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 november 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
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 November 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 November 2020 covers the EM&A
activities for the reporting month of November 2020.
1.3
Details of Sampling and Laboratory Testing Activities
1.3.1
The following
monitoring activities were undertaken for ESC CMP V in November 2020:
· Water Column Profiling of ESC CMP Vb;
· Routine Water Quality Monitoring of ESC CMPs; and
· Pit Specific Sediment Chemistry of ESC CMP Vb.
1.4
Details of Outstanding Sampling and/or Analysis
1.4.1
No outstanding sampling remained for November
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 November 2020:
· 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 – November 2020
1.5.3
Water Column Profiling was undertaken at a total of two
sampling stations (Upstream and Downstream stations) on 3 November 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
2009 - 2018 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 November 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
November 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 – November 2020
1.5.8
Routine Water Quality Monitoring of ESC CMPs was undertaken on 5 November 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 November 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 November 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
operation at ESC CMP Vb did not appear to cause any
unacceptable impacts in water quality in November 2020.
Laboratory Measurements
1.5.12
Laboratory
analysis of November 2020 results indicated that concentrations of Arsenic,
Chromium, Copper, Lead, Nickel and Zinc were detected in November 2020 samples
at most stations and the concentrations of Zinc, Chromium, Lead, Nickel and
Copper were higher at Ma Wan and Reference stations (Table B4 of Annex B; Figure 7 of Annex C).
1.5.13
For nutrients, concentrations of Total Inorganic Nitrogen (TIN) at Ma Wan
and Reference stations were higher than the WQO (0.5 mg/L) (Table B4 of Annex B; Figure 8 of Annex C). 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 similar across all stations in November 2020 (Table B4 of Annex B; Figure 8 of Annex C). The concentrations of Biochemical Oxygen Demand (BOD5) were
higher at Reference stations (Table B4 of Annex B; Figure 9 of Annex C).
1.5.14
Analyses of
results for November 2020 indicated that the SS levels at all stations complied
with the WQO and the Action and Limit Levels (Tables B1 and B4 of Annex B; Figure 10 of Annex C).
1.5.15
Overall, results
of the Routine
Water Quality Monitoring indicated that the disposal operation at ESC CMPs did not appear to
cause any unacceptable deterioration in water quality in November 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 – November 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 4 November 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 Pit-Edge station ESC-NECA and
Active-Pit stations 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 ([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.
1.5.20
For organic
contaminants, the concentrations of Total Organic Carbon (TOC) were higher at
Active-Pit stations ESC-NPCA and ESC-NPCB
in November 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
were higher than the Upper Chemical Exceedance Level (UCEL) 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 November 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 November 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.
1.6
Activities Scheduled for the Next Month
1.6.1
The following monitoring activities will be
conducted in the next monthly period of December 2020 for ESC CMP V (see Annex A for the sampling schedule ([7])([8])):
· 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.
1.7
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.
(5) Sewell RJ (1999) Geochemical Atlas of Hong Kong. Geotechnical Engineering Office, Government of the Hong Kong Special Administrative Region
(6) Whiteside PGD (2000) Natural geochemistry and contamination of marine sediments in Hong Kong. In: The Urban Geology of Hong Kong (ed Page A & Reels SJ). Geological Society of Hong Kong Bulletin No. 6, p109-121
(8) 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 will be effective for the EM&A activities since December 2020. The latest sampling schedule is provided in Annex A.