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


Agreement No. CE 63/2016 (EP)

Environmental Monitoring and Audit
for Disposal Facility to the East of Sha Chau (2017-2020) - Investigation

MONTHLY EM&A REPORT FOR June 2020

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 June 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 June 2020 covers the EM&A activities for the reporting month of June 2020.

1.3                                       Details of Sampling and Laboratory Testing Activities

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

     Water Column Profiling of ESC CMP Vb;

     Pit Specific Sediment Chemistry of ESC CMP Vb;

     Cumulative Impact Sediment Chemistry of ESC CMPs; and

     Water Quality Monitoring During Capping of ESC CMPs.

1.4                                       Details of Outstanding Sampling and/or Analysis

1.4.1                                  No outstanding sampling remained for June 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 June 2020:

     Water Column Profiling of ESC CMP Vb;

     Pit Specific Sediment Chemistry of ESC CMP Vb;

     Cumulative Impact Sediment Chemistry of ESC CMPs; and

     Water Quality Monitoring During Capping of ESC CMPs.


1.5.2                                  Water Column Profiling of ESC CMP Vb June 2020

1.5.3                                  Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 11 June 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 June 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 June 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 June 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 3 June 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 June 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 concentration of Tributyltin (TBT) was higher at Active-Pit station ESC-NPCA (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 June 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 June 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.

1.5.13                              Cumulative Impact Sediment Chemistry of ESC CMPs June 2020  

1.5.14                              Monitoring locations for Cumulative Impact Sediment Chemistry for ESC CMPs are shown in Figure 1.3.  A total of nine (9) monitoring stations were sampled on 4 and 5 June 2020.

1.5.15                              Analyses of results for the Cumulative Impact Sediment Chemistry Monitoring indicated that the concentrations of most inorganic contaminants were below the LCEL at most stations in June 2020, except concentrations of Arsenic were higher than the LCEL at Mid-field stations ESC-RMA, ESC-RMB and Capped Pit station ESC-RCB1 (Figures 6 and 7 of Annex C).  As discussed in Section 1.5.10, 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.

1.5.16                              For organic contaminants, the concentrations of TOC varied between stations in June 2020, with generally higher concentrations of TOC recorded at Mid-field station ESC-RMA and Ma Wan station (Figure 8 of Annex C).  The concentrations of TBT were below the limit of reporting at most stations, except at Far-field station ESC-RFA, Capped-pit station ESC-RCA1 and Ma Wan station, and higher concentrations were recorded at Ma Wan station (Figure 9 of Annex C).  The concentrations of High Molecular Weight PAHs were below the LCEL at all stations (Figure 10 of Annex 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 in June 2020. 

1.5.17                              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 June 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.

1.5.18                              Water Quality Monitoring during Capping of ESC CMPs June 2020

1.5.19                              The monitoring results obtained during June 2020 sampling in the wet season have been assessed for compliance with the WQOs (see Section 1.5.3 for details).  A total of ten (10) monitoring stations were sampled on 12 June 2020 as shown in Figure 1.4.   

In-situ Measurements

1.5.20                              Graphical presentation of the monitoring results (Temperature, DO, pH, Salinity and Turbidity) is shown in Figures 11-18 of Annex C.  Levels of pH at all stations in June 2020 complied with the WQO while the Levels of Salinity were higher than WQO at Impact, Intermediate and Ma Wan Stations, and the levels of DO of Surface and Mid water average were lower than the WQO at Ma Wan station (Table B3 of Annex B)Levels of DO and Turbidity complied the Action and Limit levels at most stations, except the averaged levels of DO recorded for surface and mid-depth water at Ma Wan station was below Action level (Tables B1 and B3 of Annex B).

1.5.21                              The higher Salinities recorded at Ma Wan station are likely to be caused by the larger separation distance to Pearl River mouth, which release a large amount of freshwater runoff in the area during wet season, when compared to the Reference stations.  The Reference stations are located relatively closer to nearby islands (e.g. Hong Kong Boundary Crossing Facilities, Tai Mo To, Siu Mo To) and localised freshwater runoff from the nearby islands might be resulted during wet season, resulting in lower Salinities at Reference stations.

1.5.22                              Since action level exceedance of DO (surface and mid-depth water) was recorded at Ma Wan station only and Ma Wan is located further away from ESC CMPs comparing to other stations where levels of DO compiled with the action and limit levels, the LECL exceedance of DO (surface and mid-depth water) is unlikely to be caused by the capping operations at ESC CMPs. 

Laboratory Measurements for Suspended Solids (SS)

1.5.23                              Concentrations of SS complied with the WQO at all stations.  Concentrations of SS complied with the Action and Limit Levels at all stations in June 2020 (Table B3 of Annex B; Figure 17 of Annex C). 

1.5.24                              Overall, results of the Water Quality Monitoring during Capping of ESC CMPs indicated that the capping operation at ESC CMP Vd did not appear to cause any unacceptable deterioration in water quality in June 2020.  Further statistical analysis will be undertaken in the quarterly report to investigate whether the capping operations at ESC CMP Vd is causing any unacceptable deterioration in water quality of the area.

1.6                                       Activities Scheduled for the Next Month

1.6.1                                 The following monitoring activities will be conducted in the next monthly period of July 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;

     Pit Specific Sediment Chemistry of ESC CMP Vb; and

     Demersal Trawling for ESC CMPs.

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.