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 – October 2021

November 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

Nov 2021

Various

Thomas Chan

Eric Ching

Revision A of Submission

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Document reference:

423134 | 06/05/07 | 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 October 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 October 2021

2.3.1         In-situ Measurements

2.3.2         Laboratory Measurements

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

2.5      Sediment Chemistry after a Major Storm of ESC CMP V – October 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

Sediment Chemistry after A Major Storm Monitoring Stations for ESC CMPs

Figure 2.4

Track of Tropical Cyclone Lionrock

Figure 2.5

Track of Tropical Cyclone Kompasu

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 October 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 – October 2021 covers the EM&A activities for the reporting period of October 2021 (from 1 to 31 October 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; and

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

1.4        Details of Outstanding Sampling or Analysis

No outstanding sampling remained for the reporting month (October 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

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

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

Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 7 October 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 October 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 October 2021 indicated that the SS level at the Upstream station was higher than the WQO while the SS level at the Downstream station complied with the WQO, but levels complied with 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 2021

Routine Water Quality Monitoring of ESC CMPs was undertaken on 5 October 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 October 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 all stations in October 2021.

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 October 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 lower at Impact (IPE) station (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 generally similar across stations (Table B4 of Appendix B; Figure 9 of Appendix C).

Analyses of results for the reporting period indicated that the SS levels at Intermediate (INE) and Ma Wan stations complied with the wet season WQO (11.8 mg/L) and the Action and Limit Levels. SS levels at Reference (RFE) and Impact (IPE) stations were above the wet season WQO but in compliance with 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 October 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 5 October 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 Near-Pit station ESC-NNCB 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) were higher at Active-Pit stations ESC-NPCA and ESC-NPCB (Figure 15 of Appendix C). The concentrations of 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        Sediment Chemistry after a Major Storm of ESC CMP V – October 2021

Sampling for Sediment Chemistry after a Major Storm Event was conducted at nine (9) monitoring stations (see Figure 2.3 for the locations of the monitoring stations) on 18 October 2021 after the visit of tropical cyclones Lionrock and Kompasu, which led to the issue of No. 8 Gale or Storm Signal on 9 to 10 October 2021 and 12 to 13 October 2021 respectively.  The tracks of Lionrock and Kompasu are shown in Figure 2.4 and 2.5 respectively.

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

Figure 2.5: Track of Tropical Cyclone Kompasu (Source: Hong Kong Observatory)

Analyses of results for the Sediment Chemistry after a Major Storm indicated that the concentrations of all inorganic contaminants were below the LCEL in October 2021 (Figures 16 and 17 of Appendix C).

Overall, there appeared to be no evidence showing the failure of ESC CMP V in retaining disposed mud or causing contamination of sediments after the major storm event in October 2021.

 

 

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 November 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.