Contents

Executive Summary                                                                               

1       Introduction                                                                                    

2       Summary of Environmental Monitoring and Audit Requirements       

3       Review of Chinese White Dolphin Monitoring Results                       

4       Review of Landscape Establishment Monitoring Results                   

5       Review of the Validity of EIA Predictions                                          

6       Recommendations and Conclusions                                                

 

Tables

Table 1.1: Contact Information of Key Personnel 4

 

Figures

Figure 1            Transect Line Layout in West Lantau Survey Area

Appendices

Appendix A       Project Organisation for Environmental Works

Appendix B       Chinese White Dolphin Monitoring Results

Appendix C       Landscape Establishment Monitoring Results

Appendix D       Summary of Weather Conditions

 

  


Executive Summary

This Final Environmental Monitoring and Audit (EM&A) Review Report is prepared for Agreement No. HMWSD 1/2019 (EP) “Post-Construction Monitoring of Chinese White Dolphin (Line-transect Vessel Surveys) for the Hong Kong-Zhuhai-Macao Bridge Hong Kong Link Road at West Lantau Waters – Investigation” (hereafter referred to as “the Assignment”) for the Highways Department of Hong Kong Special Administrative Region (HKSAR).

Mott MacDonald Hong Kong Limited was appointed by the Highways Department of HKSAR to undertake the Environmental Team services for this Assignment to conduct the post-construction monitoring of Chinese White Dolphin in West Lantau waters for 14 months of line-transect vessel surveys and to prepare all the post-construction phase quarterly summary reports for the Hong Kong-Zhuhai-Macao Bridge Hong Kong Link Road Project. Construction phase of the Project was completed in October 2018.

This is the Final EM&A Review Report for the 24-month post-construction phase of the Project summarising the findings of the post-construction EM&A activities in the period between November 2018 and October 2020.

Environmental Monitoring Works in the Post-Construction Phase

All Chinese White Dolphin monitoring and landscape establishment monitoring works were conducted as scheduled under the 24-month post-construction phase. As all marine-based construction activities of the Project were completed in October 2018, no construction works were involved during the post-construction monitoring period. A summary of the post-construction monitoring works is listed as below:

Parameter

Monitoring Dates

Chinese White Dolphin Monitoring (Line-transect Vessel Surveys)

5th and 12th November 2018

6th and 13th December 2018

4th and 8th January 2019

12th and 15th February 2019

6th and 20th March 2019

3rd and 24th April 2019

9th and 16th May 2019

4th and 17th June 2019

5th and 11th July 2019

12th and 28th August 2019

19th and 25th September 2019

2nd and 16th October 2019

4th and 26th November 2019

2nd and 4th December 2019

8th and 15th January 2020

5th and 12th February 2020

6th and 11th March 2020

1st and 17th April 2020

6th and 20th May 2020

2nd and 22nd June 2020

6th and 13th July 2020

6th and 10th August 2020

8th and 24th September 2020

5th and 8th October 2020

Landscape Establishment Monitoring (bi-monthly, conducted for Contract No. HY/2011/09 by other parties)

1st August 2019

23rd September 2019

29th November 2019

10th January 2020

20th March 2020

11th and 22nd May 2020

 

Conclusion of Post-Construction Monitoring

The post-construction phase EM&A programme of environmental monitoring works has been undertaken in the period between November 2018 and October 2020. The CWD usage in WL region has been monitored throughout the post-construction phase of HKLR Project to examine whether CWDs are affected by the lingering impacts from the construction works. The landscape establishment monitoring has been conducted bi-monthly and completed to ensure the aims of the landscape and visual mitigation measures proposed during EIA stage are met.

 

1          Introduction

1.1          Background of the Project

The Hong Kong-Zhuhai-Macao Bridge (HZMB) Hong Kong Link Road (HKLR) is a designated project under the Environmental Impact Assessment Ordinance (EIAO).  The Environmental Impact Assessment (EIA) Report and Environmental Monitoring and Audit (EM&A) Manual (EIA Register No.: AEIAR-144/2009) for the project were approved by the Director of Environmental Protection in October 2009 and the Environmental Permit No. EP-352/2009 (EP) was issued in November 2009.  The EP has been subject to several variations and the current one is EP No. EP-352/2009/D.

The HZMB HKLR was constructed under two works contracts namely Contract No. HY/2011/03 (HZMB HKLR – Section between Scenic Hill and Hong Kong Boundary Crossing Facilities (HKBCF)) and Contract No. HY/2011/09 (HZMB HKLR – Section between HKSAR Boundary and Scenic Hill).  In accordance with the EP, the Contractors of Contract No. HY/2011/03 and Contract No. HY/2011/09 have separately employed their own Environmental Team (ET) and ET Leader to conduct construction phase monitoring of Chinese White Dolphin (CWD) in the North Lantau (NL) and West Lantau (WL) waters following the requirements specified in the EM&A Manual and the relevant contract specifications of the two contracts.

In accordance with Section 10.3 of the EM&A Manual, an ecological monitoring and audit programme is needed which will monitor potential impacts through construction and operation activities, and will verify the assessments which were made in the EIA report.  In particular, the programme should include dolphin monitoring at NL and WL waters to be set up in order to verify the predictions of impacts and to ensure that there are no unforeseen impacts on the dolphin population during construction phase.  Such dolphin monitoring should cover the pre-construction phase, the entire period of construction phase and after the completion of construction works (i.e. post-construction phase). In accordance with Section 14.2.1 of the EM&A Manual, mitigation measures for landscape and visual impacts implemented during construction phase should be checked every 2 months to ensure compliance with the intended aims throughout the one-year landscape establishment period in the post-construction phase.

The main objective of the current Assignment commissioned by the Highways Department (HyD) is to conduct Post-Construction Monitoring of CWD in WL waters in compliance with the requirements stipulated in the EM&A Manual and the EP for the HZMB HKLR Project.  The post-construction monitoring of CWD should be conducted for 24 months upon the completion of all marine-based construction activities. CWD monitoring of the baseline (pre-construction) phase was conducted for 12 months from February 2011 to January 2012. The construction phase CWD monitoring of HZMB HKLR Project lasted for 72 months from November 2012 to October 2018 when the marine-based construction activities for the Contract No. HY/2011/09 was completed in October 2018. Subsequently, 10 months of post-construction dolphin monitoring had been carried out by the Contract, while the remaining 14 months of post-construction dolphin monitoring were completed under this Assignment, from 1 September 2019 to 31 October 2020.

In August 2019, Mott MacDonald Hong Kong Limited was appointed by the HyD to undertake the Environmental Team (ET) services for this Assignment to undertake the post-construction monitoring of CWD in WL waters (refer to Figure 1) for the HZMB HKLR Project.

This is the Final EM&A Review Report for the post-construction phase of the Project summarising the findings of the post-construction EM&A activities in the period between November 2018 and October 2020, and is submitted to fulfil Section 16.5 of the EM&A Manual.   

1.2          Project Organisation

The project organisation and lines of communication with respect to the environmental management structure are shown in Appendix A. The key personnel contact names and numbers are summarised in Table 1.1.

Table 1.1: Contact Information of Key Personnel

Party

Position

Name

Telephone

Fax

Permit Holder (HyD)

Engineer

Mr. Wei Chen

2762 3532

3188 6614

Environmental Project Office /

Independent Environmental Checker

(Ramboll Hong Kong Limited)

Environmental Project Office Leader

Mr. Y H Hui

3465 2888

3465 2899

Independent Environmental Checker

Mr. Manson Yeung

3465 2836

3465 2899

Environmental Team

(Mott MacDonald Hong Kong Limited)

Environmental Team Leader

Mr. Gary Chow

2828 5874

2827 1823

 

1.3          Summary of Environmental Status

As described in Section 1.1, the Assignment is under the post-construction phase of the HZMB HKLR Project from November 2018 to October 2020 with all marine-based construction activities completed, thus there were no construction works involved during the 24-month post-construction monitoring period.

All CWD monitoring and landscape establishment monitoring works were conducted as scheduled under the post-construction phase of the Project.

 

2          Summary of Environmental Monitoring and Audit Requirements

2.1          CWD Monitoring Requirements

According to the requirement stated in the EM&A Manual, a CWD monitoring programme was set up to conduct surveys for twice per month throughout the entire post-construction monitoring period for 24 months, adopting the line-transect vessel survey method and covering the following transect lines in the West Lantau (WL) survey area as in the AFCD long-term marine mammal monitoring programme.

The CWD monitoring works were undertaken by a dedicated survey team comprising qualified dolphin specialist and experienced CWD surveyors. The qualified dolphin specialist was approved by the AFCD and EPD.

The location of the WL survey area and all transect lines are depicted in Figure 1. The co-ordinates of all transect lines are shown in Table 1 of Appendix B.

The monitoring protocol is detailed in Section 3 of Appendix B which is consistent and compatible with the methodology for dolphin monitoring during baseline and construction phases.

Data analysis and assessment in the final review report will be more detailed including distribution analysis, encounter rate analysis, abundance and density estimates, quantitative grid analysis on habitat use, behavioural analysis, ranging pattern analysis, comparison between baseline, construction and post-construction phases of HKLR, and assessment of any recovery in dolphin usage in WL waters. Details of approach and methodology for these analyses and assessment are provided in Section 4 of Appendix B. Notably, although the official baseline dolphin monitoring under the HKLR EM&A programme was conducted during a three-month period of September 2011 to November 2011 under the requirement, this relatively short study period would not be sufficient to reliably establish the baseline condition on dolphin occurrence, as the three-month period would not take into account the seasonal variation in dolphin occurrences.  As there were additional monitoring data collected (under a separate assignment commissioned by the Highways Department) before and after the three-month official baseline period, a 12-month baseline monitoring period from February 2011 to January 2012 (which included the original baseline period of September – November 2011) is adopted instead in this Final EM&A Review Report, and such 12-month baseline monitoring period in 2011 – 2012 was still well before the commencement of HKLR construction.

2.2          Landscape Establishment Monitoring Requirements

According to the requirement stated in the EM&A Manual, landscape establishment monitoring should be carried out every two months for checking of the planting works during the one-year establishment period. Measures to mitigate landscape and visual impacts should be checked to ensure compliance with the intended aims of the measures.

The landscape establishment monitoring areas locate along South Perimeter Road and Chek Lap Kok South Road, near Scenic Road and a small section of Airport Road and Kwo Lo Wan Road. The monitoring programme was set to be conducted in bi-monthly intervals throughout the landscape establishment period for one year from July 2019. The monitoring has been conducted since July 2019 by other parties for Contract No. HY/2011/09, with details provided in Appendix C.

 

3          Review of Chinese White Dolphin Monitoring Results

3.1          Summary of Survey Effort and Dolphin Sightings

During the 24-month post-construction monitoring period from November 2018 to October 2020, a total of 48 sets of systematic line-transect vessel surveys were conducted to cover all transect lines in WL survey area twice per month. From these surveys, a total of 1,583.63 km of survey effort was collected, with 94% of the total survey effort being conducted under favourable weather conditions (i.e. Beaufort Sea State 3 or below with good visibility).  The total survey effort conducted on primary lines was 1,049.17 km, while the effort on secondary lines was 534.46 km.  Survey effort conducted on primary and secondary lines were both considered as on-effort survey data.  A summary table of the survey effort is shown in Appendix B.

During the post-construction monitoring period, a total of 173 groups of 583 dolphins were sighted. Among them, 165 groups of sighting were made on-effort, with 107 on-effort sightings made on primary lines. A summary table of the dolphin sightings is shown in Appendix B.

For the overall CWD monitoring in WL waters for the HZMB HKLR Project, 572.20 km of survey effort were conducted during the 12-month baseline monitoring period between 2011 and 2012, and another 4,765.22 km of survey effort were conducted during the 72-month construction phase monitoring period between 2012 and 2018.  A total of 113 groups of 380 dolphins were sighted during the baseline monitoring phase, while 670 groups of 2,499 dolphins were sighted during the construction phase monitoring. 

3.2          Distribution

Distribution of dolphin sightings made during the post-construction monitoring period is shown in Figure 1 of Appendix B.  The sightings were evenly distributed from Tai O Peninsula in the north to Fan Lau in the south, with higher concentration near Tai O Peninsula, Kai Kung Shan, Peaked Hill and Fan Lau (Figure 1 of Appendix B).  On the contrary, dolphin groups appeared to avoid the inshore waters between Tai O Peninsula and Kai Kung Shan, as well as the HKLR alignment and the southern end (i.e. transect line 12) of the survey area where it overlapped with the South Lantau Vessel Fairway.

The distribution patterns of dolphin sightings in WL waters amongst the nine 12-month monitoring periods spanning across the baseline, construction and post-construction phases of HKLR is shown in Figure 2 of Appendix B.  Comparing these distribution patterns, some subtle differences were found. There was a gradual decline in dolphin occurrence in the northern portion of WL survey area over the years, with apparent avoidance of the HKLR alignment in recent years when compared to the earlier years.  Moreover, dolphin usage at several key habitats including the Tai O Peninsula, Kai Kung Shan, Peaked Hill and Fan Lau Peninsula, have fluctuated across different years, with no apparent trend.  However, it is apparent that dolphin occurrence in WL waters was at the lowest level in the last 12-month monitoring period (i.e. post-construction monitoring period in 2019 – 2020).

3.3          Encounter Rate

For the entire post-construction monitoring period, the monthly encounter rates of CWD deduced from the survey effort and on-effort sighting data from the primary transect lines under favourable conditions (Beaufort 3 or below) from West Lantau survey area are shown in Table 2 of Appendix B. The average encounter rates deduced from each quarterly period were presented in Table 3 of Appendix B.

A comparison is made amongst the nine 12-month monitoring periods spanning across the baseline, construction and post-construction phases of HKLR, as shown in Table 4 of Appendix B.  It revealed that dolphin encounter rates continued to decline during the first several years of HKLR bridge construction works to the lower point in 2016 – 2017.  Then, there was a rebound in the encounter rates during 2017 – 2018, but it was subsequently followed by another decline during the post-construction monitoring period to the lowest point in encounter rate STG and the second lowest point in encounter rate ANI in 2019 – 2020.

A linear regression analysis was conducted to examine whether there were any significant differences in the average encounter rates between the baseline, construction and post-construction monitoring periods.  Such comparison showed that the p-value for the decline in average dolphin encounter rates STG and ANI were 0.000085 and 0.000980 respectively, indicating a significant downward slope across the nine 12-month monitoring periods in the baseline, construction and post-construction phases.

3.4          Density and Abundance

Densities and abundances of CWD in WL waters were estimated during different phases of the Project using the line-transect analysis method, following similar approach as in AFCD long-term marine mammal monitoring study. The following two types of comparison are conducted to review the impact of HKLR construction on CWD densities and abundances, as presented in Table 5 of Appendix B:

1.    Among the three phases of the Project, i.e. baseline phase vs. construction phase vs. post-construction phase; and

2.    Among the nine 12-month monitoring periods spanning across the three phases of the Project.

For the comparison among the three phases of the Project, the baseline phase in 2011 – 2012 recorded the highest dolphin density and abundance, with around 113 dolphins per 100 km2 or 31 dolphins. The CWD estimates dropped to a lower level during the construction phase in 2012 – 2018, with around 79 dolphins per 100 km2 in density or 22 dolphins in abundance. Then, the CWD density and abundance fell even further to the lowest level during the post-construction phase in 2018-20, with around 55 dolphins per 100 km2 or 15 dolphins.

Among the nine 12-month monitoring periods across the three phases of the Project, there was a noticeable drop between the baseline period and the first construction period, falling from 31 dolphins in 2011 – 2012 to 21 dolphins in 2012 – 2013 (as shown in Table 5 of Appendix B). After a noticeable rebound in 2013 – 2014 with 29 dolphins, the dolphin abundance progressively declined to a lower level in 2016 – 2017 with only 15 dolphins.  Then once again, there was a rebound in 2017 – 2018 with 22 dolphins during the last construction period, before falling back to the lowest level during the post-construction phase in 2018 – 2019 and 2019 – 2020 with only 15 and 14 dolphins respectively.

For the examination of any significant temporal trend among the nine 12-month monitoring periods using linear regression models, the test statistics for hypotheses Ho: b = 0 vs. H1: b < 0 is -3.7728 whose p-value ≈ 0.0000 < 5%. The hypothesis Ho is rejected at 5% level of significance.  Therefore, it can be concluded that the dolphin abundance estimates from the nine 12-month monitoring periods in WL possesses a downward sloping trend, and the decline was statistically significant.

Notably, the coefficient of variations (CVs) of estimates for all the nine 12-month monitoring periods remained fairly low (all within 15% – 22% as shown in Table 5 of Appendix B), and therefore these estimates are considered to be reliable.

3.5          Group Size

During the post-construction monitoring period, group size of CWD ranged from one to 19 animals per group in WL survey area. Among the 173 groups of dolphins, 131 groups (75.7%) were in small group sizes of 1-4 dolphins. On the contrary, 34 groups were moderate in size with 5-9 dolphins, while another eight groups were large in size with 10-19 dolphins (sighting details refer to Appendix B).

The average dolphin group size recorded during the nine 12-month monitoring periods across the three phases of the Project are also compared, as shown in Table 6 of Appendix B. When compared to the baseline phase, the average dolphin group sizes were noticeably higher in the second and third years (2013 – 2015) as well as the latter part (2017 – 2018) of the construction phase, while other years were slightly above or below the baseline average, with no apparent overall trend across different years.

Distribution of dolphins with relatively larger group sizes (with five or more animals per group) is examined during the post-construction monitoring period and is shown in Figure 3 of Appendix B.  The 34 medium-sized groups (with 5-9 animals per group) were mostly sighted in the middle portion of the WL survey area (i.e. between Tai O Peninsula and Peaked Hill), while the eight large groups (with 10-19 animals per group) were evenly distributed across the WL survey area with no particular concentration.

Distributions of dolphins with relatively larger groups during the nine 12-month monitoring periods across the three phases of the Project are also examined and presented in Figure 4 of Appendix B. The distribution pattern of dolphins with larger group sizes varied widely, with more even distribution and higher occurrences during the baseline phase (2011 – 2012), as well as the second and sixth years of construction phase (2013 – 2014 and 2017 – 2018). Notably, during the second year of post-construction monitoring (2019 – 2020), larger dolphin groups have mostly disappeared from the northern portion of WL survey area, which was in stark contrast to such distribution recorded during the baseline period.

3.6          Habitat Use

During the post-construction monitoring period from November 2018 to October 2020, the grids that recorded higher densities of dolphins were located to the north and west of Kai Kung Shan, near Peaked Hill and Fan Lau, while the grids around and to the north of Tai O Peninsula mostly recorded lower dolphin densities, as shown in Figures 5a & 5b of Appendix B. 

When compared with the habitat use pattern recorded among the nine 12-month monitoring periods across the baseline, construction and post-construction phases, it appears that the overall dolphin densities across the WL survey area has declined since the construction commenced in 2012 – 2013, as depicted in Figure 6 of Appendix B. Furthermore, among the several important dolphin habitats in this survey area (including Tai O Peninsula, Kai Kung Shan, Peaked Hill and Fan Lau), only the one at Fan Lau has consistently recorded high dolphin densities across the nine 12-month monitoring periods.

3.7          Mother-calf Pairs

Throughout the post-construction monitoring period (2018 – 2020), a total of 20 young calves were sighted with the mother in the WL survey area. These included four unspotted calves (new-born ones) and 16 unspotted juveniles (older calves). The 20 young calves comprised 3.4% of all animals sighted during the post-construction monitoring period, which was similar to the percentage recorded during the construction phase in 2012 – 2018 (3.2%), but lower than the one recorded during the baseline phase in 2011 – 2012 (5.8%).

The majority of the 20 young calves sighted during the post-construction monitoring period were distributed in the central portion of WL survey area, i.e. between the Tai O Peninsula and Peaked Hill. A few other young calves were also sighted near Fan Lau and just to the north of the HKLR alignment (see Figure 7 of Appendix B).

Distribution of young calves during the nine 12-month monitoring periods across the three phases of the Project are also presented in Figure 8 of Appendix B. In comparison with the distribution of young calves during the baseline monitoring period, the young calves appeared to have avoided the northern portion of WL survey area, especially to the north of Tai O Peninsula, during the latter half of the construction monitoring period (2015 – 2018) as well as the 24-month post-construction monitoring period (2018 – 2020).

3.8          Activities and Associations with Fishing Boats

During the post-construction monitoring period, a total of 10 and eight groups of dolphins were engaged in feeding and socializing activities respectively, while none of the 173 dolphin groups was engaged in traveling or milling/resting activity. The 10 groups of dolphins engaged in feeding activities comprised 5.8% of the total number of dolphin groups sighted during the post-construction monitoring period, which was much lower than the percentage recorded during the baseline (10.6%) or the construction monitoring period (11.0%).  On the other hand, the eight dolphin groups engaged in socializing activities during the post-construction monitoring period comprised 4.6% of the total, which was comparable to the ones recorded during the baseline (5.3%) and construction monitoring period (4.4%).

In the post-construction phase, the dolphin groups engaged in feeding activities were found sporadically throughout the WL survey area with no particular concentration, as shown in Figure 9 of Appendix B.  Notably, two of the 10 groups were found feeding near the HKLR alignment.  On the other hand, the dolphin groups engaged in socializing activities were mostly distributed in the central portion of WL survey area, between Tai O Peninsula and Peaked Hill.

Distribution of dolphin activities during the nine 12-month monitoring periods of the Project are also presented in Figure 10 of Appendix B. Distribution of feeding and socializing activities engaged by the dolphins varied widely without any particular concentration in the nine 12-month monitoring periods across the baseline, construction and post-construction phases.  

Among the 173 groups sighted during the post-construction monitoring period, three of them were associated with operating fishing vessels (two with gill-netters and one with a purse-seiner), with all of them occurred during a three-month period of February to April 2019 (see sighting details in Appendix B).  In comparison, six of the 113 dolphin groups (5.3%) and 21 of the 670 dolphin groups (3.1%) were associated with operating fishing vessels during the baseline and construction monitoring periods respectively, and both percentages were much higher than the one recorded during the post-construction monitoring period (1.7%).

3.9          Summary of Photo-identification Works

In the post-construction monitoring period, 136 individuals sighted 382 times altogether were identified (see the summary table and photographs of identified individuals in Appendix B).  Among them, 82 individuals were re-sighted once or twice.  In contrast, there were 54 individuals being re-sighted three times or more during the 24-month period, including 35 individuals being re-sighted 3 to 5 times, while 16 individuals being re-sighted 6-8 times. Two individuals (CH108 and WL123) were re-sighted nine times and another individual (WL79) were re-sighted 13 times during the post-construction monitoring period, showing their strong reliance to the WL waters in 2018 – 2020.

3.10      Individual Range Use

Ranging patterns of the 132 individuals identified during the post-construction monitoring period and accumulated with at least five re-sightings were determined by fixed kernel method, as shown in Appendix B. 

Besides some individuals (e.g. NL33, NL123, NL261, NL322, WL05) occurred in both North and West Lantau waters, there were also a number of individuals (e.g. NL156, NL224, NL242, NL259, WL11) being primarily sighted in North Lantau waters in the past, but were re-sighted in WL waters during the post-construction phase monitoring period. On the other hand, the majority of the 132 individuals were sighted well within their normal home ranges in WL waters as in the past, while some of them (e.g. WL109, WL123, WL152, WL221, WL281) have extended their range use more often into South Lantau waters during the post-construction phase monitoring period.

Among the 136 individuals sighted during the post-construction monitoring period, only 32 of them were sighted before the HKLR construction commenced in the last quarter of 2012.  To examine whether there has been any changes in their range use before and after the HKLR construction, their ranging patterns before October 2012 (i.e. range use during baseline phase) and after November 2018 (i.e. range use during post-construction phase) are compared in Appendix B. For these 32 individuals, several parameters are evaluated for any temporal changes in their range use, which include the changes in level of utilization, any expansion, contraction or shifts in range use, and how shifts from one area to another have occurred.  Further examination is also made to determine if these individuals have avoided the bridge alignment after the HKLR construction, and whether the physical presence of the bridge alignment has hindered their north-south movement between NL and WL waters.

On the level of utilization, 11 individuals have occurred much less often in the western waters of Hong Kong during the post-construction monitoring period (e.g. NL212, WL15, WL46), while the majority of individuals have occurred more or less the same between the baseline and post-construction phases.  Furthermore, 14 of the 32 individuals have either moved away from or occurred much less often in NWL waters (e.g. NL120, WL179), while another 15 individuals have utilized the Southwest Lantau waters more often during post-construction phase when compared to the baseline period (e.g. WL61, WL123).

In addition, the ranges of 13 individuals have shrunk considerably during the post-construction monitoring period (e.g. NL224, SL42, WL128), but only two have expanded at the same time (NL261 and WL61).  Eleven individuals have also shown clear range shifts during the post-construction period when compared to the baseline phase, with four clearly shifted from North Lantau to West Lantau waters (e.g. NL120, WL179), and another 11 individuals having notable expansion from West Lantau into Southwest Lantau waters during the post-construction phase (e.g. WL98, WL130, WL131).

Out of the 32 individuals, 21 of them have their ranges overlapped with the bridge alignment before HKLR construction, and therefore their range use in relation to HKLR construction is further examined.  During the post-construction monitoring period, 12 of them have avoided the HKLR alignment (e.g. WL21, WL42), and it appeared that the bridge may have limited or hindered the north-south movement of two-third of these 21 individuals across HKLR alignment (e.g. NL212, WL98 refer to ranging patterns in Appendix B).

3.11      Comparison between Baseline, Construction & Post-Construction Monitoring

There was a gradual decline in dolphin occurrence in the northern portion of WL survey area in the past decade, with apparent avoidance of the HKLR alignment in recent years.  Dolphin occurrence was also at the lowest level at the last 12-month period of post-construction monitoring in 2019 – 2020 among the nine 12-month monitoring periods across the baseline, construction and post-construction phases of the HKLR Project.

Aside from a rebound in 2017 – 2018, dolphin encounter rates continued to decline from the baseline monitoring period to the lowest point during the post-construction monitoring period. Furthermore, dolphin abundance estimates from the nine 12-month monitoring periods possesses a downward sloping trend, and such decline is statistically significant.

Regarding dolphin group size, there was no apparent overall trend in average group size across different phases of HKLR Project. Notably, during the second year of post-construction monitoring in 2019 – 2020, larger dolphin groups have mostly disappeared from the northern portion of WL survey area, which was very different from the baseline monitoring period.

Overall dolphin densities across the WL survey area have declined since the HKLR construction commenced in 2012 – 2013.  Among the several important dolphin habitats in WL waters, only the waters at Fan Lau has consistently been utilized by dolphins at a high level before, during and after HKLR construction.

Regarding occurrence of mother-calf pairs, young calves appeared to have avoided the northern portion of WL survey area during the latter half of construction monitoring period as well as the entire post-construction monitoring period.

For dolphin activities, the percentage of dolphin groups engaged in feeding activities during post-construction monitoring period was much lower than the one recorded during the baseline and construction monitoring periods, but the percentage of dolphin groups engaged in socializing activities were similar across the three phases.

Among the 21 individuals being assessed for their range use before and after HKLR construction, more than half of them have avoided the HKLR alignment during the post-construction monitoring period, and the bridge may have also limited or hindered the north-south movement of two-third of these individuals across the HKLR alignment.

3.12      Supplementary Studies

Supplementary studies have been conducted under the HKLR EM&A Programme to understand the potential impacts of underwater noise, dolphin acoustic behaviour and north-south movement from the HKLR construction works in WL. As these studies are useful for complementing the vessel-based line-transect survey results as detailed above, they will also facilitate the review on the validity of EIA predictions and assessment on the effectiveness of mitigation measures.

3.12.1        Land-based Monitoring on North-South Movement of CWD

During the EIA stage, there were concerns that during and after HKLR construction the movement of dolphins across the bridge alignment to range between NL and WL waters may be affected. Therefore, a shore-based theodolite tracking study at Sham Wat Station was conducted as part of the EM&A requirement to examine the north-south movement of dolphins before and during the HKLR bridge construction.

A total of 112 and 200 tracks of dolphin movements were obtained during the baseline and construction phases respectively. The locations (in geographical coordinates) of each track were analysed to determine whether the dolphins were entirely on the north or south side of the HKLR alignment, or crossing through the HKLR alignment. Different proportions of such crossings or non-crossings were compared between the two phases, i.e. before and during the construction works.

During the baseline period without any construction works at the waters off Sham Wat, 20% of dolphin tracks passed through the bridge alignment. However, such percentage dropped dramatically to only 5% in 2014 (the first full year of HKLR construction), when bored piling works were the most intense, and the spacing between bridge piers became progressively narrower with multiple fronts. Even though there was a strong rebound in 2015 to 29%, such percentage fell back to a much lower level in subsequent years.

The study on north-south movement of dolphins concluded that such level of movements remained at a very low level in the past several years, without any sign of recovery for dolphins crossing through the HKLR alignment back to the baseline level. It also suggested that the low level of north-south movement in recent years could be attributed by two factors: (1) the physical presence of bridge piers and narrower spacing between them which could partially obstruct dolphin movements; (2) The on-going deterioration of habitat quality in North Lantau waters that makes it less attractive for dolphins to cross the HKLR alignment from WL to NL waters (and vice versa). However, it would be difficult to conclude which of the factors, or both, has influenced the observed declining level of north-south movements in recent years.

3.12.2        Monitoring of Dolphin Acoustic Behaviour in WL

In order to understand the potential impact of bored piling works of HKLR construction, another requirement of the HZMB HKLR EM&A Programme was to investigate the dolphin acoustic behaviour at and near the bored piling sites during pre-construction phase (January – February 2013) and the initial phase of construction phase (March – July 2013).

This acoustic monitoring study revealed that there were significant increases in the ambient noise levels that were measured near bored piling pier sites during the construction phase, as compared to the condition before construction. Moreover, dolphins’ occurrence near construction area as well as their average whistling rate (utilized during socializing activities) was substantially lower during the construction phase than the pre-construction phase.

Significant decreases in both whistling and clicking rates were also observed during the afternoon of the initial construction phase, and the study suggested that such reduction may have occurred in response to the increased noise level as contributed by HKLR construction activities.

The study also suggested that the dolphins which did occur in the area shifted their behavioural patterns, perhaps spending less time socializing than during the pre-construction phase. Furthermore, the higher clicking production rates by lone animal during the initial construction phase indicated a higher level of alertness in response to construction activities in the area.

3.12.3        Monitoring of Underwater Noise in relation to Bored Piling

As the noise contributed by bored piling activities was a major concern to the dolphins at the EIA stage, another important study conducted under the Tuen Mun – Chek Lap Kok Link (TMCLKL) EM&A programme in relation to the overall HZMB construction works is also considered here as useful reference. In this monitoring study, noise level was measured at different distances from several bored piling sites of TMCLKL alignment before and during the initial phase of the piling works in 2014.

The monitoring study found that in the vicinity of the bored piling operations, there was an increase of approximately 11 dB between the baseline phase and construction phase.  However, such increase was not strictly the result of construction-related sounds emanating from the bored piling pier locations, as the acoustic records and observation logs confirmed that the soundscape was dominated by transient vessel noise in relation to the bored piling operation. In fact, based on propagation modelling results from this study, the transient noise likely masked the noise generated by the bored piling works.

It should be mentioned that coincidentally, both the acoustic behavioural study and passive acoustic monitoring study on the dolphins found that there was a substantial reduction in dolphin occurrence during the initial stage of bored piling works, as compared to the pre-construction period.

 

4          Review of Landscape Establishment Monitoring Results

4.1          Summary of Monitoring Results

Throughout the landscape establishment period during the post-construction phase of HKLR Project, landscape establishment monitoring was conducted by other parties for Contract No. HY/2011/09 on 1 August 2019 (postponed from 31 July 2019 because of inclement weather), 23 September 2019, 29 November 2019, 10 January 2020, 20 March 2020 and 11 & 22 May 2020. Monitoring results of different monitoring locations are summarised below.

Portion A

Date

Observation

1 August 2019

Some trees (Phoenix roebelenii) and shrubs (Rhododendron pulchrum) at Portion A were observed to be in poor health or dead. The Contractor was reminded to review the health of all trees and shrubs and replace them if confirmed dead.

23 September 2019

Some trees (Phoenix roebelenii) and shrubs (Rhododendron pulchrum) were observed to be in poor health or dead. The Contractor was reminded to review the health of all trees and shrubs and replace them if confirmed dead.

29 November 2019

Some trees (Phoenix roebelenii) and shrubs (Rhododendron pulchrum) were observed to be in poor health or dead. The Contractor was reminded to review the health of all trees and shrubs and replace them if confirmed dead.

10 January 2020

Some trees (Phoenix roebelenii) and shrubs (Rhododendron pulchrum) were observed to be in poor health or dead. The Contractor was reminded to review the health of all trees and shrubs and replace them if confirmed dead.

20 March 2020

Some trees (Phoenix roebelenii) and shrubs (Rhododendron pulchrum) were observed to be in poor health or dead. The Contractor was reminded to review the health of all trees and shrubs and replace them if confirmed dead

11 & 22 May 2020

No observation

 

Portion C 

Date

Observation

1 August 2019

No observation

23 September 2019

No observation

29 November 2019

No observation

10 January 2020

Some trees (Phoenix roebelenii) and shrubs (Rhododendron pulchrum) were observed to be in poor health or dead. The Contractor was reminded to review the health of all trees and shrubs and replace them if confirmed dead.

20 March 2020

Some trees (Phoenix roebelenii) and shrubs (Rhododendron pulchrum) were observed to be in poor health or dead. The Contractor was reminded to review the health of all trees and shrubs and replace them if confirmed dead

11 & 22 May 2020

No observation

 

Viaduct between P112 and P114  

Date

Observation

1 August 2019

Weeds and unwanted plants were observed at the planter area at the viaduct between P112 and P114. The Contractor was reminded to remove them and replant the approved species for groundcover according to the approved plan.

23 September 2019

Weeds and unwanted plants were observed at the planter area. The Contractor was reminded to remove them and replant the approved species for groundcover according to the approved plan.

29 November 2019

  The groundcovers (Catharanthus roseus and Lantana montevidensis) were observed to be in poor health or dead. The Contractor was reminded to review the health condition of all groundcovers and re-planted if necessary. 

  Weeds and unwanted plants were observed. The Contractor was reminded to remove them and replant the approved species for groundcovers according to the approved plan.

10 January 2020

  The groundcovers (Catharanthus roseus and Lantana montevidensis) were observed to be in poor health or dead. The Contractor was reminded to review the health condition of all groundcovers and re-planted if necessary. 

  Weeds and unwanted plants were observed. The Contractor was reminded to remove them and replant the approved species for groundcovers according to the approved plan.

20 March 2020

  The groundcovers (Catharanthus roseus and Lantana montevidensis) were observed to be in poor health or dead. The Contractor was reminded to review the health condition of all groundcovers and re-planted if necessary.

  Weeds and unwanted plants were observed. The Contractor was reminded to remove them and replant the approved species for groundcovers according to the approved plan.

11 & 22 May 2020

  The groundcovers (Catharanthus roseus and Lantana montevidensis) were observed to be in poor health or dead. The Contractor was reminded to review the health condition of all groundcovers and re-planted if necessary.

  Weeds and unwanted plants were observed. The Contractor was reminded to remove them and replant the approved species for groundcovers according to the approved plan.

 

Kwo Lo Wan Road  

Date

Observation

1 August 2019

No observation

23 September 2019

No observation

29 November 2019

Some Phoenix roebelenii were removed. The Contractor was reminded to re-plant them according to the approved plan.

10 January 2020

Some Phoenix roebelenii were removed. The Contractor was reminded to re-plant them according to the approved plan.

20 March 2020

Some Phoenix roebelenii were removed. The Contractor was reminded to re-plant them according to the approved plan.

11 & 22 May 2020

No observation

 

Airport Road 

Date

Observation

1 August 2019

Weeds and unwanted plants were observed at the planter area at Airport Road. The Contractor was reminded to remove them to ensure the healthy establishment of the target species accordingly.

23 September 2019

Weeds and unwanted plants were observed at the planter area. The Contractor was reminded to remove them to ensure the healthy establishment of the target species accordingly.

29 November 2019

Weeds and unwanted plants were observed. In addition, the Phoenix roebelenii are also in poor health or dead. The Contractor was reminded to remove the weeds and unwanted plants to ensure the healthy establishment of the target species accordingly. 

10 January 2020

Weeds and unwanted plants were observed. In addition, the Phoenix roebelenii are also in poor health or dead. The Contractor was reminded to remove the weeds and unwanted plants to ensure the healthy establishment of the target species accordingly.

20 March 2020

Weeds and unwanted plants were observed. In addition, the Phoenix roebelenii were also in poor health or dead. The Contractor was reminded to remove the weeds and unwanted plants to ensure the healthy establishment of the target species.

11 & 22 May 2020

No observation

 

Based on the observations, the Contractor was reminded to review the health condition of the plants, remove weeds and replant approved plants as needed to meet the aim of the mitigation measures proposed during EIA stage.

The landscape establishment monitoring checklist for the last monitoring in May 2020, and the relevant monitoring photos and locations of trees selected for monitoring are provided in Appendix C.

4.2          Summary of Rectification for Observation

Viaduct between P112 and P114  

For the observations found in May 2020, the Contractor completed rectification action with weeds removed and re-planted approved plants for groundcovers according to the approved plan to meet the aim of the mitigation measures. The relevant photos of rectification record in September 2020 are provided in Appendix C.

 

5          Review of the Validity of EIA Predictions

5.1          EIA Predictions on Potential Impacts

As this review report focus on the surveys conducted in WL waters, the review of EIA predictions will only concentrate on the potential impacts and associated mitigation measures in relation to the open sea portion of the HKLR section as detailed in the EIA report. This section of the 5.6 km viaduct is located between the connection point with the HZMB Main Section at the western HKSAR boundary (situated at about 4 km west of Sham Wat and 3 km north of Tai O Pier) and the western opening of the airport channel near Sha Lo Wan.

Environmental impacts that are specific to the CWD were identified in the EIA report, and the following is a summary of predictions on the main impacts for construction and operation phases that were assessed.

5.1.1           Impact on Habitat Loss

The marine section of HKLR is a viaduct supported by piers, which has resulted in some physical loss of marine habitat (seabed and water column) from construction works at locations where piers were installed to support the bridge deck. In total, there were about 112 pier sites in the open sea portion, and two piers were constructed side-by-side at each pier site to support the bridge deck. The total permanent seabed loss due to project footprint in the open sea portion of the marine section of HKLR was estimated to be 2.24 hectares. 

In addition to permanent habitat loss, the works area in each pier site caused some additional temporary loss of seabed and water column habitat during construction, which was estimated to be 5.6 hectares (but these marine habitats would not be disturbed all at the same time as the piers were constructed in sequence, according to the EIA report). 

As such habitat loss caused by the bridge piers would be small and scattered, the EIA report considered the impact on marine habitat loss to dolphins to be minor, and no mitigation measure was required.

5.1.2           Impact on Water Quality

Major potential water quality impacts that might arise during construction phase of the marine section of HKLR would include pier site dredging, construction site runoff and wastewater from construction activities as identified in the EIA report. Nevertheless, the report assessed that the water quality impact was controlled as the pier site construction would be in sequence and therefore the maximum number of pier sites simultaneously under construction would be 35, while the pier locations would also be enclosed by cofferdams and silt curtains. Moreover, the report suggested that the western waters of Hong Kong are characterized by high background levels of suspended solids while CWD are expected to adapt well in an environment of high suspended solids. 

Therefore, the EIA report predicted that dolphins were not expected to be impacted by increase of suspended solids caused by the HKLR construction works, with no mitigation measure being proposed other than the implementation of silt curtain to control sediment re-suspension and limiting the number of concurrent work fronts.

5.1.3           Impact of Marine Noise

The main concern for construction noise for the marine section of HKLR focused on noise from bored piling works, in which much of the noise originated from the engine providing the power. Metal cases for the piles were pushed into seabed sediment by machines rather than driven by hammers during bored piling. Some noises associated with driving and extraction of temporary casings would be produced, but at a much lower level than percussive piling method as suggested by the EIA report. As there were 35 pier sites in the open sea portion and the bored piling works were scheduled to be conducted in a limited number of site at any given time (17 or lower according to the EIA report), the EIA report considered that marine noise impact would be minimized. 

The EIA report also identified vessel noise as a potential disturbance factor for dolphins, although it suggested that vessels associated with marine construction activities of HKLR would produce mostly low-frequency noise below the sound that dolphin mainly utilized. Therefore, these types of work vessels were not thought to be a significant source of acoustic disturbance to dolphins. 

Overall, as a precautionary approach, marine noise impact was ranked as moderate in the EIA report.  Several mitigation measures, including the use of quiet vibratory piler, avoidance of drilling onto rock surface of bored piles for the installation of the bored pile casing during May and June, and implementation of dolphin exclusion zone, were proposed to reduce this impact. Some underwater noise monitoring for the bored piling works was also conducted during the construction phase to verify the predictions of the assessment.

5.1.4           Impact of Marine Traffic

Although vessel noise was not thought to be a major source of acoustic disturbance to dolphins by the EIA report, they might need to change their diving and surfacing patterns to avoid being hit by large vessels. The report identified that such impact would result in behavioural disturbance in areas with active marine construction. 

Nevertheless, the EIA report also suggested that most of the vessels being involved in the HKLR construction were slow-moving working barges and vessels. Therefore, the marine traffic issue would not likely to be critical, and such impact on dolphin was ranked as minor to moderate, which was mitigated by setting up regular routes for vessels to avoid dolphin hotspots, implementation of vessel speed limits of 10 knots, and training for vessel captains.

5.1.5           Impact on Habitat Fragmentation

During the operation phase, a major concern was raised in the EIA report that the series of bridge piers could restrict the movement of dolphins, as some individuals have been using both North and West Lantau waters. If dolphins restricted their movements because of physical structure of the HKLR viaduct alignment, this would be a significant impact as that would affect their ability to forage and socializing with one another. 

The main concern would be on whether the space between the bridge piers would constitute a restriction for dolphin movement or discourage dolphins to pass through the space, and if the shade of the viaduct on sea surface would affect them by avoiding to swim underneath the bridge structure. Other examples of bridge structures outside of Hong Kong were considered in the EIA report to provide evidences on the possible fragmentation impact on dolphins. 

After all considerations, the EIA report predicted that the bridge structure would not cause a significant impact on cetacean movements or distribution, and the dolphin monitoring programme was in place to cover the movement ranges of individual dolphins, and to verify the validity of such assessment.

5.1.6           Cumulative Impacts

The only development that had significant overlap with the HKLR open sea portion in temporal and spatial perspectives would be the Main Bridge section of HZMB in Guangdong waters, as one of the two artificial islands connecting the underwater tunnel section was directly linked to the HKLR at the western boundary of Hong Kong territorial waters. Such reclamation works for the artificial islands commenced in 2010 for completion in 2014 according to the EIA report, and this overlapped with the baseline and initial construction periods of the HKLR. 

The EIA report assessed that this concurrent project (reclamation of artificial islands) would involve dredging and filling works, and would have the potential to produce cumulative water quality impact including increased level in suspended solids at dolphin hotspots during construction phase. Even though construction of the Main Bridge would involve bored piling works, there was sufficient separation of the bored piling activities between the two project sites (at least 6.7 km apart), while the magnitude of any cumulative marine traffic disturbance impact was assessed to be low. 

Furthermore, reclamation for the two artificial islands as part of the HZMB Main Bridge would cause 80 hectares of marine habitat loss, but such loss was considered insignificant in comparison to the extensive range of marine habitat within the Mainland waters in the Pearl River Delta. In view of the severity of the impacts, the EIA report concluded that further mitigation measures would not be needed for these cumulative impacts.

5.1.7           Positive Effects

It should be mentioned that the EIA report listed a few potential positive effects during the operation phase of HKLR. After the opening of HZMB, it was expected a decreased demand on marine traffic between Hong Kong and Mainland, which would reduce the risk of dolphins colliding with marine vessels, especially in area with high abundance. 

There would also be another potential enhancement effect of the bridge piers, as the piles supporting emerged pile caps could greatly increase the amount of hard-surface habitat and provide opportunities for fouling organisms to settle and develop, which in turn would attract scavengers and small predators and provide food resources of higher predators such as dolphins.

5.2          Identification of shortcomings in EIA predictions

5.2.1           Dolphin Occurrence during/after Construction Works vs. Baseline Condition

Vessel-based line-transect monitoring

Dolphin occurrence was at the lowest level during the post-construction monitoring period, and there was a continuous and significant declining trend in dolphin abundance during the nine-year dolphin monitoring programme in WL. More specifically, the decline in dolphin usage was mainly at the northern portion of WL survey area, which overlapped with the HKLR alignment. The majority of assessed individual dolphins have avoided the HKLR alignment, which might have also limited or hindered the north-south movement of many individuals across the bridge alignment.

Land-based study on north-south movements

The north-south movements of dolphin groups in WL waters remained at a very low level in the past several years, without any sign of recovery for dolphins crossing through the bridge alignment back to the baseline level.

Acoustic behaviour monitoring

Dolphins occurred in the construction area have shifted their behavioural patterns, spending less time socializing at the initial stage of construction than during the baseline phase. Dolphins also had a higher level of alertness in response to construction activities in the area by increasing their clicking production rates.

Underwater noise monitoring

In the vicinity of the bored piling operations, there was a noticeable increase in underwater noise, which was mainly contributed by the transient vessel noise rather than the bored piling noise. Coincidentally, there was a substantial reduction in dolphin occurrence during the bored piling works with the elevated noise level.

5.2.2           EIA Predictions vs. Actual Situation

In contrary to the EIA predictions that the HKLR construction would not cause significant impact to dolphins in WL waters with sufficient mitigation measures in place, their occurrence has been on a significant decline during the construction phase, and there has been no sign of recovery during the post-construction phase.

In addition to the vessel-based monitoring programme, several supplementary studies were conducted to verify the predictions made in the EIA report. Those studies concluded that the north-south movements of individual dolphins remained at a low level after the HKLR bridge piers were set up, and there was no sign of recovery of such movement at this point, which also concurred with the findings from the vessel-based monitoring programme. 

Moreover, at the initial stage of HKLR construction, the ambient underwater noise was significantly higher near bored piling sites, and it appeared that dolphins were affected by shifting their acoustic behavioural patterns near the work area. Another study completed under TMCLKL EM&A programme also demonstrated that there was a noticeable increase in underwater noise during bored piling operations, which was mainly contributed by the transient vessel noise associated with the marine works, with substantial reduction in dolphin occurrence with the elevated noise level.

5.2.3           Possible Contributions to Discrepancies

There are several plausible explanations behind the discrepancies between the EIA predictions and the actual outcome of the CWD monitoring results for the HKLR EM&A programme.

It is apparent that the EIA report has underestimated the magnitude of some of its predictions for some temporary impacts on dolphins. For example, the marine noise associated with the bored piling works was significantly higher. Even though the bored piling procedure itself might not cause too much noise, the associated transient noise of moving vessels near the bored piling works (such as the ones transporting workers to and from work barges) was the likely source that had primarily contributed to the elevated noise level. This would in turn affect the dolphin acoustic behaviour and deter them to move away from the work sites. Such impact would certainly cause some temporary displacements of dolphins from their favourable habitat during the marine construction works.

Also, the EIA report has predicted that vessels involved in the HKLR construction works would mostly be slow-moving and emit low-frequency marine noise that would not affect dolphins. However, it has been frequently observed from land (during the shore-based theodolite tracking on north-south movements) and boat (during vessel surveys and acoustic monitoring surveys) that there were large number of work boats (mostly transportation boats shuttling workers to and from various marine work fronts) within the HKLR construction area. As a result, dolphins might have to shift their acoustic behavioural patterns in response, as suggested by the acoustic monitoring study at the early stage of construction works. Similar to marine noise impact, such intense and fast-moving marine traffic would also cause some temporary displacements of dolphins from their favourable habitat, at least in the northern portion of the WL survey area that overlapped with the HKLR marine works.

Due to the underestimation of construction impact, the mitigation measures suggested by the EIA report and adopted during construction to minimize the impact of noise and marine traffic have not been as effective as originally predicted, which is evidenced by the noticeable decline in dolphin occurrence in WL waters throughout the construction phase monitoring.

Nevertheless, even though the abovementioned impacts might have resulted in decline of dolphin occurrence in WL waters during the marine construction works of HKLR, these impacts should be temporary in nature, and one would have assumed that these impacts would only affect dolphins during the construction phase.  Once the construction is completed and the marine traffic with associated noise have subsided, it would be a reasonable assumption that dolphins would return to WL waters (especially to the northern portion of the survey area where the marine construction works took place), and the level of dolphin occurrence would return back to the baseline level. However, as observed in the post-construction monitoring results, there has been no sign of such recovery. In fact, dolphin abundance has continued to fall to the lowest level in 2018 – 2020 during post-construction phase. Therefore, the logical assumption is that either the operation impacts arising from the bridge construction have also been underestimated, or additional anthropogenic impacts from other projects have resulted in the lower occurrence of dolphins at the end of the post-construction monitoring.

The habitat loss caused by the marine bridge piers was predicted to be small and scattered, and therefore such impact was considered as minor in the EIA report with no mitigation measure needed.  However, the presence of the bridge piers had likely affected dolphins more by limiting their north-south movements between North and West Lantau waters, which would ultimately affect dolphin usage in West Lantau waters. The land-based monitoring on north-south movement of dolphins concluded that such level of movements remained low in the past few years, though the original intention of this monitoring requirement was to verify the validity of the EIA assessment that the bridge structure would not cause a significant impact, as such assessment was difficult to substantiate at that time.

In fact, there have been several lines of evidences that such limitation of north-south movements and reduced dolphin usage in West Lantau waters have already occurred in recent years. Firstly, the post-construction monitoring surveys showed that dolphin usage was lower in the northern portion of WL survey area when compared to the baseline condition. The surveys also showed that many individual dolphins have avoided the bridge alignment in the past two years, and the bridge might have limited or hindered the north-south movement of most of the individuals. Secondly, the shore-based theodolite tracking provided direct evidence that the north-south movements of dolphin groups remained at a very low level in the past several years with no sign of recovery. 

Furthermore, the AFCD long-term marine mammal monitoring study revealed that many individual dolphins have shifted their range use away from North Lantau to West Lantau waters, with very little movement back to North Lantau thereafter (Hung 2019 and 2020). The same study also showed that there was a large and significant decline in dolphin abundance in North Lantau, from 50 dolphins estimated in 2011 (equivalent to the baseline stage of HKLR construction) to only four dolphins estimated in 2019 (equivalent to the post-construction stage of HKLR construction) (Hung 2020), and such decline also coincided with the temporal changes in individual range use as mentioned above.

While WL waters remained the area with the highest dolphin density in Hong Kong with several important dolphin habitats consistently recorded high level of use over the years (see Hung 2019 and 2020), it is evident that dolphin occurrence in the northern portion of WL survey area has largely diminished, and this area is exactly where the bridge construction occurred and the physical structure of bridge piers are permanently present. Until there is clear evidence that the north-south movement of dolphins across the bridge alignment has resumed to the baseline level, the impact of the bridge piers to such movements should be regarded as significant and long-lasting, contrary to the prediction made in the EIA report.

Finally, it should be mentioned that habitat degradation in North Lantau waters in the past decade could contribute further to the limitation of north-south movement of dolphins moving back and forth between North and West Lantau waters, which in turn might have resulted in the decline in dolphin usage in WL waters during and after HKLR construction. In the past decades, there was a continuous decline in dolphin abundance in North Lantau, which could be attributed to the increase in high-speed ferry traffic from the Sky Pier (see Marcotte et al. 2015), the reclamation works for HKBCF and HKLR as well as the recent massive reclamation works for the third runway expansion for the Hong Kong International Airport. It is clear that the North Lantau was once an important habitat for dolphins with their widespread usage of the area (see Hung 2008), but nowadays the waters to the north of Lung Kwu Chau is the only remaining area utilized by dolphins on a regular basis, albeit at a much lower level in recent years (see Hung 2019 and 2020).

Notably, the 650 hectares of dolphin habitat loss as a result of the massive reclamation in relation to the third runway expansion was not included in the HKLR EIA report for its cumulative impact assessment, but such habitat loss has clearly contributed to the further decline in dolphin occurrence in North Lantau since the project commencement in 2016. The large-scale habitat loss from this infrastructure project is only situated a few kilometers to the north of HKLR bridge alignment, and at an area where individual dolphins have utilized as the main travelling corridor to move between Sha Chau and Lung Kwu Chau Marine Park and the West Lantau waters (Hung 2013). This would directly affect the north-south movement of dolphins across the bridge alignment, and result in their reduced usage of WL waters in recent years.

5.3          Comments on the Overall EM&A Programme

The EM&A programme requires post-construction phase monitoring for CWD and landscape establishment monitoring works. Weather conditions in the post-construction monitoring months are provided in Appendix D. All monitoring works were conducted as scheduled. The overall performance of the monitoring methodology adopted in this Assignment was deemed effective.

 

6          Recommendations and Conclusions

This Final EM&A Review Report presents the post-construction environmental monitoring works undertaken in the period between November 2018 and October 2020. All marine-based construction activities have been completed. The landscape establishment monitoring has been conducted bi-monthly and completed to ensure the aims of the landscape and visual mitigation measures proposed during EIA stage are met.

The post-construction dolphin monitoring works in WL waters have been completed in October 2020, with the results being assessed in comparison with the baseline and construction phase monitoring data collected before and during the HKLR construction. The baseline, construction phase and post-construction phase dolphin monitoring as well as several supplementary studies completed under the HKLR EM&A programme provided valuable information for the evaluation on the predictions of impact assessment during the EIA stage, as well as the adequacy and effectiveness of suggested mitigation measures. Important lessons can be learnt from such comprehensive monitoring programme for future EIA studies and EM&A programmes in Hong Kong, especially the ones within marine mammal habitats.

Nevertheless, it may take a long period of time for recovery in dolphin usage in WL waters to review the overall impacts on dolphins from the HKLR construction with other cumulative impacts. It would be useful to study the level of north-south movement of dolphins across the bridge alignment by shore-based theodolite tracking work in the future to determine recovery in dolphin usage from the effect of the HKLR operation.

The overall EM&A programme to examine the potential impacts of HKLR and evaluate the predictions of the EIA report has provided solid proof that it has been working well according to the intention of the EIA framework in Hong Kong. Important findings of this EM&A programme could be taken to fill information gap and facilitate further monitoring works, as well as to improve the impact predictions and associated mitigation measures for future infrastructure project.  This review report would also provide a good example of how EIA studies should be routinely reviewed in the future.