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


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 “the Project”) 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. 
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 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 December 2012.

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 1, 4, 6, 8, 11, 13, 15, 18, 20, 22, 24, 27, 29 and 31 December 2012) in this reporting month.

1.4                                      Details of Outstanding Sampling and/or Analysis

1.4.1                                No outstanding sampling and laboratory analysis remained from December 2012.  A summary of field activities are presented in Annex A.

1.5                                      Brief Discussion of the Monitoring Results for SB CMPs

1.5.1                                All monitoring data collected for SB CMPs in December 2012 will be 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 – November 2012

1.5.3                                Impact Water Quality Monitoring during Dredging Operations of CMP 1 was conducted three times per week in a total of fourteen sampling days in December 2012.  On the 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 are presented in Table B1 of Annex B.  Levels of Dissolved Oxygen (DO), Turbidity and Suspended Solids (SS) generally complied with the Action and Limit Levels set in the Baseline Monitoring Report ([5]), except on 15, 29 and 31 December 2012 during the mid-flood tide.

1.5.5                                On 15 December 2012, level of turbidity exceeded the Action Level at Sensitive Receiver Station WSR46 while level of SS exceeded the Action Level at Downstream Stations DS2, DS4 and DS5 and Sensitive Receiver Stations WSR45C and WSR46.  On 29 December 2012, level of turbidity exceeded the Action Level at Downstream Station DS5 and levels of SS exceeded the Action Level at Downstream Stations DS4 and DS5 and Sensitive Receiver Station WSR46.  Exceedance of Action Level of SS was recorded at Station WSR46 on 31 December 2012. 

1.5.6                                Stations DS2, DS4, DS5, WSR45C and WSR46 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.  Hence, it is unlikely that the exceedances are caused by the dredging operations of CMP 1.  In addition, high levels of SS and turbidity were occasionally recorded and such fluctuations were also observed during baseline monitoring.  The high SS and turbidity levels recorded are thus considered to be sporadic events and characteristic of water quality in this area of Hong Kong. 

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 January 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 – 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) 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.