Agreement No. CE 23/2012 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pits to the South of The Brothers
and at
20TH MONTHLY PROGRESS REPORT FOR April
2014
1.1
Background
1.1.1
Since early 1990s, contaminated sediment ([1])
arising
from various construction works (e.g. dredging and reclamation projects) in Hong Kong has been disposed of at a series of seabed pits
at East of Sha Chau
(ESC). In late 2008, a review indicated
that the existing and planned facilities at ESC would not be able to meet the
disposal demand after 2012. In order to
meet this demand, the Hong Kong Special Administrative Region Government
(HKSARG) decided to implement a new contained aquatic disposal (CAD) ([2])
facility at
the South of The Brothers (SB CMPs) which had been
under consideration for a number of years.
1.1.2
The environmental acceptability of the construction and
operation of the Project had been confirmed by findings of the associated
Environmental Impact Assessment (EIA) study completed in 2005 under Agreement No. CE 12/2002(EP) ([3]).
The Director of Environmental Protection (DEP) approved this EIA report
under the Environmental
Impact Assessment Ordinance (Cap. 499) (EIAO) in September 2005 (EIA Register No.: AEIAR-089/2005).
1.1.3
In accordance with the EIA recommendation, prior to
commencement of construction works for the SB CMPs,
the Civil Engineering and Development Department (CEDD) undertook a detailed
review and update of the EIA findings for the SB site ([4]). Findings of the EIA review undertaken in
2009/ 2010 confirmed that the construction and operation of the SB site had
been predicted to be environmentally acceptable.
1.1.4
Environmental
Permits (EPs)
(EP-312/2008/A and EP-427/2011A) were issued by the Environmental
Protection Department (EPD) to the CEDD, the Permit Holder, on 28 November 2008
for ESC CMP V and on 23 December 2011 for SB CMPs,
respectively. Under the requirements of
the EPs, an Environmental
Monitoring and Audit (EM&A) programme as set out in the EM&A Manuals ([5])
([6])
is required
to be implemented for the CMPs.
1.1.5
The present EM&A programme
undertaken under Agreement
No. CE 23/2012 (EP) covers the dredging,
disposal and capping operations of the SB CMPs as well as ESC CMPs. Detailed works schedule for both CMPs is shown in Figure 1.1.
In April 2014, the following works were being undertaken at the CMPs:
·
Capping
was being undertaken at ESC CMP IVc and CMP Va;
·
Disposal of
contaminated mud was taking place at SB CMP 1; and
·
Dredging
operations were taking place at SB CMP 2.
Figure 1.1 Works
Schedule for ESC CMPs and SB CMPs
1.2
Reporting Period
1.2.1
This 20th
Monthly Progress Report covers the EM&A activities for
the reporting month of April 2014.
1.3
Details of Sampling and
Laboratory Testing Activities
1.3.1
The following monitoring
activities have been undertaken for SB CMPs in April
2014:
·
Impact Water Quality Monitoring during Dredging
Operations was undertaken for CMP 2 three
times per week on 2, 4, 7, 9, 11, 14, 16, 18, 22, 24, 26, and29 April 2014;
·
Routine Water Quality Monitoring for CMP 1 was undertaken on 3 April 2014;
·
Water Column Profiling for CMP 1 was undertaken on 8 April 2014; and
·
Pit Specific Sediment Chemistry was undertaken for CMP 1 on 8 April 2014.
No monitoring activity was
undertaken for ESC CMPs in April 2014.
1.4
Details of Outstanding Sampling and/or Analysis
1.4.1
No outstanding sampling
remained for
April 2014. The following
laboratory analyses were still in progress during the preparation of this
monthly report and hence were not presented in this monthly report:
·
Laboratory analyses of sediment samples collected for Pit Specific Sediment
Chemistry of CMP 1
in March and April 2014; and
·
Laboratory analyses of sediment samples collected for Cumulative
Impact Sediment Chemistry of CMP 1
in February 2014.
1.4.2
A summary of field activities
conducted are presented in Annex
A.
1.5
Brief Discussion of the Monitoring Results for SB CMPs
1.5.1
Brief
discussion of the monitoring results of the following activities is presented
in this 20th Monthly Progress Report:
·
Pit Specific Sediment Chemistry of CMP 1 conducted in January and
February 2014;
·
Cumulative Impact Sediment Chemistry of CMP 1 conducted in February 2014;
·
Routine Water Quality Monitoring of CMP 1 undertaken on 3 April 2014;
·
Water Column Profiling of CMP 1 conducted on 8 April 2014;
and
·
Impact Water Quality Monitoring during Dredging Operations of CMP 2 conducted
from 2 to 29 April 2014.
1.5.2
Pit Specific
Sediment Chemistry of CMP 1 – January and February 2014
1.5.3
Monitoring locations for Pit Specific
Sediment Chemistry for CMP 1 are shown in Figure 1.2. A total of six (6) monitoring stations were
sampled in January and February
2014.
1.5.4
The
concentrations of most inorganic contaminants were
lower than the Lower Chemical Exceedance Level (LCEL)
at all stations except Arsenic, Copper and Silver in both January and February 2014
(Figures 1-2 and 6-7 of
Annex B). Concentrations of Arsenic exceeded the LCEL
at all stations except Active Pit station SB-NPAB while concentrations of
Copper and Silver exceeded the LCEL at Active Pit station SB-NPAA.
1.5.5
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 ([7]). It is presumed that
the natural concentrations of Arsenic are similar in onshore and offshore
sediments ([8]),
and relatively high Arsenic levels may thus occur throughout Hong
Kong . Therefore, the LCEL exceedances of Arsenic are unlikely to be caused by the
disposal operations at CMP 1 but rather as a result of naturally occurring
deposits.
1.5.6
Active Pit station SB-NPAA where LCEL exceedances of Copper and Silver are recorded is located
within CMP 1 which was receiving contaminated mud during the reporting
period. Therefore, the higher
concentration of contaminants recorded at the Active Pit station only are not
considered as indicating any dispersal of contaminated mud from CMP 1. Nevertheless, detailed analyses will be
presented in the Quarterly
Report to reveal any trend of increasing sediment contaminant concentrations
towards CMP 1.
1.5.7
For organic contaminants, the concentration of Total
Organic Carbon (TOC) was similar amongst stations with no consistent spatial
trend in January and February 2014 (Figures 3 and 8 of Annex
B). Concentrations of Tributyltin (TBTs) were observed
to be higher at Active Pit station SB-NPAA in January and February 2014 (Figures 4 and 9 of Annex B). Low and High Molecular Weight Polycyclic
Aromatic Hydrocarbons (Low and High MW PAHs)
concentrations were recorded below the limit of reporting at all stations
except Active Pit station SB-NPAA (Figures 5 and 10 of Annex
B). Total Dichloro-Diphenyl-Trichloroethane
(DDT), 4,4’-Dichloro-Diphenyl-Dichloroethylene (4,4’-DDE) and Total
Polychlorinated Biphenyls (PCBs) were recorded below the limit of reporting at
all stations in January and February 2014.
1.5.8
As discussed in Section 1.5.6 above, the higher concentrations of
contaminants (including metals and organic contaminants) recorded at the Active
Pit stations only are not considered as indicating any dispersal of
contaminated mud from CMP 1.
1.5.9
Overall, there is no evidence indicating any
unacceptable environmental impacts to sediment quality as a result of the
contaminated mud disposal operations at CMP 1 in January and February 2014.
1.5.10
Cumulative Impact
Sediment Chemistry of CMP 1 – February 2014
1.5.11
Monitoring locations for Cumulative
Impact Sediment Chemistry for CMP 1
are shown in Figure 1.3. A total of eleven (11) monitoring stations
were sampled in February 2014.
1.5.12
Analyses of results for the Cumulative Impact
Sediment Chemistry Monitoring indicated that the concentrations
of all metals, except Arsenic, were below the LCEL
in February
2014 (Figures 11 and
12 of Annex B).
Concentrations of Arsenic in sediments from most
stations exceeded the LCEL, except for Near Field station SB-RNB and Mid Field
station SB-RMB.
1.5.13
As discussed in Section 1.5.5,
the LCEL exceedances of Arsenic are unlikely to be
caused by the disposal operations at CMP 1 but rather as a result of naturally
occurring deposits.
1.5.14
For organic contaminants, concentration of TOC at Tai Ho Bay
Station 2 (THB2) was recorded to be higher than other stations (Figure 13 of Annex B). Concentrations of TBT were recorded to be
higher at Near-field station SB-RNB and Ma Wan station (Figure 14 of Annex
B). Total DDT, 4,4’-DDE, total PCBs as well as Low and High MW PAHs were recorded below the limit of reporting at all
stations.
1.5.15
Overall, there is no evidence indicating any
unacceptable environmental impacts to sediment quality as a result of the
contaminated mud disposal operations at CMP 1 during this monthly period.
1.5.16
Impact Water
Quality Monitoring during Dredging Operations of CMP 2 – April 2014
1.5.17
Impact Water Quality Monitoring during Dredging
Operations of CMP 2 was conducted three times per week
from 2 to 29 April 2014 during the reporting period. The laboratory analysis of SS from 26 to 29
April 2014 is in progress during the preparation of this report and the SS data
from 26 to 29 April 2014 will be presented in the 21st Monthly
Progress Report.
1.5.18
On each survey day, sampling was
conducted during both mid-ebb and mid-flood tides at two Reference (Upstream)
stations and five Impact (Downstream) stations of the dredging operations at
CMP 2. Monitoring was also
conducted at five Sensitive Receiver Stations situated in Ma Wan, Shum Shui Kok, Tai Mo To and Tai Ho
Bay. A total of twelve stations were
monitored and locations of the sampling stations are shown in Figure 1.4. Sampling at station THB2 during mid-flood
tide of 26 April 2014 was cancelled due to adverse weather condition.
1.5.19
Monitoring results are presented in Table C1 of Annex C. Daily dredging volume in April 2014 is
reported in Annex D. Levels of Dissolved Oxygen (DO), Turbidity
and Suspended Solids (SS) generally complied with the Action and Limit Levels
(see Table
C2 of Annex C for
details) set in the Baseline Monitoring Report ([9]),
except for the following occasions of exceedance
shown in Table 1.1
below.
Table 1.1 Details of Exceedances
Recorded at CMP 2 in April 2014
|
Date |
Tide |
Parameter |
Station |
Type |
|
2 April 2014 |
Mid-Ebb |
SS |
DS1 |
Action |
|
|
|
SS |
WSR46 |
Action |
1.5.20
Action Level exceedances
of SS were recorded at stations DS1 and WSR46 during mid-flood tide on 2 April
2014. Since station DS1 was located at
the boundary of the works area, the exceedance at DS1
station did not appear to indicate any unacceptable water quality impacts
outside the works area of the Project.
In addition, station WSR46 is located further away from the works area
of CMP 2 when compared to station DS2-4 at which the levels of SS did not
exceed the Action and Limit Levels. As
such, the exceedance at station WSR46 is not likely
to be caused by the dredging works at CMP 2.
1.5.21
It should be noted that high levels
of SS were occasionally recorded during baseline monitoring which are
considered to be sporadic events and characteristic of water quality in this
area of Hong Kong (baseline monitoring data
are summarised in Table C3 of Annex
C). Therefore, the
Action and Limit Level exceedances may be caused by
natural background variation in water quality of the area.
1.5.22
Overall, the results indicated that
the dredging operations at CMP 2 did not appear to cause any unacceptable
deterioration in water quality during this reporting period. Therefore, no further mitigation measures,
except for those recommended in the Environmental Permit (EP-427/2011/A),
are considered necessary for the dredging operations.
1.5.23
Routine Water
Quality Monitoring of
SB CMP 1 – April 2014
1.5.24
The monitoring results
for the Routine Water Quality Monitoring
conducted in April 2014 in the wet season have been assessed for compliance
with the Water Quality Objectives (WQOs) set by
EPD. This
consists of a review of the EPD routine water quality monitoring data for the
wet season period (April to October) of 2003-2012 from stations in the Northwestern Water Control Zone, where the CMPs are located.
For Salinity, the averaged value obtained from the Reference stations
was used for the basis as the WQO. Levels
of DO, Turbidity and SS were also assessed for compliance with the Action and
Limit Levels (see Table C2 of Annex C
for details). The monitoring results are
shown in Figures 15-20 of Annex B and
Tables
C4-C5
of Annex C.
1.5.25
Locations of monitoring stations
are presented in Figure 1.5. Sampling at station THB2 was
cancelled due to adverse weather condition
In-situ
Measurements
1.5.26
Analyses of
results for April 2014 indicated that the levels of pH and DO complied with the
WQOs at all stations (Impact, Intermediate, Reference
and Water Sensitive Receiver stations) in April 2014. The levels of Salinity complied with WQO at
most stations except for Intermediate and Ma Wan stations (Figures 15, 16 and 18 of Annex B). The higher salinities recorded
at Intermediate and Ma Wan stations are likely to be caused by its larger
separation distance from the Pearl River
mouth, which is a key source of freshwater inputs in the area, when compared to
the Reference stations.
1.5.27
The levels of DO and Turbidity
complied with the Action and Limit Levels at all stations (Figures 16
and 19
of Annex B;
Tables
C4 of Annex
C).
Laboratory
Measurements
1.5.28
Analyses of April 2014 results
indicated that concentrations of Arsenic, Cadmium, Mercury and Silver were
below their limit of reporting at all stations. Chromium, Copper,
Lead, Nickel
and Zinc were detected in samples from all stations (Figure 20 of Annex B). Concentrations of Chromium, Lead and Zinc
appeared to be similar amongst all stations while concentration of Copper was
lower at Sensitive Receiver stations. Concentration of Nickel was lower at
Intermediate station when compared to the concentration recorded as other
station.
1.5.29
For inorganic contaminants, concentrations of Total
Inorganic Nitrogen (TIN) at all stations exceeded the WQO (Figure 22 of Annex
B). It is important to note that
due to the effect of the Pearl River, the North Western WCZ has
historically experienced higher levels of TIN ([10])
. Therefore, the exceedances
of TIN WQO at all stations are unlikely to be caused by the disposal operation
at CMP 1. Levels of 5-day
Biochemical Oxygen Demand (BOD5) were noted to be lower at the
Impact and Intermediate stations (Figure 21 of Annex B). Ammoniacal-Nitrogen (NH3-N) concentration was relatively
similar amongst all stations (Figure 22 of Annex B). Concentrations of SS exceeded the WQO (12.00
mg/L for wet season) at all stations except Ma Wan station. SS at all stations
complied with the Action and Limit Levels except for Tai Mo To
(WSR46) station during the reporting period (Figure 23 of Annex B; Table C5 of Annex C). As discussed in Section 1.5.21,
the WQO and Action level exceedances of SS are
considered to be sporadic and characteristic of water quality in this area of Hong Kong .
1.5.30
Overall, results of the Routine Water
Quality Monitoring indicated that the disposal operation at CMP 1 did not
appear to cause any unacceptable deterioration in water quality in April 2014.
1.5.31
Water Column
Profiling of CMP 1 – April
2014
1.5.32
Water Column Profiling was
undertaken at a total of two sampling stations (Upstream and Downstream
stations) on 10 April 2014. The
water quality monitoring results have been assessed for compliance with the WQOs . The monitoring results were
also compared with the Action and Limit Levels set in
Baseline
Monitoring Report (see Table C2 of Annex C
for details).
In-situ
Measurements
1.5.33
Analyses of results for April 2014
indicated that levels of Salinity, pH and DO complied with the WQOs at both Downstream and Upstream stations (Table C6 of Annex C). DO and Turbidity also complied with the
Action and Limit Levels.
Laboratory
Measurements for SS
1.5.34
Analyses of results for April 2014
indicated that the SS levels at Downstream and Upstream stations complied with
the WQO and the Action and Limit Levels (Table C6 of Annex C).
1.5.35
Overall, the monitoring results
indicated that the mud disposal operation at CMP 1 did not appear to cause any
deterioration in water quality during this reporting period.
1.6
Activities Scheduled for the
Next Month
1.6.1
The following monitoring activities
will be conducted in the next monthly period of May 2014 for SB CMPs:
·
Impact Water Quality Monitoring during Dredging
Operations of CMP 2;
·
Pit Specific Sediment Chemistry of CMP 1;
·
Routine Water
Quality Monitoring of CMP 1; and
·
Water Column Profiling of CMP 1.