Agreement No. CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau
(2009-2013) - Investigation
43RD MONTHLY PROGRESS REPORTFOR CONTAMINATED MUD PITS AT SHA
CHAU January 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 January 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
January 2013.
1.3
Details of Sampling and
Laboratory Testing Activities
1.3.1
The following monitoring activities have been undertaken for
CMP V in January 2013:
·
Water Column Profiling was conducted for CMP Va on 4 January 2013;
·
Pit Specific Sediment Chemistry was conducted for
CMP Va on 11 January 2013;
·
Demersal Trawling was
conducted for CMP Va on 17 and 18 January 2013;
·
Routine Water Quality Monitoring was conducted for
CMP Va on 18 January 2013; and
·
Impact Water Quality Monitoring during Dredging
Operations was conducted for CMP Vd on 23 January
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 analysis of Pit Specific Sediment Chemistry conducted in January 2013 was 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 December 2012/January 2013
|
Monitoring activities |
Date of Monitoring |
Monitoring results presented in this report? |
|
Cumulative
Impact Sediment Chemistry Monitoring for CMP Va |
3 Dec 2012 |
Yes |
|
|
|
|
|
Pit Specific Sediment
Chemistry Monitoring for CMP Va |
7 Dec 2012 11 Jan 2013 |
Yes No. Laboratory analysis yet to be
completed during preparation of this monthly report. |
|
Water Column Profiling for
CMP Va |
4 Jan 2013 |
Yes |
|
Demersal Trawling for CMP Va |
17&18 Jan
2013 |
No. Laboratory analysis yet to be
completed during preparation of this monthly report. |
|
|
|
|
|
Routine Water
Quality Monitoring for CMP Va |
18 Jan 2013 |
Yes |
|
|
|
|
|
Impact Water
Quality Monitoring during Dredging Operations of CMP Vd |
23 Jan 2013 |
Yes |
1.5.2
Pit Specific Sediment Chemistry of CMP Va – December 2012
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 December 2012.
Concentrations of Arsenic exceeded the Lower Chemical Exceedance Level (LCEL) at all stations except at Active
Pit station NPDA while concentrations of Silver exceeded the LCEL at Active Pit
station NPDA (Figures 1-2 of Annex B). 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 for Silver which were recorded at one Active Pit station only is 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 Station NPDA and Pit Edge Station NEDB
when compared to other stations (Figure 4 of Annex B). 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), 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
Cumulative Impact Sediment Chemistry for CMP Va – December 2012
1.5.8
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.
1.5.9
Analyses of results for the Cumulative Impact Sediment Chemistry
Monitoring indicate that the concentrations of all metals, except Arsenic, were
below the LCEL in December 2012 (Figures 6 and 7 of Annex B). Concentrations of Arsenic in sediments from all
stations, except for Ma Wan station, Near Field stations RNA and 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.
1.5.10
The concentration
of TOC was similar amongst stations (Figure 8 of Annex B). TBTs were recorded in sediment samples
from Near Field (RNA and RNB), Mid Field (RMA and RMB), Far-field (RFA), Capped
Pit (RCA) and Ma Wan stations (Figure 9 of Annex B).
Concentrations of Total DDT,
4,4”-DDE, Total PCBs, Low and High M.W. PAHs were below the limit of detection at all stations.
1.5.11
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.
1.5.12
Impact Water Quality Monitoring during Dredging
Operations of CMP Vd –
January 2013
1.5.13
Impact
Water Quality Monitoring during Dredging Operations of CMP Vd was conducted on 23 January 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 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.
1.5.14
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]).
1.5.15
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).
1.5.16
Water Column Profiling for CMP Va – January 2013
In-situ Measurements
1.5.17
Water Column Profiling was undertaken at a total of two sampling
stations (Upstream and Downstream stations) in January 2013. The water quality monitoring results for January 2013
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.
Graphical presentation of the monitoring results is provided in Annex
B.
1.5.18
Analyses of results for January 2013 indicated that levels of Salinity,
pH and DO complied with the WQOs at both Upstream and Downstream stations (Figures 10 - 12 of Annex B). DO and Turbidity
complied with the Action and Limit Levels set in the EM&A Manual ([4]).
Laboratory Measurements for Suspended Solids (SS)
1.5.19
Analyses of data obtained in January 2013 indicated that the SS levels
at both Upstream and Downstream stations complied with the WQO (Figure 13 of Annex B). In addition, SS levels
at all stations complied with the Action and Limit Levels set in the EM&A Manual.
1.5.20
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.
1.5.21
Routine Water Quality Monitoring for CMP Va – January 2013
1.5.22
The results for the Routine Water Quality Monitoring
conducted during January 2013 in the dry season have been assessed for
compliance with the WQOs set by EPD as presented in Section 1.5.18 above (please see Figure 1.4 for the monitoring
locations). 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
ten stations in the reporting month.
In-situ Measurements
1.5.23
Analysis of results for January 2013 indicated that for all
stations (Impact, Intermediate and Reference), levels of pH, DO and salinity
complied with the WQOs (Figures
14-17 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 ([5])
(Figures 15 and 18 of Annex
B). All in-situ water quality
measurements showed relatively minor variations amongst Impact, Intermediate
and Reference stations (Figures
14-18 of Annex
B).
Laboratory Measurements
1.5.24
Analyses of January 2013 results indicate that
concentrations of Cadmium, 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 19 and 20 of Annex B). Concentrations of Arsenic, Chromium,
Lead and Nickel appeared to be similar amongst all stations while concentration
of Zinc was the highest at Reference stations. Levels of 5-day Biochemical Oxygen
Demand (BOD5), Total Inorganic Nitrogen (TIN) and NH3-N
were similar amongst all stations (Figures
21 and 22 of Annex C). 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 23
of Annex C).
1.5.25
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 during January 2013
|
Stations |
Temp |
Salinity |
Turbidity |
pH |
Dissolved Oxygen |
|
|
|
((C) |
|
(NTU) |
|
(%) |
(mg L-1) |
|
RFF (Reference) |
17.36 |
32.12 |
3.12 |
7.79 |
100.47 |
7.94 |
|
IPF (Impact) |
17.46 |
32.19 |
4.89 |
7.76 |
97.85 |
7.72 |
|
INF (Intermediate) |
17.46 |
32.16 |
3.09 |
7.73 |
98.62 |
7.78 |
|
Ma Wan Station |
17.60 |
32.87 |
2.54 |
7.73 |
93.10 |
7.29 |
|
WQO |
N/A |
28.91-35.33# |
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 during January 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
|
1.04 |
<LOR |
<LOR |
1.60 |
7.83 |
<LOR |
4.42 |
3.83 |
10.79 |
0.17 |
0.38 |
2.41 |
4.88 |
|
IPF
|
1.13 |
<LOR |
<LOR |
1.00 |
11.08 |
<LOR |
2.29 |
2.75 |
8.54 |
0.14 |
0.34 |
1.72 |
8.46 |
|
INF
|
<LOR |
<LOR |
<LOR |
2.19 |
7.29 |
<LOR |
2.63 |
4.58 |
8.88 |
0.12 |
0.34 |
2.15 |
5.08 |
|
Ma
Wan Station |
<LOR |
<LOR |
<LOR |
1.44 |
7.56 |
<LOR |
3.88 |
2.00 |
10.50 |
0.11 |
0.25 |
0.65 |
4.13 |
|
WQO of SS |
15.34 |
||||||||||||
1.6
Activities Scheduled for the
Next Month
1.6.1
The following monitoring activities will be conducted in the
next monthly period of February 2013 for CMP V:
· Pit
Specific Sediment Chemistry for
CMP Va;
· Cumulative
Impact Sediment Chemistry for CMP Va;
· Sediment
Toxicity for CMP Va;
· Tissue/
Whole Body Sampling for CMP Va;
· Demersal Trawling 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.