Stormwater

Property owners are responsible for stormwater management on their own property. The Stormwater treatment on properties guide provides information on how property owners can reduce, detain and treat stormwater.

Stormwater management is important for both the condition of the property and the state of the environment. Well-managed stormwater does not pose a risk to the property, and collecting stormwater for irrigation purposes saves money. Stormwater management reduces the pollution of water bodies and can promote the biodiversity of yard areas.

The property owner is responsible for the treatment of stormwater on their own property and maintains e.g. culverts, open ditches, boundary ditches, stormwater pipes and other stormwater management structures.

Open ditches and stormwater pipes or culverts located on the property are part of the property’s maintenance. Likewise, the property’s gutters, drains, leach pits, retention ponds, stormwater pumping stations and other stormwater management structures.

See more about the property’s stormwater management in HSY's video (external link, opens in a new window)(in Finnish).

The maintenance of a ditch that runs along the border of two or more properties belongs to all the properties that benefit from the ditch. Boundary ditches should be kept open and free of debris, even if most of the buildings are connected to the stormwater drain. A well-kept ditch prevents flooding by directing water forward, for example during heavy rain, when the stormwater drain cannot take more water.

Culverts of access ramps

The culvert pipe of the property’s driveway must be maintained by the property, as the driveway serves the property’s needs. See more about property maintenance obligations in the video(external link, opens in a new window) (in Finnish).

You should pay attention to snow management on your own property. Snow must be collected and stored on your own property, for example, in the places shown in the building permit. Snow is not collected on a neighbour’s or city’s land. If necessary, snow must be transported to a snow disposal site. It is the property’s own responsibility to manage the meltwater from the snow collected from its own yard, and the meltwater must not cause harm to the neighbours. The same duties apply to the leaseholder of a plot.

When building a new home or moving into a new home, the framework created by the surrounding terrain for stormwater management must be taken into account. If the property is located below a slope or at the lowest point of its surroundings, the natural flow direction of the water is towards the property. In these areas, it is particularly important to take care of sufficiently efficient drainage of your own plot. Even if the buildings in the area are connected to the stormwater drain, natural runoff always occurs in the environment when it rains or ice or snow melts on the grass, wooded area or rock. It is not necessary or even possible to control all the water on the plot. The need for management focuses on water that accumulates on built-up, impermeable surfaces, i.e. stormwater.

The city builds public stormwater systems so that stormwater can be managed harmlessly. According to the legislation, connection is mandatory, so that stormwater does not cause harm to others and the costs of construction can be covered. You can get an exemption from connecting under certain conditions.

The property’s stormwater must be treated in the following order:

1. The stormwater must be steered to a general stormwater drain if the property is located in the area of stormwater drainage (typically when a stormwater drain runs along the street) or be exempted from this obligation. Below is more information about application.

2. Stormwater must be absorbed into the ground on the property.

3.  Stormwater must be steered to the city’s other stormwater system (e.g. street ditches, park ditches), in which case consent must be applied for from the city.

The Water Services Act(external link, opens in a new window) (external link, opens in a new window)obliges the property to connect to the water supply plant’s stormwater drain. Typically, we are in the drainage area when the street has a stormwater drain. An exemption from the obligation to connect can be applied for from the Environment and Building Control Department. In order for the exemption to be granted, all the conditions specified in the act must be fulfilled:

• Connection to the stormwater drain would be unreasonable for the owner or occupier of the property.
• The release does not endanger the economic and proper management of the stormwater drainage.
• Stormwater can be removed in another appropriate way.

The application must include:

• Reasons for the unreasonableness of the connection
• Description of where stormwater is generated on the property (roofwater, drainage water from foundations, stormwater from paved surfaces such as an asphalted yard)
• Attached is a map showing the direction of stormwater (from the property to the city ditch or other common ditch, waterway or stormwater drain) and the stormwater system, such as gutters, wells, absorption areas, etc.
• Signature or powers of attorney of all property owners.

The application can be made on Espoo’s public services website(external link, opens in a new window) or with a form that can be downloaded using the link below. You can get instructions in English on how to apply for an exemption from the Environment and Building Control Department. The form with attachments is sent to the City Registry Office by e-mail to: kirjaamo@espoo.fi or to P.O. Box 41, 02070 CITY OF ESPOO.

If it is necessary to lead stormwater from the property to a public area, such as an open ditch on the street or a park, consent must be obtained in accordance with Section 103 g of the Land Use and Building Act.(external link, opens in a new window) The consents are processed in the administration of the use of the areas of the urban engineering centre. The case is handled as a stormwater management consent for the use of the public area in accordance with Section 103 g of the Land Use and Building Act and Section 16 of the Building Regulations of the City of Espoo (in Finnish).

Consent is applied for via the electronic service of the City of Espoo. In the application, you must fill in the location of the stormwater drainage on the map, as well as additional pictures or a description of how and where the water is diverted. The HVAC plan of the zoning drawing of the plot is selected as an attachment and more precise absorption and delay dimensioning is selected as an attachment in accordance with the instructions, regulations and permit decisions of the Building Control.

Provision is made for stormwater management through urban planning. To support the work with planning, regional stormwater surveys and plans for stormwater management are prepared. The local master plan and partial master plan clarify the needs of stormwater  management by catchment area and evaluate the effects of construction on surface water and groundwater. Sustainable stormwater management can be required in the land use plan, for example with regulations regarding delay or stormwater quality. As an example, the basic plan regulation regarding stormwater management used in city plan sites:

"Stormwater coming from impermeable surfaces must be delayed in the area in such a way that the dimensioned volume of delay ponds, basins or tanks must be one cubic meter for every hundred square meters of impermeable surface. The delay ponds must be emptied within 12–24 hours of being filled, and a controlled overflow must be planned for them."

At their best, stormwater structures enliven the surrounding environment and increase the diversity of urban nature. For example, rain gardens makes the neighbourhood more beautiful. Flood meadows provide new habitats for many plant and animal species whose natural habitats have become scarce. Urban planning guides and encourages the implementation of green roofs. Green roofs are useful both in managing stormwater and in improving climate resistance and the comfort of the city.

HSY (Helsinki Region Environmental Services joint municipality authority) is responsible for the stormwater trunk lines, i.e. the long pipelines that move stormwater forward. HSY’s network carries drainage water from streets and stormwater from properties. HSY maintenance cleans pipes and wells as needed. More information is available from HSY’s own customer service: www.hsy.fi/hsy/asiakaspalvelu/(external link, opens in a new window).

The infrastructure services of the City of Espoo is responsible for stormwater pumping stations, open ditches located in the public area, stormwater basins in green areas and short culvert sections of open ditches. The maintenance of infrastructure services cleans grating wells further away from the trunk line, which collect stormwater from streets and other public areas. in particular, sand and leaves collect in wells as well. Also branches, garbage, vegetation and sediment collect in open systems (ditches and basins), which must be removed from time to time.

Stormwater is taken into account in all the city’s street and park construction projects. As a rule, wells and pipes are built in new street areas; ditches, depressions and basins in the park. In the renovation project of the old street, open ditches are often abandoned and pipes that save street space are built. In the pipeline, stormwater moves more reliably and efficiently from the plots and the bends of the streets. Parks are the best place to build delay and flooding space in public areas. In a pipe, the water goes quickly as it is, but in open systems it lingers, soaks into the ground and is filtered cleaner.

Street and park areas in the planning stage: www.espoo.fi/en/street-plans. In addition, there is a home street portal where you can check the planning and construction schedule of the streets in your area: https://kotikatu.espoo.fi/(external link, opens in a new window)

Properties bordering the street area to be built will receive a notice and an invitation to both comment on the planning phase and the construction start survey.

The City of Espoo has prepared a stormwater programme to improve water quality and reduce stormwater floods. Espoo’s stormwater programme 2020 contains a description of Espoo’s geographical characteristics, stormwater actors, the current situation of stormwater management and management goals. The most important actions to achieve the goals of the stormwater programme are the improvement and development of cooperation and operating methods related to stormwater, increasing stormwater expertise and awareness, and even better stormwater information management. The aim of the stormwater programme is to bind actors who affect stormwater to adhere to common principles.

You can find answers to questions about stormwater on the Frequently Asked Questions About Water page.