No-Dig for Water Supply Construction in One of Finland's Oldest and Most Valuable Parks in the Center of Helsinki

Abstract

The paper explores the tunnel project by the Helsinki Region Environmental Services Authority, crucial for improving central Helsinki's water services. This newly designed tunnel facilitates the separation of the existing combined sewage system, thereby reducing network flooding and wastewater overflow to sea particularly during heavy rainfall. In the design process No-Dig methods were assessed to be used in Esplanadi (an esplanade and urban park in downtown Helsinki, Finland), an area of notable cultural and historical significance. The aim was to minimize the impact of construction on park users and preserve its 19th-century plants and trees. Extensive soil, bedrock, and groundwater studies were conducted in the area, including electric tomography of the park. Also, historical soil contamination was assessed. Many of the buildings in the area are founded on wooden piles, therefore, the groundwater level must not be lowered during construction. Technical consultation discussions were organized as separate meetings with three different drilling contractors. As part of the design work, a table was used to compare 17 different items or perspectives regarding open cut excavation, guided auger boring, and microtunneling. The benefits of No-Dig became very apparent in this project introducing environmental benefits, technical benefits and savings in both time and money.