• Référence: P-MU-EB0-005
• Date d’approbation: 20/06/2007
• Date de début: 12/06/2008
• Date d'évaluation: 26/11/2006
• Statut: En coursOnGo
• Agence d'implémentation: WASTEWATER MANAGEMENT AUTHORITY (WMA)
• Emplacement: PLAINES WILHEMS

The Plaines Wilhems Sewerage Project consists of the St. Martin Sewerage Treatment Plant Expansion, construction of a trunk sewer, construction of sewer reticulation systems and house connections. The works are divided into 4 components as follow:

i. Expansion of St. Martin Sewerage Treatment Plant: This involves increasing the capacity of the works to 69,000 m3/day to serve a population of 233,000. The treatment process will be changed from the system of oxidation ponds to the more complex low rate activated sludge process with biological nutrient removal, followed by tertiary treatment with rapid gravity sand filters and UV disinfection. Sludge treatment will be by anaerobic digestion followed by dewatering using centrifuges. A combined cycle heat and power plant will be installed to generate electricity from surplus biogas. Work on this component with financing by the European Union (EU) and the Government of Mauritius (GOM) was completed in March 2005 and it is currently being operated and maintained under a 3 year O&M contract with Degremont until March 2008.

ii. Construction of trunk sewer: A 25 km trunk sewer will be constructed on the western half of the Plaines Wilhems area from Curepipe in the south to St. Martin Sewerage Treatment Plant in the northwest. The trunk sewer will vary in diameter from 400mm to 1100 mm. It will be commissioned in two sections the lower one which will collect the project works being first. Two cross-connections will be made to the old trunk sewer to divert flows from the upper parts of the catchment to the new Trunk Sewer. This component includs replacement of 11 km of water supply pipes.

iii. Construction of Reticulation Systems and House Connec tions as follows:

a.Construction of Reticulation System Lot 1A: This will involve the construction of a sewer reticulation system in Southwest Quatre Bornes (Zone 6) and West Rose Hill B(Zone 9B). It will also include construction of 12,174 house connections. The project is co-financed by EIB and GoM.The project is expected to start third quarter 2008.

b.Construction of Reticulation System Lot 1B: This will involve the construction of a sewer reticulation system in West Rose Hill A(Zone 9A) of about 41 km. It will also include construction of 4,000 house connections. This is the component that the Bank will fund. 10 km of water supply pipes will be replaced under this contract. Bids submited on March 11, 2008 and they are being evaluated by central procurment Board.

c. Construction of Reticulation System Lot 2: This will involve the construction of a sewer reticulation system in Central Quatre Bornes (Zone 7), NE Quatre Bornes (Zone 8) and Sodnac (Zone 8A) of about 91 km, as well as the construction of 12,956 house connections. About 50 km of water supply pipes will be replaced under this contract. the project is finaced by Exim bank of China.

d. Construction of Additional House Connections in Unsew ered Pockets of Sewered Areas: This will involve the extension of the sewer network in already sewered areas to unsewered pockets in Curepipe and Phoenix (Zones 1 and 2) and Rose Hill (Zones 10, 11 and 12), and will include construction of approximately 4,000 additional house connections.

The ADB assisted component, Construction of Reticulation System Lot 1B in West Rose Hill A (Zone 9A), more specifically consists of (a) construction of 41 km of sewers in diameters ranging form 200 mm to 600 mm laid to a depth ranging from 1.5 to 3.0 meter for the larger diameters,(b) an estimated 823 access manholes at network nodes; (c) some 4,000 house connections and (d) the replacement of around 10km of old existing water distribution pipelines. Each house connection includes installation of a Y branch, construction of a house sewer with an inspection chamber, connections to existing chambers and the de-commissioning of soakage pits ..

The objective of the Plaines Wilhems Sewerage Project is to provide an environmentally appropriate collection, treatment of sewages and disposal of effluent and sludge from Plaines Wilhems District. It will improve the sewerage system and increase connectivity of properties in the Plaines Wilhems district. It is intended to avert and reverse the potential for environmental degradation of surface and groundwater resources by wastewater through improved collection and treatment of sewage and disposal of effluent and sludge from the Plaines Wilhems catchments area.

Most people in Mauritius still rely on on-site facilities for the disposal of human and domestic liquid waste. Sewerage coverage is only about 25% of the population, the remaining 75% usesn on site waste water disposal system (septic tanks with absorption pits, cesspits or communal sewer network followed by large leaching fields) while water supply coverage is more than 98.8%. With current levels of water consumption, there is a high possibility that ground water sources are being polluted. In major industrial plants, owing to lack of effluent control and monitoring, little or no pre-treatment of trade waste is occurring. The existing main sewerage systems in the country, including that of the Plaines Wilhems district, designed as separate foul sewer systems, frequently operate as combined sewer systems and suffer from frequent blockages and a severe lack of maintenance.

This situation has caused a lot of concern regarding the health and sanitary condition of the population and pollution of the island's lagoons and ground water resources by human excreta, industrial effluent and agricultural chemical run-off.

In Plaines Wilhems district in particular, the main problems with the existing system include the following: it cannot cope with existing peak flows; there are sewerage overflows causing polluting discharges; there is a large number of complaints regarding blockages and overflows; inappropriate on-site disposal systems where the major Curepipe acquifer is found.

It was on the basis of these concerns that the GOM produced the Sewerage Master Plan to provide a comprehensive framework for developing wastewater facilities to abate and control the wastewater pollution problems in Mauritius and provide an orderly programme for planning, financing, building, staffing, operating and maintaining developments in the sewerage sector over the 20-year period of the Master Plan. The Plaines Wilhems Sewerage project falls within this framework, hence shall contribute towards the achievement of the Government's goal of increaing sewerage connections, and thus abating and reversing the prevalent wastewater pollution and improving the health and sanitary conditions of the population of the island. ..

The benefits of the projects include:

i) Improvement of health and sanitary conditions of the population in the Plaines Wilhems district;

ii) Reversal of the current trend towards environmental pollution in the district;

iii) Increase in availability of treated wastewater for irrigation purposes;

iv) Protection of the coastal environment;

v) Controlling the pollution of surface and ground water resources;

ADHIAMBO Nancy Aileen Nereah Ogal - OWAS2

Source	Montant
BAD	UAC 13.749.825
Governement	UAC 44.449.000
Co-financier	UAC 73.529.000
Delta	UAC 642.175
Total	UAC 132.370.000