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

24th MONTHLY PROGRESS REPORT FOR August 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 August 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 24th Monthly Progress Report covers the EM&A activities for the reporting month of August 2014.

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                               The following monitoring activities have been undertaken for ESC CMPs in August 2014:

                Water Quality Monitoring during Capping was undertaken for ESC CMPs on 9 August 2014; and

                Benthic Recolonisation Studies was undertaken for ESC CMPs on 14 August 2014.

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

                Impact Water Quality Monitoring during Dredging Operations was undertaken for CMP 2 three times per week on 1, 4, 6, 8, 11, 13, 15, 18, 20, 22, 26, 28 and 30 August 2014;

                Pit Specific Sediment Chemistry for CMP 1 was undertaken on 5 August 2014;

                Routine Water Quality Monitoring for CMP 1 was undertaken on 7 August 2014;

                Sediment Toxicity Tests for CMP 1 was undertaken on 12 and 13 August 2014;

                Water Column Profiling for CMP 1 was undertaken on 14 August 2014;

                Cumulative Impact Sediment Chemistry for CMP 1 was undertaken from 19 to 21 August 2014; and

                Demersal Trawling for CMP 1 was undertaken on 20 and 21 August 2014.

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained for August 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 Benthic Recolonisation Studies of ESC CMPs in August 2014;

             Laboratory analyses of sediment samples collected for Cumulative Impact Sediment Chemistry of CMP 1 in August 2014;

             Laboratory analyses of sediment samples collected for Sediment Toxicity Tests of CMP 1 in August 2014; and

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

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

1.5                                      Brief Discussion of the Monitoring Results for ESC CMPs

1.5.1                               Brief discussion of the monitoring results of the Water Quality Monitoring during Capping of ESC CMPs conducted on 9 August 2014 is presented below.

1.5.2                                Water Quality Monitoring during Capping August 2014

1.5.3                                The monitoring results obtained during August 2014 sampling in the wet season have been assessed for compliance with the Water Quality Objectives (WQOs) through a review of the Environmental Protection Department (EPD) routine water quality monitoring data for the wet season period (April to October) of 2003 2012 from stations in the North Western Water Control Zone (WCZ), where ESC CMPs are located. For Salinity, the average value obtained from the Reference stations was used for the basis as the WQO. A total of sixteen (16) monitoring stations were sampled in August 2014 as shown in Figure 1.2. Graphical presentation of the monitoring results is provided in Annex B.

In-situ Measurements

1.5.4                                Graphical presentation of the monitoring results is shown in Figures 1-6 of Annex B. Levels of Dissolved Oxygen (DO), pH and Salinity at all stations in August 2014 complied with the WQO.

Laboratory Measurements for Suspended Solids (SS)

1.5.5                                Concentrations of SS complied with the WQO at most stations in August 2014, except for the Impact stations (Figure 7 of Annex B). However, there did not appear to be any spatial trend of increasing SS levels towards the capping operations. Further statistical analysis will be undertaken in the quarterly report to investigate whether the capping operations at ESC CMPs is causing any unacceptable deterioration in water quality of the area.

1.6                                      Brief Discussion of the Monitoring Results for SB CMPs

1.6.1                               Brief discussion of the monitoring results of the following activities for SB CMPs is presented in this 24th Monthly Progress Report:

             Pit Specific Sediment Chemistry of CMP 1 conducted in July and August 2014;

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

             Routine Water Quality Monitoring of CMP 1 conducted on 7 August 2014; and

             Water Column Profiling of CMP 1 conducted on 14 August 2014.

1.6.2                                Pit Specific Sediment Chemistry of CMP 1 July and August 2014

1.6.3                               Monitoring locations for Pit Specific Sediment Chemistry for CMP 1 are shown in Figure 1.3. A total of six (6) monitoring stations were sampled in both July and August 2014.

1.6.4                               The concentrations of all inorganic contaminants were lower than the Lower Chemical Exceedance Level (LCEL) at all stations in July and August 2014 (Figures 8-9 and 12-13 of Annex B).

1.6.5                               For organic contaminants, the concentrations of Total Organic Carbon (TOC) and Tributyltin (TBTs) were observed to be higher at Active Pit stations (Figures 10-11 and 14-15 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 July and August 2014.

1.6.6                               As higher TOC and TBTs concentrations were recorded within the Active Pit stations only which were receiving contaminated mud during the reporting month, there is no evidence indicating any dispersal of contaminants from the active pit.

1.6.7                               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 July and August 2014.

1.6.8                                Impact Water Quality Monitoring during Dredging Operations of CMP 2 August 2014

1.6.9                                Impact Water Quality Monitoring during Dredging Operations of CMP 2 was conducted three times per week from 1 to 31 August 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 22 August 2014 and during both mid-flood and mid-ebb tides of 13 August 2014 were cancelled due to adverse weather condition.

1.6.10                            Monitoring results are presented in Table C1 of Annex C. Daily dredging volume in August 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.

1.6.11                            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 1 and 30 August 2014

Date

Tide

Parameter

Station

Type

Remarks

6 August 2014

Mid-Flood

Bottom DO

WSR45C

Action

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

    Stations 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 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.

8 August 2014

Mid-Flood

Bottom DO

WSR45C

Action

18 August 2014

Mid-Ebb

Bottom DO

WSR45C

Action

18 August 2014

Mid-Flood

Bottom DO

WSR45C

Action

20 August 2014

Mid-Ebb

Bottom DO

DS5

Action

20 August 2014

Mid-Ebb

Bottom DO

WSR45C

Action

20 August 2014

Mid-Ebb

Bottom DO

WSR46

Action

20 August 2014

Mid-Flood

Bottom DO

WSR45C

Action

22 August 2014

Mid-Ebb

Bottom DO

DS5

Action

22 August 2014

Mid-Ebb

Bottom DO

WSR45C

Action

22 August 2014

Mid-Flood

Bottom DO

WSR45C

Action

11 August 2014

Mid-Ebb

Surf and Mid DO

DS4

Action

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

    Stations DS3, 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 surface and mid-depth DO, Turbidity and SS did not exceed the Action and Limit Levels during the same tidal period.

 

11 August 2014

Mid-Ebb

Surf and Mid DO

DS5

Action

11 August 2014

Mid-Ebb

Surf and Mid DO

WSR45C

Action

11 August 2014

Mid-Flood

Turbidity

DS3

Action

11 August 2014

Mid-Flood

Turbidity

DS5

Action

13 August 2014

Mid-Ebb

Surf and Mid DO

DS3

Action

13 August 2014

Mid-Ebb

Surf and Mid DO

DS4

Action

13 August 2014

Mid-Ebb

Surf and Mid DO

DS5

Action

13 August 2014

Mid-Ebb

Surf and Mid DO

WSR45C

Action

13 August 2014

Mid-Ebb

Surf and Mid DO

WSR46

Action

13 August 2014

Mid-Flood

SS

WSR45C

Action

20 August 2014

Mid-Flood

Surf and Mid DO

WSR45C

Action

28 August 2014

Mid-Ebb

SS

DS5

Action


1.6.12                            Routine Water Quality Monitoring of SB CMP 1 August 2014

1.6.13                           The water quality monitoring results have been assessed for compliance with the WQOs as discussed in Section 1.5.3. 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 16-25 of Annex B and Tables C4-C5 of Annex C. Locations of monitoring stations are presented in Figure 1.5.

In-situ Measurements

1.6.14                           Analyses of results for August 2014 indicated that the levels of pH complied with the WQOs at all stations (Impact, Intermediate, Reference and Water Sensitive Receiver stations) in August 2014 (Figure 16 of Annex B). Levels of DO were greater than WQO requirements of 4 mg/L at most stations except at Reference stations and Ma Wan station (Figure 17 of Annex B). As Reference stations and Ma Wan station are located further away from the works area of CMP 1, it is considered that the lower DO at Reference stations and Ma Wan station were possibly caused by natural background variation in water quality of the area. The levels of Salinity exceeded WQO at most stations except at Ma Wan and Shum Shui Kok stations (Figure 19 of Annex B). The lower salinities recorded at Impact, Intermediate, Tai Mo To and 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.

1.6.15                           The levels of DO and Turbidity complied with the Action and Limit Levels at all Impact, Shum Shui Kok and Tai Mo To stations (Figures 17 and 20 of Annex B; Table C4 of Annex C).

Laboratory Measurements

1.6.16                            Laboratory analysis of August 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 21-22 of Annex B). Concentrations of Arsenic, Cadmium, Chromium, Copper, Lead, Nickel and Zinc appeared to be higher at Shum Shui Kok station, but no clear spatial trend was observed. Detailed statistical analysis will be presented in the Quarterly Report to observe any spatial and temporal trends.

1.6.17                            For nutrients, concentrations of Total Inorganic Nitrogen (TIN) at all stations exceeded the WQO (0.5mg/L) (Figure 23 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 23 of Annex B). Level of 5-day Biochemical Oxygen Demand (BOD5) was similar amongst stations (Figure 24 of Annex B).

1.6.18                            Concentrations of SS exceeded the WQO (12.00 mg/L for wet season) at Reference and Tai Mo To stations. However, SS at all stations complied with the Action and Limit Levels during the reporting period (Figure 25 of Annex B; Table C5 of Annex C).

1.6.19                            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 August 2014.

1.6.20                            Water Column Profiling of CMP 1 August 2014

1.6.21                           Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 14 August 2014. The water quality monitoring results have been assessed for compliance with the WQOs as discussed in Section 1.5.3. 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

1.6.22                           Analyses of results for August 2014 indicated that levels of Salinity and pH complied with the WQOs at both Downstream and Upstream stations (Table C6 of Annex C). Levels of DO exceeded the WQO at Upstream stations and it is considered that the lower DO was possibly caused by natural background variation in water quality of the area. DO and Turbidity at Downstream stations complied with the Action and Limit Levels.

Laboratory Measurements for SS

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

1.6.24                           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.

 

1.7                                      Activities Scheduled for the Next Month

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

 

                Impact Water Quality Monitoring during Dredging Operations of CMP 2;

                Pit Specific Sediment Chemistry of CMP 1; and

                Water Column Profiling of CMP 1.

1.7.2                                The sampling schedule is presented in Annex A.

1.8                                      Study Programme

1.8.1                                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