Ecology
Ecological information about Northern Lantau came from a 9 month baseline study in 2004 and a follow up verification study in 2008. Survey information was combined with a literature review of the region. The original study area was large enough to encompass the 2 possible viaduct alignment options proposed at the time (fig. 1). The 2008 verification study looked the area 500m in distance from the accepted bridge alignment (fig. 2)
The baseline study involved several different groups of organisms (Table 1). This data, as well as the methodologies, was covered in the verification study and the EIA. The verification study employed various methodologies for different survey types (Table 1). In all, the methodology was quite sound and thorough given the short time in which they had to do their surveys.
After 2008, dive surveys were done on and around Airport Island to survey the reclamation site and surrounding areas. Survey criteria and methodologies were similar to those used in the verification study.
Table 1: Survey types and methodology of the verification and baseline study
Figure 1: Study areas of the verification and the baseline studies
EIA Results
The EIA combined data from all the surveys and literature review. A significant diversity of animals and invertebrates (Table 2) were observed. Many habitat types were also noted. Species of interest include the sea grasses Zostera japonica and Halophila ovali; the Chinese White Dolphin (Sousa chinensis) and Finless porpoise (Neophocaena phocaenoides). Mangroves and artificial reef habitats are considered to be of moderate concern. The Horseshoe crabs Carcinoscorpius rotundicauda and Tachypleus tridentatus. The Collared Scops Owl (Otus bakkamoena) and the endangered, endemic Romer’s Tree Frog (Philautus romeri) were not found in the surveys but are known to occur in this area from the literature. The commercially important Greasy-back Shrimp Metapenaeus ensis and the Sea cucumber Holothuria. The corals Leucospilota Balanophyllia sp., Chinomuricea sp. were also observed.
Within the diverse number of species, it was mainly the Sea grasses, Chinese White Dolphins and Horseshoe crabs that were of considered to need mitigation measures.
Table 2: Animal diversity found in the verification study
The EIA combined data from all the surveys and literature review. A significant diversity of animals and invertebrates (Table 2) were observed. Many habitat types were also noted. Species of interest include the sea grasses Zostera japonica and Halophila ovali; the Chinese White Dolphin (Sousa chinensis) and Finless porpoise (Neophocaena phocaenoides). Mangroves and artificial reef habitats are considered to be of moderate concern. The Horseshoe crabs Carcinoscorpius rotundicauda and Tachypleus tridentatus. The Collared Scops Owl (Otus bakkamoena) and the endangered, endemic Romer’s Tree Frog (Philautus romeri) were not found in the surveys but are known to occur in this area from the literature. The commercially important Greasy-back Shrimp Metapenaeus ensis and the Sea cucumber Holothuria. The corals Leucospilota Balanophyllia sp., Chinomuricea sp. were also observed.
Within the diverse number of species, it was mainly the Sea grasses, Chinese White Dolphins and Horseshoe crabs that were of considered to need mitigation measures.
Table 2: Animal diversity found in the verification study
Table 3: Results and assessment of habitat types from the verification study
Mitigation
The criteria used to assess the need for mitigation were as follows (p. 68):
• habitat quality
• species affected
• size/abundance of habitats/organisms affected
• duration of impacts
• reversibility of impacts
• magnitude of environmental changes
Impacts that were considered moderate and severe were considered to be significant impacts that require mitigation. Mitigation measures were designed to “Avoid, Minimize and Compensate” (p.69)
Sediments that may be released in the construction of the reclamation site will be contained by a double-layer silt curtain that will be installed around the construction site. closed-grab dredging and sediment traps will also be used to reduce loss. To determine the impacts of sediments, both polluted and not, a water quality model was used. The model took water movement sediment load and the presence of mitigation measures into account. The model predicted little or no impact to the areas of conservation interest. Silt curtains will protect the sea grass and Horseshoe crab populations within the airport channel (fig. 2).
The mitigation measures for the Chinese White Dolphin were based on the areas where the dolphins were commonly found (fig.2). Marine sanctuaries were created to mitigate habitat loss, but only one is in an area where dolphins occur regularly. Chemicals and oil are to be carefully collected and transported to avoid leaks. Marine traffic consists of slow moving ships that are not though to pose a risk of collision. One of the beneficial impacts of building the bridge will be a reduction of ferries in the area.
During the installation of the viaduct, bored piling will be used to install the support pillars. This construction method reduces the marine noise and the release of sediments. Pillars will be installed with a distance of 50m in the open sea section and 100m apart near the airport channel to form less of an obstacle to dolphin movement.
Birds that feed in the mudflats and rocky shores of Airport Island were deemed to be affected by the temporary loss of their feeding grounds. However, the creation of the reclamation site is said to increase feeding area, once completed. There is no mention as to whether or not this area may be polluted.
The cumulative impacts of concurrent projects were discussed, but none were considered to have a significant impact when combined with the viaduct and reclamation site construction. The possibility of future infrastructure was not discussed. Given that Hong Kong Disneyland is in Lantau, increased development and roads are likely to happen.
The criteria used to assess the need for mitigation were as follows (p. 68):
• habitat quality
• species affected
• size/abundance of habitats/organisms affected
• duration of impacts
• reversibility of impacts
• magnitude of environmental changes
Impacts that were considered moderate and severe were considered to be significant impacts that require mitigation. Mitigation measures were designed to “Avoid, Minimize and Compensate” (p.69)
Sediments that may be released in the construction of the reclamation site will be contained by a double-layer silt curtain that will be installed around the construction site. closed-grab dredging and sediment traps will also be used to reduce loss. To determine the impacts of sediments, both polluted and not, a water quality model was used. The model took water movement sediment load and the presence of mitigation measures into account. The model predicted little or no impact to the areas of conservation interest. Silt curtains will protect the sea grass and Horseshoe crab populations within the airport channel (fig. 2).
The mitigation measures for the Chinese White Dolphin were based on the areas where the dolphins were commonly found (fig.2). Marine sanctuaries were created to mitigate habitat loss, but only one is in an area where dolphins occur regularly. Chemicals and oil are to be carefully collected and transported to avoid leaks. Marine traffic consists of slow moving ships that are not though to pose a risk of collision. One of the beneficial impacts of building the bridge will be a reduction of ferries in the area.
During the installation of the viaduct, bored piling will be used to install the support pillars. This construction method reduces the marine noise and the release of sediments. Pillars will be installed with a distance of 50m in the open sea section and 100m apart near the airport channel to form less of an obstacle to dolphin movement.
Birds that feed in the mudflats and rocky shores of Airport Island were deemed to be affected by the temporary loss of their feeding grounds. However, the creation of the reclamation site is said to increase feeding area, once completed. There is no mention as to whether or not this area may be polluted.
The cumulative impacts of concurrent projects were discussed, but none were considered to have a significant impact when combined with the viaduct and reclamation site construction. The possibility of future infrastructure was not discussed. Given that Hong Kong Disneyland is in Lantau, increased development and roads are likely to happen.
Figure 2: Locations of Chinese White Dolphin calf sightings from 2002-2008, represented by black dots. Horseshoe crab and Sea grass populations also shown.
Our Critique
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