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

11TH MONTHLY PROGRESS REPORT FOR JULY 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) (hereafter referred to as the Project) 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 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 July 2013, the following works were being undertaken at the CMPs:

P       Capping was being undertaken at CMP IVc;

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

P       Dredging operations were taking place at SB CMP 1.

1.2                                      Reporting Period

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

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                               The following monitoring activities have been undertaken for CMP V in July 2013:

P      Pit Specific Sediment Chemistry was conducted for CMP Va on 3 July 2013;

P      Water Column Profiling was scheduled to be undertaken on 9 July 2013.  However, there was no dumping activity at CMP Va while the monitoring team was on-site.  As such, in-situ measurements and water sampling were not undertaken for Water Column Profiling in July 2013;

P      Routine Water Quality Monitoring was conducted for CMP Va on 16 July 2013; and

P      Demersal Trawling was conducted for CMP V on 30 and 31 July 2013.

1.3.2                                Impact Water Quality Monitoring during Dredging Operations of CMP 1 was conducted three times per week (ie 4, 6, 8, 10, 12, 15, 17, 19, 22, 24, 26, 29 and 31 July 2013) in this reporting month in accordance with the EM&A Manual.  It should be noted that the Impact Water Quality Monitoring during Dredging Operations of CMP 1 was not conducted on 1 July 2013 due to the adverse weather during which Typhoon signal No. 3 was hoisted. 

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained for July 2013.  Laboratory analyses of Pit Specific Sediment Chemistry of CMP Va conducted in June and July 2013 were yet to be completed and laboratory analyses of Suspended Solids (SS) for Water Quality Monitoring during Dredging Operations of CMP 1 collected on 31 July 2013 was still in progress during the preparation of this monthly report.  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                               Table 1.1 summarises the monitoring results that are presented in the current monthly report.  Brief discussion of the monitoring results is presented in this section.  Detailed discussion will be presented in the corresponding Quarterly Report.

Monitoring activities

Date of Monitoring

Monitoring results presented in this report?

Pit Specific Sediment Chemistry Monitoring for CMP Va

 

14 May 2013

6 June 2013

 

 

 

 

3 July 2013

Yes. 

 

No.  Laboratory analysis yet to be completed during preparation of this monthly report.

 

No.  Laboratory analysis yet to be completed during preparation of this monthly report.

 

Routine Water Quality Monitoring for CMP Va

 

16 July 2013

Yes.

 

 

 

Water Column Profiling for CMP Va

 

9 July 2013

No.  In-situ measurements and water sampling were not undertaken as there was no dumping activity on the monitoring day.

 

Table 1.1        Monitoring activities in May to July 2013 for CMP V

1.5.2                                Pit Specific Sediment Chemistry of CMP Va V May 2013

1.5.3                               Monitoring locations for Pit Specific Sediment Chemistry for CMP Va are shown in Figure 1.1.  A total of six monitoring stations were sampled in May 2013.  It is observed that the variations of metal concentrations at Active Pit Stations NPDA and NPDB were much larger (ie greater standard deviation) when compared to other stations (Figures 1-2 of Annex B). 

1.5.4                               Cadmium, Chromium and Nickel complied with the Lower Chemical Exceedance Level (LCEL) at all stations (Figures 1-2 of Annex B).  Concentrations of Arsenic exceeded the LCEL at Pit Edge stations NEDA and NEDB and Near Pit stations NNDA and NNDB (Figures 1-2 of Annex B).  Concentrations of Lead, Mercury and Zinc exceeded LCEL at Active Pit station NPDA while concentrations of Silver exceeded Upper Chemical Exceedance Level (UCEL) at Active Pit stations NPDA and NPDB.  Concentration of Copper exceeded UCEL at Active Pit Station NPDA. 

1.5.5                               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 ([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 exceedances of the LCEL for Arsenic are unlikely to be caused by the disposal operations at CMP Va but rather as a result of naturally occurring deposits. 

1.5.6                               In addition, the Active Pit stations NPDA and NPDB are located within CMP Va which was receiving contaminated mud during the reporting period.  As such, the exceedances of LCEL/UCEL for Copper, Lead, Mercury, Silver and Zinc which were recorded at the two stations only are not considered as indicating any dispersal of contaminated mud from CMP Va.

1.5.7                               For organic contaminants, Total Organic Carbon (TOC) concentration was similar amongst all stations (Figure 3 of Annex B).  Tributyltin (TBT) concentration was found to be higher at Active Pit stations NPDA and NPDB (Figure 4 of Annex B).  Low Molecular Weigh Polycyclic Aromatics Hydrocarbons (Low MW PAHs) and High Molecular Weight Polycyclic Aromatics Hydrocarbons (High MW PAHs) concentrations were recorded above the limit of reporting at Active Pit stations NPDA and NPDB (Figure 5 of Annex B).  Total Polychlorinated Biphenyls (PCBs), Total Dichloro-diphenyl-trichloroethane (DDT) and 4,4-Dichloro-diphenyl-dichloroethylene (4,4-DDE) were below the limit of reporting at all stations.  As explained in Section 1.5.6, Active Pit stations NPDA and NPDB are located within CMP Va which was receiving contaminated mud during the reporting period.  Therefore, the higher concentrations of contaminants (including metals and organic contaminants) recorded at the two stations only are not considered as indicating any dispersal of contaminated mud from CMP Va.  Nevertheless, detailed analysis will be presented in the Quarterly Report to reveal any trend of increasing sediment contaminant concentrations towards CMP Va.

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

1.5.9                                Routine Water Quality Monitoring for CMP Va V July 2013

1.5.10                           The results for the Routine Water Quality Monitoring conducted during July 2013 in the wet season 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 wet season period (April to October) of 1999-2010 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.  In-situ monitoring and laboratory results are shown in Tables 1.2 and 1.3, respectively, with graphical presentation provided in Annex B.  Monitoring was undertaken at a total of 10 stations in the reporting month (see Figure 1.2).

In-situ Measurements

1.5.11                           Analysis of results for July 2013 indicated that for all stations (Impact, Intermediate, Reference and Ma Wan), levels of pH and DO complied with the WQOs (Figures 6 and 7 of Annex B).  Levels of Salinity complied with the WQO at all stations, except at Ma Wan Station (Figure 9 of Annex B).   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.  Levels of DO and Turbidity within the reporting month complied with the Action and Limit Levels set in the EM&A Manual ([9]) (Figures 7 and 10 of Annex B).  All in-situ water quality measurements showed relatively minor variations amongst Impact, Intermediate and Reference stations (Figures 6-10 of Annex B).

Laboratory Measurements

1.5.12                            Analyses of July 2013 results indicate that concentrations of Cadmium, Mercury and Silver were below their limit of reporting at all stations while Arsenic, Chromium, Copper, Lead, Nickel and Zinc were detected in samples from all stations.  Concentrations of Chromium, Copper, Lead, Nickel and Zinc were slightly higher at Ma Wan station while the concentrations of Arsenic were similar amongst stations (Figures 11 and 12 of Annex B).  Levels of 5-day Biochemical Oxygen Demand (BOD5), Total Inorganic Nitrogen (TIN) and Ammoniacal-Nitrogen (NH3-N) were similar amongst all stations (Figures 13 and 14 of Annex B).  Concentrations of Suspended Solids (SS) complied with the WQO (12.74 mg/L for wet season) and Action and Limit Levels at all stations during the reporting month (Figure 15 of Annex B).

1.5.13                            Overall, the results indicated that the disposal operation at CMP Va did not appear to cause any unacceptable deterioration in water quality during this reporting period.

Table 1.2        In-situ Monitoring Results for Routine Water Quality Monitoring of CMP Va in July 2013

Stations

Temp

Salinity

Turbidity

pH

Dissolved Oxygen

 

(XC)

 

(NTU)

 

(%)

(mg L-1)

RFF (Reference)

28.05

22.05

2.05

7.69

59.95

4.18

IPF (Impact)

27.67

23.28

3.90

7.65

65.10

4.50

INF (Intermediate)

27.76

23.23

2.86

7.65

65.39

4.51

Ma Wan Station

26.13

27.90

1.58

7.54

59.51

4.12

WQO

N/A

19.85-24.26#

N/A

6.5-8.5

N/A

>4

Note:   #Not exceeding 10% of natural ambient level which is the result obtained from the Reference Station.

 

Table 1.3        Laboratory Results for Routine Water Quality Monitoring of CMP Va in July 2013

Stations

As

(µg/L)

Ag

(µg/L)

Cd

(µg/L)

Cr

(µg/L)

Cu

(µg/L)

Hg

(µg/L)

Pb

(µg/L)

Ni

(µg/L)

Zn

(µg/L)

NH3-N

(mg/L)

TIN

(mg/L)

BOD5

(mg/L)

SS

(mg/L)

 

RFF

1.58

<LOR

<LOR

0.63

8.08

<LOR

0.98

3.29

10.29

0.08

0.95

0.36

4.00

 

IPF

1.96

<LOR

<LOR

0.90

10.75

<LOR

1.13

2.75

11.25

0.08

0.75

0.29

5.38

 

INF

1.75

<LOR

<LOR

0.56

8.25

<LOR

0.65

2.13

8.33

0.10

0.89

0.27

4.46

 

Ma Wan Station

1.50

<LOR

<LOR

1.88

21.25

<LOR

1.88

4.00

20.00

0.06

0.53

0.25

3.75

 

 

WQO of SS: 12.74 mg/L

 

Note: LOR = Limit Of Reporting

 

1.6                                      Brief Discussion of the Monitoring Results for SB CMPs

1.6.1                                Monitoring data collected for SB CMPs in July 2013 are presented in this monthly report.  Detailed discussion will be presented in the corresponding Quarterly Report.

1.6.2                                Impact Water Quality Monitoring during Dredging Operations of CMP 1 V 4 to 29 July 2013

1.6.3                                Impact Water Quality Monitoring during Dredging Operations of CMP 1 was conducted three times per week for a total of twelve (12) sampling days from 4 to 29 July 2013.  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 1.  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.

1.6.4                                Monitoring results from 4 to 29 July 2013 are presented in Table C1 of Annex C.  It should be noted that sampling at station THB2 during mid-ebb tide on 24 July 2013 and during both mid-ebb and mid-flood tides on 26 July 2013 were not carried out due to adverse weather.  Levels of DO, Turbidity and SS generally complied with the Action and Limit Levels (see Table C2 for details) set in the Baseline Monitoring Report ([10]), except for the following occasions of exceedances shown in Table 1.4 below.

Table 1.4        Details of exceedances recorded at CMP 1 in July 2013

Date

Tide

Parameter

Station

Type

22 July 2013

Mid-Ebb

Turbidity

WSR46

Action

22 July 2013

Mid-Ebb

SS

WSR46

Action

26 July 2013

Mid-Ebb

Turbidity

WSR46

Action

26 July 2013

Mid-Ebb

SS

WSR46

Limit

26 July 2013

Mid-Flood

SS

WSR46

Action

1.6.5                                Action/Limit Level exceedances of Turbidity and SS were recorded at Sensitive Receiver station WSR46 during mid-ebb tide on 22 July and during both mid-ebb and mid-flood tides on 26 July 2013.  Station WSR46 is located further away from the works area of CMP 1 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.  As such, the exceedances at WSR46 are not likely to be caused by the dredging works at CMP 1.  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.  Therefore, the Action and Limit Level exceedances may be caused by natural background variation in water quality of the area. 

1.6.6                                Overall, the results indicated that the dredging operations at CMP 1 of SB 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.

1.7                                      Activities Scheduled for the Next Month

1.7.1                               The following monitoring activities will be conducted in the next monthly period of August 2013 for CMP V:

P       Pit Specific Sediment Chem-istry for CMP Va;

P       Cumulative Impact Sediment Chemistry for CMP Va;

P       Sediment Toxicity Test for CMP Va;

P       Routine Water Quality Monitoring for CMP Va;

P       Water Column Profiling for CMP Va; and

P       Demersal Trawling for CMP V.

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

1.7.3                                Impact Water Quality Monitoring during Dredging Operations for CMP 1 will be conducted three times per week in the next monthly period of August 2013.

1.7.4                                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.

1.8.2                                "_blank" 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 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])    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 (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])      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.