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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

36th MONTHLY PROGRESS REPORT FOR August 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 August 2015, the following works were being undertaken at the CMPs:

·      Capping operations at ESC CMPs;

·      Capping operations at SB CMP 1; 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 36th Monthly Progress Report covers the EM&A activities for the reporting month of August 2015.

1.3                          Details of Sampling and Laboratory Testing Activities

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

·      Benthic Recolonisation Studies of ESC CMPs was undertaken on 12 August 2015; and

·      Water Quality Monitoring During Capping of ESC CMPs was undertaken on 18 August 2015.

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

·      Water Column Profiling of CMP 2 was undertaken on 10 August 2015;

·      Routine Water Quality Monitoring of CMP 2 was undertaken on 13 August 2015;

·      Pit Specific Sediment Chemistry of CMP 2 was undertaken on 17 August 2015;

·      Demersal Trawling for CMPs was undertaken on 19 and 20 August 2015;

·      Cumulative Impact Sediment Chemistry of CMP 2 was undertaken on 19 and 21 August 2015;

·      Sediment Toxicity Test of CMP 2 was undertaken on 19 and 21 August 2015;

·      Water Quality Monitoring During Capping of CMP 1 was undertaken on 24 August 2015; and

·      Benthic Recolonisation Studies of CMP 1 was undertaken on 26 August 2015.

1.4                         Details of Outstanding Sampling and/or Analysis

1.4.1                     No outstanding sampling remained for August 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 Cumulative Impact Sediment Chemistry of SB CMP 2 in August 2015; and

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

1.4.3                     The following laboratory analyses are in progress and will be presented in the corresponding quarterly report:

·      Laboratory analyses of sediment samples collected for Benthic Recolonisation Studies of ESC CMPs and SB CMP 1 in August 2015;

·      Taxonomic identification of fishery resources collected during Demersal Trawling for SB CMPs in July and August 2015; and

·      Laboratory analyses for Sediment Toxicity Test of SB CMP 2 in August 2015.

1.5                          Brief Discussion of the Monitoring Results for ESC CMPs

1.5.1                                                     Brief discussion of the monitoring results of the Water Quality Monitoring during Capping of ESC CMPs conducted in August 2015 is presented below.  Graphical presentation of the monitoring results is provided in Annex B.

1.5.2                      Water Quality Monitoring during Capping of ESC CMPs – August 2015

1.5.3                      The monitoring results obtained during August 2015 sampling 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 ([7]).  For Salinity, the averaged value obtained from the Reference stations 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 C1 of Annex C for details).  A total of ten (10) monitoring stations were sampled in August 2015 as shown in Figure 1.2.   

In-situ Measurements

1.5.4                      Graphical presentation of the monitoring results (Temperature, DO, pH, Salinity and Turbidity) is shown in Figures 1-6 of Annex B.  Levels of Dissolved Oxygen (DO) and pH at all stations in August 2015 complied with the WQO and the Action and Limit levels (Table C1 of Annex C).  Level of Salinity at most station also complied with WQO, except for Ma Wan station.  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 flooding, when compared to the Reference stations. 

Laboratory Measurements for Suspended Solids (SS)

Concentrations of SS complied with the WQO at all stations in August 2015, except for the Impact stations (Figure 7 of Annex B; Table C2 of Annex C).  However, concentrations of SS at all stations complied with the Action and Limit Levels.  Further statistical analysis will be undertaken in the quarterly report to investigate whether the capping operations at ESC CMPs is causing any unacceptable deterioration in water quality of the area.

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 36th Monthly Progress Report:

·      Water Quality Monitoring During Capping of CMP 1 in August 2015;

·      Water Column Profiling of CMP 2 in August 2015; and

·      Routine Water Quality Monitoring of CMP 2 in August 2015.

1.6.2                      Water Quality Monitoring during Capping of SB CMP 1 – August 2015

1.6.3                      The monitoring results obtained during August 2015 sampling in the wet season have been assessed for compliance with the WQOs (see Section 1.5.3 for details).  Levels of DO and Turbidity were also assessed for compliance with the Action and Limit Levels (see Table C3 of Annex C for details).  A total of fourteen (14) monitoring stations were sampled in August 2015 as shown in Figure 1.3.  Graphical presentation of the monitoring results is provided in Annex B. 

In-situ Measurements

1.6.4                                                     Graphical presentation of the monitoring results (Temperature, DO, pH, Salinity and Turbidity) is shown in Figures 8-13 of Annex B.  Levels of pH at all stations in August 2015 complied with the WQO.  DO at most stations complied with the WQO except at Sham Shui Kok station.   However, the levels of DO at all stations complied with the Action and Limit levels in August 2015 (Table C3 of Annex C).  In addition, and the levels of Turbidity complied with the Action and Limit levels at all stations in August 2015 (Table C3 and C4 of Annex C).

1.6.5                                                     Levels of Salinity at most stations complied with the WQO except at Intermediate, Sham Shui Kok, Tai Ho Bay 2 and Ma Wan stations.  The lower Salinities recorded at Tai Ho Bay 2 and Reference stations are likely due to the close proximity of the nearby streams, which release large amount of freshwater runoff in the area during flooding.  The Salinities at other stations were higher or above the WQO as they were located further away from the Tai Ho Bay and Reference stations which experienced less freshwater runoff from the nearby streams.   

Laboratory Measurements

1.6.6                      Concentrations of SS complied with the WQO (11.6 mg/L for wet season) at Intermediate, Ma Wan and Tai Ho Bay 2 stations, but not at Reference, Impact, Tai Ho Bay 1 and Sham Shui Kok stations in August 2015 (Figure 14 of Annex B).  However, SS at all stations complied with the Action and Limit Levels in August 2015 (Table C3 and C4 of Annex C).

 

1.6.7                      For nutrients, concentrations of Ammonia (NH3) were relatively similar amongst most stations except a slightly lower value was recorded at Tai Ho Bay 2 station (Figures 15 of Annex B).  Total Inorganic Nitrogen (TIN) at Impact, Reference, Tai Ho Bay 1 and Tai Mo To stations exceeded the WQO of 0.5 mg/L in August 2015 (Figure 16 of Annex B).  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 capping operation at CMP 1. 

1.6.8                     Concentrations of Biochemical Oxygen Demand (BOD5) were similar at most stations except higher values were recorded at Reference stations in August 2015 (Figures 17 of Annex B). 

1.6.9                      Statistical analysis will be undertaken and presented in the quarterly report to investigate whether the capping operations at CMP 1 is causing any unacceptable impacts in water quality of the area.

1.6.10                   Routine Water Quality Monitoring of SB CMP 2 – August 2015

1.6.11                   The monitoring results for the Routine Water Quality Monitoring conducted in August 2015 in the wet season have been assessed for compliance with the WQOs (see Section 1.5.3 for details).  Levels of Dissolved Oxygen (DO) and Turbidity were also assessed for compliance with the Action and Limit Levels (see Table C3 of Annex C for details).  The monitoring results are shown in Figures 18-28 of Annex B and Tables C5 and C6 of Annex C.  A total of twenty (20) monitoring stations were sampled in August 2015 as shown in Figure 1.4. 

In-situ Measurements

1.6.12                                                  Graphical presentation of the monitoring results (Temperature, DO, pH, Salinity and Turbidity) is shown in Figures 18-23 of Annex B.  Analyses of results for August 2015 indicated that the levels of pH and DO complied with the WQOs at all stations (Impact, Intermediate, Reference and Water Sensitive Receiver stations) in August 2015 (Figures 18 – 20 of Annex B).   

1.6.13                                                  The levels of Salinity at Impact, Intermediate and Water Sensitive Receiver stations exceeded the WQO range in August 2015 (Figure 22 of Annex B).  The lower Salinities recorded at these stations, which lead to exceedance of the WQO, is likely to be caused by the freshwater discharged from the Pearl River Delta during the summer months which tend to form a surface layer of low salinity water at these stations with shallower depth when compared with the Reference stations.   

1.6.14                                                  The levels of DO and Turbidity complied with the Action and Limit Levels at all stations (Figures 19 and 22 of Annex B; Table C5 of Annex C).

1.6.15                   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 August 2015. 

 

Laboratory Measurements

1.6.16                   Laboratory analysis of August 2015 results indicated that concentrations of Cadmium, Chromium, Silver and Mercury were below their limit of reporting at all stations.  Arsenic, Copper, Lead, Nickel and Zinc were detected in August 2015 samples and the concentrations were similar amongst stations (Figures 24-25 of Annex B).  Results of laboratory analysis were shown in Table C6 of Annex C. 

1.6.17                   For nutrients, concentrations of TIN at all stations in August 2015 exceeded the WQO (0.5mg/L) (Figure 26 of Annex B).  As discussed in Section 1.6.7, the North Western WCZ has historically experienced higher levels of TIN and the exceedances of TIN WQO at all stations in August 2015 were unlikely to be caused by the disposal operation at CMP 2.  Ammonia Nitrogen (NH3-N) concentration was relatively similar amongst all stations (Figure 26 of Annex B).  Levels of 5-day Biochemical Oxygen Demand (BOD5) appear to be higher at Tai Ho Bay 1 and Shum Shui Kok stations in August 2015 (Figure 27 of Annex B). 

1.6.18                   Concentrations of SS complied the WQO (11.6 mg/L for wet season) at all stations, except Reference stations in August 2015.  Concentrations of SS complied with the Action and Limit Levels at all stations in August 2015 (Figure 28 of Annex B; Table C6 of Annex C).

1.6.19                   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 August 2015.  Detailed statistical analysis will be presented in the Quarterly Report to investigate any spatial and temporal trends of potential concern.

1.6.20                   Water Column Profiling of CMP 2 – August 2015

1.6.21                                                  Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 10 August 2015.  The water quality monitoring results have been assessed for compliance with the WQOs as discussed in Section 1.5.3.  The monitoring results were also compared with the Action and Limit Levels set in Baseline Monitoring Report (see Table C3 of Annex C for details). 

In-situ Measurements

1.6.22                                                  Analyses of results for August 2015 indicated that levels of Salinity, DO and pH complied with the WQOs at both Downstream and Upstream stations (Table C7 of Annex C).  In addition, DO and Turbidity at all stations complied with the Action and Limit Levels (Tables C3 and C7 of Annex C).

Laboratory Measurements for SS

1.6.23                                                 Analyses of results for August 2015 indicated that the SS levels at both Upstream and Downstream stations complied with the WQO.  Both Upstream and Downstream stations also complied with the Action and Limit Levels (Tables C3 and C7 of Annex C).

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 September 2015 for SB CMPs:

·      Pit Specific Sediment Chemistry 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 September 2015 for ESC CMPs:

·      Impact Monitoring during Dredging Operations of ESC CMPs.

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 D.

 

 

 

([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])        http://epic.epd.gov.hk/EPICRIVER/marine/?lang=en