1. Introduction
1.1
On the 18th April 2001,
Highways Department of the Government of the Hong Kong Special Administrative
Region appointed Mouchel Asia Ltd, under Agreement No. CE 13/2001, to
undertake the Improvement to Tung Chung Road between Lung Tseng Tau
and Cheung Sha Investigation and Preliminary Design Assignment (the project).
1.2
The purpose of the Project is to improve the existing
sub-standard Tung
Chung Road, and thereby provide an improved roadway for connecting north and
south Lantau. The improved road will be operated as a closed road in a similar
manner to the existing road to prevent vehicles from the rest of Hong Kong, without Lantau Closed Road
(LCR) permits, from entering South Lantau. Subject to further analysis, the
current Tung Chung Road Prohibited Zone (TCRPZ) permit system might also
require retention with appropriate modification to manage traffic on the
improved road and tightly control its growth.
1.3
The residents in South Lantau, through the auspices of
the Islands District Council, have requested that the road be constructed as a
matter of urgency. Based upon the wishes of the local residents, alternative
modes of transport, such as cable car or direct ferry services, between North
and South Lantau would not suffice.
2. Route Description
2.1
The improved road will comprise a two-lane two-way rural
road, with gradients as steep as 15%, about 6.2km long between Lung Tseng Tau
and Cheung Sha. No climbing lane has been provided in the road in order to
minimise the footprint of the works and therefore, minimise the environmental
impacts of the project, especially on the Country Park. The proposed road
improvement commences at Lung Tseng Tau, and climbs up Tung Chung Valley along
the route of the existing road as far as Tai Tung Shan Service Reservoir. South
of the reservoir, the proposed road veers east from the existing route and
crosses the small plateau at the head of the valley, before rejoining the
existing route at the crest at Pak Kung Au. South of the crest, the new road
again veers east from the existing route, and traverses the hillsides around
the southern flanks of Sunset Peak, before crossing the catchwater and
connecting with South Lantau Road to the east of Cheung Sha Sheung Tsuen.
2.2
Roadside bus laybys and taxi layby facilities are
provided near the new junction of Tung Chung Road and South Lantau Road,
together with a U-turn facility for vehicles travelling along Tung Chung Road.
3. Route Option Selection and Refinement
3.1
The proposed road is situated within an overall rural area, with the surrounding land
comprising country parks, open space and agricultural activities, with some
villages present at either end. The landscape along the route alignment
contains many elements of outstanding natural beauty, including wooded hillsides,
ridges lines of the Lantau and Sunset peaks and riverine valleys. Ecologically,
the area is distinguished by the presence of key habitats and species,
including a fresh water marsh at Fong Yuen, woodland, clean natural streams and
species of conservation interest including the rare fish the Beijiang
Thick-lipped Barb and the Romer’s Tree Frog. This overall rural nature and
minimised human disturbance, with the exception of the existing Tung Chung
Road, is the key characteristic of the existing environmental conditions of the
study area.
3.2
Maintaining these existing
environmental conditions, as far as practicable, has been a major objective
during the selection of a preferred route and design of the selected
alignment.
3.3
The preferred alignment
for the improved Tung Chung Road is shown in Figure 1. This alignment has been selected after a
comprehensive option assessment process which provided an evaluation and
comparison of 4 northern alignment options and 4 southern alignment option
combinations within the Tai Tung Shan – Cheung Sha corridor, the environmental
implications of each alternative being a key consideration. The main environmental advantages of the
selected alignment over the other options include:
C shortest
overland route between Tung Chung and
South Lantau Road, with gentle bends and no tight loop-bends;
C least
amount of bridgeworks, earthworks and
retaining walls, resulting in least amount of “muck shifting” and surplus
excavated material;
C least
potential to impact Tung Chung Stream and Cheung Sha Stream (alignment avoids
Cheung Sha Stream as far as possible);
C least
ecological impacts;
C least
landscape and visual impacts for overland route;
C least
impacts on the Country Park for overland route; and
C least
construction cost and shortest construction programme.
3.4
The avoidance and
minimisation of environmental impacts has been a key element through the
progressive design of the selected alignment.
The current preferred route has been designed in order to reach an
alignment which can be stated as representing the optimum route after balancing
all relevant factors within the engineering and topographical constraints.
3.5
The main characteristics
of the alignment which have been designed to minimise the environmental effects
of the road include:
C alignment
widened on-line as far as possible to minimise habitat loss and also on eastern
side of the existing Tung Chung Road to avoid crossing over the high ecological
value Tung Chung Stream;
C haul
road specified along the same alignment as the main route as far as practicable
to reduce the extent of temporary habitat loss;
C alignment
designed on bridge structure where appropriate and with the use of retaining
walls in order to significantly reduce the extent of cut slopes required,
having ecological benefits;
C alignment
designed to cross all key ecologically sensitive streams on structure during
both the construction and operational stages to avoid direct impacts on the
aquatic environment;
C construction
runoff in the northern section to be collected into a special pipeline and
transported to the Wong Lung Hang nullah in Tung Chung and treated via
sedimentation tanks prior to discharge. This will avoid discharge into the
northern streams which are tributaries of the highly sensitive Tung Chung
stream. In the south, all run-off
collected and treated using sedimentation tanks and oil interceptors prior to
discharge to protect the streams and the water gathering grounds;
C special
pipe also designed to carry road runoff to either end of the alignment to avoid
discharge into any stream course during the operational phase; and
C permanent
drainage system designed to avoid direct impacts on Fong Yuen Marsh and the
channelised section of Tung Chung stream which is proposed to be upgraded.
4.
Environmental Impact Assessment
4.1 The
Project is a designated project under Section A.1 of Schedule 2 of the
Environmental Impact Assessment Ordinance (EIAO). As such the statutory
procedures under the EIAO need to be followed and an environmental permit is
required prior to the commencement of construction. Thus, as part of this assignment, an Environmental
Impact Assessment (EIA) is required to assess the potential impacts of the
construction and operation of the Project.
4.2 The
assessment of construction related impacts have included: air quality, noise,
water quality, construction waste, ecology, landscape and visual and hazard to
life. The assessment of impacts during the operation of the project have
included: air quality, noise, water quality, ecology, landscape and visual,
hazard to life and heritage impacts.
4.3
The Remaining Development in Tung Chung and Tai Ho
Comprehensive Feasibility Study has proposed development north of the Tung
Chung Valley which could be affected by the operation of the improved Tung
Chung Road. Thus, for the purposes of
this report, the effects on this development together with the cumulative
effects of the two projects have been assessed. In addition, potential operational air and noise impacts at
proposed future sensitive receivers on the sale sites in Cheung Sha have also
been assessed.
5. Key Findings of the Eia
5.1
In total, eight different
environmental parameters have been evaluated as part of the EIA and the impacts
associated with each, as a result of the implementation of the project,
predicted. Where necessary, mitigation
measures have been recommended to ameliorate any impacts. The eight
environmental parameters covered by the assessment are:
C
air quality;
C
noise;
C
water quality;
C
waste management;
C
ecology;
C
landscape and visual;
C
hazard; and
C
cultural heritage.
5.2 The
project would have no effect on some parameters. The hazard assessment has predicted that, overall,
the risk on the road from the Cheung Sha Water Treatment Works will be low and
acceptable. In respect of operational air quality, the results of
the modelling show that air quality will comply with the Air Quality
Objectives. For both, no mitigation
measures are required.
5.3
Construction phase dust
impacts can be reduced to acceptable levels with the implementation of suitable
measures. A series of waste management
measures to control the sorting, storage, handling, transportation and disposal
of all forms of waste that may arise from the project have been determined and
no adverse impacts are predicted if these measures are instigated. All the recommended measures are practicable
and can be implemented. Construction noise levels can also be reduced to
acceptable levels with the use of mitigation measures. In the region of 44 dwellings
will be protected by the measures proposed.
5.4 The heritage impact assessment revealed
the presence of former agricultural terraces in Cheung Sha and the three test
pits conducted to the east of Tung Chung
Road all
contained historical material from the Qing dynasty. Based upon the distance of the finds from the alignment in Cheung
Sha and the fact that the material found in Tung Chung does not represent a
significant archaeological deposit, no mitigation measures are required.
5.5
While no direct impacts on
the 23 historical buildings and structures identified have been predicted, the
road will result in impacts of a visual nature but with the distance from the
development providing a sufficient buffer zone during the construction phase
for most of these structures. in
varying degrees of indirect impact on some buildings. Thus, mitigation for a shrine in Lung Tseng Tau in the form of a protective barrier during the
construction phase and the mitigation for the Fong Yuen nunnery in the form of retaining the existing woodland buffer
and planting of foliage along the cycle path in the vicinity of the
nunneryin order to maintain the existing environment have been recommended.
5.6
The key environmental
issues concerning the project, however, relate to operational noise, landscape
and visual impacts, water quality and ecology.
5.7
Without mitigation, the
noise modelling has concluded that a number of sensitive receivers would be
subject to operational noise levels in excess of the 70 dB(A) limit. A full
range of mitigation options have been considered for the protection of these
receivers.
5.8 Reflective barriers, with an aggregate length of about
127m and ranging in heights from 1.5m to 4.5m in Tung Chung have been proposed
in Lung Tseng Tau. Based upon these recommended mitigation measures, all
operational noise levels at properties affected by the project can be reduced
to acceptable levels. Approximately 10 dwellings will be protected by
these barriers in the Tung Chung area.
5.9 In
addition, a landscaped earth bund, together with a 4m non building area is
proposed at the future sale sites in Cheung Sha to protect the future sensitive
receivers from noise impacts from the road.
5.10
The use of retaining wall
and use of structures where appropriate along the alignment has reduced the
degree of slope works and in addition, the road will be widened on-line as far
as possible, thereby, minimising the
landscape and visual impacts of the improved road. Mitigation measures to minimise the extent of the remaining
impacts include:
C
protection and retention
of existing vegetation;
C
transplanting of trees
where appropriate;
C
protection and retention
of existing natural rocky outcrops, slope profiles, vegetation, landscape
features;
C
sensitive architectural
and chromatic treatment of new highway structures including bridges, retaining
walls and noise barriers;
C
advance planting/visual
screening; and
C
sensitively designed site
hoarding in public areas.
5.11
In addition, extensive compensatory planting of about
25ha is proposed along the alignment. It is intended that the planting will be
able to recompense for the woodland and shrubland lost and to help re-establish
the landscape pattern and reduce the visual impact of the road.
5.12 The
project will result in some landscape and visual impacts which are predicted to
remain after construction of the project despite the mitigation measures.
However, the residual impacts generated by the bridge structures and noise
barriers are considered acceptable within the overall benefits of the scheme.
5.13 The study area contains numerous streams which are of
high ecological value, including the Tung Chung Stream and the Cheung Sha
Stream which have been shown to contain aquatic species of conservation
interest. The area is also located within a water gathering ground. Based upon
the need to protect these streams from direct and indirect impacts, the
selected road alignment is proposed to be widened on-line from Tung Chung
up to the Tai Tung Shan Service Reservoir (the remaining part of the road will
be largely off-line) so as to minimise earthworks and run-off potential and
also the existing road will be widened on the east side where practiacble, such
that during construction, the existing road can be used as a buffer zone to
help prevent any pollutants from running into Tung Chung Stream. Also the
selected alignment is the furthest from the Cheung Sha stream.
5.14 However,
given the importance of the streams in the study area and the water gathering grounds, a range of mitigation measures has been proposed to
protect the aquatic resources in the study area during both the construction
and operation phases. During the construction phase, streams of high ecological
importance have been crossed on structure in order to avoid impacts and the
haul road, where it goes off-line, will also cross the streams on temporary
bridges with spans at least twice the width of the stream.
5.15 In order to protect the Tung Chung and Cheung Sha
Streams and tributaries from water borne sediments and pollutants from the
construction site, a drainage system has been devised to avoid /
minimise water quality impacts as far as possible. For the northern section of
the new road, it is proposed that the operational drainage system be
constructed ahead of the main roadworks such that it may be used to discharge the
construction site runoff, thus avoid discharging construction site runoff into
the streams all together. The discharge outfall for the northern section’s
drainage system will be located in the Wong Lung Hang nullah near Ha Ling Pei
in Tung Chung and all discharge will be treated via a sedimentation tank in
order to minimise impact on Tung Chung Bay and the seagrass bed at San Tau
SSSI. South of the crest, it is
proposed to use a series of peripheral surface channels to encase sections of
the works site to intercept and divert the surface runoff from the hinterland
and the construction site. All site
run-off will be treated by a series of sedimentation tanks prior to discharge
into adjacent streams. Oil interceptors will also be used above the catchwater
to further protect the water gathering grounds.
5.16
The key aspects of the
proposed temporary drainage system which will be adopted to ensure the protection of the
water quality in the inland streams, Tung Chung Bay and Pui O Wan during
construction are as follows:
C
system designed to have no
discharge of site run-off into Tung Chung Stream;
C
northern temporary
drainage system will avoid discharge into any streams;
C
system in the southern
area divided into small sub-catchments to enhance control and minimise impacts;
C
all run-off treated via a
sedimentation tank prior to discharge either into streams in southern area or
marine environment;
C
oil interceptors used
above catchwater to protect water gathering grounds;
C
all parts of system will
be regularly cleaned and maintained;
C
hinterland runoff
separated to protect from contamination; and
C system must be operational before the start of the
permanent works.
5.17 Based upon the inclusion of these measures, the risk
of adverse impacts to water quality during the construction phase has been
reduced to a negligible level.
5.18 In
respect of operational water
quality impacts,
contaminants in the road surface runoff
are expected to be limited and, thus, impacts on the water quality of the
streams are expected to be negligible. Notwithstanding, a specially designed
carrier pipe along the length of the road will collect and transport all road
drainage to either end of the alignment prior to discharge into the Wong Lung
Hang nullah in Tung Chung and Pui O Wan.
Thus, operational discharge into all streams along the route, and thus
the water gathering grounds, has been avoided.
5.19 Once
discharged though an outfall at Tung Chung or Pui O Wan, the road runoff would be rapidly
diluted within a few tens of metres from the discharge point. In Tung Chung,
the peak road runoff only amounts to about 1% of the total peak natural
runoff. This value is further reduced
when the dilution in the marine environment is taken into account, with the
runoff from the road being equivalent to about 1% to 2.5% of the tidal volume
depending upon the particular tide, based upon a 1:50 year storm. Similar,
levels of contribution and dilution would be expected for the southern section
of the road and the discharge into Pui O Wan. Thus, any road runoff into the
bays at either end of the alignment would not be expected to result in a
significant increase in the concentration of the water quality parameters of
interest and will not result in a significant increase in the existing
pollutant load to Tung Chung Bay or Pui O Wan.
5.20 The study area contains many key ecological
resources. While the alignment has been
designed, as far as practicable, to minimise the impacts on these habitats and
species. For example,
habitat loss has been minimised by restricting the footprint of the works and
widening the road on-line as far as possible.
In addition, impacts on key ecological streams have been avoided by the
road crossing over these on structure and the Fong Yuen marsh has also been
avoided by careful design of the permanent drainage system. However, some impacts will occur and some of the key habitats and
species of concern which may be affected to varying degrees if mitigation is
not applied include:
C
secondary woodland along
the alignment;
C
streams along the route;
C
shrub Pavetta hongkongensis, orchids Acampe
rigida and Liparis viridiflora
and tree Artocarpus hypargyreus; and
C habitats of amphibians and reptiles along the route
including the Romer’s Tree Frog.
5.21
Approximately 14.5 ha of
land will be affected permanently by the project which will include approximately 6.5ha loss of tall
shrubland, 2.25ha of secondary woodland and 5ha of plantation woodland. Impacts
on the habitats and the species have been predicted as ranging from
insignificant to moderate if mitigation is not applied. A summary of the mitigation and enhancement
measures recommended to minimise these impacts include:
C control of site run-off to protect
ecology of water courses, particularly important for the Tung Chung Stream and
the Cheung Sha Stream;
C minimisation
of working areas during construction to reduce habitat damage;
C transplantation
of the shrub Pavetta hongkongensis,
orchids Acampe rigida and Liparis viridiflora and tree Artocarpus hypargyreus;
C special
design of new culverts and culvert inlet/outlets for key streams;
C translocation
of Hong Kong Newt, Lesser Spiny Frog and Romer’s Tree Frog from key streams;
C scheduling of works in key streams to avoid the
period April to June which is the key breeding period for fish, amphibians
and odonates;
C translocation
of Romer’s Tree Frog between Lung Tseng Tau and Shek Mun Kap;
C provision of water filled pots as habitats for the Romer's Tree Frog between Lung
Tseng Tau and Shek Mun Kap;
C translocation
of isolated population of Beijiang Thick-lipped Barb to tributary of Tung Chung
Stream;
C provision
of slope surfaces at step channels for aquatic fauna to move up and down stream
at existing bridges;
C provision
of escape routes from drainage channels for amphibians;
C provision
of wildlife tunnels for faunal transfer;
C compensatory
planting of about 25ha to mitigate for
vegetation loss; and
C reinstatement
of land temporarily required during construction.
5.22 The
proposed mitigation measures are considered adequate overall to fully mitigate
all identified impacts. However,
moderate residual impacts in the short term may occur as a result of the planted woodland not
immediately compensating for the function of the mature woodland lost but this
would reduce to minor and then insignificant impacts in the longer term as the
woodland matures. Minor residual
impacts associated with the barrier effect of the new road will also occur. All
residual impacts are considered acceptable.
6. Cumulative Assessment
6.1 There
is only one key interface with the proposed improved Tung Chung Road, situated
at the northern end of its alignment, namely the proposed development in Tung
Chung and Tai Ho. The development in Tung Chung is being assessed under the
Remaining Development in Tung Chung and Tai Ho Comprehensive Feasibility Study
(CFS) currently being conducted by the Territory Development Department. The development proposals of relevance to
this study involve the development of the Tung Chung Valley.
6.2 The
assessment of cumulative impacts includes air quality, noise, water quality, waste,
ecological factors and landscape and visual impacts during both the
construction and operational phases as appropriate.
6.3 The
assessment has concluded that few cumulative
impacts will occur based upon the implementation of the two projects. Sufficient
mitigation measures to reduce any impacts to within acceptable levels have been
recommended by both the CFS and the improved Tung Chung Road and additional
mitigation measures are not considered to be required.
6.4 Cumulative
noise impacts are possible when permanent noise barrier construction in Tung
Chung for the Tung Chung Road is on-going in conjunction with either road works
or site development for the Tung Chung Valley project. Cumulative impacts can be avoided by the
careful scheduling of the works which would prevent noisy equipment working
simultaneously.
6.5 Impacts
on a proposed future school in the Tung Chung Valley from road traffic noise is
predicted. Therefore, a landscaped earth bund has been proposed between the
road and the school site and this is sufficient to reduce predicted noise
levels to within the criteria.
7. Environmental Monitoring and Audit
7.1
In accordance with the
EIA, EM&A procedures are required during the design, construction and
operational phases of the project implementation. The EM&A works during the
design phase shall comprise an iterative audit process of specific design
elements. The drainage system and
specifications for certain ecological and landscape mitigation measures
proposed by the EIA will be required to be designed during the design phase of
the project.
7.2
During the construction
and operational phases, the EM&A requirements are divided into environmental
monitoring and/or project auditing in the form of site inspection and
supervision. EM&A for dust, noise and
water quality during the construction phase is recommended in order to ensure
all proposed mitigation measures are implemented and effective. All three of
these parameters will also be subject to audit through site supervision.
7.3 Site supervision and procedures audit will be required
during the construction phase to ensure the proper handling, storage,
transportation and disposal of the various waste arisings from the
project. Audit of the implementation of
the design elements and mitigation measures to avoid ecological, landscape and
visual and heritage impacts have also been recommended by the EIA, and thus,
monitoring in the form of regular site inspections shall also be required to
ensure mitigation measures are being implemented and are effective. EM&A for both ecology and landscape and
visual resources will extend through the construction phase and into the
operational phase to ensure planting and replanting have been effective.
7.4
Operational noise monitoring shall be undertaken in
months 6 and 12 during the first year of the operation of the project to assess
the effectiveness of the direct noise mitigation measures recommended by the
EIA.
8. Overall Conclusions
8.1 The
design of the proposed improved road has been optimised to minimise the extent
and magnitude of
environmental impacts, particularly the loss of habitat by minimising the
footprint of the works as far as possible. Also, retaining walls have been used
to minimise the extent of the cut slopes and bridges have been used to traverse
the key ecologically sensitive streams and key habitats such as the Fong Yuen
Marsh have been avoided.
8.2 Where,
the implementation of the new road will result in some impacts, a comprehensive
range of mitigation measures has been recommended to reduce these impacts to
acceptable levels. Apart from the
mitigation of direct impacts, it is worth noting that
some of these measures, will not only mitigate impacts, but will also enhance
the existing environmental conditions as follows:
C the
incorporation of wildlife tunnels under the at-grade sections of road;
C sensitive
design of culverts and culvert inlets and outlets to allow fish and other
aquatic faunal access;
C provision
of escape ramps in drainage channels for amphibians;
C provision
of water filled pots for the Romer’s Tree Frog to breed in; and
C the
relocation of key floral and faunal species.
8.3 In
addition, the proposed remedial works to the existing slopes using
bio-engineering techniques (ie, hydroseeding instead of spray applied concrete)
will enhance the existing slopes, resulting in areas of higher landscape value
and after completion of the road, the existing overhead electrical cables and
many proposed utilities can be put underground in the new and obsolete road
sections.
8.4
Furthermore, the proposed special permanent
drainage system will avoid carriageway runoff from being discharged into both the Tung Chung and Cheung Sha
streams and also the water gathering grounds. This will be an improvement on
the existing conditions, whereby carriageway runoff is discharged directly into
the small streams, watercourses and hillsides directly below the existing road.
8.5 Overall,
the environmental impacts predicted for all environmental parameters can be
reduced to acceptable levels with the implementation of the recommended
mitigation measures. Low residual impacts on habitats are predicted based upon
the fact that not all habitat loss can be mitigated in the short term. Residual impacts caused by the barrier
effect of the road are expected but these will be minor in light of the
recommendation to construct wildlife tunnels at at-grade sections of the road.
8.6 Residual
landscape and visual residual impacts will occur but the landscape proposals
will substantially mitigate for the impacts in the long term.
8.7 All the
residual impacts of the project are considered acceptable within the overall
scope and benefits of the project.