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 – August 2021

 

September 2021

 

 

 

Civil Engineering and Development Department

 

 

 

Mott MacDonald

3/F International Trade Tower

348 Kwun Tong Road

Kwun Tong

Kowloon

Hong Kong

 

T +852 2828 5757

F 

mottmac.hk

 

 

 

 

 


 

 

 

  

 

 

Issue and Revision Record

Revision

Date

Originator

Checker

Approver

Description

A

Sep 2021

Various

Thomas Chan

Eric Ching

Revision A of Submission

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Document reference:

423134 | 06/05/05 | A

 

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 August 2021

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 August 2021

2.3.1         In-situ Measurements

2.3.2         Laboratory Measurements

2.4      Pit Specific Sediment Chemistry of ESC CMP Vb – in August 2021

2.5      Cumulative Impact Sediment Chemistry of ESC CMPs – in August 2021

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 (Ebb-Tide) for ESC CMPsRoutine & 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

Cumulative Impacts Sediment Quality Monitoring Stations for ESC CMPs

Figure 2.2

Pit Specific Sediment Quality Monitoring Stations for CMP V

 

 

 

Appendices

Appendix A

Sampling Schedule Sampling Schedule

Appendix B

Water Quality Monitoring Results 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. 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 August 2021, 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 – August 2021 covers the EM&A activities for the reporting period of August 2021 (from 1 to 31 August 2021).

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;

●    Cumulative Impact Sediment Chemistry of ESC CMPs;

●    Sediment Toxicity Tests of ESC CMPs; and

●    Demersal Trawling for ESC CMPs.

1.4        Details of Outstanding Sampling or Analysis

No outstanding sampling remained for the reporting month (August 2021). The following analyses are in progress and will be presented in the corresponding quarterly report:

●    Species identification of the biota samples collection from Demersal Trawling for ESC CMPs in August 2021; and

●    Sediment Toxicity Tests of ESC CMPs in August 2021.

 

 

 

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

●    Cumulative Impact Sediment Chemistry of ESC CMPs.

2.2        Water Column Profiling of ESC CMP Vb – in August 2021

Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 13 August 2021. 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 wet season period (April to October) of 2010 – 2019 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 August 2021 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 August 2021 indicated that the SS levels at both Downstream and Upstream 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 August 2021

Routine Water Quality Monitoring of ESC CMPs was undertaken on 5 August 2021. 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 B3 and B4 of Appendix B and Figures 1 to 10 of Appendix C. A total of sixteen (16) monitoring stations were sampled in August 2021 as shown in Figure 2.1.

2.3.1         In-situ Measurements

Graphical presentation of the monitoring results (Temperature, DO, pH, Salinity and Turbidity) is shown in Figures 1 to 6 of Appendix C. Analyses of results indicated that the levels of pH, Salinity and DO complied with the WQOs at most stations during the reporting period, except for higher levels of Salinity were recorded at Ma Wan station. The higher Salinities recorded at Ma Wan station are likely to be caused by the larger separation distance to Pearl River Delta mouth, which releases a large amount of freshwater runoff in the area during wet season, when compared to the Reference stations.

The levels of DO and Turbidity complied with the Action and Limit Levels at all stations (Table B3 of Appendix B; Figures 3 and 6 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 August 2021.

2.3.2         Laboratory Measurements

Laboratory analysis of samples obtained during the reporting period indicated that the concentrations of Arsenic, Chromium, Copper, Lead, Nickel, Silver and Zinc were detected in the samples at some/all stations and their concentrations of most metals and metalloids were generally similar across stations, except the concentrations of Zinc which were higher at Ma Wan and Reference (RFE) stations (Table B4 of Appendix B; Figure 7 of Appendix C).

For nutrients, concentrations of Total Inorganic Nitrogen (TIN) at all stations complied with the WQO (0.5 mg/L) (Table B4 of Appendix B; Figure 8 of Appendix C). The concentration of Ammonia Nitrogen (NH3-N) was generally similar across stations (Table B4 of Appendix B; Figure 8 of Appendix C). The concentration of Biochemical Oxygen Demand (BOD5) was slightly higher at Intermediate (INE) station in the reporting month (Table B4 of Appendix B; Figure 9 of Appendix C).

Analyses of results for the reporting period indicated that the SS levels at all stations complied with the wet season WQO (11.8 mg/L) and the Action and Limit Levels (Tables B1 and B4 of Appendix B; Figure 10 of Appendix C). 

Overall, results of the Routine Water Quality Monitoring 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.

2.4        Pit Specific Sediment Chemistry of ESC CMP Vb – in August 2021

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 3 August 2021.

The concentrations of all inorganic contaminants were lower than the Lower Chemical Exceedance Levels (LCELs) at all stations (Figures 11 and 12 of Appendix C).

For organic contaminants, the concentrations of Total Organic Carbon (TOC) were lower at Active-Pit station ESC-NPCB during the reporting period (Figure 13 of Appendix C). The concentrations of Low Molecular Weight and High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) were lower than the LECLs at all stations (Figure 14 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.

Overall, 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.

2.5        Cumulative Impact Sediment Chemistry of ESC CMPs – in August 2021

Monitoring locations for Cumulative Impact Sediment Chemistry for ESC CMPs are shown in Figure 2.3.  A total of nine (9) monitoring stations were sampled on 10 and 11 August 2021.

Analyses of results for the Cumulative Impact Sediment Chemistry Monitoring indicated that the concentrations of all inorganic contaminants were below the LCEL at all stations during the reporting period (Figures 15 and 16 of Appendix C).

For organic contaminants, the concentrations of TOC were higher at Ma Wan station (Figure 17 of Appendix C). The concentrations of High Molecular Weight PAHs were below the LCEL at all stations (Figure 18 of Appendix C). Higher concentrations of TBT were recorded at Ma Wan station (Figure 19 of Appendix C). The concentrations of Total PCBs, Total DDT, 4,4’-DDE and Low Molecular Weight PAHs were below the limit of reporting at all stations during the reporting period.

Overall, there is no evidence indicating any unacceptable environmental impacts to sediment quality 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.

 

                                    

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 September 2021 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; and

●    Pit Specific Sediment Chemistry of ESC CMP Vb.

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.