Technical Tour: Brownfield Areas in Helsinki

Join us for a technical tour exploring brownfield redevelopment in Helsinki, with a focus on the Suvilahti-Hanasaari area. The tour will depart from Market Square at 9:00 and return there at approximately 12:00.

We will travel by tour boat to Suvilahti-Hanasaari, where participants will learn about the area’s industrial history, environmental challenges, and ongoing remediation and redevelopment. The return route will pass through Kruunuvuori, a new residential neighbourhood being developed around a former oil harbour, offering another perspective on the transformation of former industrial waterfront areas in Helsinki.

Suvilahti-Hanasaari

Suvilahti-Hanasaari is an old industrial area located in the capital of Finland, Helsinki. The Suvilahti-Hanasaari area is situated by the sea, and its current extent is mostly reclaimed land from the sea. The fillings were mainly done between the 1940s and 1960s.

Several industrial sectors have operated in the Suvilahti-Hanasaari area, including a gas plant, two power plants, and a benzene factory. Due to its heavy industrial history, the soil, soil air, and groundwater in the area are partially contaminated, mainly with volatile organic compounds, benzene, PAH compounds, and metals.

In the Suvilahti area, there are two gas holders. The brick gas holder was taken into use when the gasworks began operating in 1909. The steel gas holder was introduced in 1929, when gas production in the area was expanded. Gasworks operations in the area ended permanently in 1994.

After that, the gas holders remained untouched until 2010, when they were emptied of water and plans for their future use began. The brick gas holder has been renovated and now serves as an event venue. The steel gas holder is still awaiting its final purpose and, until then, is also used as an event space. A subsurface gas collection system has been installed in the yard areas to mitigate the migration of volatile compounds into the indoor air of the event tents.

Industrial use in most of the Hanasaari area ended in 2023, and the area will be transformed into residential and commercial areas in the coming years. The area will be remediated based on a risk-assessment approach. An in situ pilot test conducted in the area evaluated the performance of various remediation methods in a complex, multi-contaminant environment. High concentrations of trichloroethylene (TCE) and tetrachloroethylene have been detected in the soil and soil air in the area intended for residential use. For this reason, a temporary test building containing conventional residential building foundations was constructed on the site to study the transport of volatile compounds into the indoor air of the test building. An in situ remediation process is currently underway in the northwestern part of the area to reduce concentrations of chlorinated solvents.