4.1
Introduction
4.1.1
In this section, the requirements,
methodology, equipment, monitoring locations, criteria and protocols for the
monitoring and audit of water quality impacts during the construction and
operational phase of the Project are presented. The key marine water monitoring components and objectives is
provided in Table 4.1a.
Construction Phase
4.1.2
The implementation of good
construction works practice as well as the mitigation measures identified in Appendix C are important to prevent pollution of marine water in the
construction phase and therefore regular site audit of all the land and marine
construction activities is recommended. Site audits shall include site
inspections and compliance audits.
4.1.3
The water quality impact assessment conducted
for this Study concluded that marine water quality impacts from the proposed
Project were mainly associated with the WCR reclamation activities including
the dredging and filling activities and the deep cement mixing (DCM) treatment.
Marine water quality monitoring should be carried out at selected stations
before and during the WCR reclamation activities as well as during the marine
piling works for construction of the CBL.
During the field trial of DCM, a water quality monitoring programme
should be implemented to confirm the water quality impact before the full-scale
implementation of DCM for seawall construction.
Operational Phase
4.1.4
For the operational phase, it is recommended to implement a
3-year post-project monitoring programme at Eastern
Channel (EDC) to confirm the suitability of the proposed recreation uses at EDC.
4.1.5
In any event of emergency sewage
bypass at the seawall, the proposed recreation zone in EDC and Junk Bay will be
closed. Water quality monitoring should
be carried out by DSD to determine when conditions are suitable for re-opening
of the EDC and Junk Bay for recreational purposes.
Table 4.1a Key Marine Water Monitoring Components
|
Description of
Monitoring
|
Objectives
|
Monitoring
Components
|
Tentative Timing
|
Action
|
|
Construction phase
monitoring during WCR reclamation and during marine piling works for CBL
|
To monitor the marine
water quality impacts from the WCR reclamation activities and marine piling
works
|
Implement baseline
monitoring
|
Before September 2010
|
ET, IE(C)
|
|
Establish baseline
condition
|
Before October 2010
|
ET, IE(C)
|
|
Agree baseline condition
|
Before November 2010
|
EPD
|
|
Implement impact
monitoring
|
November 2010 – September
2014 (During WCR reclamation);
February 2013 – Jan 2014
(During marine piling for CBL)
|
ET, IE(C)
|
|
Construction phase
monitoring during DCM
|
To monitor the marine
water quality impacts from the DCM
|
Implement water quality
monitoring during DCM field trial
|
February - May 2011 (After
the Phase 1 seawall is completed)
|
ET, IE(C)
|
|
Review / establish
monitoring requirements for full scale DCM operation
|
Before December 2011
|
IE(C)
|
|
Agree monitoring proposal
for full scale DCM operation
|
Before February 2012
|
EPD, AFCD
|
|
Implement water quality
monitoring during full scale DCM operation
|
February - April 2012 and
February - April 2014 (During full scale DCM operation)
|
ET, IE(C)
|
|
Operational phase
monitoring at EDC
|
To confirm the suitability
of the proposed water recreation uses at EDC
|
Implement water quality
monitoring at EDC
|
After completion of the
Project by 2016
|
Future operator of the
water recreation area
|
|
Review the suitability of
the proposed recreation uses at EDC
|
Continuous review during
the monitoring period
|
|
Determine whether to
discontinue the monitoring or not
|
After a 3-year post monitoring
period
|
|
Operational phase
monitoring during emergency discharge
|
To safeguard the users of
the water creation zone against the water quality impact due to emergency
sewage discharge from the TKO sewage treatment woks
|
Close the water recreation
zone and implement water quality monitoring at EDC and inner Junk Bay
|
In any event of emergency
discharge at seawall during operational phase of the Project
|
Future operator of the
water recreation area
|
|
Review the suitability of
re-opening the water recreation area
|
4.2
Construction
Phase Monitoring
4.2.1
For construction phase monitoring, the
proposed water quality monitoring schedule should be passed to EPD at least two
weeks before the first day of the monitoring month. EPD should also be notified immediately for any changes in
schedule. The monitoring stations
proposed in this section are indicative subject to further review before
construction phase. The status and
locations of water sensitive receivers and the marine activities may change
after issuing this Manual. The proposed monitoring locations should be
submitted four weeks before commencement of baseline monitoring for EPD
approval.
Impact Monitoring During WCR Reclamation and CBL piling works
4.2.2
For impact monitoring during WCR
reclamation, it is recommended to set up 7 monitoring stations at Junk Bay
Coral Site-South West (CM1), Junk bay Coral Site-Junk Island (CM2), Tseung Kwan
O Salt Water Intake (CM3), two gradient stations (CM4 and CM5) and two control
stations (C1 and C2). Monitoring stations
are shown in Figure 4.1 and Table 4.1. The 3 stations (CM1, CM2
and CM3) represent sensitive receivers, which are potentially affected by the
Project during the proposed reclamation works. The gradient stations, CM4 and
CM5 (which are close to the boundary of the mixing zone as indicated in the EIA
Report), are proposed to assist in the identification of the source of any
impact at the monitoring stations, CM2 and CM3. Stations C1 and C2 will therefore serve as control stations.
4.2.3
During CBL piling works, monitoring
should be carried out at CM1, CM2, CM3, C1 and C2 only. The 3 stations (CM1,
CM2 and CM3) represent sensitive receivers, which are potentially affected by
the Project during the proposed piling works.
Stations C1 and C2 will serve as control stations.
Table 4.1 Proposed
Marine Water Quality Stations for Baseline and Construction Phase Monitoring
|
Station
|
Description
|
Easting
|
Northing
|
|
CM1
|
Junk bay
Coral Site-South West
|
843208.60
|
816416.20
|
|
CM2
|
Junk bay
Coral Site-Junk Island
|
845285.60
|
815348.82
|
|
CM3
|
|
845512.05
|
817441.79
|
|
CM4
|
Gradient
Station-Outer Junk Bay
|
843925.93
|
816132.22
|
|
CM5
|
Gradient
Station-Inner Junk Bay
|
844761.83
|
817183.47
|
|
C1
|
Control
Station-Southeast
|
845492.57
|
813618.36
|
|
C2
|
Control
Station- Northwest
|
841702.41
|
816780.62
|
4.2.4
During the WCR reclamation and CBL
piling, monitoring should be undertaken three days per week, at mid-flood and
mid-ebb tides, with sampling/measurement at the designated monitoring stations including
the control stations. The interval
between two sets of monitoring should not be less than 36 hours except where
there are exceedances of Action and/or Limit levels, in which case the
monitoring frequency will be increased.
It is proposed to conduct the DCM field trial for engineering design
after completion of the Phase 1 seawall.
During the DCM field trial period, the monitoring frequency should be
increased to daily at both mid-flood and mid-ebb tides to collect more water
quality information at the designated monitoring stations (C1, C2, CM1 to
CM5). Table 4.2 shows the proposed monitoring frequency and water quality
parameters.
Table 4.2 Proposed
Marine Water Quality Monitoring Frequency and Parameters at Stations C1, C2,
CM1 to CM5
|
Activities
|
Monitoring
Frequency
|
Key Parameters
|
|
During
marine construction for WCR Reclamation and CBL piling
|
Three days
per week, at mid-flood and mid-ebb tides
|
Dissolved Oxygen (DO), turbidity, Suspended Solids
(SS)
|
|
During DCM
field trial
|
Daily, at
mid-flood and mid-ebb tides
|
pH, DO, turbidity, SS
|
Note: DO, pH and
turbidity should be measured in
situ whereas SS should be determined by laboratory.
4.2.5
During the DCM field trial, in-situ measurement of DO, pH and turbidity should be undertaken at 2
additional stations (at 20 m upstream and 20 m downstream of the DCM treatment
area respectively) at an hourly interval except where there are exceedances of
Limit levels at the downstream station, in which case the monitoring frequency
will be increased. The locations of the
upstream and downstream stations should be determined on-site as they are
dependent on the location of the DCM treatment area and the current direction
during the monitoring period. A review should be conducted after the DCM field
trial to determine if the same monitoring programme should be applied during
the full-scale DCM treatment.
4.2.6
All measurements should be taken at
three water depths, namely, 1 m below water surface, mid-depth and 1 m above
seabed, 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. If the impact monitoring
data collected at the sensitive receivers (i.e. Stations CM1, CM2 & CM3)
indicate that the Action or Limit levels as shown in Table 4.5 are exceeded, assessment should be conducted to compare the impact
monitoring data with those collected at the gradient stations and the control
stations as appropriate and to identify whether the exceedance is caused by the
marine construction activities . If the data analysis results indicate that the
exceedance is caused by the reclamation activities, appropriate actions
including lowering the working rate, or rescheduling of works should be taken
and additional mitigation measures should be implemented as necessary.
Baseline Monitoring
4.2.7
Baseline conditions for marine water
quality should be established and agreed with EPD prior to the commencement of
works. The purpose of the baseline
monitoring is to establish ambient conditions prior to the commencement of the
marine construction works and to demonstrate the suitability of the proposed
monitoring stations. The baseline
conditions should be established by measuring DO, pH, turbidity and SS levels
at 7 selected monitoring stations as shown in Table 4.1. The baseline monitoring report should be submitted to EPD at least
4 weeks before the commencement of marine works for agreement. The baseline monitoring report should be
certified by the IE(C) before submission to EPD.
4.2.8
The measurements should be taken at
all designated monitoring stations including control stations, 3 days per week,
at mid-flood and mid-ebb tides, for at least 4 weeks prior to the commencement
of marine works. There should not be
any marine construction activities in the vicinity of the stations during the
baseline monitoring. The interval
between 2 sets of monitoring should not be less than 36 hours.
Post-construction Monitoring
4.2.9
Upon completion of all marine works, a
post-project monitoring should be carried out for 4 weeks in the same manner as
the baseline monitoring.
Construction Site
Audits
4.2.10
Implementation of regular site audits
is to ensure that the recommended mitigation measures are to be properly
undertaken during construction phase of the Project. It can also provide an
effective control of any malpractices and therefore achieve continual
improvement of environmental performance on site.
4.2.11
Site audits should include site
inspections and compliance audits.
Site Inspections
4.2.12
Site inspections should be carried out
by the ET and should be based on the mitigation measures for water pollution
control recommended in Section 4.10. In the event that the recommended
mitigation measures are not fully or properly implemented, deficiency should be
recorded and reported to the site management. Suitable actions are to be
carried out to:
·
investigate the problems and the
causes;
·
issue action notes to the Contractor
which is responsible for the works;
·
implement remedial and corrective
actions immediately;
·
re-inspect the site conditions upon completion
of the remedial and corrective actions; and
·
record the event and discuss with the
Contractor for preventive actions.
Compliance
Audits
4.2.13
Monitoring of the treated effluent
quality from the Works Areas is required during the construction phase of the
Project. The monitoring should be carried out at the pre-determined discharge
point. Compliance audits are to be undertaken to ensure that a valid discharge
licence has been issued by EPD prior to the discharge of effluent from the
Project site. The monitoring frequency and parameters specified in the
discharge licence should be fully considered during the monitoring. All
monitoring requirements should be approved by EPD. The audit results reflect
whether the effluent quality is in compliance with the discharge licence
requirements. In case of non-compliance, suitable actions should be undertaken
to:
·
notify the site management for the
non-compliance;
·
identify the sources of pollution;
·
check the implementation status of the
recommended mitigation measures;
·
investigate the operating conditions
of the on-site treatment systems;
·
implement corrective and remedial
actions to improve the effluent quality;
·
increase monitoring frequency until
the effluent quality is in compliance with the discharge licence requirements;
and
·
record the non-compliance and propose
preventive measures.
4.2.14
The implementation schedule for the
recommended water quality mitigation measures is presented in Appendix C.
4.3
Operational
Phase Monitoring
4.3.1
It
is recommended to conduct water quality field survey at EDC after the proposed
drainage diversion works (as mentioned in Section 5.7.6 of the EIA Report) is
completed to confirm the suitability of the proposed recreation uses at
EDC. The field survey should be
conducted at a frequency of twice per year in dry season and wet season
respectively after operation of the drainage diversion works. Monitoring should be conducted at mid-food
and mid-ebb tides during each of the dry and wet season surveys. The suitability of the proposed recreation
uses at EDC should be continuously reviewed with reference to the field survey
data. After a 3-year operation period,
a review should be conducted to determine whether the field survey programme
should be discontinued. The 3-year post-project monitoring should be conducted at upper EDC
(OM1) and lower EDC (OM2) and parameters should include in-situ measurement of DO and laboratory analysis of 5-day biochemical
oxygen demand (BOD5), ammonia nitrogen (NH3) and E.coli. In-situ measurement of pH and salinity should also be measured for
calculation of the unionized ammonia (UIA) levels. Table 4.3 and Figure 4.1 shows the monitoring locations.
Table 4.3 Proposed Marine Water Quality Stations for Operational
Phase Monitoring
|
Station
|
Description
|
Easting
|
Northing
|
|
OM1
|
Upper Eastern Channel
|
845384.83
|
818324.55
|
|
OM2
|
Lower
Eastern Channel
|
845231.23
|
818075.81
|
|
OM3
|
Inner Junk
Bay
|
844761.83
|
817183.47
|
|
OM4
|
Outer Junk
Bay
|
843925.93
|
816132.22
|
4.3.2
In any event of emergency sewage
bypass at seawall of Area 86, the proposed recreation zone in EDC and Junk Bay
will be closed. Water quality
monitoring should be carried out by DSD and/or future operators of the proposed
water recreation facilities after the bypass event to determine when conditions
are suitable for re-opening of the EDC and Junk Bay for recreational
purposes. For each monitoring event,
the monitoring should be conducted at both mid-flood and mid-ebb tides to
confirm the water quality. In case of
exceedance of Limit levels, the monitoring should be carried out daily until
the baseline water quality resumes. DO and E. coli should be measured at 4 selected stations including upper EDC
(OM1), lower EDC (OM2), inner Junk Bay (OM3) and outer Junk Bay (OM4). Table 4.3 and Figure 4.1 shows the monitoring
locations.
4.3.3
All measurements should be taken at
three water depths, namely, 1 m below water surface, mid-depth and 1 m above
seabed, 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
should be monitored.
4.4
Monitoring
Equipment and Field Log
Dissolved Oxygen and Temperature Measuring Equipment
4.4.1
The instrument should be a portable
and weatherproof DO measuring instrument complete with cable and sensor, and
use a DC power source. The equipment
should be capable of measuring:
·
a DO level in the range of 0 ‑
20 mg L-1 and 0 ‑ 200% saturation; and
·
a temperature of 0 ‑ 45 degree
Celsius.
4.4.2
It should have a membrane electrode
with automatic temperature compensation complete with a cable. Sufficient
stocks of spare electrodes and cables should be available for replacement where
necessary. (For example, YSI model 59 meter, YSI 5739 probe, YSI 5795A
submersible stirrer with reel and cable or an approved similar instrument).
4.4.3
Should salinity compensation not be
built-in to the DO equipment, in-situ salinity should be measured to
calibrate the DO equipment prior to each DO measurement.
Turbidity Measurement Instrument
4.4.4
Turbidity should be measured in situ by the nephelometric method. The instrument should be portable and
weatherproof using a DC power source complete with cable, sensor and
comprehensive operation manuals. It
should have a photoelectric sensor capable of measuring turbidity between 0 -
1000 NTU (for example, Hach model 2100P or an approved similar instrument). The
cable should not be less than 25m in length. The meter should be calibrated in
order to establish the relationship between NTU units and the levels of
suspended solids. The turbidity measurement should be carried out on split water
sample collected from the same depths of suspended solids samples.
Sampler
4.4.5
A water sampler is required. It should comprise a transparent PVC
cylinder, with a capacity of not less than 2 litres, which can be effectively
sealed with latex cups at both ends.
The sampler should have a positive latching system to keep it open and
prevent premature closure until released by a messenger when the sampler is at
the selected water depth (for example, Kahlsico Water Sampler or an approved
similar instrument).
Water Depth Detector
4.4.6
A portable, battery-operated echo
sounder should be used for the determination of water depth at each designated
monitoring station. This unit can
either be hand held or affixed to the bottom of the work boat, if the same
vessel is to be used throughout the monitoring programme.
Salinity
4.4.7
A portable salinometer capable of
measuring salinity in the range of 0 - 40 parts per thousand (ppt) should be
provided for measuring salinity of the water at each monitoring location.
Sample Containers and Storage
4.4.8
Water samples for SS, UIA and E. coli determinations should be stored in suitable containers with no
preservative added, packed in ice (cooled to 4°C without being frozen) and
delivered to the laboratory and analysed as soon as possible after
collection. Sufficient volume of
samples should be collected to achieve the detection limit.
Monitoring Position Equipment
4.4.9
A hand-held or boat-fixed type digital
Differential Global Positioning System (DGPS) with way point bearing indication
or other equipment instrument of similar accuracy, should be provided and used
during water quality monitoring to ensure the monitoring vessel is at the
correct location before taking measurements. DGPS
or the equivalent instrument, calibrated at appropriate checkpoint (e.g. Quarry
Bay Survey Nail at Easting 840683.49, Northing 816709.55) should be provided
and used to ensure the monitoring station is at the correct position before
taking measurement and water samples.
Calibration of In-Situ Instruments
4.4.10
All in situ monitoring instruments
should be checked, calibrated and certified by a laboratory accredited under
HOKLAS or any other international accreditation scheme before use and
subsequently re-calibrated at three monthly intervals throughout all stages of
the water quality monitoring programme.
Responses of sensors and electrodes should be checked with certified
standard solutions before each use. Wet
bulb calibration for a DO meter should be carried out before measurement at each
monitoring location.
4.4.11
For the on site calibration of field
equipment, the BS 127:1993, Guide to Field and On-Site Test Methods for the
Analysis of Water should be observed.
4.4.12
Sufficient stocks of spare parts
should be maintained for replacements when necessary. Backup monitoring equipment should also be made available so that
monitoring can proceed uninterrupted even when some equipment is under
maintenance, calibration, etc.
Field Log
4.4.13
Other relevant data should also be
recorded, including monitoring location / position, time, water depth,
salinity, temperature, tidal stages, weather conditions and any special
phenomena or work underway nearby.
4.4.14
A sample data record sheet is shown in
Appendix B for reference.
4.5.1
Analysis of SS, UIA, BOD5
and E. coli levels should be carried out in
a HOKLAS or other international accredited laboratory. The UIA concentrations will be determined
from the laboratory analysis of ammonia nitrogen (NH3) and the in-situ measurements of salinity, DO, temperature and pH for the marine
water samples. Sufficient water samples of not less than 2 litres should be
collected at the monitoring stations for carrying out the laboratory SS, NH3,
BOD5 and E. coli determinations. The suggested
testing method and lowest detection limit are provided in Table 4.4.
Table 4.4 Analytical
Methods to be applied to Marine Water Quality Samples
|
Determinant
|
Suggested Method
|
Suggested Detection Limit
|
|
Suspended solids
|
APHA 2540D
|
1 mg L-1
|
|
Ammonia Nitrogen
|
APHA 4500-NH3
|
0.02 mg L-1
|
|
5-day biochemical oxygen
demand
|
APHA 19ed 5210B
|
2 mg L-1
|
|
E.coli
|
EPD HKSAR, Wat. Sci. Tech. Vol. 35, No. 11-12 pp 409-413
|
1 cfu per100mL
|
APHA American Public Health Association Standard Methods for the
Examination of Water and Wastewater
4.5.2
Detailed testing methods,
pre-treatment procedures, instrument use, Quality Assurance/Quality Control
(QA/QC) details (such as blank, spike recovery, number of duplicate samples per
batch, etc.), detection limits and accuracy should be submitted to EPD for
approval prior to the commencement of monitoring programme. EPD may also
request the laboratory to carry out analysis of known standards provided by EPD
for quality assurance. The testing methods and related proposal should be
checked and certified by IC(E) before submission to EPD for approval.
4.5.3
Additional duplicate samples may be
required by EPD for inter laboratory calibration. Remaining samples after
analysis should be kept by the laboratory for 3 months in case repeat analysis
is required. If in-house or non-standard methods are proposed, details of the
method verification may also be required to submit to EPD. In any circumstance,
the sample testing should have comprehensive quality assurance and quality
control programmes. The laboratory should prepare to demonstrate the programmes
to EPD or his representatives when requested.
4.6
Event
and Action Plan
4.6.1
The water quality assessment criteria,
namely Action and Limit levels are shown in Table 4.5. Should the monitoring
results of the water quality parameters at any designated monitoring stations
indicate that the water quality assessment criteria are exceeded, the actions
in accordance with the Action Plan in Table 4.6, Table 4.7 and Table 4.8 be carried out.
4.6.2
It is recommended that if monitoring
results indicate that the reclamation activities have caused an adverse impact
on water quality at the sensitive receivers, additional mitigation measures
should be recommended to rectify the non-compliance or the construction
programme should be carefully reviewed.
If the reclamation works have caused non-compliance with WSD’s seawater
quality standards at the TKO saltwater intake, WSD should be informed. The working schedule and the mitigation
measures should be reviewed by the Contractor, the IC(E), the ET Leader and the
ER, and if necessary, works should be slowed down or suspended until such
impact is reduced to an acceptable level.
4.6.3
The ET Leader should assess the
effectiveness and efficiency of the proposed mitigation measures and/or
remedial actions for the on-going construction activities. The performance of the environmental
management system (i.e. of the overall EM&A programme) should be reviewed
by the ET Leader on a quarterly basis.
The findings of this review should be included in the quarterly EM&A
summary reports, together with any recommendations to improve the performance
of the EM&A programme.
Table 4.5 Action
and Limit Levels for Marine Water Quality
|
Parameters
|
Action
|
Limit
|
|
Construction Phase – During
WCR Reclamation and CBL piling (Action & Limit Levels are applicable to
Stations CM1, CM2 and CM3
|
|
DO in mg L-1
(Surface, Middle &
Bottom)
|
Surface and Middle
5 percentile of baseline
Bottom
5 percentile of baseline
data
|
Surface and Middle
4 mg L-1 or
1 percentile of baseline
data
Bottom
2 mg L-1 or
1 percentile of baseline
data
|
|
SS in mg L-1 (depth-averaged)
|
95 percentile of baseline data or 120% of upstream control station's
SS at the same tide of the same day
|
|
|
SS in mg L-1 (surface layer at monitoring stations close
to WSD salt water intakes
|
10
|
|
|
Turbidity in NTU
(depth-averaged)
|
95 percentile of baseline data or 120% of upstream control station's
Turbidity at the same tide of the same day
|
99 percentile of baseline or 130% of upstream control station's
Turbidity at the same tide of the same day
|
|
Construction Phase - During DCM Treatment (Limit
Levels are applicable to the downstream station only) See Remark
|
|
pH values measured at 20 m upstream and 20 m downstream of the DCM
treatment area
(depth-averaged)
|
|
Limit level is exceeded if:
1.
the
pH value measured at the downstream station is above 8.5; and
2.
the
pH value measured at the downstream station is greater than the value at the
upstream station by more than 0.2.
|
|
Turbidity in NTU measured at 20 m upstream and 20 m downstream of the
DCM treatment area
(depth-averaged)
|
|
Limit level is exceeded if the turbidity measured at the downstream
station is greater than 130% of the measured value at the upstream control
station.
|
|
Operational Phase Monitoring - To safeguard the
users of the water recreation zone in EDC and inner Junk Bay (Limit Levels
are applicable to Stations OM1, OM2, OM3 and OM4)
|
|
DO in mg L-1
(Depth averaged & Bottom)
|
|
Depth-averaged
4 mg L-1
Bottom
2 mg L-1
|
|
E.coli in cfu per 100 mL
|
|
610 cfu per 100 mL
|
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 and 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.
Remark: A review would be conducted after the DCM
field trial before firming up the monitoring programme for the full scale DCM
treatment.
Table 4.6 Event
and Action Plan for Marine Water Quality During WCR Reclamation and CBL Piling
|
EVENT
|
ACTION
|
|
|
ET
|
IC(E)
|
ER
|
CONTRACTOR
|
|
|
Identify the source(s) of
impact by comparing the results with those collected at the gradient stations
and the control stations as appropriate;
If exceedance is found to
be caused by the reclamation activities, repeat in-situ measurement to confirm findings;
Check monitoring data, all
plant, equipment and Contractor's working methods;
If exceedance occurs at
WSD salt water intake, inform WSD;
Discuss mitigation
measures with IC(E) and Contractor;
Repeat measurement on next
day of exceedance.
|
Discuss with ET and
Contractor on the mitigation measures;
Review proposal on
mitigation measures submitted by Contractor and advise the ER accordingly;
Assess the effectiveness
of the implemented mitigation measures.
|
Discuss with IC(E) on the
proposed mitigation measures;
Make agreement on the
mitigation proposal.
|
Inform the ER and confirm
notification of the non-compliance in writing;
Rectify unacceptable
practice;
Check all plant and
equipment;
Amend working methods if
appropriate;
Discuss with ET and IC(E)
and propose mitigation measures to IC(E) and ER;
Implement the agree
mitigation measures.
|
|
Action level being
exceeded by two or more consecutive
sampling days at water sensitive receiver(s)
|
Identify the source(s) of
impact by comparing the results with those collected at the gradient stations
and the control stations as appropriate;
If exceedance is found to
be caused by the reclamation activities, repeat in-situ measurement to
confirm findings;
Inform IC(E) and
contractor;
Check monitoring data, all
plant, equipment and Contractor's working methods;
Discuss
mitigation measures with IC(E), and Contractor;
Ensure mitigation measures
are implemented;
Prepare to increase the
monitoring frequency to daily;
If exceedance occurs at
WSD salt water intake, inform WSD;
Repeat measurement on next
day of exceedance.
|
Discuss with ET and
Contractor on the mitigation measures;
Review proposal on
mitigation measures submitted by Contractor and advise the ER accordingly;
Assess the effectiveness
of the implemented mitigation measures.
|
Discuss with IC(E) on the
proposed mitigation measures;
Make agreement on the
mitigation proposal;
Assess the effectiveness
of the implemented mitigation measures.
|
Inform the Engineer and
confirm notification of the non-compliance in writing;
Rectify unacceptable
practice;
Check all plant and
equipment and consider changes of working methods;
Discuss with ET, IC(E) and
ER and propose mitigation measures to IC(E) and ER within 3 working days;
Implement the agreed
mitigation measures.
|
|
Limit level being exceeded
by one sampling day at water sensitive receiver(s)
|
Identify the source(s) of
impact by comparing the results with those collected at the gradient stations
and the control stations as appropriate;
If exceedance is found to
be caused by the reclamation activities, repeat in-situ measurement to
confirm findings;
Inform IC(E), contractor
and EPD
Check monitoring data, all
plant, equipment and Contractor's working methods;
Discuss
mitigation measures with IC(E), ER and Contractor;
Ensure mitigation measures
are implemented;
Increase the monitoring
frequency to daily until no exceedance of Limit level;
If exceedance occurs at
WSD salt water intake, inform WSD.
|
Discuss with ET and
Contractor on the mitigation measures;
Review proposal on
mitigation measures submitted by Contractor and advise the ER accordingly;
Assess the effectiveness
of the implemented mitigation measures.
|
Discuss with IC(E), ET and
Contractor on the proposed mitigation measures;
Request Contractor to
critically review the working methods;
Make agreement on the
mitigation measures to be implemented;
Assess the effectiveness
of the implemented mitigation measures.
|
Inform the ER and confirm
notification of the non-compliance in writing;
Rectify unacceptable
practice;
Check all plant and
equipment and consider changes of working methods;
Discuss with ET, IC(E) and
ER and submit proposal of mitigation measures to IC(E) and ER within 3
working days of notification;
Implement the agreed
mitigation measures.
|
|
|
Identify the source(s) of
impact by comparing the results with those collected at the gradient stations
and the control stations as appropriate;
If exceedance is found to
be caused by the reclamation activities, repeat in-situ measurement to
confirm findings;
Check monitoring data, all
plant, equipment and Contractor's working methods;
Discuss mitigation
measures with IC(E), ER and Contractor;
Increase the monitoring frequency to daily until no
exceedance of Limit level for two consecutive days;
If exceedance occurs at
WSD salt water intake, inform WSD.
|
Discuss with ET and
Contractor on the mitigation measures;
Review proposal on
mitigation measures submitted by Contractor and advise the ER accordingly;
Assess the effectiveness
of the implemented mitigation measures.
|
Discuss with IC(E), ET
and Contractor on the proposed mitigation measures;
Request Contractor to
critically review the working methods;
Make agreement on the
mitigation measures to be implemented;
Assess the effectiveness
of the implemented mitigation measures;
Consider and instruct, if
necessary, the Contractor to slow down or to stop all or part of the marine
work until no exceedance of Limit level.
|
Inform the ER and confirm
notification of the non-compliance in writing;
Rectify unacceptable
practice;
Check all plant and
equipment and consider changes of working methods;
Discuss with ET, IC(E) and
ER and submit proposal of mitigation measures to IC(E) and ER within 3
working days of notification;
Implement the agreed
mitigation measures;
As directed by the
Engineer, to slow down or to stop all or part of the construction activities.
|
Table 4.7 Event
and Action Plan for Marine Water Quality During DCM Field Trial
|
Event
|
Action
|
|
Limit level being exceeded at the station downstream of the DCM
treatment area
|
1. ET to inform the IC(E), the ER and the contractor.
2. ET to repeat the in-situ measurements at
a 15-minute intervals until no exceedance is recorded for 2 consecutive
measurements.
3. ER and the Contractor to check all plant, equipment, mitigation
measures and Contractor's working methods.
4. The contractor to stop the DCM field trial or slow down the DCM
process until no exceedance is recorded for 2 consecutive measurements.
|
Table 4.8 Event
and Action Plan for Marine Water Quality During Operational Phase
|
Event
|
Action
|
During Emergency Discharge Event
|
|
Limit level being exceeded
|
Conduct daily monitoring; Continue to close the recreational area
until no exceedance is confirmed for 2 consecutive monitoring events.
|
4.7
Mitigation
Measures
4.7.1
Mitigation measures for water quality
control have been recommended in the EIA Report. The Contractor should be responsible for the design and
implementation of these measures.
4.7.2
Recommended mitigation measures to
minimise the adverse impacts on water quality during construction and operation
phases are detailed in Section 4.10 below.
Construction Phase
4.7.3
In
view of the close vicinity of the coral community to the work site, silt
curtain should be installed around the reclamation site.
4.7.4
Dredging and filling works should be
carried out in a controlled manner such that release of sediments into the
marine environment would be minimised.
The following list of measures should be followed:
4.7.5
The modelling results indicated that
the maximum permissible production rates of dredging activities should not
exceed 1,400 m3/day for Phase 1 reclamation.
4.7.6
For
filling activities for Phase 1 reclamation, no more than 12 dump cycles
should be performed each day. The
maximum volume of filling per dump cycle should not exceed 250 m3.
4.7.7
For
backfilling using public fill, the maximum fine content of fills should not
exceed 5%.
4.7.8
For
each reclamation phase, core filing activities should be carried out after
completion of the seawall of that particular phase.
4.7.9
Any gaps that may need to be provided
for marine access should be shielded by silt curtains to control sediment plume
dispersion away from the site. Filling
activities for seawall construction should be carried out behind a silt
curtain.
4.7.10
Closed-grab dredger should be used for
dredging. Dredging activities should be
carried out behind a silt curtain.
4.7.11
Properly maintained closed mechanical
grabs should be used to minimise spillage and should be sealed tightly while
being lifted.
4.7.12
All barges and hopper dredgers should
be fitted with tight seals to their bottom opening to prevent leakage of
materials.
4.7.13
The decks of all vessels should be
kept tidy and free of oil or other substances that might be accidentally or
otherwise washed overboard.
4.7.14
Loading of barges and hoppers should
be controlled to prevent splashing of dredged materials to the surrounding
environment and barges and hoppers should under no circumstances be filled to a
level which would cause overflowing of material or sediment laden water during
loading and transportation.
4.7.15
All barges and dredgers should
maintain adequate clearance between vessels and the seabed at all states of the
tide and should operate at a reduced speeds to ensure that undue turbidity is
not generated by turbulence from vessel movement or propeller wash.
4.7.16
To reduce any
potential for water quality impact during the field trial of DCM, it is recommended to conduct the field trial after completion of
the Phase 1 reclamation seawall so that the trial location can take
place in a more sheltered location behind the Phase 1 reclamation.
4.7.17
It is also recommended that silt
curtains should be employed during both the DCM field trial and during
full-scale DCM for seawall construction to minimize the potential for water
quality impacts due to any unforeseen sediment release. A sand blanket should also be placed on top
of the mud prior to DCM treatment to avoid seabed sediment disturbance. The sand fill layer is to be around 1 m deep
covering the area of DCM treatment.
4.7.18
Because the cement slurry injection
uses highly pressured air and liquids, there is a possibility that slurry waste
could leach out to the water body. It
is recommended that the cement slurry injection pressure should be carefully
controlled to prevent leaching out of cement slurry and the slurry waste should
be either properly disposed outside the site or used for back filling during
reclamation after the slurry has solidified.
4.7.19
It is recommended to carry out water
quality monitoring and audit during the DCM field trial. In-situ measurements of DO, turbidity and pH should be
measured at both upstream and downstream of the DCM field trial. If the measurements
indicate that the field trial have caused significant changes in water quality
conditions at the downstream station in terms of turbidity and pH, appropriate
actions should be taken to stop the field trial and
mitigation measures such as slowing down the DCM process, or rescheduling of
works would be implemented to reduce the impacts. It is also recommended that water monitoring should be collected
at selected water sensitive receivers during the field trial to confirm the
water quality impact. More detailed
water quality assessment and water quality monitoring requirements for the DCM
should be prepared based on the monitoring data of the field trial. All these
should be summarized in a report to be submitted to EPD and AFCD for approval
before starting the DCM operation. The monitoring requirements should be
submitted to EPD at least 4 weeks before commencement of the DCM operation.
4.7.20
All wastewater generated from the
piling activities should be collected by a derrick lighter or other collection
system and be treated before controlled discharge. Spoil should be collected by
sealed hopper barges for proper disposal.
4.7.21
In
view of the close vicinity of the coral community to the work site, silt
curtain should be installed around the marine piling activities to reduce the
any impact due accidental release of excavated sediment.
4.7.22
To minimise the potential water
quality impacts from construction site runoff and various construction
activities, the practices outlined in ProPECC PN 1/94
Construction Site Drainage should be adopted.
Surface Run-off
4.7.23
Surface run-off from construction
sites should be discharged into storm drains via adequately designed sand/silt
removal facilities such as sand traps, silt traps and sedimentation
basins. Channels or earth bunds or sand
bag barriers should be provided on site to properly direct stormwater to such
silt removal facilities. Perimeter
channels at site boundaries should be provided where necessary to intercept
storm run-off from outside the site so that it will not wash across the
site. Catchpits and perimeter channels
should be constructed in advance of site formation works and earthworks.
4.7.24
Silt removal facilities, channels and
manholes should be maintained and the deposited silt and grit should be removed
regularly, at the onset of and after each rainstorm to ensure that these
facilities are functioning properly at all times. Any practical options for the diversion and re-alignment of
drainage should comply with both engineering and environmental requirements in
order to ensure adequate hydraulic capacity of all drains. Minimum distances of
100 m should be maintained between the discharge points of construction site
runoff and the existing TKO saltwater intake.
4.7.25
There is a need to apply to EPD for a
discharge licence for discharge of effluent from the construction site under the WPCO. The discharge quality must meet the requirements specified in the
discharge licence. All the runoff and wastewater generated from the works areas
should be treated so that it satisfies all the standards listed in the
TM-DSS. Reuse and recycling of the
treated effluent can minimise water consumption and reduce the effluent discharge
volume. The beneficial uses of the treated effluent may include dust
suppression, wheel washing and general cleaning. It is anticipated that only a
small quantity of wastewater would be generated from the works areas.
4.7.26
Construction works should be
programmed to minimize soil excavation works in rainy seasons (April to
September). If excavation in soil could
not be avoided in these months or at any time of year when rainstorms are
likely, for the purpose of preventing soil erosion, temporary exposed slope
surfaces should be covered e.g. by tarpaulin, and temporary access roads should
be protected by crushed stone or gravel, as excavation proceeds. Intercepting channels should be provided
(e.g. along the crest / edge of excavation) to prevent storm runoff from
washing across exposed soil surfaces.
Arrangements should always be in place to ensure that adequate surface
protection measures can be safely carried out well before the arrival of a
rainstorm.
4.7.27
Earthworks final surfaces should be
well compacted and the subsequent permanent work or surface protection should
be carried out immediately after the final surfaces are formed to prevent
erosion caused by rainstorms.
Appropriate drainage like intercepting channels should be provided where
necessary.
4.7.28
Measures should be taken to minimize
the ingress of rainwater into trenches. If excavation of trenches in wet
seasons is necessary, they should be dug and backfilled in short sections. Rainwater pumped out from trenches or
foundation excavations should be discharged into storm drains via silt removal
facilities.
4.7.29
Open stockpiles of construction
materials (e.g. aggregates, sand and fill material) on sites should be covered
with tarpaulin or similar fabric during rainstorms. Measures should be taken to prevent the washing away of
construction materials, soil, silt or debris into any drainage system.
4.7.30
Manholes (including newly constructed
ones) should always be adequately covered and temporarily sealed so as to
prevent silt, construction materials or debris from getting into the drainage
system, and to prevent storm run-off from getting into foul sewers. Discharge of surface run-off into foul
sewers must always be prevented in order not to unduly overload the foul
sewerage system.
4.7.31
Good site practices should be adopted
to remove rubbish and litter from construction sites so as to prevent the
rubbish and litter from spreading from the site area. It is recommended to clean the construction sites on a regular
basis.
Groundwater
4.7.32 Under normal circumstances, groundwater pumped out of wells, etc.
for the lowering of ground water level in basement or foundation construction,
and groundwater seepage pumped out of tunnels or caverns under construction
should be discharged into storm drains after the removal of silt in silt
removal facilities.
4.7.33
However, groundwater pumped out during
construction of the northern cycle track footbridge and southern footbridge as
well as the proposed sewage pumping station for TKO landfill development should
not be discharged into the storm system as the groundwater may potentially be contaminated
by leachate seepage from the TKO landfill.
The pumped out groundwater should be temporarily held in storage tanks
on site as the volume is anticipated to be small. It is recommended that the groundwater should be collected and
tankered off site by a licensed wastewater collector for treatment and disposal
at TKO PTW. The site investigation works at the detailed design stage of the
Project should include groundwater sampling and analysis to determine the
composition of groundwater. The monitoring
results of groundwater quality should be submitted to EPD and DSD
for their approval. Should the groundwater quality be
found to exceed the TM standard for discharge into foul sewers, suitable treatment and disposal method of contaminated groundwater should
be recommended. It is proposed that a packaged treatment unit be installed at the
site should pre-treatment be required.
All the required on-site pre-treatment of the collected groundwater
should be implemented to the satisfaction of the EPD. Sampling should be conducted for the groundwater to ensure that the groundwater quality meets the TM-DSS
prior to the discharge of groundwater to the TKO PTW. Estimate of the volume of groundwater should be
made at the detailed design stage based on the site investigation data.
Boring and Drilling Water
4.7.34
Water used in ground boring and
drilling for site investigation or rock / soil anchoring should as far as
practicable be recirculated after sedimentation. When there is a need for final disposal, the wastewater should be
discharged into storm drains via silt removal facilities.
Wastewater from Concrete
Batching and Precast Concrete Casting
4.7.35
Wastewater generated from the washing
down of mixing trucks and drum mixers and similar equipment should whenever
practicable be recycled. The discharge
of wastewater should be kept to a minimum.
4.7.36
To prevent pollution from wastewater
overflow, the pump sump of any water recycling system should be provided with
an on-line standby pump of adequate capacity and with automatic alternating
devices.
4.7.37
Under normal circumstances, surplus
wastewater may be discharged into foul sewers after treatment in silt removal
and pH adjustment facilities (to within the pH range of 6 to 10). Disposal of wastewater into storm drains
will require more elaborate treatment.
Wheel Washing Water
4.7.38
All vehicles and plant should be
cleaned before they leave a construction site to ensure no earth, mud, debris
and the like is deposited by them on roads.
A wheel washing bay should be provided at every site exit if practicable
and wash-water should have sand and silt settled out or removed before
discharging into storm drains. The
section of construction road between the wheel washing bay and the public road
should be paved with backfall to reduce vehicle tracking of soil and to prevent
site run-off from entering public road drains.
Bentonite Slurries
4.7.39
Bentonite slurries used in diaphragm
wall and bore-pile construction should be reconditioned and reused wherever
practicable. If the disposal of a
certain residual quantity cannot be avoided, the used slurry may be disposed of
at the marine spoil grounds subject to obtaining a marine dumping licence from
EPD on a case-by-case basis.
4.7.40
If the used bentonite slurry is
intended to be disposed of through the public drainage system, it should be
treated to the respective effluent standards applicable to foul sewer, storm
drains or the receiving waters as set out in the WPCO Technical Memorandum on
Effluent Standards.
Water for Testing &
Sterilization of Water Retaining Structures and Water Pipes
4.7.41
Water used in water testing to check
leakage of structures and pipes should be reused for other purposes as far as
practicable. Surplus unpolluted water could be discharged into storm drains.
4.7.42
Sterilization is commonly accomplished
by chlorination. Specific advice from
EPD should be sought during the design stage of the works with regard to the
disposal of the sterilizing water. The
sterilizing water should be reused wherever practicable.
Wastewater from Building
Construction
4.7.43
Before commencing any demolition
works, all sewer and drainage connections should be sealed to prevent building
debris, soil, sand etc. from entering public sewers/drains.
4.7.44
Wastewater generated from building
construction activities including concreting, plastering, internal decoration,
cleaning of works and similar activities should not be discharged into the
stormwater drainage system. If the
wastewater is to be discharged into foul sewers, it should undergo the removal
of settleable solids in a silt removal facility, and pH adjustment as
necessary.
Acid Cleaning, Etching and
Pickling Wastewater
4.7.45
Acidic wastewater generated from acid
cleaning, etching, pickling and similar activities should be neutralized to
within the pH range of 6 to 10 before discharging into foul sewers. If there is no public foul sewer in the
vicinity, the neutralized wastewater should be tinkered off site for disposal
into foul sewers or treated to a standard acceptable to storm drains and the receiving
waters.
Wastewater from Site Facilities
4.7.46
Wastewater collected from canteen
kitchens, including that from basins, sinks and floor drains, should be
discharged into foul sewer via grease traps capable of providing at least 20
minutes retention during peak flow.
4.7.47
Drainage serving an open oil filling
point should be connected to storm drains via a petrol interceptors with peak
storm bypass.
4.7.48
Vehicle and plant servicing areas,
vehicle wash bays and lubrication bays should as far as possible be located
within roofed areas. The drainage in
these covered areas should be connected to foul sewers via a petrol
interceptor. Oil leakage or spillage
should be contained and cleaned up immediately. Waste oil should be collected and stored for recycling or
disposal in accordance with the Waste Disposal Ordinance.
Sewage from Workforce
4.7.49 The presence of construction workers generates sewage. It is recommended to provide sufficient
chemical toilets in the works areas.
The toilet facilities should be more than 30 m from any
watercourse. A licensed waste collector
should be deployed to clean the chemical toilets on a regular basis.
4.7.50
Notices should be posted at
conspicuous locations to remind the workers not to discharge any sewage or
wastewater into the nearby environment.
Regular environmental audit on the construction site can provide an
effective control of any malpractices and can encourage continual improvement
of environmental performance on site.
It is anticipated that sewage generation during the construction phase
of the project would not cause water pollution problem after undertaking all
required measures.
Accidental Spillage of
Chemicals
4.7.51
Contractor must register as a chemical
waste producer if chemical wastes would be produced from the construction
activities. The Waste Disposal Ordinance (Cap 354) and its subsidiary
regulations in particular the Waste Disposal (Chemical Waste) (General)
Regulation should be observed and complied with for control of chemical wastes.
4.7.52
Any service shop and maintenance
facilities should be located on hard standings within a bunded area, and sumps
and oil interceptors should be provided. Maintenance of vehicles and equipment
involving activities with potential for leakage and spillage should only be
undertaken within the areas appropriately equipped to control these discharges.
4.7.53
Disposal of chemical wastes should be
carried out in compliance with the Waste Disposal Ordinance. The Code of Practice on the
Packaging, Labelling and Storage of Chemical Wastes
published under the Waste Disposal Ordinance details the requirements to deal
with chemical wastes. General requirements are given as follows:
·
Suitable containers should be used to hold the chemical wastes to avoid
leakage or spillage during storage, handling and transport.
·
Chemical waste containers should be suitably labelled, to notify and
warn the personnel who are handling the wastes, to avoid accidents.
·
Storage area should be selected at a safe location on site and adequate
space should be allocated to the storage area.
4.7.54
To
minimize the potential water quality impacts from the construction works
located at or near any river channels, natural streams or seafront, the
practices outlined in ETWB TC (Works) No. 5/2005 “Protection of natural streams/rivers from adverse impacts arising from
construction works” should be adopted where applicable.
Relevant mitigation measures are listed below:
·
The proposed works should preferably be
carried out within the dry season where the flow in the storm culvert/river
channel/stream is low.
·
The use of less or smaller construction
plants may be specified to reduce the disturbance to the riverbed.
·
Temporary sewerage system should be designed
to prevent wastewater from entering the river, streams and sea.
·
Temporary storage of materials (e.g.
equipment, filling materials, chemicals and fuel) and temporary stockpile of
construction materials should be located well away from any water courses during
carrying out of the construction works.
·
Stockpiling of
construction materials and dusty materials should be covered and located away
from any water courses.
·
Construction debris
and spoil should be covered up and/or disposed of as soon as possible to avoid
being washed into the nearby water receivers.
·
Construction activities,
which generate large amount of wastewater, should be carried out in a distance
away from the waterfront, where practicable.
·
Mitigation measures to control site runoff from entering the nearby
water environment should be implemented to minimize water quality impacts. Surface channels should be provided along
the edge of the waterfront within the work sites to intercept the runoff.
·
Construction effluent, site run-off and sewage should be properly
collected and/or treated.
·
Any works site inside the storm water courses should be temporarily
isolated, such as by placing of sandbags or silt curtains with lead edge at
bottom and properly supported props to prevent adverse impact on the storm
water quality.
·
Silt curtain should be installed around the construction activities for the proposed landing
steps at the seafront of TCS to minimize the potential impacts due to accidental
spillage of excavated materials.
·
Proper shoring may need to be erected in order to prevent soil/mud from
slipping into the storm culvert/river/stream/sea.
·
Supervisory staff should be assigned to station on site to closely
supervise and monitor the works.
Operational Phase
4.7.55
The EDC and inner Junk Bay are
proposed to be used for secondary contact recreation. To reduce the water quality impact on the EDC and inner Junk Bay
under the ultimate development scenario, it is recommended to divert all storm
discharges from Catchment M and 60% of the total discharges from Catchment L to
the southern boundary of TCS (refer to Section 5.7.7 of the EIA Report).
4.7.56
It
is recommended to conduct water quality field survey at EDC after the proposed
drainage diversion works (as mentioned in Section 5.7.6 of the EIA Report) is
completed to confirm the suitability of the proposed recreation uses at
EDC. The field survey should be
conducted at a frequency of twice per year in dry season and wet season
respectively after operation of the drainage diversion works. The suitability of the proposed recreation uses
at EDC should be continuously reviewed with reference to the field survey
data. After a 3-year operation period,
a review should be conducted to determine whether the field survey programme
should be discontinued.
4.7.57
In the very unlikely event of any sewage
bypass occurring at the seawall, the proposed secondary contact recreation zone
in EDC and Junk Bay should be closed. It is recommended that relevant
government departments including EPD and LCSD shall be informed by DSD as soon
as possible of any emergency bypass so that appropriate actions can be taken to
prevent any water sports activities to be carried out in EDC and Junk Bay. The Plant operators should
maintain good communications with various concerned parties. A list of address, email address, phone and
fax number of key persons in relevant departments responsible for action should be
made available to the plant operators.
Water quality monitoring should be carried out by DSD to determine when
conditions are suitable for re-opening of the EDC and Junk Bay for recreational
purposes.
4.7.58
All cleansing effluent generated from
the proposed Pak Shing Kok high level fresh water service reservoir
should be collected by a licensed waste collector for proper disposal
and should not be discharged into the nearby water environment.
4.7.59
The emergency bypass location of the
sewage pumping station for the recreational development at TKO landfill will be
designed to be located 500 m away from the TKO saltwater intake. A standby pump will be provided to minimize
the potential water quality impact from sewage overflow.
4.7.60 Connection of sewage generated from the administration building at
the WCR toll plaza to the existing gravity sewer in TCS is considered not
feasible (about 1km away). As the
sewage quantity generated from the site (about 80 employed population) is small
(about 5m3/d), sewage would be collected in holding tank and
transferred by lorry to TKO Preliminary Treatment Works (PTW) for
treatment. Transfer of
sewage should be arranged within office hours of the TKO PTW to facilitate
normal plant operators. The proposed sewage tankering away services should be
provided on a regular basis to prevent any discharge of sewage to the nearby
storm system. If the future operator of the administration building
changes the sewage disposal scheme, using either a pumping scheme or a
small treatment plant due to change of development parameter, the proposed
holding tank could still be used to withhold the raw sewage in case of
emergency. It is therefore not expected that there would be raw sewage
discharges into the Junk Bay provided that the measures recommended above are
properly implemented.
4.7.61
For handling, treatment and disposal
of other operational stage effluent, the practices outlined in ProPECC PN 5/93
should be adopted where applicable. The
following relevant recommendations should be followed:
·
Drainage outlets
provided in open areas and areas subjected to a substantial amount of
wind-blown rain, including open carparks, balconies, podiums, yards, etc.,
should be connected to storm drains.
·
Drainage outlets
provided in covered areas, including covered podiums and other roofed areas,
should be discharged to foul sewers.
·
Subsoil drains of
slopes, road embankments and earth retaining structures, and groundwater
collection drains for basements, subways and tunnels, and similar drains,
should under normal circumstances, be connected to storm water drains. Silt removal facilities should be provided
where necessary. A separate drainage
system that connects to foul sewers should be provided to collect wastewater
from basements, subways and tunnels and similar areas.
·
Drainage serving the
proposed open lorry park should be connected to storm water drains via a petrol
interceptor that would allow storm water bypass during peak flow periods.
·
Drainage serving any
covered carparks should be connected to foul sewers via petrol interceptors.
·
To prevent hazards
from sewage overflowing from the proposed pumping station for handling sewage
arising from TKO landfill site, sewage pump sumps should be provided with a
standby pump whose capacity should not be less than any of the duty pumps, and
duty pumps should not be required to operate more than 10 on-off cycles per
hour.
·
Surface water
drainage should be provided for discharging storm water off slopes and from
open surfaces. Such drainage as
normally collected in open surface channels should be led to storm water drains
via silt removal facilities. Runoff in
kerb gutters of roads or channels of building platforms should pass through a
gully pit with necessary gratings to prevent objects from entering the storm
water drains.
4.7.62
For maintenance of stormwater drainage
system, reference should be made to Environment, Transport and Works Bureau
(ETWB) Technical Circular (Works) No. 14/2004 “Maintenance of Stormwater
Drainage Systems and Natural Watercourses” where applicable. The circular sets out the departmental
responsibilities for the maintenance of stormwater drainage systems and natural
watercourses in government and private lands.
4.7.63
The implementation schedule for the
recommended water quality mitigation measures is presented in Appendix C.