The Municipality of Asker (Norway) is at risk of not meeting the water quality targets set by the European Union Water Framework Directive within the stipulated timeframe. While there are multiple factors negatively impacting water quality in the municipality, wastewater is likely to be a major contributor. Infiltration and inflow water (I/I-water) leads to a number of unwanted consequences, of which direct discharge of untreated wastewater through overflow points is particularly important. In Aker municipality the portion of I/I-water is about 63%, while the goal is to achieve a level of about 30. This study utilises a socio-economic cost-effectiveness analysis of measures to prevent sewer overflows into waterbodies. The most effective alternative identified in the analysis is a complete renovation of old pipes in combination with troubleshooting for fault connected stormwater, when compared to alternatives considering upsizing/retention. I/I-water did cost the municipality of Asker NOK 34 million in 2017, when using a price of NOK 16,434 Tot-P for each kg of Tot-P let into the recipients. If the phosphorus cost is equal to or lesser than NOK 17,806/kg Tot-P, then it will not be socioeconomically justified to reduce I/I-water.


  • the articel identifies three different measures against consequences of I/I-water and does an analysis of what measure that provide the best cost/benefit ratio.

  • in addition we have done a calculation of what the I/I- water did cost the municiplity of Asker in 2017.

  • in the articel we do a litterature study of previous studies considering the willingness to pay to achive better water quality in the recipients.

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