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 2018
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). Detailed works
schedule for ESC CMP V and SB CMPs is shown in Figure
1.1. In
October 2018, the following work was being undertaken:
¡P Disposal of contaminated mud at ESC CMP Vd.
Figure 1.1 Works Schedule for ESC CMP V and SB
CMPs
1.2
Reporting Period
1.2.1
This Monthly
EM&A Report for
October 2018 covers the EM&A
activities for the reporting month of October 2018.
1.3
Details of Sampling and
Laboratory Testing Activities
1.3.1
The following monitoring
activities were undertaken for ESC CMP V in October 2018:
¡P
Water Column Profiling of ESC CMP Vd;
¡P
Routine Water Quality Monitoring of ESC CMPs; and
¡P
Pit Specific Sediment Chemistry of ESC CMP Vd.
1.3.2
No monitoring activities were
scheduled to be undertaken for SB CMP in October 2018.
1.4
Details of Outstanding
Sampling and/or Analysis
1.4.1
No outstanding sampling remained for October 2018.
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:
¡P Laboratory analyses of sediment samples collected for Pit Specific Sediment Chemistry of ESC CMP
Vd in October 2018.
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
2018:
¡P
Water Column Profiling of ESC CMP Vd in October 2018;
¡P
Routine Water Quality Monitoring of ESC CMPs in October
2018;
¡P
Pit Specific Sediment Chemistry of ESC CMP Vd in September
2018; and
¡P
Sediment Chemistry after a Major Storm of ESC CMP V in September 2018.
1.5.2
Water
Column Profiling of ESC CMP Vd ¡V October 2018
1.5.3
Water Column Profiling
was undertaken at a total of two sampling stations (Upstream and Downstream
stations) on 3 October 2018. 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 2007 - 2016
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 2018 indicated that levels of Salinity
and pH complied with the WQOs at both Downstream and
Upstream stations and levels of DO were higher than the WQO (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 October
2018 indicated that the SS levels complied with the WQO and
the Action and Limit Level at both Downstream and Upstream stations (Tables
B1 and B2 of Annex B).
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.
1.5.6
Routine
Water Quality Monitoring of ESC CMP V ¡V October 2018
1.5.7
Routine Water Quality Monitoring of ESC CMP V was undertaken on
2 October 2018. 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 2018
as shown in Figure
1.2.
In-situ
Measurements
1.5.8
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 2018 indicated that the levels of pH, Salinity and DO complied with the WQOs at all stations (Impact,
Intermediate, Reference and Ma Wan stations) in October 2018.
1.5.9
The levels of DO and Turbidity
also complied with the Action and Limit Levels at all stations (Table
B3 of Annex B; Figures
3 and 6 of Annex
C).
1.5.10
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 October 2018.
Laboratory Measurements
1.5.11
Laboratory analysis of October
2018 results indicated that concentrations of Cadmium, Chromium, Silver and
Mercury were below their limit of reporting at all stations. Arsenic, Nickel, Lead, Copper and Zinc were detected in October 2018 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).
1.5.12
For nutrients, concentrations of
Total Inorganic Nitrogen (TIN) at most stations in October 2018 were higher than the WQO, except
at Ma Wan station (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
October 2018 (Table B4 of Annex B; Figure 8 and
9 of Annex
C).
1.5.13
Analyses of results for October 2018 indicated
that the SS levels at most stations were
lower than the WQO (10.8 mg/L for wet season),
except the exceedance of SS recorded at the Impact stations. However, the SS
levels complied with the Action and Limit Levels at all stations (Tables B1 and B4 of Annex
B; Figure 10 of Annex C).
1.5.14
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 October 2018.
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 Vd ¡V September 2018
1.5.16
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 6 September 2018.
1.5.17
The concentrations of all
inorganic contaminants were lower than the Lower Chemical Exceedance Level (LCEL) at all stations in September 2018 (Figures 11 and
12 of Annex C).
1.5.18
For organic contaminants, the
concentrations of Total Organic Carbon (TOC) were generally similar in
September 2018, except higher concentrations of TOC were recorded at the
Active-Pit station ESC-NPAA (Figure 13 of Annex C). The concentration of Tributyltin
(TBT) was generally similar amongst stations in September 2018 (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 most stations in September 2018, except High Molecular Weight PAHs
were detected at Pit-Edge station ESC-NEAA (Figure 15 of Annex C).
1.5.19
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 September
2018. 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.
1.5.20
Sediment
Chemistry after a Major Storm of ESC CMP
V ¡V September
2018
1.5.21
Sampling for Sediment Chemistry
after a Major Storm Event was conducted at nine (9) monitoring stations (Figure 1.4)
on 20 September 2018 after the visit of tropical cyclone Mangkhut, which led to
the issue of No. 10 Hurricane Signal on 16 September 2018. The track of Mangkhut are shown in Figures 1.5.
Figure
1.5 Track of
Tropical Cyclone Mangkhut (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 station ESC-RCB and
Mid-field stations ESC-RMA and ESC-RMB in September 2018 (Figures 16 and 17 of Annex C).
1.5.23
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 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.
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 September 2018.
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 2018
for ESC
CMP V (see Annex A for the sampling schedule):
¡P
Water Column Profiling of ESC CMP Vd;
¡P
Routine Water Quality Monitoring of ESC CMPs; and
¡P
Pit Specific Sediment Chemistry of ESC CMP Vd.