The first road construction project in Austria conducted as a Public Private Partnership (PPP) project comprises of
1.5 km of new roads in the eastern region of Austria. The northern part of Vienna is encircled by three multilane
motorway sections, namely the S1 West, S1 East and S2. Near Eibesbrunn, the southern section of the A5 motorway
branches off to the north and connects the urban catchment area of Mistelbach with Vienna.
The concession project includes the financing, planning, construction, operation and maintenance for a period of
33 years. It consists of 51.5 km of motorways (mostly four-lane), six open cut tunnels with a total length of 7.0 km,
1.4 km of mined tunnel, 74 other engineered structures, 14 junctions, two service areas and numerous noise protection walls.
|
BGG Consult (commissioned by the provincial government of Niederösterreich) had already been responsible for the
geotechnical and hydrogeological consulting of the environmental impact assessment procedure and the building permit
application. During this phase, subsoil exploration works were supervised and processed. Based on these, geotechnical
and hydrogeological expert’s reports were compiled.
During construction, BGG Consult is now commissioned by the construction consortium to supervise all geotechnical
and hydrogeological activities. This includes the optimisation of foundations, building pits and dewatering concepts
as well as the supervision and monitoring of the extensive earth works.
In addition, BGG Consult is responsible for the preservation of the hydrogeological evidence.
|
Construction below ground water:
The Stetten and Kreuzenstein antipollution tunnels (APT) as well as the underpasses of the Northern Railway Line and the
Vienna - Laa/Thaya Railway Line are situated in the sections of the S1. For all of these, structures have to be built
below the ground water level. In the case of the Stetten APT, the dewatering was carried out with open methods. In addition,
pipes for tension release were lowered in order to avoid soil heave. The Kreuzenstein APT is built under the protection of
closed sheet pile walls. In this case, the dewatering was done by means of bored wells within the construction pit.
This method was also used at the S2 tunnel and the crossing of the Vienna - Laa/Thaya Railway Line. In the case of the
underpass below the Northern Railway Line, the impervious layer was found 25 m below surface and the aquifer could not be
sealed off by sheet piles. Therefore, the concrete floor was cast below ground water, in between sheet piles. The buoyancy
control was secured by means of driven ductile steel piles.
Prior to the implementation of the measures, BGG Consult performed numerical ground water calculations in order to identify
the impact on the hydrogeological environment.
|