The major potential air quality impacts during the construction phase of the project would result from dust arising from site clearance and preparation, demolition of existing structures, excavation and filling, open site erosion, casting of road segments. Cumulative construction dust impacts might also be resulted from a number of major projects planned in the area which include Shenzhen Western Corridor, Yuen Long Highway Widening, Hung Shui Kiu New Development Area, Route 10 North Lantau to Yuen Long Highway, and San Wai Sewage Treatment Works Expansion and Upgrading.
Practicable and effective dust suppression measures should be implemented to minimize the dust nuisance arising from the construction activities. In particular, the relevant dust control requirements set out in Parts I, III and IV of Schedule 1 of the Air Pollution Control (Construction Dust) Regulation should be adopted by the site agent while carrying out construction works.
Major air quality impact during the operational phase of the project would arise from the tailpipe emissions of the vehicles traveling on the proposed Deep Bay Link and the stack emissions from the major existing and future sources in the area.
Computer dispersion modeling was undertaken to assess the potential operational phase cumulative air quality impacts due to traffic emissions from the proposed Deep Bay Link and the future road network in the area and the stack emissions from the major existing and future sources in the area. The modeling results showed no exceedance of the respective Air Quality Objectives (AQO) for nitrogen dioxide, respirable suspended particulates, carbon monoxide, and sulphur dioxide at all the identified existing and future air sensitive receivers in the vicinity of the proposed Deep Bay Link. Mitigation measures for operational phase air quality impacts would therefore not be required.
The major noise impacts associated with DBL project are from the construction activities and the operational road traffic. Noise sensitive receivers are located along DBL. Majority of them are existing village houses and some medium-rise private developments. There is also a major planned development area the HSKNDA in the vicinity.
Construction phase impacts are mainly related to the construction of carriageway. The noisiest work task would be the foundation works for elevated bridge structures. Noise reduction methods include increasing effort levels of mitigation measures together with specific measures: the purpose-built site hoarding and the use of quiet equipment are proposed. Only four NSRs were found likely to have residual impacts from foundation works. The impact at 3 of the 4 NSRs could be reduced to within relevant limits by the special measures during construction stage. The 4th NSR E13 at Tsoi Yuen Tsuen representing about 6 dwellings would be subject to residual impact of 4dB for a duration of about 5 weeks.
Cumulative impacts from other likely concurrent projects like Yuen Long Highway Widening, Route 10, Hung Shui Kiu New Development Area and Shenzhen-Hong Kong Western Corridor are addressed and impacts are generally predicted to be acceptable.
Unavoidable night works are likely required for limited alignment construction crossing over major roads (Castle Peak Road and Yuen Long Highway) and the West Rail and LRT due to safety and public annoyance or inconvenience when closure of roads and rails during daytime. Before these unavoidable night works to be carried, the future contractor has to apply for a Construction Noise Permit (CNP) under NCO for carrying nighttime construction work subject to the approval by the Authority with adequate justifications and mitigation measures.
Operational phase impacts are primarily come from road traffic using DBL. The elevated DBL itself has provided screening for low-rise NSRs. In order to alleviate the excessive traffic noise impacts, low-noise surfacing of all sections with speed limit greater than 70km/hr is proposed. Direct measures in the form of noise barriers are proposed along critical locations. For planned NSRs in HSKNDA, the potential impacts their mitigation measures and planning constraints were identified for further consideration. Adverse impacts in relation to traffic noise are not expected with mitigation measures in place.
During the construction phase, realignment of the local stream courses, which intersect with the proposed road alignment, would be required in order not to disrupt the flows downstream from the project sites. Use of box culverts and open channels for flow diversion could evade disruption of the stream flows. Besides, minor works may also be needed to realign some of the existing pipeworks and storm drains so as to maintain the normal functions of the facilities.
Construction activities including excavation and filling activities, construction of foundation, road sections and associated facilities would generate site runoff. The nature of site runoff is usually characterized by high concentration of suspended solids. Suitable mitigation measures as recommended in ProPECC PN 1/94 need to be undertaken. Wastewater treatment systems for removal of suspended solids should be provided on site. A discharge licence issued by EPD should be obtained prior to discharging of the treated effluent. A construction site drainage layout and management plan for water pollution control should be in place at the early stage of the project. A special treatment system for wastewater from bore piling work adjacent to the Deep Bay mudflat is also recommended and should be included in the tender documents. Through the implementation of mitigation measures and Best Management Practices, the water quality impacts associated with the DBL project would be reduced to acceptable levels.
The potential water quality impacts arising from the operational phase of the DBL project mainly include storm runoff from the DBL highway and accidental spillage of chemicals during accidents. As there would be no boundary control facilities, the vehicle recovery area and weighing station would not generate any domestic sewage, sewage generation is not an issue.
The road runoff from the DBL highway contains vehicle-generated pollutants. The key concern is the direct discharge to the Deep Bay mudflat during low tides. This may affect the birds and fauna feeding at the mudflat. Use of vacuum air sweepers/trucks is recommended to remove pollutants at source on a regular basis on the DBL section that drains directly into Deep Bay. Standard HyD gullies with silt traps should also be installed along the road sections of the DBL highway.
Marine Department has in place a Maritime Oil Spill Response Plan to deal with oil spill in Hong Kong waters. In addition, an emergency plan should be developed to deal with accidental spillage of chemicals when an accident occurs. Staff training should be provided to response to the emergency cases. Development of a good management plan for the operation of DBL could enhance the water pollution control. No adverse water quality impacts are anticipated during the operational phase of the DBL project.
An assessment of the potential environmental impacts of waste arising from the construction of the Project has been conducted. Since there is no large scale excavation or fill activities proposed, only a small amount 14,000 m3 of excavated material will require disposal. A small portion of wastes about 19,700 m3 will be generated from the site clearance of existing structures. Other than that only general construction wastes are expected. Operational impacts on the proposed route are expected to be minimal.
Key issues include the need for effective waste management planning during the construction phase. Waste management methods and practices and other environmental control measures have been recommended to ensure that potential impacts are avoided or controlled to acceptable levels.
Provided all the suggested mitigation measures such as proper handling a disposal of wastes are successfully implemented, the potential environmental impacts associated with the management of waste would be insignificant. An on-site Waste Management Plan should be formulated prior to construction of the Project. The recommendations of the Waste Management Plan shall be fully implemented. No residual impact has been identified.
This preliminary investigation has identified land uses within the proposed DBL alignment with the potential to give rise to land contamination for examples industrial workshops, car repairing and maintenance sites, open storage areas, etc. The proposed alignment would only encroach a small portion of these concern sites and about 10 sites would require further investigation.
Considering the rapid changing of landuses in the areas, the Contamination Assessment Plan (CAP) should be updated with reference to concurrent site conditions. It would be necessary to carry out a further site appraisal to review the findings of this EIA, including the number and location of sampling points and testing parameters. Such revised CAP should be submitted to EPD for approval before the actual sampling works begin. Upon receipt of the EPD's approval, the CAP will be implemented and the findings of the investigations will be reported in the Contamination Assessment Report (CAR).
The CAP together with the sampling and testing work are planned to start after the land is available to DBL through early negotiations or resumption and the subsequent CAR and RAP should be approved by the EPD before commencement of any construction work which may disturb the ground of the concerned sites. Contaminated soil should be remedied before construction work could be started on the concerned site.
The important habitats and features along the route of the Deep Bay Link are:
The major ecological impacts identified are:
0.73 ha of fishponds would be resumed as the result of the scheme. 0.73 ha of agricultural land in the vicinity of Ngau Hom Shek would be made available for the establishment of a wetland compensation area consisting of a marshy area and pond targeted for ardeids and other bird species using fish ponds in the vicinity. There would be no net loss of fishpond habitat.
Tree groups, woodland, scrub and plantation along the route would be lost, however there would be planting on verges which would increase overall the area covered by trees and woodland (12.7 ha to be planted to compensate for loss of 8.7 ha.)
A range of habitats of lesser importance would also be affected, including hillside grassland, agricultural land, rough grassland and wasteland. It would not be necessary to mitigate for the all losses of these habitats, the conservation of which is a lower priority than fishponds.
Depending on where the egretry at Ngau Hom Shek is located at the time of construction (the birds have moved on a frequent basis), there may be a loss of breeding habitat for herons and egrets. The numbers which could be affected are 10 pairs of herons and egrets (based on 2002 figures). However because of the mobility of this egretry historically, it is likely that these birds would find alternative nesting sites elsewhere. All of the bamboo in the existing egretry should be transplanted to the western edge of the wetland compensation area in Ngau Hom Shek. Therefore this residual impact is likely to be minor.
The road would cause fragmentation, however this effect was not considered to be major cause for concern given that the landscape was already highly degraded and fragmented in the vicinity of much of the DBL route. Many species (especially birds) are highly mobile and able to move freely and quickly colonise new habitats. Other less mobile species would be able to make use of the proposed underpasses associated with the stream corridors or would move under elevated sections of road.
There would also be minor residual impacts associated with disturbance, (movement and noise). The proposed planting and noise barriers would effectively reduce these effects to a low level.
To conclude, residual ecological impacts from DBL, after implementation of the recommended mitigation measures and the 1:1 compensation of fishpond loss, were deemed minor and acceptable.
Two forms of aquaculture are practiced along the proposed road alignment: oyster culture and pond fish culture. An active oyster bed is located within the study area at Ngau Hom Shek. In terms of capture fisheries, small-scale net trapping is carried out within the inter-tidal zone at Ngau Hom Shek. It is a family based traditional fishing activity and it is rarely seen elsewhere in Hong Kong.
Construction of the proposed DBL would require resuming 0.73 ha of fishponds, representing approximately 10% of the total of both active and inactive/abandoned ponds within the study area. Of these only one will be lost permanently. Overall the impact on fisheries would be insignificant.
DBL alignment is relatively away from any potential historical buildings. Major clan graves of historical or cultural significant were not found affected within the proposed resumption limits, while it was considered major cemeteries in relation to village culture as a whole should be preserved instead. The proposed alignment has taken into account the significance of identified cemeteries and burial grounds. Major Tang cemetery and Chan cemetery was avoided. The only impacted cemetery is the Permitted Burial Ground No. 22 which would require relocation in association with the future Route 10 Project.
Four sites of cultural heritage with archaeological significance have been identified at the locations within or very close to the direct impact zone of the propose DBL alignment, including the selected landing point of Shenzhen Western Corridor. The four sites are the Ngau Hom Shek Beach Site, the Ngau Hom Shek Hill Site, the Tsing Chuen Wai Site and the Lam Tei Site. The DBL, especially the location of pilecaps, should be designed to minimize the impact to the four sites of cultural heritage. Archaeological surveys and salvage excavation are proposed for the Ngau Hom Shek Beach Site, the Tsing Chuen Wai Site and the Lam Tei Site. The Ngau Hom Shek Hill Site, which is slightly outside the impact zone of DBL, should be protected from indirect impact potentially caused by the construction, and facilities and activities related to the construction should be kept away from this site during the entire process of construction.
Upon completion of assessing all the archaeological sites, mitigation measures are proposed in order to reduce the potential impacts associated with the DBL project.
The potentially most significant impacts during the construction and operation phases and their prescribed mitigation measures include the following: Landscape Impacts There will be moderate to substantial impacts to the woodland areas during construction phase. The extent of loss is expected to be around 12,000m², including orchard and plantation trees. This can be mitigated to some extent through the transplanting of some existing trees and the planting of new stock. Mitigation via new planting within the road alignment will be more established after completion and several years after commencement of operation. The impact is expected to be reduced to slight / moderate.
There will be moderate to substantial impacts during construction to mangrove and mudflat areas and to agriculture, orchards and plantations. This will be due to the construction of the SWC. Replanting of mangroves is expected to result in slight/moderate residual impacts 10 years after commencement of operations. The re-planting mitigation is detailed under the ecological impact study. The planting of new native woodland is expected to help mitigate the impact to the agricultural areas, orchards and plantations. Residual impacts after 10 years of operation are expected to be negligible.
There is expected to be moderate to substantial impacts during construction to the landscape character of the village coastal lowland and the sea edge. Given the nature of the construction the character of these areas will be permanently and irreversibly changed. At Year 10 operation, the impacts are expected to remain at moderate to substantial.
There are a total of 5,829 trees within the proposed alignment. These include native woodland, orchard and plantation trees. Of these, 1,671 trees are proposed to be retained, 373 transplanted and 3,785 are proposed to be felled. A proposed 6,473 new trees are proposed within the Compensatory and Master Landscape Plan. Most of these will be native woodland species. Visual Impacts Residents in the Coastal Protection Area and at the village of Ngau Hom Shek will experience moderate visual impact during construction. This will be a result of the construction works associated with the mainline connecting with the SWC and the temporary works areas to the east of the village. This impact is expected to remain as moderate due to the significant and permanent magnitude of change to the area.
There is expected to be moderate and substantial visual impacts during construction to residents in existing and proposed developments east of San Hing Tsuen and the undetermined area northwest of San Hing Tsuen (VSR11) and residents in residential developments and CDA area east of Lam Tei Tsuen (VSR12). These residents will have direct, close views of the construction of the works including the mainline and Lam Tei interchange ramps. These residents will experience the construction of a 5.4km elevated mainline (dual-3 lane trunk road of approximately 33m wide) sitting on concrete columns which are spaced at 30- 40 metres. The deck will be elevated from 29mPD to 41mPD which translates into a relative height of approximately 8 to 28 metres. On top of the road there will be noise barriers along the side and median. The tallest of these barriers is a cantilever barrier of 5.5m height with a 2.5m extension to be located on the eastern side of the mainline and along the ramps at Lam Tei interchange. Additionally, there are more noise barriers of similar dimensions proposed for the Yuen Long Highway widening.
The magnitude of change to these areas will be large during construction and operation phases and the impacts are difficult to mitigate. The noise barriers proposed to use vision panels which will help reduce the visual bulk of the structure of overall. However, the mass of the road deck, ramps and columns will still be significant. In addition, there are concerns regarding glare created by the use of vision panels due to reflected sunlight. In addition the visual impacts expected by the construction of Route are expected to exacerbate the situation for these VSRs. Route 10 is expected to add road structure and substantial slope cutting to the visual environment.
The completion of construction of the DBL is scheduled for mid 2006. Since the VSRs identified within the future HSK NDA will not be constructed before the DBL is completed, these VSRs are not expected to be subjected to construction impacts. However, during operation phase, moderate to substantial residual impacts are expected upon the residential and community facilities at HSK NDA (VSR 5), the proposed village type development and community facilities at HSK NDA (VSR6), the developments east of San Hing Tsuen and the undetermined area northwest of San Hing Tsuen (VSR11), the residential developments and CDA area east of Lam Tei Tsuen (VSR12), and the amenity area of HSK NDA located adjacent to the DBL mainline. The mainline structures and associated noise barriers and semi-enclosure will have significant visual impact upon these receivers. Mitigation in the form of screen planting and earth mounding will assist in ameliorating these impacts but the residual impacts will remain moderate to substantial.