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

 

47TH MONTHLY PROGRESS REPORTFOR CONTAMINATED MUD PITS AT SHA CHAU MAY 2013

1.1                                      Background

1.1.1                               Since 1992, the East of Sha Chau (ESC) 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 2013, the following works were being undertaken at the CMPs:

           Capping was being undertaken at CMP IVc;

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

           Dredging of CMP Vd was in progress and completed on 15 May 2013.

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

1.2                                      Reporting Period

1.2.1                                This Monthly Progress Report covers the monitoring period of May 2013.

1.3                                      Details of Sampling and Laboratory Testing Activities

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

           Impact Water Quality Monitoring during Dredging Operations for CMP Vd was conducted on 7 May 2013;

           Pit Specific Sediment Chemistry was conducted for CMP Va on 14 May 2013;

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

           Water Column Profiling was scheduled to be undertaken on 28 May 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 May 2013.

 

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

1.4                                      Details of Outstanding Sampling and / or Analysis

1.4.1                               No outstanding sampling remained and laboratory analyses of Pit Specific Sediment Chemistry conducted in April and May 2013 were yet to be completed during preparation of this monthly report.

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

23 Apr 2013

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

 

14 May 2013

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

Impact Water Quality Monitoring during Dredging Operations of CMP Vd

7 May 2013

Yes

 

 

 

Water Column Profiling for CMP Va

 

28 May 2013

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

 

 

 

Routine Water Quality Monitoring for CMP Va

16 May 2013

Yes

Table 1.1 Monitoring activities in April / May 2013

1.5.2                                Impact Water Quality Monitoring during Dredging Operations of CMP Vd May 2013

1.5.3                                Impact Water Quality Monitoring during Dredging Operations of CMP Vd was conducted on 7 May 2013. 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 Vd (Figure 1.1). Monitoring was also conducted at 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). Where water depth was less than 6 m, the mid-depth station was omitted. If water depth was less than 3 m, only the mid-depth station was monitored.

1.5.4                               Monitoring results are presented in Table B1 of Annex B. Levels of Dissolved Oxygen (DO), Turbidity and Suspended Solids (SS) complied with the Action and Limit Levels set in the Baseline Monitoring Report ([1]).

1.5.5                               Overall, there appears to be no unacceptable water quality impacts causing by the dredging operations at CMP Vd and no additional measures are thus considered required except for those stated in the Environmental Permit (EP-312/2008).

1.5.6                                Routine Water Quality Monitoring for CMP Va May2013

1.5.7                               The results for the Routine Water Quality Monitoring conducted during May 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 C. Monitoring was undertaken at a total of 10 stations in the reporting month (see Figure 1.2).

In-situ Measurements

1.5.8                               Analysis of results for May 2013 indicated that for all stations (Impact, Intermediate, Reference and Ma Wan), levels of pH and DO complied with the WQOs (Figures 1 and 2 of Annex C). Levels of Salinity complied with the WQO at all stations, except at Ma Wan Station (Figure 4 of Annex C). 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 ([2]) (Figures 2 and 5 of Annex C). All in-situ water quality measurements showed relatively minor variations amongst Impact, Intermediate and Reference stations (Figures 1-5 of Annex C).

Laboratory Measurements

1.5.9                                Analyses of May 2013 results indicate that concentrations of Arsenic, Cadmium, Chromium, Lead, Mercury and Silver were below their limit of reporting at all stations while Copper, Nickel and Zinc were detected in samples from all stations. Concentrations of Copper and Zinc were slightly higher at Impact stations while concentrations of Nickel were similar amongst all stations (Figure 6 of Annex C). Levels of 5-day Biochemical Oxygen Demand (BOD5), Total Inorganic Nitrogen (TIN) and Ammoniacal-Nitrogen (NH3-N) were similar amongst all stations (Figures 7 and 8 of Annex C). Concentrations of 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 9 of Annex C).

1.5.10                            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 May 2013

Stations

Temp

Salinity

Turbidity

pH

Dissolved Oxygen

 

(C)

 

(NTU)

 

(%)

(mg L-1)

RFF (Reference)

25.24

22.24

3.19

7.70

87.45

6.34

IPF (Impact)

25.13

23.14

2.41

7.76

85.67

6.19

INF (Intermediate)

25.05

23.13

1.89

7.75

84.84

6.14

Ma Wan Station

24.45

26.88

1.36

7.72

87.39

6.26

WQO

N/A

20.01-24.46#

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 May 2013

Stations

As

(g/L)

Ag

(g/L)

Cd

(g/L)

Cr

(g/L)

Cu

(g/L)

Hg

(g/L)

Pb

(g/L)

Ni

(g/L)

Zn

(g/L)

NH3-N

(mg/L)

TIN

(mg/L)

BOD5

(mg/L)

SS

(mg/L)

 

RFF

<LOR

<LOR

<LOR

<LOR

2.83

<LOR

<LOR

4.17

4.58

0.19

1.25

1.03

6.04

 

IPF

<LOR

<LOR

<LOR

<LOR

6.54

<LOR

<LOR

3.83

6.67

0.19

1.15

0.78

3.58

 

INF

<LOR

<LOR

<LOR

<LOR

2.13

<LOR

<LOR

3.83

2.25

0.19

1.16

0.82

4.63

 

Ma Wan Station

<LOR

<LOR

<LOR

<LOR

3.63

<LOR

<LOR

3.38

7.13

0.17

0.80

0.90

4.63

 

 

WQO of SS: 12.74 mg/L

 

Note: LOR = Limit Of Reporting

 

1.6                                      Activities Scheduled for the Next Month

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

           Pit Specific Sediment Chemistry for CMP Va;

           Cumulative Impact Sediment Chemistry for CMP Va; and

           Water Column Profiling for CMP Va.

1.6.2                               Water Quality Monitoring during Capping will be conducted for CMP IVc in the next monthly period of June 2013.

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 D.


 



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