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

18TH MONTHLY PROGRESS REPORT FOR February 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 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 February 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.

1.2                                      Reporting Period

1.2.1                                This 18th Monthly Progress Report covers the EM&A activities for the reporting month of February 2014.

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                               Water Quality Monitoring during Capping Operations at ESC CMPs was undertaken on 14 February 2014.

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

         Impact Water Quality Monitoring during Dredging Operations was undertaken for CMP 2 three times per week on 4, 6, 8, 11, 13, 15, 18, 20, 22, 25, and 27 February 2014;

         Routine Water Quality Monitoring was undertaken for CMP 1 on 5, 7, 10, 12, 14, 17, 19, 21, 24, 26 and 28 February 2014;

         Demersal Trawling for CMP 1 was undertaken out on 11 and 12 February 2014;

         Pit Specific Sediment Chemistry was undertaken for CMP 1 on 18 February 2014;

         Cumulative Impact Sediment Chemistry was undertaken on 20 and 22 February 2014; and

         Water Column Profiling for CMP 1 was undertaken on 21 February 2014.

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained for February 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 December 2013, January and February 2014;

         Laboratory analyses of sediment samples collected for Cumulative Impact Sediment Chemistry of CMP 1 in February 2014;

         Laboratory analyses of water samples collected for Routine Water Quality Monitoring for CMP 1 from 17 to 29 January 2014; and

         Laboratory analyses of Suspended Solids (SS) samples collected for Water Quality Monitoring during Dredging Operations of CMP 2 on 27 February 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 is presented in this 18th Monthly Progress Report:

         Impact Water Quality Monitoring during Dredging Operations of CMP 2 conducted from 10 January to 25 February 2014;

         Routine Water Quality Monitoring of CMP 1 undertaken from 5 to 28 January 2014;

         Water Column Profiling of CMP 1 conducted on 21 February 2014; and

         Cumulative Impact Sediment Chemistry conducted in December 2013.

1.5.2                                Impact Water Quality Monitoring during Dredging Operations of CMP 2 10 January to 25 February 2014

1.5.3                                Monitoring data collected for CMP 2 from 10 January to 25 February 2014 are presented in this monthly report. Detailed discussion will be presented in the corresponding Quarterly Report.

1.5.4                                Impact Water Quality Monitoring during Dredging Operations of CMP 2 was conducted three times per week from 10 January to 25 February 2014. 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 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 1.1.

1.5.5                                Monitoring results from 10 January to 25 February 2014 are presented in Table C1 of Annex C. Daily dredging volume in January and February 2014 is reported in Annex D. Levels of Dissolved Oxygen (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 ([7]), except for the following occasions of exceedances shown in Table 1.1 below.

Table 1.1 Details of Exceedances Recorded at CMP 2 in January and February 2014

Date

Tide

Parameter

Station

Type

10 January 2014

Mid-Flood

SS

DS1

Action

 

 

SS

DS2

Action

13 January 2014

Mid-Flood

SS

DS1

Action

17 January 2014

Mid-Flood

SS

DS1

Action

 

 

SS

DS2

Action

 

 

Turbidity

DS2

Limit

24 January 2014

Mid-Flood

SS

DS2

Action

 

 

SS

DS3

Action

1.5.6                                SS exceedance was recorded at station DS1 only on 13 January 2014 (mid-flood). Since station DS1 was located at the boundary of the works area, the sole exceedance at this station did not appear to indicate any unacceptable water quality impacts outside the works area of the Project. On 24 January 2014, SS exceedances were recorded at stations DS2 and DS3 but not station DS1 which is located closer to the dredging operations. As such, the exceedances recorded are unlikely to be caused by the dredging operations at CMP 2. The SS exceedances recorded on 10 and 17 January 2014 (mid-flood) at stations DS1 and DS2 did not appear to indicate any trend of increasing SS towards the dredging operations with higher SS concentration recorded at DS2. Overall, it did not appear that the SS exceedances were caused by the dredging operations at CMP 2.

1.5.7                                Turbidity exceedance on 17 January 2014 (mid-flood) was recorded at station DS2 which were was further away from the works area when compared to station DS1 at which the level of Turbidity 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.

 

1.5.8                                It should be noted that high levels of Turbidity and 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.

1.5.9                                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.

1.5.10                            Routine Water Quality Monitoring of SB CMP 1 January 2014

1.5.11                           Monitoring results from 3 to 15 January 2014 were presented in 17th Monthly Progress Report. Daily monitoring results for 18 to 29 January 2014 are shown in Tables C4 and C5 of Annex C . Monthly averaged and daily monitoring results for January 2014 are presented with graphical presentation in Figure 1-Figure 20 of Annex B.

1.5.12                           The monitoring results for the Routine Water Quality Monitoring conducted for January 2014 in the dry 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 dry season period (November to March) 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).

1.5.13                           Monthly averaged and daily monitoring results for February 2014 will be presented with graphical presentation in the next monthly report when all monitoring results for February 2014 are received.

1.5.14                           Locations of monitoring stations were presented in Figure 1.2 and Figure 1.3.

In-situ Measurements

1.5.15                           Analyses of results indicated that for all the stations (Impact, Intermediate, Reference and Water Sensitive Receiver stations), both daily and monthly average levels of pH, DO and Salinity complied with the WQOs in January 2014 (Figure 1, 2, 4, 12, 15, and 16 of Annex B).

1.5.16                           In January 2014, daily and monthly average levels of DO and Turbidity at all the stations complied with the Action and Limit Levels (Tables C5 and C7 of Annex C).


Laboratory Measurements

1.5.17                            In January, monthly average concentrations of Nickel and Zinc were slightly higher at Tai Ho Bay Station 2 and Tai Ho Bay Station 1, respectively (Figure 6 and 7 of Annex B). Monthly average concentrations of the other metals were similar amongst stations (Figures 6-7 of Annex B). Monthly average levels of 5-day Biochemical Oxygen Demand (BOD5), Ammoniacal-Nitrogen (NH3-N) and Total Inorganic Nitrogen (TIN) in January 2014 were similar amongst station (Figures 8 and 9 of Annex B). The monthly average concentration of TIN did not show any exceedance with the WQO in January 2014 (Figure 9 of Annex B).

1.5.18                            Analyses of January 2014 results indicated that daily concentrations of Cadmium, Mercury and Silver were below their limits of reporting at all the stations (Figure 17, 19 and 23 of Annex B). The daily concentrations of Arsenic, Chromium, Copper, Lead, Nickel and Zinc indicated variations over time at all the stations throughout January 2014.

1.5.19                            Daily recorded levels of TIN, BOD5 and NH3-N were observed to fluctuate over time throughout January 2014 (Figure 26-28 of Annex B). Compliance with TIN WQO (0.50 mg/L) was observed at all the stations in the monitoring period except for the measurement at Tai Ho Bay station 1(THB1) on 9 January 2014. This only exceedance of TIN WQO did not appear to provide any evidence of unacceptable water quality impacts due to the mud disposal activities.

1.5.20                            Daily levels of SS complied with the Action and Limit Levels set in the EM&A Manual and occasionally exceeded SS WQO (14.4 mg/L for dry season) (Figure 29 of Annex B) in January 2014. The monthly average levels of SS compiled with the WQO at all stations (Figure 10 of Annex B). These occasional exceedances recorded for daily SS levels are thus not likely to be caused by mud disposal works, but sporadic events and characteristic of water quality in this area of Hong Kong.

1.5.21                            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 January 2014.


Recommendations

1.5.22                            From the results of the Routine Water Quality Monitoring conducted in October 2013, November 2013 and January 2014 for CMP 1, there did not appear to be any unacceptable deterioration in water quality in all of the sampling events which were conducted three times a week during the monitoring period. In accordance with the EM&A Manual, it is recommended to adjust the sampling frequency to eight (8) times per year which is the same as the frequency of Routine Water Quality Monitoring for CMP V. It is anticipated that this adjusted sampling frequency is adequate for tracking the potential change in contaminant concentrations in seawater which may take a long time to appear while at the same time address the potential seasonal difference in seawater quality.

1.5.1                                Water Column Profiling of CMP 1 February 2014

1.5.2                               Water Column Profiling was undertaken at a total of two sampling stations (Upstream and Downstream stations) on 21 February 2014. The water quality monitoring results have been assessed for compliance with the WQOs (Table C8 of Annex C). The monitoring results were also compared with the Action and Limit Levels set in the Baseline Monitoring Report.

In-situ Measurements

1.5.3                               Analyses of results for February 2014 indicated that levels of Salinity, pH and DO complied with the WQOs at both Upstream and Downstream stations (Table C8 of Annex C). DO and Turbidity complied with the Action and Limit Levels.

Laboratory Measurements for Suspended Solids (SS)

1.5.4                               Analyses of data obtained on 21 February 2014 indicated that the SS levels at Downstream and Upstream stations complied with the WQO (Table C8 of Annex C). In addition, SS levels at all the stations complied with the Action and Limit Levels.

1.5.5                               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.

 

1.5.6                                Cumulative Impact Sediment Chemistry of CMP 1 December 2013

1.5.7                               Monitoring locations for Cumulative Impact Sediment Chemistry for CMP 1 are shown in Figure 1.4. A total of eleven (11) monitoring stations were sampled in December 2013.

1.5.8                                Analyses of results for the Cumulative Impact Sediment Chemistry Monitoring indicated that the concentrations of all metals, except Arsenic, were below the Lower Chemical Exceedance Level (LCEL) in December 2013 (Figures 30 and 31 of Annex B). Concentrations of Arsenic in sediments from all stations exceeded the LCEL, except for Near Field station SB-RNB and Mid Field station SB-RMB.

1.5.9                                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 ([8]). It is presumed that the natural concentrations of Arsenic are similar in onshore and offshore sediments ([9]), and relatively high Arsenic levels may thus occur throughout Hong Kong. Therefore, the LECL exceedances of Arsenic are unlikely to be caused by the disposal operations at CMP 1 but rather as a result of naturally occurring deposits.

1.5.10                            For organic contaminants, concentration of Total Organic Carbon (TOC) at Tai Ho Bai Station 2 (THB2) was recorded to be higher than other stations (Figure 32 of Annex B). Concentrations of Tributyltin (TBT) were recorded to be higher at Near-field station SB-RNB and Ma Wan station (Figure 33 of Annex B). Total Dichloro-diphenyl-trichloroethane (DDT) and 4,4-Dichloro-diphenyl-dichloroethylene (4,4-DDE) were recorded below the limit of detection at most stations with no apparent spatial trend (Figure 34 of Annex B). Concentrations of Total Polychlorinated Biphenyls (PCBs) as well as Low and High Molecular Weight Polycyclic Aromatic Hydrocarbons (Low and High MW PAHs) were recorded below the limit of reporting at all the stations.

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 1 during this monthly 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 March 2014 for SB CMPs:

         Impact Water Quality Monitoring during Dredging Operations of CMP 2;

         Pit Specific Sediment Chemistry of CMP 1; and

         Water Column Profiling of CMP 1.

1.6.2                                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]) 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.

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

([9]) 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