ABSTRACT
The City of Oslo is currently constructing several tunnels for a new water supply for the city. The tunnels are built under the most populated areas in Norway. In these areas there are numerous geothermal wells, as energy sources for heating and cooling purposes for domestic and industrial properties. Tunnel excavation adjacent to geothermal wells poses some risks. Not only could the well suffer damage, but there’s also the potential for grouting cement into the heating system of a building or causing the wellhead to blow out. To mitigate these risks, we’ve undertaken a comprehensive effort to map all existing wells within the project area and evaluated a broad zone of influence, and finally a set of measures to mitigate the risks. This involves identifying the correct well owners, pinpointing their precise locations, documenting their configurations and capacities, and assessing the probability of potential damage. Each well is then assigned a likelihood assessment for potential damage and a corresponding plan for monitoring and managing it throughout the tunnel construction process. Having excavated approximately 8 kilometers using drill and blast (D&B) methods and an additional 10 kilometers employing tunnel boring machines (TBM) through urban areas, we’ve encountered numerous energy wells along the way. Some of these wells were damaged, while others remained unharmed. Through these experiences, we’ve gained insights on zones of influence and mechanisms on well damages that we would like to share, and that can provide input for future tunnel projects.
