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 December 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                                  A proposal on the change of number of sample replication of water quality & sediment monitoring and 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 Annex A

 

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

1.3                                       Details of Sampling and Laboratory Testing Activities

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

  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.

1.4                                       Details of Outstanding Sampling and/or Analysis

1.4.1                                  No outstanding sampling remained for December 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 December 2020:

     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.

1.5.2                                  Water Column Profiling of ESC CMP Vb December 2020

1.5.3                                  Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 3 December 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 dry season period (November to March) of 2010 - 2019 from stations in the Northwestern Water Control Zone (WCZ), where the ESC CMPs are located ([1]).  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 December 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 for December 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                                  Routine Water Quality Monitoring of ESC CMPs December 2020

1.5.8                                  Routine Water Quality Monitoring of ESC CMPs was undertaken on 4 December 2020.  The monitoring results have been assessed for compliance with the WQOs (see Section 1.5.3 for details).  The monitoring results are shown in Tables B3 and B4 of Annex B and Figures 1 - 10 of Annex C.  A total of ten (10) monitoring stations were sampled in December 2020 as shown in Figure 1.2.

In-situ Measurements

1.5.9                                  Graphical presentation of the monitoring results (Temperature, DO, pH, Salinity and Turbidity) is shown in Figures 1 - 6 of Annex CAnalyses of results indicated that the levels of pH, Salinity and DO complied with the WQOs at all stations in December 2020.   

1.5.10                             The levels of DO and Turbidity complied with the Action and Limit Levels at all stations (Table B3 of Annex B; Figures 3 and 6 of Annex C). 

1.5.11                             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 December 2020.

Laboratory Measurements

1.5.12                              Laboratory analysis of December 2020 results indicated that concentrations of Arsenic, Chromium, Copper, Lead, Nickel and Zinc were detected in December 2020 samples at most stations. The concentrations of Arsenic, Chromium, Lead and Zinc were generally similar across stations; the concentrations of Nickel were higher at Impact stations; and the concentrations of Copper were higher at Ma Wan station (Table B4 of Annex B; Figure 7 of Annex C).

1.5.13                              For nutrients, concentrations of Total Inorganic Nitrogen (TIN) at all stations complied with the WQO (0.5 mg/L) (Table B4 of Annex B; Figure 8 of Annex C).  The concentrations of Ammonia Nitrogen (NH3-N) were similar across all stations in December 2020 (Table B4 of Annex B; Figure 8 of Annex C).  The concentrations of Biochemical Oxygen Demand (BOD5) were lower at Ma Wan stations (Table B4 of Annex B; Figure 9 of Annex C). 

1.5.14                              Analyses of results for December 2020 indicated that the SS levels at Impact, Intermediate, and Reference and Ma Wan stations were higher than the WQO (12.8 mg/L), but all stations complied with the Action and Limit Levels (Tables B1 and B4 of Annex B; Figure 10 of Annex C).  Considering the higher values were recorded not only at Impact and intermediate stations, but also at Reference and Ma Wan stations, the exceedances of SS WQO at these stations were unlikely to be caused by the disposal operation at ESC CMPs. 

1.5.15                              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 in December 2020.  Detailed statistical analysis will be presented in the Quarterly Report to investigate any spatial and temporal trends of potential concern.

 

1.5.16                              Pit Specific Sediment Chemistry of ESC CMP Vb December 2020

1.5.17                              Monitoring locations for Pit Specific Sediment Chemistry for ESC CMP Vb are shown in Figure 1.3.  A total of six (6) monitoring stations were sampled on 7 December 2020. 

1.5.18                              The concentrations of most inorganic contaminants were lower than the Lower Chemical Exceedance Levels (LCELs) at most stations, except for Arsenic (Figures 11 and 12 of Annex C).  The concentrations of Arsenic were higher than the LCEL at Near-Pit station ESC-NNCA, Pit-Edge station ESC-NECA, Active-Pit stations ESC-NPCA and ESC-NPCB.  

1.5.19                              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.

1.5.20                              For organic contaminants, the concentrations of Total Organic Carbon (TOC) were higher at Active-Pit stations ESC-NPCA and ESC-NPCB in December 2020 (Figure 13 of Annex C).  The concentrations of Low Molecular Weight and High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) were lower than the LECLs at Near-Pit and Pit-Edge stations. However, the concentrations of Low Molecular Weight PAHs and the concentrations of High Molecular Weight PAHs were higher than the LCEL at Active-Pit stations ESC-NPCA and ESC-NPCB (Figure 14 of Annex C).  The concentrations of Tributyltin (TBT) were higher at Active-Pit stations ESC-NPCA and ESC-NPCB (Figure 15 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 December 2020. 

1.5.21                              Considering that the higher levels of TOC, TBT, Low Molecular Weight and High Molecular Weight PAHs occurred within Active-Pit stations ESC-NPCA and ESC-NPCB only, 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 in December 2020.

1.5.22                              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.

1.5.23                              Cumulative Impact Sediment Chemistry of ESC CMPs December 2020  

1.5.24                              Monitoring locations for Cumulative Impact Sediment Chemistry for ESC CMPs are shown in Figure 1.4.  A total of nine (9) monitoring stations were sampled on 8 and 9 December 2020.

1.5.25                              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 December 2020, except concentrations of Arsenic were higher than the LCEL at Mid-field stations ESC-RMA, ESC-RMB, Near-field station ESC-RNB1, Capped Pit stations ESC-RCA1, ESC-RCB1 and Ma Wan station (Figures 16 and 17 of Annex C).  As discussed in Section 1.5.19, 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.

1.5.26                              For organic contaminants, the concentrations of TOC were higher at Far-field stations ESC-RFA and ESC-RFB (Figure 18 of Annex C).  The concentrations of TBT were higher at Ma Wan station (Figure 19 of Annex C).  The concentrations of High Molecular Weight PAHs were below LECL (Figure 20 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 December 2020. 

1.5.27                              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 December 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 January 2021 for ESC CMP V (see Annex 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

     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