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

26th MONTHLY PROGRESS REPORT FOR OCTOBER 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 October 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 26th Monthly Progress Report covers the EM&A activities for the reporting month of October 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 October 2014.

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

         Impact Water Quality Monitoring during Dredging Operations was undertaken for CMP 2 three times per week on 3, 5, 7, 9, 11, 13, 15, 18, 20, 22, 24, 27, 29 and 31 October 2014;

         Water Column Profiling for CMP 1 was undertaken on 8 October 2014;

         Routine Water Quality Monitoring for CMP 1 was undertaken on 14 October 2014; and

         Pit Specific Sediment Chemistry for CMP 1 was undertaken on 16 October 2014.

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained for October 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 water samples collected for Routine Water Quality Monitoring of CMP 1 in October 2014.

         Laboratory analyses of sediment samples collected for Pit Specific Sediment Chemistry of CMP 1 in October 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 26th Monthly Progress Report:

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

         Pit Specific Sediment Chemistry of CMP 1 conducted in September 2014;

         Sediment Chemistry after a Major Storm for CMP 1 conducted in September 2014;

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

         Water Column Profiling of CMP 1 conducted on 8 October 2014.

1.5.2                                Cumulative Impact Sediment Chemistry of CMP 1 August 2014

1.5.3                               Monitoring locations for Cumulative Impact Sediment Chemistry for CMP 1 are shown in Figure 1.2. A total of eleven (11) monitoring stations were sampled in August 2014.

1.5.4                                Analyses of results for the Cumulative Impact Sediment Chemistry Monitoring indicated that the concentrations of most inorganic contaminants, except Arsenic, were below the Lower Chemical Exceedance Level (LCEL) in August 2014 (Figures 1 and 2 of Annex B). Concentration of Arsenic exceeded the LCEL at Capped Pit station SB-RCA.

1.5.5                                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 ([7]). It is presumed that the natural concentrations of Arsenic are similar in onshore and offshore sediments ([8]), 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 CMP 1 but rather as a result of naturally occurring deposits.

1.5.6                                For organic contaminants, concentration of Total Organic Carbon (TOC) at Tai Ho Bay Station 2 (THB2) was recorded to be higher than other stations (Figure 3 of Annex B). Concentrations of Tributyltin (TBTs) were recorded to be higher at Near-field station SB-RNB and Mid-field station SB-RMB (Figure 4 of Annex B). Total Dichloro-Diphenyl-Trichloroethane (DDT), 4,4-Dichloro-Diphenyl-Dichloroethylene (4,4-DDE), Total Polychlorinated Biphenyls (PCBs) as well as Low and High Molecular Weight Polycyclic Aromatic Hydrocarbons (MW PAHs) were recorded below the limit of reporting at all stations.

1.5.7                               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 August 2014.

1.5.8                                Pit Specific Sediment Chemistry of CMP 1 September 2014

1.5.9                               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 September 2014.

1.5.10                           The concentrations of all inorganic contaminants were lower than the LCEL at all stations in September 2014 (Figures 5 and 6 of Annex B).

1.5.11                           For organic contaminants, the concentrations of TOC and TBTs were observed to be higher at Active Pit station SB-NPAB (Figures 7 and 8 of Annex B). Low MW PAHs, High MW PAHs, Total DDT, 4,4-DDE and Total PCBs were recorded below the limit of reporting at all stations in September 2014.

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

1.5.13                           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 September 2014.

1.5.14                            Sediment Chemistry after a Major Storm of CMP 1 September 2014

1.5.15                            Sampling for Sediment Chemistry after a Major Storm Event was conducted at eleven (11) monitoring stations (Figure 1.2) on 19 September 2014 after the visit of Typhoon Kalmaegi, which led to the issue of Gale or Storm Wind Signal No.8 on 16 September 2014. The track of Doksuri is shown in Figure 1.4.

Figure 1.4 Track of Typhoon Kalmaegi from 12 to 17 September 2014 (Source: Hong Kong Observatory)

1.5.16                            Analyses of results for the Sediment Chemistry after a Major Storm indicated that the concentrations of most inorganic contaminants, except Arsenic, were below the LCEL (Figures 9 and 10 of Annex B). Concentration of Arsenic exceeded the LCEL at Capped Pit stations SB-RCA and SB-RCB. As discussed in Section 1.5.5, the slight exceedances of the LCEL for Arsenic are unlikely to be caused by the disposal operations at CMP 1 but rather as a result of naturally occurring deposits.

1.5.17                            Overall, there appeared to be no evidence showing the failure of CMPs in retaining disposed mud or causing contamination of sediments after the major storm event in September 2014.

 

1.5.18                            Impact Water Quality Monitoring during Dredging Operations of CMP 2 October 2014

1.5.19                            Impact Water Quality Monitoring during Dredging Operations of CMP 2 was conducted three times per week from 1 to 31 October 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 (12) stations were monitored and locations of the sampling stations are shown in Figure 1.5.

1.5.20                            Monitoring results are presented in Table C1 of Annex C. Daily dredging volume in October 2014 is reported in Annex D. Levels of Dissolved Oxygen (DO), Turbidity and Suspended Solids (SS) generally complied with the Action and Limit Levels (see Table C2 of Annex C for details) set in the Baseline Monitoring Report ([9]), except for the following occasion of exceedances discussed in Table 1.1 below.

1.5.21                            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 31 October 2014

Date

Tide

Parameter

Station

Type

Remarks

7 October 2014

Mid-Flood

Turbidity

DS2

Action

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

    Stations DS2, DS3, WSR45C and WSR46 are located further away from the works area of CMP 2 when compared to station DS1 at which the levels of Turbidity and SS did not exceed the Action and Limit Levels during the same tidal period.

 

9 October 2014

Mid-Flood

SS

DS3

Action

9 October 2014

Mid-Flood

Turbidity

WSR45C

Limit

9 October 2014

Mid-Flood

Turbidity

WSR46

Action

11 October 2014

Mid-Flood

SS

DS2

Action

20 October 2014

Mid-Flood

SS

DS2

Action

20 October 2014

Mid-Flood

SS

DS3

Action

27 October 2014

Mid-Ebb

SS

DS2

Action

27 October 2014

Mid-Flood

SS

DS2

Action

29 October 2014

Mid-Flood

SS

DS2

Action

 

22 October 2014

Mid-Flood

Turbidity

DS1

Limit

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:

    Action / Limit Level Exceedances of Turbidity and SS were recorded at Stations DS1 and DS2 which are located in the vicinity of the works area during one tidal period only, and exceedances were not recorded at stations WSR45C and WSR46 which are the nearest WSRs. It is thus considered that the exceedances were not indicating any unacceptable impacts from the dredging operations to the nearby WSRs.

22 October 2014

Mid-Flood

Turbidity

DS2

Limit

22 October 2014

Mid-Flood

SS

DS1

Action

22 October 2014

Mid-Flood

SS

DS2

Action

 

 

 

 

 

 

 

 

 

 

9 October 2014

Mid-Ebb

SS

DS1

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:

    Station DS1 is located close to the works area whilst stations DS4 and DS5 are located further away from the works area of CMP 2 when compared to stations DS2-3 at which the levels of Turbidity and SS did not exceed the Action and Limit Levels during the same tidal period. These exceedances were thus not considered as indicating any unacceptable impacts from the dredging operations to WSR outside the works area.

9 October 2014

Mid-Ebb

Turbidity

DS4

Action

9 October 2014

Mid-Ebb

Turbidity

DS5

Action

9 October 2014

Mid-Ebb

SS

DS4

Action

9 October 2014

Mid-Ebb

SS

DS5

Action

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


1.5.22                            Water Column Profiling of CMP 1 October 2014

1.5.23                           Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 8 October 2014. The water quality monitoring results 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 CMP is located. 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

1.5.24                           Analyses of results for October 2014 indicated that levels of Salinity, turbidity, DO and pH complied with the WQOs at both Downstream and Upstream stations (Table C3 of Annex C).

Laboratory Measurements for SS

1.5.25                           Analyses of results for September 2014 indicated that the SS levels at Upstream station complied with the WQO. The Downstream station exceeded the WQO. SS levels at all stations complied with the Action and Limit Levels (Table C3 of Annex C).

1.5.26                           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 November 2014 for SB CMPs:

    Pit Specific Sediment Chemistry of CMP 1;

    Impact Monitoring during Dredging Operations of CMP 2;

    Routine Water Quality Monitoring of CMP 1; and

    Water Column Profiling of CMP 1.

1.6.2                                No monitoring activity is scheduled to be undertaken in the next monthly period of November 2014 for 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 E.


 



([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]) Sewell RJ (1999) Geochemical Atlas of Hong Kong.Geotechnical Engineering Office, Government of the Hong Kong Special Administrative Region

([8]) 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

([9]) 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.