The new tender came after the finance and transportation ministries approved changing their plan for the tunnels. The new digging method will cut the time needed for the work and not require pumping out groundwater. But there are disadvantages too. The new method will require more work on the surface during construction, which will lead to more traffic jams and other disruptions - in particular within Tel Aviv.
The 23-kilometer Red Line from Bat Yam to Petah Tikva will be divided into three sections. Some 11 kilometers will be underground from Menashiya in south-west Tel Aviv via Jabotinsky Street to Ramat Gan and Bnei Brak, and on to the Geha junction. Out of the 33 planned stations, 23 will be underground, about a kilometer apart on average.
The official approval for funding the light rail project from the state budget will only come after the Sukkot holiday, and will require cabinet approval. The original tender was for a Buy, Operate and Transfer (BOT ) project financed by the tender winner, but MTS ran into financing problems as a result of the global financial crisis.
Wednesday's tender was only for the planning of three large shafts through which the tunnel boring machine would be introduced. The proposed method for tunneling is called "cut and cover," in which the tunneling digs up the surface as it proceeds and then is covered up. This is the method commonly used in Israel for most underground projects up to now. Part of the construction of the new Tel Aviv-Jerusalem high speed rail line is using this method. The tunneling machine will be lowered into the shafts and large underground spaces, through which both building materials and the material dug up will brought in and out.
MTS had proposed "deep mining," in which almost all the work takes place underground. However, due to Tel Aviv's high groundwater level, engineering professionals were worried that not all the possible problems were taken into account in the deep mining proposal.
Source Haaretz
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