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
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 August 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 August 2020 covers the EM&A
activities for the reporting month of August 2020.
1.3
Details of Sampling and Laboratory Testing Activities
1.3.1
The following
monitoring activities were undertaken for ESC CMP V in August 2020:
· Water Column Profiling of ESC CMP Vb;
· Routine Water Quality Monitoring of ESC CMPs;
· Water Quality Monitoring During Capping of ESC CMPs;
· Pit Specific Sediment Chemistry of ESC CMP Vb;
· Cumulative Impact Sediment Chemistry of ESC CMPs;
· Sediment Chemistry after a Major Storm of ESC CMP V;
· Sediment Toxicity Tests of ESC CMP V; and
· Demersal Trawling for ESC CMPs.
1.4
Details of Outstanding Sampling and/or Analysis
1.4.1
No outstanding sampling remained for August 2020.
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 August 2020; and
· Sediment Toxicity Tests of ESC CMPs in August 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 August 2020:
· Water Column Profiling of ESC CMP Vb;
· Routine Water Quality Monitoring of ESC CMPs;
· Water Quality Monitoring During Capping of ESC CMPs;
· Pit Specific Sediment Chemistry of ESC CMP Vb;
· Cumulative Impact Sediment Chemistry of ESC CMPs; and
· Sediment Chemistry after a Major Storm of ESC CMP V.
1.5.2
Water Column Profiling of ESC CMP Vb – September 2020
1.5.3
Water Column Profiling was undertaken at a total of two
sampling stations (Upstream and Downstream stations) on 11 August 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 wet season period (April to October) 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 August 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 August 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 – August 2020
1.5.8
Routine Water Quality Monitoring of ESC CMPs was undertaken on 4 August 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
sixteen (16) monitoring stations were sampled in August 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 for August 2020
indicated that the levels of pH, Salinity and DO complied with the WQOs at all
stations in August 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 August 2020.
Laboratory
Measurements
1.5.12
Laboratory
analysis of August 2020 results indicated that concentrations of Arsenic,
Cadmium, Chromium, Copper, Lead, Mercury, Nickel and Zinc were detected in
August 2020 samples at all stations and the concentrations of most metals and
metalloids were similar amongst the stations, except the concentrations of
Nickel and Lead were higher at Intermediate stations, the concentrations of
Chromium and Mercury were higher at Impact stations when compared to other
stations (Table B4 of Annex B; Figure 7 of Annex C). Some of the values for Copper and Zinc were found to be outliers and
thus excluded from analysis.
1.5.13
For nutrients, concentrations of Total Inorganic Nitrogen (TIN) at all
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 higher at Ma Wan station in August
2020 (Table B4 of Annex B; Figure 8 of Annex C). The concentrations of
Biochemical Oxygen Demand (BOD5) were lower at Ma Wan station (Table B4 of Annex B; Figure 9 of Annex C).
1.5.14
Analyses of
results for August 2020 indicated that the SS levels at Intermediate and Impact
stations were higher than the WQO, and 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).
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 August 2020.
Detailed statistical analysis will be presented in the Quarterly Report to
investigate any spatial and temporal trends of potential concern.
1.5.16
Water Quality Monitoring during
Capping of ESC CMPs – August 2020
1.5.17
The monitoring results obtained during August 2020 sampling in the wet
season have been assessed for compliance with the WQOs (see Section 1.5.3 for details). A total of ten
(10) monitoring stations were sampled on 10 August 2020 as shown in Figure
1.3.
In-situ Measurements
1.5.18
Graphical
presentation of the monitoring results (Temperature, DO, pH, Salinity and
Turbidity) is shown in Figures
11-16 of Annex C. Levels of pH and DO at all
stations in August 2020 complied with the WQO, while the Levels of Salinity
were higher than WQO at Ma Wan Station (Table B5 of Annex B). Levels of DO and Turbidity complied with the Action
and Limit levels at all stations (Tables B1 and B5 of Annex B). The higher Salinities
recorded at Ma Wan station are likely to be caused by the larger separation
distance to Pearl River mouth, which release a large amount of freshwater
runoff in the area during wet season, when compared to the Reference
stations.
Laboratory Measurements for Suspended Solids (SS)
1.5.19
Concentrations of
SS complied with the WQO and the Action and Limit Levels at all stations in
August 2020 (Table B5 of Annex B; Figure 17 of Annex C).
1.5.20
Overall, results
of the Water Quality Monitoring during Capping of ESC CMPs indicated that the
capping operation at ESC CMP Vd did not appear to
cause any unacceptable deterioration in water quality in August 2020. Further statistical analysis will be
undertaken in the quarterly report to investigate whether the capping
operations at ESC CMP Vd is causing any unacceptable
deterioration in water quality of the area.
1.5.21
Pit Specific Sediment Chemistry of
ESC CMP Vb – August 2020
1.5.22
Monitoring
locations for Pit Specific
Sediment Chemistry for ESC CMP Vb are shown in Figure
1.4. A total of six (6) monitoring stations were sampled on 12 August 2020.
1.5.23
The concentrations of most inorganic contaminants were lower than the
Lower Chemical Exceedance Levels (LCELs) at most stations, except for Arsenic (Figures
18 and 19 of Annex C). The
concentrations of Arsenic were higher than the LCEL at Pit-Edge station ESC-NECA and
Active-Pit station ESC-NPCB.
1.5.24
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.
1.5.25
For organic
contaminants, the concentrations of Total Organic Carbon (TOC) were higher at
Active-Pit stations ESC-NPCA and ESC-NPCB in August 2020 (Figure 20 of Annex C). The concentrations of Low Molecular Weight and High
Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) were lower than the LCELs at all
stations (Figure 21 of Annex C).
The concentrations of Tributyltin (TBT) were higher
at Active-Pit stations ESC-NPCA and ESC-NPCB (Figure 22 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 August 2020.
1.5.26
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
August 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.
1.5.27
Cumulative Impact Sediment Chemistry
of ESC CMPs – August 2020
1.5.28
Monitoring
locations for Cumulative Impact Sediment Chemistry for ESC CMPs are shown in Figure
1.5. A total of nine (9) monitoring stations were sampled on 5 and 6
August 2020.
1.5.29
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 August 2020, except concentrations of Arsenic were higher than the
LCEL at Mid-field stations ESC-RMA, ESC-RMB and Capped Pit station ESC-RCB1 (Figures 23 and 24 of Annex C). As discussed in Section 1.5.24, 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.
1.5.30
For organic contaminants, the concentrations of TOC and TBT varied between
stations in August 2020, with the generally higher concentrations of TOC and
TBT recorded at Ma Wan station (Figure 25 and 26 of Annex C). The concentrations of Total PCBs, Total DDT, 4,4’- DDE, Low Molecular Weight and High
Molecular Weight PAHs were below the
limit of reporting at all stations in August 2020.
1.5.31
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
August 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.
1.5.32
Sediment Chemistry after a Major
Storm of ESC CMP V – August 2020
Sampling for Sediment Chemistry after a Major Storm Event was conducted at nine (9) monitoring stations (see Figure 1.4 for the locations of the monitoring stations) on 21 August 2020 after the visit of tropical cyclone Higos, which led to the issue of No. 9 Gale or Storm Signal on 19 August 2020. The track of higos are shown in Figure 1.6.
Figure 1.6 Track of
Tropical Cyclone Higos (Source: Hong Kong
Observatory)
1.5.33
Analyses of
results for the Sediment
Chemistry after a Major Storm indicated that the concentrations of most inorganic contaminants were
below the LCEL, except Arsenic at Near-field station ESC-RNB1, Mid-field stations
ESC-RMA and ESC-RMB, Far-field stations ESC-RFA and ESC-RFB and Ma Wan Station
in August 2020 (Figures 27 and 28 of Annex C).
1.5.34
As discussed in Section
1.5.24, 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.
Overall, there appeared to be no evidence showing the failure of ESC CMP V in retaining disposed mud or causing contamination of sediments after the major storm event in August 2020.
1.6
Activities Scheduled for the Next Month
1.6.1
The following monitoring activities will be conducted
in the next monthly period of September 2020 for ESC CMP V (see Annex A for the sampling schedule ([7])):
· Water Column Profiling of ESC CMP Vb; and
· Pit Specific Sediment Chemistry of ESC CMP Vb.
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