Agreement No. CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau (2009-2013) - Investigation

 

35th MONTHLY PROGRESS REPORT FOR CONTAMINATED MUD PITS AT SHA CHAU May 2012

 

1.1                                      Background

1.1.1                                Since 1992, the East of Sha Chau area has been the site of a series of dredged Contaminated Mud Pits (CMPs) designed to provide confined marine disposal capacity for contaminated mud arising from the HKSARs dredging and reclamation projects.  In May 2012, 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         The dredging of CMP Vc was in progress.   

The Environmental Monitoring and Audit (EM&A) programme for the CMPs at the East of Sha Chau area (ESC) presently covers the above operations.

1.2                                      Reporting Period

1.2.1                                This Monthly Progress Report covers the reporting month of May 2012.

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                                The following monitoring activities have been undertaken for CMP V in May 2012:

P      Pit Specific Sediment Chemistry Monitoring was conducted for CMP Va on 15 May 2012;

P      Routine Water Quality Monitoring was conducted for CMP Va on 16 May 2012;

P      Impact Water Quality Monitoring during Dredging Operations was conducted for CMP Vc on 17 May 2012; and

P      Water Column Profiling was conducted for CMP Va on 18 May 2012.

1.3.2                                A summary of field activities is presented in Annex A. 

1.4                                      Details of Outstanding Sampling and / or Analysis

1.4.1                                No outstanding sampling and laboratory analysis remained from May 2012.

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.  All monitoring data collected in May 2012 will be presented in this monthly report.

Table 1.1         Monitoring results presented in the May 2012 Monthly Report

Date of Monitoring

Monitoring Component

15 May 2012

Pit Specific Sediment Chemistry Monitoring for CMP Va

16 May 2012

Routine Water Quality Monitoring for CMP Va

17 May 2012

Impact Water Quality Monitoring during Dredging Operations for CMP Vc

18 May 2012

Water Column Profiling for CMP Va

1.5.2                                Brief discussion of the monitoring results is presented in this section.  Detailed discussion will be presented in the corresponding Quarterly Report.

 

1.5.3                                Pit Specific Sediment Chemistry Monitoring of CMP Va V May 2012

1.5.4                                Monitoring locations for Pit Specific Sediment Chemistry for CMP Va are shown in Figure 1.1.  Concentrations of metals were generally below the Lower Chemistry Exceedance Level (LCEL) (Figures 1 and 2 of Annex B) and no exceedance of Upper Chemistry Exceedance Level (UCEL) was recorded in May 2012.  Concentrations of Copper, Lead and Zinc exceeded the LCEL at Active Pit station NPDA.  Concentrations of Silver exceeded the LCEL at Active Pit stations NPDA and NPDB.  Concentrations of Arsenic exceeded the LCEL at all stations, except Active Pit station NPDB and Near-Pit station NNDB stations, in May 2012.  It is important to note that relatively high natural levels of Arsenic are present in Hong Kongs marine sediments.  Therefore, the slight 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.  In addition, the Action Pit stations are located within CMP Va which was receiving contaminated mud during the reporting month.  Therefore, the exceedances of LCEL recorded at the Action Pit stations alone (for Copper, Lead, Silver and Zinc) are not considered as indicating any dispersal of contaminated mud from CMP Va and thus not indicating any unacceptable environmental impacts from the mud disposal operations. 

1.5.5                                For organic contaminants, PCBs were all below the limit of reporting at all stations in May 2012.  Levels of Low and High Molecular Weight Polycyclic Aromatics Hydrocarbons (Low and High M.W. PAHs) were higher than the limit of reporting in only a few samples collected in May 2012.  TOC and TBTs concentrations were the highest at Active Pit stations (NPDA) in May 2012 when compared to other stations (Figures 3 and 4 of Annex B). Concentrations of 4,4-DDE were higher than the limit of reporting at Active Pit stations (NPDA and NPDB) for May 2012, whereas concentrations of DDT were all lower than the limit of reporting at all stations (Figure 5 of Annex B). 

1.5.6                                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.

1.5.7                                Routine Water Quality Monitoring of CMP Va V May 2012

1.5.8                                The results for the Routine Water Monitoring conducted during May 2012 in the wet season have been assessed for compliance with the Water Quality Objectives (WQOs) (please see Figure 1.2 for the monitoring locations).  This consists of a review of the Environmental Protection Department (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 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 Table 1.2 and 1.3 respectively, with graphical presentation provided in Annex B.

In-situ Measurements

1.5.9                                Analyses of results for May 2012 indicated that for all stations (Impact, Intermediate and Reference), levels of pH, Salinity and DO generally complied with the WQOs (Figures 8, 9 and 11 of Annex B).  Levels of DO and Turbidity within the reporting month also complied with the Action and Limit Levels set in the EM&A Manual ([1]).  All in-situ water quality measurements showed relatively minor variations between Impact, Intermediate and Reference stations (Figures 6 to 11 of Annex B). 

Laboratory Measurements 

1.5.10                            Analyses of May 2012 results indicate that Arsenic, Cadmium, Mercury and Silver concentrations were below their limit of reporting at all stations.  Concentrations of Copper, Lead, Nickel and Chromium appeared to be similar among all stations.  Concentrations of Zinc appeared to be higher at Reference stations. 

1.5.11                            For parameters other than metals, levels of 5-day Biochemical Oxygen Demand (BOD5), Total Inorganic Nitrogen (TIN) and NH3-N were similar among all stations (Figures 14 and 15 of Annex B).  Concentrations of TSS did not exceed WQO and complied with the Action and Limit Levels at all stations within the reporting month (Figure 16 of Annex B).

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

Table 1.2        In-situ Monitoring Results for Routine Water Quality Monitoring during May 2012

Stations

Temp

Salinity

Turbidity

pH

Dissolved Oxygen

 

(XC)

 

(NTU)

 

(%)

(mg L-1)

RFE (Reference)

26.29

24.15

3.12

7.83

73.53

5.18

IPE (Impact)

26.65

22.64

4.21

7.92

81.08

5.73

INE (Intermediate)

26.28

24.60

4.15

7.93

80.63

5.67

Ma Wan Station

27.32

20.27

0.85

8.16

111.59

7.90

WQO

N/A

21.73-26.56#

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 during May 2012

Stations

As

Ag

Cd

Cr

Cu

Hg

Pb

Ni

Zn

NH3-N

TIN

BOD5

TSS

RFF

<LOR

<LOR

<LOR

1.05

11.40

<LOR

1.5

3.70

21.50

0.08

0.85

1.77

3.95

IPF

<LOR

<LOR

<LOR

<LOR

5.68

<LOR

<LOR

2.88

7.20

0.07

1.02

1.77

4.73

INF

<LOR

<LOR

<LOR

<LOR

3.70

<LOR

<LOR

2.68

8.15

0.06

0.97

1.94

4.55

Ma Wan Station

<LOR

<LOR

<LOR

<LOR

12.00

<LOR

1.00

3.38

9.13

0.07

1.17

1.66

<LOR

WQO of TSS

13.00

1.5.13                            Water Column Profiling for CMP Va V May 2012

In-situ Measurements

1.5.14                            The water quality monitoring results for May 2012 have been assessed for compliance with the WQOs set by EPD (please refer to Section 1.5.8 for details of setting the WQOs).   Graphical presentation of the monitoring results is provided in Annex B.

1.5.15                            Analyses of results for May 2012 indicated that levels of Salinity, pH and Dissolved Oxygen (DO) all complied with the WQOs at both Upstream and Downstream stations (Figures 17, 18 and 19 in Annex B).  DO and Turbidity complied with the Action and Limit Levels set in the EM&A Manual ([2]).

Laboratory Measurements for Total Suspended Solids (TSS)

1.5.16                            Analyses of data obtained in May 2012 indicated that the TSS levels at both Upstream and Downstream stations complied with the WQO (Figure 20 in Annex B).  TSS levels measured in May 2012 complied with the Action and Limit Levels set in the EM&A Manual.

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

1.5.18                            Impact Water Quality Monitoring during Dredging Operations of CMP Vc V May 2012

1.5.19                            Impact Water Quality Monitoring during Dredging Operations of CMP V was conducted on 17 May 2012 for CMP Vc.  On the 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 Vc (Figure 1.3).  Monitoring was also conducted at the Ma Wan station.  At each station, in-situ measurements of water quality parameters as well as water samples were taken from three depths in the water column (ie surface: 1 m below sea surface, mid-depth and bottom: 1 m above the seabed).

1.5.20                            Monitoring results are presented in Table C1 of Annex C.  Levels of DO, Turbidity and TSS complied with the Action and Limit Levels set in the Baseline Monitoring Report ([3]). 

1.5.21                            Overall, the results indicated that the dredging operations at CMP Vc 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-312/2008), are considered required for the dredging operations of CMP Vc.  

1.6                                      Activities Scheduled for the Next Month

1.6.1                                The following monitoring programmes will be conducted in the next monthly period of June 2012:

CMP IV

P           Water Quality Monitoring during Capping for CMP IVc;

CMP V

P           Pit Specific Sediment Chemistry for CMP Va;

P           Cumulative Impact Sediment Chemistry for CMP Va;

P           Water Column Profiling for CMP Va; and

P           Impact Water Quality Monitoring during Dredging Operations for CMP Vc.

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 D.


 



([1])   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).

([2])    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).

([3])    ERM (2009)  Baseline Monitoring Report.  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 September 2009.