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
22nd MONTHLY PROGRESS REPORT FOR june 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 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 June 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 22nd Monthly Progress Report covers the EM&A activities for the
reporting month of June 2014.
1.3
Details of Sampling and
Laboratory Testing Activities
1.3.1
Water Quality Monitoring during Capping was undertaken for ESC CMPs on 6 June 2014.
1.3.2
The following monitoring activities have been
undertaken for SB CMPs in June 2014:
· Impact Water Quality Monitoring during Dredging Operations was undertaken for CMP 2 three times per week on 3, 5, 7, 9, 11, 13, 16, 18, 20, 23, 25, 27 and 30 June 2014;
· Water Column Profiling for CMP 1 was undertaken on 10 June 2014;
· Pit Specific Sediment Chemistry for CMP 1 was undertaken on 12 June 2014; and
· Cumulative Impact Sediment Chemistry for CMP 1 was undertaken on 17 and 19 June 2014.
1.4
Details of Outstanding Sampling and/or Analysis
1.4.1
No outstanding sampling remained for June 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 May and
June 2014; and
·
Laboratory analyses of sediment samples collected for Cumulative
Impact Sediment Chemistry of CMP 1 in June 2014.
1.4.2
A summary of field activities conducted are presented
in Annex A.
1.5
Brief Discussion of the Monitoring Results for ESC CMPs
1.5.1
Brief discussion of the monitoring
results of the Water Quality Monitoring during Capping of ESC CMPs conducted on 6 June 2014 is presented below.
1.5.2
Water Quality Monitoring during Capping – June 2014
1.5.3
The monitoring results obtained during June 2014
sampling in the wet season have been assessed for compliance with the Water
Quality Objectives (WQOs) through a review of the Environmental Protection
Department (EPD) routine water quality monitoring data for the wet season
period (April to October) of 2003 – 2012 from stations in the North Western
Water Control Zone (WCZ), where ESC CMPs are located. For Salinity, the
average value obtained from the Reference stations was used for the basis as
the WQO. A total of 10 monitoring stations were sampled in June 2014 as
shown in Figure 1.2. Graphical presentation of the monitoring results is provided in
Annex B.
In-situ Measurements
1.5.4
Graphical presentation of the monitoring results is
shown in Figures 1-6 of Annex B. Levels of Dissolved Oxygen (DO), pH and Salinity at
most stations in June 2014 complied with the WQO except for the Salinity at Ma
Wan station. The higher Salinity recorded at Ma
Wan station is likely to be caused by its greater separation distance from the
Pearl River mouth, which is a key source of freshwater inputs in the area, when
compared to the Reference stations.
Laboratory Measurements for Suspended Solids (SS)
1.5.5
Concentrations of SS complied with the WQO at all
stations in June 2014 (Figure 7 of Annex B).
Overall, the results indicated that the capping operations at ESC CMPs
did not appear to cause any unacceptable deterioration in water quality.
1.6
Brief Discussion of the
Monitoring Results for SB CMPs
1.6.1
Brief discussion of the monitoring
results of the following activities for SB CMPs is presented in this 22nd
Monthly Progress Report:
·
Pit Specific Sediment Chemistry of CMP 1 conducted in April 2014;
·
Impact Water Quality Monitoring during Dredging Operations of CMP 2 conducted in June 2014; and
·
Water Column Profiling of CMP 1 conducted on 10 June 2014.
1.6.2
Pit Specific Sediment Chemistry of CMP 1 – April 2014
1.6.3
Monitoring locations for Pit Specific
Sediment Chemistry for CMP 1 are shown in Figure 1.3. A total of six (6) monitoring stations were sampled in April
2014.
1.6.4
The concentrations of most inorganic contaminants were lower than the Lower Chemical Exceedance
Level (LCEL) at all stations except for Arsenic in April 2014 (Figures 8-9 of Annex B). Concentrations of Arsenic exceeded the LCEL at most
stations except for Active Pit stations SB-NPAA and SP-NPAB.
1.6.5
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.
1.6.6
For organic contaminants, the concentration of Total Organic Carbon
(TOC) was similar amongst stations with no consistent spatial trend in April
2014 (Figure
10 of Annex B.
Concentrations of Tributyltin (TBTs) were observed to
be higher at Active Pit station SB-NPAB in April 2014 (Figure 11 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
12 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 April 2014.
1.6.7
Active Pit station SB-NPAB is located within CMP 1 which was receiving
contaminated mud during the reporting period. Therefore, the higher
concentrations of contaminants recorded at this 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.
1.6.8
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 April 2014.
1.6.9
Impact Water Quality Monitoring during Dredging
Operations of CMP 2 – June 2014
1.6.10
Impact Water Quality Monitoring during Dredging Operations of CMP 2 was conducted three times per week from 3 to 30 June 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 1.4. Sampling at station THB2 during mid-ebb tides of 11 and 23 June
2014, during mid-flood tide of 16 June 2014 as well as during both mid-flood
and mid-ebb tides of 7 and 25 June 2014 were cancelled due to adverse weather
condition.
1.6.11
Monitoring results are presented in Table C1 of Annex C. Daily dredging volume in June 2014 is reported in Annex D. Levels of DO, Turbidity and 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 occasion of exceedances
shown in Table 1.1 below.
Table 1.1 Details of Exceedances Recorded at CMP 2 between 3 and 30 June 2014
|
Date |
Tide |
Parameter |
Station |
Type |
|
7 June 2014 |
Mid-Ebb |
Bottom DO |
DS2 |
Action |
|
7 June 2014 |
Mid-Ebb |
Bottom DO |
WSR45C |
Action |
|
13 June 2014 |
Mid-Flood |
SS |
DS1 |
Action |
1.6.12
Action Level exceedances of
bottom DO were recorded at stations DS2 and WSR45C during mid-ebb tide on 7
June 2014. Stations DS2 and WSR45C are located further away from the
works area of CMP 2 when compared to station DS1 at which the levels of bottom
DO did not exceed the Action and Limit Levels during the same tidal
period. In addition, these Action Level exceedances
of bottom DO were recorded during one tidal period only and the dredging rate
was well within the limit as specified under the EP, it is considered that the exceedances were isolated sporadic event which may be
caused by natural background variation in water quality characteristics of the
monitoring area. As such, the exceedances at stations
DS2 and WSR45C are not likely to be caused by the dredging works at CMP 2.
Action Level Exceedance of SS was recorded at station DS1 only which is located at the boundary of the works area during one tidal period on 13 June 2014, and given that the dredging rate was well within the limit as specified under the EP, it is considered that the exceedance was not indicating any unacceptable impacts from the dredging operations to the nearby Water Sensitive Receivers (WSRs).
1.6.13
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.
1.6.14
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.
1.6.15
Water Column Profiling of CMP 1 – June 2014
1.6.16
Water Column Profiling was undertaken at a total of two
sampling stations (Upstream and Downstream stations) on 10 June 2014. The water quality monitoring results have been assessed for
compliance with the WQOs as discussed in Section 1.5.3. 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
1.6.17
Analyses of results for June 2014 indicated that
levels of Salinity, pH and DO complied with the WQOs at both Downstream and
Upstream stations (Table C4 of Annex C). DO and
Turbidity also complied with the Action and Limit Levels.
Laboratory Measurements for SS
1.6.18
Analyses of results for June 2014 indicated that the
SS levels at Downstream and Upstream stations complied with the WQO and the
Action and Limit Levels (Table C4 of Annex C).
1.6.19
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.
1.7
Activities Scheduled for the
Next Month
1.7.1
The following monitoring activities will be conducted
in the next monthly period of July 2014 for SB CMPs:
l Impact Water Quality Monitoring during Dredging Operations of CMP 2;
l Pit Specific Sediment Chemistry of CMP 1;
l Routine Water Quality Monitoring of CMP 1;
l Water Column Profiling of CMP 1; and
l Demersal Trawling of CMP 1.
1.7.2
No monitoring activities are scheduled to be
undertaken in the next monthly period of July 2014 for ESC CMPs.
1.7.3
The sampling schedule is presented in Annex A.
1.8
Study Programme
1.8.1
A summary of the Study programme is presented in Annex E
([1])
According to the Management Framework of Dredged/ Excavated Sediment of ETWB
TC(W) No. 34/2002, contaminated sediment in general shall mean those sediment
requiring Type 2 – Confined Marine Disposal as determined according to this
TC(W).
([2])
CAD options may involve use of excavated borrow pits,
or may involve purpose-built excavated pits. CAD sites are those which
involve filling a seabed pit with contaminated mud and capping it with
uncontaminated material such that the original seabed level is restored and the
contaminated material is isolated from the surrounding marine environment.7
([3])
Detailed Site Selection Study for a Proposed Contaminated Mud Disposal Facility
within the Airport East/ East of Sha Chau Area
(Agreement No. CE 12/2002(EP))
([4])
Under the CEDD study Contaminated Sediment Disposal Facility to the South of
The Brothers (Agreement No. FM 2/2009)
([5]) ERM (2012) Environmental Monitoring and Audit
(EM&A) Manual. Final First Review. Environmental Monitoring and Audit
for Contaminated Mud Pits to the South of the Brothers and at East Sha Chau (2012-2017) – Investigation. Agreement No. CE 23/2012(EP). Submitted to EPD in November 2012.
([6]) ERM (2010) Environmental Monitoring and Audit
(EM&A) Manual. Final Second Review. Environmental Monitoring and
Audit for Contaminated Mud Pit at Sha Chau
(2009-2013) – Investigation. Agreement No. CE 4/2009(EP). Submitted to EPD in
November 2010.
([7]) Sewell RJ (1999) Geochemical
Atlas of Hong Kong. Geotechnical Engineering Office, Government of the
Hong Kong Special Administrative Region