Report No. : GEO Report No. 76

Report Title : Report on the Landslides at Hut No. 26 Kau Wa Keng Upper Village of 4 June 1997 (1998), 100 p. (Bilingual)

Author : Halcrow Asia Partnership Ltd.

Abstract

On 4 June 1997, two landslides occurred at a slope above Castle Peak Road, Kau Wa Keng. The larger of the two damaged a squatter hut and resulted in one fatality and slight injuries to five other people. The landslide involved the sudden collapse of parts of registered cut Slopes Nos. 11NW-A/C415 and C416 and the hillside above. A comprehensive investigation into the landslides was carried out for the Geotechnical Engineering Office (GEO) during the period June 1997 to February 1998 by GEO's landslide investigation consultants, Halcrow Asia Partnership Ltd (HAP) with input and assistance from the GEO. This detailed study included review of documentary information, analysis of rainfall records, interviews with witnesses to the landslides, site survey, ground investigation, theoretical seepage and stability analyses and diagnosis of the causes of failure.

The investigation concluded that the landslide which resulted in the fatality was probably primarily caused by a significant rise in groundwater pressure in the weathered granite hillside, following very heavy rainfall that immediately preceded the failure.

In this report, two options are recommended for consideration as the interim risk guidelines. These have been developed based on a detailed review of current international practices and benchmarking against the risk acceptance criteria for Potentially Hazardous Installations (PHI) given in the Hong Kong Planning Standards and Guidelines dated 1993. A presentation of the initial findings was given by the consultants to CED colleagues and geotechnical consultants on 13 October 1997 and also to the Slope Safety Technical Review Board in the November 1997 meeting. Comments received have been taken into account in finalising the Report. The draft report of the study was also reviewed by Dr J. Wrigley of the Environmental Protection Department, whose assistance is gratefully acknowledged.

Details of the investigation and its findings are included in this report.

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