1
PROJECT
DESCRIPTION
1.1 The
Project
The Project is classified as a Designated Project by
virtue of Item C.10 (A Marine Dumping Area) and C.12 (A Dredging Operation
Exceeding 500,000 m3) of Part I of Schedule 2 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:
i.
Dredging of a series of seabed pits within the
proposed East of Sha Chau Facility Boundary (Part 1, Figure 2.4b);
ii.
Backfilling each dredged pit with contaminated mud
that has been classified as requiring Type 2 disposal in accordance with ETWBTC
34/2002; and,
iii.
Capping each backfilled pit with uncontaminated mud
and/or public fill effectively isolating the contaminated mud from the
surrounding marine environment.
1.2 Project
Design
Despite the proven acceptability and
close proximity of the existing facility, the purpose of the assessment was to
thoroughly evaluate the East of Sha Chau Facility in terms of acceptability of
predicted impacts to water quality from dredging, backfilling and capping of
the pits and also concurrent activities.
This Section describes an
engineering design for the proposed East of Sha Chau Facility, which is based
on maximising disposal capacity, ensuring continuity in use of the site, and
ensuring that environmental impacts are environmentally acceptable and no
greater than those associated with existing CMP operations. The information presented in this
section is taken from the preliminary design and will be refined at the
detailed engineering design stage.
The Project involves the sequential
disposal of contaminated mud into a series of dredged pits, provisionally
titled Pits A, B, C and D. The
sequential construction and operation of the pits has been used to develop
scenarios for sediment transport modelling, assess marine traffic issues and
identify key environmental issues for water quality, ecology, fisheries, human
health, noise and heritage assessments.
1.3 Backfill
Levels
Previous purpose-dredged
contaminated mud disposal facilities at the East of Sha Chau area have had
backfill levels to 3m below original seabed. Recently, however, the very large disused sand borrow pits
now used as CMPIV have an allowed backfill level up to 6m. This greater depth was deemed necessary
because of the greater surface area of material that would be subject to
exposure to the effects of storm waves.
In contrast to the above, the preliminary
design of the East of Sha Chau Facility consists of smaller, shallower pits
that would minimise exposure of contaminated mud thus reducing the potential
for dispersion outside of the pit boundary. As a result of these design features, the same backfill
level design of 3m below original seabed level that has been employed in the
design of the East Sha Chau Facility.
1.4 Cap
Thickness
Caps at previous
CMPs in the East Sha Chau Area have consisted of 3 m layer of uncontaminated
material placed by controlled bottom dumping from barges. Additional clean mud has been added
later to compensate for long-term consolidation of the contaminated mud. Such practice has been employed in the
design of the East of Sha Chau Facility.
The rationale for the design of the cap design ([1]) ([2]) is to
keep the contaminated material beyond the reach of bioturbation and to protect
it against storm erosion.
The potential for damage and
breaching of the cap due to anchorage has been considered, but the shallow
water of the East of Sha Chau Facility restricts the size of vessel which can
anchor in the area which, in turn, restricts the size of anchor and the
penetration depth.
1.5 Construction
Programme
Once the EIA Report has been
formally approved by Government, CEDD will obtain an Environmental Permit (EP)
for construction of the Project.
Once the EP has been obtained the first pit is expected to be dredged during
2008 in order to be ready to receive contaminated mud in early 2009. According to arisings estimates the
fourth pit at the East of Sha Chau Facility will be backfilled and capped
during the first half of 2015. It
should be noted that should the rate at which contaminated mud arises change
(either increasing or decreasing) then the fourth pit maybe capped earlier or
later than 2015. The tentative
construction programme is presented in Figure 1.1a. It should be noted that the timeline
presents predicted timeframes for each works component.
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Figure 1.1a Indicative
Works Sequencing at the East of Sha Chau Facility
1.6 Concurrent
Projects
A requirement in the Study Brief is to
examine the cumulative effects of other projects concurrent with construction
and operations at the East of Sha Chau Facility. Projects that have been identified as occurring potentially
at the same time are detailed below:
·
Disposal at North Brothers
·
Reclamations along North Lantau Coastline
-
Potential New Town Extension at Tung Chung East and
Tung Chung West
-
Lantau Logistics Park
-
Potential Theme Park
-
Reclamations at Yam O
·
Permanent Aviation Fuel Facility (PAFF)
·
Highway Projects
-
Tuen Mun to Chek Lap Kok link
-
North Lantau Highway Connection to the Hong Kong -
Zhuhai - Macao Bridge
·
Sewage Discharges
-
Siu Ho Wan Sewage Treatment Work (STW)
-
Pillar Point Sewage Treatment Work (STW)
The significance of the above
Projects to the proposed East of Sha Chau Facility is discussed in more detail
in the Water Quality Impact Assessment (Part 3, Section 2).