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) - Investigation
21st MONTHLY PROGRESS REPORT FOR May
Since early 1990s, contaminated sediment ()
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) ()
the South of The Brothers (SB CMPs) which had been
under consideration for a number of years.
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) ().
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).
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 (). 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.
(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 ()
to be implemented for the CMPs.
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 May 2014, the following works were being undertaken at the CMPs:
was being undertaken at ESC CMP IVc and CMP Va;
contaminated mud was taking place at SB CMP 1; and
operations were taking place at SB CMP 2.
Figure 1.1 Works
Schedule for ESC CMPs and SB CMPs
Monthly Progress Report covers the EM&A activities for
the reporting month of May 2014.
Details of Sampling and
Laboratory Testing Activities
The following monitoring
activities have been undertaken for SB CMPs in May
Impact Water Quality Monitoring during Dredging Operations
was undertaken for CMP 2 three
times per week on 1, 3, 5, 7, 9, 12, 14, 16, 19, 21, 23, 26, 28 and 30 May
Pit Specific Sediment Chemistry was undertaken for CMP 1 on 8 May 2014;
Routine Water Quality Monitoring for CMP 1 was undertaken on 13 May 2014; and
Water Column Profiling for CMP 1 was undertaken on 15 May 2014.
No monitoring activity was
undertaken for ESC CMPs in April 2014.
No outstanding sampling
May 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 April and May 2014; and
A summary of field activities
conducted are presented in Annex
of the monitoring results of the following activities is presented in this 21st
Monthly Progress Report:
· Pit Specific Sediment
Chemistry of CMP 1 conducted
in March 2014;
· Impact Water Quality
Monitoring during Dredging Operations of CMP 2 conducted from 26 April to
30 May 2014;
Routine Water Quality Monitoring of CMP 1 undertaken on 13 May 2014;
Water Column Profiling of CMP 1 conducted on 16 May 2014.
Sediment Chemistry of CMP 1 – March 2014
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 March 2014.
concentrations of most inorganic contaminants were lower
than the Lower Chemical Exceedance Level (LCEL) at
all stations except Arsenic in March 2014 (Figures 1-2 of Annex B). Concentrations of Arsenic exceeded the LCEL
at all stations except Near Pit station SB-NNAB and Active Pit station
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 (). It is presumed that
the natural concentrations of Arsenic are similar in onshore and offshore
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
For organic contaminants, the concentration of Total
Organic Carbon (TOC) was similar amongst stations with no consistent spatial
trend in March 2014 (Figure 3 of Annex B). Concentrations of Tributyltin
(TBTs) were observed to be higher at Active Pit
stations SB-NPAA and SB-NPAB in March 2014 (Figure 4 of Annex
B). High Molecular Weight
Polycyclic Aromatic Hydrocarbons (High MW PAHs)
concentrations were recorded below the limit of reporting at all stations
except at Active Pit station SB-NPAB (Figure 5 of Annex
B). Low MW PAHs,
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
Active Pit stations SB-NPAA and SB-NPAB are located
within CMP 1 which was receiving contaminated mud during the reporting
period. Therefore, the higher
concentration of contaminants recorded at the Active Pit stations 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.
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 March 2014.
Quality Monitoring during Dredging Operations of CMP 2 – 26 April to 30 May
Impact Water Quality Monitoring during Dredging
Operations of CMP 2 was conducted three times per week
from 26 April to 30 May 2014 during the reporting period. 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 1.3. Sampling at station THB2 during mid-flood
tides of 26 April, 19 and 21 May 2014 as well as during both mid-flood and
mid-ebb tides of 9, 12, 16 and 23 May 2014 were cancelled due to adverse
Monitoring results are presented in Table C1 of Annex C. Daily dredging volume in May 2014 is reported
in Annex D. Levels of Dissolved Oxygen (DO), Turbidity
and Suspended Solids (SS) generally complied with the Action and Limit Levels
C2 of Annex C for
details) set in the Baseline Monitoring Report (),
except for the following occasion of exceedance shown
Table 1.1 Details of Exceedances
Recorded at CMP 2 between 26 April and 31 May 2014
16 May 2014
Action Level exceedance
of SS was recorded at stations DS2 during mid-ebb tide on 16 May 2014. Station DS2 is located further away from the
works area of CMP 2 when compared to station DS1 at which the levels of SS did
not exceed the Action and Limit Levels.
As such, the exceedance at station DS2 is not
likely to be caused by the dredging works at CMP 2.
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.
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.
Quality Monitoring of
SB CMP 1 – May 2014
The monitoring results for
Water Quality Monitoring conducted in May 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 6-15 of Annex
B and Tables C4-C5 of Annex C.
Locations of monitoring stations
are presented in Figure 1.4. Sampling at station THB2 was cancelled
due to adverse weather condition
results for May 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 May 2014 (Figures 6-7 of Annex B). The levels of Salinity exceeded WQO at
Impact, Intermediate, Tai Mo To and Tai Ho Bay stations (Figure 9 of Annex B). The lower salinities recorded
at these stations are likely to be caused by the close proximity to the nearby
streams, which release a large amount of freshwater runoff in the area during
flooding, when compared to the Reference stations.
The levels of DO and Turbidity
complied with the Action and Limit Levels at all stations (Figures 7
of Annex B;
C4 of Annex
Analyses of May 2014 results
indicated that concentrations of Cadmium, Mercury and Silver were below their
limit of reporting at all stations. Arsenic, Chromium, Copper,
and Zinc were detected in samples from most stations (Figures 11-12 of Annex B). Concentrations of Arsenic, Chromium, Lead and
Nickel appeared to be similar amongst all stations with no apparent spatial
trend observed (Figure
11 of Annex B). Concentrations of Copper
and Zinc were slightly higher at Ma Wan station when compared to other stations
(Figure 12 of Annex B).
For nutrients, concentrations of Total Inorganic
Nitrogen (TIN) at most stations exceeded the WQO (0.5mg/L) except at Ma Wan
station (Figure 13 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 ()
. Therefore, the exceedances
of TIN WQO at all stations are unlikely to be caused by the disposal operation
at CMP 1. Ammonia Nitrogen (NH3-N)
concentration was relatively similar amongst all stations (Figure 13 of Annex
B). Level of 5-day
Biochemical Oxygen Demand (BOD5) was higher at Ma Wan stations (Figure 14 of Annex B).
Concentrations of SS exceeded the WQO (12.00 mg/L
for wet season) at Reference and Intermediate stations. However, SS at all stations
complied with the Action and Limit Levels during the reporting period (Figure 15 of Annex B; Table C5 of Annex C). As discussed in Section 1.5.13,
the WQO exceedances of SS are considered to be
sporadic and characteristic of water quality in this area of Hong
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 May 2014.
Profiling of CMP 1 – May
Water Column Profiling was
undertaken at a total of two sampling stations (Upstream and Downstream
stations) on 15 May 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
Monitoring Report (see Table C2 of Annex C
Analyses of results for May 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
Analyses of results for May 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).
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.
Activities Scheduled for the
The following monitoring activities will
be conducted in the next monthly period of June 2014 for SB CMPs:
Water Quality Monitoring during Dredging Operations of CMP
Specific Sediment Chemistry of CMP 1;
Impact Sediment Chemistry of CMP 1; and
· Water Column
Profiling of CMP 1.
Water Quality Monitoring for Capping
will be undertaken in the next monthly period of June 2014 for ESC CMPs.
The sampling schedule is presented
in Annex A.
A summary of the Study programme is
presented in Annex E.