Report No. : GEO Report No. 185

Report Title : A Review of Capping Practice for Contaminated Mud Pits (2006), 45 p.

Author : W.W. Ding & E.K.M. Chiu

Abstract

Seabed pits in Hong Kong waters used for disposal of contaminated mud are capped with clean mud, in order to isolate the contaminated mud from the surrounding marine environment. Due to an acute shortage of capacity in handling the public fill material, it is proposed to use this material for capping the contaminated mud pits. As the nature of public fill material is different to that of clean mud, it is necessary to look into the suitability of the public fill material as a capping medium.

A literature review on overseas and local practice and experience on capping work was carried out. The review findings indicated that sandy public fill material consisting of occasional cobbles is likely to be suitable for capping purpose. Preliminary calculation carried out as part of the review provided an indication on the maximum allowable thickness of each capping layer to be formed without causing disturbance to the already placed contaminated mud. A field trial had been carried out and demonstrated a workable method of placing granular public fill to form a cap.

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