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

15TH MONTHLY PROGRESS REPORT FOR NOVEMBER 2013

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 East of Sha Chau (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 undertaken under Agreement No. CE 23/2012 (EP) covers the dredging, disposal and capping operations of the SB CMPs as well as CMPs at East of Sha Chau (ESC).  In November 2013, the following works were being undertaken at the CMPs:

·           Capping was being undertaken at 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.

1.2                                      Reporting Period

1.2.1                                This Monthly Progress Report covers the EM&A activities for the reporting month of November 2013.

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                               No monitoring activities were undertaken for CMP V in the monitoring month of November 2013.

1.3.2                               The following monitoring activities have been undertaken for SB CMPs in November 2013 in accordance with the EM&A Manual:

·           Impact Water Quality Monitoring during Dredging Operations was undertaken for CMP 2 three times per week on 1, 5, 7, 9, 11, 13, 15, 18, 20, 22, 25, 27 and 29 November 2013; 

·           Routine Water Quality Monitoring was conducted for CMP 1 three times per week on 2, 5, 7, 9, 12, 14, 16, 19, 21, 23, 26, 28 and 30 November 2013;

·           Water Column Profiling was undertaken for CMP 1 on 7 November 2013; and,

·           Pit Specific Sediment Chemistry was conducted for CMP 1 on 12 November 2013.

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained for November 2013.  The following laboratory analyses were still in progress during the preparation of this monthly report:

·           Laboratory analyses of sediment samples collected for Pit Specific Sediment Chemistry of CMP 1 in October and November 2013;

·           Laboratory analyses of Suspended Solids (SS) samples collected for Water Quality Monitoring during Dredging Operations of CMP 2 from 18 to 29 November 2013; and

·           Laboratory analyses of water samples collected for Routine Water Quality Monitoring of CMP 1 from 19 October to 30 November 2013. 

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

1.5                                      Brief Discussion of the Monitoring Results for CMP V

1.5.1                                Brief discussion of the monitoring results of Cumulative Impact Sediment Chemistry Monitoring conducted in August 2013 is presented in this 15th Monthly Report.  Detailed discussion will be presented in the corresponding Quarterly Report.

1.5.2                                Cumulative Impact Sediment Chemistry of CMP V – August 2013

1.5.3                               Monitoring locations for Cumulative Impact Sediment Chemistry for CMP V are shown in Figure 1.1.  A total of nine monitoring stations were sampled in August 2013. 

1.5.4                                Analyses of results for the Cumulative Impact Sediment Chemistry Monitoring indicated that the concentrations of all metals, except Arsenic, were below the Lower Chemical Exceedance Level (LCEL) in August 2013 (Figures 1 and 2 of Annex B).  Concentrations of Arsenic in sediments from all stations, except for Near Field stations RNA and RNB and Ma Wan Station, exceeded the LCEL. 

1.5.5                                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 LECL exceedances of Arsenic are unlikely to be caused by the disposal operations at CMP Va but rather as a result of naturally occurring deposits.  The slight exceedances of the LCEL for the Arsenic do not necessarily indicate any unacceptable impacts to sediment quality caused by disposal operation at CMP Va.

1.5.6                                The concentration of Total Organic Carbon (TOC) shows variation amongst stations (Figure 3 of Annex B).  Tributyltin (TBTs) were recorded in sediment samples from all stations and Ma Wan station was recorded with a higher concentration (Figure 4 of Annex B).  Concentrations of Total Polychlorinated Biphenyls (PCBs), Low and High Molecular Weight Polycyclic aromatic hydrocarbons (Low and High MW PAHs), total Dichloro-diphenyl-trichloroethane (DDT) and 4,4’-Dichloro-diphenyl-dichloroethylene (4,4’-DDE) were recorded below the limit of detection at all the stations. 

1.5.7                               Overall, there is no evidence indicating any unacceptable environmental impacts to sediment quality as a result of the contaminated mud disposal operations at CMP Va during this monthly period.

1.6                                      Brief Discussion of the Monitoring Results for SB CMPs

1.6.1                               Brief discussion of the monitoring results of Pit Specific Sediment Chemistry of CMP 1 conducted in September 2013, Impact Water Quality Monitoring during Dredging Operations of CMP 2 conducted from 30 October to 15 November 2013 and Water Column Profiling conducted in November 2013 is presented in this 15th Monthly Report.  Detailed discussion will be presented in the corresponding Quarterly Report.

1.6.2                                Pit Specific Sediment Chemistry of CMP 1 – September 2013

1.6.3                               Monitoring locations for Pit Specific Sediment Chemistry for CMP 1 are shown in Figure 1.2.  A total of six monitoring stations were sampled in September 2013. 

1.6.4                               The concentrations of all the metals except Arsenic complied with the LCEL at all stations in September 2013 (Figures 5 and 6 of Annex B).  Concentrations of Arsenic exceeded the LCEL at all stations except Active Pit station SB-NPAB (Figures 5 and 6 of Annex B).    

1.6.5                               As discussed in Section 1.5.5 above, relatively high natural levels of Arsenic are present in Hong Kong’s marine sediments and hence the slight LCEL exceedances of Arsenic do not necessarily indicate any adverse impacts to sediment quality caused by disposal operation at CMP 1.

1.6.6                               TOC concentration indicated variations amongst the stations in September 2013 (Figure 7 of Annex B).  TBT concentrations were found to be higher at Active Pit Station SB-NPAB and Near Pit Station SB-NNAB (Figure 8 of Annex B) in September 2013. 

1.6.7                               Low and High MW PAHs concentrations were recorded below the limit of reporting at all stations except for High MW PAHs concentration at Active Pit station SB-NPAB in September 2013 (Figure 9 of Annex B). 

1.6.8                               Total DDT, 4,4’-DDE and Total PCBs were recorded below the limit of reporting at all the stations in September 2013.

1.6.9                               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 (including metals and organic contaminants) recorded at the Active Pit station only are not considered as indicating any dispersal of contaminated mud from CMP 1.  Nevertheless, detailed analysis will be presented in the Quarterly Report to reveal any trend of increasing sediment contaminant concentrations towards CMP 1.

1.6.10                           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 during this monthly period.  

1.6.11                            Impact Water Quality Monitoring during Dredging Operations of CMP 2 – 30 October to 15 November 2013

1.6.12                            Monitoring data collected for CMP 2 from 30 October to 15 November 2013 are presented in this monthly report.  Detailed discussion will be presented in the corresponding Quarterly Report.

1.6.13                            Impact Water Quality Monitoring during Dredging Operations of CMP 2 (i.e. from 30 October to 15 November 2013) was conducted three times per week for a total of eight (8) sampling days.  On each survey day, sampling was conducted during both mid-ebb and mid-flood tides at two Reference (Upstream) stations upstream and five Impact (Downstream) stations downstream of the dredging operations at CMP 2.  Monitoring was also conducted at five Sensitive Receiver Stations (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 1.3.

1.6.14                            Monitoring results from 30 October to 15 November 2013 are presented in Table C1 of Annex C.  Daily dredging record of the reporting period is presented 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 occasions of exceedances shown in Table 1.1 below.

Table 1.1        Details of exceedances recorded at SB CMP 2 in October / November 2013

Date

Tide

Parameter

Station

Type

30 October 2013

Mid-Flood

Turbidity

DS5

Limit

 

 

SS

DS5

Action

1 November 2013

Mid-Ebb

Turbidity

DS1

Action

 

 

SS

DS1

Action

 

Mid-Flood

SS

DS1

Action

 

 

SS

DS3

Action

5 November 2013

Mid-Flood

SS

DS3

Action

 

 

SS

DS4

Action

7 November 2013

Mid-Flood

Turbidity

DS1

Limit

 

 

SS

DS1

Limit

 

 

SS

DS2

Action

 

 

SS

DS3

Action

 

 

SS

DS4

Action

 

 

SS

WSR45C

Action

11 November 2013

Mid-Flood

SS

DS4

Action

13 November 2013

Mid-Flood

SS

DS3

Action

 

 

SS

DS5

Action

15 November 2013

Mid-Flood

SS

WSR46

Action

1.6.15                            It should be noted that the exceedances on 30 October 2013 and 5, 11, 13 and 15 November 2013 (mid-flood tide) were recorded at stations which are located further away from the works area when compared to station DS1 at which the levels of SS and Turbidity did not exceed the Action and Limit Levels during the same tidal period on the same day.  As such, these recorded exceedances are not likely to be caused by the dredging works at CMP 2. 

1.6.16                            Linear Regression was conducted to determine any significant spatial trend of SS levels recorded at stations DS1 to DS4 during the mid-flood tide on 7 November 2013.  The results of the statistical analysis did not indicate any significant spatial trend of increasing SS levels with proximity to the dredging operations (i.e. r2 value < 0.6).  As such, there did not appear to be any evidence of unacceptable water quality impact as a result of the dredging operations at the CMP 2 although exceedances were recorded during the mid-flood tide on 7 November 2013. 

1.6.17                            Exceedances at DS1 and other stations were also detected on 1 November (mid-ebb and mid-flood).  However, these exceedances did not indicate any trend of increasing SS or Turbidity levels toward the dredging operations.  Instead, high levels of Turbidity and SS and low levels of DO were occasionally recorded during baseline monitoring which are considered to be sporadic events and characteristic of water quality in this area of Hong Kong.  Therefore, the Action and Limit Level exceedances may be caused by natural background variation in water quality of the area.

1.6.18                            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.

1.6.19                            Water Column Profiling for CMP 1 – November 2013

In-situ Measurements

1.6.20                           Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) in November 2013.  The water quality monitoring results for November 2013 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 dry season period (November to March) of 2003-2012 from stations in the Northwestern Water Control Zone, where the CMPs are located.  For Salinity, the average value obtained from the Upstream station was used for the basis as the WQO. Graphical presentation of the monitoring results is provided in Annex B.

1.6.21                           Analyses of results for November 2013 indicated that levels of Salinity, pH and DO complied with the WQOs at both Upstream and Downstream stations (Figures 10-12 of Annex B).  DO and Turbidity complied with the Action and Limit Levels set in the EM&A Manual ([10]).

Laboratory Measurements for Suspended Solids (SS)

1.6.22                           Analyses of data obtained in November 2013 indicated that the SS levels at Downstream and Upstream stations complied the WQO (Figure 13 of Annex B).  In addition, SS levels at all stations complied with the Action and Limit Levels set in the EM&A Manual.

1.6.23                           Overall, the 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                               Pit Specific Sediment Chemistry, Cumulative Impact Sediment Chemistry, and Water Column Profiling for CMP 1 as well as Impact Water Quality Monitoring during Dredging Operations for CMP 2 will be conducted in the next monthly period of December 2013.

1.7.2                               Water Quality Monitoring during Capping for CMP IVc and CMP V and Benthic Recolonisation Studies for CMP IV will be conducted in the next monthly period of December 2013.

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.

([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.

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