Prague - Tonnes of soil collapsed into a future ring road tunnel in Prague's Stromovka park Tuesday, creating a crater of about 20 metres in diameter. Nobody was injured, and the damages are not that great, City Hall said. Builders drilling the tunnel said heavy rain was to blame.

The tunnel is part of a road connecting Malovanka in the Břevnov district with Trója, via Letná.

Critics of the ring road say it will worsen air pollution in some districts, while City Hall insists it will help clear the air in Prague. The city also said the incident was nothing serious and that it would not threaten the timetable of the project, worth dozens of billions of crowns.

Heavy rain

The Geotechnical Monitoring Council, consisting of about 15 experts who met immediately after the incident, said heavy rain was to blame, along with the composition of soil above the Blanka tunnel.

Jiří Toman, director of the city department for investment, said the rock in Stromovka was "light", comprising of sediments from the Vltava river.

Fears confirmed

Stromovka, or the royal deer-park, is one of the most precious parks in Prague. It was probably established by Přemysl Otakar II in the 13th century. Since 1988, the 105-hectare park has been a protected natural landmark.

"Our concerns that the new ring road with several tunnels may harm Stromovka have been confirmed," said Martin Skalský from the Arnika association, one of the critics of the new road.

He added tht City Hall had promised it would not allow heavy machinery in the park but did not keep its promise. It said heavy machinery working from above saved a lot of money.

Builders reinforced the tunnel ceiling, but it did not help. Toman said they would now fill the crater with concrete and the top with soil.

"When it has hardened, we will go on drilling," said Toman.

This part of the ring road should be completed in 2011.

Adapted and republished by the Prague Daily Monitor