LEGAL, ADMINISTRATIVE AND PLANNING ISSUES FOR SUBSURFACE DEVELOPMENT IN HELSINKI

In the past decade, Helsinki has witnessed considerable growth in underground construction: in 1989, the city had developed 4.5 million m3 of underground space, averaging an annual underground building rate of approximately 300,000 m3 during the 1980s. To encourage the planned development use of such space,the city has incorporated subsurface development into its city planning system. The paper also describes a sophisticated geotechnical and map information system that is now used in developing plans for subsurface developments in Helsinki. The volume and variety of underground construction in the Finnish capital has also revealed administrative and legal deficiencies regarding subsurface development. A committee established by the Ministry of the Environment has investigated current practice with regard to planning and building permits related to underground space, and has recommended the development of rules and regulations specific to subsurface uses. The paper also describes the ''prebuilding'' method of obtaining additional building land through the use of geo-construction techniques such as soil improvement and infilling of shore areas.