The road and rail subway is 11m underground, and was originally built nearly a century ago.Current stringent safety requirements and the poor condition of the original tunnel meant it had to be demolished and rebuilt.Two contractors, HF Wiebe GmbH & Co and Heinrich Hecker GmbH & Co, worked on the tunnel rebuild, which crosses the river Weser on two viaducts.In June 2007, a coffer dam was erected on either side of the tunnel passage, enabling the construction site to be drained and protecting the tunnel from the canal water, Meva said.The tunnel was then demolished, including its foundations, with the new tunnel developed by August 2008. “While the old passage existed of two tunnels that were arched at the top, the new passage is rectangular – housing both the street and rail,” the company said.The reconstructed passage, made of reinforced concrete, is 15m wide and 39m long.Meva formwork, Mammut, was used in the tunnel’s construction, including the 11m high walls at the end of the housing, and in developing the two transverse walls at the tunnel’s southern mouth.“At its back end and parallel to the canal, tub walls were formed with the Meva wall formwork StarTec,” the company said.“All finishing work such as ground and canal work, as well as removing the coffer dams and sheet pilings, will be accomplished in December 2008.”
