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

37th MONTHLY PROGRESS REPORT FOR September 2015

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 September 2015, the following works were being undertaken at the CMPs:

       Dredging operation at ESC CMP Vd;

       Capping operations at ESC CMP Va; and

       Disposal of contaminated mud at SB CMP 2.

Figure 1.1 Works Schedule for ESC CMPs and SB CMPs

1.2                                      Reporting Period

1.2.1                                This 37th Monthly Progress Report covers the EM&A activities for the reporting month of September 2015.

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                                The following monitoring activities have been undertaken for ESC CMPs in September 2015:

       Impact Water Quality Monitoring during Dredging Operations of ESC CMPs was undertaken on 24, 26, 28 and 30 September 2015.

 

1.3.2                                The following monitoring activities have been undertaken for SB CMPs in September 2015:

       Pit Specific Sediment Chemistry of CMP 2 was undertaken on 1 September 2015; and

       Water Column Profiling of CMP 2 was undertaken on 2 September 2015.

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained for September 2015.

1.4.2                                A summary of field activities conducted are presented in Annex A. 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 Cumulative Impact Sediment Chemistry of SB CMP 2 in August 2015; and

       Laboratory analyses of sediment samples collected for Pit Specific Sediment Chemistry of SB CMP 2 in September 2015.

 

1.5                                      Brief Discussion of the Monitoring Results for ESC CMPs

1.5.1                               Brief discussion of the monitoring results of the Impact Water Quality Monitoring during Dredging Operations of ESC CMP Vd conducted in September 2015 is presented below.

1.5.2                                Impact Water Quality Monitoring during Dredging Operations of ESC CMP Vd 24 to 30 September 2015

1.5.3                                Dredging operation of ESC CMP Vd commenced on 8 September 2015 and dredging activities were not carried out on 15, 16, 17 and 19 September 2015. Impact Water Quality Monitoring during Dredging Operations of ESC CMP Vd was conducted three times per week in September 2015 starting from 24 September 2015. 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 ESC CMP Vd. Monitoring was also conducted at one Sensitive Receiver Station situated in Ma Wan. A total of eight (8) stations were monitored and locations of the sampling stations are shown in Figure 1.2.

1.5.4                                Monitoring results are presented in Table B1 of Annex B. Daily dredging volume in September 2015 is reported in Annex C. Levels of Dissolved Oxygen (DO), Turbidity and Suspended Solid (SS) generally complied with the Action and Limit Levels (see Table B2 of Annex B for details) set in the Baseline Monitoring Report ([7]), except for the following occasion of exceedances discussed in Table 1.1 below.

1.5.5                                As presented in Table 1.1, the results indicated that the dredging operations at ESC CMP Vd did not appear to cause any unacceptable deterioration in water quality during this reporting period. Therefore, no further action, except for those recommended in the Environmental Permit (EP-312/2008/A), are considered necessary for the dredging operations.

 


Table 1.1 Details of Exceedances Recorded for Impact Water Quality Monitoring during Dredging Operations of ESC CMP Vd between 24 and 30 September 2015

Date

Tide

Parameter

Station

Type

Remarks

26 September 2015

Mid-Ebb

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

28 September 2015

Mid-Flood

Turbidity

DS2

Limit

28 September 2015

Mid-Flood

Turbidity

DS3

Action

28 September 2015

Mid-Ebb

Turbidity

DS1

Action

It is suspected that the non-compliance of Turbidity was related to the dredging activities at CMP Vd. Linear Regression Analysis was carried out and there was no spatial trend of increasing turbidity with proximity to the pit due to dredging activities. Moreover, level of Turbidity in Sensitive Receiver station (MW1) did not exceed the Action and Limit Level. Therefore, it is considered that the high levels of Turbidity were localized around the dredging location.

In addition, levels of suspended solid (SS) at all stations complied with the Action and Limit levels. Therefore, it is considered that the dredging operations did not cause adverse water quality impact in terms of SS levels, which are more representative to determine the effects of dredging operation to nearby sensitive receivers (e.g. fisheries).

The Contractor was informed on the exceedances and ensured the proper execution of the good dredging practice measures, e.g. reduced operations speed of the dredger and tightly closed the grab during translocating the dredged material from the seabed to the barge. Subsequent water quality monitoring on 30 September 2015 indicated that DO, Turbidity and SS levels at all stations complied with the Action and Limit levels.

28 September 2015

Mid-Ebb

Turbidity

DS2

Action

28 September 2015

Mid-Ebb

Turbidity

DS3

Action

28 September 2015

Mid-Ebb

Turbidity

DS4

Limit

28 September 2015

Mid-Ebb

Turbidity

DS5

Limit


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 37th Monthly Progress Report:

       Pit Specific Sediment Chemistry of CMP 2 in August 2015; and

       Water Column Profiling of CMP 2 in September 2015;

1.6.2                                Pit Specific Sediment Chemistry of CMP 2 August 2015

1.6.3                               Monitoring locations for Pit Specific Sediment Chemistry for CMP 2 are shown in Figure 1.3. A total of six (6) monitoring stations were sampled in August 2015.

1.6.4                               Copper exceeded the Upper Chemical Exceedance Level (UCEL) at Active Pit stations SB-NPBA and SB-NPBB (Figure 1 of Annex D). Mercury exceeded the Lower Chemical Exceedance Level (LCEL) at Active Pit station SB-NPBB and Near Pit station SB-NNBA (Figure 2 of Annex D). Exceedances of UCEL were also recorded for Silver at Active Pit station SB-NPBA (Figure 2 of Annex D). The concentrations of other inorganic contaminants (Arsenic, Cadmium, Chromium, Nickel, Lead and Zinc) were lower than the LCEL at all stations (Figures 1 and 2 of Annex D).

1.6.5                               Higher Copper and Silver concentrations were recorded within the Active Pit station only which were receiving contaminated mud during the reporting month. Higher Mercury concentrations were recorded at one Active Pit station and one Near Pit station while the stations between them, Pit Edge stations, was recorded with lower concentration. Therefore, there is no evidence indicating any dispersal of contaminants from the active pit due to the disposal activities.

1.6.6                               For organic contaminants, the concentrations of Total Organic Carbon (TOC) were similar at all stations, except lower concentration was recorded in Pit Edge station NEBB (Figure 3 of Annex D). Tributyltin (TBT) concentrations were observed to be higher at Active Pit station SB-NPBA (Figure 4 of Annex D). Low and High Molecular Weight Polycyclic Aromatic Hydrocarbons (PAHs), Total Polychlorinated Biphenyls (PCBs), 4,4-dichlorodiphenyldichloroethylene (DDE) and Total dichlorodiphenyltrichloroethane (DDT) concentrations were below the limit of reporting at most stations, except High MW PAHs at Active Pit stations SB-NPBA and SB-NPBB and Low MW PAHs at Active Pit station SB-NPBB (Figure 5 of Annex D).

 

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 2 in August 2015. Statistical analysis will be undertaken and presented in the quarterly report to investigate whether there are any unacceptable impacts in the area caused by the contaminated mud disposal.

1.6.8                                Water Column Profiling of CMP 2 September 2015

1.6.9                               Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 2 September 2015. 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 2004 - 2013 from stations in the Northwestern Water Control Zone (WCZ), where the CMPs are located ([8]). For Salinity, the averaged value obtained from the Reference stations was used for the basis as the WQO. Levels of DO and Turbidity were also assessed for compliance with the Action and Limit Levels (see Table B3 of Annex B for details).

In-situ Measurements

1.6.10                           Analyses of results for September 2015 indicated that levels of Salinity, DO and pH complied with the WQOs at both Downstream and Upstream stations (Table B4 of Annex B). In addition, DO and Turbidity at all stations complied with the Action and Limit Levels (Tables B3 and B4 of Annex B).

Laboratory Measurements for SS

1.6.11                           Analyses of results for September 2015 indicated that the SS levels at both Upstream and Downstream stations complied with the WQO. Both Upstream and Downstream stations also complied with the Action and Limit Levels (Tables B3 and B4 of Annex B).

Overall, the monitoring results indicated that the mud disposal operation at CMP 2 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 October 2015 for SB CMPs:

       Pit Specific Sediment Chemistry of CMP 2;

       Routine Water Quality Monitoring of CMP 2; and

       Water Column Profiling of CMP 2.

1.7.2                               The following monitoring activities will be conducted in the next monthly period of October 2015 for ESC CMPs:

       Impact Monitoring during Dredging Operations of ESC CMP Vd.

1.7.3                                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 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]) ERM (2009). Draft Second Review of the EM&A Manual. Under Agreement No. CE 4/2009 (EP) EM&A for Contaminated Mud Pit at Sha Chau (2009-2013) Investigation