Agreement No. CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau
(2009-2013) - Investigation
15th
MONTHLY PROGRESS REPORT FOR CONTAMINATED MUD PITS AT SHA CHAU - September 2010
1.1
Background
Since 1992, the East of Sha Chau area has been the site of a series of dredged
contaminated mud pits (CMPs) designed to provide
confined marine disposal capacity for contaminated mud arising from the HKSAR’s dredging and reclamation projects. CMP IVc is
presently in operation for backfilling by contaminated mud and is anticipated
to reach its capacity in 2011. A series
of four newly constructed seabed pits at the East of Sha
Chau area, CMP Va-d, will
be provided for the disposal of contaminated mud after CMP IVc
is full. Dredging operations are now
taking place to construct CMP Vb. The
environmental monitoring and audit (EM&A) programme for the CMPs at the East of Sha Chau area presently covers disposal operations at CMP IVc and dredging operations at CMP Vb.
1.2
Reporting Period
This Monthly Progress Report
covers the monitoring period of September 2010.
1.3
Details of Sampling and
Laboratory Testing Activities
No field sampling activities were scheduled in
this monthly period for CMP IVc. For
CMP V, sampling for Impact Water Quality
Monitoring during Dredging Operations was conducted on
7, 9, 11, 13, 15, 17, 20, 22, 24, 27 and 29 September 2010. A summary of field activities are presented in Annex A.
1.4
Details of Outstanding Sampling
and / or Analysis
No outstanding sampling and laboratory analysis remained from September
2010.
1.5
Brief Discussion of the
Monitoring Results
Results of Impact Water Quality
Monitoring during Dredging Operations for September 2010 are presented for
CMP V. Detailed results will be
discussed in the relevant Quarterly
Reports.
1.5.1
CMP V
Impact Water Quality Monitoring during Dredging
Operations of CMP V – September 2010
Impact
Water Quality Monitoring during Dredging Operations of CMP V was conducted
on 7,
9, 11, 13, 15, 17, 20, 22, 24, 27 and 29 September 2010. On each survey day, sampling was conducted
during both mid-ebb and mid-flood tides at two Reference (Upstream) stations
upstream and five Impact (Downstream) stations downstream of the dredging operations
at CMP V. Monitoring was also conducted
at the Ma Wan station. At each station, in-situ measurements of water quality
parameters as well as water samples were taken from three depths in the water
column (ie surface: 1 m below sea surface, mid-depth
and bottom: 1 m above the seabed).
Monitoring results are
presented in Table B1 of Annex B.
Generally, levels of Dissolved Oxygen (DO), Turbidity and Total
Suspended Solids (TSS) complied with the Action and Limit Levels set in the Baseline Monitoring Report ([1]). However,
very occasional exceedances of Action Levels are
recorded for Turbidity and TSS (Table B1 of Annex B). Student’s t-tests were then
employed to investigate any significant differences in levels of Turbidity
and/or TSS between Reference (US1 and US2) and Impacts stations where exceedance(s) of Action Level(s) was/were reported (p-value = 0.05). Results of the statistical analysis show that
except for the exceedances recorded at DS1 during the
mid-flood monitoring on 27 September 2010, levels of Turbidity and TSS did not
show any significant differences between Reference (US1 and US2) and Impact
stations. It is thus considered that
these exceedances are more likely to be caused by
natural background fluctuation in water quality rather than indicating any
adverse impacts from the dredging operations of CMP V. It should be noted that the Impact station
where exceedances were recorded on 27 September 2010
(ie DS1) is located at the boundary of the works area
and the absence of exceedance at other downstream
stations (DS2 to DS5) indicates that the sediment plume did not extend beyond
the works area. Therefore, it is also
considered that the recorded exceedances do not
indicate any adverse water quality impacts caused by the dredging works of CMP
V.
1.6
Activities Scheduled for the
Next Month
Impact Water Quality
Monitoring during Dredging will be undertaken for CMP V in the next monitoring month for three
times per week. No monitoring will be
conducted for the disposal operations of CMP IV in October 2010.
The sampling schedule is presented in Annex A.
1.7
Study Programme
A summary of the Study programme is presented in Annex C.