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Advisory Council on the Environment

Status Report on Sand Dredging and Mud Disposal in Hong Kong

(ACE Paper 34/2001)
For information

Purpose

To provide the regular six-monthly status report to Members on sand dredging and mud disposal in Hong Kong. The last status report to Members was in February 2001(ACE Paper 7/2001).

Marine Sand Resources, Mud Disposal Areas and Major Reclamation Areas

2. The locations of sand resources, mud disposal areas and major reclamation areas in Hong Kong are shown in the drawing MFC-001B (Attachment A). Sand dredging is currently active at three marine borrow areas - East Lamma Channel and West Po Toi are supplying sand for the Penny's Bay Reclamation Stage 1 Project, South Tsing Yi is supplying sand for the Container Terminal 9 Project. Uncontaminated mud disposal at South Cheung Chau, East Ninepins, and South Tsing Yi continues. Contaminated mud disposal continues at East Sha Chau.

Marine Borrow Areas

3. Sand dredging at the East Lamma Channel Marine Borrow Area has been operating smoothly since its commencement in December 2000 and is expected to continue in the next few months. The comprehensive environmental monitoring and audit (EM&A) programme includes water quality monitoring at 21 stations, ecology monitoring surveys at 5 coastal sites, and beach geomorphology surveys at 6 gazetted beaches. Although occasional water quality exceedances were recorded over the dredging period, further in-situ measurements in accordance with the Action Plan confirmed neither consecutive exceedances nor unacceptable adverse impacts on the nearby sensitive receivers.

4. Sand dredging at the West Po Toi Marine Borrow Area commenced on 28 May 2001. On 7 June 2001, the dive survey of the environmental monitoring programme identified sedimentation on some of the corals located at Northeastern Po Toi and dredging was suspended on 8 June 2001 to allow time for the investigation into the sedimentation. A dive survey on 18 June 2001, jointly conducted by AFCD's coral expert and the Environmental Team, confirmed that the sedimentation of corals recorded on 7 June 2001 had disappeared and that apart from about 3% of the previously sedimented area, there had been no damage. Details of the incident were presented to ACE EIA-Subcommittee at its meeting on 9 July 2001 (ACE EIA Paper 6/2001). As it had not been possible to draw definitive conclusions as to the cause of the sedimentation, upon being advised by the Independent Environmental Checker and EPD, dredging was resumed on 11 July 2001, initially at a lower dredging rate for 4 weeks as an observation period. The results of the EM&A programme which includes water quality monitoring at coral impact and control sites, twice-weekly dive surveys at impact coral sites and monthly full ecological survey at all impact and control sites since resumption of dredging has not indicated unacceptable impacts. Sand dredging at this borrow area is anticipated to continue in the next few months.

5. Sand dredging at the South Tsing Yi Marine Borrow Area has been progressing since November 2000. The environmental monitoring and audit programme of the project, including the nearby reclamation site, comprises water quality monitoring at 34 stations. EM&A results so far gave no indication of unacceptable adverse impact on the nearby sensitive receivers.

Disposal of Uncontaminated Mud

6. The open sea floor mud disposal grounds at South Cheung Chau and East Ninepins are being used for disposal of uncontaminated mud for various projects of Hong Kong. Disposal of uncontaminated mud at the exhausted sandpit at East Tung Lung Chau was carried out for two weeks just before the on-set of the rainy season. The disposal is suspended during the rainy season and will resume in October 2001. The exhausted sandpit at south of Tsing Yi is being exclusively used by the Container Terminal 9 Project for disposal of uncontaminated mud.

7. Water quality monitoring results of the uncontaminated mud disposal so far indicate no adverse impact on the environment. The monitoring works will continue in order to ensure that that impact on the environment is kept at an acceptable level.

8. The environmental impact assessment to study the impacts of uncontaminated mud disposal in the exhausted sandpits at the Brothers is at its early stage. Details of the study are being discussed for agreement with EPD.

Disposal of Contaminated Mud

9. Disposal of contaminated mud from various projects of Hong Kong continues at the East Sha Chau site with the Container Terminal 9 Project being the main user. The comprehensive environmental monitoring at East Sha Chau indicates that the disposal of contaminated mud has not adversely affected the marine environment. With the current rate of disposal, it is anticipated that capacity at East Sha Chau will be exhausted by 2007.

10. The report of the consultancy study entitled Strategic Assessment and Site Selection for Contaminated Mud Disposal has been completed. Details of the findings and recommendations of the study were discussed in the last ACE meeting on 21 July 2001 as well as the last ACE EIA Sub-committee meeting (ACE-EIA Paper 4/2001) on 9 July 2001.

Attachment


Attachment A: Drawing No. MFC-001B - Marine Fill Resources, Mud Disposal Areas and Major Reclamations

Marine Fill Committee Secretariat
Geotechnical Engineering Office Civil Engineering Department August 2001

 

 

 

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