ANALYSIS OF DEFECTS IN 180KM OF PIPE SEWERS IN SOUTHERN WATER AUTHORITY

This report describes an analysis of the defects found during closed circuit television survey inspection of the sewers of the Southern Water Authority. Structurally damaged pipes were found in marginally less than 5.6 per cent of the total length surveyed with large displaced and open joints being found in some 0.8 per cent. The relation between these defects and the age of construction, the lengths, depths, diameter and material of the pipes, the location of the sewer, soil type and whether the sewer carried foul sewage, surface water or a combination of both are examined. Almost a quarter of connections were found to be faulty and it is concluded that their substitution by junctions would remove a major source of structural defects from pipe sewers. Other findings are that sewers constructed since 1945 have a much lower rate of structural defects than older sewers, that current methods of structural design are adequate and recommends CCTV surveying of newly constructed sewers and sewers proposed for adoption. (Author/TRRL)