ENVIRONMENTAL IMPACT
ASSESSMENT
The environmental assessment of construc- tion and operational impacts is based on the current Master Plan. All estimates of en- vironmental impact rely on projected con- struction and operation methods which continue to evolve. Many impacts are projected decades into the future and can be very sensitive to changes in technology, the economy, populations and political events. To compensate for this high degree of uncertainty, impacts have been assessed conservatively (ile. tending to over-es- timate) and the operational impact assess- ment will need to be updated as the Master Plan is periodically revised.
In order to assure that recommended monitoring, modelling and on-site mitiga- tion programmes are properly imple- mented, and that all environmental guidelines and criteria are complied with. it is proposed that an environmental scientist and the necessary technical support staff will be a permanent part of the airport staff.
Construction Impacts
Noise
With the assistance of the Environmental Protection Department (EPD), miligation measures were designed which minimize the noise emitted front the airport construction site and propose finding for the acquisition and operation of air conditioners for those Noise Sensitive Receivers (NSRs) which arc still projected to receive unacceptable noise levels. NSRs arc. for example, houses, schools and hospitals. The air conditioners will allow these receivers to keep windows closed and the walls will provide insulation from external noise. With the implementation of these mitigation measures, analysis shows that Hong Kong Government allowable noise levels for all NSRs can be achieved.
Air Quality
The creation of dust during the airport site preparation project is unavoidable. For tunately, the remote location of the site and
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the prevailing wind patterns will limit the potential impacts at receptors on Lantau Island. Based on computer modelling results, the greatest potential impacts are expected in the initial construction period and when the wind is from the north over Chek Lap Kok. Under these "worst case" conditions, the dust plume created by the blasting operations could contribute to in- creased dust levels along the coastline of North Lantau, but only for several minutes during each occurrence.
Water Quality
Computer modelling was used to simulate effects of the airport reclamation works on tidal flow and water quality. It was found that the reclamation had an insignificant impact on flows remote from Chek Lap Kok. Locally, water speed in the channel between West Brother Island and the northeastern corner of the reclamation would increase, possibly resulting in local erosion, and water speed to the west of the reclamation and in East Tung Chung Bay would decrease, which could result in in- creased local siltation and potential decreases in water quality, should the area be subject to additional pollutant loading. In order to maintain the current frequency of flushing in East Tung Chung Bay, and to preserve the North Lantau shoreline, a sea channel concept was developed to separate the airport from North Lantau. Provided existing flows are maintained around the south of Chek Lap Kok, as is proposed, water quality and siltation patterns should not change significantly as a result of the airport reclamation.
Potential impacts arising from dredging and dumping operations at the airport, bor- row areas and disposal sites were simulated using sediment dispersion and transport models. It was found that dredging at the airport site and at the borrow areas would have a small impact. Sampling and analysis of marine mud at Chek Lap Kok and the marine borrow arcas showed no significant contamination with heavy metals. Modelling also showed that nutrient loading from sedi- ments disturbed by dredging at Chek Lap
Kok is not expected to cause an adverse environmental impact.
Marine Ecology
The impact of airport construction on marine life will be the destruction of marine bollom fauna in the immediate vicinity of dredging, reclamation and dumping opera- tions, and disturbance to fauna in the sur- rounding areas through the dispersion of suspended sediments. The marine bottom communities in the North Lantau area are already acclimatized to periods of high suspended solids and sediment deposition. due to the effects of the Pearl River discharge, and are known to recolonize naturally depopulated arcas. Long term adverse ef- fects on marine ecology are therefore ex- pected to be insignificant.
Shoreline communities on Chek Lap Kok will be almost entirely destroyed during construction. The seawalls of the reclamation will offer some scope for recolonization by rocky shore fauna, but in lower diversity due to the lack of microhabitat variation. The formation of a flushing channel will permit retention of shoreline communities on North Lantau. although changes to wave exposure and localized tidal flushing may cause the present rock cliff and sandy shore com- munities to be replaced over time by shel- tered rocky communities dominated by oysters, or muddy shore communities.
Terrestrial Ecology
Although the impacts of airport construction will be to destroyalmost all the terrestrial flora and fauna, and to displace all the island's birdlife, it is proposed that these impacts will be mitigated through the creation or preser- vation of similar habitats at other locations within the Territory. A study of the terrestrial flora and fauna of Chek Lap Kok identified the island's wetland habitats as the most valu- able. These contain mangroves, including a relatively rare species which has a restricted distribution in Hong Kong. The fresh water areas are home 10 Romer's Treefrog. This rare species is endemic to Hong Kong. A study is currently being conducted to assist in
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