For discussion
on 15 January 1999


Subhead 700 General other non-recurrent
Item 524 Consultancy service for developing an improved process in assessing slope stability

    Members are invited to approve an increase in commitment from $90.5 million by $25 million to $115.5 million to meet unforeseen increases in the cost of the project to develop an improved process in assessing slope safety.


The approved commitment is insufficient to meet the consultancy cost of the project to develop an improved process in assessing slope stability.


2. The Director of Civil Engineering (DCE), with the support of the Secretary for Works, proposes to increase the approved commitment of this project from $90.5 million by $25 million to $115.5 million.


3. On 1 December 1995, Members approved a commitment of $90.5 million for engaging consultants to develop an improved process in assessing slope safety. We planned to implement this project in three phases through three separate Landslide Investigation Consultancies (LICs), each lasting for two years. The first commenced in January 1997 and the second in February 1998. We plan to start the third in February 1999.

4. The first two phases of the project have so far made good progress. We have formulated a preliminary methodology involving a systematic review of landslides, selection of sites for investigation and determination of the necessary follow-up action through integrated assessment. The trial implementation of the new methodology in 1997 and 1998 has led to a better understanding of the various types of slope failures that occur in Hong Kong, and we have further refined the methodology based on the experience gained from the trial. The new methodology has also enabled the identification of sites requiring out-of-turn investigations and follow-up action that are necessary to enhance public safety. The Slope Safety Technical Review Board1 has reviewed the progress and interim results of the project and fully supports the Civil Engineering Department's (CED's) efforts.

5. Hundreds of landslides occur every year in Hong Kong, ranging from about 200 in an average year to over 800 in a very wet year. We worked out the original estimate of $90.5 million for the project on the basis of the average weather pattern for the three-year period of 1997, 1998 and 1999. However, actual experience of the first two years turned out to be far from normal.

6. The rainfall in 1997, which was an El-nino year, was the heaviest on record since 1884, and was over 50% above the average. The Geotechnical Engineering Office (GEO) of the CED noted a total of 550 landslides, though the majority of these did not directly result in serious consequences. The large number of landslides provided a good opportunity for testing the preliminary methodology, and greatly facilitated the development and refinement of the methodology. Nevertheless, workload under this project has increased because many of these landslides required integrated assessment for determining the necessary follow-up action in the interest of public safety. As a result, expenditure for the first LIC was significantly higher than expected. The final requirement for this first phase turned out to be $50 million, as compared to an original estimate of $30 million.

7. As for 1998, there has also been heavier rainfall than the average, with the rainfall in the first six months more than 65% of the average, and that in the first eight months, more than 25%. The GEO has so far noted over 260 landslides. The expenditure for the second LIC is likely to increase from the original estimate of $30 million to $35 million.

8. We are planning for the third LIC to start in February 1999. However, given the larger than expected expenditure for the first two LICs, the approved commitment of $90.5 million will not be sufficient to cover the third LIC. As the final consultancy will consolidate the experience of the trial implementation and is crucial to devising the most efficient and cost-effective arrangements for long-term implementation, we are seeking additional funds of $25 million to enable the satisfactory completion of the whole project.

9. DCE has considered the feasibility of redeploying in-house staff for the third LIC. He concludes that this is not possible as all available staff resources have been fully engaged on other duties. Consultants are considered more suitable for this ad hoc project as they have the flexibility of calling on additional support to reinforce the investigation teams in a wet year at short notice.


10. We estimate the total cost of the consultancy to be $115.5 million, broken down as follows -

Approved commitment

$ million
Revised estimate

$ million
Proposed increase
in commitment

$ million
(a) Staff cost 73.7 96.7 23.0
(b) Ground investigation cost 16.8 18.8 2.0

_____ _____ _____
Total 90.5 115.5 25.0

_____ _____ _____

11. The estimated increase of $25 million is based on the assumption that 1999 will see an average rainfall.

12. As regards paragraph 10(a), the increase in staff cost by $23 million is due to the increase in workload as a result of the large number of landslides in 1997 and 1998, which have been wetter than the average. A breakdown of the staff cost is at the Enclosure.

13. As regards paragraph 10(b), the increase in ground investigation cost by $2 million is due to the projected increase in workload in investigating major landslides.

14. Subject to approval, we plan to phase the expenditure as follows -

Year$ million
1997-1998 (actual) 30.0
1998-1999 45.0
1999-2000 30.5
2000-2001 10.0

Total 115.5


15. The consultancy will not give rise to any recurrent expenditure.


16. Following an independent review of CED's investigation into the cause of the Kwun Lung Lau landslide in July 1994, Professor N R Morganstern submitted a report in November 1994 giving advice on the adequacy of Hong Kong's approach to slope safety and recommended, inter alia, that CED should introduce an integrated approach in the slope stability assessment process.

17. On 1 December 1995, the Finance Committee approved a commitment of $90.5 million for CED to engage consultants to assist in the development and trial implementation of a more integrated approach in the slope stability assessment process. Under the integrated approach, CED has to examine all reported landslips after each rainstorm and to study documentary information on each landslip site and its surrounding area. The purpose is that if the landslips occur in areas suspected to have common generic stability problems, CED will conduct out-of-turn investigations of the slopes in these areas.

18. The scope of the project comprises the following key tasks -

  1. examining landslide reports, inspecting landslide sites and studying background information to identify sites requiring an integrated approach in slope stability assessment;

  2. investigating landslides to improve understanding of slope stability problems in Hong Kong;

  3. assessing stability of the selected sites by the integrated approach;

  4. reviewing annually the system and criteria for identifying such sites; and

  5. recommending an appropriate system for long-term implementation.


Works Bureau
January 1999

Enclosure to FCR(98-99)63

Breakdown of the proposed increase in staff cost for
Consultancy Service for Developing an Improved Process
for Slope Stability Assessment

MPS points
Estimated fee
($ million)
Professional 123 40 2.4 18.5
Technical 89 16 2.4 4.5

Total 23.0



1. A multiplier factor of 2.4 is applied to the average Master Pay Scale (MPS) point to arrive at the full staff costs including the consultants' overheads and profit, as the staff will be employed in the consultants' offices (At 1 April 1998, MPS point 40 = $62,780 per month and MPS point 16 = $21,010 per month).

2. The consultant will continue to be remunerated on a time charge basis according to the salary cost of staff deployed for the task. The reason for adopting the time charge basis is that we are not certain of the exact amount of work involved, which depends on the actual rainfall and the number, scale and complexity of landslides, and that the methodology is still under development and requires refinement during the course of the trial implementation. We cannot therefore estimate the fees in terms of lump sum or cost per landslide site processed.

1.The Slope Safety Technical Review Board was set up to advise the Government on technical aspects of slope safety following the 1994 Kwun Lung Lau landslide. The Board is made up of three experts of high international standing in the geotechnical field.