2.1 The Project Requirements and Programme
The southern portion of the Rambler Channel between Tsing Yi
and Kwai Chung has been developed into
Developments within the container shipping industry have seen
the introduction of ultra-large container ships (ULCS) to the main
intercontinental shipping routes. These vessels have a maximum draft of 15.5m.
The current average seabed level within the KTCB is approximately -15.6mCD,
while depths in parts of the approaches to the KTCB are shallower. Therefore,
it is proposed under this Project to deepen the seabed level of the KTCB and
its marine access route to provide adequate depth of water to enable the new
generation of ULCS to call at the KTCP. The Project layout is shown in Figure 2.1.
The Project’s objective is to lower the
seabed in the KTCB and its access fairways and channels so as to maintain an adequate
clearance for ULCS at all times. For the purpose of determining the functional
least depth of dredging, the maximum draft of an ULCS is taken to be 15.5m. It
is recommended in Marine Department’s “The Complete
Berthing Guidelines for
In order to determine
the appropriate maintained seabed level, an assessment of the sedimentation
rates within the Project area since 1990 has been carried out. The assessment concludes that the
potential for sedimentation within the Project area is low. However, it
is not known with certainty that the conditions which existed in the period
covered by the assessment will prevail for the service life of the KTCP. In order to account for
possible increases in the sediment load in the Pearl River Estuary, yet still
achieving a sensible balance between capital and maintenance dredging works, a
target seabed level of -17.5mCD has been adopted.
In Section 2.2.1 of
Port Works Design Manual Part 1, the Chart Datum (CD) is 0.146m below the
Principal Datum (PD). Therefore, the target seabed level is -17.646mPD. For
construction tolerance, the final seabed level should not be shallower than the
targeted level, nor should it be 0.3m deeper than the targeted level.
In addition to the
foregoing, modification of the Tsing Yi Submarine Sewage Outfall and
demolition of the Kwai Chung Submarine Sewage
Outfall are included as
part of the scope of works for this Project. For the Tsing Yi Submarine Sewage
Outfall modification works, this will involve removal of the rock armour,
replacement of the existing riser pipes and non-return valves, and followed by
the re-application of rock armour. Demolition of the Kwai Chung Submarine Sewage Outfall will only involve the
dismantling of the pipe section that is above the dredge level. The
dredged volume quoted in the Study Brief was 5.5Mm3; however, as the
engineering design has progressed in parallel with this EIA, the dredged volume
has been refined to be at 4.4Mm3.
This provides environmental benefit through the reduction in the volume
of material to be dredged and disposed of as well as reducing the extent of
potential impacts on the receiving water column.
According to the
latest estimate, the Project is tentatively scheduled to commence works in the
second half of 2011, to be substantially completed within 2 years except for a
small area near Container Terminal no. 1 and 5.
2.2 The Study Area and Surrounding Environment
The Kwai Tsing Container Port (KTCP),
located in the north-western part of the harbour in the reclamation along Rambler Channel between Kwai Chung and Tsing
Yi Island, comprises nine container terminals with 24 berths of 7,804 m
of deep sea frontage and is operated by five companies, each responsible for
maintaining a strip of seabed of approximately 50 m wide along the
terminals. In addition to KTCP, the
study area also includes a portion of Northern Fairway south of Tsing Yi Island
and a section of Western Fairway west of
2.3 Need for the Project and Consequences of not Proceeding with the Project
Hong Kong’s
container port is the third busiest in the world after
In the short term,
with the trend of the increasing size of container vessels, current container ships occasionally have to wait for high tide to
depart from Kwai Tsing Container Port due to insufficient depth of the KTCB.
Such limitations reduce the efficiency in cargo-handling operations,
potentially harm the reputation of Kwai Tsing Container Port and conceivably
could encourage vessels to make alternative arrangements including the
diversion of traffic to Shenzhen and other regional ports.
The execution of
this Project is therefore necessary to keep the container basin deep enough to
maintain current efficiencies and to facilitate the growing size of container
ships in the short term. In addition, it
is also needed to meet the draft requirement of ULCS and to maintain the
competitiveness of the Kwai Tsing Container Port and
In the absence of this Project, the insufficient depth of KTCB and its approach channel will cause Kwai Tsing Container Port to
become less efficient given the increased vessel sizes, including the inability
to physically berth and accommodate the ULCS. The long-term development
potential of the Kwai Tsing Container Port will inevitably be constrained by
the depth of KTCB and its approach channel. International shipping lines will
no longer continue to call into the Hong Kong port but turn to
2.4 Consideration of Alternative Construction Methods and Sequence of Work
The “do nothing”
scenario is described in the preceding section 2.3. The current depth of the KTCB limits the
efficiency of KTCP and threatens the long term position of
The new
generation of ULCS is expected to have a draft of 15.5m. This means that in
order for these ULCS to access the container terminals at KTCP, a minimum water
depth of about 17m would be required. Current seabed levels thus constrain
access by ULCS to tides higher than +1.5mCD. Such restrictions on the
permissible access time for ULCS would severely hinder the operational flexibility and efficiency of these
container ships, and would be an impractical option for both shipping lines and
terminal operators. Consequently, a
“do nothing” option is not considered viable for the long term economy of
2.4.2 Alternative Locations
KTCP is currently the only port in
2.4.3 Alternatives to Treatment and Disposal of Dredged Sediment
Other than the conventional method of dredging and disposal
of dredged material, consideration has been given to the potential for
treatment and reuse of the dredged material
in order to minimise the volumes
of sediment requiring disposal, based on the nature of sediment
including moisture content and level of contamination. Selection of treatment
options (in-situ and ex-situ treatment including dewatering or decontamination,
etc) has to take into account the handling of a vast quantity of dredged
material, i.e. about 4.4 Mm3 and the fact that marine sediment
within the container basin is likely contaminated due to the historical release
of contaminants from previous factories on Tsing Yi Island. Reuse of the
sediment as landfill cover is not possible as sediment is not accepted at landfill sites in
Treatment options which have been considered include mechanical dewatering, physical separation, brick making, bioremediation, chemical treatment, stabilisation and thermal treatment. The viability of these treatment methods are summarised below, with further details of these methods provided in Chapter 4.
¡ Mechanical dewatering - considered inappropriate for this project due to the slow nature of the process and the additional implications resulting from the generation of contaminated water. Disposal of remaining residual sediment still has to be resolved.
¡ Physical separation - effective only for sandy material and would not be suited to the clay-based nature of the sediment arising from the Project.
¡ Brick making – similar to physical separation, the nature of the dredged sediment would be unsuitable for brick making.
¡ Bioremediation – this method would be effective for sediment containing organic contaminants, but not heavy metal contaminants; hence, its applicability would be restricted.
¡ Chemical treatment – this method is contaminant-specific, and would not be suitable if a wide range of contaminants is identified.
¡ Stabilisation treatment - involves binding the contaminants to prevent their release. This type of treatment may not be sufficient to ensure the sediment would be acceptable for reuse, nor will this method reduce the volume of sediment that requires disposal; therefore, this option is not considered appropriate for the Project.
¡ Thermal treatment – this option would lead to other adverse environmental impacts as well as requiring extensive pilot testing and an additional environmental impact assessment to be conducted.
The above summary shows that it is difficult to identify a practical treatment method for the dredged material that would be
generated by this Project. Other
constraints include: limitation of the Project programme, need to minimise
disturbance to the KTCP operations as far as possible, land-take requirements,
environmental consequences of treatment methods, disposal of residual material
and viability of reuse options. It was
concluded after a detailed study that the treatment options considered would
not be feasible, especially given the volume of material to be treated.
An alternative
option involving the creation of an artificial island to dispose of the dredged
material would have been considered if there was reclamation associated with
this Project. The practicalities of
coordinating with other reclamation projects, unrelated to this Project, may
still be considered by the future Contractor if the timing, programme,
contractual and environmental management arrangements could be
coordinated. However, the risks
associated with such arrangements are high.
To ensure a secure outcome
for the Project, conventional dredging and disposal of the dredged material is
therefore considered as the recommended option.
2.4.4 Dredging Programme
The current dredging programme is tentatively stated as being between 2011 and 2013, to allow the KTCP to receive ULCS by 2013. In order to meet this deadline, it is envisaged that 24-hour dredging operations will be required. In order to avoid disruption to the operation of the KTCP and to maintain safe marine access, dredging operations have to take into account movements of marine traffic as well as environmental considerations. On the environmental side, the dredging programme has considered the effect of other concurrent projects in the vicinity of the Project, and also projects involving dredging which are farther away but which could potentially have “cumulative effects” on this Project.
It is currently envisaged that implementation of the dredging
works will involve the simultaneous
use of dredgers in the Western Fairway, Northern Fairway and the KTCB
i.e. a maximum of 3 dredgers at any one time.
Consideration has been
given to ensure that potential
conflicting demands of vessel traffic and dredging works are resolved through
deliberation of, inter alia, marine traffic, types of dredgers and
environmental factors.
It was also seen that within the Project area, a hotspot was found near Container Terminal no. 1 and 5 (S2). As such, it would be prudent to isolate S2 to a later stage such that the majority (c. 99%) of the navigational (i.e. capital work) dredging can proceed without affecting the overall construction programme. Besides, it is envisaged that dredging in dry season where sea water temperature is relatively lower can help in controlling the release of unionized ammonia (UIA). This is especially good for dredging of hotspot area to minimize the impact in terms of UIA to water sensitive receivers.
2.4.5 Conventional Dredging Method
As part of the
detailed engineering studies associated with this Project, it has been
identified that equipment which
could be deployed is constrained by a number of factors, including:
layout and seabed composition (materials
to be dredged) of the KTCB; need to maintain undisrupted operation of
the KTCP during the dredging
works; programme; and need to avoid adverse environmental impacts.
The nature of the
dredged material is one of the key factors determining the equipment to be used
for dredging. Initial ground
investigations indicated the presence of soft marine deposits over the majority
of the Project area. Subsequently,
additional detailed investigations revealed some harder materials at a small
area in the north-eastern (NE) corner of the KTCB.
Characteristics of
the materials to be dredged define the options available for dredging plant,
such as, trailer suction hopper dredgers or cutter suction dredgers or grab
dredgers. The most commonly used
types of dredger in
The GD generally results in smaller environmental impact as compared to the other types of dredger, especially when fitted with a frame-type silt curtain. However, a GD operates in a stationary mode and is slower to manoeuvre compared to TSHD.
In
Findings of the Marine Traffic
Impact Assessment (MTIA) (completed under Agreement No. CE
63/2008) indicate
that dredging works within the
KTCB and its approaches using either
multiple grab dredgers or TSHDs will not result in unacceptable marine traffic
impacts. However, the busy nature of the
marine environment at KTCB requires that appropriate management measures be
implemented and that in-field conformance to high standards of safety
management be maintained.
As mentioned earlier, some hard material was found within the
NE corner of the KTCB. Such material may not be readily removed by GD, and may require the use of a
cutter suction dredger (CSD). The potential environmental impacts of
a CSD are limited to the
generation of sediment plume in the immediate vicinity of the stationary CSD whilst in operation. A CSD’s
operation is very localized when engaged in the removal of hard materials
with large particle size, and
therefore, associated environmental effect will be limited to a small area.
Other types of dredger, such as bucket ladder dredgers and
backhoe dredgers, have not been commonly used in
2.4.6 Keyhole Dredging Method
2.4.6.1 Background
This innovative technique was investigated in
2.4.6.2 Project Credentials
Keyhole dredging has been pioneered by a leading Dutch
dredging company but it does not appear to have been used on a wide scale
outside of
It is concluded that the effectiveness of the technique when applied over an extensive area has not been demonstrated.
2.4.6.3 Environmental Impact
An important rationale behind the development of keyhole dredging was that it obviates the need for overburden removal. However, the technique disturbs the seabed and pollutants released to the water column from contaminated sediment are recognised as a real consequence of the method.
There are no
records of qualitative and quantitative trials which examined the potential
environmental impact of this technique. It is considered that the use of this
method for lowering the seabed in KTCB and its approaches could not be adopted
without first conducting extensive site trials to monitor the potential effects
of the method on nearby sensitive receivers, including the fish culture zones,
It has been proposed in available literature that the potential release of pollutants from contaminated sediment can be mitigated by placing a sand blanket on the seabed before commencement of keyhole drilling. While this might prove effective in containing the pollution of the water column, it would still introduce a number of new issues to the Project, including the following:
¡ a sand supply would need to be identified, investigated and approved for use; an EIA of the borrow site might also be required and this is outside the EIA Study Brief for the Project;
¡ the placement of sand on the seabed could affect the navigation of large container vessels within the basin and the approaches, and so would need to be introduced locally to the extraction operation, attracting potential time and cost penalties;
¡ the sand would need to be removed upon completion of the extraction, introducing the risk of dredging contaminated mud with the sand); and
¡ the volume of material extracted would need to be increased to ensure that the additional thickness of sand did not protrude above the target dredge level.
2.4.6.4 Marine Traffic Impact
The plant required for keyhole dredging is significantly
larger than a grab dredging pontoon. In
addition, the size of pumps which would be necessary to handle the
2.4.6.5 Commercial
There appears to be only one contractor in the world using the keyhole dredging technique. A commitment to this method for this Project could thus have a negative impact on the tender cost and the range of tenders received.
2.4.6.6 Summary
Keyhole dredging has not been proven to be successful on the scale demanded by this Project and adverse environmental impacts are likely. The method would have a greater impact on marine traffic in the basin and fairway than conventional grab dredging, with increased risks of collision and loss-of-life potential. In the light of the foregoing discussion, the use of keyhole dredging is considered to be not feasible for this Project and was not recommended for further consideration. As such, convention dredging is selected as the preferred option for this Project.
2.5 Selection of Preferred Option
2.5.1 Dredging Equipment
In selecting the preferred dredging option, consideration has been given to aspects including technical feasibility, environmental
acceptability, public interest and the findings from the Marine Traffic Impact
Assessment (MTIA). The benefits and
disbenefits of different dredging options which are relevant to this Project
are summarised as follow:
Table 2.1: Benefits
and Disbenefits of Dredgers which could be used for this Project
Dredging options |
Benefits |
Disadvantages |
Using grab dredger (Typical dredging rate: 4000 m3 / 24 hours) |
·
Least amount of sediment
release, therefore lesser environmental impact ·
Fixed position, and so
other vessels can plan movements around the working area ·
Silt curtain can be applied
around the dredging area to reduce the dispersion of sediment plume ·
Relatively small
operating area ·
Accurate dredging |
·
Slower rate of production |
Using cutter suction dredger (Typical dredging rate: 700 m3/hour) |
·
Enables excavation of hard
materials ·
Faster production rate
than grab dredger (only if overflowing is not a constraint) ·
More manoeuvrability than
grab dredger |
·
More marine sediment
produced by volume due to high water content ·
Silt curtain cannot be
applied in this Project due to adverse impact on shipping in the KTCB and its
approaches. Frame type silt curtain cannot be used |
Using trailer suction hopper
dredger (Typical dredging rate: 7200 m3/24 hrs) |
·
Easy to manoeuvre as the
dredger is self-propelled ·
Potentially higher rate
of production |
·
More marine sediment
produced by volume due to high water content ·
Movement of suction pipe
and draghead causes turbidity and resuspension of sediment, resulting in more
significant environmental impact ·
Overflow will not be
permitted from hopper during loading to avoid causing sediment resuspension;
this will have a major negative impact on the productivity of the TSHD and
could render the method not feasible in terms of programming ·
Silt curtain cannot be
applied for this Project due to constraints including those of marine traffic ·
Operation interferes with
other marine traffic |
Table 2.2 below provides a summary of the aspects considered in
identifying the preferred dredging option.
Table 2.2: Selection
of Preferred Dredging Option
|
Dredging Method |
||
Aspects
Considered |
GD |
CSD |
TSHD |
Disturbance
to marine traffic |
Moderate |
Least |
Least |
Loss Rate of Suspended Solids (SS) |
Least |
Moderate |
Most |
Manoeuvrability |
Least |
Moderate |
Moderate |
Accuracy of dredging |
Most |
Moderate |
Least |
Speed of Work (production rate) |
Slow |
Slow1 |
Slow[1] |
Ease of
mitigation of impact of elevated SS in
the KTCB |
ü |
X |
X |
Removal of
hard material |
X |
ü |
X |
Removal of
Contaminated sediment |
ü |
X |
X |
Removal of
Uncontaminated sediment |
ü |
ü |
ü |
Protection of
water quality at Fish Culture Zones |
ü |
ü |
X |
Protection of
water quality at Bathing Beaches |
ü |
ü |
X |
Public Option
and perception |
ü |
X |
X |
Preferred
Dredging Option |
ü |
ü |
X |
Given the aforementioned findings and considerations, the
grab dredgers have been identified as the preferred equipment for dredging for KTCB, as they are able to meet the technical requirements while limiting
environmental impacts. Since grab
dredgers are not effective in the removal of hard material, a CSD is likely to be needed to carry out dredging at the NE corner of KTCB dredging area. The
estimated volume of hard material
that will require excavation is approximately 92,000 m3. Since the hard material forms a very small
component of the entire dredging operation (accounting for only about 2% of the total dredged volume), the
choice of CSD is not likely to significantly alter the overall environmental impacts associated with the
Project. Nonetheless the impacts associated with both
dredgers have been assessed in the subsequent sections of the EIA.
2.5.2
Dredging
Rationale
Owing to the
distinctive nature of this Project, considerations have been given to balancing
Construction Programme, Marine Traffic Impact and Environmental aspects to
determine the most favourable dredging rationale for this Project. In making
the balance, the first principle is to ensure the outcome fulfils the needs of
the Project, i.e. that the dredging operation can be undertaken within the
anticipated programme. At the same time, environmentally and marine traffic
issues have been taken into account such that the proposed activities will not
result in unacceptable levels of environmental impact and will minimise
obstruction to the operation of the container terminals.
Taking into account
the foregoing, it was calculated that a maximum of three grab dredgers (shown
to be more environmentally friendly, see Section
2.5.1) would be able to complete the dredging operation within the
programme of this Project, without compromising the environment and existing
marine traffic conditions (based on findings in Marine Traffic Impact
Assessment). Due to the presence of hard
material in the NE corner of the container basin, a CSD is also likely to be
needed.
2.6
Existing Submarine Outfall within
The Project will also involve modification of the Tsing Yi Submarine Sewage Outfall and dismantling of the abandoned Kwai Chung Submarine Sewage Outfall, such that these outfalls will not impose any hazards to future marine traffic after the lowering of KTCB’s seabed.
2.6.1 Tsing Yi Submarine Sewage Outfall
The Tsing Yi Submarine Sewage Outfall (TYSSO) is approximately 328m long, starting from the junction chamber in the vicinity of the existing Tsing Yi Preliminary Treatment Works. A reinforced concrete (RC) pipe of 1650mm diameter was adopted to connect the junction chamber and a 1200mm diameter drop shaft. The TYSSO was an exempted Designated Project (DP) under the EIAO for the previous HATS Stage 1 project. Under this Project, the proposed modification works will not alter the capacity and alignment of this outfall; as such, no material change is expected to be associated with the TYSSO works.
In order to conform to the target seabed level, the modification works of the TYSSO will involve the removal of the existing rubble layer to a level below -18.9mCD (i.e. -19.05mPD), and followed by cutting down of the existing riser pipes. Tailor-made collars will be adopted to connect the existing riser pipes to the new non-return valves. The tailor-made collar will be combined by two semi-circular pipes and bolted together to form a circular shape surrounding the existing riser pipe. The tail of the collar will be welded to the existing riser pipe to prevent leakage of treated sewage. The new non-return valves, which function in the same way as the existing non-return valves, will be connected to the existing riser pipes through the collars by bolting. Similar to the existing conditions, the riser pipes protected by concrete pipes will be extruded from the proposed dredging level to avoid blockage by siltation. The surrounding rock fill and armour will be replaced around the modified diffusers to afford the same level of protection as existed prior to dredging. It is understood from DSD that the TYSSO was originally designed for continuous screened sewage discharge to the sea. Upon the commissioning of HATS Stage 1 system in 2001, the outfall changed to serve as an emergency by-pass just in case of the failure of HATS's tunnelling system.
For the design flow discharged from the Tsing Yi Preliminary Treatment Works, changes of flow rates / velocities at the diffuser ports due to the proposed modification works will be insignificant. With sea water level at +1.3mPD and gradient of effluent plume at 0.15:1 (H:V, under still water condition), for one diffuser, the volume of water body for dilution is increased from 136m3 to 200m3 after the modification works. Thus, with the diffuser ports shortened by approximately 2.45m due to the proposed modification works, the increased volume of water body due to dredging will provide improved dilution of the screened and de-gritted sewage. It is also noted that ambient current velocity, densities of jet effluent and ambient water, which will affect the dilution effect all have no significant change after the modification work and thus no material change to its operation after the modification works. More discussion on the effect of modification works can be found in Chapter 3.
2.6.2 Kwai Chung Submarine Outfall
The Kwai Chung Submarine Sewage Outfall is a submarine outfall which is connected to the Kwai Chung Primary Treatment Works constructed between 1976 and 1981 (before the enactment of EIAO), consisting of 2 nos. of 1650mm diameter steel pipelines of approximately 900m long, with the eastern and western diffusers each of approximately 170m long. It has currently ceased operation as confirmed by DSD.
The said sewage outfall will be demolished by chiselling, which is
localised in terms of the resulting impact and is unlikely to release suspended
solids (SS) or other materials to the receiving environment. As only approximately half of the outfall is
above the target seabed level of -17.5mCD, this top half of the concrete pipe
will be demolished, and will remain
in the bottom half of the pipe.
2.6.3
Summary
Based on the nature
of works as described above, there is insignificant environmental impact in
terms of water quality or waste management associated with the modification and
dismantling of the two submarine sewage outfalls. Particularly for the Tsing Yi
Submarine Sewage Outfall, the modification works will not in any way modify its
performance and hence, will not result in the addition of pollution loading to
the environment.
2.7 Need for Maintenance Dredging
The following information has been used to identify the
changes in seabed levels for assessing the sedimentation rate within the works
area in the
a. Hydrographic data provided by the Marine Department for bathymetric surveys carried out in the Study Area as follows:-
i. Northern Fairway and
ii. Western Fairway – 1999, 2002, 2004, 2006 and 2008.
b. Dredging histories obtained from the Port Works (previously Technical Services) Division of the Civil Engineering Department and the Marine Department on the removal of high spots in local locations during development of Container Terminal CT9.
c. Bathymetric survey completed in November 2009 under this Project.
The computer software “Surfer” was used to analyse the changes
in seabed levels through the generation of “sedimentation isopachytes”, by
subtracting contours of successive survey data to identify zones of sediment
accumulation within the Study Area.
Figures 2.2 to
2.13 show the recorded seabed levels within
It should be noted that natural flow in the Rambler Channel has been significantly altered in the past 30 years as a result of the construction of the KTCP, which has had the effect of channelizing the natural flow through the Rambler Channel. This was particularly noted following the construction of CT9 which has caused the current velocities within the narrow channel to become higher than before its construction. Surveys since 2003 have indicated that within the levels of accuracy of the survey techniques, a slight but persistent lowering of seabed levels has been taking place.
Figures 2.14 to 2.15 show the recorded seabed levels in the Western Fairway and the East Lamma Channel between 1999 and 2008 and the corresponding isopachytes of sediment accumulation, which indicated no significant siltation occurring in these areas.
Notwithstanding the above, it is appropriate to presume that maintenance dredging will be required,
though at less frequent intervals and with a much smaller volume of material to
be removed than in the past.
Additionally, the
Container Terminal Operators (CTOs) are reported to have been undertaking
maintenance dredging within the berth boxes.
The records for these maintenance works since year 2000 are summarised
in Table 2.3.
Table 2.3: Volume of Maintenance Dredging undertaken by Container Terminal Operators; 2000 - 2009
Terminal No. |
Operator |
Approximate Maintenance Dredge Volumes (m3) from Year 2000 to 2009 |
ANNUAL MAX |
|||||||||
2000 |
2001 |
2002 |
2003 |
2004 |
2005 |
2006 |
2007 |
2008 |
2009 |
|||
1 |
MTL |
15,667 |
-- |
53,0001 |
-- |
-- |
-- |
-- |
12,333 |
-- |
12,667 |
26,5001 |
2 |
MTL |
15,667 |
12,500 |
12,500 |
-- |
-- |
-- |
-- |
12,333 |
-- |
12,667 |
15,667 |
3 |
DPW |
-- |
-- |
9,000 |
11,000 |
1,600 |
-- |
-- |
-- |
17,000 |
-- |
17,000 |
4 |
HIT |
-- |
50,0003 |
-- |
-- |
-- |
-- |
65,0002 |
-- |
-- |
-- |
50,0003 |
5 |
MTL |
15,667 |
12,500 |
12,500 |
-- |
-- |
-- |
-- |
12,333 |
-- |
12,667 |
15,667 |
6 |
HIT |
50,0003 |
50,0003 |
10,000 |
-- |
35,000 |
-- |
65,0002 |
-- |
19,800 |
-- |
50,0003 |
7 |
HIT |
50,0003 |
-- |
10,000 |
-- |
35,000 |
-- |
-- |
-- |
19,800 |
13,000 |
50,0003 |
8 East4 |
COSCO/HIT |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
0 |
8 West4 |
ACT |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
0 |
9 |
HIT |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
4,300 |
20,000 |
20,000 |
Totals |
147,000 |
125,000 |
107,000 |
11,000 |
71,600 |
0 |
130,000 |
37,000 |
60,900 |
71,000 |
|
|
Notes: 1. Figure for CT1 in 2002 covered
two years, so annual maximum is half of this value. 2. These figures included lowering
of the seabed and are therefore not taken as maintenance dredging maxima. 3. HIT advised that it will not
dredge more than 100,000m3 of materials annually. 4. COSCO/HIT and ACT advised that
they have no plans to undertake maintenance dredging. |
From the information provided, a “worst credible” maintenance scenario has been developed, based on the highest annual maintenance dredging volumes attained by each of the operators over the past ten years. In arriving at an annual maintenance dredging volume of 225,000m3 (within the berth boxes), volumes of capital dredging to lower the seabed within berth boxes have been ignored, as these are not considered to be maintenance dredging. Furthermore, where dredging intervals at particular terminals exceed one year, the dredged volume is divided by the interval to provide an estimate of the annual volume. The value includes an allowance of 30,000m3, being the estimated annual volume of maintenance dredging undertaken by the Port Works Division (PWD) of CEDD and as notified by PWD accordingly. It is considered that the aggregate volume of maintenance dredging thus derived is conservative, yet appropriate for inclusion in the assessment of Water Quality and Waste in Sections 3 and 4 of this Report.
2.8 Interface with Planned Projects
The dredging work
under this Project (referred to as the “Subject Project” for clarity in this
section) is tentatively scheduled to commence in mid-2011 for completion by
mid-2013. The following
projects have been identified as
potentially concurrent projects. The description below outlines the projects
and available details related to their execution, with the locations of these
projects as indicated in Figure 2.16.
1. Construction of Container Terminal No.10 (CT10) at Southwest Tsing Yi
The nature of the project is to develop a container terminal on a proposed reclamation site (approximately 180ha) and a proposed land formation site (approximately 130ha) at Southwest Tsing Yi, including all infrastructure works and connecting roads. Part of the proposed reclamation site to the south of Tsing Yi is located next to the Subject Project. There is currently no detailed construction programme or plant inventory for this project.
2.
Proposed dredging for marine sand at South of Tsing Yi
The project has been confirmed by the Civil
Engineering and Development Department (CEDD) as being inactive
at present.
3. Marine borrow and dumping areas at South of Tsing Yi
This is
a disposal facility for sediment suitable for Type 1 – Open Sea Disposal. This
disposal facility is currently not being used, as confirmed by CEDD.
4.
Proposed laying of submarine cable between
The nature of this
project is to lay a submarine cable between
5. Proposed submarine cable from Tong Fuk to Chung Hom Kok
The nature of
the project is to install an approximately 37km long submarine cable of 34mm in
diameter in the existing foreshore and seabed within the HKSAR waters from Tong
Fuk (on Lantau Island) to Chung Hom Kok, involving injection jetting operation. The submarine cable will be buried in a
narrow trench of approximately 0.25m in width to a depth between 3m and 9m in
the seabed. This project has been referred in the Project Profile of the Subject Project.
However, information regarding project alignment and construction
programme are not available at this stage. As is the case for Item (4)
above, in view of the relatively small scale of this project compared to the
Subject Project, it has not been considered in the assessment of concurrent
projects.
6. Dredging operations and seawalls modification works carried out by the Container Terminals’ Operators associated with this Project
The CTO will carry out their maintenance dredging within their berth boxes at the same time as the Subject Project. It is proposed that for the duration of dredging for the Subject Project, there will not be any overlapping of dredging operations between the Subject Project and the maintenance dredging by the CTO. This will be achieved by suspending dredging in the KTCB for the Subject Project while maintenance dredging work is in progress such that the overall environmental effect is still within the assessment contained in the EIA Report.
7. Wan Chai
Development Phase II and Central – Wan Chai Bypass
The project
comprises reclamation works including associated dredging works in Wan Chai
North and
¡
¡
Wan
Chai Reclamation (WCR) Stages 3 and 4;
¡
Temporary
Public Cargo Working Area (TPCWA); and
¡
The dredging works
will be carried out by closed grab dredger at a maximum rate of 6,000m3
per day and the total dredged sediment is estimated to be 1.15Mm3.
The project has been considered in this EIA given both projects may potentially
influence water quality in the Victoria Harbour Water Control Zone.
8. Shatin to
Central Link (SCL) – Cross Harbour Section (Phase II – Hung Hom to Admiralty)
This project is an
approximately 6 km extension of the East Rail Line from a new Hung Hom station
crossing the harbour to new stations at Hong Kong Convention and
9. Installation
of Submarine Gas Pipelines and Associated Facilities from To Kwa Wan to North
Point for former
The project will be undertaken
by Towngas Company and comprises construction of new gas pipelines from
To Kwa Wan to North Point. The project
will include a trench for installation of a twin submarine gas pipeline across the
10. Tuen Mun – Chek Lap Kok Link (TM-CLKL)
The nature of the project is to construct an approximately 5km long dual
2-lane road tunnel between Tuen Mun Area 40 and the Hong Kong Zhuhai Macao Bridge (HZMB) Hong
Kong Boundary Crossing Facilities (HKBCF) at
north-east of the Airport Island, including construction of approximately
11. Hong
Kong - Zhuhai -
The project involves construction
of an approximately
9.4km viaduct from HKSAR boundary to Scenic Hill on the Airport Island, an approximately
1.1km tunnel through Scenic Hill and underpassing the Airport Road and the
Airport Railway, reclamation adjacent to the eastern side of the Airport
Island, together with a section of at-grade road leading to the HKBCF.
According to the tentative construction programme, the construction will
commence in 2011 and end in 2015. Details of this project were included in the
assessment of concurrent projects.
12. HZMB
The project involves reclamation (approximately 130ha),
infrastructure on the reclamation for serving the HKBCF, and works on the
13.
The scope of the project includes dredging, construction of seawalls, and reclamation of a land platform of approximately 112ha, with 72ha for the development of the LLP and the remaining 40ha at the western portion for possible logistics park extension or other compatible uses. The site of this project is about 9.5km to the west of the proposed dredging areas of the Subject Project. However, it has been confirmed by CEDD that there is no programme for the construction of the LLP and it is therefore not considered as a concurrent project.
14. Backfilling North Brothers Marine Borrow Area (NBMBA)
The operation of the
open sea disposal ground at
15. Existing Dredging/
Filling of the Contaminated Mud Pits in
The projects include dredging of a series of seabed pits besides the
existing pits at East Sha Chau; backfilling
each dredged pit with contaminated mud that has been classified as requiring Type 2 disposal in accordance
with ETWBTC 34/2002; and capping each
backfilled pit with uncontaminated mud and/or public fill to effectively
isolate the contaminated mud from the surrounding marine environment.
According to the approved EIA report of HZMB HKBCF project, the dredging
works for the contaminated mud disposal facility at East Sha Chau is expected to be operating between 2011 and
2013. Details of this project
were included in the assessment of concurrent projects.
16. Proposed Dredging Works of the Contaminated Mud Pits in South of Brothers
The key scope of the
project includes dredging of a series of
seabed pits within the proposed South Brothers Facility Boundary, backfilling
each dredged pit with contaminated mud and capping with uncontaminated mud or
public fill. The contaminated mud disposal
facility at South Brothers is
scheduled to facilitate filling works in 2012 as confirmed by CEDD; however,
only dredging works for the disposal facility to the south of the Brothers is
expected to be carried out in mid 2011. Details of this project were included
in the assessment of concurrent projects.
A summary of the
above mentioned potentially concurrent projects is provided in Table 2.4. The
programmes of the Subject Project and the potentially concurrent projects are
provided in Table 2.5.
Table 2.4: Summary
of potentially concurrent projects
No. |
Project |
Timeline |
Approx. distance to Subject Project (SP) |
Included/Excluded in Assessment |
Comments |
Source of Information |
1 |
Construction of Container Terminal No.10 (CT10) in Southwest Tsing Yi |
N/A |
Southwest of Tsing Yi |
Excluded |
On hold as confirmed by CEDD. |
CEDD |
2 |
Proposed dredging for marine sand at South of Tsing Yi |
N/A |
N/A |
Excluded |
On hold as confirmed by CEDD. |
CEDD |
3 |
Marine borrow and dumping areas at South Tsing Yi |
N/A |
N/A |
Excluded |
Currently not being used as confirmed by CEDD |
CEDD |
4 |
Proposed laying of submarine cable between |
N/A |
N/A |
Excluded |
Unavailable Project details |
Public Domain |
5 |
Proposed submarine cable from Tong Fuk to Chung Hom Kok |
N/A |
N/A |
Excluded |
Unavailable Project details |
Public Domain |
6 |
Dredging operations carried out by the container terminal’s operators (CTO) in association with this Project |
Same time as the SP |
Berth Boxes within the |
Included |
Administrative control will be in place to ensure no overlapping of dredging operations for the Subject Project and any of the CTO maintenance works. |
Container Terminal Operators |
7 |
Wan Chai Development Phase II and Central – Wan Chai
Bypass |
2011 to 2013 |
7 km |
Included |
The dredging and
filling works in Wan
Chai and |
EIA Report (Register
No. AEIAR-125/2008) |
8 |
Shatin to
Central Link – Cross Harbour Section (Phase II – Hung Hom to Admiralty) |
2011 to 2018 |
8 km |
Included |
Potential cumulative impacts with the Subject Project may arise during the entrustment work of this project involving advance dredging works, scheduled to be tentatively from the 2nd quarter of 2011 to the 3rd quarter of 2013. |
MTRC |
9 |
Installation
of Submarine Gas Pipelines and Associated Facilities from To Kwa Wan to North
Point for former Kai Tak Airport Development |
Jan 2012 to
June 2014 |
10 km |
Included |
Potential cumulative impacts with the
Subject Project may arise during the trench dredging works of this project
scheduled between the 2nd and 4th quarter of 2012. |
HKCG |
10 |
Tuen Mun – Chek Lap Kok Link (TM-CLKL) |
Late 2011 to
End 2016 |
16 km |
Included |
Potential cumulative
impacts with the Subject Project may arise during the dredging and filling
works of this project scheduled in phases from November 2011 to February 2014
|
EIA Report (Register
No. AEIAR-146/2009) |
11 |
Hong Kong – Zhuhai – |
2011 to 2015 |
20 km |
Included |
Potential
cumulative impacts with the Subject Project may arise during the dredging and
filling works of this project scheduled in phases from March 2011 to end of
January 2013. |
EIA Report (Register
No. AEIAR-144/2009) |
12 |
HZMB |
3rd
Quarter 2010 to |
18 km |
Included |
Potential
cumulative impacts with the Subject Project may arise during the dredging and
filling works of this project scheduled in phases from September 2010 to May
2014. |
EIA Report (Register
No. AEIAR-145/2009) |
13 |
|
N/A |
9.5 km |
Excluded |
On hold as
confirmed by CEDD. |
CEDD |
14 |
Backfilling North Brothers Marine Borrow Area |
N/A |
14 km |
Excluded |
Backfilling is not anticipated, as confirmed by CEDD. |
CEDD |
15 |
Existing
Dredging/ Filling of the Contaminated Mud Pits in |
2011 to 2013 |
16 km |
Included |
Dredging works for this project is
expected to be carried out from 2011 to 2013. Potential cumulative impacts
with the Subject Project may arise. |
HZMB HKBCF EIA Report
(Register No. AEIAR-145/2009) |
16 |
Proposed Dredging Works of the Contaminated Mud Pits in South of Brothers |
Operation in
Mid 2012 |
14 km |
Included |
Dredging works are expected to be carried out in 2011. |
CEDD |
Table 2.5: Concurrent Projects Programme
Item |
|
|
|
2011 |
2012 |
2013 |
|||||||||
Project |
Period |
Source |
Q1 |
Q2 |
Q3 |
Q4 |
Q1 |
Q2 |
Q3 |
Q4 |
Q1 |
Q2 |
Q3 |
Q4 |
|
S.P. |
Providing Sufficient Water Depth for |
Mid 2011-Mid 2013 |
CEDD |
|
|
|
|
|
|
|
|
|
|
|
|
1 |
Container Terminal No.10 |
N/A |
CEDD |
|
|
|
|
|
|
|
|
|
|
|
|
2 |
Dredging for marine sand at South of Tsing
Yi |
N/A |
CEDD |
|
|
|
|
|
|
|
|
|
|
|
|
3 |
Marine borrow and dumping areas at South
Tsing Yi |
N/A |
CEDD |
|
|
|
|
|
|
|
|
|
|
|
|
4 |
Proposed laying of submarine cable between
|
N/A |
Pls refer to S2.8 for details |
|
|
|
|
|
|
|
|
|
|
|
|
5 |
Proposed submarine cable from Tong Fuk to
Chung Hom Kok |
N/A |
Pls refer to S2.8 for details |
|
|
|
|
|
|
|
|
|
|
|
|
6 |
Dredging operations by the container
terminal’s operators |
Same as the SP |
Container Terminal
Operators |
|
|
|
|
|
|
|
|
|
|
|
|
7 |
Wan Chai Development Phase II and Central
– Wan Chai Bypass (part) |
2011-2013 |
EIA Report (Reg.No. AEIAR-125/2008) |
|
|
|
|
|
|
|
|
|
|
|
|
8* |
Shatin to Central Link - Cross Harbour
Section |
Q2 2011-Q3 2013 |
MTRC |
|
|
|
|
|
|
|
|
|
|
|
|
9 |
Installation of Submarine Gas Pipelines
from To Kwa Wan to North Point - Trench Dredging |
Q2-Q4 2012 |
HKCG |
|
|
|
|
|
|
|
|
|
|
|
|
10 |
Tuen Mun – Chek Lap Kok Link |
Nov 2011-Feb 2014 |
EIA Report (Reg.No. AEIAR-146/2009) |
|
|
|
|
|
|
|
|
|
|
|
|
11 |
HZMB – |
Mar 2011-Jan 2013 |
EIA Report (Reg.No. AEIAR-144/2009) |
|
|
|
|
|
|
|
|
|
|
|
|
12 |
HZMB – |
Sep 2010-May 2014 |
EIA Report (Reg.No. AEIAR-145/2009) |
|
|
|
|
|
|
|
|
|
|
|
|
13 |
|
N/A |
Project Profile (App. No. PP-230/2004); |
|
|
|
|
|
|
|
|
|
|
|
|
14 |
Backfilling North Brothers Marine Borrow
Area |
N/A |
CEDD |
|
|
|
|
|
|
|
|
|
|
|
|
15 |
Existing Dredging/ Filling of the
Contaminated Mud Pits in |
2011-2013 |
EIA Report (Reg.No. AEIAR-146/2009) |
|
|
|
|
|
|
|
|
|
|
|
|
16 |
Proposed Dredging Works of the
Contaminated Mud Pits in South of Brothers |
From mid 2011 |
CEDD |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
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|
|
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|
S.P. = Subject
Project |
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|
HZMB = |
|
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||
For the listed projects, only the period of
dredging and filling works is included |
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* Only the period of entrustment work involving
dredging dredging and filling works is included |
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Included in
Assessment |
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Excluded from
Assessment |
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[1] The prohibition of overflowing from TSHDs and barges of CSD reduces their efficiency, and effectively nullifies any dredging rate advantage over grab dredging; this effect is exacerbated with increasing separation between dredging site and disposal facility.