PWSC(97-98)92
For discussion
on 10 December 1997
ITEM FOR PUBLIC WORKS
SUBCOMMITTEE OF FINANCE COMMITTEE
HEAD 704 - DRAINAGE
Public Safety - Landslip prevention
54BL -Investigation of sewers and drains affecting the safety of cut slopes
Members are invited to recommend to Finance Committee the upgrading of 54BL to Category A at an estimated cost of $57.6 million in money-of-the-day prices for the engagement of consultants to investigate the physical conditions of public sewers and drains buried behind and adjacent to cut slopes.
PROBLEM
Sewers and drains buried behind cut slopes are susceptible to leakage. This may endanger the stability of the slopes, and, in some cases, may cause landslip. However, we do not have sufficient information about the conditions of those sewers and drains.
PROPOSAL
2.The Director of Drainage Services (DDS), with the support of the Secretary for Works, proposes to upgrade 54BL to Category A at an estimated cost of $57.6 million in money-of-the-day (MOD) prices for the engagement of consultants to investigate the physical conditions of public sewers and drains buried behind and adjacent to cut slopes.
PROJECT SCOPE AND NATURE
3.The scope of the investigation comprises the following works -
- systematic identification of all public sewers and drains behind and adjacent to approximately 5 520 cut slopes registered under the 1977-78 Catalogue of Slopes1 ;
- internal pipe survey on the structural conditions of all identified sewers and drains;
- setting up of a database containing an inventory of the identified sewers and drains together with the results of the internal pipe survey; and
- development of proposals and cost-effective options for remedial works along with a prioritized implementation programme.
JUSTIFICATION
4.In November 1994, Professor Norbert R Morgenstern submitted a report to the Governor on the adequacy of Government's approach to slope safety with suggestions for improvements. We subsequently undertook to develop a programme to monitor and repair buried services to prevent slope failures caused by leaking sewers and drains buried behind and adjacent to cut slopes. Such leakages are mainly due to deterioration of the sewers and drains following prolonged years of service and the opening of pipe joints as a result of ground movement. At present, we do not have sufficient information to formulate such a programme.
5.We estimate that about 5 520 cut slopes in the Catalogue will require detailed investigation. The full scale investigation demands considerable resources over a specified period. Having examined the ways and means of implementing the detailed investigation, we conclude that we do not have the necessary in-house resources to undertake the works. We therefore propose to engage consultants to conduct an investigation to identify those sewers and drains behind cut slopes in the Catalogue, to carry out surveys of these buried services and to recommend remedial works. We will also develop an asset inventory and management system for effective management of these sewers and drains.
FINANCIAL IMPLICATIONS
6.We estimate the capital cost of the project to be $57.6 million in MOD prices (see paragraph 7 below), made up as follows -
|
|
|
$ million |
|
| (a) |
Internal pipe survey contract works
|
|
32.2
|
| (b) |
Consultants' fees for -
|
|
8.0
|
|
(i)identification of sewers and drains affecting cut slopes
|
2.2
|
|
(ii)preparation of tender and related documents for internal pipe survey
|
0.4
|
|
(iii)supervision of internal pipe survey
|
3.2
|
|
(iv)setting up of inventory and survey database
|
1.2
|
|
(v)development of remedial works proposals and options along with an implementation programme |
1.0
|
| (c) |
Consultants' expenses (including computer facilities, production of reports, etc)
|
|
0.5
|
| (d) |
Contingencies |
|
4.0
|
|
Sub-total | 44.7 | (at
December
1996 prices)
|
| (e) | Inflation allowance | 12.9
|
| Total | 57.6 | (in MOD
prices)
|
A breakdown by man-months of the estimate for consultants' fees is at the Enclosure.
7.Subject to approval, we will the phase expenditure as follows -
| Year |
$ million
(Dec 1996) |
Price
adjustment
factor |
$ million
(MOD)
|
| 1998 - 99 |
6.2 |
1.16358 |
7.2
|
| 1999 - 2000 |
24.3 |
1.26830 |
30.8
|
| 2000 - 01 |
14.2 |
1.38244 |
19.6
|
|
44.7 | | 57.6
|
8.We have derived the MOD estimates on the basis of the Government's forecasts of trend labour and construction prices for the period 1998 to 2001. We will tender the proposed consultancy on a lump sum basis with provision for inflation adjustment as the consultancy period will last longer than 12 months. We will tender the internal pipe survey works under a re-measurement contract because the extent as well as the methods of the survey may have to be varied to suit site conditions. The re-measurement contract will have no provision for inflation adjustment as the contract period will be less than 21 months.
9.The proposed study will not give rise to any recurrent expenditure.
PUBLIC CONSULTATION
10.As this is an investigation study, we consider public consultation unnecessary.
ENVIRONMENTAL IMPLICATIONS
11.The proposed investigation will not have any long term environmental impact. For short term impacts during investigation, we will implement standard pollution control measures to control dust, noise and site
run-off nuisances to within established criteria.
LAND ACQUISITION
12.The proposed investigation does not require land acquisition.
BACKGROUND INFORMATION
13.The Secretary for Works undertook a review of slope safety measures in 1994. In the review, he recommended that a programme be developed to monitor and repair buried services at housing estates and other developments where leakage might affect slope stability. We presented a summary of the initial findings of the review to the Planning, Lands and Works Panel on 20 December 1994, and published a report on the review on 3 March 1995.
14.We made a commitment in the 1995 Policy Address to inspect and repair public sewers and drains which may affect the stability of slopes.
15.On 12 July 1996, Finance Committee approved the upgrading of 52BL *Investigation of sewers and drains affecting the safety of fill slopes and retaining walls' to Category A at an estimated cost of $64.3 million in
money-of-the-day prices. The scope of works of 52BL is to carry out investigation on the physical condition of those sewers and drains behind and adjacent to 4 920 fill slopes and retaining walls registered under the 1977-78 Catalogue of Slopes. The investigation commenced in August 1996 for completion in December 1998.
16.In developing the programme, we have decided to give priority to fill slopes and retaining walls as they are more vulnerable to attack by leakage from defective sewers and drains. Based on the experience gained in the investigation of sewers and drains affecting the safety of fill slopes and retaining walls, we have worked out a separate proposal on the investigation of those sewers and drains behind and adjacent to 5 520 cut slopes. We upgraded 54BL to Category B in September 1997. Subject to approval, we plan to commence the proposed investigation for completion in July 2000.
Works Bureau
November 1997
(LL294)
1.Consultants engaged by the Civil Engineering Department compiled the 1977-78 Catalogue of Slopes in 1978. The catalogue contains 4 920 man-made fill slopes and retaining walls and 5 520 cut slopes scattered throughout the whole territory. The catalogue forms a database of information for Government's further investigation and design of landslip preventive measures.
Enclosure to PWSC(97-98)92
54BL - Investigation of sewers and drains affecting the safety of cut slopes
Breakdown of estimates for consultants' fees
Consultants'
staff costs |
|
Estimated
man
months
|
Average
MPS
salary
point |
Multiplier
factor |
Estimated
fee
($ million)
|
| (a)Identification of sewers and drains affecting cut slopes
|
Professional
Technical
|
3
31 |
40
16
|
3
3 |
0.50
1.73
|
| (b)Preparation of tender and related documents for internal pipe survey
|
Professional
Technical
|
2
1 |
40
16
|
3
3 |
0.33
0.06
|
| (c)Supervision of internal pipe survey
|
Professional
Technical
|
122
180 |
40
16
|
2.1
2.1 |
2.33
0.89
|
| (d)Setting up of inventory and survey database
|
Professional
Technical
|
4
10 |
40
16
|
3
3 |
0.66
0.56
|
| (e)Development of remedial works proposals and options along with implementation programme
|
Professional
Technical
|
5
2 |
40
16
|
3
3 |
0.83
0.11
|
|
Total consultant's staff costs | 8.00
|
| Out-of-pocket expenses
|
| (a)Internal pipe survey contract works
| | | 32.2
|
| (b)Consultants' expenses (including computer facilities, production of reports, etc.)
| | | 0.50
|
| Total out-of-pocket expenses | 32.70
|
Notes
1.A multiplier factor of 3 is applied to the average 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 1.4.96, MPS pt. 40 = $55,390 p.m. and MPS pt. 16 = $18,595 p.m.)
2.Out-of-pocket expenses are the actual costs incurred. The consultants are not entitled to any additional payment for overheads or profit in respect of these items.
3.The figures given above are based on estimates prepared by the Director of Drainage Services. We will only know the actual man months and actual fees when we have selected the consultants through the usual competitive lump sum fee bid system.
(LL294)
