Sewerage Reticulation

Sewerage Backlog and the Environment

The environment generally and the receiving waters of the surface run-off in particular suffered badly from the lack of sewer construction during the Second World War and periods of depression, and correction only really commenced in the 1960s, when land sub-dividers were required to provide sewers and other essential services in their sub divisions. To facilitate this service and treat the wastes before the ultimate transfer and treatment works could be provided, quite sophisticated 'neighbourhood' or 'package' activated sludge type sewerage treatment plants were developed. They have proved highly successful to the benefit of the community served and the environment at large (Fig. 36).

36 Neighbourhood Plant Installed

Another development to minimise the disruption and possible damage to existing buildings and services in back-log areas was the development of machines for boring from 150 mm up to 450 mm diameter holes in which to lay the reticulation pipes and thus avoid the need for trenching. This cost-saving, where the surface is occupied by an expensive development, such as a swimming pool, has proved substantial (Fig. 37).

37 Retic Boring Machine

Tunnelling

The pumping of sewerage, which is corrosive, contains intractable solids and has wide variation in flows, presents economic and technical problems. In order to establish gravity flow in main transfer sewers, it is often necessary to lay them below practical open-cut excavation limits, by tunnelling. Considerable advances have been made in Australia, in particular in Melbourne, in constructing sewer tunnels. In Melbourne alone, between 1967 and 1985, 135 km of large bore water supply and sewerage tunnels were constructed.

Australian Academy of Technological Sciences and Engineering