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Drainage and storm water

Storm water is rainwater and melted snow that runs off streets, lawns, roofs and other sites and surfaces. Storm water reflects human activity, which distinguishes it from other run-off water.

Storm water conducted to municipal wastewater treatment

Properties must be connected to the storm water sewer network in the operating area of a municipal water management authority (Water Services Act Article 17 b). This responsibility concerns both old operating properties and new properties under construction. Properties in Helsinki make an agreement with the Helsinki Region Environmental Services Authority (HSY), which issues a statement on the point of connection.

Properties can apply for an exemption from connecting to the network from the City of Helsinki Environment Services (Water Services Act Article 17 c). The application must be made in writing and can be made using a standard form issued by the Environment Services.

Water Services Act

Storm water outside the operating area of a water management authority

If the property is located outside the operating area of a water management authority, the storm water management of the property is governed by the Land Use and Building Act (132/1999) and the City of Helsinki building regulations. According to the City of Helsinki building regulations, Article 17, storm water can be absorbed at the site if soil conditions allow. In special cases, storm water can be conducted to an operational open ditch network.

City of Helsinki storm water regulations

The regulations describe how to protect property against sea water flooding, flooding from waterways and storm water flooding caused by heavy rainfall and melting snow. The regulations provide instructions for how to prepare for flooding.

The City of Helsinki Instructions on Prevention and Control of Floods

25.02.2020 11:31