Contents
1.1 Background
1.2 Reporting Period
1.3 Details of Sampling and Laboratory Testing Activities
1.4 Details of Outstanding Sampling and/or Analysis
1.5 Brief Discussion of the Monitoring Results for ESC CMP V
1.6 Activities Scheduled for the Next Month
1.7 Study Programme
Annexes
Annex B Water Quality Monitoring Results
Annex C Graphical Presentations
1.1
Background
1.1.1
The Civil Engineering and
Development Department (CEDD) is managing a number of marine disposal
facilities in Hong Kong waters, including the Contaminated Mud Pits (CMPs) to
the South of The Brothers (SB) and to the East of Sha
Chau (ESC) for the disposal of contaminated sediment, and open-sea disposal
grounds located to the South of Cheung Chau (SCC), East of Tung Lung Chau
(ETLC) and East of Ninepins (ENP) for the disposal of uncontaminated
sediment. Two Environmental Permits (EPs), EP-312/2008/A and
EP-427/2011/A, were issued by the Environmental Protection Department (EPD) to
the CEDD, the Permit Holder, on 28 November 2008 and 23 December 2011 for the
Dredging, Management and Capping of Contaminated Sediment Disposal Facilities
at ESC CMP V and SB CMPs, respectively.
1.1.2
Under the requirements of the two
EPs for ESC CMP V and
SB CMPs, EM&A programmes which encompass water and sediment chemistry, fisheries
assessment, tissue and whole body analysis, sediment toxicity and benthic recolonisation studies as set out in the EM&A Manuals
are required to be implemented. EM&A programmes
have been continuously carried out during the operation of the CMPs at ESC and
SB. A review of the collection and analysis of such environmental
data from the monitoring programme demonstrated that there had not been any
adverse environmental impacts resulting from disposal activities ([1]) ([2]). The current programme will assess the impacts resulting
from dredging, disposal and capping operations of CMP V as well as capping
operations of SB CMPs.
1.1.3
A
proposal on the change of number of sample replication of water quality &
sediment monitoring and combination of routine water quality monitoring and
water quality monitoring during capping operation was submitted to EPD and
agreed by EPD on 3 December 2020. The proposed changes have been
effective for the EM&A activities since December
2020. The latest sampling schedule is provided in Annex A.
1.1.4
The present EM&A programme under
Agreement No. CE 63/2016 (EP) covers the dredging, disposal and capping operations of the
ESC CMP V as well as the capping operations of the SB CMPs (see Annex A for the EM&A programme). The scheduled EM&A
programme for SB CMPs was completed in December 2018. Detailed works
schedule for ESC CMP V is shown in Figure 1.1. In January 2021, the following works were
undertaken:
· Disposal of contaminated mud at ESC CMP Vb; and
· Capping operations at ESC CMP Vd.
Figure 1.1 Works Schedule for ESC CMP V
1.2
Reporting Period
1.2.1
This Monthly
EM&A Report for
January 2021 covers the EM&A
activities for the reporting month of January 2021.
1.3
Details of Sampling and
Laboratory Testing Activities
1.3.1
The following monitoring activities
were undertaken for ESC CMP V in January 2021:
· Water Column Profiling of ESC CMP Vb;
· Routine Water Quality Monitoring of ESC CMPs;
· Pit Specific Sediment Chemistry of ESC CMP Vb; and
· Demersal Trawling for ESC CMPs.
1.4
Details of Outstanding
Sampling and/or Analysis
1.4.1
No outstanding sampling remained
for January 2021.
1.4.2
The following analyses are in
progress and will be presented in the corresponding quarterly report:
· Species identification of the biota samples collected from Demersal Trawling for ESC CMPs in January 2021.
1.5
Brief Discussion of the
Monitoring Results for ESC CMP V
1.5.1
Brief discussion of the monitoring results of the following
activities for ESC CMP V is presented in this Monthly
EM&A Report for January 2021:
· Water Column Profiling of ESC CMP Vb;
· Routine Water Quality Monitoring of ESC CMPs; and
· Pit Specific Sediment Chemistry of ESC CMP Vb.
1.5.2
Water Column Profiling of ESC CMP Vb
– January 2021
1.5.3
Water Column Profiling was undertaken at a total of two sampling stations
(Upstream and Downstream stations) on 6 January 2021. The monitoring results 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 2010 - 2019 from stations in the Northwestern Water Control Zone (WCZ), where the ESC CMPs
are located ([3]).
For Salinity, the averaged value obtained from the Reference (Upstream) station
was used for the basis as the WQO. Levels of Dissolved Oxygen (DO) and
Turbidity were also assessed for compliance with the Action and Limit Levels
(see Table B1 of Annex B for
details).
In-situ
Measurements
1.5.4
Analyses of results for January 2021
indicated that levels of Salinity, pH and DO complied with the WQOs at both
Downstream and Upstream stations (Table B2 of Annex B). Levels of DO and Turbidity at all stations complied
with the Action and Limit Levels (Tables B1 and B2 of Annex B).
Laboratory Measurements for
Suspended Solids (SS)
1.5.5
Analyses of results for January 2021
indicated that the SS levels at both Downstream and Upstream stations complied
with the WQO and the Action and Limit Levels (Tables
B1 and B2 of Annex B).
1.5.6
Overall, the monitoring results
indicated that the mud disposal operation at ESC CMP Vb
did not appear to cause any deterioration in water quality during this
reporting period.
1.5.7
Routine Water Quality Monitoring of ESC CMPs – January 2021
1.5.8
Routine Water Quality Monitoring of ESC CMPs was undertaken on 5 January 2021. The monitoring results have been assessed for compliance
with the WQOs (see Section
1.5.3 for details). The
monitoring results are shown in Tables B3 and B4 of Annex B and Figures
1 - 10 of Annex
C.
A total of ten (10) monitoring stations were sampled in January 2021 as shown
in Figure 1.2.
In-situ
Measurements
1.5.9
Graphical presentation of the
monitoring results (Temperature, DO, pH, Salinity and Turbidity) is shown in Figures 1 - 6 of Annex C. Analyses of results indicated that the levels of pH,
Salinity and DO complied with the WQOs at all stations in January 2021.
1.5.10
The levels of DO and Turbidity complied with the Action and
Limit Levels at all stations (Table B3 of Annex B; Figures 3 and 6 of Annex C).
1.5.11
Overall, in-situ measurement results of the Routine
Water Quality Monitoring indicated that the
disposal and capping operation at ESC CMPs did not appear to cause any unacceptable
impacts in water quality in January 2021.
Laboratory
Measurements
1.5.12
Laboratory analysis of January 2021
results indicated that concentrations of Arsenic, Chromium, Copper, Lead,
Nickel and Zinc were detected in January 2021 samples at most stations and
their concentrations were generally similar across stations (Table B4 of Annex
B; Figure
7 of Annex
C).
1.5.13
For nutrients, concentrations of
Total Inorganic Nitrogen (TIN) at all stations complied with the WQO (0.5 mg/L)
(Table B4 of Annex B; Figure
8 of Annex
C), except for Impact and Ma Wan
stations. It should be noted that due to the effect of the Pearl River,
the North Western WCZ has historically experienced higher levels of TIN ([4]).
Therefore, the exceedances of TIN WQO at these stations are unlikely to be
caused by the disposal operation at ESC CMPs. The concentrations of
Ammonia Nitrogen (NH3-N) were higher at Ma Wan station in January
2021 (Table B4 of Annex B; Figure
8 of Annex
C). The concentrations of
Biochemical Oxygen Demand (BOD5) were lower at Impact stations (Table B4 of Annex
B; Figure
9 of Annex
C).
1.5.14
Analyses of results for January 2021
indicated that the SS levels at most stations complied with the WQO (12.8
mg/L), except for Ma Wan station. The SS levels at all stations complied
with the Action and Limit Levels (Tables B1 and B4 of Annex B; Figure
10 of Annex
C).
Overall, results
of the Routine Water Quality Monitoring indicated that the disposal and capping operation at
ESC CMPs did not appear to cause any unacceptable deterioration in water
quality in January 2021. Detailed statistical analysis will be presented
in the Quarterly Report to investigate any spatial and temporal trends of
potential concern.
1.5.15
Pit Specific Sediment Chemistry of ESC CMP Vb – January 2021
1.5.16
Monitoring locations for Pit Specific Sediment Chemistry for ESC CMP Vb are shown in Figure 1.3. A total of six (6) monitoring stations were
sampled on 4 January 2021.
1.5.17
The concentrations of most inorganic contaminants were lower
than the Lower Chemical Exceedance Levels (LCELs) at most stations, except for Arsenic (Figures 11 and 12 of Annex C). The concentrations of Arsenic were higher than the
LCEL at Near-Pit stations ESC-NNCA and
ESC-NNCB, Pit-Edge station ESC-NECA, Active-Pit stations ESC-NPCA and ESC-NPCB.
1.5.18
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 ([5]).
It is presumed that the natural concentrations of Arsenic are similar in
onshore and offshore sediments ([6]), and relatively high Arsenic
levels may thus occur throughout Hong Kong. Therefore, the LECL
exceedances of Arsenic are unlikely to be caused by the disposal operations at
ESC CMP Vb but rather as a result of naturally occurring
deposits.
1.5.19
For organic
contaminants, the concentrations of Total Organic Carbon (TOC) were higher at
Near-Pit station ESC-NNCA and Pit-Edge station ESC-NECA
in January 2021 (Figure
13 of Annex C). The concentrations of Low Molecular Weight and High
Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) were lower than the LECLs at
all stations (Figure
14 of Annex C). The concentrations of Tributyltin (TBT) were
higher at Active-Pit stations ESC-NPCA and ESC-NPCB (Figure 15 of Annex C). The
concentrations of Total Polychlorinated Biphenyls (PCBs), Total dichloro-diphenyl-trichloroethane
(DDT) and 4,4’-dichlorodiphenyldichloroethylene (DDE)
were below the limit of reporting at all stations in January 2021.
1.5.20
Overall,
there is no evidence indicating any unacceptable environmental impacts to
sediment quality outside the pit area as a result of the contaminated mud
disposal operations at ESC CMP Vb in January 2021.
1.5.21
Statistical
analysis will be undertaken and presented in the corresponding quarterly report
to investigate whether there are any unacceptable impacts in the area caused by
the contaminated mud disposal.
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 2021 for ESC CMP V (see Annex
A for the sampling schedule):
· Water Column Profiling of ESC CMP Vb;
· Routine Water Quality Monitoring of ESC CMPs;
· Pit Specific Sediment Chemistry of ESC CMP Vb;
· Cumulative Impact Sediment Chemistry of ESC CMPs;
· Sediment Toxicity Tests of ESC CMPs; and
· Demersal Trawling for ESC CMPs.
1.7
Study Programme
1.7.1
A summary of the Study Programme is
presented in Annex D.
([1]) ERM (2013) Final Report. Submitted under Agreement No. CE 4/2009 (EP) Environmental Monitoring and Audit for Contaminated Mud Pit at East Sha Chau. For CEDD.
([2]) ERM (2017) Final Report. Submitted under Agreement No. CE 23/2012 (EP) Environmental Monitoring and Audit for Contaminated Mud Pits to the South of The Brothers and at East Sha Chau (2012 - 2017). For CEDD.