For discussion PWSC(97-98)2
on 23 April 1997

ITEM FOR PUBLIC WORKS SUBCOMMITTEE
OF FINANCE COMMITTEE

HEAD 704 - DRAINAGE
Environmental Protection - Sewerage and sewage treatment
125DS - Tolo Harbour sewerage of unsewered areas

Members are invited to recommend to Finance Committee -

1. the upgrading of part of 125DS entitled "Tolo Harbour sewerage of unsewered areas, stage I phase IIA" to Category A at an estimated cost of $89 million in money-of-the-day prices; and
2. the retention of the remainder of 125DS in Category B.

---

PROBLEM
PROPOSAL
PROJECT SCOPE AND NATURE
JUSTIFICATION
FINANCIAL IMPLICATIONS
PUBLIC CONSULTATION
ENVIRONMENTAL IMPLICATIONS
LAND ACQUISITION
BACKGROUND INFORMATION
125DS - Tolo Harbour sewerage of unsewered areas Updated Cost Estimate and Implementation Plan
125DS - Tolo Harbour sewerage of unsewered areas Stage I Phase IIA
125DS - Tolo Harbour sewerage of unsewered areas

---

PROBLEM

Domestic sewage from unsewered areas in Sha Tin and Tai Po contributes to water pollution in Tolo Harbour.

PROPOSAL

2. The Director of Drainage Services, with the support of the Secretary for Planning, Environment and Lands, proposes to upgrade part of 125DS to Category A at an estimated cost of $89 million in money-of-the-day (MOD) prices for implementing necessary sewerage works at 17 unsewered areas in Sha Tin and Tai Po.

PROJECT SCOPE AND NATURE

3. The part of the project we propose to upgrade to Category A covers 17 unsewered areas shown in the site plan at Enclosure 1. The scope of works comprises the construction of -

1. 11 kilometres of sewers, ranging from 150 millimetres to 300 millimetres in diameter;
2. eight sewage pumping stations, three in Sam Mun Tsai, two in Wo Liu Hang, and one each in Wu Kai Sha, Hong Lok Yuen and Tai Po Kau San Wai; and
3. one dry weather flow interceptor in Ha Wo Che.

4. The remaining works of 125DS for retention in Category B comprise detailed design, site investigation and environmental impact assessment for stage II works and construction of stage I phases ID, IIB, IIC and stage II sewerage works. Details of the phasing and the remaining works are outlined at Enclosure 2.

JUSTIFICATION

5. In 1986, we established the Tolo Harbour Action Plan to reduce pollutants entering Tolo Harbour. One of the actions specified in the Plan was the provision of sewerage to unsewered areas in the Tolo Harbour catchment area. A consultancy study conducted under 95DS "Tolo Harbour catchment sewerage of unsewered areas - consultants' fees and investigations" recommended short-term and long-term measures to prevent direct discharge of untreated domestic sewage into Tolo Harbour.

6. We included 125DS in Category C in August 1990 for long-term water pollution abatement works in unsewered areas of the Tolo Harbour catchment. The entire project aims at collecting sewage flows from unsewered developments at 165 locations into existing sewerage reticulated systems in Sha Tin and Tai Po and the provision of new communal septic tanks for remote locations.

7. At present, domestic sewage from unsewered areas in Sha Tin and Tai Po is partially treated by private treatment facilities before being discharged into Tolo Harbour via stormwater drainage systems and stream courses. Most of these treatment facilities are septic tanks in village houses. Such tanks can remove large settleable solids from sewage but not polluted matter. Their performance is also unreliable because the owners of the tanks often fail to maintain them properly. As a result, discharged sewage from unsewered areas has become a major source of pollution in Tolo Harbour.

8. We propose to provide sewers for domestic connection in unsewered areas within the project area in order to prevent uncontrolled direct domestic discharge into Tolo Harbour. We will provide a dry weather flow interceptor to intercept polluted flows in a stream course and convey them to public sewers. Due to a difference in height levels and the need to avoid deep excavation in narrow alleyways when laying sewers (deep excavation may affect adjoining village houses built on shallow foundations), we will construct pumping stations to uplift the sewage collected to the existing public sewers.

9. The proposed sewerage facilities will serve a total of 12 600 people. Upon completion, we will be able to reduce the quantity of poorly treated sewage entering Tolo Harbour by 3 530m³ each day.

FINANCIAL IMPLICATIONS

10. We estimate the capital cost of the project to be $89 million in MOD prices (see paragraph 11 below), made up as follows -

A breakdown by man month of the estimates for consultants’ fees is at Enclosure 3.

11. Subject to approval, we will phase the expenditure as follows -

12. We have derived the MOD estimate on the basis of the Government's forecasts of trend labour and construction prices for the period 1997 to 2002. We will tender the proposed works as a standard remeasurement contract because we are uncertain about the existence and location of underground utilities such as electric cables, telephone cables, stormwater drains and water pipes. The contract will allow for adjustments to the tender price due to inflation as the contract period will be longer than 21 months.

13. We estimate the total annually recurrent expenditure to be $2,655,400. We will charge the expenditure to the Sewage Services Trading Fund. Subject to the Legislative Council passing a Resolution on appropriation of assets to the Trading Fund, the sewerage works under the project will, upon completion, become assets in the Fund valued at cost.

14. Based on the current level of sewage charges and water consumption, the proposed project by itself would lead to an increase in sewage charges by about 0.3%.

PUBLIC CONSULTATION

15. We consulted Sha Tin District Board and Tai Po District Board on the proposed stage I phase II works on 7 November 1996 and 8 November 1996 respectively. Members of both District Boards supported the implementation of the proposed works.

ENVIRONMENTAL IMPLICATIONS

16. The proposed works will intercept polluted sewage flows from 17 unsewered areas in Sha Tin and Tai Po for delivery to the Sha Tin and Tai Po sewage treatment works. There they will be treated before discharge, thus improving the water quality in Tolo Harbour.

17. We completed an Environmental Impact Assessment (EIA) in November 1996 under 179DS "Tolo Harbour sewerage of unsewered areas, stage I phase II - consultants' fees and investigations". The EIA concluded that we will need to install mitigation devices such as deodorizers and filters at the sewage pumping station at Hong Lok Yuen. These will be installed underground to control possible odour arising from the station’s operations. The estimated cost of $50,000 has been included in the overall project cost. For short term impacts, we will control noise, dust and site run-off nuisances during construction through the implementation of mitigation measures in the works contract.

LAND ACQUISITION

18. The project does not require land acquisition.

BACKGROUND INFORMATION

19. We included 125DS in Category C in August 1990 for long-term water pollution abatement works in 165 unsewered areas of the Tolo Harbour catchment.

20. In February 1991, we upgraded part of 125DS to Category A as 137DS "Tolo Harbour sewerage of unsewered areas stage I phase I - consultants’ fees and design" for employing consultants to carry out the detailed design, site investigation and EIA for the stage I phase I works. We upgraded stage I phase IA, IB and IC works to Category A in January 1993, June 1994 and January 1997 respectively. The implementation programme for these phases of the project is at Enclosure 2.

21. In July 1994, we upgraded part of 125DS to Category A as 179DS "Tolo Harbour sewerage of unsewered areas stage I phase II - consultants’ fees and investigations" for employing consultants to carry out the detailed design, site investigation and EIA for the stage I phase II works. The unsewered areas covered in stage I phase II are listed at Enclosure 4.

22. We are now ready to proceed with stage I phase IIA works. The consultants have completed site investigation, detailed design and tender documents for the works involved. We plan to start the proposed works in October 1997 for substantial completion in October 1999, with minor house connection works to be completed by October 2001.

Planning, Environment and Lands Branch
April 1997
(LL213)

---

Enclosure 2 to PWSC (97-98)2

125DS - Tolo Harbour sewerage of unsewered areas Updated Cost Estimate and Implementation Plan

Legend: * Part of 125DS we now propose to upgrade to Category A

# The remainder of 125DS after upgrading

---

Enclosure 3 to PWSC(97-98)2

125DS - Tolo Harbour sewerage of unsewered areas Stage I Phase IIA

Details of Consultants' Fees

Breakdown of estimates for consultants' fees

Notes:

1. A multiplier factor of 3 is applied to the average MPS point to arrive at the full staff costs including the consultants' overhead 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.) A multiplier factor of 2.1 is applied in the case of site staff supplied by the consultants.

2. The consultants' fees for construction stage are based on the lump sum fees calculated in accordance with the consultancy agreement the Director of Drainage Services has with the consultants undertaking the design and investigations of the stage I phase II project. The resident site staff costs are based on estimates prepared by the Director of Drainage Services. We will only know the actual man months and actual costs when we have completed the construction works.

---

Enclosure 4 to PWSC(97-98)2

125DS - Tolo Harbour sewerage of unsewered areas

Names of unsewered areas of stage I phase II

---