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

1.3                          Details of Sampling and Laboratory Testing Activities

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

     Water Column Profiling of ESC CMP Vb;

     Routine Water Quality Monitoring of ESC CMPs; 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 April 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 April 2020:

     Water Column Profiling of ESC CMP Vb;

     Routine Water Quality Monitoring of ESC CMPs; and

     Pit Specific Sediment Chemistry of ESC CMP Vb.


1.5.2                     Water Column Profiling of ESC CMP Vb April 2020

1.5.3                     Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 3 April 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 April 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 April 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 April 2020

1.5.8                     Routine Water Quality Monitoring of ESC CMPs was undertaken on 8 April 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 sixteen (16) monitoring stations were sampled in April 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 April 2020 indicated that the levels of pH, Salinity and DO complied with the WQOs at most stations in April 2020, except the Salinity in Ma Wan was higher than WQO.  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.

1.5.10                  The levels of DO and Turbidity complied with the Action and Limit Levels at most stations, except the levels of Turbidity were higher than Action level at Impact stations (Table B3 of Annex B; Figures 3 and 6 of Annex C).  Upon further investigation, it is noticed that capping activities at ESC CMP Vd were conducted during the time of sampling on 8 April 2020 and thus the higher levels of Turbidity recorded at Impact stations could be related to the capping operation.  Considering that the action level exceedance of Turbidity occurred within Impact stations only but not at the Intermediate and Ma Wan stations, there is no evidence indicating any unacceptable environmental impacts to nearby water sensitive receivers as a result of the mud disposal operations at ESC CMPs in April 2020.

Laboratory Measurements

1.5.11                  Laboratory analysis of April 2020 results indicated that concentrations of Arsenic, Chromium, Copper, Mercury, Lead, Nickel and Zinc were detected in April 2020 samples at most stations and the concentrations of these metals and metalloids were similar amongst the stations, except the concentrations of Zinc and Copper were higher at Ma Wan station and Reference stations, respectively (Table B4 of Annex B; Figure 7 of Annex C).    

1.5.12                  For nutrients, concentrations of Total Inorganic Nitrogen (TIN) at Reference, Impact and Intermediate 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 the stations and the concentrations of 5-day Biochemical Oxygen Demand (BOD5) were highest at Impact stations in April 2020 (Table B4 of Annex B; Figure 8 and 9 of Annex C). 

1.5.13                  Analyses of results for April 2020 indicated that the SS levels at most stations complied with the Action and Limit Levels, except the SS levels at Impact stations exceeded the Action level (Tables B1 and B4 of Annex B; Figure 10 of Annex C).  As discussed in Section 1.5.10 above, capping activities at ESC CMP Vd were conducted during the time of sampling on 8 April 2020 and the higher levels of SS recorded at Impact stations could be related to the capping operation.  The action level exceedance was recorded for Impact stations only but not at the Intermediate and Ma Wan stations, thus there is no evidence indicating any unacceptable environmental impacts to nearby water sensitive receivers as a result of the mud disposal operations at ESC CMPs in April 2020.

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

1.5.15                   Pit Specific Sediment Chemistry of ESC CMP Vb April 2020

1.5.16                  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 2 April 2020. 

1.5.17                  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 stations ESC-NECA & ESC-NECB, while the concentrations of Copper were higher than the Upper Chemical Exceedance Level (UCEL) at Active-Pit station ESC-NPCB.

1.5.18                  For organic contaminants, the concentrations of Total Organic Carbon (TOC) were higher at Active-Pit stations in April 2020 (Figure 13 of Annex C).  The concentrations of Low Molecular Weight and High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) were lower than the LCELs at most stations except at Active-Pit station ESC-NPCB where concentrations of Low Molecular Weight and High Molecular Weight PAHs were higher than LCELs (Figure 14 of Annex C).  Total Polychlorinated Biphenyls (PCBs) was below the limit of reporting at most stations except at Active-Pit station ESC-NPCB (Figure 15 of Annex C).  The concentrations of Tributyltin (TBT), Total dichloro-diphenyl-trichloroethane (DDT) and 4,4-dichlorodiphenyldichloroethylene (DDE) were below the limit of reporting at all stations in April 2020. 

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                  Considering that the higher levels of Copper, Low Molecular Weight and High Molecular Weight PAHs occurred within Active-Pit station ESC-NPCB only but not at the Pit-Edge and Near-Pit stations, 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 April 2020.

1.5.21                  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 May 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.