6. ECOLOGY

6.1 Introduction

6.1.1 The Monthly Report shall provide a statement on the general state of ecology in the study area, and confirm that required mitigation measures are being implemented. Effectiveness of the mitigation measures will also be assessed based upon the monitoring data.

6.1.2 The extent of the works areas should be regularly checked during the construction phase. Any trespass by the Contractor outside the limit of the works, including any damage to habitats should be reported to the Engineer.

6.1.3 The progress of the engineering works should be regularly reviewed on site to identify the earliest practical opportunities for implementing ecological mitigation measures.

6.2 During Construction Phase

6.2.1 Ecological monitoring is recommended during construction phase of the SWC. The mitigation measures should be included into contract clauses for SWC construction. The implementation of the measures should be audited as part of the EM&A procedures during the construction period. Details of the recommended monitoring projects are listed in the paragraphs below.

6.2.2 Inspection of the clearance of oyster beds within works area: The area within the 50m works area will be restored from oyster beds to mudflats to mitigate the temporary and permanent loss of intertidal habitat caused by the pier construction sites and the piers. Oyster beds would be removed before the commencement of construction works. This area should be inspected for the compliance of clearance.

6.2.3 Seagrass bed relocation: One month before the commencement of construction works, any seagrass beds within the 50m works area boundaries should be marked by visible markings and their total extent will be calculated. An area of exposed mudflat of the equal size will be identified in Pak Nai (Figure EM 6.1). Seagrass together with the sediment underneath will be divided into plugs of practical size, removed from Ngau Hom Shek and relocated to the identified area in Pak Nai. The surface of the plugs should be leveled with surrounding sediment at the relocation site. Relocated seagrass plugs should be monitored quarterly for survival and growth during construction phase.

6.2.4 Mangrove loss: The works area boundaries within the mangal at the shoreline at Ngau Hom Shek should be marked to ensure that work crews and equipment confine all construction activities to the designated works area. Markings should be readily visible, and should be replaced immediately if damaged. Number of mangrove seedlings to be planted and location of planting should be determined during the design and construction stage of the project. Replanting should be conducted within 4 months after the mudflat restoration (clearance of construction materials and wastes) is completed.

6.2.5 Work disturbance on inter-tidal bird communities: Distribution of feeding shorebirds on inter-tidal mudflats near construction sites of the alignment will be studied. Distances of feeding birds on mudflat within 500 m of both sides of the construction site will be recorded. Birds feeding on exposed mudflats and tidelines will be recorded separately. Survey will be carried out when more than 100 m mudflat is exposed, as in the EIA study. A graph showing the distribution pattern of feeding birds around the construction site will be plotted. A control site will be set up on mudflats at Sheung Pak Nai (Figure EM 6.1). Distribution pattern of feeding birds on both sides of a strip of mudflat of equal width as the construction sites will be studied in the same way as in the construction site. Distribution patterns of birds at the construction site and control site will be compared using statistical test. Bird abundance and species richness in the construction site and the control site will also be compared with the baseline data of these two locations collected during the field surveys for the EIA study (Table 3.10 & 3.11 in Appendix 9A of the EIA report). The data from the control site will provide information on the bird density and composition in the outer Deep Bay area, while the data from the construction site can reflect the potential effect of construction works on birds. Any changes of bird density recorded in the construction site will be adjusted by the changes of bird density in the control site. Discussion on any changes of species composition recorded in the construction site will also make reference to the results from the control site. Sampling frequency will be once per month throughout the construction phase. If a 30% net reduction (after adjustment) of bird density was recorded in the construction site, the ET and the on-site engineer will be alerted to any noncompliance of mitigation measures or site practices. The monitoring frequency will also be increased to once per week (Table 6.2) until the recorded bird density stores and complies with the 30% allowance of Trigger level. If the net reduction continues and exceeds 50% (allowance of Action level, see Table 6.2), disturbance mitigation measures such as erection of disturbance barrier will be applied. The weekly monitoring frequency will be maintained until the recorded bird density stores and complies with the 30% allowance of Trigger level.

Table 6.2       Trigger and Action levels for Bird density

6.2.6 Mudflat restoration: The works area boundaries for the project within the mudflat should be marked to ensure that work crews and equipment confine all construction activities to the designated works area. Markings should be readily visible, and should be replaced immediately if damaged. Construction materials and wastes, or equipment must be cleared from the mudflats within two months after the construction period. The profile of the mudflat will be restored to its original conditions.

6.3 During Operation Phase

6.3.1 Ecological monitoring is recommended during operation phase of the SWC. The mitigation measures should be included into contract clauses for SWC operation. The implementation of the measures should be audited as part of the EM&A procedures during the operation period. Details of the procedures are listed below.

6.3.2 Operation disturbance on inter-tidal bird communities: Distribution of feeding shorebirds on inter-tidal mudflats near the bridge will be studied. Distances of feeding birds on mudflat within 500 m of both sides of the bridge will be recorded. Birds feeding on exposed mudflats and tidelines will be recorded separately. Survey will be carried out when more than 100 m mudflat is exposed, as in the EIA study. A graph showing the distribution pattern of feeding birds around the bridge will be plotted. A control site will be set up on mudflats at Sheung Pak Nai (Figure EM 6.1). Distribution pattern of feeding birds on both sides of a strip of mudflat of equal width as the bridge will be studied in the same way as in the bridge. Distribution patterns of birds near the bridge and control site will be compared using statistical test. Bird abundance and species richness in the bridge and the control site will also be compared with the baseline data at these two locations collected during the field surveys for the EIA study (Table 3.10 & 3.11 in Appendix 9A of the EIA report). The data from the control site will provide information on the bird density and composition in the outer Deep Bay area, while the data from the bridge can reflect the potential effect of bridge structure on birds. Any changes of bird density recorded in the bridge will be adjusted by the changes of bird density in the control site. Discussion on any changes of species composition recorded in the bridge will also make reference to the results from the control site. In order to study the effect of shade of the bridge on birds, bird abundance and species richness on inter-tidal mudflat right below the bridge will be sampled. Bird abundance and species richness under bridge will be compared with those on mudflat without bridge. Sampling frequency will be once per two months. If a 30% net reduction (after adjustment) of bird density was recorded in the bridge, the monitoring frequency will also be increased to once per week (Table 6.3) until the recorded bird density stores and complies with the 30% allowance of Trigger level. If the net reduction continues and exceeds 50% (allowance of Action level, see Table 6.3), locations and measures to enhance bird feeding resources, with reference to the results of the bridge shade effect study, will be explored. The weekly monitoring frequency will be maintained until the recorded bird density stores and complies with the 30% allowance of Trigger level. The monitoring should be carried out for at least 2 years.

Table 6.3 Trigger and Action levels for Bird density

6.3.3 Monitoring of bridge lighting and bird collisions: Specific types of bridge lighting were recommended to minimise the probability of bird collisions with the bridge and associated structures. The focus of the lighting scheme was to protect birds during inclement weather (mist, fog, rain). The recommendation was made that bridge lighting schemes be designed such that flood lights that would be suitable during clear weather could be considered to be supplemented by special lighting during inclement weather, subject to review during detailed design stage. The design and operation of this lighting scheme, together with its performance in terms of bird mortality, should be monitored during the first 3 years of the operation of the bridge. The types of illumination used should be recorded for all weather conditions, and records of any bird fatalities should be documented by date, time, location, weather conditions, type of illumination, number of dead birds by species, and estimated cause of death. Sea surface will be scanned for any floating dead birds. Results of the monitoring study should be used to guide illumination of the bridge in future. Monitoring effort should be concentrated in autumn migration, winter, and spring migration seasons (particularly due to higher frequency of misty weather), because these are the times of year when most birds are moving through or residing in Deep Bay. Various combinations of illumination scheme, weather condition, season of year, and time of day should be monitored. The study should be quantitative and designed to enable robust statistical analyses. Monthly surveys are recommended. However, additional surveys will be carried out after days of inclement weather (e.g., misty days, very cold days).

6.3.4 Mangrove loss: Number of mangrove seedlings planted and location of planting should be checked for compliance with the plan determined during the design and construction stage of the project. Compensatory mangrove planting should be monitored quarterly for survival and growth for 2 years.