Drainage Works

Excavation of the drainage is the first operation to be carried out on the site, the 9km long road was divided into three and an engineering team were assigned to each. The distance from the established centre line at the middle of the road to the centre of the drainage was 11.4m wide and the drainage is about 1.8m wide. The side of the drainage is pegged and then dusted (application of white sand for easy excavation by the excavator). After the dusting of the drainage path the excavator starts to digging. The material recovered from the digging is either classified as suitable or unsuitable material. The good (suitable) materials are retained for future filling of the cross section while the bad (unsuitable) materials are taken away by truck to be disposed somewhere else. The good materials are identified by the compatibility of the soil and the percentage of humus present in the soil. The good material contains a very low percentage of humus. There are two methods of constructing drainage works, which are precast drainage and in-situ drainage