Agreement No. CE 23/2012 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pits to the South of The Brothers
and at
33rd MONTHLY PROGRESS REPORT FOR May 2015
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 May 2015, the following works were
being undertaken at the CMPs:
·
Capping
operations at ESC CMPs;
·
Capping
operations at SB CMP 1; and
·
Disposal of
contaminated mud at SB CMP 2.
Figure 1.1 Works
Schedule for ESC CMPs and SB CMPs
1.2
Reporting Period
1.2.1
This 33rd Monthly Progress
Report covers the EM&A activities for
the reporting month of May 2015.
1.3
Details of Sampling and Laboratory Testing
Activities
1.3.1
No monitoring
activities have been undertaken for ESC CMPs in May 2015.
1.3.2
The following
monitoring activities have been undertaken for SB CMPs
in May 2015:
·
Routine Water Quality Monitoring of CMP 2 was undertaken on 11 May 2015;
·
Pit Specific Sediment Chemistry of CMP 2 was undertaken on 12 May 2015;
and
·
Water Column Profiling of CMP 2 was undertaken on 13 May 2015.
1.4
Details of Outstanding Sampling and/or
Analysis
1.4.1
No outstanding sampling remained for May 2015.
The following laboratory analyses were still in progress during the
preparation of this monthly report and hence are not presented in this monthly
report:
·
Laboratory analyses of sediment samples collected for Pit Specific Sediment Chemistry of CMP 2
in May 2015.
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 for SB CMPs is presented in this
33rd Monthly Progress Report:
·
Routine Water Quality Monitoring of CMP 2 conducted
in April (laboratory measurements) and May 2015;
·
Laboratory analyses of sediment samples collected
for Pit Specific Sediment Chemistry of CMP 2 in April 2015; and
·
Water Column Profiling of CMP 2 undertaken on 13
May 2015.
1.5.2
Routine Water Quality Monitoring of SB CMP 2 – April and May 2015
1.5.3
The monitoring
results for the Routine
Water Quality Monitoring conducted in April and May 2015 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 2004 - 2013 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 Dissolved Oxygen (DO) and Turbidity were also
assessed for compliance with the Action and Limit Levels (see Table C1 of Annex C for details).
The monitoring results are shown in Figures 1-15 of Annex B and Table C2 of Annex
C.
A total of fourteen (14) monitoring
stations were sampled in April 2015 and May 2015 as
shown in Figure
1.2. The in-situ data for April 2015 has been discussed in 32nd Monthly Progress Report.
In-situ
Measurements
1.5.4
Analyses of results for May 2015 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 2015 (Figures
1-5 of Annex B).
However, the levels of Salinity at all stations (Impact, Intermediate
and Water Sensitive Receiver stations) were out of the range of WQO. Salinities at Impact, Intermediate, Ma
Wan, Shum Shui Kok and Tai
Mo To stations exceeded the WQO while salinities at Tai Ho Bay stations were
lower than the WQO. The lower
salinities recorded at Tai Ho Bay and Reference stations are likely due to the
close proximity of the nearby streams, which release large amount of freshwater
runoff in the area during flooding.
The Salinities at other stations were above the WQO as they were located
further away from the Tai Ho Bay and Reference stations which experienced less freshwater
runoff from the nearby streams.
1.5.5
The levels of
DO and Turbidity complied with the Action and Limit Levels at all stations (Figures 3 and 5 of Annex B; Table C1 of Annex C).
1.5.6
Overall, in-situ measurement results of the Routine Water Quality Monitoring indicated that the disposal operation at CMP 2 did not
appear to cause any unacceptable impacts in water
quality in May 2015.
Laboratory
Measurements
Laboratory analysis of April
and May 2015 results indicated that concentrations of Cadmium, Mercury and
Silver were below their limit of reporting at all stations.
Arsenic, Chromium, Copper, Lead, Nickel and Zinc were
detected in April and May 2015 samples and the concentrations were similar
amongst stations (Figures 6-7 and 11-12 of Annex B). Results of laboratory analysis were shown
in Table C3 of Annex C.
1.5.7
For nutrients, concentrations of
Total Inorganic Nitrogen (TIN) at all stations in April 2015 complied the WQO (0.5mg/L) while all station
in May 2015 exceeded the WQO (Figures 8 and 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 ([7])
. In addition, a
higher TIN concentration was recorded at Reference stations than Impact
station. Therefore, the exceedances of TIN WQO at all stations in May were unlikely
to be caused by the disposal operation at CMP 2. Ammonia Nitrogen (NH3-N) concentration
was relatively similar amongst all stations (Figures 8 and 13 of Annex
B). Levels of 5-day Biochemical Oxygen Demand
(BOD5) appear to be higher at Shum Shui Kok, Tai Mo To and Tai Ho Bay 2 stations in April 2015 and
at Impact stations in May 2015 (Figures 9 and 14 of Annex
B).
1.5.8
Concentrations of SS exceeded the
WQO (11.6 mg/L for wet season) at Tai Mo To and Tai Ho Bay 1 stations
in April 2015 and at Impact and Shum Shui Kok stations in May 2015. However, concentrations of SS complied with the Action and Limit
Levels at all stations in April and May 2015 (Figures 10 and 15 of Annex B; Table C3 of Annex C).
1.5.9
Overall,
results of the Routine Water Quality Monitoring indicated that the disposal operation at CMP 2 did
not appear to cause any unacceptable deterioration in water quality in April
and May 2015. Detailed statistical
analysis will be presented in the Quarterly Report to observe any spatial and
temporal trends.
1.5.10
Pit Specific Sediment Chemistry of CMP 2 – April 2015
1.5.11
Monitoring
locations for Pit Specific Sediment Chemistry for CMP 2 are shown in Figure 1.3. A total
of six (6) monitoring stations were sampled in April 2015.
1.5.12
The concentrations of most inorganic contaminants were lower than the Lower Chemical Exceedance Level (LCEL) at most stations except for
Chromium, Copper, Nickel, Silver and Zinc at Active Pit station SB-NPBB and
Mercury at Near-Pit stations SB-NNBA and SB-NNBB in April 2015 (Figures 16-17 of Annex B). Chromium, Nickel and Zinc exceeded the
LCEL at Active Pit station SB-NPBB while Copper and Silver exceeded the Upper Chemical Exceedance Level
(UCEL) at
Active Pit station SB-NPBB in April 2015. Mercury
exceeded the LCEL at Near-Pit stations SB-NNBA and SB-NNBB in April 2015. As higher Chromium,
Copper, Nickel, Silver and Zinc concentrations
were recorded within the Active Pit station only which were receiving
contaminated mud during the reporting month while higher mercury concentrations
were recorded at the Near-Pit stations only, there is no evidence indicating
any dispersal of contaminants from the active pit.
1.5.13
For organic contaminants, the
concentrations of Total Organic Carbon (TOC) were observed to be slightly
higher in Active-Pit station SB-NPBB, Pit-Edge SB-NEBA and Near-Pit SB-NNBA (Figure 18 of Annex B). Tributyltin
(TBT), total dichlorodiphenyltrichloroethane (DDT), 4,4’-dichlorodiphenyldichloroethylene
(DDE), Total Polychlorinated Biphenyls (PCBs), Low and High Molecular Weight Polycyclic
Aromatic Hydrocarbons (MW PAHs) were below the limit
of reporting at most stations (except for High MW PAHs
at Impact station SB-NPBB) in April 2015 (Figure 19 of Annex B).
1.5.14
Overall, there is no evidence
indicating any unacceptable environmental impacts to sediment quality as a
result of the contaminated mud disposal operations at CMP 2 in April 2015. Statistical analysis will be undertaken
in the quarterly report to investigate whether there are any unacceptable
impacts in the area caused by the contaminated mud disposal.
1.5.15
Water Column Profiling of CMP 2 – May 2015
1.5.16
Water Column Profiling was undertaken at a total of two sampling stations (Upstream
and Downstream stations) on 13 May 2015.
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 C1 of Annex C for details).
In-situ Measurements
1.5.17
Analyses of
results for May 2015 indicated that levels of Salinity, DO and pH complied with
the WQOs at both Downstream and Upstream stations (Table C4 of Annex C). DO and
Turbidity at all stations complied with the Action and Limit Levels (Tables
C1 and C4
of Annex C).
Laboratory Measurements for SS
1.5.18
Analyses of
results for May 2015 indicated
that the Suspended Solid (SS) levels at both Upstream
and Downstream stations exceeded the WQO.
It is considered that the exceedance of SS was
possibly caused by natural background variation of water quality in the
area. However, both Upstream and Downstream
stations complied with the Action and Limit Levels (Tables C1 and C4 of Annex C).
1.5.19
Overall, the
monitoring results indicated that the mud disposal operation at CMP 2 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 June 2015
for SB CMPs:
·
Pit Specific Sediment Chemistry of CMP 2;
·
Cumulative Impact Specific Chemistry of CMP 2;
·
Water Column Profiling of CMP 2; and
·
Water Quality Monitoring during Capping Operations
of CMP 1.
1.6.2
The following monitoring activity will be
conducted in the next monthly period of June 2015 for ESC CMPs.
·
Water Quality Monitoring during Capping of ESC CMP.