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 Program
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 March 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 March 2020 covers the EM&A activities for the
reporting month of March 2020.
1.3
Details of Sampling and
Laboratory Testing Activities
1.3.1
The following monitoring activities were undertaken
for ESC CMP V in March 2020:
· Water Column Profiling of ESC CMP Vb; 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 March 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 March 2020:
· Water Column Profiling of ESC CMP Vb; and
· Pit Specific Sediment Chemistry of ESC CMP Vb.
1.5.2
Water Column Profiling of ESC CMP Vb – March
2020
1.5.3 Water Column Profiling was undertaken at a total of two
sampling stations (Upstream and Downstream stations) on 4 March 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]). 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 March 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 March 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
Pit Specific Sediment Chemistry of ESC CMP Vb
– March 2020
1.5.8
Monitoring locations for Pit Specific
Sediment Chemistry for ESC CMP Vb are shown in Figure
1.2. A total of six (6) monitoring
stations were sampled on 3 March 2020.
1.5.9
The concentrations of most inorganic contaminants were
lower than the Lower Chemical Exceedance Levels (LCELs) at most stations, except for Arsenic and Copper (Figures
1 and 2 of Annex C). The concentrations of Arsenic were higher than the
LCEL at Active-Pit station ESC-NPCB,
Pit-Edge stations ESC-NECA and Near-Pit station ESC-NNCA. The
concentrations of Copper were higher than the LCEL at Active-Pit station ESC-NPCB
1.5.10
For organic contaminants, the concentrations of Total Organic
Carbon (TOC) were higher at Active-Pit stations in March 2020 (Figure 3 of Annex C). The
concentrations of Tributyltin (TBT) were below
the limit of reporting at all stations except at Near-Pit station ESC-NNAA (Figure 4 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-NPCA (Figure
5 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 March 2020.
1.5.11 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.
Considering that the higher levels of Copper, Low Molecular Weight and High Molecular Weight PAHs occurred within Active-Pit stations 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 March 2020.
1.5.12
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
April 2020 for ESC CMP V (see Annex A for the sampling schedule ([6]) :
· 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.
([4]) Sewell RJ (1999) Geochemical Atlas of Hong Kong. Geotechnical Engineering Office, Government of the Hong Kong Special Administrative Region