Agreement No. CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau (2009-2013) - Investigation
16th MONTHLY PROGRESS REPORT FOR CONTAMINATED MUD PITS AT SHA CHAU - October 2010
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 and capping operations at CMP IV and dredging operations at CMP Vb.
This Monthly Progress Report covers the monitoring period of October 2010.
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 2, 5, 7, 9, 11, 13, 15, 18, 20 and 25 October 2010. A summary of field activities are presented in Annex A.
No outstanding sampling and laboratory analysis remained from October 2010.
Results of Impact Water Quality Monitoring during Dredging Operations for October 2010 are presented for CMP V. Detailed results will be discussed in the relevant Quarterly Reports.
Impact Water Quality Monitoring during Dredging Operations of CMP V was conducted for three times per week in October 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 (). However, occasional exceedances of these 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 exceedances of Action and Limit Levels were reported (p-value = 0.05).
With the exception of TSS levels recorded at impact station DS5 during the mid-ebb tide on 7 October and at station DS1 during the mid-flood tide on 25 October 2010, results of the statistical analysis did not show any significant differences in levels of Turbidity and TSS between Reference (US1 and US2) and Impact stations (p-value > 0.05; Table B1 of Annex B). It is thus considered that these exceedances are more likely to be caused by background fluctuation in water quality rather than indicating any adverse impacts from the dredging operations of CMP V. Although recordings of TSS were recorded at DS5 and DS1 above the levels recorded at the reference stations, these were isolated events and were tracked with future monitoring.
Overall, there appears to be no evidence of any unacceptable adverse water quality impacts arising from the dredging operations of CMP V at ESC.
Impact Water Quality Monitoring during Dredging will be undertaken for CMP V in the next monitoring month. No monitoring will be conducted for the disposal operations of CMP IV in November 2010.
The sampling schedule is presented in Annex A.
A summary of the Study programme is presented in Annex C.