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 September 2017

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).  Detailed works schedule for ESC CMP V and SB CMPs is shown in Figure 1.1.  In September 2017, the following works were being undertaken:

·      Dredging operation at ESC CMP Vb;

·      Disposal of contaminated mud at ESC CMP Vd; and

·      Capping operation at SB CMP 2.

Figure 1.1      Works Schedule for ESC CMP V and SB CMPs

1.2                         Reporting Period

1.2.1                          This Monthly EM&A Report for September 2017 covers the EM&A activities for the reporting month of September 2017.

1.3                          Details of Sampling and Laboratory Testing Activities

1.3.1                           The following monitoring activities were undertaken for ESC CMP V in September 2017:

·      Water Quality Monitoring during Dredging of ESC CMP Vb was undertaken on 1, 6, 8, 11, 13, 15, 18, 20, 22 and 25 September 2017;

·      Water Column Profiling of ESC CMP Vd was undertaken on 7 September 2017; and

·      Pit Specific Sediment Chemistry of ESC CMP Vd was undertaken on 12 September 2017.

1.3.2                           The following monitoring activities were undertaken for SB CMPs in September 2017:

·      Water Quality Monitoring During Capping of SB CMPs was undertaken on 29 September 2017.

1.4                         Details of Outstanding Sampling and/or Analysis

1.4.1                           No outstanding sampling remained for September 2017.

1.4.2                           The following laboratory analyses are in progress during the preparation of this monthly report and will be presented in the next monthly report once the data are available:

·      Laboratory analyses of sediment samples collected for Pit Specific Sediment Chemistry of ESC CMP Vd in September 2017; and

·      Laboratory analyses of water samples collected for Water Quality Monitoring During Capping of SB CMPs in September 2017.

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 September 2017:

·      Water Quality Monitoring During Dredging of ESC CMP Vb in September 2017; and

·      Water Column Profiling of ESC CMP Vd in September 2017.

1.5.2                      Impact Water Quality Monitoring during Dredging Operations of ESC CMP Vb – September 2017

1.5.3                          Dredging activities were carried out on 1 – 2, 4 – 16, 18 – 25 September 2017 during this reporting period and monitoring was conducted on 1, 6, 8, 11, 13, 15, 18, 20, 22 and 25 September 2017.  During each survey day, monitoring was conducted during both mid-ebb and mid-flood tides at two Reference (Upstream) stations and five Impact (Downstream) stations around the dredging operations at ESC CMP Vb.  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. Levels of Dissolved Oxygen (DO), Turbidity and Suspended Solid (SS) were assessed for compliance with the Action and Limit Levels (see Table B1 of Annex B for details) set in the Baseline Monitoring Report ([3]).

1.5.4                           Monitoring results are presented in Table B2 of Annex B.  Daily dredging volume in September 2017 is reported in Annex C.  Levels of DO, Turbidity and SS generally complied with the Action and Limit Levels (see Table B1 of Annex B for details) set in the Baseline Monitoring Report ([4]), except for the following occasions discussed in Table 1.1 below.

1.5.5                           The results indicated that the dredging operations at ESC CMP Vb 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 at ESC CMP Vb between 1 and 25 September 2017

Date

Tide

Parameter

Station

Type of Exceedance

Remarks

8 September 2017

Mid-Ebb

Turbidity

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 reasons:

·   The exceedance was not considered as indicating any unacceptable impacts from the dredging operations to Water Sensitive Receivers (WSRs) outside the works area because Stations DS4 and DS5 are located further away from the works area of CMP Vb when compared to stations DS1 at which the levels of Turbidity did not exceed the Action and Limit Levels during the same tidal period.

·   In addition, levels of 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).

 

8 September 2017

Mid-Ebb

Turbidity

DS5

Limit

22 September 2017

Mid-Ebb

Turbidity

DS4

Action

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

22 September 2017

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 reasons:

·   The exceedances of Limit Levels were only recorded within a limited range at Impact stations DS1, DS2 and DS3 which are within ~1 km distance downstream from the dredging operation during one tidal period and exceedances were not recorded at any WSR stations.  In addition, the dredging rate was well within the limit as specified under the EP.  As such, there did not appear to be any evidence of unacceptable water quality impact as a result of the dredging operations at the CMP Vb.

·   In addition, levels of 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).

22 September 2017

Mid-Flood

Turbidity

DS2

Limit

22 September 2017

 

 

 

 

 

 

 

 

 

 

 

 

Mid-Flood

 

 

 

 

 

 

 

 

 

 

 

 

Turbidity

DS3

Limit

 

 

 

 

 

1.5.6                      Water Column Profiling of ESC CMP Vd – September 2017

1.5.7                           Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 7 September 2017.  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 2006 - 2015 from stations in the Northwestern Water Control Zone (WCZ), where the ESC CMPs are located ([5]).  For Salinity, the averaged value obtained from the Reference (Upstream) station 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 B1 of Annex B for details). 

In-situ Measurements

1.5.8                           Analyses of results for September 2017 indicated that levels of DO, Salinity and pH complied with the WQOs at both Downstream and Upstream stations (Table B3 of Annex B).  In addition, levels of DO and Turbidity at all stations complied with the Action and Limit Levels (Tables B1 and B3 of Annex B). 

Laboratory Measurements for Suspended Solids (SS)

1.5.9                           Analyses of results for September 2017 indicated that the SS levels complied with the WQO and the Action and Limit Levels at both Upstream and Downstream stations (Tables B1 and B3 of Annex B). 

1.5.10                        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.

1.6                          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 Monthly EM&A Report for September 2017:

·      Water Quality Monitoring during Capping Operations of SB CMPs in September 2017.

1.6.2                                                      Water Quality Monitoring during Capping of SB CMPs – September 2017

1.6.3                           Capping works at SB CMP 2 were conducted in September 2017 to supplement and revert the portion of consolidated capping layer to design level and was completed in September 2017.  Post-water quality monitoring was then conducted on 29 September 2017 after the completion of capping works at SB CMP 2.  The monitoring results obtained have been assessed for compliance with the WQOs (see Section 1.5.7 for details).  Levels of DO and Turbidity were also assessed for compliance with the Action and Limit Levels (see Table B4 of Annex B for details).  A total of fourteen (14) monitoring stations were sampled in September 2017 as shown in Figure 1.3.  Graphical presentation of the monitoring results is shown in Figures 1 - 6 of Annex D.

In-situ Measurements

1.6.4                                                     The levels of pH at all stations in September 2017 complied with the WQO (Table B5 of Annex B; Figure 1 of Annex D).  The levels of Turbidity at all stations complied with the Action and Limit levels in September 2017 (Table B5 of Annex B; Figure 2 of Annex D).  The levels of DO at all stations complied with the WQO and the Action and Limit levels in September 2017 (Table B5 of Annex B; Figure 4 of Annex D).  The levels of Salinity at Intermediate, Ma Wan, Sham Shui Kok and Tai Mo To stations are higher than the WQOmax in September 2017 (Table B5 of Annex B; Figure 6 of Annex D).  The Salinities at these stations were higher than the WQOmax as they were located further away from the Tai Ho Bay and Reference stations, thus experiencing less freshwater runoff from the nearby streams.  The levels of Salinity at Tai Ho Bay 2 station are lower than the WQOmin in September 2017 (Table B5 of Annex B; Figure 6 of Annex D).  The lower Salinity levels at Tai Ho Bay 2 station are likely to be caused by the freshwater runoff from the nearby streams.

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 2017 for ESC CMP V (see Annex A for the sampling schedule):

·         Routine Water Quality Monitoring of ESC CMP Vd;

·         Water Column Profiling of ESC CMP Vd; and

·         Pit Specific Sediment Chemistry of ESC CMP Vd. 

1.7.2                          No monitoring activities are scheduled in the next monthly period of October 2017 for SB CMPs.

1.8                         Study Programme

1.8.1                           A summary of the Study programme is presented in Annex E.

 
 

([1])    ERM (2013)  Final Report.  Submitted under Agreement No. CE 4/2009 (EP) Environmental Monitoring and Audit for Contaminated Mud Pit at East Sha Chau.  For CEDD.

([2])     ERM (2017)  Final Report.  Submitted under 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).  For CEDD.

([3])        ERM - Hong Kong, Ltd (2009) Baseline Monitoring Report.  For the Civil Engineering & Development Department, Hong Kong SAR Government.

([4])        ERM - Hong Kong, Ltd (2009) Baseline Monitoring Report.  For the Civil Engineering & Development Department, Hong Kong SAR Government.

([5])        http://epic.epd.gov.hk/EPICRIVER/marine/?lang=en