Agreement No. CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau (2009-2013) -
Investigation
34th MONTHLY PROGRESS REPORT FOR CONTAMINATED MUD PITS AT SHA
CHAU April 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
April 2012, 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
·
The
dredging of CMP Vc 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
1.2.1
This Monthly Progress Report covers the
reporting month of April 2012.
1.3
Details of Sampling and
Laboratory Testing Activities
1.3.1
The
following monitoring activities have been undertaken for CMP V in April 2012:
·
Pit Specific Sediment Chemistry was
conducted for CMP Va on 17 April 2012;
·
Routine Water Quality Monitoring was
conducted for CMP Va on 24 April 2012;
·
Water Column Profiling was conducted for
CMP Va on 25 April 2012; and
·
Impact Water Quality Monitoring during
Dredging Operations was conducted for CMP Vc
on 26 April 2012.
1.3.2
A summary of
field activities is presented in Annex A. A summary of monitoring data submitted by the
Contractor for this reporting month is presented in Table 1.1.
Table 1.1 Summary
of monitoring data submitted by the Contractor for the reporting month
|
Key
Task |
Monitoring
Component |
Date of Results Received from the Contractor |
|
CMP Vc |
|
|
|
Impact Monitoring
during Dredging Operations |
Water Quality |
11 May 2012 |
|
|
|
|
1.4
Details of Outstanding
Sampling and / or Analysis
1.4.1
No
outstanding sampling and laboratory analysis remained from April 2012.
1.5
Brief Discussion of the
Monitoring Results for CMP V
1.5.1
Table 1.2 summarises the monitoring results that are presented in the current
monthly report. All monitoring data
collected in April 2012 will be presented in this monthly report.
Table 1.2 Monitoring
results presented in the April 2012 Monthly Report
|
Date
of Monitoring |
Monitoring
Component |
|
17 April 2012 |
Pit Specific
Sediment Chemistry for CMP Va |
|
24 April 2012 |
Routine Water
Quality Monitoring for CMP Va |
|
25 April 2012 |
Water Column
Profiling for CMP Va |
|
26 April 2012 |
Impact Water Quality
Monitoring during Dredging Operations for CMP Vc |
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 – April 2012
1.5.4
Monitoring locations for Pit Specific Sediment Chemistry for CMP Va are shown in Figure 1.1. Concentrations of metals at all stations in
April 2012 were below the Lower Chemistry Exceedance
Level (LCEL), with the exception of Copper, Lead, Silver and Arsenic (Figures 1 and 2 of Annex B). Concentrations of Copper and Lead exceeded
the LCEL at Active Pit station (NPDA).
Concentrations of Silver exceeded the LCEL at Active Pit (NPDA) and
Pit-Edge (NEDB) stations. Concentrations
of Arsenic exceeded the LCEL at all stations in April 2012. It is important to note that relatively high
natural levels of Arsenic are present in Hong Kong’s marine sediments (see Section 1.5.3 above). 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.
1.5.5
For organic contaminants, PCBs were all below the limit of reporting at
all stations in April 2012. Levels of
Low and High Molecular Weight Polycyclic Aromatics Hydrocarbons (Low and High
M.W. PAHs) were higher than the limit of reporting in
only a few samples collected in April 2012.
TOC concentrations were the highest at Active Pit stations (NPDA) in
April 2012 when compared to other stations (Figure
3 of Annex B).
Highest concentrations of TBTs were recorded
at Pit-Edge stations (NEDB) in sediment samples collected in April 2012, but
were not detected in any interstitial water samples (Figure 4 of Annex B).
Concentrations of DDT and 4,4”-DDE were higher
than the limit of reporting at all stations for April 2012, except for Pit-Edge
(NEDB) and Near-Pit (NNDB) stations (Figure
5 of Annex B).
Sediments were mainly composed of silt and clay (63.9 – 73.3%) materials
and sand (21.9 – 34.1%; Figure 6 of Annex B).
1.5.6
It should be noted that the Action Pit stations are located within CMP Va which were receiving contaminated mud during the reporting
month. Therefore, the higher
concentrations of contaminants (eg for TOC) 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 did not appear to be any 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
Routine Water Quality Monitoring of CMP Va – April 2012
1.5.9
The results for the Routine Water Monitoring
conducted during April 2012 in the wet season have been assessed for compliance with the Water
Quality Objectives (WQOs) (please see Figure 1.2 for the monitoring locations). This consists of a review of the
Environmental Protection Department (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. In-situ
monitoring
and laboratory results are shown in Table
1.2 and 1.3 respectively, with
graphical presentation provided in Annex B.
In-situ
Measurements
1.5.10
Analyses of results for April 2012 indicated that for
all stations (Impact, Intermediate and Reference), levels of pH, Salinity and
DO complied with the WQOs (Figure 9, 10 and 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 ([1]). All in-situ
water quality measurements showed relatively minor variations between Impact,
Intermediate and Reference stations (Figure
7 to 12 of Annex B).
Laboratory
Measurements
1.5.11
Analyses of April 2012 results indicate that majority of metal
concentrations (ie Arsenic, Cadmium, Mercury and
Silver) were below their limits of reporting at all stations. Copper, Lead, Nickel and Zinc were detected
in samples from all stations while Chromium levels were above the limit of
reporting at Impact and Ma Wan stations (Figure
13 and 14 of Annex B). Concentrations of Copper, Lead, Nickel and
Chromium appeared to be similar among all stations. Concentrations of Zinc were higher at Ma Wan
and followed by Impact stations. The
higher concentration of Zinc recorded at the Impact Station will be further
analyzed in the Quarterly Report in order to determine any spatial trend of
potential concern (ie increasing Zinc concentrations
with proximity to the pit). Levels of
5-day Biochemical Oxygen Demand (BOD5), Total Inorganic Nitrogen
(TIN) and NH3-N were similar among all stations (Figure 15 and 16 of Annex B). Concentrations of TSS exceeded WQO (13 mg/L
for wet season) at Impact and Intermediate stations (Figure 17 of Annex B) but they complied
with the Action and Limit Levels within the reporting month.
1.5.12
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 April 2012
|
Stations |
Temp |
Salinity |
Turbidity |
pH |
Dissolved Oxygen |
|
|
|
(°C) |
|
(NTU) |
|
(%) |
(mg L-1) |
|
RFE
(Reference) |
23.63 |
22.49 |
7.12 |
7.75 |
78.54 |
5.85 |
|
IPE
(Impact) |
23.74 |
22.28 |
13.83 |
7.71 |
84.17 |
6.27 |
|
INE
(Intermediate) |
23.80 |
23.23 |
10.40 |
7.83 |
88.35 |
6.53 |
|
Ma
Wan Station |
23.85 |
22.33 |
5.24 |
7.74 |
86.26 |
6.41 |
|
WQO |
N/A |
20.24-24.73# |
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 April 2012
|
Stations |
As |
Ag |
Cd |
Cr |
Cu |
Hg |
Pb |
Ni |
Zn |
NH3-N |
TIN |
BOD5 |
TSS |
|
RFF
|
<LOR |
<LOR |
<LOR |
<LOR |
12.03 |
<LOR |
<LOR |
5.18 |
13.03 |
0.41 |
1.59 |
0.98 |
9.48 |
|
IPF
|
<LOR |
<LOR |
<LOR |
<LOR |
14.07 |
<LOR |
1.67 |
4.59 |
37.02 |
0.29 |
1.50 |
1.12 |
18.28 |
|
INF
|
<LOR |
<LOR |
<LOR |
<LOR |
9.25 |
<LOR |
0.66 |
3.75 |
13.25 |
0.23 |
1.36 |
1.05 |
13.30 |
|
Ma
Wan Station |
<LOR |
<LOR |
<LOR |
1.19 |
19.25 |
<LOR |
2.13 |
4.13 |
70.88 |
0.29 |
1.48 |
1.20 |
7.75 |
|
WQO of TSS |
13.00 |
||||||||||||
1.5.13
Water Column Profiling for CMP Va – April 2012
In-situ
Measurements
1.5.14
The water quality monitoring results for April 2012 have
been assessed for compliance with the WQOs set by EPD
(please refer to Section 1.5.2 for
details of setting the WQOs). Graphical presentation of the monitoring
results is provided in Annex B.
1.5.15
Analyses of results for April 2012
indicated that levels of Salinity, pH and Dissolved Oxygen (DO) all complied
with the WQOs at both Upstream and Downstream
stations (Figure 18, 19 and 20 in 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)
1.5.16
Analyses of data obtained in April 2012 indicated that
the TSS levels at both Upstream and Downstream stations complied with the
WQO (Figure 21 in Annex B). TSS levels measured in April 2012 complied
with the Action and Limit Levels set in the EM&A Manual.
1.5.17
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.
1.5.18
Impact Water Quality Monitoring during Dredging
Operations of CMP Vc – April
2012
1.5.19
Impact Water
Quality Monitoring during Dredging Operations of CMP V was conducted
on 26 April 2012 for CMP Vc. 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 Vc (Figure 1.3). 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).
1.5.20
Monitoring results are presented in Table C1 of Annex C. Levels of DO, Turbidity and TSS complied with
the Action and Limit Levels set in the Baseline
Monitoring Report ([3]).
1.5.21
Overall, the results indicated that the dredging
operations at CMP Vc did not appear to cause any
unacceptable deterioration in water quality during this reporting period.
1.5.22
Therefore, no further mitigation measures,
except for those recommended in the Environmental Permit (EP-312/2008), are considered required for the dredging operations
of CMP Vc.
1.6
Activities Scheduled for the Next Month
1.6.1
The
following monitoring programmes will be conducted in the next monthly period of
May 2012:
·
Pit Specific Sediment Chemistry 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 Vc.
The sampling schedule is presented in Annex A.
1.7
Study Programme
1.7.1
A summary
of the Study Programme is presented in Annex D.