For discussion PWSC(97-98)22
on 21 May 1997
ITEM FOR PUBLIC WORKS SUBCOMMITTEE OF FINANCE COMMITTEE
HEAD 704 - DRAINAGE
Environmental Protection - Sewerage and sewage treatment
161DS - Shek Wu Hui sewage treatment works - upgrading
Members are invited to recommend to Finance Committee the upgrading of 161DS to Category A at an estimated cost of $504.2 million in money-of-the-day prices.
PROBLEM
Shek Wu Hui sewage treatment works (STW) is unable to cope with the forecast sewage flow and pollution loads due to new developments in the sewage catchment which includes Sheung Shui and Fanling new towns and villages in the vicinity of Kwu Tung, along Sha Tau Kok Road and between Wo Hop Shek and Hong Lok Yuen.
PROPOSAL
2. The Director of Drainage Services, with the support of the Secretary for Planning, Environment and Lands, proposes to upgrade 161DS to Category A at an estimated cost of $504.2 million in money-of-the-day (MOD) prices for the upgrading of Shek Wu Hui STW. A plan showing the proposed works is at Enclosure 1.
PROJECT SCOPE AND NATURE
3. The scope of the project comprises the construction of -
- sedimentation tanks including two primary and two final tanks;
- aeration tanks, including construction of six new tanks and modification works for six existing tanks, and a blower house;
- sludge treatment facilities including one digester, one holding tank, one gas holder, two dewatering presses and two primary sludge thickeners;
- ultra-violet disinfection equipment;
- methanol storage/dosing system and process monitoring and control system;
- replacement of four fine screens and three sludge pumps; and
- miscellaneous works including building services, switch gears and valves installation, pipeworks, cabling and ancillary works.
JUSTIFICATION
4. Currently, the quantity of sewage flow to Shek Wu Hui STW has reached its design capacity of 59 880m3per day. We need to increase its capacity to meet the forecast sewage flow of 80 000m3 per day up to 2011. Designed before 1984, Shek Wu Hui STW is unable to cater for the forecast additional sewage flow of about 20 000m3 per day made up of -
- 8 000m3 per day from the future developments in Sheung Shui and Fanling new towns. We estimate that the population in these areas will increase from the existing 192 000 to 229 600 by 2011;
- 6 200m3 per day from the estimated population of 37 500 by 2011 in the villages mentioned in paragraph 1 above due to the provision of sewerage systems for the areas;
- 800m3 per day of leachate partially treated from North East New Territories Landfill located in Ta Kwu Ling; and
- 5 000m3 per day from the future flow of Sheung Shui Slaughterhouse.
5. Moreover, Shek Wu Hui STW does not possess equipment specially designed for nutrient removal and disinfection. The additional flow from future developments in North District, in particular the leachate from North East New Territories Landfill and the discharge from Sheung Shui Slaughterhouse, will increase the pollution loads to the plant substantially especially in terms of nutrient and pathogen1 loading. To ensure that the quality of the treated effluent will comply with the current standard of discharge into River Indus, we need to upgrade Shek Wu Hui STW by incorporating nutrient removal and disinfection facilities into the plant.
1Pathogen are disease-causing micro-organisms.
6. If we do not implement the project, the existing Shek Wu Hui STW will not be able to handle the future sewage flow volume and pollution loads. The effluent quality will deteriorate and exceed the effluent standard. The poor quality effluent will also become a pollution source to River Indus and eventually pollute the water quality in Deep Bay.
FINANCIAL IMPLICATIONS
7. We estimate the capital cost of the proposed works to be $504.2 million in MOD prices (see paragraph 8 below), made up as follows -
|
|
$ million
|
|
|---|
|
(a) Sedimentation tanks
|
|
44.1
|
|
|
(i) Civil works
|
29.7
|
|
|
|
(ii) Electrical and mechanical works
|
14.4
|
|
|
|
|
|
(b) Aeration tanks and blower house
|
|
98.6
|
|
|
(i) Civil works
|
70.0
|
|
|
|
(ii) Electrical and mechanical works
|
28.6
|
|
|
|
|
|
(c) Sludge treatment facilities
|
|
69.6
|
|
|
(i) Civil works
|
16.1
|
|
|
|
(ii) Electrical and mechanical works
|
53.5
|
|
|
|
|
|
(d) Ultra-violet disinfection equipment
|
|
35.9
|
|
|
(i) Civil works
|
4.5
|
|
|
|
(ii) Electrical and mechanical works
|
31.4
|
|
|
|
|
|
(e) Methanol storage/ dosing system, and process monitoring and control system
|
|
32.7
|
|
|
|
|
(f) Replacement of fine screens and sludge pumps
|
|
15.0
|
|
|
|
|
(g) Miscellaneous works
|
|
46.4
|
|
|
|
|
(h) Overseas inspections of equipment
|
|
0.3
|
|
|
(i) Contingencies
|
|
33.7
_____
|
|
Sub-total
|
|
376.3
|
(at December
1996 prices)
|
|
(j) Inflation allowance
|
|
127.9
_____
|
|
Total
|
504.2
_____
|
(in MOD prices) |
A breakdown of the estimate for fees of overseas inspections of equipment is at Enclosure 2.
8. Subject to approval, we will phase expenditure as follows -
|
Year
|
$ million
(Dec 1996)
|
Price
adjustment
factor
|
$ million
(MOD)
|
|---|
|
1997 - 1998
|
4.5
|
1.06750
|
4.8 |
|
1998 - 1999
|
89.6
|
1.16358
|
104.3 |
|
1999 - 2000
|
105.8
|
1.26830
|
134.2 |
|
2000 - 2001
|
85.3
|
1.38244
|
117.9 |
|
2001 - 2002
|
60.5
|
1.50686
|
91.2 |
|
2002 - 2003
|
19.8
|
1.64248
|
32.5 |
|
2003 - 2004
|
10.8
|
1.79030
|
19.3 |
|
_____
|
|
_____ |
|
Total
|
376.3
|
|
504.2 |
|
_____
|
|
_____ |
9. We have derived the MOD estimate on the basis of the Government's forecast of trend labour and construction prices for the period 1997 to 2004. We will tender the civil engineering works of the project under a lump-sum contract because we can clearly define the scope of the upgrading works. The tender price will be subject to adjustment for inflation because the contract period will be longer than 21 months.
10. We will tender the electrical and mechanical works under a standard fixed price lump-sum contract because the major part of the works will be the supply and installation of electrical and mechanical equipment of which we can clearly define the scope of the works.
11. We estimate the additional annually recurrent expenditure to be $17.2 million. We will charge this expenditure to the Sewage Services Trading Fund. Subject to the Legislative Council passing a Resolution on appropriation of assets to the Trading Fund, the proposed works will, upon completion, become assets in the Fund valued at cost.
12. Based on the current level of sewage charges and water consumption, the proposed project by itself would lead to an increase in sewage charges of about 1.5%.
PUBLIC CONSULTATION
13. We made presentations on the proposed works to the North District Board on 8 December 1994 and to the District Development and Environmental Improvement Subcommittee of the North District Board on 10 September 1996. Members of the North District Board supported the implementation of the project.
ENVIRONMENTAL IMPLICATIONS
14. The consultants conducted an Environmental Review (ER) for the proposed extension under the North District sewage master plan study in 1994, and updated the findings in 1996. The ER concluded that the impact of the proposed upgrading works could be controlled and that no Environmental Impact Assessment is required. The proposed works, when completed, will improve the quality of the surrounding waterbody. To mitigate odour from the proposed works, we have built in to the design sludge thickeners with covers and install activated carbon deodorisation units.
15. For short term impacts, we will control noise, dust and site run-off nuisances during construction to within established guidelines through the implementation of mitigation measures in the relevant works contracts.
LAND ACQUISITION
16. The project does not require any land acquisition.
Background INFORMATION
17. In 1994, we completed the North District sewerage master plan study under 113DS "North District sewerage master plan study - consultants fees and investigation" which identified the need for upgrading Shek Wu Hui STW.
18. We upgraded 161DS to Category B in October 1994 for the implementation of the proposed works.
19. We have completed the detailed design and preparation of working drawings for the proposed works using in-house staff resources. We plan to start the proposed works in November 1997 for completion in July 2001. We will complete part of the proposed works for receiving flow from Sheung Shui Slaughterhouse in mid-1999 to match the commissioning of the Slaughterhouse.
Planning, Environment and Lands Branch
May 1997
(JJ181)
Enclosure 2 to PWSC(97-98)22
161DS - Shek Wu Hui sewage treatment works - upgrading
Breakdown of estimate for fees of overseas inspections
|
No. of staff by rank
|
Cost breakdown
|
|
|---|
|
Air passage
$
|
Subsistence allowance
$
|
Miscellaneous reimbursable expenses
$
|
Sub-total
$
|
|---|
|
1. One senior engineer or engineer
|
72,424
|
47,620
|
10,000
|
130,044 |
|
2. One inspector of works
|
72,424
|
47,620
|
10,000
|
130,044
_______ |
|
|
|
Grand Total
|
260,088
______
|
|
|
|
|
|
|
|
|
Say
|
300,0001 |
|
|
|
|
_______ |
Remarks
1. We have made the following assumptions in estimating the cost required for the above overseas inspections -
|
Equipment
requiring inspection
|
Potential manufacturers
come from
|
Anticipated no.
of trips/days
|
|---|
|
Air blowers
|
)
)
|
|
|
Sludge pumps and the related variable speed drives
|
)
)
) UK/Germany/Switzerland
)
|
two trips2 , total 15 days |
|
Sludge dewatering presses
|
)
)
|
|
|
Process monitoring system
|
)
|
|
|
Aeration system
|
)
) US/Canada
|
one trip, 7 days |
|
Ultra-violet disinfection system
|
)
)
|
|
|
Sludge thickeners
|
) Australia/
) New Zealand
|
one trip, 7 days |
|
Pipes and pipe fittings
|
)
|
|
1 In PWSC papers, we usually round the costs of each item to the nearest hundred thousand dollars.
2 In respect of the variable speed drives for the sludge pumps, we need to attend combined tests after the manufacturers have fitted them to the pumps. We expect that the supppliers of variable speed drives will need some time to transport these drives to the manufacturing factories of the pumps for assembling as they may not be manufactured at the same place. As both the transportation and the assembling process will take time to complete, we plan to make a second trip to attend the tests after the assembling.
2. The rate of subsistence allowance, cost of air passage and reimbursable expenses for officers attending the inspections are subject to the relevant provisions in the Civil Service Regulations. The bases of calculations are as follows -
|
UK/Germany/Switzerland
|
US/Canada
|
Australia/New Zealand |
|
Air passage
|
$18,037 x 2 officers x 2 trips
= $72,148
|
$23,946 x 2 officers
= $47,892
|
$12,404 x 2 officers
= $24,808 |
|
Subsistence allowance
|
$1,770 per day x 2 officers x 15 days
= $53,100
|
$1,560 per day x 2 officers x 7 days
= $21,840
|
$1,450 per day x 2 officers x 7 days
= $20,300 |
|
Miscellaneous reimbursable expenses3
|
$10,000 ($5,000 per trip)
|
$5,000
|
$5,000 |
3. The actual expenditure for overseas inspection will depend on various factors such as the manufacturing programme and place of manufacture of the equipment.
3 Miscellaneous reimbursable expenses include those for airport tax, photographs and local transportation.
(JJ181)
Last Updated on 16 August 1999
