- The limestone bluff of Astangu poses threat to careless walkers.
- The first tunnel collapse happened more than ten years ago.
- Cars were driven over the unstable area.
It was discovered on Monday that a tunnel of an ammunition depot under heritage protection had collapsed in Astangu limestone bluff in the Haabersti district of Tallinn and the collapsing could continue.
The city officials surrounded the dangerous area with a warning tape and the district government warns the people walking in the area to be attentive and careful. «The owner of the land plot is aware of the situation and has begun to investigate the ways of safeguarding the people walking in the area in cooperation with the Environment Board,» said Oleg Silyanov (Center Party), head of the Haabersti district government.
«Now it is the task of the landowner to set up proper guard rails so that cars could not drive there and no one would climb there,» said Boris Dubovik, the head of the Tallinn Heritage Protection Department. He added that the ownership of the tunnels needs to be determined. «The fact that someone owns the land plot does not automatically mean that they also own underground monuments,» said the heritage conservationist.
Not just ground
The ground collapsed next to an unofficial pathway along the limestone bank of Astangu. This path is used for walking and enjoying the views from the cliffs, as well as for driving off-road vehicles. The rise to the limestone shore is too steep and rough for ordinary cars.
This was not a simple sinking of the ground but the collapse of a tunnel which was once built for ammunition storage and runs across the path. It is apparent even from some distance that that the part of the tunnel under the path is in danger of collapsing. This tunnel first fell in more than a decade ago, and large trees are now growing in the earlier collapse site. Now a large part of the tunnel collapsed near the edge of the limestone bank.
According to historian Robert Treufeldt, the construction of the Astangu tunnels began in 1912, when Russia began to build a huge naval base. «It was done with great solemnity, Emperor Nicholas II arrived in person to lay the cornerstone here,» Treufeldt said.
He explained that although the tunnels are listed in the register of monuments as ammunition depots of Peter the Great’s naval fortress, they are still part of the naval base. «The Peter naval fortress was one part of the coastal defense, and the other part was the naval base. The Russian navy, which had a fleet base here and which was also part of the Peter the Great’s naval fortress protecting the surrounding city, built a large ammunition depot in Astangu. There were several of such depots, the largest of them was initially planned in Paljassaar, but it was not built because it was too close to the base,» said Treufeldt.
Then they started planning the depots starting from Mäeküla on the top of the cliff all the way to Tabasalu. It was initially planned to build 39 tunnels, but as the funding for the construction was constantly reduced, only six tunnels were finally built and never really completed.
«There was no time to line the tunnels carved into limestone. The concrete lining currently visible in two of the tunnels was poured after World War II when the tunnels were planned to be used. The Republic of Estonia did not need the tunnels. The Soviet authorities were interested in them, but the completion turned out to be too expensive, and they eventually built above-ground depots in Astangu, the remains of which can still be seen today,» Treufeldt explained.
What were the tunnels used for?
According to Treufeldt, it was unclear whether the Soviet army used the Astangu tunnels, because no one had access to them at that time. Probably the Soviet authorities tried to do something there, but not with much success. «These were ammunition depots of Soviet railway cannons, for which a separate railway was built from Kopi to Astangu. But that, too, could not be put to use and in the end a road was built to the depots,» Treufeldt said.
He described the railway artillery battery as an entire train fitted with cannons so heavy that they could have hardly been transported by any other means. The railway cannons had completely separate firing positions, which can be seen, for example, on the Pakri peninsula, north of Paldiski, until today.
The Astangu ammunition depots
It is under state protection as an important part of the entire complex of military fortifications of Peter the Great naval fortress, an important facility in terms of military history and settlement history of Tallinn, as well as engineering and construction technology. It is one of the most attractive and extensive early 20th century military monuments in Tallinn and as a rare underground structure important in the context of Estonia’s construction history.
The plans foresaw the cutting (blasting) of U-shaped tunnels seven meters high, nine meters wide and 200 meters long under a layer of limestone of some 10 meters thick. The exits of the two tunnels connected at the end were 50 meters apart. Each tunnel was to have two parallel railways for trolleys. The 0.9-meter-thick stone lining of the ceiling-walls, which resemble flat Gothic vaults, was to be separated from the wet stone layers by tin insulation. The stone lining had to be covered with a layer of concrete.
The changing situation also affected the tunnel construction plans: instead of the 33-39 U-tunnels envisaged in the project, it was first decided to build 15 tunnels but then only six. In the early spring of 1916, the cleaning of the limestone bank began: trees and bushes as well as collapsed stones were removed.
The beginning of the main construction effort was delayed until the early spring of 1917. By June 19, 46 percent of the rock had been excavated, 15 percent of the lining had been built and up to 70 percent of drainage had been built. In addition, a railway trench was built at the foot of the bluff; barracks were constructed on the top of it. Tunnel No 3 could already be used as a temporary explosives depot for the builders. At the same time, tunnels No 5 and No 6 were still only in their initial stages. The authorities decided that work on these two tunnels could be abandoned.