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

22nd MONTHLY PROGRESS REPORT FOR june 2014

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 2014, the following works were being undertaken at the CMPs:

·       Capping was being undertaken at ESC CMP IVc and CMP Va;

·       Disposal of contaminated mud was taking place at SB CMP 1; and

·       Dredging operations were taking place at SB CMP 2.

Figure 1.1       Works Schedule for ESC CMPs and SB CMPs

1.2                         Reporting Period

1.2.1                     This 22nd Monthly Progress Report covers the EM&A activities for the reporting month of June 2014.

 

1.3                          Details of Sampling and Laboratory Testing Activities

1.3.1                     Water Quality Monitoring during Capping was undertaken for ESC CMPs on 6 June 2014.

1.3.2                     The following monitoring activities have been undertaken for SB CMPs in June 2014:

·          Impact Water Quality Monitoring during Dredging Operations was undertaken for CMP 2 three times per week on 3, 5, 7, 9, 11, 13, 16, 18, 20, 23, 25, 27 and 30 June 2014;

·          Water Column Profiling for CMP 1 was undertaken on 10 June 2014;

·          Pit Specific Sediment Chemistry for CMP 1 was undertaken on 12 June 2014; and

·          Cumulative Impact Sediment Chemistry for CMP 1 was undertaken on 17 and 19 June 2014.

1.4                         Details of Outstanding Sampling and/or Analysis

1.4.1                     No outstanding sampling remained for June 2014.  The following laboratory analyses were still in progress during the preparation of this monthly report and hence were not presented in this monthly report:

·       Laboratory analyses of sediment samples collected for Pit Specific Sediment Chemistry of CMP 1 in May and June 2014; and

·       Laboratory analyses of sediment samples collected for Cumulative Impact Sediment Chemistry of CMP 1 in June 2014.

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 the Water Quality Monitoring during Capping of ESC CMPs conducted on 6 June 2014 is presented below.

1.5.2                      Water Quality Monitoring during Capping – June 2014

1.5.3                      The monitoring results obtained during June 2014 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 2003 – 2012 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 10 monitoring stations were sampled in June 2014 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 is shown in Figures 1-6 of Annex B.  Levels of Dissolved Oxygen (DO), pH and Salinity at most stations in June 2014 complied with the WQO except for the 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.    

Laboratory Measurements for Suspended Solids (SS)

1.5.5                      Concentrations of SS complied with the WQO at all stations in June 2014 (Figure 7 of Annex B).  

Overall, the results indicated that the capping operations at ESC CMPs did not appear to cause any unacceptable deterioration in water quality.

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 22nd Monthly Progress Report:

·       Pit Specific Sediment Chemistry of CMP 1 conducted in April 2014;

·       Impact Water Quality Monitoring during Dredging Operations of CMP 2 conducted in June 2014; and

·       Water Column Profiling of CMP 1 conducted on 10 June 2014.

1.6.2                      Pit Specific Sediment Chemistry of CMP 1 – April 2014

1.6.3                     Monitoring locations for Pit Specific Sediment Chemistry for CMP 1 are shown in Figure 1.3.  A total of six (6) monitoring stations were sampled in April 2014. 

1.6.4                     The concentrations of most inorganic contaminants were lower than the Lower Chemical Exceedance Level (LCEL) at all stations except for Arsenic in April 2014 (Figures 8-9 of Annex B).  Concentrations of Arsenic exceeded the LCEL at most stations except for Active Pit stations SB-NPAA and SP-NPAB. 

1.6.5                     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 ([7]).  It is presumed that the natural concentrations of Arsenic are similar in onshore and offshore sediments ([8]), 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 1 but rather as a result of naturally occurring deposits. 

1.6.6                     For organic contaminants, the concentration of Total Organic Carbon (TOC) was similar amongst stations with no consistent spatial trend in April 2014 (Figure 10 of Annex B.  Concentrations of Tributyltin (TBTs) were observed to be higher at Active Pit station SB-NPAB in April 2014 (Figure 11 of Annex B).  High Molecular Weight Polycyclic Aromatic Hydrocarbons (High MW PAHs) concentrations were recorded below the limit of reporting at all stations except at Active Pit station SB-NPAB (Figure 12 of Annex B).  Low MW PAHs, Total Dichloro-Diphenyl-Trichloroethane (DDT), 4,4’-Dichloro-Diphenyl-Dichloroethylene (4,4’-DDE) and Total Polychlorinated Biphenyls (PCBs) were recorded below the limit of reporting at all stations in April 2014. 

1.6.7                     Active Pit station SB-NPAB is located within CMP 1 which was receiving contaminated mud during the reporting period.  Therefore, the higher concentrations of contaminants recorded at this Active Pit station only are not considered as indicating any dispersal of contaminated mud from CMP 1.  Nevertheless, detailed analyses will be presented in the Quarterly Report to reveal any trend of increasing sediment contaminant concentrations towards CMP 1. 

1.6.8                     Overall, there is no evidence indicating any unacceptable environmental impacts to sediment quality as a result of the contaminated mud disposal operations at CMP 1 in April 2014.

1.6.9                     Impact Water Quality Monitoring during Dredging Operations of CMP 2 – June 2014

1.6.10                   Impact Water Quality Monitoring during Dredging Operations of CMP 2 was conducted three times per week from 3 to 30 June 2014 during the reporting period.  On each survey day, sampling 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 CMP 2.  Monitoring was also conducted at five Sensitive Receiver Stations situated in Ma Wan, Shum Shui Kok, Tai Mo To and Tai Ho Bay.  A total of twelve stations were monitored and locations of the sampling stations are shown in Figure 1.4.  Sampling at station THB2 during mid-ebb tides of 11 and 23 June 2014, during mid-flood tide of 16 June 2014 as well as during both mid-flood and mid-ebb tides of 7 and 25 June 2014 were cancelled due to adverse weather condition.

1.6.11                   Monitoring results are presented in Table C1 of Annex C.  Daily dredging volume in June 2014 is reported in Annex D.    Levels of DO, Turbidity and SS generally complied with the Action and Limit Levels (see Table C2 of Annex C for details) set in the Baseline Monitoring Report ([9]), except for the following occasion of exceedances shown in Table 1.1 below.

Table 1.1    Details of Exceedances Recorded at CMP 2 between 3 and 30 June 2014

Date

Tide

Parameter

Station

Type

7 June 2014

Mid-Ebb

Bottom DO

DS2

Action

7 June 2014

Mid-Ebb

Bottom DO

WSR45C

Action

13 June 2014

Mid-Flood

SS

DS1

Action

1.6.12                   Action Level exceedances of bottom DO were recorded at stations DS2 and WSR45C during mid-ebb tide on 7 June 2014.  Stations DS2 and WSR45C are located further away from the works area of CMP 2 when compared to station DS1 at which the levels of bottom DO did not exceed the Action and Limit Levels during the same tidal period.  In addition, these Action Level exceedances of bottom DO were recorded during one tidal period only and the dredging rate was well within the limit as specified under the EP, it is considered that the exceedances were isolated sporadic event which may be caused by natural background variation in water quality characteristics of the monitoring area.  As such, the exceedances at stations DS2 and WSR45C are not likely to be caused by the dredging works at CMP 2.

Action Level Exceedance of SS was recorded at station DS1 only which is located at the boundary of the works area during one tidal period on 13 June 2014, and given that the dredging rate was well within the limit as specified under the EP, it is considered that the exceedance was not indicating any unacceptable impacts from the dredging operations to the nearby Water Sensitive Receivers (WSRs).

1.6.13                   It should be noted that high levels of SS were occasionally recorded during baseline monitoring which are considered to be sporadic events and characteristic of water quality in this area of Hong Kong (baseline monitoring data are summarised in Table C3 of Annex C).  Therefore, the Action and Limit Level exceedances may be caused by natural background variation in water quality of the area.

1.6.14                   Overall, the results indicated that the dredging operations at CMP 2 did not appear to cause any unacceptable deterioration in water quality during this reporting period.  Therefore, no further mitigation measures, except for those recommended in the Environmental Permit (EP-427/2011/A), are considered necessary for the dredging operations.

1.6.15                   Water Column Profiling of CMP 1 – June 2014

1.6.16                  Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 10 June 2014.  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 C2 of Annex C for details). 

In-situ Measurements

1.6.17                  Analyses of results for June 2014 indicated that levels of Salinity, pH and DO complied with the WQOs at both Downstream and Upstream stations (Table C4 of Annex C).  DO and Turbidity also complied with the Action and Limit Levels.

Laboratory Measurements for SS

1.6.18                  Analyses of results for June 2014 indicated that the SS levels at Downstream and Upstream stations complied with the WQO and the Action and Limit Levels (Table C4 of Annex C).

1.6.19                  Overall, the monitoring results indicated that the mud disposal operation at CMP 1 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 2014 for SB CMPs:

l Impact Water Quality Monitoring during Dredging Operations of CMP 2; 

l Pit Specific Sediment Chemistry of CMP 1;

l Routine Water Quality Monitoring of CMP 1;

l Water Column Profiling of CMP 1; and

l Demersal Trawling of CMP 1.

1.7.2                     No monitoring activities are scheduled to be undertaken in the next monthly period of July 2014 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 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]) Sewell RJ (1999) Geochemical Atlas of Hong Kong. Geotechnical Engineering Office, Government of the Hong Kong Special Administrative Region

([8]) 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

([9]) ERM (2012) Baseline Monitoring Report. 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 October 2012.