Occurrence and general characteristics of deposits in the Athens storm sewers

The sewer system of the city of Athens is composed of a separate network at the most part and of a very minor segment of combined network serving the oldest part of the city. The maintenance of the network is inadequate. Therefore, no information is available about the deposits of sewer sediments within the network. A recent pilot investigation is summarised here, which showed that: (1) Deposits do exist in the Athens storm sewer system and may constitute a serious problem for the proper hydraulic function of the network. (2) The sediment discharge capacity of the network during moderate storm events seems to be modest, as deposits of very fine material were traced at certain locations. (3) The finer deposits have high organic loads, which may have been caused by illegal connections of domestic and industrial sewers. These deposits are likely to develop some kind of cohesiveness because dry periods are usually long for the Athens climate.