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

19TH MONTHLY PROGRESS REPORT FOR March 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 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 March 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.

1.2                                      Reporting Period

1.2.1                                This 19th Monthly Progress Report covers the EM&A activities for the reporting month of March 2014.

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                               The following monitoring activities have been undertaken for SB CMPs in March 2014:

·             Impact Water Quality Monitoring during Dredging Operations was undertaken for CMP 2 three times per week on 1, 3, 5, 7, 11, 13, 15, 17, 19, 21, 24, 26, 28 and 31 March 2014; 

·             Water Column Profiling for CMP 1 was undertaken on 8 March 2014; and

·             Pit Specific Sediment Chemistry was undertaken for CMP 1 on 12 March 2014.

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained for March 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 January, February and March 2014; and

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

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

1.5                                      Brief Discussion of the Monitoring Results for SB CMPs

1.5.1                               Brief discussion of the monitoring results of the following activities is presented in this 19th Monthly Progress Report:

·             Pit Specific Sediment Chemistry of CMP 1 conducted in December 2013.

·             Routine Water Quality Monitoring of CMP 1 undertaken from 5 to 28 February 2014;

·             Impact Water Quality Monitoring during Dredging Operations of CMP 2 conducted from 27 February to 31 March 2014; and

·             Water Column Profiling of CMP 1 conducted on 8 March 2014.

1.5.2                                Impact Water Quality Monitoring during Dredging Operations of CMP 2 –27 February to 31 March 2014

1.5.3                                Monitoring data collected for CMP 2 from 27 February to 31 March 2014 are presented in this monthly report.  Detailed discussion will be presented in the corresponding Quarterly Report.

1.5.4                                Impact Water Quality Monitoring during Dredging Operations of CMP 2 was conducted three times per week from 27 February to 31 March 2014.  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 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 1.1.

1.5.5                                Monitoring results from 27 February to 31 March 2014 are presented in Table C1 of Annex C.  Daily dredging volume in March 2014 is reported in Annex D.  Levels of Dissolved Oxygen (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 ([7]), except for the following occasions of exceedance shown in Table 1.1 below.

Table 1.1        Details of Exceedances Recorded at CMP 2 in February and March 2014

Date

Tide

Parameter

Station

Type

15 March 2014

Mid-Ebb

SS

DS2

Action

 

 

SS

DS3

Action

17 March 2014

Mid-Ebb

SS

WSR45C

Action

19 March 2014

Mid-Ebb

SS

DS2

Action

 

 

SS

DS3

Action

 

 

SS

DS5

Action

 

 

Turbidity

DS5

Action

 

Mid-Flood

SS

WSR45C

Action

 

 

SS

WSR46

Action

 

 

Turbidity

WSR46

Action

21 March 2014

Mid-Ebb

SS

WSR45C

Action

 

Mid-Flood

SS

DS1

Action

31 March 2014

Mid-Ebb

Turbidity

WSR46

Limit

 

 

SS

DS4

Action

 

 

SS

DS5

Action

 

 

SS

WSR46

Action

 

Mid-Flood

SS

DS3

Action

 

 

SS

DS5

Action

 

 

SS

WSR45C

Action

 

 

SS

WSR46

Action

1.5.6                                Except for the exceedances recorded during the mid-flood period on 21 March 2014, the other SS and Turbidity were recorded at stations which were located further away from the works area when compared to Impact 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.  

1.5.7                                SS exceedance was recorded at station DS1 only on 21 March 2014 (mid-flood).  Since station DS1 was located at the boundary of the works area, the sole exceedance at DS1 station did not appear to indicate any unacceptable water quality impacts outside the works area of the Project.  Overall, it did not appear that the SS exceedance was caused by the dredging operations at CMP 2.

1.5.8                                It should be noted that high levels of Turbidity and 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.

1.5.9                                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.

1.5.10                            Routine Water Quality Monitoring of SB CMP 1 – February 2014

1.5.11                            Monitoring results for February 2014 are shown in Tables C4-C7 of Annex C.  Monthly averaged and daily monitoring results for February 2014 are presented with graphical presentation in Figure 1-Figure 27 of Annex B. 

1.5.12                            The monitoring results for the Routine Water Quality Monitoring conducted for February 2014 in the dry season have been assessed for compliance with the Water Quality Objectives (WQOs) set by 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 averaged value obtained from the Reference stations was used for the basis as the WQO.  Levels of DO, Turbidity and SS were also assessed for compliance with the Action and Limit Levels (see Table C2 of Annex C for details).

1.5.13                           Locations of monitoring stations are presented in Figure 1.2 and Figure 1.3.

In-situ Measurements

1.5.14                           Analyses of results indicated that for all the stations (Impact, Intermediate, Reference and Water Sensitive Receiver stations), both daily and monthly average levels of pH, DO and Salinity complied with the WQOs in February 2014 (Figure 1, 2, 4, 12, 15, and 16 of Annex B).   

1.5.15                           In February 2014, daily and monthly average levels of DO and Turbidity at all the stations complied with the Action and Limit Levels (Tables C4 and C6 of Annex C).  

Laboratory Measurements

1.5.16                            Analyses of February 2014 results indicated that concentrations of Mercury and Silver were below their limit of reporting at all the stations.  Concentrations of Cadmium and Chromium were mostly below their limit of reporting except for a few occasions.  The daily concentrations of Arsenic, Copper, Lead, Nickel and Zinc indicated variations over time at all the stations throughout February 2014.  Daily recorded levels of 5-day Biochemical Oxygen Demand (BOD5), Ammoniacal-Nitrogen (NH3-N) and Total Inorganic Nitrogen (TIN) were observed to fluctuate over time throughout February 2014 (Figure 24-26 of Annex B).  Compliance with TIN WQO (0.50 mg/L) was observed at all the stations in the monitoring period. 

1.5.17                            In February 2014, monthly averaged concentrations of Copper and Zinc were slightly higher at Ma Wan station (Figure 6 of Annex B).  Monthly average concentrations of the other metals were similar amongst stations (Figure 7 of Annex B).  Monthly average levels of BOD5, NH3-N and TIN were similar amongst stations (Figures 8 and 9 of Annex B).  The monthly average concentration of TIN did not show any exceedance of the WQO in February 2014 (Figure 9 of Annex B).

1.5.18                            Daily levels of SS complied with the Action and Limit Levels set in the EM&A Manual and occasionally exceeded SS WQO (14.4 mg/L for dry season) in February 2014 (Figure 27 of Annex B).  The monthly average level of SS compiled with the WQO at all stations (Figure 10 of Annex B).  These occasional exceedances recorded for daily SS levels are thus not likely to be caused by mud disposal works, but sporadic events and characteristic of water quality in this area of Hong Kong.

1.5.19                            Overall, results of the Routine Water Quality Monitoring indicated that the disposal operation at CMP 1 did not appear to cause any unacceptable deterioration in water quality in February 2014.

Recommendations

1.5.20                            From the results of the Routine Water Quality Monitoring conducted in October 2013, November 2013, January 2014 and February 2014 for CMP 1, there did not appear to be any unacceptable deterioration in water quality in all of the sampling events which were conducted three times a week during the monitoring period.  In accordance with the EM&A Manual, it is recommended to adjust the sampling frequency to eight (8) times per year which is the same as the frequency of Routine Water Quality Monitoring for CMP V.  It is anticipated that this adjusted sampling frequency is adequate for tracking the potential change in contaminant concentrations in seawater which may take a long time to appear while at the same time address the potential seasonal difference in seawater quality.

1.5.21                            Water Column Profiling of CMP 1 – March 2014

1.5.22                           Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 8 March 2014.  The water quality monitoring results have been assessed for compliance with the WQOs (Table C8 of Annex C).  The monitoring results were also compared with the Action and Limit Levels set in Baseline Monitoring Report. 

In-situ Measurements

1.5.23                           Analyses of results for March 2014 indicated that levels of Salinity, pH and DO complied with the WQOs at both Upstream and Downstream stations (Table C8 of Annex C).  DO and Turbidity complied with the Action and Limit Levels.

Laboratory Measurements for Suspended Solids (SS)

1.5.24                           Analyses of data obtained on 8 March 2014 indicated that the SS levels at Downstream and Upstream stations complied with the WQO (Table C8 of Annex C).  In addition, SS levels at all the stations complied with the Action and Limit Levels.

1.5.25                           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.

1.5.26                            Pit Specific Sediment Chemistry of CMP 1 – December 2013

1.5.27                           Monitoring locations for Pit Specific Sediment Chemistry for CMP 1 are shown in Figure 1.4.  A total of six (6) monitoring stations were sampled in December 2013. 

1.5.28                           The concentrations of all the metals except Arsenic were lower than the Lower Chemical Exceedance Level (LCEL) at all stations in December 2013 (Figures 28 and 29 of Annex B).  Concentrations of Arsenic exceeded the LCEL at all stations except Active Pit station SB-NPAB and Near Pit station SB-NNAB. 

1.5.29                            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 ([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 LECL exceedances of Arsenic are unlikely to be caused by the disposal operations at CMP 1 but rather as a result of naturally occurring deposits. 

1.5.30                           For organic contaminants, the concentration of Total Organic Carbon (TOC) concentration was similar amongst stations in December 2013 (Figure 30 of Annex B).  Concentrations of Tributyltin (TBTs) were observed to be higher at Active Pit station SB-NPAA and SB-NPAB in December 2013 (Figure 31 of Annex B).  Low and High Molecular Weight Polycyclic Aromatic Hydrocarbons (Low and High MW PAHs) concentrations were recorded below the limit of reporting at all stations except Active Pit station SB-NPAB (Figure 32 of Annex B).  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 the stations in December 2013. 

1.5.31                           Active Pit stations SB-NPAA and SB-NPAB are 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 stations 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.

1.5.32                           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                                      Activities Scheduled for the Next Month

1.6.1                               The following monitoring activities will be conducted in the next monthly period of April 2014 for SB CMPs:

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

·             Pit Specific Sediment Chemistry of CMP 1;

·             Routine Water Quality Monitoring of CMP 1; and

·             Water Column Profiling of CMP 1.

1.6.2                                The sampling schedule is presented in Annex A.

1.7                                      Study Programme

1.7.1                                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])        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.

([8])    Sewell RJ (1999) Geochemical Atlas of Hong Kong. Geotechnical Engineering Office, Government of the Hong Kong Special Administrative Region

([9])    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