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 2017

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).  Detailed works schedule for ESC CMP V and SB CMPs is shown in Figure 1.1.  In October 2017, the following work was being undertaken:

·      Disposal of contaminated mud at ESC CMP Vd.

Figure 1.1      Works Schedule for ESC CMP V and SB CMPs

1.2                         Reporting Period

1.2.1                     This Monthly EM&A Report for October 2017 covers the EM&A activities for the reporting month of October 2017.

1.3                          Details of Sampling and Laboratory Testing Activities

1.3.1                      The following monitoring activities were undertaken for ESC CMP V in October 2017:

·      Pit Specific Sediment Chemistry of ESC CMP Vd was undertaken on 3 October 2017;

·      Routine Water Quality Monitoring of ESC CMP V was undertaken on 4 October 2017;

·      Water Column Profiling of ESC CMP Vd was undertaken on 6 October 2017; and

·      Sediment Chemistry after a Major Storm of ESC CMP V was undertaken on 19 October 2017.

1.3.2                      No monitoring activities were scheduled to be undertaken for SB CMPs in October 2017.

1.4                         Details of Outstanding Sampling and/or Analysis

1.4.1                      No outstanding sampling and analysis remained for October 2017.

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 2017:

·      Water Column Profiling of ESC CMP Vd in October 2017;

·      Routine Water Quality Monitoring of ESC CMP V in October 2017;

·      Pit Specific Sediment Chemistry of ESC CMP Vd in September and October 2017; and

·      Sediment Chemistry after a Major Storm of ESC CMP V in August and October 2017.

1.5.2                      Water Column Profiling of ESC CMP Vd – October 2017

1.5.3                      Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 6 October 2017.  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 2006 - 2015 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 2017 indicated that levels of DO, Salinity and pH complied with the WQOs at both Downstream and Upstream stations (Table B2 of Annex B).  In addition, levels of DO at all stations complied with the Action and Limit Levels (Tables B1 and B2 of Annex B).  Levels of Turbidity at Downstream station exceeded the Action Level, however the exceedances was not considered as indicating any unacceptable impacts from the disposal operations as disposal activities were not carried out during the monitoring period on 6 October 2017.

Laboratory Measurements for Suspended Solids (SS)

1.5.5                      Analyses of results for October 2017 indicated that the SS levels were higher than the WQO at Downstream station.  However, both Upstream and Downstream stations complied with 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 Vd did not appear to cause any deterioration in water quality during this reporting period.

 

1.5.7                      Routine Water Quality Monitoring of ESC CMP V – October 2017

1.5.8                      Routine Water Quality Monitoring of ESC CMP V was undertaken on 4 October 2017.  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 October 2017 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 C.  Analyses of results for October 2017 indicated that the levels of pH, Salinity and DO complied with the WQOs at all stations (Impact, Intermediate, Reference and Ma Wan stations) in October 2017 (Table B3 of Annex B; Figures 1, 3 and 5 of Annex C). 

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 Vd did not appear to cause any unacceptable impacts in water quality in October 2017. 

Laboratory Measurements

1.5.12                                                   Laboratory analysis of October 2017 results indicated that concentrations of Cadmium, Silver and Mercury were below their limit of reporting at all stations.  Arsenic, Chromium, Nickel, Lead, Copper and Zinc were detected in October 2017 samples and the concentrations of these metals and metalloids were similar amongst stations (Table B4 of Annex B; Figure 7 of Annex C).  

1.5.13                                                   For nutrients, concentrations of Total Inorganic Nitrogen (TIN) at all stations in October 2017 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 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 CMP Vd.  Concentrations of Ammonia Nitrogen (NH3-N) were similar amongst all stations in October 2017 (Table B4 of Annex B; Figure 8 of Annex C).  Levels of 5-day Biochemical Oxygen Demand (BOD5) were relatively similar amongst all stations in October 2017 (Table B4 of Annex B; Figure 9 of Annex C). 

1.5.14                                                   Analyses of results for October 2017 indicated that the SS levels at Reference and Intermediate stations were higher than the WQO (11.0 mg/L for wet season), however SS levels compiled with the Action and Limit Levels at all stations (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 CMP Vd did not appear to cause any unacceptable deterioration in water quality in October 2017.  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 Vd – September and October 2017

1.5.17                                                   Monitoring locations for Pit Specific Sediment Chemistry for ESC CMP Vd are shown in Figure 1.3.  A total of six (6) monitoring stations were sampled in September and October 2017. 

1.5.18                                                   The concentrations of most inorganic contaminants were lower than the Lower Chemical Exceedance Level (LCEL) at all stations in September and October 2017, except Arsenic, Copper and Silver in September 2017 and Arsenic in October 2017 (Figures 11, 12, 15 and 16 of Annex C).  In September 2017, concentrations of Arsenic exceeded the LCEL at Active Pit station ESC-NPAB while concentrations of Copper and Silver exceeded the LCEL at Active Pit station ESC-NPAA (Figures 11 and 12 of Annex C).  In October 2017, concentrations of Arsenic exceeded the LCEL at Active Pit station ESC-NPAB (Figure 15 of Annex C).

1.5.19                                                   Whilst the average concentration of Arsenic in the Earth’s crust is generally ~2mg/kg, significantly higher Arsenic concentrations (median = 14 mg/kg) have been recorded in Hong Kong’s 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 Vd but rather as a result of naturally occurring deposits.

1.5.20                                                   Since the Active Pit stations are located within ESC CMP Vd which were receiving contaminated mud during the reporting period, the exceedances of LCEL for Copper and Silver recorded at the Action Pit stations only are not considered as indicating any dispersal of contaminated mud from ESC CMP Vd. 

1.5.21                                                   For organic contaminants, the concentrations of Total Organic Carbon (TOC) were similar in September and October 2017 (Figures 13 and 17 of Annex C).  The concentrations of Tributyltin (TBT) were higher at Active Pit station ESC-NPAA in September and October 2017 (Figures 14 and 18 of Annex C).  Low and High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs), Total Polychlorinated Biphenyls (PCBs), Total dichloro-diphenyl-trichloroethane (DDT) and 4,4’-dichlorodiphenyldichloroethylene (DDE) concentrations were below the limit of reporting at all stations in September and October 2017.

1.5.22                                                   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 Vd in September and October 2017.  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 – August and October 2017

1.5.24                   Sampling for Sediment Chemistry after a Major Storm Event was conducted at nine (9) monitoring stations (Figure 1.4) on 31 August 2017 and 19 October 2017 after the visit of tropical cyclones Hato and Khanun, which led to the issue of No. 10 Hurricane Signal on 23 August 2017 and No. 8 Northeast Gale or Storm Signal on 15 October 2017, respectively.    The tracks of Hato and Khanun are shown in Figures 1.5 and 1.6.

Figure 1.5      Track of Tropical Cyclone Hato from 20 to 24 August 2017 (Source: Hong Kong Observatory)
Track of Hato: 20 – 24 August 2017

Figure 1.6      Track of Tropical Cyclone Khanun from 12 to 16 October 2017 (Source: Hong Kong Observatory)

1.5.25                   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 Near-field station ESC-RNB, Mid-field stations ESC-RMA and ESC-RMB, Far-field stations ESC-RFA and ESC-RFB and Copper at Ma Wan station in August 2017 (Figures 19 and 20 of Annex C).  In October 2017, the concentrations of most inorganic contaminants were below the LCEL, except Arsenic at Mid-field stations ESC-RMA and ESC-RMB and Far-field station ESC-RFB (Figures 21 and 22 of Annex C).

1.5.26                   As discussed in Section 1.5.19, the natural levels of Arsenic are relatively high in Hong Kong’s marine sediment ([7]), the slight exceedances of LCEL for Arsenic are unlikely to be caused by the disposal of contaminated mud at ESC CMPs but rather as a result of naturally occurring deposits. 

 

1.5.27                   Ma Wan station is located further away from the works area of ESC CMPs when compared the Near-field, Mid-field and Far-field stations at which the level of Copper did not exceed the LCEL, therefore the exceedance of LCEL for Copper recorded at Ma Wan station only is not considered as indicating any dispersal of contaminated mud from ESC CMP Vd. 

1.5.28                   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 August and October 2017. 

1.6                          Brief Discussion of the Monitoring Results for SB CMPs

1.6.1                                                           Brief discussion of the monitoring results of the following activities for SB CMPs is presented in this Monthly EM&A Report for October 2017:

·      Water Quality Monitoring during Capping Operations of SB CMPs in September 2017.

1.6.2                                                          Water Quality Monitoring during Capping of SB CMPsSeptember 2017

1.6.3                           Capping works at SB CMP 2 were conducted in September 2017 to supplement and revert the portion of consolidated capping layer to design level and was completed in September 2017.  Post-water quality monitoring was then conducted on 29 September 2017 after the completion of capping works at SB CMP 2.  The monitoring results obtained have been assessed for compliance with the WQOs (see Section 1.5.3 for details).  A total of fourteen (14) monitoring stations were sampled in September 2017 as shown in Figure 1.7.  Results of in-situ measurements were presented in the Monthly EM&A Report for September 2017.  The results of laboratory measurements are presented in the section below.  Graphical presentation of the laboratory monitoring results is shown in Figures 23 - 26 of Annex C.

 

Laboratory Measurements

1.6.4                           The concentrations of SS were higher than the WQO (11.0 mg/L for wet season) at Sham Shui Kok station in September 2017 (Table B6 of Annex B; Figure 23 of Annex C).  However, levels of SS at all stations complied with the Action and Limit Levels (Tables B5 and B6 of Annex B).

1.6.5                           For nutrients, concentrations of NH3-N were lower at Reference, Tai Ho Bay 1 and Tai Ho Bay 2 stations (Table B6 of Annex B; Figure 24 of Annex C).  The levels of TIN at most stations were higher than WQO of 0.5 mg/L, except for Ma Wan station (Table B6 of Annex B; Figure 25 of Annex C).  As discussed in Section 1.5.13, the North Western WCZ has historically experienced higher levels of TIN ([8]).  The exceedances of TIN WQO at these stations are unlikely to be caused by the capping operation at CMP 2.  Levels of BOD5 were higher at

Tai Ho Bay 2 station in September 2017 (Table B6 of Annex B; Figure 26 of Annex C). 

1.6.6                          Overall, the monitoring results indicated that the capping operation at CMP 2 did not appear to cause any unacceptable deterioration in water quality in September 2017.  Statistical analysis will be undertaken and presented in the quarterly report to investigate whether the capping operations at CMP 2 is causing any unacceptable impacts in water quality of the area.

1.7                         Activities Scheduled for the Next Month

1.7.1                     The following monitoring activities will be conducted in the next monthly period of November 2017 for ESC CMP V (see Annex A for the sampling schedule):

·      Routine Water Quality Monitoring of ESC CMP Vd;

·      Water Column Profiling of ESC CMP Vd; and

·      Pit Specific Sediment Chemistry of ESC CMP Vd. 

1.7.2                     No monitoring activities are scheduled in the next monthly period of November 2017 for SB CMPs.

1.8                         Study Programme

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

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