4. WATER QUALITY

4.1 Introduction

4.1.1 The EIA identified activities and locations during the construction of the KT13 that may have potential impacts on water quality. The EIA recommended a number of mitigation measures that should be implemented to control the potential impacts to within acceptable limits. A monitoring programme is recommended for baseline conditions and during the construction phase to assess and ensure the performance of the proposed measures.

4.1.2 This section of the Manual lists all the recommended mitigative and preventive measures in the EIA for the protection of water quality during construction phase, and the up to date requirements for baseline and construction phase water quality monitoring. The Contractor is required to implement these listed measures and to undertake water quality monitoring as specified in this section, in addition to complying with all the water quality related legislation of HKSAR.

4.2 Water Quality Parameters

4.2.1 The selection of water quality monitoring parameters shall be based on the recommendations in the EIA report. The monitoring shall be carried out by the ET to ensure that any deteriorating water quality can be readily detected and action be taken in time to rectify the situation.

4.2.2 In addition to the water quality parameters, selected relevant data shall also be measured, such as monitoring location/position, time, water depth, water temperature, salinity, DO saturation, weather conditions, tidal stage, and any special phenomena and work underway at the construction site.

4.2.3 The data format of the water quality monitoring record and a sample monitoring record sheet are shown in Appendix B for reference.

4.3 Sampling Procedures and Monitoring Equipment

4.3.1 Water samples for all monitoring parameters shall be collected, stored, preserved and analysis according to the Standard Methods, APHA 17 ed. and/or methods agreed by the Director of Environmental Protection. In-situ measurements at monitoring locations including DO, turbidity, salinity and water depth shall be collected using equipment with the characteristics and functions listed in the following sections.

Dissolved oxygen and temperature measuring equipment

4.3.2 The equipment shall have the following characteristics and functions.

(a) The instrument shall be a portable, weatherproof dissolved oxygen measuring instrument complete with cable, sensor, comprehensive operation manuals, and with the use of a DC power source. (e.g. YSI model 59 meter, YSI 5739 probe, YSI 5795A submersible stirrer with reel and cable or an approved similar instrument). It shall be capable of measuring:-

- a dissolved oxygen level in the range of 0-20 mg/l and 0-200% saturation; and

- a temperature of 0-45 degree Celsius.

(b) 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.

(c) Should 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.

Turbidity Measurement Instrument

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

Suspended Solids

4.3.4 The equipment shall have the following characteristics and functions.

(a) Sampling shall be carried out using a water sampler which 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 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 (e.g. Kahlsico Water Sampler or an approved similar instrument).

(b) Water samples for suspended solids measurement shall 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.

Water Depth Detector

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

4.4 Laboratory Measurement/Analysis

4.4.1 Analysis of suspended solids, ammonia, and zinc concentration, shall be carried out in a HOKLAS or other international accredited laboratory. Water samples of about 1000ml shall be collected at the monitoring stations for carrying out the laboratory SS determination. The detection limit shall be 1 mg/L or better. The SS determination work shall start within 24 hours after collection of the water samples. 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 the EPD. All the analysis shall be witnessed by the ET. 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 Locations of the sites to be monitored during baseline and impact monitoring are shown in Table 4.1 and Figures 4.1a and 4.1b. The status and locations of water quality sensitive receivers may change after issuing this manual. In such a case, the ET Leader shall propose updated monitoring locations and seek approval from the IEC and EPD.

Table 4.1

Proposed Monitoring Locations for Water Quality

Monitoring Location	Description	Purpose of Placing Sampling Location
W1	Upstream of all works proposed under KT13 and of the stream	Establish background levels of parameters to be monitored, control station
W2	In a short section left unmodified to retain dry weather flow	Monitor and audit potential impacts from Section B works to unmodified stream.
W3	Upstream of the section to be left unmodified for ecological benefits	Monitor and audit potential impacts from Section B works to unmodified stream section, to ensure quality of water supplying the egretry and associated wetland habitats
W4	Upstream of the discharge point of a local brook into the main KT13 stream	Establish background levels of parameters to be monitored for this incoming water, control station.
W5	Upstream of the discharge point of a second local brook into the main KT13 stream	Establish background levels of parameters to be monitored for this incoming water, control station.
W6	Immediately above the discharge point to Kam Tin Main Drainage Channel	Monitor and audit potential impacts from all KT13 works, check water quality discharging to Kam Tin River Main Drainage Channel.

4.5.2 When alternative monitoring locations are proposed, they shall be chosen based on the following criteria:

(a) at locations close to and preferably at the boundary of the mixing zone of the major site activities as indicated in the EIA final report, which are likely to have water quality impacts;

(b) close to the sensitive receptors which are directly or likely to be affected;

(c) for monitoring locations located in the vicinity of the sensitive receptors, care shall be taken to cause minimal disturbance during monitoring;

(d) two or more control stations which shall be at locations representative of the project site in its undisturbed condition. Control station shall be located, as far as is practicable, both upstream and downstream of the works area.

4.5.3 Control stations 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 shall be outside the area of influence of the works and, as far as practicable, not affected by any other works.

4.5.4 Measurements shall be taken at 3 water depths, namely, 1m below water surface, mid-depth and 1m above stream or sea bed, except where the water depth less than 6m, the mid-depth station may be omitted. Should the water depth be less than 3m, only the mid-depth station will be monitored.

4.5.5 Duplicates in-situ measurements and samples collected from each independent sampling event are required for all parameters to ensure a robust statistically interpretable dataset.

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 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, control and reference monitoring stations. The baseline conditions shall be established by measuring the water quality parameters specified in Table 4.2. The measurement shall be taken at all designated monitoring stations including control stations for 3 days per week for 4 consecutive 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 the IEC and EPD on an appropriate set of data to be used as baseline reference.

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

Table 4.2

Water Quality Monitoring Locations, Parameter, Frequency

and Duration for Baseline

Locations	Parameters	Frequency	Duration
W1 W2 W3 W4 W5 W6	DO, pH, turbidity, temperature, suspended solids, ammonia, zinc	3 days per week	Four weeks

4.7 Impact Monitoring

4.7.1 During the course of the construction works, monitoring shall be undertaken according to the parameters, frequencies, and duration described in Table 4.3. The interval between two sets of monitoring shall not be less than 36 hours except where there are exceedances of AL levels, in which case the monitoring frequency will be increased.

Table 4.3

Locations, Parameters, Frequencies and Durations during Construction Phases

Parameter	Locations	Frequency
DO/pH/Temperature/Turbidity/ SS/Ammonia/Zinc	W1, W2, W3, W4, W5, W6	3 days per week throughout construction phase.

4.7.2 The proposed water quality monitoring schedule shall be faxed to IEC and EPD on or before the first day of the monitoring month. EPD shall also be notified immediately for any changes in schedule by fax.

4.8 Event and Action Plan for Water Quality

4.8.1 The Action and Limit levels for water quality are shown in Table 4.4. Should the monitoring results at any designated monitoring stations indicate that the Action and Limit levels are exceeded, the actions specified in Table 4.5 shall be carried out.

Table 4.4

Action and Limit Levels for Water Quality

Parameters	Action	Limit
DO in mg/l (Surface, Middle & Bottom)	Surface & Middle 5%-ile of baseline data for surface and middle layer Bottom 5%-ile of baseline data for bottom layer.	Surface & Middle 4mg/l or 1%-ile of baseline data for surface and middle layer Bottom 2mg/l or 1%-ile of baseline data for bottom layer
pH, turbidity, SS, ammonia and Zinc (depth-averaged)	95%-ile of baseline data or 120% of upstream control station’s SS Turbidity, ammonia, Zinc and pH at the same tide of the same day	99%-ile of baseline or 130% of upstream control station’s SS Turbidity, ammonia, zinc and pH at the same tide of the same day

Notes:

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

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

- For pH, non-compliance of the water quality limits occurs when monitoring result is outside the specified range.

- 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

Table 4.5 Event and Action Plan for Water Quality

Event	ET Leader	IEC	ER	Contractor
Action level being exceeded by one sampling day	Repeat in-site measurement to confirm findings; Identify Source(s) of impact; Inform IEC an Contractor; Check monitoring data, all plant, equipment and Contractor’s working methods; Discuss mitigation measures with IEC and Contractor; Repeat measurement on next day of exceedance	Discuss with ET and Contractor on the mitigation measures Review proposals on mitigation measures submitted by Contractor and advise the ER accordingly Assess the effectiveness of the implemented mitigation measures.	Discuss with IEC on the proposed mitigation measures; Make agreement on the mitigation measures to be implemented;	Inform the ER and confirm notification of the non-compliance in writing; Rectify unacceptable practice; Check al plant and equipment; Consider changes of working methods; Discuss with ET and IEC and propose mitigation measures to IEC and ER; Implement the agreed mitigation measures.
Action level being exceeded by more than one consecutive sampling days	Repeat in-situ measurement to confirm findings; Identify source(s) of impact; Inform IEC and Contractor; Check monitoring data, all plant, equipment and Contractor’s working methods; Discuss mitigation measures with IEC and Contractor; Ensure mitigation measures are implemented; Prepare to increase the monitoring frequency to daily; Repeat measurement on next day of exceedance.	Discuss with ET and Contractor on the mitigation measures Review proposals on mitigation measures submitted by Contractor and advise the ER accordingly Assess the effectiveness of the implemented mitigation measures.	Discuss with IEC on the proposed mitigation measures; Made agreement on the mitigation measures to be 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; Consider changes of working methods; Discuss with ET and IEC and propose mitigation measures to IEC and ER within 3 working days; Implement the agreed mitigation measures.
Limit level being exceeded by one sampling day	Repeat in-situ measurement to confirm findings; Identify source(s) of impact; Inform IEC, contractor and EPD; Check monitoring data, all plant, equipment and Contractor’s working methods; Discuss mitigation measures with IEC, ER and Contractor; Ensure mitigation measures are implemented; Increase the monitoring frequency to daily until no exceedance of Limit level.	Discuss with ET and Contractor on the mitigation measures Review proposals on mitigation measures submitted by Contractor and advise the R accordingly Assess the effectiveness of the implemented mitigation measures.	Discuss with IEC, ET and Contractor on the proposed mitigation measures; Request Contract to critically review the working methods; Made agreement on the mitigation measures to be 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; consider changes of working methods; Discuss with ET, IEC and ER and propose mitigation measures to IEC and ER within 3 working days; Implement the agreed mitigation measures/
Limit level being exceeded by more than one consecutive sampling days	Repeat in-situ measurement to confirm fundings; Identify source(s) of impact; Inform IEC, contractor and EPD; Check monitoring data, all plant, equipment and Contractor’s working methods; Discuss mitigation measures with IEC, ER and Contractor; Ensure mitigation measures are implemented; Increase the Monitoring frequency to daily until no exceedance of Limit level for two consecutive days.	Discuss with ET and Contractor on the mitigation measures Review proposals on mitigation measures submitted by Contractor and advise the ER accordingly Assess the effectiveness of the implemented mitigation measures.	Discuss with IEC, ET and Contractor on the proposed mitigation measures; Request Contractor to critically review the working methods; Make agreement on the mitigation measures to be implemented; Assess the effectiveness of the implemented mitigation measures; Consider and instruct, if necessary, the Contractor to slow down or to stop all or part of the marine work until no exceedance of Limit level.	Inform the ER and confirm notification of the non-compliance in writing; Rectify unacceptable practice; Check all plant and equipment; Consider changes of working methods; Discuss with ET, IEC and ER and propose mitigation measures to IEC and ER within 3 working days; Implement the agreed mitigation measures; As directed by the Engineer, to slow down or to stop all or part of the marine work or construction activities.

4.9 Water Quality Mitigation Measures

4.9.1 The following paragraphs discuss the proposed mitigation measures for protection of water quality during construction phase.

General

4.9.2 The Contractor shall observe and comply with the Water Pollution Control Ordinance (WPCO) and its subsidiary regulations. The Contractor shall carry out the works in such a manner as to minimise adverse impacts on the water quality during execution of the works. In particular the Contractor shall arrange his method of working to minimise the effects on the water quality within and outside the site and on the transport routes.

4.9.3 The Contractor shall follow the practices, and be responsible for the design, construction, operation and maintenance of all the mitigation measures as specified in ProPECC PN 1/94 - Construction Site Drainage. The design of the mitigation measures shall be submitted by the Contractor to the Engineer for approval.

4.9.4 As part of the ecological mitigation measure to minimise impact on the existing stream course, a restriction to minimise the working area to 75m length of stream at any one time has been proposed. Such restriction would also reduce the likely water quality impact.

Site Formation

4.9.5 Temporary earth bunds and/or sand bag barriers should be used to direct stormwater run-off to temporary settlement area. The settlement area should be within the channel itself. A cofferdam should be formed to keep the working area dry. The channel will be dug out to a depth of around 1–2m for a length of approximately 12m, to form a sedimentation area. The volume will be approximately 50m³ (with a channel width of 3.5m).

4.9.6 Sediment flowing downstream should settle in this settlement pond, while run-off from the surface should be channel through a local site drainage system into the settlement area. The settlement area should be maintained and the deposited materials should be removed regularly, at the onset of and after each rainstorm to ensure proper functioning at all times. No sediment removal shall be allowed in rainy weather.

4.9.7 Open stockpiles susceptible to erosion should be covered with tarpaulin or similar fabric, especially during the wet season (Apr-Sep) or when heavy rainstorm is predicted.

Stream Diversion and Dredging of Streams

4.9.8 The Contractor should provide temporary drainage diversion during construction to ensure continuous water flow to the untouched portion of the stream.

4.9.9 The use of containment structure such as temporary earth bunds, sand bags, sheetpile barriers or other similar techniques is recommended to facilitate a dry or at least confined excavation within watercourses.

4.9.10 Excavated sediment from streams and channel is likely to be wet and contaminated. The material should be stored in covered impermeable skips and disposed on the same day, or within 1 day, to avoid both odour and inadvertent release of contaminants to nearby water bodies.

Concreting Work

4.9.11 Runoff should be carefully channelled to prevent concrete-contaminated water from entering watercourses. Adjustment of pH can be achieved by adding a suitable neutralising reagent to wastewater prior to discharge. Re-use of the supernatant from the sediment pits for washing out of concrete lorries should be practised.

4.9.12 Any exceedance of acceptable range of pH levels in the nearby water bodies caused by inadvertent release of site runoff containing concrete should be monitored and rectified under the EM&A programme for this Project.

Site Workshop or Depot

4.9.13 Any Contractor generating waste oil or other chemicals as a result of his activities should register as a chemical waste producer and provide a safe storage area for chemicals on site. The storage site should be located away from existing water courses. Hard standing compounds should drain via an oil interceptor. To prevent spillage of fuels or other chemicals to water courses, all fuel tanks and storage areas should be sited on sealed areas, within a bund of a capacity equal to 110% of the storage capacity of the largest tank. Disposal of the waste oil should be done by a licensed collector. Oil interceptors should be regularly inspected and cleaned to avoid wash-out of oil during storm conditions. A bypass should be provided to avoid overload of the interceptor's capacity. Good housekeeping practices should be implemented to minimise careless spillage and to keep the storage and the work space in a tidy and clean condition. Appropriate training including safety codes and relevant manuals should be given to the personnel who regularly handle the chemicals on site.

Presence of Additional Population (Workers)

4.9.14 Sewage arising from the additional population of workers on site should be collected in a suitable storage facility, such as portable chemical toilets. An adequate number of portable toilets should be provided for the construction workforce. The portable toilets should be maintained in a state that will not deter the workers from using them. The collected wastewater from sewage facilities and also from eating areas or washing facilities must be disposed of properly, in accordance with the WPCO requirements. Wastewater collected should be discharged into foul sewers and collected by licensed collectors.

4.9.15 Either chemical toilets or other types of sewage treatment facilities without local discharge of wastewater shall be used to handle the foul water effluent arising from the project sites.

4.9.16 Proper waste handling, storage, collection and disposal measures as recommended in the Waste chapter should be implemented by the Contractor.

Summary of Mitigation Measures for Construction Phase

4.9.17 The potential impacts on water quality during the construction phase of the Work and the associated recommendation of mitigation measures are summarized in Table 4.5.

Table 4.6

Summary of Mitigation Measures for Construction Impacts

Impact from Construction	Mitigation Measures
General water quality impacts.	To strictly follow the requirements in ProPECC PN 1/94. Minimise working area to 75m length of stream.
Increase of suspended solids and turbidity from silty site run-off during site formation.	After diversion of stream water, section of channel under construction will be used as a settlement area for construction site runoff. Sediments will be cleared from this settlement area before and after each rainstorm. No sediment removal will be allowed in rainy weather. Open stockpiles will be covered with tarpaulin during wet season.
Release of contaminated and uncontaminated sediments into stream water during stream diversion and dredging of the stream.	Ensure continuous water flow to the stream by providing temporary drainage diversion during construction. Use of containment structures during excavation. Excavated material to be stored in covered impermeable skips and transported away from site on the same day or within 1 day.
Elevation of pH, ammonia and suspend solids in water courses from concrete washings.	Monitoring and control of pH levels in nearby water bodies as part of the EM&A programme.
Release of oil and grease washings used in the site workshop.	The Contractor shall register as chemical waste producer if waste oil is generated. Waste oil and other chemical waste shall be collected by licenced contractors.
Increase of sewage and other wastewater from additional workers.	Provision of mobile chemical toilets and the collection and disposal of sewage by licenced contractors to government sewers. Implement proper on-site waste management.