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) - Investigation

38th MONTHLY PROGRESS REPORT FOR October 2015

1.1                                      Background

1.1.1                                Since early 1990s, contaminated sediment ([1]) arising from various construction works (e.g. dredging and reclamation projects) in Hong Kong has been disposed of at a series of seabed pits at East of Sha Chau (ESC).  In late 2008, a review indicated that the existing and planned facilities at ESC would not be able to meet the disposal demand after 2012.  In order to meet this demand, the Hong Kong Special Administrative Region Government (HKSARG) decided to implement a new contained aquatic disposal (CAD) ([2]) facility at the South of The Brothers (SB CMPs) which had been under consideration for a number of years.

1.1.2                                The environmental acceptability of the construction and operation of the Project had been confirmed by findings of the associated Environmental Impact Assessment (EIA) study completed in 2005 under Agreement No. CE 12/2002(EP) ([3]).  The Director of Environmental Protection (DEP) approved this EIA report under the Environmental Impact Assessment Ordinance (Cap. 499) (EIAO) in September 2005 (EIA Register No.: AEIAR-089/2005).

1.1.3                                In accordance with the EIA recommendation, prior to commencement of construction works for the SB CMPs, the Civil Engineering and Development Department (CEDD) undertook a detailed review and update of the EIA findings for the SB site ([4]).  Findings of the EIA review undertaken in 2009/ 2010 confirmed that the construction and operation of the SB site had been predicted to be environmentally acceptable.

 

1.1.4                                Environmental Permits (EPs) (EP-312/2008/A and EP-427/2011A) were issued by the Environmental Protection Department (EPD) to the CEDD, the Permit Holder, on 28 November 2008 for ESC CMP V and on 23 December 2011 for SB CMPs, respectively.  Under the requirements of the EPs, an Environmental Monitoring and Audit (EM&A) programme as set out in the EM&A Manuals ([5]) ([6]) is required to be implemented for the CMPs.

1.1.5                                The present EM&A programme under Agreement No. CE 23/2012 (EP) covers the dredging, disposal and capping operations of the SB CMPs as well as ESC CMPs.  Detailed works schedule for both CMPs is shown in Figure 1.1.  In October 2015, the following works were being undertaken at the CMPs:

·       Dredging operation at ESC CMP Vd;

·       Capping operations at ESC CMP Va; and

·       Disposal of contaminated mud at SB CMP 2.

Figure 1.1       Works Schedule for ESC CMPs and SB CMPs

1.2                                      Reporting Period

1.2.1                                This 38th Monthly Progress Report covers the EM&A activities for the reporting month of October 2015.

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                                The following monitoring activities have been undertaken for ESC CMPs in October 2015:

·      Impact Water Quality Monitoring during Dredging Operations of ESC CMPs was undertaken on 2, 5, 7, 9, 12, 14, 16, 19, 21, 23, 26, 28 and 30 October 2015.

 

1.3.2                                    The following monitoring activities have been undertaken for SB CMPs in October 2015:

·       Water Column Profiling of CMP 2 was undertaken on 13 October 2015;

·       Pit Specific Sediment Chemistry of CMP 2 was undertaken on 15 October 2015; and

·       Routine Water Quality Monitoring of CMP 2 was undertaken on 16 October 2015.

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained for October 2015. 

1.4.2                                A summary of field activities conducted are presented in Annex A.  The following laboratory analyses were still in progress during the preparation of this monthly report and hence are not presented in this monthly report:

·       Laboratory analyses of sediment samples collected for Pit Specific Sediment Chemistry of SB CMP 2 in October 2015.

1.5                                      Brief Discussion of the Monitoring Results for ESC CMPs

1.5.1                                    Brief discussion of the monitoring results of the Impact Water Quality Monitoring during Dredging Operations of ESC CMP Vd conducted in October 2015 is presented below.

1.5.2                                                                               Impact Water Quality Monitoring during Dredging Operations of ESC CMP Vd – 2 to 31 October 2015

1.5.3                                Impact Water Quality Monitoring during Dredging Operations of ESC CMP Vd was conducted three times per week in October 2015.  On each survey day, monitoring was conducted during both mid-ebb and mid-flood tides at two Reference (Upstream) stations and five Impact (Downstream) stations of the dredging operations at ESC CMP Vd.  Monitoring was also conducted at one Sensitive Receiver Station situated in Ma Wan.  A total of eight (8) stations were monitored and locations of the sampling stations are shown in Figure 1.2. 

1.5.4                                Monitoring results are presented in Table B1 of Annex B.  Daily dredging volume in October 2015 is reported in Annex C.  It should be noted that dredging activities were not carried out on 3, 4, 16 – 20 and 23 – 31 October 2015 during the reporting period.  Levels of Dissolved Oxygen (DO), Turbidity and Suspended Solid (SS) generally complied with the Action and Limit Levels (see Table B2 of Annex B for details) set in the Baseline Monitoring Report ([7]), except for the following occasion of exceedances discussed in Table 1.1 below.

1.5.5                                As presented in Table 1.1, the results indicated that the dredging operations at ESC CMP Vd did not appear to cause any unacceptable deterioration in water quality during this reporting period.  Therefore, no further action, except for those recommended in the Environmental Permit (EP-312/2008/A), are considered necessary for the dredging operations.

 

Table 1.1        Details of Exceedances Recorded for Impact Water Quality Monitoring during Dredging Operations of ESC CMP Vd between 2 and 30 October 2015

Date

Tide

Parameter

Station

Type

Remarks

2 October 2015

Mid-Flood

Turbidity

DS2

Limit

The exceedance was not considered as indicating any unacceptable impacts from the dredging operations to Water Sensitive Receivers (WSRs) outside the works area because Stations DS2 are located further away from the works area of CMP Vd when compared to station DS1 at which the levels of Turbidity did not exceed the Action and Limit Levels during the same tidal period.

 

26 October 2015

Mid-Flood

Turbidity

DS2

Limit

These exceedances were not considered as indicating any unacceptable impacts from the dredging operations to WSRs outside the works area because dredging activities were not carried out during the period of 3, 4, 16 – 20 and 23 – 31 October 2015.

28 October 2015

Mid-Ebb

Turbidity

DS3

Limit

28 October 2015

Mid-Ebb

Turbidity

DS5

Limit

30 October 2015

Mid-Flood

Turbidity

DS2

Action

30 October 2015

Mid-Flood

SS

DS1

Action

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 38th Monthly Progress Report:

·       Pit Specific Sediment Chemistry of CMP 2 in September 2015;

·       Cumulative Impact Sediment Chemistry of CMP 2 in August 2015;

·       Routine Water Quality Monitoring of CMP 2 in October 2015; and

·       Water Column Profiling of CMP 2 in October 2015.

1.6.2                                Pit Specific Sediment Chemistry of CMP 2 – September 2015

1.6.3                                                                               Monitoring locations for Pit Specific Sediment Chemistry for CMP 2 are shown in Figure 1.3.  A total of six (6) monitoring stations were sampled in September 2015. 

1.6.4                                                                               The concentrations of most inorganic contaminants (Arsenic, Cadmium, Chromium, Lead, Mercury, Nickel and Zinc) were lower than the Lower Chemical Exceedance Level (LCEL) at all stations, except Copper and Silver (Figures 1 and 2 of Annex D).  Copper exceeded the LCEL at Active Pit stations SB-NPBA and SB-NPBB (Figure 1 of Annex D) while Silver exceeded the Upper Chemical Exceedance Level (UCEL) and LCEL and at Active Pit station SB-NPBA and SB-NPBB, respectively (Figure 2 of Annex D).   

1.6.5                                                                               Higher Copper and Silver concentrations were recorded within the Active Pit stations only which were receiving contaminated mud during the reporting month.  Therefore, there is no evidence indicating any dispersal of contaminants from the active pit due to the disposal activities.

1.6.6                                                                               For organic contaminants, the concentrations of Total Organic Carbon (TOC) were similar at all stations, except lower concentrations were recorded in Pit Edge station SB-NEBB and Active Pit station SB-NPBB (Figure 3 of Annex D).  Tributyltin (TBT) concentrations were observed to be higher at Active Pit stations SB-NPBA and SB-NPBB (Figure 4 of Annex D).  Low and High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs), Total Polychlorinated Biphenyls (PCBs), 4,4’-dichlorodiphenyldichloroethylene (DDE) and Total dichlorodiphenyltrichloroethane (DDT) concentrations were below the limit of reporting at most stations, except High MW PAHs at Active Pit stations SB-NPBB (Figure 5 of Annex D).   

 

1.6.7                                                                               Overall, there is no evidence indicating any unacceptable environmental impacts to sediment quality as a result of the contaminated mud disposal operations at CMP 2 in September 2015.  Statistical analysis will be undertaken and presented in the quarterly report to investigate whether there are any unacceptable impacts in the area caused by the contaminated mud disposal.

1.6.8                                Cumulative Impact Sediment Chemistry of SB CMPs – August 2015

1.6.9                                                                               Monitoring locations for Cumulative Impact Sediment Chemistry for SB CMPs are shown in Figure 1.4.  A total of eleven (11) monitoring stations were sampled in August 2015. 

1.6.10                            Analyses of results for the Cumulative Impact Sediment Chemistry Monitoring indicated that the concentrations of all inorganic contaminants were generally below the LCEL in August 2015, except Arsenic at Tai Ho Bay Station 2 (THB2) (Figures 6 and 7 of Annex D).  It should be noted that 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 ([8]).  It is presumed that the natural concentrations of Arsenic are similar in onshore and offshore sediments ([9]), and relatively high Arsenic levels may thus occur throughout Hong Kong.  Therefore, the LCEL exceedances of Arsenic are unlikely to be caused by the disposal operations at CMP 2 but rather as a result of naturally occurring deposits.

1.6.11                            For organic contaminants, concentrations of TOC at Near-field stations SB-RNA and SB-RNB and Mid-field stations SB-RMA and SB-RMB were recorded to be lower than other stations (Figure 8 of Annex D).  Concentrations of TBTs were recorded to be higher at Ma Wan station (Figure 9 of Annex D).  Total DDT, 4,4’-DDE, Total PCBs as well as Low and High Molecular Weight PAHs were recorded below the limit of reporting at all stations.

1.6.12                            Overall, there is no evidence indicating any unacceptable environmental impacts to sediment quality as a result of the contaminated mud disposal operations at CMP 2 in August 2015.  Statistical analysis will be undertaken and presented in the quarterly report to investigate whether there are any unacceptable impacts in the area caused by the contaminated mud disposal.

 

1.6.13                            Routine Water Quality Monitoring of SB CMP 2 – October 2015

1.6.14                            The monitoring results for the Routine Water Quality Monitoring conducted in October 2015 in the wet season 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 2004 - 2013 from stations in the Northwestern Water Control Zone (WCZ), where the CMPs are located ([10]).  For Salinity, the averaged value obtained from the Reference stations was used for the basis as the WQO.  Levels of DO and Turbidity were also assessed for compliance with the Action and Limit Levels (see Table B3 of Annex B for details).  The monitoring results are shown in Figures 10-19 of Annex D and Tables B4 and B5 of Annex B.  A total of fourteen (14) monitoring stations were sampled in October 2015 as shown in Figure 1.5. 

In-situ Measurements

1.6.15                                                                           Graphical presentation of the monitoring results (Temperature, DO, pH, Salinity and Turbidity) is shown in Figures 10-15 of Annex D.  Analyses of results for October 2015 indicated that the levels of pH, DO and Salinity complied with the WQOs at all stations (Impact, Intermediate, Reference and Water Sensitive Receiver stations) in October 2015 (Figures 10 – 12, 14 of Annex D).   

1.6.16                                                                           The levels of DO and Turbidity complied with the Action and Limit Levels at all stations (Table B4 of Annex B; Figures 12 and 15 of Annex D).

1.6.17                            Overall, in-situ measurement results of the Routine Water Quality Monitoring indicated that the disposal operation at CMP 2 did not appear to cause any unacceptable impacts in water quality in October 2015. 

Laboratory Measurements

1.6.18                            Laboratory analysis of October 2015 results indicated that concentrations of Arsenic, Cadmium, Chromium, Lead, Silver and Mercury were below their limit of reporting at all stations.  Copper, Nickel and Zinc were detected in October 2015 samples and the concentrations were similar amongst stations (Figure 16 of Annex D).  Results of laboratory analysis were shown in Table B5 of Annex B. 

1.6.19                            For nutrients, concentrations of Total Inorganic Nitrogen (TIN) at all stations in October 2015 exceeded the WQO (0.5 mg/L) (Figure 17 of Annex D).  It should be noted that the North Western WCZ has historically experienced higher levels of TIN and the exceedances of TIN WQO at these stations are unlikely to be caused by the disposal operation at CMP 2.  Ammonia Nitrogen (NH3-N) concentration was relatively similar amongst all stations (Figure 17 of Annex D).  Levels of 5-day Biochemical Oxygen Demand (BOD5) appear to be higher at Shum Shui Kok and Tai Mo To stations in October 2015 (Figure 18 of Annex D). 

1.6.20                            Concentrations of SS exceeded the WQO (11.6 mg/L for wet season) at most stations, except Impact, Tai Mo to and Tai Ho Bay 2 stations in October 2015.  However, concentrations of SS complied with the Action and Limit Levels at all stations in October 2015 (Figure 19 of Annex D; Table B5 of Annex B).

1.6.21                            Overall, results of the Routine Water Quality Monitoring indicated that the disposal operation at CMP 2 did not appear to cause any unacceptable deterioration in water quality in October 2015.  Detailed statistical analysis will be presented in the Quarterly Report to investigate any spatial and temporal trends of potential concern.

1.6.22                            Water Column Profiling of CMP 2 – October 2015

1.6.23                                                                           Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 13 October 2015.  The monitoring results have been assessed for compliance with the WQOs (see Section 1.6.14 for details).    

In-situ Measurements

1.6.24                                                                           Analyses of results for October 2015 indicated that levels of Salinity, DO and pH complied with the WQOs at both Downstream and Upstream stations (Table B6 of Annex B).  In addition, DO and Turbidity at all stations complied with the Action and Limit Levels (Tables B3 and B6 of Annex B).

Laboratory Measurements for SS

1.6.25                                                                         Analyses of results for October 2015 indicated that the SS levels only complied with the WQO at Downstream stations.  However, both Upstream and Downstream stations complied with the Action and Limit Levels (Tables B3 and B6 of Annex B).

Overall, the monitoring results indicated that the mud disposal operation at CMP 2 did not appear to cause any deterioration in water quality during this reporting period.

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 2015 for SB CMPs:

·       Pit Specific Sediment Chemistry of CMP 2;

·       Routine Water Quality Monitoring of CMP 2; and

·       Water Column Profiling of CMP 2.

1.7.2                               The following monitoring activities will be conducted in the next monthly period of November 2015 for ESC CMPs:

·       Impact Monitoring during Dredging Operations of ESC CMP Vd.

1.7.3                                The sampling schedule is presented in Annex A.

1.8                                      Study Programme

1.8.1                                A summary of the Study programme is presented in Annex E.

 


([1])       According to the Management Framework of Dredged/ Excavated Sediment of ETWB TC(W) No. 34/2002, contaminated sediment in general shall mean those sediment requiring Type 2 – Confined Marine Disposal as determined according to this TC(W).

([2])        CAD options may involve use of excavated borrow pits, or may involve purpose-built excavated pits.  CAD sites are those which involve filling a seabed pit with contaminated mud and capping it with uncontaminated material such that the original seabed level is restored and the contaminated material is isolated from the surrounding marine environment.7

([3])       Detailed Site Selection Study for a Proposed Contaminated Mud Disposal Facility within the Airport East/ East of Sha Chau Area (Agreement No. CE 12/2002(EP))

([4])       Under the CEDD study Contaminated Sediment Disposal Facility to the South of The Brothers (Agreement No. FM 2/2009)

([5])          ERM (2012) Environmental Monitoring and Audit (EM&A) Manual. Final First Review.  Environmental Monitoring and Audit for Contaminated Mud Pits to the South of the Brothers and at East Sha Chau (2012-2017) – Investigation.  Agreement No. CE 23/2012(EP). Submitted to EPD in November 2012.

([6])         ERM (2010) Environmental Monitoring and Audit (EM&A) Manual. Final Second Review.  Environmental Monitoring and Audit for Contaminated Mud Pit at Sha Chau (2009-2013) – Investigation.  Agreement No. CE 4/2009(EP). Submitted to EPD in November 2010.

([7])        ERM (2009).  Draft Second Review of the EM&A Manual.  Under Agreement No. CE 4/2009 (EP) EM&A for Contaminated Mud Pit at Sha Chau (2009-2013) – Investigation