The update of the Riihimäki groundwater protection plan has been completed.

The update of the Riihimäki groundwater protection plan was approved by the Riihimäki City Council on March 31, 2025. The protection plan describes the current situation of Riihimäki groundwater areas, the risks to groundwater, and measures that can be used to ensure the quality and adequacy of groundwater in the future.

The Vantaajoki and Helsinki Region Water Conservation Association updated the Riihimäki groundwater protection plan. The work was guided by a steering group with representation from different areas of responsibility of the City of Riihimäki, Riihimäen Vesi, Häme Economic Development, Transport and Environment Centre, Kanta-Häme Rescue Department and Etelä-Häme Environmental Health.

Riihimäki's water supply is focused on the Herajoki groundwater area.

The city of Riihimäki has a Class 1 groundwater area that is important for the water supply of the Herajoki River, as well as a small part of the Class 1 groundwater area of ​​the Hirvenoja River. Riihimäki's water supply is concentrated in the Herajoki groundwater area.

The chemical and quantitative status of the Herajoki groundwater area is classified as good, but the groundwater area is also classified as a risk area.

Contaminated lands and industry pose risks to groundwater

Risks to groundwater include, among others, contaminated land, industrial and business activities, oil tanks, oil spills and accidents involving hazardous substances, energy wells, wastewater from scattered settlements, agriculture and animal farms, soil extraction, road traffic and anti-slip measures, sewage networks and stormwater, and river flooding. For example, the Mattila industrial area is located almost entirely within the groundwater area of ​​the River Herajoki.

The plan presents measures to protect groundwater

The groundwater protection plan has assessed the most urgent measures to safeguard the groundwater in the Herajoki groundwater area. These include, among others, further rehabilitation of the contaminated property of the former Teboil distribution station in the Mattila area and continued follow-up monitoring, continued groundwater monitoring of the former Riihimäen Lasi Oy landfill, and investigations of the state of the soil and groundwater and assessment of the need for cleaning in MATTI sites where a need for investigation or land use restrictions have been identified.

New area reservations should be allocated to groundwater areas in the future only if it can be demonstrated that there will be no changes to the quality or quantity of groundwater. All oil tanks located in groundwater areas should be inspected periodically.

How can an individual resident protect groundwater?

For an individual resident, the greatest risk of groundwater contamination is usually the improper handling of chemicals on the property. For example, an old underground heating oil tank is a significant risk. It is best to replace the heating system with something more environmentally friendly and at the same time ensure that the old tank is properly emptied and removed from the ground. Heating oil tanks must be inspected periodically by an authorized inspection company. In Riihimäki, above-ground and basement tanks are also subject to regular inspection obligations.

The Environmental Protection Department is currently monitoring the up-to-dateness of oil tank inspections by requesting information from residents via letter regarding the latest inspection of the tanks.

The groundwater protection plan can be found on the city's website. Water protection page from the right edge.

The boundaries of groundwater areas can be found Riihimäki city map service. Select the information displayed on the map > Water > Groundwater areas.