Stormwater

In built-up areas, stormwater is rainwater, snowmelt or leaching water that flows from roofs or other impermeable surfaces and flows from plots in ditches, pipelines or stormwater drains to streams, rivers, lakes and the sea. If the sewers are not able to take in all the stormwater, a flood can occur.

Photo: Saara Olsen

Stormwater and climate change

As Espoo becomes denser, climate change increases the risk of heavy rains and floods.

At best, stormwater solutions support the city’s greenery, comfort and natural diversity and help adapt to a changing climate. Stormwater carries many pollutants with it, which weaken the quality of surface and groundwater and destroy biological communities. Stormwater management can improve the condition of waterways and ensure the preservation of groundwater quality and surface level.

Read more about adapting to climate change on the city’s website: www.espoo.fi/en/climate-change-adaptation

Stormwater programme

The stormwater programme presents concrete actions for managing stormwater and gives tips for stormwater planning. Espoo’s first stormwater programme was approved by the City Council in 2012. The update of the programme in 2020 has taken into account the stormwater floods of recent years, increased research knowledge, experience gained from construction projects and changes in legislation.

The goal of the stormwater programme is to improve stormwater management, reduce stormwater floods and prevent damage caused by stormwater. Responsible actors have been defined for the actions aimed at achieving the goals. In addition, the programme discusses Espoo’s characteristics, stormwater flood risks, stormwater-related legislation, resource needs and stormwater information management.

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, 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)(in Finnish).

Boundary ditches

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) (in Finnish).

Snowmelt

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.

Taking into account the terrain surrounding the property

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.

Construction site water management

Construction site water refers to water or sludge formed on construction sites, with the exception of domestic waste water generated in the social and sanitary facilities of construction site booths. More information is available about the treatment of stormwater during construction in the City of Espoo’s construction site water guide (in Finnish).

Construction site water cannot be discharged as such into the terrain, stormwater drains or waterways. Environmentally-friendly treatment and a stormwater management plan must be implemented in advance for water generated on the construction site.

Management of drilling water generated at geothermal well sites

The fine aggregate and sludge formed by the drilling of a geothermal well must be treated in such a way that it does not cause harm to the environment, neighbours or the sewer network. The treated drilling water discharged into the water body must not be inferior in quality to natural water. The municipalities of the Helsinki Metropolitan Area and HSY have jointly produced a guide for the treatment of water at geothermal well sites, the compliance of which is the responsibility of the contractor, the person undertaking the project or the main designer.

The property’s obligation to connect to general stormwater systems and exemptions

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.

Applying for exemption

The Water Services Act (external link)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) 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.

Applying for consent to discharge stormwater into a public area or into a city ditch

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). 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.

Urban planning

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.

Maintenance

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).

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 under construction

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)

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.

Stormwater programme

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.

The ditch between our property and the neighbour’s is blocked. Whose responsibility is it to clear the ditch?

It is a boundary ditch, and both properties are responsible for the maintenance of the ditch.

Leaves and twigs have collected in the open ditch between our plot and the sidewalk and it does not drain properly. Who cleans up the leaves and twigs?

The maintenance responsibility of the property owner also includes the small area bordering the plot and the ditch located in it. However, no more than 15 meters from the plot boundary. Removing trash, leaves and twigs is the property owner’s responsibility, but digging and deepening the ditch belongs to the city.

I want to pipe the ditch between our property and the neighbour’s. What permits are needed?

Piping a boundary ditch always requires the neighbour’s consent. Piping planning also requires a suitable expert to prevent flooding problems. However, piping ditches located on properties is not recommended, because they are significantly more difficult to maintain. The flood caused by a blocked pipe and the resulting damages are the responsibility of the property owner(s).

The ditch in the city’s park area is badly overgrown and floods our property. Whose responsibility is it to clear the ditch?

The maintenance of the ditches in a public park area belongs to the city.

Behind my property is a steep rocky area and a forest, from which water constantly flows into our yard. Whose responsibility is it to direct the water away from our yard?

The water that rains and melts in the natural area is not stormwater, but normal surface runoff. There is no obligation to manage them, but the responsibility remains with the property. The surrounding area should be taken into account, for example by providing sufficient drainage or by making the yard drains in such a way that the water does not damage the building.

My neighbour is building a house and water from the construction site flows into our yard. Where can I report this?

It is always best to try to deal with problem regarding stormwater between the neighbours. The construction work, from the start of the work to the final inspection, is supervised by the building inspectorate. After the construction work is completed, stormwater and surface water management on the property must be in accordance with the valid building permit.

I want to lead the stormwater generated on my property through the retention basin in my yard to the open ditch in the public area. What permits do I need?

Placing pipes and other structures in the city area requires a placement permit and sometimes an excavation permit. Leading water to the city area or to an open ditch requires consent according to Section 103 g of the Land Use and Building Act. These are applied for electronically through the city’s service. If a stormwater drain is located next to the property, the property may also have to apply for an exemption from the obligation to connect to the stormwater drain from the Environmental and Building Control Department.

How long does it take to process permits and investigate stormwater issues?

One official/officer has up to several dozens of cases related to permits and stormwater issues. The processing time for one permit and problem situation varies from a few weeks to several months, including all supplements, hearings and statements. It is therefore advisable to start the permit process in time and to start solving stormwater problems by talking to the parties involved yourself.