1. Introduction

1.1 Background

The Environmental Protection Department (EPD) of the Government of the Hong Kong Special Administrative Region (the Government) proposed to construct the Integrated Waste Management Facilities (IWMF) Phase 1 on an artificial island near Shek Kwu Chau (SKC), south of Lantau Island for the purpose of treating municipal solid waste and generating electricity from the waste treatment process for its own use and export surplus electricity, if any, to the power grid.

The EIA Report (EIA-201/2011) was approved by the EPD on 17 January 2012 with the Environmental Permit (EP) of the Project issued on 19 January 2012 (EP-429/2012) and a variation of the EP on 14 October 2016 (EP-429/2012/A). A Further EP (FEP-01/429/2012/A) was granted to Keppel Seghers-Zhen Hua Joint Venture for the reclamation works and construction of the IWMF on 27 December 2017. Another latest Further EP (FEP-02/429/2012/B) was granted to CLP Power for the installation of the 132kV submarine cable circuits connecting Cheung Sha, South Lantau and Shek Kwu Chau Artificial Island (the Project) on 25 May 2020.

1.2 Purpose of this Baseline Water Quality Monitoring Report

The purpose of this Baseline Water Quality Monitoring Report is to present the results of the baseline water quality prior to the commencement of cable installation works in accordance with the Updated Environmental Monitoring and Audit (EM&A) Manual and determine Action and Limit levels during the cable installation accordingly.

1.3 Structure of this Report

Following this introductory section, the structure of this baseline water quality monitoring report is set out below:-

n Section 2 details the monitoring requirements specified in the Updated EM&A Manual, including monitoring locations and methodology;

n Section 3 summarises the results and findings of the baseline water quality monitoring exercise, discusses details on influencing factors;

n Section 4 determines the Action and Limit Levels based on the monitoring results;

n Section 5 stipulates the Event and Action Plan for this Project;

n Section 6 concludes the baseline water quality monitoring exercise.

2. Monitoring Requirements

In accordance with the Updated EM&A Manual of the Project, baseline water quality monitoring shall be carried out three (3) times per week for at least four (4) weeks at five (5) monitoring stations to establish the ambient conditions prior to the commencement of construction works for cable installation for the Project and to demonstrate the suitability of the proposed control monitoring stations. Baseline water quality monitoring was conducted for four weeks from 12 July to 9 August 2023. The baseline conditions were established by measuring relevant water quality parameters at the designated monitoring stations for the Project, including control stations at mid-ebb and mid-flood tides. Further details of the baseline water quality monitoring under this Project are presented in the following sections.

2.1 Monitoring Locations

The water quality monitoring locations for baseline water quality monitoring are shown in Figure 2.1 and detailed in Table 2.1.

Table 2.1 Location of Water Quality Monitoring Stations

Station	Description	Easting	Northing
C1A	Control Station	812823	806300
C2A	Control Station	818869	806808
S1A	Submarine Cable Landing Site	813430	809962
S2A	Submarine Cable	814808	808515
S3A	Submarine Cable Landing Site	816203	805178

2.2 Monitoring Methodology

2.2.1 Monitoring Equipment

Table 2.2 summarises the equipment used in the baseline monitoring works. All of the monitoring equipment complied with the requirements as set out in the Updated EM&A Manual. Copies of the calibration certificates are attached in Appendix A.

Table 2.2 Water Quality Monitoring Equipment

Equipment	Brand and Model
Water Sampling Equipment	Wildlife Supply Company Horizontal Alpha™ Bottles
Positioning Device	Garmin 20X Personal Navigator
Water Depth Gauge	Xyorca XY-453
Multiparameter Meter (measurement of DO, Temperature, Turbidity, pH and Salinity)	YSI ProDSS (S/N: 15M100005; 16H104233; 21K101468)

2.2.2 Monitoring Parameters and Frequency

Table 2.3 summarises the monitoring parameters, monitoring period and frequencies of the water quality monitoring.

Table 2.3 Water Quality Monitoring Parameters and Frequency

Monitoring Stations

Parameters (Unit)

Depth

Frequency and Replications

C1A

C2A

S1A

S2A

S3A

n Temperature (°C)

n pH

n Salinity (ppt)

n Dissolved Oxygen (DO) (mg/L and % saturation)

n Turbidity (NTU)

n Suspended Solids (SS) (mg/L)

3 water depths: 1 m below sea surface, mid-depth and 1 m above seabed.

If the water depth is less than 3 m, mid-depth sampling only.

If water depth is less than 6 m, mid-depth may be omitted.

Baseline monitoring: 3 days per week, at mid-flood and mid-ebb tides, for at least 4 weeks prior to the commencement of construction work.

Two (2) replicates in-situ measurements and water samples.

In addition to the water quality parameters, other relevant data were also measured and recorded in Water Quality Monitoring Logs, including the monitoring location, time, weather and sea conditions, water depth, tidal stages, special phenomena and work activities undertaken around the monitoring and works area that may influence the monitoring results.

2.2.3 Operational/ Analytical Procedures

At each sampling depth, two consecutive measurements of DO level, DO Saturation, Temperature, Turbidity, Salinity and pH were taken. Where the difference in the value between the first and second readings of each set was more than 25% of the value of the first reading, the reading was discarded and further readings were taken. Two samples were collected for laboratory analysis of SS content. Following collection, water samples for laboratory analysis were stored in high density polythene bottles (1L) with no preservatives added, packed in ice (cooled to 4°C without being frozen) and kept in dark during both on-site temporary storage and shipment to the testing laboratory. The samples were delivered to the laboratory as soon as possible and the laboratory determination works started within 24 hours after collection of the water samples. Sufficient volume of samples was collected to achieve the reporting limit.

The sample testing was performed by ALS Technichem (HK) Pty Ltd (HOKLAS Registration No. 066). Comprehensive quality assurance and control procedures were in place in order to ensure quality and consistency in results.

2.3 QA/QC Requirements

2.3.1 Calibration of In-situ Instruments

All in situ monitoring equipment for the measurement of temperature, dissolved oxygen, turbidity, pH and salinity were checked, calibrated and certified by a laboratory accredited under HOKLAS before use, and subsequently re-calibrated at 3 monthly intervals throughout all stages of water quality monitoring programme. In-situ checking for the monitoring equipment, including responses of sensors and electrodes, were performed with certified standard solutions before each use. Wet bulb calibration for a dissolved oxygen meter was carried out before commencement of monitoring and after completion of all measurements each day. A zero check in distilled water was performed with the turbidity and salinity probes. The respective probes were then calibrated with a solution of known NTU (Formazin solution), salinity (sodium chloride & potassium chloride mixture) and pH (pH standard buffer solution) to check the accuracy of the monitoring equipment. All certified standard solutions used were within the validity period.

On-site calibration of field equipment followed the “Guide to On-Site Test Methods for the Analysis of Waters”, BS 1427:2009. Sufficient stocks of spare parts were maintained for replacement when necessary. Backup monitoring equipment was also made available to ensure monitoring could proceed uninterrupted even when equipment is under maintenance, calibration etc.

2.3.2 Decontamination Procedures

Water sampling equipment used during the course of the monitoring programme was decontaminated by manual washing and rinsed clean seawater/ distilled water after each sampling event. All disposable equipment was discarded after sampling.

2.3.3 Sampling Management and Supervision

All sampling bottles were labelled with sample ID (including the indication of sampling station and tidal stage e.g. C1A/ME/S REPLICATE 1), laboratory number and sampling date. Water samples were dispatched to the testing laboratory for analysis as soon as possible after the sampling. All samples were stored in a cool box and kept at less than 4°C but without frozen. All water samples were handled under chain of custody protocols and relinquished to the laboratory representatives at locations specified by the laboratory. The laboratory determination works started within 24 hours after collection of water samples.

2.3.4 Quality Control Measures for Sample Testing

The sample testing was performed by ALS Technichem (HK) Pty Ltd. The following quality control programme was performed by the laboratory for every batch of 20 samples:

n One method blank; and

n One set of quality control (QC) samples (including method QC and sample duplicate).

3. Baseline Water Quality Monitoring Results

Baseline water quality monitoring was conducted at five (5) monitoring stations (C1A, C2A, S1A, S2A, S3A) between 12 July to 9 August 2023. Monitoring session on 17 July 2023 was rescheduled to 9 August 2023 due to No. 8 Gale or Storm Signal in force. The detailed monitoring schedule is shown in Appendix B. The monitoring results at each monitoring station are shown in Appendix C. Graphical presentation of water quality (DO, Turbidity and SS) at the monitoring stations is given in Appendix D.

From the baseline water quality monitoring exercise covering a total of 12 days, water quality data including dissolved oxygen, turbidity, water temperature and suspended solids are collected.

A total of 674 records of dissolved oxygen were collected for all three water depths of the water column, ranging from 1.2 mg/L to 13.1 mg/L and with an average of 5.9 mg/L.

A total of 674 records of turbidity were collected for all three water depths of the water column, ranging from 0.0 NTU to 14.9 NTU and with an average of 3.2 NTU.

A total of 674 records of water temperature were collected for all three water depths of the water column, ranging from 23.6°C to 31.2°C and with an average of 28.2°C.

A total of 674 records of suspended solids were collected for all three water depths of the water column, ranging from 2 mg/L to 11 mg/L and with an average of 3.2 mg/L.

No marine construction works were observed in the vicinity of all monitoring stations during the baseline monitoring period. The baseline monitoring results are thus considered representation of the ambient water quality of the Project area.

Mean, standard deviation and range of data at each station is provided below in Table 3.1. As shown, while variation in data is observed across different stations, the overall average and variation of control and impact stations are quite similar and the differences are small.

Table 3.1 Summary of Baseline Water Quality Monitoring Results

Stations

Water Temperature (°C)

Dissolved Oxygen (mg/L)

Turbidity (NTU)

Suspended Solids (mg/L)

Mid-Ebb

Mid-Flood

Mid-Ebb

Mid-Flood

Mid-Ebb

Mid-Flood

Mid-Ebb

Mid-Flood

C1A

28.1±1.5

(24.0-30.1)

28.1±1.5

(24.3-30.5)

6.0±2.4

(1.8-12.5)

5.6±2.4

(1.6-12.0)

2.7±3.1

(0.2-12.1)

3.7±3.7

(0.2-13.7)

3±1

(2-6)

3±1

(2-6)

C2A

28.1±1.5

(23.9-30.2)

28.0±1.7

(24.0-30.9)

5.8±2.3

(1.2-9.9)

5.4±2.6

(1.9-11.9)

2.7±2.6

(0.1-11.9)

4.0±4.4

(0.1-14.9)

3±1

(2-7)

3±1

(2-6)

S1A

28.8±1.3

(26.6-31.1)

29.1±1.3

(26.4-31.0)

6.8±2.3

(3.1-12.9)

7.0±2.7

(1.5-13.1)

3.5±3.6

(0.1-13.0)

3.2±2.6

(0.3-8.8)

3±1

(2-7)

4±2

(2-11)

S2A

28.4±1.4

(25.6-30.8)

28.4±1.3

(25.6-31.2)

6.1±2.7

(1.5-12.5)

6.0±2.7

(1.2-12.6)

3.5±4.1

(0.0-13.6)

3.2±3.3

(0.1-12.6)

3±1

(2-6)

3±2

(2-9)

S3A

27.8±1.6

(23.6-30.3)

28.1±1.5

(24.1-30.4)

5.2±2.3

(1.5-12.2)

5.4±2.5

(1.7-11.5)

2.5±2.5

(0.1-9.0)

3.3±3.5

(0.0-13.0)

3±1

(2-7)

3±2

(2-8)

All Control

28.0±1.5

(23.9-30.9)

5.7±2.4

(1.2-12.5)

3.3±3.5

(0.1-14.9)

3±1

(2-7)

All Impact

28.4±1.5

(23.6-31.2)

6.0±2.6

(1.2-13.1)

3.2±3.3

(0.0-13.6)

3±2

(2-11)

Note: Average value ± standard deviation and the range of values (in bracket) are presented in each cell.

4. Action and Limit Levels

The water quality monitoring results indicated there were natural fluctuations in the marine environment. Impact water quality monitoring data will be evaluated against Action and Limit Levels determined using baseline data to determine water quality compliance. Action and Limit Levels of key assessment parameters for baseline water quality monitoring including DO, Turbidity and SS are determined in accordance with requirements set out in the Updated EM&A Manual which are summarised in Table 4.1.

Table 4.1 Action and Limit Levels for Marine Water Quality

Parameters	Action Level	Limit Level
Construction Phase Impact Monitoring
DO in mg/L	≤ 5 %-ile of baseline data	≤ 4
SS in mg/L	≥ 95 %-ile of baseline data or 120% of control station’s SS at the same tide of the same day of measurement	≥ 99 %-ile of baseline or 130% of control station’s SS at the same tide of the same day of measurement
Turbidity in NTU	≥ 95 %-ile of baseline data or 120% of control station’s turbidity at the same tide of the same day of measurement	≥ 99 %-ile of baseline or 130% of control station’s turbidity at the same tide of the same day of measurement

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.

The calculated Action and Limit levels are shown in Table 4.2.

Table 4.2 Calculated Action and Limit Levels for Marine Water Quality

Parameters	Action Level	Limit Level
Construction Phase Impact Monitoring
DO in mg/L	≤ 2.1	≤ 1.5
SS in mg/L	≥ 6 or 120% of control station’s SS at the same tide of the same day of measurement	≥ 8 or 130% of control station’s SS at the same tide of the same day of measurement
Turbidity in NTU	≥ 10.7 or 120% of control station’s turbidity at the same tide of the same day of measurement	≥ 13.1 or 130% of control station’s turbidity at the same tide of the same day of measurement

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.

3. In view of the relatively low measured DO level in the baseline monitoring exercise, the pre-determined limit level of 4 mg/L is not applicable. The first percentile (1 %-ile) value of baseline data (i.e. 1.5 mg/L) is adopted as the limit level for DO.

5. Event and Action Plan

Should non-compliance of the criteria for water quality occur, action in accordance with the Event and Action Plan presented in Table 5.1 below shall be carried out and review works would be conducted.

Table 5.1 Event and Action Plan for Construction Phase Marine Water Quality

EVENT

ACTION

IEC

CONTRACTOR

Action level being exceeded by one sampling day

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;

(The above actions should be taken within 1 working day after the exceedance is identified)

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.

(The above actions should be taken within 1 working day after the exceedance is identified)

Discuss with IEC on the proposed mitigation measures;

Make agreement on the mitigation measures to be implemented.

(The above actions should be taken within 1 working day after the exceedance is identified)

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 and IEC and propose mitigation measures to IEC and ER within 3 working days;

Implement the agreed mitigation measures.

(The above actions should be taken within 1 working day after the exceedance is identified)

Action level being exceeded by more than one consecutive sampling days

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;

(The above actions should be taken within 1 working day after the exceedance is identified)

Repeat measurement on next working 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.

(The above actions should be taken within 1 working day after the exceedance is identified)

Discuss with IEC on the proposed mitigation measures;

Make agreement on the mitigation measures to be implemented;

Assess the effectiveness of the implemented mitigation measures.

(The above actions should be taken within 1 working day after the exceedance is identified)

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 and IEC and propose mitigation measures to IEC and ER within 3 working days;

Implement the agreed mitigation measures.

(The above actions should be taken within 1 working day after the exceedance is identified)

Limit level being exceeded by one sampling day

Repeat in situ measurement to confirm findings;

Check monitoring data, plant, equipment and Contractor’s working methods;

Identify source(s) of impact and record in notification of exceedance;

Inform IEC, Contractor and EPD;

Discuss mitigation measure with IEC, ER and Contractor;

(The above actions should be taken within 1 working day after the exceedance is identified)

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.

(The above actions should be taken within 1 working day after the exceedance is identified)

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.

(The above actions should be taken within 1 working day after the exceedance is identified)

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.

(The above actions should be taken within 1 working day after the exceedance is identified)

Limit level being exceeded by more than one consecutive sampling days

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.

(The above actions should be taken within 1 working day after the exceedance is identified)

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.

(The above actions should be taken within 1 working day after the exceedance is identified)

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.

(The above actions should be taken within 1 working day after the exceedance is identified)

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 ER, to slow down or to stop all or part of the marine work or construction activities.

(The above actions should be taken within 1 working day after the exceedance is identified)

Executive summary

1. Introduction

1.1 Background

1.2 Purpose of this Baseline Water Quality Monitoring Report

1.3 Structure of this Report

2. Monitoring Requirements

2.1 Monitoring Locations

2.2 Monitoring Methodology

2.2.1 Monitoring Equipment

2.2.2 Monitoring Parameters and Frequency

2.2.3 Operational/ Analytical Procedures

2.3 QA/QC Requirements

2.3.1 Calibration of In-situ Instruments

2.3.2 Decontamination Procedures

2.3.3 Sampling Management and Supervision

2.3.4 Quality Control Measures for Sample Testing

3. Baseline Water Quality Monitoring Results

4. Action and Limit Levels

5. Event and Action Plan

6. Conclusion