Contents
1.1 Background
1.2 Reporting Period
1.3 Details of Sampling and Laboratory Testing Activities
1.4 Details of Outstanding Sampling and/or Analysis
1.5 Brief Discussion of the Monitoring Results for ESC CMP V
1.6 Activities Scheduled for the Next Month
1.7 Study Programme
Annexes
Annex B Water Quality Monitoring Results
Annex C Graphical Presentations
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 A proposal on the change of number of sample replication of water quality & sediment monitoring and combination of routine water quality monitoring and water quality monitoring during capping operation was submitted to EPD and agreed by EPD on 3 December 2020. The proposed changes have been effective for the EM&A activities since December 2020. The latest sampling schedule is provided in Annex A.
1.1.4 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 March 2021, the following works were undertaken:
· Disposal of contaminated mud at ESC CMP Vb; and
· Capping operations at ESC CMP Vd.
Figure 1.1 Works Schedule for ESC CMP V
1.2 Reporting Period
1.2.1 This Monthly EM&A Report for March 2021 covers the EM&A activities for the reporting month of March 2021.
1.3 Details of Sampling and Laboratory Testing Activities
1.3.1 The following monitoring activities were undertaken for ESC CMP V in March 2021:
· Water Column Profiling of ESC CMP Vb;
· Routine Water Quality Monitoring of ESC CMPs; and
· Pit Specific Sediment Chemistry of ESC CMP Vb.
1.4 Details of Outstanding Sampling and/or Analysis
1.4.1 No outstanding sampling remained for March 2021.
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 March 2021:
· Water Column Profiling of ESC CMP Vb;
· Routine Water Quality Monitoring of ESC CMPs; and
· Pit Specific Sediment Chemistry of ESC CMP Vb.
1.5.2 Water Column Profiling of ESC CMP Vb – March 2021
1.5.3 Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 5 March 2021. 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 dry season period (November to March) of 2010 - 2019 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 March 2021 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 March 2021 indicated that the SS levels at both Downstream and Upstream stations complied with the WQO and the Action and Limit Levels (Tables B1 and B2 of Annex B).
1.5.6 Overall, the monitoring results indicated that the mud disposal operation at ESC CMP Vb did not appear to cause any deterioration in water quality during this reporting period.
1.5.7 Routine Water Quality Monitoring of ESC CMPs – March 2021
1.5.8 Routine Water Quality Monitoring of ESC CMPs was undertaken on 4 March 2021. The monitoring results have been assessed for compliance with the WQOs (see Section 1.5.3 for details). The monitoring results are shown in Tables B3 and B4 of Annex B and Figures 1 - 10 of Annex C. A total of ten (10) monitoring stations were sampled in March 2021 as shown in Figure 1.2.
In-situ Measurements
1.5.9 Graphical presentation of the monitoring results (Temperature, DO, pH, Salinity and Turbidity) is shown in Figures 1 - 6 of Annex C. Analyses of results indicated that the levels of pH, Salinity and DO complied with the WQOs at all stations in March 2021.
1.5.10 The levels of DO and Turbidity complied with the Action and Limit Levels at all stations (Table B3 of Annex B; Figures 3 and 6 of Annex C).
1.5.11 Overall, in-situ measurement results of the Routine Water Quality Monitoring indicated that the disposal and capping operation at ESC CMPs did not appear to cause any unacceptable impacts in water quality in March 2021.
Laboratory Measurements
1.5.12 Laboratory analysis of March 2021 results indicated that concentrations of Arsenic, Chromium, Copper, Lead, Nickel and Zinc were detected in March 2021 samples at all stations and their concentrations were generally similar across stations, except the concentrations of Zinc were higher at Ma Wan station (Table B4 of Annex B; Figure 7 of Annex C).
1.5.13 For nutrients, concentrations of Total Inorganic Nitrogen (TIN) at most stations complied with the WQO (0.5 mg/L) except the concentrations were higher than the WQO at Intermediate stations (Table B4 of Annex B; Figure 8 of Annex C). It should be noted that due to the effect of the Pearl River, the North Western WCZ has historically experienced higher levels of TIN ([4]). Therefore, the exceedances of TIN WQO at these stations are unlikely to be caused by the disposal operation at ESC CMPs. The concentrations of Ammonia Nitrogen (NH3-N) were higher at Intermediate stations in March 2021 (Table B4 of Annex B; Figure 8 of Annex C). The concentrations of Biochemical Oxygen Demand (BOD5) were below the limit of reporting at all stations (Table B4 of Annex B).
1.5.14 Analyses of results for March 2021 indicated that the SS levels at most stations complied with the WQO (12.8 mg/L), except for Reference and Intermediate stations. However, the SS levels of all stations complied with the Action and Limit Levels (Tables B1 and B4 of Annex B; Figure 9 of Annex C).
1.5.15 Overall, results of the Routine Water Quality Monitoring indicated that the disposal and capping operation at ESC CMPs did not appear to cause any unacceptable deterioration in water quality in March 2021. Detailed statistical analysis will be presented in the Quarterly Report to investigate any spatial and temporal trends of potential concern.
1.5.16 Pit Specific Sediment Chemistry of ESC CMP Vb – March 2021
1.5.17 Monitoring locations for Pit Specific Sediment Chemistry for ESC CMP Vb are shown in Figure 1.3. A total of six (6) monitoring stations were sampled on 3 March 2021.
1.5.18 The concentrations of most inorganic contaminants were lower than the Lower Chemical Exceedance Levels (LCELs), except for Arsenic (Figures 10 and 11 of Annex C). The concentrations of Arsenic were higher than the LCEL at Pit-Edge stations ESC-NECA and ESC-NECB.
1.5.19 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 ([5]). It is presumed that the natural concentrations of Arsenic are similar in onshore and offshore sediments ([6]), 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 Vb but rather as a result of naturally occurring deposits.
1.5.20 For organic contaminants, the concentrations of Total Organic Carbon (TOC) were higher at Active-Pit station ESC-NPCA in March 2021 (Figure 12 of Annex C). The concentrations of Low Molecular Weight and High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) were lower than the LECLs at all stations (Figure 13 of Annex C). The concentrations of Tributyltin (TBT) were higher at Active-Pit station ESC-NPCB (Figure 14 of Annex C). The concentrations of Total Polychlorinated Biphenyls (PCBs), Total dichloro-diphenyl-trichloroethane (DDT) and 4,4’-dichlorodiphenyldichloroethylene (DDE) were below the limit of reporting at all stations in March 2021.
1.5.21 Overall, there is no evidence indicating any unacceptable environmental impacts to sediment quality outside the pit area as a result of the contaminated mud disposal operations at ESC CMP Vb in March 2021.
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 April 2021 for ESC CMP V:
· Water Column Profiling of ESC CMP Vb;
· Routine Water Quality Monitoring of ESC CMPs; and
· Pit Specific Sediment Chemistry of ESC CMP Vb.