Agreement No. CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau
(2009-2013) - Investigation
44TH MONTHLY PROGRESS REPORT FOR CONTAMINATED MUD PITS AT SHA
CHAU FEBRUARY 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 February 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.
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 February 2013.
1.3
Details of Sampling and Laboratory Testing Activities
1.3.1
The following monitoring
activities have been undertaken for CMP V in February 2013:
·
Pit Specific Sediment Chemistry was conducted for CMP Va
on 1 February 2013;
·
Cumulative Impact Sediment Chemistry was conducted for CMP Va
on 7 February 2013;
·
Sediment Toxicity Tests was conducted for CMP Va
on 20 February 2013;
·
Demersal Trawling was conducted for CMP Va on 21 and 22 February
2013;
·
Routine Water Quality Monitoring was conducted for CMP Va
on 25 February 2013;
·
Impact Water Quality Monitoring during Dredging Operations for CMP Vd were conducted on 27 February 2013; and
·
Water Column Profiling was scheduled to be undertaken on 27 February 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.
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,
Cumulative
Impact Sediment Chemistry, Sediment Toxicity Tests
and
Demersal Trawling conducted
in February 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 January / February 2013
|
Monitoring
activities |
Date
of Monitoring |
Monitoring
results presented in this report? |
|
Pit Specific Sediment
Chemistry Monitoring for CMP Va |
11 Jan 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 |
No. Laboratory analysis yet to be
completed during preparation of this monthly report. |
|
|
|
|
|
Sediment Toxicity Tests |
20 Feb 2013 |
No. Laboratory analysis yet to be completed
during preparation of this monthly report. |
|
|
|
|
|
Demersal Trawling for
CMP Va |
21,22 Feb 2013 |
No. The results will be presented in the
subsequent quarterly report. |
|
|
|
|
|
Routine Water Quality
Monitoring for CMP Va |
25 Feb 2013 |
Yes |
|
Water Column Profiling for
CMP Va |
27 Feb 2013 |
No in-situ measurements and water sampling as there was no dumping
activity on the monitoring day. |
|
Impact Water Quality
Monitoring during Dredging Operations of CMP Vd |
27 Feb 2013 |
Yes |
1.5.2
Pit Specific
Sediment Chemistry of CMP Va
– January 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 January 2013.
Concentrations of Arsenic exceeded the Lower Chemical Exceedance Level (LCEL) at Pit Edge stations NEDA and NEDB
and Near Pit station NNDA.
Concentrations of Mercury and Zinc exceeded the LCEL at Active Pit
station NPDA while concentrations of Silver exceeded the Upper Chemical Exceedance Level (UCEL) and LCEL at Active Pit stations
NPDA and NPDB, respectively (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 stations are
located within CMP Va which was receiving
contaminated mud during the reporting period. As such, the exceedances
of LCEL/UCEL for Mercury, Silver and Zinc which were recorded at Active Pit
stations 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) concentration was higher at Active Pit stations NPDA and NPDB when
compared to other stations (Figure 4 of Annex B). High Molecular Weight Polycyclic
Aromatics Hydrocarbons (High MW PAHs) concentrations were below the limit of
reporting at all stations except at Active Pit stations (NPDA and NPDB) and
Pit-Edge station (NEDB) (Figure 5 of Annex B). Low Molecular Weigh Polycyclic Aromatics
Hydrocarbons (Low MW PAHs) concentrations were below the limit of reporting at
all stations except at Active Pit stations (NPDA and NPDB). 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.
1.5.5
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. Nevertheless,
detailed analysis will be presented in the Quarterly Report to reveal any trend of
increasing sediment contaminant concentrations towards CMP Va.
1.5.6
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
Impact Water
Quality Monitoring during Dredging Operations of CMP Vd – February 2013
1.5.8
Impact Water Quality Monitoring during Dredging
Operations of CMP Vd was conducted
on 27 February 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 1.2). 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 is less than 6 m,
the mid-depth station was omitted.
If water depth is less than 3 m, only the mid-depth station was
monitored.
1.5.9
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]).
1.5.10
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).
1.5.11
Routine Water
Quality Monitoring for CMP Va
– February 2013
1.5.12
The results for the Routine Water
Quality Monitoring conducted during February 2013 in the dry 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
dry season period (November to March) 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 B. Monitoring was undertaken at a total of
10 stations in the reporting month (see Figure 1.3).
In-situ
Measurements
1.5.13
Analysis of results for February
2013 indicated that for all stations (Impact, Intermediate, Reference and Ma
Wan), levels of pH, DO and salinity complied with the WQOs (Figures 6-9 of
Annex B). Levels of DO and Turbidity within the reporting
month complied with the Action and Limit Levels set in the EM&A Manual ([4])
(Figures 7 and 10 of Annex B). All in-situ
water quality measurements showed relatively minor variations amongst Impact,
Intermediate and Reference stations (Figures 6-10 of Annex B).
Laboratory
Measurements
1.5.14
Analyses of February 2013 results
indicate that concentrations of Cadmium, Chromium, Mercury and Silver were below
their limit of reporting at all stations.
Arsenic, Copper, Lead, Nickel and Zinc were detected in samples from all
stations (Figures 11 and 12 of Annex B). Concentrations of Arsenic, Lead and
Nickel appeared to be similar amongst all stations while concentration of Zinc
was the highest at Ma Wan Station.
Levels of 5-day Biochemical Oxygen Demand (BOD5), Total
Inorganic Nitrogen (TIN) and NH3-N were similar amongst all stations
(Figures
13 and 14 of Annex B). Concentrations of SS complied with the
WQO (15.34 mg/L for dry season) and Action and Limit Levels at all stations
within the reporting month (Figure 15 of Annex B).
1.5.15
Overall, the results indicated
that the disposal operation at CMP Va did not appear
to cause any deterioration in water quality during this reporting period.
Table 1.2 In-situ
Monitoring Results for Routine Water Quality Monitoring of CMP Va in February 2013
|
Stations |
Temp |
Salinity |
Turbidity |
pH |
Dissolved Oxygen |
|
|
|
(°C) |
|
(NTU) |
|
(%) |
(mg L-1) |
|
RFF
(Reference) |
18.78 |
31.07 |
3.83 |
8.12 |
110.70 |
8.57 |
|
IPF
(Impact) |
18.80 |
30.98 |
3.87 |
8.13 |
114.53 |
8.87 |
|
INF
(Intermediate) |
19.04 |
30.55 |
5.90 |
8.13 |
113.00 |
8.74 |
|
Ma
Wan Station |
18.78 |
31.35 |
1.30 |
7.96 |
103.36 |
7.99 |
|
WQO |
N/A |
27.97-34.18# |
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 February 2013
|
Stations |
As (µg/L) |
Ag (µg/L) |
Cd (µg/L) |
Cr (µg/L) |
Cu (µg/L) |
Hg (µg/L) |
Pb (µg/L) |
Ni (µg/L) |
Zn (µg/L) |
NH3-N (mg/L) |
TIN (mg/L) |
BOD5 (mg/L) |
SS (mg/L) |
|
|
|
RFF
|
1.38 |
<LOR |
<LOR |
<LOR |
1.60 |
<LOR |
<LOR |
1.42 |
3.42 |
0.02 |
0.21 |
0.95 |
4.88 |
|
|
|
IPF
|
1.25 |
<LOR |
<LOR |
<LOR |
0.94 |
<LOR |
<LOR |
1.38 |
2.29 |
0.02 |
0.20 |
0.87 |
8.46 |
|
|
|
INF
|
1.50 |
<LOR |
<LOR |
<LOR |
1.23 |
<LOR |
<LOR |
1.75 |
2.42 |
0.02 |
0.29 |
1.28 |
5.08 |
|
|
|
Ma
Wan Station |
1.50 |
<LOR |
<LOR |
<LOR |
2.63 |
<LOR |
0.56 |
<LOR |
5.50 |
0.05 |
0.29 |
0.62 |
4.13 |
|
|
|
|
WQO of SS: 15.34mg/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 March 2013 for CMP V:
·
Pit Specific Sediment Chemistry for CMP Va;
·
Water Column Profiling for CMP Va; and
·
Impact Water Quality Monitoring during Dredging
Operations for CMP Vd.