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 August 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 August 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 August 2019 covers the EM&A activities for
the reporting month of August 2019.
1.3
Details of Sampling and Laboratory
Testing Activities
1.3.1
The
following monitoring activities were undertaken for ESC CMP V in August 2019:
· 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;
· Demersal Trawling for ESC CMPs; 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 August
2019.
1.4.2
The following laboratory analyses
were still in progress during the preparation of this monthly report and hence
is not presented in this monthly report:
· Laboratory analyses of sediment samples collected for Cumulative Impact Sediment Chemistry of ESC CMP V in August 2019.
1.4.3
The
following analyses are in progress and will be presented in the corresponding
quarterly report:
· Laboratory analyses for Sediment Toxicity Test of ESC CMP V in August 2019; and
· Species identification of the biota samples collected from Demersal Trawling for ESC CMPs in August 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 August 2019:
· Water Column Profiling of ESC CMP Vd;
· Routine Water Quality Monitoring of ESC CMPs;
· Pit Specific Sediment Chemistry of ESC CMP Vd; and
· Sediment Chemistry after a Major Storm of ESC CMP V.
1.5.2
Water
Column Profiling of ESC CMP Vd – August 2019
1.5.3
Water
Column Profiling was undertaken at a total of two sampling stations (Upstream and
Downstream stations) on 13 August 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 August 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 August 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 – August 2019
1.5.8
Routine
Water Quality Monitoring of ESC CMP V
was undertaken on
8 August 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
ten (10) monitoring stations were sampled in August 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 August 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
August 2019, except higher levels of Salinity were recorded at Ma Wan
station.
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 Vd did not appear to cause any unacceptable impacts in
water quality in August 2019.
Laboratory Measurements
1.5.12
Laboratory
analysis of August 2019 results indicated that concentrations of Cadmium,
Mercury and Silver were below their limit of reporting at all stations.
Arsenic, Chromium, Copper, Lead, Nickel and Zinc were detected in August 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
August 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 August 2019 (Table B4 of Annex B; Figure 8 and 9 of Annex C).
1.5.14
Analyses
of results for August 2019 indicated that the SS levels at all stations were
lower than the WQO (10.8 mg/L for wet season) and 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 CMP Vd did not appear to cause any unacceptable deterioration
in water quality in August 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 – August 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 5 August 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 and
Copper were slightly higher than the LCEL at Active Pit stations ESC-NPAB and
ESC-NPAA, respectively (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. In addition, slight exceedance of
Copper was recorded within one Active-Pit station ESC-NPAA only but not at the
Pit-Edge and Near-Pit stations.
1.5.19
For
organic contaminants, the concentrations of Total Organic Carbon (TOC) varied
between stations in August 2019 and were
generally higher at Active-Pit stations ESC-NPAA and ESC-NPAB (Figure 13 of
Annex C). The concentrations of Tributyltin (TBT) were higher
at Active-Pit station ESC-NPAA in August 2019 (Figure 14 of
Annex C). Low 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. High Molecular Weight PAHs were detected at
Near-Pit station ESC-NNAB and Pit-Edge ESC-NEAA in the reporting month (Figure
15 of Annex C).
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 August 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.
1.5.21
Sediment
Chemistry after a Major Storm of ESC CMP V – August 2019
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 7 August 2019 after the visit of tropical cyclone Wipha, which led to the issue of No. 8 Gale Signal on 31 July 2019. The track of Wipha are shown in Figure 1.5.
Figure 1.5 Track of
Tropical Cyclone Wipha (Source:
Hong Kong Observatory)
1.5.22
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 Capped Pit stations ESC-RCA and ESC-RCB,
Mid-field stations ESC-RMA and ESC-RMB and Near-field station ESC-RNB as well
as Copper at Ma Wan Station in August 2019 (Figures 16 and 17 of Annex C).
1.5.23
As
mentioned in Section
1.5.18, it is presumed
that the natural concentrations of Arsenic are similar in onshore and offshore
sediments, and relatively high Arsenic levels may thus occur throughout Hong
Kong. Therefore, the slight exceedances of LCEL
for Arsenic are unlikely to be caused by the disposal of contaminated mud at
ESC CMPs but rather as a result of naturally occurring deposits. For the
exceedance of Copper, it was only recorded at Ma Wan Station but not the other
monitoring stations.
1.5.24
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 2019.
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 2019 for ESC CMP V (see Annex A for the sampling schedule ([7])):
· Water Column Profiling of ESC CMP Vd; and
· Pit Specific Sediment Chemistry of ESC CMP V.
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