4.1 The EIA Report predicted that the discharge of additional treated effluent from the normal operation of the Project would not have adverse impact on the marine water quality in Victoria Harbour. Effluent quality from the TPSTW Stage V will be governed by the Water Pollution Control Ordinance and the associated discharge licence conditions after the Project on commission. A comprehensive post project monitoring (PPM) programme will be implemented to confirm the predictions of the water quality made in the EIA report.
4.2 With upgrading of the Tai Po and Sha Tin effluent pumping stations and associated facilities, the Project would not cause any adverse impact on the water quality of Tolo Harbour under normal operation. Nevertheless, a 3-month water quality monitoring will be carried out after full commissioning of the Project to collect water quality information at the WSD seawater intakes at Tai Po and Sha Tin during normal operation.
4.3 Marine water quality monitoring is also recommended for various sensitive receivers within the Tolo Harbour during emergency discharge or maintenance periods of the Tolo Harbour Effluent Export Scheme (THEES) Tunnel under both construction and operational phases. An event and action plan under emergency condition or THEES maintenance discharges has been formulated in this EM&A Manual.
4.4 Monitoring of the quality of treated effluent discharged from the works areas during the construction phase shall also be carried out as part of the EM&A.
4.5 In this section, the requirements, methodology, equipment, monitoring locations, criteria and protocols for the monitoring and audit of water quality impacts arising from the Project are presented.
Marine Water Quality
4.6 Marine water quality monitoring shall be carried out during construction phase of the Project under the following conditions:
· Leakage of submarine pipeline is confirmed;
· Emergency discharge of untreated sewage;
· Emergency discharge of treated effluent during shutdown of Tai Po Effluent Pumping Station; and
· Maintenance of THEES.
4.7 It is recommended to set up 6 monitoring stations at Tai Po (W1) and Sha Tin (W2) WSD seawater intakes, Pak Sha Tau (C1) and Gruff Head (C12) Coral Colonies, Yim Tin Tsai Marine Fish Culture Zone (FC2) and a gradient station (G1) respectively. These 6 stations are shown in Figure 4.1. The 4 stations (W1, W2, FC2 & C1) represent sensitive receivers, which are likely affected by the Project under emergency discharges, THEES maintenance periods or pipe leakage events. The gradient station, G1 is proposed to assist in the identification of the source of any impact at the monitoring stations, FC2. Station C12 is far away from the Project discharge points and would unlikely be affected by the Project and will therefore serve as a control station.
4.8 The coordinates of the proposed monitoring stations are listed in Table 4.1.
Table 4.1 Proposed Marine Water Quality Monitoring Stations
|
Station |
Description |
Easting |
Northing |
|
W1 |
WSD Seawater Intake at Tai Po |
837688.18 |
834676.19 |
|
W2 |
WSD Seawater Intake at Sha Tin |
840222.64 |
830058.70 |
|
FC2 |
Yim Tin Tsai Marine Fish Culture Zone |
839321.74 |
834828.84 |
|
G1 |
Gradient Station |
838474.91 |
834702.06 |
|
C1 |
Pak Sha Tau Corals |
843778.51 |
834659.42 |
|
C12 |
Gruff Head Corals (Control Station) |
851027.82 |
837940.83 |
4.9 Measurements shall be taken at three 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. Shall 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. Necessary change in the monitoring locations shall be reviewed and approved by EPD, AFCD and WSD before the commencement of the monitoring.
4.10 A six-month baseline monitoring programme covering both dry and wet seasons is proposed at a frequency of once per month to establish the baseline water quality conditions at the 6 stations prior to the commencement of the Project. The purpose of the baseline monitoring is to establish ambient conditions without any discharge from the Project. The baseline monitoring programme shall be ceased in the events of any emergency discharges or during the maintenance period of THEES during the baseline period.
4.11 During the construction phase, in the event of pipe leakage or emergency discharge of untreated sewage or treated effluent during shutdown of Tai Po Effluent Pumping Station, daily marine water monitoring shall be conducted throughout the whole pipe leakage event or emergency discharge period until the normal water quality resumes or at least 1 week after the normal plant operation is restored. For THEES maintenance, marine water quality data shall be collected throughout the whole discharge period at a frequency of 3 times per week until the baseline water quality is restored or at least 4 weeks after the end of maintenance period. During each monitoring event, water samples shall be collected at both mid-flood and mid-ebb tides and the interval between 2 monitoring events should not be less than 36 hours.
4.12 It is recommended that relevant government departments including EPD, WSD and AFCD shall be informed of any emergency discharge or THEES maintenance events. The Plant operators shall maintain good communications with various concerned parties. A list of address, email address, phone and fax number of key persons in various departments responsible for action shall be made available to the Plant operators. The event and action plan under pipe leakage, emergency condition or THEES maintenance discharges is provided in Table 4.2.
4.13 Dual power supply or ring main from CLP shall be provided for the Project to avoid any loss of electrical supply. In addition, standby facilities for the main treatment units, standby parts / accessories to the equipment shall also be provided to minimize the chance of emergency discharge.
Water Quality Parameters
4.14 Dissolved oxygen (DO), turbidity, suspended solids (SS), 5-day biochemical oxygen demand (BOD5), total inorganic nitrogen (TIN), ammonia nitrogen (NH3-N), chlorophyll-a and E.coli levels shall be monitored. DO and turbidity shall be measured in-situ whereas SS, BOD5, TIN, NH3-N, chlorophyll-a and E.coli shall be determined by laboratory.
Site Record
4.15 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 nearby. A sample data record sheet is shown in Appendix C for reference.
4.16 For any wastewater discharged from the construction works areas, a valid discharge licence shall be obtained from EPD prior to the discharge of effluent from the Project. The monitoring frequency and parameters specified in the discharge licence shall be fully considered during the monitoring.
4.17 The instrument shall be a portable and weatherproof DO measuring instrument complete with cable and sensor, and use a DC power source. The equipment shall 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.
4.18 It shall have a membrane electrode with automatic temperature compensation complete with a cable. Sufficient stocks of spare electrodes and cables shall 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).
4.19 Shall salinity compensation not be built-in to the DO equipment, in-situ salinity shall be measured to calibrate the DO equipment prior to each DO measurement.
4.20 Turbidity shall be measured in situ by the nephelometric method. The instrument shall be portable and weatherproof turbidity measuring instrument using a DC power source complete with cable, sensor and comprehensive operation manuals. It shall have a photoelectric sensor capable of measuring turbidity between 0 - 1000 NTU (for example, Hach model 2100P or an approved similar instrument). The cable shall not be less than 25m in length. The meter shall be calibrated in order to establish the relationship between NTU units and the levels of suspended solids.
4.21 A water sampler is required. It shall 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 shall 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).
4.22 A portable, battery-operated echo sounder shall 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.
4.23 A portable salinometer capable of measuring salinity in the range of 0 - 40 parts per thousand (ppt) shall be provided for measuring salinity of the water at each monitoring location.
4.24 The instrument shall consist of a potentiometer, a glass electrode, a reference electrode and a temperature-compensating device. It shall be readable to 0.1pH in a range of 0 to 14. Standard buffer solutions of at least pH 7 and pH 10 shall be used for calibration of the instrument before and after use. Details of the method shall comply with APHA, 19th ed. 4500-HTB.
4.25 Water samples for SS, TIN and NH3-N shall 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 shall be collected to achieve the required detection limit.
4.26 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, shall be provided and used during marine water monitoring to ensure the monitoring vessel is at the correct location before taking measurements.
4.27 All in situ monitoring instruments shall 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 shall 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.
4.28 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.
4.29 Analysis of SS, BOD5, NH3-N, TIN chlorophyll-a and E.coli levels 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 analysis of SS, BOD5, TIN, NH3-N, chlorophyll-a and E.coli. The analysis shall commence within 24 hours after collection of the water samples. The analyses shall follow the standard methods described in American Public Health Association (APHA) Standard Methods for the Examination of Water and Wastewater, 19th edition or other approved methods. 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. 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.
Mitigation Measures
4.30 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 shall be adopted. It is recommended to install perimeter channels in the works areas to intercept runoff at site boundary prior to the commencement of any earthwork. To prevent storm runoff from washing across exposed soil surfaces, intercepting channels shall be provided. Drainage channels are also required to convey site runoff to sand/silt traps and oil interceptors. Provision of regular cleaning and maintenance can ensure the normal operation of these facilities throughout the construction period. Any practical options for the diversion and re-alignment of drainage shall comply with both engineering and environmental requirements in order to ensure adequate hydraulic capacity of all drains. Minimum distances of 100 m shall be maintained between the discharge points of construction site runoff and the existing WSD seawater intake at Tai Po.
4.31 A discharge licence needs to be applied from EPD for discharging effluent from the construction site. The discharge quality is required to meet the requirements specified in the discharge licence. All the runoff and wastewater generated from the works areas shall be treated so that it satisfies with all the standards listed in the Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters. 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 the wastewater generated from the works areas would be in small quantity.
4.32 The construction programme shall be properly planned to minimise soil excavation, if any, in rainy seasons. This prevents soil erosion from exposed soil surfaces. Any exposed soil surfaces shall also be properly protected to minimise dust emission. In areas where a large amount of exposed soils exist, earth bunds or sand bags shall be provided. Exposed stockpiles shall be covered with tarpaulin or impervious sheets at all time. The stockpiles of materials shall be placed in the locations away from any stream courses so as to avoid releasing materials into the water bodies. Final surfaces of earthworks shall be compacted and protected by permanent work. It is suggested that haul roads shall be paved with concrete and the temporary access roads are protected using crushed stone or gravel, wherever practicable. Wheel washing facilities shall be provided at all site exits to ensure that earth, mud and debris would not be carried out of the works areas by vehicles.
4.33 Good site practices shall be adopted to clean the rubbish and litter on the construction sites so as to prevent the rubbish and litter from dropping into the nearby environment. It is recommended to clean the construction sites on a regular basis.
4.34 The presence of workforce for the construction generates sewage. It is recommended to provide sufficient chemical toilets in the works areas. The toilet facilities shall not be less than 30 m from any watercourse. A licensed waste collector shall be deployed to clean the chemical toilets on a regular basis. The construction workers can also make use of the existing toilet facilities within the TPSTW as necessary.
4.35 Notices shall be posted at conspicuous locations to remind the workers not to discharge any sewage or wastewater into the nearby environment during the construction phase of the project. Implementation of environmental audit on the construction site can provide an effective control of any malpractices and can achieve 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.
4.36 It is required to 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 shall be observed and complied with for control of chemical wastes.
4.37 Any service shop and minor maintenance facilities shall be located on hard standings within a bunded area, and sumps and oil interceptors shall be provided. Maintenance of vehicles and equipment involving activities with potential for leakage and spillage shall only be undertaken with the areas appropriately equipped to control these discharges.
4.38 Disposal of chemical wastes shall 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 shall be used to hold the chemical wastes to avoid leakage or spillage during storage, handling and transport.
· Chemical waste containers shall be suitably labelled to notify and warn the personnel who are handling the wastes to avoid accidents.
· Storage area shall be selected at a safe location on site and adequate space shall be allocated to the storage area.
4.39 During the maintenance period of THEES, DSD shall install silt curtains at the WSD Seawater Intakes at Tai Po and Sha Tin. An action plan for THEES maintenance discharge is given in Table 4.2.
4.40 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.
4.41 Site audits shall include site inspections and compliance audits.
4.42 Site inspections shall be carried out by the ET and shall be based on the mitigation measures for water pollution control recommended in Sections 4.30 to 4.39. In the event that the recommended mitigation measures are not fully or properly implemented, deficiency shall 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.
4.43 Monitoring of the treated effluent quality from the Works Areas is required during the construction phase of the Project. The monitoring shall 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 shall be fully considered during the monitoring. All monitoring requirements shall 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 shall 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.
4.44 The implementation for the recommended mitigation measures is presented in Appendix B.
4.45 During the operational phase, water quality monitoring programme shall include the following four tasks:
· Marine water quality monitoring;
· Effluent monitoring;
· Water quality monitoring at seawater intakes; and
· Dye test.
Marine Water Quality
4.46 Marine water quality monitoring shall be carried out during operation phase of the Project under the following conditions:
· Leakage of submarine pipeline is confirmed;
· Emergency discharge of untreated sewage;
· Emergency discharge of treated effluent during shutdown of Tai Po Effluent Pumping Station; and
· Maintenance of THEES.
4.47 The monitoring programme during construction phase of the Project as discussed in Sections 4.6 to 4.11 shall continue in the first 3 years after commissioning of the Stage V upgrading works. The monitoring requirements, including monitoring parameters and locations shall be maintained.
4.48 After 3 years of post monitoring period, a review shall be conducted by DSD to determine whether such monitoring shall be continued. The review results shall be submitted to the EPD, AFCD and all the relevant parties. Any amendment on the monitoring programme shall be agreed by EPD and AFCD.
Effluent Quality
4.49 It is proposed to monitor the effluent under normal operation. The samples shall be taken from 1m below the surface to ensure that the surface scum is not included in the sample. Parameters to be monitored include pH, BOD5, SS, TIN, NH3-N and E.coli. A valid discharge licence shall be obtained from EPD prior to the discharge of effluent from the Project. The monitoring frequency, locations and parameters specified in the discharge licence shall be fully considered during the monitoring.
4.50 The effluent results reflect whether the effluent quality is in compliance with the discharge licence requirements. In case of non-compliance, suitable actions shall be undertaken to notify the plant operator for the non-compliance and identify the sources of exceedance. The operating conditions of the treatment systems shall be investigated. Corrective and remedial actions shall be implemented to improve the effluent quality. The monitoring team shall also increase monitoring frequency until the effluent quality is in compliance with the discharge licence requirements. The non-compliance and propose preventive measures shall be documented.
4.51 Daily effluent monitoring is recommended during emergency discharge and THEES maintenance periods. The samples shall be taken at the Tai Po effluent pumping station and/or Shatin effluent pumping station before the effluent is discharged into the Tolo Harbour.
Water Quality Monitoring at Seawater Intakes
4.52 A water quality monitoring programme shall be conducted at the WSD Seawater Intakes at Tai Po (W1) and Sha Tin (W2) during the first wet season (from June to August) after commissioning of the Project.
4.53
4.53 The parameters to be monitored under this
water quality monitoring programme shall include SS and NH3-N.
Frequency of the water monitoring programme should be
twice per month and should cover the effects of different tidal status (at
least one for high tide and one
for low tide) for each seawater intake.
Dye Test
4.54 It is recommended to conduct regular dye test once every 2 years to detect any major leakage of the submarine pipeline within Tolo Harbour. The procedures to be followed in the event that pipe leakage is suspected or identified are provided in Table 4.2.
Table 4.2 Event and Action Plan for Emergency Discharge / Accidental Spillage at Tolo Harbour
|
Event |
Action Plan |
|
Pipe leakage as detected by dye test |
1. Carry out investigation to determine the reason of such detection and identify the location of any leakage. 2. If pipe leakage is confirmed, inform EPD and WSD. 3. Determine possible remedial measures such as pipe repairing work. 4. Ensure remedial actions are properly implemented. 5. Assess effectiveness of the remedial actions and keep EPD, AFCD and WSD informed of the results. 6. If leakage continues, consider what portion of the work is responsible and reassess the remedial actions. 7. Arrange meeting with EPD, AFCD and WSD to discuss the required remedial actions if necessary and ensure all necessary remedial actions are properly implemented. 8. Conduct daily effluent and marine water monitoring (as discussed in Sections 4.6 to 4.11 and 4.45 to 4.51) until the baseline water quality levels are restored or at least 1 week after the leakage is abated. 9. The monitoring data collected in Item 8 above shall be compared with the baseline data collected under normal operation of the Project to identify the degree of impact caused by the pipe leakage.
|
|
Failure of power supply, treatment units or equipment |
1. Investigate the reason of failure. 2. Determine possible remedial measures and identify the need of emergency discharge. 3. If emergency discharge is required,inform EPD and WSD. 4. Ensure remedial measures are implemented. 5. Assess the effectiveness of the implemented remedial measures and identify alternative measures if necessary. 6. Discuss with EPD, AFCD and WSD for the required remedial actions if necessary and ensure all necessary remedial actions are properly implemented. 7. Conduct daily effluent and marine water monitoring (as discussed in Sections 4.6 to 4.11 and 4.45 to 4.51) until the baseline water quality levels are restored or at least 1 week after normal plant operation is resumed (whichever is longer). 8. The monitoring data collected in Item 7 above shall be compared with the baseline data collected under normal operation of the Project to identify the degree of impact caused by the emergency discharge (if any).
|
|
THEES Maintenance period |
1. Inform EPD, WSD and AFCD of the maintenance event before any discharge. 2. Conduct daily effluent and marine water monitoring (as discussed in Sections 4.6 to 4.11 and 4.45 to 4.51) until the baseline water quality levels are restored or at least 4 weeks after termination of the maintenance period (whichever is longer). 3. Install silt curtains at Tai Po and Shatin seawater intakes during the whole discharge period until the baseline water quality levels are restored. 4. The monitoring data collected in Item 2 above shall be compared with the baseline data collected under normal operation of the Project to identify the degree of impact caused by the THEES maintenance discharge.
|
4.55 A PPM programme will be implemented to confirm the predictions of the water quality made in the EIA report. The extent of PPM programme is subject to the prevailing environmental conditions at the time before commissioning of the Project.
4.56 For the STSTW Stage III, a comprehensive PPM programme is scheduled in mid 2006 to verify the predictions of the water quality in the receiving water. Under the Tolo Harbour Effluent Export Scheme (THEES), the treated effluent from both STSTW and TPSTW are discharged into Victoria Harbour (around Kwun Tong Area) via Kai Tak Nullah. The scope of PPM for both STW is similar and their associated works are complementary to one another. The original intention was to conduct a PPM for the THEES following the commission of STSTW Stage III and a PPM after commissioning of Tai Po Stage V to take into account of the updated environmental conditions prevailing at relevant stages.
4.57 The Southeast Kowloon Development (SEKD) Study, which will affect the location of the Kai Tak Nullah (somewhere in Kowloon Bay) is unknown at this stage. The need of a comprehensive PPM would depend on the prevailing environmental conditions at the time before commissioning of the Project. Without knowing the status of SEKD and the final discharge location of THEES, a conservative PPM programme is proposed, which include one year baseline monitoring before commissioning and one year impact monitoring after commissioning. The elements of the PPM programme are similar to Agreement No. CE1/98 such requirements as monitoring of effluent quality, effluent dispersion plum, marine water quality. Details of the programme will be subject to EPD’s endorsement. The PPM programme is enclosed as Annex E for reference.