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 JuLy 2019
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 July 2019, disposal of contaminated mud at
ESC CMP Vd was undertaken.
Figure 1.1 Works Schedule for ESC CMP V
1.2
Reporting Period
1.2.1
This Monthly EM&A Report for July 2019 covers
the EM&A activities for the reporting month of July 2019.
1.3
Details of Sampling and Laboratory Testing Activities
1.3.1
The
following monitoring activities were undertaken for ESC CMP V in July 2019:
· Water Column
Profiling of ESC CMP Vd;
· Routine Water
Quality Monitoring of ESC CMPs;
· Pit Specific
Sediment Chemistry of ESC CMP Vd; and
· Demersal
Trawling for ESC CMPs
1.4
Details of Outstanding Sampling and/or Analysis
1.4.1
No
outstanding sampling remained for July
2019.
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 July 2019.
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 July 2019:
· Water Column
Profiling of ESC CMP Vd;
· Routine Water
Quality Monitoring of ESC CMPs; and
· Pit Specific Sediment
Chemistry of ESC CMP Vd.
1.5.2
Water Column Profiling of ESC CMP Vd
– July 2019
1.5.3
Water
Column Profiling was undertaken at a total of two sampling stations (Upstream and
Downstream stations) on 11 July 2019. 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
2008 - 2017 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 July 2019 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
for July 2019 indicated that the SS levels at both Downstream and Upstream
stations were 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 Vd
did not appear to cause any deterioration in water quality during this
reporting period.
1.5.7
Routine Water Quality Monitoring of
ESC CMP V – July 2019
1.5.8
Routine
Water Quality Monitoring of ESC CMP V
was undertaken on
12 July 2019. 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 July 2019 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 July 2019
indicated that the levels of pH, Salinity and DO generally complied with the
WQOs at most stations (Impact, Intermediate, Reference and Ma Wan stations) in
July 2019, except higher levels of Salinity were recorded at Ma Wan station and
lower levels of Salinity were recorded at Impact stations as well as the levels
of DO were lower than the WQO at Intermediate, Reference and Ma Wan
stations.
1.5.10
However,
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 Vd did not appear to cause any unacceptable impacts in
water quality in July 2019.
Laboratory
Measurements
1.5.12
Laboratory
analysis of July 2019 results indicated that concentrations of Cadmium and
Silver were below their limit of reporting at all stations. Arsenic,
Chromium, Copper, Lead, Mercury, Nickel and Zinc were detected in July 2019
samples at most stations and the concentrations of these metals and metalloids
were similar amongst the stations (Table B4 of Annex B; Figure 7 of Annex C).
1.5.13
For
nutrients, concentrations of Total Inorganic Nitrogen (TIN) at all stations in
July 2019 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 CMP Vd. Concentrations of Ammonia
Nitrogen (NH3-N) and 5-day Biochemical Oxygen Demand (BOD5)
were generally similar amongst the stations in July 2019 (Table B4 of Annex B; Figure 8 and 9 of Annex C).
1.5.14
Analyses
of results for July 20109 indicated that the SS levels at all stations were
lower than the WQO (10.8 mg/L for wet season) and compiled 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 CMP Vd did not appear to cause any unacceptable deterioration
in water quality in July 2019. 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 Vd – July 2019
1.5.17
Monitoring
locations for Pit Specific
Sediment Chemistry for ESC CMP Vd are shown in Figure
1.3. A total of six (6) monitoring stations were sampled on 3 July 2019.
1.5.18
The
concentrations of most inorganic contaminants were lower than the Lower
Chemical Exceedance Levels (LCELs) at most stations, except concentrations of Arsenic
were slightly higher than the LCEL at Active Pit stations ESC-NPAA and ESC-NPAB
(Figures 11 and 12 of Annex C). 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 Vd but rather as a
result of naturally occurring deposits.
1.5.19
For
organic contaminants, the concentrations of Total Organic Carbon (TOC) varied
between stations in July 2019 and were higher
at Active-Pit stations ESC-NPAA and ESC-NPAB (Figure 13 of Annex C). The
concentrations of Tributyltin (TBT) were higher at Near-Pit station ESC-NNAB in
July 2019 (Figure 14 of Annex C). Low and
High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) , Total Polychlorinated
Biphenyls (PCBs), Total dichloro-diphenyl-trichloroethane (DDT) and
4,4’-dichlorodiphenyldichloroethylene (DDE) concentrations were below the limit
of reporting at all stations.
1.5.20
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 Vd in July 2019. 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 August 2019 for ESC CMP V (see Annex A for the sampling schedule ([7])):
· Water Column
Profiling of ESC CMP Vd;
· Routine Water
Quality Monitoring of ESC CMPs;
· Pit Specific
Sediment Chemistry of ESC CMP Vd;
· Cumulative
Impact Sediment Chemistry of ESC CMP V;
· Sediment
Toxicity Tests of ESC CMP V; and
· Demersal
Trawling for 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