Testing and Processing # 1979 Brigthon
Over the years tree root penetration of sewers has been a major problem in Australia in the condition of lcw annual rainfall and long dry periods as experienced in South Australia and also the subtropical Northern areas, with accelerated growth conditions of heat and moisture. As a result root growth takes the form of aggressive systems which become very extended in their search for moisture. In the zone of the installed pipe the probability of root contact with the pipe line is increased by the pipe trench acting as a water course. Moisture within the trench zone can also come from the pipe system itself as a result of leaks from imperfect joints, line fractures, or by moisture on the external surfaces of permeable pipes. The significance of root penetration of existing sewer systems can be gauged from reports that in 1970/71 tree root caused 1941 pipeline blockages in Adelaide (11, and that in 1977/78 5786 pipeline blockages occurred in Brisbane with an estimated rectification cost of $A 130,000 (2).