Agreement No. CE 23/2012 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pits at the South of The Brothers and at East Sha Chau (2012-2017) - Investigation

14TH MONTHLY PROGRESS REPORT FOR DECEMBER 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 December 2013, the following works were being undertaken at the CMPs:

P             Capping was being undertaken at CMP IVc and CMP Va;

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

P             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 December 2013.

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                               The following monitoring activities have been undertaken for CMP IV and V in the monitoring month of December 2013:

P             Water Quality Monitoring during Capping was carried out for CMP IVc and CMP Va on 3 December 2013; and

P             Benthic Recolonisation Studies for CMP IV was conducted on 12 December 2013.

1.3.2                               The following monitoring activities have been undertaken for SB CMPs in December 2013:

P             Impact Water Quality Monitoring during Dredging Operations was undertaken for CMP 2 three times per week (2, 4, 6, 9, 11, 13, 16, 18, 20, 23, 27, 29 and 31 December 2013); 

P             Water Column Profiling for CMP 1 was undertaken on 5 December 2013;

P             Cumulative Impact Sediment Chemistry was conducted for CMP 1 on 10 December 2013; and

P             Pit Specific Sediment Chemistry was conducted for CMP 1 on 17 December 2013.

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained for December 2013.  The following laboratory analyses were still in progress during the preparation of this monthly report and hence were not included in this monthly report:

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

P             Laboratory analyses of sediment samples collected for Cumulative Impact Sediment Chemistry of CMP 1 in December 2013; and

P             Laboratory analyses of Suspended Solids (SS) samples collected for Water Quality Monitoring during Dredging Operations of CMP 2 from 11 to 31 December 2013.

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 16th Monthly Report.  Detailed discussion will be presented in the corresponding Quarterly Report.

P             Impact Water Quality Monitoring during Dredging Operations of CMP 2 conducted from 18 November to 9 December 2013;

P             Water Column Profiling of CMP 1 conducted in December 2013;

P             Routine Water Quality Monitoring of CMP 1 undertaken from 17 October to 30 November 2013; and

P             Pit Specific Sediment Chemistry of CMP 1 conducted in October 2013.

1.5.2                                Impact Water Quality Monitoring during Dredging Operations of CMP 2 V 18 November to 9 December 2013

1.5.3                                Monitoring data collected for CMP 2 from 18 November to 9 December 2013 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 (i.e. from 18 November to 9 December 2013) was conducted three times per week for a total of nine (9) 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 1.1.

1.5.5                                Monitoring results from 18 November to 9 December 2013 are presented in Table C1 of Annex C.  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 exceedances shown in Table 1.1 below.

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

Date

Tide

Parameter

Station

Type

18 November 2013

Mid-Ebb

SS

DS1

Action

 

 

SS

DS2

Action

20 November 2013

Mid-Flood

SS

DS2

Action

 

 

SS

DS4

Action

 

 

SS

DS5

Action

22 November 2013

Mid-Ebb

SS

WSR46

Action

 

Mid-Flood

SS

DS4

Action

 

 

SS

DS5

Action

25 November 2013

Mid-Ebb

SS

DS1

Action

 

Mid-Flood

Turbidity

DS1

Limit

 

 

SS

DS1

Limit

 

 

SS

DS2

Action

29 November 2013

Mid-Flood

Turbidity

DS1

Limit

 

 

SS

DS1

Limit

2 December 2013

Mid-Flood

SS

DS1

Action

6 December 2013

Mid-Flood

SS

WSR45C

Action

1.5.6                                Exceedances at DS1 and other stations were detected during the same tidal period on 18 (mid-ebb) and 25 November 2013 (mid-flood).  Exceedances at DS1 only were also recorded on 25 November (mid-ebb), 29 November (mid-flood) and 2 December 2013 (mid-flood) whilst no exceedances at other stations were detected during the same tidal period on the same day.  These exceedances did not indicate any trend of increasing SS or Turbidity levels toward the dredging operations or any evidence of unacceptable water quality impact as a result of the dredging operations at the CMP 2. 

1.5.7                                It should be noted that the exceedances on 20 November (mid-flood tide), 22 November (mid-ebb and mid-flood tides) and 6 December 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, Turbidity and DO 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. 

1.5.8                                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.

1.5.9                                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                            Water Column Profiling for CMP 1 V December 2013

In-situ Measurements

1.5.11                           Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) in December 2013.  The water quality monitoring results for December 2013 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 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.

1.5.12                           Analyses of results for December 2013 indicated that levels of Salinity, pH and DO complied with the WQOs at both Upstream and Downstream stations (Figures 1-3 of Annex B).  DO and Turbidity complied with the Action and Limit Levels set in the EM&A Manual ([8]).


Laboratory Measurements for Suspended Solids (SS)

1.5.13                           Analyses of data obtained in December 2013 indicated that the SS levels at Downstream and Upstream stations complied with the WQO (Figure 4 of Annex B).  In addition, SS levels at all stations complied with the Action and Limit Levels set in the EM&A Manual.

1.5.14                           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.

1.5.15                            Routine Water Quality Monitoring for SB CMP 1 V October/ November 2013

1.5.16                           The results for the Routine Water Quality Monitoring conducted on 17, 19, 22, 24, 26, 29 and 31 October 2013 in the wet season and those undertaken on 2, 4, 6, 8, 12, 14, 16, 19, 21, 23, 26, 28 and 30 November 2013 in the dry season have been assessed for compliance with the WQOs set by EPD.  This consists of a review of the EPD routine water quality monitoring data for the wet season period (April to October) of 2003-2012 and the dry season period (November to March) of 2003-2012 from stations in the Northwestern Water Control Zone, where the CMPs are located. 

1.5.17                           For Salinity, the average value obtained from the Upstream Station was used for the basis as the WQO.  Daily in-situ monitoring and daily laboratory results are shown in Tables C3 and C4 of Annex C.  Monthly averaged in-situ measurement and laboratory analyses results for October and November 2013 are illustrated in Table C5 and C6 of Annex C, with graphical presentation provided in Annex B.  Locations of monitoring stations were presented in Figure 1.2 and 1.3.

In-situ Measurements

1.5.18                           Analysis of results indicated that for all the stations (Impact, Intermediate, Reference and Ma Wan), both daily and monthly average levels of pH, DO and Salinity complied with the WQOs (Tables C3 and C5 of Annex C).   

1.5.19                           Daily and monthly average levels of DO and Turbidity in October and November 2013 complied with the Action and Limit Levels set in the EM&A Manual ([9]) (Tables C3 and C5 of Annex C). 

Laboratory Measurements

1.5.20                            Monthly averaged concentrations of metals and nutrients are presented in Figures 10-13 and Figures 20-23 of Annex B.  Graphical presentations of monitoring results on individual monitoring days are presented in Figures 31-42 and Figures 50-61 of Annex B. 

1.5.21                            Monthly average concentration of Zinc was slightly higher at Ma Wan station in October 2013 (Figure 10 of Annex B) whilst the monthly average concentrations of other metals were similar amongst stations in October and November 2013 (Figures 10, 11, 20 and 21).  Monthly average levels of 5-day Biochemical Oxygen Demand (BOD5), Total Inorganic Nitrogen (TIN) and Ammoniacal-Nitrogen (NH3-N) in October and November 2013 were similar amongst station (Figures 12, 13, 22 and 23 of Annex B). 

1.5.22                            Occasional exceedances of WQO (0.50 mg/L) in TIN levels were recorded in October and November 2013 with no consistent trend of increasing TIN concentration with proximity to the pit or with time (Table C4).  The monthly average concentration of TIN did not show any exceedance with the WQO in both October and November 2013 (Table C6).  As such, these isolated exceedances did not appear to indicate any evidence of unacceptable water quality impacts due to the mud disposal activities.

1.5.23                            Exceedances of SS WQOs (12.0 mg/L for wet season and 14.4 mg/L for dry season) were occasionally recorded in October and November 2013 for individual monitoring days (Table C4), however, further investigation of the monthly average SS levels showed that the exceedances of WQO were recorded at the Impact, Intermediate, Reference and other sensitive receiver stations in October and at Intermediate station only in November 2013 (Table C6).  Therefore, the WQO exceedances may be caused by natural background variation in water quality of the area rather than indicating any unacceptable impacts from the mud disposal operations.

1.5.24                            Overall, the results indicated that the disposal operation at CMP 1 did not appear to cause any unacceptable deterioration in water quality during monitoring period of October and November 2013.

1.5.25                            Pit Specific Sediment Chemistry of CMP 1 V October 2013

1.5.26                           Monitoring locations for Pit Specific Sediment Chemistry for CMP 1 are shown in Figure 1.4.  A total of six monitoring stations were sampled in October 2013. 

1.5.27                           The concentrations of all the metals except Arsenic complied with the LCEL at all stations in October 2013 (Figures 63 and 64 of Annex B).  Concentrations of Arsenic exceeded the LCEL at all stations except Active Pit station SB-NPAB. 

1.5.28                            Whilst the average concentration of Arsenic in the Earths crust is generally ~2mg/kg, significantly higher Arsenic concentrations (median = 14 mg/kg) have been recorded in Hong Kongs onshore sediments ([10]).  It is presumed that the natural concentrations of Arsenic are similar in onshore and offshore sediments ([11]), 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 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 1.

1.5.29                           TOC concentration indicated variations amongst the stations in October 2013 (Figure 65 of Annex B).  TBT concentrations were found to be higher at Near Pit Station SB-NNAB (Figure 66 of Annex B) in October 2013. 

1.5.30                           Low and High MW PAHs concentrations as well as Total DDT, 4,4-DDE and Total PCBs concentrations were recorded below the limit of reporting at all stations in October 2013. 

1.5.31                           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                               Pit Specific Sediment Chemistry, Demersal Trawling, Routine Water Quality Monitoring 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 January 2014.

1.6.2                                No monitoring activities will be conducted for CMP IV and CMP V in the next monthly period of January 2014.

1.6.3                                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 V 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) V 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) V 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) V Investigation. Agreement No. CE 23/2012(EP). Submitted to EPD in October 2012.

([8])    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) V Investigation Agreement No. CE 4/2009 (EP).

([9])   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) V Investigation Agreement No. CE 4/2009 (EP).

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

([11]) 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