Agreement No. CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau
(2009-2013) - Investigation
45TH MONTHLY PROGRESS REPORT FOR CONTAMINATED MUD PITS AT SHA
CHAU MARCH 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 March 2013, 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 Dredging of CMP Vd was in
progress.
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 March 2013.
1.3
Details of Sampling and Laboratory Testing Activities
1.3.1
The following monitoring
activities have been undertaken for CMP V in March 2013:
¡P Pit
Specific Sediment Chemistry was
conducted for CMP Va on 12 March 2013;
¡P Impact Water Quality Monitoring during Dredging Operations for CMP Vd
were conducted on 16 March 2013; and
¡P Water
Column Profiling was
scheduled to be undertaken on 26 March 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 March 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 March 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.
Table 1.1 Monitoring
activities in February / March 2013
|
Monitoring
activities |
Date
of Monitoring |
Monitoring
results presented in this report? |
|
Pit Specific Sediment
Chemistry Monitoring for CMP Va |
1 Feb 2013 12 Mar 2013 |
Yes No. Laboratory analysis yet to be
completed during preparation of this monthly report. |
|
Cumulative Impact Sediment
Chemistry Monitoring for CMP Va |
7 Feb 2013 |
Yes |
|
|
|
|
|
Impact Water Quality
Monitoring during Dredging Operations of CMP Vd |
16 Mar 2013 |
Yes |
|
|
|
|
|
Water Column Profiling for
CMP Va |
26 Mar 2013 |
No. In-situ
measurements and water sampling were not undertaken as there was no
dumping activity on the monitoring day. |
1.5.2
Pit Specific
Sediment Chemistry of CMP Va
¡V February 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 February 2013.
Concentrations of Arsenic exceeded the Lower Chemical Exceedance Level (LCEL) at Pit Edge stations NEDA and NEDB
and Near Pit stations NNDA and NNDB.
Concentrations of Copper, Mercury and Zinc exceeded the LCEL at Active
Pit station NPDA while concentrations of Silver exceeded the Upper Chemical Exceedance Level (UCEL) at Active Pit station NPDA (Figures 1-2 of
Annex B). It is also observed that the variations
of metal concentrations at Active Pit Stations 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 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 Active Pit station is
located within CMP Va which was receiving
contaminated mud during the reporting period. As such, the exceedances
of LCEL/UCEL for Copper, Mercury, Silver and Zinc which were recorded at Active
Pit station NPDA only are not considered as indicating any dispersal of
contaminated mud from 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), High Molecular Weight Polycyclic
Aromatics Hydrocarbons (High MW PAHs) and Low
Molecular Weigh Polycyclic Aromatics Hydrocarbons (Low MW PAHs)
concentrations were higher at Active Pit stations NPDA when compared to other
stations (Figures 4 and 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. As described in Section 1.5.3, the higher
concentrations of contaminants (including metals and organic contaminants)
recorded at the Active Pit stations only are not considered as indicating any
dispersal of contaminated mud from 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.
1.5.6
Cumulative
Impact Sediment Chemistry for CMP Va
¡V February 2013
1.5.7
Monitoring locations for Cumulative Impact Sediment
Chemistry for CMP Va are shown in Figure 1.2. A total of nine monitoring stations were
being sampled.
1.5.8
Analyses of results for the
Cumulative Impact Sediment Chemistry Monitoring indicated that the concentrations
of all metals, except Arsenic, were below the LCEL
in February 2013 (Figures 6 and 7 of Annex B). Concentrations
of Arsenic in sediments from all stations, except for Near Field station RNB,
exceeded the LCEL. As discussed in Section 1.5.3
above, relatively
high natural levels of Arsenic are present in Hong Kong ¡¦s
marine sediments and hence the slight exceedances of
the LCEL for the Arsenic do not necessarily indicate any adverse impacts to sediment
quality caused by disposal operation at CMP Va.
1.5.9
The concentration of TOC was similar amongst stations (Figure 8 of Annex
B). TBTs were
recorded in sediment samples from all stations except Near Field station RNB
and Capped Pit station RCB with a higher concentration recorded in Ma Wan
station (Figure 9 of Annex B).
Concentrations of Total DDT, 4,4¡¦-DDE, Total PCBs, Low and
High MW PAHs were below the limit of detection at all stations.
1.5.10
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.
1.5.11
Impact Water Quality Monitoring during Dredging
Operations of CMP Vd ¡V March
2013
1.5.12
Impact Water Quality Monitoring during Dredging
Operations of CMP Vd was
conducted on 16 March 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 1.3). 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.
1.5.13
Monitoring results are presented
in Table
C1 of Annex
C. Levels
of Dissolved Oxygen (DO), Turbidity and Suspended Solids (SS) complied with the
Action and Limit Levels set in the Baseline Monitoring Report ([3]).
1.5.14
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).
1.6
Activities Scheduled for the Next Month
1.6.1
The following monitoring
activities will be conducted in the next monthly period of April 2013 for CMP
V:
¡P Pit
Specific Sediment Chemistry for
CMP Va;
¡P Water
Column Profiling for CMP
Va; and
¡P Impact
Water Quality Monitoring during Dredging Operations for CMP Vd.