Lapinlahti Park’s natural and scenic values are taken into account in the planning of the harbour tunnel. 

The harbour tunnel being planned starts from West Harbour, emerges at the southern edge of Lapinlahti Park and connects from there to Länsiväylä. Mitigating the environmental impact on Lapinlahti Park is important for the port and a prerequisite for tunnel implementation. Most of Lapinlahti Park will remain intact despite the construction of the harbour tunnel. As far as the park areas in the detailed plan are concerned, the tunnel worksite will only impact roughly 1% of the surface area of the park.

Two endangered species live in Lapinlahti Park: the Siberian flying squirrel and the depressaria chaerophylli butterfly. In the tunnel planning, the Port of Helsinki has paid particular attention to the habitats of these species, as well as preventing and mitigating other harmful environmental impacts. The tunnel design has settled on the technical solution of a thin rock roof. The solution means that the entrance to the tunnel at the southern edge of Lapinlahti Park will be implemented with a significantly smaller open pit compared to previous plans. The solution makes it possible to:

• preserve the trees in the core area of the Siberian flying squirrel
• preserve more turnip-rooted chervil areas, improving the living conditions of the depressaria chaerophylli butterfly in the park
• preserve the Lapinlahti dog park in its current location and keep it in use throughout construction.

Living conditions of the Siberian flying squirrel to be secured 

The Siberian flying squirrel is a protected species under the EU Habitats Directive and the Finnish Nature Conservation Act. The destruction or deterioration of its breeding and resting sites is prohibited. The Siberian flying squirrel has three identified core areas in Lapinlahti Park, one of which is partly located along the planned route of the tunnel. The core area of the Siberian flying squirrel can be preserved in its entirety using the thin rock roof construction technique, which will allow the open pit of the tunnel entrance to be significantly shortened. In addition, the Siberian flying squirrel’s habitat will be protected through the following means:

• by scheduling construction activities causing noise and vibration to take place outside of the Siberian flying squirrel’s nesting period, i.e. March-July
• by saving trees and planting protective trees specified as implementation planning progresses
• by setting up nesting boxes for Siberian flying squirrels. 

To guide the planning, the Port of Helsinki has requested an opinion from the ELY Centre on how the planned measures affect the environmental impacts of the project. According to the ELY Centre’s assessment, the plan does not weaken the Siberian flying squirrel’s habitat.

Turnip-rooted chervil transplanting to safeguard the depressaria chaerophylli habitat

The depressaria chaerophylli is a highly endangered species in Finland and must be particularly protected in accordance with the Nature Conservation Act. It is a moth species whose larvae live and feed on turnip-rooted chervil.

The Port of Helsinki will secure the living conditions of depressaria chaerophylli in Lapinlahti Park. This will be achieved by increasing significant quantities of turnip-rooted chervil elsewhere in the park through sowing and supplementary planting, for which a multi-annual planting plan for turnip-rooted chervil has been drawn up. The aim is to ensure that there are enough turnip-rooted chervil growth areas in the park to prevent the deterioration of depressaria chaerophylli’s habitat.

The implementation of the turnip-rooted chervil planting plan began in autumn 2024 with the preparation and sowing of test sites. The effectiveness of the plan will be monitored annually going forward. The results of the monitoring will be utilised in the planning and to revise the turnip-rooted chervil planting plan, if necessary.

The Port requested a statement on the turnip-rooted chervil planting plan from the ELY Centre, which was in favour of the plan. The ELY Centre considered the addition of turnip-rooted chervil in the park the most significant measure. The scope of planting areas guaranteeing adequate compensation is currently being reviewed.

The use of the thin rock roof construction technique in the tunnel is also crucial for the living conditions of depressaria chaerophylli. It will allow the rocky tunnel section of the harbour tunnel to be extended, while reducing the length of the open pit section. The method will preserve the existing turnip-rooted chervils better than the original plan.

The Port of Helsinki also wants to ensure that authorities and other stakeholders are able to assess the key environmental impacts of the tunnel project in a genuinely transparent manner.

Dog park to remain in Lapinlahti

The technical solution of the thin rock roof also enables the preservation of the Lapinlahti dog park in its current location. It will also remain in normal use throughout the tunnel construction project.

No significant restrictions on the use of the dog park will be put in place, as its entrance will be further away from the site. The only temporary restrictions on use are due to noisy work phases such as drilling and rock transport. However, due to the local terrain, the noisy stages are very short-lived. According to the current schedule, the noisiest stages of construction in Lapinlahti Park will be carried out in 2028 and 2029.