4 WATER QUALITY

4.1 Introduction

4.1.1 The water quality assessment in the EIA Report identified that the key issue in terms of water quality would be related to excavation works duringfor the earth channel construction of the proposed drainage improvement works. To minimizeise potential impacts on the water quality of water sensitive receivers during the channel construction, construction methods with minimal disturbance to the watercourses have been recommended and the excavation works would be carried out under dry condition. The EIA concluded that other identified potential water quality impacts could be minimiszed by implementing the recommended mitigation measures for the construction works, such as control measures on runoff and drainage from the works areas to minimise construction run-off, and proper site management and good site practices. In addition, water quality monitoring and audit would be carried out to detect any deterioration of water quality and to ensure the recommended mitigation measures are properly implemented during the construction phase.

4.2 Water Quality Parameters

4.2.1 The ET shall be responsible for monitoring the parameters, as presented in Table 4.1, to ensure that any deterioration of water quality in the Sai Kung River, Pak Kong River and Ho Chung Channel iswould be readily detected and timely action iscan be undertaken to rectify the situation.

Table 4.1 Water Quality Parameters

Parameter	Type of Analysis
Dissolved Oxygen (DO) (mg L^-1 and % saturation)	In situ measurement
Temperature (^OC)
pH value
Turbidity (NTU)
Water Depth
Suspended Solids (SS) (mg L^-1)	Laboratory analysis

4.2.2 These parameters are selected for monitoring on the following basis:

· To reflect the background water quality near and within the working area

· To reflect tThe nature of the construction activities

4.2.3 In association with the water quality parameters, relevant data shall also be measured, including monitoring location/position, time, weather conditions, and any special phenomena and work underway at the construction site.

4.2.4 A sample monitoring record sheet and data format are shown in Appendix B.

4.3 Monitoring Equipment

4.3.1 Water quality monitoring equipment with the following specifications shall be supplied and maintained by the ET.

Dissolved Oxygen and Temperature Measuring Equipment

4.3.2 The instrument should be a portable, weatherproof dissolved oxygen-measuring instrument equipped with cable, sensor, comprehensive operation manuals, and use a DC power source. It should be capable of measuring:

· dissolved oxygen level in the range of 0-20 mg/l L^-1 and 0-200% saturation; and

· temperature of 0 - 45 °C.

4.3.3 It should have a membrane electrode with automatic temperature compensation completennected with a cable. Sufficient stocks of spare electrodes and cables should be available for replacement where necessary (e.g. YSI model 59 meter, YSI 5739 probe, YSI 5795A submersible stirrer with reel and cable or an approved similar instrument).

Turbidity Measurement Instrument

4.3.4 The instrument should be a portable, weatherproof turbidity-measuring instrument complete with comprehensive operation manual. The equipment should use a DC power source. It should have a photoelectric sensor capable of measuring turbidity between 0-1000 NTU and be completed with a cable (e.g. Hach model 2100P or an approved similar instrument).

Suspended Solids

4.3.5 A water sampler should comprises a transparent PVC cylinder, with a capacity of not less than 2 litres, and 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 (e.g. Kahlsico Water Sampler or an approved similar instrument).

4.3.6 Water samples for suspended solids measurement shall be collected in high- density polythene bottles, packed in ice (coolhilled to 4 °C without being frozen), and delivered to the laboratory as soon as possible after collection.

pH

4.3.7 pH meter (e.g. Hanna - HI 9024) or equivalent) should be used to measure pH valuelevel of the water samples in situ. which should be collected in high density polythene bottles, packed in ice (cooled to 4 °C without being frozen), and delivered to the laboratory as soon as possible after collection.

Positioning Device

4.3.8 The locations of water monitoring points should be located using a hand-held or boat-fixed digital Global Positioning System (GPS) or other equivalent instrument of similar accuracy. This is to ensure that the water sampling locations are correct during the water quality monitoring work.

Water Depth Detector

4.3.9 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 handheld or affixed to the bottom of the work boat, if the same vessel is to be used throughout the monitoring programme.

Water Sampling Equipment

4.3.10 A transparent PVC or glass cylinder, which has a volume of not less than 2 litres and can be sealed at both ends with cups, should be used for collection of water samples at various depths. The water sampler should be equipped with a positive latching system. During water sampling, a messenger is released to trigger the closure of the water sampler at suitable water depth.

4.3.11 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 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 should be carried out before measurement at each monitoring location.

4.3.12 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.

4.3.13 Sufficient stocks of spare parts should 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.

4.4 Measurement and Laboratory Analysis

4.4.1 Analysis of suspended solids shall be carried out in a HOKLAS or other international accredited laboratory. Water samples of about 1,000ml shall be collected at the monitoring stations for carrying out the laboratory SS determination. The detection limit shall be 1mg/L or better. The SS determination shall follow APHA 17ed 2540D or equivalent methods subject to approval of EPD.

4.4.2 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. The ET Leader shall provide the ER with one copy of the relevant chapters of the “Standard Methods for the Examination of Water and Wastewater” updated edition and any other relevant document for his reference.

4.4.3 For the testing methods of other parameters as recommended by EIA or required by EPD, 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 shall be submitted to EPD for approval prior to the commencement of monitoring programme. The QA/QC shall be in accordance with the requirement 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 programmes to EPD or his representatives when requested.

4.5 Monitoring Locations

4.5.1 The proposed monitoring locations in the three river courses are shown in Figures 4.1 to 4.3. Control monitoring points (WS1a/W1b, WS4, and SW6a/W6b) would be located upstream of the construction section at each river and impact monitoring stations (SW2, SW3, SW5 and SW7) would be proposed downstream of each river. The monitoring locations could be adjusted by the ET Leader to suit the location of the construction work site but prior agreement must be obtained from the IC(E) and the EPD.

4.6 Baseline Monitoring

4.6.1 Baseline conditions for water quality shall be established and agreed with EPD prior to the commencement of works. The purposes of the baseline monitoring are to establish ambient conditions prior to the commencement of the works and to demonstrate the suitability of the proposed impact and, control and reference monitoring stations. The baseline conditions shall normally be established by measuring the water quality parameters specified in Table 4.1. The measurements shall be taken at all designated monitoring stations including control stations for 3 days per week for 4 consecutive weeks, applicable with a period of six weeks prior to commencement of the works.

4.6.2 There shall not be any construction activities in the vicinity of the stations during the baseline monitoring.

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

4.6.4 Baseline monitoring schedule shall be sent to EPD 1 week prior to the commencement of baseline monitoring. The interval between 2 sets of monitoring shall not be lesser than 36 hours.

4.7 Impact Monitoring

4.7.1 During the construction period, impact monitoring shall be carried out on twice per week at during the first three months. If exceedances are not recorded during the three monththree-month’s period, the monitoring frequency can then be reduced to once per week, with sampling/measurement at the designated monitoring stations. However, the ET Leader should report and seek agreement from IC(E), ER and approvalthen from EPD before changing the monitoring frequency.

4.7.2 All monitoring information including date and time, weather conditions, operator, identification and description of monitoring locations, works, progress and construction activities, sample ID, method, analytical data and calculation etc., shall be recorded in the monitoring data sheet.

4.1.1 Upon completion of the construction activities, a post project monitoring exercise on selected local stream water quality shall be undertaken for four weeks in the same manner as the impact monitoring.

4.7.3 The water quality monitoring schedule shall be sent to EPD on or before the first day of the monitoring month, EPD shall be notified immediately of any changes in schedule in written format. The Action and Limit levels for the three subject river’s water quality monitoring are shown in Table 4.2. Should the monitoring results at any designated monitoring stations indicate that the Action and Limit levels are exceeded, the actions specified in Table 4.3 shall be carried out.

Table 4.2 Action and Limit Levels for Local Stream Water Quality

Parameter	Action Level	Limit Level
DO in mg/L (mid-depth)	5%ile of baseline data	4 mg/L or 40% saturation at 15 ^oC
SS in mg/L (mid-depth)	95%ile of baseline data or 120% of upstream control station’s SS on the same day of measurement	99%ile of baseline data, or 130% of upstream control station’s SS on the same day of measurement
Turbidity in NTU (mid-depth)	95%ile of baseline data or 120% of upstream control station’s turbidity on the same day of measurement	99%ile of baseline or 130% upstream control station’s turbidity on the same day of measurementdata

Notes:

1. For DO, non-compliance of the water quality limits occurs when monitoring result is lower than the limits.

2. For SS and turbidity, non-compliance of the water quality limits occurs when monitoring result is higher than the limits.

Table 4.3 Action and Limit Levels for Water Quality Monitoring

Event	Action
	ET	IC(E)	ER	Contractor
Action Level being exceeded by one sampling day	1. Repeat in-situ measurement to confirm findings; 2. Identify reasons for non-compliance and sources of impact; 3. Inform IC(E) and Contractor; 4. Check monitoring data, all plant, equipment and Contractor’s working methods; 5. Discuss mitigation measures with IC(E) and Contractor; 1.6. Repeat measurement on next day of exceedance.	1. Discuss with ET and Contractor on the mitigation measures; 2. Review proposals on mitigation measures submitted by Contractor and advise the ER accordingly; 3. Assess the effectiveness of the implemented mitigation measures.	1. Discuss with IC(E) on the proposed mitigation measures; 2. make agreement on the mitigation measures to be implemented; 3. Assess the effectiveness of the implemented mitigation measures.	1. Inform the ER and confirm notification of the non-compliance in writing; 2. Rectify unacceptable practice; 3. Check all plant and equipment; 4. Consider changes of working methods; 5. Discuss with ET and IC(E) and propose mitigation measures to IC(E) and ER; 6. Implement the agreed mitigation measures.
Action Level being exceeded by more than two consecutive sampling days	1. Repeat in-situ measurement to confirm findings; 2. Identify reasons for non-compliance and sources of impact; 3. Inform IC(E) and Contractor; 4. Check monitoring data, all plant, equipment and Contractor’s working methods; 5. Discuss mitigation measures with IC(E) and Contractor; 6. Ensure mitigation measures are implemented; 7. Prepare to increase the monitoring frequency to daily; 8. Repeat measurement on next day of exceedance.	1. Discuss with ET and Contractor on the mitigation measures; 2. Review proposals on mitigation measures submitted by Contractor and advise the ER accordingly; 3. Assess the effectiveness of the implemented mitigation measures.	1. Discuss with IC(E) on the proposed mitigation measures; 2. Make agreement on the mitigation measures to be implemented; 3. Assess the effectiveness of the implemented mitigation measures.	1. Inform the ER and confirm notification of the non-compliance in writing; 2. Rectify unacceptable practice; 3. Check all plant and equipment; 4. Consider changes of working methods; 5. Discuss with ET and IC(E) and propose mitigation measures to IC(E) and ER within 3 working days; 6. Implement the agreed mitigation measures.
Limit Level being exceeded by one sampling day	1. Repeat in-situ measurement to confirm findings; 2. Identify reasons for non-compliance and sources of impact; 3. Inform IC(E), Contractor and EPD; 4. Check monitoring data, all plant, equipment and Contractor’s working methods; 5. Discuss mitigation measures with IC(E), ER and Contractor; 6. Ensure mitigation measures are implemented; 7. Increase the monitoring frequency to daily until no exceedance of Limit Level. 1.Increase the monitoring frequency to daily until no exceedance of Limit Level.	1. Discuss with ET and Contractor on the mitigation measures; 2. Review proposals on mitigation measures submitted by Contractor and advise the ER accordingly; 3. Assess the effectiveness of the implemented mitigation measures.	1. Discuss with IC(E), ET and Contractor on the proposed mitigation measures; 2. Request Contractor to critically review the working methods; 3. Make agreement on the mitigation measures to be implemented; 4. Assess the effectiveness of the implemented mitigation measures.	1. Inform the ER and confirm notification of the non-compliance in writing; 2. Rectify unacceptable practice; 3. Check all plant and equipment; 4. Consider changes of working methods; 5. Discuss with ET, IC(E) and ER and propose mitigation measures to IC(E) and ER within 3 working days; 6. Implement the agreed mitigation measures.
Limit Level being exceeded by more than two consecutive sampling days	1. Repeat in-situ measurement to confirm findings; 2. Identify reasons for non-compliance and sources of impact; 3. Inform IC(E), Contractor and EPD; 4. Check monitoring data, all plant, equipment and Contractor’s working methods; 5. Discuss mitigation measures with IC(E), ER and Contractor; 6. Ensure mitigation measures are implemented; 7. Increase the monitoring frequency to daily until no exceedance of Limit Level for two consecutive days.	1. Discuss with ET and Contractor on the mitigation measures; 2. Review proposals on mitigation measures submitted by Contractor and advise the ER accordingly; 3. Assess the effectiveness of the implemented mitigation measures.	1. Discuss with IC(E), ET and Contractor on the proposed mitigation measures; 2. Request Contractor to critically review the working methods; 3. Make agreement on the mitigation measures to be implemented; 4. Assess the effectiveness of the implemented mitigation measures; 5. 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.	1. Inform the ER and confirm notification of the non-compliance in writing; 2. Rectify unacceptable practice; 3. Check all plant and equipment; 4. Consider changes of working methods; 5. Discuss with ET, IC(E) and ER and propose mitigation measures to IC(E) and ER within 3 working days; 6. Implement the agreed mitigation measures; 7. As directed by the ER, to slow down or to stop all or part of the marine work or construction activities.

4.8 Water Quality Mitigation Measures

4.8.1 Mitigation measures recommended for the construction and operation phases of the Project are summarizeised below. The implementation schedule of the recommended water quality mitigation measures is presented in Appendix A.

Construction Phase

Channel Excavation Works

4.8.2 Regarding to the impacts on water quality, it is very important to properly schedule the construction activities. The excavation works for the earth channel construction would be carried out along the three streams. Wet excavation should be reduced as much as possible. Due to the characteristics of narrow width and small water flow of the original channel, the excavation can be carried out in dry condition (even in wet season) by diverting the stream flow from upstream by a temporary drainage channel or narrowing the river/stream with a temporary earth bund or barrier. Containment measures such as bunds and barriers should be used within the river/stream to prevent water from entering the excavation area. The temporary drainage channel would be backfilled when the construction works are completed or the temporary diversion is no longer required. Although flooding of the proposed contaminant section seldom occurs during the dry season, the excavation would consider to temporarily stop when flood water enter the containment causing leakage of runoffs to stream water.

4.8.3 To further minimise the leakage and loss of sediments during excavation, tightly sealed closed grab excavators should be employed in river sections where material to be handled is wet. Where material is dry and in non-river sections, conventional excavations can be used.

Construction Run-off and Drainage

4.8.4 The site practices outlined in ProPECC PN 1/94 “Construction Site Drainage” should be followed as far as practicable in order to minimise surface runoff and the chance of erosion, and also to retain and reduce any suspended solids prior to discharge. These practices include the following items:

· Before commencing any site formation work, all sewer and drainage connections should be sealed to prevent debris, soil, sand etc. from entering public sewers/drains.

· Temporary ditches should be provided to facilitate run-off discharge into appropriate watercourses, via a silt retention pond.

· Boundaries of earthworks should be marked and surrounded by dykes or embankments for flood protection, as necessary.

· Sand/silt removal facilities such as sand traps, silt traps and sediment basins should be provided to remove sand/silt particles from runoff to meet the requirements of the Technical Memorandum standard under the Water Pollution Control Ordinance. The design of silt removal facilities should be based on the guidelines provided in ProPECC PN 1/94. All drainage facilities and erosion and sediment control structures should be inspected monthly and maintained to ensure proper and efficient operation at all times and particularly during rainstorms.

· Water pumped out from foundation excavations should be discharged into silt removal facilities.

· Careful programming of the works to minimise surface excavations for the drainage improvement works during the wet season. If excavation of soil cannot be avoided during the wet season, exposed slope surfaces should be covered by a tarpaulin or other means. Other measures that need to be implemented before, during, and after rainstorms are summarizeised in ProPECC PN 1/94.

· Exposed soil areas should be minimizeised to reduce potential for increased siltation and contamination of runoff.

· Earthwork final surfaces should be well compacted and subsequent permanent work should be immediately performed.

· Open stockpiles of construction materials or construction wastes on-site should be covered with tarpaulin or similar fabric during rainstorms.

General Construction Activities

4.8.5 Debris and refuse generated on-site should be collected, handled and disposed of properly to avoid entering the adjacent watercourses. Stockpiles of cement and other construction materials should be kept covered when not being used.

4.8.6 Oils and fuels should only be used and stored in designated areas which have pollution prevention facilities. To prevent spillage of fuels and solvents to the river/streams, all fuel tanks and storage areas should be provided with locks and be sited on sealed areas, within bunds of a capacity equal to 110% of the storage capacity of the largest tank. The bund should be drained of rainwater after a rain event.

Sewage from Construction Workforce

4.8.7 Temporary sanitary facilities, such as portable chemical toilets, should be employed on-site where necessary to handle sewage from the workforce. A licensed contractor would be responsible for appropriate disposal and maintenance of these facilities.

Operation Phase

4.8.8 Desilting of the three river channels should be carried out during periods of low flow (i.e. dry season, from November to March).

Accidental Spillage of Chemicals on Site

4.8.9 In case of the occurrence of accidental spillage of chemicals, it is required to take immediate actions to control the release of chemicals into the nearby water bodies. It is recommended that the contractor of the project should develop an emergency plan to deal with accidental spillage of chemicals in the construction site.

4.8.10 Good site practices would avoid the accidents to occur. Areas for chemical storage should be securely locked and kept as far from the drainage systems or stream courses as possible. The storage area should have an impermeable floor and bunding of capacity to accommodate 110% of the volume of the largest container or 20% by volume of the chemical waste stored in that area, whichever is the greatest, to minimise the impacts from any potential accidents.

4.8.11 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 waster containers should be suitably labelled to notify and warn the personnel who are handling the wastes to avoid accidents; and

· Storage area should be selected at a safe location on site and adequate space should be allocated to the storage area.