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 October 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 October 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 October 2019 covers the EM&A activities for the reporting month of October 2019.
1.3 Details of Sampling and Laboratory Testing Activities
1.3.1 The following monitoring activities were undertaken for ESC CMP V in October 2019:
· Water Column Profiling of ESC CMP Vd;
· Routine Water Quality Monitoring of ESC CMPs; and
· Pit Specific Sediment Chemistry of ESC CMP Vd.
1.4 Details of Outstanding Sampling and/or Analysis
1.4.1 No outstanding sampling remained for October 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 October 2019:
· Water Column Profiling of ESC CMP Vd in October 2019;
· Routine Water Quality Monitoring of ESC CMPs in October 2019; and
· Pit Specific Sediment Chemistry of ESC CMP Vd in October 2019.
1.5.2 Water Column Profiling of ESC CMP Vd – October 2019
1.5.3 Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 10 October 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 October 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 October 2019 indicated that the SS levels at both Downstream and Upstream stations were 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 Vd did not appear to cause any deterioration in water quality during this reporting period.
1.5.7 Routine Water Quality Monitoring of ESC CMPs – October 2019
1.5.8 Routine Water Quality Monitoring of ESC CMP V was undertaken on 9 October 2019. 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 sixteen (16) monitoring stations were sampled in October 2019 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 for October 2019 indicated that the levels of pH, Salinity and DO complied with the WQOs at all stations in October 2019.
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 operation at ESC CMP Vd did not appear to cause any unacceptable impacts in water quality in October 2019.
Laboratory Measurements
1.5.12 Laboratory analysis of October 2019 results indicated that concentrations of Arsenic, Cadmium, Chromium, Copper, Lead, Mercury, Nickel, Silver and Zinc were detected in October 2019 samples at most stations and the concentrations of these metals and metalloids were similar amongst the stations, except the concentration of Zinc was higher at reference station (Table B4 of Annex B; Figure 7 of Annex C).
1.5.13 For nutrients, concentrations of Total Inorganic Nitrogen (TIN) at impact stations in October 2019 was higher than the WQO (0.5 mg/L) (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 impact station is unlikely to be caused by the disposal operation at ESC CMP Vd. Concentrations of Ammonia Nitrogen (NH3-N) and 5-day Biochemical Oxygen Demand (BOD5) were generally similar amongst the stations in October 2019 (Table B4 of Annex B; Figure 8 and 9 of Annex C).
1.5.14 Analyses of results for October 2019 indicated that the SS levels at all stations were lower than the WQO (10.8 mg/L for wet season) and complied with the Action and Limit Levels (Tables B1 and B4 of Annex B; Figure 10 of Annex C).
1.5.15 Overall, results of the Routine Water Quality Monitoring indicated that the disposal operation at ESC CMP Vd did not appear to cause any unacceptable deterioration in water quality in October 2019. 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 Vd – October 2019
1.5.17 Monitoring locations for Pit Specific Sediment Chemistry for ESC CMP Vd are shown in Figure 1.3. A total of six (6) monitoring stations were sampled on 8 October 2019.
1.5.18 The concentrations of most inorganic contaminants were lower than the Lower Chemical Exceedance Levels (LCELs) at most stations, except for Arsenic, Copper and Silver at Active-Pit stations (Figures 11 and 12 of Annex C). The concentrations of Arsenic were higher than the LCEL at Active-Pit station ESC-NPAA. The concentrations of Copper were higher than the Upper Chemical Exceedance Level (UCEL) at Active-Pit station ESC-NPAB. The concentrations of Silver were higher than the LCEL at Active-Pit station ESC-NPAB.
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 Vd but rather as a result of naturally occurring deposits.
1.5.20 Considering that the higher levels of Copper and Silver occurred within Active-Pit stations only but not at the Pit-Edge and Near-Pit stations, 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 October 2019.
1.5.21 For organic contaminants, the concentrations of Total Organic Carbon (TOC) varied between stations in October 2019 and were higher at Active-Pit stations ESC-NPAA and ESC-NPAB (Figure 13 of Annex C). The concentrations of Tributyltin (TBT) were also higher at Active-Pit stations ESC-NPAA and ESC-NPAB in October 2019 (Figure 14 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. The concentrations of Low Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs) and High Molecular Weight PAHs were lower than LCEL at most of the stations, except they exceeded UCEL at Active-Pit station ESC-NPAB (Figure 15 of Annex C).
1.5.22 Considering that the higher levels of PAHs occurred within one Active-Pit station only but not at the Pit-Edge and Near-Pit stations, 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 October 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 November 2019 for ESC CMP V (see Annex A for the sampling schedule ([7]):
· Water Column Profiling of ESC CMP Vd;
· Routine Water Quality Monitoring of ESC CMPs; and
· Pit Specific Sediment Chemistry of ESC CMP V.