Agreement No. CE 23/2012 (EP)
Environmental Monitoring and Audit
for Contaminated Mud Pits at the South of The Brothers and at East Sha Chau (2012-2017) - Investigation

14TH MONTHLY PROGRESS REPORT FOR OCTOBER 2013

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 East of Sha Chau (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 undertaken under Agreement No. CE 23/2012 (EP) covers the dredging, disposal and capping operations of the SB CMPs as well as CMPs at East of Sha Chau (ESC). In October 2013, the following works were being undertaken at the CMPs:

             Capping was being undertaken at 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.

1.2                                      Reporting Period

1.2.1                                This Monthly Progress Report covers the EM&A activities for the reporting month of October 2013.

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                               No monitoring activities were undertaken for CMP IV and V in the monitoring month of October 2013.

1.3.2                               The following monitoring activities have been undertaken for SB CMPs in September 2013:

             Pit Specific Sediment Chemistry was conducted for CMP 1 on 11 October 2013;

             Routine Water Quality Monitoring was conducted for CMP 1 on 3, 5, 8, 11, 13, 15, 17, 19, 21, 24, 26, 29 and 31 October 2013;

             Water Column Profiling was undertaken on 24 October 2013; and,

             Impact Water Quality Monitoring during Dredging Operations was undertaken for SB CMP 2 three times per week (i.e. 2, 4, 7, 10, 12, 14, 16, 18, 21, 23, 25, 28 and 30 October 2013) in this reporting month in accordance with the EM&A Manual.

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained for October 2013. Laboratory analyses of Pit Specific Sediment Chemistry of SB CMP 1 conducted in September and October 2013 and laboratory analysis of Cumulative Impact Sediment Chemistry Monitoring of CMP V undertaken in August 2013 are yet to be completed. Laboratory analyses of Suspended Solids (SS) for Water Quality Monitoring during Dredging Operations of CMP 2 collected on 30 October 2013 was still in progress during the preparation of this monthly report. A summary of field activities conducted are presented in Annex A.

1.5                                      Brief Discussion of the Monitoring Results for CMP V

1.5.1                               Brief discussion of the monitoring results of Pit Specific Sediment Chemistry Monitoring conducted in August 2013 is presented in this 14th Monthly Report. Detailed discussion will be presented in the corresponding Quarterly Report.

1.5.2                                Pit Specific Sediment Chemistry of CMP Va August 2013

1.5.3                               Monitoring locations for Pit Specific Sediment Chemistry for CMP Va are shown in Figure 1.1. A total of six monitoring stations were sampled in August 2013. It is observed that the variations of metal concentrations at Active Pit Stations NPDA were much larger (i.e. greater standard deviation) when compared to other stations (Figures 1 and 2 of Annex B).

1.5.4                               Cadmium, Chromium, Lead, Zinc, Mercury and Nickel complied with the Lower Chemical Exceedance Level (LCEL) at all stations in August 2013 (Figures 1 and 2 of Annex B). Concentrations of Arsenic exceeded the LCEL at Active Pit station NPDB, Pit Edge stations NEDA and NEDB and Near Pit station NNDA (Figures 1 of Annex B). Concentrations of Copper and Silver exceeded LCEL at Active Pit station NPDA (Figures 1 and 2 of Annex B).

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 exceedances of the LCEL for Arsenic are unlikely to be caused by the disposal operations at CMP Va but rather as a result of naturally occurring deposits.

1.5.6                               In addition, the Active Pit station NPDA is located within CMP Va which was receiving contaminated mud during the reporting period. As such, the exceedances of LCEL for Copper and Silver which were recorded at the Active station NPDA only are not considered as indicating any dispersal of contaminated mud from CMP Va.

1.5.7                               Total Organic Carbon (TOC) concentration was similar amongst all stations in August 2013 (Figure 3 of Annex B). Tributyltin (TBT) concentration was found to be higher at Active Pit station NPDA (Figure 4 of Annex B) in August 2013.

1.5.8                               Low Molecular Weigh Polycyclic Aromatics Hydrocarbons (Low MW PAHs) concentrations at Active station NPDA were recorded above the limit of reporting in August 2013. High Molecular Weight Polycyclic Aromatics Hydrocarbons (High MW PAHs) concentrations at Active Pit stations NPDA and NPDB and Pit-edge station NEPA were also detected above the limit of reporting in August 2013 (Figure 5 of Annex B). However, these detected concentrations of Low and High MW PAHs were below LCELs.

1.5.9                               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 the stations in August 2013.

1.5.10                           As explained in Section 1.5.6, Active Pit stations NPDA and NPDB are located within CMP Va which was receiving contaminated mud during the reporting period. Therefore, the higher concentrations of contaminants (including metals and organic contaminants) recorded at the two stations only are not considered as indicating any dispersal of contaminated mud from CMP Va. Nevertheless, detailed analysis will be presented in the Quarterly Report to reveal any trend of increasing sediment contaminant concentrations towards CMP Va.

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 Va during this monthly period.

1.6                                      Brief Discussion of the Monitoring Results for SB CMPs

1.6.1                                Impact Water Quality Monitoring during Dredging Operations of CMP 2 2 to 28 October 2013

1.6.2                                Monitoring data collected for CMP 2 from 2 to 28 October 2013 are presented in this monthly report. Detailed discussion will be presented in the corresponding Quarterly Report.

1.6.3                                Impact Water Quality Monitoring during Dredging Operations of CMP 2 (i.e. from 2 October to 28 October 2013) was conducted three times per week for a total of nine (9) sampling days. On each survey day, sampling was conducted during both mid-ebb and mid-flood tides at two Reference (Upstream) stations upstream and five Impact (Downstream) stations downstream of the dredging operations at CMP 2. Monitoring was also conducted at five Sensitive Receiver Stations (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 1.2.

1.6.4                                Monitoring results from 2 to 28October are presented in Table C1 of Annex C. 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 ([9]), except for the following occasions of exceedances shown in Table 1.1 below.

Table 1.1 Details of exceedances recorded at SB CMP 2 in October 2013

Date

Tide

Parameter

Station

Type

4 October 2013

Mid-Ebb

Turbidity

WSR46

Limit

 

 

SS

WSR46

Action

 

Mid-Flood

Turbidity

DS3

Action

 

 

SS

DS2

Action

 

 

SS

DS3

Action

7 October 2013

Mid-Ebb

Turbidity

DS1

Limit

 

 

Turbidity

DS2

Action

 

 

Turbidity

DS3

Limit

 

 

Turbidity

DS4

Limit

 

 

Turbidity

DS5

Limit

 

 

SS

DS1

Limit

 

 

SS

DS3

Action

 

 

SS

DS4

Action

 

 

SS

DS5

Action

 

Mid-Flood

Turbidity

DS1

Limit

 

 

SS

DS1

Limit

 

 

SS

WSR46

Action

10 October 2013

Mid-Ebb

Turbidity

DS1

Action

 

Mid-Flood

Turbidity

DS1

Limit

 

 

Turbidity

DS2

Action

 

 

SS

DS1

Limit

18 October 2013

Mid-Ebb

SS

DS1

Action

 

Mid-Flood

Turbidity

WSR46

Action

 

 

SS

WSR45C

Action

 

 

SS

WSR46

Action

21 October 2013

Mid-Flood

SS

DS1

Action

23 October 2013

Mid-Flood

Turbidity

DS1

Limit

 

 

SS

DS1

Action

 

 

SS

DS4

DS4

25 October 2013

Mid-Flood

Turbidity

DS1

Limit

 

 

SS

DS1

Limit

 

 

SS

DS2

Action

 

 

SS

DS3

Action

28 October 2013

Mid-Flood

Turbidity

DS1

Limit

 

 

SS

DS1

Limit

 

 

SS

DS3

Action

1.6.5                                It should be noted that the exceedances on 4 (mid-ebb and mid-flood tides) and 18 October 2013 (mid-flood tide) were recorded at stations which are located further away from the works area when compared to station DS1 at which the levels of SS, Turbidity and DO did not exceed the Action and Limit Levels during the same tidal period on the same day. As such, these recorded exceedances are not likely to be caused by the dredging works at CMP 2.

1.6.6                                Linear Regression was conducted to determine any significant spatial trend of Turbidity and SS levels recorded at stations DS1 to DS5 on 7 October 2013. Results of the statistical analysis did not indicate any significant spatial trend of increasing Turbidity and SS levels with proximity to the dredging operations (i.e. r2 value < 0.6). The statistical analysis was also performed for SS levels at stations DS1 to DS5 recorded on 25 October 2013 (mid-flood). Although a significant spatial trend was observed, the exceedances of Action and 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 and exceedances were not recorded at any WSR stations. In addition, the spatial trend was only recorded on one tide within only one monitoring day. 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.

1.6.7                                Exceedances at DS1 and other stations were also detected on 10, 18 (mid-ebb), 21 (mid-flood), 23 (mid-flood), 25 (mid-flood) and 28 October 2013 (mid-flood). However, these exceedances did not indicate any trend of increasing SS or Turbidity levels toward the dredging operations. Instead, high levels of Turbidity and SS and low levels of DO were occasionally recorded during baseline monitoring which are considered to be sporadic events and characteristic of water quality in this area of Hong Kong. Therefore, the Action and Limit Level exceedances may be caused by natural background variation in water quality of the area.

1.6.8                                Overall, 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.

 

1.6.9                                Routine Water Quality Monitoring for SB CMP 1 October 2013

1.6.10                           The results for the Routine Water Quality Monitoring conducted on 3, 5, 8, 11, 13 and 15 October 2013 in the wet season 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 2002-2011 from stations in the Northwestern Water Control Zone, where the CMPs are located. For Salinity, the average value obtained from the Upstream Station was used for the basis as the WQO. In-situ monitoring and laboratory results are shown in Tables C3 and C4 of Annex C, with graphical presentation provided in Annex B. Locations of monitoring stations were presented in Figure 1.3 and 1.4.

In-situ Measurements

1.6.11                           Analysis of results for 3, 5, 8, 11, 13 and 15 October 2013 indicated that for all the stations (Impact, Intermediate, Reference and Ma Wan), levels of pH, DO and Salinity complied with the WQOs (Annex B). All in-situ water quality measurements showed relatively minor variations amongst Impact, Intermediate and Reference stations (Annex B).

1.6.12                           Levels of Turbidity within the reporting month generally complied with the Action and Limit Levels set in the EM&A Manual ([10]) (Figures 10, 20, 30, 40, 50 and 60 of Annex B). Variation of Turbidity amongst all the stations was observed throughout the monitoring period.

Laboratory Measurements

1.6.13                            Data interpretation on monthly average concentrations of metals and nutrients will be presented when monitoring data are made available upon completion of laboratory analysis. Graphical presentations of monitoring results on individual monitoring days from 3 to 15 October 2013 are presented in Annex B.

1.6.14                            Exceedances of Suspended Solids (SS) WQO (12.2 mg/L for wet season) were occasionally recorded (Figure 15, 25, 35, 45, 55 and 65 of Annex B). The exceedances of WQO were recorded at Reference stations, Impact stations and other Water Sensitive Receiver stations on the same monitoring day (3, 5, 8, and 15 October 2013). The reference stations are located with a sufficient distance from the mud pits and considered unlikely to be affected disposal works. In addition, the SS levels at Impact stations were recorded lower than those at Reference or Intermediate stations. Hence, it is considered that the exceedances of WQO are unlikely to be caused by mud disposal operations. In addition, high levels of SS were occasionally recorded during baseline monitoring which are considered to be sporadic events and characteristic of water quality in this area of Hong Kong. Concentrations of SS complied with the Action and Limit Levels at all stations during the reporting month.

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

1.6.16                            Water Column Profiling for CMP 1 October 2013

In-situ Measurements

1.6.17                           Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) in October 2013. The water quality monitoring results for October 2013 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 2002-2011 from stations in the Northwestern Water Control Zone, where the CMPs are located. For Salinity, the average value obtained from the Upstream station was used for the basis as the WQO. Graphical presentation of the monitoring results is provided in Annex B.

1.6.18                           Analyses of results for October 2013 indicated that levels of Salinity, pH and DO complied with the WQOs at both Upstream and Downstream stations (Figures 66-68 of Annex B). DO and Turbidity complied with the Action and Limit Levels set in the EM&A Manual ([11]).


Laboratory Measurements for Suspended Solids (SS)

1.6.19                           Analyses of data obtained in October 2013 indicated that the SS levels at Downstream and Upstream stations exceeded the WQO (Figure 69 of Annex B) but the SS levels at Downstream stations are significantly smaller than those at Upstream stations indicating by statistical analysis. In addition, SS levels at all stations complied with the Action and Limit Levels set in the EM&A Manual.

1.6.20                           Overall, the 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                               Pit Specific Sediment Chemistry, Routine Water Quality Monitoring and Water Column Profiling for CMP 1 as well as Impact Water Quality Monitoring during Dredging Operations for CMP 2 will be conducted in the next monthly period of November 2013.

1.7.2                                No monitoring activities will be conducted for CMP IV and CMP V in the next monthly period of November 2013.

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 D.


 



([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.

([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.

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

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