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) - Investigation

23rd MONTHLY PROGRESS REPORT FOR july 2014

1.1                                      Background

1.1.1                                Since early 1990s, contaminated sediment ([1]) arising from various construction works (e.g. dredging and reclamation projects) in Hong Kong has been disposed of at a series of seabed pits at East of Sha Chau (ESC). In late 2008, a review indicated that the existing and planned facilities at ESC would not be able to meet the disposal demand after 2012. In order to meet this demand, the Hong Kong Special Administrative Region Government (HKSARG) decided to implement a new contained aquatic disposal (CAD) ([2]) facility at the South of The Brothers (SB CMPs) which had been under consideration for a number of years.

1.1.2                                The environmental acceptability of the construction and operation of the Project had been confirmed by findings of the associated Environmental Impact Assessment (EIA) study completed in 2005 under Agreement No. CE 12/2002(EP) ([3]). The Director of Environmental Protection (DEP) approved this EIA report under the Environmental Impact Assessment Ordinance (Cap. 499) (EIAO) in September 2005 (EIA Register No.: AEIAR-089/2005).

1.1.3                                In accordance with the EIA recommendation, prior to commencement of construction works for the SB CMPs, the Civil Engineering and Development Department (CEDD) undertook a detailed review and update of the EIA findings for the SB site ([4]). Findings of the EIA review undertaken in 2009/ 2010 confirmed that the construction and operation of the SB site had been predicted to be environmentally acceptable.

 

1.1.4                                Environmental Permits (EPs) (EP-312/2008/A and EP-427/2011A) were issued by the Environmental Protection Department (EPD) to the CEDD, the Permit Holder, on 28 November 2008 for ESC CMP V and on 23 December 2011 for SB CMPs, respectively. Under the requirements of the EPs, an Environmental Monitoring and Audit (EM&A) programme as set out in the EM&A Manuals ([5]) ([6]) is required to be implemented for the CMPs.

1.1.5                                The present EM&A programme under Agreement No. CE 23/2012 (EP) covers the dredging, disposal and capping operations of the SB CMPs as well as ESC CMPs. Detailed works schedule for both CMPs is shown in Figure 1.1. In July 2014, the following works were being undertaken at the CMPs:

      Capping was being undertaken at ESC CMP IVc and CMP Va;

      Disposal of contaminated mud was taking place at SB CMP 1; and

      Dredging operations were taking place at SB CMP 2.

Figure 1.1 Works Schedule for ESC CMPs and SB CMPs

1.2                                      Reporting Period

1.2.1                                This 23rd Monthly Progress Report covers the EM&A activities for the reporting month of July 2014.

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                               No monitoring activity was scheduled to be undertaken for ESC CMPs in July 2014.

1.3.2                               The following monitoring activities have been undertaken for SB CMPs in July 2014:

      Impact Water Quality Monitoring during Dredging Operations was undertaken for CMP 2 three times per week on 2, 4, 7, 9, 11, 14, 16, 21, 23, 25, 28 and 30 July 2014;

      Water Column Profiling for CMP 1 was undertaken on 12 July 2014;

      Routine Water Quality Monitoring for CMP 1 was undertaken on 17 July 2014;

      Pit Specific Sediment Chemistry for CMP 1 was undertaken on 22 July 2014;

      Demersal Trawling for CMP 1 was undertaken on 30 and 31 July 2014.

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained for July 2014. The following laboratory analyses were still in progress during the preparation of this monthly report and hence are not presented in this monthly report:

      Laboratory analyses of sediment samples collected for Pit Specific Sediment Chemistry of CMP 1 in July 2014; and

      Identification of Catch from Demersal Trawling of CMP 1 and subsequent chemical analysis for the biota samples in July 2014.

1.4.2                                A summary of field activities conducted are presented in Annex A.

1.5                                      Brief Discussion of the Monitoring Results for SB CMPs

1.5.1                               Brief discussion of the monitoring results of the following activities for SB CMPs is presented in this 23rd Monthly Progress Report:

      Pit Specific Sediment Chemistry of CMP 1 conducted in May and June 2014;

      Cumulative Impact Sediment Chemistry of CMP 1 conducted in June 2014;

      Impact Water Quality Monitoring during Dredging Operations of CMP 2 conducted in July 2014;

      Water Column Profiling of CMP 1 conducted on 12 July 2014; and

      Routine Water Quality Monitoring of CMP 1 conducted on 17 July 2014.

1.5.2                                Pit Specific Sediment Chemistry of CMP 1 May and June 2014

1.5.3                               Monitoring locations for Pit Specific Sediment Chemistry for CMP 1 are shown in Figure 1.2. A total of six (6) monitoring stations were sampled in both May and June 2014.

1.5.4                               The concentrations of all inorganic contaminants were lower than the Lower Chemical Exceedance Level (LCEL) at all stations in May and June 2014 (Figures 1-2 and 5-6 of Annex B).

1.5.5                               For organic contaminants, the concentration of Total Organic Carbon (TOC) was similar amongst stations with no consistent spatial trend in both May and June 2014 (Figures 3 and 7 of Annex B). Concentrations of Tributyltin (TBTs) were observed to be higher at Active Pit stations SB-NPAB and SB-NPAA in May and June 2014, respectively (Figures 4 and 8 of Annex B). Low Molecular Weight Polycyclic Aromatic Hydrocarbons (Low MW PAHs), High MW PAHs, Total Dichloro-Diphenyl-Trichloroethane (DDT), 4,4-Dichloro-Diphenyl-Dichloroethylene (4,4-DDE) and Total Polychlorinated Biphenyls (PCBs) were recorded below the limit of reporting at all stations in both May and June 2014.

1.5.6                               Overall, there is no evidence indicating any unacceptable environmental impacts to sediment quality as a result of the contaminated mud disposal operations at CMP 1 in May and June 2014.

1.5.7                                Cumulative Impact Sediment Chemistry of CMP 1 June 2014

1.5.8                               Monitoring locations for Cumulative Impact Sediment Chemistry for CMP 1 are shown in Figure 1.3. A total of eleven (11) monitoring stations were sampled in June 2014.

1.5.9                                Analyses of results for the Cumulative Impact Sediment Chemistry Monitoring indicated that the concentrations of all inorganic contaminants were below the LCEL in June 2014 (Figures 9 and 10 of Annex B).

1.5.10                            For organic contaminants, concentration of TOC at Tai Ho Bay Station 2 (THB2) was recorded to be higher than other stations (Figure 11 of Annex B). Concentrations of TBT were recorded to be higher at Near-field station SB-RNB and Mid-field station SB-RMB (Figure 12 of Annex B). Total DDT, 4,4-DDE, Total PCBs as well as Low and High MW PAHs were recorded 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 CMP 1 during this monthly period.

1.5.12                            Impact Water Quality Monitoring during Dredging Operations of CMP 2 July 2014

1.5.13                            Impact Water Quality Monitoring during Dredging Operations of CMP 2 was conducted three times per week from 1 to 31 July 2014 during the reporting period. On each survey day, monitoring was conducted during both mid-ebb and mid-flood tides at two Reference (Upstream) stations and five Impact (Downstream) stations of the dredging operations at CMP 2. Monitoring was also conducted at five Sensitive Receiver Stations situated in Ma Wan, Shum Shui Kok, Tai Mo To and Tai Ho Bay. A total of twelve stations were monitored and locations of the sampling stations are shown in Figure 1.4. Monitoring at station THB2 during mid-ebb tide of 25 July 2014 and during both mid-flood and mid-ebb tides of 14 July 2014 were cancelled due to adverse weather condition. Monitoring on 18 July 2014 at all stations was cancelled due to adverse weather condition.

1.5.14                            Monitoring results are presented in Table C1 of Annex C. Daily dredging volume in July 2014 is reported in Annex D. Levels of DO, Turbidity and SS generally complied with the Action and Limit Levels (see Table C2 of Annex C for details) set in the Baseline Monitoring Report ([7]), except for the following occasion of exceedances discussed in Table 1.1 below.

1.5.15                            As presented in Table 1.1, the results indicated that the dredging operations at CMP 2 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-427/2011/A), are considered necessary for the dredging operations.

Table 1.1 Details of Exceedances Recorded at CMP 2 between 2 and 30 July 2014

Date

Tide

Parameter

Station

Type

Remarks

7 July 2014

Mid-Ebb

Bottom DO

DS2

Action

These exceedances were not considered as indicating any unacceptable impacts from the dredging operations to WSR outside the works area due to the following reasons:

    Stations DS2, DS4, DS5, WSR45C and WSR46 are located further away from the works area of CMP 2 when compared to station DS1 at which the levels of DOB did not exceed the Action and Limit Levels during the same tidal period.

    The lower DO levels recorded at stations DS2, DS4, DS5, WSR45C and WSR46 during this reporting period were possibly caused by the presence of thermocline within the water column, as indicated by the relatively larger drop in water temperature from the surface to the bottom water depths (see Annex E for the raw data). The thermocline would prevent mixing of surface layer water of higher DO with water underneath (ie at mid and bottom depths) and thus reducing DO levels at mid and bottom depths.

7 July 2014

Mid-Ebb

Bottom DO

DS4

Action

7 July 2014

Mid-Ebb

Bottom DO

DS5

Action

7 July 2014

Mid-Ebb

Bottom DO

WSR45C

Action

7 July 2014

Mid-Flood

Bottom DO

WSR45C

Action

16 July 2014

Mid-Flood

Bottom DO

WSR45C

Action

16 July 2014

Mid-Flood

Bottom DO

WSR46

Action

21 July 2014

Mid-Ebb

Bottom DO

WSR45C

Action

9 July 2014

Mid-Ebb

Bottom DO

WSR45C

Action

Dredging works were not being undertaken during these days. The Action Level exceedances of DO and SS recorded were thus not considered as indicating any unacceptable impacts from the dredging operations to WSR outside the works area.

9 July 2014

Mid-Ebb

Bottom DO

WSR46

Action

9 July 2014

Mid-Flood

Bottom DO

WSR45C

Action

9 July 2014

Mid-Flood

Bottom DO

WSR46

Action

11 July 2014

Mid-Flood

SS

WSR45C

Action

14 July 2014

Mid-Ebb

Surf and Mid DO

DS3

Action

14 July 2014

Mid-Flood

Bottom DO

WSR45C

Action


1.5.16                            Routine Water Quality Monitoring of SB CMP 1 July 2014

1.5.17                           The monitoring results for the Routine Water Quality Monitoring conducted in July 2014 in the wet season have been assessed for compliance with the Water Quality Objectives (WQOs) set by EPD. This consists of a review of the EPD routine water quality monitoring data for the wet season period (April to October) of 2003-2012 from stations in the Northwestern Water Control Zone, where the CMPs are located. For Salinity, the averaged value obtained from the Reference stations was used for the basis as the WQO. Levels of DO, Turbidity and SS were also assessed for compliance with the Action and Limit Levels (see Table C2 of Annex C for details). The monitoring results are shown in Figures 13-22 of Annex B and Tables C4-C5 of Annex C. Locations of monitoring stations are presented in Figure 1.5.

In-situ Measurements

1.5.18                           Analyses of results for July 2014 indicated that the levels of pH complied with the WQOs at all stations (Impact, Intermediate, Reference and Water Sensitive Receiver stations) in July 2014 (Figure 13 of Annex B). Levels of DO were lower than WQO requirements of 4 mg/L at most stations except at Tai Ho Bay stations THB1 and THB2 (Figure 14 of Annex B). As discussed in Table 1.1 above, the lower DO were possibly caused by the presence of thermocline within the water column that prevent mixing of surface layer water of higher DO with water underneath. The levels of Salinity exceeded WQO at most stations except at Impact stations (Figure 16 of Annex B). The lower salinities recorded at Tai Ho Bay stations are likely to be caused by the close proximity to the nearby streams, which release a large amount of freshwater runoff in the area during flooding, when compared to the Reference stations. The higher salinities recorded at Intermediate, Ma Wan, Shum Shui Kok and Tai Mo To stations are likely to be caused by the larger separation distance to Pearl River mouth, which release a large amount of freshwater runoff in the area during flooding, when compared to the Reference stations.

1.5.19                           The levels of DO exceeded the Limit Levels at Intermediate, Ma Wan, Shum Shui Kok and Tai Mo To stations while the levels of Turbidity exceeded the Action Level at Shum Shui Kok station (Figures 14 and 17 of Annex B; Table C4 of Annex C). As discussed in Table 1.1 above, these stations are located further away from CMP 1 when compared to Impact stations at which the levels of DO and Turbidity did not exceed the Action and Limit Levels during the same tidal period. In addition, the lower DO were possibly caused by the presence of thermocline within the water column that prevent mixing of surface layer water of higher DO with water underneath. Therefore, it is considered that the exceedances were caused by natural background variation in water quality of the area.

Laboratory Measurements

1.5.20                            Laboratory analysis of July 2014 results indicated that concentrations of Mercury and Silver were below their limit of reporting at all stations. Arsenic, Cadmium, Chromium, Copper, Lead, Nickel and Zinc were detected in samples from most stations (Figures 18-19 of Annex B). Concentrations of Arsenic, Cadmium, Chromium, Lead and Nickel appeared to be similar amongst all stations with no apparent spatial trend observed (Figure 18 of Annex B). Concentrations of Copper and Zinc were slightly higher at Tai Mo To station when compared to other stations (Figure 19 of Annex B).

1.5.21                            For nutrients, concentrations of Total Inorganic Nitrogen (TIN) at most stations exceeded the WQO (0.5mg/L) except at Sham Shui Kok and Tai Ho Bay 2 stations (Figure 20 of Annex B). It is important to note that due to the effect of the Pearl River, the North Western WCZ has historically experienced higher levels of TIN ([8]) . Therefore, the exceedances of TIN WQO at all stations are unlikely to be caused by the disposal operation at CMP 1. Ammonia Nitrogen (NH3-N) concentration was relatively similar amongst all stations (Figure 20 of Annex B). Level of 5-day Biochemical Oxygen Demand (BOD5) was similar amongst stations (Figure 21 of Annex B).

1.5.22                            Concentrations of SS exceeded the WQO (12.00 mg/L for wet season) at Reference, Sham Shui Kok, Tai Mo To and Tai Ho Bay 1 stations. However, SS at all stations complied with the Action and Limit Levels except at Sham Shui Kok station during the reporting period (Figure 15 of Annex B; Table C5 of Annex C). As discussed in Table 1.1 above, Sham Shui Kok station is located further away from CMP 1 when compared to Impact stations at which the levels of SS did not exceed the Action and Limit Levels during the same tidal period, therefore, the action level exceedance of SS is considered to be sporadic and characteristic of water quality in this area of Hong Kong.

1.5.23                            Overall, results of the Routine Water Quality Monitoring indicated that the disposal operation at CMP 1 did not appear to cause any unacceptable deterioration in water quality in July 2014.

1.5.24                            Water Column Profiling of CMP 1 July 2014

1.5.25                           Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 12 July 2014. The water quality monitoring results have been assessed for compliance with the WQOs as discussed in Section 1.5.17. The monitoring results were also compared with the Action and Limit Levels set in Baseline Monitoring Report (see Table C2 of Annex C for details).

In-situ Measurements

1.5.26                           Analyses of results for July 2014 indicated that levels of Salinity, pH and DO complied with the WQOs at both Downstream and Upstream stations (Table C6 of Annex C). DO and Turbidity also complied with the Action and Limit Levels.

Laboratory Measurements for SS

1.5.27                           Analyses of results for June 2014 indicated that the SS levels at Downstream and Upstream stations complied with the WQO and the Action and Limit Levels (Table C6 of Annex C).

1.5.28                           Overall, the monitoring results indicated that the mud disposal operation at CMP 1 did not appear to cause any deterioration in water quality during this reporting period.

1.6                                      Activities Scheduled for the Next Month

1.6.1                               The following monitoring activities will be conducted in the next monthly period of August 2014 for SB CMPs:

      Impact Water Quality Monitoring during Dredging Operations of CMP 2;

      Pit Specific Sediment Chemistry of CMP 1;

      Cumulative Impact Sediment Chemistry of CMP 1;

      Sediment Toxicity Tests of CMP 1;

      Routine Water Quality Monitoring of CMP 1;

      Water Column Profiling of CMP 1; and

      Demersal Trawling of CMP 1.

1.6.2                                The following monitoring activities will be conducted in the next monthly period of August 2014 for ESC CMPs:

      Water Quality Monitoring during Capping Operations of ESC CMPs; and

      Benthic Recolonisation Studies of ESC CMPs.

1.6.3                                The sampling schedule is presented in Annex A.

1.7                                      Study Programme

1.7.1                                A summary of the Study programme is presented in Annex F.


 



([1]) According to the Management Framework of Dredged/ Excavated Sediment of ETWB TC(W) No. 34/2002, contaminated sediment in general shall mean those sediment requiring Type 2 Confined Marine Disposal as determined according to this TC(W).

([2]) CAD options may involve use of excavated borrow pits, or may involve purpose-built excavated pits. CAD sites are those which involve filling a seabed pit with contaminated mud and capping it with uncontaminated material such that the original seabed level is restored and the contaminated material is isolated from the surrounding marine environment.7

([3]) Detailed Site Selection Study for a Proposed Contaminated Mud Disposal Facility within the Airport East/ East of Sha Chau Area (Agreement No. CE 12/2002(EP))

([4]) Under the CEDD study Contaminated Sediment Disposal Facility to the South of The Brothers (Agreement No. FM 2/2009)

([5]) ERM (2012) Environmental Monitoring and Audit (EM&A) Manual.Final First Review. Environmental Monitoring and Audit for Contaminated Mud Pits to the South of the Brothers and at East Sha Chau (2012-2017) Investigation. Agreement No. CE 23/2012(EP). Submitted to EPD in November 2012.

([6]) ERM (2010) Environmental Monitoring and Audit (EM&A) Manual.Final Second Review. Environmental Monitoring and Audit for Contaminated Mud Pit at Sha Chau (2009-2013) Investigation. Agreement No. CE 4/2009(EP). Submitted to EPD in November 2010.

([7]) ERM (2012) Baseline Monitoring Report.Environmental Monitoring and Audit for Contaminated Mud Pits to the South of the Brothers and at East Sha Chau (2012-2017) Investigation. Agreement No. CE 23/2012(EP). Submitted to EPD in October 2012.

([8]) http://www.epd.gov.hk/epd/misc/marine_quality/1986-2005/textonly/eng/index.htm