4 WATER QUALITY

4.1 Water Quality Parameters

4.1.1 As identified in the EIA Report, a key water quality issue of the construction phase will be dredging and sandfilling works for the seawall foundation. Marine water quality monitoring shall be carried out during the construction phase to ensure that any unacceptable increase in suspended solids / turbidity and decrease in dissolved oxygen due to dredging and filling activities could be readily detected and timely action be taken to rectify the situation.

4.1.2 Dissolved oxygen (DO), turbidity and suspended solids (SS) levels shall be monitored at designated marine water quality monitoring stations during the construction phase. DO and turbidity should be measured in situ whereas SS should be determined by laboratory.

4.1.3 The water quality impact assessment undertaken in the EIA study concluded that adverse impacts on water quality arising from the release of heavy metals and nutrients in contaminated sediment are expected during the dredging works. A quantification of the release of heavy metals and nutrients from the sediment elutriate tests indicated that the predicted instantaneous concentrations in the marine waters surrounding the dredging site would exceed the UK Water Quality Standards. The monitoring of heavy metals and nutrients (in the form of total inorganic nitrogen) in the water column (dissolved phase) is therefore considered necessary during the dredging works.

4.1.4 Water quality parameters, including nitrite, sulphide and ammonia nitrogen, that may form corrosive substances in water and affect the normal operation of the seawater intakes and pumping stations shall also be monitored. Other relevant data shall also be recorded, including monitoring location / position, time, water depth, pH value, salinity, temperature, tidal stages, weather conditions and any special phenomena or work underway at the construction site.

4.1.5 The proposed water quality monitoring schedule shall be passed on to EPD at least two weeks before the first day of the monitoring month. EPD shall also be notified immediately for any changes in schedule by fax. It should be noted that further specific requirements for water quality monitoring and mitigation measures requested by individual seawater intake operators will be included in the EM&A programme after consultation.

4.2 Monitoring Equipment

Dissolved Oxygen and Temperature Measuring Equipment

(i) The instrument should be a portable and weatherproof dissolved oxygen (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.

(ii) It should have a membrane electrode with automatic temperature compensation complete with a cable.

(iii) 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

4.2.1 The instrument should be a portable and weatherproof turbidity measuring instrument using a DC power source. It should have a photoelectric sensor capable of measuring turbidity between 0 - 1000 NTU (for example, Hach model 2100P or an approved similar instrument).

Sampler

4.2.2 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

4.2.3 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

4.2.4 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

4.2.5 Water samples for SS, heavy metals, total inorganic nitrogen (TIN), nitrite, ammonia nitrogen and sulphide determinations should be stored in high density polythene bottles 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 stated in Table 4.1. Acid preservatives should also be added to those samples for heavy metal analysis.

Monitoring Position Equipment

4.2.6 A hand-held or boat-fixed type digital Differential Global Positioning System (DGPS) with way point bearing indication and Radio Technical Commission for maritime (RTCM) Type 16 error message ‘screen pop-up’ facilities (for real-time auto-display of error messages and DGPS corrections from the Hong Kong Hydrographic Office), or other equipment instrument of similar accuracy, should be provided and used during marine water monitoring to ensure the monitoring vessel is at the correct location before taking measurements.

Calibration of In-Situ Instruments

4.2.7 The pH meter, DO meter and turbidimeter shall be checked and calibrated before use. DO meter and turbidimeter shall be certified by a laboratory accredited under HOKLAS or any other international accreditation scheme, and subsequently re-calibrated at 3 monthly intervals throughout all stages of the water quality monitoring. Responses of sensors and electrodes should be checked with certified standard solutions before each use. Wet bulb calibration for a DO meter shall be carried out before measurement at each monitoring location.

4.2.8 Sufficient stocks of spare parts shall be maintained for replacements when necessary. Backup monitoring equipment shall also be made available so that monitoring can proceed uninterrupted even when some equipment is under maintenance, calibration, etc.

4.3 Laboratory Measurement / Analysis

4.3.1 Duplicate samples from each independent sampling event are required by EPD for all parameters. Analysis of suspended solids, heavy metals, TIN, sulphide, nitrite, ammonia, colour, threshold odour number and synthetic detergent shall be carried out in a HOKLAS or other international accredited laboratory. Sufficient water samples shall be collected at the monitoring stations for carrying out the laboratory SS, heavy metals, TIN, nitrite, ammonia nitrogen, sulphide, colour, threshold odour number and synthetic detergent determinations, with detection limits of each parameter shown in Table 4.1. The SS determination work shall start within 24 hours after collection of the water samples. The analyses shall follow the standard methods according to Table 4.1 and as described in American Public Health Association (APHA) Standard Methods for the Examination of Water and Wastewater, 19th edition, unless otherwise specified.

Table 4.1 Analytical Methods to be applied to Marine Water Quality Samples

Determinant	Standard Method	Detection Limit
Suspended solids (mg L^-1)	APHA 2540 D	0.1 mg L^-1
Copper (Cu) (mg L^-1)	APHA 3120 B	0.003 mg L^-1
Zinc (Zn) (mg L^-1)	APHA 3120 B	0.005 mg L^-1
Arsenic (As) (mg L^-1)	APHA 3120 B	0.003 mg L^-1
Mercury (Hg) (mg L^-1)	APHA 3112 B	0.0002 mg L^-1
Total Inorganic Nitrogen (mg L^-1)	APHA 4500-Norg or equivalent methods subject to approval of EPD	0.1 mg L^-1
Nitrite (mg L^-1)	APHA 4500-NO2^- B	0.1 mg L^-1
Ammonia Nitrogen (mg L^-1)	APHA 4500-NH3 B and C	0.1 mg L^-1
Sulphide (mg L^-1)	APHA 4500-S^2- D	0.1 mg L^-1
Colour (Hazen unit)	APHA 2120 C	10 Hazen unit
Threshold Odour Number	APHA 2150 B	5 odour unit
Synthetic Detergent	APHA 5540 C and D	1 mg L^-1

4.3.2 If a site laboratory is set up or a non-HOKLAS and non-international accredited laboratory is hired for carrying out the laboratory analysis, the laboratory equipment, analytical procedures, and quality control shall be approved by EPD. All the analysis shall be witnessed by the ER. The ET Leader shall provide the ER with one copy of the relevant chapters of the “APHA Standard Methods for the Examination of Water and Wastewater” 19th edition and any other relevant document for his reference.

4.3.3 For the test methods of other parameters as recommended by EIA or required by DEP, detailed testing methods, pre-treatment procedures, instruments use, QA/QC details (such as blank, spike recovery, number of duplicate samples per batch, etc.), detection limit and accuracy shall be submitted to EPD for approval prior to the commencement of monitoring programme. The QA/QC shall be in accordance with the requirements of HOKLAS or international accredited scheme. The QA/QC results shall be reported. EPD may also request the laboratory to carry out analysis of known standards provided by EPD for quality assurance. Additional duplicate samples may be required by EPD for inter laboratory calibration. Remaining samples after analysis shall 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 shall have comprehensive quality assurance and quality control programmes. The laboratory shall prepare to demonstrate the programme to DEP or his representatives when requested.

4.4 Monitoring Locations

4.4.1 The marine water quality monitoring stations during the construction works are shown in Figure 4.1. These stations are chosen based on the following criteria:

(i) Close to the sensitive receivers (that is, the seawater intakes of the operating saltwater pumping stations) which are directly or likely to be affected;

(ii) For monitoring locations in the vicinity of the sensitive receivers, care should be taken to cause minimal disturbance during monitoring. Other monitoring locations (M1 to M5) are chosen to cover the mixing zone of pollutants generated when marine works are undertaken; and

(iii) Two control stations that shall be at locations representative of the project site in its undisturbed condition. Control stations should be located, as far as is practicable, both upstream and downstream of the works area.

4.4.2 The co-ordinates of the proposed monitoring stations are listed in Table 4.2. As shown in Figure 4.1, the proposed locations for the sensitive receiver monitoring stations represent the sensitive receivers that are predicted to be affected during construction.

Table 4.2 Proposed Marine Water Quality Monitoring Stations

Station	Easting	Northing	Remark
CR1 (Prince’s Building Group intakes)	834701.6	816397.8	-
CR2 (HSBC & Hotel Furama intakes)	835046.7	816086.7	-
CR3 (Queensway Government Offices)	835190.5	816050.8	-
R1 (Intakes for Telecom House / Hong Kong Academy for Performing Art and MTRC South Intake)	835659.2	815865.5	Impact monitoring should be ended after decommission of the intakes
R2 (Intake for HKCEC Phase I)	835836.3	815906.9	Impact monitoring should be ended after decommission of the intake
R3 (Intakes for Great Eagle Centre / China Resources Building / Wan Chai Tower / Revenue Tower / Immigration Tower)	835940.6	815889.3	Impact monitoring should be ended after decommission of the intakes
R4 (Intakes for HKCEC Extension and reprovisioned intakes)	835857.4	816219.4	-
R5 (Water Supplies Department Wan Chai salt water intake)	836231.8	815922.2	Impact monitoring should be ended after decommission of the intake
R6 (Intake for Sun Hung Kai Centre)	836269.9	815932.3	Impact monitoring should be ended after decommission of the intake
R7 (Intakes for Excelsior Hotel and World Trade Centre)	837014.1	815993.5	Impact monitoring should be ended after decommission of the intakes
R8 (Intake for Windsor House)	837195.3	816144.3	Impact monitoring should be ended after decommission of the intake
R9 (Water Supplies Department Quarry Bay salt water intake)	839692.5	817045.6	-
R10 (Water Supplies Department Sai Wan Ho salt water intake)	841057.9	816476.2	-
R11 (Water Supplies Department Central Water Front salt water intake)	833887.6	816534.0	-
R12 (Water Supplies Department Sheung Wan Water Front salt water intake)	833397.4	816754.1	-
R13 (Water Supplies Department Kennedy Town salt water intake)	830731.9	815996.5	-
P1 (Reprovisioned intake of Sun Hung Kai Centre and temporary reprovisioned Water Supplies Department Wan Chai salt water intake)	836283.2	816060.6	Impact monitoring should be commenced after commission of the intakes
P2 (Reprovisioned intakes of Windsor House, Excelsior Hotel and World Trade Centre)	837283.9	816255.4	Impact monitoring should be commenced after commission of the intakes
M1	834101.8	817150.7	-
M2	835597.2	816631.1	-
M3	836551.1	816754.4	-
M4	837484.1	817240.7	-
M5	838893.1	817770.3	-
C1	829916.3	817796.5	Impact monitoring should be undertaken only at mid-ebb tide
C2	843611.3	815723.9	Impact monitoring should be undertaken only at mid-flood tide

4.4.3 Control stations (C1 & C2) are necessary to compare the water quality from potentially impacted sites with the ambient water quality. Control stations shall be located within the same body of water as the impact monitoring stations but should be outside the area of influence of the works and, as far as practicable, not affected by any other works. The control stations shown in Figure 4.1a&b are indicative subject to further review before construction phase. During the review, the location of the impact stations for boundary of mixing zones will also be re-visited. The revised station sitings shall be submitted 4 weeks before commencement of baseline monitoring for EPD approval.

4.4.4 Five monitoring stations (M1 – M5) located in Victoria Harbour midway between Kowloon and Hong Kong Island are proposed to monitor off-site dispersion and to identify the mixing zones of pollutants produced during marine works.

4.4.5 Measurements shall be taken at 3 water depths, namely, 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. The status and locations of water sensitive receivers and the marine activities may change after issuing this Manual. If such cases exist, the ET Leader shall propose with justification for changes to monitoring locations or other requirements of the EM&A programme, and seek approval from the IC(E) and EPD.

4.5 Baseline Monitoring

4.5.1 Baseline conditions for marine water quality shall 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 works and to demonstrate the suitability of the proposed impact and control monitoring stations. The baseline conditions shall normally be established by measuring the water quality parameters specified in Section 4.1. The measurements shall be taken at all designated monitoring stations including control stations, three days per week, at mid-flood and mid-ebb tides, for at least four weeks prior to the commencement of marine works. Replicate in-situ measurements and samples collected from each independent sampling event shall be collected to ensure a robust statistically interpretable database. Table 4.3 summarises the baseline monitoring programme for each water quality parameter.

Table 4.3 Summary of Baseline Monitoring Programme for Marine Water Quality

Parameter	Stations	Frequency	Duration
DO, temperature, turbidity, pH, salinity, SS	All	Three days per week	Four weeks
Copper, zinc, arsenic, mercury, TIN	C1, C2, M1, M2, M3, M4 and M5	Three days per week	Four weeks
Sulphide, nitrite, ammonia nitrogen	CR1, CR2, CR3, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, P1 and P2	Three days per week	Four weeks
Colour, threshold odour number, synthetic detergent	R5, R9, R10, R11, R12, R13 and P1	Three days per week	Four weeks

4.5.2 Baseline monitoring programme may overlap with other reclamation activities (for example, Central Reclamation Phase III and Yau Tong Bay Development reclamation). The monitoring exercise should be scheduled as far as possible to avoid concurrent reclamation activities such that representative ambient data could be sampled.

4.5.3 Other relevant data shall also be recorded, such as: monitoring location / position, time, water depth, tidal stages, weather conditions and any special phenomena underway near the monitoring station. There shall not be any marine construction activities in the vicinity of the stations during the baseline monitoring.

4.5.4 In exceptional cases when insufficient baseline monitoring data or questionable results are obtained, the ET Leader shall seek approval from the IC(E) and EPD on an appropriate set of data to be used as baseline reference.

4.5.5 Baseline monitoring schedule shall be faxed to EPD two weeks prior to the commencement of baseline monitoring. The interval between two sets of monitoring shall not be less than thirty-six hours.

4.6 Impact Monitoring

4.6.1 During the dredging and filling works for the seawall foundation and reclamation construction, monitoring shall be undertaken three days per week, at mid-flood and mid-ebb tides, with sampling / measurement at the designated monitoring stations. Replicate in-situ measurements and samples collected from each independent sampling event shall be collected to ensure a robust statistically interpretable database. The interval between two sets of monitoring shall not be less than thirty-six hours except where there are exceedances of Action and / or Limit levels, in which case the monitoring frequency will be increased. Two consecutive measures of DO concentration, DO saturation and turbidity will be taken in situ at 1 m below the surface, mid-depth and 1 m above the seabed at each location. If the water depth is less than 6 m, the mid-depth measurement may be omitted subject to the approval of the ER. If the depth is less than 3 m, only the mid-depth measurements need to be taken subject to the approval of the ER. The monitoring probes shall be retrieved out of water after the first measurement and then redeployed for the second measurement. Where the difference in value between the first and second readings of DO or turbidity parameters is more than 25% of the value of the first reading, the reading shall be discarded and further readings shall be taken. Water samples for SS, heavy metals, TIN, nitrite, ammonia nitrogen, sulphide, colour, threshold odour number and synthetic detergent measurements shall be collected at the same three depths. Table 4.4 summarises the impact monitoring programme for each water quality parameter.

Table 4.4 Summary of Impact Monitoring Programme for Marine Water Quality

Parameter	Stations	Frequency	Duration
DO, temperature, pH, salinity and SS	C1, C2, M1, M2, M3, M4, M5, CR1, CR2, CR3, R4, R9, R10, R11, R12 and R13	Three days per week	Entire duration of marine works
	R1, R2, R3, R5, R6, R7 and R8	Three days per week	From the commencement of marine works until decommission of sea water intakes
	P1 and P2	Three days per week	From the commission of reprovisioned sea water intakes until the completion of marine works
Turbidity	C1, C2, M1, M2, M3, M4 and M5	Three days per week	Entire duration of marine works
	R1, R2, R3, R5, R6, R7 and R8	Three days per week	From the commencement of marine works until decommission of sea water intakes
	CR1, CR2, CR3, R4, R9, R10, R11, R12 and R13	Three days per week (once per day at R4 when dredging is undertaken in the vicinity of R4)	Entire duration of marine works
	P1 and P2	Three days per week (once per day at P1 and / or P2 when dredging is undertaken in the vicinity of P1 and / or P2)	From the commission of reprovisioned sea water intakes until the completion of marine works
Copper, zinc, arsenic, mercury and TIN	C1, C2, M1, M2, M3, M4 and M5	Three days per week	Entire duration of dredging works
Sulphide, nitrite, ammonia nitrogen	CR1, CR2, CR3, R4, R9, R10, R11, R12 and R13	Three days per week	Entire duration of marine works
	R1, R2, R3, R5, R6, R7 and R8	Three days per week	From the commencement of marine works until decommission of sea water intakes
	P1 and P2	Three days per week	From the commission of reprovisioned sea water intakes until the completion of marine works

4.6.2 If the impact monitoring results indicate that dredging / filling works have caused adverse impacts on water quality at the monitoring stations close to the salt water intakes (for instance, non-compliance with Water Supplies Department (WSD) seawater quality standards), appropriate actions including the lowering of production rates for dredging and filling, or rescheduling of works to avoid the peak salt water intake hours, should be taken and additional mitigation measures should be implemented as necessary. Water quality monitoring frequency has to be increased to once per day when dredging / filling is undertaken in the vicinity of seawater intakes. 24-hour monitoring of turbidity at the intakes should be implemented as and when necessary.

4.7 Post-construction Monitoring

4.7.1 Upon completion of all marine-based construction activities, a post-project monitoring exercise on water quality shall be carried out for four weeks in the same manner as the impact monitoring. Replicate in-situ measurements and samples collected from each independent sampling event shall be collected to ensure a robust statistically interpretable database. Table 4.5 summarises the post-construction monitoring programme for each water quality parameter.

Table 4.5 Summary of Post-Construction Monitoring Programme for Marine Water Quality

Parameter	Stations	Frequency	Duration
DO, temperature, turbidity, pH, salinity, SS	C1, C2, M1, M2, M3, M4, M5, CR1, CR2, CR3, R4, R9, R10, R11, R12, R13, P1 and P2	Three days per week	Four weeks
Copper, zinc, arsenic, mercury, TIN	C1, C2, M1, M2, M3, M4 and M5	Three days per week	Four weeks
Sulphide, nitrite, ammonia nitrogen	CR1, CR2, CR3, R4, P1 and P2	Three days per week	Four weeks
Colour, threshold odour number, synthetic detergent	R9, R10, R11, R12, R13 and P1	Three days per week	Four weeks

4.8 Event and Action Plan for Construction Water Quality

4.8.1 Marine water quality criteria, namely Action and Limit levels, are shown in Table 4.6. These criteria should be applied to ensure that any deteriorating water quality could be readily detected. When the monitoring results of the water quality parameters at any designated monitoring stations exceed the water quality criteria, the actions in accordance with the Event and Action Plan in Table 4.7 shall be carried out.

4.8.2 It is recommended that if monitoring results indicate that the dredging or filling works have caused an adverse impact on water quality at the WSD saltwater intakes or cooling water intakes, WSD and the owners of cooling water intakes should be informed. Additional mitigation measures should be recommended to rectify the non-compliance or the construction programme should be carefully reviewed to slow down the rate of dredging or filling such that the water quality at these sensitive receivers is in compliance with the EPD Water Quality Objectives (WQOs), WSD’s seawater quality standards and the recommended thresholds for cooling water intakes. 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.

4.8.3 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 (that is, 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 4.6 Action and Limit Levels for Marine Water Quality

Parameters	Action	Limit
DO in mg L^-1 (Surface, Middle & Bottom)	Surface and Middle 1 percentile of baseline data; or midway between 5 percentile of baseline data and limit level Bottom 1 percentile of baseline data or midway between 5 percentile of baseline data and limit level	Surface and Middle 4 mg L^-1 Bottom 2 mg L^-1
SS in mg L^-1 (depth-averaged) at monitoring stations M1, M2, M3, M4, M5 and control stations C1 and C2	95 percentile of baseline data or 120% of upstream control station's SS at the same tide of the same day	99 percentile of baseline or 130% of upstream control station's SS at the same tide of the same day
SS in mg L^-1 (surface layer) at monitoring stations R5, R9, R10, R11, R12, R13 and P1 close to WSD salt water intakes	10	10
SS in mg L^-1 (surface layer) at monitoring station R1 (or R4 after reprovision) close to MTRC cooling water intake	30	40
SS in mg L^-1 (surface layer) at monitoring stations CR1, CR2, CR3, R2, R3, R4, R6, R7, R8 and P1 close to other cooling water intake	- ^(7)	- ^(7)
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
TIN in mg L^-1 (depth-averaged)	95 percentile of baseline data or 0.4 mg L^-1	99 percentile of baseline data or 0.4 mg L^-1
Copper in mg L^-1 (depth-averaged)	5	5
Zinc in mg L^-1 (depth-averaged)	40	40
Arsenic in mg L^-1 (depth-averaged)	25	25
Mercury in mg L^-1 (depth-averaged)	0.3	0.3
Colour in Hazen unit (surface layer) at monitoring stations R5, R9, R10, R11, R12, R13 and P1 close to WSD salt water intakes	20	20
Threshold odour number in odour unit (surface layer) at monitoring stations R5, R9, R10, R11, R12, R13 and P1 close to WSD salt water intakes	100	100
Synthetic detergent in mg L^-1 (surface layer) at monitoring stations R5, R9, R10, R11, R12, R13 and P1 close to WSD salt water intakes	5	5

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, TIN, Cu, Zn, As and Hg, non-compliance of the water quality limits occurs when monitoring result is higher than the limits. The SS limit levels correspond to the WSD and MTRC water quality target levels, while the limit levels of Cu, Zn, As and Hg correspond to the UK water quality standards.

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. No action and limit levels are set for sulphide, nitrite and ammonia nitrogen as they are not generated from the marine works. Sulphide discharged from the outfalls is monitored as it is a corrosive substance that may damage the facilities of the pumping stations. Nitrite and ammonia are monitored as they may accumulate within embayed waters with storm water outfalls nearby.

6. The action and limit levels of colour, threshold odour unit and synthetic detergent correspond to the WSD water quality target levels.

7. To be determined after consultation or agreed with EPD prior to the commencement of the impact monitoring programme.

Table 4.7 Event and Action Plan for Marine Water Quality

Event	ET Leader	IC(E)	ER	Contractor
Action level being exceeded by one sampling day	Repeat in situ measurement on next day of exceedance to confirm findings; Identify source(s) of impact; Inform IC(E), contractor and ER; Check monitoring data, all plant, equipment and Contractor's working methods. If exceedance occurs at WSD salt water intake or cooling water intake, inform WSD and the owner of cooling water intake, respectively.	Check monitoring data submitted by ET and Contractor’s working methods.	Confirm receipt of notification of non-compliance in writing; Notify Contractor.	Inform the ER and confirm notification of the non-compliance in writing; Rectify unacceptable practice; Amend working methods if appropriate.
Action level being exceeded by two or more consecutive sampling days	Repeat measurement on next day of exceedance to confirm findings; Identify source(s) of impact; Inform IC(E), contractor, ER 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 Action level; If exceedance occurs at WSD salt water intake or the cooling water intake, inform WSD or the owner of the cooling water intake, respectively.	Check monitoring data submitted by ET and Contractor’s working method; Discuss with ET and Contractor on possible remedial actions; Review the proposed mitigation measures submitted by Contractor and advise the ER accordingly; Supervise the implementation of mitigation measures.	Discuss with IC(E) on the proposed mitigation measures; Ensure mitigation measures are properly implemented; 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; Submit proposal of additional mitigation measures to ER within 3 working days of notification and discuss with ET, IC(E) and ER; Implement the agreed mitigation measures.
Limit level being exceeded by one sampling day	Repeat measurement on next day of exceedance to confirm findings; Identify source(s) of impact; Inform IC(E), contractor, ER and EPD; Check monitoring data, all plant, equipment and Contractor's working methods; Discuss mitigation measures with IC(E), ER and Contractor; If exceedance occurs at WSD salt water intake or the cooling water intake, inform WSD or the owner of the cooling water intake, respectively.	Check monitoring data submitted by ET and Contractor’s working method; Discuss with ET and Contractor on possible remedial actions; Review the proposed mitigation measures submitted by Contractor and advise the ER accordingly.	Confirm receipt of notification of failure in writing; Discuss with IC(E), ET and Contractor on the proposed mitigation measures; Request Contractor to review the working methods.	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; Submit proposal of mitigation measures to ER within 3 working days of notification and discuss with ET, IC(E) and ER.
Limit level being exceeded by two or more consecutive sampling days	Repeat measurement on next day of exceedance to confirm findings; Identify source(s) of impact; Inform IC(E), contractor, ER 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 for two consecutive days; If exceedance occurs at WSD salt water intake or the cooling water intake, inform WSD or the owner of the cooling water intake, respectively.	Check monitoring data submitted by ET and Contractor’s working method; Discuss with ET and Contractor on possible remedial actions; Review the Contractor’s mitigation measures whenever necessary to assure their effectiveness and advise the ER accordingly; Supervise the implementation of 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; Ensure mitigation measures are properly implemented; Consider and instruct, if necessary, the Contractor to slow down or to stop all or part of the construction activities until no exceedance of Limit level.	Take immediate action to avoid further exceedance; Submit proposal of mitigation measures to ER within 3 working days of notification and discuss with ET, IC(E) and ER; Implement the agreed mitigation measures; Resubmit proposals of mitigation measures if problem still not under control; As directed by the Engineer, to slow down or to stop all or part of the construction activities until no exceedance of Limit level.

4.9 Water Quality Mitigation Measures

Construction Phase

Construction Design

4.9.1 The following measures have been implemented in the design of reclamation phasing to ensure the continuous operation of the existing waterfront facilities and, simultaneously, to minimise the impacts on water quality:

· a number of small and confined areas of land formation are planned;

· containment of fill within each of these areas by seawalls is proposed, with the seawall constructed first (to above high water mark) and filling being carried out behind the completed seawalls. Any gaps that may need to be provided for marine access will be shielded by silt curtains to control sediment plume dispersion away from the site. Filling should be carried out behind the silt curtain; and

· a partially dredged reclamation that is dictated by the minimum extent of dredging required for foundations of seawalls, roads and drainage culverts is proposed.

Specific Mitigation Measures for Scenario 2A (between March 2004 and August 2005)

4.9.2 As presented in EIA Report, exceedence of target SS levels at the MTRC cooling water intakes and WSD salt water intakes are predicted during both dry and wet seasons. To minimise the potential SS impact, specific mitigation measures are recommended, including:

(i) deployment of silt curtains around the closed grab dredgers to contain SS within the construction site during dredging and seawall trench sand filling;

(ii) deployment of silt screens at the cooling water intakes and WSD salt water intakes to further minimise the intake of SS within the sea water.

Table 4.8 Maximum Dredging and Filling Rates of WDII - Scenario 2A

Activity	Maximum Production Rate (m^3 per week)
Dredging
Causeway Bay Shoreline Zone	31,500
Wan Chai Shoreline Zone	31,500
Cross Harbour Water Mains	14,000
Wan Chai East Submarine Sewage Pipeline	7,000
Seawall Trench Sand Filling
Causeway Bay Shoreline Zone	13,125
Wan Chai Shoreline Zone	26,250

4.9.3 The silt curtain and silt screen^([1]) are considered appropriate mitigation measures of SS impact for Scenario 2A that includes critical but short-term marine works at WCR1 (18 working days for dredging and 28 working days for seawall trench sand filling). Reduction of dredging rates for the Scenario 2A works to reduce SS impacts is not considered appropriate due to consequential delays to the project completion. Table 4.9 summarises the application of silt curtains and silt screens under Scenario 2A.

Table 4.9 Application of Silt Curtains and Silt Screens under Scenario 2A

Mitigation Measures	Location of Applications
Silt Curtains	· Construction sites where dredging and seawall trench sand filling are undertaken, including CBR1, WCR1, WCR3E, Wan Chai PCWA, Breakwater of Kellett Island Marina and FRAE of CRIII.
Silt Screens	· WSD salt water intakes at Wan Chai, Central Water Front, Sheung Wan, Quarry Bay, Sai Wan Ho and Siu Sai Wan. · Cooling water intakes for Windsor House, Excelsior Hotel and World Trade Centre, Sun Hung Kai Centre, Great Eagle Centre / China Resources Building, Wan Chai Tower / Revenue Tower / Immigration Tower, HKCEC Phase I, HKCEC Extension, Telecom House / Hong Kong Academy for Performing Arts / Shun On Centre, MTRC South Intake, Prince’s Building Group at CRIII, Queensway Government Offices at CRIII, Admiralty Centre at CRIII, HSBC and Hotel Furama at CRIII.

Specific Mitigation Measures for Scenario 2B (between September 2005 and September 2007)

4.9.4 As presented in the EIA Report, exceedence of recommended SS levels at the cooling water intakes and WSD salt water intakes are predicted during both dry and wet seasons. It is noted that the WSD Wan Chai salt water intake, which will be temporarily reprovisioned after the completion of the Scenario 2A, will be subject to substantial impact from the adjacent marine works at WCR2E (of which 95% of the predicted maximum SS elevation will be from the dredging works at WCR2E alone). To effectively minimise the potential SS impact at the seawater intakes, specific mitigation measures for Scenario 2B are recommended, including:

(i) seawall trench dredging at CBR2E and WCR2E, within 150 m radius from the adjacent operating seawater intakes on WCR1, shall not be more than 1,500 m³ per day;

(ii) dredging within CBR2E and WCR2E shall only be undertaken behind the partially constructed seawall (above high water mark) extended at least 150 m length from the adjacent reprovisioned intakes on the newly completed seawall (thus, sediment within CBR2E and WCR2E will be effectively contained and SS impact upon the adjacent intakes will be minimised);

(iii) any dredging in WCR3W and WCR2W, within 150 m radius from the adjacent operating seawater intakes on WCR1, shall not be more than 1,500 m³ per day; any dredging in HKCEC2E, within 150 m radius from the adjacent operating seawater intakes on the north side of HKCEC Extension, shall not be more than 1,500 m³ per day;

(iv) deployment of silt curtains around the grab dredgers to contain SS within the construction site during dredging and seawall trench sand filling (this will reduce the dispersion of SS by a factor of 4 or about 75%);

(v) deployment of a silt screen at the WSD Wan Chai and Quarry Bay salt water intakes to further minimise the intake of SS within the sea water, as silt curtains recommended in item (iv) are considered not sufficient.

4.9.5 Table 4.10 summarises the recommended maximum dredging and filling rates during reclamation. Table 4.11 summarises the application of silt curtains and silt screens under Scenario 2B.

Table 4.10 Maximum Dredging and Filling Rates of WDII - Scenario 2B

Activity	Maximum Production Rate (m^3 per week)
Dredging
Causeway Bay Reclamation Zone ^(1)	31,500
Wan Chai Reclamation Zone ^(1)	31,500
HKCEC Reclamation Zone ^(1)	31,500
Seawall Trench Sand Filling
Causeway Bay Reclamation Zone	13,125
Wan Chai Reclamation Zone	13,125
HKCEC Reclamation Zone	13,125

Note: (1) Reduced dredging rates of 1,500 m³ per day are applicable within 150 m of operating seawater intakes for seawall trench dredging at CBR2E and WCR2E, and at WCR2W, WCR3W and HKCEC2E (see Section 4.9.4).

Table 4.11 Application of Silt Curtains and Silt Screens under Scenario 2B

Mitigation Measures	Location of Applications
Silt Curtains	· Construction sites where dredging and seawall trench sand filling are undertaken, including CBR2E, CBR2W, WCR2E, WCR2W, WCR3W, HKCEC2E and HKCEC2W.
Silt Screens	· Reprovisoned WSD salt water intake at Wan Chai and WSD salt water intake at Quarry Bay. · Cooling water intakes for Windsor House, Excelsior Hotel and World Trade Centre, Sun Hung Kai Centre, Great Eagle Centre / China Resources Building, Wan Chai Tower / Revenue Tower / Immigration Tower, HKCEC Phase I, HKCEC Extension, Telecom House / Hong Kong Academy for Performing Arts / Shun On Centre, MTRC South Intake, Prince’s Building Group at CRIII, Queensway Government Offices at CRIII, Admiralty Centre at CRIII, HSBC and Hotel Furama at CRIII.

Other Mitigation Measures

4.9.6 Other good site practices that should be undertaken during sand filling and dredging include:

· mechanical grabs, if used, should be designed and maintained to avoid spillage and sealed tightly while being lifted. For dredging of any contaminated mud, closed watertight grabs must be used;

· all vessels should be sized so that adequate clearance is maintained between vessels and the seabed in all tide conditions, to ensure that undue turbidity is not generated by turbulence from vessel movement or propeller wash;

· all hopper barges and dredgers should be fitted with tight fitting seals to their bottom openings to prevent leakage of material;

· construction activities should not cause foam, oil, grease, scum, litter or other objectionable matter to be present on the water within the site or dumping grounds;

· loading of barges and hoppers should be controlled to prevent splashing of dredged material into the surrounding water. Barges or hoppers should not be filled to a level that will cause the overflow of materials or polluted water during loading or transportation; and

· before commencement of the reclamation works, the holder of Environmental Permit has to submit plans showing the phased construction of the reclamation, design and operation of the silt curtain.

Operational Phase

4.9.7 As presented in the EIA Report, adverse water quality impact associated with the operation of WDII is not anticipated. Thus, operational mitigation measures are not considered necessary. Provision of upstream pollutant trapping device to the extended box culvert in the Causeway Bay Typhoon Shelter should be considered. Regular desilting, undertaken as a measure to minimise the risk of flooding, will also ensure effective pollution load reduction. Sediment traps will be incorporated in the new interceptor culvert design for desilting purpose, which will enable more efficient removal of sediment. Regular maintenance and refuse collection are proposed at locations of embayed waters and locations with potential floating refuse entrapment problems. Mitigation measures for the extended box culvert at typhoon shelter, including silt traps and provisions for facilitating maintenance, should also be implemented.

4.9.8 The implementation schedule for the recommended water quality mitigation measures is presented in Appendix A.

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([1]) Silt curtains should be made from impervious material such as coated nylon and primarily redirect flow around the dredging area rather than blocking the entire water column. In contrast, silt screens are made from synthetic geotextile fabrics, which allow water to flow through but retain a fraction of the suspended solids.