Agreement No. CE 59/2020 (EP)

 

Environmental Monitoring and

Audit for Disposal Facility to

the East of Sha Chau (2021-

2026) – Investigation

 

Monthly EM&A Report for

Contaminated Mud Pits to the East of Sha Chau

– November 2024

December 2024

 

Civil Engineering and Development Department

 

Mott MacDonald

3/F Manulife Place

348 Kwun Tong Road

Kwun Tong

Kowloon

Hong Kong

 

T +852 2828 5757

mottmac.hk

 

 

 

 

 

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Issue and Revision Record

Revision

Date

Originator

Checker

Approver

Description

A

Dec 2024

Various

Liz Lo

Thomas Chan

Revision A of Submission

B

Dec 2024

Various

Liz Lo

Thomas Chan

Revision B of Submission

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Document reference:

423134 | 06/05/44 | B

 

Information class:

Standard

 

This document is issued for the party which commissioned it and for specific purposes connected with the above-captioned project only. It should not be relied upon by any other party or used for any other purpose.

We accept no responsibility for the consequences of this document being relied upon by any other party, or being used for any other purpose, or containing any error or omission which is due to an error or omission in data supplied to us by other parties.

This document contains confidential information and proprietary intellectual property. It should not be shown to other parties without consent from us and from the party which commissioned it.

 

Contents

1       Introduction

1.1      Background

1.2      Reporting Period

1.3      Details of Sampling and Laboratory Testing Activities

1.4      Details of Outstanding Sampling or Analysis

2       Brief Discussion of Monitoring Results for ESC CMP V

2.1      Introduction

2.2      Water Column Profiling of ESC CMP Vb – in November 2024

2.2.1        In-situ Measurements

2.2.2        Laboratory Measurements for Suspended Solids (SS)

2.3      Routine Water Quality Monitoring of ESC CMPs – in October 2024

2.4      Routine Water Quality Monitoring of ESC CMPs – in November 2024

2.4.1        In-situ Measurements

2.4.2        Laboratory Measurements

2.5      Pit Specific Sediment Chemistry of ESC CMP Vb – in November 2024

2.6      Sediment Chemistry after a Major Storm of ESC CMP V – in November 2024

3       Future Key Issues

3.1      Activities Scheduled for the Next Reporting Period

3.2      Study Programme

 

Tables

Table 1.1

Works Schedule for ESC CMP V Works Schedule for ESC CMP V

 

Figures

Figure 2.1

Routine & Capping Water Quality Sampling Stations (Flood-Tide) for ESC CMPs

Figure 2.2

Pit Specific Sediment Quality Monitoring Stations for CMP V

Figure 2.3

Sediment Chemistry after a Major Storm Monitoring Stations for ESC CMPs

Figure 2.4

Track of Tropical Cyclone Toraji

 

Appendices

Appendix A

Sampling Schedule

Appendix B

Water Quality Monitoring Results

Appendix C

Graphical Presentations

Appendix D

Study Programme

 

 

 

 

1         Introduction

1.1         Background

The Civil Engineering and Development Department (CEDD) is managing a number of marine disposal facilities in Hong Kong waters, including the Contaminated Mud Pits (CMPs) to the East of Sha Chau (ESC) for the disposal of contaminated sediment, and various open-sea disposal grounds located to the South of Cheung Chau (SCC), East of Tung Lung Chau (ETLC) and East of Ninepins (ENP) for the disposal of uncontaminated sediment.

Environmental Permits (EPs) (Ref. No. EP-312/2008/A) was issued by the Environmental Protection Department (EPD) to the CEDD, the Permit Holder, on 28 November 2008 for the Project - Disposal of Contaminated Sediment – Dredging, Management and Capping of Sediment Disposal Facility at Sha Chau.

Under the requirements of the EP, EM&A programmes which encompass water and sediment chemistry, fisheries assessment, tissue and whole body analysis, sediment toxicity and benthic recolonisation studies as set out in the EM&A Manuals are required to be implemented. EM&A programmes have been continuously carried out during the operation of the CMPs at ESC. A review of the collection and analysis of such environmental data from the monitoring programme demonstrated that there had not been any adverse environmental impacts resulting from disposal activities.[1],[2] The current programme will assess the impacts resulting from dredging, disposal and capping operations of CMP V.

A proposal on the change of number of sample replication of water quality and sediment monitoring as well as combination of routine water quality monitoring and water quality monitoring during capping operation was submitted to EPD and agreed by EPD on 3 December 2020. The proposed changes have been effective for the EM&A activities since December 2020. In early 2022, after implementing the Phase 1 optimisation for at least one year, a further data review was conducted. The monitoring data has been reviewed and demonstrated that the data robustness and representativeness are maintained. Therefore, a technical note presenting the data review results served as a supplementary information was submitted to EPD and presented that Phase 2 optimization of sample replication of water quality and sediment monitoring for the Project will be implemented in 2022. EPD expressed no comment on the review and note the implementation of Phase 2 optimization of sample replication on 18 May 2022, and thus this optimization has been effective for the EM&A activities since July 2022.

The latest sampling schedule is provided in Appendix A.

The present EM&A programme under Agreement No. CE 59/2020 (EP) covers the dredging, disposal and capping operations of the ESC CMP V (see Appendix A for the EM&A programme.) Detailed works schedule for ESC CMP V is shown in Table 1.1. In November 2024, the following works were undertaken:

●    Disposal of contaminated mud at ESC CMP Vb; and

●    Capping operations at ESC CMP Vd.

Table 1.1: Works Schedule for ESC CMP V

1.2         Reporting Period

This Monthly EM&A Report for Contaminated Mud Pits to the East of Sha Chau – November 2024 covers the EM&A activities for the reporting period of November 2024 (from 1 to 30 November 2024).

1.3         Details of Sampling and Laboratory Testing Activities

The following monitoring activities were undertaken for ESC CMP V during the reporting period:

●    Water Column Profiling of ESC CMP Vb;

●    Routine Water Quality Monitoring of ESC CMPs;

●    Pit Specific Sediment Chemistry of ESC CMP Vb; and

●    Sediment Chemistry after a Major Storm of ESC CMP V.

1.4         Details of Outstanding Sampling or Analysis

Laboratory analysis data of Sediment Chemistry after a Major Storm of ESC CMP V in November 2024 are still under consolidation, which will be presented in the Monthly EM&A Report of the next reporting period.

 

 

 

 

2         Brief Discussion of Monitoring Results for ESC CMP V

2.1         Introduction

This section presents a brief discussion of the results obtained from the following monitoring activities for ESC CMP V during the reporting period:

●    Water Column Profiling of ESC CMP Vb;

●    Routine Water Quality Monitoring of ESC CMPs;

●    Pit Specific Sediment Chemistry of ESC CMP Vb; and

●    Sediment Chemistry after a Major Storm of ESC CMP V.

 

2.2         Water Column Profiling of ESC CMP Vb – in November 2024

Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 5 November 2024. The monitoring results have been assessed for compliance with the Water Quality Objectives (WQOs) set by Environmental Protection Department (EPD). This consists of a review of the EPD routine water quality monitoring data for the dry season period (November to March) of 2014 – 2023 from stations in the North Western Water Control Zone (WCZ), where the ESC CMPs are located.[3] For Salinity, the averaged value obtained from the Reference (Upstream) station was used for the basis as the WQO. Levels of Dissolved Oxygen (DO) and Turbidity were also assessed for compliance with the Action and Limit Levels (see Table B1 of Appendix B for details).

2.2.1          In-situ Measurements

Analyses of results for November 2024 indicated that levels of Salinity, pH and DO complied with the WQOs at both Downstream and Upstream stations (Table B2 of Appendix B). Levels of DO and Turbidity at all stations complied with the Action and Limit Levels (Tables B1 and B2 of Appendix B).

2.2.2          Laboratory Measurements for Suspended Solids (SS)

Analyses of results for November 2024 indicated that the SS level at both Upstream and Downstream stations complied with the WQO and the Action and Limit Levels (Tables B1 and B2 of Appendix B).

Overall, the monitoring results indicated that the mud disposal operation at ESC CMP Vb did not appear to cause any deterioration in water quality during this reporting period.

2.3         Routine Water Quality Monitoring of ESC CMPs – in October 2024

Further to Section 2.3.2 of the Monthly EM&A Report for Contaminated Mud Pits to the East of Sha Chau – October 2024, laboratory analysis data of dissolved metals and metalloid, except mercury, of Routine Water Quality Monitoring of ESC CMPs conducted in October 2024 has been presented in the aforementioned report. The laboratory analysis data of Mercury has been presented in Tables B3 of Appendix B and Figures 2 of Appendix C. For sake of completeness, the laboratory analysis data of other dissolved metals and metalloid in October 2024 is presented again in Tables B3 of Appendix B and Figures 1 to 2 of Appendix C for easy reference. The concentrations of Mercury remains in low level with no significant trends.

Laboratory analysis data of Nutrients and Suspended Solid in Routine Water Quality Monitoring of ESC CMPs in October 2024 is presented again in Table B4 of Appendix B for easy reference.

Based on the above data analysis, the conclusion drew in the Monthly EM&A Report for Contaminated Mud Pits to the East of Sha Chau – October 2024 is still valid, where the results of the Routine Water Quality Monitoring which indicated that the disposal and capping operation at ESC CMPs did not appear to cause any unacceptable deterioration in water quality in October 2024. Detailed statistical analysis will be presented in the Quarterly EM&A Report to investigate any spatial and temporal trends of potential concern.

2.4         Routine Water Quality Monitoring of ESC CMPs – in November 2024

Routine Water Quality Monitoring of ESC CMPs was undertaken on 6 November 2024. The monitoring results have been assessed for compliance with the WQOs (see Section 2.2 above for details). The monitoring results are shown in Tables B5 to B7 of Appendix B and Figures 3 to 13 of Appendix C. A total of ten (10) monitoring stations were sampled in November 2024 as shown in Figure 2.1.

2.4.1          In-situ Measurements

Graphical presentation of the monitoring results (Temperature, DO, pH, Salinity and Turbidity) is shown in Figures 3 to 8 of Appendix C. Analyses of results indicated that the levels of pH, and DO complied with the WQOs at all stations in November 2024.

The levels of DO and Turbidity complied with the Action and Limit Levels at all stations (Table B5 of Appendix B; Figures 5 and 8 of Appendix C).

Overall, in-situ measurement results of the Routine Water Quality Monitoring indicated that the disposal and capping operation at ESC CMPs did not appear to cause any unacceptable impacts in water quality in November 2024.

2.4.2          Laboratory Measurements

Laboratory analysis of samples obtained in November 2024 indicated that the concentrations of Arsenic, Cadmium, Chromium, Copper, Mercury, Nickel and Zinc were detected in the samples at some/ all stations and their concentrations were generally similar across stations; except the concentrations of Mercury were only detected at Intermediate station. (Table B6 of Appendix B; Figure 9 and 10 of Appendix C).

For nutrients, concentrations of Total Inorganic Nitrogen (TIN) were lower than the WQO (0.5 mg/L) at all stations. (Table B7 of Appendix B; Figure 11 of Appendix C). The concentrations of Ammonia Nitrogen (NH3-N) were only detected at Intermediate (INF) and Ma Wan stations. The concentrations of Biochemical Oxygen Demand (BOD5) were only detected at Reference (RFF), Impact (IPF) and Intermediate (INF) stations. (Table B7 of Appendix B; Figure 11 and 12 of Appendix C)

Analyses of results for the reporting period indicated that the SS levels complied with the dry season WQO (13.0 mg/L) and Action and Limit Levels at all stations. (Tables B1 and B7 of Appendix B; Figure 13 of Appendix C).

Based on the available results of the Routine Water Quality Monitoring which indicated that the disposal and capping operation at ESC CMPs did not appear to cause any unacceptable deterioration in water quality during the reporting period. Detailed statistical analysis will be presented in the Quarterly EM&A Report to investigate any spatial and temporal trends of potential concern.

2.5         Pit Specific Sediment Chemistry of ESC CMP Vb – in November 2024

Monitoring locations for Pit Specific Sediment Chemistry for ESC CMP Vb are shown in Figure 2.2. A total of six (6) monitoring stations were sampled on 4 November 2024.

The concentrations of all inorganic contaminants were lower than the Lower Chemical Exceedance Levels (LCELs) at all stations. (Figures 14 and 15 of Appendix C).

For organic contaminants, the concentrations of Total Organic Carbon (TOC) were higher at Active-Pit station ESC-NPCB. (Figure 16 of Appendix C). The concentrations of Low Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) were higher at Pit-Edge station ESC-NECA. (Figures 17 of Appendix C).

For High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs), the concentrations were higher at Pit-Edge station ESC-NECA, where the concentration is higher than LCEL. (Figures 17 of Appendix C).

The concentrations of Tributyltin (TBT), Total Polychlorinated Biphenyls (PCBs), Total dichloro-diphenyl-trichloroethane (DDT) and 4,4’-dichlorodiphenyldichloroethylene (DDE) were below the limit of reporting at all stations during the reporting period.

It is observed that the elevated level concentrations of High Molecular Weight PAHs (i.e. higher than LCEL) only occurred within Pit-Edge station NECA, but the concentrations of other organic and all inorganic contaminants were lower than the LCELs at the Pit-Edge station.

The slightly elevated level of High Molecular Weight PAH at Pit-Edge station are possible induced by external factors rather than disposal operations. Therefore, there is no evidence indicating any unacceptable environmental impacts to sediment quality outside the pit area as a result of the contaminated mud disposal operations at ESC CMP Vb during the reporting period.

Statistical analysis will be undertaken and presented in the corresponding Quarterly EM&A Report to investigate whether there are any unacceptable impacts in the area caused by the contaminated mud disposal.

2.6         Sediment Chemistry after a Major Storm of ESC CMP V – in November 2024

Tropical Cyclone Warning Signal No. 8 has been hoisted for Typhoon Toraji on 13 November 2024. According to the Updated EM&A Manual under Project “Disposal of Contaminated Sediment – Dredging, Management and Capping of Sediment Disposal Facility at Sha Chau” (EP-312/2008/A), a Post-storm Sediment Sampling would be held within one week of the major storm event.

Since several sampling stations are encroached into the North Lantau Marine Park (NLMP) which is newly established on 1 November 2024, extra permit is required for the sampling works under Marine Parks and Marine Reserves Regulation (CAP. 476A). The permit application was submitted to Agriculture, Fisheries and Conservation Department (AFCD) on 13 November 2024 and approved on 22 November 2024. Therefore, the sampling for Sediment Chemistry after a Major Storm Event was conducted on 26 November 2024 after permit approval.

The sampling was conducted at nine (9) monitoring stations (see Figure 2.3 for the locations of the monitoring stations). The tracks of Toraji are shown in Figure 2.4.

Figure 2.4: Track of Tropical Cyclone Toraji (Source: Hong Kong Observatory)

Refer to Section 1.4, laboratory analysis data of Sediment Chemistry after a Major Storm of ESC CMP V in November 2024 are still under consolidation, which will be presented in the Monthly EM&A Report of the next reporting period.

3         Future Key Issues

3.1         Activities Scheduled for the Next Reporting Period

The following monitoring activities will be conducted in the next reporting period of December 2024 for ESC CMP V (see Appendix A for the sampling schedule):

●    Water Column Profiling of ESC CMP Vb;

●    Routine Water Quality Monitoring of ESC CMPs;

●    Pit Specific Sediment Chemistry of ESC CMP Vb; and

●    Cumulative Impact Sediment Chemistry of ESC CMPs.

 

3.2         Study Programme

A summary of the Study Programme is presented in Appendix D.

 

[1] ERM (2013) Final Report. Submitted under Agreement No. CE 4/2009 (EP) Environmental Monitoring and Audit for Contaminated Mud Pit at East Sha Chau. For CEDD.

[2] ERM (2017) Final Report. Submitted under Agreement No. CE 23/2012 (EP) Environmental Monitoring and Audit for Contaminated Mud Pits to the South of The Brothers and at East Sha Chau (2012 - 2017). For CEDD.