The Challenge

Iringa city is located 500 km south-west of Dar es Salaam and is the Capital of the Iringa region. The town is located some 1,500 m above sea level on a plateau on top of an escarpment overlooking the Little Ruaha river valley. The river is the major raw water resource, together with the Kitwiru springs. Both sources supply approximately 12,000 m3 raw water per day. However, the existing raw water treatment plant has insufficient capacity to treat the water to an acceptable quality and the transmission and distribution network also needs some extension. In addition, the current sewerage system covers only a small part of the town and wastewater is treated at a plant on the outskirts of the city.

The Approach

In 2005, and with the financial support of the KfW and the European Development Fund (EDF), the Iringa Urban Water Supply & Sewerage Authority (IRUWASA) decided to upgrade the existing water supply system and expand the area covered by the sewerage system to correct the deficiencies in water and sewer treatment. A joint venture of local designers and international consultants was charged with the planning. A feasibility study was initiated to provide solutions for a prompt, adequate supply of good quality, safe water and sewerage services at affordable prices for Iringa municipal residents.

The Solution

The final design report presented the following conclusions and activities: One of the existing traditional water treatment lines is in fairly good condition and will play an ongoing part in the current system. After some minor rehabilitation work it will be able to provide 1,600 m3 of clean water per day. The second, more simple treatment line is producing water of minor quality and will be incorporated in the new treatment plant to be built. This new treatment plant will include three raw water pumps, a new sand trap, an additional flocculator and an upgraded sedimentation tank with a volume of approximately 1,550 m3. The sludge from the sedimentation tanks will not be discharged into the river, but dried now on two drying beds. A new clear water tank, with a volume of 2,500 m3, in combination with an improved clear water pumping station with four water pumps, will also be erected.

The tapping of springs at Kitwiru by a pumping station will be increased from 3,000 m3/day to 4,000 m3 /day by using stronger pumping equipment to cover the increasing need for drinking water. The chlorination of all water, from Little Ruahu river as well as from the Kitwiru springs, will be carried out by a new common chlorination plant, erected near the drinking water pumping station. The new, improved raw water and drinking water capacities also make an extended network of transmission mains and distribution lines necessary. Around 30,000 m of transmission lines in diameters DN200 mm to DN500 mm made of steel and PVC will be laid. The distribution network totalling approx. 300,000 m will consist of PVC, HDPE and steel pipes, mostly in diameter DN 50 mm. An estimated 174 km of the network needs to be newly installed. From the old tanks storing drinking water, only one concrete tank can be incorporated in the new system, and will serve as extra capacity. Thirteen new tanks will be constructed, with a total volume of approximately 6,000 m3, to ensure the continuous and safe supply of drinking water for the whole city.

The huge project also includes the extension of the wastewater network. It is intended to establish an additional 4,000 m of PVC pipes in diameter DN 150 mm, together with 70 manholes. The new pipeline will connect another 600 buildings to the public sewer network and will provide approximately 3,000 people with a new sewage connection.

The tender documents for the construction works were completed and submitted to interested bidders in early 2008. A joint venture of Jos. Hansen & Soehne GmbH with their wholly owned civil construction subsidiary, JR International Bau GmbH, entered a bid in March 2008 and in June 2008 it was successfully awarded the contract for the construction works. The project has a construction period of 24 months from commencement until completion.

The project is a good sample of a meaningful investment in water and sanitary services in Africa.