and ASRs at Sai Tso Wan.
·
Large construction area
would impose greater environmental implication.
|
N
|
|
Tsing Yi Option 2
|
|
· Affect
large number of trees (~909 nos. of trees) at
existing slope.
· Closer
to the two existing PHIs (~10m) and ASRs at Sai Tso Wan.
· Large construction area would impose greater environmental
implication and generate higher amount of construction waste.
|
N
|
|
Tsing Yi Option 3 (Recommended)
|
· Omission
of viaduct connection leads to smaller construction works area and minimise
landscape and visual impacts.
· Affect smaller number of trees (~461 nos. of
trees) at existing slope.
· The
works area is reduced by 15 ha as compare
with Tsing Yi Option 1 and 2
|
|
Y
|
General
2.7.6.1
The
signature element of the proposed TYLL will be the approximately 3.3km
long-span bridges crossing over the MWF and the KSMF from Tsing Yi Connection
to North Lantau Interchange. The mainline of TYLL will then connect to Route 11
in a dual-2-lane arrangement. Four slip
roads of TYLL will also be provided as listed below: -
(a)
North
Lantau Highway eastbound and TYLL eastbound;
(b)
North
Lantau Highway westbound and TYLL westbound;
(c)
HKIW-NEL
Link southbound and TYLL westbound; and
(d)
HKIW-NEL
Link northbound and TYLL eastbound.
2.7.6.2
The
TYLL will connect to Route 11, North Lantau Highway, and the proposed HKIW–NEL
Link at North Lantau Interchange. There are two alignment options considered for
two long-span bridges cum associated connection at North Lantau Interchange,
namely Main Bridges cum North Lantau Option 1 and Main Bridges cum North Lantau
Option 2 (see Figures 2.6 and 2.7)
which are presented below.
2.7.6.3
Main
Bridges cum North Lantau Option 1 is developed based on the proposed alignment
in the Project Profile, and consists of an
earth-anchored twin-tower suspension bridge across MWF, and a cable-stayed
bridge across KSMF. There is a portion
of the viaduct structure in between the cable-supported bridges.
2.7.6.4
One
land anchorage at Tsing Yi and one marine anchorage are required for the
suspension bridge across MWF. A large
marine anchorage is required to support the larger resultant force from the
bridge structure acting on the anchorage.
2.7.6.5
A
major constraint to this bridge form for KSMF would be the Disneyland Height
Restriction. Although technically
feasible, a relaxation to the restriction is required in
order to proceed with this bridge form.
In addition, the Lantau backspan stay-cable may interfere with the
existing helicopter flight path. The design of the cable-stayed bridge would
take into consideration the challenging interfacing issues and offer helicopter
pilots sufficient horizontal and vertical clearances with the bridge structural
elements for the safe operation of helicopters.
2.7.6.6
A
straight backspan alignment is required to facilitate the efficient design and
construction of the cable-stayed bridge, hence limiting the flexibility for
optimising the North Lantau Interchange alignment. The requirements for the connection at North
Lantau, constrained by the need for a tie-in with HKIW-NEL Link, also lead to a
widened Lantau side span of the cable-stayed bridge to cater for the merging /
diverging arrangement for the proposed slip roads (two lanes for
each direction) connecting HKIW-NEL Link.
Widening of the side span by the same width is required to minimise
unbalanced effects on the cable-stayed system.
The unconventional deck arrangement will complicate the design and
construction of the cable-stayed bridge, and an increase in site formation and
tunnelling works are also required on Lantau Island.
Main Bridges cum North Lantau Option 2 (Recommended)
2.7.6.7
Main
Bridges cum North Lantau Option 2 consists of an earth-anchored twin-tower
suspension bridge across MWF and an earth-anchored single-tower suspension
bridge across KSMF. There is a portion
of ground-supported viaduct structure in between the suspension bridges.
2.7.6.8
One
land anchorage is required for each suspension bridge. The suspension cables for both bridges are
also rigidly supported by the common marine anchorage adjacent to the
south-eastern corner of the Ma Wan Island shoreline. The shared marine anchorage is lowered to
below deck level. The size of the marine
anchorage is also optimised as the horizontal forces from the two suspension
bridges can be balanced and thus reduce the size of the common anchorage. Part of the common anchorage will be embedded
below ground.
2.7.6.9
On
the western side of the single-tower suspension bridge across KSMF, the
prismatic cable-supported portion of the bridge deck terminates at the Lantau
shoreline. This arrangement allows the
main alignment of TYLL to turn northeast towards Route 11 upon approaching
Lantau Island thus minimising the extent of slope cut required for the
construction of the proposed North Lantau Interchange. The slope cutting on the North Lantau side
will be reduced compared to Option 1 due to elimination of the straight side-span.
Summary of Alignment Option Considered
2.7.6.10
A
summary of the above options for Main Bridges cum North Lantau Interchange is
given below with the recommended option identified.
Table 2.3 Summary of alignment
options for Main Bridges cum North Lantau Interchange
|
Alignment
Option
|
Pros
|
Cons
|
Recommended
Option (Y/N)
|
|
|
Engineering
Factors
|
|
Main Bridges cum North Lantau Option 1
|
·
Full closure to KSMF is not required for cable-stayed bridge
construction.
|
·
KSMF cable-stayed bridge does not comply with Disneyland Height Restrictions.
·
Reduces the airspace at North Lantau Interchange for helicopter
flights.
·
Increased deck width of Lantau side span is required to cater for the
merging/diverging length.
·
Significant increase in site formation and tunnelling works required
on North Lantau Island.
|
N
|
|
|
Main Bridges cum North Lantau Option 2
(Recommended)
|
· Complies
with Disneyland Height Restrictions.
· Curved
alignment begins at Lantau Shoreline with reduced site formation works.
|
· One-off
short duration of full closure at KSMF is required.
|
Y
|
|
|
Environmental
Factors
|
|
Main Bridges cum North Lantau Option 1
|
|
·
Require reclamation at North Lantau and larger reclamation area in Ma
Wan. The total reclamation area is
approximately 26.3 ha.
·
Generate large amount of marine sediment due to larger reclamation
area.
·
Affect larger number of trees (2,420 nos. of trees).
|
N
|
|
|
Main Bridges cum North Lantau Option 2
(Recommended)
|
· Reclamation
at North Lantau is not required.
· The total
reclamation
area is approximately 19.8ha.
Reduced the overall area of reclamation by approximately
6.5 ha as compared with Main Bridges cum North Lantau Option 1.
· Minimise
slope cutting at North Lantau which in turn preserves the natural features of
the area hence minimising ecological impacts and tree felling.
· Affect smaller number of trees (1,920 nos. of
trees).
|
|
Y
|
|
2.8.1
Recommended Alignment for the
Project
2.8.1.1
The
Recommended Alignment is an integration of Tsing Yi Option 3 (Recommended) of
Tsing Yi connection and Main Bridges cum North Lantau Option 2 (Recommended) as
discussed in Section 2.7 above, which is highlighted in the following
sections. The Recommended Alignment is shown in detail in Figure 2.1.1 to Figure 2.1.4.
2.8.1.2
The
Recommended Alignment has the advantages as illustrated below:
(a)
Additional reclamation, site formation, slope cutting
and tunnel works are avoided, resulting in cost saving with less generation of
C&D materials, less environmental impacts and less impact to the natural terrain;
(b)
Encroachment of bridge towers into MWF is avoided,
hence less impact to marine traffic;
(c)
Aerodynamic interference between the existing Lantau
Link and the proposed TYLL, which results if the long span bridges are located
close to each other, is avoided; and
(d)
The provision of connection to Tsing Yi North Coastal
Road, and shorter travelling distance, render better traffic performance.
Tsing Yi Connection
2.8.1.3
Tsing
Yi Option 3 has the advantages below:
(a) Tsing
Yi Option 1 does not allow the traffic from CTT westbound to TYLL
westbound. A slip road connecting Cheung
Tsing Highway northbound and TYLL westbound is therefore proposed to facilitate
the westbound traffic of CTT to have a direct access to TYLL westbound and thus
better connectivity with CTT; and
(b)
With the provision of the slip road mentioned above,
both bound traffic between TYLL and the existing local road, i.e. Tsing Yi Road
West, can be maintained and the pair of slip roads running along Sai Tso Wan
Road proposed in the Tsing Yi Option 2 is no longer required. The enhanced Tsing Yi Connection under the
Recommended Alignment will be more cost-effective land impact is also
minimised.
Main Bridges cum North Lantau
Interchange
2.8.1.4
Main
Bridges cum North Lantau Option 2 has the advantages below:
(a)
On the western side of the single-tower suspension
bridge, the prismatic cable-supported portion of the bridge deck will terminate
at the approach to Lantau shoreline and allow the alignment of TYLL mainline to
turn northeast earlier towards Route 11 and thus can greatly minimise the
extent of site formation and slope cutting works for the construction of the
proposed North Lantau Interchange, resulting in cost saving with less
generation of C&D materials, less environmental impacts and less impact to
the natural terrain;
(b)
Owing to the termination of the bridge deck of
single-tower suspension bridge at the Lantau shoreline mentioned above, this
will not impose constraints on the design of the proposed North Lantau
Interchange and the connection with the slip roads of the interfacing projects;
(c)
The common marine anchorage for both suspension
bridges near the south-eastern corner of Ma Wan Island is modified. There will be a section of about 200 m long
free of suspenders in between the two suspension bridges. This section will be in the form of concrete
viaducts, resulting in cost saving with a shorter length of the side span of
the single-tower suspension bridge at the south of Ma Wan;
(d)
Taking into
account the bridge form for crossing the KSMF and the
modified layout of North Lantau Interchange, the alignment option with
single-tower suspension bridge form will have a noticeable lower overall
construction cost;
(e)
The airspace in the vicinity of the KSMF will continue
to be free in absence of a bridge tower on Lantau side and thus no interference
with the existing helicopter flight path; and
(f)
Single-tower suspension bridge will only have one
bridge tower located at the south of Ma Wan hence complying the Disneyland
Height Restrictions.
2.8.2
Work Area(s) / Site(s) and Their
Locations
2.8.2.1
The
works areas / sites were identified based on their intended use during
construction phase of the Project. Works
areas serve as locations for site offices and material storage during the
construction period. Works sites include
on-site construction activities such as site formation, excavation and
foundation works, etc. Transient and localised activities like temporary
traffic management schemes, outside the works areas / sites but within the
Project area are required. These
activities are not anticipated to have critical environmental impacts when good
site practices and control measures (e.g. Recommended Pollution Control Clauses
promulgated by EPD) are implemented. The
works areas / sites are shown in Figure 2.2 as the Project Boundary. The
works areas / sites will be reinstated and handed over upon Project completion
in 2033 tentatively.
2.8.2.2
The
Recommended Alignment of TYLL requires four reclamation areas with a total area
of 19.8 ha, to accommodate and protect the proposed bridge towers and anchorage
against ship collision impact. Tsing Yi Tower, Ma Wan South Tower, Ma Wan
South Anchorage and Kap Shui Mun Tower are the proposed bridge towers /
anchorage to be constructed on the reclamation areas. The reclamation areas are
shown in Figure 2.1.1.
2.8.2.3
There
are construction haul roads proposed at both ends of the TYLL. The construction haul roads at North Lantau
Interchange are mainly required for construction vehicles to transport
construction materials and personnels to works sites when there is no direct
connection to public road. The
construction haul roads at Tsing Yi Connection are required for the
construction vehicles / plants to access the proposed road realignment /
modification works on the existing slopes. The alignment
of construction haul roads can be adjusted on-site to minimise the impacts on
surrounding environment by maintaining separation distances from sensitive
receivers and implementing good site control measures. The construction haul roads shall be
reinstated upon Project completion.
2.9.1
Overview
2.9.1.1
The
key construction elements of the Project include tunnel, cable supported
bridges crossing MWF and KSMF, reclamation areas for the proposed bridge towers
and anchorage, viaducts and at-grade roads, see Figures 2.8.1
to 2.8.13. This section provides an
overview of the construction planning for the Project, focusing on key aspects
such as the anticipated methods and sequence of works for the essential
construction elements.
2.9.2
Construction Methodology for Tunnel
2.9.2.1
Considering
the available geological information, it is suggested that tunnel excavation
for the Project will primarily take place in areas with favourable geological
conditions. The commonly deployed
excavation methods, include drill-and-blast and mechanical methods such as
drill-and-break, would be adopted. The
choice of tunnel construction method primarily depends on local constraints and
the proximity of sensitive areas.
2.9.2.2
The
primary method of construction for the tunnel is expected to be the
drill-and-blast method, which involves controlled blasting to excavate medium
to hard rock. The potential
environmental impacts, specifically concerning noise, dust, and visual
disturbances, will be significantly decreased and limited to areas in close proximity to the portals. Considering the relatively short
length of the tunnel, daily delivery of explosive from Mines Division is
sufficient for the blasting works, thus no project specific magazine is
considered required.
2.9.2.3
Compared
to mechanical breaking methods, such as using rock breakers or excavators, the
drill-and-blast method is more effective for tunnel excavation. It
significantly reduces the construction period, providing both financial
benefits and faster project commissioning.
2.9.2.4
In
urban construction projects, the Tunnel Boring Machine (TBM) is frequently used
for tunnel construction. However, it is not deployed for constructing the tunnel in this
specific project. North Lantau mainly composes of igneous rocks,
which poses a challenge to TBM which is more likely to be utilised for softer
ground profiles. Moreover, TBM necessitate accurate navigation to ensure the
tunnel is constructed in the correct direction and right angle. Consequently,
challenges may arise when working on curved tunnels of shorter lengths under
TYLL. Furthermore, the cost of applying TBM is higher than employing
drill-and-blast method.
2.9.3
Construction Methodology for
Reclamation
2.9.3.1
As
stated in Chapter 4 of Project Administration Handbook (PAH) for Civil
Engineering Works published by Civil Engineering and Development Department, it
is Government Policy to leave the marine mud in-situ subject to site condition,
any dredging required shall have full justification and all relevant
implications reviewed.
2.9.3.2
In
view of thick marine deposits layer and its weak soil properties in TYLL, it is
technically required to dredge the whole layer of marine deposits and replace
it with firm materials for controlling the settlement of the reclaimed islands
and to ensure stability of the seawall structures. Taking into account the depth of the dredged trench, the extent and quantity of the
dredging work will be excessive.
2.9.3.3
It
is therefore considered that the fully dredged method is not applicable for the
whole reclamation extent of TYLL. It would only be applicable in local areas where non-dredged methods,
such as Deep Cement Mixing (DCM) and jet grouting methods, could not be carried
out on site. According to the geotechnical condition, rocks (potentially of
varying weathering grades), boulders / cobbles / gravels, sandy materials,
dumped materials and debris are present at the seabed in these areas. In view of these seabed features and the
relatively thin layers of marine deposits in local areas, dredging of limited
depths to remove thin and local marine deposits as well as various boulders /
cobbles / gravels / debris may be considered as a more practical method. In
case dredging is unavoidable, efforts will be made to minimise the extent of
dredging.
2.9.3.4
To
enhance the strength and stiffness of the thick soft marine deposits so as to control the stability of the seawalls and long-term
settlement of the reclaimed areas, DCM is proposed to be deployed as the
primary ground treatment works supporting the proposed bridge tower and
anchorage structures. The use of DCM for
seabed treatment is considered as the most robust option with the least
shortcomings when compared with other ground treatment schemes given the
Project’s needs. Non-dredged reclamation with the marine deposits left in place
may be adopted to avoid the need for dredging and disposal of thick marine
deposits especially for the reclamation of the Tsing Yi and Ma Wan South Towers
of the proposed bridge crossing MWF.
2.9.3.5
Dredging
of soft marine deposits is proposed in areas where thin layer of marine
deposits is found across the entire reclamation site including areas of the
proposed reclamation for the towers of proposed bridges crossing MWF and KSMF
and Ma Wan South anchorage, when the DCM method is ineffective. Furthermore, there may be local areas where
the soft marine deposit is underlain directly by in-situ soils (e.g.
saprolite), which is relatively hard for the DCM rigs to penetrate and
therefore embedment condition of the DCM clusters is not expected to be
acceptable. To ensure adequate control
of residual settlement in the reclamation area and stability of the seawall
structures, dredging is recommended for these thin layers of marine
deposits. For areas where thick marine
deposits are present, there may be seabed features of boulders / cobbles /
gravels / debris which are potential obstructions for the DCM works. Consideration should be given to the combined
ground treatment pile-supported using removal of shallow obstructions followed
by DCM treatment.
1. Installation of silt curtain;
2. Dredging for seawall and four main reclamation
areas simultaneously (Approx.12 numbers of dredgers);
3. Installation of geotextile, sand blanket and
primary silt curtain;
4. Carry out DCM (approx. 50%) for main reclamation area;
5. Backfilling of fully dredged zone;
6. Installation of rockfill; and
7. Reclamation filling to formation level.
2.9.3.7
Regarding
to the construction method of pile-supported VIPS, the bored piles would be
used for supporting the above VIPS. It aims to provide the protection of bridge
structures instead of the reclamation sea wall.
2.9.4.1
The
Main Bridges of the proposed TYLL is currently designed as a combination of
twin-tower suspension bridge across MWF and single-tower suspension bridge
across KSMF, connecting North Lantau and Tsing Yi West. The main components of the Main Bridges of
TYLL include the foundations, towers, cable anchorages, suspension cables and bridge decks.
2.9.4.2
The
towers of the Main Bridges of TYLL are typically supported by large diameter
bored pile foundations. The piled foundations are each in the form of
a pile cap on top of a pile group for efficient load transfer, and they are
commonly use in sea crossings if the site and ground conditions warrant load
transfer to lower strata. Piled foundations
offer advantages such as
optimal use of construction materials, accelerating construction, reducing
noise and minimising vibrations.
2.9.4.3
The
Main Bridge towers
will be of concrete construction using either
jump form or slip form methods for the
in-situ concrete pour. The choice of construction materials
and methods takes into account factors such as
construction time, cost, durability, and maintenance requirements.
2.9.4.4
The
anchorages for the suspension cables will be located at the landing points on
both sides of each
bridge and, at Ma Wan South, a shared, common anchorage will be founded on
reclamation.
A commonly adopted type of anchorage is the gravity type anchorage,
which involves a substantial underground concrete mass structure. A significant amount of concrete would be required for constructing
both the anchorages and the bridge towers. To enable efficient and timely concrete
production for the Project, it is anticipated that the contractor would establish a
temporary concrete batching plant with an estimated capacity of approximately
not more than 10,000 tonnes within the works area, subject to contractor’s
design. A tentative, available location for a temporary concrete batching plant is
shown in Figure 2.10.
2.9.4.5
To
protect the bridge towers, marine bridge piers and marine anchorage in Ma Wan
and Tsing Yi, reclamations in Ma Wan and Tsing Yi are unavoidable. Holistic engineering consideration has been
taken to minimise the clearance between the edge of reclamation and the
foundation of bridge tower / pier / anchorage, to avoid physical collision between vessel and bridge structure.
2.9.4.6
After
the construction of towers and anchorages are completed, the construction
process will proceed with the installation of suspension cables. Subsequently, the suspenders will be
installed, followed by the erection of the bridge deck. The bridge deck will be made of steel and
will be prefabricated off-site in segments.
These segments will then be transported to the site by barge and lifted
into place for installation. To ensure
navigation safety during the
installation of the deck segments, suitable temporary marine traffic
management will be implemented.
2.9.5
Construction Methodology for
Viaducts
2.9.5.1
Viaducts
will be required for the mainline crossing North Lantau Interchange and Tsing
Yi Connection, and the associated slip roads.
The viaducts will be primarily constructed by using precast concrete
segmental method so as to minimise the on-site casting
work. In other words, the viaduct
segments will be manufactured at an off-site casting yard, transported to the
construction site and assembled together to complete
the whole viaduct structure. This method
promotes the efficiency of the construction activities and need for on-site
concrete casting.
2.9.5.2
Alternatively,
when site constraints limit accessibility for delivering precast deck segments,
cast-in-situ construction using formwork and falsework would be considered as
an alternative option.
2.9.6
Construction Methodology for Rock
Cuttings
2.9.6.1
The
rock hills at Lantau Island near Yi Chuen and Tso Wan will be excavated for
site formation for the proposed at-grade roads and tunnel portals. According to the available geological data,
the construction of the proposed anchorages at both ends of the main bridge
will also require rock excavation.
2.9.6.2
To
optimise cost and time efficiency for the Project, it is proposed to adopt open
blasting for the large amount of rock cuttings at North Lantau Interchange. The selected locations for open blasting are
primarily in areas with low population density.
To ensure safety and suppress dust generation, additional measures such
as blasting screens, blast cages, and blast mats will be implemented. A well-designed open blasting design will also be utilised to
effectively manage and control the effects of flyrock.
2.9.6.3
Conventional
rock excavation using mechanical breaking with pre-splitting would still be
considered for the construction of anchorage at Tsing Yi due to the smaller
volume of land excavation when compared to the North Lantau Interchange.
2.9.6.4
Regarding
habitat preservation and waterflow retention, the following measures are
envisaged:
·
In order to preserve the headwater of
the north-branching tributary in watercourse at North Lantau, it is proposed to
replace the intersecting section with a box culvert and relocating the
permanent structures to avoid encroachment;
·
Implement temporary stream
diversions to maintain waterflow and minimise run-off
as well as subsequent impact on watercourses and associated fauna; and
· Establish work exclusion zones around watercourses
and use elevated platforms to minimise impact on banks and stream beds.
2.9.7
Summary of Construction Methodology
2.9.7.1
Possible
construction methods which have been investigated for the construction of the
Project and the reasons for selection are summarised in Table 2.4.
Table 2.4 Comparison and
Summary of Possible Construction Methods for the TYLL
|
Section
|
Possible
Construction Method
|
Pros
|
Cons
|
|
Tunnel
|
Drill-and-blast
(Recommended)
|
· Significantly decrease and limit potential
environmental impacts, specifically concerning noise, dust, and visual
disturbances to areas in close proximity to the
portals
· More
effective for rock tunnel excavation than mechanical breaking methods,
which significantly reduces the construction period, providing both financial
benefits and a faster project commissioning
|
· Risk of storage and delivery of explosives to
work site.
|
|
Tunnel Boring Machine
|
· Less labour required for the construction of
tunnel.
|
· Less suitable for hard ground profiles such a
those found in North Lantau.
· Land required for set of launching shaft and receiving shaft
which would impose significant impact on natural terrain causing
consequential ecological impact.
|
|
Reclamation
|
DCM (Recommended primary ground treatment method)
|
· Considered as the most robust option with the
least shortcomings when compared with other ground treatment schemes given
the Project’s needs.
· Avoid the need for disposal of thick marine
deposits.
|
· Ineffective in areas with shallow depth of marine
deposits.
|
|
Fully dredged method (Recommended for areas where
DCM is ineffective)
|
· For areas with soft marine deposits where DCM is
ineffective, it is technically required to dredge the whole layer of marine
deposits and replace it with firm materials for controlling the settlement of
the reclaimed islands and to ensure stability of the seawall structures
|
·
Disturbance of seabed may cause generation of
suspended solids.
|
|
Pile-supported VIPS
|
Bored pile
(Recommended)
|
·
The bored piles would be used for supporting the
VIPS. It aims to provide the protection to bridge structures.
·
Reduction in vibration
and noise generated during the piling process
|
· More expensive
|
|
Driven pile
|
· Less expensive
|
· Generation of significant noise and vibration
during the piling process.
· Percussion piling may cause disturbance to the
seabed and generate suspended solids.
|
|
Main Bridges- foundations
|
Large diameter bored pile foundations for tower
support (Recommended)
|
· Accelerate
construction
· Reduce
noise and minimising vibrations
|
·
More expensive
|
|
Driven pile
|
·
Less expensive
|
· Generation of significant noise and vibration
during the piling process.
· Percussion piling may cause disturbance to the
seabed and generate suspended solids.
· Driven piles may not have enough capacity for the
large loads from the towers
|
|
Main Bridges- tower
|
Jump form or slip form methods for tower
construction (Recommended)
|
·
Considered as the most
robust option taking account into the construction time, cost, durability,
and maintenance requirements.
·
Less C&D materials / waste generated
|
· Require another trade of skilled workers and
additional construction equipment.
|
|
Timber formwork for tower construction
|
· Conventional construction method and require less
special skilled labour force and specialists when comparing with other
construction methods
|
· More
C&D materials / waste to be generated
|
|
Viaducts
|
Precast concrete segmental method (Recommended)
|
· Better control of quality and workmanship for
works in fabrication yard.
· Minimise the need for on-site concrete casting.
· Use of steel mould as formwork in the fabrication
yard can reduce the generation of C&D waste / materials on site.
· More efficient construction works as the deck
segments can be casted concurrently with superstructure works.
|
· Require another trade of skilled workers and
additional construction equipment for erecting precast segments.
|
|
Cast in-situ concrete
|
· Conventional construction method and require less
special skilled labour force and specialists when comparing with other
construction methods
|
· Use of timber formwork, thus more C&D waste /
materials will be generated.
· Site conditions in terms of accessibility and
weather can be highly critical to the work, requirement of extreme measures
in some situations to control all stages in the production process.
· Substantial falsework required.
· Longer construction time.
|
|
Rock Cuttings
|
Open blasting (Recommended for Lantau side)
|
· Optimise
cost and time efficiency for hard rock slopes.
· Noise only
generated at specific times.
|
·
Risk of storage and delivery
of explosives to work site.
|
|
Hydraulic excavation (Recommended for Tsing Yi
side)
|
·
Explosives not required, thus reducing risk to the
two PHIs at Tsing Yi.
|
·
Longer periods of continuous noise generation.
·
Longer construction time
|
2.10
Implementation Programme
2.10.1.1
Currently,
the project is in the investigation phase, with ongoing progress in developing
the alignment scheme, conducting the traffic impact assessment, EIA, gazettal,
engineering study and other major statutory procedures.
·
Close liaison with the
contractors of other concurrent projects in order to
avoid overlapping of construction activities and allow sufficient buffer for
works at project interface due to potential delays in the programme so that the
cumulative effects of environmental impacts could be minimised.
Land Based Works
·
Temporary stream diversion
to maintain the downstream water flow, works exclusion zones and elevated
platforms will also be implemented before construction works around
watercourses where required to minimise the ecological impact. As the impact on
amphibians and other aquatic species of conservation interest are mitigated
through translocation works (if applicable) after pre-construction survey, the
environmental impact has been minimised such that a specific sequence of
land-based works is not considered necessary.
·
Blast cages or roof-over protective cover would be provided before the
commencement of open blasting works to minimise the air and noise impacts of
blasting. During the construction of drill and blast tunnels, a blast door will
be installed in the tunnel openings to prevent the escape of fugitive dust from
blasting before further blasting works within the tunnels. Therefore, the air
and noise impacts are minimised for most periods of the tunnel construction
through the blast door. With these mitigation measures, the carrying out of the
construction of the two tunnels and slip roads concurrently would result in a
similar environmental impact and is assumed in conducting the assessment in
lieu of a specific construction sequence.
Marine Works
·
Silt curtains will be
installed before reclamation works to minimise the marine water quality, marine ecology and fisheries impacts of the
works. The worst-case scenario has been
considered for the water quality impacts of the reclamation works in Chapter
5 based on a tentative construction sequence in Appendix 5.2.
·
The use of VIPS for vessel
protection of the deflection pier at North Lantau reduces the time required for
the construction works there when compared to using reclamation for vessel
protection, requiring only about 10 months to complete the piling works. This
further minimises the marine water quality, marine ecology and fisheries
impacts of the works. The sediment release rate for VIPS is minuscule,
being less than 1% of the sediment release rate of the reclamation works.
Therefore, it is considered that a specific sequence of works for VIPS is not
necessary.
Table 2.5 Summary
of Key Construction Works for the Project
|
Description
|
Tentative Construction Programme
|
|
Tsing Yi Connection
|
Q1
2027 to Q2 2031
|
|
Suspension bridge over Ma Wan Fairway
|
Q1
2027 to Q2 2033
|
|
Viaduct connecting two cable-supported bridges
|
Q1
2028 to Q4 2031
|
|
Suspension bridge over Kap Shui Mun Fairway
|
Q1
2027 to Q2 2030
|
|
North Lantau Interchange
|
Q1
2027 to Q2 2031
|
2.11.1
Overview
2.11.1.1
Due
consideration has been given to address the environmental challenges
encountered in the design of the Project.
Environmental protection will be prioritised and fulfilled to the
greatest extent possible. Various key
actions have been implemented to address these environmental challenges, which
will be discussed in the following sections.
2.11.2
Minimisation of extensive retaining
structures on existing geotechnical features at Tsing Yi
2.11.2.1
As
mentioned in Section 2.7.4, the alignment has been refined by incorporating the above viaduct into Tsing Sha Highway, at same
time providing a direct
connection from CTT westbound to TYLL westbound. The recommended alignment is
adopted to reduce the length of retaining structures by approximately 115m on
existing geotechnical features, as well as reduce the numbers of affected
existing geotechnical features such as the man-made slope and the extension of
retaining wall. With the omission of the
TYRW-TYLL Viaduct connection that required land adjacent to Sai Tso Wan Road, land resumption is greatly
reduced and the number of affected nearby ASRs and NSRs is reduced. By adopting this alignment design, it would
also minimise the landscape and visual impacts at the Tsing Yi Connection.
2.11.3
Avoidance of Reclamation at North
Lantau Shoreline
2.11.3.1
The
alignment selected in the previous feasibility study and presented in the
Project Profile has included reclamations in North Lantau, Ma Wan and Tsing
Yi. Further to the refinement on the alignment, the extent of the proposed
reclamation works is further reviewed to minimise the footprints of the proposed
reclaimed areas with due consideration on the engineering, environmental and
port operation aspects.
2.11.3.2
To
protect the deflection pier at North Lantau, pile-supported VIPS is proposed to
be adopted in the area of existing shoreline. The VIPS
structure will be supported by bored piles with a superstructure and hanger
slab to protect the pier from vessel impact, thus reclamation is no longer
required at North Lantau.
The short-term nature, around 10 months subject to actual ground conditions of
the piling activities is expected to cause minimal disturbance to surrounding
marine fish and fisheries-sensitive receivers.
2.11.3.3
The avoidance of reclamation at North
Lantau would benefit the
preservation of the intertidal zone and ecosystem along the shoreline,
including six species of conservation importance at the intertidal zone, a
majority being locally very common shorebirds, such as Great Egret, Pacific
Reef Heron, White-throated Kingfisher etc. Moreover, the surfaces of supporting structures for the pile-supported VIPS,
present new opportunities for the recruitment, settlement and colonisation of
marine benthos, thereby enhancing the overall quality of associated marine
ecosystems in the vicinity.
2.11.4
Minimisation of Reclamation and
Dredging Extents for the Reclamation in Ma Wan and Tsing Yi
2.11.4.1
Marine
anchorages in Ma Wan are combined into a single common anchorage. This approach reduces the material required
for anchorage construction and minimises excavation work. As a result, both the environmental impact of
material excavation and disturbances to the marine environment are
reduced. Furthermore, the combination of
anchorages can reduce the overall area of Ma Wan reclamation.
2.11.4.2
This
reduction of reclamation area has reduced the total amount of dredged
sediments, hence reducing the associated water quality impacts during the
construction phase. The extent of
channel narrowing at both MWF and KSMF are also reduced, hence reducing the
change in hydrodynamic regime under operational phase.
2.11.4.3
In
consideration of the different reclamation methods, different reclamation
approaches from dredging to non-dredging were investigated. Dredging activities would churn up
sedimentary materials and additional amount of fill materials would be required
to fill the dredged trench, inducing larger water quality impacts. Quantitative water quality modelling is conducted to assess the impacts
induced by the dredging works. The
disposal of large amount of sediment generated would also cause significant
waste management implications and secondary environmental impacts from the induced marine traffic (e.g. air quality and marine ecological impacts).
Therefore, it is proposed that non-dredging method using DCM should be
applied subject to engineering design. This method does not require additional
filling of the dredged trench, which would minimise the filling activities and
the associated water quality impacts. Additionally, the amount of
dredged sediment was reduced by approximately 32,840m3 by adopting
DCM when comparing with the design scheme under the previous stage. This would
minimise the waste
management implications (e.g. disposal of dredged materials) and secondary environmental impacts from
the marine traffic induced from the disposal of marine sediments. Based on
current ground investigation, it is estimated that DCM would be applied to
about 50% of the reclamation area subject to actual ground conditions as shown
in Figure 6.1 and Figure 6.2.
2.11.4.4 Combined
with the adoption of the VIPS, the total reclamation area in the
current scheme (about 19.8 hectares) is reduced by about 4.1 hectares (17%)
when compared with the original scheme in the Project Profile (about 23.9
hectares).
2.11.5.1
The
Project alignment connects Route 11, North Lantau Highway, HKIW-NEL Link and
then pass through hilly terrains in North Lantau to Tsing Yi. Measures in the
alignment design to minimising slope cutting have been considered and adopted
to minimising slope cutting, in order to (i) minimise disruption and impacts to
the landscape resources and characters, (ii) minimise the number of trees
impacted, (iii) minimise potential impacts to the natural habitats and the
associated ecology and (iv) minimise the amount of excavation spoil and construction waste
generated. Total generated C&D materials including
slope cutting has been reduced by 42% comparing with the design scheme under
the previous feasibility study stage of the Project. The reduction and recycling
measures for C&D materials during the planning and design stages, as well
as through layout optimisation and construction methods is to be considered.
2.11.5.2
The
Recommended Alignment of Lantau landing point is shifted northwards, thus
enabling the slope cutting location of the North Lantau Interchange to shift
eastwards towards a lower terrain. The
modification of the alignment also minimises the substantial slope cutting
along the northeast face of Fa Peng Teng. These design modifications
substantially preserve the natural features of the area, reduce the
volume of excavated materials as well as the associated construction dust
impacts.
2.11.5.3
At
the Tsing Yi Connection, with the omission of the TYRW-TYLL Viaduct, the length
of retaining structures on existing geotechnical features (see also Section 2.11.2) is minimised as the need for clearance of land adjacent to Sai Tso Wan
Road is no longer required. The anchorage of main bridge at Tsing Yi side has
been further reviewed to avoid direct impact to the adjacent Cheung Tsing
Highway structure by shift the anchorage westwards, allowing the anchorage sit
at the toe of the existing slope. This
refinement not only substantially minimised the constructability difficulty on
existing slope and avoid direct impact to the adjacent highway structure but
also minimise the landscape and visual impact at Tsing Yi side.
2.11.6
Avoidance of Direct Impact to
Ecological Sensitive Area
2.11.6.1
The
recommended TYLL alignment and its associated works footprint were thoroughly
considered, evaluated and selected from several alternative alignment options
proposed in previous stage studies (S.2.7 refers).
This process has resulted
in the current alignment option, which aims to avoid potential direct and
indirect impacts on recognised sites of conservation importance and other
ecologically sensitive areas, such as the Ma Wan Egretry and Night Roost
located approximately 1.3 km north of the project boundaries.
2.11.7
Minimisation of Habitat Loss
2.11.7.1
The
Recommended Alignment was tailored to minimise encroachment into natural
habitats and ecological resources of high ecological importance, resulting in a
final optimised layout that would result in no loss of any natural terrestrial
habitats in Tsing Yi. However, a small area (approx. 0.005 ha) of the
intertidal zone in Ma Wan South will be lost as a result of
the proposed works. Due
to engineering constraints posed by the site conditions and the inherent
requirement to connect TYLL with other planned roads and highways, areas of
natural terrestrial habitats in North Lantau, including shrubland / grassland, watercourse
and intertidal zone, would be inevitably impacted.
2.11.7.2
To
minimise the extent of habitat loss and its impact on the ecology in this area,
the proportion and extent of slope works, and at-grade roads were minimised and strategically positioned along
existing developed area. Some road
sections in North Lantau have opted for tunnel or viaduct form to minimise the
footprint of at-grade works and to avoid ecological impact, i.e. the viaduct
section at Yi Chuen and tunnel connecting HKIW-NEL Link, which avoid impact on
concerned watercourse.
2.11.8
Summary
2.11.8.1
Due
consideration has been given above to address the environmental challenges
encountered in the design of the Project.
Environmental protection will be prioritised and fulfilled to the
greatest extent possible. Various key
actions have been implemented to address the environmental challenges and
summarised in Table 2.6.
Table 2.6 Summary of Alternative Mitigation
Measures
|
Alternative Mitigation Measures
|
Details
|
Environmental Benefits
|
Environmental / Engineering Disbenefits
|
|
Reduce and reuse inert C&D Materials
|
·
Minimise
slope works in North Lantau and Tsing Yi to reduce generation of excavated
soil and yard waste; and
·
On-site
reuse of inert C&D materials like reclamation filling.
|
·
Reduce
total amount of inert C&D materials for disposal; and
·
Minimise
transporting of C&D materials to Public Fill Reception Facilities (PFRFs)
thus reducing potential air quality and noise impacts arising from the
transportation vehicles / vessels.
|
·
NIL
|
|
Encourage recycling of yard waste
|
·
Yard
waste is encouraged to be sent to the Yard Waste Recycling Centre in Y-Park
for recycling prior to disposal at the designated landfill site.
|
·
Generate
new products from yard waste; and
·
Indirectly
increasing the lifespan of existing landfill.
|
·
Yard
waste might need to be stored on-site for a period; and
·
Increase
in administration cost.
|
|
Adopting GPS or equivalent system
|
·
Tracking and monitoring of all dump trucks to prohibit illegal dumping
and landfilling of C&D materials.
|
·
Prohibit illegal dumping.
|
·
NIL
|
|
Disposal / treatment methods for marine sediment
|
·
Adoption
of DCM as a primary ground treatment method for reclamation.
|
·
Avoid
the need for disposal of thick marine deposits; and
·
Reduce
disposal and transportation of marine sediment.
|
·
Ineffective
in areas with shallow depth of marine deposits;
·
May
involve specialised equipment, materials, and expertise, leading to higher
upfront costs compared to traditional dredging
|
|
Adopt
pile-supported VIPS in
the area of existing shoreline.
|
·
Avoidance
of reclamation at North Lantau shoreline; and
·
Protect
the deflection pier at North Lantau from vessel impact.
|
·
Reclamation is no longer
required at North Lantau, which benefit the preservation of the intertidal
zone and ecosystem along the shoreline; and
·
Alleviate
the water pollution caused by the construction of reclamation land.
|
·
The
VIPS and other pile-supported structures require ongoing maintenance to ensure
their structural integrity, especially in a harsh marine environment.
|
|
Adoption of Eco-shoreline
|
·
Incorporation
of eco-shoreline design in the future coastal structures such as seawalls on
the reclaimed land as well as surfaces and supporting structures on the
pile-supported VIPS; and
·
Incorporation
of elements that diversify microhabitats and enhance the quality of
settlement substrates.
|
·
Present
new opportunities for the recruitment, settlement and colonisation of marine
benthos, thereby enhancing the overall quality of associated marine
ecosystems in the vicinity;
·
Encourage
recruitment and settlement of corals and other benthos; and
·
Provide
sheltering habitats for marine wildlife.
|
·
Increase
in construction cost and maintenance cost.
|
2.12.1.1
Concurrent
projects in the vicinity of the Project site are identified. The status of these concurrent projects is
based on the available information obtained during the course
of the EIA Study. It should be
noted that the implementation of individual project would be subject to further
development and subsequent actions of the respective project proponent.
2.12.1.2
Two
proposed projects, namely the Ma Wan South Development (MWSD) and development
at Hongkong United
Dockyards (HUD), were identified during the course of
this EIA study. For MWSD, there is no concrete implementation
programme nor approved rezoning proposal / planning application and associated
design plan of these projects are available at the time of this EIA study.
While rezoning applications are required for these projects, the current
planning application for the HUD development (Application No. Y/TY/2) is still
being processed under the Town Planning Ordinance at the time of this EIA
study. Besides, the rezoning proposal
for the MWSD has not commenced. On the above basis,
the potential cumulative environmental impacts of these projects would be
assessed qualitatively in this EIA study.
2.12.1.4
A
list of the tentative concurrent projects identified at the time of this EIA
study is summarised in Table 2.7, while locations of these concurrent projects
are indicated in Appendix 2.1.
2.12.1.5
Various
cumulative impacts for different concurrent projects have been identified and
detailed justification on consideration of various cumulative environmental
impacts from individual concurrent project has been included in the
corresponding technical assessment sections of this EIA report.