Contract No.
HY/2011/03
Hong Kong-Zhuhai-Macao Bridge Hong Kong Link Road
Section between Scenic Hill and Hong Kong Boundary Crossing
Facilities
Monthly EM&A Report No.108 (September 2021)
15 October 2021
Revision
1
Main
Contractor Designer
Contents
Executive Summary
1.4 Construction
Works Undertaken During the Reporting Month
2....... Air Quality Monitoring
2.4 Monitoring
Parameters, Frequency and Duration
2.6 Monitoring
Schedule for the Reporting Month
3.4 Monitoring
Parameters, Frequency and Duration
3.6 Monitoring
Schedule for the Reporting Month
4....... Water
Quality Monitoring
4.3 Monitoring
Parameters, Frequency and Duration
4.6 Monitoring
Schedule for the Reporting Month
6.1 Sedimentation
Rate Monitoring
6.3 Mudflat
Ecology Monitoring Methodology
6.4 Event
and Action Plan for Mudflat Monitoring
6.5 Mudflat
Ecology Monitoring Results and Conclusion
7....... Environmental Site
Inspection and Audit
7.2 Advice
on the Solid and Liquid Waste Management Status
7.3 Environmental
Licenses and Permits
7.4 Implementation
Status of Environmental Mitigation Measures
7.5 Summary
of Exceedances of the Environmental Quality Performance Limit
7.6 Summary
of Complaints, Notification of Summons and Successful Prosecution
8.1 Construction
Programme for the Coming Months
8.2 Environmental
Monitoring Schedule for the Coming Month
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 Calibration
Certificates
Appendix D Monitoring
Schedule
Appendix E Monitoring
Data and Graphical Plots
Appendix F Event
and Action Plan
Appendix I Mudflat
Monitoring Results
Appendix K Cumulative
Statistics on Complaints
Appendix L Environmental
Licenses and Permits
Appendix M Implementation
Schedule of Environmental Mitigation Measures
Appendix N Record
of ¡§Notification of Summons and Prosecutions¡¨
Appendix O Location
of Works Areas
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 Environmental Impact Assessment (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.
This is the 108th
Monthly 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 to 30 September 2021.
Environmental
Monitoring and Audit Progress
The monthly EM&A programme
was undertaken in accordance with the Updated EM&A Manual for HKLR (Version
1.0). A summary of the monitoring activities during this reporting month is
listed below:
1-hr TSP Monitoring at
AMS5 |
3, 9, 15, 21, 27 and 30 September
2021 |
24-hr TSP Monitoring at
AMS5 |
2, 8, 14, 20, 24 and 29 September 2021 |
Noise Monitoring |
9, 15, 21 and 27
September 2021 |
Water Quality Monitoring |
Not applicable. Water
quality monitoring was temporarily suspended during the reporting month. |
Chinese White Dolphin
Monitoring |
Not applicable. Dolphin
monitoring was temporarily suspended during the reporting month. |
Site Inspection |
1, 8,
15, 24 and 30 September 2021
|
Mudflat Monitoring (Ecology) |
3, 6,
16 and 17 September 2021
|
Mudflat Monitoring (Sedimentation Rate) |
4
September 2021
|
The existing air quality
monitoring location AMS6 - Dragonair / CNAC (Group) Building (HKIA) was
handed over to Airport Authority Hong Kong on 31 March 2021. 1-hr and 24-hr
TSP monitoring at AMS6 was temporarily suspended starting from 1 April 2021.
A new alternative air quality monitoring location is still under
processing. |
Breaches of Action and Limit Levels
A summary of environmental exceedances
for this reporting month 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) |
N.A. (See Remark 1) |
N.A. (See Remark 1) |
Turbidity level |
N.A. (See Remark 1) |
N.A. (See Remark 1) |
|
Dissolved oxygen level (DO) |
N.A. (See Remark 1) |
N.A. (See Remark 1) |
Remark: 1) Not applicable. Water
quality monitoring was temporarily suspended during the reporting month.
Complaint Log
There was no complaint
received in relation to the environmental impacts during this reporting month.
Notifications
of Summons and Prosecutions
There were no notifications
of summons or prosecutions received during this reporting month.
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.
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.
The existing air quality monitoring location AMS6 - Dragonair / CNAC
(Group) Building (HKIA) was handed over to Airport Authority Hong Kong on 31
March 2021. 1-hr and 24-hr TSP monitoring at AMS6 was temporarily suspended
starting from 1 April 2021. A new alternative air quality monitoring location
is still under processing.
The role and
responsibilities as the IEC of the Contract has been taken up by Mr Brian Tam
instead of Mr Manson Yeung since 12 April 2021.
Future Key
Issues
The future key issues
include potential noise, air quality, water quality and ecological impacts and
waste management arising from the following construction activities to be
undertaken in the upcoming month:
¡P
New reclamation along
the east coast of the approximately 23 hectares.
¡P
Tunnel of Scenic Hill
(Tunnel SHT) from Scenic Hill to the new reclamation, of approximately 1km in
length with three (3) lanes for the east bound carriageway heading to the HKBCF
and four (4) lanes for the westbound carriageway heading to the HZMB Main
Bridge.
¡P
An abutment of the
viaduct portion of the HKLR at the west portal of Tunnel SHT and associated
road works at the west portal of Tunnel SHT.
¡P
An at grade road on
the new reclamation along the east coast of the HKIA to connect with the HKBCF,
of approximately 1.6 km along dual 3-lane carriageway with hard shoulder for
each bound.
¡P
Road links between
the HKBCF and the HKIA including new roads and the modification of existing
roads at the HKIA, involving viaducts, at grade roads and a Tunnel HAT.
¡P
A highway operation
and maintenance area (HMA) located on the new reclamation, south of the
Dragonair Headquarters Building, including the construction of buildings,
connection roads and other associated facilities.
¡P
Associated civil,
structural, building, geotechnical, marine, environmental protection,
landscaping, drainage and sewerage, tunnel and highway electrical and
mechanical works, together with the installation of street lightings, traffic
aids and sign gantries, water mains and fire hydrants, provision of facilities
for installation of traffic control and surveillance system (TCSS),
reprovisioning works of affected existing facilities, implementation of
transplanting, compensatory planting and protection of existing trees, and
implementation of an environmental monitoring and audit (EM&A) program.
Table 1.1 Contact
Information of Key Personnel
Party |
Position |
Name |
Telephone |
Fax |
Supervising
Officer¡¦s Representative |
(Chief Resident Engineer, CRE) |
Jackson Wong |
3968 4802 |
2109 1882 |
Environmental Project Office / Independent Environmental Checker |
Environmental Project Office Leader |
Y. H. Hui |
3465 2888 |
3465 2899 |
Independent Environmental Checker |
Brian Tam |
9700 6767 |
3465 2899 |
|
Contractor |
Project Manager |
S. Y. Tse |
3968 7002 |
2109 2588 |
Environmental Officer |
Federick Wong |
3968 7117 |
2109 2588 |
|
Environmental Team (Meinhardt Infrastructure and Environment Limited) |
Environmental Team Leader |
Claudine Lee |
2859 5409 |
2559 0738 |
24 hours complaint
hotline |
--- |
--- |
5699 5730 |
--- |
|
Table 1.2 Construction Activities During Reporting Month
Description of Activities |
Site Area |
Landscape
maintenance works |
SHT East Portal |
Table 2.1 Action
and Limit Levels for 1-hour TSP
Monitoring Station |
Action Level, µg/m3 |
Limit Level, µg/m3 |
AMS 5 ¡V Ma Wan Chung Village (Tung Chung) |
352 |
500 |
AMS 6 ¡V Dragonair / CNAC (Group) Building (HKIA) |
360 |
Table 2.2 Action
and Limit Levels for 24-hour TSP
Monitoring Station |
Action Level, µg/m3 |
Limit Level, µg/m3 |
AMS 5 ¡V Ma Wan Chung Village (Tung Chung) |
164 |
260 |
AMS 6 ¡V Dragonair / CNAC (Group) Building (HKIA) |
173 |
260 |
Table 2.3 Air
Quality Monitoring Equipment
Equipment |
Brand and Model |
Portable direct reading dust meter (1-hour
TSP) |
Sibata Digital Dust Indicator (Model No.
LD-5R) |
High Volume Sampler |
Tisch Environmental Mass Flow Controlled
Total Suspended Particulate (TSP) High Volume Air Sampler (Model No. TE-5170) |
Table 2.4 Locations
of Impact Air Quality Monitoring
Stations
Monitoring
Station |
Location |
AMS5 |
Ma Wan Chung Village (Tung Chung) |
AMS6 |
Dragonair / CNAC (Group) Building (HKIA) |
Table 2.5 Air
Quality Monitoring Parameters, Frequency and Duration
Parameter |
Frequency
and Duration |
1-hour TSP |
Three times every 6 days while the highest dust impact was expected |
24-hour TSP |
Once every 6 days |
(a) The HVS was installed in the vicinity of the air sensitive receivers.
The following criteria were considered in the installation of the HVS.
(i) A horizontal platform with appropriate support to secure the sampler
against gusty wind was provided.
(ii) The distance between the HVS and any obstacles, such as buildings, was
at least twice the height that the obstacle protrudes above the HVS.
(iii) A minimum of 2 meters separation from walls, parapets and penthouse for
rooftop sampler was provided.
(iv) No furnace or incinerator flues are nearby.
(v) Airflow around the sampler was unrestricted.
(vi) Permission was obtained to set up the samplers and access to the
monitoring stations.
(vii) A secured supply of electricity was obtained to operate the samplers.
(viii) The sampler was located more than 20 meters from any dripline.
(ix) Any wire fence and gate, required to protect the sampler, did not
obstruct the monitoring process.
(x) Flow control accuracy was kept within ¡Ó2.5% deviation over 24-hour
sampling period.
(b)
Preparation of Filter Papers
(i)
Glass fibre filters, G810 were labelled and sufficient filters that were
clean and without pinholes were selected.
(ii)
All filters were equilibrated in the conditioning environment for 24
hours before weighing. The conditioning environment temperature was around
(iii)
All filter papers were prepared and analysed by ALS Technichem (HK) Pty
Ltd., which is a HOKLAS accredited laboratory and has comprehensive quality
assurance and quality control programmes.
(c) Field
Monitoring
(i) The power supply was checked to ensure the HVS works properly.
(ii) The filter holder and the area surrounding the filter were cleaned.
(iii) The filter holder was removed by loosening the four bolts and a new
filter, with stamped number upward, on a supporting screen was aligned
carefully.
(iv) The filter was properly aligned on the screen so that the gasket formed
an airtight seal on the outer edges of the filter.
(v)
The swing bolts were fastened to hold the filter holder down to the
frame. The pressure applied was
sufficient to avoid air leakage at the edges.
(vi) Then the shelter lid was closed and was secured with the aluminium
strip.
(vii) The HVS was warmed-up for about 5 minutes to establish run-temperature
conditions.
(viii) A new flow rate record sheet was set into the flow recorder.
(ix)
On site temperature and atmospheric pressure readings were taken and the
flow rate of the HVS was checked and adjusted at around 1.1 m3/min,
and complied with the range specified in the Updated EM&A Manual for HKLR
(Version 1.0) (i.e. 0.6-1.7 m3/min).
(x) The programmable digital timer was set for a sampling period of 24
hours, and the starting time, weather condition and the filter number were
recorded.
(xi) The initial elapsed time was recorded.
(xii) At the end of sampling, on site temperature and atmospheric pressure
readings were taken and the final flow rate of the HVS was checked and
recorded.
(xiii)
The final elapsed time was recorded.
(xiv)
The sampled filter was removed carefully and folded in half length so
that only surfaces with collected particulate matter were in contact.
(xv)
It was then placed in a clean plastic envelope and sealed.
(xvi) All monitoring information was recorded on a standard data sheet.
(xvii) Filters were then sent to ALS Technichem (HK) Pty Ltd. for analysis.
(d)
Maintenance and Calibration
(i) The HVS and its accessories were maintained in good working condition,
such as replacing motor brushes routinely and checking electrical wiring to
ensure a continuous power supply.
(ii) 5-point calibration of the HVS was conducted using TE
(iii) Calibration certificate of the HVSs are provided in Appendix C.
(a) Measuring Procedures
The measuring procedures of
the 1-hour dust meter were in accordance with the Manufacturer¡¦s Instruction
Manual as follows:-
(i)
Turn the power on.
(ii)
Close the air collecting opening cover.
(iii)
Push the ¡§TIME SETTING¡¨ switch to [BG].
(iv)
Push ¡§START/STOP¡¨ switch to perform background measurement for 6
seconds.
(v)
Turn the knob at SENSI ADJ position to insert the light scattering
plate.
(vi)
Leave the equipment for 1 minute upon ¡§SPAN CHECK¡¨ is indicated in the
display.
(vii)
Push ¡§START/STOP¡¨ switch to perform automatic sensitivity adjustment.
This measurement takes 1 minute.
(viii)
Pull out the knob and return it to MEASURE position.
(ix)
Push the ¡§TIME SETTING¡¨ switch the time set in the display to 3 hours.
(x)
Lower down the air collection opening cover.
(xi)
Push ¡§START/STOP¡¨ switch to start measurement.
(b) Maintenance
and Calibration
(i) The 1-hour TSP meter
was calibrated at 1-year intervals against a Tisch Environmental Mass Flow
Controlled Total Suspended Particulate (TSP) High Volume Air Sampler.
Calibration certificates of the Laser Dust Monitors are provided in Appendix C.
Table 2.6 Summary
of 1-hour TSP Monitoring Results During the Reporting Month
Monitoring Station |
Average (mg/m3) |
Range (mg/m3) |
Action Level (mg/m3) |
Limit Level (mg/m3) |
AMS5 |
29 |
17 - 46 |
352 |
500 |
AMS6 |
/ |
/ |
360 |
500 |
Table 2.7 Summary of 24-hour TSP Monitoring Results During the
Reporting Month
Monitoring Station |
Average (mg/m3) |
Range (mg/m3) |
Action Level (mg/m3) |
Limit Level (mg/m3) |
AMS5 |
31 |
12 - 53 |
164 |
260 |
AMS6 |
/ |
/ |
173 |
260 |
Table 3.1 Action
and Limit Levels for Noise during Construction Period
Monitoring Station |
Time Period |
Action Level |
Limit Level |
NMS5 ¡V Ma Wan Chung
Village (Ma Wan Chung Resident Association) (Tung Chung) |
0700-1900 hours on normal
weekdays |
When one documented
complaint is received |
75 dB(A) |
Table 3.2 Noise
Monitoring Equipment
Equipment |
Brand and Model |
Integrated Sound Level
Meter |
B&K 2238 |
Acoustic Calibrator |
B&K 4231 |
Table 3.3 Locations
of Impact Noise Monitoring Stations
Monitoring Station |
Location |
NMS5 |
Ma Wan Chung Village (Ma Wan
Chung Resident Association) (Tung Chung) |
Table 3.4 Noise
Monitoring Parameters, Frequency and Duration
Parameter |
Frequency and Duration |
30-mins measurement at
each monitoring station between 0700 and 1900 on normal weekdays (Monday to
Saturday). Leq, L10 and L90 would be
recorded. |
At least once per week |
(a) The sound level meter was
set on a tripod at a height of
(b)
The battery condition was
checked to ensure the correct functioning of the meter.
(c)
Parameters such as
frequency weighting, the time weighting and the measurement time were set as
follows:-
(i) frequency weighting:
A
(ii) time weighting: Fast
(iii) time
measurement: Leq(30-minutes) during non-restricted hours i.e. 07:00
¡V 1900 on normal weekdays
(d)
Prior to and after each
noise measurement, the meter was calibrated using the acoustic calibrator for
94.0 dB(A) at 1000 Hz. If the
difference in the calibration level before and after measurement was more than
1.0 dB(A), the measurement would be considered invalid and repeat of noise
measurement would be required after re-calibration or repair of the equipment.
(e)
During the monitoring
period, the Leq, L10 and L90 were
recorded. In addition, site
conditions and noise sources were recorded on a standard record sheet.
(f)
Noise measurement was
paused during periods of high intrusive noise (e.g. dog barking, helicopter
noise) if possible. Observations were recorded when intrusive noise was
unavoidable.
(g)
Noise monitoring was
cancelled in the presence of fog, rain, wind with a steady speed exceeding
(a) The microphone head of the sound level
meter was cleaned with soft cloth at regular intervals.
(b) The meter and calibrator
were sent to the supplier or HOKLAS laboratory to check and calibrate at yearly
intervals.
(c) Calibration certificates
of the sound level meters and acoustic calibrators are provided in Appendix C.
Table 3.5 Summary
of Construction Noise Monitoring Results During the Reporting Month
Monitoring Station |
Average Leq (30 mins),
dB(A) |
Range of Leq (30 mins),
dB(A) |
Limit Level Leq (30 mins),
dB(A) |
NMS5 |
61 |
58 - 63 |
75 |
Table 4.1 Action
and Limit Levels for Water Quality
Parameter (unit) |
Water Depth |
Action Level |
Limit Level |
Dissolved Oxygen (mg/L)
(surface, middle and bottom) |
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.
Table 4.2 Water
Quality Monitoring Equipment
Equipment |
Brand and Model |
DO and Temperature Meter,
Salinity Meter, Turbidimeter and pH Meter |
N.A. (See Remark 1) |
Positioning Equipment |
N.A. (See Remark 1) |
Water Depth Detector |
N.A. (See Remark 1) |
Water Sampler |
N.A. (See Remark 1) |
Remark: 1. Not applicable. Water quality monitoring was temporarily suspended
during the reporting month. |
Table 4.3 Impact
Water Quality Monitoring Parameters and Frequency
Monitoring Stations |
Parameter, unit |
Frequency |
No. of depth |
Impact Stations: Control/Far Field
Stations: Sensitive Receiver
Stations: |
¡P
Depth, m ¡P
Temperature, oC ¡P
Salinity, ppt ¡P
Dissolved Oxygen
(DO), mg/L ¡P
DO Saturation, % ¡P
Turbidity, NTU ¡P
pH ¡P Suspended Solids (SS), mg/L |
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). |
Remark:
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) were 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) since 21 August 2019.
2) The water quality monitoring programme was temporarily suspended
during the reporting month since no marine works were scheduled or conducted,
therefore no water quality monitoring was conducted.
Table 4.4 Impact
Water Quality Monitoring Stations
Monitoring Stations |
Description |
Coordinates |
|
Easting |
Northing |
||
IS5 |
Impact Station (Close to
HKLR construction site) |
811579 |
817106 |
IS(Mf)6 |
Impact Station (Close to
HKLR construction site) |
812101 |
817873 |
IS7 |
Impact Station (Close to
HKBCF construction site) |
812244 |
818777 |
IS8(N) |
Impact Station (Close to
HKBCF construction site) |
814413 |
818570 |
IS(Mf)9 |
Impact Station (Close to
HKBCF construction site) |
813273 |
818850 |
IS10(N) |
Impact Station (Close to
HKBCF construction site) |
812942 |
820881 |
SR3(N) |
Sensitive receivers (San
Tau SSSI) |
810689 |
816591 |
SR4(N2) |
Sensitive receivers (Tai
Ho Inlet) |
814688 |
817996 |
SR5(N) |
Sensitive Receivers
(Artificial Reef in NE Airport) |
812569 |
821475 |
SR10A(N) |
Sensitive receivers (Ma
Wan Fish Culture Zone) |
823644 |
823484 |
SR10B(N2) |
Sensitive receivers (Ma
Wan Fish Culture Zone) |
823689 |
823159 |
CS2(A) |
Control Station (Mid-Ebb) |
805232 |
818606 |
CS(Mf)5 |
Control Station
(Mid-Flood) |
817990 |
821129 |
|
(a) The in-situ
water quality parameters including dissolved oxygen, temperature, salinity and
turbidity, pH were measured by multi-parameter meters.
(a) Digital Differential Global Positioning Systems
(DGPS) were used to ensure that the correct location was selected prior to
sample collection.
(b) Portable, battery-operated echo sounders were used
for the determination of water depth at each designated monitoring station.
(c) All in-situ measurements were taken at 3 water
depths, 1 m below water surface, mid-depth and 1 m above sea bed, except where
the water depth was less than 6 m, in which case the mid-depth station was
omitted. Should the water depth be less than 3 m, only the mid-depth station
was monitored.
(d) At each measurement/sampling depth, two consecutive
in-situ monitoring (DO concentration and saturation, temperature, turbidity,
pH, salinity) and water sample for SS. The probes were retrieved out of the
water after the first measurement and then re-deployed for the second
measurement. Where the difference in the value between the first and second
readings of DO or turbidity parameters was more than 25% of the value of the
first reading, the reading was discarded and further readings were taken.
(e) Duplicate samples from each independent sampling
event were collected for SS measurement. Water samples were collected using the
water samplers and the samples were stored in high-density polythene bottles.
Water samples collected were well-mixed in the water sampler prior to
pre-rinsing and transferring to sample bottles. Sample bottles were pre-rinsed
with the same water samples. The sample bottles were then be packed in
cool-boxes (cooled at 4oC without being frozen), and delivered to
ALS Technichem (HK) Pty Ltd. for the analysis of suspended solids
concentrations. The laboratory determination work would be started within 24
hours after collection of the water samples. ALS Technichem (HK) Pty Ltd. is a
HOKLAS accredited laboratory and has comprehensive quality assurance and
quality control programmes.
(f) The analysis method and detection limit for SS is
shown in Table 4.5.
Table 4.5 Laboratory
Analysis for Suspended Solids
Parameters |
Instrumentation |
Analytical
Method |
Detection
Limit |
Suspended Solid (SS) |
Weighting |
APHA 2540-D |
0.5mg/L |
(g) Other relevant data were recorded, including
monitoring location / position, time, water depth, tidal stages, weather
conditions and any special phenomena or work underway at the construction site
in the field log sheet for information.
Table 5.1 Action
and Limit Levels for Dolphin Monitoring
|
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 encounter
rate of number of dolphin sightings.
2.
ANI means quarterly
encounter rate of total number of dolphins.
3.
For North Lantau
Social Cluster, AL will be trigger if either NEL or NWL fall below the criteria; LL will be triggered if both NEL and NWL fall below the criteria.
Table 5.2 Co-ordinates
of Transect Lines
Line No. |
Easting |
Northing |
|
Line No. |
Easting |
Northing |
||
1 |
Start Point |
804671 |
815456 |
|
13 |
Start Point |
816506 |
819480 |
1 |
End Point |
804671 |
831404 |
|
13 |
End Point |
816506 |
824859 |
2 |
Start Point |
805476 |
820800* |
|
14 |
Start Point |
817537 |
820220 |
2 |
End Point |
805476 |
826654 |
|
14 |
End Point |
817537 |
824613 |
3 |
Start Point |
806464 |
821150* |
|
15 |
Start Point |
818568 |
820735 |
3 |
End Point |
806464 |
822911 |
|
15 |
End Point |
818568 |
824433 |
4 |
Start Point |
807518 |
821500* |
|
16 |
Start Point |
819532 |
821420 |
4 |
End Point |
807518 |
829230 |
|
16 |
End Point |
819532 |
824209 |
5 |
Start Point |
808504 |
821850* |
|
17 |
Start Point |
820451 |
822125 |
5 |
End Point |
808504 |
828602 |
|
17 |
End Point |
820451 |
823671 |
6 |
Start Point |
809490 |
822150* |
|
18 |
Start Point |
821504 |
822371 |
6 |
End Point |
809490 |
825352 |
|
18 |
End Point |
821504 |
823761 |
7 |
Start Point |
810499 |
822000* |
|
19 |
Start Point |
822513 |
823268 |
7 |
End Point |
810499 |
824613 |
|
19 |
End Point |
822513 |
824321 |
8 |
Start Point |
811508 |
821123 |
|
20 |
Start Point |
823477 |
823402 |
8 |
End Point |
811508 |
824254 |
|
20 |
End Point |
823477 |
824613 |
9 |
Start Point |
812516 |
821303 |
|
21 |
Start Point |
805476 |
827081 |
9 |
End Point |
812516 |
824254 |
|
21 |
End Point |
805476 |
830562 |
10 |
Start Point |
813525 |
821176 |
|
22 |
Start Point |
806464 |
824033 |
10 |
End Point |
813525 |
824657 |
|
22 |
End Point |
806464 |
829598 |
11 |
Start Point |
814556 |
818853 |
|
23 |
Start Point |
814559 |
821739 |
11 |
End Point |
814556 |
820992 |
|
23 |
End Point |
814559 |
824768 |
12 |
Start Point |
815542 |
818807 |
|
24* |
Start Point |
805476* |
815900* |
12 |
End Point |
815542 |
824882 |
|
24* |
End Point |
805476* |
819100* |
Note:
Co-ordinates in red and marked with asterisk are revised co-ordinates of
transect line.
Methodology
6.1.1
To avoid
disturbance to the mudflat and nuisance to navigation, no fixed
marker/monitoring rod was installed at the monitoring stations. A high precision
Global Navigation Satellite System (GNSS) real time location fixing system (or
equivalent technology) was used to locate the station in the precision of 1mm,
which is reasonable under flat mudflat topography with uneven mudflat surface
only at micro level. This method
has been used on Agricultural Fisheries and Conservation Department¡¦s (AFCD)
project, namely Baseline Ecological Monitoring Programme for the Mai Po Inner
Deep Bay Ramsar Site for measurement of seabed levels.
6.1.2
Measurements
were taken directly on the mudflat surface. The Real Time Kinematic GNSS (RTK
GNSS) surveying technology was used to measure mudflat surface levels and 3D
coordinates of a survey point. The
RTK GNSS survey was calibrated against a reference station in the field before
and after each survey. The
reference station is a survey control point established by the Lands Department
of the HKSAR Government or traditional land surveying methods using professional
surveying instruments such as total station, level and/or geodetic GNSS. The coordinates system was in HK1980
GRID system. For this contract, the
reference control station was surveyed and established by traditional land
surveying methods using professional surveying instruments such as total station,
level and RTK GNSS. The accuracy
was down to mm level so that the reference control station has relatively
higher accuracy. As the reference
control station has higher accuracy, it was set as true evaluation relative to
the RTK GNSS measurement. All
position and height correction were adjusted and corrected to the reference
control station. Reference station
survey result and professional land surveying calibration is shown as Table 6.1:
Table 6.1 Reference
Station Survey result and GNSS RTK calibration result of Round 1
Reference Station |
Easting (m) |
Northing (m) |
Baseline reference elevation (mPD) (A) |
Round 1 Survey (mPD) (B) |
Calibration Adjustment (B-A) |
T1 |
811248.660mE |
816393.173mN |
3.840 |
3.817 |
-0.023 |
T2 |
810806.297mE |
815691.822mN |
4.625 |
4.653 |
+0.028 |
T3 |
810778.098mE |
815689.918mN |
4.651 |
4.660 |
+0.009 |
T4 |
810274.783mE |
816689.068mN |
2.637 |
2.709 |
+0.072 |
6.1.3
The precision
of the measured mudflat surface level reading (vertical precision setting) was
within 10 mm (standard deviation) after averaging the valid survey records of
the XYZ HK1980 GRID coordinates.
Each survey record at each station was computed by averaging at least
three measurements that are within the above specified precision setting. Both digital
data logging and written records were collected in the field. Field data on
station fixing and mudflat surface measurement were recorded.
Monitoring Locations
6.1.4
Four
monitoring stations were established based on the site conditions for the
sedimentation monitoring and are shown in Figure 6.1.
Monitoring Results
6.1.5
The baseline
sedimentation rate monitoring was in September 2012 and impact sedimentation
rate monitoring was undertaken on 4 September 2021. The mudflat surface levels
at the four established monitoring stations and the corresponding XYZ HK1980
GRID coordinates are presented in Table
6.2 and Table 6.3.
Table 6.2 Measured
Mudflat Surface Level Results
Baseline Monitoring
(September 2012) |
Impact Monitoring
(September 2021) |
|||||
Monitoring
Station |
Easting
(m) |
Northing
(m) |
Surface
Level (mPD) |
Easting
(m) |
Northing
(m) |
Surface
Level (mPD) |
S1 |
810291.160 |
816678.727 |
0.950 |
810291.169 |
816678.715 |
1.159 |
S2 |
810958.272 |
815831.531 |
0.864 |
810958.266 |
815831.526 |
0.991 |
S3 |
810716.585 |
815953.308 |
1.341 |
810716.589 |
815953.330 |
1.456 |
S4 |
811221.433 |
816151.381 |
0.931 |
811221.452 |
816151.409 |
1.136 |
Table 6.3 Comparison
of measurement
Comparison of measurement |
Remarks
and Recommendation |
|||
Monitoring Station |
Easting (m) |
Northing (m) |
Surface Level (mPD) |
|
S1 |
0.009 |
-0.012 |
0.209 |
Level continuously increased |
S2 |
-0.006 |
-0.005 |
0.127 |
Level continuously increased |
S3 |
0.004 |
0.022 |
0.115 |
Level continuously increased |
S4 |
0.019 |
0.028 |
0.205 |
Level continuously increased |
6.1.6
This measurement result was generally and
relatively higher than the baseline measurement at S1, S2, S3 and S4. The
mudflat level is continuously increased.
6.2.1
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.
6.2.2
Water quality monitoring in San Tau (monitoring
station SR3(N)) was conducted in September 2021 as part of mudflat monitoring.
The monitoring parameters included dissolved oxygen (DO), turbidity and
suspended solids (SS). The water
monitoring results for station SR3(N) were extracted and summarised below:
Table 6.4 Water
Quality Monitoring Results (Depth Average) at Station SR3(N)
Date |
Mid Ebb Tide |
Mid Flood Tide |
||||
DO (mg/L) |
Turbidity (NTU) |
SS (mg/L) |
DO (mg/L) |
Turbidity (NTU) |
SS (mg/L) |
|
02-Sep-2021 |
7.3 |
3.6 |
3.1 |
7.0 |
3.8 |
3.4 |
04-Sep-2021 |
6.5 |
4.4 |
3.4 |
6.4 |
4.6 |
3.5 |
07-Sep-2021 |
5.3 |
4.2 |
9.0 |
5.2 |
3.6 |
9.2 |
09-Sep-2021 |
5.3 |
4.7 |
4.5 |
5.4 |
4.2 |
5.2 |
11-Sep-2021 |
5.2 |
5.1 |
6.1 |
5.3 |
5.4 |
6.1 |
14-Sep-2021 |
5.2 |
4.6 |
4.2 |
5.5 |
5.3 |
3.9 |
16-Sep-2021 |
5.4 |
5.2 |
3.3 |
5.3 |
5.1 |
3.6 |
18-Sep-2021 |
6.4 |
5.2 |
4.8 |
6.2 |
5.5 |
3.2 |
21-Sep-2021 |
6.0 |
5.1 |
6.5 |
6.0 |
4.4 |
6.5 |
23-Sep-2021 |
6.4 |
5.7 |
5.6 |
5.7 |
5.5 |
5.4 |
25-Sep-2021 |
6.5 |
4.7 |
3.2 |
6.8 |
5.2 |
3.2 |
28-Sep-2021 |
6.3 |
5.2 |
1.6 |
6.6 |
4.8 |
1.1 |
30-Sep-2021 |
6.6 |
5.6 |
1.7 |
6.6 |
5.4 |
2.0 |
Average |
6.0 |
4.9 |
4.4 |
6.0 |
4.8 |
4.3 |
|
Sampling Zone
6.3.1
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 I). 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 I). Survey of horseshoe crabs, seagrass beds and
intertidal communities were conducted in every sampling zone. The present
survey was conducted in September 2021 (totally 4 sampling days 3rd
(for ST), 6th (for TC1), 16th (for TC2) and 17th
(for TC3).
6.3.2
Since the field survey
of June 2016, increasing number of trashes and even big trashes (Figure 2.3 of Appendix I) 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
6.3.3
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 3rd (for ST), 6th
(for TC1), 16th (for TC2) and 17th (for TC3) September
2021, which were sunny and hot days.
6.3.4
In June 2017, a big
horseshoe crab was tangled by a trash gill net in ST mudflat (Figure 2.3 of Appendix I). 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
6.3.5
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 3rd (for
ST), 6th (for TC1), 16th (for TC2) and 17th
(for TC3) September 2021, which were sunny and hot days.
Intertidal Soft Shore Communities
6.3.6
The intertidal soft shore community surveys
were conducted in low tide period on 3rd (for ST), 6th
(for TC1), 16th (for TC2) and 17th (for TC3) September
2021. 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.
6.3.7
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.
6.3.8
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.
6.3.9
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
6.3.10 Data collected from direct counting 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.
6.4.1
In the event
of the impact monitoring results indicating that the density or the
distribution pattern of intertidal fauna and seagrass is found to be
significant different to the baseline condition (taking into account natural
fluctuation in the occurrence and distribution pattern such as due to seasonal
change), appropriate actions should be taken and additional mitigation measures
should be implemented as necessary.
Data should then be re-assessed and the need for any further monitoring
should be established. The action plan, as given in Table 6.5 should be undertaken within a period of 1 month after a
significant difference has been determined.
Table 5.5 Event
and Action Plan for Mudflat Monitoring
Event |
ET Leader |
IEC |
SO |
Contractor |
Density or the distribution pattern of horseshoe
crab, seagrass or intertidal soft shore communities recorded in the
impact or post-construction monitoring are significantly lower than or
different from those recorded in the baseline monitoring. |
Review historical data to ensure differences are as a result of
natural variation or previously observed seasonal differences; Identify source(s) of impact; Inform the IEC, SO and Contractor; Check monitoring data; Discuss additional monitoring and any other measures, with the IEC and
Contractor. |
Discuss monitoring with the ET and the Contractor; Review proposals for additional monitoring and any other measures
submitted by the Contractor and advise the SO accordingly. |
Discuss with the IEC additional monitoring requirements and any other
measures proposed by the ET; Make agreement on the measures to be implemented. |
Inform the SO and in writing; Discuss with the ET and the IEC and propose measures to the IEC and the
ER; Implement the agreed measures. |
Notes:
ET ¡V Environmental Team
IEC ¡V Independent Environmental Checker
SO ¡V Supervising Officer
Horseshoe Crabs
6.5.1
In total of 10 and 7 individuals of of Carcinoscorpius
rotundicauda and Tachypleus tridentatus were
found in present
survey. The recorded individuals were mainly distributed along the shoreline in ST and
TC3. 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 I and the present survey result regarding horseshoe
crab are presented in Table 3.1 of Appendix I. The complete survey records are presented
in Annex II of Appendix
I.
6.5.2
For Carcinoscorpius
rotundicauda, more
individuals (8 ind.) were found in ST with average body size 39.83 mm (prosomal
width ranged 31.26 ¡V 48.81 mm). In TC3, 2 individuals with average body size
38.12 mm (prosomal width ranged 35.56 ¡V 40.67 mm) were found in present survey.
The search record in ST (1.33 ind. hr-1. Person-1) and
TC3 (0.33 ind. hr-1. Person-1) were very low. No Carcinoscorpius
rotundicauda was recorded in TC1 and TC2 in present
survey.
6.5.3
For Tachypleus tridentatus, 7 individuals with average body size 40.92 mm
(prosomal width ranged 37.87 ¡V 44.25 mm) were found in ST. In TC3, only one
individual with body size 38.78 mm (prosomal width ranged 38.78mm) was found in
present survey. The search records in ST (1.00 ind. hr-1. Person-1)
and TC3 (0.17 ind. hr-1. Person-1) were very low. No Tachypleus
tridentatus was found in TC1 and TC2 in
present survey.
6.5.4
No mating pair or large individual (≥100mm) was found in present survey.
6.5.5
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 I). 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 I shows 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 I). No mating pair
was found in September 2021 (present survey).
6.5.6
No large individuals (prosomal
width >100mm) of Carcinoscorpius rotundicauda and Tachypleus tridentatus was recorded in September 2021
(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 I. 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.
6.5.7
No marked individual of horseshoe crab was recorded in
September 2021 (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.
6.5.8
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
6.5.9
Figure 3.5 and 3.6 of Appendix
I 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.
6.5.10
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 and TC3. From December 2018 to September 2019, the search records of Carcinoscorpius rotundicauda change from very low to low while the change of Tachypleus tridentatus was similar during
this period. Relatively higher population fluctuation of Carcinoscorpius rotundicauda was observed in TC3. From March 2020 to September 2020, the search
records of both species, Carcinoscorpius
rotundicauda and Tachypleus tridentatus, were increased
to moderate level in ST. However, the search records of both species, Carcinoscorpius rotundicauda and Tachypleus tridentatus,
were decreased from very
low to none in TC3 in this period. From March
2021 to September 2021 (present survey), the search records of both species, Carcinoscorpius
rotundicauda and Tachypleus tridentatus, were kept at low-moderate
level in both ST and TC3. It is similar to the previous findings of June. It
shows another growing phenomenon of horseshoe crab and it may due to the weather
variation of starting of wet season. The survey results were different from
previous findings that there were usually higher search records in September.
One possible reason was that September of 2021 was one of the hottest months in
Hong Kong in record. As such, hot and shiny weather decreased horseshoe crab
activity.
6.5.11
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.
Seasonal variation of horseshoe crab population
6.5.14
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
I). 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
ind. 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. In December 2020, the number of Carcinoscorpius rotundicauda and Tachypleus
tridentatus greatly decreased to 3 ind. and 7 ind., respectively. In September 2021 (present survey), the number of Carcinoscorpius
rotundicauda and Tachypleus tridentatus gradually decreased to 10
ind. and 7 ind., respectively in comparing with the September of previous
record. The drop of abundance may be related to the hot weather in September
2021. Throughout the monitoring period, similar distribution of horseshoe crabs
population were found.
6.5.15
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
I) 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.
6.5.16
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 Chung
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).
6.5.17
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. The
population size of Tachypleus tridentatus slightly decreased in ST from
March 2021 to September 2021 and the mean proposal width of them slightly
decreased to about 40.9mm.
6.5.18
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
6.5.19 Figure 3.7 of Appendix I 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.
6.5.20
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 33.97mm which is smaller
than that in December
2019. It was in normal fluctuation. From June 2020 to December 2020, no horseshoe crab was recorded in TC3. In
September 2021 (present survey), only one Tachypleus tridentatus with
body size (prosomal width 38.78mm) was found in TC3. The decrease in the species
population was considered to be related to hot weather in September, which may
affect their activity. 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
6.5.21 Figure 3.8 of Appendix I 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.
6.5.22 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.
6.5.23
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.
6.5.24
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, 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. In September 2021 (present survey), the population size of both horseshoe
crab species in ST was kept as low-moderate level while their body sizes were
mostly in small to medium range (~31¡V 48mm).
Impact of the HKLR project
6.5.25 It was the 36th 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 seasonal variation, no abnormal phenomenon of horseshoe
crab individual, such as large number of dead individuals on the shore had been
reported. The survey results of present survey were different from previous
findings that there were usually higher search records in September. One
possible reason was that September of 2021 was one of the hottest month in Hong
Kong in record. As such, hot and shiny weather decreased horseshoe crab
activity.
Seagrass Beds
6.5.26
Two seagrass
species Halophila ovalis and Zostera japonica were found in present
survey. Halophila ovalis was found in TC3 and ST and Zostera japonica
was found in ST. In ST, there were three small sized and three large sized of Halophila
ovalis found at tidal zone 1.5m above C.D nearby mangroves plantation. The
larger strand had area ~480m2 in high vegetation coverage (60 ¡V
70%), ~450m2 in high vegetation coverage (70 ¡V 80%) and ~288m2
in high vegetation coverage (80 ¡V 90%) At close vicinity, three small sized
(~4m2 -45m2) of Halophila ovalis beds were
observed at tidal zone 1.5m above C.D. All the small sized of Halophila
ovalis beds were in moderate to high vegetation coverage ranging from
50-80%. In TC3, 1 large patch and 2 small patches of Halophila ovalis
were found at tidal zone 1.5m above C.D. The larger strand had area ~350m2
in high vegetation coverage (70 ¡V 80%), while two small patches with area size
in ~30m2 and 64m2 had moderate coverage (50 to 70%). Another seagrass species Zostera
japonica was found at tidal zone 1.5m above C.D nearby mangroves plantation
with ~20m2 in moderate to high vegetation coverage (70 - 80%). Table
3.2 of Appendix
I summarizes the results of present seagrass beds survey and the
photograph records of the seagrass are shown on Figure 3.9 of Appendix
I. The complete record throughout the monitoring period is presented in Annex III of Appendix
I.
6.5.27
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 I). 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.
6.5.28
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
6.5.29
Figure
3.11 of Appendix I 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 March 2021, while no patch of Zostera japonica was found.
From June 2021, the species
was recorded again in area of 45m2. The recorded area of the
seagrass bed in present survey was slightly decreased to 20m2.
6.5.30
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.
6.5.31
In
December 2014, all the seagrass patches of Halophila
ovalis disappeared in ST. Figure
3.12 of Appendix
I 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
unfavorable conditions (Fong, 1998).
Unfavourable conditions to seagrass Halophila ovalis
6.5.32
Typhoon or strong water current was suggested as one unfavourable
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.
6.5.33
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).
6.5.34
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.
6.5.35
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
6.5.36 Figure 3.12 of Appendix I 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
6.5.37 In September
2017, the whole seagrass bed of Halophila
ovalis disappeared again along the shore of TC3 and ST (Figure 3.12 of Appendix I). 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.
6.5.38 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.
6.5.39 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.
6.5.40 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 I). 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
March 2021, the seagrass bed area in ST slightly
decreased from 1200 m2 to 942.05 m2, which were in normal fluctuation. From March 2021 to September 2021, the seagrass bed
area in ST increased from 942.05 m2 to 1299 m2, which
were in normal fluctuation.
Impact
of the HKLR project
6.5.41 It was the 36th
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 increased from March 2021 to September 2021.
Intertidal Soft Shore Communities
Substratum
6.5.42
Table 3.3 and Figure
3.13 of Appendix I 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: 70%; M: 40%) were recorded at high and mid tidal levels. Low
percentages of ¡¥Gravels and Boulders¡¦ (10%) and high percentage of ¡¥Soft mud¡¦ (50%) were recorded at low tidal level.
¡P
In TC2, high percentages of ¡¥Gravels and Boulders¡¦ (H: 70%) was recorded at
high tidal level. At mid tidal level was comprised of similar percentage of
three types of substratum. At low tidal level was majorly comprised by ¡§Sands¡¨
(50%), followed by ¡§Soft Mud¡¨ (40%) and ¡¥Gravels and Boulders¡¦ (10%).
¡P
In
TC3, higher percentage of ¡¥Gravels and Boulders¡¦ was recorded at high tidal level (H: 70%). At low and mid tidal levels,
three types of substratum were recorded in similar percentage.
¡P
In ST,
¡¥Gravels and Boulders¡¦ was the main substratum type (H: 70%; M: 60%) at high
tidal level and mid tidal level. At low tidal level, ¡¥Sands¡¦ was the main
substratum type (50%) following by ¡¥Soft Mud¡¦ (40%) and ¡¥Sand¡¦ (10%).
6.5.43
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
6.5.44
Table 3.4 of Appendix I lists the total abundance, density and
number of taxon of every phylum in this survey. A total of 9018 individuals
were recorded. Mollusca was the most abundant phylum (total abundance 7897 ind.,
density 263 ind. m-2, relative abundance 87.6%). The second was
Arthropoda (786 ind., 26 ind. m-2, 8.7%) which followed by Annelida
(164 ind., 5 ind. m-2, 1.8%) and Sipuncular (105 ind., 4 ind. m-2,
1.2%). Relatively other phyla were very low in abundances (density <1 ind. m-2,
relative abundance < 0.3%). Moreover, the most diverse phylum was
Mollusca (31 taxa) followed by Arthropoda (6 taxa) and Annelida (3 taxa). There
were 2 taxa recorded for Sipuncula and 1 taxon for other phyla.
6.5.45 The taxonomic
resolution and complete list of recorded fauna are shown in Annexes IV and V of Appendix I 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
6.5.46
In March 2021, an increased number of sea slugs and their eggs were
observed in all sampling zones. It may due to the breeding season of sea slug
and the increased of algae on the intertidal. In September 2021 (present
survey), sea slughs and their eggs were not recorded in any sampling location
6.5.47
Table 3.5 of Appendix I shows the
number of individual, relative abundance and density of each phylum in every
sampling zone. The total abundance (1862¡V 3033 ind.) varied among the four
sampling zones while the phyla distributions were similar. In general, Mollusca
was the most dominant phylum (no. of individuals: 1703 ¡V 2747 ind.; relative
abundance 77.7 ¡V 90.6%; density 227 ¡V 366 ind. m-2). Other phyla
were much lower in number of individuals. Arthropoda (114 ¡V 372 ind.; 6.1 ¡V
17%; 15 ¡V 50 ind. m-2), Sipuncula (14 ¡V 37 ind.; 0.8 ¡V 1.2%; 2 ¡V 5
ind. m-2) were common phyla relatively. Other phyla were very low in
abundance in all sampling zones.
Dominant species in every
sampling zone
6.5.48
Table 3.6 of Appendix I 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 95 ind. m-2). Other listed
species of lower density (<42 ind. m-2) were regarded as common
species.
6.5.50
In TC2, the substratum types were mainly ' Gravels
and Boulders' at high tidal level.
The rock oyster Saccostrea cucullata (95 ind. m-2, 28%) was dominant at low to moderate
density. The gastropod Monodonta labio (62 ind. m-2, 18%) was of low to moderate density. At mid
tidal level (mixtures of three substratum types), rock oyster Saccostrea cucullata (78 ind. m-2, 24%) was dominant at low to moderate
density. The gastropods Monodonta labio (60 ind. m-2, 19%) was at low ¡V moderate density level. Substratum
types ¡¥Sands¡¦ and ¡¥Soft Mud¡¨ were mainly distributed at low tidal level, rock
oyster Saccostrea cucullata (23 ind. m-2, 21%) was dominant at low density while the
gastropod Monodonta labio (16 ind. m-2, 15%) was at low level.
6.5.53
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 (1124 ind.), gastropods Monodonta
labio (617 ind.) and Batillaria multiformis (87 ind.) were the most
common species on gravel and boulders substratum. Rock oyster Saccostrea
cucullata (S: 843 ind.¡¦ M: 447 ind.) was the most common species on sandy
and soft mud substrata.
Biodiversity and abundance of
soft shore communities
6.5.54
Table 3.7 of Appendix I 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.
6.5.55
Among
the sampling zones, the mean
species number was varied from 11 ¡V 22 spp. 0.25 m-2 among the four sampling zones.The mean
densities of TC3 (404 ind. m-2) was higher than ST (292 ind. m-2) followed by TC2 (257 ind. m-2) and TC1 (248 ind. m-2). The higher densities of TC3 and ST are due
to the relatively high number of individuals in each quadrat. TC2 was
relatively higher in H¡¦ (2.43) and followed by TC1 (2.27) and TC3 (2.27) and
then ST (1.97). Comparing with ST(J: 0.77), TC2 (J: 0.83) and TC1 (J: 0.80),
TC3 (0.80) was higher in J which was due to its higher species number and even
taxa distribution.
6.5.56
In the
present survey, no clear trend of mean species number, mean density, H¡¦ and J observed among the tidal level.
6.5.57
Figures 3.14
to 3.17 of Appendix I show the temporal changes of mean species
number, mean density, H¡¦ and J at
every tidal level and in every sampling zone along 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.
Impact of the HKLR project
6.5.59
It was
the 36th 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.
6.6.1
AFCD, 2018. Potamidid Snails in Hong Kong Mangrove. Agriculture,
Fisheries and Conservation Department Newsletter - Hong Kong Biodiversity Issue
#25, 2-11
6.6.2
Chan, K.K., Caley, K.J., 2003. Sandy Shores,
Hong Kong Field Guides 4. The Department of Ecology & Biodiversity, The
University of Hong Kong. pp 117.
6.6.3
Dai, A.Y., Yang, S.L., 1991. Crabs of the
China Seas. China Ocean Press. Beijing.
6.6.4
Dong, Y.M., 1991. Fauna of ZheJiang
Crustacea. Zhejiang Science and Technology Publishing House. ZheJiang.
6.6.5
EPD, 1997. Technical Memorandum on
Environmental Impact Assessment Process (1st edition). Environmental
Protection Department, HKSAR Government.
6.6.6
Fauchald, K., 1977. The polychaete worms.
Definitions and keys to the orders, families and genera. Natural History Museum
of Los Angeles County, Science Series 28. Los Angeles, U.S.A..
6.6.7
Fong, C.W., 1998. Distribution of Hong Kong
seagrasses. In: Porcupine! No. 18. The School of Biological Sciences, The
University of Hong Kong, in collaboration with Kadoorie Farm & Botanic
Garden Fauna Conservation Department, p10-12.
6.6.8
Li, H.Y., 2008. The Conservation of Horseshoe
Crabs in Hong Kong. MPhil Thesis, City University of Hong Kong, pp 277.
6.6.9
Longstaff, B.J., Dennison, W.C., 1999.
Seagrass survival during pulsed turbidity events: the effects of light
deprivation on the seagrasses Halodule pinifolia and Halophila ovalis. Aquatic Botany 65 (1-4), 105-121.
6.6.10
Longstaff, B.J., Loneragan, N.R., O¡¦Donohue,
M.J., Dennison, W.C., 1999. Effects of light deprivation on the survival and
recovery of the seagrass Halophila ovalis
(R. Br.) Hook. Journal of Experimental Marine Biology and Ecology 234 (1),
1-27.
6.6.11
Nakaoka, M., Aioi, K., 1999. Growth of
seagrass Halophila ovalis at dugong
trails compared to existing within-patch variation in a Thailand intertidal
flat. Marine Ecology Progress Series 184, 97-103.
6.6.12
Pielou, E.C., 1966. Shannon¡¦s formula as a
measure of species diversity: its use and misuse. American Naturalist 100, 463-465.
6.6.13
Qi, Z.Y., 2004. Seashells of China. China
Ocean Press. Beijing, China.
6.6.14
Qin, H., Chiu, H., Morton, B., 1998. Nursery
beaches for Horseshoe Crabs in Hong Kong. In: Porcupine! No. 18. The School of
Biological Sciences, The University of Hong Kong, in collaboration with
Kadoorie Farm & Botanic Garden Fauna Conservation Department, p9-10.
6.6.15
Shannon, C.E., Weaver, W., 1963. The Mathematical
Theory of Communication. Urbana: University of Illinois Press, USA.
6.6.16
Shin, P.K.S., Li, H.Y., Cheung, S.G., 2009.
Horseshoe Crabs in Hong Kong: Current Population Status and Human Exploitation.
Biology and Conservation of Horseshoe Crabs (part 2), 347-360.
6.6.17
Supanwanid, C., 1996. Recovery of the
seagrass Halophila ovalis after
grazing by dugong. In: Kuo, J., Philips, R.C., Walker, D.I., Kirkman, H. (eds),
Seagrass biology: Proc Int workshop, Rottenest Island, Western Australia.
Faculty of Science, The University of Western Australia, Nedlands, 315-318.
6.6.18
Vermaat, J.E., Agawin, N.S.R., Duarte, C.M.,
Fortes, M.D., Marba. N., Uri, J.S., 1995. Meadow maintenance, growth and
productivity of a mixed Philippine seagrass bed. Marine Ecology Progress Series
124, 215-225.
6.6.19
Yang, D.J, Sun, R.P., 1988. Polychaetous
annelids commonly seen from the Chinese waters (Chinese version). China
Agriculture Press, China
Table 7.1 Summary
of Environmental Site Inspections
Date of Audit |
Observations |
Actions Taken by
Contractor / Recommendation |
Date of Observations
Closed |
18, 27 Mar 2020; 1, 8, 15, 22, 28 Apr 2020; 6, 13, 20, 29 May 2020; 3,
10, 17, 26 Jun 2020; 2, 8, 15, 22, 31 Jul 2020; 5, 12, 21, 28 Aug 2020; 2, 9,
16, 23, 29 Sep 2020; 7, 14, 21, 30 Oct 2020; 4, 11, 18, 27 Nov 2020; 2, 9,
16, 23, 29 Dec 2020; 6, 13, 20, 29 Jan 2021; 3, 10, 17, 26 Feb; 3, 11, 17, 26
Mar; 1, 7, 15, 21, 29 Apr 2021, 6, 12, 20, 28 May 2021; 2, 9, 16, 25 Jun
2021; 2, 7, 14, 21, 30 Jul 2021; 4, 11, 18, 27 Aug 2021 |
1.
Gaps
of silt curtains were observed at Portion X. |
1.
The
silt curtains maintenance work is in progress at Portion X. The Contractor was reminded to maintain the silt curtains at Portion X. |
Follow-up actions for the observations will
be inspected during site inspection in Oct 2021. |
1 Sep
2021 |
1. Gaps of silt curtains were observed/ part of silt curtains
were missing at Portion X. |
1.
The silt curtains maintenance
work is in progress at Portion X. The Contractor was reminded to maintain the
silt curtains at Portion X. |
Follow-up actions for the observations will
be inspected during site inspection in Oct 2021. |
8 Sep
2021 |
1.
Gaps
of silt curtains were observed/ part of silt curtains were missing at Portion
X. |
1. The silt curtains maintenance work is in progress at Portion X. The
Contractor was reminded to maintain the silt curtains at Portion X. |
Follow-up actions for the observations will
be inspected during site inspection in Oct 2021. |
15 Sep
2021 |
1.
Gaps
of silt curtains were observed/ part of silt curtains were missing at Portion
X. |
1. The silt curtains maintenance work is in progress at Portion X. The
Contractor was reminded to maintain the silt curtains at Portion X. |
Follow-up actions for the observations will
be inspected during site inspection in Oct 2021. |
24 Sep
2021 |
1.
Gaps
of silt curtains were observed/ part of silt curtains were missing at Portion
X. |
1. The silt curtains maintenance work is in progress at Portion X. The
Contractor was reminded to maintain the silt curtains at Portion X. |
Follow-up actions for the observations will
be inspected during site inspection in Oct 2021. |
30 Sep 2021 |
1. Gaps of silt curtains were observed/ part of silt curtains
were missing at Portion X. |
The Contractor was recommended to: 1.
maintain
the silt curtains properly at Portion X. |
Follow-up actions for the observations
issued for the last weekly site inspection of the reporting month will be
inspected during the next site inspection. |
Table 8.1 Construction
Activities for October 2021
Site Area |
Description of Activities |
SHT East Portal |
Landscape maintenance
works |