Agreement No.
CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau (2009-2013) - Investigation
48TH MONTHLY PROGRESS REPORT FOR CONTAMINATED MUD PITS AT SHA
CHAU JUNE 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 HKSAR¡¦s dredging and reclamation
projects. In June 2013, the
following works were being undertaken at the CMPs:
¡P
Capping was being undertaken at CMP IVc; and
¡P
Disposal of contaminated mud was taking place at CMP Va.
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 June 2013.
1.3
Details of Sampling and Laboratory Testing Activities
1.3.1
The
following monitoring activities have been undertaken for CMP V in June 2013:
¡P
Pit Specific Sediment
Chemistry was
conducted for CMP Va on 6 June 2013;
¡P
Cumulative Impact Sediment
Chemistry was
conducted for CMP Va on 14 June 2013;
¡P
Water Column Profiling was scheduled to be
undertaken on 18 June 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 June 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 May and June 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 14 May 2013 6 June 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. |
|
Cumulative Impact Sediment
Chemistry Monitoring for CMP Va |
14 June 2013 |
No. Laboratory analysis
yet to be completed during preparation of this monthly report. |
|
Water Column Profiling for
CMP Va |
18 June 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 April to June 2013
1.5.2
Pit Specific
Sediment Chemistry of CMP Va ¡V April 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 April 2013. Most contaminants complied with the
Lower Chemical Exceedance Level (LCEL) at all stations except for Arsenic,
Copper, Mercury and Silver.
Concentrations of Arsenic exceeded the LCEL at Pit Edge station NEDB and
Near Pit stations NNDA and NNDB (Figures 1-2 of Annex B).
Concentrations of Copper and Mercury exceeded LCEL at Pit Edge station
NEDA while concentration of Silver exceeded LCEL and Upper Chemical Exceedance
Level (UCEL) at Active Pit station NPDB and Pit Edge station NEDA,
respectively. It is observed that
the variations of metal concentrations at Active Pit Stations and Pit Edge
station NEDA were much larger (ie greater standard deviation) when compared to
other stations. Whilst the average
concentration of Arsenic in the Earth¡¦s crust is generally ~2mg/kg,
significantly higher Arsenic concentrations (median = 14 mg/kg) have been
recorded in Hong Kong ¡¦s onshore sediments ([1]). It is presumed that the natural concentrations of Arsenic are similar in
onshore and offshore sediments ([2]), 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. In addition, the Active Pit station NPDB
and Pit Edge station NEDA are located within and near the boundary of the CMP
Va which was receiving contaminated mud during the reporting period. As such, the exceedances of LCEL/UCEL
for Copper, Mercury and Silver which were 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.
1.5.4
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 station NPDB and Near Pit station NNDA (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 station NPDB and Near Pit station NNDA only (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.
The Active Pit station NPDB and Near Pit station NNDA is located within
and near the boundary of 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.
1.5.5
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.
1.6
Activities Scheduled for the Next Month
1.6.1
The
following monitoring activities will be conducted in the next monthly period of
July 2013 for CMP V:
¡P
Pit Specific Sediment
Chemistry for CMP
Va;
¡P
Water Column Profiling for CMP Va; and
¡P
Demersal Trawling for CMP V.