3.1.1.1
Further to the recommendations of the Option Assessment and
subsequent alignment developments detailed in Section 2 of this report, the
preferred Trunk Road T2 is shown in Figure 3.1 and will comprise:
·
a dual two-lane trunk road of
approximately 3.0km long with
about 2.7km of the trunk road in form of
tunnel;
· ventilation and administration buildings and a traffic control and surveillance system; and
· associated civil, electrical, mechanical, landscaping and environmental protection and mitigation works.
3.1.1.2
The works for the Trunk Road T2 project are grouped under the following
major geographical headings:
a)
The South Apron Section – all works for the Trunk Road T2 Project
located at the South Apron of the former Kai Tak Airport, including a
ventilation building, a section of at-grade road, a section of depressed road,
a section of cut and cover tunnel, a vertical launching shaft for the tunnel
boring machines (TBM), a section of twin TBM tunnel and ancillary works.
b)
The Subsea Tunnel Section – all works for the Trunk Road T2 project in
the sea between the South Apron and Cha Kwo Ling, including twin subsea TBM
tunnels.
c)
The Cha Kwo Ling Section – all works for the Trunk Road T2 project
located at the former Cha Kwo Ling Public Cargo Works Area (PCWA), including a
section of cut and cover tunnel, a vertical receiving shaft for the TBMs, a
section of twin TBM tunnels, a ventilation building and an administration
building located inside the Lam Tin Interchange. The site formation and road works required to
form the Lam Tin Interchange including the administration building, are under
the scope of the Tseung Kwan O –Lam Tin Tunnel (TKO-LTT) project.
3.1.1.3
Details of the various elements of the selected Trunk Road T2 alignment
are described in the sections below. The general horizontal layout of the
preferred alignment is shown in Figure 3.1 while the vertical profile is
show in Figure 3.2 – Figure 3.2b.
3.2
South
Apron
3.2.1.1
Site clearance for the works in the South Apron will include the removal
of small trees and shrubs, removal of fences and gates across the site. At the location of the proposed Barging
Point there is an existing temporary structure to be removed at the
commencement of the Trunk Road T2 project works.
3.2.2 At-grade Road
3.2.2.1
The proposed Trunk Road T2 starts at an interface with the Central
Kowloon Route (CKR) at Chainage 5758m and is a dual 2-lane road. The trunk road continues at-grade for
approximately 100m along the South Apron until it passes over the existing
Jordan Valley Box Culvert (JVBC).
3.2.2.2
The construction of the at-grade section
of road will generate small quantities of excavated materials from the,
typically 2 to 3 metre deep, trench works and excavation works for the
construction of the drainage network, the roads and the foundations for sign gantries. Small amounts of the material
excavated for their construction will be temporarily stockpiled and used to
backfill the trenches and sign gantry foundations.
3.2.2.3
The layout of the at-grade section, along
with the depressed road section, can be seen in Figure 3.3 and a typical section of the
at-grade road given in Figure 3.5a.
3.2.3.1
After the Trunk Road T2 passes over the JVBC it begins to descend,
within a depressed road section, for approximately 170m. This allows the level of the road to lower
from the existing South Apron ground level of approximately +5mPD to -3.3mPD,
at which point the road achieves sufficient depth for the road to be fully
enclosed and the depressed road section connects to a tunnel section.
3.2.3.2
The depressed road section of
the Trunk Road T2 will be contained within a reinforced concrete “u-shaped”
section, consisting of a slab under the road and retaining walls on both sides
of the road section. The
layout of the depressed road section can be seen in Figure 3.3 and a typical
section of the depressed road is shown in Figure 3.5b. The retaining walls will vary in height from 2m high to 10m high, as the road lowers in level, to
retain the surrounding South Apron ground level. Tubular or sheet pile
walling will be used to support the excavation to allow the construction of the
open trough section. The selection of
each type of steel pile walling is related to the method adopted by the
contractor. It is anticipated that the
sheet piles will be extracted and removed from site by the contractor for
re-use on other projects or left in place and not require disposal.
3.2.3.3
The existing ground water level on the
South Apron is at about +3.3mPD, which is based on the results of the ground water monitoring from KL/2009/02. Therefore, in order to construct the
depressed road section in a dry working environment the ground water will be
lowered by pumping out of the groundwater within the plan area of the depressed
road section. The sheet pile walling will
be driven down to a level to enable control of the ground water flow under the
excavation such that dry construction conditions can be maintained.
3.2.3.4
The depressed road section will generate approximately 30,500m3 of
excavated materials. Based upon a review
of the geological profile in this area, all of the material excavated will be
fill material. This section is proposed
to be the last major section of the alignment to be excavated, with the
excavated materials being exported off site via the barging point to a public
fill site rather than placed in the stockpile works area. In order to handle
this material, and the other materials to be exported form the Trunk Road T2
site, a platform will be constructed within the land of the proposed
barging point to allow tipping of the material from trucks to barges. The platform will be adjustable to allow for
the variation in tidal levels. Good
practice dust control procedures for handling the materials will be applied
including a 3–sided enclosure on the unloading ramp and water sprays to control
dust as the materials are placed in the barges.
3.2.4 Cut and Cover Tunnel Section
3.2.4.1
From the connection with the depressed road section the Trunk Road T2
continues to descend at a gradient of about 5% within a fully enclosed twin
cell rectangular tunnel section (refer to Figure 3.5c),
that will be constructed using the cut and cover method. This reinforced concrete cut and cover
section is approximately 570m long (from chainage 6050 to 6620) and reaches a
road level of approximately -28.6mPD.
The chainage 6620 is close to the southern edge of the South Apron, at
which point the cut and cover tunnel section connects to the subsea tunnel section.
3.2.4.2
The planned programme of works is such
that the cut and cover section for the Trunk Road T2 will commence first with
the excavated materials being stockpiled on site or directly removed to Public
Fill Reception Facilities (PFRF). The
planned stockpile area is for this material is at Works Area 4 (see Section 3.4 below) which has an
anticipated capacity of 50,000m3.
Once this capacity is reached further material will be exported off site
for disposal at PFRF. Throughout the
duration of the construction works, the materials within the stockpile will be
used for backfilling over the completed sections of cut and cover tunnel and so
provide a source of material to be managed by the Contractor to avoid importing
fill materials for the project and minimise export of excavated materials from
the site.
3.2.4.3
During excavation for the cut and cover
sections of tunnel at both the South Apron and Cha Kwo Ling, it is anticipated
that quantities of underlying marine muds will be excavated. As these materials are not suitable for
disposal at a public fill reception facility (PFRF), they may have to be
disposed of to East Sha Chau Contaminated Mud pits. The preferred alternative is that the marine
mud is treated on site by mixing with sand and cement such that as much as
possible can be used as fill materials for areas such as the future at-grade
roads (e.g. under the at-grade Road D4, the location of which is shown in Figure
3.3) or landscaped areas such as in the promenade areas at the former Cha Kwo Ling Public Cargo Working Area (PCWA).
3.2.4.4
For the majority of the cut and cover
sections between Chainages 6050 to 6620 (refer to Figures 3.2 & 3.2a), it is anticipated that
diaphragm walling will be used to support the excavation. However, for the section of tunnel in front
of the Public Works Central Laboratory (PWCL) (Chainages 6480 to 6560), it is
anticipated that contiguous large diameter bored piles will be used to support
the excavation and further limit ground movement adjacent to the PWCL. For the
total cut and cover road section, a quantity of approximately 470,000m3
will be excavated for re-use where possible in filling over the tunnel or to be
exported via the barging point.
3.2.4.5
For shallower sections of the cut and
cover tunnel, either tubular steel or sheet pile walling will be used to
support the excavation, depending on the depth of excavation and numbers of
layers of propping to be adopted for the excavation.
3.2.4.6
It is assumed that the Contractor will
adopt a “bottom-up” approach for the construction of most of the cut and cover
tunnel. The Contractor will install the
diaphragm or pile walling from existing ground level. The ground between the diaphragm/pile walls
would be excavated progressively and temporary steel props installed to
stabilise the walls. Layers of the
temporary steel props would be installed as the excavation gets deeper until
the final design level for the bottom of the cut and cover tunnel section is
reached. The contractor would then
construct the bottom concrete slab of the cut and cover tunnel. This would be followed by the construction of
the top slab of the cut and cover tunnel.
The contractor would then progressively backfill soil onto the top of the
cut and cover tunnel, removing the layers of the temporary steel props as the
backfilling increases in level, until the level of the backfill has reached the
existing South Apron ground level.
3.2.4.7
One anticipated exception to the typical
“bottom-up” approach will be at the existing road junction at TD4 and
3.2.4.8
For the section of cut and cover tunnel
from Chainages 6480 to 6620, construction of the tunnel sections would be
within a cofferdam constructed within diaphragm walls. The section of tunnel from Chainages 6480 to
6620 is the section of the Trunk Road T2 where the eastbound and westbound
carriageways diverge to achieve a spacing of approximately 13.2m between the
two 13.2m diameter circular sections of the subsea tunnel. This spacing between the two tunnel bores has
been selected to provide a conservatively safe block of soil between the two
tunnel bores and ensure stability of the two adjacent tunnel sections as they
are constructed. This wider spacing
between the carriageways results in an area between the carriageways that is
not essential for the permanent works.
Thus, two options were considered, namely to construct the two
carriageways in two short independent sections of cut and cover tunnels or to
construct a single large cut and cover tunnel section that encompassed both
carriageways.
3.2.4.9
The option of having two independent cut
and cover tunnel sections would have resulted in four diaphragm walls (two per
carriageway) and would have increased the amount of bentonite material to be
disposed of, and would have constrained the subsea tunnelling operations that
could take advantage of the larger space in a single cut and cover section as
fabrication and operation space for subsea tunnel operations.
3.2.4.10
Therefore, a single large cut and cover
tunnel section has been adopted as the preferred design. For this approach, the
two outside walls for the cut and cover tunnel section between Chainages 6480
and 6620 will be constructed using diaphragm walls. To support the top slab of the tunnel a
single central row of columns with barrette pile foundations is adopted.
3.2.4.11
Construction of this section of cut and
cover tunnel will adopt the “bottom-up” approach. Following construction of the
bottom slab and walls of the cut and cover tunnel, it is anticipated that the
top slab of the cut and cover section would be constructed and previously
excavated materials used to partially fill over this section of tunnel up to
ground level and form a working area for the TBM ancillary works. Equipment delivery and spoil removal openings
would be left in the top of the cut and cover section with walled shafts up to
ground level. Following completion of
all TBM works, these openings in the top slab would be closed and the shafts
would be backfilled to ground level using stockpiled material.
3.2.4.12
As described for the depressed road
section, the existing ground water level on the South Apron is at about
+3.3mPD, based on the results of the ground water monitoring from
KL/2009/02. Therefore, in order to
construct the cut and cover tunnel sections in a dry working environment, the ground
water will be lowered by pumping out of the water within the plan area of the
tunnel section. The diaphragm/pile
walling will be installed down to a level to enable control of the ground water
flow under the excavation such that dry construction conditions can be
maintained.
3.2.5
3.2.5.1
Two ventilation buildings and an administration building are planned for
the Trunk Road T2 project. These
buildings are located at, or close to the ends of Trunk Road T2. At the South Apron, the ventilation building
is proposed to be located at Site 3A4, adjacent to the DSD desilting compound
under construction for the Jordan Valley Box Culvert as shown in Figure
3.4. The
ventilation building will be a reinforced concrete structure, two storeys in
height, with operation and plant rooms designed to monitor and control the
tunnel air from the eastbound and westbound tunnels of the trunk road. It is anticipated that the building will have a
basement to reduce the total height above ground. The tunnel air will be exhausted from the
roof of the ventilation building. The
exhaust from the building will be expelled upwards at a velocity around 8m/s
via a stack on the top of the building.
The stack size will be 2 x 25m2 discharging the exhaust
vertically at a height of approximately +18mPD. There will
be no mid-tunnel exhaust for this project.
3.2.5.2
No administration building is located at the South Apron. For tunnel operation the facilities located
on the South Apron will be very minor and limited to kiosks close to the interface with
CKR, next to the at-grade road section. This would not generate any operational
waste or emissions.
3.3
Subsea
Tunnel Alignment
3.3.1 Alignment and Construction
3.3.1.1
As mentioned in Section 2,
the “deep level” option of alignment Option 1 has been selected as the
preferred alignment for detailed assessment in this EIA study. The length of the subsea tunnel for this
preferred option is about 2.1km. The
twin 13.2m diameter tunnel sections are embedded a minimum of 13.2m below the
seabed. The typical cross section of each of the subsea tunnel sections is
illustrated in Figure 3.5d, and shows the two lane traffic
envelope, ventilation ducts, E&M, drainage and services equipment enclosed
within a concrete lining. This concrete
lining is made up of precast concrete
segmental units that are joined together to form 1m long rings, that are
installed behind the TBM as it progresses towards the receiving shaft. As described in Section 2, the tunnel is proposed to be constructed using the TBM
method in order to avoid disturbance to the seabed and minimise the amount of
dredged material to be removed, providing water quality, waste management,
marine archaeology and ecology and fisheries benefits. The TBM method has
developed over the last few years to become a reliable method for constructing
large diameter highway and railway tunnels with significant environmental
benefits over other construction methods.
3.3.1.2
The tunnel alignment follows a
southeast-ward direction from the South Apron, passing under the Kwun Tong
Typhoon Shelter (KTTS), and its associated breakwaters, and then the sea
beyond, before turning further eastward towards the Cha Kwo Ling shoreline.
3.3.1.3
The design and procurement period for the TBM is about 15 to 18 months plus a 5 month mobilisation period. Two TBMs will be used in parallel to form the twin Trunk Road
T2 tunnels (an eastbound tunnel and a westbound tunnel) and both TBMs will be launched from the South Apron,
tunnelling towards the receiving pit at Cha Kwo Ling. The TBM for Bore 1 is proposed to be launched
at the end of 2017, while the TBM for Bore 2 will commence in January 2018.
3.3.1.4
The subsea tunnels commence at a 140m long x 45m wide launching shaft
within the South Apron (chainage 6480 to 6620), Figure 3.6, and with a lowest level of approximately -29mPD. The ground level at this location is
approximately +5.0mPD. The subsea tunnel
will then run southward under the KTTS, where the lowest tunnel bottom level
will reach approximately -42mPD, and then heads towards the Cha Kwo Ling
shoreline where it ends at a receiving shaft within the former PWCA and Cha Kwo
Ling. The vertical alignment of the
tunnel is shown in Figures 3.2 to 3.2b. As shown in these figures, the tunnel rises up towards the shorelines but
maintains a depth of cover above the tunnel as it passes under the existing
seawalls at either end of the tunnel and, therefore, does not result in any
seabed loss or disturbance.
3.3.1.5
As noted in the text on the South Apron cut and cover tunnel section, construction of the subsea tunnels will commence
at the South Apron launching shaft where an area of land is required for
construction of the launching shaft for the TBMs (Figure 3.6). The launching shaft will be constructed by open excavation method
supported by diaphragm walls. Excavated materials will be backfilled on the
completed section of cut and cover tunnel, while excess excavated materials
will be disposed off-site to the PFSF. The TBMs will start boring from the launching
shaft and then continue under the KTTS until they reach the receiving shaft at the former PCWA at Cha Kwo Ling (Figure 3.7). The TBMs
will then be dismantled and removed via the receiving shaft.
3.3.1.6
The proposed launching shaft located at the South Apron (chainage 6480
to 6620, Figure 3.6) is where all the construction
waste materials from the subsea tunnelling works will be removed. The mixed largely alluvium and CDG, excavated
materials from the TBMs will be dried and pressed to remove excess water and to
recycle the bentonite (drilling fluid).
The cleaned drilling fluid will be returned to the TBM system for
re-use. As the TBM works may progress
for up to 24 hours per day, 7 days per week, and the public fill facilities are
only open during day time hours, a temporary stockpile area will be used to
temporarily store the TBM excavated materials until normal working hours and
removal by barge from the barging point.
3.3.1.7
The excavated material will be placed in the temporary stockpile area
in Works Area 3 (see Section 3.5
below), adjacent to the launching shaft via an enclosed conveyor system. Noise barriers will be erected around the
stockpile to mitigate noise from the placing of the excavated material onto the
stockpile.
3.3.1.8
During normal working hours (assumed to be 07:00 to 19:00), the
excavated materials would be moved from the temporary stockpile area to the
barging point via a fully enclosed conveyor system to minimise dust and noise
emissions.
3.3.1.9
The planning for the tunnel includes for a cross passage between the
twin tunnels at 100m intervals. The
subsea tunnel section is aligned to pass through mainly the alluvium/CDG layers
under the seabed. The cross-passages
will be constructed between the tunnel bores and will also encounter
alluvium/CDG. It is anticipated that
ground freezing will be used for temporary stabilisation of the walls of the
cross-passages until the permanent concrete lining is installed for the cross-passages. An alternative to ground freezing would be
grouting of the ground to form a stable ground condition for excavation. However, ground freezing is preferred as
there would be no grout materials added to the excavated soil which can be
disposed off in a similar manner to the rest of the tunnel excavated material
and the provision of the ground freezing can be more accurately controlled
within the tunnel. In the case the
grouting options are adopted by the contractor, the grout would be added to the
soil and this would be treated as an inert material, to be excavated and
handled similar to the rest of the tunnel excavated materials. For the subsea
section a quantity of approximately 630,000m3 will be excavated for exporting
via the barging point.
3.3.1.10
For the planning of the programming of the
TBM works, two major options were considered:
a)
The use of two TBM’s, both commencing at the South Apron and progressing to CKL; or
b)
The use of a single TBM
commencing at the South Apron and progressing to CKL. Once the TBM had completed one of the tunnel
bores it would either be dismantled and transported back
to the South Apron to carry out the second tunnel bore or it would be turned
around and shifted onto the alignment of the second tunnel bore to commence
tunnelling form CKL back to the South Apron.
3.3.1.11
The use of
a single TBM was considered to have significant disadvantages, including;
i)
The overall programme for the tunnel works would be longer and posed a
risk to completing the project for the 2021 first year of operation.
ii)
The disassembly and transportation of the TBM from CKL to the South Apron would have
involved significant additional construction activities that also posed a risk
to the progress of the project.
iii)
The turning of the TBM “around” at the CKL would have required a second
set of TBM support facilities, including a second barging point, stationed at
the CKL end of the tunnel resulting in increased costs and increased
environmental impacts when compared with a single support facility. The option of a floating TBM support facility
moored to either the South Apron or CKL seawall was considered as not preferred due to risk for
environmental impact of having the tunnel slurry pumped to a floating support
facility moored to the respective seawall.
3.4.1.1
For the works at Cha Kwo Ling, site clearance will include the removal
of the former PCWA offices and removal of the existing wall between the PCWA
and the training area.
3.4.2 Cut and Cover Tunnel
3.4.2.1
A cut and cover tunnel in the form of a reinforced concrete box structure
will function as both the receiving shaft for the two TBMs and as the cut and
cover section connecting between the Trunk Road T2 and the TKO-LTT
alignments. This section of receiving
shaft/cut and cover tunnel, of approximately 110m length, will be constructed
within the Cha Kwo Ling area. The tunnel
will connect to the TKO-LTT at a road level of approximately -26.9mPD at the
Cha Kwo Ling landfall about Chainage 8767m.
For this CKL cut and cover road section, a quantity of approximately
72,000m3 will be excavated for re-use where possible in filling over
the tunnel or to be exported via existing roads to the Barging Point proposed
at the South Apron.
3.4.2.2
The cut and cover tunnel at
CKL is anticipated to be constructed in open excavation supported by diaphragm
walls. Excavated materials will initially be transported by trucks back to the
stockpile area at the South Apron for re-use or disposal off site. Following completion of the TBM and cut and
cover tunnel construction works the receiving shaft would be backfilled with
material transported by road from the South Apron.
3.4.2.3
Consideration was given to the
use of part of the works area WA5 at CKL as a stockpile area for the excavated
materials. However, the use of the South
Apron as the stockpile area for the CKL excavated materials was preferred for
the following reasons:
i)
The space available at CKL is
insufficient to store all of the excavated materials from the CKL cut and cover
tunnel section and will be required for the works for the construction of the
ventilation building and removal of the TBM.
ii)
The barging point to be set up
at the South Apron could be used efficiently to export of the excess excavated
materials.
iii)
A proportion of the materials
to be excavated at CKL would be marine muds.
The Works Area WA4 at the South Apron is to be set up to treat such
materials for re-use as fill material and use of those facilities for treating
the CKL would be more efficient rather than having two split facilities.
3.4.3
3.4.3.1
One of the Trunk Road T2’s ventilation buildings is located inside the
Lam Tin Interchange and is provided for tunnel ventilation. The building will be located at the end of
the connecting section of TKO-LTT tunnel that connects the Cha Kwo Ling end of
Trunk Road T2 tunnel as shown in Figure 3.4. The
ventilation building will be three storeys in height with a top level of approximately +18mPD and
tunnel air from the two tunnel tubes will be exhausted at the roof of the
building, vertically upwards via a stack with a velocity around 6m/s. The stack
vents will be 2 x 25m2 venting vertically from the roof of the vent
building at +18mPD.
3.4.3.2
Administration facilities and space for the Trunk Road T2 project will be located within the
administration building designed and constructed under the TKO-LTT project. As stated
above, the site formation
for the Lam Tin
Interchange, including for the Trunk Road T2’s eastern ventilation building, will be part of the scope of the TKO-LTT project and have been assessed under the TKO-LTT
EIA. The administration building will be
located within the Lam Tin Interchange and on the Cha Kwo Ling side of Trunk
Road T2 (Figure 3.1) and would be
composed of administration offices, training office, meeting areas, control
rooms, traffic control surveillance system (TCSS) room, and associated areas,
such as parking spaces for maintenance and recovery vehicles.
3.5.1.1
Five works areas have been
identified for locating site offices, stockpiles and using as support areas for
the TBM works to construct the undersea tunnel, during the construction period
of the Project. The locations of the
works areas are shown in Figure 3.8 and described in Table 3.1 below.
Table 3.1 Details of Proposed Works Areas
|
Works
Area Reference |
Location |
Current
Use |
Proposed
Use |
|
WA1 |
At the South Apron adjacent to the site
of T2’s proposed western ventilation
building |
Not used |
Storage
of construction equipment, plant maintenance and cutting and bending of
reinforcement along with site offices. |
|
WA2 |
At the South Apron adjacent to the Kwun Tong Typhoon shelter seawall |
1.
(STT)KX2569: Sureguard Logistics Limited-Open storage of goods and dangerous
goods 2.
(TGLA)GLA-TNK 1334: Water Supplies Dept - Works Area 3. |
Works
area for TBM launching shaft, support facilities for TBM operations and
storage area for tunnel lining segments, plant maintenance and Barging Point.
|
|
WA3 |
At the South Apron next to the Kerry Godown
Dangerous Goods Storage Facility |
Currently
used as a bus parking lot. |
Stockpiling
of excavated materials |
|
WA4 |
At the South Apron next to the taxiway
bridge. |
Currently
used to store excavated material from the CEDD contract KL/2009/01. |
Stockpiling
of excavated materials |
|
WA5 |
At the former Cha Kwo Ling Public Cargo
Working Area |
Currently
unused. |
Works
area for TBM retrieval shaft, storage of construction equipment, plant maintenance
and cutting and bending of reinforcement along with site offices. |
3.5.1.2
All of the proposed Works Areas
are currently formed on developed land within short distances from the Trunk
Road T2 alignment, with some already being used as works areas for on-going construction projects. None of the sites are vegetated and no tree
removal is required for their use. The
potential environmental impacts of these nearby works areas have been assessed
together with the main site.
3.6.1.1
The barging point is proposed
at the Government Logistics Department Kowloon Bay Cargo Handling Area. The excavated materials from
the TBM will be removed from the site by connecting
a conveyor system to the barging point. The capacity of the barging point for removal
of the construction waste materials will be a rate of 750m3 per
hour, assuming working hours between 07:00 and 19:00 per day
3.6.1.2
The proposed temporary barging point has a vertical seawall face and
has been used for berthing and loading/unloading purpose by marine vessels of various Government Departments.
No temporary facilities would be needed to be constructed above the
sea. The barging point will comprise one
vehicle unloading ramp only and a conveyor belt unloading chute.
3.6.1.3
Delivery of materials from the temporary stockpile area next to the TBM
would be via a fully enclosed conveyor belt.
Delivery of materials from the remainder of the site would be by truck
and delivered to the barges by via an adjustable ramp.
3.6.1.4
The ramp is proposed to be enclosed within a permanent enclosed 3-sided
tipping hall with built-in water spraying system to reduce dust dispersion.
3.7.1.1
There are no slope works
proposed for this Trunk Road T2 project.
3.8.1.1
Stormwater drainage systems
will be provided to collect stormwater from the carriageway surfaces. The stormwater will enter into gullies along
the kerb lines. The gullies will be
fitted with sumps to trap silt and grit prior to discharging the stormwater
into the stormwater drainage systems.
The drainage systems will eventually discharge the stormwater into the
sea at discrete locations.
3.8.1.2
Operational sewage will be
generated from the eastern and western ventilation buildings, but, again, in
relatively small quantities as summarised in Table
3.2 below, based upon the staffing estimates
required for the Trunk Road T2 project.
Table 3.2 Estimated Sewage Generation
|
Location |
Staff |
Average
Dry Weather Flow (m3/day) |
|
South Apron Landfall (including eastern
ventilation building) |
2 |
0.16 |
|
Cha Kwo Ling Landfall (including western
ventilation building) |
70 |
5.6 |
3.8.1.3
The sewage generated would be discharged to the
local drainage systems at these two areas, which have sufficient capacity to
handle this small contribution from the Trunk Road T2.
3.9.1.1
The construction works
(including testing and commissioning) are anticipated
to commence on site in late 2015, with completion of the construction works by the end of 2020, with Trunk Road T2 commencing operation in 2021. An outline of the anticipated construction
programme is shown in Appendix 3A with the general phasing
of the works described
below.
3.9.1.2
It is anticipated that the normal working hours for surface works will
be 07:00 to 19:00, Monday to Friday, with alternative Saturday (excluding
General Holidays). For the tunnelling works,
it is assumed that the TBM operations will continue on a shift basis with a
typical working period of 20 hours per day, allowing for 4 hours per day
“down-time” for the TBM equipment and operators.
3.9.1.3
General phasing of the works on site are detailed below and shown in Figures 3.9a to 3.9n:
·
General site clearance and setting up works areas on South Apron;
·
Stage 1 – Commence works on Launching shaft for TBM works;
·
Stage 2 – Continue works for launching shaft and construct facilities
for barging point on the South Apron;
·
Stage 3 – Continue works for launching shaft and set up of mixing area
for treatment of excavated marine mud;
·
Stage 4 - Continue works for launching shaft and including excavation
works within the launching shaft area.
Excavated materials up to the area WA4’s maximum capacity of 50,000m3
to be stockpiled in WA4 including all marine muds, other excavated materials
will be transported to the barging point via the site haul road and exported
from site. Commence works on the
eastbound cell of the cut and cover tunnel between Chainages 6050 to 6445;
·
Stage 5 – Construction of cut and cover sections in launching shaft and
partial backfilling of launching shaft to use previously excavated materials
and to create a platform for the TBM support facilities. Continue works on the eastbound cell of the
cut and cover tunnel between Chainages 6050 to 6445;
·
Stage 6 - Establishment of TBM support facilities in Works Area 2 (WA2)
and in area above launching shaft ready for commencement of TBM
construction. Continue construction of
the eastbound cell of the cut and cover tunnel between Chainages 6050 to 6445
with excavated materials up to the area’s maximum capacity of 50,000m3 to be
stockpiled in WA4 including all marine muds(for treatment as it is delivered to
the stockpile area), other excavated materials will be transported to the
barging point via the site haul road and exported from site;
·
Stage 7 - Commencement of the eastbound TBM. Completion of the
eastbound cell of the cut and cover section between Chainages 6050 to 6445
including backfilling with stockpiled materials, followed by diversion of road
TD4 onto the ground over the eastbound cell.
Site clearance at Cha Kwo Ling;
·
Stage 8 - Construction of the westbound cell of the cut and cover
tunnel between Chainages 6050 to 6445 with excavated materials up to the areas
maximum capacity of 50,000m3 to be stockpiled in WA4 including all marine muds
(for treatment as it is delivered to the stockpile area), other excavated
materials will be transported to the barging point via the site haul road and
exported from site. Commence westbound TBM tunnelling and continue with TBM works
in eastbound tunnel. Commence works for
TBM receiving shaft at Cha Kwo Ling;
·
Stage 9 - Completion of the westbound cell of the cut and cover section
between Chainages 6050 to 6445 including backfilling with stockpiled materials,
followed by construction of at-grade roads on top of tunnel. Continue with TBM works in eastbound and
westbound tunnels;
·
Stage 10 - Completion of the westbound cell of the cut and cover
section between Chainages 6050 to 6445 including backfilling with stockpiled
materials, followed by construction of at-grade roads on top of tunnel. Commence construction works for the cut and
cover tunnel section between Chainages 6445 to 6480, Construction of the
depressed road section between Chainages 5880 to 6050 with excavated materials
to be stockpiled in WA4. Continue with TBM works in eastbound and westbound
tunnels;
·
Stage 11 - Construction of the depressed road section between Chainages
5880 to 6050 with excavated materials to be stockpiled in WA4. Continue construction works of the cut and
cover tunnel section between Chainages 6445 to 6480, with excavated materials
to be stockpiled in Works Area WA4, other excavated materials will be
transported to the barging point via the site haul road and exported from site.
Commence construction of western and eastern ventilation buildings. Completion of westbound and eastbound TBM
tunnels;
·
Stage 12 – Completion of construction works of the cut and cover tunnel
section between Chainages 6445 to 6480, with fill material being used from the
stockpile area in WA4. Construction of western and eastern ventilation
buildings. Completion of receiving shaft
for TBM at Cha Kwo Ling;
·
Stage 13 - . Construction of the cut and cover tunnel section between
Chainages 6445 to 6480, with excavated materials to be stockpiled in WA4.Other
excavated materials will be transported to the barging point via the site haul
road and exported from site. Completion of western and eastern ventilation
buildings. Completion of receiving shaft
for TBM at Cha Kwo Ling; and.
·
Stage 14 - Completion of all Trunk Road T2 civil works and installation
of finishes and Traffic Control and Surveillance System (TCSS). Other at-grade works for South Apron
development carried out.
3.9.1.4
The following programme assumptions are recognised as key to the
determination of the overall construction programme.
·
The works area WA2 must be constructed early in the contract to allow
for the barging point to remove the current stockpile materials from the former
contract KL/2009/01
·
The design and procurement of the TBM is assumed to take 18 months from
the commencement of the contract to mobilisation of the first TBM on site.
·
The construction of the launching shaft at the South Apron will be
complete and a working platform at ground level created over it to allow for
the establishment of the TBM support facilities.
·
Two TBMs are assumed for the construction of the tunnel, both
progressing from the South Apron.
·
The section of cut and cover tunnel under the future road D4 (and
partially under the existing road TD4) will be constructed in phases with
temporary traffic arrangements to shift the traffic on TD4 to create space for
the construction of each cell.
3.10.1.1
Similar to Trunk Road T2, the
construction of CKR is initially planned to commence construction in early 2015
for completion in 2020 and commencing operation in 2021. (Figure 3.11) As the projects are likely to be constructed concurrently
and will be operational at the same time, detailed coordination of the
interfacing construction activities will be required, including construction
access and temporary stockpiling areas.
3.10.2.1
Similar to Trunk Road T2, the
construction of TKO-LTT is initially planned to commence construction in early 2016 for
completion in 2020, and commencing operation in in 2021. (Figure 3.12) As the projects are likely
to be constructed concurrently and will be operational at the same time,
detailed coordination of the interfacing construction activities will be
required, including construction access, temporary stockpiling areas and arrangement
of Trunk Road T2’s
ventilation / administration buildings.
3.10.3 South Apron Works
3.10.3.1
The South Apron area had
already been fully decontaminated by the Decommissioning of the
l footbridges FB-02 and
03;
l Road D4;
l
construction of the KTD roads L10 and L18;
l
extension of
l
the Centre of
Excellence in Paediatrics at Site C of Site 3C1 of KTD which will start construction in 2013 for completion by 2017.
3.10.3.2
The locations of these infrastructure works are
shown in Figure
3.10.
These concurrent projects are generally minor works that would generally
involve insignificant quantities of excavated materials for the construction of the drainage
network for the roads and foundations for sign gantries. For the footbridges there would, also, be the
construction of bored pile foundations which will generate some excavated
material.
3.10.4 Other Concurrent Projects
3.10.4.1
In addition to the interface with the major concurrent projects
described above, there would be a footbridge FB-06 at the outlet of Tsui Ping
Nullah and a site formation and infrastructure works project at the ex-Cha Kwo
Ling Kaolin Mine Site adjacent to TKO-LTT’s Lam Tin Interchange. Details of other concurrent projects during
either the construction and/or the operational phases, together with details of how these are
assessed in the EIA, are described in the summary table of concurrent projects
included as Appendix 3C.
3.11
Traffic
Data and Assumptions
3.11.1.1
A Local Area Model was developed to provide traffic forecasts for EIA
purposes. The EIA requires cumulative
traffic forecasts and, hence, EIA flows were produced assuming the entire Route
6 (including CKR, TKO-LTT and T2) were all in place by the programmed first
operational year of 2021.
3.11.1.2
The first operational year for the Trunk Road T2 is 2021. Design year peak hour traffic forecasts have,
therefore, been prepared for the years 2021, 2026 and 2036 which reflect the
full operation of the Trunk Road T2 for the purpose of Traffic Impact
Assessment (TIA). For the purpose of
EIA, traffic data for the prevailing year of 2009 and the forecast scenarios of
2021, 2026 and 2036 (i.e. opening year and 15 years after opening) will be
developed. A summary of the traffic data
and the road links included in the EIA are presented in Appendix 3D.
3.11.1.3
For the air impact assessment, specific information on the traffic
forecasts is required to conform to the latest EMFAC-HK formats. Specifically, the following information has
been provided:
· Peak hour traffic forecasts in the units of veh/hr (exact years to be confirmed) of major roads within 500m radius coverage of the Project (including the exposed sections of Trunk Road T2 and roads in Kai Tak South Apron);
· Forecasts broken down into 16 vehicle types as stated in the EMFAC-HK;
· Design speed for the road sections;
· Trips (veh) per day expressed as a daily profile (broken down by hour);
· Vehicle kilometres travelled (VKT) which is calculated by multiplying the flows within the corresponding roads lengths within the 500m coverage, broken down by the 16 vehicle types; and
· Daily profile (broken down by hour) of average vehicle travel speeds.
3.11.1.4
The relevant traffic forecasts for EIA purposes have been presented in Technical
Notes No.TN2 and TN3, and submitted to Transport Department for review. Letters from Transport Department confirming
no adverse comments are also included in Appendix 3D.
3.12
Environmental
Conditions in the Absence of the Project and Environmental
Benefits
3.12.1.1
The proposed Trunk Road
T2, together with the Central Kowloon Route (CKR) and Tseung Kwan O Lam Tin
Tunnel (TKO-LTT) will form the new strategic highway network, namely the Route
6 linking the Kowloon West with the Kowloon East. Trunk Road T2 will connect with CKR at
3.12.1.2
From a road connectivity perspective, in the absence of Trunk Road T2,
TKO-LTT would serve the Hong Kong Island to Tseung
Kwan O traffic unaffected (through the Eastern Harbour Crossing), but
significantly less so for Central Kowloon to Tseung Kwan O traffic. On an independently-operated basis, that is
without Trunk Road T2, TKO-LTT functions primarily as a “bridging” link between
Tseung Kwan O and Lam Tin/Kwun Tong only.
Traffic toward Central Kowloon from Lam Tin, Yau Tong, Tseung Kwan O
from either the existing TKO Tunnel or the future TKO-LTT would mainly rely on
the district and strategic roads, including Kwun Tong Bypass, Kwun Tong Road
and Kai Fuk Road and would result in the notable increase in the usage of these
roads with the traffic growth and may experience capacity issues.
3.12.1.3
Thus, Trunk Road T2 is considered a necessity to be in place in order
to provide connection between CKR and TKO-LTT as
Trunk Road T2 is a parallel route to the existing Kwun Tong Bypass. It would cater the traffic growth within the
Kowloon East area after commissioning of CKR and TKO-LTT, and would, also,
relieve traffic congestion of the district and strategic roads, Kwun Tong
Bypass,
3.12.1.4
Without the Trunk Road T2 connection, the existing roads passing
through the highly populated areas of Kwun Tong and
3.13
Designated
Projects Under the EIAO
3.13.1.1
The Trunk Road T2 project
constitutes a Schedule 2 designated project (DP) under the EIAO requiring an
Environmental Permit (EP) to be granted by the Director of Environmental
Protection (DEP) before it may be either constructed or operated. By the nature of the alignment and design of
Trunk Road T2, the project is a designated project with elements including
Items A.1 and A.7 under Schedule 2 of the EIAO.
Table 3.3 summarises the
identified individual DP under this Project.
Table 3.3 Schedule 2 Designated Project under this Project
|
Designated Project |
Nature of Works |
Part I of Schedule 2 |
Reason for Inclusion |
|
DP1 |
Trunk Road T2 |
Items A.1 and A.7 |
Trunk road and road tunnel more than 800m
in length |
Note:
Before the Trunk Road T2 project starts construction, the public cargo
working areas at Kwun Tong and Cha Kwo Ling will be decommissioned. Thus, Item B.4, Part I, Schedule 2 of the
EIAO is not considered relevant.