Contract No. HY/2011/03

Hong Kong-Zhuhai-Macao Bridge Hong Kong Link Road

Section between Scenic Hill and Hong Kong Boundary Crossing Facilities

 

 

 

 

 

 

Quarterly EM&A Report No. 34 (December 2020 to February 2021)

 

25 March 2021

 

Revision 0

 

 

 

 

 

 

 

 

 

 

 

 

 

Main Contractor                                                                                                Designer


 


 

Contents

Executive Summary

1...... Introduction. 1

1.1                       Basic Project Information. 1

1.2                       Project Organisation. 1

1.3                       Construction Programme. 1

1.4                       Construction Works Undertaken During the Reporting Period. 2

2....... EM&A Requirement 3

2.1                       Summary of EM&A Requirements. 3

2.2                       Action and Limit Levels. 4

2.3                       Event Action Plans. 5

2.4                       Mitigation Measures. 5

3....... Environmental Monitoring and Audit 6

3.1                       Implementation of Environmental Measures. 6

3.2                       Air Quality Monitoring Results. 6

3.3                       Noise Monitoring Results. 7

3.4                       Water Quality Monitoring Results. 7

3.5                       Dolphin Monitoring Results. 7

3.6                       Mudflat Monitoring Results. 8

3.7                       Solid and Liquid Waste Management Status. 23

3.8                       Environmental Licenses and Permits. 23

4....... Environmental Complaint and Non-compliance. 24

4.1                       Environmental Exceedances. 24

4.2                       Summary of Environmental Complaint, Notification of Summons and Successful Prosecution. 24

5....... Comments, Recommendations and Conclusion. 25

5.1                       Comments. 25

5.2                       Recommendations. 25

5.3                       Conclusions. 25

 

 

 

 

 

 

 

 

 

Figures

 

Figure 1.1        Location of the Site

Figure 2.1         Environmental Monitoring Stations

Figure 2.2         Transect Line Layout in Northwest and Northeast Lantau Survey Areas

 

                        

Appendices

 

Appendix A       Environmental Management Structure

Appendix B       Construction Programme

Appendix C       Location of Works Areas

Appendix D       Event and Action Plan  

Appendix E       Implementation Schedule of Environmental Mitigation Measures

Appendix F       Site Audit Findings and Corrective Actions

Appendix G      Air Quality Monitoring Data and Graphical Plots

Appendix H       Noise Monitoring Data and Graphical Plots

Appendix I        Not Used

Appendix J       Not Used

Appendix K       Waste Flow Table

Appendix L       Summary of Environmental Licenses and Permits

Appendix M      Record of ¡§Notification of Summons and Prosecutions¡¨

Appendix N       Cumulative Statistics on Complaints

Appendix O      Mudflat Monitoring Results


Executive Summary

The Hong Kong-Zhuhai-Macao Bridge (HZMB) Hong Kong Link Road (HKLR) serves to connect the HZMB Main Bridge at the Hong Kong Special Administrative Region (HKSAR) Boundary and the HZMB Hong Kong Boundary Crossing Facilities (HKBCF) located at the north eastern waters of the Hong Kong International Airport (HKIA).

The HKLR project has been separated into two contracts. They are Contract No. HY/2011/03 Hong Kong-Zhuhai-Macao Bridge Hong Kong Link Road-Section between Scenic Hill and Hong Kong Boundary Crossing Facilities (hereafter referred to as the Contract) and Contract No. HY/2011/09 Hong Kong-Zhuhai-Macao Bridge Hong Kong Link Road-Section between HKSAR Boundary and Scenic Hill.

China State Construction Engineering (Hong Kong) Ltd. was awarded by Highways Department as the Contractor to undertake the construction works of Contract No. HY/2011/03. The main works of the Contract include land tunnel at Scenic Hill, tunnel underneath Airport Road and Airport Express Line, reclamation and tunnel to the east coast of the Airport Island, at-grade road connecting to the HKBCF and highway works of the HKBCF within the Airport Island and in the vicinity of the HKLR reclamation.  The Contract is part of the HKLR Project and HKBCF Project, these projects are considered to be ¡§Designated Projects¡¨, under Schedule 2 of the Environmental Impact Assessment (EIA) Ordinance (Cap 499) and EIA Reports (Register No. AEIAR-144/2009 and AEIAR-145/2009) were prepared for the Project.  The current Environmental Permit (EP) EP-352/2009/D for HKLR and EP-353/2009/K for HKBCF were issued on 22 December 2014 and 11 April 2016, respectively. These documents are available through the EIA Ordinance Register. The construction phase of Contract was commenced on 17 October 2012.

BMT Hong Kong Limited was appointed by the Contractor to implement the Environmental Monitoring & Audit (EM&A) programme for the Contract in accordance with the Updated EM&A Manual for HKLR (Version 1.0) and provided environmental team services to the Contract until 31 July 2020. 

Meinhardt Infrastructure and Environment Limited has been appointed by the Contractor to implement the Environmental Monitoring & Audit (EM&A) programme for the Contract in accordance with the Updated EM&A Manual for HKLR (Version 1.0) and provide environmental team services to the Contract with effective from 1 August 2020. Ramboll Hong Kong Limited was employed by HyD as the Independent Environmental Checker (IEC) and Environmental Project Office (ENPO) for the Project.

This is the thirty-fourth Quarterly EM&A report for the Contract which summarizes the monitoring results and audit findings of the EM&A programme during the reporting period from 1 December 2020 to 28 February 2021.

Environmental Monitoring and Audit Progress

The EM&A programme were undertaken in accordance with the Updated EM&A Manual for HKLR (Version 1.0). A summary of the monitoring activities during this reporting period is presented as below:

Monitoring Activity

Monitoring Date

Dec 2020

Jan 2021

Feb 2021

Air Quality

1-hr TSP at AMS5 and AMS6

1, 7, 11, 17, 23 and 29

4, 8, 13, 19, 25 and 29

4, 10, 16, 22 and 26

24-hr TSP at

AMS5

4, 10, 16, 22 and 28

2, 7, 12, 18, 22 and 28

3, 8, 11, 16, 20 and 25

24-hr TSP at

AMS6

3, 10, 11, 16, 20 and 25

Noise

1, 7, 17, 23 and 29

4, 13, 19 and 25

4, 10, 16 and 22

Water Quality

Not applicable.(see remark 1)

Not applicable.(see remark 1)

Not applicable.(see remark 1)

Chinese White Dolphin

Not applicable.(see remark 1)

Not applicable.(see remark 1)

Not applicable.(see remark 1)

Mudflat Monitoring (Ecology)

10, 11, 15 and 16

-         

-

Mudflat Monitoring (Sedimentation rate)

7

-

-

Site Inspection

2, 9, 16, 23 and 29

6, 13, 20 and 29

3, 10, 17 and 26

Remarks: 1) Water quality monitoring and dolphin monitoring were temporarily suspended during the reporting period.

 

Due to timer problem at monitoring station AMS6 - Dragonair / CNAC (Group) Building (HKIA), 24-hr TSP monitoring at AMS6 was rescheduled from 8 February 2021 to 10 February 2021.

Breaches of Action and Limit Levels

A summary of environmental exceedances for this reporting period is as follows:

Environmental Monitoring

Parameters

Action Level (AL)

Limit Level (LL)

Air Quality

1-hr TSP

0

0

24-hr TSP

0

0

Noise

Leq (30 min)

0

0

Water Quality

Suspended solids level (SS)

Not applicable. (see remark 1)

Not applicable. (see remark 1)

Turbidity level

Not applicable. (see remark 1)

Not applicable. (see remark 1)

Dissolved oxygen level (DO)

Not applicable. (see remark 1)

Not applicable. (see remark 1)

Dolphin Monitoring

Quarterly Analysis (Dec 2020 to Feb 2021)

Not applicable. (see remark 2)

Not applicable. (see remark 2)

Remarks:

1) Water quality monitoring was temporarily suspended during the reporting period. Thus, no water quality monitoring results and exceedances from December 2020 to February 2021 are presented.

2) Dolphin monitoring was temporarily suspended during the reporting period. Thus, no quarterly analysis of dolphin monitoring results and exceedances from December 2020 to February 2021 are presented.

Implementation of Mitigation Measures

Site inspections were carried out to monitor the implementation of proper environmental pollution control and mitigation measures for the Project. Potential environmental impacts due to the construction activities were monitored and reviewed.

Complaint Log

There was one complaint received in relation to the environmental impacts during this reporting period.

Notifications of Summons and Prosecutions

There were no notifications of summons or prosecutions received during this reporting period.


 

Reporting Changes

This report has been developed in compliance with the reporting requirements for the subsequent EM&A reports as required by the Updated EM&A Manual for HKLR (Version 1.0). 

The proposal for the change of Action Level and Limit Level for suspended solid and turbidity was approved by EPD on 25 March 2013.

The revised Event and Action Plan for dolphin monitoring was approved by EPD on 6 May 2013.

The original monitoring station at IS(Mf)9 (Coordinate: 813273E, 818850N) was observed inside the perimeter silt curtain of Contract HY/2010/02 on 1 July 2013, as such the original impact water quality monitoring location at IS(Mf)9 was temporarily shifted outside the silt curtain.  As advised by the Contractor of HY/2010/02 in August 2013, the perimeter silt curtain was shifted to facilitate safe anchorage zone of construction barges/vessels until end of 2013 subject to construction progress.  Therefore, water quality monitoring station IS(Mf)9 was shifted to 813226E and 818708N since 1 July 2013.  According to the water quality monitoring team¡¦s observation on 24 March 2014, the original monitoring location of IS(Mf)9 was no longer enclosed by the perimeter silt curtain of Contract HY/2010/02. Thus, the impact water quality monitoring works at the original monitoring location of IS(Mf)9 has been resumed since 24 March 2014.

Transect lines 1, 2, 7, 8, 9 and 11 for dolphin monitoring have been revised due to the obstruction of the permanent structures associated with the construction works of HKLR and the southern viaduct of TM-CLKL, as well as provision of adequate buffer distance from the Airport Restricted Areas.  The EPD issued a memo and confirmed that they had no objection on the revised transect lines on 19 August 2015.

The water quality monitoring stations at IS10 (Coordinate: 812577E, 820670N) and SR5 (811489E, 820455N) are located inside Hong Kong International Airport (HKIA) Approach Restricted Areas. The previously granted Vessel's Entry Permit for accessing stations IS10 and SR5 were expired on 31 December 2016. During the permit renewing process, the water quality monitoring location was shifted to IS10(N) (Coordinate: 813060E, 820540N) and SR5(N) (Coordinate: 811430E, 820978N) on 2, 4 and 6 January 2017 temporarily. The permit has been granted by Marine Department on 6 January 2017. Thus, the impact water quality monitoring works at original monitoring location of IS10 and SR5 has been resumed since 9 January 2017.

Transect lines 2, 3, 4, 5, 6 and 7 for dolphin monitoring have been revised and transect line 24 has been added due to the presence of a work zone to the north of the airport platform with intense construction activities in association with the construction of the third runway expansion for the Hong Kong International Airport. The EPD issued a memo and confirmed that they had no objection on the revised transect lines on 28 July 2017. The alternative dolphin transect lines are adopted starting from August¡¦s dolphin monitoring.

A new water quality monitoring team has been employed for carrying out water quality monitoring work for the Contract starting from 23 August 2017. Due to marine work of the Expansion of Hong Kong International Airport into a Three-Runway System (3RS Project), original locations of water quality monitoring stations CS2, SR5 and IS10 are enclosed by works boundary of 3RS Project. Alternative impact water quality monitoring stations, naming as CS2(A), SR5(N) and IS10(N) was approved on 28 July 2017 and were adopted starting from 23 August 2017 to replace the original locations of water quality monitoring for the Contract.

The role and responsibilities as the ET Leader of the Contract was temporarily taken up by Mr Willie Wong instead of Ms Claudine Lee from 25 September 2017 to 31 December 2017.

The topographical condition of the water monitoring stations SR3 (Coordinate: 810525E, 816456N), SR4 (Coordinate: 814760E, 817867N), SR10A (Coordinate: 823741E, 823495N) and SR10B (Coordinate: 823686E, 823213N) cannot be accessed safely for undertaking water quality monitoring. The water quality monitoring has been temporarily conducted at alternative stations, namely SR3(N) (Coordinate 810689E, 816591N), SR4(N) (Coordinate: 814705E, 817859N) and SR10A(N) (Coordinate: 823644E, 823484N) since 1 September 2017. The water quality monitoring at station SR10B was temporarily conducted at Coordinate: 823683E, 823187N on 1, 4, 6, 8 September 2017 and has been temporarily fine-tuned to alternative station SR10B(N2) (Coordinate: 823689E, 823159N) since 11 September 2017. Proposal for permanently relocating the aforementioned stations was approved by EPD on 8 January 2018.

The works area WA5 was handed over to other party on 22 June 2013.

According to latest information received in July 2018, the works area WA7 was handed over to other party on 28 February 2018 instead of 31 January 2018.

Original WQM stations IS8 and SR4(N) are located within the active work area of TCNTE project and the access to the WQM stations IS8 (Coordinate: E814251, N818412) and SR4(N) (Coordinate: E814705, N817859) are blocked by the silt curtains of the Tung Chung New Town Extension (TCNTE) project. Alternative monitoring stations IS8(N) (Coordinate: E814413, N818570) and SR4(N2) (Coordinate: E814688, N817996) are proposed to replace the original monitoring stations IS8 and SR4(N). Proposal for permanently relocating the aforementioned stations was approved by EPD on 20 August 2019. The water quality monitoring has been conducted at stations IS8(N) and SR4(N2) on 21 August 2019.

There were no marine works conducted by Contract No. HY/2011/03 since July 2019. A proposal for temporary suspension of marine related environmental monitoring (water quality monitoring and dolphin monitoring for the Contract No. HY/2011/03) was justified by the ET leader and verified by IEC in mid of September 2019 and it was approved by EPD on 24 September 2019. Water quality monitoring and dolphin monitoring for the Contract will not be conducted starting from 1 October 2019 until marine works (i.e. toe loading removal works) be resumed. As discussed with Contract No. HY/2012/08, they will take up the responsibility from Contract No. HY/2011/03 for the dolphin monitoring works starting from 1 October 2019.

According to information received in January 2020, the works area WA3 and WA4 were handed over to Highways Department on 23 December 2019 and 14 March 2019 respectively.

The role and responsibilities as the IEC of the Contract has been taken up by Mr. Manson Yeung instead of Mr. Ray Yan since 18 May 2020.

Mr. Leslie Leung was Environmental Team Leader of the Contract for July 2020. The role and responsibilities as the Environmental Team Leader of the Contract has been taken up by Ms. Claudine Lee with effective from 1 August 2020.

 

 


1        Introduction

1.1                 Basic Project Information

1.1.1       The Hong Kong-Zhuhai-Macao Bridge (HZMB) Hong Kong Link Road (HKLR) serves to connect the HZMB Main Bridge at the Hong Kong Special Administrative Region (HKSAR) Boundary and the HZMB Hong Kong Boundary Crossing Facilities (HKBCF) located at the north eastern waters of the Hong Kong International Airport (HKIA).

1.1.2       The HKLR project has been separated into two contracts. They are Contract No. HY/2011/03 Hong Kong-Zhuhai-Macao Bridge Hong Kong Link Road-Section between Scenic Hill and Hong Kong Boundary Crossing Facilities (hereafter referred to as the Contract) and Contract No. HY/2011/09 Hong Kong-Zhuhai-Macao Bridge Hong Kong Link Road-Section between HKSAR Boundary and Scenic Hill.

1.1.3       China State Construction Engineering (Hong Kong) Ltd. was awarded by Highways Department (HyD) as the Contractor to undertake the construction works of Contract No. HY/2011/03.  The Contract is part of the HKLR Project and HKBCF Project, these projects are considered to be ¡§Designated Projects¡¨, under Schedule 2 of the Environmental Impact Assessment (EIA) Ordinance (Cap 499) and EIA Reports (Register No. AEIAR-144/2009 and AEIAR-145/2009) were prepared for the Project.  The current Environmental Permit (EP) EP-352/2009/D for HKLR and EP-353/2009/K for HKBCF were issued on 22 December 2014 and 11 April 2016, respectively. These documents are available through the EIA Ordinance Register. The construction phase of Contract was commenced on 17 October 2012. The works area WA5 and WA7 were handed over to other party on 22 June 2013 and 28 February 2018 respectively. The works area WA3 and WA4 were handed over to Highways Department on 23 December 2019 and 14 March 2019 respectively. Figure 1.1 shows the project site boundary. The works areas are shown in Appendix C.

1.1.1       BMT Hong Kong Limited was appointed by the Contractor to implement the EM&A programme for the Contract in accordance with the Updated EM&A Manual for HKLR (Version 1.0) and provided environmental team services to the Contract until 31 July 2020.

1.1.2       Meinhardt Infrastructure and Environment Limited has been appointed by the Contractor to implement the Environmental Monitoring & Audit (EM&A) programme for the Contract in accordance with the Updated EM&A Manual for HKLR (Version 1.0) and provide environmental team services to the Contract with effective from 1 August 2020. Ramboll Hong Kong Limited was employed by HyD as the Independent Environmental Checker (IEC) and Environmental Project Office (ENPO) for the Project. The project organization with regard to the environmental works is provided in Appendix A.

1.1.3       This is the thirty-fourth Quarterly Environmental Monitoring and Audit (EM&A) report for the Contract which summarizes the monitoring results and audit findings of the EM&A programme during the reporting period from 1 December 2020 to 28 February 2021.

1.2                Project Organisation

1.2.1       The project organization structure and lines of communication with respect to the on-site environmental management structure with the key personnel contact names and numbers are shown in Appendix A. 

1.3                Construction Programme

1.3.1       A copy of the Contractor¡¦s construction programme is provided in Appendix B. 

 

1.4                Construction Works Undertaken During the Reporting Period

1.4.1       A summary of the construction activities undertaken during this reporting period is shown in

Table 1.1. The Works areas of the Contract are showed in Appendix C.

 

Table 1.1        Construction Activities during Reporting Period

Description of Activities

Site Area

Landscaping Works

Portion X and Airport Road

E&M Works

Airport Road

Finishing Works for Highway Operation and Maintenance Area Building

Portion X

Finishing Works for Scenic Hill Tunnel Ventilation Building

West Portal

Extension of Security Fencing

West Portal

Removal of Temporary Bus Stop and Construction of Pedestrian Footpath

Tung Yiu Road

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


2        EM&A Requirement

2.1                Summary of EM&A Requirements

2.1.1       The EM&A programme requires environmental monitoring of air quality, noise, water quality, dolphin monitoring and mudflat monitoring as specified in the approved EM&A Manual.

2.1.2       A summary of Impact EM&A requirements is presented in Table 2.1. The locations of air quality, noise and water quality monitoring stations are shown as in Figure 2.1. The transect line layout in Northwest and Northeast Lantau Survey Areas is presented in Figure 2.2.

Table 2.1        Summary of Impact EM&A Requirements

Environmental Monitoring

Description

Monitoring Station

Frequencies

Remarks

Air Quality

1-hr TSP

AMS 5 & AMS 6

At least 3 times every 6 days

While the highest dust impact was expected.

24-hr TSP

At least once every 6 days

--

Noise

Leq (30mins),
L10
(30mins) and
L90
(30mins)

NMS 5

At least once per week

Daytime on normal weekdays (0700-1900 hrs).

Water Quality

¡P   Depth

¡P   Temperature

¡P   Salinity

¡P   Dissolved Oxygen (DO)

¡P   Suspended Solids (SS)

¡P   DO Saturation

¡P   Turbidity

¡P   pH

¡P   Impact Stations:
IS5, IS(Mf)6, IS7, IS8/IS8(N),
IS(Mf)9 & IS10(N),

¡P   Control/Far Field Stations:
CS2(A) & CS(Mf)5,

¡P   Sensitive Receiver Stations:
SR3(N), SR4(N)/
SR4(N2), SR5(N), SR10A(N) & SR10B(N2)

Three times per week during mid-ebb and mid-flood tides (within ¡Ó 1.75 hour of the predicted time)

3

(1 m below water surface, mid-depth and 1 m above sea bed, except where the water depth is less than 6 m, in which case the mid-depth station may be omitted.  Should the water depth be less than 3 m, only the mid-depth station will be monitored).

Dolphin

Line-transect Methods

Northeast Lantau survey area and Northwest Lantau survey area

Twice per month

--

Mudflat

Horseshoe crabs, seagrass beds, intertidal soft shore communities, sedimentation rates and water quality

San Tau and Tung Chung Bay

Once every 3 months

--

Remarks:

1) Original WQM stations IS8 and SR4(N) are located within the active work area of TCNTE project and the access to the WQM stations IS8 (Coordinate: E814251, N818412) and SR4(N) (Coordinate: E814705, N817859) are blocked by the silt curtains of the Tung Chung New Town Extension (TCNTE) project. Alternative monitoring stations IS8(N) (Coordinate: E814413, N818570) and SR4(N2) (Coordinate: E814688, N817996) are proposed to replace the original monitoring stations IS8 and SR4(N). Proposal for permanently relocating the aforementioned stations was approved by EPD on 20 August 2019. The water quality monitoring has been conducted at stations IS8(N) and SR4(N2) on 21 August 2019.

2) The water quality monitoring programme and dolphin monitoring programme were temporarily suspended during the reporting period, since no marine works were scheduled or conducted.

2.2                Action and Limit Levels

2.2.1       Table 2.2 presents the Action and Limit Levels for the 1-hour TSP, 24-hour TSP and noise level.

Table 2.2       Action and Limit Levels for 1-hour TSP, 24-hour TSP and Noise

Environmental Monitoring

Parameters

Monitoring Station

Action Level

Limit Level

Air Quality

1-hr TSP

AMS 5

352 µg/m3

500 µg/m3

AMS 6

360 µg/m3

24-hr TSP

AMS 5

164 µg/m3

260 µg/m3

AMS 6

173 µg/m3

Noise

Leq (30 min)

NMS 5

When one documented complaint is received

75 dB(A)

 

2.2.2       The Action and Limit Levels for water quality monitoring are given as in Table 2.3.

Table 2.3       Action and Limit Levels for Water Quality

Parameter (unit)

Water Depth

Action Level

Limit Level

Dissolved Oxygen (mg/L)

Surface and Middle

5.0

4.2 except 5 for Fish Culture Zone

Bottom

4.7

3.6

Turbidity (NTU)

Depth average

27.5 or 120% of upstream control station¡¦s turbidity at the same tide of the same day;

The action level has been amended to ¡§27.5 and 120% of upstream control station¡¦s turbidity at the same tide of the same day¡¨ since 25 March 2013.

47.0 or 130% of turbidity at the upstream control station at the same tide of same day;

The limit level has been amended to ¡§47.0 and 130% of turbidity at the upstream control station at the same tide of same day¡¨ since 25 March 2013.

Suspended Solid (SS) (mg/L)

Depth average

23.5 or 120% of upstream control station¡¦s SS at the same tide of the same day;

The action level has been amended to ¡§23.5 and 120% of upstream control station¡¦s SS at the same tide of the same day¡¨ since 25 March 2013.

34.4 or 130% of SS at the upstream control station at the same tide of same day and 10mg/L for Water Services Department Seawater Intakes;

The limit level has been amended to ¡§34.4 and 130% of SS at the upstream control station at the same tide of same day and 10mg/L for Water Services Department Seawater Intakes¡¨ since 25 March 2013

Notes:

                        (1)    Depth-averaged is calculated by taking the arithmetic means of reading of all three depths.

                        (2)    For DO, non-compliance of the water quality limit occurs when monitoring result is lower that the limit.

                        (3)    For SS & turbidity non-compliance of the water quality limits occur when monitoring result is higher than the limits.

                        (4)    The change to the Action and limit Levels for Water Quality Monitoring for the EM&A works was approved by EPD on 25 March 2013. Therefore, the amended Action and Limit Levels are applied for the water monitoring results obtained on and after 25 March 2013.

 

2.2.3       The Action and Limit Levels for dolphin monitoring are shown in Tables 2.4 and 2.5.

Table 2.4        Action and Limit Level for Dolphin Impact Monitoring

 

North Lantau Social Cluster

NEL

NWL

Action Level

STG < 70% of baseline &
ANI < 70% of baseline

STG < 70% of baseline &
ANI < 70% of baseline

Limit Level

STG < 40% of baseline &
ANI < 40% of baseline

Remarks:

                    (1)         STG means quarterly average encounter rate of number of dolphin sightings.

                    (2)         ANI means quarterly average encounter rate of total number of dolphins.

                    (3)         For North Lantau Social Cluster, AL will be triggered if either NEL or NWL fall below the criteria; LL will be triggered if both NEL and NWL fall below the criteria.

 

Table 2.5        Derived Value of Action Level (AL) and Limit Level (LL)

 

North Lantau Social Cluster

NEL

NWL

Action Level

STG < 4.2 & ANI < 15.5

STG < 6.9 & ANI < 31.3

Limit Level

(STG < 2.4 & ANI < 8.9) and (STG < 3.9 & ANI < 17.9)

Remarks:

                    (1)         STG means quarterly average encounter rate of number of dolphin sightings.

                    (2)         ANI means quarterly average encounter rate of total number of dolphins.

                    (3)         For North Lantau Social Cluster, AL will be triggered if either NEL or NWL fall below the criteria; LL will be triggered if both NEL and NWL fall below the criteria.

 

2.3                Event Action Plans

2.3.1       The Event Actions Plans for air quality, noise, water quality, dolphin monitoring and mudflat monitoring and Action Plan for Landscape Works are annexed in Appendix D.

 

2.4                Mitigation Measures

2.4.1       Environmental mitigation measures for the contract were recommended in the approved EIA Report. Appendix E lists the recommended mitigation measures and the implementation status. 

 


3        Environmental Monitoring and Audit

3.1                Implementation of Environmental Measures

3.1.1       In response to the environmental site audit findings, the Contractor have rectified most of the observations as identified in environmental site inspections undertaken during the reporting period. Details of site audit findings and the corrective actions during the reporting period are presented in Appendix F.

3.1.2       Summary of environmental site inspections of landscape works for the Contract works area are presented in Appendix F. The landscape work for the Contract was conducted during the reporting period. The implementation of mitigation measures for landscape and visual resources recommended in the EIA Report were monitored during the reporting period. Landscape and visual mitigation measures in accordance with the EP, EIA and EM&A Manual were implemented by the Contractor.

3.1.3       A summary of the Implementation Schedule of Environmental Mitigation Measures (EMIS) is presented in Appendix E. Most of the necessary mitigation measures were implemented properly. 

3.1.4       Regular marine travel route for marine vessels were implemented properly in accordance to the submitted plan and relevant records were kept properly.

3.1.5       Dolphin Watching Plan was implemented during the reporting period. No dolphins inside the silt curtain were observed. The relevant records were kept properly. 

3.2                Air Quality Monitoring Results

3.2.1       The monitoring results for 1-hour TSP and 24-hour TSP are summarized in Tables 3.1 and 3.2 respectively. Detailed impact air quality monitoring results and relevant graphical plots are presented in Appendix G.

Table 3.1       Summary of 1-hour TSP Monitoring Results Obtained During the Reporting Period

Reporting Period

Monitoring

Station

Average (mg/m3)

Range (mg/m3)

Action Level (mg/m3)

Limit Level (mg/m3)

Dec 2020

AMS5

215

80 - 334

352

500

AMS6

160

90 - 360

360

Jan 2021

AMS5

141

57 - 226

352

AMS6

90

42 - 176

360

Feb 2021

AMS5

114

26 -226

352

AMS6

72

24 - 124

360

 


 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 3.2       Summary of 24-hour TSP Monitoring Results Obtained During the Reporting Period

Reporting Period

Monitoring

Station

Average (mg/m3)

Range (mg/m3)

Action Level (mg/m3)

Limit Level (mg/m3)

Dec 2020

AMS5

84

64 ¡V 121

164

260

AMS6

110

71 - 165

173

Jan 2021

AMS5

98

78 ¡V 114

164

AMS6

115

91 - 146

173

Feb 2021

AMS5

49

13 - 79

164

AMS6

49

11 - 81

173

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.2.2       No Action and Limit Level exceedances of 1-hr TSP and 24-hr TSP were recorded at AMS5 and AMS6 during the reporting period.

3.3                Noise Monitoring Results

3.3.1       The monitoring results for construction noise are summarized in Table 3.3 and the monitoring results and relevant graphical plots for this reporting period are provided in Appendix H.

Table 3.3 Summary of Construction Noise Monitoring Results Obtained During the Reporting Period

Reporting period

Monitoring Station

Average Leq (30 mins), dB(A)*

Range of Leq (30 mins), dB(A)*

Action Level

Limit Level Leq (30 mins), dB(A)

Dec 2020

NMS5

58

55 - 63

When one documented complaint is received

75

Jan 2021

56

56 - 56

Feb 2021

57

54 - 61

*A correction factor of +3dB(A) from free field to facade measurement was included. 

3.3.2       No Action/Limit Level exceedances for noise were recorded during daytime on normal weekdays of the reporting period. 

3.3.3       Other noise sources during the noise monitoring included insect noise, aircraft/helicopter noise, construction activities by other parties and human activities nearby.

3.4                Water Quality Monitoring Results

3.4.1       The water quality monitoring programme was temporarily suspended during the reporting period since no marine works were scheduled or conducted. Therefore, no water quality monitoring was conducted and no water monitoring results are presented during the reporting period. 

3.5                Dolphin Monitoring Results

3.5.1       The dolphin monitoring programme was temporarily suspended during the reporting period since no marine works were scheduled or conducted. Therefore, no quarterly analysis of dolphin monitoring results and exceedances from December 2020 to February 2021 are presented.

3.6                Mudflat Monitoring Results

Sedimentation Rate Monitoring

3.6.1       The baseline sedimentation rate monitoring was in September 2012 and impact sedimentation rate monitoring was undertaken on 7 December 2020. The mudflat surface levels at the four established monitoring stations and the corresponding XYZ HK1980 GRID coordinates are presented in Table 3.9 and Table 3.10.

Table 3.9        Measured Mudflat Surface Level Results

Baseline Monitoring
(September 2012)

Impact Monitoring
(December 2020)

Monitoring Station

Easting
(m)

Northing (m)

Surface Level
(mPD)

Easting
(m)

Northing (m)

Surface Level

(mPD)

S1

810291.160

816678.727

0.950

810291.159

816678.729

1.125

S2

810958.272

815831.531

0.864

810958.275

815831.532

0.958

S3

810716.585

815953.308

1.341

810716.576

815953.307

1.439

S4

811221.433

816151.381

0.931

811221.451

816151.379

1.092

 

Table 3.10      Comparison of Measurement

Comparison of measurement

Remarks and Recommendation

Monitoring Station

Easting
(m)

Northing (m)

Surface Level
(mPD)

S1

-0.001

0.002

0.175

Level continuously increased

S2

0.003

0.001

0.094

Level continuously increased

S3

-0.009

-0.001

0.098

Level continuously increased

S4

0.018

-0.002

0.161

Level continuously increased

 

3.6.2       This measurement result was generally and relatively higher than the baseline measurement at S1, S2, S3 and S4. The mudflat level is continuously increased.

Water Quality Monitoring

3.6.3       The mudflat monitoring covered water quality monitoring data. Reference was made to the water quality monitoring data of the representative water quality monitoring station (i.e. SR3(N)) as in the EM&A Manual. The water quality monitoring location (SR3(N)) is shown in Figure 2.1. 

3.6.4       Impact water quality monitoring in San Tau (monitoring station SR3(N)) was conducted in December 2020 as part of mudflat monitoring. The monitoring parameters included dissolved oxygen (DO), turbidity and suspended solids (SS).

3.6.5       The impact water monitoring result for SR3(N) were extracted and summarised in Table 3.11:


 

Table 3.11  Impact Water Quality Monitoring Results (Depth Average)

Date

Mid Ebb Tide

Mid Flood Tide

DO (mg/L)

Turbidity (NTU)

SS (mg/L)

DO (mg/L)

Turbidity (NTU)

SS (mg/L)

01-Dec-2020

7.3

4.1

6.4

7.4

4.2

5.7

03-Dec-2020

7.4

3.4

6.6

7.6

3.3

5.9

05-Dec-2020

6.1

4.5

3.0

6.3

4.2

3.5

08-Dec-2020

7.6

3.3

6.4

7.4

3.3

6.3

10-Dec-2020

7.6

4.7

10.2

7.7

4.6

8.1

12-Dec-2020

6.7

3.3

2.4

6.8

3.3

3.1

15-Dec-2020

7.7

4.6

8.8

7.6

4.6

9.0

17-Dec-2020

7.7

4.6

11.8

7.6

4.6

16.2

19-Dec-2020

6.8

3.3

3.1

6.7

3.3

3.1

22-Dec-2020

8.1

6.3

7.9

7.9

6.6

9.0

24-Dec-2020

7.8

5.1

9.4

7.8

4.1

9.1

26-Dec-2020

7.3

3.2

2.5

6.8

2.6

2.5

29-Dec-2020

8.2

5.4

4.9

8.2

4.4

5.9

31-Dec-2020

7.4

7.4

12.3

7.4

7.5

9.4

Average

7.4

4.5

6.8

7.4

4.3

6.9

Mudflat Ecology Monitoring

Sampling Zone

3.6.6       In order to collect baseline information of mudflats in the study site, the study site was divided into three sampling zones (labeled as TC1, TC2, TC3) in Tung Chung Bay and one zone in San Tau (labeled as ST) (Figure 2.1 of Appendix O). The horizontal shoreline of sampling zones TC1, TC2, TC3 and ST were about 250 m, 300 m, 300 m and 250 m, respectively (Figure 2.2 of Appendix O). Survey of horseshoe crabs, seagrass beds and intertidal communities were conducted in every sampling zone. The present survey was conducted in December 2020 (totally 4 sampling days on 10th, 11th, 15th and 16rd December 2020).

3.6.7       Since the field survey of June 2016, increasing number of trashes and even big trashes (Figure 2.3 of Appendix O) were found in every sampling zone. It raised a concern about the solid waste dumping and current-driven waste issues in Tung Chung Wan. Respective measures (e.g. manual clean-up) should be implemented by responsible governmental agency units.

Horseshoe Crabs

3.6.8       Active search method was adopted for horseshoe crab monitoring by two experienced surveyors in every sampling zone. During the search period, any accessible and potential area would be investigated for any horseshoe crab individuals within 2-3 hour of low tide period (tidal level below 1.2 m above Chart Datum (C.D.)). Once a horseshoe crab individual was found, the species was identified referencing to Li (2008). The prosomal width, inhabiting substratum and respective GPS coordinate were recorded. A photographic record was taken for future investigation. Any grouping behavior of individuals, if found, was recorded. The horseshoe crab surveys were conducted on 10th (for ST), 11th (for TC1), 15th (for TC2) and 16th (for TC3) December 2020, which were cool and sunny days.

3.6.9       In June 2017, a big horseshoe crab was tangled by a trash gill net in ST mudflat (Figure 2.3 of Appendix O). It was released to sea once after photo recording. The horseshoe crab of such size should be inhabiting sub-tidal environment while it forages on intertidal shore occasionally during high tide period. If it is tangled by the trash net for few days, it may die due to starvation or overheat during low tide period. These trash gill nets are definitely ¡¥fatal trap¡¦ for the horseshoe crabs and other marine life. Manual clean-up should be implemented as soon as possible by responsible governmental agency units.

Seagrass Beds

3.6.10    Active search method was adopted for seagrass bed monitoring by two experienced surveyors in every sampling zone. During the search period, any accessible and potential area would be investigated for any seagrass beds within 2-3 hours of low tide period. Once seagrass bed was found, the species, estimated area, estimated coverage percentage and respective GPS coordinates were recorded. The seagrass beds surveys were conducted on 10th (for ST), 11th (for TC1), 15th (for TC2) and 16th (for TC3) December 2020, which were cool and sunny days.

Intertidal Soft Shore Communities

3.6.11    The intertidal soft shore community surveys were conducted in low tide period on 10th (for ST), 11th (for TC1), 15th (for TC2) and 16th (for TC3) December 2020. In every sampling zone, three 100m horizontal transect lines were laid at high tidal level (H: 2.0m above C.D.), mid tidal level (M: 1.5m above C.D.) and low tidal level (L: 1.0m above C.D.). Along every horizontal transect line; ten random quadrats (0.5 m x 0.5m) were placed.

3.6.12    Inside a quadrat, any visible epifauna was collected and was in-situ identified to the lowest practical taxonomical resolution. Whenever possible a hand core sample (10 cm internal diameter ´ 20 cm depth) of sediments was collected in the quadrat. The core sample was gently washed through a sieve of mesh size 2.0 mm in-situ. Any visible infauna was collected and identified. Finally, the top 5 cm surface sediment was dug for visible infauna in the quadrat regardless of hand core sample was taken.

3.6.13    All collected fauna were released after recording except some tiny individuals that were too small to be identified on site. These tiny individuals were taken to laboratory for identification under dissecting microscope.

3.6.14    The taxonomic classification was conducted in accordance to the following references: Polychaetes: Fauchald (1977), Yang and Sun (1988); Arthropods: Dai and Yang (1991), Dong (1991); Mollusks: Chan and Caley (2003), Qi (2004), AFCD (2018).

Data Analysis

3.6.15    Data collected from direct search and core sampling was pooled in every quadrat for data analysis. Shannon-Weaver Diversity Index (H¡¦) and Pielou¡¦s Species Evenness (J) were calculated for every quadrat using the formulae below,

H¡¦= -£U ( Ni / N ) ln ( Ni / N ) (Shannon and Weaver, 1963)

J = H¡¦ / ln S, (Pielou, 1966)

where S is the total number of species in the sample, N is the total number of individuals, and Ni is the number of individuals of the ith species.

Mudflat Ecology Monitoring Results and Conclusion

Horseshoe Crabs

3.6.16    In total of 3 and 7 individuals of Carcinoscorpius rotundicauda and Tachypleus tridentatus were found in present survey. The recorded individuals were mainly distributed along the shoreline in ST. All of them were observed on similar substratum (fine sand or soft mud, slightly submerged). Photo records of the observed horseshoe crab are shown in Figure 3.1 of Appendix O and the present survey result regarding horseshoe crab are presented in Table 3.1 of Appendix O. The complete survey records are presented in Annex II of Appendix O.

3.6.17    Carcinoscorpius rotundicauda, were only found in ST (3 ind.) with average body size 46.45 mm (prosomal width ranged 36.31 mm ¡V 55.02 mm). The search records in ST was moderate (ST: 0.50 ind. hr-1. Person-1). No Carcinoscorpius rotundicauda was found in TC1, TC2 and TC3 in present survey.

3.6.18    For Tachypleus tridentatus, 7 individuals with average body size 41.13 mm (prosomal width ranged 28.34 ¡V 56.49 mm) were found in ST. The search record in ST was moderate (1.17 ind. hr-1. Person-1). No Tachypleus tridentatus was found in TC1, TC2 and TC3 in present survey.

3.6.19    In the survey of March 2015, there was one important finding that a mating pair of Carcinoscorpius rotundicauda was found in ST (prosomal width: male 155.1mm, female 138.2mm). It indicated the importance of ST as a breeding ground of horseshoe crab. In June 2017, mating pairs of Carcinoscorpius rotundicauda were found in TC2 (male 175.27 mm, female 143.51 mm) and TC3 (male 182.08 mm, female 145.63 mm) (Figure 3.2 of Appendix O). In December 2017 and June 2018, one mating pair was of Carcinoscorpius rotundicauda was found in TC3 (December 2017: male 127.80 mm, female 144.61 mm; June 2018: male 139 mm, female 149 mm). In June 2019, 2 mating pairs of Tachypleus tridentatus with large body sizes (male 150mm and Female 200mm; Male 180mm and Female 220mm) was found in TC3. Another mating pair of Tachypleus tridentatus was found in ST (male 140mm and Female 180mm). In March 2020, a pair of Tachypleus tridentatus with large body sizes (male 123mm and Female 137mm was recorded in TC1. Figure 3.2 of Appendix Oshows the photographic records of mating pairs found. The recorded mating pairs were found nearly burrowing in soft mud at low tidal level (0.5-1.0 m above C.D.). The smaller male was holding the opisthosoma (abdomen carapace) of larger female from behind. A mating pair was found in TC1 in March 2020, it indicated that breeding of horseshoe crab could be possible along the coast of Tung Chung Wan rather than ST only, as long as suitable substratum was available. Based on the frequency of encounter, the shoreline between TC3 and ST should be more suitable mating ground. Moreover suitable breeding period was believed in wet season (March ¡V September) because tiny individuals (i.e. newly hatched) were usually recorded in June and September every year (Figure 3.3 of Appendix O). No mating pair was found in December 2020 (present survey).

3.6.20    No large individuals (prosomal width >100mm) of Carcinoscorpius rotundicauda and Tachypleus tridentatus was recorded in December 2020 (present survey). In December 2018, one large individual of Carcinoscorpius rotundicauda was found in TC3 (prosomal width 148.9 mm). In March 2019, 3 large individuals (prosomal width ranged 220 ¡V 310mm) of Carcinoscorpius rotundicauda were observed in TC2. In June 2019, there were 3 and 7 large individuals of Tachypleus tridentatus were recorded in ST (prosomal width ranged 140 ¡V 180mm) and TC3 (prosomal width ranged 150 ¡V 220mm), respectively. In March 2020, a mating pair of Tachypleus tridentatus was recorded in TC1 with prosomal width 123 mm and 137mm. Based on their sizes, it indicated that individuals of prosomal width larger than 100 mm would progress its nursery stage from intertidal habitat to sub-tidal habitat of Tung Chung Wan. The photo records of the large horseshoe crab are shown in Figure 3.4 of Appendix O. These large individuals might move onto intertidal shore occasionally during high tide for foraging and breeding. Because they should be inhabiting sub-tidal habitat most of the time. Their records were excluded from the data analysis to avoid mixing up with juvenile population living on intertidal habitat.

3.6.21    No marked individual of horseshoe crab was recorded in December 2020 (present survey). Some marked individuals were found in the previous surveys of September 2013, March 2014 and September 2014. All of them were released through a conservation programme in charged by Prof. Paul Shin (Department of Biology and Chemistry, The City University of Hong Kong (CityU)). It was a re-introduction trial of artificial bred horseshoe crab juvenile at selected sites. So that the horseshoe crabs population might be restored in the natural habitat. Through a personal conversation with Prof. Shin, about 100 individuals were released in the sampling zone ST on 20 June 2013. All of them were marked with color tape and internal chip detected by specific chip sensor. There should be second round of release between June and September 2014 since new marked individuals were found in the survey of September 2014.

3.6.22    The artificial bred individuals, if found, would be excluded from the results of present monitoring programme in order to reflect the changes of natural population. However, the mark on their prosoma might have been detached during moulting after a certain period of release. The artificially released individuals were no longer distinguishable from the natural population without the specific chip sensor. The survey data collected would possibly cover both natural population and artificially bred individuals.

Population difference among the sampling zones

3.6.23    Figure 3.5 and 3.6 of Appendix O show the changes of number of individuals, mean prosomal width and search record of horseshoe crabs Carcinoscorpius rotundicauda and Tachypleus tridentatus in respectively in each sampling zone throughout the monitoring period.

3.6.24    To consider the entire monitoring period for TC3 and ST, medium to high search records (i.e. number of individuals) of both species (Carcinoscorpius rotundicauda and Tachypleus tridentatus) were usually found in wet season (June and September). The search record of ST was higher from September 2012 to June 2014 while it was replaced by TC3 from September 2014 to June 2015. The search records were similar between two sampling zones from September 2015 to June 2016. In September 2016, the search record of Carcinoscorpius rotundicauda in ST was much higher than TC3. From March to June 2017, the search records of both species were similar again between two sampling zones. It showed a natural variation of horseshoe crab population in these two zones due to weather condition and tidal effect. No obvious difference of horseshoe crab population was noted between TC3 and ST. In September 2017, the search records of both horseshoe crab species decreased except the Carcinoscorpius rotundicauda in TC3. The survey results were different from previous findings that there were usually higher search records in September. One possible reason was that the serial cyclone hit decreased horseshoe crab activity (totally 4 cyclone records between June and September 2017, to be discussed in 'Seagrass survey' section). From December 2017 to September 2018, the search records of both species increased again to low-moderate level in ST. From December 2018 to March 2020, the search records of Carcinoscorpius rotundicauda change from very low to low while the change of Tachypleus tridentatus was similar during this period. From June 2020 to September 2020, the search records of both species, Carcinoscorpius rotundicauda and Tachypleus tridentatus, were increased to moderate level in ST. However, none of them were recorded in TC3. Relatively higher population fluctuation of Carcinoscorpius rotundicauda was observed in TC3. In December 2020 (present survey), the search records of both species, Carcinoscorpius rotundicauda and Tachypleus tridentatus, were decreased to low level in ST. None of them were recorded in TC3 from June 2020 to December 2020. It is similar to the previous findings of December. It may due to the weather variation of dry season.

3.6.25    For TC1, the search record was at low to moderate level throughout the monitoring period. The change of Carcinoscorpius rotundicauda was relatively more variable than that of Tachypleus tridentatus. Relatively, the search record was very low in TC2. There were occasional records of 1 to 4 individuals between March and September throughout the monitoring period. The maximum record was 6 individuals only in June 2016.

3.6.26    About the body size, larger individuals of Carcinoscorpius rotundicauda were usually found in ST and TC1 relative to that in TC3 from September 2012 to June 2017. But the body size was higher in TC3 and ST followed by TC1 from September 2017 to March 2020. From June 2020 to December 2020 (present survey), there was no individuals of Carcinoscorpius rotundicauda recorded in TC3 but in ST. The body size of Carcinoscorpius rotundicauda in ST was recorded gradually increased (from mean prosomal width 23.6mm to 49.6mm) since March 2020 to September 2020. In December 2020 (present survey), the body size of Carcinoscorpius rotundicauda in ST was recorded slightly decreased (from mean prosomal width 49.6mm to 46.5mm). For Tachypleus tridentatus, larger individuals were usually found in ST and TC3 followed by TC1 throughout the monitoring period. In June 2019, all found horseshoe crabs were large individuals and mating pairs. It is believed that the sizes of the horseshoe crabs would be decrease and gradually rise afterward due to the stable growth of juveniles after the spawning season. From June 2019 to December 2020 (present survey), Tachypleus tridentatus were only recorded in TC3 and ST. The body size in TC3 was increased from September 2019 to December 2019 then decreased in March 2020 and no recorded species in TC3 for two consecutive years from June 2020 to December 2020 (present survey). It showed a natural variation of horseshoe crab population in TC3. Apart from natural mortality, migration from nursery soft shore to subtidal habitat was another possible cause. The body size in ST was gradually growth since December 2019 to September 2020 from mean prosomal width 30.2mm to 54.6mm. It indicated that a stable growth of juveniles after the spawning season. In December 2020 (present survey), the body size in ST was slightly dropped. It was predicted that the sizes of the horseshoe crabs decrease and gradually rise afterward due to the stable growth of juveniles after the spawning season.  

3.6.27    In general, it was obvious that the shoreline along TC3 and ST (western shore of Tung Chung Wan) was an important nursery ground for horseshoe crab especially newly hatched individuals due to larger area of suitable substratum (fine sand or soft mud) and less human disturbance (far from urban district). Relatively, other sampling zones were not a suitable nursery ground especially TC2. Possible factors were less area of suitable substratum (especially TC1) and higher human disturbance (TC1 and TC2: close to urban district and easily accessible). In TC2, large daily salinity fluctuation was a possible factor either since it was flushed by two rivers under tidal inundation. The individuals inhabiting TC1 and TC2 were confined in small foraging area due to limited area of suitable substratum. Although there were mating pairs of seldomly found in TC1 and TC2, the hatching rate and survival rate of newly hatched individuals were believed very low.

Seasonal variation of horseshoe crab population

3.6.28    Throughout the monitoring period, the search records of horseshoe crabs were fluctuated and at moderate ¡V very low level in June (Figures 3.5 and 3.6 of Appendix O). Low ¡V Very low search record was found in June 2013, totally 82 individuals of Tachypleus tridentatus and 0 ind. of Carcinoscorpius rotundicauda were found in TC1, TC3 and ST. Compare with the search record of June 2013, the numbers of Tachypleus tridentatus were gradually decreased in June 2014 and 2015 (55 ind. in 2014 and 18 ind. in 2015); the number of Carcinoscorpius rotundicauda raise to 88 and 66 individuals. in June 2014 and 2015 respectively. In June 2016, the search record increased about 3 times compare with June 2015. In total, 182 individuals of Carcinoscorpius rotundicauda and 47 individuals. of Tachypleus tridentatus were noted, respectively. Then, the search record was similar to June 2016. The number of recorded Carcinoscorpius rotundicauda (133 ind.) slightly dropped in June 2017. However, that of Tachypleus tridentatus rapidly increased (125 ind.). In June 2018, the search record was low to moderate while the numbers of Tachypleus tridentatus dropped sharply (39 ind.).  In June 2019, 10 individuals of Tachypleus tridentatus were observed in TC3 and ST. All of them, however, were large individuals (prosomal width >100mm), their records are excluded from the data analysis to avoid mixing up with the juvenile population living on intertidal habitat. Until September 2020, the number of Carcinoscorpius rotundicauda and Tachypleus tridentatus gradually increased to 39 ind. and 28 ind., respectively. Throughout the monitoring period, similar distribution of horseshoe crabs population were found in September. Most of the horseshoe crabs were found in TC3 and ST.

3.6.29    In December 2020 (present survey), the number of Carcinoscorpius rotundicauda and Tachypleus tridentatus greatly decreased to 3 ind. and 7 ind., respectively. Throughout the monitoring period, similar distribution of horseshoe crabs population were found in December. All the horseshoe crabs were found in ST.

3.6.30    The search record of horseshoe crab declined obviously in all sampling zones during dry season especially December (Figures 3.5 and 3.6 of Appendix O) throughout the monitoring period. Very low ¡V low search record was found in December from 2012 to 2015 (0-4 ind. of Carcinoscorpius rotundicauda and 0-12 ind. of Tachypleus tridentatus). The horseshoe crabs were inactive and burrowed in the sediments during cold weather (<15 ºC). Similar results of low search record in dry season were reported in a previous territory-wide survey of horseshoe crab. For example, the search records in Tung Chung Wan were 0.17 ind. hr-1person-1 and 0.00 ind. hr-1 person-1 in wet season and dry season respectively (details see Li, 2008). Compare with the search record of December from 2012 to 2015, which of December 2016 were much higher relatively. There were totally 70 individuals of Carcinoscorpius rotundicauda and 24 individuals of Tachypleus tridentatus in TC3 and ST. Since the survey was carried in earlier December with warm and sunny weather (~22 ºC during dawn according to Hong Kong Observatory database, Chek Lap Kok station on 5 December 2016), the horseshoe crab was more active (i.e. move onto intertidal shore during high tide for foraging and breeding) and easier to be found. In contrast, there was no search record in TC1 and TC2 because the survey was conducted in mid-December with colder and cloudy weather (~20 ºC during dawn on 19 December). The horseshoe crab activity would decrease gradually with the colder climate. In December of 2017, 2018 and 2019 very low search records were found again as mentioned above.

3.6.31    From September 2012 to December 2013, Carcinoscorpius rotundicauda was less common species relative to Tachypleus tridentatus. Only 4 individuals were ever recorded in ST in December 2012. This species had ever been believed of very low density in ST hence the encounter rate was very low. In March 2014, it was found in all sampling zones with higher abundance in ST. Based on its average size (mean prosomal width 39.28 mm - 49.81 mm), it indicated that breeding and spawning of this species had occurred about 3 years ago along the coastline of Tung Chun Wan. However, these individuals were still small while their walking trails were inconspicuous. Hence there was no search record in previous sampling months. Since March 2014, more individuals were recorded due to larger size and higher activity (i.e. more conspicuous walking trail).

3.6.32    For Tachypleus tridentatus, sharp increase of number of individuals was recorded in ST during the wet season of 2013 (from March to September). According to a personal conversation with Prof. Shin (CityU), his monitoring team had recorded similar increase of horseshoe crab population during wet season. It was believed that the suitable ambient temperature increased its conspicuousness. However similar pattern was not recorded in the following wet seasons. The number of individuals increased in March and June 2014 and followed by a rapid decline in September 2014. Then the number of individuals fluctuated slightly in TC3 and ST until March 2017. Apart from natural mortality, migration from nursery soft shore to subtidal habitat was another possible cause. Since the mean prosomal width of Tachypleus tridentatus continued to grow and reached about 50 mm since March 2014. Then it varied slightly between 35 - 65 mm from September 2014 to March 2017. Most of the individuals might have reached a suitable size (e.g. prosomal width 50 - 60 mm) strong enough to forage in sub-tidal habitat. In June 2017, the number of individuals increased sharply again in TC3 and ST. Although mating pair of Tachypleus tridentatus was not found in previous surveys, there should be new round of spawning in the wet season of 2016. The individuals might have grown to a more conspicuous size in 2017 accounting for higher search record. In September 2017, moderate numbers of individual were found in TC3 and ST indicating a stable population size. From September 2018 to March 2020, the population size was low while natural mortality was the possible cause. From June 2020 to September 2020, the population size of Tachypleus tridentatus increased to moderate level in ST while the mean proposal width of them continued to grow and reach about 55mm. It indicated that a stable growth of juveniles after the spawning season. In December 2020 (present survey), the population size of Tachypleus tridentatus decreased to low level in ST and the mean proposal width of them decreased to about 41mm. It may due to the natural mortality.

3.6.33    Recently, Carcinoscorpius rotundicauda was a more common horseshoe crab species in Tung Chung Wan. It was recorded in the four sampling zones while the majority of population located in TC3 and ST. Due to potential breeding last year, the number of Tachypleus tridentatus became increased ST. Since TC3 and ST were regarded as important nursery ground for both horseshoe crab species, box plots of prosomal width of two horseshoe crab species were constructed to investigate the changes of population in details.

Box plot of horseshoe crab populations in TC3

3.6.34    Figure 3.7 of Appendix O shows the changes of prosomal width of Carcinoscorpius rotundicauda and Tachypleus tridentatus in TC3. As mentioned above, Carcinoscorpius rotundicauda was rarely found between September 2012 and December 2013 hence the data were lacking. In March 2014, the major size (50% of individual records between upper (top box) and lower quartile (bottom box)) ranged 40 ¡V 60 mm while only few individuals were found. From March 2014 to September 2018, the median prosomal width (middle line of whole box) and major size (whole box) decreased after March of every year. It was due to more small individuals found in June indicating new rounds of spawning. Also, there were slight increasing trends of body size from June to March of next year since 2015. It indicated a stable growth of individuals. Focused on larger juveniles (upper whisker), the size range was quite variable (prosomal width 60 ¡V 90 mm) along the sampling months. Juveniles reaching this size might gradually migrate to sub-tidal habitats.   

3.6.35    For Tachypleus tridentatus, the major size ranged 20-50 mm while the number of individuals fluctuated from September 2012 to June 2014. Then a slight but consistent growing trend was observed from September 2014 to June 2015. The prosomal width increased from 25 ¡V 35 mm to 35 ¡V 65 mm. As mentioned, the large individuals might have reached a suitable size for migrating from the nursery soft shore to subtidal habitat. It accounted for the declined population in TC3. From March to September 2016, slight increasing trend of major size was noticed again. From December 2016 to June 2017, similar increasing trend of major size was noted with much higher number of individuals. It reflected new round of spawning. In September 2017, the major size decreased while the trend was different from previous two years. Such decline might be the cause of serial cyclone hit between June and September 2017 (to be discussed in the 'Seagrass survey' section). From December 2017 to September 2018, increasing trend was noted again. It indicated a stable growth of individuals. From September 2018 to that of next year, the average prosomal widths were decreased from 60mm to 36mm. It indicated new rounds of spawning occurred during September to November 2018. In December 2019, an individual with larger body size (prosomal width 65mm) was found in TC3 which reflected the stable growth of individuals. In March 2020, the average prosomal width (middle line of the whole box) of Tachypleus tridentatus in TC3 was 33.97 mm which is smaller than that in December 2019. It was in normal fluctuation. From June 2020 to December 2020 (present survey), no horseshoe crab was recorded in TC3. Across the whole monitoring period, the larger juveniles (upper whisker) usually reached 60 ¡V 80 mm in prosomal width, even 90 mm occasionally. The juveniles reaching this size might gradually migrate to sub-tidal habitats.

Box plot of horseshoe crab populations in ST

3.6.36    Figure 3.8 of Appendix O shows the changes of prosomal width of Carcinoscorpius rotundicauda and Tachypleus tridentatus in ST. As mentioned above, Carcinoscorpius rotundicauda was rarely found between September 2012 and December 2013 hence the data were lacking. From March 2014 to September 2018, the size of major population decreased and more small individuals (i.e. lower whisker) were recorded after June of every year. It indicated new round of spawning. Also, there were similar increasing trends of body size from September to June of next year between 2014 and 2017. It indicated a stable growth of individuals. The larger juveniles (i.e. upper whisker usually ranged 60 ¡V 80 mm in prosomal width except one individual (prosomal width 107.04 mm) found in March 2017. It reflected juveniles reaching this size would gradually migrate to sub-tidal habitats.

3.6.37    For Tachypleus tridentatus, a consistent growing trend was observed for the major population from December 2012 to December 2014 regardless of change of search record. The prosomal width increased from 15-30 mm to 60 ¡V 70 mm. As mentioned, the large juveniles might have reached a suitable size for migrating from the nursery soft shore to subtidal habitat. From March to September 2015, the size of major population decreased slightly to a prosomal width 40 ¡V 60 mm. At the same time, the number of individuals decreased gradually. It further indicated some of large juveniles might have migrated to sub-tidal habitat, leaving the smaller individuals on shore. There was an overall growth trend. In December 2015, two big individuals (prosomal width 89.27 mm and 98.89 mm) were recorded only while it could not represent the major population. In March 2016, the number of individual was very few in ST that no box plot could be produced. In June 2016, the prosomal width of major population ranged 50 ¡V 70 mm. But it dropped clearly to 30 ¡V 40 mm in September 2016 followed by an increase to 40 ¡V 50 mm in December 2016, 40 ¡V 70 mm in March 2017 and 50 ¡V 60mm in June 2017. Based on overall higher number of small individuals from June 2016 to September 2017, it indicated another round of spawning. From September 2017 to June 2018, the major size range increased slightly from 40 ¡V 50 mm to 45 ¡V 60 mm indicating a continuous growth. In September 2018, decrease of major size was noted again that might reflect new round of spawning. Throughout the monitoring period, the larger juveniles ranged 60¡V 80 mm in prosomal width. Juveniles reaching this size would gradually migrate to sub-tidal habitats.

3.6.38    As a summary for horseshoe crab populations in TC3 and ST, there were spawning of Carcinoscorpius rotundicauda from 2014 to 2018 while the spawning time should be in spring. The population size was consistent in these two sampling zones. For Tachypleus tridentatus, small individuals were rarely found in both zones from 2014 to 2015. It was believed no occurrence of successful spawning. The existing individuals (that recorded since 2012) grew to a mature size and migrated to sub-tidal habitat. Hence the number of individuals decreased gradually. From 2016 to 2018, new rounds of spawning were recorded in ST while the population size increased to a moderate level.

3.6.39    In March 2019 to June 2019, no horseshoe crab juveniles (prosomal width <100mm) were recorded in TC3 and ST. All recorded horseshoe crabs were large individuals (prosomal width >100mm) or mating pairs which were all excluded from the data analysis. From September 2019 to September 2020, the population size of both horseshoe crab species in ST gradually increased to moderate level while their body sizes were mostly in small to medium range (~23 ¡V 55mm). It indicated the natural stable growth of the horseshoe crab juveniles). In December 2020 (present survey), the population size of both horseshoe crab species in ST dropped to low level while their body sizes were mostly in small to medium range (~28 ¡V 56mm). It showed the natural mortality and seasonal variation of horseshoe crab.

Impact of the HKLR project

3.6.40    It was the 33rd survey of the EM&A programme during construction period. Based on the monitoring results, no detectable impact on horseshoe crab was revealed due to HKLR project. The population change was mainly determined by natural growth variation, no abnormal phenomenon of horseshoe crab individual, such as large number of dead individuals on the shore) had been reported.  

Seagrass Beds

3.6.41    Only seagrass species Halophila ovalis was found in present survey, which was found in TC3 and ST. In ST, there were two small sized and one large sized of seagrass beds found at tidal zone 1.5 m above C.D nearby mangroves plantation. The larger strand had area ~900 m2 in high vegetation coverage (90 ¡V 100%). At close vicinity, two small sized (~4 and 50 m2) of Halophila ovalis beds were observed at tidal zone 1.5 above C.D. The ~4m2 of Halophila ovalis beds were in moderate to high vegetation coverage (70-80%) while the ~50m2 and ~900m2 of Halophila ovalis beds were in high vegetation coverage (90 ¡V 100%) respectively. In TC3, three small patches of Halophila ovalis were found at tidal zone 1.5 ¡V 2.0m above C.D. These seagrass patch had area 30m2 ¡V 54m2. They were in moderate to high vegetation coverage (50 ¡V 100%). Another seagrass species Zostera japonica was not found in present survey. Table 3.2 of Appendix O summarizes the results of present seagrass beds survey and the photograph records of the seagrass are shown on Figure 3.9 of Appendix O. The complete record throughout the monitoring period is presented in Annex III of Appendix O

3.6.42    Since the commencement of the EM&A monitoring programme, two species of seagrass Halophila ovalis and Zostera japonica were recorded in TC3 and ST (Figure 3.10 of Appendix O). In general Halophila ovalis was occasionally found in TC3 in few, small to medium patches. But it was commonly found in ST in medium to large seagrass bed. Moreover it had sometimes grown extensively and had covered significant mudflat area at 0.5 ¡V 2.0 m above C.D. between TC3 and ST. Another seagrass species Zostera japonica was found in ST only. It was relatively lower in vegetation area and co-existed with Halophila ovalis nearby the mangrove strand at 2.0 m above C.D.

3.6.43    According to the previous results, majority of seagrass bed was confined in ST, the temporal change of both seagrass species were investigated in details:

Temporal variation of seagrass beds

3.6.44    Figure 3.11 of Appendix O shows the changes of estimated total area of seagrass beds in ST along the sampling months. For Zostera japonica, it was not recorded in the 1st and 2nd surveys of monitoring programme. Seasonal recruitment of few, small patches (total seagrass area: 10 m2) was found in Mach 2013 that grew within the large patch of seagrass Halophila ovalis. Then, the patch size increased and merged gradually with the warmer climate from March to June 2013 (15 m2). However, the patch size decreased and remained similar from September 2013 (4 m2) to March 2014 (3 m2). In June 2014, the patch size increased obviously again (41 m2) with warmer climate followed by a decrease between September 2014 (2 m2) and December 2014 (5 m2). From March to June 2015, the patch size increased sharply again (90 m2). It might be due to the disappearance of the originally dominant seagrass Halophila ovalis resulting in less competition for substratum and nutrients. From September 2015 to June 2016, it was found coexisting with seagrass Halophila ovalis with steady increasing patch size (from 44 m2 to 115 m2) and variable coverage. In September 2016, the patch size decreased again to (38 m2) followed by an increase to a horizontal strand (105.4 m2) in June 2017. And it did no longer co-exist with Halophila ovalis. Between September 2014 and June 2017, an increasing trend was noticed from September to June of next year followed by a rapid decline in September of next year. It was possibly the causes of heat stress, typhoon and stronger grazing pressure during wet season. However, such increasing trend was not found from September 2017 to December 2020 (present survey) while no patch of Zostera japonica was found.

3.6.45    For Halophila ovalis, it was recorded as 3 ¡V 4 medium to large patches (area 18.9 - 251.7 m2; vegetation coverage 50 - 80%) beside the mangrove vegetation at tidal level 2 m above C.D. in September 2012. The total seagrass bed area grew steadily from 332.3 m2 in September 2012 to 727.4 m2 in December 2013. Flowers were observed in the largest patch during its flowering period. In March 2014, 31 small to medium patches were newly recorded (variable area 1 ¡V 72 m2 per patch, vegetation coverage 40-80% per patch) in lower tidal zone between 1.0 and 1.5 m above C.D. The total seagrass area increased further to 1350 m2. In June 2014, these small and medium patches grew and extended to each other. These patches were no longer distinguishable and were covering a significant mudflat area of ST. It was generally grouped into 4 large patches (1116 - 2443 m2) of seagrass beds characterized of patchy distribution, variable vegetable coverage (40 - 80%) and smaller leaves. The total seagrass bed area increased sharply to 7629 m2. In September 2014, the total seagrass area declined sharply to 1111m2. There were only 3 - 4 small to large patches (6 - 253 m2) at high tidal level and 1 large patch at low tidal level (786 m2). Typhoon or strong water current was a possible cause (Fong, 1998). In September 2014, there were two tropical cyclone records in Hong Kong (7th-8th September: no cyclone name, maximum signal number 1; 14th - 17th September: Kalmaegi, maximum signal number 8SE) before the seagrass survey dated 21st September 2014. The strong water current caused by the cyclone, Kalmaegi especially, might have given damage to the seagrass beds. In addition, natural heat stress and grazing force were other possible causes reducing seagrass beds area. Besides, very small patches of Halophila ovalis could be found in other mud flat area in addition to the recorded patches. But it was hardly distinguished due to very low coverage (10 - 20%) and small leaves.

3.6.46    In December 2014, all the seagrass patches of Halophila ovalis disappeared in ST. Figure 3.12 of Appendix O shows the difference of the original seagrass beds area nearby the mangrove vegetation at high tidal level between June 2014 and December 2014.Such rapid loss would not be seasonal phenomenon because the seagrass beds at higher tidal level (2.0 m above C.D.) were present and normal in December 2012 and 2013. According to Fong (1998), similar incident had occurred in ST in the past. The original seagrass area had declined significantly during the commencement of the construction and reclamation works for the international airport at Chek Lap Kok in 1992. The seagrass almost disappeared in 1995 and recovered gradually after the completion of reclamation works. Moreover, incident of rapid loss of seagrass area was also recorded in another intertidal mudflat in Lai Chi Wo in 1998 with unknown reason. Hence, Halophila ovalis was regarded as a short-lived and r-strategy seagrass that could colonize areas in short period but disappears quickly under unfavourable conditions (Fong, 1998).

Unfavourable conditions to seagrass Halophila ovalis

3.6.47    Typhoon or strong water current was suggested as one unfavorable condition to Halophila ovalis (Fong, 1998). As mentioned above, there were two tropical cyclone records in Hong Kong in September 2014. The strong water current caused by the cyclones might have given damage to the seagrass beds.

3.6.48    Prolonged light deprivation due to turbid water would be another unfavorable condition. Previous studies reported that Halophila ovalis had little tolerance to light deprivation. During experimental darkness, seagrass biomass declined rapidly after 3 - 6 days and seagrass died completely after 30 days. The rapid death might be due to shortage of available carbohydrate under limited photosynthesis or accumulation of phytotoxic end products of anaerobic respiration (details see Longstaff et al., 1999). Hence the seagrass bed of this species was susceptible to temporary light deprivation events such as flooding river runoff (Longstaff and Dennison, 1999).

3.6.49    In order to investigate any deterioration of water quality (e.g. more turbid) in ST, the water quality measurement results at two closest monitoring stations SR3 and IS5 of the EM&A programme were obtained from the water quality monitoring team. Based on the results from June to December 2014, the overall water quality was in normal fluctuation except there was one exceedance of suspended solids (SS) at both stations in September. On 10th September 2014, the SS concentrations measured during mid-ebb tide at stations SR3 (27.5 mg/L) and IS5 (34.5 mg/L) exceeded the Action Level (23.5 mg/L and 120% of upstream control station¡¦s reading) and Limit Level (34.4 mg/L and 130% of upstream control station¡¦s reading) respectively. The turbidity readings at SR3 and IS5 reached 24.8-25.3 NTU and 22.3-22.5 NTU respectively. The temporary turbid water should not be caused by the runoff from upstream rivers. Because there was no rain or slight rain from 1st to 10th September 2014 (daily total rainfall at the Hong Kong International Airport: 0-2.1 mm; extracted from the climatological data of Hong Kong Observatory). The effect of upstream runoff on water quality should be neglectable in that period. Moreover, the exceedance of water quality was considered unlikely to be related to the contract works of HKLR according to the ¡¥Notifications of Environmental Quality Limits Exceedances¡¦ provided by the respective environmental team. The respective construction of seawall and stone column works, which possibly caused turbid water, was carried out within silt curtain as recommended in the EIA report. Moreover, there was no leakage of turbid water, abnormity or malpractice recorded during water sampling. In general, the exceedance of suspended solids concentration was considered to be attributed to other external factors, rather than the contract works.

3.6.50    Based on the weather condition and water quality results in ST, the co-occurrence of cyclone hit and turbid waters in September 2014 might have combined the adverse effects on Halophila ovalis that leaded to disappearance of this short-lived and r-strategy seagrass species. Fortunately, Halophila ovalis was a fast-growing species (Vermaat et al., 1995). Previous studies showed that the seagrass bed could be recovered to the original sizes in 2 months through vegetative propagation after experimental clearance (Supanwanid, 1996). Moreover it was reported to recover rapidly in less than 20 days after dugong herbivory (Nakaoka and Aioi, 1999). As mentioned, the disappeared seagrass in ST in 1995 could recover gradually after the completion of reclamation works for international airport (Fong, 1998).The seagrass beds of Halophila ovalis might recolonize in the mudflat of ST through seed reproduction as long as there was no unfavourable condition in the coming months.

Recolonization of seagrass beds

3.6.51    Figure 3.12 of Appendix O shows the recolonization of seagrass bed in ST from December 2014 to June 2017. From March to June 2015, 2 - 3 small patches of Halophila ovalis were newly found co-inhabiting with another seagrass species Zostera japonica. But the total patch area of Halophila ovalis was still very low compare with previous records. The recolonization rate was low while cold weather and insufficient sunlight were possible factors between December 2014 and March 2015. Moreover, it would need to compete with seagrass Zostera japonica for substratum and nutrient, because Zostera japonica had extended and covered the original seagrass bed of Halophila ovalis at certain degree. From June 2015 to March 2016, the total seagrass area of Halophila ovalis had increased rapidly from 6.8 m2 to 230.63 m2. It had recolonized its original patch locations and covered its competitor Zostera japonica. In June 2016, the total seagrass area increased sharply to 4707.3m2. Similar to the previous records of March to June 2014, the original patch area of Halophila ovalis increased further to a horizontally long strand. Another large seagrass beds colonized the lower tidal zone (1.0 - 1.5 m above C.D.). In September 2016, this patch extended much and covered significant soft mud area of ST, resulting in sharp increase of total area (24245 m2). It indicated the second extensive colonization of this r-selected seagrass. In December 2016, this extensive seagrass patch decreased in size and had separated into few, undistinguishable patches. Moreover, the horizontal strand nearby the mangrove vegetation decreased in size. The total seagrass bed decreased to 12550 m2. From March to June 2017, the seagrass bed area remained generally stable (12438 - 17046.5 m2) but the vegetation coverage fluctuated (20 - 50% in March 2017 to 80-100% in June 2017). The whole recolonization process took about 2.5 years.

Second disappearance of seagrass bed

3.6.52    In September 2017, the whole seagrass bed of Halophila ovalis disappeared again along the shore of TC3 and ST (Figure 3.12 of Appendix O). Similar to the first disappearance of seagrass bed occurred between September and December 2014, strong water current (e.g. cyclone) or deteriorated water qualities (e.g. high turbidity) was the possible cause.

3.6.53    Between the survey periods of June and September 2017, there were four tropical cyclone records in Hong Kong (Merbok in 12 - 13th, June; Roke in 23rd, Jul.; Hato in 22 - 23rd, Aug.; Pakhar in 26-27th, Aug.) (Online database of Hong Kong Observatory). All of them reaches signal 8 or above, especially Hato with highest signal 10.

3.6.54    According to the water quality monitoring results (July to August 2017) of the two closest monitoring stations SR3 and IS5 of the respective EM&A programme, the overall water quality was in normal fluctuation. There was an exceedance of suspended solids (SS) at SR3 on 12 July 2017. The SS concentration reached 24.7 mg/L during mid-ebb tide, which exceeded the Action Level ( 23.5 mg/L). But it was far below the Limit Level ( 34.4 mg/L). Since such exceedance was slight and temporary, its effect to seagrass bed should be minimal.

3.6.55    Overall, the disappearance of seagrass beds in ST has believed the cause of serial cyclone hit in July and August 2017. Based on previous findings, the seagrass beds of both species were expected to recolonize in the mudflat as long as the vicinal water quality was normal. The whole recolonization process (from few, small patches to extensive strand) would be gradually lasting at least 2 years. From December 2017 to March 2018, there was still no recolonization of few, small patches of seagrass at the usual location (Figure 3.12 of Appendix O). It was different from the previous round (March 2015 - June 2017). Until June 2018, the new seagrass patches with small-medium size were found at the usual location (seaward side of mangrove plantation at 2.0 m C.D.) again, indicating the recolonization. However, the seagrass bed area decreased sharply to 22.5 m2 in September 2018. Again, it was believed that the decrease was due to the hit of the super cyclone in September 2018 (Mangkhuton 16th September, highest signal 10). From December 2018 to June 2019, the seagrass bed area increased from 404 m2 to 1229 m2 while the vegetation coverage is also increased. (December 2018: 5 ¡V 85%; March 2019: 50 ¡V 100% and June 2019: 60 ¡V 100%). Relatively, the whole recolonization process would occur slower than the previous round (more than 2 years). From September 2019 to December 2020 (present survey), the seagrass bed area slightly decreased from 1200 m2 to 954 m2 which were in normal fluctuation.

Impact of the HKLR project

3.6.56    It was the 33rd survey of the EM&A programme during construction period. Throughout the monitoring period, the disappearance of seagrass beds was believed the cause of cyclone hits rather than impact of HKLR project. The seagrass bed was recolonizing since there had been a gradual increase in the size and number from December 2018 to June 2019 after the hit of the super cyclone in September 2018. The seagrass bed area slightly decreased from September 2019 to December 2020 (present survey) which were in normal fluctuation.

Intertidal Soft Shore Communities

Substratum

3.6.57    Table 3.3 and Figure 3.13 of Appendix O show the substratum types along the horizontal transect at every tidal level in all sampling zones. The relative distribution of substratum types was estimated by categorizing the substratum types (Gravels & Boulders / Sands / Soft mud) of the ten random quadrats along the horizontal transect. The distribution of substratum types varied among tidal levels and sampling zones:

¡P         In TC1, high percentages of ¡¥Gravels and Boulders¡¦ (H: 80%; M: 60%) were recorded at high and mid tidal levels. Equal percentages of ¡¥Gravels and Boulders¡¦ (50%) and ¡¥Soft mud¡¦ (50%) were recorded at low tidal level.

¡P         In TC2, high percentages of ¡¥Gravels and Boulders¡¦ (H: 70%; M: 60%) were recorded at high and mid tidal levels. Relatively higher percentages of ¡¥Soft mud¡¦ (50%) and ¡¥Gravels and Boulders¡¦ (40%) were recorded at low tidal level.

¡P         In TC3, higher percentage of ¡¥Gravels and Boulders¡¦ (H: 70%; M: 60%; L: 60%) were recorded at high, mid and low tidal level.

¡P         In ST, ¡¥Gravels and Boulders¡¦ was the main substratum type (H: 80%; M: 70%) at high tidal level and mid tidal level. At low tidal level, ¡¥Soft Mud¡¦ was the main substratum type (50%) following by ¡¥Gravels and Boulders¡¦ (40%) and ¡¥Sand¡¦ (10%).

3.6.58    There was neither consistent vertical nor horizontal zonation pattern of substratum type in all sampling zones. Such heterogeneous variation should be caused by different hydrology (e.g. wave in different direction and intensity) received by the four sampling zones.

Soft shore communities

3.6.59    Table 3.4 of Appendix O lists the total abundance, density and number of taxon of every phylum in this survey. A total of 11025 individuals were recorded. Mollusca was the most abundant phylum (total abundance 10639 ind., density 355 ind. m-2, relative abundance 96.5%). The second was Arthropoda (200 ind., 7 ind. m-2, 1.8%) which followed by Sipuncula (86 ind., 3 ind. m-2, 0.8%) and Annelida (46 ind., 2 ind. m-2, 0.4%). Relatively other phyla were very low in abundances (density <2 ind. m-2, relative abundance £0.3%). Moreover, the most diverse phylum was Mollusca (32 taxa) followed by Arthropoda (7 taxa) and Annelida (3 taxa). There were 2 taxa recorded for Sipuncula and 1 taxon for other phyla.

3.6.60    The taxonomic resolution and complete list of recorded fauna are shown in Annexes IV and V of Appendix O respectively. As reported in June 2018, taxonomic revision of three potamidid snail species was conducted according to the latest identification key published by Agriculture, Fisheries and Conservation Department (details see AFCD, 2018), the species names of following gastropod species were revised:

¡P     Cerithidea cingulata was revised as Pirenella asiatica

¡P     Cerithidea djadjariensis was revised as Pirenella incisa

¡P     Cerithidea rhizophorarum was revised as Cerithidea moerchii

Moreover, taxonomic revision was conducted on another snail species while the specie name was revised:

¡P         Batillaria bornii was revised as Clypeomorus bifasciata 

3.6.61    Table 3.5 of Appendix O shows the number of individual, relative abundance and density of each phylum in every sampling zone. The total abundance (2227 ¡V 3176 ind.) varied among the four sampling zones while the phyla distributions were similar. In general, Mollusca was the most dominant phylum (no. of individuals: 2146 ¡V 3061 ind.; relative abundance 95.8 ¡V97.4%; density 286 - 408 ind. m-2). Other phyla were much lower in number of individuals. Arthropoda (35 - 61 ind.; 1.2 - 2.2%; 5 - 8 ind. m-2), Sipuncula (15 - 35 ind.; 0.7 - 1.0%; 2 - 4 ind. m-2) were common phyla relatively. Other phyla were very low in abundance in all sampling zones.

Dominant species in every sampling zone

3.6.62    Table 3.6 of Appendix O lists the abundant species in every sampling zone. In the present survey, most of the listed abundant species were of high or very high density (>100 ind. m-2), which were regarded as dominant species. Few of the listed species were of low to moderate densities (42 ¡V 100 ind. m-2). Other listed species of lower density (<42 ind. m-2) were regarded as common species.

3.6.63    In TC1, the substratum was mainly ¡¥Gravels and Boulders¡¦ at high and mid tidal levels. At high tidal level, the rock oyster Saccostrea cucullata (mean density 133 ind. m-2; relative abundance 38%) was the dominant species found at high density and the gastropod Monodonta labio (87 ind. m-2; relative abundance 25%) were of low to moderate densities. At mid tidal level, the rock oyster Saccostrea cucullata (140 ind. m-2, 37%) was of dominant species with high density. Meanwhile, the gastropod Monodonta labio (82 ind. m-2, 21%) found at low to moderate density. At low tidal level (main substratum types ¡¥Soft mud¡¦), the rock oyster Saccostrea cucullata (158 ind. m-2, 36%) was dominant at high density and the gastropod Monodonta labio (85 ind. m-2, 19%) was of low to moderate densities/

3.6.64    In TC2, the substratum types were mainly 'Gravels and Boulders' at high tidal level. The rock oyster Saccostrea cucullata (141 ind. m-2, 31%) and the gastropod Monodonta labio (104 ind. m-2, 23%) were dominant at high density. The gastropod Batillaria multiformis (82 ind. m-2, 18%) were at low - moderate density. At mid tidal level (major substratum type ¡¥Gravels and Boulders¡¦), rock oyster Saccostrea cucullata (127 ind. m-2, 29%) was dominant at high density. The gastropods Batillaria zonalis (96 ind. m-2, 22%) and Monodonta labio (92 ind. m-2, 21%) were at low ¡V moderate density level. Substratum types ¡¥Gravels and Boulders¡¦ was mainly distributed at low tidal level, rock oyster Saccostrea cucullata (138 ind. m-2, 36%) was dominant at high density while the gastropod Monodonta labio (88 ind. m-2, 23%) was at low ¡V moderate density level.

3.6.65    In TC3, the substratum type was mainly ¡¥Gravels and Boulders¡¦ at high tidal level. The rock oyster Saccostrea cucullata (141 ind. m-2, 52%) was of dominant species at high density. At mid tidal level, ¡¥Gravels and Boulders¡¦ was the mainly substratum type. The rock oyster Saccostrea cucullata (76 ind. m-2, 26%) , the gastropod Batillaria multiformis (76 ind. m-2, 26%), the gastropod Monodonta labio (44 ind. m-2, 15%) were at low ¡V moderate density level. At low tidal level, the major substratum type was ¡¥Gravels and Boulders¡¦. There was dominated by rock oyster Saccostrea cucullate (146 ind. m-2, 44%) at high density.

3.6.66    In ST, the major substratum type was ¡¥Gravels and Boulders¡¦ at high tidal level. At high tidal level, the rock oyster Saccostrea cucullata (151 ind. m-2, 35%) was abundant at high densities. The gastropods Batillaria multiformis (66 ind. m-2, 15%) and Monodonta labio (92 ind. m-2, 22%) were at low - moderate density. At mid tidal level, the main substratum type was ¡¥Gravels and Boulders¡¦. The rock oyster Saccostrea cucullata (136 ind. m-2, 42%) was the dominant species at high density, and followed by the gastropod Monodonta labio (73 ind. m-2, 22%) at low to moderate density. At low tidal level (major substratum: ¡¥Soft mud¡¦), the rock oyster Saccostrea cucullata (103 ind. m-2, 31 %) was the dominant species at high density. The gastropod Monodonta labio (52 ind. m-2, 16%) was the species at low ¡V moderate density.

3.6.67    In general, there was no consistent zonation pattern of species distribution across all sampling zones and tidal levels. The species distribution was determined by the type of substratum primarily. In general, rock oyster Saccostrea cucullata (2507 ind.), gastropods Monodonta labio (1262 ind.) and Batillaria multiformis (389 ind.) were the most common species on gravel and boulders substratum. Rock oyster Saccostrea cucullata (S: 717 ind.¡¦ M: 752 ind.) was the most common species on sandy and soft mud substrata.

Biodiversity and abundance of soft shore communities

3.6.68    Table 3.7 of Appendix O shows the mean values of species number, density, and biodiversity index H¡¦ and species evenness J of soft shore communities at every tidal level and in every sampling zone. As mentioned above, the differences among sampling zones and tidal levels were determined by the major type of substratum primarily.

3.6.69    Among the sampling zones, the mean species number was similar (12 ¡V 15 spp. 0.25 m-2) among the four sampling zones. The mean densities of TC1 (423 ind. m-2) was higher than TC1 (398 ind. m-2) followed by ST (361 ind. m-2) and TC3 (297 ind. m-2). The higher densities of TC2 and TC1 are due to the relatively high number of individuals in each quadrat. TC1 and ST were relatively higher in H¡¦ (1.90 and 1.97) and followed by TC2 and TC3 (both 1.87). Comparing with TC1, TC3 and ST (all J: 0.73), TC2 (0.77) were higher in J which were due to their higher species number and even taxa distribution.

3.6.70    In the present survey, no clear trend of mean species number, mean density, H¡¦ and J observed among the tidal level.

3.6.71    Figures 3.14 to 3.17 of Appendix O show the temporal changes of mean species number, mean density, H¡¦ and J at every tidal level and in every sampling zonealong the sampling months. In general, all the biological parameters fluctuated seasonally throughout the monitoring period. Lower mean species number and density were recorded in dry season (December) but the mean H' and J fluctuated within a limited range.

3.6.72    From June to December 2017, there were steady decreasing trends of mean species number and density in TC2, TC3 and ST regardless of tidal levels. It might be an unfavorable change reflecting environmental stresses. The heat stress and serial cyclone hit were believed the causes during the wet season of 2017. From March 2018 to December 2020 (present survey), increases of mean species number and density were observed in all sampling zones. It indicated the recovery of intertidal community.

Impact of the HKLR project

3.6.73    It was the 33rd survey of the EM&A programme during the construction period. Based on the results, impacts of the HKLR project were not detected on intertidal soft shore community. Abnormal phenomena (e.g. rapid, consistent or non-seasonal decline of fauna densities and species number) were not recorded.

 

3.7                Solid and Liquid Waste Management Status

3.7.1       The Contractor registered with EPD as a Chemical Waste Producer on 12 July 2012 for the Contract. Sufficient numbers of receptacles were available for general refuse collection and sorting.

3.7.2       The summary of waste flow table is detailed in Appendix K.

3.7.3       The Contractor was reminded that chemical waste containers should be properly treated and stored temporarily in designated chemical waste storage area on site in accordance with the Code of Practice on the Packaging, Labelling and Storage of Chemical Wastes.

3.8                Environmental Licenses and Permits

3.8.1       The valid environmental licenses and permits during the reporting period are summarized in Appendix L.


4        Environmental Complaint and Non-compliance

4.1                Environmental Exceedances

4.1.1       The summaries of the environmental exceedances are presented as follows:

Air Quality

4.1.2       No Action Level and Limit level exceedances of 1-hr TSP and 24-hr TSP were recorded at AMS5 and AMS6 during the reporting period.

Noise  

4.1.3       No Action/Limit Level exceedances for noise were recorded during daytime on normal weekdays of the reporting period. 

Water Quality

4.1.4       The water quality monitoring programme was temporarily suspended during the reporting period since no marine works were scheduled or conducted. Therefore, no water quality monitoring was conducted and no water monitoring results or exceedances are presented during the reporting period. 

Dolphin

4.1.5       The dolphin monitoring programme was temporarily suspended during the reporting period since no marine works were scheduled or conducted. Therefore, no quarterly analysis of dolphin monitoring results and exceedances from December 2020 to February 2021 are presented.

4.2                Summary of Environmental Complaint, Notification of Summons and Successful Prosecution

4.2.1       There was no complaint received in relation to the environmental impacts during this reporting period.

4.2.2       The details of cumulative statistics of Environmental Complaints are provided in Appendix N.

4.2.3       No notification of summons and prosecution was received during the reporting period. Statistics on notifications of summons and successful prosecutions are summarized in Appendix M.