Agreement No. CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau (2009-2013) - Investigation
40th MONTHLY PROGRESS REPORT FOR CONTAMINATED MUD PITS AT SHA
CHAU October 2012
1.1
Background
1.1.1
Since 1992,
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 October 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.
1.1.2
The
Environmental Monitoring and Audit (EM&A) programme for the CMPs at the
East of Sha Chau area (ESC) presently covers the above operations.
1.2
Reporting Period
This Monthly
Progress Report covers the monitoring period of October 2012.
1.3
Details of Sampling and
Laboratory Testing Activities
1.3.1
The following
monitoring activities have been undertaken for CMP V in October 2012:
¡P
Water Column Profiling was conducted for CMP Va on 8 October 2012;
¡P
Pit Specific Sediment Chemistry was conducted for CMP Va on 24 October 2012;
¡P
Impact Water Quality Monitoring during Dredging Operations was conducted for CMP Vd on
25 October 2012; and
¡P
Routine Water Quality Monitoring was conducted for CMP Va on 26 October 2012.
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 and laboratory analysis remained from October 2012.
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. All monitoring data
collected for CMP V in October 2012 will be presented in this monthly report.
Table 1.1 Monitoring
activities in October 2012
|
Monitoring
activities |
Date
of Monitoring |
Monitoring results presented in this report? |
|
Water Column
Profiling for CMP Va |
8 October 2012 |
Yes |
|
Pit Specific
Sediment Chemistry Monitoring for CMP Va |
24 October 2012 |
Yes |
|
Impact Water
Quality Monitoring during Dredging Operations of CMP Vd |
25 October 2012 |
Yes |
|
Routine Water
Quality Monitoring for CMP Va |
26 October 2012 |
Yes |
1.5.2
Brief
discussion of the monitoring results is presented in this section. Detailed discussion will be presented in
the corresponding Quarterly Report.
1.5.3
Pit Specific Sediment Chemistry of CMP Va ¡V October
2012
1.5.4
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 October 2012 were below the
Lower Chemistry Exceedance Level (LCEL), with the
exception of Arsenic, Copper and Silver (Figures 1 and 2 of Annex B). Concentrations of
Arsenic exceeded the LCEL at Pit-Edge (NEDA, NEDB) and Near-Pit (NNDA) stations
while concentrations of Copper and Silver exceeded the LCEL at Active Pit
(NPDB) station. 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
deposits. In addition, the Active
Pit station is located within CMP Va which was receiving contaminated mud
during the reporting period. Therefore,
the exceedances of LCEL for Copper and Silver which were recorded at the Active
Pit station alone is not considered as indicating any dispersal of contaminated
mud from CMP Va.
1.5.5
For organic contaminants, Total
Polychlorinated Biphenyls (PCBs), Low Molecular Weight Polycyclic Aromatics
Hydrocarbons (Low M.W. PAHs), Total DDT and 4,4¡¦-DDE were below the limit of
reporting at all stations in October 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 October 2012 when compared to other
stations (Figure 4 of Annex B). High Molecular Weight
Polycyclic Aromatics Hydrocarbons (High M.W. PAHs) were higher than the limit
of reporting at the Active Pit stations NPDA and NPDB for October 2012.
1.5.6
As described in Section
1.5.4, 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.
1.5.7
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.
1.5.8
Impact Water Quality Monitoring during Dredging
Operations of CMP Vd ¡V October 2012
1.5.9
Impact Water Quality Monitoring
during Dredging Operations of CMP Vd was
conducted on 25 October 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 (Figure 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
seabed).
1.5.10
Monitoring
results are presented in Table C1 of Annex C. Levels of Dissolved Oxygen (DO),
Turbidity and Total Suspended Solids (TSS) complied with the Action and Limit
Levels set in the Baseline Monitoring Report ([1]).
1.5.11
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).
1.5.12
Water Column Profiling for CMP Va
¡V October 2012
In-situ Measurements
1.5.13
Water Column
Profiling was undertaken at a total of two sampling stations in October
2012. The water quality monitoring results for October 2012 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 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.
1.5.14
Analyses of
results for October 2012 indicated that levels of Salinity, pH and 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 ([2]).
Laboratory Measurements for Total Suspended Solids
(TSS)
1.5.15
Analyses of data
obtained in October 2012 indicated that the TSS levels at Upstream
station exceeded the WQO (Figure 8 of Annex B). However, TSS
levels at all stations measured in October 2012 complied with the Action and
Limit Levels set in the EM&A Manual.
1.5.16
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.
1.5.17
Routine Water Quality Monitoring for CMP Va ¡V
October 2012
1.5.18
The results
for the Routine Water Quality Monitoring conducted during October 2012 in the wet season have
been assessed for compliance with the WQOs set by
EPD as presented in Section 1.5.13 above (please see Figure 1.3 for the monitoring locations). In-situ monitoring and laboratory results are shown in Table 1.2 and 1.3 respectively, with graphical presentation provided
in Annex B.
Monitoring was undertaken at a total of sixteen stations in the
reporting month.
In-situ Measurements
1.5.19
Analyses of
results for October 2012 indicated that for all stations (Impact, Intermediate
and Reference), levels of pH and DO complied with the WQOs (Figures 9-11 of Annex B). Levels
of Salinity complied with WQO at all stations, except at Ma Wan station (Figure 12 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 ([3])
(Figures
10 and 13 of Annex B). All in-situ water quality measurements showed
relatively minor variations between Impact, Intermediate and Reference stations
(Figures 9 to 13 of Annex B).
Laboratory Measurements
1.5.20
Analyses of
October 2012 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 while Chromium levels were below the
limits of reporting at Ma Wan Station (Figures
14 and 15 of Annex B).
Concentrations of Arsenic, Copper, Lead and Nickel appeared to be
similar amongst all stations while concentration of Zinc was highest at Ma Wan
station. Levels of 5-day
Biochemical Oxygen Demand (BOD5), Total Inorganic Nitrogen (TIN) and
NH3-N were similar among all stations (Figures
16 and 17 of Annex B).
Concentrations of TSS exceed WQO (12.74 mg/L for wet season) at
Intermediate Stations while all of them complied with the Action and Limit
Levels at all stations within the reporting month (Figure
18 of Annex B).
Table 1.2 In-situ Monitoring
Results for Routine Water Quality Monitoring during October 2012
|
Stations |
Temp |
Salinity |
Turbidity |
pH |
Dissolved Oxygen |
|
|
|
(¢XC) |
|
(NTU) |
|
(%) |
(mg L-1) |
|
RFE
(Reference) |
26.83 |
27.78 |
6.15 |
7.85 |
83.11 |
5.68 |
|
IPE
(Impact) |
26.73 |
28.49 |
4.60 |
7.92 |
87.59 |
5.98 |
|
INE
(Intermediate) |
26.68 |
28.48 |
4.62 |
7.88 |
89.42 |
6.11 |
|
Ma
Wan Station |
26.71 |
31.14 |
3.75 |
7.95 |
88.26 |
5.94 |
|
WQO |
N/A |
25.00-30.55 |
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 October 2012
|
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) |
TSS (mg/L) |
|
RFE
|
1.88 |
<LOR |
<LOR |
0.81 |
4.98 |
<LOR |
0.59 |
2.98 |
8.40 |
0.07 |
0.73 |
0.82 |
8.93 |
|
IPE
|
1.95 |
<LOR |
<LOR |
0.65 |
4.43 |
<LOR |
0.93 |
2.88 |
10.30 |
0.05 |
0.60 |
1.29 |
10.68 |
|
INE
|
1.98 |
<LOR |
<LOR |
0.64 |
4.55 |
<LOR |
0.51 |
2.08 |
7.38 |
0.04 |
0.58 |
0.94 |
13.03 |
|
Ma
Wan Station |
1.75 |
<LOR |
<LOR |
<LOR |
6.25 |
<LOR |
1.44 |
2.63 |
15.50 |
0.04 |
0.38 |
0.93 |
11.75 |
|
WQO of TSS |
12.74 |
||||||||||||
1.5.21
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.
1.6
Activities Scheduled for the
Next Month
1.6.1
The following
monitoring programmes will be conducted in the next monthly period of November
2012:
¡P
Pit Specific Sediment Chemistry for CMP Va;
¡P
Routine Water Quality Monitoring for CMP Va;
¡P
Water Column Profiling for CMP Va; and
¡P
Impact Water Quality Monitoring during Dredging
Operations for CMP Vd.
1.6.2
The sampling
schedule is presented in Annex A.
1.7
Study Programme
A summary of the Study Programme is presented in Annex D