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

21st MONTHLY PROGRESS REPORT FOR May 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 undertaken 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 May 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 21st Monthly Progress Report covers the EM&A activities for the reporting month of May 2014.

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                               The following monitoring activities have been undertaken for SB CMPs in May 2014:

         Impact Water Quality Monitoring during Dredging Operations was undertaken for CMP 2 three times per week on 1, 3, 5, 7, 9, 12, 14, 16, 19, 21, 23, 26, 28 and 30 May 2014;

         Pit Specific Sediment Chemistry was undertaken for CMP 1 on 8 May 2014;

         Routine Water Quality Monitoring for CMP 1 was undertaken on 13 May 2014; and

         Water Column Profiling for CMP 1 was undertaken on 15 May 2014.

No monitoring activity was undertaken for ESC CMPs in April 2014.

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained for May 2014. The following laboratory analyses were still in progress during the preparation of this monthly report and hence were not presented in this monthly report:

         Laboratory analyses of sediment samples collected for Pit Specific Sediment Chemistry of CMP 1 in April and May 2014; and

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 is presented in this 21st Monthly Progress Report:

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

       Impact Water Quality Monitoring during Dredging Operations of CMP 2 conducted from 26 April to 30 May 2014;

       Routine Water Quality Monitoring of CMP 1 undertaken on 13 May 2014; and

       Water Column Profiling of CMP 1 conducted on 16 May 2014.

 

1.5.2                                Pit Specific Sediment Chemistry of CMP 1 March 2014

1.5.3                               Monitoring locations for Pit Specific Sediment Chemistry for CMP 1 are shown in Figure 1.2. A total of six (6) monitoring stations were sampled in March 2014.

1.5.4                               The concentrations of most inorganic contaminants were lower than the Lower Chemical Exceedance Level (LCEL) at all stations except Arsenic in March 2014 (Figures 1-2 of Annex B). Concentrations of Arsenic exceeded the LCEL at all stations except Near Pit station SB-NNAB and Active Pit station SB-NPAB.

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, the concentration of Total Organic Carbon (TOC) was similar amongst stations with no consistent spatial trend in March 2014 (Figure 3 of Annex B). Concentrations of Tributyltin (TBTs) were observed to be higher at Active Pit stations SB-NPAA and SB-NPAB in March 2014 (Figure 4 of Annex B). High Molecular Weight Polycyclic Aromatic Hydrocarbons (High MW PAHs) concentrations were recorded below the limit of reporting at all stations except at Active Pit station SB-NPAB (Figure 5 of Annex B). Low 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 March 2014.

1.5.7                               Active Pit stations SB-NPAA and SB-NPAB are located within CMP 1 which was receiving contaminated mud during the reporting period. Therefore, the higher concentration of contaminants recorded at the Active Pit stations only are not considered as indicating any dispersal of contaminated mud from CMP 1. Nevertheless, detailed analyses will be presented in the Quarterly Report to reveal any trend of increasing sediment contaminant concentrations towards CMP 1.

1.5.8                               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 March 2014.

1.5.9                                Impact Water Quality Monitoring during Dredging Operations of CMP 2 26 April to 30 May 2014

1.5.10                            Impact Water Quality Monitoring during Dredging Operations of CMP 2 was conducted three times per week from 26 April to 30 May 2014 during the reporting period. On each survey day, sampling 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 1.3. Sampling at station THB2 during mid-flood tides of 26 April, 19 and 21 May 2014 as well as during both mid-flood and mid-ebb tides of 9, 12, 16 and 23 May 2014 were cancelled due to adverse weather condition.

1.5.11                            Monitoring results are presented in Table C1 of Annex C. Daily dredging volume in May 2014 is reported in Annex D.[RC1]  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 exceedance shown in Table 1.1 below.

Table 1.1 Details of Exceedances Recorded at CMP 2 between 26 April and 31 May 2014

Date

Tide

Parameter

Station

Type

16 May 2014

Mid-Ebb

SS

DS2

Action

1.5.12                            Action Level exceedance of SS was recorded at stations DS2 during mid-ebb tide on 16 May 2014. Station DS2 is located further away from the works area of CMP 2 when compared to station DS1 at which the levels of SS did not exceed the Action and Limit Levels. As such, the exceedance at station DS2 is not likely to be caused by the dredging works at CMP 2.

1.5.13                            It should be noted that 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 (baseline monitoring data are summarised in Table C3 of Annex C). Therefore, the Action and Limit Level exceedances may be caused by natural background variation in water quality of the area.

1.5.14                            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.

 

1.5.15                            Routine Water Quality Monitoring of SB CMP 1 May 2014

1.5.16                            The monitoring results for the Routine Water Quality Monitoring conducted in May 2014 in the wet season have been assessed for compliance with the Water Quality Objectives (WQOs) set by EPD. This consists of a review of the EPD routine water quality monitoring data for the wet season period (April to October) of 2003-2012 from stations in the Northwestern Water Control Zone, where the CMPs are located. For Salinity, the averaged value obtained from the Reference stations was used for the basis as the WQO. 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 6-15 of Annex B and Tables C4-C5 of Annex C.

1.5.17                           Locations of monitoring stations are presented in Figure 1.4. Sampling at station THB2 was cancelled due to adverse weather condition

In-situ Measurements

1.5.18                           Analyses of results for May 2014 indicated that the levels of pH and DO complied with the WQOs at all stations (Impact, Intermediate, Reference and Water Sensitive Receiver stations) in May 2014 (Figures 6-7 of Annex B). The levels of Salinity exceeded WQO at Impact, Intermediate, Tai Mo To and Tai Ho Bay stations (Figure 9 of Annex B). The lower salinities recorded at these 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.

1.5.19                           The levels of DO and Turbidity complied with the Action and Limit Levels at all stations (Figures 7 and 10 of Annex B; Table C4 of Annex C).

Laboratory Measurements

1.5.20                            Analyses of May 2014 results indicated that concentrations of Cadmium, Mercury and Silver were below their limit of reporting at all stations. Arsenic, Chromium, Copper, Lead, Nickel and Zinc were detected in samples from most stations (Figures 11-12 of Annex B). Concentrations of Arsenic, Chromium, Lead and Nickel appeared to be similar amongst all stations with no apparent spatial trend observed (Figure 11 of Annex B). Concentrations of Copper and Zinc were slightly higher at Ma Wan station when compared to other stations (Figure 12 of Annex B).

 

1.5.21                            For nutrients, concentrations of Total Inorganic Nitrogen (TIN) at most stations exceeded the WQO (0.5mg/L) except at Ma Wan station (Figure 13 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 ([10]) . 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 13 of Annex B). Level of 5-day Biochemical Oxygen Demand (BOD5) was higher at Ma Wan stations (Figure 14 of Annex B).

1.5.22                            Concentrations of SS exceeded the WQO (12.00 mg/L for wet season) at Reference and Intermediate stations. However, SS at all stations complied with the Action and Limit Levels during the reporting period (Figure 15 of Annex B; Table C5 of Annex C). As discussed in Section 1.5.13, the WQO exceedances of SS are considered to be sporadic and characteristic of water quality in this area of Hong Kong.

1.5.23                            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 May 2014.

1.5.24                            Water Column Profiling of CMP 1 May 2014

1.5.25                           Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 15 May 2014. The water quality monitoring results have been assessed for compliance with the WQOs. 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

1.5.26                           Analyses of results for May 2014 indicated that levels of Salinity, pH and DO complied with the WQOs at both Downstream and Upstream stations (Table C6 of Annex C). DO and Turbidity also complied with the Action and Limit Levels.

Laboratory Measurements for SS

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

1.5.28                           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 June 2014 for SB CMPs:

    Impact Water Quality Monitoring during Dredging Operations of CMP 2;

    Pit Specific Sediment Chemistry of CMP 1;

    Cumulative Impact Sediment Chemistry of CMP 1; and

    Water Column Profiling of CMP 1.

1.6.2                                Water Quality Monitoring for Capping will be undertaken in the next monthly period of June 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.

([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]) http://www.epd.gov.hk/epd/misc/marine_quality/1986-2005/textonly/eng/index.htm


 [RC1]Data to be provided by CEDD