For discussion FCR(95-96)86
on 1 December 1995


Subhead 700 General other non-recurrent

Members are invited to approve a new commitment of $90.5 million for engaging consultants to develop an improved process in assessing slope stability.


The present system to identify potentially unsafe slopes needs to be improved to take into account relevant site conditions and special geological features in an area.


2. The Director of Civil Engineering (DCE) proposes to employ consultants for a period of three years to develop an improved process in assessing slope stability.


3. In November 1994, Professor N R Morgenstern submitted a report to the Governor on the adequacy of Government’s approach to slope safety with suggestions for improvement. The Administration subsequently undertook to implement the recommendations on enhancing stability of slopes as soon as possible. One of Professor Morgenstern’s recommendations for long term improvement is that there should be an integrated approach in the slope stability assessment process.

4. At present, DCE investigates slopes in order of priority set by ranking formulae under the Slope Categorisation System. He then initiates work on those slopes found not up to the safety standard and which could lead to high consequences of life in case of failure. Professor Morgenstern considers that we should supplement the present method and take an integrated approach.

5. Under the proposed integrated approach, the Civil Engineering Department (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. To adopt this approach, CED will have to deploy experienced staff will be required to visit a large proportion of the landslip sites to collect and confirm critical information on the landslip reports and to study some of the landslips in detail with a view to deciding on the need to apply an integrated approach to certain slopes and to acquiring better knowledge of slope stability problems in Hong Kong. As a large number of landslides occur in Hong Kong each year (ranging from 200 in an average dry year to over 800 in a very wet year), this new activity requires substantial staff resources.

6. DCE has examined the ways and means of implementing the recommendation. He concludes that existing staff resources in his department have already been fully stretched due to the accelerated Landslip Preventive Measures Programme, remedial works on the many landslides which occurred in recent wet years, and increased public demand on slope safety information. He is therefore unable to redeploy existing resources to cover this very substantial additional workload.

7. DCE proposes to engage consultants to implement this recommendation on a trial basis in the next three wet seasons for the following reason -

  1. the new approach has not been tried out in Hong Kong. The department has no in-house expertise for the task;
  2. even if the department is to create additional posts now, DCE will not be able to recruit experienced staff immediately to discharge thesuch duty in the short term;
  3. consultants can mobilise their resources more quickly in response to demand. For instance, if required, they may call on their overseas support to reinforce their staff force in a very wet year; and
  4. we intend to carry out the new approach on a trial basis before committing ourselves to the long term need for a permanent team.

8. We expect the consultants to undertake the following tasks -

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

9. The proposed consultancy will serve as a scoping exercise to collect information for better planning of the ways and means to tackle the task. The experience gained from the consultancy will enable DCE to formulate a long term strategy in implementing an integrated approach in slope stability assessment and to devise efficient and cost-effective arrangements for fulfilling the strategy.


10. DCE estimates that the non-recurrent expenditure will be $90.5 million, broken down as follows -

$ million

(a) Staff cost


(b) Reimbursement of ground investigation cost




The estimate of $90.5 million is based on an average weather pattern for three years. Details are at the Enclosure.

11. The cash flow of the consultancy will be -

$ million











Subject to Members’ approval of the proposal, we will include sufficient provision in the 1996-97 draft Estimates.

12. DCE plans to start the consultancy at the beginning of the wet season of 1996. The consultants will have to complete all detailed studies started in the three-year period by 1999.

13. The project will not result in any direct recurrent expenditure. At the end of the consultancy, DCE will consider and propose arrangements for the long term implementation of a more integrated approach based on experience gained in the present project.


14. A retaining wall at Kwun Lung Lau, Kennedy Town failed in July 1994. The Geotechnical Engineering Office (GEO) investigated into the cause of the failure. After an independent review of the investigation, Professor Morgenstern submitted a report to the Governor on 30 November 1994 giving advice on the adequacy of our current approach to slope safety in Hong Kong and suggested improvements. One of his five recommended measures to enhance slope stability in Hong Kong is that the GEO should introduce an integrated approach in the slope stability assessment process.

15. The Administration has decided to implement Professor Morgenstern's recommendations as soon as possible. We presented a summary of the initial findings of the review to the Legislative Council Panel on Planning, Lands and Works on 20 December 1994 and published a report on 3 March 1995.

16. The report of the Select Committee on Kwun Lung Lau Landslip and Related Issues published by the Legislative Council on 19 July 1995 recommended that the Government should submit six-monthly progress reports to the Legislative Council Panel on Planning, Lands and Works regarding the implementation of the various improvement measures.

Works Branch
November 1995

Enclosure to FCR(95-96)86xx

Estimated cost of engaging consultants to develop an improved process in assessing stability of slopes

Staff Cost

We will remunerate the consultants on a time charge basis according to the salary cost of staff deployed for the task. This form of remuneration is most suitable for this project because consultants in Hong Kong do not have experience in the exact amount of work involved and cannot estimate the fees in terms of lump sum or cost per landslip site processed.

2. The staffing scale and fees will be subject to competitive bidding. For the purpose of a reasonable cost estimate for this consultancy, we suggest a staffing scale based on the likely volume of work involved as well as our experience with other consultancies of similar nature and scale. The estimated fee scales are based on the full staff cost of comparable ranks in the civil service plus 50% on-cost. These rates are being used for an existing $35 million contract for Systematic Identification and Registration of Slopes (PWSC 1994/43) which is very similar in nature to the present project. The total estimated staff cost of the present proposal is as follows -

Number of
Consultancy Staff Estimated Staff Cost





Senior professionals






Senior Technical Officers



Technical Officers



Senior Survey Officer



Personal Secretary



Clerical Officer



Assistant Librarian


Total staff cost per year


Total staff cost for three3 years


3. The technical staff (ten posts of two Senior Technical Officers and eight Technical Officers) assist in collection of documentary information, field inspections, investigation supervision, stability analyses and report preparation.

4. The survey staff (two Senior Survey Officers) conduct site surveys for the detailed investigation.

5. The five professionals examine landslip reports, review documentary information, investigate landslips, select sites for study by the more integrated approach, carry out studies and compile reports.

6. The two senior professionals select sites for study by the more integrated approach and oversee the work of the professionals.

7. The partner draws up criteria for selecting sites for study by the more integrated approach, sets up action procedures, monitors progress and performance of the scheme, and makes recommendations for long term implementation.

8. The team is served by one personal secretary, one clerical officer and one assistant librarian for typographical support and record management. In particular, the assistant librarian assists in cataloguing and keeping the project reports in the Geotechnical Information Unit for public reference in future.

Ground Investigation

9. Ground investigation cost is estimated as follows -

(a) In an average dry year, there will be :

200 landslides

(b) Assuming 5% of landslides requires ground investigation, there will be (200 x 5%) :

10 sites

(c) Assuming each site requires 7 boreholes to investigate, there will be (10 x 7) :

70 boreholes

(d) Assuming each borehole costs :


(e) Total ground investigation cost per year :
($80,000 x 70 boreholes)

$5.6 million

(f) Total ground investigation cost in three years :
($5.6 million x 3 years)

$16.8 million

Last Updated on 2 December 1998