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

1.3                          Details of Sampling and Laboratory Testing Activities

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

     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 and/or Analysis

1.4.1                     No outstanding sampling remained for October 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 October 2020:

     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.

 


1.5.2                                                     Water Column Profiling of ESC CMP Vb October 2020

1.5.3                     Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 6 October 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 October 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 October 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 October 2020

1.5.8                     Routine Water Quality Monitoring of ESC CMPs was undertaken on 8 October 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 October 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 for October 2020 indicated that the levels of pH, Salinity and DO complied with the WQOs at all stations in October 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 operation at ESC CMP Vb did not appear to cause any unacceptable impacts in water quality in October 2020.

Laboratory Measurements

1.5.12                                                 Laboratory analysis of October 2020 results indicated that concentrations of Arsenic, Chromium, Copper, Lead, Mercury and Zinc were detected in October 2020 samples at most stations and the concentrations of most metals and metalloids were similar amongst the stations, except the concentrations of Zinc and Lead 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 Reference stations were higher than the WQO (0.5 mg/L) (Table B4 of Annex B; Figure 8 of Annex C).  It should be noted that due to the effect of the Pearl River, the North Western WCZ has historically experienced higher levels of TIN ([4]).  Therefore, the exceedances of TIN WQO at these stations are unlikely to be caused by the disposal operation at ESC CMPs.  The concentrations of Ammonia Nitrogen (NH3-N) were similar across all station in October 2020 (Table B4 of Annex B; Figure 8 of Annex C).  The concentrations of Biochemical Oxygen Demand (BOD5) were lower at Impact station (Table B4 of Annex B; Figure 9 of Annex C). 

1.5.14                                                 Analyses of results for October 2020 indicated that the SS levels at all stations compiled with the WQO and the Action and Limit Levels (Tables B1 and B4 of Annex B; Figure 10 of Annex C).    

1.5.15                                                 Overall, results of the Routine Water Quality Monitoring indicated that the disposal operation at ESC CMPs did not appear to cause any unacceptable deterioration in water quality in October 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 October 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 October 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 and Copper (Figures 11 and 12 of Annex C).  The concentrations of Arsenic were higher than the LCEL at Pit-Edge station ESC-NECA, Active-Pit stations ESC-NPCA and ESC-NPCB.  The concentrations of Copper were higher than LCEL at Active-Pit station 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 ([5]).  It is presumed that the natural concentrations of Arsenic are similar in onshore and offshore sediments ([6]), 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 October 2020 (Figure 13 of Annex C).  The concentrations of Low Molecular Weight and High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) were higher 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 October 2020. 

1.5.21                                                   Considering that the higher levels of Copper, 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 October 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                   Sediment Chemistry after a Major Storm of ESC CMP V October 2020

Sampling for Sediment Chemistry after a Major Storm Event was conducted at nine (9) monitoring stations (see Figure 1.4 for the locations of the monitoring stations) on 16 October 2020 after the visit of tropical cyclone Nangka, which led to the issue of No. 8 Gale or Storm Signal on 13 October 2020.  The track of Nangka are shown in Figure 1.5.

Figure 1.5      Track of Tropical Cyclone Nangka (Source: Hong Kong Observatory)

1.5.24                  Analyses of results for the Sediment Chemistry after a Major Storm indicated that the concentrations of most inorganic contaminants were below the LCEL, except Arsenic at Mid-field station ESC-RMA, Far-field station ESC-RFB, Capped Pit Station ESC-RCA1 and Ma Wan Station in October 2020 (Figures 16 and 17 of Annex C). 

1.5.25                  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

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 2020.

1.6                         Activities Scheduled for the Next Month

1.6.1                     The following monitoring activities will be conducted in the next monthly period of November 2020 for ESC CMP V (see Annex A for the sampling schedule ([7])):

     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])        http://www.epd.gov.hk/epd/misc/marine_quality/1986-2005/textonly/eng/index.htm

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

([6])     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

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