Agreement No. CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau (2009-2013) - Investigation
36th MONTHLY PROGRESS REPORTFOR CONTAMINATED MUD PITS AT SHA
CHAU June 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 HKSAR¡¦s dredging and reclamation projects. In June 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.
1.1.2
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 June 2012.
1.3
Details of Sampling and
Laboratory Testing Activities
1.3.1
The following monitoring activities
have been undertaken for CMP IVc in June 2012:
¡P
Water Quality
Monitoring during Capping was conducted on 7 June 2012.
1.3.2
The
following monitoring activities have been undertaken for CMP V in June 2012:
¡P
Pit Specific Sediment Chemistry Monitoring was conducted for CMP Va on 4 June 2012;
¡P
Cumulative Impact Sediment Chemistry Monitoring was conducted for CMP Va on 5 and 6 June 2012;
¡P
Impact Water Quality Monitoring during Dredging Operations was conducted for CMP Vc on
8 June 2012; and
¡P
Water Column Profiling was conducted for CMP Va on 11 June 2012.
1.3.3
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 June 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 for CMP V in June 2012 will be presented in this monthly report.
Table 1.1 Monitoring
results presented in the June 2012 Monthly Report
|
Date
of Monitoring |
Monitoring
Component |
|
4 June 2012 |
Pit Specific
Sediment Chemistry Monitoring for CMP Va |
|
5 and 6 June
2012 |
Cumulative
Impact Sediment Chemistry Monitoring for CMP Va |
|
8 June 2012 |
Impact Water
Quality Monitoring during Dredging Operations for CMP Vc |
|
11 June 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 of CMP Va ¡V
June 2012
1.5.4
Monitoring locations for Pit Specific Sediment Chemistry for CMP Va are
shown in Figure 1.1. Concentrations of metals at all stations
in June 2012 were below the Lower Chemistry Exceedance Level (LCEL), with the
exception of Lead and
Arsenic (Figure 1 of Annex B).
Concentrations of Lead exceeded the LCEL at Active Pit station
NPDB. Concentrations of Arsenic
exceeded the LCEL at all stations except Active Pit station NPDB and Near Pit
station NNDB in June 2012. It is
important to note that relatively high natural levels of Arsenic are present in
Hong Kong¡¦s 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.
1.5.5
For organic contaminants, PCBs were below the limit of reporting at all
stations in June 2012. Levels of
Low and High Molecular Weight Polycyclic Aromatics Hydrocarbons (Low and High
M.W. PAHs) were higher than the limit of reporting at Active Pit stations only
(ie NPDA and NPDB). Total Organic
Carbon (TOC)
concentrations were similar amongst all stations (Figure 3 of Annex B). Tributyltins (TBTs) concentration was the highest at Active Pit station NPDB when compared
to other stations (Figure 4 of Annex B).
Concentrations of 4,4¡¨-DDE were higher than the
limit of reporting at Active Pit station NPDB only, whereas concentrations of
DDT were lower than the limit of reporting at all stations (Figure 5 of Annex B).
1.5.6
It should be noted that the Action Pit stations are located within CMP
Va which were receiving contaminated mud during the reporting month. Therefore, the higher concentrations of
contaminants recorded at the Action Pit stations alone are not considered as
indicating any dispersal of contaminated mud from CMP Va and thus also not
appeared to indicate any unacceptable environmental impacts from the mud
disposal operations. 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
Cumulative Impact Sediment Chemistry for CMP Va ¡V June 2012
1.5.8
Monitoring locations for Cumulative Impact Sediment Chemistry for CMP Va are shown
in Figure 1.2.
1.5.9
Analyses of results for the Cumulative Impact
Sediment Chemistry Monitoring indicated that the concentrations of all metals,
except Arsenic, were below the LCEL (Figures
6 and 7). Concentrations of
Arsenic in sediments from all stations, except Near Field (RNB) and Ma Wan
Station (MW), exceeded the LCEL. As
presented in Section 1.5.4 above, the
slight exceedances of LCEL for Arsenic do not necessarily indicate any adverse
impacts to sediment quality caused
by disposal operations at CMP Va.
Generally, there were only minor differences in metal concentrations
amongst the stations.
1.5.10
The concentration of TOC was higher at the Mid Field
station RMA than at other stations (Figure
8 of Annex B). TBTs were recorded in sediment samples at Near Field (RNA),
Mid Field (RMA and RMB) and Far Field (RFA) stations (Figure 9 of Annex B). Total DDT, DDE, Total PCBs, Low and High
Molecular Weight PAHs were below the limit of detection at all stations.
1.5.11
Overall, the contaminated mud disposal operations
at CMP Va did not appear to cause any deterioration in sediment quality of the
area.
1.5.12
Water Column Profiling for CMP Va
¡V June 2012
In-situ Measurements
1.5.13
The water quality monitoring results for June 2012
have been assessed for compliance with the WQOs set by EPD. 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.
Graphical presentation of the monitoring results is provided in Annex B.
1.5.14
Analyses of results for June 2012 indicated that
levels of Salinity, pH and Dissolved Oxygen (DO) complied with the WQOs at both
Upstream and Downstream stations (Figures
10, 11 and 12 in Annex B).
DO and Turbidity complied with the Action and Limit Levels set in the
EM&A Manual ([1]).
Laboratory Measurements for Total Suspended Solids
(TSS)
1.5.15
Analyses of data obtained in June 2012 indicated that the
TSS levels at both Upstream and Downstream stations complied with the WQO (Figure 13 in Annex B). TSS levels measured in June 2012
complied with the Action and Limit Levels set in the EM&A Manual.
1.5.16
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.
1.5.17
Impact Water Quality Monitoring during Dredging
Operations of CMP Vc ¡V June 2012
1.5.18
Impact Water
Quality Monitoring during Dredging Operations of CMP V was conducted
on 8 June 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).
1.5.19
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 ([2]).
1.5.20
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 July 2012:
CMP V
¡P
Pit Specific Sediment Chemistry for CMP Va;
¡P
Demersal Trawling for CMP Va;
¡P
Routine Water Quality Monitoring 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.