New tracks in Stockholm improve train traffic

For more than 20 years, there has been a political discussion about more rail lines running through Stockholm. For the same length of time, hundreds of thousands of travellers have endured heavy trafficked rolling stock. At both mornings and evenings, the long-distance, high-speed, commuter and even freight trains have waited in queues at entrances. In an interview for the Global Railway Review, Mr. Kjell-Åke Averstad, Project Manager at Banverket, discusses the issues about the improvement of rail traffic in Stockholm and his impressions of the most valuable rail line being built in Sweden – the City Line.

500 trains per day must pass through the 2-track entrances and exits at Stockholm Central Station, known as the ‘Wasp’s Waist’. This is a fitting description of what the passage looks like. But all this will be over in a couple of years as the commuter train will be set free. The new Swedish government gave its approval last winter and by 2017, the commuter train will have its own train tunnel running under the Swedish capital – the City Line.

“We have been stuck at the starting blocks several times. The wait has cost us money. Finally we have received the go-ahead and we are now ready”, says Mr. Averstad. The long wait has, in spite of everything, had its good side in that every aspect of the project has been meticulously elucidated.

In the autumn, Mr. Kjell-Åke Averstad will tender out four large contracts. He comments, “This will be interesting. In order to generate good competition and get competent people, we are looking for tunnel builders on the international market. We are aware that this is a hot market. Many large infrastructure projects are underway in Sweden and Europe. Perhaps we will look for labour from even farther away in the world”.

The City Line will be built as a project within the auspices of the state-run Swedish Rail Authority. The government has guaranteed the financing. The cost is estimated at 16 billion Swedish crowns. The city of Stockholm will take a large portion, as will several counties surrounding Lake Mälaren.

These counties have invested heavily in attracting the capital-city dwellers to move from Stockholm to residences in provincial areas. One selling point has been the good communications.

The promises have not been kept and criticism has been harsh! Distance commuters also get stuck in train queues morning and evening.

Eight of ten

This region currently consists of just more than a third of the entire population of Sweden. And it is growing! If the trend continues as it has, the need for rail traffic will be approximately 50% higher than present figures. Last winter, the Swedish government looked again at this hot issue. Now, a negotiator has been sent to these counties. He got them on board and after much delay the Swedish Rail Authority has now been able to get the project started.

The entrances and exits at Stockholm Central Station are extremely sensitive. Eight of ten train voyages either begin or end in Stockholm. A significant disturbance in the ‘Wasp’s Waist’ can have consequences in the larger part of the Swedish rail network.

The City Line will be a 6km long tunnel and will have two new underground stations, one of which will be under the tube station at Stockholm Central Station. A service tunnel will be built parallel to the track tunnel. This will play a vital role in the event of accidents and maintenance of the installations. The City Line will take into serious consideration that safety requirements have been made more stringent following recent tunnel accidents, such as Mont Blanc and Baku. The service tunnel will be a safe route for emergency vehicles. Emergency exits with air-locks will be placed every 300 metres.

Near the Lakebed

Stockholm is a city on and by the water. A 371-metre-long concrete tunnel will therefore be built in order to join the southern and north portions of the inner city.

The underside of the tunnel will essentially follow the lakebed, which is unusual. Normally, tunnels are located deeper and under the lakebeds. Here, at one point, the roof of the tunnel will only lie four metres under the surface of the water.

The tunnel shall consist of two pipes. One of them is for a double-track and the other a service tunnel. The latter also serves as a rescue and escape route. There shall be two air-locks to get to and from the track tunnel.

The region around Söderström – as the body of water there is called – is one of the most important cultural sites in Stockholm. The tunnel runs below Riddarholmen, which is part of the Old City. The historical protection of this neighbourhood is so great that no construction traffic is permitted from that direction.

The conditions for the design of the tunnel are, to a great extent, characterised by the fact that it is not located so deep. The abutments in the rock on each side shall be constructed so that the tunnel could survive a collision by a passing ship. On the south side, the natural movements of changes in temperature shall be countered by means of a so-called moving joint.

It is worth mentioning that the tunnel is located in an area not heavily travelled by large sea vessels.

In the middle of the culture

How the tunnel is to be built is still not certain. Nobody has yet been awarded the contract. However, the construction area itself limits freedom of movement. One proposition points to the tunnel sections being manufactured on a building platform in the middle of the water. It will be a very closely monitored task keeping in mind all the restrictions in the area. The tunnel is located in a medieval cultural centre with “special stipulations against intrusive measures”.

The tunnel itself will largely be carved out using explosives in the bedrock. The rock is of a good quality and is best suited for blasting, especially when carving out steep slopes.

However, it will take a few years until the actual work of building the track tunnel begins. First, the workers need to go down to the level where the tunnel will be placed.

The first work-tunnels will start being drilled during the beginning of 2008. There will be a total of eight, the longest one more than 5km. These will be the routes in and out of the track tunnels and the stations. It is estimated that 4.5 million tonnes of rock will be removed. Once the City Line is complete, some of the work-tunnels will serve a new function as an approach and escape route.

It is a large and complicated construction – probably the most complex currently underway in Sweden. It will be necessary to blast, drill and dig through an already dense traffic facility under the buildings, streets and water mains of Stockholm. Exacting requirements will be placed regarding sealing and water seepage, noise and vibration according to the ever more strict building regulations.

Vital water

Stockholm is more than 700 years old. The City Line will be built below groundwater levels in layers of earth and bedrock along long stretches. Therefore, one vital task has been the comprehensive inventory which was done to protect culture-historical buildings. Yet, other environments could also be affected. Clever solutions will be needed to reinforce or protect those objects affected when the City Line is laid in.

The groundwater is important for buildings founded on wooden stakes or other wooden constructions. If the groundwater level falls, the wood becomes susceptible to the oxygen in the air. As a consequence, the biological degeneration is accelerated and there is a risk that the wood could rot. Among other buildings, there are three churches, one of which was built in the eighteenth century and several other very old buildings which shall be secured before the tunnel builders blast out the track tunnel.

Regard for the old environments and the buildings mean that the requirement for comprehensive sealing works will be extensive in the City Line. The entire length of tunnel will be injected with cement in order to seal the entire rock formations’ system of cracks. This will be no one-time event. The entire system will be successively inspected during the blasting of the tunnels.

Seven to eleven

Measurements of groundwater had already begun three years ago. At no fewer than 350 locations, the water level is monitored and there may be more locations as time goes on.

These conditions will result in filling-in – infiltrating – the water so that the groundwater does not fall to dangerous levels. The project entails building wells that can always be used for such infiltrations. The plan for this is to be done using the municipal water supply.

However, on the one hand, if the groundwater can be seen as a little bit tricky, then we can be all the more grateful for the rock in Stockholm. The rock sorts which will be forced out for the City tunnel are regarded as easy to handle. The largest proportion consists of granite and gneiss. But in addition to all the stone and rubble, 100,000 tonnes of earth shall be removed from the rock.

This means a lot of lorries! Three work tunnels are built first in order to create transport routes in and out of the track stretch. This work will take years – and many lorry loads. At each place, 100 lorries shall go in – and afterwards come out with stone, gravel and clay – working from 7am until 11pm.

The people of Stockholm should be used to this. During the years after the turn of the millennium, large infrastructure works have been plentiful; among these is the large motorway around the city.

Strong emotions

The large building projects have tested the patience of the people of Stockholm. “We have already encountered locally organised resistance to the City Line. Everyone knows it is needed, but nobody wants it blasted under his own house”, says Mr. Averstad.

On the other hand, project managers have dealt with this before. They are experienced and chastened by the intense attention that such large projects get with the general public and in the media.

The one new station, at Odenplan in the northern end of the inner city, has already stirred strong emotions among some of the residents. The realisation that every day some 200 large lorries will drive in and out of the work tunnels has generated concerns among many families with children in the area. This is a prosperous part of the city and the discussion has been intensive. Aside from the Swedish Rail Authority’s work, there are simultaneous plans to construct a large underground shopping centre in the same area.

The Swedish Rail Authority can offer those who are greatly disturbed to move to temporary residences during times when the work is most intense.

Five-minute reward

“No matter how hard we try we cannot build a tunnel in nine years without affecting the daily lives of the residents”, says Mr. Averstad. “In a few years, we will be blasting in those locations where the City Line runs very close to the tube. We will then need to halt the tube traffic, within limits, for a few weeks each summer. During the interruption, busses will be put in place. Experience tells me that such measures rouse strong emotions in spite of the fact that we choose the time of year when the traffic is least dense. But once the City Line is complete, the reward will be a travel time of less than five minutes between Södermalm and Odenplan”.

Once the City Line is built, Odenplan will become a very important hub in the public transit service in Stockholm. It will become Sweden’s second largest station in terms of the number of travellers. The only one larger will be the other station being built for the City Line. It is built 40 metres below ground level and will be located beneath the tube station ‘T-Central’ at Stockholm Central Station. This will mean both close proximity to the long-distance trains and to new entrances and exits to the most upbeat business streets in downtown Stockholm.

Station City is built with two platforms, each 225 metres long and more than 15 metres wide. The trains stopping here need longer delay times. However, using two platforms and two tracks in each direction, the first train does not need to leave the platform before the next one comes in.

Conceived late

The Swedish railway first came about in the 1860’s. This was about 20 years after the first railways were running in Europe. That is why Stockholm has a relatively sparse rail network compared with many other large European cities. This is encumbered development and has contributed to many decades of long discussion about an expansion of the two tracks in and out of Stockholm Central Station.

At the same time, pressure is increasing on the sensitive stretch of which more than half of all train traffic in Sweden is directly or indirectly dependent. All it takes is one faulty signal or a door that will not close or other such problems to create chaos in the timetables.

“However, we are grateful that those who built the railway in 1871 laid the track all the way through Stockholm. The tracks are joined with the railway coming from the north”, says Mr. Averstad. “Once we can separate the commuter trains from the long-distance trains in 2017, it will be very good, looking at the demands in a future perspective as well”.

Once the City Line is opened to traffic, the track capacity on the lines through Stockholm will be doubled. This increased capacity means that it will be possible to make planned railway investments in the Mälar Valley aimed at creating fast and frequent connections by regional and commuter train services. The Swedish Rail Authority’s Future Plan for the Railways means that during the period 2004-2015 track extensions can start on the Mälar Line, the Svealand Line, the Western Main Line, on the southern part of the Nynäs Line and on the line leading to Södertälje Centre.

Longer commuter trips

Work can also start on the Eastern Link, which is a completely new line running between Järna, Nyköping, Norrköping and Linköping. Once these extensions have been completed, it will be possible to increase commuter train services through Stockholm even during peak travel periods.

Regional rail traffic can also be increased between Stockholm and, for example, Eskilstuna, Västerås and Katrineholm. The Eastern Link will improve conditions for commuting between Stockholm, Nyköping and Östergötland and will provide better long-distance rail traffic between Stockholm and Malmö.

Mr. Kjell-Åke Averstad recently received a copy of a historic script from the Royal Library. It is a report from 1870 regarding the construction of the railway in Stockholm. Already then, the investigator determined that the stretch was “the most valuable part of the Swedish railways”.

Mr. Averstad commented, “We have the same attitude. It’s not the costs we look at first – it’s the benefits. We are investing in the most valuable part of the Swedish railway network – that is how it should be seen.”

Nobody is spared

There are still a few more years until the project blasts out the actual train tunnels. Firstly, a number of legal aspects must be addressed. These include, among other things, the environmental consequences.

The entire description of the project has been on display in Stockholm City. According to Swedish law, everyone affected has an opportunity to voice objections toward the so-called detail plan. However, preparatory work is in full swing.

First, the blasting of six work tunnels is prepared. This makes it possible to go down underground in order to carry out the nine-year-long task. Several of the tunnels will also become service and escape routes.

Nobody will be spared from this big building project. Many people will be disturbed.

“We will offer evacuation for shorter or longer periods for those who will be significantly disturbed”, says Kjell-Åke Averstad, “However, this is also the most valuable stretch of rail in Sweden that we are building.”

About the author

Kjell-Åke Averstad is a civil engineer and project manager at Citybanan in Stockholm, Sweden. He has worked with railways for over 20 years and has been responsible for many of the larger railway projects in Sweden, namely those in the Mälardalen and Stockholm area. Among these is the railway running from Stockholm city-centre to Arlanda, Stockholm’s international airport. Prior to his current position at Citybanan, Kjell-Åke Averstad has also worked as Banverket’s Regional Manager for two of the largest cities in Sweden, Stockholm and Gothenburg.