Location and Scale of Project
2.1 The proposed site of the Project is located on the eastern coast of Lung Kwu Chau as shown in Figure 2.1. Lung Kwu Chau is situated within the gazetted Sha Chau and Lung Kwu Chau Marine Park. Due to the remoteness of the site, the island is uninhabited with no infrastructure other than the existing jetty and the Doppler VHF Omni-directional Range and Distance Measuring Equipment (DVOR/DME) Station. The location of the existing jetty is also shown on Figure 2.1.
2.2 The scope of this project comprises the construction of a precast concrete blockwork jetty and a concrete catwalk, dredging of an approach channel, installation of miscellaneous facilities and demolition of the existing jetty.
2.3 A jetty was constructed at nearby Sha Chau to serve the radar station set up by CAD on the island for the new airport at Chek Lap Kok. To date it appears that no environmental concerns have been raised in connection with the operation of this radar station and the associated jetty, which is also located within the Sha Chau and Lung Kwu Chau Marine Park. The structural form of the Sha Chau jetty is similar to that proposed under the preliminary design of the jetty at Lung Kwu Chau, although the jetty at Sha Chau is larger in size. A jetty has also been provided at Siu Mo To to serve the DVOR/DME station located there.
Construction and Operational Activities
2.4 The major activities involved during the construction stage of the Project are dredging for foundation of the jetty and catwalk and approach channel, preparation of precast concrete blocks, laying of rock bedding, setting of precast concrete blocks, construction of concrete catwalk, extension of an existing footpath, installation of miscellaneous facilities (handrailings, bollards, fenders, navigation light, tide gauge and marine notice boards) and demolition of the existing jetty. A maximum production rate for the dredging works is 500 m3 per day and it is anticipated that only one dredger will be working on-site at any time.
2.5 The main construction activities include:
i.
Trenches for the foundations of catwalk and pier head
will firstly be dredged.
ii.
Rock
fill will then be deposited to the foundation trenches to form the rubble mound
to the jetty structure.
iii.
For
the catwalk, concreting work above the rubble mound will be carried out during
low tide.
iv.
For
the pier head, precast seawall blocks will firstly be placed and then
concreting on deck surface will be carried out above seawater.
v.
Approach channel to the jetty will be dredged.
vi.
Demolition
of existing jetty.
vii.
Extension
of an existing footpath.
2.6 During the operation stage, the only activities at the proposed jetty will be the berthing and mooring of vessels for the purpose of servicing and maintaining the DVOR/DME station and for emergency repair work, and maintenance dredging of the approach channel. The frequency of maintenance dredging is estimated to be 5 years. Maintenance dredging would be carried out at areas where results of sounding survey show that the seabed level is too shallow for navigation.
Project Programme
2.7 The construction of the Project is scheduled to commence in March 2003 for completion in December 2003. The construction period is 10 months for the entire construction, in which about 3 to 5 months are for dredging and marine foundation works. Dredging for both the approach channel and the foundation of catwalk and pier head is estimated to take around 2 weeks each to complete. These durations include the time required for plant mobilization and sounding surveys before and after dredging, and therefore the actual duration of dredging works will be less. The tentative construction programme is presented in Figure 2.2.
2.8 It is expected that this Project has no major interaction with other projects.
Need of the Project
2.9 The DVOR/DME Station on Lung Kwu Chau was commissioned in April 1996. The station provides tracked guidance on bearing and distance information to the aircrafts approaching and departing from the Chek Lap Kok Airport.
2.10 The existing ruined and abandoned jetty at Lung Kwu Chau is too small and the water depth too shallow to permit access of CAD’s repair vessels for the routine servicing and maintenance of the DVOR/DME Station being operated on the island. Reconstruction of the existing jetty at Lung Kwu Chau is also required to enable the CAD’s vessels to berth at the island and carry out emergency repair work for the DVOR/DME Station. The DVOR/DME Station is an essential navigational aid for air traffic control in Hong Kong, and therefore it has to be maintained regularly and, whenever failures occur, the station needs to be repaired without delay such that normal air traffic control is maintained and flight safety is not compromised.
2.11 At present the transportation of equipment and personnel for servicing and maintaining the DVOR/DME Station has to rely on helicopters. This mode of transportation is not always available, however, especially during night-time, low visibility and/or adverse weather conditions, such as typhoon, rainstorm and thunderstorm situations, for safety reasons. Repair of the equipment at the DVOR/DME Station is usually needed under adverse weather conditions, such as after the passage of a typhoon near Hong Kong, as these are typically the times that equipment failures occur and require emergency visits to the island for immediate recovery actions. Aviation safety is a top priority and no government can afford to leave any aviation equipment damaged without repairing or attempting to repair it at the very first instance. Moreover, there are severe limitations on the use of helicopters as heavy and bulky equipment cannot be transported by helicopters (such as a standby generator which is required for the station). In case of rainstorm or when the typhoon signal number three or higher is hoisted and in the event of any vital navigation aid equipment failure, CAD’s vessels would travel to Lung Kwu Chau to carry out emergency repair work. This flexibility could not be provided by the present helicopter service.
2.12 With regard to ad-hoc repairing activities for the DVOR/DME Station carried out by CAD, past experience indicates that there could be frequent occasions for urgent or emergency repair incidents (such as equipment/system failures due to lightning strikes, floodings, fire alarms, antenna damages, etc.) that would require daily visits of CAD’s staff to the island over a period of several days. Based on CAD’s records, a total of 216 helicopter trips were made to the station over the past 2 years, with 42 trips related to emergency repairs. The frequency of using the jetty is expected to be increasing in the coming years in view of the aging of the equipment and systems installed there.
2.13 In addition to providing access for CAD’s vessels whose staff would go to the station on a weekly basis to carry out routine maintenance activities, it is understood that the proposed jetty may also be used by staff from other government departments. These departments include Fire Services Department, Electrical & Mechanical Services Department, Architectural Services Department, Marine Department, Agriculture, Fisheries & Conservation Department, as well as utilities companies such as PCCW HKT and CLP Power, in connection with their routine maintenance and emergency repair operations for the equipment/building works/building services and electrical facilities associated with the DVOR/DME Station.
Consideration Of Alternative Transport Modes
2.15 Given the remoteness and exposed nature of Lung Kwu Chau there is no shelter and drinking water supply on the island. An option of government staff being stationed on the island during expected adverse weather situations as a precautionary measure, such as during the approach of a typhoon, is not considered to be feasible in view of personnel safety. In addition, the introduction of additional facilities and infrastructure on the island, which is a designated Site of Special Scientific Interest (SSSI), would have the potential for greater environmental impact and disturbance. Construction activities for the provision of infrastructure and facilities would inevitably cause a greater degree of habitat loss and disturbance within the SSSI than the proposed Project. Furthermore, the increased frequency and duration of human presence inside the presently uninhabited SSSI would be expected to result in greater disturbance to the terrestrial ecology. Additional structures on the hillside of the island may also be of greater landscape and visual impact concern.
Consideration Of Alternative Jetty Location and Design Options
2.16
The proposed Project has been gazetted twice some 6 to 7 years ago under
the Foreshore and Sea-bed (Reclamations) Ordinance. A proposed site on the eastern side of Lung Kwu Chau was gazetted
on 17 September 1993 and was objected by villagers at Lung Kwu Tan mainly on
Fung Shui grounds. A proposed site on
the western side of Lung Kwu Chau was gazetted on 15 April 1994 and objection
was received from The Hong Kong Marine Conservation Society on marine ecology
concerns with respect to the Chinese White Dolphin. The Hong Kong Marine Conservation Society objected to the proposed
western site and appeared to favour the proposed site on the east, and
suggested that the existing jetty on the eastern site be extended to provide
the necessary access. Subsequently, the
site of the jetty proposed on the eastern coast of Lung Kwu Chau was presented
to the Lung Kwu Tan villagers by CAD in collaboration with District
Office (Tuen Mun) at a meeting in January 2000. Preliminary support from local villagers to
the jetty location was obtained in the meeting, based on which this
Project has proceeded further and the present EIA Study has commenced.
2.17 In the vicinity of the existing small jetty, two alternative locations (Options 2 and 3) have been identified in addition to the initially proposed jetty location given in the EIA Study Brief (Option 1 as shown in Figure 2.1). An evaluation of the environmental aspects of these alternative locations was undertaken, with respect to the issues of water quality/dredged sediment, ecology, archaeology and visual/landscape (Table 2.1 refers).
2.18 The comparison table incorporates the observations and discussions made at the site visit on 18 April 2001 to inspect these three location options. During the site visit attended by CED, CAD, AFCD, AMO, DO/Tuen Mun and the Consultants, consensus was reached on the proposed location at the south of the bay at the bulkhead (Option 3, refer to Figure 2.1) being the preferred option, subject to consultation with the Lung Kwu Tan villagers on this location.
2.19 Option 3 was preferred after the evaluation of the environmental benefits and disbenefits of the three options. Comparing with Option 1, the length of the catwalk in Option 3 was substantially reduced and the dredging area for approach channel was smaller (a dredging area of 1,978 m2 for Option 3 on comparison to 8,300m2 for Option 1). This would minimise the area of seabed affected by the construction activities and the associated water quality, ecology, archaeology and visual/landscape impacts. Option 2 is a less preferred location for the jetty compared to Option 3. This location has a natural shoreline, with the highest density of intertidal organisms. Extension of a path to this location would cause major disturbance to the coastal terrestrial habitats owing to the need for major construction works. In addition, Option 2 is sited near the shipwreck area to the north of the bay where soft corals are attached to the wreck. Option 3 was preferred to Option 2 as the majority of the shore and backshore areas of Option 3 are already exposed to significant human disturbance.
Preferred Jetty Location and Design Option
2.20 The preferred jetty location option (refer to Figure 2.3) incorporates the recommendations raised at the Marine Parks Committee meeting held on 9 November 2001. The main environmental benefits of the proposed jetty location are that it would require a smaller dredging area for the approach channel (1,978 m2) and cause less intrusion into the bay of the adjacent beach, and therefore would have less impact on the Chinese White Dolphin. Support from the Lung Kwu Tan villagers for the preferred jetty location option (Option 3) has also been obtained. The Tuen Mun District Council (TMDC) was consulted on the preferred jetty location option in July 2002 and no comments were received. The Marine Parks Committee was consulted on 10 July 2002 on the detailed findings of this EIA Study, based on the preferred jetty location and design option supported by the Marine Parks Committee in the earlier consultation in November 2001. Only a few minor comments were raised by the committee members.
2.21
Based on the preferred jetty location,
the scope of the Project comprises the following:
·
construction of a
precast concrete blockwork jetty (10 m by 20 m) with a single berth;
·
construction of a
concrete catwalk (approximately 22 m long);
·
dredging of an
approach channel to a level of –2.5 mCD in front of the berth;
·
installation of
miscellaneous facilities on the jetty, including lighting, navigation light,
fendering, handrails, bollards, tide gauge, etc;
·
demolition of the
existing jetty upon completion of the proposed jetty;
·
extension of an
existing footpath.
2.22 The environmental benefits and disbenefits of alternative design options for the jetty have been considered and are summarized in Table 2.2 for ease of comparison. The following design option is preferred:
a) Adopt a blockwork structure to eliminate the need for any piling works which would be the most significant potential source of impact on Chinese White Dolphins.
b) Use pre-cast structures for the jetty and catwalk design to minimise the construction period and the duration of associated environmental impact.
c) Provide openings along the bottom of the catwalk to allow seawater circulation. It is recommended that the number/size of openings beneath the catwalk be maximized as far as practicable to allow seawater circulation.
d) Minimise overall jetty structure to minimise dredging works and associated impacts.
2.23 The proposed general arrangement under the preliminary design of the jetty is illustrated in Figure 2.4 and has incorporated the above recommendations.
Temporary Site Office
2.24 A site search has been undertaken to locate a suitable site for setting up the temporary site office for the Project. The proposed locations are from Siu Lam to West Tuen Mun area (Figure 2.5). The proposed period of occupancy is between February 2003 to August 2004. The allocation of the site area is being considered by DLO/TM. With sufficient check and balance mechanisms built in the approval procedures, the application has to undergo internal clearance and due considerations have to be given to comments from various concerned departments.
2.25 The site area would be used for setting up site offices for both the Engineer and the Contractor. Details of the site offices would be proposed by the Contractor and would mainly include layout of accesses, conference rooms, supervisory staff’s rooms, contractor’s office, storage rooms, sanitary facilities, concrete cubes curing tanks and car parking spaces. No significant environmental impacts would be expected from the proposed activities to be carried out at the site office.
Table 2.1 Environmental Comparison of Alternative Jetty Location Options
|
Environmental Issue |
Option 1 |
Option 2 – Alternative at
north of bay |
Option 3 – Alternative at
south of bay at bulkhead (Selected Option) |
|
Water quality / dredged sediment |
Largest jetty structure and approach channel would result in highest
impact on water quality from marine construction works including dredging;
and greatest volume of dredged sediment requiring disposal (14,300 m3)
|
Smaller jetty structure
with lower impact on water quality. Smaller dredged volume of 6,600 m3 |
Smaller jetty structure
with lower impact on water quality.
Smaller dredged volume of 5,550 m3 |
|
Marine ecology |
Longest catwalk (about 62 m
long and 5m wide, with an area of 310 m2) and largest approach
channel (about 8,300 m2) in the middle of the bay would result in
the highest impact on marine ecological resources within the Sha Chau &
LKC Marine Park, including the important Chinese White Dolphin. Largest loss of subtidal habitats |
This location has a natural shoreline, with the highest density of intertidal organisms. Although Option 2 would involve a similar jetty size compared to Option 3, the larger approach channel (3,200m2) and proximity to the shipwreck area which is a favourite site of the Chinese White Dolphin and has soft corals would also make this location less favourable. |
Shorter catwalk (about 22 m
long and 5m wide, with an area of 110 m2) and smaller approach channel
(1,978 m2) with lower impact on marine ecological resources within
the Sha Chau & LKC Marine Park including the important Chinese White
Dolphin Lower impact than Option 2
as both the shore and backshore habitats have been previously disturbed |
|
Terrestrial ecology |
Limited impact on
terrestrial habitat from construction of short footpath extension connecting
proposed jetty and existing footpath |
High impact from
construction of new access route / footpath on the rugged natural coastal
habitat (longer land route than Option 3) |
Limited impact from construction
of new access route / footpath on coastal / backshore habitat which has been
largely disturbed |
|
Land archaeology |
Low impact potential on the
LKC Archaeological Site due to shorter length of footpath |
Higher impact potential
from construction of new access route / footpath (longer land route than
Option 3 and substantial excavation is likely to be required) |
Low impact potential from
construction of new access route / footpath that follows disturbed land |
|
Marine archaeology |
Higher impact potential on
the LKC Archaeology Site due to greater disturbance of seabed area for
approach channel (about 8,300 m2) |
Lower impact potential from
smaller disturbance of seabed area for approach channel (3,200m2) |
Lower impact potential from
smaller disturbance of seabed area for approach channel (1,978 m2) |
|
Visual / landscape |
Larger jetty structure would result in greater visual intrusion and
landscape loss of natural sea water area. Short footpath
extension would result in limited landscape loss of natural coastal features |
Smaller jetty structure would result in less visual intrusion and less
landscape loss of natural sea water area. Footpath would result in highest landscape loss of natural rugged
coastal features (longer land route than Option 3) |
Smaller jetty structure would result in less visual intrusion and less
landscape loss of natural sea water area. Footpath would result in limited landscape loss of existing disturbed
coastal features |
|
Cultural / Feng Shui |
Preliminary support obtained from local villagers at Lung Kwu Tan |
Consultation
with local villagers undertaken and support has been obtained |
Consultation with local villagers undertaken and support has been
obtained |
Table 2.2 Summary of Alternative Design Options
|
Design Option |
Environmental Benefit |
Environmental Disbenefit |
Remarks |
|
Vessel Type: |
|
|
|
|
Shallow draught vessel |
Minimize catwalk / jetty
length; Minimize scale of dredging
for approach channel & associated water quality impact. |
|
Key factors in determining
the scale of dredging for approach channel are vessel draught & length. Not considered practicable
due to adverse weather conditions and vessel stability constraints. |
|
High manoeuvrability vessel / small size |
Reduce length of catwalk / jetty size; Minimize scale of dredging &
associated water quality impact. |
|
|
|
Jetty Structure: |
|
|
|
|
Rubble mound catwalk with
openings in causeway under catwalk |
Openings would enhance
seawater circulation; Rubble mound foundations would provide habitat for recolonisation and would compensate for the loss of intertidal habitat; Rubble mounds would blend with rocky boulder shoreline. |
|
|
|
Open bridge type structure
(with piled support) for catwalk and jetty head |
Enhance seawater
circulation; Minimize visual intrusion; Minimize scale of dredging
& associated water quality impact; Reduce loss of intertidal,
seabed habitat & benthic communities. |
Piling/ pile foundation
would result in noise disturbance to dolphins, but bored piling would
minimize impact compared to percussive piling; Less area for
recolonisation by intertidal fauna; Disturbance associated with
greater maintenance activities. |
Higher cost and maintenance
requirements for piled support & reinforced/prestressed concrete bridge
catwalk. |
|
Construction Method: |
|
|
|
|
Use of pre-cast structures for jetty & catwalk |
Shorten construction period
& duration of impact. |
|
|
|
Underwater piling |
|
Mitigation may be required to minimize noise impact
on dolphins e.g. use of bubble curtain. |
|