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 April 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 April 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 April 2020 covers the EM&A
activities for the reporting month of April 2020.
1.3
Details of Sampling and Laboratory Testing Activities
1.3.1
The following
monitoring activities were undertaken for ESC CMP V in April 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 April 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 April 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 – April 2020
1.5.3
Water Column Profiling was undertaken at a total of two
sampling stations (Upstream and Downstream stations) on 3 April 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 April 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
April 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 – April 2020
1.5.8
Routine Water Quality Monitoring of ESC CMPs was undertaken on 8 April 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 April 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 April 2020
indicated that the levels of pH, Salinity and DO complied with the WQOs at most
stations in April 2020, except the Salinity in Ma Wan was higher than
WQO. 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.
1.5.10
The levels of DO
and Turbidity complied with the Action and Limit Levels at most stations,
except the levels of Turbidity were higher than Action level at Impact stations
(Table B3 of Annex B; Figures 3 and 6 of Annex C). Upon further investigation,
it is noticed that capping activities at ESC CMP Vd
were conducted during the time of sampling on 8 April 2020 and thus the higher
levels of Turbidity recorded at Impact stations could be related to the capping
operation. Considering that the action level
exceedance of Turbidity occurred within Impact stations only but not at the
Intermediate and Ma Wan stations, there is no evidence indicating any
unacceptable environmental impacts to nearby water sensitive receivers as a
result of the mud disposal operations at ESC CMPs in April 2020.
Laboratory Measurements
1.5.11
Laboratory
analysis of April 2020 results indicated that concentrations of Arsenic,
Chromium, Copper, Mercury, Lead, Nickel and Zinc were detected in April 2020
samples at most stations and the concentrations of these metals and metalloids
were similar amongst the stations, except the concentrations of Zinc and Copper
were higher at Ma Wan station and Reference stations, respectively (Table B4 of Annex B; Figure 7 of Annex C).
1.5.12
For nutrients, concentrations of Total Inorganic Nitrogen (TIN) at
Reference, Impact and Intermediate 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 the stations and the
concentrations of 5-day Biochemical Oxygen Demand (BOD5) were
highest at Impact stations in April 2020 (Table B4 of Annex B; Figure 8 and 9 of Annex C).
1.5.13
Analyses of
results for April 2020 indicated that the SS levels at most stations complied with the
Action and Limit Levels, except the SS levels at Impact stations exceeded the
Action level (Tables B1
and B4 of Annex B; Figure 10 of Annex C). As discussed in Section 1.5.10 above, capping activities at ESC
CMP Vd were conducted during the time of sampling on
8 April 2020 and the higher levels of SS recorded at Impact stations could be
related to the capping operation. The action level exceedance was
recorded for Impact stations only but not at the
Intermediate and Ma Wan stations, thus there is no evidence indicating any
unacceptable environmental impacts to nearby water sensitive receivers as a
result of the mud disposal operations at ESC CMPs in April 2020.
1.5.14
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 April 2020. 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 – April 2020
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 2 April 2020.
1.5.17
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 stations ESC-NECA &
ESC-NECB, while the concentrations of Copper were higher than the Upper Chemical Exceedance Level (UCEL) at Active-Pit station ESC-NPCB.
1.5.18
For organic contaminants, the concentrations of Total Organic Carbon
(TOC) were higher at Active-Pit stations in April 2020 (Figure 13 of Annex C). The concentrations of Low Molecular Weight and High
Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) were lower than the LCELs at most
stations except at Active-Pit station ESC-NPCB where concentrations of Low Molecular
Weight and High Molecular Weight PAHs were higher than LCELs (Figure 14 of Annex C).
Total Polychlorinated Biphenyls (PCBs) was below the limit of reporting at most
stations except at Active-Pit station ESC-NPCB (Figure
15 of Annex C). The concentrations of Tributyltin (TBT), Total dichloro-diphenyl-trichloroethane
(DDT) and 4,4’-dichlorodiphenyldichloroethylene (DDE)
were below the limit of reporting at all stations in April 2020.
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
Considering that the higher levels of Copper, Low Molecular Weight and High Molecular
Weight PAHs occurred within Active-Pit station ESC-NPCB
only but not at the Pit-Edge and Near-Pit
stations, 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 April 2020.
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 May 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