Contents

1.1                       Background                                                                  

1.2                       Reporting Period                                                       

1.3                       Details of Sampling and Laboratory Testing Activities                                                        

1.4                       Details of Outstanding Sampling and/or Analysis                                                                           

1.5                       Brief Discussion of the Monitoring Results for ESC CMP V                                                                 

1.6                       Activities Scheduled for the Next Month      

1.7                       Study Programme                                                       

Annexes

 

Annex A       Sampling Schedule

Annex B       Water Quality Monitoring Results

Annex C       Graphical Presentations

Annex D       Study Programme


1.1                             Background

1.1.1                         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 South of The Brothers (SB) and to the East of Sha Chau (ESC) for the disposal of contaminated sediment, and 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.  Two Environmental Permits (EPs), EP-312/2008/A and EP-427/2011/A, were issued by the Environmental Protection Department (EPD) to the CEDD, the Permit Holder, on 28 November 2008 and 23 December 2011 for the Dredging, Management and Capping of Contaminated Sediment Disposal Facilities at ESC CMP V and SB CMPs, respectively.

1.1.2                         Under the requirements of the two EPs for ESC CMP V and SB CMPs, 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 and SB.  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 as well as capping operations of SB CMPs.

1.1.3                         The present EM&A programme under Agreement No. CE 63/2016 (EP) covers the dredging, disposal and capping operations of the ESC CMP V as well as the capping operations of the SB CMPs (see Annex A for the EM&A programme).  The scheduled EM&A programme for SB CMPs was completed in December 2018.  Detailed works schedule for ESC CMP V is shown in Figure 1.1.  In September 2020, the following works were undertaken:

    Disposal of contaminated mud at ESC CMP Vb; and

    Capping operations at ESC CMP Vd.

Figure 1.1        Works Schedule for ESC CMP V

 

1.2                             Reporting Period

1.2.1                         This Monthly EM&A Report for September 2020 covers the EM&A activities for the reporting month of September 2020.

1.3                             Details of Sampling and Laboratory Testing Activities

1.3.1                         The following monitoring activities were undertaken for ESC CMP V in September 2020:

          Water Column Profiling of ESC CMP Vb; and

          Pit Specific Sediment Chemistry of ESC CMP Vb.

1.4                             Details of Outstanding Sampling and/or Analysis

1.4.1                         No outstanding sampling remained for September 2020.

1.5                             Brief Discussion of the Monitoring Results for ESC CMP V

1.5.1                         Brief discussion of the monitoring results of the following activities for ESC CMP V is presented in this Monthly EM&A Report for August 2020:

    Water Column Profiling of ESC CMP Vb; and

    Pit Specific Sediment Chemistry of ESC CMP Vb.

 


1.5.2                         Water Column Profiling of ESC CMP Vb September 2020

1.5.3                         Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 3 September 2020.  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 2009 - 2018 from stations in the Northwestern 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 Annex B for details).

In-situ Measurements

1.5.4                         Analyses of results for September 2020 indicated that levels of Salinity, pH and DO complied with the WQOs at both Downstream and Upstream stations (Table B2 of Annex B).  Levels of DO and Turbidity at all stations complied with the Action and Limit Levels (Tables B1 and B2 of Annex B).

Laboratory Measurements for Suspended Solids (SS)

1.5.5                         Analyses of results September 2020 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 Annex B).   

1.5.6                         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.

1.5.7                         Pit Specific Sediment Chemistry of ESC CMP Vb September 2020

1.5.8                         Monitoring locations for Pit Specific Sediment Chemistry for ESC CMP Vb are shown in Figure 1.2.  A total of six (6) monitoring stations were sampled on 2 September 2020. 

1.5.9                         The concentrations of most inorganic contaminants were lower than the Lower Chemical Exceedance Levels (LCELs) at most stations, except for Arsenic (Figures 1 and 2 of Annex C).  The concentrations of Arsenic were higher than the LCEL at Near-Pit station ESC-NNCA, Pit-Edge station ESC-NECA and Active-Pit station ESC-NPCB.

1.5.10                       Whilst the average concentration of Arsenic in the Earths crust is generally ~2mg/kg, significantly higher Arsenic concentrations (median = 14 mg/kg) have been recorded in Hong Kongs onshore sediments ([4]).  It is presumed that the natural concentrations of Arsenic are similar in onshore and offshore sediments ([5]), and relatively high Arsenic levels may thus occur throughout Hong Kong.  Therefore, the LECL exceedances of Arsenic are unlikely to be caused by the disposal operations at ESC CMP Vb but rather as a result of naturally occurring deposits.

1.5.11                       For organic contaminants, the concentrations of Total Organic Carbon (TOC) were higher at Active-Pit station ESC-NPCB in September 2020 (Figure 3 of Annex C).  The concentrations of Low Molecular Weight and High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) were lower than the LCELs at all stations (Figure 4 of Annex C).  The concentrations of Tributyltin (TBT) were higher at Active-Pit stations ESC-NPCA and ESC-NPCB (Figure 5 of Annex 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 in September 2020. 

1.5.12                       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 in September 2020.  Statistical analysis will be undertaken and presented in the corresponding quarterly report to investigate whether there are any unacceptable impacts in the area caused by the contaminated mud disposal.

1.6                             Activities Scheduled for the Next Month

1.6.1                         The following monitoring activities will be conducted in the next monthly period of October 2020 for ESC CMP V (see Annex A for the sampling schedule ([6])):

    Water Column Profiling of ESC CMP Vb;

    Routine Water Quality Monitoring of ESC CMPs; and

    Pit Specific Sediment Chemistry of ESC CMP Vb.

1.7                             Study Programme

1.7.1                         A summary of the Study Programme is presented in Annex 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.

([3])     http://epic.epd.gov.hk/EPICRIVER/marine/?lang=en

([4])   Sewell RJ (1999) Geochemical Atlas of Hong Kong. Geotechnical Engineering Office, Government of the Hong Kong Special Administrative Region

([5])   Whiteside PGD (2000) Natural geochemistry and contamination of marine sediments in Hong Kong. In: The Urban Geology of Hong Kong (ed Page A & Reels SJ). Geological Society of Hong Kong Bulletin No. 6, p109-121

([6])   The scheduled EM&A Programme for SB CMPs was completed in December 2018.