4. WATER QUALITY MONITORING
4.1 Monitoring Locations
4.1.1 The water monitoring works for the Contract are covered by Contract No. HY/2013/01 “Hong Kong-Zhuhai-Macao-Bridge HKBCF – Passenger Clearance Building”. The ET of the Contract or another ET of the HZMB project is required to conduct impact water quality monitoring at the stations shown in Table 4.1 and Figure 3.
Table 4.1 Water Quality Monitoring Stations
|
Station |
Description |
Easting |
Northing |
|
IS5 |
Impact Station (Close to HKBCF construction site) |
811579 |
817106 |
|
IS(Mf)6 |
Impact Station (Close to HKBCF construction site) |
812101 |
817873 |
|
IS7 |
Impact Station (Close to HKBCF construction site) |
812244 |
818777 |
|
IS8 |
Impact Station (Close to HKBCF construction site) |
814251 |
818412 |
|
IS(Mf)9 |
Impact Station (Close to HKBCF construction site) |
813273 |
818850 |
|
IS10(N) |
Impact Station (Close to HKBCF construction site) |
812942 |
820881 |
|
IS(Mf)11 |
Impact Station (Close to HKBCF construction site) |
813562 |
820716 |
|
IS(Mf)16 |
Impact Station (Close to HKBCF construction site) |
814328 |
819497 |
|
IS17 |
Impact Station (Close to HKBCF construction site) |
814539 |
820391 |
|
SR3 |
Sensitive receivers (San Tau SSSI) |
810525 |
816456 |
|
SR4(N) |
Sensitive receivers (Tai Ho) |
814705 |
817859 |
|
SR5(N) |
Control Station |
812569 |
821475 |
|
SR6 |
Sensitive receivers (Sha Chau and Lung Kwu Chau Marine Park) |
805837 |
821818 |
|
SR7 |
Sensitive receivers (Tai Mo Do) |
814293 |
821431 |
|
SR10A(1) |
Sensitive receivers(Ma Wan FCZ) 1 |
823741 |
823495 |
|
SR10B(N)(1) |
Sensitive receivers(Ma Wan FCZ) 2 |
823683 |
823187 |
|
CS(Mf)3(N) |
Control Station |
808814 |
822355 |
|
CS(Mf)5 |
Control Station |
817990 |
821129 |
|
CS4 |
Control Station |
810025 |
824004 |
|
CS6 |
Control Station |
817028 |
823992 |
|
CSA(2] |
Control Station |
818103 |
823064 |
Note:
(1) Additional monitoring station for ma Wan FCZ
(2) Additional control monitoring station for Ma Wan FCZ
Remarks:
The ET of the Contract should conduct impact water quality monitoring at the WQMs listed in the table as part of EM&A programme according to latest notification from ENPO if water quality monitoring is no longer covered by another ET of the HZMB project. The ET of the Contract shall communicate and share the monitoring data to the ET(s) of the other contracts if the water quality monitoring station(s) is/are as part of EM&A programme.
4.2...... Monitoring Requirements
4.2.1... The monitoring requirements, monitoring equipment, monitoring parameters, frequency and duration, monitoring methodology, monitoring schedule, meteorological information are detailed in the monthly EM&A Reports prepared by Contract No. HY/2013/01.
4.2.2... The event and action plan is provided in Appendix D.
4.2.3... The Action and Limit Levels for Water Quality are provided in Table 4.2.
........... Table 4.2 Action and Limit Levels for Water Quality
|
Parameters |
Action |
Limit |
|
DO in mg/L (Surface, Middle & Bottom) |
Surface and Middle 5.0 Bottom 4.7 |
Surface and Middle = 4.2 (except 5 mg/L for FCZ) Bottom = 3.6 |
|
SS in mg/L (depth-averaged) at all monitoring stations and control stations |
23.5 and 120% of upstream control station's SS at the same tide of the same day* |
34.4 and 130% of upstream control station's SS at the same tide of the same day and 10mg/L for WSD Seawater intakes* |
|
Turbidity in NTU (depth-averaged) |
27.5 and 120% of upstream control station's turbidity at the same tide of the same day* |
47.0 and 130% of upstream control station's turbidity at the same tide of the same day* |
* Remarks: Reference is made to EPD approval of adjustment of water quality assessment criteria issued and became effective on 18 February 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 limits occurs when monitoring result is lower than the limits.
3. For turbidity, SS, non-compliance of the water quality limits occurs when monitoring result is higher than the limits.
4. All the figures given in the table are used for reference only and the EPD may amend the figures whenever it is considered as necessary.
5. The 1%-ile of baseline data for dissolved oxygen (surface and middle) and dissolved oxygen (bottom) are 4.2mg/L and 3.6mg/L respectively.
4.2.4... If exceedance(s) at these stations is/are recorded by the ET of the Contract or referred by the other ET under the HZMB project to the Contract, the ET of the Contract will carry out an investigation and findings will be reported in the monthly EM&A Report.
4.3...... Monitoring Results
4.3.1... The monitoring results for the monitoring stations showed in Table 4.1 are reported in the monthly EM&A Report prepared for Contract No. HY/2013/01. There was Action and Limit Level exceedance recorded at different WQM stations during mid-ebb and mid-flood tide on twelve days. The summary of water quality exceedances are shown in Table 4.3.
Table 4.3 Action and Limit Levels for Water Quality
|
Station |
Exceedance Level |
DO (S&M) |
DO (Bottom) |
Turbidity |
SS |
||||
|
Ebb |
Flood |
Ebb |
Flood |
Ebb |
Flood |
Ebb |
Flood |
||
|
IS5 |
Action |
0 |
1 (8 Sep) |
3 (1 Sep, 13 Sep, 18 Sep) |
3 (1 Sep, 13 Sep, 29 Sep) |
1 (8 Sep) |
0 |
1 (8 Sep) |
0 |
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
IS(Mf6) |
Action |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
IS7 |
Action |
1 (8 Sep) |
0 |
2 (8 Sep, 29 Sep) |
0 |
0 |
0 |
0 |
0 |
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
IS8 |
Action |
0 |
3 (8 Sep, 11 Sep, 22 Sep) |
1 (29 Sep) |
1 (11 Sep) |
0 |
0 |
0 |
2 (18 Sep, 25 Sep) |
|
Limit |
0 |
0 |
0 |
0 |
0 |
1 (15 Sep) |
0 |
0 |
|
|
IS(Mf)9 |
Action |
0 |
3 (8 Sep, 11 Sep, 22 Sep) |
0 |
1 (13 Sep) |
0 |
0 |
0 |
0 |
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
IS10(N) |
Action |
5 (8 Sep, 11 Sep, 13 Sep, 22 Sep, 29 Sep) |
3 (8 Sep, 11 Sep, 22 Sep) |
6 (1 Sep, 15 Sep, 18 Sep, 22 Sep, 27 Sep, 29 Sep) |
4 (1 Sep, 11 Sep, 15 Sep, 29 Sep) |
0 |
1 (8 Sep) |
0 |
0 |
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
1 (8 Sep) |
|
|
IS(Mf)11 |
Action |
3 (11 Sep, 15 Sep, 22 Sep) |
5 (8 Sep, 11 Sep, 13 Sep, 15 Sep, 22 Sep) |
4 (1 Sep, 11 Sep, 18 Sep, 29 Sep) |
4 (1 Sep, 8 Sep, 11 Sep, 29 Sep) |
0 |
2 (6 Sep, 8 Sep) |
0 |
1 (8 Sep) |
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
IS(Mf)16 |
Action |
1 (8 Sep) |
3 (8 Sep, 11 Sep, 22 Sep) |
5 (8 Sep, 11 Sep, 13 Sep, 18 Sep, 29 Sep) |
2 (11 Sep, 13 Sep) |
0 |
0 |
0 |
0 |
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
IS17 |
Action |
4 (8 Sep, 11 Sep, 13 Sep, 15 Sep) |
3 (8 Sep, 11 Sep, 22 Sep) |
7 (1 Sep, 6 Sep, 8 Sep, 11 Sep, 13 Sep, 15 Sep, 27 Sep) |
4 (8 Sep, 11 Sep, 13 Sep, 29 Sep) |
0 |
0 |
0 |
0 |
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
SR3 |
Action |
2 (8 Sep, 22 Sep) |
1 (8 Sep) |
0 |
0 |
0 |
0 |
0 |
0 |
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
SR4(N) |
Action |
0 |
2 (11 Sep, 22 Sep) |
0 |
1 (8 Sep) |
0 |
0 |
0 |
0 |
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
SR5(N) |
Action |
3 (11 Sep, 13 Sep, 22 Sep) |
2 (11 Sep, 22 Sep) |
4 (1 Sep, 11 Sep, 27 Sep, 29 Sep) |
3 (8 Sep, 11 Sep, 29 Sep) |
0 |
0 |
0 |
0 |
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
SR6 |
Action |
3 (11 Sep, 18 Sep, 22 Sep) |
7 (6 Sep, 8 Sep, 11 Sep, 15 Sep, 18 Sep, 20 Sep, 22 Sep) |
1 (18 Sep) |
5 (8 Sep, 11 Sep, 15 Sep, 18 Sep, 20 Sep)
|
0 |
1 (8 Sep) |
0 |
1 (20 Sep) |
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
SR7 |
Action |
1 (11 Sep) |
2 (11 Sep, 22 Sep) |
0 |
1 (8 Sep) |
0 |
0 |
0 |
0 |
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
SR10A |
Action |
0 |
0 |
0 |
7 (6 Sep, 8 Sep, 11 Sep, 13 Sep, 15 Sep, 20 Sep, 27 Sep) |
0 |
0 |
0 |
0 |
|
Limit |
4 (6 Sep, 8 Sep, 13 Sep, 22 Sep) |
8 (6 Sep, 8 Sep, 11 Sep, 13 Sep, 15 Sep, 18 Sep, 20 Sep, 22 Sep) |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
SR10B(N) |
Action |
0 |
0 |
3 (11 Sep, 27 Sep, 29 Sep) |
7 (6 Sep, 11 Sep, 13 Sep, 15 Sep, 22 Sep, 25 Sep, 27 Sep) |
0 |
0 |
0 |
0 |
|
Limit |
4 (6 Sep, 8 Sep, 11 Sep, 22 Sep) |
10 (6 Sep, 8 Sep, 11 Sep, 13 Sep, 15 Sep, 18 Sep, 20 Sep, 22 Sep, 25 Sep, 27 Sep) |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
Limit |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
Note: S&M: Surface & Middle
4.3.2... Regarding
the exceedance on 1 September 2017, there was marine transportation on the date
of exceedance. Regarding marine transportation, the vessels was sized to make
sure adequate clearance is maintained between vessels and the sea bed at all
states of the tide to ensure that undue turbidity is not generated by
turbulence from vessel movement or propeller wash. Regarding
marine-based works in Box Culvert B, the work undertaken in the current stage
is the preparation work of precast installation which was suspended on the date
of exceedance due to safety issues. But silt curtain was still maintained to
enclose the work area of the outlet of the box culvert fully. All sea water
flow into the work area of box culvert B will be treated by desilting
facilities before discharge in accordance with the discharge license approved
by EPD for Contract No. HY/2013/03. It was unlikely to consume any dissolved
oxygen to cause the DO exceedances recorded at the concerned WQM stations
during mid-flood and mid-ebb tide on 1 September 2017. Besides, the water
quality mitigation measures as mentioned in EM&A Manual and EP were fully
implemented in Contract No. HY/2013/03. Hence, the exceedance on 1 September
2017 was not related to Contract No. HY/2013/03.
4.3.3... Regarding the exceedance on 6 September
2017, there was marine transportation on the date of exceedance. Regarding
marine transportation, the vessels was sized to make sure adequate clearance is
maintained between vessels and the sea bed at all states of the tide to ensure
that undue turbidity is not generated by turbulence from vessel movement or
propeller wash. For SS exceedance recorded at the WQM station IS8, SR4(N) and SR6, the concerned WQM stations where the
exceedances were recorded were not close to the marine delivery route of Contract
No. HY/2013/03, while there was no notification of exceedance received at the
WQM stations closer to the marine delivery route, such as IS10(N).
For turbidity exceedance recorded at the WQM station IS(Mf)11
closer to the marine delivery route, there was no turbidity exceedance recorded
at WQM station IS10(N) which also close to the marine delivery route. Regarding
marine-based works in Box Culvert B, the work undertaken at the date of
exceedance was preparation work of precast installation which had a cofferdam
to separate seawater and works area. Silt curtain was also maintained to
enclose the work area of the outlet of the box culvert fully. All sea water
flows into the work area of box culvert B will be treated by desilting
facilities before discharge in accordance with the discharge license approved
by EPD for Contract No. HY/2013/03. It was unlikely to consume any dissolved
oxygen or generate suspended solid to cause the DO, turbidity and SS
exceedances recorded at the concerned WQM stations during mid-flood and mid-ebb
tide on 6 September 2017. Besides, the concerned WQM stations where DO and SS
exceedances recorded were far away from the works areas (i.e. box Culvert B),
while there was only Action Level exceedance of turbidity but no notification
of exceedance of DO and SS received at the WQM stations closer to the works
areas, such as IS(Mf)11. Therefore, the exceedances on 6 September 2017 was
considered not related to construction site activities of Contract No.
HY/2013/03. Besides, the water quality mitigation measures as mentioned in
EM&A Manual and EP were fully implemented in Contract No. HY/2013/03.
Hence, the exceedance on 6 September 2017 was not related to Contract No.
HY/2013/03.
4.3.4 Regarding
the exceedance on 8 September 2017, there was no marine transportation on the
date of exceedance. Regarding marine-based works in Box Culvert B, the work
undertaken at the date of exceedance was preparation work of precast
installation which had a cofferdam to separate seawater and works area. Silt
curtain was also maintained to enclose the work area of the outlet of the box
culvert fully. All sea water flows into the work area of box culvert B will be
treated by desilting facilities before discharge in accordance with the
discharge license approved by EPD for Contract No. HY/2013/03.Besides, no
organic matter discharge from the works areas (i.e. box Culvert B) was
observed. It was unlikely to consume any dissolved oxygen to cause DO
exceedances recorded at the concerned WQM stations during mid-flood and mid-ebb
tide on 8 September 2017. For turbidity and SS exceedance recorded at the WQM
station IS10(N) closer to the works area Box Culvert
B, there was no turbidity and SS exceedance recorded at the same WQM station
under similar work environment on 06 September 2017 and 11 September 2017. For
turbidity and SS exceedance recorded at the WQM station IS(Mf)11
closer to the works area Box Culvert B, there was no turbidity and SS
exceedance recorded at the same WQM station under similar work environment on
11 September 2017. For turbidity and SS exceedance recorded at the WQM station
IS5 and SR6, the exceedance recorded at the concerned WQM station is far away
from the marine works area of Contract No. HY/2013/03. It was unlikely that the works undertaken
by Contract No. HY/2013/03 caused turbidity or SS exceedance recorded at the
concerned WQM stations during mid-flood and mid-ebb tide on 8 September 2017.
Besides, the water quality mitigation measures as mentioned in EM&A Manual
and EP were fully implemented in Contract No. HY/2013/03. Hence, the exceedance
on 8 September 2017 was not related to Contract No. HY/2013/03.
4.3.5 Regarding
the exceedance on 11 September 2017, there was marine transportation on the
date of exceedance. Regarding marine transportation, the vessels was sized to
make sure adequate clearance is maintained between vessels and the sea bed at
all states of the tide to ensure that undue turbidity is not generated by
turbulence from vessel movement or propeller wash. Regarding marine-based works
in Box Culvert B, the work undertaken at the date of exceedance was preparation
work of precast installation which had a cofferdam to separate seawater and
works area. Silt curtain was also maintained to enclose the work area of the
outlet of the box culvert fully. All sea water flows into the work area of box
culvert B will be treated by desilting facilities before discharge in
accordance with the discharge license approved by EPD for Contract No.
HY/2013/03. It was unlikely to consume any dissolved oxygen to cause the DO
exceedances recorded at the concerned WQM stations during mid-flood and mid-ebb
tide on 11 September 2017. Besides, no organic matter discharge from the works
areas (i.e. box Culvert B) was observed, while there was only Action Level
exceedance of DO at the WQM stations closer to the works areas, such as IS(Mf)11. Therefore, the exceedances on 11 September 2017
was considered not related to construction site activities of Contract No.
HY/2013/03. Besides, the water quality mitigation measures as mentioned in
EM&A Manual and EP were fully implemented in Contract No. HY/2013/03.
Hence, the exceedance on 11 September 2017 was not related to Contract No.
HY/2013/03.
4.3.6 Regarding
the exceedance on 13 September 2017, there was marine transportation on the
date of exceedance. Regarding marine transportation, the vessels was sized to
make sure adequate clearance is maintained between vessels and the sea bed at
all states of the tide to ensure that undue turbidity is not generated by
turbulence from vessel movement or propeller wash. Regarding marine-based works
in Box Culvert B, the work undertaken at the date of exceedance was preparation
work of precast installation which had a cofferdam to separate seawater and
works area. Silt curtain was also maintained to enclose the work area of the
outlet of the box culvert fully. All sea water flows into the work area of box
culvert B will be treated by desilting facilities before discharge in
accordance with the discharge license approved by EPD for Contract No.
HY/2013/03. Besides, no organic matter discharge from the works areas (i.e. box
Culvert B) was observed. It was unlikely to consume any dissolved oxygen to
cause the DO exceedances recorded at the concerned WQM stations during mid-flood
and mid-ebb tide on 13 September 2017. Besides, the water quality mitigation
measures as mentioned in EM&A Manual and EP were fully implemented in
Contract No. HY/2013/03. Hence, the exceedance on 13 September 2017 was not
related to Contract No. HY/2013/03.
4.3.7 Regarding
the exceedance on 15 September 2017, there was marine transportation on the
date of exceedance. Regarding marine transportation, the vessels was sized to
make sure adequate clearance is maintained between vessels and the sea bed at
all states of the tide to ensure that undue turbidity is not generated by
turbulence from vessel movement or propeller wash. For turbidity exceedance
recorded at the WQM station IS8, the concerned WQM stations where the
exceedances were recorded were not close to the marine delivery route of
Contract No. HY/2013/03, while there was no notification of exceedance received
at the WQM stations closer to the marine delivery route, such as IS(Mf)11. Regarding marine-based works in Box Culvert B, the
work undertaken at the date of exceedance was preparation work of precast
installation which had a cofferdam to separate seawater and works area. Silt
curtain was also maintained to enclose the work area of the outlet of the box
culvert fully. All sea water flows into the work area of box culvert B will be
treated by desilting facilities before discharge in accordance with the
discharge license approved by EPD for Contract No. HY/2013/03. Besides, no
organic matter discharge from the works areas (i.e. box Culvert B) was
observed. It was unlikely that the works undertaken by Contract No. HY/2013/03 consumed
any dissolved oxygen to cause DO exceedances recorded at the concerned WQM
stations during mid-flood and mid-ebb tide on 15 September 2017. For turbidity
exceedance, the exceedance recorded at the concerned WQM station (i.e. IS8) is
far away from the marine works area of Contract No. HY/2013/03, while there was
no notification of exceedance received at the WQM stations closer to the works
areas, such as IS(Mf)11. Besides, fast boats moving
around near the monitoring location during measurement period as mentioned in
Notification of Action/Limit Level Exceedance may be one of the reason for
turbidity exceedance. It was unlikely that the works undertaken by Contract No.
HY/2013/03 caused turbidity exceedance recorded at the concerned WQM stations
during mid-flood tide on 15 September 2017. Besides, the water quality
mitigation measures as mentioned in EM&A Manual and EP were fully
implemented in Contract No. HY/2013/03. Hence, the exceedance on 15 September
2017 was not related to Contract No. HY/2013/03.
4.3.8 Regarding
the exceedance on 18 September 2017, there was marine transportation on the
date of exceedance. Regarding marine transportation, the vessels was sized to
make sure adequate clearance is maintained between vessels and the sea bed at
all states of the tide to ensure that undue turbidity is not generated by
turbulence from vessel movement or propeller wash. For SS exceedance recorded
at the WQM station IS8, the concerned WQM stations where the exceedances were
recorded were not close to the marine delivery route of Contract No.
HY/2013/03, while there was no notification of exceedance received at the WQM
stations closer to the marine delivery route, such as IS(Mf)11.
Regarding marine-based works in Box Culvert B, the work undertaken at the date
of exceedance was preparation work of precast installation which had a
cofferdam to separate seawater and works area. Silt curtain was also maintained
to enclose the work area of the outlet of the box culvert fully. All sea water
flows into the work area of box culvert B will be treated by desilting
facilities before discharge in accordance with the discharge license approved
by EPD for Contract No. HY/2013/03. Besides, no organic matter discharge from
the works areas (i.e. box Culvert B) was observed. It was unlikely to consume any
dissolved oxygen to cause the DO exceedances recorded at the concerned WQM
stations during mid-flood and mid-ebb tide on 18 September 2017. For SS
exceedance, the exceedance recorded at the concerned WQM station (i.e. IS8) is
far away from the marine works area of Contract No. HY/2013/03, while there was
no notification of exceedance received at the WQM stations closer to the works
areas, such as IS(Mf)11. It was unlikely that the
works undertaken by Contract No. HY/2013/03 caused SS exceedance recorded at
the concerned WQM station during mid-flood tide on 18 September 2017. Besides,
the water quality mitigation measures as mentioned in EM&A Manual and EP
were fully implemented in Contract No. HY/2013/03. Hence, the exceedance on 18
September 2017 was not related to Contract No. HY/2013/03.
4.3.9 Regarding
the exceedance on 20 September 2017, there was marine transportation on the date
of exceedance. Regarding marine transportation, the vessels was sized to make
sure adequate clearance is maintained between vessels and the sea bed at all
states of the tide to ensure that undue turbidity is not generated by
turbulence from vessel movement or propeller wash. For turbidity exceedance
recorded at the WQM station SR6, the concerned WQM stations where the
exceedances were recorded were not close to the marine delivery route of
Contract No. HY/2013/03, while there was no notification of exceedance received
at the WQM stations closer to the marine delivery route, such as IS(Mf)11. Regarding marine-based works in Box Culvert B, the
work undertaken at the date of exceedance was preparation work of precast
installation which had a cofferdam to separate seawater and works area. Silt
curtain was also maintained to enclose the work area of the outlet of the box
culvert fully. All sea water flows into the work area of box culvert B will be
treated by desilting facilities before discharge in accordance with the
discharge license approved by EPD for Contract No. HY/2013/03. In addition, the
exceedances recorded at the concerned WQM stations (i.e. SR6, SR10A and SR10B(N)) are far away from the marine works area of
Contract No. HY/2013/03, while there was no notification of exceedance received
at the WQM stations closer to the works areas, such as IS(Mf)11.
It was unlikely to consume any dissolved oxygen to cause the DO exceedances
recorded at the concerned WQM stations during mid-flood tide on 20 September 2017.
Besides, the water quality mitigation measures as mentioned in EM&A Manual
and EP were fully implemented in Contract No. HY/2013/03. Hence, the exceedance
on 20 September 2017 was not related to Contract No. HY/2013/03.
4.3.10 Regarding the exceedance on 22 September 2017, there was
marine transportation on the date of exceedance. Regarding marine
transportation, the vessels was sized to make sure adequate clearance is
maintained between vessels and the sea bed at all states of the tide to ensure that
undue turbidity is not generated by turbulence from vessel movement or
propeller wash. Regarding marine-based works in Box Culvert B, the work
undertaken at the date of exceedance was preparation work of precast
installation which had a cofferdam to separate seawater and works area. Silt
curtain was also maintained to enclose the work area of the outlet of the box
culvert fully. All sea water flows into the work area of box culvert B will be
treated by desilting facilities before discharge in accordance with the
discharge license approved by EPD for Contract No. HY/2013/03. Besides, no
organic matter discharge from the works areas (i.e. box Culvert B) was
observed. It was unlikely to consume any dissolved oxygen to cause the DO
exceedances recorded at the concerned WQM stations during mid-flood tide on 22
September 2017. Besides, the water quality mitigation measures as mentioned in
EM&A Manual and EP were fully implemented in Contract No. HY/2013/03.
Hence, the exceedance on 22 September 2017 was not related to Contract No.
HY/2013/03.
4.3.11 Regarding the exceedance on 25 September 2017, there was marine
transportation on the date of exceedance. Regarding marine transportation, the
vessels was sized to make sure adequate clearance is maintained between vessels
and the sea bed at all states of the tide to ensure that undue turbidity is not
generated by turbulence from vessel movement or propeller wash. For SS
exceedance recorded at the WQM station IS8, the concerned WQM stations where
the exceedances were recorded were not close to the marine delivery route of
Contract No. HY/2013/03, while there was no notification of exceedance received
at the WQM stations closer to the marine delivery route, such as IS(Mf)11. Regarding marine-based works in Box Culvert B, the
work undertaken at the date of exceedance was preparation work of precast
installation which had a cofferdam to separate seawater and works area. Silt
curtain was also maintained to enclose the work area of the outlet of the box
culvert fully. All sea water flows into the work area of box culvert B will be
treated by desilting facilities before discharge in accordance with the
discharge license approved by EPD for Contract No. HY/2013/03. In addition, the
concerned WQM station where exceedances were recorded (i.e. SR10B(N))
was far away from the marine works area of Contract No. HY/2013/03, while there
was no notification of exceedance received at the WQM stations closer to the
works areas, such as IS(Mf)11. It was unlikely to consume
any dissolved oxygen to cause the DO exceedances recorded at the concerned WQM
stations during mid-flood and mid-ebb tide on 25 September 2017. For SS
exceedance, the exceedance recorded at the concerned WQM station (i.e. IS8) is
far away from the marine works area of Contract No. HY/2013/03, while there was
no notification of exceedance received at the WQM stations closer to the works
areas, such as IS(Mf)11. It was unlikely that the
works undertaken by Contract No. HY/2013/03 caused SS exceedance recorded at
the concerned WQM station during mid-flood tide on 25 September 2017. Besides,
the water quality mitigation measures as mentioned in EM&A Manual and EP
were fully implemented in Contract No. HY/2013/03. Hence, the exceedance on 25
September 2017 was not related to Contract No. HY/2013/03.
4.3.12 Regarding the exceedance on 27 September 2017, there was
marine transportation on the date of exceedance. Regarding marine
transportation, the vessels was sized to make sure adequate clearance is
maintained between vessels and the sea bed at all states of the tide to ensure
that undue turbidity is not generated by turbulence from vessel movement or
propeller wash. Regarding marine-based works in Box Culvert B, the work
undertaken at the date of exceedance was preparation work of precast
installation which had a cofferdam to separate seawater and works area. Silt
curtain was also maintained to enclose the work area of the outlet of the box
culvert fully. All sea water flows into the work area of box culvert B will be
treated by desilting facilities before discharge in accordance with the
discharge license approved by EPD for Contract No. HY/2013/03. In addition, the
concerned WQM stations where the exceedances were recorded were far away from
the marine works area of Contract No. HY/2013/03, while there was no
notification of exceedance received at the WQM stations closer to the works
areas, such as IS(Mf)11. It was unlikely to consume any
dissolved oxygen to cause the DO exceedances recorded at the concerned WQM
stations during mid-flood tide on 27 September 2017. Besides, the water quality
mitigation measures as mentioned in EM&A Manual and EP were fully
implemented in Contract No. HY/2013/03. Hence, the exceedance on 27 September
2017 was not related to Contract No. HY/2013/03.
4.3.13 Regarding the exceedance on 29 September 2017, there was marine
transportation on the date of exceedance. Regarding marine transportation, the
vessels was sized to make sure adequate clearance is maintained between vessels
and the sea bed at all states of the tide to ensure that undue turbidity is not
generated by turbulence from vessel movement or propeller wash. Regarding
marine-based works in Box Culvert B, the work undertaken at the date of
exceedance was preparation work of precast installation which had a cofferdam
to separate seawater and works area. Silt curtain was also maintained to
enclose the work area of the outlet of the box culvert fully. All sea water
flows into the work area of box culvert B will be treated by desilting facilities
before discharge in accordance with the discharge license approved by EPD for
Contract No. HY/2013/03. It was unlikely to consume any dissolved oxygen to
cause the DO exceedances recorded at the concerned WQM stations during
mid-flood tide on 29 September 2017. Besides, the water quality mitigation
measures as mentioned in EM&A Manual and EP were fully implemented in
Contract No. HY/2013/03. Hence, the exceedance on 29 September 2017 was not
related to Contract No. HY/2013/03.
4.3.14 After investigation, it was concluded that the exceedances were
not related to Contract No. HY/2013/03 due to the above reasons. The
investigation reports 002 & 003 (including the causes of exceedance, action
taken and recommendation for mitigation) for Action or Limit Level
Non-compliance were provided in Appendix
J. There was no Action and Limit Level exceedance recorded on other
monitoring dates at the monitoring stations shown as shown at Table 4.1 by the Environmental Team of
Contract No. HY/2010/02 during the reporting period.
4.3.15 Although the exceedances were not relevant to Contract No. HY/2013/03, the Contractor was reminded to continue to fully maintain all water quality mitigation measures and ensure the silt curtain is fully maintained to prevent any water quality impact to seawater.