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

10TH MONTHLY PROGRESS REPORT FOR JUNE 2013

1.1                                      Background

1.1.1                                Since early 1990s, contaminated sediment ([1]) arising from various construction works 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) (hereafter referred to as ížthe ProjectíĘ) 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                                An Environmental Permit (EP-427/2011) was issued by the Environmental Protection Department (EPD) to the CEDD, the Permit Holder, on 3 November 2011 and varied on 23 December 2011 (EP-427/2011/A).  Under the requirements of Condition 4 of the EP (EP-427/2011/A), an Environmental Monitoring and Audit (EM&A) programme as set out in the EM&A Manual ([5]) is required to be implemented for the SB CMPs.  The present EM&A programme undertaken under Agreement No. CE 23/2012 (EP) covers the dredging, disposal and capping operations of the SB CMPs.

1.2                                      Reporting Period

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

1.3                                      Details of Sampling and Laboratory Testing Activities

1.3.1                                Impact Water Quality Monitoring during Dredging Operations of CMP 1 was conducted three times per week (ie 4, 6, 8, 11, 13, 15, 17, 20, 24, 26 and 28 June 2013) in this reporting month in accordance with the EM&A Manual.  It should be noted that the Impact Water Quality Monitoring during Dredging Operations of CMP 1 was not conducted on 22 June 2013 due to the adverse weather and Typhoon signal No. 3 was hoisted. 

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling remained from June 2013.  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                                Monitoring data collected for SB CMPs from 27 May to 28 June 2013 are presented in this monthly report.  Detailed discussion will be presented in the corresponding Quarterly Report.

 

1.5.2                                Impact Water Quality Monitoring during Dredging Operations of CMP 1 íV May and June 2013

1.5.3                                Impact Water Quality Monitoring during Dredging Operations of CMP 1 was conducted three times per week for a total of fourteen (14) sampling days from 27 May to 28 June 2013.  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 1.  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 1.1.

1.5.4                                Monitoring results from 27 May to 28 June 2013 are presented in Table B1 of Annex B.  It should be noted that sampling at station THB2 during mid-ebb tide on 11 June 2013 and during mid-flood tides on 15 and 24 June 2013 were not carried out due to adverse weather.  Levels of Dissolved Oxygen (DO), Turbidity and Suspended Solids (SS) at most of the stations generally complied with the Action and Limit Levels (see Table B2 for details) set in the Baseline Monitoring Report ([6]), except for the following occasions of exceedances shown in Table 1.1 below.

Table 1.1        Details of exceedances recorded at CMP 1 between 27 May and 28 June 2013

Date

Tide

Parameter

Station

Type

27 May 2013

Mid-Ebb

Turbidity

WSR46

Action

6 June 2013

Mid-Flood

Turbidity

WSR45C

Action

11 June 2013

Mid-Flood

SS

THB2

Action

13 June 2013

Mid-Ebb

Turbidity

DS1

Action

13 June 2013

Mid-Ebb

SS

DS1

Limit

15 June 2013

Mid-Ebb

SS

DS1

Limit

15 June 2013

Mid-Ebb

SS

THB1

Limit

20 June 2013

Mid-Flood

SS

WSR46

Action

24 June 2013

Mid-Ebb

Turbidity

THB2

Action

24 June 2013

Mid-Ebb

SS

THB2

Limit

24 June 2013

Mid-Flood

SS

WSR46

Action

26 June 2013

Mid-Flood

SS

DS4

Action

1.5.5                                Action/Limit Level exceedances of Turbidity and SS were recorded at Impact station DS1 during mid-ebb tide on 13 and 15 June 2013.  Since station DS1 is located in close proximity to the works area of CMP 1 (ie at the boundary of the works area) and the exceedances were recorded during one tidal period only, it is considered that the sediment plume, if any, was transient in nature and limited to the close vicinity of the works area as predicted in the EIA review of the Project ([7]).  Hence, the dredging works did not appear to cause any unacceptable deterioration in water quality.

1.5.6                                Exceedances were recorded at stations DS4, THB1, THB2, WSR45C and WSR46 on other occasions.  These stations are located further away from the works area of CMP 1 when compared to station DS1 at which the levels of SS and Turbidity did not exceed the Action and Limit Levels during the same tidal period.  As such, the exceedances at these stations (ie DS4, THB1, THB2, WSR45C and WSR46) are not likely to be caused by the dredging works at CMP 1.  In addition, THB2 is located downstream of Tai Ho Stream which will be influenced by the erosion of uphill sediments during heavy rain.  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.  Therefore, the Action and Limit Level exceedances may be caused by natural background variation in water quality of the area.

1.5.7                                Overall, the results indicated that the dredging operations at CMP 1 of SB 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                                      Activities Scheduled for the Next Month

1.6.1                                Impact Water Quality Monitoring during Dredging Operations for CMP 1 will be conducted three times per week in the next monthly period of July 2013.  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 C.


 



([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 íV 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) íV Investigation.  Agreement No. CE 23/2012(EP). Submitted to EPD in November 2012.

([6])        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) íV Investigation.  Agreement No. CE 23/2012(EP). Submitted to EPD in October 2012.

([7])       Under the CEDD study Contaminated Sediment Disposal Facility to the South of The Brothers (Agreement No. FM 2/2009)