This Section presents the recommend site and disposal option
based on the environmental performance of the East of Sha Chau and South
Brothers Facilities presented in Part 4, Section 1. Impacts to marine traffic due to the
construction and operation of the facility are reviewed, as are potential cost
implications. Based on a review of
the above, the recommended site and disposal option is presented
.
An evaluation of both the East of Sha Chau and South
Brothers Facilities has been undertaken to determine the acceptability of the
environmental impacts associated with their development and operation. Due to potential planning constraints
on the North Lantau coastline, such as the landing point of the North Lantau
Highway Connection of the Hong Kong Section of the Hong Kong Zhuhai Macau
Bridge and the proposed reclamation of the Lantau Logistics Park, it is
proposed that to avoid the possibility of cumulative impacts occurring during
the construction of new developments, East of Sha Chau would be the preferred
site.
It is
important to note, however, that in terms of overall impacts, both facilities
are considered to be acceptable on the grounds that both meet the relevant
assessment criteria. Should the
area currently selected for the East of Sha Chau Facility not be available when
required, unacceptable adverse impacts associated with proceeding sequentially
with the South Brothers Facility, if considered necessary, would not be
expected to occur (see Annex A).
If proceeding with the South Brothers
Facility, it is recommended that, following the guidelines of the EIAO TM,
the precautionary principle be applied and operations in Pit A should be
activated first. Activity in Pit B
should only proceed if monitoring results for Pit A demonstrate sufficiently
the acceptability of environmental impacts. In addition, due to the proximity of Tai Ho Bay and the, at
present, uncertainty in the landing point of the North Lantau Highway
Connection of the Hong Kong Section of the Hong Kong Zhuhai Macau Bridge and
the proposed reclamation of the Lantau Logistics Park, operations at Pit C
should be avoided following the precautionary principle.
A Marine Traffic Impact Assessment (MTIA) has been conducted
for the proposed construction and operation of the East of Sha Chau and South
Brothers Facilities. The MTIA has
been conducted to identify if the risk associated with traffic activity falls within
acceptable levels. The complete
assessment is presented in Annex F. The key findings of the assessment are detailed below.
A review of the existing constraints and hazards has been
conducted and the summarised as follows:
·
Current
operations, and future proposed sites are set south of the Urmston Road,
adjacent to restricted waterspaces associated with the HKIA.
·
The
East of Sha Chau Facility will be subject to very similar currents to those
that impact the present operations.
However, currents within the South Brothers Facility will be
significantly less. It may also be
concluded that the South Brothers Facility is considerably less exposed to wave
impacts than the East of Sha Chau Facility.
·
It
is apparent that periods of very low visibility (<1.0 km) are rare, with
only 0.4 days per year being impacted in this manner.
·
There
are approximately 1,500 vessel movements per day through the waterspaces
adjacent to the sites.
·
The
historic level of activity associated with disposal and capping operations (at
an average of 16 movements per day) equates to approximately 1% of marine
traffic within the Study Area.
·
Operations
to date have been conducted in a safe manner.
A risk assessment of the proposed East of
Sha Chau and South Brothers Facility has been conducted. The following conclusions have been
developed.
·
A baseline
risk assessment has been carried out to correlate local traffic density and
annual collision rates and so to provide a tool for the assessment of future
risks. Such a relationship has
been identified, and the good accuracy is considered to provide a satisfactory
and reliable foundation for the assessment of the future disposal activity.
·
From the
time horizon of the Study (2005-2014), the peak year 2008 and 2010 scenarios
were selected for the Quantitative Risk Assessment of the risk to life in
associated with the proposed disposal activity. For each of these years, it is identified that the hazard to
life falls well within the acceptable level. Hence, no specific mitigation measures are required for the
disposal activity at the proposal facilities.
·
This
finding is consistent with the perception of marine safety in the region of
present disposal activity.
There were few apparent differences in risk levels between
the East of Sha Chau and South Brothers Facility, with the former presenting
marginally lower risks. It is
important to note that both present and future risk levels for both facilities
fall well within acceptable limits and that this finding is consistent with the
perception of marine safety in the region of present disposal activity.
However, while the risk assessment projects that future
risks will be acceptable, this is dependent upon the continued vigilance of the
operator in the safe conduct of the disposal activity.
The preliminary design of the contaminated mud disposal
facility at East of Sha Chau and South Brothers has been based around the
assumption that a minimum of 8 Mm3 of contaminated sediments can be
accommodated in each area. Cost
implications are divided into capital and recurrent costs. These implications are discussed below
and apply to each facility.
The estimates of capital cost have been based on the
assumption that grab dredgers sourced from the local fleet will undertake all
dredging operations. The following
assumptions have been made for each facility with respect to use and disposal
of the materials dredged to form the pits:
1.
All material dredged from the first pit (Pit A) will be
taken off-site for disposal;
2.
All
material dredged from the second pit (Pit B) will be taken off-site for
disposal or used to cap Pit IVc at East of Sha Chau;
3.
A
proportion of the material dredged from the third pit (Pit C) will be used to
cap Pit A, the remainder will be taken off-site for disposal;
4.
A proportion of the material dredged from any fourth
pit (Pit D – East of Sha Chau only) will be used to cap Pit B, the remainder
will be taken off-site for disposal;
5.
Capping
of Pits C and D will be undertaken with material dredged from elsewhere in Hong
Kong. This material is assumed to
be delivered to the site at no cost (ie. the cost will be borne by the donor
project); and
6.
Capping
does not include the top-up volumes required to restore the original seabed levels. The practicality of doing this during
the facility operational lifetime of the facility will need to be assessed
after detailed design studies have been completed but, if it is possible, it
would result in only minor cost savings of the order of $2 to 3 million.
Capping costs (excluding the cost of
dredging the material used for capping) are estimated to be HK$ 13 per m3. Dredging costs vary between
approximately HK$ 8 and HK$ $17 per m3, depending on the depths from
which the material is dredged and the destination of the dredged material (ie.
use as capping material in adjacent pits or remote off-site disposal). An additional 30% is added to all costs
to cover construction overheads (profit, risk, establishment costs etc) and a
further 2.5% to the total to cover supervision costs.
In summary, based on the above
assumptions the contaminated mud facility has been estimated to cost
approximately HK$ 25/m3, equating to a potential total of HK$ 200M.
Recurrent costs include management and EM&A and are
estimated to be of the order of HK$ 25M per year for the duration of
operations. It should be noted
that in addition, periodic surveys to check the condition of the capped pits
would be required after the facility is closed.
The comparison of facilities based on their environmental
performance indicated that both facilities are of equal environmental
performance. Due to potential
planning constraints on the North Lantau coastline, such as the landing point
of the North Lantau Highway Connection of the Hong Kong Section of the Hong
Kong Zhuhai Macau Bridge and the proposed reclamation of the Lantau Logistics
Park, it is proposed that to avoid the possibility of cumulative impacts
occurring during the construction of new developments, East of Sha Chau would
be the preferred site.
The result of a marine traffic impact assessment on
both sites also indicates that the South Brothers Facility presents marginally
lower risks when compared to the East Sha Chau Facility.
Costs for both facilities have been calculated to be the
same.
Based
on the above, the multi-pit purpose-dredged Contained Aquatic Disposal facility
(CAD) at East of Sha Chau is recommended for detailed design and
implementation. Should the area
currently selected for the East of Sha Chau Facility not be available when
required, unacceptable adverse impacts associated with proceeding sequentially
with the South Brothers Facility, if considered necessary, would not be
expected to occur. If proceeding
with the South Brothers Facility, it is recommended that, following the
guidelines of the EIAO TM, the precautionary principle be applied and
operations in Pit A should be activated first. Activity in Pit B should only proceed if monitoring results
for Pit A demonstrate sufficiently the acceptability of environmental
impacts. In addition, due to the
proximity of Tai Ho Bay and the, at present, uncertainty in the landing point
of the North Lantau Highway Connection of the Hong Kong Section of the Hong
Kong Zhuhai Macau Bridge and the proposed reclamation of the Lantau Logistics
Park, operations at Pit C should be avoided following the precautionary
principle.