Agreement No. CE 63/2016 (EP)
Environmental Monitoring and Audit
for Disposal Facility to the East of Sha Chau (2017-2020) - Investigation
MONTHLY EM&A REPORT FOR June 2019
1.1 Background
1.1.1 The Civil Engineering and Development Department (CEDD) is managing a number of marine disposal facilities in Hong Kong waters, including the Contaminated Mud Pits (CMPs) to the South of The Brothers (SB) and to the East of Sha Chau (ESC) for the disposal of contaminated sediment, and open-sea disposal grounds located to the South of Cheung Chau (SCC), East of Tung Lung Chau (ETLC) and East of Ninepins (ENP) for the disposal of uncontaminated sediment. Two Environmental Permits (EPs), EP-312/2008/A and EP-427/2011/A, were issued by the Environmental Protection Department (EPD) to the CEDD, the Permit Holder, on 28 November 2008 and 23 December 2011 for the Dredging, Management and Capping of Contaminated Sediment Disposal Facilities at ESC CMP V and SB CMPs, respectively.
1.1.2 Under the requirements of the two EPs for ESC CMP V and SB CMPs, EM&A programmes which encompass water and sediment chemistry, fisheries assessment, tissue and whole body analysis, sediment toxicity and benthic recolonisation studies as set out in the EM&A Manuals are required to be implemented. EM&A programmes have been continuously carried out during the operation of the CMPs at ESC and SB. A review of the collection and analysis of such environmental data from the monitoring programme demonstrated that there had not been any adverse environmental impacts resulting from disposal activities ([1]) ([2]). The current programme will assess the impacts resulting from dredging, disposal and capping operations of CMP V as well as capping operations of SB CMPs.
1.1.3 The present EM&A programme under Agreement No. CE 63/2016 (EP) covers the dredging, disposal and capping operations of the ESC CMP V as well as the capping operations of the SB CMPs (see Annex A for the EM&A programme). The scheduled EM&A programme for SB CMPs was completed in December 2018. Detailed works schedule for ESC CMP V is shown in Figure 1.1. In June 2019, disposal of contaminated mud at ESC CMP Vd was undertaken.
Figure 1.1 Works Schedule for ESC CMP V
1.2 Reporting Period
1.2.1 This Monthly EM&A Report for June 2019 covers the EM&A activities for the reporting month of June 2019.
1.3 Details of Sampling and Laboratory Testing Activities
1.3.1 The following monitoring activities were undertaken for ESC CMP V in June 2019:
· Water Column Profiling of ESC CMP Vd;
· Pit Specific Sediment Chemistry of ESC CMP Vd; and
· Cumulative Impact Sediment Chemistry of ESC CMPs.
1.4 Details of Outstanding Sampling and/or Analysis
1.4.1 No outstanding sampling remained for June 2019.
1.5 Brief Discussion of the Monitoring Results for ESC CMP V
1.5.1 Brief discussion of the monitoring results of the following activities for ESC CMP V is presented in this Monthly EM&A Report for June 2019:
· Water Column Profiling of ESC CMP Vd in June 2019;
· Pit Specific Sediment Chemistry of ESC CMP Vd in June 2019; and
· Cumulative Impact Sediment Chemistry of ESC CMPs in June 2019.
1.5.2 Water Column Profiling of ESC CMP Vd – June 2019
1.5.3 Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 5 June 2019. The monitoring results have been assessed for compliance with the Water Quality Objectives (WQOs) set by Environmental Protection Department (EPD). This consists of a review of the EPD routine water quality monitoring data for the wet season period (April to October) of 2008 - 2017 from stations in the Northwestern Water Control Zone (WCZ), where the ESC CMPs are located ([3]). For Salinity, the averaged value obtained from the Reference (Upstream) station 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 B1 of Annex B for details).
In-situ Measurements
1.5.4 Analyses of results for June 2019 indicated that levels of Salinity, pH and DO complied with the WQOs at both Downstream and Upstream stations (Table B2 of Annex B). Levels of DO and Turbidity at all stations complied with the Action and Limit Levels (Tables B1 and B2 of Annex B).
Laboratory Measurements for Suspended Solids (SS)
1.5.5 Analyses of results for June 2019 indicated that the SS levels at both Downstream and Upstream stations were higher than the WQO. However, the SS levels complied with the Action and Limit Levels at both Downstream and Upstream stations (Tables B1 and B2 of Annex B).
1.5.6 Overall, the monitoring results indicated that the mud disposal operation at ESC CMP Vd did not appear to cause any deterioration in water quality during this reporting period.
1.5.7 Pit Specific Sediment Chemistry of ESC CMP Vd – June 2019
1.5.8 Monitoring locations for Pit Specific Sediment Chemistry for ESC CMP Vd are shown in Figure 1.2. A total of six (6) monitoring stations were sampled on 3 June 2019.
1.5.9 The concentrations of most inorganic contaminants were lower than the Lower Chemical Exceedance Levels (LCELs) at most stations, except concentrations of Arsenic were higher than the LCEL at Active Pit station ESC-NPAA and Pit-Edge station ESC-NEAB (Figures 1 and 2 of Annex C). 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 ([4]). It is presumed that the natural concentrations of Arsenic are similar in onshore and offshore sediments ([5]), and relatively high Arsenic levels may thus occur throughout Hong Kong. Therefore, the LECL exceedances of Arsenic are unlikely to be caused by the disposal operations at ESC CMP Vd but rather as a result of naturally occurring deposits.
1.5.10 For organic contaminants, the concentrations of Total Organic Carbon (TOC) varied between stations in June 2019 and were higher at Active-Pit station ESC-NPAA (Figure 3 of Annex C). The concentrations of Tributyltin (TBT) were also higher at Active-Pit station ESC-NPAA in June 2019 (Figure 4 of Annex C). The concentrations of High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) were detected at Near-Pit station ESC-NNAB and Active-Pit stations ESC-NPAA and ESC-NPAB in June 2019 (Figure 5 of Annex C). Low Molecular Weight PAHs, Total Polychlorinated Biphenyls (PCBs), Total dichloro-diphenyl-trichloroethane (DDT) and 4,4’-dichlorodiphenyldichloroethylene (DDE) concentrations were below the limit of reporting at all stations.
1.5.11 Overall, there is no evidence indicating any unacceptable environmental impacts to sediment quality as a result of the contaminated mud disposal operations at ESC CMP Vd in June 2019. Statistical analysis will be undertaken and presented in the corresponding quarterly report to investigate whether there are any unacceptable impacts in the area caused by the contaminated mud disposal.
1.5.12 Cumulative Impact Sediment Chemistry of ESC CMPs – June 2019
1.5.13 Monitoring locations for Cumulative Impact Sediment Chemistry for ESC CMPs are shown in Figure 1.3. A total of nine (9) monitoring stations were sampled on 3 and 4 June 2019.
1.5.14 Analyses of results for the Cumulative Impact Sediment Chemistry Monitoring indicated that the concentrations of most inorganic contaminants were below the LCEL at most stations in June 2019, except concentrations of Arsenic were higher than the LCEL at Mid-field stations ESC-RMA and ESC-RMB, Far-field station ESC-RFB and Ma Wan station and concentrations of Copper were higher than the LCEL at Ma Wan station (Figures 6 and 7 of Annex C). As discussed in Section 1.5.9, the LECL exceedances of Arsenic are unlikely to be caused by the disposal operations at ESC CMP Vd but rather as a result of naturally occurring deposits.
1.5.15 For organic contaminants, the concentrations of TOC varied between stations in June 2019, with the generally higher concentrations of TOC recorded at Mid-field station ESC-RMA (Figure 8 of Annex C). The concentrations of TBT were generally similar against stations (Figure 9 of Annex C). The concentrations of Low Molecular Weight PAHs were detected at Capped-Pit stations ESC-RCA and ESC-RCB and High Molecular Weight PAHs were detected at Capped-Pit stations ESC-RCA and ESC-RCB, Far-field station ESC-RFB and Ma Wan station (Figure 10 of Annex C). Total Polychlorinated Biphenyls (PCBs), Total dichloro-diphenyl-trichloroethane (DDT) and 4,4’-dichlorodiphenyldichloroethylene (DDE) concentrations were below the limit of reporting at all stations.
1.5.16 Overall, there is no evidence indicating any unacceptable environmental impacts to sediment quality as a result of the contaminated mud disposal operations at ESC CMP Vd in June 2019. Statistical analysis will be undertaken and presented in the corresponding quarterly report to investigate whether there are any unacceptable impacts in the area caused by the contaminated mud disposal.
1.6 Activities Scheduled for the Next Month
1.6.1 The following monitoring activities will be conducted in the next monthly period of July 2019 for ESC CMP V (see Annex A for the sampling schedule ([6])):
· Water Column Profiling of ESC CMP Vd;
· Routine Water Quality Monitoring of ESC CMPs;
· Pit Specific Sediment Chemistry of ESC CMP Vd; and
· Demersal Trawling for ESC CMPs.