Agreement No. CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau (2009-2013) - Investigation
39th MONTHLY PROGRESS REPORT FOR CONTAMINATED MUD PITS AT SHA
CHAU September 2012
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 September 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 Vd was in progress.
Environmental Monitoring and Audit (EM&A) programme for the CMPs at the
East of Sha Chau area (ESC) presently covers the above operations.
Progress Report covers the monitoring period of September 2012.
monitoring activities have been undertaken for CMP V in September 2012:
Water Quality Monitoring during Dredging Operations was conducted for
CMP Vd on 5 September 2012;
Specific Sediment Chemistry was
conducted for CMP Va on 6 September 2012; and
Column Profiling was
conducted for CMP Va on 24 September 2012.
A summary of field activities are presented in Annex A.
sampling and laboratory analysis remained from September 2012.
Table 1.1 summarises the monitoring results that are presented in the current
monthly report. All monitoring data
collected for CMP V in September 2012 will be presented in this monthly report.
Table 1.1 Monitoring
activities in September 2012
Monitoring results presented in this report?
Quality Monitoring during Dredging Operations of CMP Vd
5 September 2012
Sediment Chemistry Monitoring for CMP Va
6 September 2012
Profiling for CMP Va
discussion of the monitoring results is presented in this section. Detailed discussion will be presented in
the corresponding Quarterly Report.
Pit Specific Sediment Chemistry of CMP Va ¡V
Monitoring locations for Pit
Specific Sediment Chemistry for CMP Va are shown in Figure 1.1. A total of six monitoring
stations were being sampled.
Concentrations of metals at all stations in September 2012 were below
the Lower Chemistry Exceedance Level (LCEL), with the
exception of Arsenic (Figures 1 and 2 of Annex B). Concentrations of Arsenic exceeded the LCEL
at Active Pit (NPDA), Pit-Edge (NEDA, NEDB) and Near-Pit (NNDA) stations in
September 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
For organic contaminants, Total
Polychlorinated Biphenyls (PCBs), Total DDT and 4,4¡¦-DDE were below the limit
of reporting at all stations in September 2012. Total Organic Carbon (TOC) concentration
was similar amongst all stations (Figure 3 of Annex B). TBT concentration was
the highest at Active Pit station NPDB in September 2012 when compared to other
stations (Figure 4 of Annex B). Low and High Molecular
Weight Polycyclic Aromatics Hydrocarbons (Low and High M.W. PAHs) were higher
than the limit of reporting at the Active Pit station NPDB and Near-Pit station
NNDA for September 2012.
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 not considered as indicating any
unacceptable environmental impacts from the mud disposal operations. Nevertheless, detailed analysis will be
presented in the Quarterly Report to reveal any
trend of increasing sediment contaminant concentrations towards CMP Va.
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
Impact Water Quality Monitoring during Dredging
Operations of CMP Vd ¡V September 2012
Impact Water Quality Monitoring
during Dredging Operations of CMP Vd was
conducted on 5 September 2012. 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
1.2). 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
results are presented in Table C1 of Annex C. Levels of Dissolved Oxygen (DO), Turbidity
and Total Suspended Solids (TSS) generally complied with the Action and Limit
Levels set in the Baseline Monitoring Report ().
Turbidity and TSS exceeded the Limit and Action Levels in the downstream
station DS3 during the mid-flood tide, respectively. Station DS3 is located even further away
from the works area of CMP Vd than DS1 and DS2, and the compliance of Action
and Limit Levels at other downstream stations (i.e. DS1, 2, 4 and 5) outside
the works area would indicate that there is no evidence of any unacceptable
adverse water quality impacts arising from the dredging operations of CMP Vd
(please refer to Figure
1.2) for the indicative locations of the
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).
Water Column Profiling for CMP Va ¡V September 2012
Profiling was undertaken at a total of two sampling stations in September
2012. The water quality monitoring results have been assessed for
compliance with the Water Quality Objectives (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.
results for September 2012 indicated that levels of Salinity, pH and Dissolved
Oxygen (DO) all complied with the WQOs at both Upstream and Downstream stations
(Figures 5 ¡V 7 of Annex B). DO and Turbidity complied with the
Action and Limit Levels set in the EM&A Manual ().
Laboratory Measurements for Total Suspended Solids
Analyses of data
obtained in September 2012 indicated that the TSS levels at both Upstream and
Downstream stations exceeded the WQO (Figure 8 of Annex B). However, TSS
levels measured in September 2012 complied with the Action and Limit Levels set
in the EM&A Manual.
results indicated that the mud disposal operation at CMP Va did not appear to
cause any deterioration in water quality during this reporting period.
monitoring programmes will be conducted for CMP V in the next monthly period of
Pit Specific Sediment Chemistry for CMP Va;
Routine Water Quality Monitoring for CMP Va;
Water Column Profiling for CMP Va; and
Impact Water Quality Monitoring during Dredging
Operations for CMP Vd.
schedule is presented in Annex A.
A summary of the Study Programme is presented in Annex D.