The ground investigations aim to determine what solutions can be used to restore the Töölönlahti shore to an as natural state as possible. The investigations are carried out with the necessary equipment. The main research methods are drilling and soil sampling. The investigation points are spaced approximately 20–50 metres from each other.
The work will be carried out in the park area in February 2023. Drilling is carried out in the winter, when the soil is frozen, to minimise damage to the ground. The actual drilling involves a thin rod pressed into the ground, leaving only a hole with a diameter of a few centimetres. The drilling is planned so as not to damage the trees. The work can, at times, hinder access to the park trails.
“Drilling is demanding work. We aim to complete the investigations as quickly as possible and ask the residents for their understanding during the work. It is important for the smoothness and safety of the work that the drilling can be done with as few interruptions as possible,” says Project Director Jere Saarikko from the City of Helsinki Urban Environment Division.
The renovation aims to incorporate only the necessary work to stop the progression of erosion, patch up any eroded beach slope areas and create sufficient growing areas for new trees. The objective is to ensure that the beach slope continues to be covered with natural coastal vegetation.
What are ground investigations, and why are they necessary
The western and northern Töölönlahti shores are located in a soft clay layer area. Over the years, land masses have been brought to the park for site fill. Some such areas are located near the shoreline on soft clay layers. The soft ground base has sunk to some extent under the site fill layers, and the properties of the soil layers have changed.
To plan the park’s renovation, we need up-to-date information on the ground base. Drilling and soil sampling are used to examine the ground layers and their strength properties. The investigations will determine how much weight can be added to the soil layer and how it affects the waterfront walkway.
Draft park plan to be completed in the spring
A park plan is being prepared for the planned renovation of Hesperia and Hakasalmi Parks. The draft park plan will be completed at the beginning of the year and made available to the public at a residents’ event and the www.hel.fi/suunnitelmat website under Street and park plans. The construction schedule will be specified later.