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 September 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 September 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 September 2019 covers the EM&A
activities for the reporting month of September 2019.
1.3
Details of Sampling and Laboratory Testing Activities
1.3.1
The
following monitoring activities were undertaken for ESC CMP V in September
2019:
· Water Column Profiling of ESC CMP Vd; and
· Pit Specific Sediment Chemistry of ESC CMP Vd.
1.4
Details of Outstanding Sampling and/or Analysis
1.4.1
No outstanding sampling remained for September
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 September 2019:
· Water Column Profiling of ESC CMP Vd in September 2019;
· Pit Specific Sediment Chemistry of ESC CMP Vd in September 2019; and
· Cumulative Impact Sediment Chemistry of ESC CMPs in August 2019.
1.5.2
Water Column Profiling of ESC CMP Vd – September 2019
1.5.3
Water
Column Profiling was undertaken at a total of two sampling stations (Upstream and
Downstream stations) on 17 September 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 September 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 September 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 Pit Specific Sediment Chemistry of ESC CMP Vd – September 2019
1.5.8 Monitoring locations for Pit Specific Sediment Chemistry for ESC CMP Vd are shown in Figure 1.2. A total of six (6) monitoring
stations were sampled on 16 September 2019.
1.5.9 The concentrations of most inorganic
contaminants were lower than the Lower Chemical Exceedance Levels (LCELs) at
most stations, except for Arsenic, Copper and Silver at Active-Pit stations (Figures 1 and 2 of Annex C). The
concentrations of Arsenic were higher than the LCEL at Active-Pit station
ESC-NPAA. The concentrations of Copper were higher than the LCEL at
Active-Pit stations ESC-NPAA and ESC-NPAB. The concentrations of Silver
were higher than the LCEL at Active-Pit station ESC-NPAB.
1.5.10 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 Vd
but rather as a result of naturally occurring deposits.
1.5.11 Considering that the higher levels of Copper and Silver
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 Vd in September 2019.
1.5.12 For
organic contaminants, the concentrations of Total Organic Carbon (TOC) varied
between stations in September 2019 and were higher
at Active-Pit stations ESC-NPAA and ESC-NPAB (Figure 3 of
Annex C). The concentrations of Tributyltin (TBT) were also
higher at Active-Pit stations ESC-NPAA and ESC-NPAB in September 2019 (Figure 4 of
Annex C). Low Molecular Weight Polycyclic Aromatic
Hydrocarbons (PAHs), High Molecular Weight 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.
1.5.13 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 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.
1.5.14 Cumulative Impact Sediment Chemistry of ESC CMPs –
August 2019
1.5.15 Monitoring locations for
Cumulative Impact Sediment Chemistry for ESC CMPs are shown in Figure
1.3. A total of nine (9) monitoring stations were sampled on 20 and
21 August 2019.
1.5.16 Analyses of results for the Cumulative Impact Sediment Chemistry Monitoring indicated that the concentrations
of most inorganic contaminants were below the LCEL at most stations in August 2019, except
concentrations of Arsenic were higher than the LCEL at Near-field station
ESC-RNB, Mid-field stations ESC-RMA and ESC-RMB, Capped Pit station ESC-RCB and
Ma Wan station and concentrations of Zinc were higher than the LCEL at Ma Wan
station (Figures 5 and 6 of Annex C). As discussed in Section 1.5.10, the LCEL 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. The LCEL
exceedance of Zinc was only recorded in Ma Wan station but not in other
stations located closer to ESC CMP Vd.
Therefore, the LCEL exceedance of Zinc is unlikely to be caused by disposal
operations at ESC CMP Vd.
1.5.17 For organic contaminants, the
concentrations of TOC varied between stations in August 2019, with the generally
higher concentrations of TOC recorded at Far-field station ESC-RFA (Figure 7 of Annex C). The concentrations of TBT were generally similar against stations, except at Man Wan Station
where higher concentrations were recorded (Figure 8 of Annex C). Low Molecular Weight PAHs,
High Molecular Weight 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.
1.5.18
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.
1.6
Activities Scheduled for the Next Month
1.6.1
The following monitoring activities will be
conducted in the next monthly period of October 2019 for ESC CMP V (see Annex A for the sampling schedule ([6])):
· Water Column Profiling of ESC CMP Vd;
· Routine Water Quality Monitoring of ESC CMPs; 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.
([4]) Sewell RJ (1999) Geochemical Atlas of Hong Kong. Geotechnical Engineering Office, Government of the Hong Kong Special Administrative Region