Agreement No. CE 63/2016 (EP)
Environmental Monitoring and Audit
for Disposal Facility to the East of Sha Chau
(2017-2020) - Investigation
MONTHLY EM&A REPORT FOR October 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 October 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 October 2020 covers the EM&A
activities for the reporting month of October 2020.
1.3
Details of Sampling and Laboratory Testing Activities
1.3.1
The following
monitoring activities were undertaken for ESC CMP V in October 2020:
·
Water Column Profiling of ESC CMP Vb;
· Routine Water
Quality Monitoring of ESC CMPs;
· Pit Specific
Sediment Chemistry of ESC CMP Vb; and
· Sediment Chemistry
after a Major Storm of ESC CMP V.
1.4
Details of Outstanding
Sampling and/or Analysis
1.4.1
No outstanding sampling remained for October 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 October 2020:
· Water Column
Profiling of ESC CMP Vb;
· Routine
Water Quality Monitoring of ESC CMPs;
· Pit Specific Sediment
Chemistry of ESC CMP Vb; and
· Sediment Chemistry
after a Major Storm of ESC CMP V.
1.5.2
Water Column Profiling of ESC CMP Vb – October 2020
1.5.3
Water Column Profiling was undertaken at a total of two
sampling stations (Upstream and Downstream stations) on 6 October 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 October 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 October 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 – October 2020
1.5.8
Routine Water Quality Monitoring of ESC CMPs was undertaken on 8 October 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 October 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 October 2020 indicated that the levels of pH,
Salinity and DO complied with the WQOs at all stations in October 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 October 2020.
Laboratory Measurements
1.5.12
Laboratory
analysis of October 2020 results indicated that concentrations of Arsenic,
Chromium, Copper, Lead, Mercury and Zinc were detected in October 2020 samples
at most stations and the concentrations of most metals and metalloids were
similar amongst the stations, except the concentrations of Zinc and Lead 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
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 station in October 2020 (Table B4 of Annex B; Figure 8 of Annex C). The concentrations of Biochemical Oxygen Demand (BOD5) were
lower at Impact station (Table B4 of Annex
B; Figure 9 of Annex
C).
1.5.14
Analyses of
results for October 2020 indicated that the SS levels at all stations compiled
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 October 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 – October 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 October 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 and Copper (Figures
11 and 12 of Annex C). The concentrations of Arsenic were higher than the
LCEL at Pit-Edge
station ESC-NECA, Active-Pit stations ESC-NPCA and ESC-NPCB. The concentrations of Copper were higher than LCEL at Active-Pit station 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 October 2020 (Figure
13 of Annex
C). The concentrations of Low
Molecular Weight and High Molecular Weight Polycyclic Aromatic Hydrocarbons
(PAHs) were higher 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 October 2020.
1.5.21
Considering that the higher levels of Copper, 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 October 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
Sediment Chemistry after a Major
Storm of ESC CMP V – October 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 16 October 2020 after the
visit of tropical cyclone Nangka, which led to the issue
of No. 8 Gale or Storm Signal on 13 October 2020. The track
of Nangka are shown in Figure 1.5.
Figure 1.5 Track of
Tropical Cyclone Nangka (Source:
Hong Kong Observatory)
1.5.24
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 Mid-field station ESC-RMA, Far-field station
ESC-RFB, Capped Pit Station ESC-RCA1 and Ma Wan Station in October 2020 (Figures 16 and 17 of Annex
C).
1.5.25
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.
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 October 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 November 2020 for ESC CMP V (see Annex
A for the sampling schedule ([7])):
· Water Column
Profiling of ESC CMP Vb;
· Routine Water
Quality Monitoring of ESC CMPs; 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