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along the shoreline in this area of the coast. Approximately 20 wrecked small ships and boats were counted along a 3 km stretch of coast to the east of Tema. |
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The maintenance of the sewerage system in Tema is operated by the TDC, which uses a labour gang to perform local digdown repairs and rodding operations. They use pitch fibre pipes to replace structurally inadequate or completely blocked sewers which do not respond to rodding. Rodding is initially carried out on blocked sewers, and experience suggests that a combination of sand and inappropriate materials discharged down the WC cause the great majority of blockages. The steel rods that are used readily clear blockages that contain items which a corkscrew-type tool can cope with. Thus the rods are used in both tension and torsion as the tool rotates. Sand deposits are difficult to displace with this type of approach. |
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It is clear from an examination of these expensive First World technologies that they are inherently unsuitable for use in developing countries. However, in areas of high-density housing where there are individual house connections to the water distribution network, some kind of sewerage is not only appropriate, but essential. |
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5.3
The Asafo Simplified Sewerage Scheme |
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Asafo is a central district of Kumasi with an estimated population of 20 000 people that has recently been sewered using simplified sewerage. This is part of the Kumasi Sanitation Programme which aims to completely eradicate the deplorable practice of public pan latrines. The main lines of the Asafo simplified sewerage system were laid out among the buildings roughly perpendicular to the local contours to take maximum advantage of the available gradients. The Asafo schemes was designed with the features described in Table 5.1. |
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With inspection chambers costing less than manholes due to reduced excavation, materials and construction costs, the savings made compared with a conventional sewerage scheme are in the order of between 20 per cent and 50 per cent (Bakalian et al., 1994). Conventional sewerage design requires a minimum level of cover that requires extensive excavation. The Asafo project had a minimum level of cover of 0.5 m in non-trafficked areas, and |
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