Agreement No. CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau (2009-2013) - Investigation
35th MONTHLY PROGRESS REPORT FOR CONTAMINATED MUD PITS AT SHA
CHAU May 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 May 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 Vc was in progress.
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 May 2012.
1.3
Details of Sampling and
Laboratory Testing Activities
1.3.1
The
following monitoring activities have been undertaken for CMP V in May 2012:
¡P Pit
Specific Sediment Chemistry Monitoring was conducted for CMP Va on 15 May 2012;
¡P Routine
Water Quality Monitoring was
conducted for CMP Va on 16 May 2012;
¡P Impact
Water Quality Monitoring during Dredging Operations was conducted for
CMP Vc on 17 May 2012; and
¡P Water
Column Profiling was
conducted for CMP Va on 18 May 2012.
1.3.2
A summary
of field activities is presented in Annex A.
1.4
Details of Outstanding
Sampling and / or Analysis
1.4.1
No outstanding
sampling and laboratory analysis remained from May 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 in May 2012 will be presented in this monthly report.
Table 1.1 Monitoring
results presented in the May 2012 Monthly Report
|
Date
of Monitoring |
Monitoring
Component |
|
15 May 2012 |
Pit Specific
Sediment Chemistry Monitoring for CMP Va |
|
16 May 2012 |
Routine Water
Quality Monitoring for CMP Va |
|
17 May 2012 |
Impact Water
Quality Monitoring during Dredging Operations for CMP Vc |
|
18 May 2012 |
Water Column
Profiling for CMP Va |
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 Monitoring of CMP Va
¡V May 2012
1.5.4
Monitoring locations for Pit Specific Sediment Chemistry for CMP Va are
shown in Figure 1.1. Concentrations of metals were generally
below the Lower Chemistry Exceedance Level (LCEL) (Figures 1 and 2 of Annex B) and no exceedance of Upper Chemistry
Exceedance Level (UCEL) was recorded in May 2012. Concentrations of Copper, Lead and Zinc
exceeded the LCEL at Active Pit station NPDA. Concentrations of Silver exceeded the
LCEL at Active Pit stations NPDA and NPDB.
Concentrations of Arsenic exceeded the LCEL at all stations, except
Active Pit station NPDB and Near-Pit station NNDB stations, in May 2012. 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 Action
Pit stations are located within CMP Va which was receiving contaminated mud
during the reporting month.
Therefore, the exceedances of LCEL recorded at the Action Pit stations
alone (for Copper, Lead, Silver and Zinc) are not considered as indicating any
dispersal of contaminated mud from CMP Va and thus not indicating any
unacceptable environmental impacts from the mud disposal operations.
1.5.5
For organic contaminants, PCBs were all below the limit of reporting at
all stations in May 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 May 2012. TOC and TBTs concentrations were the highest
at Active Pit stations (NPDA) in May 2012 when compared to other stations (Figures 3 and 4 of Annex B). Concentrations
of 4,4¡¨-DDE were higher than the limit of reporting at
Active Pit stations (NPDA and NPDB) for May 2012, whereas concentrations of DDT
were all lower than the limit of reporting at all stations (Figure 5 of Annex B).
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
Routine Water Quality Monitoring of CMP Va ¡V May 2012
1.5.8
The results for the Routine Water Monitoring
conducted during May 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
1.5.9
Analyses of results for May 2012 indicated that for
all stations (Impact, Intermediate and Reference), levels of pH, Salinity and
DO generally complied with the WQOs (Figures
8, 9 and 11 of Annex B). Levels of DO
and Turbidity within the reporting month also 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 (Figures
6 to 11 of Annex B).
Laboratory Measurements
1.5.10
Analyses of May 2012 results indicate that Arsenic,
Cadmium, Mercury and Silver concentrations were below their limit of reporting
at all stations. Concentrations of
Copper, Lead, Nickel and Chromium appeared to be similar among all
stations. Concentrations of Zinc
appeared to be higher at Reference stations.
1.5.11
For parameters other than metals, levels of 5-day
Biochemical Oxygen Demand (BOD5), Total Inorganic Nitrogen (TIN) and
NH3-N were similar among all stations (Figures 14 and 15 of Annex B).
Concentrations of TSS did not exceed WQO and complied with the Action
and Limit Levels at all stations within the reporting month (Figure 16 of Annex B).
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 May 2012
|
Stations |
Temp |
Salinity |
Turbidity |
pH |
Dissolved Oxygen |
|
|
|
(¢XC) |
|
(NTU) |
|
(%) |
(mg L-1) |
|
RFE
(Reference) |
26.29 |
24.15 |
3.12 |
7.83 |
73.53 |
5.18 |
|
IPE
(Impact) |
26.65 |
22.64 |
4.21 |
7.92 |
81.08 |
5.73 |
|
INE
(Intermediate) |
26.28 |
24.60 |
4.15 |
7.93 |
80.63 |
5.67 |
|
Ma
Wan Station |
27.32 |
20.27 |
0.85 |
8.16 |
111.59 |
7.90 |
|
WQO |
N/A |
21.73-26.56# |
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 May 2012
|
Stations |
As |
Ag |
Cd |
Cr |
Cu |
Hg |
Pb |
Ni |
Zn |
NH3-N |
TIN |
BOD5 |
TSS |
|
RFF
|
<LOR |
<LOR |
<LOR |
1.05 |
11.40 |
<LOR |
1.5 |
3.70 |
21.50 |
0.08 |
0.85 |
1.77 |
3.95 |
|
IPF
|
<LOR |
<LOR |
<LOR |
<LOR |
5.68 |
<LOR |
<LOR |
2.88 |
7.20 |
0.07 |
1.02 |
1.77 |
4.73 |
|
INF
|
<LOR |
<LOR |
<LOR |
<LOR |
3.70 |
<LOR |
<LOR |
2.68 |
8.15 |
0.06 |
0.97 |
1.94 |
4.55 |
|
Ma
Wan Station |
<LOR |
<LOR |
<LOR |
<LOR |
12.00 |
<LOR |
1.00 |
3.38 |
9.13 |
0.07 |
1.17 |
1.66 |
<LOR |
|
WQO of TSS |
13.00 |
||||||||||||
1.5.13
Water Column Profiling for CMP Va
¡V May 2012
In-situ Measurements
1.5.14
The water quality monitoring results for May 2012 have
been assessed for compliance with the WQOs set by EPD (please refer to Section 1.5.8 for details of setting the WQOs). Graphical presentation of the
monitoring results is provided in Annex B.
1.5.15
Analyses of results for May 2012 indicated that levels
of Salinity, pH and Dissolved Oxygen (DO) all complied with the WQOs at both
Upstream and Downstream stations (Figures 17, 18 and 19 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 May 2012 indicated that
the TSS levels at both Upstream and Downstream stations complied with the WQO (Figure 20 in Annex B). TSS levels measured in May 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 ¡V May 2012
1.5.19
Impact Water
Quality Monitoring during Dredging Operations of CMP V was conducted
on 17 May 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. 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
June 2012:
CMP IV
¡P
Water Quality Monitoring during Capping for CMP IVc;
CMP V
¡P
Pit Specific Sediment Chemistry for CMP Va;
¡P
Cumulative Impact Sediment Chemistry for CMP Va;
¡P
Water Column Profiling for CMP Va; and
¡P
Impact Water Quality Monitoring during Dredging
Operations for CMP Vc.
1.6.2
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.