Author(s): A. Tennakoon; J. R Argue
Linked Author(s): Amitha Tennakoon
Keywords: ‘at capacity’; Detention; Extended detention; ‘soakwells’; Source control; Stormwater
Abstract: The stormwater infrastructure of the City of Gosnells, WA, is ‘at capacity'. The cost of conventional upgrade ahead of further urbanisation has been estimated as $120 million. An alternative, cost-effective approach has been adopted based on WSUD ‘source control' principles. There are two soil domains: sand and sandy-clay, and, medium to heavy clay. The adopted criterion for stormwater control is set at ARI, Y = 100-years, determined for the (site) worst case resulting from application of storm durations 6 mins to 72 hours. Three design scenarios result: (1) large lots in sand or sandy-clay soil require full retention/disposal on site with no outflow to street drainage; (2) Small lots (A < 350 m2) in sand or sandy-clay require retention/disposal on site with permissible outflow equivalent to pre-development ARI, Y = 5-years; (3) All lots in medium to heavy clay soil require full detention on site with permissible outflow equivalent to pre-development ARI, Y = 5-years. A design spreadsheet has been prepared: this provides details of ‘soakwell' and detention installations and provision for outflow.
Year: 2011