Collection of domestic wastewater is best achieved by a full sewerage water drain age system. Unfortunately this method is most expensive and there is relatively few communities in hot climate which afford it. A modern hygienic method of night soil collection is the only realistic alternative. Treatment is required principally to destroy pathogenic agents in sewage or night

The first unit operation generally encountered in wastewater treatment plants is screening. A screen is a device with openings, generally of uniform size, that is used to retain solids found in the influent wastewater to the treatment pant. The principal role of screening is to remove coarse materials (pieces of wood, plastics, rags, papers, leaves, roots etc.) from the

Tunnels are constructed To avoid the expensive acquisition of valuable built up land, tearing up pavements and holding up traffic for long periods in large cities. When the depth of ordinary cutting exceeds 20m and the ground rises rapidly for a considerable distance after wards. To avoid the excessive cost of maintenance of an open cut subjected to land slides or snow

Pavement considered flexible and the failure mechanism is assumed to be plastic deformation due to the communicative load over the life of pavement. Elastic Deformation: Temporary deforms the foundation material and compresses the air that fills the voids of the base and subgrade. In truly elastic deflection, permanent unevenness does not occur, even under repeated

An opening through an embankment for the conveyance of water by mean of pipe or an enclosed channel. Generally selection and type of material depends on the comparative cost, location of structure, availability of skilled labor, time limitations.