Disposal of stormwater runoff by soakage in Perth, Western Australia

Extensive use is made in Perth of soakage basins (referred to locally as sumps) for the disposal of runoff from roads in urban areas and soak wells for the disposal of roof runoff. Software packages such as PCSUMP, INFIL and MODRET as well as “rules of thumb” have been used to design the soakage basins. This paper discusses the advantages and disadvantages of these design software packages as well as presenting a new simplified design method. Methods of assessing soil permeability and other considerations in the design of sumps and soak wells are presented together with advice on related issues including cracking of houses near sumps and proximity of sumps to bridge foundations.