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Agreement No. CE 59/2020 (EP) Environmental Monitoring and Audit for Disposal Facility to the East of Sha Chau (2021- 2026) Investigation |
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Monthly EM&A Report for Contaminated Mud Pits to the East of Sha
Chau September 2023 |
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October 2023 |
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Civil Engineering and Development
Department |
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Mott MacDonald 3/F Manulife Place 348 Kwun Tong Road Kwun Tong Kowloon Hong Kong T +852 2828 5757 mottmac.hk |
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Issue and Revision Record
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Revision |
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Originator |
Checker |
Approver |
Description |
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A |
Oct 2023 |
Various |
Liz Lo |
Thomas Chan |
Revision A of Submission |
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B |
Oct 2023 |
Various |
Liz Lo |
Thomas Chan |
Revision B of Submission |
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Document reference: |
423134 | 06/05/30 | B |
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Information class: |
Standard |
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This document is issued for the party which commissioned it and for specific purposes connected with the above-captioned project only. It should not be relied upon by any other party or used for any other purpose. We accept no responsibility for the consequences of this document being relied upon by any other party, or being used for any other purpose, or containing any error or omission which is due to an error or omission in data supplied to us by other parties. This document contains confidential information and proprietary intellectual property. It should not be shown to other parties without consent from us and from the party which commissioned it. |
Contents
1.3 Details of Sampling and Laboratory Testing Activities
1.4 Details of Outstanding Sampling or Analysis
2 Brief Discussion of Monitoring Results for ESC CMP V
2.2 Water Column Profiling of ESC CMP Vb in September 2023
2.2.2 Laboratory Measurements for Suspended Solids (SS)
2.3 Routine Water Quality Monitoring of ESC CMPs in September 2023
2.4 Pit Specific Sediment Chemistry of ESC CMP Vb in September 2023
2.5 Sediment Chemistry after a Major Storm of ESC CMP V in September 2023
3.1 Activities Scheduled for the Next Reporting Period
Tables
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Works Schedule for ESC CMP V Works Schedule for ESC CMP V |
Figures
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Routine & Capping Water Quality Sampling Stations (Flood-Tide) for ESC CMPs |
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Sediment Chemistry after a Major Storm Monitoring Stations for ESC CMPs |
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Appendices
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1
Introduction
1.1
Background
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 East of Sha Chau (ESC) for the disposal of contaminated sediment, and various 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.
Environmental Permits (EPs) (Ref. No. EP-312/2008/A) was issued by the Environmental Protection Department (EPD) to the CEDD, the Permit Holder, on 28 November 2008 for the Project - Disposal of Contaminated Sediment Dredging, Management and Capping of Sediment Disposal Facility at Sha Chau.
Under the requirements of the EP, 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. 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.
A proposal on the change of number of sample replication of water quality and sediment monitoring as well as 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. In early 2022, after implementing the Phase 1 optimisation for at least one year, a further data review was conducted. The monitoring data has been reviewed and demonstrated that the data robustness and representativeness are maintained. Therefore, a technical note presenting the data review results served as a supplementary information was submitted to EPD and presented that Phase 2 optimization of sample replication of water quality and sediment monitoring for the Project will be implemented in 2022. EPD expressed no comment on the review and note the implementation of Phase 2 optimization of sample replication on 18 May 2022, and thus this optimization has been effective for the EM&A activities since July 2022.
The latest sampling schedule is provided in Appendix A.
The present EM&A programme under Agreement No. CE 59/2020 (EP) covers the dredging, disposal and capping operations of the ESC CMP V (see Appendix A for the EM&A programme.) Detailed works schedule for ESC CMP V is shown in Table 1.1. In September 2023, the following works were undertaken:
● Disposal of contaminated mud at ESC CMP Vb; and
● Capping operations at ESC CMP Vd.
Table 1.1: Works Schedule for ESC CMP V
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1.2
Reporting Period
This Monthly EM&A Report for Contaminated Mud Pits to the East of Sha Chau September 2023 covers the EM&A activities for the reporting period of September 2023 (from 1 to 30 September 2023).
1.3
Details of
Sampling and Laboratory Testing Activities
The following monitoring activities were undertaken for ESC CMP V during the reporting period:
● Water Column Profiling of ESC CMP Vb;
● Routine Water Quality Monitoring of ESC CMPs;
● Pit Specific Sediment Chemistry of ESC CMP Vb;
● Sediment Chemistry after a Major Storm of ESC CMP V;
1.4
Details of
Outstanding Sampling or Analysis
No outstanding sampling remained for the reporting month (September 2023).
2
Brief Discussion of Monitoring
Results for ESC CMP V
2.1
Introduction
This section presents a brief discussion of the results obtained from the following monitoring activities for ESC CMP V during the reporting period:
● Water Column Profiling of ESC CMP Vb;
● Routine Water Quality Monitoring of ESC CMPs;
● Pit Specific Sediment Chemistry of ESC CMP Vb; and
● Sediment Chemistry after a Major Storm of ESC CMP V.
2.2
Water Column
Profiling of ESC CMP Vb in September 2023
Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 5 September 2023. 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 2012 2021 from stations in the North Western 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 Appendix B for details).
2.2.1
In-situ Measurements
Analyses of results for September 2023 indicated that levels of Salinity, pH and DO complied with the WQOs at both Downstream and Upstream stations (Table B2 of Appendix B). Levels of DO and Turbidity at all stations complied with the Action and Limit Levels (Tables B1 and B2 of Appendix B).
2.2.2
Laboratory Measurements for Suspended Solids (SS)
Analyses of results for September 2023 indicated that the SS level at both Upstream and Downstream stations complied with the WQO and the Action and Limit Levels (Tables B1 and B2 of Appendix B).
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.
2.3
Routine Water Quality Monitoring of ESC CMPs in September
2023
Routine Water Quality Monitoring of ESC CMPs was undertaken on 6 September 2023. The monitoring results have been assessed for compliance with the WQOs (see Section 2.2 above for details). The monitoring results are shown in Tables B3, B4 and B5 of Appendix B and Figures 1 to 11 of Appendix C. A total of ten (10) monitoring stations were sampled in September 2023 as shown in Figure 2.1.
2.3.1
In-situ Measurements
Graphical presentation of the monitoring results (Temperature, DO, pH, Salinity and Turbidity) is shown in Figures 1 to 6 of Appendix C. Analyses of results indicated that the levels of pH and DO complied with the WQOs at all stations in September 2023, except for higher levels of Salinity were recorded at Ma Wan station. The higher Salinities recorded at Ma Wan station are likely to be caused by the larger separation distance to Pearl River Delta mouth, which releases a large amount of freshwater runoff in the area during wet season, when compared to the Reference stations.
The levels of DO and Turbidity complied with the Action and Limit Levels at all stations (Table B3 of Appendix B; Figures 3 and 6 of Appendix C).
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 September 2023.
2.3.2
Laboratory Measurements
Laboratory analysis of samples obtained during the reporting period indicated that the concentrations of Arsenic, Cadmium, Chromium, Copper, Lead, Mercury, Nickel and Zinc were detected in the samples at some/ all stations and their concentrations were generally similar across stations; except the concentrations of Mercury were slightly higher at Reference (RFF) station. The concentrations of Lead were only detected at Reference (RFF) station. (Table B4 of Appendix B; Figure 7 and 8 of Appendix C).
For nutrients, concentrations of Total Inorganic Nitrogen (TIN) were higher than the WQO (0.5 mg/L) at Reference (RFF), Impact (IPF) and Intermediate (INF) stations. (Table B5 of Appendix B; Figure 9 of Appendix 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 concentration of Ammonia Nitrogen (NH3-N) were generally similar across all stations. (Table B5 of Appendix B; Figure 9 of Appendix C). The concentrations of Biochemical Oxygen Demand (BOD5) were below limit of reporting at all stations. (Table B5 of Appendix B).
Analyses of results for the reporting period indicated that the SS levels complied with the wet season WQO (11.7 mg/L)and Action and Limit Levels at all stations. (Tables B1 and B5 of Appendix B; Figure 10 of Appendix C).
Based on the available results of the Routine Water Quality Monitoring which indicated that the disposal and capping operation at ESC CMPs did not appear to cause any unacceptable deterioration in water quality during the reporting period. Detailed statistical analysis will be presented in the Quarterly EM&A Report to investigate any spatial and temporal trends of potential concern.
2.4
Pit Specific Sediment Chemistry of ESC CMP Vb in September 2023
Monitoring locations for Pit Specific Sediment Chemistry for ESC CMP Vb are shown in Figure 2.2. A total of six (6) monitoring stations were sampled on 4 September 2023.
The concentrations of most inorganic contaminants were lower than the Lower Chemical Exceedance Levels (LCELs) at all stations, except for Arsenic. The concentrations of Arsenic were higher than the LCEL at Near-Pit station ESC-NNCA and Pit-Edge station ESC-NECA. (Figures 11 and 12 of Appendix C).
Whilst the average concentration of Arsenic in the Earths crust is generally ~2mg/kg, significantly higher Arsenic concentrations (median = 14 mg/kg) have been recorded in Hong Kongs 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 LCEL 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.
For organic contaminants, the concentrations of Total Organic Carbon (TOC) were higher at Active-Pit station ESC-NPCB. (Figure 13 of Appendix C). The concentrations of Low Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) were higher at Active-Pit station ESC-NPCB. (Figures 14 of Appendix C).
For High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs), the concentrations were higher than LCEL at Active-Pit station ESC-NPCB. (Figures 14 of Appendix C). The concentrations of Tributyltin (TBT) was higher at Active Pit station ESC-NPCB (Figure 15 of Appendix 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 during the reporting period.
Considering that the higher levels (i.e. concentrations higher than LCEL) of High Molecular Weight PAHs are only occurred within Active-Pit station ESC-NPCB only, 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 during the reporting period.
Statistical analysis will be undertaken and presented in the corresponding Quarterly EM&A Report to investigate whether there are any unacceptable impacts in the area caused by the contaminated mud disposal.
2.5
Sediment Chemistry after a Major Storm of ESC CMP V in September 2023
Sampling for Sediment Chemistry after a Major Storm Event was conducted at nine (9) monitoring stations (see Figure 2.3 for the locations of the monitoring stations) on 5 September 2023 after the visit of tropical cyclones Saola, which led to the issue of No. 8 Storm Signal on 1 September 2023. The tracks of Saola are shown in Figure 2.4.
Figure 2.4: Track of Tropical Cyclone Saola (Source: Hong Kong Observatory)
%20Sep%202023_Rev%20B_files/image004.jpg)
Analyses of results for the Sediment Chemistry after a Major Storm indicated that the concentrations of all inorganic contaminants were below the LCEL in September 2023, except for Arsenic. The concentrations of Arsenic were higher than the LCEL at Near-field station ESC-RNB1, Mid-field stations ESC-RMA and Far-field station ESC-RFB. (Figures 16 and 17 of Appendix C).
As discussed in Section 2.4, the LCEL 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.
Overall, there appeared to be no evidence showing the failure of ESC CMP V in retaining disposed mud or causing contamination of sediments after the major storm event in September 2023.
3
Future Key Issues
3.1
Activities Scheduled for the Next Reporting Period
The following monitoring activities will be conducted in the next reporting period of October 2023 for ESC CMP V (see Appendix A for the sampling schedule):
● Water Column Profiling of ESC CMP Vb;
● Routine Water Quality Monitoring of ESC CMPs; and
● Pit Specific Sediment Chemistry of ESC CMP Vb.
3.2
Study Programme
A summary of the Study Programme is presented in Appendix D.
[1] ERM (2013) Final Report. Submitted under Agreement No. CE 4/2009 (EP) Environmental Monitoring and Audit for Contaminated Mud Pit at East Sha Chau. For CEDD.
[2] ERM (2017) Final Report. Submitted under Agreement No. CE 23/2012 (EP) Environmental Monitoring and Audit for Contaminated Mud Pits to the South of The Brothers and at East Sha Chau (2012 - 2017). For CEDD.
[4] https://www.epd.gov.hk/epd/misc/marine_quality/1986-2005/eng/08_western_content.htm
[5] Sewell RJ (1999) Geochemical Atlas of Hong Kong. Geotechnical Engineering Office, Government of the Hong Kong Special Administrative Region
[6] Whiteside PGD (2000) Natural geochemistry and contamination of marine sediments in Hong Kong. In: The Urban Geology of Hong Kong (ed. Page A & Reels SJ). Geological Society of Hong Kong Bulletin No. 6, p109-121