Agreement No. CE 4/2009 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pit at Sha Chau (2009-2013) - Investigation
36th MONTHLY PROGRESS REPORTFOR CONTAMINATED MUD PITS AT SHA CHAU June 2012
1.1.1 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. In June 2012, the following works were being undertaken at the CMPs:
¡P Capping was being undertaken at CMP IVc;
¡P Disposal of contaminated mud was taking place at CMP Va; and
¡P The dredging of CMP Vc was in progress.
1.1.2 The Environmental Monitoring and Audit (EM&A) programme for the CMPs at the East of Sha Chau area (ESC) presently covers the above operations.
1.2.1 This Monthly Progress Report covers the reporting month of June 2012.
1.3.1 The following monitoring activities have been undertaken for CMP IVc in June 2012:
¡P Water Quality Monitoring during Capping was conducted on 7 June 2012.
1.3.2 The following monitoring activities have been undertaken for CMP V in June 2012:
¡P Pit Specific Sediment Chemistry Monitoring was conducted for CMP Va on 4 June 2012;
¡P Cumulative Impact Sediment Chemistry Monitoring was conducted for CMP Va on 5 and 6 June 2012;
¡P Impact Water Quality Monitoring during Dredging Operations was conducted for CMP Vc on 8 June 2012; and
¡P Water Column Profiling was conducted for CMP Va on 11 June 2012.
1.3.3 A summary of field activities is presented in Annex A.
1.4.1 No outstanding sampling and laboratory analysis remained from June 2012.
1.5.1 Table 1.1 summarises the monitoring results that are presented in the current monthly report. All monitoring data collected for CMP V in June 2012 will be presented in this monthly report.
Table 1.1 Monitoring results presented in the June 2012 Monthly Report
Date of Monitoring
4 June 2012
Pit Specific Sediment Chemistry Monitoring for CMP Va
5 and 6 June 2012
Cumulative Impact Sediment Chemistry Monitoring for CMP Va
8 June 2012
Impact Water Quality Monitoring during Dredging Operations for CMP Vc
11 June 2012
Water Column Profiling for CMP Va
1.5.2 Brief discussion of the monitoring results is presented in this section. Detailed discussion will be presented in the corresponding Quarterly Report.
1.5.4 Monitoring locations for Pit Specific Sediment Chemistry for CMP Va are shown in Figure 1.1. Concentrations of metals at all stations in June 2012 were below the Lower Chemistry Exceedance Level (LCEL), with the exception of Lead and Arsenic (Figure 1 of Annex B). Concentrations of Lead exceeded the LCEL at Active Pit station NPDB. Concentrations of Arsenic exceeded the LCEL at all stations except Active Pit station NPDB and Near Pit station NNDB in June 2012. It is important to note that relatively high natural levels of Arsenic are present in Hong Kong¡¦s marine sediments. Therefore, the slight exceedances of the LCEL for Arsenic are unlikely to be caused by the disposal operations at CMP Va but rather as a result of naturally occurring deposits.
1.5.5 For organic contaminants, PCBs were below the limit of reporting at all stations in June 2012. Levels of Low and High Molecular Weight Polycyclic Aromatics Hydrocarbons (Low and High M.W. PAHs) were higher than the limit of reporting at Active Pit stations only (ie NPDA and NPDB). Total Organic Carbon (TOC) concentrations were similar amongst all stations (Figure 3 of Annex B). Tributyltins (TBTs) concentration was the highest at Active Pit station NPDB when compared to other stations (Figure 4 of Annex B). Concentrations of 4,4¡¨-DDE were higher than the limit of reporting at Active Pit station NPDB only, whereas concentrations of DDT were lower than the limit of reporting at all stations (Figure 5 of Annex B).
1.5.6 It should be noted that the Action Pit stations are located within CMP Va which were receiving contaminated mud during the reporting month. Therefore, the higher concentrations of contaminants recorded at the Action Pit stations alone are not considered as indicating any dispersal of contaminated mud from CMP Va and thus also not appeared to indicate any unacceptable environmental impacts from the mud disposal operations. Overall, there is no evidence indicating any unacceptable environmental impacts to sediment quality as a result of the contaminated mud disposal operations at CMP Va during this monthly period.
1.5.8 Monitoring locations for Cumulative Impact Sediment Chemistry for CMP Va are shown in Figure 1.2.
1.5.9 Analyses of results for the Cumulative Impact Sediment Chemistry Monitoring indicated that the concentrations of all metals, except Arsenic, were below the LCEL (Figures 6 and 7). Concentrations of Arsenic in sediments from all stations, except Near Field (RNB) and Ma Wan Station (MW), exceeded the LCEL. As presented in Section 1.5.4 above, the slight exceedances of LCEL for Arsenic do not necessarily indicate any adverse impacts to sediment quality caused by disposal operations at CMP Va. Generally, there were only minor differences in metal concentrations amongst the stations.
1.5.10 The concentration of TOC was higher at the Mid Field station RMA than at other stations (Figure 8 of Annex B). TBTs were recorded in sediment samples at Near Field (RNA), Mid Field (RMA and RMB) and Far Field (RFA) stations (Figure 9 of Annex B). Total DDT, DDE, Total PCBs, Low and High Molecular Weight PAHs were below the limit of detection at all stations.
1.5.11 Overall, the contaminated mud disposal operations at CMP Va did not appear to cause any deterioration in sediment quality of the area.
1.5.13 The water quality monitoring results for June 2012 have been assessed for compliance with the WQOs set by EPD. This consists of a review of the Environmental Protection Department (EPD) routine water quality monitoring data for the wet season period (April to October) of 1999-2010 from stations in the Northwestern Water Control Zone, where CMPs are located. For Salinity, the average value obtained from the upstream station was used for the basis as the WQO. Graphical presentation of the monitoring results is provided in Annex B.
1.5.14 Analyses of results for June 2012 indicated that levels of Salinity, pH and Dissolved Oxygen (DO) complied with the WQOs at both Upstream and Downstream stations (Figures 10, 11 and 12 in Annex B). DO and Turbidity complied with the Action and Limit Levels set in the EM&A Manual ().
Laboratory Measurements for Total Suspended Solids (TSS)
1.5.15 Analyses of data obtained in June 2012 indicated that the TSS levels at both Upstream and Downstream stations complied with the WQO (Figure 13 in Annex B). TSS levels measured in June 2012 complied with the Action and Limit Levels set in the EM&A Manual.
1.5.16 Overall, the results indicated that the mud disposal operation at CMP Va did not appear to cause any deterioration in water quality during this reporting period.
1.5.18 Impact Water Quality Monitoring during Dredging Operations of CMP V was conducted on 8 June 2012 for CMP Vc. On the 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 Vc (Figure 1.3). 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).
1.5.20 Overall, the results indicated that the dredging operations at CMP Vc 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-312/2008), are considered required for the dredging operations of CMP Vc.
1.6.1 The following monitoring programmes will be conducted in the next monthly period of July 2012:
¡P Pit Specific Sediment Chemistry for CMP Va;
¡P Demersal Trawling for CMP Va;
¡P Routine Water Quality Monitoring for CMP Va;
¡P Water Column Profiling for CMP Va; and
¡P Impact Water Quality Monitoring during Dredging Operations for CMP Vc.
1.6.2 The sampling schedule is presented in Annex A.
1.7.1 A summary of the Study Programme is presented in Annex D.