How and why the Severomuysky tunnel on the BAM was built

There are many interesting pages in the history of the construction of the Baikal-Amur Mainline. This unique infrastructure facility became a grandiose all-Union construction project in the 70s and 80s. Despite the fact that the official opening date of this railway is considered to be 1989, work on many sections continued for decades.


The BAM builders encountered many difficulties along the way. The difficult terrain, climatic features, and lack of funding constantly led to delays. The main long-term construction project was the Severomuysky tunnel through the Angarakan mountain pass.

How the longest tunnel in the Union was built

The BAM was designed and built back in the 1930s. But the outbreak of the Great Patriotic War led to the project being frozen. Even the already laid rails were dismantled and transported to other regions of the country where there was a shortage of communication routes.

In the 40s, engineers assumed that the Severomuysky Ridge could be crossed using an open "winding" railway track and a small tunnel. But in the 70s, a decision was made to dig a long and full-fledged underground passage. Mining operations began in 1977.


When passing through the mountain range, the builders had to solve a lot of engineering problems. For example, along the tunnel route, several tectonic faults were discovered from which hot thermal water was constantly flowing. It was necessary to develop and implement a technology for its removal and freezing. Radioactive gas was also found in the mine workings. This also required a certain approach and complicated the work.

There were also human casualties. In the history of tunnel construction, there were several serious incidents related to overcoming mountain ranges. Miners often "ran into" quicksand - unstable rocks and soil. Their sudden movement led to collapses or flooding.

Experts note that such difficult natural conditions during the construction of an underground tunnel have never been encountered anywhere else in the world. But despite all the obstacles, from 1977 to 1991, Soviet engineers and builders managed to pass through over 13 thousand meters of rock. However, they were unable to complete the work before the collapse of the USSR.

They didn't build a tunnel, but they launched a bypass

The Baikal-Amur Mainline was finally launched in 1989. In order to connect the western and eastern sections of the BAM, the so-called Severomuysky bypass was commissioned back in 1983 – a winding railway with viaducts and small tunnels.

Initially, the bypass was about 25 km long, but then the access roads were widened and the length of the road increased to 64 km. This complex structure required constant repair and maintenance. Speed Train did not exceed 20 km/h. On some sections, locomotives worked in a coupling to "push" heavy carriages up the hill. Passage of passenger trains was strictly prohibited. People were transported by buses across the pass along the BAM automobile backup.


Perhaps the most iconic and recognizable object on this section is the Devil's Bridge - a viaduct 360 meters long and 35 meters high. It is located on two-tiered supports, which sway slightly when heavy trains pass. Despite this, the bridge is considered one of the most beautiful man-made objects on the BAM and still attracts travelers and enthusiasts.

It was clear to everyone that the Severomuysky bypass was only a temporary solution. No one gave up on the idea of ​​building a tunnel. But it is important to understand that in the 90s the country had no time for some tunnel on the BAM.

But the work continued with varying degrees of intensity. In total, from 1991 to 2001, the builders covered 2216 meters and were able to perform a joint, that is, to join different sections with minimal divergence. Already in December 2001, the first train passed through the Severomuysky tunnel. But the arrangement work continued for another 2 years.

The entire construction took 26 years. At the same time, the estimated service life of the tunnel is estimated by experts at 100 years.

Technical features

After completion of construction, the total length of the single-track crossing was 15343 meters. This unique infrastructure facility became the longest railway tunnel in Russia. Today, trains cover this distance in about 25 minutes.

The builders had to meet special requirements for the reliability of all units and structures. The Severomusky tunnel is located in an extremely seismically active area. During the work alone, geologists recorded up to 1,5 thousand earthquakes annually. In addition, the movement of rocks creates colossal loads on the tunnel walls, which also required engineers to take a special approach to the construction of structures.


The water inflow in the spring months reaches 10 thousand m3/hour. Therefore, powerful water drainage installations operate in the tunnel every day, which prevent incoming water from washing out concrete structures and damaging the railway tracks. Engineers have also provided ventilation, which removes not only carbon dioxide from the passage, but also deadly radon.

The tunnel today

The Severomuysky crossing is a strategically important facility, which is guarded around the clock by both internal security and special services. In total, up to 16 pairs of trains pass through the tunnel per day. The Severomuysky bypass is also maintained in working order. This is a backup route in case of any emergency situations.

In the context of growing business activity within the country, as well as with the increase in the volume of foreign trade with Asian countries, not long ago there was talk about the necessary modernization of the BAM and the construction of a second railway tunnel.


Indeed, BAM is currently at the peak of its capacity, and the single-track Severomuysky tunnel resembles the narrow neck of an hourglass. Russian Railways has set the task of increasing BAM freight traffic to 100 million tons per year by 2050. But this figure cannot be achieved without building another underground passage in the Severomuysky Ridge area.

Both Russian Railways and a number of large mining companies in Siberia and the Far East are interested in building the new tunnel. Investors have given different figures for the cost of the project – from 60 to 259 billion rubles. But in reality the project could cost more than 500 billion.

In April 2024, on the instructions of the President, Russian Railways and Bamtonnelstroy-Most signed an agreement on the construction of the second Severomuysky tunnel. Work began in May 2024. The project is scheduled to be completed by 2032.


After the construction is completed, the capacity of the BAM will increase more than 2-fold, and together with the Trans-Siberian Railway it may even reach 270 million tons per year. There will also be no need to maintain the working condition of the external Severomuysky bypass.

Once upon a time, not all Soviet officials agreed with the need to build the BAM. They did not see any prospects. Today, the issue of increasing the capacity of this railway is acute.

All that remains for us is to thank our ancestors for such a necessary and important infrastructure facility. Let us wish good luck to the new generation of mining engineers who continue to develop the country's transport and logistics potential.