– It is to prevent the buildings over the railway tunnel Romeriksporten from being damaged and sinking, says Brede Nermoen in Bane Nor. The water is sprayed into the ground to protect about 130 buildings and infrastructure such as roads and rails for subways and trains. The drinking water used corresponds to the consumption of 1,200 Oslo citizens. 25-year-old problem To understand what is happening, we must return to a 25-year-old construction scandal. Then the train tunnel Romeriksporten was built for the Gardermoen line. The first signs of problems could be seen in Østmarka. The water level dropped dramatically in several ponds in the area. The first picture is of Nordre Puttjern more or less normal with water. Others are by the pond with much less water, the third shows the damage in the terrain. Extensive groundwater leaks into Romeriksporten were also discovered. In retrospect, damage was reported to 150 houses. Many with sentence injuries. The explanation for what happened is simple. In the loose masses that lie above the train tunnel, there is groundwater. When much of this water leaks into the tunnel, the groundwater level drops. Sand and clay grains are packed closer together. The ground sinks a little. It also affects the life of plants and animals. – When the tunnel was built, there was no focus and requirements for sealing in relation to the surrounding environment, says Nermoen in Bane Nor. After extensive sealing work, Romeriksporten was officially opened in August 1999. One year delayed. Romeriksporten is Norway’s longest train tunnel. Photo: Ørn E. Borgen / SCANPIXPhoto: Ørn E. Borgen / SCANPIX According to Bane Nor, the tunnel is dense enough to function as a railway tunnel. But a good deal of water is still leaking into the tunnel. – We would have liked it to be drier. Today, tunnels are built in a completely different way. Pumping in water 23 years after the opening of Romeriksporten, there is still a risk of settlement damage over the tunnel. There are four areas: Godlia Hellerud Ellingsrud Strømmen station STRØMMEN STATION: – We do not want sentences under the track on the main line here, says Nermoen in Bane Nor.Photo: Erlend Dalhaug Daae / NRKPhoto: Erlend Dalhaug Daae / news If it is not pumped water into the ground, it can sink by a few centimeters. – It is not the case that buildings can collapse. The water comes from 24 wells at the four sites. – The method is widely used and well known. It has been used in Oslo for many years before Romeriksporten was built, among other things in connection with the Fortress Tunnel. Brede Nermoen believes the method can easily be compared to a bouncy castle: – When you turn off the fan that constantly blows air into a bouncy castle, it collapses. Brede Nermoen is head of planning and technology at Bane Nor. Photo: Anne Heidi Røstad / news Can not save water After the tunnel was opened, work has been done to seal it more. The leaks have also decreased because it is growing again. However, more than 8,000 liters of drinking water are still injected into the ground every hour. This daily hedging costs not only money for Bane Nor, but also precious drops from Oslo’s water supply. Since January, the people of Oslo have been asked to save on water. And in early May, all residents received a text message where the prayer was clear: shower shorter, turn off the tap by brushing teeth, avoid watering the lawn. If there is dry and hot weather in the time ahead, new water restrictions may be introduced. Measure level in case of water shortage Measure level 1 Reduce the water flow in Akerselva from 1500 l / s to 1000 l / s (minimum water flow) Increase leak detection and repairs on the pipe network Inform the public and stakeholders and implement measures, including concrete proposals for measures that the population can implement (water saving campaign) Start import of water from neighboring municipalities and Nedre Romerike waterworks Implement water saving campaign Conduct dialogue meetings with the Urban Environment Agency, the Funeral Service and the Port of Oslo on reduced water use in their operations Measure level 2 Stop all use of municipal water for irrigation, water fillers, fountains etc. Reduce water supply in Akers Apply to NVE and notify the State Administrator of regulation of reservoirs below LRV (lowest regulated water level) from 750 l / s to 500 l / s Introduce restrictions on garden irrigation Introduce restrictions on car washing Make technical preparations for pumping water from Lutvann to Nøklevann and from Nøklevann up in the tunnel from Elvåga to Skullerud Establish pumps in the catchment area to lower reservoirs under LRV Plan and make preparations to start water production from Langlia and Alnsjøen, boiling warning required Notify the Norwegian Food Safety Authority and the Norwegian Board of Health of the start of water production from Langlia and Alnsjøen emergency response facilities Open the canal between Lille and Store Sandungen Consider implementing further measures for the public and businesses to reduce the use of drinking water Pump water from Lutvann to Nøklevann and from Nøklevann up into the tunnel from Elvåga to Skullerud water treatment plant Introduce restrictions on the use of Nøklevann for recreational purposes as long as water is pumped from Nøklevann and up into the tunnel from Elvåga to Skullerud water treatment plant Establish pumps in Maridalsvannet’s outlet to maintain minimum water flow in Akerselva if the water level in Maridalsvannet drops below LRV Lower reservoirs below LRV and implement a minimum water flow of 250 l / s to Akerselva provided that the application is granted by NVE Bane Nor uses drinking water because this is practical. The water supply has a good distribution network. – Otherwise we would have had to build our very own supply facilities. It would be very expensive. And Bane Nor believes it is not possible to save water. – Then there is a danger that sentences will occur which then cause building damage. – Only method Kristin H. Holmøy is professor of engineering geology at NTNU. She says this about the method Bane Nor uses: – This is the only method you can use to maintain the groundwater level and to avoid settlement damage in the loose materials over Romeriksporten. According to her, it is almost impossible to seal a tunnel after it has been built. Cement or other sealant can quickly find channels and open cracks in the rock. – If it hits a channel that re-enters the tunnel, you risk the cement ending up in the ditch inside the tunnel. Something that can easily happen after the tunnel has been built, says Holmøy. Continues indefinitely New methods are constantly being developed to seal tunnels afterwards. Bane Nor hopes that a good solution for Romeriksporten will emerge in the future. Today, they do not know how long they must continue to pump water into the ground at Romeriksporten. – We do not have an overview of how long we have to infiltrate, but we will by all means avoid damage to the buildings. We will not shut down until we have full control over it, says Brede Nermoen in Bane Nor. Bane Nor follows up 130 buildings with settlement measurements. Every other year, NGI examines whether there are any changes. news has requested a comment on the case from the Environment and Transport Agency Councilor Siren Stav (MDG), who is responsible for Oslo’s drinking water. In an e-mail, the city council department replies that the city council does not have the opportunity to prioritize this.
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Every day, 193,000 liters of drinking water are used to prevent houses in Oslo from sinking – news Oslo and Viken – Local news, TV and radio
