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 A Sampling Schedule
Annex B Water Quality Monitoring Results
Annex C Graphical Presentations
Annex D Study Programme
Environmental Monitoring and Audit
for Disposal Facility to the East of Sha Chau (2017-2020) - Investigation
MONTHLY EM&A REPORT FOR December 2020
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 December 2020, 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
December 2020 covers the EM&A activities for
the reporting month of December 2020.
1.3
Details of Sampling and
Laboratory Testing Activities
1.3.1
The following monitoring activities
were undertaken for ESC CMP V in December 2020:
· Water Column Profiling of ESC CMP Vb;
· Routine Water Quality Monitoring of ESC CMPs;
· Pit Specific Sediment Chemistry of ESC CMP Vb; and
· Cumulative Impact Sediment Chemistry of ESC CMPs.
1.4
Details of Outstanding
Sampling and/or Analysis
1.4.1
No outstanding sampling remained
for December 2020.
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 December 2020:
· Water Column Profiling of ESC CMP Vb;
· Routine Water Quality Monitoring of ESC CMPs;
· Pit Specific Sediment Chemistry of ESC CMP Vb; and
· Cumulative Impact Sediment Chemistry of ESC CMPs.
1.5.2
Water Column Profiling of ESC CMP Vb – December 2020
1.5.3
Water Column Profiling was undertaken at a total of two sampling stations (Upstream
and Downstream stations) on 3 December 2020. 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 ([1]).
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 December
2020 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 December
2020 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 – December 2020
1.5.8
Routine Water Quality Monitoring of ESC CMPs was undertaken on 4 December 2020. 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 December 2020 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 December 2020.
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 December 2020.
Laboratory Measurements
1.5.12
Laboratory analysis of December 2020
results indicated that concentrations of Arsenic, Chromium, Copper, Lead,
Nickel and Zinc were detected in December 2020 samples at most stations. The
concentrations of Arsenic, Chromium, Lead and Zinc were generally similar
across stations; the concentrations of Nickel were higher at Impact stations;
and the concentrations of Copper were higher at Ma Wan station (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). The
concentrations of Ammonia Nitrogen (NH3-N) were similar across all stations in
December 2020 (Table B4 of Annex B; Figure 8 of Annex C). The
concentrations of Biochemical Oxygen Demand (BOD5) were lower at Ma Wan
stations (Table B4 of Annex B; Figure 9 of Annex C).
1.5.14
Analyses of results for December
2020 indicated that the SS levels at Impact, Intermediate, and Reference and Ma
Wan stations were higher than the WQO (12.8 mg/L), but all stations complied
with the Action and Limit Levels (Tables B1 and B4 of Annex B; Figure 10 of Annex C).
Considering the higher values were recorded not only at Impact and intermediate
stations, but also at Reference and Ma Wan stations, the exceedances of SS WQO at these stations were unlikely to
be caused by the disposal operation at ESC CMPs.
1.5.15
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
December 2020. Detailed statistical analysis will be presented in the
Quarterly Report to investigate any spatial and temporal trends of potential
concern.
1.5.16
Pit Specific Sediment Chemistry of ESC CMP Vb –
December 2020
1.5.17
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 7 December 2020.
1.5.18
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 station ESC-NNCA,
Pit-Edge station ESC-NECA, Active-Pit stations ESC-NPCA and ESC-NPCB.
1.5.19
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 ([4]). It is presumed that the natural
concentrations of Arsenic are similar in onshore and offshore sediments ([5]),
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.
1.5.20
For organic contaminants, the concentrations
of Total Organic Carbon (TOC) were higher at Active-Pit stations ESC-NPCA and ESC-NPCB in December
2020 (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
Near-Pit and Pit-Edge stations. However, the concentrations of Low Molecular
Weight PAHs and the concentrations of High
Molecular Weight PAHs were higher than the LCEL at Active-Pit stations ESC-NPCA
and ESC-NPCB (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 December 2020.
1.5.21
Considering
that the higher levels of TOC, TBT, Low
Molecular Weight and High Molecular Weight PAHs occurred within Active-Pit
stations ESC-NPCA and ESC-NPCB only, 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 December 2020.
1.5.22
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.
1.5.23
Cumulative Impact Sediment Chemistry of ESC CMPs –
December 2020
1.5.24
Monitoring locations for Cumulative
Impact Sediment Chemistry for ESC CMPs are shown in Figure 1.4. A total of nine (9) monitoring stations were
sampled on 8 and 9 December 2020.
1.5.25
Analyses of results for the Cumulative Impact Sediment Chemistry Monitoring indicated that the concentrations of most inorganic
contaminants were below the LCEL at most
stations in December 2020, except
concentrations of Arsenic were higher than the LCEL at Mid-field stations
ESC-RMA, ESC-RMB, Near-field station ESC-RNB1, Capped Pit stations ESC-RCA1,
ESC-RCB1 and Ma Wan station (Figures 16 and 17 of Annex C). As
discussed in Section 1.5.19, 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.
1.5.26
For organic contaminants, the
concentrations of TOC were higher at Far-field stations ESC-RFA and ESC-RFB (Figure 18 of Annex C). The
concentrations of TBT were higher at Ma Wan station (Figure
19 of Annex C). The
concentrations of High Molecular Weight PAHs were below LECL (Figure 20 of Annex C). The
concentrations of Total PCBs, Total DDT, 4,4’- DDE and Low Molecular Weight PAHs were below
the limit of reporting at all stations in December 2020.
1.5.27
Overall,
there is no evidence indicating any unacceptable environmental impacts to
sediment quality as a result of the contaminated mud disposal operations at ESC
CMP Vb in December 2020. 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 January 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; 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.