The Project is classified as a Designated Project under
the Environmental Impact Assessment Ordinance (Cap.
499) (EIAO). The works that are the subject of the
EIA Study include the construction and operation phases of the Project. The key components of the Project
include the following:
·
Installation
of submarine gas pipelines connecting the proposed Gas Receiving Stations (GRSs) at the Black Point Power Station (BPPS) and gas
export facilities in southern Guangdong Province (Item H.2 of Part I of Schedule 2 of EIAO); and
·
Dredging
operation exceeding 500,000 m3 for the reclamation and pipeline
trenches (Item C.12 of Part I of Schedule
2 of EIAO).
The proposed Project involves the construction of two
submarine gas pipelines and the associated GRSs. The first pipeline and GRS (i.e. First
Phase) must be completed in 2012 to provide facilities to accommodate a timely
replacement for the Yacheng 13-1 gas supply. It is expected that the Second Phase
could commence construction within 24 months of commissioning of the First
Phase. The information presented in
this section is taken from the existing preliminary design and will be subject
to further study at the detailed design phase.
The preferred scenario for the Project to be taken
forward in this EIA has been described in Section
2. On the basis of this
selection, the preliminary layout plans for the proposed Project are presented
in Figure 3.1.
The construction and operation of the two submarine
pipelines and the two associated GRSs will involve
the following key work elements:
·
Marine
sediment dredging;
·
Seawall
construction and land reclamation;
·
Submarine
gas pipeline installation, testing, commissioning and operation; and
·
GRS
construction, testing, commissioning and operation.
A general summary of each of these key elements is
presented below.
3.2.1
Marine Sediment Dredging
Dredging of marine sediments will be required for:
·
Construction
of seawalls and reclamation for the GRS; and
·
Pre-trenching
for submarine gas pipeline installation at the shore approach and for crossing
the
Dredging requirements for each of the above are
discussed in the following sections.
3.2.2
Seawall Construction & Land
Reclamation
A new reclamation area to the north of the BPPS will
be required to provide approximately 0.5 ha of land as the platform area for one
of the proposed GRSs. Permanent vertical seawalls will be
constructed around the seaward boundaries of the reclamation to protect it from
wave and tidal action. The vertical
seawall option will result in a smaller seabed area affected and smaller volume
of dredged sediment than that for sloping seawall, and is suitable in areas
where spatial constraints exist.
The preliminary layout of the proposed seawalls together with typical
sections is shown in Figure 3.2. The total length of vertical seawalls to
be built along the reclamation is approximately 200 m.
Dredging will be undertaken to remove the
soft material beneath the seawalls to ensure that these structures are stable
to enable construction of GRS facilities immediately after reclamation. Approximately 0.108 Mm3 of
soft marine sediments (in situ
volume) will be dredged (Table 3.1). Minor dredging works (about 0.012 Mm3
in situ volume)
will also be required to provide sufficient depth for the construction
barges ([1]).
A small amount of rock trimming may be required to provide a level
platform for seawall construction, which may be undertaken using a hydraulic
breaker.
Rock fill is placed into the seawall trenches up to
the existing seabed level to provide a foundation for the seawall blocks. Sand fill is placed into the reclamation
area to initially raise the ground level to +2.5 mPD
after which, public fill is compacted in layers to the finished level of +6 mPD. An
extended period of consolidation or settlement of fill materials, and ground improvement
works ([2])
such as the installation of
vertical drain with surcharge pre-loading, are not anticipated using this
method given the small size of the proposed reclamation.
At this stage it is expected that the seawall
trenches and reclamation will be formed using sand/ rock/ public fill sourced
locally or within the Pearl River Delta region. The total volume of fill material needed
is expected to be about 0.17 Mm3.
3.2.3
Submarine Gas Pipeline Installation
The installation of two submarine natural gas pipelines
connecting the new gas export facilities in southern
The design of the submarine gas pipelines is
described in Section 3.3.3. Dredging of marine sediments and jetting
will be required to bury the gas pipelines to a safe depth. Dredging will be required for the shore
approach and crossing the Urmston Road and will be undertaken in soft marine sediments
with an approximate in situ quantity
of 0.194 Mm3 for each pipeline trench required to be removed. The remaining sections of the pipelines
will be installed by jetting.
Approximately 0.329 Mm3 of rock and sand
fill material shall be required to protect each pipeline from anchor drop and
drag.
A summary of dredging and filling requirements for
this Project is provided in Table 3.1.
Table 3.1 Summary
of Dredging (in situ) and Filling (Bulk) Quantities of this Project
|
|
Pipeline 1 |
Pipeline 2 |
Reclamation with Vertical Seawall |
|
|
N/A |
N/A |
0.5 ha |
|
Affected Seabed
Footprint Area |
7.8 ha |
7.8 ha |
1.35 ha |
|
Dredging Volume |
0.194 Mm3 |
0.194 Mm3 |
0.108 Mm3 |
|
Additional
Dredging for Construction Barge |
N/A |
N/A |
0.012 Mm3 |
|
Total Fill
Required |
0.329 Mm3 |
0.329 Mm3 |
0.170 Mm3 |
3.2.4
GRS Construction
To accommodate the two GRSs
at the BPPS, a total area of approximately 1.5 ha of land is needed. Whilst about 0.5 ha of reclaimed land
will be needed for the Second Phase GRS, the remaining 1 ha for the First Phase
GRS will be from existing land within the site boundary of BPPS. This piece of land is located next to
the existing GRS of the BPPS. The
preliminary layout of the proposed reclamation is shown in Figure 3.3.
Facilities at the existing GRS of the BPPS will need
to be modified or relocated to accommodate the First Phase GRS, referred to as
the co-located GRS. Such
modification works will be undertaken prior to, and will continue in parallel
with, the construction of the GRSs. Details of the GRS construction works
are described in Section 3.3.2.
3.3.1
General Construction Sequence
The Project will involve two phases of construction
works:
·
First Phase: installation of the first pipeline (Pipeline 1) and
construction of the co-located GRS; and
·
Second Phase: installation of the second pipeline (Pipeline 2) and
construction of the reclamation and the associated GRS.
The construction of the two phases is expected to be
separate with the First Phase construction commencing in 2011 in order to
receive the replacement gas in 2012.
The Second Phase of construction is expected to commence within 24
months following commissioning of the First Phase.
The conceptual construction sequence is presented
below. It should be noted that this
sequence has been based on the preliminary design and will be subject to
further study at the detailed design stage.
1.
Site
preparation for co-located GRS and construction within BPPS site boundary.
2.
Once
approval is obtained to undertake marine works, dredging of the shore approach
and
3.
Dredged
material will be removed to approved disposal sites by
barge.
4.
Use
of suitable fill material for the bedding of the submarine gas pipeline,
followed by pipeline laying and jetting (of applicable sections) and subsequent
rock-filling as armour rock protection.
5.
Commissioning
of Pipeline 1 and the co-located GRS.
6.
Once
approval is obtained to undertake marine works, dredging will be undertaken at
the proposed locations for seabed formation and seawall construction for the
second GRS, as well as for the installation of Pipeline 2 leading to the
reclamation.
7.
Dredged
material will be removed to approved disposal sites by
barge.
8.
Backfilling
works to commence behind partially-completed seawalls to form the GRS
reclamation. A sand blanket layer
followed by rock fill and soft soil materials, of suitable size and grading,
will be deposited into the reclamation area until the required level is
reached.
9.
Vertical
seawall construction to commence, followed by backfilling to the formation
level and the completion of the seawalls.
10. Use of suitable fill material for the
bedding of the submarine gas pipeline, followed by pipeline laying and jetting
(of applicable sections) and subsequent rock-filling as armour rock protection.
11. Construction of the GRS on the newly
reclaimed land.
12. Commissioning of Pipeline 2 and the
associated GRS.
3.3.2
GRS Construction
Design Basis
To accommodate the necessary gas receiving facilities
of the GRS at least 0.5 ha of land is needed. Facilities associated with the GRS are not
complex and the site area requirements are small, generally comprising:
·
Emergency
Shutdown valves;
·
PIG
receiver, with associated service piping;
·
Station
inlet header;
·
Inlet
filter-separators (duty and standby runs);
·
Metering
runs (duty and standby runs);
·
Pipeline
gas heaters (duty and standby runs);
·
Pressure
control runs (duty and standby runs);
·
Vent
stack; and
·
Station
export header.
Piping and equipment will generally be skid-mounted
(size permitting) and placed on prepared concrete footings. Larger piping and equipment assemblies
will be delivered to site as discreet subassemblies and assembled on-site. Sensitive instrumentation will be housed
in air-conditioned instrument enclosures that are commonly prefabricated
portable buildings.
Gas will be received via the offshore pipeline and
the first major piece of equipment in the station will be an Emergency Shutdown
(ESD) valve, which can be closed by means of the station ESD system in the
event of an emergency, isolating the GRS from the source of gas.
Downstream of the ESD valve will be the station inlet
header that will distribute the gas to inlet filter units. Parallel to the inlet filters oriented
inline with the incoming pipeline will be a pig receiver, enabling the running
of cleaning and inspection pigs in the pipeline. A schematic process flow diagram for the
proposed new facilities is presented in Figure 3.4.
Downstream of the Gas Inlet filters, the gas passes
through the metering skid and into the gas heaters, for gas conditioning,
before the pressure of the gas is letdown at the pressure reduction station and
supplied to the station export header.
Land Based Works for Co-located GRS (First Phase)
Co-location of the new GRS with the existing GRS of
BPPS will require land clearance within the existing GRS site boundary to
accommodate the new GRS facility.
To provide the required land area for the proposed new GRS, the existing
vent stack is to be decommissioned and a new vent stack will be constructed to
the northeast corner of the facility.
The existing GRS will be connected to the new vent stack.
Construction of the co-located GRS next to the
existing GRS of BPPS will involve the following stages of modification and
construction works (Figures 3.5a, b and c):
·
Stage
1: a new vent stack, which will be built on a structural tower support, will be
constructed at the northeast corner of the GRS site. New independent pipe racks that run
adjacent to the current existing pipe rack will be constructed. Minor preparation works will be
undertaken at the vent header for tie-ins.
The existing vent stack will be decommissioned and removed from
site. New fences will be
constructed at the boundary of the new GRS site. Minor fencing modification works will
also be undertaken at the existing GRS for accommodating the proposed future
mixing facility.
·
Stage
2: the pipeline shore approach would be erected by breaking the existing
seawall, trenching, installing a box culvert followed by the installation of
the pipeline and riser. Once the
pipeline has been installed the trench would be backfilled and the seawall
would be reinstated to its original condition.
·
Stage
3: all new pipe racks and pipe rack modification would be erected along side
the existing GRS facilities.
·
Stage
4: New gas receiving facility (e.g. heating station, metering station,
filtering station, pressure reduction facility and pig receiving station) will
be constructed at the new GRS site, and the new pipeline will be connected to
the new GRS. Provision for a future
mixing facility tie-in would be provided at the proposed location.
Marine Works for GRS on Reclamation (Second Phase)
The reclamation at BPPS will include the construction
of permanent, vertical seawalls around the seaward boundaries of the
reclamation. Backfilling works for
the reclamation are assumed to commence behind partially-completed seawalls.
Reclamation activities will include:
·
Dredging
of sediments in the area where the seawall will be located. A small amount of rock trimming may be
required to provide a level platform for seawall construction;
·
Placement
of sand and rock fill material and concreting works to construct the seawall;
and
·
Infill
of the area behind the seawall with sand and public fill materials to create
the formed site.
The rock or public fill material will be brought in
to the site by split-bottom or derrick barges. These barges have been widely used in
reclamation works throughout
The public fill materials could be obtained from
existing fill banks, such as those located at Tuen Mun Area 38.
Transportation of materials from the fill bank will be the Contractor’s
responsibility. It could also be
obtained from the public filling barging points at different locations around
It is assumed that no marine borrow area would be
allocated by the government within
Pelican barges have been widely used in reclamation
works as its application would not be limited by water depth. With the aid of a conveyor belt
installed at the front of the vessel, the sand material could be deposited up
to a level of +2.5 mPD. Marine access would be maintained
throughout the construction period through good sequence planning such that the
pelican barges can deposit the sand fill material at the designated deposition
area.
3.3.3
Submarine Natural Gas Pipeline Installation
Design Basis
The two proposed pipelines will be installed in two
separate trenches (Figure 3.6). The preferred alignment avoids direct
impacts to ecologically sensitive habitats within the Sha
Chau and
Due to the relatively short construction time and
proven installation methods, impacts to marine traffic are expected to be
minimal.
The pipelines will have a design life of 25 years and
will be situated below the seabed to a depth that would be dependent on the
conditions and location of the area to be traversed. The preliminary construction methodology
for the pipelines is presented below covering both the onshore and submarine
works.
Onshore Section of Pipeline
The land-based construction works associated with the
Project would include laying the pipelines into open trenches followed by direct
burial. The pipelines would,
typically, be buried at about
Offshore Section of Pipeline: Pipeline Protection
The marine-based burial depth would typically be up
to 5 m below the existing seabed level to the top of the pipe. Typical cross sections of the trench
designs that may be used for the submarine pipelines are shown in Figure
3.7. For marine areas that
are considered to pose a threat to the integrity of the pipeline system through
anchor drop/drag, additional protective measures would be required and may
include rock armouring. The
pipelines would be coated externally with an anti-corrosion coating and wrap
and, would have an outer layer of steel reinforced concrete weight coating. There are three types of protection
proposed for the pipelines, as follows:
·
Type
1: 1.5 m burial with 0.5 m sand bedding and 1.5 m Armour Rock Protection;
·
Type
2: 5 m natural fill burial with 1 m Armour Rock Protection; and
·
Type
3: 3 m burial with 3 m Armour Rock Protection.
Trench Types 1 and 2 (Figure 3.7) are
designed for Type 1 hazards (i.e., trawling and small anchors), with additional
protection against dropped objects and small (2 – 5 MT) anchors within the
landfall approaches of Black Point.
Protection measures will also prevent damage to the pipelines through
any potential future dredging works.
Type 2 protection is applied for the majority of the route selection.
Trench Type 3 (Figure 3.7) provides maximum
protection to the pipelines. It is
designed to protect against both Type 1 and Type 2 hazards, with additional
protection against accidental anchor drop (up to 19 MT anchors) and drag by
seagoing vessels. This protection
is provided at the location where the pipelines cross high density shipping areas
(
Pipe-laying
The lay-barge method is the most common form of
pipeline installation. It is a
process whereby individual pipe lengths (usually
Dredging & Jetting
The proposed pipeline design requires a burial depth
of 1.5 m to 5 m. For submarine
utility installations, dredging or jetting involves the removal/ displacement
of marine sediments from the seabed to form the trench, into which the pipeline
is laid. Dredging/ jetting can be a
comparatively fast way to construct a pipeline trench and is necessary in areas
where extra pipeline protection is required (e.g. rock armour protection). Many dredging techniques, such as grab,
trailing suction hopper and cutter suction dredging are available and chosen
depending on the prevailing environmental conditions (e.g. shear strength of
marine deposits). The selection of
installation method for the gas pipelines has been discussed in Section 2 and depicted in Figure
3.6.
Dredging is planned to be carried out by grab
dredgers, while jetting will be done by a jetting machine. The potential impacts of these methods
are discussed further in the Water
Quality Impact Assessment (Section 6).
A summary of dredging requirements for different
sections of the pipelines is provided in Table
3.2. Pipeline sections are
defined based on marine traffic pattern and the associated level of anchor
drop/ drag risk for determining the pipeline protection requirements.
Table 3.2 Summary
of Dredging Volume (in situ) for Different Sections for One Submarine Gas
Pipeline
|
Pipeline Section |
Approximate Length (m) |
Approximate Trench Width (m) |
Approximate Affected Seabed Area (ha) |
Dredging Volume |
|
Section 1 |
110 |
3 |
0.03 |
0.001 Mm3 |
|
Section 2 |
2,400 |
5 |
1.20 |
-- |
|
Section 3 |
1,800 |
35 |
6.19 |
0.193 Mm3 |
|
Section 4 |
750 |
5 |
0.38 |
-- |
|
Total |
5,060 |
- |
7.8 |
0.194
Mm3 |
Note: Sections 2 and 4 of the pipelines will be
installed by jetting.
Armour Rock Placement
Rock armour is necessary to achieve adequate
protection against anchor drop and drag.
The vessel will manoeuvre to the designated area where the rocks will be
placed on top of the pipelines. A
barge will transport rocks from a quarry to the material storage barge.
Rock dumping is based on the use of typical Hong Kong
Derrick Lighters (1,800 – 3,000 T) configured to place rocks using grabs (as
has been adopted in previous projects in Hong Kong). These units have the capability to place
2,400/3,600 T/day of graded rock.
It is possible that the Contractor may elect to utilize specialized
side-dump equipment for some of the deeper water areas (e.g. Trench Type 3). It is also likely that the Contractor
will manipulate the numbers of units working in any area depending on the
equipment available at any time and on its actual progress vs
planned.
Black Point Power Station Landfall
Upon arrival of the pipelines at BPPS the existing
seawall will need to be opened to allow the pipelines to land. In order to reduce the amount of
demolition and later reinstatement works of the seawall structure it is
proposed that a cofferdam shall be provided for the shore approach works. Initially, the rock armour of the
existing seawall will be removed across the width of the proposed cofferdam
using a crane barge with a grab.
The cofferdam comprising parallel rows of sheet piles
will then be installed through the seawall. The cofferdam shall be formed
perpendicular to the shoreline out to sea to a sufficient distance beyond the
existing seawall. Any remaining
marine deposits within the shore approach cofferdam will be removed using grab
dredgers. The grab dredgers will
also similarly be used in conjunction with onshore backhoes in the near shore
areas to form the required approach profile through the BPPS seawall. The excavated rockfill
material from the seawall will be stored for later reinstatement works.
Once complete, the pipeline initiation operation will
commence by winching the pipeline to shore through the pre-formed trench within
the cofferdam structure. Following
installation of the pipeline the section of seawall within the pipeline trench
will be reinstated by backfilling with the stored rockfill
material previously removed from the BPPS seawall. The sheet piles will be subsequently
removed and the rock armour reinstated over the front of the seawall and around
the pipeline structure.
Operation of the facilities will include the
following aspects:
·
Receipt
of natural gas via pipelines; and
·
Send
out for use by the Black Point Power Station.
The proposed Project facilities are expected to be
automated and unmanned during the operation phase. However it is expected that during the
early operation phase a few personnel will work at the GRSs. It is also envisaged that maintenance
activities will be scheduled and will be routine in nature. As part of the EIA,
hydrocarbon hazards have been identified and quantified for this specific
project (Section 12).
Table 3.3 presents a summary of the project
details. The proposed Project
requires approximately 0.5 ha of reclaimed land, resulting in the construction
of 200 m of new artificial coastline.
A maximum total dredged volume of 0.508 Mm3 (in situ volume) of marine sediments will
be generated over the two phases of construction. It is noted that First Phase
Construction is expected to generate no more than 0.194 Mm3 (in situ volume) of marine sediments for
off-site disposal.
Table 3.3 Summary
Table of Key Issues
|
Issue |
Summary |
|
|
First
Phase Construction – Pipeline 1 & Co-located GRS |
||
|
Area of Seabed Affected
by Pipeline Footprint |
7.8 ha |
|
|
Dredging Volume
(in situ volume) |
0.194 Mm3
for Submarine Gas Pipeline Trench |
|
|
Length of
Submarine Pipeline (km) |
About 5 km in
HKSAR waters |
|
|
|
|
|
|
Second
Phase Construction – Pipeline 2 & GRS on Reclamation |
||
|
Reclaimed Land
(ha) |
0.5 ha |
|
|
Area of Seabed
Affected by Reclamation Footprint |
1.35 ha |
|
|
Area of Seabed
Affected by Pipeline Footprint |
7.8 ha |
|
|
Length of New
Artificial Seawall |
200 m |
|
|
Length of Existing
Seawall Lost due to Reclamation |
100 m |
|
|
Dredging
Volumes (in situ volume) |
Gas Receiving
Stations & Associated Seawalls |
= 0.12 Mm3 |
|
|
Submarine Gas
Pipeline Trench |
= 0.194 Mm3 |
|
Length of
Submarine Pipeline (km) |
About 5 km in HKSAR
waters |
|
Depletion of the Yacheng
13-1 field is expected to start as early as 2012 and hence there is an urgent
need for a replacement gas supply, and the timely permitting and construction of
associated pipelines and facilities to bring this gas to
The preliminary construction programme is
provided in Figure 3.8.
As noted in the programme the present plan is that the Project will be
constructed in phases. The first
pipeline and GRS (i.e. First Phase) must be completed in 2012 to provide
facilities to accommodate a timely replacement for the Yacheng
13-1 gas supply.
It is expected that the Second Phase could
commence construction within 24 months of commissioning of the First
Phase. Whilst the construction of
each of the submarine gas pipelines is expected to be completed in
approximately 10 months, site formation works for the reclamation (Second
Phase) would be expected to take 8 months.
3.7.1
Installation of Submarine Gas Pipeline(s)
in PRC Waters
Installation of Pipeline 1 in PRC waters is expected
to follow the broad construction programme of First Phase construction of this Project
to allow gas delivery. In the
absence of detailed implementation schedule it is conservatively assumed that
dredging works in PRC waters may be concurrent with those in HKSAR waters.
Given that Second Phase construction of this Project
is expected to commence within 24 months following commissioning of the first
pipeline and GRS, installation of Pipeline 2 in PRC waters is expected to take
place within the same timeframe.
3.7.2
Other Concurrent Construction Projects
At present the only known projects that is planned to
be constructed in sufficient proximity of the proposed GRSs
at BPPS and the submarine gas pipelines are the following HKSAR Government
projects:
·
Sludge
Treatment Facilities, which have been proposed to be located at Tsang Tsui (i.e. east of the existing CAPCO Ash Lagoons at Tsang Tsui and west of the WENT Landfill) at > 1.2 km from the
proposed reclamation and pipelines; and
·
The Sludge Treatment Facilities are currently
scheduled to commence construction in early 2010 for completion by the end of
2012. However, given the separation
distance cumulative impacts are unlikely to occur. The WENT Landfill Extensions are
scheduled to commence its first phase construction in 2016 when this Project is
expected to be in operation.
Cumulative impacts are therefore also unlikely to occur.
Information from the Shenzhen Port Tonggu Channel Developing Office indicates that maintenance
dredging of the Tonggu Waterway may take place
annually. Updated information to
determine if there is any overlap with the construction for this Project is not
available and this will be reviewed at a later stage.
Various activities have been proposed for the Nim Wan and Tsang Tsui areas
including an Animal Carcass Treatment Facility and Waste-to-energy
Facility. The programmes for these
projects remain uncertain.
Nevertheless, the separation distance from this Project (at least
Latest information ([3]) ([4])
([5])
has suggested that the HK-Zhuhai-Macau Bridge (HZMB) is targeted to be commissioned
by 2015. The construction schedules
of the HZMB and associated facilities are as follows:
·
Construction
of the Hong Kong Link Road (HKLR) will start in 2011, for completion in 2015,
with a construction period of 4 years;
·
Construction
of the Hong Kong Boundary Crossing Facilities (HKBCF) will start in the 3rd
quarter of 2010, for first phase completion by End 2015, and second
(final) phase completion by End 2016.
·
Construction
for the Tuen Mun - Chek Lap Kok Link (TM-CLKL) will
commence in late 2011, with a target opening date for the entire road link at
the end of 2016. However, the part
of the southern reclamation may be carried out in conjunction with the
reclamation for HKBCF which will commence earlier and in the 3rd
quarter of 2010.
Therefore, these projects may be constructed
concurrently with the construction works of the submarine pipelines. No other projects are presently planned
to be constructed in sufficient proximity to the Project to cause cumulative
effects. Cumulative assessments
where applicable have been conducted and are presented in the relevant
technical section in the remainder of this EIA Report.