The city of Douarnenez (15,000 inhabitants) decided to provide sustainable and good bathing water quality on its beaches in north-western France. Therefore a water treatment masterplan was developed in order to bring information and solutions adapted to rain and sewage water treatment. The existing network comprises 102km of sewage water linear and  68km of rainwater linear. The sewage water masterplan brought to light salt water intrusions in the network, requiring the monitoring of overflows. Therefore a specific action plan was set, comprising video inspections, smoke and dye tests. This plan revealed the presence of bad sewage water / rain water connections and set the long term measures against the network malfunctions during wet weather.


o On-site inspections and setting of the state of play
o Analysis at the outlets
o Sewage and storm water measurement series
o Storm water network modelling
o Video inspections of the network, smoke and dye tests
o Drafting of a quantified and prioritized program of works on the storm water network


City of Douarnenez authorities

Key figures

Period of services

November 2012 - November 2013

Key challenges