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

34th MONTHLY PROGRESS REPORT FOR JUne 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 June 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 34th Monthly Progress Report covers the EM&A activities for the reporting month of June 2015.

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                                                                               The following monitoring activity has been undertaken for ESC CMPs in June 2015:

       Water Quality Monitoring during Capping of ESC CMPs was undertaken on 2 June 2015.

 

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

       Pit Specific Sediment Chemistry of CMP 2 was undertaken on 8 June 2015;

       Cumulative Impact Specific Chemistry of CMP 2 was undertaken 9 June 2015;

       Water Quality Monitoring during Capping Operations of CMP 1 was undertaken on 10 June 2015; and

       Water Column Profiling of CMP 2 was undertaken on 11 June 2015.

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained for June 2015. 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 CMP 2 in June 2015; and

       Laboratory analyses of sediment samples collected for Cumulative Impact Specific Chemistry of CMP 2 in June 2015.

1.4.2                                A summary of field activities conducted are presented in Annex A.

1.5                                      Brief Discussion of the Monitoring Results for ESC CMPs

1.5.1                                Brief discussion of the monitoring results of Water Quality Monitoring during Capping of ESC CMPs conducted on 2 June 2015 is presented below.

1.5.2                                Water Quality Monitoring during Capping June 2015

1.5.3                                The monitoring results obtained during June 2015 sampling in the wet season have been assessed for compliance with the Water Quality Objectives (WQOs) through a review of the Environmental Protection Department (EPD) routine water quality monitoring data for the wet season period (April to October) of 2004 2013 from stations in the North Western Water Control Zone (WCZ), where ESC CMPs are located. For Salinity, the average value obtained from the Reference stations was used for the basis as the WQO. A total of sixteen (16) monitoring stations were sampled in June 2015 as shown in Figure 1.2. Graphical presentation of the monitoring results is provided in Annex B.

In-situ Measurements

1.5.4                                Graphical presentation of the monitoring results (Temperature, Dissolved Oxygen (DO), pH, Salinity and Turbidity) is shown in Figures 1-6 of Annex B. Levels of DO, pH and Salinity at most stations in June 2015 complied with the WQO except Salinity at Ma Wan station. The higher Salinity recorded at Ma Wan station is likely to be caused by its greater separation distance from the Pearl River mouth, which is a key source of freshwater inputs in the area, when compared to the Reference stations. The turbidity complied with the Action and Limit levels at all stations in June 2015 (Table C1 of Annex C).

Laboratory Measurements for Suspended Solids (SS)

1.5.5                                Concentrations of SS complied with the WQO at most stations except at Impact stations in June 2015 (Figure 7 of Annex B; Table C2 of Annex C). However, the SS complied with the Action and Limit levels at all stations in June 2015 (Table C1 of Annex C). 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 34th Monthly Progress Report:

       Laboratory analyses of sediment samples collected for Pit Specific Sediment Chemistry of CMP 2 in May 2015;

       Water Quality Monitoring during Capping Operations of CMP 1 conducted on 10 June 2015; and

       Water Column Profiling of CMP 2 undertaken on 11 June 2015.

1.6.2                                Pit Specific Sediment Chemistry of CMP 2 May 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 May 2015.

1.6.4                                                                               Zinc exceeded the Lower Chemical Exceedance Level (LCEL) at Active Pit station SB-NPBA while Nickel exceeded the Upper Chemical Exceedance Level (UCEL) at Active Pit station SB-NPBB. In addition, Copper and Silver exceeded the UCEL at Active Pit stations SB-NPBA and SB-NPBB in May 2015. The concentrations of other inorganic contaminants (Cadmium, Chromium, Mercury, Lead and Arsenic) were lower than the LCEL at all stations. As higher Copper, Nickel, Silver and Zinc concentrations were recorded within the Active Pit stations only which were receiving contaminated mud during the reporting month, there is no evidence indicating any dispersal of contaminants from the active pit.

1.6.5                                                                               For organic contaminants, the concentrations of Total Organic Carbon (TOC) were similar at most stations except lower values were recorded at Pit Edge station SB-NEBB and Near Pit station SB-NNBB (Figure 10 of Annex B). Tributyltin (TBT) concentrations were observed to be higher at Active Pit station SB-NPBA and Near Pit station SB-NNBB (Figure 11 of Annex B). Total dichlorodiphenyltrichloroethane (DDT), 4,4-dichlorodiphenyldichloroethylene (DDE), Total Polychlorinated Biphenyls (PCBs), Low and High Molecular Weight Polycyclic Aromatic Hydrocarbons (MW PAHs) were below the limit of reporting at most stations (except High MW PAHs at Active Pit station SB-NPBA) in May 2015 (Figure 12 of Annex B).

1.6.6                                                                               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 May 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.

1.6.7                                Water Quality Monitoring during Capping Operations of CMP 1 June 2015

1.6.8                                The monitoring results obtained during June 2015 sampling in the wet season 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 June 2015 as shown in Figure 1.4. Graphical presentation of the monitoring results is provided in Annex B.

In-situ Measurements

1.6.9                                                                               Graphical presentation of the monitoring results (Temperature, Dissolved Oxygen (DO), pH, Salinity and Turbidity) is shown in Figures 13-18 of Annex B. Levels of pH at all stations in June 2015 complied with the WQO. DO at most stations complied with the WQO except at Intermediate and Ma Wan stations. As Intermediate and Ma Wan stations are located further away from the CMP 1 and DO at the Impact stations complied with the WQO, it is considered that the WQO exceedances of DO at these stations were possibly caused by the natural background variation in water quality of the area, but not from the capping operation of CMP 1. The DO and turbidity complied with the Action and Limit levels at all stations in June 2015 (Table C3 and C4 of Annex C).

1.6.10                                                                           Levels of Salinity exceeded the WQO at most stations except at Tai Ho Bay stations. The lower Salinities recorded at Tai Ho Bay and Reference stations are likely due to the close proximity of the nearby streams and Pearl River mouth, which release large amount of freshwater runoff in the area during flooding. The Salinities at other stations were 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

1.6.11                            Concentrations of SS complied with the WQO (11.6 mg/L for wet season) at most stations in June 2015 except at Tai Ho Bay station 1 (Figure 19 of Annex B). However, SS at all stations complied with the Action and Limit Levels in June 2015 (Table C3 and C4 of Annex C).

1.6.12                            For nutrients, concentrations of Ammonia (NH3) were relatively similar amongst most stations except a slightly lower value was recorded at Reference and Tai Ho Bay stations (Figures 20 of Annex B). Concentrations of Biochemical Oxygen Demand (BOD5) were similar at most stations except higher values were recorded at Tai Ho Bay stations in June 2015. Total Inorganic Nitrogen (TIN) at all stations exceeded the WQO of 0.5 mg/L in June 2015 (Figure 22 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 all stations are unlikely to be caused by the capping operation at CMP 1.

1.6.13                            Since lower BOD5 was recorded for both Impact and Reference stations, the higher concentration at Tai Ho Bay stations is likely due to the natural fluctuation of BOD5 in the environment. Therefore, there is no evidence indicating any degradation of water quality due to the capping activities at CMP 1.

1.6.14                            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.

 

1.6.15                            Water Column Profiling of CMP 2 June 2015

1.6.16                                                                           Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 11 June 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

1.6.17                                                                           Analyses of results for June 2015 indicated that levels of Temperature, Salinity, DO and pH complied with the WQOs at both Downstream and Upstream stations (Table C5 of Annex C). DO and Turbidity at all stations complied with the Action and Limit Levels (Tables C3 and C5 of Annex C).

Laboratory Measurements for SS

1.6.18                                                                           Analyses of results for June 2015 indicated that the Suspended Solid (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 C5 of Annex C).

1.6.19                                                                           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 July 2015 for SB CMPs:

       Pit Specific Sediment Chemistry of CMP 2;

       Demersal Trawling for CMP 2;

       Water Column Profiling of CMP 2; and

       Routine Water Quality Monitoring of CMP 2.

1.7.2                                No monitoring activity is scheduled to be conducted in the next monthly period of July 2015 for 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.