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:
·
Storage, transfer and trans-shipment of
liquefied natural gas with a storage capacity of not less than 200 tonnes (item
L.2 of Part I of Schedule 2 of EIAO);
·
Dredging operation for the approach channel
and turning basin that exceeds 500,000 m3 (item C.12 of Part I of Schedule 2 of EIAO); and,
·
Reclamation works (including associated
dredging works) of more than 5 ha in size (item C.1 of Part I of Schedule 2 of EIAO).
The
proposed Project involves the construction of a LNG receiving terminal together
with its related developments and supporting infrastructure (Figure 3.1). The information presented in this section is
taken from the preliminary design and will be subject to further study at the
detailed engineering design stage.
The
preferred scenario/alternative to be taken forward in this EIA has been
described in Part 3 – Section 2. This has been identified as the Base Case
Layout (Option 1). On the basis of this
selection, the preliminary layout plan is presented in Figure 3.1. Shown on the drawing is
the third tanks which will be constructed in the expansion case. A laydown area is
also included for construction of all three tanks. An on-site construction facility area has
been included in the layout for storage of construction equipment and later for
maintenance equipment. The key elements
of the Project are as follows:
·
Marine Dredging;
·
Land Excavation;
·
Land Reclamation;
·
LNG Jetty Construction; and,
·
LNG Terminal Facility Construction.
A
general summary of each of these key elements is presented in turn below followed
by a description of the key construction and operational activities in Sections 3.3 and 3.4.
3.2.1
Dredging
Dredging
of marine sediments will be required for the following
installations/facilities:
·
Approach channel and Turning basin;
·
Seawall for reclamation; and,
·
Seawater intake/outfall.
Dredging requirements for each of the above are
discussed below. Representative
geological cross sections showing the extent and depth of the marine sediment dredging
requirements for each of the above facilities are shown in Figure 3.2.
Approach
Channel and
Marine sediments will be required to
be dredged to allow safe navigation of the LNG carrier to the Black Point
Terminal. Due to the required draft of
the LNG carrier a project seabed dredging level of approximately -15 mPD is required for the approach route from the pilot
embarkation at the anticipated boarding station south of Ngan
Chau, through the Ma Wan Channel, along the
Seawall
and Reclamation
Approximately 16 hectares (ha) of
land will be reclaimed to the south of the Black Point Power Station in order
to provide sufficient space for the terminal facilities. The Partially Dredged Method of reclamation
has been adopted for the Black Point site as discussed in Section 2.2.1.
The use of ground improvement
techniques including vertical drains and surcharging have been considered in
order to accelerate the dissipation of pore water pressures and hence consolidation
settlements.
The
preferred layout option for the Black Point Site involves approximately a 700 m
length of sloping seawall and a 400m length of vertical seawall. An existing cooling water intake from Black Point
Power Station runs along the north-eastern shoreline of the proposed
reclamation. The cooling water intake
culvert is presumed to be supported on a rock base above the seabed. In order to reduce the disturbance to the
cooling water intake culverts, vertical seawall structures are adopted adjacent
to the intake culverts to maintain a clearance of 50 m from the seawall
dredging works.
To
reduce the hydrodynamic effects on the locality, the sloping revetment type
seawall is adopted along the remaining length of the reclamation boundary as it
will dissipate the wave energy more efficiently than a vertical seawall and
hence reduce wave reflection back towards the jetty structures. Also the sloping seawall has a more natural
appearance and is therefore more aesthetically attractive. Typical
sections through the proposed seawalls are shown in Figure
3.3.
Dredging
will be undertaken to remove the soft material beneath the seawalls to ensure that
these structures are stable.
Approximately 0.63 Mm³ of soft marine sediments will be dredged under
the seawalls. A small amount of rock
trimming may also be required to provide a level platform for seawall
construction, which may be undertaken using a hydraulic breaker.
Approximately 0.785 Mm³ of rock
shall be required beneath the seawalls which shall be largely sourced from the
on-land excavation works. The remaining
excavated rock material and soft soil material from the land works shall be
used within the reclamation. The
remaining reclamation volume will be filled with approximately 1.56 Mm3 of
marine sand fill and 0.54 Mm³ of public fill.
The
quality of marine sand fill to be used for the reclamation including the fines
content is detailed in Tables 3.1 and
3.2.
Table 31.1 Particle Size Distribution of Sand Fill
|
Type
of Fill Material |
Percentage
by Mass Passing (%) |
||
|
BS
test sieve size |
|||
|
75mm |
20mm |
63mm |
|
|
Underwater fill material (Type 1) |
100 |
- |
0-30 |
|
Underwater fill material (Type 2) |
100 |
- |
0-25 |
Table 31.2 Geotechnical Parameters of Sand Fill
|
|
Bulk Density (kN/m3) |
Friction Angle (o) |
Cohesion (kN/m2) |
|
Underwater fill |
19 |
30 |
0 |
3.2.2
Seawater
Intake/Outfall
The
design of the seawater intake and outfall for the Black Point terminal is
described in Part 3 – Section 3.3.3. Dredging of marine sediments will be required
to bury the intake pipe to a safe depth.
All dredging will be undertaken in soft marine sediments for which an
approximate quantity of 34,500 m3 will be required to be removed.
3.2.3
Land
Excavation
Excavation of around approximately
220,000 m3 of soft material (i.e., soil) will be required to be
excavated from the Black Point headland.
An additional quantity of approximately 770,000 m3 of hard
material (i.e., rock) will also be required to be removed.
3.2.4
Land
Reclamation
Reclamation of about 16 ha of land
extending from the Black Point headland will be made using marine sand fill and
fill generated through excavation works.
Approximately 320,000 m3 of public fill material will need to
be imported to supplement the existing 220,000 of m3 of available
soft material for construction of the Black Point terminal. The works will involve construction of about
1.1 km of vertical and sloping seawall.
The reclamation area will be primarily for the LNG terminal process area
and other associated facilities such as the lay down area and administration
buildings.
3.2.5
LNG
Jetty
Construction
of a 100 m long trestle leading to the jetty structures and unloading arms will be required to the northwest
of the reclamation site (Figure
3.1).
The primary use of the jetty will be to unload LNG from the LNG
carriers.
3.2.6
LNG Terminal Facilities
Once the land has
been formed the construction of LNG terminal infrastructures and facilities
will include LNG Storage Tanks (capacity of 160,000 to 180,000 m3
with approximate dimensions of 90 m external diameter by 49 to 64 m height to
the top of the dome of the tank, ie +70mPD), Low
Pressure and High Pressure pumping systems, Vaporization (Re-gasification)
Area, Vents (low pressure and high pressure), Process Area, Maintenance
Workshop, Administration Building, Guard House, Utility Area, Control Room.
Terminal storage
capacity is determined by a number of factors including gas usage patterns,
peak demand, demand growth, distance from LNG sources, and ship size. Tanks are sized to allow offtake
of the contents of an LNG carrier and to provide such additional storage
capacity to allow for uninterrupted gas supply in the event of shipment delays
due to storms, etc. and to accommodate seasonal demand patterns. Based on simulations[1], the terminal will
initially require two tanks, each with capacity up to 180,000m3,
with a potential third tank to meet future expansion
3.3.1
General
Construction Sequence
To
accommodate the necessary infrastructures of the LNG terminal at Black Point, a
total area of approximately 32 ha of land is required. Not all of this land will, however, be
physically altered. The majority of the
land will be formed through and balanced cut and fill reclamation. This will necessitate excavation of the Black
Point headland which will also provide screening for the LNG tanks. As the marine approach to the site is
shallow, floating pontoons will be initially used to reach the deeper water to
provide initial access for marine vessels.
Dredging will be carried out as soon as practical to obtain closer shore
access once approval to undertake marine dredging is attained. Heavy machinery will be mobilised to site
either via barge or road access using the temporary haul roads formed on land
as necessary. The conceptual
construction sequence is presented below.
It should be noted that this sequence has been based on preliminary
design and will be subject to further study during the detailed design stage.
1.
Barging points will be set up at the
waterfront with sufficient water depth to allow berthing of barges.
2.
The on-land site works will commence with
the removal of the scrub and vegetation on the existing slope prior to slope
cutting works.
3.
The removal of the soft materials on the
surface of slopes will continue shortly afterwards. In conjunction with these works, a temporary
haul road will be constructed which will allow heavy machinery to be mobilised
and transported to the crown of the cut slope.
4.
Immediately upon completion of the haul
roads, drilling rigs will be mobilised to the crown of the proposed slope for
the sinking of holes for blasting operation.
5.
Blasting works would be carried out continuously
on a daily basis until the final formation level is reached.
6.
Once approval is obtained to undertake
marine works, dredging will be undertaken for the seawalls and reclamation in
parallel with the blasting works.
7.
Dredged material will be removed to approved disposal/storage sites by barges.
8.
Rock material excavated from the site will
be reused as to the extent practical for the foundation of seawalls assuming their
quality and properties meet the requirements of the core material for seawall
construction. Excess material will be
barged away to an appropriate approved stockpile or quarry for use elsewhere in
9.
A sand blanket layer followed by rock fill
and soft soil materials, of suitable size and grading from the blasting and
excavation works, will be deposited into reclamation works until the required
formation level is reached.
10.
Two batching plants will be erected on site
as early as possible to provide the necessary steady supply of concrete for the
superstructure works and the proposed slope protection measures.
A more detailed description of the
construction activities is presented below.
3.3.2
Land
Based Works
The
site will require levelling, preparation and excavation for the landside works to
a level of approximately +6 mPD, which should largely
comprise rock excavation. This will
involve blasting followed by grading with earthmovers to ensure a suitable
construction surface. Approximately 95%
of the excavated material will be suitable for use within the reclamation. However, due to uncertainties between the
relative timing of the land excavation works and the marine reclamation works
it may be necessary to temporarily store and process the excavated material
off-site. The remaining 5% is assumed to
be topsoil, which is unsuitable for reclamation purposes and will be used for
landscaping on the site to the extent practical.
In
general, the land-based works would be expected as follows:
1.
Formation of access haul roads
2.
Slope cutting works
3.
Seawall and reclamation works
4.
Slope protection works
5.
Drainage works
6.
LNG Tank Construction
7.
Construction of Associated Facilities
a.
Batching Plants
b.
Magazine Storage
c.
Operating Facilities
Each of these proposed works are
discussed below.
Formation
of Access Roads
The
existing slopes at Black Point are estimated to be inclined at between an
average of 45 ~ 50° which is too steep to permit direct access to construction
plant. As slope cutting work are
required to commence from the upper levels of the existing terrain working
progressively downwards good road access will be required. A temporary haul road is, therefore,
necessary to be constructed to facilitate the mobilization of construction
plant to the initial excavation areas.
The haulage road will also be used for mobilization and transportation
of drilling rigs, excavators, explosives and protective cages etc which will be
essential for the slope cutting works.
The road will also be used to transport excavated materials from the
site to the barging points for disposal off site or directly onto the
reclamation area. If necessary, soft
material may need to be temporarily stock piled at the site depending on the
rate of excavation and permitting process.
It is expected that the slope cutting works may be carried out on the
southern and northern slopes simultaneously.
Slope
Cutting Works
The
site formation works will be carried out from several berms
formed at pre-determined levels to accommodate the necessary drainage works and
landscaping works. The berms are typically provided at 10 m vertical intervals and
will likely be used to provide a temporary working platform for the drilling
and blasting works.
Construction
plant will be mobilized on site to undertake the excavation works including bulldozers,
excavators, wheel loaders trucks etc.
The
majority of material excavated from Black Point shall be used within the
reclamation. However, due to the
relative timing of the excavation and reclamation works and the limited space
available on site it may be necessary to temporarily store the excavated
material at a designated stockpile site.
Black Point is located on a headland with limited road access. Marine-based transportation mode such as
barges for the disposal or removal of the excavated materials is, therefore,
recommended. For this purpose barging
points will need to be set up on site.
Waste management is discussed in Part
3 – Section 7 of this EIA Report.
Seawall
and Reclamation Construction
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 +6 mPD. In this regard, the only issue is to maintain
a marine access throughout the construction period through good sequence
planning such that the pelican barges can deposit the sand fill material at the
designated deposition area. In this
manner double handling of deposited fill material using land-based trucks would
also be kept at a minimum.
The
rock filling or public filling will be undertaken by derrick barges through end
tipping, after the sand fill has reached a level of +2.5 mPD
and treated with vibro-compaction. The fill materials will be placed by truck
and compacted by bulldozer in layer increments of 300 mm thickness or
less. The public fill materials can be
obtained from the existing fill banks located at Tuen
Mun Area 38 although transportation of materials will
be the Contractor’s responsibility. It
could also be obtained from the public filling barging points at different
locations around
The
ground improvement techniques for the placed fill materials include vibro-compaction. Vibro-compaction is the most commonly used ground
improvement method applied in drained reclamations to densify
the fill material to reduce long-term creep settlement. It is carried out by controlled penetration
and retraction of a vibrating poker (vibroflot)
within the fill layer.
The
vibration is applied at a high frequency and with the assistance of a water jet
or compressed air. Using this method the
inter-granular forces between the soil particles are temporary nullified and
liquefaction occurs, allowing the particles to be rearranged into a denser
matrix. The degree of compaction is
controlled by the energy input and spacing of the compaction points, typically
at between 2.5 m and 4 m.
This
ground improvement technique is effective in densifying
the ground at the lower levels although it is less effective within the surface
few metres and therefore a traditional roller compaction method is normally
employed for these layers. In addition,
trial compaction shall be performed to determine the optimal values of spacing
and depth before full-scale implementation.
Slope
Protection Measures
After
the blasting works progress, the exposed rock surfaces will be mapped and
appropriate slope protective measures designed and incorporated. The drilling rigs at the site will be used to
install stabilisation measures, which will likely comprise of dowels and
anchors.
Drainage
System
Appropriate
drainage systems shall be installed after the slope cutting works are completed
in conjunction with appropriate de-silting processes. During the construction stage, a temporary
surface channel shall be constructed along the perimeter of the site such that
any surface run off will be collected and treated before discharging into the
sea.
The
temporary drainage system during the construction phase shall be formulated by
the Contractor to be compatible with his method of works and construction
programme. The temporary drainage shall
follow EPD’s Practice
Note ProPecc PN 1/94.
Appropriate
mitigation measures to prevent impacts to water quality are discussed in the Water Quality Impact Assessment (Part 3 – Section 6 of this EIA Report).
LNG
Tank Construction
The construction of the LNG tanks is
one of the key elements of the works. At
the initial operation stage, two tanks shall be available for operation, with a
third tank for future expansion. The
180,000m3 tanks have an external diameter of about 90 m with an
overall height up to 64 m (ie +70mPD) although there
could be some variations in the final detailed design. This EIA Report will assess the worst case
scenario which comprises three tanks.
The
full containment system of LNG tanks has been selected for this project. Typical LNG storage tanks are a full
containment design and are composed of a 9% nickel steel inner tank container,
which is surrounded by an insulator. An
external concrete outer tank will be constructed around the outermost surface
to protect the insulator and the 9% nickel steel container. The full containment tank is capable of containing
the LNG liquid and performing controlled venting of the vapour from any LNG
leakage.
After
the external reinforced concrete tank wall has been completed, the roof is then
air raised. The
9% nickel steel tank will be constructed within the concrete tank. Steel plates will be welded on site within
the outer tank. A temporary platform
will be erected within the concrete tank to facilitate the steel work
construction, lifting and installation process.
Following
construction the tanks will be hydrotested for
integrity. The assessment of any
potential impacts associated with hydrotesting
activities are discussed in the Water
Quality Impact Assessment (Part 3 –
Section 6 of this EIA Report). Potential
impacts of hydrotesting activities on marine ecology
and fisheries are assessed in Part 3 –
Section 9 and Part 3 – Section 10 respectively.
Construction
of Associated Facilities
Batching Plant
A
continuous and undisturbed supply of concrete will be required for the
construction of the critical structural elements and in particular the external
concrete walls for the large LNG Tank structures and the associated processing
units. To secure the supply of concrete
for construction two batching plants will be erected on site. The plants would be expected to be of a
relatively small size and will likely be located near the waterfront with a
dedicated berth for the import and storage of sand, cement and aggregates.
Potential
air quality impacts associated with the batching plant are discussed in Part 3 – Section 4 of this EIA Report.
Magazine Storage
The
use of explosives for blasting is essential in the large-scale site preparation
works. The explosive will be classified
as Category 1 Dangerous Goods.
For
safety and security reasons, stringent control on the storage and usage of
explosives will be employed. Various
requirements on the implementation of such a facility have been provided and
are summarised below.
·
Max 1,000 kg of explosive,
·
Brick and earth bund,
·
400 m from densely populated areas (based
upon a 1,000 kg store),
·
45 m away from (440v) to 75 m away from
(1KV) electric cables,
·
Approval of Police Commissioner,
·
Secure facilities,
·
Lightning conductor,
·
Non ferrous hinges on doors,
·
Fence offset 6 m and at least 2.5 m high
and secure,
·
Guard, guardhouse, watchdog and telephone,
·
Flood lighting,
·
Fire fighting equipment,
·
Level ground,
·
Notices and Warning Signs and other minor
conditions.
The above requirements will be
incorporated during the detailed design stage.
Operating Facilities
Following
the completion of the land works the formed site will be handed over for
permanent facilities construction. The
facilities portion of the work will include installation of the following:
a.
Jetty including unloading arms,
b.
Process Area,
c.
Two full containment cryogenic LNG Tanks
(capacity of up to 180,000 m3 each) with a third tank for
future expansion,
d.
Low Pressure and High Pressure pumping
systems,
e.
Vaporization (Re-gasification) Area,
f.
Vents (low pressure and high pressure),
g.
Maintenance Workshop,
h.
i.
Guard House,
j.
Utility Area,
k.
Control Room.
The
basic features of the above are discussed in Part 1 – Section 3.
The
LNG terminal will be designed and operated according to the European
Standard EN 1473 – Installation and Equipment for Liquefied Natural Gas -
Design of Onshore Installations ([2]). The tanks will
be designed and constructed to BS 7777 ([3]) standard. Other
design parameters are shown in the Basis of Design (Table 3.3).
Table 31.3 Project Design Features
|
Key Parameter |
Preliminary
Design Value / Codes |
|
LNG Carrier Capacity (m3) |
125,000 to 215,000 |
|
Maximum Number of LNG Storage Tanks |
3 |
|
LNG Tank Size (m3) |
160,000 - 180,000 |
|
Land Requirement (Ha) |
~32 |
|
|
Major Design
Codes |
|
Terminal |
EN1473 |
|
LNG Tanks |
BS 7777 – 2 – 1993 |
|
LNG Carriers |
IGC/OCIMF/SIGTTO/Class |
|
Gas Pipeline to BPPS |
ASME B31.8, IGE/TD/1, DNV 81 |
3.3.3
Marine Works
Marine works associated with the LNG
Terminal will be divided into the following works:
·
Seawall and Reclamation,
·
LNG Jetty,
·
Seawater Intake/Outfall.
A
description of the works associated with each of the above key construction
activities are presented below. The
information presented in this section will be further studied at the detailed
engineering design stage.
Seawall
and Reclamation Construction
To
ensure stability, the LNG tanks are to be constructed within the base formation
of the cut slopes and founded on rock.
Associated plant facilities will, therefore, need to be located on the
reclamation land. To reduce potential
for water quality impacts to occur during the construction stage, reclamation
work will commence following the installation of seawalls.
Reclamation extending from the Black
Point headland will be formed using partially dredged methods of
reclamation. Reclamation activities for
the project will include the construction of a seawall, which will involve:
·
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 excavated rock and fill
material and concreting works to construct the seawall;
·
Infill of the area behind the seawall with
excavated rock and fill materials to create the formed site;
·
Surcharge of the filled site to assist
settlement; and
·
Removal of surcharge material and
completion of formed site.
Dredging
in the seawall area may be carried out using either Trailing Suction Hopper
Dredgers (TSHDs) or grab dredgers or a combination of
both. Dredging plant is discussed
further in the Water Quality Impact
Assessment (Part 3 – Section 6 of
this EIA Report).
A
permanent seawall and vertical block-work will be constructed around the
seaward boundary of the reclamation to protect the reclamation site from wave
and tidal action.
The
rock filling or public filling will be undertaken by derrick barges and treated
with vibro-compaction. Details of the filling activities are
reported in Section 3.3.2.
LNG Jetty
Construction of a 100 m long trestle
leading to the jetty structures and unloading arms will be undertaken to the northeast of the
reclamation site. The jetty and associated facilities
will typically consist of an unloading platform, walkways, four breasting
dolphins, and six mooring dolphins. The
jetty will be capable of accommodating an LNG carrier with capacities ranging
from 125,000 m3 up to a class of 215,000 m3. The main activity at the jetty will be
unloading of the LNG carriers to onshore tanks.
Unloading arms will be provided to unload the LNG. LNG liquid and vapour pipelines and utility
piping and cabling will run to shore along the access trestle. Steel framed walkways connect all dolphins to
the unloading platform. The alignment of
the jetty is presented in Figure
3.1 whereas the conceptual layout of
the jetty is provided in Figure
3.4.
The unloading platform will support
four LNG liquid unloading arms, one vapour return arm, an associated cryogenic pipework, and a gangway that provides access to the LNG
carrier. The platform will also be
provided with firewater monitors, an operator shelter and an environmental
(e.g., meteorological) monitoring system.
The platform will be sized with sufficient open space to permit a small
truck or maintenance crane to make a three point turn. The elevation of the top
of the unloading platform is at + 9.5 mPD. The unloading platform will consist of a
concrete platform supported by piles.
The conceptual plan of the elevation of the unloading platform is shown
on Figure 3.5
whereas the conceptual plan and elevation of the mooring and breasting dolphin is shown on Figure 3.6.
Piling for the Jetty
In
order to resist the horizontal loading generated by the berthing of LNG
carriers, piles have to be designed using either steel or reinforced
concrete. There are two basic methods of
pile installation including:
·
Bored piles; and,
·
Percussive piles.
A
comparison of these methods is presented in the Consideration of Alternative Construction Methods (Part 2 – Section 2 of this EIA Report).
Bored
Piles
In
the marine environment high strength bored piles require a steel shell to act
as a formwork for casting the reinforced concrete. The shell will need to be advanced by
vibratory methods.
Percussive
Piles
The
standard design for heavily loaded oil and gas jetties and also heavily loaded
container terminal decks in
Standard
practice in
General
designs for the bubble curtain include either the operation of a incorporating
a steel ring that releases air bubbles either on the seabed or below the
surface around the piling barge.
Designs
for the bubble jacket involve the release of air bubbles close to the seabed
inside a steel jacket fitted with neoprene spacers to prevent the jacket
contacting the pile. The bubbles
displace water upwards creating an air pocket around the pile that reduces
sounds being transmitted to the water outside the steel jacket. The design of the bubble curtain/jacket will
depend on the detailed design of the piled structures. Examples of bubble curtain/jacket are shown
in Figure 3.8.
Potential
impacts of underwater sounds are discussed in the Marine Ecological Assessment (Part
3 – Section 9 of this EIA
Report).
Associated Facilities
Service Berth
A service berth
shall be provided for delivery of the construction plant and materials, fresh
water, removal of waste and for transporting workers to and from the site
during the construction stage.
The service
berth should be in the form of a simple vertical seawall with sufficient water
depth for the berthing of support vessels.
Sufficient working area shall also be provided adjacent to the berth
such that the materials / equipments could be offloaded for inspection and be
delivered to the work site using trucks.
As no berth is available at the Black Point site, a temporary berth
shall need to be set up to facilitate the mobilization of plant for the initial
work phases.
Barging Points
Barging points will be used for the
unloading of spoil material into the hopper of a barge.
Floating
Pontoons
Due to the
potential delay in the provision of a permanent service berth, a floating
pontoon is recommended to provide a temporary marine access to the site. A flat top barge with an access bridge
connected to a seawall or directly onto the shore would likely be used. An appropriate anchor system will be
incorporated to maintain the pier at a fixed position.
Seawater Intake/Outfall
In
order to provide water for regasification of LNG,
seawater will be extracted from the waters surrounding the reclamation
site. In order to draw in the warmest
water to the vaporisers for optimum efficiency in the regasification
process the seawater intake will be designed to be as high as possible within
the water column. For this purpose the
intake will be installed through the revetment of the seawall structure (Figure 3.7).
The
returned seawater leaving the ORV's will be
discharged to the sea (Figure
3.1) through a box culvert and spargers. The spargers will lie on the seabed at a depth of approximately
-7 mPD. The
outfall will be buried to an approximate depth of –1.5m below the sea bed with
rock armour protection. Dredging works
will be undertaken using grab dredgers.
3.4
Operation and Maintenance of the LNG Terminal
Facilities
The
LNG terminal will serve as a fuel import, storage and supply facility. Operation of the terminal facilities will
include the following significant process operations:
·
LNG carrier approach, berthing and
departure;
·
LNG unloading from carriers at LNG jetty
and transfer to shore;
·
LNG storage in onshore tanks;
·
Re-gasification of the LNG to natural gas
in LNG vaporisers; and,
·
Final send out of natural gas via a short onshore
pipeline to the BPPS. The onshore
pipeline is expected to be within the boundary of the BPPS.
3.4.1
LNG
Receiving Terminal
At
the receiving terminal, the LNG will be stored at near atmospheric pressure in
cryogenic full containment LNG storage tanks and, when required, brought back
to a gaseous state prior to being dispatched via an onshore pipeline to Black
Point. LNG will be pumped from the LNG
carrier through loading arms on the jetty and to the storage tanks onshore via
insulated loading lines. In response to
the gas demand, LNG will be pumped from the storage tanks to the
vaporisers. The resultant natural gas
will then be metered, heated and transported to the neighbouring Black Point
Power Station.
LNG
Terminal Perimeter Fence
As
part of the EIA, hydrocarbon hazards have been identified and quantified for
this specific project (Section 13). The modelling of
potential releases for the LNG terminal has given rise to the requirement to
create buffer zones based on the category of equipment in particular
areas. This has been evaluated so that
possible scenarios necesitate the required external
safe perimeter zone by distance (buffer zone) sometimes mitgated
by fire barriers so that potential accidental releases do not affect
populations outside the LNG Plant. The
distance to the perimeter is based on potential leak scenarios, the hydrocarbon
inventories, and the possible radiation affects from an ignited event. It
should be noted that the evaluated events are still low frequency events.
British Standard BS EN 1473:1997 installation and equipment for liquified natural gas, design of onshore installations and
NFPA 59A Standard for the Production, Storage and Handling of Liquified Natural Gas have been used as a basis. The derived perimeter location has been
adjusted to cater for the topography of the land, wind direction and experience
from previous site installations worldwide.
For safety reasons, members of the public will not be allowed within the
confines of this zone. No development
will be undertaken inside the zone other than a fence being erected along the
buffer zone boundary. This allows for
both public safety and security of the facility. The buffer zone increases the
total land area required to some 32 ha overall.
3.4.2
LNG
Carrier (LNGC)
Two
tugboats will accompany the LNG carrier after embarkation of the pilot. Two
additional tugs will be available in the vicinity of the Tsing
Ma bridge to provide assistance as necessary and
remain for the rest of the transit.
Before making the turn into the Ma Wan channel, and until clear on a
westerly heading, one tugboat will be made fast to the stern of the
carrier. For other segments of the
transit, tugboats will participate in a passive mode and assist as required.
Prior
to a LNG carrier berthing at the Black Point receiving terminal, transit is
through the final approach channel into the adjacent turning basin. During the turning manoeuvre, four tugboats
will control the carrier. When the
manoeuvre is complete, tugboats provide assistance in aligning the carrier for
a parallel approach and controlled speed for landing on the jetty fenders. The tugboats will hold the carrier alongside
until secured to the mooring dolphins.
At the jetty, the carrier will be
connected with the receiving terminal through the unloading arms. Two tugboats will remain on stand-by in close
proximity to the terminal throughout the unloading operation. The LNG in the carrier will be unloaded to
the storage tanks at a rate of approximately 14,000 m³ hr-1, using
the carrier’s own pumps. The discharge
of LNG from the carrier takes approximately 18 hours. In addition, approximately 3 hours for
mooring, cool down, connecting unloading arms, and cargo measurement, and approximately
3 hours for cargo measurement, arm purging, disconnecting arms, and unmooring.
It
is envisaged, based on the preliminary terminal throughput, that one LNG
carrier will berth at the terminal every five to eight days. In accordance with Study Brief Section 3.2 (vi), the Landscape and
Visual Impact Assessment (Part 3 – Section 11) will assess the impact of
the LNG terminal and the LNG carriers.
During
the discharge operation, ballast water will be taken onboard from the
surrounding water into the double hull compartments to compensate for cargo
discharge. No ballast water will be
discharged in
3.4.3
Control
of LNGC Berthing Operations
The LNG jetty will be designed to accommodate the
size and type of LNG carriers that are required to meet the cargo volume
requirements. Each LNG carrier will be
compared against predetermined acceptance criteria before being approved for
the terminal.
In addition, the requirements of the carrier's
security plan shall be implemented consistent with the "International Ship & Port Facility
Security Code" (ISPS) ([4]) .
Once berthed, staff will complete various safety
checks collectively and unloading operations will not commence until the
Ship/Shore Safety Checklist included in the ‘International Guide for Oil Tankers and Terminals ([5]) ’ has been completed satisfactorily.
3.4.4
Control of LNG
Unloading Operations
During
cargo discharge the vapour pressure in the LNG carrier cargo tanks will be
maintained by returning vapour from the tanks onshore. With this balanced system, under normal
circumstances, hydrocarbons will not be released to the atmosphere.
3.4.5
Safety
Zones
While
an LNG carrier is moored at Black Point, the waters and waterfront facility
located within a defined boundary will be constituted as a safety zone to avoid
potential collision from passing traffic.
The dimension of this zone is under review with the objective of
providing optimum safety for the moored carrier.
3.4.6
Onshore
Modes of Operation
The
LNG terminal will have two main modes of operation:
·
Unloading
Mode – The
unloading mode is the period when an LNG carrier is moored on the jetty and is
connected to the onshore storage tank by means of unloading arms. The pumps on the LNG carrier will transfer
the LNG in both the unloading and the re-circulation lines to the onshore
storage tanks. At the end of unloading,
pressurised nitrogen gas will be used to purge the arms of LNG before
disconnecting.
·
Holding
Mode – The
holding mode is the period when no unloading takes place, while send-out to the
transportation gas pipeline continues. The purpose of the holding mode is to
allow cryogenic conditions to be maintained in the unloading and circulation
system. In order to maintain these
conditions LNG will be circulated via the unloading line to the jetty head and
back to the onshore storage tanks or the send-out system via the re-circulation
line.
During
both of these modes of operation, LNG will be pumped out of the onshore storage
tanks and boosted to the pressure required by the end user before being routed
to the gas transportation pipeline via the LNG vaporisers.
3.4.7
Drainage
System
Operational
Site Drainage
Stationary
equipment that could release hydrocarbons and that are not located in a curbed
area will be installed on skids containing drain pans. An open drain system will collect spills and
rainwater from all equipment skids and other appropriate areas. The drain fluids are collected in an oily
water sump and pumped to a CPI-type oily water separator unit for
separation. Clean water will flow to the
seawater return basin. Oil and hydrocarbon
liquids shall be removed and sent to a reclaiming facility. Clean water from the separator will be
monitored for oil content before being discharged.
Drainage
from open areas that are not subject to hydrocarbon spills will flow to sea via
the seawater outfall. Should a
hydrocarbon spill in these areas occur from mobile equipment fuel, oil or
hydraulic hoses, prompt spill clean up should occur using strategically placed
spill clean up supplies.
Engine
wastes, such as lube oil, hydraulic fluid and engine coolant shall be
transferred to a waste treatment facility for reclaiming or disposal. Solid wastes shall be sent to a proper
disposal location.
Table 3.4
presents the summary of the project site construction details. The Black Point Option requires 32 ha area,
half of which will come from reclamation, with 3.15 Mm3 dredging
volume. Approximately 1 Mm3
of excavation is required on land, all of the
excavated materials will be reused for reclamation. In addition, 1.8 Mm3 soil have to
be imported to fill the reclamation area.
Table 31.4 Summary of Site Construction Description
Parameter |
- BLACK POINT - |
|
Overall Project Area (ha) |
32 ha |
|
Land Based Works Area (ha) |
5 ha |
|
Reclamation Area (ha) |
16 ha |
|
Site Development Area |
21 ha |
|
Dredging Volumes (Mm3) |
Seawall =
0.63 Mm3 Berthing Trench & Intake/Outfall = 0.03 Mm3 TOTAL =
3.15 Mm3 |
|
Length of Natural Coastline
Affected (m) |
600 m |
|
Volume of Excavated Construction
& Demolition Materials |
Soil (Total = 220,000 m3) Site Formation = 220,000 m3 Rock (Total = 770,000 m3) Site Formation = 770,000 m3 |
|
Volume of Fill Requirements |
Soil (Total = 2,100,000 m3) Reclamation = 2,100,000 m3 Rock (Total = 785,000 m3) Seawall =
785,000 m3 |
|
Volume of Excavated Construction
& Demolition Materials for Disposal |
Soil =
0 m3 Rock =
0 m3 |
|
Volume of Imported Fill |
Soil =
1,880,000 m3 Rock =
15,000 m3 |
|
Length of Submarine Utilities |
N/A |
The preliminary construction
programme is presented in Annex 3A. Site preparation works, including land works
and reclamation, are expected to be about 18 months. The reclamation works is assumed as a fast
track in order to meet the startup
schedule. Marine works, including
dredging for berth box, piling, and superstructure, are expected to be
completed in about 36 months. The
construction programme emphasises the project’s urgency as it would enable the
timely replacement of the depleting gas supply from the Yacheng
field (off Hainan Island - South China Sea) which is currently forecasted for
the next decade (please refer to Part 1 –
Section 2).
Following
the completion of the land works and reclamation and basic infrastructure, the
formed site will be handed over for permanent facilities construction. The
facilities portion of the work will include installation of the on-site road,
permanent drainage, equipment, piping, buildings, and the electrical power and
control systems for the process portion of the LNG terminal facilities.
There may
be the possibility for overlap between construction
works associated with the marine works of the proposed Emissions Control
Project at the Castle Peak Power Station ‘B’ Units. However, cumulative impacts are not expected
to occur due to the remoteness (> 4 km) between the two project works areas.
There are
presently no planned or committed projects that could have the potential for
cumulative impacts to occur with the construction of the Black Point
terminal. The Animal Carcass Treatment
Facilities (ACTF), Sludge Treatment Facilities and Waste-to-energy Facilities
(WEF) have been proposed to be constructed at Tsang Tsui
(located at least 2 km from Black Point), however, the programme remains
uncertain and the separation distance is such that cumulative effects are
highly unlikely. Discussions with the
relevant departments on the construction schedules of the WENT Landfill, Hong
Kong Zhuhai Macau Bridge EIA and Value Added
Logistics Park have also indicated that these are unlikely to be carried out
concurrently with the construction works for the Black Point LNG terminal.
Water
quality cumulative impacts are discussed in Part
3 - Section 6.